JP6142064B1 - Power converter for grid connection - Google Patents

Abstract

In a grid interconnection power converter, power factor constant control and accurate isolated operation detection are compatible. The delay time and convergence time of a second PI controller used for reactive current feedback control are both the delay time and convergence time of the first PI controller used for feedback control with constant power factor (constant power factor control). A shorter time was set. That is, the responsiveness of the feedback control process of the reactive current control circuit is made faster than the responsiveness of the feedback control process of the constant power factor control circuit. As a result, the reactive current control circuit reflects the reactive power injection amount before the new reactive power control value for constant power factor control is output from the constant power factor control circuit when an isolated operation occurs. There is a high possibility that feedback control for outputting current can be completed. Accordingly, the interference between the reactive current feedback control process and the constant power factor control process is reduced, and both the constant power factor control and the accurate isolated operation detection can be achieved. [Selection] Figure 11

Description

  The present invention relates to a grid interconnection power conversion device applied to a distributed power source.

  In recent years, in order to utilize natural energy from a solar cell, a power storage hybrid power generation system combining a solar power generation system and a power storage device has been spread all over the world. In the field of such an electric storage hybrid power generation system, there is an increasing demand for mounting one function in a single power conversion device, that is, a function linked to a commercial system and a function of supplying power to a self-sustained system in the event of a power failure.

  In the future, it is expected that voltage management of distribution lines will become difficult due to the expansion of the introduction of energy storage hybrid power generation systems. In general, the power company side uses a tap control device (SVR (Step Voltage Regulator)), a reactive power compensator (STATCOM (STATic synchronous COMPensator)), and the like to maintain an appropriate voltage of the distribution line. However, in recent years, in order to perform voltage management of the nearest distribution line from the storage hybrid power generation system side, the storage hybrid power generation system has a function of controlling the power factor of output power to be constant during grid connection operation (hereinafter referred to as “ The power factor constant control function is abbreviated to be required.

  In addition, a grid interconnection power conversion device such as a power storage hybrid power generation system or a power conditioner requires a function of disconnecting from the grid (an independent operation prevention function) in the event of a power failure or grid fault. That is, it is a function that detects a voltage change or a frequency change that occurs at the time of a power failure or a system failure, stops the grid connection, and prevents a dangerous single operation state. The islanding operation detection method includes a passive islanding detection method and an active islanding detection method. In JEM (Japan Electrical Manufacturers' Association Standard) 1498, “frequency feedback method with step injection” is defined as a standard type active isolated operation detection method.

  When the power converter of the above-described “frequency injection method with step injection” detects a fluctuation in the commercial system frequency, a frequency feedback reactive power injection amount calculation unit (or “ Frequency feedback section ”) and even if the fluctuation of the commercial system frequency is very small at the time of isolated operation, the commercial system frequency decreases when at least one of the fundamental voltage and the harmonic voltage in the commercial power system changes. A reactive power step injection amount calculation unit (or “step injection unit”) that calculates a delayed reactive power injection amount that is step-injected in order to cause a change in direction.

  In the frequency feedback type power converter having the reactive power step injection amount calculation unit, as described in Patent Document 1, a first reactive power change amount deriving unit (the frequency feedback reactive power injection amount calculation unit includes Equivalent) derived for the isolated operation detection, the amount of change in reactive power according to the frequency deviation of the commercial grid power supply (that is, the magnitude of the fluctuation of the commercial grid frequency) was derived to suppress the voltage rise. In the case where interference is caused by the amount of change in reactive power, there is known one that stops output of power from the power converter.

  Further, in the above-described frequency feedback power converter, as described in Patent Document 2, the first reactive power change amount deriving unit (corresponding to the above-described frequency feedback reactive power injection amount calculating unit) is configured to detect isolated operation. If the reactive power variation Δq1 derived for the frequency deviation of the commercial power supply is interfered by the reactive power variation Δq2 derived for suppressing the voltage rise, the phase difference changing unit is activated. By changing the phase difference between the voltage and the current output from the power conversion unit in a direction that cancels out the phase difference corresponding to the reactive power variation Δq2 derived for suppressing the voltage rise, What is known to prevent a decrease in the accuracy of isolated operation detection is known.

JP-A-2015-180123 JP, 2015-180122, A

  However, when the power feedback device of the frequency feedback method as described above is provided with the function of constant power factor control, the reactive power output for power factor constant control and the isolated operation detection There is a possibility that the reactive power injected into the antenna interferes. Specifically, in order to detect isolated operation, the reactive power of the injection amount calculated by the frequency feedback reactive power injection amount calculation unit is canceled by the reactive power output for power factor constant control, There is a possibility that the isolated operation state cannot be detected promptly.

  Further, by applying the invention described in Patent Document 1, the reactive power output for power factor constant control interferes with the reactive power of the injection amount calculated by the frequency feedback reactive power injection amount calculation unit. In this case, when the output of power from the power converter is stopped, it is impossible to achieve both power factor constant control and single operation detection.

  Further, by applying the invention described in Patent Document 2, the reactive power output for power factor constant control interferes with the reactive power of the injection amount calculated by the frequency feedback reactive power injection amount calculation unit. By changing the phase difference between the voltage and current output from the power conversion unit in a direction that cancels out the phase difference corresponding to the amount of change in reactive power derived for power factor constant control, There are the following problems when the accuracy of isolated operation detection is prevented from being lowered. In other words, in a power conversion device for grid connection of solar cells, active power and reactive power constantly fluctuate due to a sudden change in input power caused by a sudden change in solar radiation, etc. Thus, it is extremely difficult to reliably cancel the amount of reactive power derived for constant power factor control only by changing the phase difference between the voltage and current output from the power converter. . In Patent Document 2, the reactive power change Δq1 corresponding to the frequency deviation of the commercial power supply is not interfered by the reactive power change Δq2 derived for other purposes (suppression of voltage rise). (For example, when the reactive power q2 that is the fast reactive power is changing in the increasing direction, the first reactive power change amount deriving unit (frequency feedback reactive power injection amount calculating unit) In the case where the amount of change in the fast reactive power is derived as Δq1, the above-described canceling process is not performed. Therefore, an accurate isolated operation is caused by the influence of the reactive power variation Δq2 derived for other purposes. Detection cannot be performed. Therefore, even when the invention described in Patent Document 2 is applied, it is difficult to achieve both power factor constant control and accurate isolated operation detection.

  The present invention solves the above-described problem, and an object of the present invention is to provide a grid interconnection power conversion device capable of achieving both power factor constant control and accurate isolated operation detection.

In order to solve the above problems, a grid interconnection power converter according to the first aspect of the present invention is a grid interconnection power converter for linking a distributed power source to a commercial power grid, Commercial system frequency measuring means for measuring the commercial system frequency, which is the frequency of the system voltage, and reactive power injection amount calculating means for calculating the reactive power injection quantity according to the fluctuation of the commercial system frequency measured by the commercial system frequency measuring means And a first PI controller that generates a first correction value based on a deviation between the power factor command value and the power factor feedback value of the output power from the grid interconnection power converter, and the first correction value Based on the power factor constant control means for generating and outputting the reactive power control value for feedback control so that the power factor of the output power from the grid interconnection power converter converges on the power factor command value And before Reactive current command value calculated based on the reactive power control value output from the constant power factor control means and the reactive power injection amount calculated by the reactive power injection amount calculation means, and the grid interconnection power converter And a second PI controller that receives the feedback value of the reactive current output from the input terminal and generates a second correction value based on a deviation between the reactive current command value and the feedback value of the reactive current. Based on the correction value, reactive current control means for performing feedback control so that the amplitude of the reactive current output from the grid interconnection power converter converges to the reactive current command value, and the reactive power injection invalidity on the basis of the commercial power system frequency, the independent operation detecting means for the system interconnection electric power conversion device detects whether the islanding state, the reactive power when the power is injected When the reactive power injection amount calculated by the input amount calculating means is 0, the reactive power control value, which is an output value from the constant power factor control means, is updated and calculated by the reactive power injection amount calculating means. Switching means for switching so that the reactive power control value is not updated when the reactive power injection amount is not 0, and the reactive power injection amount calculating means is a commercial system frequency measured by the commercial system frequency measuring means corresponding to the amount of change, the frequency feedback reactive power injection amount calculating means for calculating the reactive power injection quantity in the direction to promote the variation of the grid frequency is including ones.

  The grid interconnection power converter may include both an active islanding detection function using the frequency feedback reactive power injection amount calculating means and a passive islanding detection function as the islanding operation detection function. .

In this grid interconnection power converter, the first response time, which is the total time of the delay time and the convergence time of the first PI controller, and the total time of the delay time and the convergence time of the second PI controller The second response time is based on an active islanding detection time limit that is an upper limit value of time required for active islanding detection and a passive islanding detection time limit that is an upper limit value of time required for passive islanding detection. It is desirable to set them.
The grid interconnection power conversion device according to the second aspect of the present invention is a grid interconnection power conversion device for linking a distributed power source to a commercial power grid, and has a frequency of a commercial grid voltage. Commercial system frequency measuring means for measuring commercial system frequency, reactive power injection amount calculating means for calculating reactive power injection amount according to fluctuations in commercial system frequency measured by the commercial system frequency measuring means, and the grid interconnection A first PI controller that generates a first correction value based on a deviation between the power factor command value and the power factor feedback value of the output power from the power converter for power use, and based on the first correction value, Power factor constant control means for generating and outputting a reactive power control value for feedback control so that the power factor of the output power from the system power converter converges to the power factor command value, and the power factor constant Control means Reactive current command value calculated based on the output reactive power control value and the reactive power injection amount calculated by the reactive power injection amount calculating means, and the reactive current output from the grid interconnection power converter And a second PI controller that generates a second correction value based on a deviation between the reactive current command value and the reactive current feedback value, and based on the second correction value, When reactive current control means for performing feedback control so that the reactive current amplitude output from the grid interconnection power converter converges to the reactive current command value, and when reactive power of the reactive power injection amount is injected An independent operation detecting means for detecting whether or not the grid interconnection power converter is in an isolated operation state based on the commercial system frequency of the reactive power injection amount calculating means The frequency feedback reactive power injection amount calculating means for calculating the reactive power injection amount in the direction of promoting the fluctuation of the commercial system frequency according to the fluctuation amount of the commercial system frequency measured by the commercial system frequency measuring means, As an isolated operation detection function, it has both an active isolated operation detection function using the frequency feedback reactive power injection amount calculation means and a passive isolated operation detection function, the delay time and convergence time of the second PI controller, Both are set to a time shorter than the delay time and the convergence time of the first PI controller, the first response time which is the total time of the delay time and the convergence time of the first PI controller, and the second PI controller The second response time, which is the sum of the delay time and the convergence time, is set to the active islanding detection time limit, which is the upper limit of the time required for active islanding detection, and the passive unit time. This is set based on a passive islanding detection time limit, which is an upper limit value of the time required for islanding operation detection.
In this grid interconnection power converter, the reactive power injection amount calculating means has no fluctuation in the commercial system frequency measured by the commercial system frequency measuring means in addition to the frequency feedback reactive power injection amount calculating means, Reactive power step for calculating a slow reactive power injection amount that is step-injected in order to cause a fluctuation in a direction in which the commercial system frequency decreases when at least one of a fundamental voltage and a harmonic voltage in the commercial power system changes. It is desirable to include injection amount calculation means.

  The grid interconnection power converter further includes current limiting means for limiting the amplitudes of the effective current and the reactive current output from the grid interconnection power converter based on an output limit command value. The means limits the active current amplitude based on the output restriction command value and the rated apparent power of the grid interconnection power converter regardless of the reactive power injection amount, It is desirable to limit the active power output from the grid interconnection power converter.

