JP2008061356A - Islanding operation detedctor and detection method, power conditioner incorporating islanding operation detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an islanding operation detector for detecting islanding operation immediately by injecting reactive power similar to that under steady state from a correction effective current command value and a correction reactive current command value where the phase difference between the system voltage and the PLL block is taken into account while leaving the slow frequency follow-up performance as it is, thereby detecting the frequency changing suddenly upon occurrence of islanding operation. <P>SOLUTION: If the frequency of system voltage of a power line changes suddenly when islanding operation is started, a correction current command value determination means 8 determines a correction effective current command value (P2) and a correction reactive current command value (Q2), based on the phase difference (θ) between the frequency (f1) of system voltage and the frequency (f2) detected by a PLL (Phase Locked Loop), and the effective current command value (P1) and the reactive current command value (Q1) under steady state before islanding operation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an isolated operation detection device that detects and prevents an isolated operation in which a distributed power supply is operated independently from a state in which the distributed power supply is connected to the system power supply, and the independent operation The present invention relates to an operation detection method, and more particularly, to an isolated operation detection apparatus and an isolated operation detection method for detecting isolated operation by injecting reactive power according to a command value to a system power supply at a system frequency that changes sharply during isolated operation.

  In recent years, when multiple distributed power supplies are connected to the grid power supply and connected to the system, and an accident occurs in the grid power supply, the phenomenon differs from the case where a single distributed power supply is connected. appear.

  Also, the frequency change is detected by detecting the frequency change during single operation and injecting reactive power proportional to the frequency change to amplify the frequency change (if the frequency rises, inject reactive power in advance, if the frequency falls Injected reactive power with delay). As a result, a method is adopted in which the frequency change is increased, and when the frequency change exceeds a certain threshold, it is determined that the islanding operation is performed.

  In addition, distributed power sources are gas turbines, gas engines, solar power, wind power, small-scale hydropower, power conditioners that use micro gas turbines and fuel cells, etc. It is in.

  In addition, isolated operation of distributed power supply is a state in which a fault occurs in the grid power supply that is operating in an interconnected state, and power is supplied from the distributed power supply to the load. The impact on the people and equipment involved will increase.

  In particular, when a large number of distributed power sources are operated in an interconnected manner, an isolated operation exceeding the pole transformer unit is assumed, and it is necessary to detect the isolated operation at a higher speed than in the past.

  A conventional grid-connected power conditioner for a distributed power source performs output current control with a power factor of 1 in synchronization with the cycle (frequency) of the grid power source. As a means for synchronizing with the grid cycle, A PLL (Phase Locked Loop) is used. Note that the PLL may be realized by hardware or software.

  When the number of interconnected distributed power sources is small, it is only necessary to assume the single operation in each household unit. For this reason, the detection time for the single operation (active method) is defined as 0.5 to 1.0 seconds. It is a relatively slow standard. Since the reactive power injection that amplifies the frequency change is also gradually increased, the system frequency does not change suddenly. For this reason, a quick response was not required for the PLL loop of the power conditioner. However, with the widespread use of distributed power sources such as photovoltaic power generation systems in recent years, isolated operation exceeding the unit of pole transformer is assumed, and speeding up of independent operation detection in the case of power system high and low accidents is expected. It is necessary.

  FIG. 8 shows a block configuration diagram of a distributed power supply system to which a conventional isolated operation detection device is applied. In FIG. 8, a distributed power supply system 50a includes a distributed power supply 2 such as a solar battery, and a power operated by connecting the distributed power supply 2 to the system power supply AC via the power line PL and operating in conjunction with the system power supply AC. Independent operation that is connected to the conditioner 3a and the power line PL, detects the isolated operation of the distributed power supply 2 when the system power supply AC is stopped, shuts off the interconnection relay RL1, and stops the isolated operation of the distributed power supply 2 It is comprised from the detection apparatus 4c.

  The isolated operation detection device 4c includes an interconnection relay RL1 that cuts off the distributed power supply 2 from the power line PL, a frequency measurement means 5 that measures the frequency of the system voltage VL, a phase comparator 6a, a loop filter 6b, and a variable frequency transmitter 6c. The PLL block 6 that is adjusted to the same frequency as the frequency measured by the frequency measuring means 5 and output, the Sin waveform generating means 7a that generates the Sin waveform based on the frequency supplied from the PLL block 6, and the Cos waveform Cos waveform generating means 7b for generating, current command value storage means for storing the effective current command value (P1) 10a and reactive current command value (Q1) 10b, a multiplier for multiplying the effective current command value (P1) 10a and the Sin waveform 12a, the multiplier 12b for multiplying the reactive current command value (Q1) 10b and the Cos waveform, and the multiplication results of the multiplier 12a and the multiplier 12b are added. From the PI controller 14 that executes PI control based on the outputs from the calculator 13 and the adder 13, the PWM pattern generator 15 that generates the PWM pattern by executing the PWM with the PI-controlled signal, and the PWM pattern generator 15 Inverter 16 that generates reactive power with the PWM pattern control signal, and a relay RL2 that injects or cuts off reactive power generated by inverter 16 to power line PL.

