JP2017073840A - Controller, control method for system interconnection inverter, system interconnection inverter device, and starting method for system interconnection inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller for commercial three-phase system interconnection inverter which allows for system interconnection, by suppressing the rush current to a capacitor constituting a LC circuit, without providing any special rush current prevention circuit.SOLUTION: A controller for system interconnection inverter includes a system interconnection operation control unit 40A generating a PWM control signal for controlling a commercial three-phase system interconnection inverter, a start-up operation control unit 40B generating a PWM control signal for matching the amplitude, phase and operation frequency of the output voltage from the inverter with those of the commercial three-phase system voltage before interconnecting the commercial three-phase system, a PWM control unit 40C performing PWM control of the inverter based on the PWM control signals from system interconnection operation control unit and start-up operation control unit, and an operation mode switching unit 40D for switching to the system interconnection control by the system interconnection operation control unit, when a determination is made that the output voltage, or the like, of the inverter started by the start-up operation control unit has matched with that of the commercial three-phase system.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a control device, a control method, a system connection inverter device, and a start method of the system connection inverter device that include an inverter that is connected to a commercial three-phase system.

  A distributed power source such as a solar cell or a fuel cell converts a direct current power into an alternating current power and adjusts the commercial system frequency, the phase of the commercial system voltage, and the like to connect with the commercial system. Power conditioner ”).

  A power conditioner includes a DC / DC converter that adjusts a DC voltage generated by a distributed power source to a predetermined DC voltage value, an inverter that converts DC power output from the DC / DC converter into AC power, and an output of the inverter A grid-connected inverter device including an LC filter that removes high-frequency components from the grid, and a grid-connected relay for connecting to a commercial power supply.

  When connecting to a commercial system using such a grid-connected inverter device, in order to avoid the deterioration of the capacitor constituting the LC filter and the deterioration of the grid-connected relay contact, the inrush current from the commercial system to the capacitor is reduced. It is necessary to suppress it. In particular, when a solar cell panel is used, the necessity and the necessity are high because interconnection and disconnection with a commercial system are repeated once a day.

  Patent Document 1 discloses a grid-connected inverter device in which an AC output terminal of a grid-connected inverter is connected to a system via an output filter including at least a shunt-connected filter capacitor and a switch. In the open state, the filter capacitor is charged with a current that is approximately 90 ° ahead of the system voltage by the inverter. After the filter capacitor is set to approximately the same voltage value and phase as the system voltage, the switch is turned on for interconnection operation. A grid-connected inverter device configured as described above has been proposed.

  Patent Document 2 includes a parallel circuit of a resistor and a switch as a capacitor inrush current prevention circuit provided on the output side of the inverter, and the control unit of the power conditioner stops the inverter, and the power system rather than the capacitor. The relay contact for grid connection provided on the side is short-circuited, and the switch contact is controlled to switch between the short-circuited state and the open state, and the switch failure diagnosis based on the output current value of the inverter before and after the switching There has been proposed a power conditioner having a control configuration for performing the above.

  Patent Document 3 discloses an LC filter having an inrush current suppression resistor arranged in series with a capacitor and an inrush current suppression resistor short-circuit switch arranged in parallel with the inrush current suppression resistor, and an AC filtered by the LC filter. Determine the failure of the inrush current suppression resistor short circuit switch based on the control state of the grid connection switch that outputs power to the AC power supply and the control state of the inrush current suppression resistor short circuit switch and the output current from the filter. A power converter including a control device is disclosed.

  In Patent Document 4, a DC power source that generates DC power or a DC load driven by DC power and a power system through which three-phase AC power flows are provided, and DC-AC conversion or AC-DC between them is provided. A power conversion device including a switching circuit that performs conversion, a connection switch that connects a DC power supply or the DC load and the switching circuit, and an interconnection switch that connects the switching circuit and the power system A DC-side capacitor for smoothing the DC power between the connection switch and the switching circuit, and a filter circuit for passing the AC power in a predetermined frequency band between the switching circuit and the interconnection switch The power system that is input without going through the interconnection switch at the time of start-up An initial charging circuit that rectifies the AC power to generate DC power, supplies the generated DC power to the DC-side capacitor via a charging resistor, and performs charging. The DC switch is turned off and the DC power is generated by the rectifying operation of the initial charging circuit and the switching circuit is operated to charge the DC capacitor, and the filter capacitor is charged through the switching circuit. Then, when each capacitor rises to a predetermined charging voltage, the switching circuit is temporarily stopped to further charge the DC side capacitor to the rectified voltage of the power system, and then at the same timing as when the switching circuit is stopped. Connection of the switching circuit and the power system by turning on the interconnection switch, Connection of the DC power supply or the DC load and the switching circuit by turning on a connection switch, and restarting the operation of the switching circuit, the switching circuit of the DC power supply or the DC load and the power system There is disclosed a power conversion device characterized by comprising a startup control means for controlling to establish a connection via the power supply.