  In this grid interconnection power converter, the current limiting means is configured so that the active power output from the grid interconnection power converter is a value obtained by multiplying the output limit command value and the rated apparent power. Further, it is desirable that the amplitude of the effective current is limited, and the output limit command value is a value from 0 to the power factor command value.

  In this grid interconnection power converter, the frequency feedback reactive power injection amount calculating means is configured to inject the reactive power when the fluctuation amount of the commercial grid frequency measured by the commercial grid frequency measuring means is equal to or less than a predetermined threshold. It is desirable that the amount be zero.

  In this grid interconnection power converter, the magnitude of reactive power output from the grid interconnection power converter is changed according to the magnitude of active power output from the grid interconnection power converter Thus, it is desirable to make the power factor of the output power from the grid interconnection power converter constant.

The grid interconnection power converter according to the first aspect of the present invention includes the switching unit, and when the reactive power injection amount calculated by the reactive power injection amount calculating unit is 0 using the switching unit. Updates the reactive power control value, which is the output value from the constant power factor control means, and does not update the reactive power control value when the reactive power injection amount calculated by the reactive power injection amount calculation means is not zero. I made it. Thus, when reactive power is generated from the reactive power injection amount calculating means (when the reactive power injection amount calculated by the reactive power injection amount calculating means is not 0), the feedback control function of the power factor constant control means is set. It is possible to temporarily stop and reduce the influence of the reactive power output for feedback control of constant power factor control on the reactive power injected for islanding operation detection. Therefore, it is possible to achieve both power factor constant control and accurate isolated operation detection.

1 is a schematic system configuration diagram of a power storage hybrid power generation system (system interconnection power conversion device) according to an embodiment of the present invention. The schematic block diagram of the control circuit of the said electrical storage hybrid electric power generation system. The control block diagram of the constant power factor control circuit in the said control circuit. Explanatory drawing of the process in the commercial system frequency measurement circuit in FIG. The figure which shows the relationship between the power factor command value and the command value of output restriction | limiting in the output restriction | limiting of the said electrical storage hybrid electric power generation system. Explanatory drawing of the update timing of the reactive current command value in the said control circuit. (A) is explanatory drawing of the frequency deviation and reactive power characteristic which the frequency feedback reactive power injection circuit in FIG. 2 uses, (b) is explanatory drawing of the process in the reactive power step injection circuit in FIG. Explanatory drawing of the determination method of the independent operation state in the said electrical storage hybrid electric power generation system. The charge / discharge electric power control block diagram for bidirectional | two-way DC / DC converters in the said control circuit. Correspondence relationship between charge / discharge power command value, active power, reactive power, apparent power, and operation for active isolated operation detection when performing charge / discharge power control at night in the above-mentioned storage hybrid power generation system FIG. (A) is explanatory drawing of the design method of the parameter of PI controller in the said electrical storage hybrid electric power generation system, (b) is a figure which shows the setting value of the parameter in the said PI controller. (A) represents the point where the active islanding detection test was performed in order to confirm the effectiveness of the device for reducing the interference between the power factor constant control process and the islanding operation detection process in the electricity storage hybrid power generation system. A graph and (b) are tables showing parameter setting values in the experimental system in which the islanding operation detection test was performed. The graph which shows the experimental result of the independent driving | operation detection test in the point 1 in Fig.12 (a). The graph which shows the experimental result of the independent operation detection test in the point 2 in Fig.12 (a). The graph which shows the experimental result of the independent operation detection test in the point 3 in Fig.12 (a). The graph which shows the experimental result of the independent driving | operation detection test in the point 4 in Fig.12 (a). The graph which shows the experimental result of the independent driving | operation detection test in the point 5 in Fig.12 (a).

  DESCRIPTION OF EMBODIMENTS Hereinafter, a grid interconnection power converter according to an embodiment of the present invention will be described with reference to the drawings. This embodiment demonstrates the example in case the power converter device for grid connection in a claim is an electrical storage hybrid electric power generation system. FIG. 1 shows a schematic system configuration of a power storage hybrid power generation system 1 according to the present embodiment.

  The power storage hybrid power generation system 1 is a combination of a so-called power conditioner with a solar battery 2 that is a distributed power source and a storage battery 3 that stores power output from the solar battery 2. It is possible to link to

The storage hybrid power generation system 1 is a DC / DC (converting voltage of DC power output from the solar battery 2 in order to convert the solar battery 2 and DC power generated by the solar battery 2 into optimum output power. Direct Current to Direct Current) converter 4a, bidirectional DC / DC converter 4b for charging / discharging storage battery 3, and DC / DC for converting DC output power from these DC / DC converters 4a and 4b into AC power. An AC (Direct Current to Alternating Current) inverter 5 (hereinafter abbreviated as “inverter 5”) is provided. The power storage hybrid power generation system 1 also includes an electrolytic capacitor C _dc for smoothing a DC bus voltage, an LC filter 6, a control circuit 7a, a control circuit 7b, and a grid interconnection relay S _Grid .

  In the power storage hybrid power generation system 1 of the present embodiment, the main parts of the inverter 5 and the bidirectional DC / DC converter 4b are configured by an IPM (Intelligent Power Module) 8 for a three-phase inverter. The IPM 8 for a three-phase inverter is a power semiconductor element incorporating a drive circuit for switching elements SW1 to SW6 composed of an IGBT (Insulated Gate Bipolar Transistor) and a self-protection function. In the present embodiment, among the six switching elements S1 to S6 in the IPM 8 for the three-phase inverter, the switching elements S1 to S4 are used as the switching elements of the inverter 5, and the switching elements S5 and S6 are used as the bidirectional DC / DC converter. It is used as a switching element of 4b. As shown in FIG. 1, among the three-phase output lines in the IPM 8 for a three-phase inverter, the u-phase and w-phase output lines are connected to a single-phase two-wire commercial system 9, and the v-phase output line is It is connected to the storage battery 3.

The bidirectional DC / DC converter 4b includes switching elements S5 and S6 built in the IPM 8 for three-phase inverter and a DC reactor L _BAT in addition to these drive circuits. R _{BAT in} FIG. 1 is an internal resistance of the DC reactor L _BAT . The electrolytic capacitor C _dc also serves as a capacitor necessary for DC / DC conversion in the bidirectional DC / DC converter 4b.

The DC / DC converter 4a performs maximum power point tracking control (hereinafter referred to as MPPT (Maximum Power Point Tracking) control) of the solar cell 2 based on the control by the control circuit 7b, and the output power from the solar cell 2 is maximum. The input voltage from the solar cell 2 is adjusted so as to be (optimal). Specifically, the DC / DC converter 4a performs the step-up / step-down operation up to a predetermined input voltage so that the solar cell 2 can output the maximum output power based on the control by the control circuit 7b, and the maximum power point tracking control. I do. The switching element _{S PV} in DC / DC converter 4a is constituted by IGBT, it is switched PWM (Pulse Width Modulation) signal sent from the control circuit 7b.

  The inverter 5 converts DC power based on power input from at least one of the DC / DC converter 4a and the bidirectional DC / DC converter 4b into AC power. Switching elements S1 to S4 in inverter 5 are switched by a PWM signal sent from control circuit 7a of power storage hybrid power generation system 1.

The LC filter 6 includes two AC reactors L _inv connected in series to each power supply line and a capacitor C _inv connected between the power supply lines. From the AC voltage output from the inverter 5, harmonic components are generated. (Mainly, the carrier frequency of the PWM signal) is removed. R _inv and R _c in the figure indicate the internal resistance of each AC reactor L _{inv and} the internal resistance of each capacitor C _inv , respectively. Further, i _{c in} FIG. 1 indicates a current flowing through the capacitor C _inv (capacitor passing current).

The control circuits 7a and 7b are configured using so-called microcomputers. The control circuit 7a mainly controls the bidirectional DC / DC converter 4b and the inverter 5, and the control circuit 7b controls the DC / DC converter 4a. As shown in FIG. 1, an input signal (measurement point) of the control circuit 7a includes a DC bus voltage V _dc , an output current i _inv of the inverter 5, a load current i _load flowing through an AC load Z _Load in the home, a commercial system The voltage e _uw , the output voltage e _inv of the inverter 5, the charge / discharge current I _{BAT of} the storage battery 3, the voltage V _{BAT of the} storage battery 3, the output voltage V _{PV of} the solar battery 2, and the output current I _PV of the solar battery 2. The output signal of the control circuit 7a in FIG. 1 includes an output signal for controlling the _grid interconnection relay S _Grid , an output signal for controlling the switching elements S1 to S4 of the inverter 5, and a bidirectional DC / DC converter 4b. Output signals for controlling the switching elements S5 and S6. The input signals (measurement points) of the control circuit 7b are the DC bus voltage V _dc , the output voltage V _{PV of} the solar cell 2, and the output current I _PV of the solar cell 2, and the output signal of the control circuit 7b is which is an output signal for controlling the switching element _{S PV} of the DC / DC converter 4a.

The grid connection relay S _Grid is a switch for switching between a connected state and a disconnected state to the commercial power system 9 of the power storage hybrid power generation system 1.

The commercial power system 9 includes a commercial system power supply 10 and a system impedance. R _Grid and L _{Grid in} FIG. 1 indicate system impedance resistance and inductive reactance. In FIG. 1, i _sp indicates the output current of the power storage hybrid power generation system 1, i _Grid indicates the reverse power flow current of the power storage hybrid power generation system 1, and Z _load is connected to the commercial power system side. Indicates the AC load in the home.

FIG. 2 is a control block diagram of the control circuit 7a of the electricity storage hybrid power generation system 1. The control blocks in FIG. 2 mainly include a power factor constant control block A, a DC bus voltage constant control block B (a control block for making the value of the DC bus voltage V _dc constant), and a reactive current control block. C, an inverter output current control block D, and an isolated operation detection control block E. Each circuit in FIG. 2 is a circuit created using basic functional blocks of a microcomputer.

As shown in FIG. 2, the control circuit 7 a includes an output current estimation circuit 11 that is a kind of addition point, a PLL _v 12 that is a PLL (Phase Locked Loop) synchronization circuit of the commercial system voltage e _uw , and an output current i _sp . PLL _i 13, which is a PLL synchronization circuit, power factor feedback value generation circuit 14, constant power factor control circuit 15, DC bus voltage constant control circuit 16, active current limiter 17, effective component generation circuit 18, invalid component generation circuit 19, output Current control circuit 20, PWM output control circuit 21 for inverter 5 (abbreviated as PWM in the figure), commercial system frequency measurement circuit 22, isolated operation detection circuit 23, frequency feedback reactive power injection circuit 24, reactive power step injection circuit 25 , Reactive current feedback value generation circuit 26, multiplier 27, multiplier 28, reactive current control circuit 29 And a reactive current limiter 30 and a multiplier 35. The power factor constant control circuit 15 includes a first PI controller 41, and the reactive current control circuit 29 includes a second PI controller 32. In addition, the islanding detection circuit 23 includes a passive islanding detection circuit 31 for realizing a passive islanding detection function.

When F _active shown in FIG. 2 is set to 1, the control circuit 7a is a standard type active isolated operation detection method defined by JEM (Japan Electrical Manufacturers' Association) 1498 “frequency feedback with step injection”. Based on the “method”, the active _islanding detection is performed, and when F _active is set to 0, the control circuit 7a masks the active islanding detection function based on the “frequency feedback method with step injection” and passively Single operation detection by the automatic single operation detection method. In the following description, the processing when F _active is set to 1 will be mainly described.