  In the distributed power supply system 50a, when the system power supply AC goes down due to an accident or the like, the frequency of the system voltage VL changes on the power line PL of the AC power supplied from the distributed power supply 2 through the power conditioner 3a (frequency Decrease or increase).

  The isolated operation detecting device 4c detects a change in the frequency of the system voltage VL with the frequency measuring means 5, detects the changed frequency with the time determined by the responsiveness of the PLL block 6, and detects with the Sin waveform generating means 7a. A Sin waveform having the frequency thus obtained is generated, and a Cos waveform having the frequency detected by the Cos waveform generating means 7b is generated.

  Subsequently, the Sin waveform is multiplied by the active current command value P1, the Cos waveform is multiplied by the reactive current command value Q1, the multiplication results are added, and PI (proportional / integral) control is performed based on the added calculation result. After that, PWM (pulse width modulation) control is performed on the PI control signal to generate a PWM pattern.

  The inverter 16 is driven by the PWM pattern signal to generate reactive power, and the reactive power is injected into the power line PL.

  Normally, the reactive power injection is gentle, so the frequency change accompanying the reactive power injection is also gentle, the phase difference between the system frequency and the frequency derived by the PLL is small, and the reactive power is injected almost according to the command value. When this system frequency change exceeds a certain threshold, it is determined that the system is operating independently.

  FIG. 10 is a block diagram of a distributed power supply system to which a power conditioner incorporating a conventional islanding detection device is applied. In FIG. 10, a distributed power supply system 50b is connected to a distributed power supply 2 such as a solar cell and a distributed power supply 2 via a power line PL and operated in conjunction with the system power supply AC. It is comprised from the power conditioner 3c which incorporates the inverter part 4d which has an independent operation detection function.

  The power conditioner 3 c includes a booster circuit 17 that boosts the DC voltage supplied from the distributed power source 2.

  The inverter unit 4d having a single operation detection function built in the power conditioner 3c has the same configuration as the single operation detection device 4c of FIG. The isolated operation detection device 4d has the same configuration except that the inverter 16 and the power line PL are connected in series to the power line PL, except that the isolated operation detection device 4c is different.

  In addition, since the part regarding the isolated operation detection function of the inverter part 4d which has an isolated operation detection function is the same as the isolated operation detection apparatus 4C shown in FIG. 8, description is abbreviate | omitted.

  Further, the frequency measurement means 5, the PLL block 6, the Sin waveform generation means 7a, the Cos waveform generation means 7b, the current command value storage means, the multiplier 12a, the multiplier 12b, the adder 13, the PI control unit 14, and the PWM pattern generator Reference numeral 15 denotes a microprocessor based software or hardware.

  In addition, in the prior art, in a gate control device for a grid interconnection inverter using a PLL circuit including a phase comparator, a loop filter, a voltage control oscillator, and a counter in the gate device, a sudden load change, etc. Japanese Patent Application Laid-Open No. H10-260260 discloses a technique for preventing the occurrence of pulse loss and unnecessary pulses against the disturbance of the above.

As a result, even if a disturbance such as a sudden load change occurs and the phase operation signal PH1 fluctuates greatly, the gate signal phase changes smoothly depending on the response of the loop filter. It can be maintained in a reliable operating state.
Japanese Patent Laid-Open No. 6-78462 (refer to the object, effects of the invention and FIG. 3)

In the conventional distributed power supply system 50a, 50b, when only a small amount is connected, as described above, the time allowed for the isolated operation detection is relatively long as 0.5 to 1.0 seconds. The response time of 6 was not a problem. However, when a large number of distributed systems are linked, it is required to significantly reduce the time required for detecting an isolated operation after the isolated operation occurs.

  FIG. 9 shows a characteristic diagram of reactive power injected by a conventional isolated operation detection device. In FIG. 9, when the frequency change after the occurrence of the independent operation is gradual, the power according to the command value at the active power command value (real axis P) and the reactive power command value (imaginary axis Q) is injected into the system. This characteristic corresponds to the distributed power supply system 50a shown in FIG.

  Independent operation occurs from a steady state, and in response to a gradual change in system frequency, reactive power is rapidly injected to amplify it and change the frequency sharply. As a result, the system frequency suddenly changes, the response of the PLL block 6 cannot follow the rapidly changed frequency, a phase shift of the phase difference θ occurs, the leading reactive power decreases, and the frequency change becomes slow, There is a problem that the isolated operation detection time is extended and the isolated operation detection time is delayed.

  In addition, when there is no phase shift, the active power is sucked in due to the power consumption of the device. However, due to the occurrence of the phase shift, the effective power is discharged and the DC voltage (DDV) of the inverter 16 decreases. There is a problem that current control cannot be performed and reactive power cannot be injected.

Fig. 11 shows the characteristics of reactive power to be injected in the case of a power conditioner. In the case of a power line conditioner, since the DC power at the distributed power source is converted into AC power, the effective power discharge becomes large. In Fig. 11, when the frequency change after the occurrence of independent operation is gradual, the power according to the command value of the active power command value (real axis P) and the reactive power command value (imaginary axis Q) is injected into the system. .