JP 1997-28040 A Japanese Patent Laying-Open No. 2015-27146 Japanese Patent Laid-Open No. 2015-23650 JP 2011-193633 A

  However, in the grid-connected inverter device disclosed in Patent Document 1, it is necessary to control the current flowing in the capacitor to about several percent of the rated current of the inverter, and the problem that the control for that becomes very complicated, Since the capacitor is charged with a DC component of about several percent of the capacitor current generated at this time (about 0.1 to 0.01% of the rated current of the inverter), there is also a problem that an inrush current flows when the contact is turned on. In addition, it is necessary to provide a resistor in order to discharge such a direct current component, and there is a problem that the cost increases due to an increase in the number of components.

  According to the configurations disclosed in Patent Documents 2 and 3, in addition to the inrush current prevention circuit, it is necessary to detect a failure of a short-circuit switch provided in the inrush current prevention circuit, which also increases the cost due to an increase in the number of components. It was not the configuration that solved the problem of inviting.

  In order to prevent an inrush current, the power conversion device disclosed in Patent Document 4 first charges a capacitor on the DC / AC side of the main circuit, and when the voltage exceeds a predetermined voltage, performs an operation stop process and then turns on the interconnection switch. The system is configured to perform grid-connected operation, and it is inevitable that the switch-on time of the grid switch will vary. The applied voltage is increased, and an overcurrent is generated, which may cause damage to the components of the inverter device.

  In view of the above-described problems, an object of the present invention is to provide a grid-connected inverter control device capable of grid-linking by suppressing inrush current to a capacitor constituting an LC filter without providing a special inrush current prevention circuit. It is in the point which provides the starting method of a control method, a grid connection inverter apparatus, and a grid connection inverter apparatus.

  In order to achieve the above-mentioned object, a first characteristic configuration of a control device for a grid-connected inverter according to the present invention is an inverter linked to a commercial three-phase system as described in claim 1 of the claims. And a system-connected inverter control device including an LC filter that removes harmonic components of the output current of the inverter, and generates a PWM control signal for controlling the inverter in connection with a commercial three-phase system And a PWM for matching the amplitude, phase and operating frequency of the output voltage of the inverter with the amplitude, phase and system frequency of the commercial three-phase system voltage before connecting to the commercial three-phase system. A start-up operation control unit that generates a control signal; a PWM control unit that performs PWM control of the inverter based on PWM control signals from the grid-connected operation control unit and the start-up operation control unit; When it is determined that the amplitude, phase, and operating frequency of the output voltage of the inverter activated by the activation operation control unit have reached a matching state with the commercial three-phase system, switching to grid interconnection control by the grid interconnection operation control unit is performed. And an operation mode switching unit.

  When linking to the commercial three-phase system, first, the start-up operation control unit matches the amplitude, phase, and operating frequency of the inverter output voltage with the amplitude, phase, and system frequency of the commercial three-phase system voltage. Since the operation mode switching unit that switches to grid interconnection control by the operation control unit is provided, it is possible to prevent inrush current from flowing into the capacitor constituting the LC filter without providing a separate circuit element such as a protective resistor. become able to.

  In the second characteristic configuration, as described in claim 2, in addition to the first characteristic configuration described above, the PWM control unit is connected to the grid interconnection from the start-up operation control unit by the operation mode switching unit. Until the control is switched to the operation control unit, the inverter is PWM-controlled by a third harmonic injection PWM (Third Harmonic Injected PWM) control signal.

  Even if the DC bus voltage is somewhat low, the amplitude, phase, and system frequency of the commercial three-phase system voltage can be matched, and the range of use of the generated power of the distributed power supply can be expanded.

  In the third feature configuration, as described in claim 3, in addition to the first or second feature configuration described above, the operation mode switching unit is predetermined from the start of the startup control by the startup operation control unit. When it cannot be determined that the matching state has been reached in time, the fault determination counter is updated so that the amplitude, phase and operating frequency of the inverter output voltage are matched with the amplitude, phase and system frequency of the commercial three-phase system voltage. The configuration is such that the processing is repeated.