  Commercial system frequency measurement circuit 22, power factor constant control circuit 15, reactive current control circuit 29, isolated operation detection circuit 23, frequency feedback reactive power injection circuit 24, first PI controller 41, second PI controller 32, reactive power The step injection circuit 25 includes a commercial system frequency measurement unit, a power factor constant control unit, a reactive current control unit, an isolated operation detection unit, a frequency feedback reactive power injection amount calculation unit, a first PI controller, and a second PI control, respectively. This corresponds to a reactive power step injection amount calculation means. The effective current limiter 17 and the reactive current limiter 30 correspond to current limiting means in the claims.

The power factor constant control block A includes an output current estimation circuit 11, a PLL _v 12, a PLL _i 13, a power factor feedback value generation circuit 14, and a power factor constant control circuit 15. The DC bus voltage constant control block B includes a DC bus voltage constant control circuit 16. The reactive current control block C includes a reactive current control circuit 29. The inverter output current control block D includes an effective component generation circuit 18, an invalid component generation circuit 19, an output current control circuit 20, and a PWM output control circuit 21. The isolated operation detection control block E includes a commercial system frequency measurement circuit 22, an isolated operation detection circuit 23, a frequency feedback reactive power injection circuit 24, and a reactive power step injection circuit 25.

First, the circuits included in the power factor constant control block A will be described. The output current estimation circuit 11 subtracts the value of the capacitor passing current _ic calculated by the following equation (1) from the measured value of the inverter output current i _inv , thereby causing the commercial hybrid system 1 to The value of the output current _isp output to the power supply 9 is calculated. Incidentally, _{i c} in the formula (1) represents a capacitor current flowing through the capacitor _{C inv} in FIG. 1 (a capacitor passing current), _{C inv} in the formula (1) shows the capacitance of the capacitor _{C inv} .

PLL _v 12 is a PLL synchronization circuit of the commercial power system voltage _{e uw,} based on the measured value of the commercial power system voltage _{e uw} is an AC voltage signal, the and phase angle theta _uw commercial system voltage _{e uw} and operating frequency _{f PLL} Calculate and output. Also, _PLL i 13 is a PLL synchronization circuit of the output current _{i sp,} the value of the estimated output current _{i sp} is inputted with the output current estimation circuit 11, based on the estimated value of the output current _{i sp,} and calculates the phase angle theta _sp output current _{i sp,} and outputs.

Power factor feedback value generating circuit 14 is obtained from the _PLL v 12 and the phase angle theta _uw output from _PLL i 13 and theta _sp, the phase difference Δφ between the commercial system voltage _{e uw} and output current _{i sp} (θ _uw - The value of cos (Δφ) generated based on θ _sp ) is output to the power factor constant control circuit 15 as the power factor feedback value PF.

As shown in FIG. 3, the constant power factor control circuit 15 generates a correction value based on the deviation between the power factor command value PF ^* of the output power from the power storage hybrid power generation system 1 and the power factor feedback value PF. The controller 41 is included, and based on this correction value, feedback control is performed so that the power factor (driving power factor) of the output power from the power storage hybrid power generation system 1 converges to the power factor command value PF ^* . Reactive power control value PF _out is generated and output.

More specifically, as shown in FIG. 3, the constant power factor control circuit 15 includes addition points SP5 and SP6, a limiter 42, a reactive power control value calculation circuit, in addition to the first PI controller 41 described above. 43, a multiplier 44, and a switch S _PF (“switching means” in the claims).

In addition point SP5, the deviation of said power factor command value PF ^* and power factor feedback value (driving power factor feedback value) PF is calculated. The first PI controller 41 generates a correction value (“first correction value” in the claims) according to the deviation. At the addition point SP6, the correction value generated by the first PI controller 41 and the power factor command value PF ^* are added, and the total value of these values is output. The limiter 42 limits the value of the total value to a range of 0 to 1 and outputs it as a power factor target value PF ^* _real . The reactive power control value calculation circuit 43 calculates the absolute value of the reactive power control value PF _out by the following equation (2) based on the power factor target value PF ^* _real . As shown in FIG. 3, the multiplier 44 multiplies the output value from the reactive power control value calculation circuit 43 by “+1” or “−1” to generate a reactive power control value PF _out .

If the sign of the reactive power control value PF _out is positive (+), it is delayed reactive power, and if it is negative (−), it is advanced reactive power. The switching process for updating the reactive power control value PF _out using the switch S _PF will be described in detail later. When the driving power factor is 1, the power factor command value PF ^* = 1, and this power factor command value PF ^* = 1 is set to a constant power factor control circuit 15 (constant power factor) shown in FIG. When input to the control block), the value of the reactive power control value PF _out output from the constant power factor control circuit 15 becomes zero.

Next, the DC bus voltage constant control circuit 16 included in the DC bus voltage constant control block B will be described. The DC bus voltage constant control circuit 16 is a circuit that controls the DC bus voltage V _dc to be constant. DC bus voltage constant control circuit 16, based on the difference between the feedback value of the DC bus voltage V _dc, the DC bus voltage command value V ^* _dc is a command value of the DC bus voltage V _dc, the active ingredient from the inverter 5 The effective current command value I ^* _p , which is the control target value of the output current, is calculated. More specifically, the DC bus voltage constant control circuit 16, a feedback value of the DC bus voltage V _dc is, performs the PID control operation so as to converge to the DC bus voltage command value V ^* _dc, active current and the calculated value The command value I ^* _p is output to the active current limiter 17.

  Next, the commercial system frequency measurement circuit 22, the isolated operation detection circuit 23, the frequency feedback reactive power injection circuit 24, and the reactive power step injection circuit 25 included in the isolated operation detection control block E will be described.

The commercial system frequency measurement circuit 22 includes a zero cross detection circuit configured by a binarization circuit that binarizes an AC voltage signal. As shown in FIG. 4A, the commercial system frequency measuring circuit 22 binarizes the signal waveform of the commercial system voltage _euw indicated by a broken line with a binarization circuit with a voltage value of zero as a threshold value. Then, a square wave (indicated by a solid line in the figure) having a duty ratio of 50% and the same frequency as the commercial system frequency is generated. Then, the commercial frequency measurement circuit 22 calculates the time difference between the intermediate value between the falling edge and the rising edge of the square wave and the intermediate value between the next falling edge and the rising edge as a sampling frequency of 2.5 MHz. By counting with (accuracy of 0.4 μs), the commercial system frequency f _grid corresponding to the commercial system voltage e _uw is measured. The above sampling frequency (2.5 MHz) is an example, and is not limited to this value.

Next, returning to FIG. 2, the frequency feedback reactive power injection circuit 24 and the reactive power step injection circuit 25 included in the isolated operation detection control block E will be described. Although details will be described later, the frequency feedback reactive power injection circuit 24 varies the commercial system frequency according to the commercial system frequency f _grid fluctuation amount (frequency deviation Δf _grid ) measured by the commercial system frequency measurement circuit 22. The reactive power injection amount K _fvar in the direction that promotes is calculated and output. Further, the reactive power step injection circuit 25 has no fluctuation in the commercial system frequency f _grid measured by the commercial system frequency measurement circuit 22, and at least one of the fundamental voltage and the harmonic voltage in the commercial power system 9 fluctuates. Then, the lagging reactive power injection amount K _step that is step-injected in order to cause fluctuation in the direction in which the commercial system frequency f _grid decreases is calculated and output. In the present specification, the state "no change in the grid frequency f _grid", in addition to the state without any variation in the grid frequency f _grid, the state variation is small the grid frequency f _grid, i.e., This includes a state in which the frequency deviation Δf _grid is in the low-sensitive zone region (a region where the absolute value of the frequency deviation Δf _grid is equal to or less than the threshold value f _stop (see FIG. 7A)). In the following description, the frequency feedback reactive power injection circuit 24 and the reactive power step injection circuit 25 may be collectively referred to as a reactive power injection amount calculation circuit 34. The reactive power injection amount calculation circuit 34 corresponds to the reactive power injection amount calculation means in the claims.

In the isolated operation detection circuit 23, the operation frequency f _PLL of the commercial system voltage e _uw obtained by PLL _v 12, the commercial system frequency f _grid measured by the commercial system frequency measurement circuit 22, and the harmonic voltage effective value THD _V is input. When F _active is set to 1, the islanding operation detection circuit 23 uses the commercial grid frequency f when the reactive power injection amount calculated by the reactive power injection amount calculation circuit 34 is injected. _{Based on the grid} and the operating frequency f _PLL , it is detected whether or not the power storage hybrid power generation system 1 is in a single operation state. That is, the isolated operation detection circuit 23 performs active isolated operation detection based on a frequency feedback method with step injection.

If the F _active is set to 0, the isolated operation detecting circuit 23, the commercial power system frequency _{f grid,} the operating frequency _{f PLL,} and based on the harmonic voltage effective value THD _V, the passive islanding detection circuit 31 It is used to detect islanding by a passive islanding detection method. The reason for designing in this way is that the passive islanding detection method does not inject reactive power when the islanding state occurs, so compared to the active islanding detection method (frequency feedback method with step injection), It is difficult to capture fluctuations in the commercial system frequency f _grid and the operating frequency f _PLL . However, when the power storage hybrid power generation system 1 is linked to the commercial power grid 9, the harmonic voltage effective value THD _V is determined from the total distortion of the commercial power grid voltage, whereas the power storage hybrid power generation system 1 Is in a single operation state, the harmonic voltage effective value THD _V is determined from the total distortion of the output current i _sp . Therefore, in the passive islanding detection method, in order to accurately detect the islanding state, the change in the harmonic voltage effective value THD _V is monitored, and the change in the harmonic voltage effective value THD _V is taken into consideration. It is necessary to detect operation. Therefore, as described above, the independent operation detecting circuit 23 is not only a commercial power system frequency f _grid and the operating frequency f _PLL, based on the harmonic voltage effective value THD _V, islanding detection by passive islanding detection method Is done.

  As described above, the power storage hybrid power generation system 1 includes an active islanding detection function using the reactive power injection amount calculation circuit 34 and the islanding operation detection circuit 23, and a passive islanding using the passive islanding detection circuit 31. Both driving detection functions are provided.

Next, the reactive current control circuit 29 included in the reactive current control block C will be described. The reactive current control circuit 29 is calculated based on the reactive power control value PF _out output from the constant power factor control circuit 15 and the total reactive power injection amount K _Q calculated by the reactive power injection amount calculation circuit 34. The reactive current command value I ^* _q and the reactive current feedback value _Iq output from the power storage hybrid power generation system 1 are input. More specifically, the reactive current command value I ^* _q is generated as follows. First, at the addition point SP3, the total value of the reactive power injection amount K _fvar calculated by the frequency feedback reactive power injection circuit 24 and the delayed reactive power injection amount K _step calculated by the reactive power step injection circuit 25 is calculated. Ask. When the F _active is set to 1 (when active _islanding operation is detected), the multiplier 35 in the figure _performs the total value of the reactive power injection amount (K _fvar + K _step ) as it is. When the reactive power injection amount K _Q is output and F _active is set to 0 (when passive _islanding operation is detected), the total value of the reactive power injection amount (K _fvar + K _step ) is masked. Thus, the total reactive power injection amount _{KQ is set} to zero.

The reactive power injection amount calculation circuit 34 of the present embodiment generates a step reactive power injection operation (when the delayed reactive power injection amount K _step calculated by the reactive power step injection circuit 25 is not 0). Is designed so that the operation of frequency feedback reactive power injection is not performed (the reactive power injection amount K _fvar calculated by the frequency feedback reactive power injection circuit 24 becomes 0).