  Independent operation occurs from a steady state, and in response to a gradual change in system frequency, reactive power is rapidly injected to amplify it and change the frequency sharply. As a result, the system frequency suddenly changes, the response of the PLL block 6 cannot follow the suddenly changed frequency, the phase shift of phase θ occurs, the reactive power decreases, the frequency change becomes slow, and the single operation There is a problem that the detection time is slow.

  In the characteristics shown in FIGS. 9 and 11, the PLL block 6 cannot immediately follow the phase shift (phase difference θ), so that there is a fundamental problem that the isolated operation detection time cannot be shortened.

  The present invention has been made to solve such a problem. The object of the present invention is to correct the effective active command value and the correction in consideration of the phase difference between the system voltage and the PLL block while the frequency followability of the PLL block remains slow. Even when there is a phase shift from the reactive current command value, an independent operation detection device and an independent operation detection device that detect isolated operation at high speed by injecting reactive power according to the command value and abruptly changing the system frequency. The purpose is to provide a built-in power conditioner.

  In order to solve the above problems, an isolated operation detection apparatus according to the present invention is operated by a distributed power supply connected to a system power supply, injects reactive power into the system power supply, and is generated by a system power supply down. An isolated operation detection device for detecting operation, when the frequency of the system voltage of the power line changes suddenly during the isolated operation, the frequency (f1) of the system voltage and the frequency (f2) detected by the PLL (Phase Locked Loop) Correction current for determining the corrected active current command value (P2) and the corrected reactive current command value (Q2) based on the phase difference (θ) of the current, the active current command value (P1) and the reactive current command value (Q1) A command value determining means is provided.

  In the isolated operation detection device according to the present invention, the frequency of the system voltage (f1) and the frequency (f2) detected by the PLL (Phase Locked Loop) when the frequency of the system voltage of the power line changes suddenly during the isolated operation. A corrected current command value for determining a corrected active current command value (P2) and a corrected reactive current command value (Q2) based on the phase difference (θ), the active current command value (P1), and the reactive current command value (Q1). Since the determining means is provided, based on the corrected active current command value (P2) and the corrected reactive current command value (Q2), the reactive power is quickly injected according to the command value determined from the change in frequency. A suddenly changed frequency can be detected.

  The correction current command value determining means according to the present invention is a phase difference calculating means for calculating a phase difference (θ) between the frequency (f1) of the system voltage and the frequency (f2) detected by the PLL (Phase Locked Loop). Current command value storage means for setting and storing the effective current command value (P1) and the reactive current command value (Q1), the phase difference θ calculated by the phase difference calculation means, and the current command value storage means Correction current command value calculation means for calculating a corrected effective current command value (P2) and a corrected reactive current command value (Q2) based on the active current command value (P1) and the reactive current command value (Q1) stored in You may make it have.

  The correction current command value determining means according to the present invention includes a phase difference calculating means for calculating a phase difference (θ) between the frequency (f1) of the system voltage and the frequency (f2) detected by the PLL (Phase Locked Loop), and effective Current command value storage means for setting and storing the current command value (P1) and reactive current command value (Q1), the phase difference θ calculated by the phase difference calculation means, and the active current command stored in the current command value storage means Since it has correction current command value calculation means for calculating the corrected effective current command value (P2) and the corrected reactive current command value (Q2) based on the value (P1) and the reactive current command value (Q1), the PLL (Phase Locked Loop) Even if the frequency followability is slow, the command value determined from the change in frequency is based on the phase difference (θ), the corrected effective current command value (P2), and the corrected reactive current command value (Q2). Inject reactive power be able to.

  Furthermore, this invention may comprise a power conditioner by incorporating the isolated operation detection device described above.

  The power conditioner according to the present invention can integrate the isolated operation detection device and the power conditioner into one by incorporating the isolated operation detection device.

  In addition, the islanding operation detection method of the islanding operation detection apparatus according to the present invention is the operation of the distributed power source that is operated when the distributed power source is connected to the system power source, the reactive power is injected into the system power source, and the system power source is down An isolated operation detection method for an isolated operation detection device for detecting an isolated operation, in which step S1 for measuring the frequency (f1) of the system voltage, step S2 for outputting the frequency (f2) detected by the PLL, and the measured system Step S3 for calculating the phase difference (θ) based on the frequency (f1) of the voltage and the frequency (f2) detected by the PLL, and the phase difference (θ), active current command value (P1), and reactive current command value (Q1) ) Based on the corrected effective current command value (P2) and the corrected reactive current command value (Q2), step S4 for determining the corrected active current command value (P2) and the corrected reactive current command value (Q2). In addition, step S5 for injecting reactive power and step S6 for detecting the frequency (f1) and determining the isolated operation may be provided.