  When it is in a state that can be matched inherently, such as when it is determined that it does not fall below a predetermined threshold even if a predetermined time elapses due to factors such as malfunction of the AC voltage detection circuit or distortion of the commercial system voltage, By repeating the matching process, it is possible to secure an opportunity to be properly matched and grid-connected. By providing a threshold value for the value of the failure determination counter, the accuracy of failure determination can be increased.

  In the fourth feature configuration, as described in claim 4, in addition to the third feature configuration described above, the operation mode switching unit, when the count number of the failure determination counter exceeds a predetermined determination number of times, The configuration is such that the operation stop processing is performed.

  If the grid connection is difficult due to a failure of the switching element of the grid interconnection inverter, this fact is notified immediately, and the occurrence of a serious accident or the like can be prevented.

  In the fifth feature configuration, in addition to any one of the first to fourth feature configurations described above, the operation mode switching unit may include any two of the commercial three-phase systems. A convergence condition is satisfied in which the difference between the line voltage and the output voltage of the inverter corresponding to each line voltage, and the difference between the maximum voltage value of the commercial three-phase system and the maximum output voltage value of the inverter are not more than a predetermined threshold value. And that it is determined that the alignment state has been reached.

  By defining such convergence conditions, it becomes possible to objectively determine whether or not they are consistent.

  In the sixth feature configuration, in addition to any one of the first to fifth feature configurations described above, the start-up operation control unit includes lines before and after the grid interconnection relay. The voltage between the inverters is measured, and the amplitude, phase and operating frequency of the output voltage of the inverter are matched with the amplitude, phase and grid frequency of the commercial system voltage based on the measured value, and the operation mode switching unit reaches the matching state. If it is determined that the system connection operation is performed, the system connection relay is turned on to start the system connection operation control unit.

  With the above-described configuration, the inrush current to the capacitor of the LC filter can be suppressed and the system can be interconnected quickly.

  The first characteristic configuration of the control method of the grid-connected inverter according to the present invention is an LC that removes harmonic components of the output current of the inverter and the inverter linked to the commercial three-phase system as described in claim 7. A grid-connected inverter control method provided with a filter, a grid-connected operation control step for generating a PWM control signal for controlling the inverter linked to a commercial three-phase system, and a commercial three-phase system, A start-up operation control step for generating a PWM control signal for matching the amplitude, phase and operating frequency of the output voltage of the inverter with the amplitude, phase and system frequency of a commercial three-phase system before connection; A PWM control step for PWM control of the inverter based on a PWM control signal from the operation control step and the start-up operation control step; and the start-up operation control step Operation mode switching to switch to grid interconnection control by the grid interconnection operation control step when it is determined that the amplitude, phase, and operation frequency of the output voltage of the inverter activated by the loop have reached a matching state with the commercial three-phase system And a step.

  In the second feature configuration, as described in claim 8, in addition to the first feature configuration described above, the PWM control step includes the system interconnection from the start-up operation control step by the operation mode switching step. Until the control is switched to the operation control step, the inverter is PWM-controlled by the third harmonic injection PWM control signal.

  In the third feature configuration, as described in claim 9, in addition to the first or second feature configuration described above, the operation mode switching step is predetermined from the start of the start control by the start operation control step. When it cannot be determined that the matching state has been reached in time, the fault determination counter is updated so that the amplitude, phase and operating frequency of the inverter output voltage are matched with the amplitude, phase and system frequency of the commercial three-phase system voltage. The configuration is such that the processing is repeated.

  In the fourth feature configuration, as described in claim 10, in addition to the third feature configuration described above, in the operation mode switching step, when the count number of the failure determination counter exceeds a predetermined determination count, The configuration is such that the operation stop processing is performed.

  In the fifth feature configuration, in addition to any one of the first to fourth feature configurations described above, the operation mode switching step includes any two of the commercial three-phase systems. A convergence condition is satisfied in which the difference between the line voltage and the output voltage of the inverter corresponding to each line voltage, and the difference between the maximum voltage value of the commercial three-phase system and the maximum output voltage value of the inverter are not more than a predetermined threshold value. And that it is determined that the alignment state has been reached.