The reactive power control value PF _out output from the constant power factor control circuit 15 and the total reactive power injection amount K _Q are added at an addition point SP4 (see FIG. 2). The multiplier 28 calculates the total value of the reactive power control value PF _out and the reactive power injection amount K _Q input from the addition point SP4, as a _peak value 2P _uw / E _uw. Multiply by _max and output the multiplication result to the reactive current control circuit 29 as the reactive current command value I ^* _q . Here, P _uw indicates active power output from the power storage hybrid power generation system 1, and E _{uw. max} indicates the maximum value (amplitude) of the commercial system voltage e _uw . Additional active power _{P uw} and the maximum value _{E uw} commercial system voltage _{e uw. “max”} is calculated by the following equations (3) to (5), respectively.

Of the input values to the reactive current control circuit 29, the reactive current feedback value _Iq is generated as follows. First, as shown in FIG. 2, the reactive current feedback value generation circuit 26 determines the tan (Δφ based on the phase difference Δφ (θ _uw −θ _sp ) between the commercial system voltage e _uw and the output current i _sp. ) Value. Then, the multiplier 27 calculates the value of tan (Δφ) output from the reactive current feedback value generation circuit 26 and the _peak value 2P _uw / E _uw. Multiply by _max and output the multiplied value to the reactive current control circuit 29 as the reactive current feedback value _Iq . The reactive power Q _uw and the apparent power S _uw output from the storage hybrid power generation system 1 are calculated by the following equations (6) and (7), respectively. Further, the output power P _PV from the solar battery 2 is calculated by the following equation (8).

The reactive current command value I ^* _q and the reactive current feedback value _Iq are input to the second PI controller 32 of the reactive current control circuit 29. The second PI controller 32 generates a correction value based on the deviation between the reactive current command value I ^* _q and the reactive current feedback value _Iq . The reactive current control circuit 29 determines that the reactive current amplitude (maximum value) output from the power storage hybrid power generation system 1 is the reactive current command value I ^* _q based on the correction value generated by the second PI controller 32. Feedback control is performed so as to converge. Further, the reactive current command value I ^* _q and the reactive current feedback value _Iq are _converted into the effective current _peak value 2P _uw / E _{uw. The} reason for designing to a value corresponding to _max is that the driving power factor is kept constant even when the output restriction command value (I ^* _{P.lim in the following} equation (10)) is changed when performing output suppression control described later. This is so that it can be made. Here, also by changing the command value of the output limit, the maximum value of the commercial system voltage e _uw (amplitude) E _{uw. Since max} does not change, as described above, the reactive current command value I ^* _q and the reactive current feedback value _Iq are set to the effective current _peak value 2P _uw / E _uw. Even when the command value for output restriction is changed by setting the value according to _max , the magnitude of the reactive power Q _uw is changed according to the magnitude of the active power P _uw whose output is restricted, and the driving force The rate can be made constant. In addition, also from said Formula (6), it turns out that the magnitude _| size of the reactive power _Quw output from the electrical storage hybrid electric power generation system 1 changes according to the magnitude _| size of the active power _Puw .

Next, the effective current limiter 17 and the reactive current limiter 30 will be described. The active current limiter 17 and the reactive current limiter 30 determine the amplitudes of the effective current and the reactive current output from the power storage hybrid power generation system 1 as output command values (hereinafter referred to as “output limit command values”) I ^* _{P. Limiting} is performed using limiter values (I _P.lim , I _Q.lim ) calculated based on _lim . That is, when the operating power factor of the storage hybrid power generation system 1 is changed, the active current limiter 17 and the output power from the storage hybrid power generation system 1 do not exceed the rated output power (rated apparent power). The reactive current limiter 30 is configured to output an effective output current command value I _{uw. p} , and the output current command value I _{uw. q} is the limiter value IP of each output current command value _{. lim} , _{IQ .} Suppress (restrict) by _lim . An effective output current command value I _{uw. That} is an output value from the effective current limiter 17 to the effective component generation circuit 18 _{. p} is an absolute value of the effective current command value I ^* _p , the limiter value I _P. When it is smaller than _lim , it is the effective current command value I ^* _p , and the active current command value I ^* _p is the limiter value (upper limit value) IP of the output current command value for the effective portion _{. If} it is _{equal to} or greater than _{lim, then IP . When} the effective current command value I ^* _p is equal to or _smaller than the limit value (lower limit value) (−I _P.lim ) of the effective output current command value, it is (−I _P.lim ). Invalid output current command value I _{uw. Also for} the suppression (limitation) of _q , the output current command value I _uw. The same as in the case of _p .

The following formulas (9) and (10) are expressed by the limiter value IP of the effective output current command value _{. lim} and the limiter value I _{Q. It} is a defining expression with _lim .

In the above formulas (9) and (10), S _rated is the rated apparent power of the power storage hybrid power generation system 1, and E _rated is the nominal voltage of the commercial power system 9. In addition, I ^* _{P. lim} is an output restriction command value. As shown in the equation (10), the limiter value I _{Q. In} addition to the above-described rated apparent power S _rated and the nominal voltage E _rated of the commercial power system 9, _lim is the output limit command value I ^* _{P. lim} , the power factor command value PF ^* (of the output power from the storage hybrid power generation system 1), and the upper limit value K _flim of the frequency feedback reactive power injection amount K _fvar .

In the present embodiment, when the step injection operation is generated (when the delayed reactive power injection amount K _step calculated by the reactive power step injection circuit 25 is not 0), the frequency feedback injection operation is performed. The reactive power injection amount K _fvar calculated by the frequency feedback reactive power injection circuit 24 is designed to be zero. Here, the maximum value (0.1 p.u. (per unit)) of the retarded reactive power injection amount K _step injected in the step injection is the maximum value of the reactive power injection amount K _fvar injected in the frequency feedback injection. Since it is smaller than (0.25 p.u.), the upper limit value K _flim of the frequency feedback reactive power injection amount K _{fvar is also} the upper limit value of the total reactive power injection amount K _Q (K _Q = K _fvar + K _step ). Therefore, as shown in the above equation (10), the limiter value I _{Q. lim} is defined in consideration of the upper limit K _flim described above.

Next, with reference to FIG. 5, output limitation in the power storage hybrid power generation system 1 will be described. As shown in FIG. 5, it is understood that the output limitation in the electricity storage hybrid power generation system 1 is considered separately when the power factor command value PF ^* which is the command value of the driving power factor is 1 and when it is not 1. easy. That is, when the power factor command value PF ^* is set to 1, the output limit command value I ^* _{P. It} is considered that the setting value of _lim can be set in the range of 0 to 1 (output of 0% to 100%). When the power factor command value PF ^* is set to a value of 1 or less and the constant control of the (operation) power factor is performed, the set value of the power factor command value PF ^* is the lower limit value PF _{min of the} driving power factor. Output limit command value I ^* _P. It is considered that the set value of _lim can be set in the range of 0 to the power factor command value PF ^* . The reason for designing in this way is to suppress the effective power P _uw so that the output power from the storage hybrid power generation system 1 does not exceed the designed rated apparent power when performing constant power factor control. .

Output limit command value I ^* _P. and it was designed setting range of _lim, as shown in FIG. 5, the limiter value I _P. output current command value for the active component and reactive component _lim , _{IQ .} By defining _lim as shown in equations (9) and (10), when performing constant power factor control (ignoring reactive power due to reactive power injection), The output (apparent) power can be controlled (suppressed) so as not to exceed the rated apparent power of the designed power storage hybrid power generation system 1.

For example, when the power factor command value PF ^* is 1 and the rated apparent power S _rated is output, the active power P _uw and the apparent power S _uw and the output limit command value I ^* _P. The relationship between _lim and the total reactive power injection amount K _Q is shown in equations (11) and (12). As shown in the equations (11) and (12), in this power storage hybrid power generation system 1, even if the reactive power injection operation (total reactive power injection amount K _Q ) occurs, the active power P _uw due to the increase in reactive power It was designed so that the reduction phenomenon can be avoided and the effective output power is not affected. In this power storage hybrid power generation system 1, even when the power factor command value PF ^* is other than 1, as shown in the above equation (9), the active current limiter 17 has the total reactive power injection amount K _Q. Regardless of the size, the output limit command value I ^* _P. By limiting the amplitude of the effective current output from the storage hybrid power generation system 1 based on the _lim , the rated apparent power S _rated of the storage hybrid power generation system 1 and the nominal voltage E _rated of the commercial power system 9 The power P _uw is limited. As a result, even if a reactive power injection operation occurs, it is possible to avoid a reduction in the active power P _uw due to an increase in the reactive power, and it is possible to prevent the output power from being affected.

Further, in the electricity storage hybrid power generation system 1, the effective current limiter 17 indicates that the effective power P _uw output from the electricity storage hybrid power generation system 1 is the output restriction command value I ^* _P. As a value obtained by multiplying the _lim and rated apparent power S _rated, limiting the amplitude of the effective current outputted from the power storage hybrid power generation system 1, as shown in FIG. 5, the output limit command value I ^* _{P. lim} was set to a value from 0 to the power factor command value PF ^* . Thereby, the upper limit value of the active power P _uw output from the power storage hybrid power generation system 1 is multiplied by the power factor command value PF ^* and the rated apparent power S _rated regardless of whether or not the reactive power injection operation occurs. The value can not be exceeded.

In the above JEM 1498 standard, the upper limit value K _flim of the reactive power injection amount K _fvar by the frequency feedback unit (frequency feedback reactive power injection circuit 24) is 0.25 p. u. It is stipulated. Therefore, when a reactive power injection operation occurs, from √ (1 + 0.25 ² ) ≈1.03, the instantaneous apparent power corresponds to about 1.03 times the instantaneous active power at maximum. In addition, when an unstable element is given to the power system by the reactive power injection operation, it is necessary to lower the upper limit value K _flim of the frequency feedback injection amount, but by reducing the upper limit value of the reactive power injection amount, There is a possibility that the time required for driving detection may be extended.

Next, the effective component generation circuit 18, the invalid component generation circuit 19, the output current control circuit 20, and the PWM output control circuit 21 included in the inverter output current control block D will be described. The effective component generation circuit 18 outputs an effective output current command value I _uw. The instantaneous value of the current command value of the active component is generated by multiplying _p by the sine value sin (θ _uw ) of the phase angle θ _uw of the commercial system voltage e _uw output from the PLL _v 12. The reactive component generation circuit 19 outputs an invalid output current command value I _{uw. q} is multiplied by the cosine value cos (θ _uw ) of the phase angle θ _uw of the commercial system voltage e _uw output from the PLL _v 12 to generate an instantaneous value of the current command value of the invalid component.

The output value from the effective component generation circuit 18 and the output value from the invalid component generation circuit 19 are added at the addition point SP2, and become the output current command value i ^* _{inv of} the inverter 5. This output current command value i ^* _inv is sent to the output current control circuit 20. The output current control circuit 20 performs feedback control using an unillustrated PI controller or the like so that the feedback value of the output current i _inv from the inverter 5 follows the output current command value i ^* _inv. The output duty ratio D is calculated. This duty ratio D is input to the PWM output control circuit 21. Based on the input output duty ratio D, the PWM output control circuit 21 generates a PWM signal having a pulse width corresponding to the output duty ratio D. On / off of each switch SW1, SW2, SW3, SW4 of the inverter 5 is controlled based on these PWM signals.

Next, timing for updating the reactive current command value I ^* _q will be described with reference to FIG. In this power storage hybrid power generation system 1, the reactive current command value I ^* _q is updated every half cycle of the output current _isp , and the absolute value | _isp | is the maximum value _isp. It is limited to a time within a predetermined range before and after the time indicating _max or the time indicating the maximum value. That is, the reactive current command value I ^* _q is updated at a timing t _up within a range of | i _sp | ≧ (i _sp.max −Δl _q.cst ) as shown in FIG. Specifically, the reactive current command value I ^* _q is set to | i _sp | ≧ 0.95 i _sp. It is desirable to update at a time within the range of _max .