  The islanding operation detection method of the islanding operation detection apparatus according to the present invention is a system in which a distributed power source is connected to a system power source, and reactive power is injected into the system power source. A step S1 for measuring the frequency (f1) of the system voltage, a step S2 for outputting the frequency (f2) detected by the PLL, and the measured system voltage Step S3 for calculating the phase difference (θ) based on the frequency (f1) and the frequency (f2) detected by the PLL, and the phase difference (θ), active current command value (P1), and reactive current command value (Q1) Based on step S4 for determining the corrected effective current command value (P2) and the corrected reactive current command value (Q2) based on the corrected effective current command value (P2) and the corrected reactive current command value (Q2), Since step S5 for injecting reactive power and step S6 for detecting the frequency (f1) and determining the isolated operation are provided, the corrected effective current command value (P2) and the corrected reactive current command value (Q2) Based on the above, it is possible to quickly inject reactive power according to a command value determined from a change in frequency, and to detect a frequency that has suddenly changed due to the injected reactive power.

  In the isolated operation detection device according to the present invention, the frequency of the system voltage (f1) and the frequency (f2) detected by the PLL (Phase Locked Loop) when the frequency of the system voltage of the power line changes suddenly during the isolated operation. A corrected current command value for determining a corrected active current command value (P2) and a corrected reactive current command value (Q2) based on the phase difference (θ), the active current command value (P1), and the reactive current command value (Q1). Since the determining means is provided, based on the corrected active current command value (P2) and the corrected reactive current command value (Q2), the reactive power is quickly injected according to the command value determined from the change in frequency. A suddenly changed frequency can be detected, and an isolated operation can be detected quickly and stably.

  The correction current command value determining means according to the present invention includes phase difference calculating means for calculating a phase difference (θ) between the frequency (f1) of the system voltage and the frequency (f2) detected by the PLL (Phase Locked Loop). Current command value storage means for setting and storing the effective current command value (P1) and reactive current command value (Q1), the phase difference θ calculated by the phase difference calculation means, and the effective command value stored in the current command value storage means Since it has correction current command value calculating means for calculating the corrected effective current command value (P2) and the corrected reactive current command value (Q2) based on the current command value (P1) and the reactive current command value (Q1). Even if the frequency followability of the PLL (Phase Locked Loop) is slow, the command value determined from the frequency change based on the phase difference (θ), the corrected effective current command value (P2), and the corrected invalid current command value (Q2) Injection of reactive power The single operation can be detected in a short time, and the single operation can be detected in a short time.

  Furthermore, the power conditioner according to the present invention incorporates the above-described isolated operation detection device, whereby the isolated operation detection device and the power conditioner can be integrated into one, and can be configured in a compact manner.

  Moreover, the islanding operation detection method of the islanding operation detection device according to the present invention includes step S1 for measuring the frequency (f1) of the system voltage, step S2 for outputting the frequency (f2) detected by the PLL, and the measured system voltage. Step S3 for calculating the phase difference (θ) based on the frequency (f1) of the current and the frequency (f2) detected by the PLL, and the phase difference (θ), active current command value (P1) and reactive current command value (Q1) Step S4 for determining the corrected active current command value (P2) and the corrected reactive current command value (Q2) based on the above, and the reactive power based on the corrected active current command value (P2) and the corrected reactive current command value (Q2). Since the step S5 for injecting and the step (S6) for detecting the frequency (f1) and determining the single operation are provided, the corrected effective current command value (P2) and the corrected invalid current finger Based on the command value (Q2), reactive power can be quickly injected according to the command value determined from the change in frequency, and the frequency that has suddenly changed due to the injected reactive power can be detected. Can be detected.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In the present invention, the distributed power source that is operating in conjunction with the system power source can quickly operate the isolated operation that occurs when the system power source is down (failure), and the frequency that is suddenly changed by the injected reactive power, and It detects reliably and detects single operation.

  FIG. 1 is an overall configuration diagram of an embodiment of a distributed power supply system according to the present invention. In FIG. 1, the distributed power supply system is operated by connecting a system power supply AC and a plurality (k units) of distributed power supplies 2.

  One (one) distributed power source is composed of a distributed power source 2, a power conditioner 3, and an independent operation detection device 4, and is connected to the system power source AC. The system power supply AC may be a low-voltage system or a high-voltage system. Further, the isolated operation detection device 4 may be built in the power conditioner 3.

  When the system power source AC goes down while the k distributed power sources 2 are connected to the system power source AC, a so-called single operation occurs in which power is supplied from the k distributed power sources 2 to the system side. However, as a phenomenon of the occurrence of isolated operation, the frequency (for example, 50 Hz) of the system voltage on the power line connecting the power conditioner 3 and the system side changes (increases or decreases from 50 Hz).

  The isolated operation detection device 4 detects a change in the frequency (for example, 50 Hz) of the system voltage on the power line and determines the isolated operation, but only changes in the frequency (for example, 50 Hz) of the system voltage during the isolated operation. Since the change is gradual and difficult to detect, reactive power that amplifies the frequency change is injected into the power line, the frequency that changes sharply due to the injection of reactive power is detected, and the presence or absence of isolated operation is determined. Shut off power supply 2 from the system side.

  And the isolated operation detection device 4 quickly detects the isolated operation by injecting the reactive power according to the command value determined from the frequency change by correcting the phase shift accompanying the system frequency sudden change during the isolated operation. Become a point.

