JP2016178765A - System interconnection device for distributed power source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a DC component caused by an external factor in a system interconnection device for a distributed power source.SOLUTION: A system interconnection device 10 for a distributed power source comprises: an ideal current integration value calculation part 45 for calculating an integration value of a first current relating to a system power source 20 as a first integration value for a predetermined period from an AC voltage of the system power source 20; a PLL current integration value calculation part 46 for calculating an integration value of a second current relating to an output current of an inverter 13 as a second integration value for a predetermined period from the output current of the inverter 13; an integration value difference calculation part 50 for calculating a difference between the first integration value calculated by the ideal current integration value calculation part 45 and the second integration value calculated by the PLL current integration value calculation part 46 as an integration value difference; and a correction current amount calculation part 51 for calculating a correction current amount that is equal to a DC component to flow out to the output current of the inverter 13 from the integration value difference calculated by the integration value difference calculation part 50.SELECTED DRAWING: Figure 1

Description

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

  As a type of a grid interconnection device for a distributed power source, one disclosed in Patent Document 1 is known. As shown in FIG. 1 of Patent Document 1, the grid interconnection device includes a current detector 150 that operates with a single power source to detect an alternating current output toward the commercial frequency system 140, and a current detection A DC component extraction circuit 160 that operates with both power sources having the same voltage as the voltage value of a single power source of the current detector 150 in order to extract a DC component included in the AC current detected by the detector 150; A / D converter 170 that operates with a single power source having the same voltage as the voltage value of the single power source and a DC component digitized by A / D converter 170 are used to digitize the direct current component extracted by To operate a single power source having the same voltage as the voltage value of the single power source in order to calculate a feedback signal for reducing the DC component included in the alternating current output toward the commercial frequency system 140. That the CPU140, which is to have a.

JP 2014-042419 A

  In the grid interconnection device of the distributed power source described in Patent Document 1 described above, when a DC component is generated due to an external factor, for example, when the frequency fluctuation of the grid power source is repeated, the DC component is There was a possibility that it could not be reduced sufficiently.

  The present invention has been made to solve the above-described problem, and an object of the present invention is to reduce a direct current component generated by an external factor in a system interconnection device of a distributed power source.

  In order to solve the above-mentioned problems, the invention of the grid interconnection device of the distributed power source according to claim 1 is directed to a power generation device that generates DC power and can be connected to the system power source, and DC power from the power generation device. An inverter that converts AC power and outputs it to the system power supply side, a converter that boosts DC power from the power generator and outputs it to the inverter, a first voltage detection unit that detects AC voltage of the system power supply, and an output of the inverter A current detection unit that detects a current; a second voltage detection unit that detects a DC output voltage of the converter; and a control device that controls the inverter, wherein the control device is a system power supply detected by the first voltage detection unit A first integral value calculation unit that calculates an integral value of the first current related to the system power supply as a first integral value over a predetermined period, and an inverter output power detected by the current detection unit. From the second integral value calculation unit that calculates the integral value of the second current related to the output current of the inverter as a second integral value over a predetermined period, and the first integral value calculated by the first integral value calculation unit, The difference between the second integral value calculated by the second integral value calculation unit and the integral value difference calculation unit that calculates the difference as the integral value difference, and the integral value difference calculated by the integral value difference calculation unit, to the output current of the inverter. A correction current amount calculation unit that calculates a correction current amount equal to the DC component that flows out.

  According to this, the correction current amount calculation unit is based on the first integrated value (integrated value of the first current related to the system power supply) calculated over a predetermined period from the AC voltage of the system power supply and the output current of the inverter. A DC component that flows into the output current of the inverter based on the difference between the second integral value computed over the predetermined period (the second current integral value associated with the inverter output current) and the integral value computed A correction current amount equal to is calculated. As a result, the target voltage of the inverter can be calculated using this correction current amount. Therefore, it is possible to appropriately set the target voltage of the inverter in a predetermined period, and it is possible to reduce the direct current component generated by an external factor.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the outline | summary of one Embodiment of the grid connection apparatus of the distributed power source by this invention. It is a block diagram which shows the control apparatus shown in FIG. It is a block diagram which shows the control apparatus shown in FIG. It is a time chart which shows operation | movement of the grid connection apparatus 10 when the frequency of a system voltage reduces. The upper part shows the system voltage, and the lower part shows the output current. It is a time chart which shows operation | movement of the grid connection apparatus 10 when the frequency of a system voltage increases. The upper part shows the system voltage, and the lower part shows the output current.