As described above, the reason why the update time of the reactive current command value I ^* _q is designed every half cycle of the output current _isp (that is, every half cycle of the commercial system frequency) is as follows. That is, in this embodiment, as shown in the above formula (3) and (4), active power _{P uw} and commercial system voltage _e maximum value of _{uw (amplitude) E uw. The} timing for updating _max is set for each half cycle of the commercial system frequency. For this reason, the _peak value 2P _uw / E _uw. The update timing of the reactive current feedback value _Iq generated based on _max is also every half cycle of the commercial system frequency. Therefore, the timing of updating the reactive current command value I ^* _q also to the same manner as the update timing of the feedback value I _q reactive current, a reactive current command value I ^* _q for each half cycle of the output current i _sp update I tried to do that. As described above, the reactive current command value I ^* _q is updated every half cycle of the output current _isp , whereby the responsiveness of the constant power factor control can be improved.

In addition, as described above, the update time of the reactive current command value ^I _{* q,} the absolute value _{| i sp |} maximum value _{i sp. By} setting the time indicating _max or a time close thereto, the stability of reactive power control and the stability of the output current i _inv from the inverter 5 can be improved. The reason for this will be described below.

In general, the amplitude of the output current i _sp fluctuates by drawing a sine curve based on the commercial grid frequency. However, when the zero cross point of the sine curve, that is, when the absolute value | i _sp | of the output current shows a minimum value, When the reactive current command value I ^* _q is updated, the reactive current command value I ^* _inv is calculated as the product of the reactive component (the reactive current output value command value I _uw.q and COS (θ _uw ) included in the output current command value i ^* _inv. The output current command value i ^* _inv changes greatly at the timing when the influence of (value) increases. As a result, the output current i _inv overshoot or undershoot tends to occur, and there is a possibility that the stability of the output current i _inv is impaired.

However, the grid an every half cycle of the frequency, the absolute value of the reverse flow current | i _{sp |} When reactive current target value at a time near term or in the maximum value is updated, the output current command value i ^* _{Since the} output current i _inv is controlled at a timing when the influence of the invalid component (value calculated by the product of the invalid output current command value I _uw.q and COS (θ _uw )) included in _inv becomes small The stability of reactive power control and the stability of the output current i _inv from the inverter 5 can be improved.

Next, the reactive power injection amount calculation circuit 34 will be supplementarily described. First, the above-described frequency feedback reactive power injection circuit 24 is a circuit that calculates the reactive power injection amount according to the commercial system frequency f _grid measured by the commercial system frequency measurement circuit 22, and according to the frequency deviation Δf _grid at a certain point in time. Then, the reactive power injection amount K _fvar is calculated based on the frequency deviation / reactive power characteristic (see FIG. 7A) in which the reactive power injection amount is determined so that the subsequent frequency deviation gradually increases.

The frequency feedback reactive power injection circuit 24 calculates the frequency deviation Δf _grid as follows. The commercial system frequency f _grid inputted from the commercial system frequency measuring circuit 22 to the frequency feedback reactive power injection circuit 24 is updated every cycle. For this reason, the frequency feedback reactive power injection circuit 24 shows the cycle data (data representing the cycle of the AC signal of the commercial grid voltage e _uw ) obtained based on the input commercial grid frequency f _grid in FIG. As shown, it is updated every cycle. Then, as shown in FIG. 4C, the frequency feedback reactive power injection circuit 24 calculates a moving average of periodic data for the latest 40 ms at intervals of 5 ms, and stores it in a memory circuit (not shown) in the control circuit 7a. Remember. Then, as shown in FIG. 4B, the frequency deviation is obtained by subtracting the moving average of the period data for the latest 40 ms from the moving average of the period of 80 ms 200 ms before the latest moving average calculation time. (Deviation amount of period data) Δf _grid is calculated.

FIG. 7A shows the frequency deviation / reactive power characteristics used by the frequency feedback reactive power injection circuit 24 described above. The frequency feedback reactive power injection circuit 24 calculates the reactive power injection amount K _fvar based on the frequency deviation / reactive power characteristics, calculates the above frequency deviation Δf _grid, and is within a half cycle of the commercial system frequency f _grid. Then, the calculated reactive power injection amount K _fvar is injected.

In the present embodiment, in order to reduce the degree of interference between the frequency feedback injection operation by the frequency feedback reactive power injection circuit 24 and the above power factor constant control, as shown in FIG. In addition, a threshold value f _stop is provided, and when the absolute value of the frequency deviation Δf _grid is equal to or smaller than the threshold value f _stop , the frequency feedback injection operation is not performed. More specifically, in the present embodiment, the first-stage gain in the low sensitivity band region (the region where the absolute value of the frequency deviation Δf _grid is equal to or less than the threshold f _stop ) in the frequency deviation / reactive power characteristic is set to zero. As a result, when the frequency deviation Δf _grid is a minute value, the frequency feedback injection operation can be prevented, so that the stability of the power factor constant control can be improved and the upper system is stabilized. Can be achieved. In the present embodiment, the maximum value _{K flim} of the reactive power injected amount _{K fvar} is, ± 0.25P. u. Is set to

Next, the reactive power step injection circuit 25 will be supplementarily described. The reactive power step injection circuit 25 has no fluctuation in the commercial grid frequency f _grid at a certain point in time, and when at least one of the fundamental voltage E _uw and the harmonic voltage THD _{V in} the commercial power grid 9 varies, the commercial grid frequency f A constant amount of slow reactive power injection amount K _step that is step-injected in order to cause fluctuation in the direction in which the _grid decreases is calculated and output. In the present specification, the state "no change in the grid frequency f _grid", in addition to the state without any variation in the grid frequency f _grid, the state variation is small the grid frequency f _grid, i.e., A state in which the frequency deviation Δf _grid is in the low-sensitive zone region of FIG. 7A is included.

As shown in FIG. 7 (b), the reactive power step injection circuit 25 has all the following conditional expressions for the harmonic voltage fluctuation when the frequency deviation Δf _grid is the low-sensitive band region in FIG. 7 (a). If it is determined that the upper limit is satisfied, the upper limit is set to 0.1 p. u. Is injected in a direction in which the current phase is delayed as viewed from the power storage hybrid power generation system 1, that is, in a direction in which the commercial system frequency f _grid is lowered.

THD _v (z) −THD _avr (z)> 2V
THD _v (z-1) −THD _avr (z)> 2V
THD _v (z-2) −THD _avr (z)> − 0.5 V
│THD _v (z-3) -THD _avr (z) │ <0.5V
│THD _v (z-4) -THD _avr (z) │ <0.5V
│THD _v (z-5) -THD _avr (z) │ <0.5V

As shown in the following formulas (13) to (19), in this embodiment, the total harmonic voltage effective value from the second order to the seventh order is adopted as a preferable aspect as the harmonic voltage effective value THD _v . Furthermore, higher harmonics may be included. In the following description, the total harmonic voltage effective value is simply referred to as a harmonic voltage effective value. In the following formulas (13) to (19), T _ADC is the sampling time of the A / D converter, and n is the harmonic order.

Further, when the reactive power step injection circuit 25 determines that the fundamental voltage fluctuation satisfies all the following conditional expressions when the frequency deviation Δf _grid is in the low-sensitive band region in FIG. Within 3 cycles, the upper limit is 0.1 p. u. The reactive power to be injected is injected in the direction in which the current phase is delayed as viewed from the power storage hybrid power generation system 1, that is, in the direction in which the commercial system frequency _fgrid decreases.

E _{uw. rms} (z) -E _{u. rms. avr} (z)> 2.5V
E _{uw. rms} (z-1) -E _{u. rms. avr} (z)> 2.5V
E _{uw. rms} (z-2) -E _{u. rms. avr} (z)> − 0.5V
│E u _{. rms} (z-3) -E _{u. rms. avr} (z) | <0.5V
│E u _{. rms} (z-4) -E _{u. rms. avr} (z) | <0.5V
│E u _{. rms} (z-5) -E _{u. rms. avr} (z) | <0.5V

Next, a supplementary explanation will be given of the operation of the above-described isolated operation detection circuit 23. In general, when the commercial grid voltage _euw is normal (202 ± 10 V), if the commercial grid frequency f _grid changes suddenly, it can be correctly detected that the power storage hybrid power generation system 1 is in the single operation state. However, when a phenomenon occurs in which the power equipment fails due to a lightning strike and the voltage of the power transmission and distribution network drops momentarily, it is caused by a drop in the commercial system voltage _euw and a phase shift (rapid change). When the commercial system frequency f _grid changes suddenly, there is a risk that unnecessary detection is made that the power storage hybrid power generation system 1 is in the single operation state due to a large fluctuation in this frequency.

However, when the phase suddenly changes due to a momentary drop or the like, the commercial system frequency _fgrid fluctuates instantaneously at the time of the sudden change, but is stable before and after that, whereas it is stable before and after the single operation. Fluctuation tends to increase. Therefore, in this power storage hybrid power generation system 1, as shown in FIG. 8, the isolated operation detection circuit 23 has the operation frequency f _PLL obtained by PLL _v 12 and the commercial system frequency measured by the commercial system frequency measurement circuit 22. When both f _grids change in one direction in a plurality of continuous system cycles, it is determined that the state is an isolated operation. Thereby, the isolated operation detection circuit 23 can avoid the unnecessary detection and accurately detect the isolated operation state of the power storage hybrid power generation system 1.

Further, the control circuit 7a of the power storage hybrid power generation system 1 has a charge / discharge power control block for the bidirectional DC / DC converter 4b in addition to the control block shown in FIG. As shown in FIG. 9, the charge / discharge power control block includes a charge / discharge power control circuit 51 for controlling the charge / discharge operation by the bidirectional DC / DC converter 4b, and PWM output control for the bidirectional DC / DC converter 4b. A circuit 52 is included. The charge / discharge power control circuit 51 performs bidirectional DC / DC based on the input charge / discharge power command value P ^* _BAT , charge / discharge power _PBAT, and the measured value (feedback value) of the DC bus voltage _Vdc. An output duty ratio d _BAT for the converter 4b is calculated. This duty ratio d _BAT is input to the PWM output control circuit 52. The PWM output control circuit 52 generates a PWM signal having a pulse width corresponding to the output duty ratio d _BAT based on the input output duty ratio d _BAT . On / off of each switch SW5, SW6 of the bidirectional DC / DC converter 4b is controlled based on these PWM signals. As shown in FIG. 9, the charge / discharge power command value P ^* _BAT is defined as a discharge power command value if positive, and a charge power command value if negative.

Next, the relationship between charge / discharge power control and power factor constant control in the power storage hybrid power generation system 1 will be described. In general, in a power storage hybrid power generation system that combines a solar cell and a power storage device (corresponding to storage battery 3 in FIG. 1), the role of the power storage device is as follows: (1) Surplus generated by solar power generation in the daytime _Absorbing power, or power whose output from the inverter is suppressed (for example, in this embodiment, power whose output from the inverter 5 is suppressed when the output limit command value I ^* _P.lim ≠ 1), (2) Supplying absorbed power to household loads at night, and (3) Charging with the rated charging current until full charge forcibly before power failure notice time, and shifting to independent operation at the time of power failure Is to supply power to a self-supporting load.