  FIG. 2 is a block diagram of an embodiment of a distributed power supply system to which the isolated operation detection device according to the present invention is applied. In FIG. 2, the same parts as those in the distributed power supply system 50a shown in FIG. The distributed power system 1a includes a distributed power source 2 such as a solar cell, a power conditioner 3a that connects the distributed power source 2 to the system power source AC via the power line PL, and operates in conjunction with the system power source AC. An independent operation detection device 4a connected to the power line PL, detecting the isolated operation of the distributed power supply 2 when the system power supply AC is stopped, shutting off the interconnection relay RL1, and stopping the isolated operation of the distributed power supply 2. It is composed of

  The isolated operation detection device 4a includes an interconnection relay RL1 that cuts off the distributed power source 2 from the power line PL, a frequency measurement means 5 that measures the frequency of the system voltage VL, a phase comparator 6a, a loop filter 6b, and a variable frequency transmitter 6c. The PLL block 6 that is adjusted to the same frequency as the frequency measured by the frequency measuring means 5 and output, the Sin waveform generating means 7a that generates the Sin waveform based on the frequency supplied from the PLL block 6, and the Cos waveform Cos waveform generating means 7b for generating is provided.

  In addition, the isolated operation detection device 4a has the frequency (f1) of the system voltage VL and the frequency (f2) detected by the PLL (Phase Locked Loop) when the frequency of the system voltage VL of the power line PL changes suddenly during the isolated operation. Correction current for determining the corrected active current command value (P2) and the corrected reactive current command value (Q2) based on the phase difference (θ) of the current, the active current command value (P1) and the reactive current command value (Q1) Command value determining means 8 is provided.

  The correction current command value determination means 8 is a phase difference calculation means (phase difference calculation) for calculating the phase difference (θ) between the frequency (f1) of the system voltage VL and the frequency (f2) detected by the PLL (Phase Locked Loop). 9, current command value storage means 10 for setting and storing active current command value (P1) 10a and reactive current command value (Q1) 10b, phase difference θ calculated by phase difference calculation means 9, and current command value storage Correction current for calculating the corrected effective current command value (P2) 11a and the corrected reactive current command value (Q2) 11b based on the active current command value (P1) 10a and the reactive current command value (Q1) 10b stored in the means 10 Command value calculation means 11.

FIG. 3 is a diagram showing an embodiment change image of the system (voltage) frequency and the PLL frequency according to the present invention. In FIG. 3, when the frequency of the system voltage VL (shown by a solid line) changes suddenly, the PLL frequency (shown by a broken line) changes gradually because the frequency followability of the PLL is slow.

  The phase difference calculation means 9 converts the frequency difference between the system (voltage) frequency and the PLL frequency into a phase difference θ and outputs the phase difference θ. Therefore, when the phase difference θ (= 0), the corrected effective current command value (P2) 11a and The corrected reactive current command value (Q2) 11b is equal to the active current command value (P1) 10a and the reactive current command value (Q1) 10b (P2 = P1, Q2 = Q1).

  Therefore, the corrected effective current command value (P2) 11a and the corrected reactive current command value (Q2) 11b are equivalent to the phase difference θ (= 0), regardless of the PLL phase lag. Immediately improve to the same state.

  Further, the isolated operation detection device 4a includes a multiplier 12a that multiplies the corrected active current command value (P2) 11a and the Sin waveform, a multiplier 12b that multiplies the corrected reactive current command value (Q2) 11b and the Cos waveform, and a multiplier 12a. And an adder 13 for adding the multiplication results of the multiplier 12b, a PI control unit 14 for executing PI control based on the output from the adder 13, and executing PWM with the PI-controlled signal to generate a PWM pattern The PWM pattern generator 15, the inverter 16 that generates reactive power in response to the PWM pattern control signal from the PWM pattern generator 15, and the interconnection relay RL 2 that injects or blocks the reactive power PM generated by the inverter 16 into the power line PL.

  In the distributed power supply system 1a, when the system power supply AC goes down due to an accident or the like, the frequency of the system voltage VL on the power line PL of AC power supplied from the distributed power supply 2 through the power conditioner 3a changes suddenly (frequency Decrease or increase).

  The isolated operation detection device 4a detects a sudden change in the frequency of the system voltage VL by the frequency measuring means 5, supplies a frequency (for example, f2) at which the PLL block 6 changes slowly to the phase difference calculating means 9, and measures the frequency. The suddenly changed frequency (for example, frequency f1) detected by the means 5 is supplied to the phase difference calculating means 9.

  The frequency difference (f1-f2) is calculated by the phase difference calculating means 9 between the frequency detected by the frequency measuring means 5 (for example, the frequency f1) and the frequency detected by the PLL block 6 (for example, the frequency f2), and the phase difference θ Is converted to output.

  Next, the corrected effective current command value (P2) 11a and the corrected reactive current command value (Q2) 11b are calculated based on the active current command value (P1) 10a, the reactive current command value (Q1) 10b, and the phase difference θ. .