  In the sixth feature configuration, as described in claim 12, in addition to any of the first to fifth feature configurations described above, the start-up operation control step includes a line before and after the grid interconnection relay. The voltage between the inverters is measured, and the amplitude, phase and operating frequency of the output voltage of the inverter are matched with the amplitude, phase and grid frequency of the commercial grid voltage based on the measured value, and the operation mode switching step reaches the matching state. If it is determined that the system connection operation is performed, the system connection relay is turned on to start the system connection operation control step.

  The characteristic configuration of the grid-connected inverter device according to the present invention includes an inverter linked to a commercial three-phase grid, an LC filter that removes harmonic components of the output current of the inverter, and And a control device for a grid-connected inverter having any one of the first to sixth characteristic configurations.

  The characteristic configuration of the method for starting the grid-connected inverter device according to the present invention includes an inverter linked to a commercial three-phase system and an LC filter that removes harmonic components of the output current of the inverter as described in claim 14 And a control method for the grid-connected inverter having any one of the first to sixth characteristic configurations described above.

  As described above, according to the present invention, the control device and the control of the grid interconnection inverter capable of grid interconnection by suppressing the inrush current to the capacitor constituting the LC filter without providing a special inrush current prevention circuit. It has become possible to provide a method, a grid interconnection inverter device, and a start method of the grid interconnection inverter device.

The circuit block diagram of the photovoltaic power generation system which is an example of the distributed power supply to which this invention was applied The control block diagram of the grid connection inverter by this invention (A) is an image diagram of SPWM output, (b) is an image diagram of third harmonic injection PWM output. Start-up operation control flowchart for grid-connected inverter Illustration of simulation results during start-up operation Explanatory diagram of simulation results during grid connection operation

  Hereinafter, a control device for a grid-connected inverter, a control method for the grid-connected inverter, a grid-connected inverter device, and a startup method for the grid-connected inverter device according to the present invention will be described with reference to the drawings.

FIG. 1 shows a solar battery power generation apparatus 100 that is an example of a distributed power source. The solar battery power generation device 100 is configured to include a solar battery panel SP and a power conditioner PC to which the solar battery panel SP is connected, and is connected to a commercial three-phase grid e _Grid via a _grid interconnection relay S _Grid . . Note that the present invention is not limited to the case where the power supply device connected to the power conditioner PC is the solar cell panel SP, but is a case where another power generation device such as a fuel cell, a power storage device, or the like is connected. Is applicable.

The power conditioner PC includes a DC / DC converter 1 that boosts the DC voltage generated by the solar battery panel SP to a predetermined DC link voltage _Vdc , and a predetermined frequency and voltage value so as to be linked to a commercial three-phase system. And an LC filter 4 that removes harmonic components from the output of the inverter 3.

  A grid interconnection inverter device 30 is configured by the inverter 3 and the LC filter 4, and a control block for controlling the grid interconnection inverter device 30 is a control device 40 of the grid interconnection inverter. The switches S1, S2, S3, S4, S5, and S6 provided in the inverter 3 are PWM controlled by the control device 40, and three-phase AC power that matches the frequency, phase, and amplitude of the commercial three-phase system is output. Harmonic components are removed from the output by the filter 4 to output sinusoidal three-phase AC power.

In FIG. 1, reference symbol V _dc is a DC link voltage, i _u , i _v , and i _w are inverter output currents, L _f and C _f are LC filters, and i _{u · sp} , i _{v · sp} , i _{w · sp} are output _{current, e uv.sd} the inverter output voltage between _uv, the inverter output voltage between _{e Vw.Sd} is _vw, commercial system voltage between _{e uv} is _{uv, S Grid} is system interconnection _{relay, Z Load} Is the AC load of a commercial three-phase system.

  FIG. 2 shows functional blocks of a control device 40 for a grid-connected inverter that includes a microcomputer, a memory, a peripheral circuit, and the like. The control device 40 includes a grid interconnection operation control unit 40A, a start-up operation control unit 40B, a PWM control unit 40C, and an operation mode switching unit 40D. In the control device 40, a three-phase alternating current is equivalent to two phases. After the two-phase conversion is performed by αβ conversion for conversion to alternating current, a necessary control calculation is performed, and the result is inversely converted to control the inverter 3.

The grid interconnection operation control unit 40A is a control block that generates a PWM control signal for controlling the inverter 3 in linkage with a commercial three-phase system, and a DC voltage control unit that controls the DC bus voltage Vdc constant; Reactive power control unit that injects reactive power to adjust the reverse power flow voltage to the commercial three-phase system and to detect isolated operation, and the command values P ^* _uw and Q ^* _uw to the command values i ^* _α and i ^* _β PQ / αβ conversion unit for conversion, uvw / αβ conversion unit for converting commercial three-phase system voltage and current into αβ phase voltage and current, and duty ratio d _{α. grid} , d _β. and a three-phase inverter output current control unit that calculates _grid , and configured to execute reactive power control.