FIG. 10 shows the charge / discharge power command value P ^* _BAT , active power P _uw , reactive power Q _uw , and apparent power S _uw when charge / discharge power control is performed at night in the power storage hybrid power generation system 1. The correspondence relationship with the operation for detecting active islanding is shown. In FIG. 10, if the reactive power Q _uw is positive, it is defined as delayed power, and if it is negative, it is defined as advanced power. Further, it is defined that the discharging operation is performed if the active power P _uw is positive, and the charging operation is performed if it is negative. In addition, PF in a figure is a power factor feedback value (feedback value of a driving power factor) in the said FIG. 3, and is substantially equal to a driving power factor. Here, when the reactive power injection operation is generated during the power factor constant control, it is considered that the driving power factor is momentarily reduced. For example, as shown in FIG. 10, when a reactive power injection operation occurs and reactive power of K _Q · P _uw is injected, the driving power factor is changed from (R1 / S _uw ) to (R1 / S _u I think it will drop for a moment in _uw '). Further, in the power factor constant control in the power storage hybrid power generation system 1, when the rated power is output, as shown in FIG. 10, the apparent power _Suw is also shown in FIG. 10 during charge / discharge power control at night. It has the characteristic that control can be performed so as not to exceed the rated apparent power shown. When the reactive power injection operation occurs when the rated power is output, as shown in FIG. 10, the instantaneous apparent power S _uw ′ is caused by the reactive power of K _Q · P _uw as described above. Exceeds the rated apparent power for a moment.

Next, the device for reducing the interference between the power factor constant control process and the isolated operation detection process, which is employed in the power storage hybrid power generation system 1 of the present embodiment, will be described. The first of the devices is that when reactive power is generated from the reactive power injection amount calculation circuit 34 (reactive power is injected from the reactive power injection amount calculation circuit 34 to the commercial power supply 10), the constant power factor control circuit 15 The reactive power control value PF _out , which is an output value from, is not updated. More Specifically, as shown in FIG. 3, the power factor constant control circuit 15, a switch S _PF for switching the presence or absence of the updating of the reactive power control value PF _out. Then, as shown in the following equations (20) and (21), the reactive power injection amount (reactive power injection amount K _fvar and slow phase reactive power injection amount K _step ) calculated by the reactive power injection amount calculation circuit 34 is calculated. When the sum is 0, the switch S _PF is switched to 1 to update the reactive power control value PF _out that is an output value from the constant power factor control circuit 15, and is calculated by the reactive power injection amount calculation circuit 34. When the sum of the reactive power injection amounts is not 0, the switch _SPF is switched to 0 so that the reactive power control value PF _out is not updated. Here, “not updating the reactive power control value PF _out ” means that the constant power factor control circuit 15 outputs the same value as the latest output value as the reactive power control value PF _out .

As described above, when reactive power from the reactive power injection amount calculation circuit 34 is generated, the reason why the reactive power control value PF _out that is the output value from the constant power factor control circuit 15 is not updated is as follows. Street. That is, when the reactive power injection process for detecting the isolated operation by the reactive power injection amount calculating circuit 34 and the feedback control process by the constant power factor control circuit 15 are performed simultaneously, the reactive power injection amount is calculated for detecting the isolated operation. Even when reactive power is injected by the circuit 34, the injected reactive power may be canceled by the reactive power output for feedback control with constant power factor control, making it impossible to detect isolated operation. There is sex. Therefore, when reactive power from the reactive power injection amount calculation circuit 34 is generated, the reactive power control value PF _out which is the output value from the constant power factor control circuit 15 is not updated, thereby maintaining the constant power factor control circuit. The feedback control function of 15 is temporarily stopped to reduce the influence of reactive power output for feedback control of constant power factor control on reactive power injected for islanding operation detection. It is.

A second idea for reducing the interference between the constant power factor control process and the isolated operation detection process is to provide a difference in the responsiveness between the reactive current control circuit 29 and the constant power factor control circuit 15. In order to provide this difference in responsiveness, in the present embodiment, the first PI control that takes into account the _{active islanding} detection time limit T _active and the passive _islanding detection time limit T _passive stipulated in the grid connection regulations of each country. The design method of the response time (delay time + convergence time) of the controller 41 and the second PI controller 32 is adopted. In this design method, the delay times and convergence times of the first PI controller 41 and the second PI controller 32 are designed using the following equations (22) to (29). In this design method, the isolated operation detection time period (the upper limit value of the time required for isolated operation detection) is divided into an _active isolated operation detection time period T _active and a passive isolated operation detection time period T _passive . In the following formulas (22) and (27), the values of the detection time periods defined in the grid connection regulations of each country are set in these isolated operation detection time periods T _active and T _passive . The delay time T _D1 and the convergence time T _I1 of the first PI controller 41 are determined based on the following equations (22) and (23). As shown in Expression (22), the delay time T _D1 of the first PI controller 41 is set to a times the maximum value of the _{active islanding} detection time limit T _active and the passive _islanding detection time limit T _passive. . Further, as shown in Expression (23), the convergence time T _I1 of the first PI controller 41 is set to b times the delay time T _D1 . Further, as shown in Expression (26), the delay time T _D2 of the second PI controller 32 is set to half of the commercial system cycle T _Grid , and as shown in Expression (27), the convergence of the second PI controller 32 is set. The time T _I2 is set to c times the minimum value of the _{active islanding} detection time limit T _active and the passive _islanding detection time limit T _passive .

By setting as described above, the response of the first PI controller 41 of the constant power factor control circuit 15 based on the maximum value of the detection time period (active _islanding detection time limit T _active and passive _islanding operation detection time period T _passive ). The time (delay time T _D1 + convergence time T _I1 ) is designed, and based on the minimum value of the detection time period (active _islanding detection time limit T _active and passive _islanding operation detection time period T _passive ), the reactive current control circuit 29 The response time (delay time T _D2 + convergence time T _I2 ) of the 2PI controller 32 is designed. At this time, by adjusting the values of the coefficients a, b, and c in the equations (22), (23), and (27), the second PI controller 32 of the reactive current control circuit 29 is obtained as shown in the equation (29). The response time (delay time T _D2 + convergence time T _I2 ) is considerably shorter than the response time (delay time T _D1 + convergence time T _I1 ) of the first PI controller 41 of the constant power factor control circuit 15. As a result, when a single operation state occurs, before the reactive power control value PF _out is output from the power factor constant control circuit 15 for a new reactive power control value PF _out for feedback control with a constant power factor, the reactive current control circuit 29 The possibility that the feedback control for outputting the reactive current reflecting the reactive power injection amount calculated by the reactive power injection amount calculation circuit 34 from the power storage hybrid power generation system 1 can be completed is extremely high. Therefore, it is possible for the isolated operation detection circuit 23 to detect whether or not it is in the isolated operation state without being affected by the reactive power control value PF _out output for feedback control with a constant power factor. Therefore, the isolated operation state can be reliably detected within the _active isolated operation detection time limit T _active when the isolated operation state is generated.

In addition, the setting patterns of the _{active islanding} detection time limit T _active and the passive _islanding detection time limit T _passive are different depending on the grid connection regulations of each country, and the three detection time period setting patterns (T _active > T _passive , _Tactive < _Tpassive , _Tactive = _Tpassive ) exists. However, the responsiveness of the constant power factor control circuit 15 (first PI controller 41) is set to the reactive current control circuit 29 regardless of any of these three detection time limit setting patterns according to the above equation (29). It can be designed to be surely slower than the responsiveness of the (second PI controller 32).

In the case of _{active islanding} detection time limit T _active = passive _islanding operation detection time period T _passive , if T _active and T _passive are set to T _island (T _island = T _active = T _passive ), power factor The delay time T _D1 and convergence time T _I1 of the first PI controller 41 of the constant control circuit 15 and the delay time T _D2 and convergence time T _I2 of the second PI controller 32 of the reactive current control circuit 29 are expressed by the following equation (30 ) To (33). In this case, in order to satisfy the condition of the expression (29), it is necessary to adjust the values of the coefficients a, b, and c in the following expressions (30), (31), and (33).

Moreover, in Japan, the isolated operation detection time limit in the solar power generation system for single-phase grid connection is determined as follows.
(1) Active _islanding detection time limit T _active (when F _active = 1 in FIG. 2): within 0.2 seconds (2) Passive _islanding operation detection time limit T _passive (F _active = 0 in FIG. 2) :) Within 0.5 seconds

Considering the above two types of isolated operation detection time limits, in order to reduce the interference between the constant power factor control process and the isolated operation detection process, in Japan, the response time of the constant power factor control circuit 15 is set to the above two types. It is necessary to design for 0.5 second or more, which is the upper limit value of the longer detection time (passive islanding detection time limit) of the islanding operation detection time. Further, as described above, the power storage hybrid power generation system 1 of the present embodiment employs the “frequency feedback method with step injection” defined as the standard active isolated operation detection method. The reactive current control circuit 29 performs processing for injecting the reactive power injection amount (K _fvar , K _step ) in order to detect isolated operation within 0.2 seconds in accordance with the criterion of (1). It is necessary to design the response time to 0.2 seconds or less. In the present embodiment, both the constant power factor control circuit 15 and the reactive current control circuit 29 use PI controllers (the first PI controller 41 and the second PI controller 32 described above).

In this embodiment, the parameters of the PI controller are designed based on the Ziegler-Nichols step response method. In the step response method of Ziegler-Nichols, as shown in FIG. 11A, the delay time of the PI controller is T _D, the convergence time to _the target value is T _{I, and the} target value is K. Moreover, the setting value of each said parameter in the electrical storage hybrid electric power generation system 1 of this embodiment is shown in the table | surface of FIG.11 (b). As shown in this table, for the first PI controller 41 of the constant power factor control circuit 15, the delay time T _D1 is 0.5 seconds (a = 1), and the convergence time T _I1 is 1 second (b = 2). Designed. On the other hand, for the second PI controller 32 of the reactive current control circuit 29, the delay time T _D2 is 0.01 seconds (a half cycle of the commercial system cycle T _{Grid at} a commercial system frequency of 50 Hz), and the convergence time T _I2 is Designed in 0.1 second (c = 0.5).

Here, the reason for designing the delay time _{T D2} of the 2PI controller 32 of the reactive current control circuit 29 to 0.01 seconds, as shown in FIG. 2, and (3) to (5) or the like, disabled Current control (update of reactive current command value I ^* _q and reactive current feedback value _Iq ) is performed every half cycle of commercial system cycle T _Grid (every 0.01 seconds when commercial system frequency is 50 Hz). Because it is. Also, the reason for designing the convergence time _{T I2} of the 2PI controller 32 of the reactive current control circuit 29 in 0.1 seconds, are two. The first reason is that the reactive power injection amount according to the target value can be injected after 0.1 second in the single operation state. The second reason is that the isolated operation detection time (using the frequency feedback method with step injection) is set to about 0.1 seconds. Incidentally, the first 1PI controller 41 proportional gain _{K p} and the time constant _{T i} of the 2PI controller 32 is determined based on equation (34) and (35) below.

The design method of the first PI controller 41 and the second PI controller 32 as described above has the following advantages.
(1) By providing a difference in response time between the reactive current control circuit 29 and the constant power factor control circuit 15, it is theoretically possible to reduce interference between the isolated operation detection process and the constant power factor control process.
(2) the delay time _{T D1} of the 1PI controller 41 of the power factor constant control circuit 15, a passive islanding operation upper limit value of the detection time period is more than 0.5 seconds in Japan (to be precise, 0.5 sec ) Can reduce the influence of the constant power factor control process (reactive power output for feedback control of the constant power factor control) on the isolated operation detection process.
(3) From (1) and (2) above, it is possible to achieve both power factor constant control and single operation detection. As a result, it is possible to perform accurate isolated operation detection while maintaining high accuracy of the driving power factor of the power storage hybrid power generation system 1.