  Subsequently, the Sin waveform and the corrected active current command value P2 are multiplied, the Cos waveform and the corrected reactive current command value Q2 are multiplied, the multiplication results are added, and PI (proportional / integral) control is performed based on the added calculation result. After performing the above, PWM (pulse width modulation) control is performed on the PI control signal to generate a PWM pattern.

  The inverter 16 is driven by the PWM pattern signal to generate reactive power PM, and the reactive power PM (abruptly changed frequency) that is the same as that in the steady state is injected into the power line PL.

Since the reactive power PM injected into the power line PL matches the command value determined from the change in frequency, the frequency changes abruptly, and high-speed detection of the isolated operation of the distributed power source 2 becomes possible.

  In addition, the frequency measuring means 5, the PLL block 6, the Sin waveform generating means 7a, the Cos waveform generating means 7b, the correction current command value determining means 8, the multiplier 12a, the multiplier 12b, and the adder 13 constituting the isolated operation detecting device 4a. The PI control unit 14 and the PWM pattern generator 15 may be configured by software based on a microprocessor or may be configured by hardware.

  FIG. 4 is a characteristic diagram of reactive power injected by the isolated operation detection device according to the present invention. In FIG. 4, when an isolated operation occurs and the frequency of the system voltage VL on the power line PL changes suddenly (increase or decrease in frequency), the system frequency and the PLL frequency cause a phase shift. In FIG. 4, the active power command value P1, the reactive power command value Q1, the active power command value P2, and the reactive power command value Q2 are represented by the corresponding power, but the active current command value P1 and the reactive current command value shown in FIG. This corresponds to Q1, corrected effective current command value P2, and corrected reactive current command value Q2.

  As shown in the upper diagram of FIG. 4, in the control based on the active current command value P1 and the reactive power command value Q1, there is a phase shift between the system frequency and the PLL frequency, and the reactive power according to the command value determined from the change in frequency. Can not be injected. Using the phase difference θ, the corrected active power command value P2 and the corrected reactive power command value Q2, the reactive power phase shift is corrected (vector correction) so that reactive power can be injected according to the command value determined from the change in frequency. To do.

  The active power command value P1 and the reactive power command value Q1 are calculated using the corrected active power command value P2, the corrected reactive power command value Q2, and the phase difference θ required for correcting the phase shift from the lower diagram of FIG. It is represented by (2).

P1 = P2cosθ−Q2sinθ ...... Formula (1)
Q1 = Q2cosθ + P2sinθ ...... Formula (2)
When P2 and Q2 are calculated from Equation (1) and Equation (2), they are expressed by Equation (3) and Equation (4).

P2 = P1 cos θ + Q1 sin θ ...... Formula (3)
Q2 = Q1 cos θ−P1 sin θ ...... Formula (4)
As is clear from FIG. 4, the corrected reactive power command value P2 and the corrected reactive power command value Q2 in which the phase shift (phase difference θ) of the reactive power in the upper diagram of FIG. 4 is expressed by Equation (3) and Equation (4). Without changing the vector direction from the above figure, only the magnitude is changed, and the output power, which is the combined vector of the corrected active power command value P2 and the corrected reactive power command value Q2, is restored to the original phase shift. The system frequency and PLL frequency can cancel the effect of phase shift.

When the phase difference θ between the corrected active power command value P2 and the corrected reactive power command value Q2 becomes zero (0), the corrected active power command value is calculated from the lower diagram of FIG. 4 or from the equations (3) and (4). It is clear that P2 and corrected reactive power command value Q2 become active power command value P1 and reactive power command value Q1. This characteristic corresponds to the distributed power supply system 1a shown in FIG.

  FIG. 5 is a block diagram of a distributed power supply system to which a power conditioner incorporating the isolated operation detection device according to the present invention is applied. In FIG. 5, a distributed power supply system 1b is connected to a distributed power supply 2 such as a solar battery and a distributed power supply 2 via a power line PL, and is operated in conjunction with the distributed power supply AC. It is comprised from the power conditioner 3b which incorporates the inverter part 4d which has an independent operation detection function.

  The power conditioner 3 b includes a booster circuit 17 that boosts the DC voltage supplied from the distributed power source 2.

  The inverter unit 4d having a single operation detection function built in the power conditioner 3b has a configuration similar to that of the single operation detection device 4c of FIG. The isolated operation detection device 4d has the same configuration except that the inverter 16 and the power line PL are connected in series to the power line PL, except that the isolated operation detection device 4a is different.

  In addition, since the part regarding the isolated operation detection function of the inverter part 4d which has an isolated operation detection function is the same as the isolated operation detection apparatus 4a shown in FIG. 2, description is abbreviate | omitted.

  The power conditioner 3b can integrate the single operation detection device and the power conditioner into one by incorporating the inverter unit 4d having the single operation detection function.

  As described above, the power conditioner 3b according to the present invention has a built-in inverter unit 4d having an isolated operation detection function, so that the isolated operation detection device and the power conditioner can be integrated into one, and the power conditioner 3b is configured in a compact manner. Can do.