  Hereinafter, an embodiment of a system interconnection device for a distributed power source according to the present invention will be described. As shown in FIG. 1, the grid interconnection device 10 is a device that links and disconnects a fuel cell 11 that is a power generation device and an AC grid power supply 20. The grid interconnection device 10 includes a fuel cell 11, which is a power generation device, a converter 12, an inverter 13, a smoothing circuit 14, a disconnecting relay 15, and a control device 16.

The fuel cell 11 is a power generator that generates DC power. The power generation device may be a power generation device (for example, a solar cell, a gas engine, or the like) that generates DC power other than the fuel cell 11.
The converter 12 boosts the DC power from the fuel cell 11 and outputs it to the inverter 13. The converter 12 includes a reactor, a switching element such as an IGBT (insulated gate bipolar transistor), a diode, a capacitor, and the like (not shown). An input side terminal 12 a of the converter 12 is connected to the positive side of the fuel cell 11, and an input side terminal 12 b of the converter 12 is connected to the negative side of the fuel cell 11.

The output side terminal 12 c of the converter 12 is connected to the input side terminal 13 a of the inverter 13 through the electric wire 17. The output side terminal 12 d of the converter 12 is connected to the input side terminal 13 b of the inverter 13 via the electric wire 18. A voltage sensor 31 (DC intermediate voltage sensor) that measures the output voltage (DC intermediate voltage) of the converter 12 is provided between the electric wires 17 and 18. The detection signal of the voltage sensor 31 is input to the control device 16, and the control device 16 applies a pulse signal having a duty ratio determined by performing arithmetic processing to the gate of the switching element, whereby the output voltage of the converter 12 is predetermined. Feedback control is performed to achieve a voltage of. The voltage sensor 31 (DC intermediate voltage sensor) is a second voltage detection unit that detects the DC output voltage of the converter 12.
A capacitor 19 is provided between the electric wires 17 and 18.

  The inverter 13 converts DC power from the converter 12, that is, the fuel cell 11 into AC power, and outputs the AC power to the system power supply 20 side. The inverter 13 includes input side terminals 13a and 13b and output side terminals 13c and 13d. The output side terminal 13c of the inverter 13 is connected to an electric wire 21 to which a system power source 20 (for example, U phase) is connected. The output side terminal 13d of the inverter 13 is connected to an electric wire 22 to which a system power source 20 (for example, V phase) is connected.

  The inverter 13 is configured by full-bridge connection of first to fourth switching elements 13e to 13h such as an IGBT. The first and second switching elements 13e and 13f are connected in series between the input side terminal 13a and the input side terminal 13b. A connection point between the first switching element 13e and the second switching element 13f is connected to the output side terminal 13c. The third and fourth switching elements 13g and 13h are connected in series between the input side terminal 13a and the input side terminal 13b. The third and fourth switching elements 13g and 13h are connected in parallel to the first and second switching elements 13e and 13f. A connection point between the third switching element 13g and the fourth switching element 13h is connected to the output side terminal 13d.

  The operation of the inverter 13 is controlled by the control device 16. Specifically, the inverter 13 switches the first to fourth switching elements 13e to 13h according to the PWM control from the control device 16, and converts the DC power from the converter 12 into AC power. Thus, the inverter 13 outputs the converted AC power to the electric wires 21 and 22.