Next, the advantage (1) will be described in detail. In the electricity storage hybrid power generation system 1 of the present embodiment, the second PI control of the reactive current control circuit 29 is performed as shown in FIG. 11B in order to reduce the degree of interference between the constant power factor control process and the isolated operation detection process. Both the delay time T _D2 and the convergence time T _I2 of the device 32 are set to be shorter than the delay time T _D1 and the convergence time T _I1 of the first PI controller 41 of the constant power factor control circuit 15. In other words, the responsiveness of the feedback control process of the reactive current control circuit 29 is set to be faster than the responsiveness of the feedback control process of the constant power factor control circuit 15. As a result, when a single operation state occurs, before the reactive power control value PF _out is output from the power factor constant control circuit 15 for a new reactive power control value PF _out for feedback control with a constant power factor, the reactive current control circuit 29 The possibility that the feedback control for outputting the reactive current reflecting the reactive power injection amount calculated by the reactive power injection amount calculation circuit 34 from the power storage hybrid power generation system 1 can be completed is extremely high. Therefore, it is possible for the isolated operation detection circuit 23 to detect whether or not it is in the isolated operation state without being affected by the reactive power control value PF _out output for feedback control with a constant power factor. Increases nature.

Next, the advantage (2) will be described in detail. In this power storage hybrid power generation system 1, when F _active is set to 0, the single operation detection by the passive single operation detection method is performed, but the delay time T of the first PI controller 41 of the constant power factor control circuit 15 is detected. By designing _D1 to be 0.5 seconds, which is the upper limit of the passive islanding detection time limit in Japan, constant power factor control processing (reactive power output for feedback control of constant power factor control) In addition to the active islanding detection process, the influence on the passive islanding detection process can be reduced.

As described above, according to the electricity storage hybrid power generation system 1 of the present embodiment, two devices have been devised to reduce interference between the constant power factor control process and the isolated operation detection process. In other words, (a) when reactive power is generated from the reactive power injection amount calculation circuit 34, a device that does not update the reactive power control value PF _out that is an output value from the constant power factor control circuit 15, and (b) invalidity A contrivance is to provide a difference in response between the current control circuit 29 and the constant power factor control circuit 15.

In order to confirm the effectiveness of the contrivance (design method) for reducing the interference between the power factor constant control process and the islanding detection process, an active islanding detection function using the above-mentioned “frequency feedback method with step injection” The isolated operation detection test using was carried out at five representative points (points 1 to 5) shown in FIG. In FIG. 12A, P _Grid and Q _Grid indicate active power and reactive power in the reverse flow power at the power receiving point. In addition, the x-coordinate and y-coordinate values of each point in the figure are values representing the active power and reactive power of the reverse flow power as a ratio to the rated apparent power S _rated . Moreover, FIG.12 (b) shows the setting value of the parameter in the experimental system which performed this isolated operation detection test.

In this isolated operation detection test, as shown in FIG. 12A, the points around point 1 of (P _Grid , Q _Grid ) = (0, 0), which is the most severe condition in the isolated operation detection test, are shown. The experiment was conducted. Here, the reason why the point 1 of (P _Grid , Q _Grid ) = (0, 0) is the most severe condition in the isolated operation detection test will be described. In general, when active power or reactive power is flowing at a power receiving point between a distributed power source and a commercial power source, when the system shifts to a single operation, the output from the power conversion device such as a storage hybrid power generation system and the system load ( Since the active power and reactive power are unbalanced with respect to the AC load) and the commercial system frequency and the commercial system voltage change, it can be easily detected that the system is in the single operation state. On the other hand, the output from the power converter and the power consumption of the system load (AC load) are perfectly balanced both in terms of active power and reactive power. When shifting to a single operation in a state of not flowing (corresponding to point 1 of (P _Grid , Q _Grid ) = (0, 0) in FIG. 12A), the commercial system frequency and the commercial system voltage change. Because it does not, it is difficult to detect that the single operation state has been entered.

Next, the experimental result of the isolated operation detection test at each point shown in FIG. 12A will be described from the experimental result of point 1 of (P _Grid , Q _Grid ) = (0, 0) which is the most severe condition. . FIG. 13 shows the experimental results of point 1. In this experiment, as shown in FIG. 13, the reactive power injection from the reactive power injection amount calculation circuit 34 is started about four cycles after the single operation state, and after that, It was confirmed that reactive power was injected near the peak of the output current _isp . Then, as shown in FIG. 13, about 116.2 ms after entering the single operation state, the single operation detection circuit 23 detected the single operation state, and it was confirmed that the storage hybrid power generation system 1 stopped the operation. . From this experimental result, it was confirmed that about 0.1 second after entering the single operation state, it was possible to inject the reactive power as much as the target value. In addition, it was confirmed that the time required for the isolated operation detection was about 0.1 seconds. These experimental results show that the parameter design of each PI controller (the first PI controller 41 and the second PI controller 32) shown in FIG. 11B is valid.

  FIG. 14 shows the experimental results of the isolated operation detection test at point 2 in FIG. In this experiment, power factor constant control (power factor command value 0.8 (advance phase)) is performed before the power storage hybrid power generation system 1 enters the single operation state. Then, about 52.2 ms after the reactive power was injected and the single operation state was entered, the single operation detection circuit 23 detected the single operation state, and it was confirmed that the storage hybrid power generation system 1 stopped the operation. .

FIG. 15 shows the experimental results of the isolated operation detection test at point 3 in FIG. In this experiment, as shown in FIG. 15, the reactive power injection from the reactive power injection amount calculation circuit 34 is started about 1.5 cycles after the single operation state, and thereafter, the electric storage hybrid power generation system 1 It was confirmed that reactive power injection was performed in the vicinity of the peak of the output current _isp from. Then, about 50.4 ms after entering the single operation state, it was confirmed that the single operation detection circuit 23 detected the single operation state and the power storage hybrid power generation system 1 stopped operating.

FIG. 16 shows the experimental results of the isolated operation detection test at point 4 in FIG. In this experiment, as shown in FIG. 16, the reactive power injection from the reactive power injection amount calculation circuit 34 is started approximately two cycles after the single operation state, and thereafter, from the power storage hybrid power generation system 1. It was confirmed that reactive power was injected near the peak of the output current _isp . Then, about 55 ms after entering the single operation state, the single operation detection circuit 23 detected the single operation state, and it was confirmed that the power storage hybrid power generation system 1 stopped operating.

FIG. 17 shows the experimental results of the isolated operation detection test at point 5 in FIG. In this experiment, as shown in FIG. 17, the reactive power injection from the reactive power injection amount calculation circuit 34 is started approximately one cycle after the single operation state, and thereafter, the storage hybrid power generation system 1 It was confirmed that reactive power was injected near the peak of the output current _isp . Then, about 48 ms after entering the single operation state, the single operation detection circuit 23 detected the single operation state, and it was confirmed that the electric storage hybrid power generation system 1 stopped the operation.

The experimental results shown in FIGS. 12 to 17 are summarized as follows.
(1) In all the experiments, the isolated operation state was detected within 0.2 seconds after entering the isolated operation state, and it was confirmed that the electricity storage hybrid power generation system 1 stopped the operation.
(2) In all experiments, it was confirmed that reactive power injection started near the peak of the output current _isp from the storage hybrid power generation system 1.
(3) The validity of the parameter design of each PI controller could be confirmed from the experimental results of the isolated operation detection test at point 1 of (P _Grid , Q _Grid ) = (0, 0).

As described above, according to the electricity storage hybrid power generation system 1 of the present embodiment, the delay time T _D2 and the convergence time T _I2 of the second PI controller 32 used for the reactive current (amplitude) feedback control are both The first PI controller 41 used for constant rate control was set to a time shorter than the delay time T _D1 and the convergence time T _I1 . That is, the responsiveness of the feedback control process of the reactive current control circuit 29 is set to be faster than the responsiveness of the feedback control process of the constant power factor control circuit 15. As a result, when a single operation state occurs, before the reactive power control value PF _out is output from the power factor constant control circuit 15 for a new reactive power control value PF _out for feedback control with a constant power factor, the reactive current control circuit 29 The possibility that the feedback control for outputting the reactive current reflecting the reactive power injection amount calculated by the reactive power injection amount calculation circuit 34 from the power storage hybrid power generation system 1 can be completed is extremely high. Therefore, it is possible for the isolated operation detection circuit 23 to detect whether or not it is in the isolated operation state without being affected by the reactive power control value PF _out output for feedback control with a constant power factor. Increases nature. Accordingly, the reactive current feedback control process of the reactive current control circuit 29 is set to be faster than the response of the feedback control process of the constant power factor control circuit 15 as described above. In addition, the degree of interference with the power factor constant control process can be reduced to achieve both power factor constant control and accurate single operation detection.

Further, according to the power storage hybrid power generation system 1 of this embodiment, the switch S _PF provided to the power factor constant control circuit 15, by using the switch S _PF, reactive power injected calculated by the reactive power injection amount calculating circuit 34 When the sum of the amounts is 0, the reactive power control value PF _out which is an output value from the constant power factor control circuit 15 is updated, and the sum of the reactive power injection amounts calculated by the reactive power injection amount calculation circuit 34 is updated. When it is not 0, the reactive power control value PF _out is not updated. Thereby, when reactive power is generated from the reactive power injection amount calculation circuit 34, the feedback control function of the constant power factor control circuit 15 is temporarily stopped and output for feedback control of the constant power factor control. The influence of reactive power on the reactive power injected for islanding detection can be reduced.

Furthermore, according to the electricity storage hybrid power generation system 1 of the present embodiment, the total time of the delay time T _D1 and the convergence time T _I1 of the first PI controller 41 of the constant power factor control circuit 15 (“first response in claims”) Time ”) and the total time of delay time T _D2 and convergence time T _I2 of second PI controller 32 of reactive current control circuit 29 (“ second response time ”in the claims) are used for active islanding detection. It was set based on an active _islanding detection time limit T _active which is an upper limit value of the time required and a passive _islanding detection time limit T _passive which is an upper limit value of the time required for _{passive islanding} detection. The total time of the delay time _{T D2} and convergence time _{T I2} of the 2PI controller 32 of the reactive current control circuit 29, and set based on the active islanding detection time period _{T active} and passive islanding detection time period _{T passive} Thus, the requirements for the active islanding detection time limit and the passive islanding detection time limit stipulated in the grid interconnection regulations of each country can be easily satisfied. The total time of the delay time T _D1 and the convergence time T _I1 of the first PI controller 41 of the constant power factor control circuit 15 is based on the _{active islanding} detection time limit T _active and the passive _islanding detection time limit T _passive. The power factor constant control process (reactive power output for feedback control of constant power factor control) is not only affected by the active islanding detection process, but also by the passive islanding detection process. The effect can also be reduced.

Further, according to the power storage hybrid power generation system 1 of this embodiment, the active current limiter 17, regardless of the size of the total reactive power injection quantity K _Q, output limit command value I ^* _{P. The} effective power P _uw is limited by limiting the amplitude of the effective current output from the power storage hybrid power generation system 1 based on _lim and the rated apparent power S _{rated of the} power storage hybrid power generation system 1. As a result, even if a reactive power injection operation occurs, it is possible to avoid a reduction in the active power P _uw due to an increase in the reactive power, and it is possible to prevent the output power from being affected.

Moreover, according to the electricity storage hybrid power generation system 1 of the present embodiment, the active current limiter 17 is configured so that the active power P _uw output from the electricity storage hybrid power generation system 1 is the output restriction command value I ^* _{P. The} effective current amplitude output from the power storage hybrid power generation system 1 is limited so as to be a value obtained by multiplying the _lim by the rated apparent power S _rated and the output limit command value I ^* _{P. lim} was set to a value from 0 to the power factor command value PF ^* . Thereby, the upper limit value of the active power P _uw output from the power storage hybrid power generation system 1 is multiplied by the power factor command value PF ^* and the rated apparent power S _rated regardless of whether or not the reactive power injection operation occurs. The value can not be exceeded.