Note that the command value Q ^* _uw is set to 0 at the time of start-up for linking to the commercial system and at the initial stage of the system connection, and the operation is controlled at the operating power factor of 1.

The start-up operation control unit 40B generates a PWM control signal for matching the amplitude, phase, and operation frequency of the output voltage of the inverter 3 with the amplitude, phase, and system frequency of the commercial three-phase system before connecting to the commercial three-phase system. The output voltage Esd. A block that P-controls (proportional control) the amplitude so that max becomes the maximum value Emax of the commercial system voltage, and a duty that becomes a sin component of the αβ phase by multiplying the command value that is the output by 2 / (Vdc / Emax) Ratio d _{α. The} duty ratio d _β. A block for generating _sd is provided. k represents a sampling time at k hours.

The PWM control unit 40C is an inverter based on duty ratio control signals (d _α.grid , d _β.grid, d _α.sd, d _β.sd ) from the grid interconnection operation control unit 40A and the start-up operation control unit 40B. 3 is a control block that performs PWM control, and an αβ / uvw conversion unit and a third harmonic injection unit that injects a third harmonic into its output and outputs command values d ^* _u , d ^* _v , d ^* _w And an SPWM output control unit that outputs a third harmonic injection PWM signal for controlling the switches S1, S2, S3, S4, S5, and S6 of the inverter 3 based on the command value and the reference triangular wave voltage. Yes.

  When the operation mode switching unit 40D determines that the amplitude, phase, and frequency of the output voltage of the inverter 3 activated by the start operation control unit 40B in the initial stage have reached a state of matching with the commercial three-phase system, the system interconnection operation control unit It is a control block switched to grid interconnection control by 40A.

  When the operation mode switch SW is switched to 0 by the operation mode switching unit 40D, the inverter 3 is controlled by the grid interconnection operation control unit 40A, and when the operation mode switch SW is switched to 1, the startup operation control unit 40B controls the inverter 3 Is done.

Formulas for converting the active / reactive power command values P ^* _uvw and Q ^* _uvw into αβ-phase output current command values i ^* _α and i ^* _β are defined by [Equation 1]. Equations for converting the line voltage e _uv between _uv and the line voltage _evw between v-w into αβ phase AC voltages e _α , e _β and output currents i _α , i _β Determined by [Equation 3]. The calculation method of instantaneous active / reactive power is determined by [Equation 4].

The output duty ratios d _u , d _v , d _w of the uvw phase converted from the output duty ratios d _α , d _{β of the} αβ phase by the αβ / uvw conversion unit are obtained by the following equation (5). The output duty ratios d ^* _u , d ^* _v , d ^* _w including the third harmonic injection can be obtained by the following equation (6). _Formulas for _{obtaining the} αβ phase AC voltages e _α.sd , e _β.sd and the maximum value E _sd.max of the output voltage from the inverter output voltages e _uv.sd , e _vw.sd are defined by [Equation 7].

The third harmonic injection unit will be described. First, it is shown in FIG. 3 (a) an image drawing for comparing the output duty ratio _{d u} the carrier frequency of SPMW. FIG. 3B shows an image drawing for comparing the third harmonic injection PWM and the carrier frequency.

As shown in FIG. 3 (a), the peak value of the output duty ratio d _u when not performed third harmonic injection is one. As shown in FIG. 3B, when third harmonic injection is performed, the peak value of the output duty ratio d ^* _u is 0.869 as shown in FIG. 3B. That is, when performing the third harmonic injection waveform of around 60 degrees of the sine wave corresponds to the peak value of the outputs duty ratio d _u of SPMW.

  In a commercial three-phase grid-connected inverter device, the third harmonic component of the line voltage can be canceled by appropriately superimposing the third harmonic, and the output voltage utilization ratio (ratio of DC bus voltage to commercial grid voltage) ) Can be improved by about 15.07%.

In the case of normal SPWM, the command value V ^* _dc.min of the minimum voltage of the DC bus voltage when performing constant control of the DC bus voltage V _dc is determined by the formula [Equation 8], whereas the third harmonic is injected. In this case, the command value V ^* _dc.min of the minimum voltage of the DC bus voltage is determined by the formula [Equation 9].