  FIG. 6 is a characteristic diagram of reactive power injected by the power conditioner according to the present invention. In FIG. 6, when an isolated operation occurs and the frequency of the system voltage VL on the power line PL changes suddenly (increase or decrease in frequency), a phase shift occurs between the system frequency and the PLL frequency. The electric power becomes smaller than the command value determined from the change in frequency. In FIG. 6, the active power command value P1, the reactive power command value Q1, the active power command value P2, and the reactive power command value Q2 are represented by corresponding power, but the active current command value P1 and the reactive current command value shown in FIG. This is the same as Q1, corrected effective current command value P2, and corrected reactive current command value Q2.

  As shown in the upper diagram of FIG. 6, in the control based on the active current command value P1 and the reactive power command value Q1, a phase shift occurs between the system frequency and the PLL frequency. It becomes smaller than the command value determined from Using the phase difference θ, the corrected active power command value P2, and the corrected reactive power command value Q2 shown in the figure below, the phase shift is corrected and reactive power according to the command value determined from the change in frequency is injected.

  The corrected active power command value P2 and the corrected reactive power command value Q2 are expressed by Equations (3) and (4) using the active power command value P1, the reactive power command value Q1, and the phase difference θ.

  As apparent from FIG. 6, the phase shift (phase difference θ) in the upper diagram of FIG. 6 is expressed by the vectors of the corrected active power command value P2 and the corrected reactive power command value Q2 expressed by the equations (3) and (4). Without changing the direction from the above figure, only the magnitude is changed, and the output power, which is a combined vector of the corrected active power command value P2 and the corrected reactive power command value Q2, is restored to the original phase shift, and the system frequency And the PLL frequency can negate the effect of phase shift. This characteristic corresponds to the distributed power supply system 1b shown in FIG.

  As described above, the correction current command value determining means 8 according to the present invention calculates the phase difference (θ) between the frequency (f1) of the system voltage and the frequency (f2) detected by the PLL (Phase Locked Loop). Calculation means 9, current command value storage means for setting and storing active current command value (P1) and reactive current command value (Q1), phase difference θ calculated by phase difference calculation means 9, and current command value storage means Correction current command value calculating means for calculating the corrected effective current command value (P2) and the corrected reactive current command value (Q2) based on the active current command value (P1) and the reactive current command value (Q1) stored in Therefore, even if the frequency followability of the PLL (Phase Locked Loop) is slow, the frequency of the frequency is determined based on the phase difference (θ), the corrected effective current command value (P2), and the corrected reactive current command value (Q2). According to the command value determined from the change Reactive power can be injected, and an isolated operation can be detected in a short time.

  As described above, the isolated operation detection device 4a according to the present invention detects the frequency (f1) of the system voltage and the PLL (Phase Locked Loop) when the frequency of the system voltage of the power line suddenly changes during the isolated operation. Based on the phase difference (θ) from the frequency (f2), the active current command value (P1), and the reactive current command value (Q1), the corrected active current command value (P2) and the corrected reactive current command value (Q2) Since the correction current command value determining means 8 for determining the current value is provided, the reactive power according to the command value determined from the change in the frequency can be quickly obtained based on the correction active current command value (P2) and the correction reactive current command value (Q2). It is possible to detect the frequency that has been injected and suddenly changed due to the injected reactive power, and to detect a single operation quickly and stably.

  Next, the isolated operation detection method of the isolated operation detection device according to the present invention will be described. FIG. 7 is an operation flowchart of the main part of one embodiment of the isolated operation detecting method of the isolated operation detecting apparatus according to the present invention. The operation flow will be described with reference to FIG.

  The islanding operation detection method of the islanding operation detection apparatus according to the present invention is a system in which a distributed power source is connected to a system power source, and reactive power is injected into the system power source. In step S1, the system voltage frequency (f1) is measured in step S1. The operation of step S1 is executed by the frequency measuring means 5.

  In step S2, the frequency (f2) detected by the PLL is output. The operation of step S2 is executed by the PLL block 6.

  In step S3, the phase difference (θ) is calculated based on the measured frequency (f1) of the system voltage and the frequency (f2) detected by the PLL. The operation of step S3 is executed by the phase difference calculation means 9.

  In step S4, a corrected effective current command value (P2) and a corrected reactive current command value (Q2) are determined based on the phase difference (θ), the active current command value (P1), and the reactive current command value (Q1). The operation of step S4 is executed by the correction current command value determining means 8.

  In step S5, reactive power according to the command value determined from the change in frequency is injected based on the corrected active current command value (P2) and the corrected reactive current command value (Q2). The operation of step S5 is executed by the inverter 16.

  In step S6, the frequency (f1) suddenly changed by the injected reactive power is detected, and the isolated operation is determined. The operation of step S6 is executed by the frequency measuring means 5 and a control means (not shown).