  The smoothing circuit 14 includes reactors 14a and 14b and a capacitor 14c. Reactors 14a and 14b are provided on the electric wires 21 and 22, respectively. The capacitor 14 c is provided on the connection wire 23 that connects the wires 21 and 22 between the reactors 14 a and 14 b and the system power supply 20. The smoothing circuit 14 removes the high-frequency component of the AC power output from the inverter 13, changes the output voltage of the inverter 13 to a sinusoidal waveform, and outputs it to the system power supply 20.

  The disconnection relay (system interconnection relay) 15 includes a first disconnection relay 15a and a second disconnection relay 15b. The disconnection relay 15 is a switch provided in each of the electric wires 21 and 22, and is a normally open type switch disposed between a connection point with the connection electric wire 23 and the inverter 13. The first disconnecting relay 15a is disposed between a connection point with the connection electric wire 23 and the reactor 14a. The 2nd disconnection relay 15b is arrange | positioned between the connection point with the connection electric wire 23, and the reactor 14b. The operation (connected state / open state) of the first disconnecting relay 15a and the second disconnecting relay 15b is controlled by a control signal from the control device 16, respectively.

  Specifically, the first disconnecting relay 15 a is arranged on one of the electric wires 21 and 22, and the second disconnecting relay 15 b is arranged on the other electric wire 22. When the first disconnecting relay 15a and the second disconnecting relay 15b are connected, the grid interconnection device 10 and the grid power supply 20 are linked, and the first disconnecting relay 15a and the second disconnecting relay 15b are opened. Then, the grid interconnection device 10 and the grid power supply 20 are disconnected. In this way, the disconnection relay 15 is controlled by the control device 16, whereby the grid interconnection device 10 and the grid power supply 20 are linked or disconnected, and the power supply is controlled.

One of the electric wires 21 and 22 is provided with a current sensor 32 (for example, a current transformer type or a shunt type) that detects a current (reactor current) flowing through the reactor 14a (or 14b). A detection signal of the current sensor 32 is input to the control device 16. The current sensor 32 is a current detection unit (output current sensor) that detects the output current of the inverter 13.
Further, a system voltage detection circuit 33 that detects a system voltage is connected to the electric wires 21 and 22. A detection signal from the system voltage detection circuit 33 is input to the control device 16. The system voltage detection circuit 33 is a first voltage detection unit that detects an AC voltage of the system power supply 20.

  The control device 16 controls at least the inverter 13. The control device 16 includes a microcomputer (not shown), and the microcomputer includes an input / output interface, a CPU, a RAM, and a ROM (all not shown) connected through a bus. The CPU acquires detection results of the voltage sensor 31, the current sensor 32, and the system voltage detection circuit 33, controls the converter 12 and the inverter 13, and controls opening / closing of the disconnect relay 15. The RAM temporarily stores variables necessary for executing the program, and the ROM stores the program.

  2A and 2B, the control device 16 includes a voltage phase calculation unit 41, a zero-cross determination unit 42, a target output current instantaneous value calculation unit 43, a current phase calculation unit 44, an ideal current integral value calculation unit 45, a PLL. Current integrated value calculation unit 46, PLL phase calculation unit 47, reference sine wave calculation unit 48, mixer 49, integral value difference calculation unit 50, correction current amount calculation unit 51, target current calculation unit 52, correction voltage calculation unit 53, A target voltage calculator 54 and a PWM calculator 55 are provided.

The voltage phase calculation unit 41 calculates the waveform of the system voltage from the AC voltage (system voltage) of the system power supply 20 acquired from the system voltage detection circuit 33, that is, calculates the phase, frequency, etc. of the system voltage.
The zero cross determination unit 42 determines the zero cross from the waveform of the system voltage acquired from the voltage phase calculation unit 41. Zero crossing means that the system voltage becomes 0, and there are two patterns when changing from negative to positive, or changing from positive to negative.