When the effective value E _Grid.rms of the commercial system voltage is 200V, the command value V ^* _dc.min of the minimum voltage of the DC bus voltage in the case of SPWM is 346V, and the minimum value of the DC bus voltage in the case of the third harmonic injection PWM The command value V ^* _dc.min of the voltage is 301V.

  In other words, by using the third harmonic injection PWM, the amplitude, phase and system frequency of the commercial three-phase system voltage can be matched even when the DC bus voltage is about 45V low, and the use range of the generated power of the distributed power source Will spread. For example, in the case of photovoltaic power generation, it is possible to operate at a lower voltage when starting up in the morning.

Hereinafter, a startup sequence for grid interconnection executed by the grid interconnection inverter control device will be described.
As shown in FIG. 4, at the start of grid connection operation, the operation mode switching unit 40D sets the operation mode switch SW to 1 and activates the startup operation control unit 40B with the _{grid connection} relay S _Grid turned off. (S1).

The start-up operation control unit 40B starts the mobile operation by the soft start process (S2), and converts the output voltage of the inverter 3 and the amplitude and phase of the commercial system voltage using the α-phase system voltage after three-phase to two-phase conversion. And the feedback control so that the system frequency is matched, the duty ratio d _{α. sd} , d _{β. The grid} is output (S3).

Here, since all the information on the phase and the frequency is included in the αβ phase commercial system voltages e _α and e _β , only the instantaneous value of the AC voltage needs to be controlled. The peak value Emax of the commercial system voltage is converted by the formula [Equation 1], and the peak value Emax · sd of the output voltage of the inverter 3 is converted by the formula [Equation 6].

From the time of start-up operation control section 40B by the activation of the operation control start when aligned until a predetermined time elapses (S4 (N), S5 ( Y)), switching the switching circuit S _w in the system interconnection operation control unit 40A side Then, the value of the failure determination counter is reset (S6), and the grid interconnection relay S _Grid is turned on (S7).

If they are not matched within the predetermined time (S4 (Y)), it is determined that a failure has occurred, the value of the failure determination number counter is incremented (S8), and the value of the failure determination number counter is preset. (S9 (Y)), the grid interconnection relay S _Grid is stopped without being turned on (S10), and a warning process for notifying the state is executed (S11). Until the value of the failure determination number counter reaches a preset value (S9 (N)), a restart process for performing the alignment process again is executed (S12).

  The predetermined time required for failure determination is not particularly limited and may be set as appropriate. In this embodiment, it is set to about 10 seconds. Further, the threshold of the failure determination number counter, that is, the number of failure determinations may be set as appropriate, and is set to 3 in this embodiment. In addition, what is necessary is just to set the threshold value of a failure determination frequency | count counter to 1 when making the reference | standard which leads to an operation stop process strict. In this case, the failure determination unit immediately starts when the difference between the amplitude, phase and frequency of the output voltage of the inverter and the amplitude, phase and frequency of the commercial system voltage does not fall below the predetermined threshold even if the predetermined time elapses. It will be determined as a failure.

The criterion for determining whether or not the alignment state has been reached is according to the following equation [Equation 10]. That is, the switching condition to the grid interconnection operation is whether or not the difference in the amplitude value between the output voltage of the inverter 3 and the commercial grid voltage is equal to or less than K · E _{Grid · rms} . The value of K is a value set in the range of 0 to 1, and is preferably set to K = 0.1 in consideration of the allowable fluctuation range 202V ± 20V when the commercial system voltage is 200V, for example.

  The predetermined time is sufficient as long as it is necessary for detecting a failure of the inverter 3 or the like, and may be set to several hundred milliseconds, for example. If the switching element of the inverter 3 is damaged, the amplitude, phase, and system frequency of the commercial system voltage cannot be matched, or if a problem occurs in the sensor that monitors the output voltage of the inverter, the amplitude, phase of the commercial system voltage Since the system frequency cannot be matched, in such a case, the operation is promptly stopped and a warning is issued.

  That is, by the above-described grid-connected inverter control apparatus, a control method for a grid-connected inverter including an inverter coupled to a commercial three-phase system and an LC filter that removes harmonic components of the output current of the inverter, that is, A grid-connected operation control step for generating a PWM control signal for controlling the inverter in conjunction with the commercial three-phase system, and the amplitude, phase and operating frequency of the inverter output voltage before linking with the commercial three-phase system The start operation control step for generating a PWM control signal for matching the amplitude, phase and system frequency of the commercial three-phase system, and the inverter based on the PWM control signal from the system interconnection operation control step and the start operation control step PWM control step for PWM control, and amplitude, phase and phase of the output voltage of the inverter started by the start operation control step Rolling frequency determines that led to alignment with the commercial three-phase system, the operation mode switching step of switching the system interconnection control by the system interconnection operation control step is executed.