  Thus, the islanding operation detection method of the islanding operation detection device according to the present invention measures step S1 for measuring the frequency (f1) of the system voltage and step S2 for outputting the frequency (f2) detected by the PLL. Step S3 for calculating the phase difference (θ) based on the frequency (f1) of the system voltage and the frequency (f2) detected by the PLL, and the phase difference (θ), active current command value (P1) and reactive current command value ( Step S4 for determining the corrected active current command value (P2) and the corrected reactive current command value (Q2) based on Q1), and the corrected active current command value (P2) and the corrected reactive current command value (Q2) based on Step S5 for injecting reactive power according to the command value determined from the frequency change, and Step S6 for detecting the frequency (f1) suddenly changed by the injected reactive power and determining the single operation Therefore, based on the corrected active current command value (P2) and the corrected reactive current command value (Q2), reactive power is quickly injected according to the command value determined from the frequency change, and suddenly changes depending on the injected reactive power. The detected frequency can be detected, and the isolated operation can be detected quickly and stably.

  The isolated operation detection device according to the present invention is determined from a change in frequency from a corrected active current command value and a corrected reactive current command value in consideration of the phase difference between the system voltage and the PLL block while the frequency followability of the PLL block remains slow. Injects reactive power according to the command value, detects the frequency that suddenly changes due to the injected reactive power, and immediately detects isolated operation. Applicable to all isolated operation detection devices that execute isolated operation detection from the sudden change frequency. can do.

Overall configuration diagram of an embodiment of a distributed power supply system according to the present invention Block diagram of an embodiment of a distributed power supply system to which an isolated operation detection device according to the present invention is applied Image of change of embodiment of system (voltage) frequency and PLL frequency according to the present invention One characteristic diagram of the reactive power which the isolated operation detection device concerning this invention injects Block configuration diagram of a distributed power supply system to which a power conditioner incorporating a stand-alone operation detection device according to the present invention is applied Characteristic diagram of reactive power injected by power conditioner according to the present invention Main part operation flow diagram of one embodiment of an isolated operation detection method of an isolated operation detection device according to the present invention Block diagram of a distributed power supply system to which a conventional isolated operation detection device is applied A characteristic diagram of reactive power injected by a conventional islanding detection device Block configuration diagram of a distributed power supply system to which a power conditioner incorporating a conventional isolated operation detection device is applied Another characteristic diagram of reactive power injected by conventional isolated operation detector

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b Distributed type power supply system 2 Distributed type power supply 3, 3a, 3b Power conditioner 4, 4a, 4b Independent operation detection device 5 Frequency measuring means 6 PLL block 6a Phase comparator 6b Loop filter 6c Variable frequency transmitter 7a Sin waveform generation Means 7b Cos waveform generation means 8 Correction current command value determination means 9 Phase difference calculation means 10 Current command value storage means 10a Effective current command value (P1)
10b Reactive current command value (Q1)
11 Correction current command value calculation means 11a Correction effective current command value (P2)
11b Corrected reactive current command value (Q2)
12a, 12b Multiplier 13 Adder 14 PI controller 15 PWM pattern generator 16 Inverter 17 Booster circuit RL1, RL2, RL Linkage relay PL Power line AC System power supply VL System voltage PM Reactive power

Claims (4)

An isolated operation detection device that operates by connecting a distributed power source to a system power source, injects reactive power into the system power source, and detects an isolated operation of the distributed power source caused by the down of the system power source,
When the frequency of the system voltage of the power line changes suddenly at the start of the independent operation, the phase difference (θ between the frequency (f1) of the system voltage and the frequency (f2) detected by the PLL (Phase Locked Loop) ), An effective current command value (P1) and a reactive current command value (Q1), and a corrected current command value determining means for determining a corrected active current command value (P2) and a corrected reactive current command value (Q2). An isolated operation detection device comprising:   The correction current command value determining means includes a phase difference calculating means for calculating a phase difference (θ) between a frequency (f1) of the system voltage and a frequency (f2) detected by the PLL (Phase Locked Loop); Current command value storage means for setting and storing the current command value (P1) and the reactive current command value (Q1), the phase difference θ calculated by the phase difference calculation means, and the current command value storage means Correction current command value calculating means for calculating a corrected effective current command value (P2) and a corrected reactive current command value (Q2) based on the effective current command value (P1) and the reactive current command value (Q1). The isolated operation detection device according to claim 1, wherein   A power conditioner comprising the isolated operation detection device according to claim 1 or 2. An isolated operation detection method of an isolated operation detection device that operates by connecting a distributed power supply to a system power supply, injects reactive power into the system power supply, and detects an isolated operation of the distributed power supply caused by the system power supply down. Because
Step S1 for measuring the frequency (f1) of the system voltage;
Step S2 for outputting the frequency (f2) detected by the PLL;
Calculating a phase difference (θ) based on the measured frequency (f1) of the system voltage and the frequency (f2) detected by the PLL;
Step S4 for determining a corrected active current command value (P2) and a corrected reactive current command value (Q2) based on the phase difference (θ), the active current command value (P1), and the reactive current command value (Q1);
Step S5 for injecting reactive power based on the corrected active current command value (P2) and the corrected reactive current command value (Q2);
Step S6 for detecting the frequency (f1) and determining an isolated operation;
An islanding operation detection method for an islanding operation detection device, comprising:

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