Further, according to the electricity storage hybrid power generation system 1 of the present embodiment, the frequency feedback reactive power injection circuit 24 has the absolute value of the frequency deviation Δf _grid (the fluctuation amount of the commercial system frequency f _grid measured by the commercial system frequency measurement circuit 22). ) Is less than or equal to the threshold f _stop , the reactive power injection amount K _fvar is _set to zero. As a result, when the frequency deviation Δf _grid is a minute value, the frequency feedback injection operation can be prevented, so that the degree of interference between the frequency feedback injection operation and the constant power factor control is reduced, and the power factor is reduced. The stability of constant control can be improved and the host system can be stabilized.

Variations:
In addition, this invention is not restricted to the structure of said embodiment, A various deformation | transformation is possible in the range which does not change the meaning of invention. Next, a modified example of the present invention will be described.

Modification 1:
In the above embodiment, an example in which the grid interconnection power conversion device of the present invention is a power storage hybrid power generation system 1 in which a power conditioner is combined with a solar battery that is a distributed power source and a storage battery has been described. . However, the grid interconnection power conversion device to which the present invention is applied is not limited thereto, and may be, for example, a power storage hybrid power generation system including a wind power generation device or a fuel cell as a distributed power source, A power conditioner for connecting a distributed power source such as a solar cell, a wind power generator, or a fuel cell to a single-phase or three-phase commercial power system may be used.

Modification 2:
In the above embodiment, the grid interconnection power conversion device (storage hybrid power generation system) of the present invention has both an active islanding detection function using a frequency feedback method with step injection and a passive islanding detection function. Although the example in the case of having provided was shown, it does not necessarily need to be provided with the passive islanding detection function.

Modification 3:
In the above embodiment, the delay time _{T D1} of the 1PI controller 41 of the power factor constant control circuit 15, or 0.5 seconds (to be precise, 0.5 seconds) has been designed, necessarily, such It is not necessary to set the response time of the power factor constant control circuit 15 (the total time of the delay time T _D1 and the convergence time T _I1 of the first PI controller 41) as an upper limit value of the passive islanding detection time limit of 0. Even when designed for 5 seconds or more, it is possible to obtain an effect of reducing interference between the constant power factor control process and the isolated operation detection process.

Modification 4:
In the above embodiment, in order to reduce the interference between the power factor constant control process and the islanding operation detection process, when the reactive power from the reactive power injection amount calculation circuit 34 is generated ((a), the power factor is constant). And a device that does not update the reactive power control value PF _out that is an output value from the control circuit 15 and (b) a device that provides a difference in the responsiveness between the reactive current control circuit 29 and the constant power factor control circuit 15). . However, the grid-connected power converter of the present invention does not necessarily have to employ both of these two devices. For example, the above-described device (a) is not used and the above ( Only the device of b) (device that provides a difference in response between the reactive current control circuit 29 and the constant power factor control circuit 15) may be employed.

Modification 5:
In the above embodiment, the isolated operation detection circuit 23 has a plurality of systems in which both the operation frequency f _PLL obtained by the PLL _v 12 and the commercial system frequency f _grid measured by the commercial system frequency measurement circuit 22 are continuous. In the case of changing in one direction with the cycle, an example in which it is determined that the state is an independent operation state is shown. However, as described above, the determination of the single operation state is not made based on both the operation frequency f _PLL obtained by the PLL _v 12 and the commercial system frequency f _grid measured by the commercial system frequency measurement circuit 22. Instead, only one value of the operating frequency f _PLL and the commercial system frequency f _grid may be used for the determination of the single operation state. For example, the operation frequency f _PLL which is determined by the PLL v ₁₂ is the case where changes in one direction by a plurality of system cycles continuous, it may be determined that the islanding state.

Modification 6:
In the above embodiment, the output current i _sp from the storage hybrid power generation system 1 is subtracted from the measured value of the inverter output current i _{inv by} the value of the capacitor passing current _ic calculated by the above equation (1). However, it is not always necessary to obtain the value of the output current i _{sp by} the above calculation, and it may be obtained by measurement.

Modification 7
In the above embodiment, the grid interconnection power conversion device (storage hybrid power generation system) of the present invention is ineffective with the frequency feedback reactive power injection circuit 24 in the active islanding detection process using the frequency feedback method with step injection. Although an example in which both the power step injection circuit 25 calculates and injects reactive power has been shown, in the active islanding detection process, the injection operation of the reactive power step injection circuit 25 is masked (K _step = 0). Even if only the frequency feedback reactive power injection circuit 24 calculates and injects reactive power, it is possible to achieve both power factor constant control and accurate isolated operation detection.

Modification 8:
In the above embodiment, an example in which the control circuits 7a and 7b are configured using so-called microcomputers has been described. However, the control circuits 7a and 7b are not limited thereto, and may be, for example, a system LSI. Good.

1 Storage hybrid power generation system (power conversion device for grid connection)
2 Solar cell (distributed power supply)
9 Commercial power system 15 Power factor constant control circuit (Power factor constant control means)
17 Effective current limiter (current limiting means)
22 Commercial system frequency measurement circuit (commercial system frequency measurement means)
23. Single operation detection circuit (Single operation detection means)
24 Frequency feedback reactive power injection circuit (frequency feedback reactive power injection amount calculation means)
25 Reactive power step injection circuit (reactive power step injection amount calculation means)
29 Reactive current control circuit (Reactive current control means)
30 Reactive current limiter (current limiting means)
32 Second PI controller 34 Reactive power injection amount calculation circuit (Reactive power injection amount calculation means)
41 First PI Controller I _q Reactive Current Feedback Value I ^* _{P. lim} output limit command value I ^* _q reactive current command value K _fvar reactive power injection amount K _step slow phase reactive power injection amount PF power factor feedback value PF _out reactive power control value PF ^* power factor command value P _uw active power S _PF switch (Switching means)
S _rated rated apparent power

Claims (9)

A grid interconnection power converter for linking a distributed power source to a commercial power grid,
Commercial system frequency measurement means for measuring a commercial system frequency, which is a frequency of the commercial system voltage,
Reactive power injection amount calculating means for calculating a reactive power injection amount according to fluctuations in the commercial system frequency measured by the commercial system frequency measuring means;
A first PI controller that generates a first correction value based on a deviation between a power factor command value and a power factor feedback value of the output power from the grid interconnection power converter, and based on the first correction value; Power factor constant control means for generating and outputting a reactive power control value for feedback control so that the power factor of the output power from the grid interconnection power converter converges to the power factor command value;
Reactive current command value calculated based on the reactive power control value output from the constant power factor control means and the reactive power injection amount calculated by the reactive power injection amount calculation means, and the grid interconnection power conversion A second PI controller that receives a feedback value of the reactive current output from the device and generates a second correction value based on a deviation between the reactive current command value and the reactive current feedback value. 2 reactive current control means for performing feedback control so that the amplitude of the reactive current output from the grid interconnection power converter converges on the reactive current command value based on the two correction values;
Based on the commercial grid frequency when the reactive power of the reactive power injection amount is injected, an isolated operation detecting means for detecting whether the grid interconnection power converter is in an isolated operation state ,
When the reactive power injection amount calculated by the reactive power injection amount calculating means is 0, the reactive power control value that is an output value from the constant power factor control means is updated, and the reactive power injection amount calculating means A switching means for switching so as not to update the reactive power control value when the calculated reactive power injection amount is not 0 ,
The reactive power injection amount calculating means calculates a reactive power injection amount in a direction that promotes the fluctuation of the commercial grid frequency according to the fluctuation quantity of the commercial grid frequency measured by the commercial grid frequency measuring means. power converter for system interconnection, characterized in including that the power injection amount calculating means. 2. The grid interconnection according to claim 1 , comprising both an active islanding detection function using the frequency feedback reactive power injection amount calculating means and a passive islanding detection function as the islanding operation detection function. Power converter. A first response time that is a total time of a delay time and a convergence time of the first PI controller, and a second response time that is a total time of the delay time and the convergence time of the second PI controller are active independently. claims, characterized the active islanding detection timing is the upper limit of the time required for the operation detecting, that set on the basis of the passive islanding detection timing is the upper limit of the time required for passive islanding detection The power converter for grid connection according to 2 . A grid interconnection power converter for linking a distributed power source to a commercial power grid,
  Commercial system frequency measurement means for measuring a commercial system frequency, which is a frequency of the commercial system voltage,
  Reactive power injection amount calculating means for calculating a reactive power injection amount according to fluctuations in the commercial system frequency measured by the commercial system frequency measuring means;
  A first PI controller that generates a first correction value based on a deviation between a power factor command value and a power factor feedback value of the output power from the grid interconnection power converter, and based on the first correction value; Power factor constant control means for generating and outputting a reactive power control value for feedback control so that the power factor of the output power from the grid interconnection power converter converges to the power factor command value;
  Reactive current command value calculated based on the reactive power control value output from the constant power factor control means and the reactive power injection amount calculated by the reactive power injection amount calculation means, and the grid interconnection power conversion A second PI controller that receives a feedback value of the reactive current output from the device and generates a second correction value based on a deviation between the reactive current command value and the reactive current feedback value. 2 reactive current control means for performing feedback control so that the amplitude of the reactive current output from the grid interconnection power converter converges on the reactive current command value based on the two correction values;
  Based on the commercial grid frequency when the reactive power of the reactive power injection amount is injected, it comprises an isolated operation detecting means for detecting whether the grid interconnection power converter is in an isolated operation state,
  The reactive power injection amount calculating means calculates a reactive power injection amount in a direction that promotes the fluctuation of the commercial grid frequency according to the fluctuation quantity of the commercial grid frequency measured by the commercial grid frequency measuring means. Including power injection amount calculation means,
  As an isolated operation detection function, it has both an active isolated operation detection function using the frequency feedback reactive power injection amount calculation means and a passive isolated operation detection function,
  The delay time and convergence time of the second PI controller are both set to a time shorter than the delay time and convergence time of the first PI controller,
  A first response time that is a total time of a delay time and a convergence time of the first PI controller, and a second response time that is a total time of the delay time and the convergence time of the second PI controller are active independently. It is set based on the active islanding detection time limit, which is the upper limit of the time required for operation detection, and the passive islanding detection time limit, which is the upper limit of the time required for passive islanding detection. System power converter. In addition to the frequency feedback reactive power injection amount calculation means, the reactive power injection amount calculation means has no fluctuation in the commercial system frequency measured by the commercial system frequency measurement means, and the fundamental voltage and harmonics in the commercial power system Reactive power step injection amount calculating means for calculating a slow phase reactive power injection amount that is step-injected in order to cause a fluctuation in a direction in which the commercial system frequency decreases when at least one of the voltages fluctuates. The grid connection power converter according to any one of claims 1 to 4 . Further comprising current limiting means for limiting the amplitude of the active current and reactive current output from the grid interconnection power converter based on the output limit command value;
The current limiting means limits the amplitude of the active current based on the output limit command value and the rated apparent power of the grid interconnection power converter regardless of the reactive power injection amount. The active power output from the grid interconnection power converter is limited by the grid interconnection power converter according to any one of claims 1 to 5. The current limiting means limits the amplitude of the active current so that the active power output from the grid interconnection power converter is a value obtained by multiplying the output limit command value and the rated apparent power. ,
The grid connection power converter according to claim 6, wherein the output restriction command value is a value from 0 to the power factor command value. The frequency feedback reactive power injection amount calculating means sets the reactive power injection amount to 0 when the fluctuation amount of the commercial system frequency measured by the commercial system frequency measuring means is equal to or less than a predetermined threshold. The grid connection power converter according to any one of claims 1 to 7 , wherein the power converter is connected to the grid. By changing the magnitude of reactive power output from the grid interconnection power converter according to the magnitude of active power output from the grid interconnection power converter, the grid interconnection power The power converter for grid interconnection according to any one of claims 1 to 8 , wherein a power factor of output power from the converter is made constant.