  The PWM control step is configured to perform PWM control of the inverter by the third harmonic injection PWM control signal until the control is switched from the startup operation control step to the grid interconnection operation control step by the operation mode switching step.

  The operation mode switching step updates the failure determination counter when it cannot be determined that the matching state has been reached within a predetermined time from the start of the start control by the start operation control step, and the amplitude, phase and operation frequency of the output voltage of the inverter Is repeated to match with the amplitude, phase and system frequency of the commercial three-phase system voltage, and when the count number of the failure determination counter exceeds the predetermined number of determinations, the operation stop process is performed.

  In addition, the operation mode switching step includes any two line voltages of the commercial three-phase system and the difference between the inverter output voltages corresponding to each line voltage, and the commercial three-phase system voltage maximum value and the inverter output voltage maximum value. When the convergence condition that each of the differences is equal to or less than a predetermined threshold is satisfied, it is determined that the matching state has been reached.

  In the present invention, the starting operation control step measures the line voltage before and after the grid interconnection relay, and based on the measured value, the amplitude and phase of the inverter output voltage, the operating frequency and the amplitude and phase of the commercial grid voltage When the system frequency is matched and the operation mode switching step is determined to have reached the matching state, the system interconnection relay is turned on to start the system interconnection operation control step.

FIG. 5 shows a simulation result of the control method of the grid interconnection inverter according to the present invention. At startup, the relay S _Grid connected to the commercial system was turned off to match the amplitude, phase, and system frequency of the commercial system voltage, the position of the switch SW was set to 0, and the startup operation control step was executed.

  Thereafter, when it was confirmed that the mathematical formula [Equation 10] was satisfied, the relay connected to the commercial system was turned on, and the position of the switch SW was switched to 1 to switch to the system interconnection control step. The DC bus voltage was soft-started for 1 second between 420V and the target value (380V). It was confirmed that when the DC bus voltage was close to 380 V, constant control was performed and output up to the rating (9.9 kW).

FIG. 6 shows a simulation waveform at the moment when the commercial system is linked. It was confirmed that the maximum value of the inrush current of the output currents i _u.sp , i _v.Sp , and i _w.Sp of each phase was within about ± 2 A at the moment of connection with the system. Here, it was confirmed that even if the third harmonic injection PWM is used in the PWM modulation system before and after connecting with the system, the system connection operation is smoothly performed without any problem.

  Each of the above-described embodiments is merely an example of an isolated operation detection apparatus and an isolated operation detection method according to the present invention, and specific configurations (hardware and software), various numerical values, and the like of each component block are described in the present invention. Needless to say, it is possible to change and design appropriately within a range in which the effects of the above can be achieved.

1: DC / DC converter 3: Inverter 4: LC filter 30: Grid-connected inverter device 40: Grid-connected inverter control device 40A: Grid-linked operation control unit 40B: Start-up operation control unit 40C: PWM control unit 40D: Operation mode switching unit 100: distributed power source (solar cell power generator)
PC: Power conditioner SP: Solar battery panel S1, S2, S3, S4, S5, S6: Switching element of inverter device linked to commercial three-phase system

Claims (14)