The target output current instantaneous value calculation unit 43 calculates the target output current instantaneous value I ^Peak_lim _n of the inverter 13 from the DC intermediate voltage (detected DC intermediate voltage) output from the converter 12 acquired from the DC intermediate voltage sensor 31. Specifically, the target output current instantaneous value calculation unit 43 first calculates a DC intermediate voltage average value that is an average value of the detected DC intermediate voltages. Second, the difference between the DC intermediate voltage average value and the DC intermediate voltage target is calculated. Third, PI processing is performed based on the difference (that is, feedback control of PI operation is performed) to calculate a target output current instantaneous value. Fourth, upper / lower limit processing is performed on the target output current instantaneous value subjected to PI processing to calculate a target output current instantaneous value I ^Peak_lim _n after the upper / lower limit processing. n represents the current computation cycle, and n-1 represents the previous computation cycle.

  The current phase calculation unit 44 calculates the waveform of the inverter output current from the output current (inverter output current) of the inverter 13 acquired from the output current sensor 32, that is, calculates the phase, frequency, etc. of the inverter output current.

The ideal current integral value calculation unit 45 acquires the system voltage waveform from the voltage phase calculation unit 41, acquires information about zero cross from the zero cross determination unit 42, and the target output current instantaneous value I from the target output current instantaneous value calculation unit 43. ^Peak_lim _n is acquired, and the integrated value of the first current related to the system power supply 20 is calculated as a first integrated value over a predetermined period from these (first integrated value calculating unit). That is, the ideal current integrated value calculation unit 45 calculates by integrating the area of the ideal current waveform corresponding to the voltage phase of the system power supply 20 for a predetermined period. An ideal current waveform is represented by I ^Peak_lim _n × sin (θ). θ is the phase of the system voltage.

  The predetermined period is set to a period corresponding to a half period or one period of the system voltage from the time when the system voltage detected by the system voltage detection circuit 33 changes from negative to positive or from positive to negative (that is, zero crossing time). Yes. In the present embodiment, the predetermined period is set to a half cycle of the system voltage from the time when the system voltage changes from negative to positive.

ここで、Angle^V_start _ｎは、積分を開始する位相（開始位相）であり、ゼロクロス時点の系統電圧の位相である。Angle^V_End _ｎは、積分を終了する位相（終了位相）であり、開始位相Angle^V_start _ｎに系統電圧の半周期分（π：１８０度）を加算した値である。 The ideal current integral value calculation unit 45 calculates the area I ^sum_base _n of the ideal current waveform, which is the first integral value, using the following equation (1).

Here, Angle ^V_start _n is a phase (start phase) at which integration is started, and is a phase of the system voltage at the time of zero crossing. Angle ^V_End _n is a phase (end phase) for ending the integration, and is a value obtained by adding a half cycle (π: 180 degrees) of the system voltage to the start phase Angle ^V_start _n .

The PLL current integral value calculation unit 46 acquires the waveform of the inverter output current from the current phase calculation unit 44, acquires information about the zero cross from the zero cross determination unit 42, and the target output current instantaneous value from the target output current instantaneous value calculation unit 43. I ^Peak_lim _n is acquired, and the integrated value of the second current related to the inverter output current is calculated as a second integrated value over a predetermined period from these (second integrated value calculation unit). In other words, the PLL current integral value calculation unit 46 calculates by integrating the area of the actual current waveform of the inverter output current for a predetermined period. The actual current waveform is represented by I ^Peak_lim _n × sin (φ). φ is the phase of the inverter output current.

  The predetermined period is set to a period corresponding to a half period or one period of the system voltage from the time when the system voltage detected by the system voltage detection circuit 33 changes from negative to positive or from positive to negative (that is, zero crossing time). Yes. In the present embodiment, the predetermined period is set to a half cycle of the system voltage from the time when the system voltage changes from negative to positive.

ここで、Angle^PLL _ｎは、積分を開始するインバータ出力電流の位相（開始位相）であり、ゼロクロス時点のインバータ出力電流の位相である。Angle^V_End _ｎは、積分を終了するインバータ出力電流の位相（終了位相）であり、上述した系統電圧の終了位相と同一の位相である。 The PLL current integral value calculation unit 46 calculates the area I ^sum_PLL _n of the actual current waveform, which is the second integral value, by the following formula 2.