A system-connected inverter control device comprising an inverter connected to a commercial three-phase system and an LC filter that removes harmonic components of the output current of the inverter,
A grid-connected operation control unit that generates a PWM control signal for controlling the inverter in linkage with a commercial three-phase system;
A start-up operation control unit that generates a PWM control signal for matching the amplitude, phase, and operation frequency of the output voltage of the inverter with the amplitude, phase, and system frequency of the commercial three-phase system voltage before linking with the commercial three-phase system When,
A PWM control unit that PWM-controls the inverter based on PWM control signals from the grid-connected operation control unit and the start-up operation control unit;
When it is determined that the amplitude, phase, and operating frequency of the output voltage of the inverter activated by the activation operation control unit have reached a matching state with the commercial three-phase system, switching to grid interconnection control by the grid interconnection operation control unit is performed. An operation mode switching unit;
The control apparatus of the grid connection inverter provided with.   The PWM control unit PWM-controls the inverter by a third harmonic injection PWM control signal until the operation mode switching unit switches control from the startup operation control unit to the grid interconnection operation control unit. The control apparatus of the grid connection inverter of Claim 1 comprised.   The operation mode switching unit updates the failure determination counter when it cannot be determined that the matching state has been reached within a predetermined time from the start of the start control by the start operation control unit, and the amplitude and phase of the output voltage of the inverter 3. The system-connected inverter control device according to claim 1, wherein the control device is configured to repeat the process of matching the operation frequency with the amplitude, phase, and system frequency of the commercial three-phase system voltage.   The control device for a grid-connected inverter according to claim 3, wherein the operation mode switching unit is configured to perform an operation stop process when the count number of the failure determination counter exceeds a predetermined determination number.   The operation mode switching unit includes any two line voltages of the commercial three-phase system and a difference between the output voltages of the inverter corresponding to each line voltage, and a voltage maximum value of the commercial three-phase system and a maximum output voltage of the inverter. 5. The control device for a grid-connected inverter according to claim 1, wherein the control device is configured to determine that the matching state has been reached when a convergence condition in which each of the value differences is equal to or less than a predetermined threshold is satisfied. .   The start-up operation control unit measures the line voltage before and after the grid interconnection relay, and based on the measured value, the amplitude, phase, operating frequency and commercial system voltage amplitude, phase, system frequency of the inverter output voltage The operation mode switching unit is configured to turn on the grid interconnection relay and start the grid interconnection operation control unit when it is determined that the alignment state has been reached. The control apparatus of the grid connection inverter in any one of 5. A control method for a grid-connected inverter comprising an inverter linked to a commercial three-phase system and an LC filter that removes harmonic components of the output current of the inverter,
A grid-connected operation control step for generating a PWM control signal for controlling the inverter in linkage with a commercial three-phase system;
A start-up operation control step for generating a PWM control signal for matching the amplitude, phase and operating frequency of the output voltage of the inverter with the amplitude, phase and system frequency of the commercial three-phase system before linking with the commercial three-phase system; ,
PWM control step for PWM controlling the inverter based on PWM control signals from the grid interconnection operation control step and the startup operation control step;
When it is determined that the amplitude, phase, and operation frequency of the output voltage of the inverter activated by the activation operation control step has reached a matching state with the commercial three-phase system, the system is switched to grid interconnection control by the grid interconnection operation control step. An operation mode switching step;
A control method for a grid-connected inverter comprising:   In the PWM control step, the inverter is PWM controlled by a third harmonic injection PWM control signal until the control is switched from the start operation control step to the grid interconnection operation control step by the operation mode switching step. The control method of the grid connection inverter of Claim 5 comprised.   The operation mode switching step updates the failure determination counter when it cannot be determined that the matching state has been reached within a predetermined time from the start of the start control by the start operation control step, and the amplitude and phase of the output voltage of the inverter The control method of the grid interconnection inverter according to claim 7 or 8, wherein the process of matching the operation frequency with the amplitude, phase and grid frequency of the commercial three-phase grid voltage is repeated.   The method for controlling a grid-connected inverter according to claim 9, wherein the operation mode switching step is configured to perform an operation stop process when the count number of the failure determination counter exceeds a predetermined determination number.   The operation mode switching step includes any two line voltages of the commercial three-phase system and the difference between the output voltages of the inverter corresponding to each line voltage, and the voltage maximum value of the commercial three-phase system and the maximum output voltage of the inverter. The method for controlling a grid-connected inverter according to any one of claims 7 to 10, wherein when the convergence condition that each value difference is equal to or less than a predetermined threshold is satisfied, it is determined that the matching state has been reached. .   The starting operation control step measures the line voltage before and after the grid interconnection relay, and based on the measured value, the amplitude, phase, operating frequency and commercial system voltage amplitude, phase, system frequency of the inverter output voltage 8. When it is determined that the operation mode switching step has reached a matching state, the grid interconnection relay is turned on to start the grid interconnection operation control step. The control method of the grid connection inverter in any one of from 11.   An inverter connected to a commercial three-phase system, an LC filter that removes harmonic components of the output current of the inverter, and a control device for the grid-connected inverter according to claim 1. Grid connected inverter device. A method of starting a grid-connected inverter device comprising an inverter linked to a commercial three-phase system and an LC filter that removes harmonic components of the output current of the inverter,
A starting method for a grid interconnection inverter device controlled by the control method for a grid interconnection inverter according to any one of claims 7 to 12.