Here, Angle ^PLL _n is the phase (starting phase) of the inverter output current at which integration is started, and is the phase of the inverter output current at the time of zero crossing. Angle ^V_End _n is the phase (end phase) of the inverter output current that ends the integration, and is the same phase as the end phase of the system voltage described above.

The PLL phase calculation unit 47 acquires the system voltage waveform (phase) from the voltage phase calculation unit 41, acquires the PLL reference frequency, and calculates the current phase (basic PLL phase Angel ^PLL _n-1 ) in the previous calculation cycle. And the basic PLL phase Angel ^PLL _n is calculated from them. The PLL phase calculation unit 47 calculates the current phase in order to synchronize the phase of the output current with the phase of the system voltage. The PLL is a Phase Locked Loop, and is to generate an output signal (inverter output current) synchronized with an input signal (system voltage). The PLL reference frequency is a reference frequency for PLL control and is set to a predetermined frequency.

  The PLL phase calculation unit 47 can also acquire the reactive power phase and add the reactive power phase to calculate the basic PLL phase. The reactive power is the power required for reactance in the impedance of the load circuit, and the reactive power increases as the power factor decreases. The reactive power phase can be calculated as follows. The effective power P is apparent power (= current effective value I × voltage effective value E) × cos α, and cos α = P / (I × E). The reactive power phase α can be calculated from this cos α. The effective current value I can be calculated from the instantaneous value of the inverter output current. The effective voltage value E can be calculated from the output voltage of the inverter 13. When the instantaneous current value I is positive, the reactive power phase α is a leading phase, and when it is negative, the reactive power phase α is a lagging phase.

Reference sine wave calculating unit 48 obtains the basic PLL phase Angel ^PLL _n from the PLL phase calculating unit 47 calculates a fundamental sine wave S _base from the basic PLL phase Angel ^PLL _n.
The mixer 49 acquires the target output current instantaneous value I ^Peak_lim _n from the target output current instantaneous value calculation unit 43, acquires the basic sine wave S _base from the reference sine wave calculation unit 48, and _{generates the} basic output current I _{inv_ref} from these. Calculate.

なお、前回演算周期において演算された積分値差I^ｓｑ _ｎ−１を考慮するようにしてもよい。この場合、上記数３の右辺に積分値差I^ｓｑ _ｎ−１を加算すればよい。 The integral value difference calculator 50 calculates the difference between the first integral value I ^sum_base _n acquired from the ideal current integral value calculator 45 and the second integral value I ^sum_PLL _n acquired from the PLL current integral value calculator 46 as an integral value difference. Calculation is performed as I ^sq _n (integral value difference calculation unit). The integral value difference calculation unit 50 calculates the integral value difference I ^sq _{n according} to the following formula 3. The integrated value difference I ^sq _n is an area difference for a predetermined period between the area of the ideal current waveform and the area of the actual current waveform of the inverter output current. This area difference corresponds to the correction current area. This correction current area is a direct current component generated and superimposed by an external factor.

Note that the integral value difference I ^sq _n−1 calculated in the previous calculation cycle may be taken into consideration. In this case, the integral value difference I ^sq _n−1 may be added to the right side of the above equation 3.

ここで、ｆ^PLL_base _ｎは、ＰＬＬ基準周波数である。ｔｃは、インバータ１３のキャリア周期である。ＰＬＬ基準周波数は、ＰＬＬ制御のための基準周波数であり、所定周波数に設定されている。ＰＬＬ制御は、出力電流の位相を系統電圧の位相と同期させる位相同期制御である。 The correction current amount calculation unit 51 calculates a correction current amount ΔI ^sq _n equal to the direct current component flowing into the inverter output current from the integral value difference I ^sq _n acquired from the integral value difference calculation unit 50 (correction current amount calculation unit ). The correction current amount calculation unit 51 calculates the correction current amount ΔI ^sq _n by the following formula 4.

Here, f ^PLL_base _n is a PLL reference frequency. tc is the carrier period of the inverter 13. The PLL reference frequency is a reference frequency for PLL control, and is set to a predetermined frequency. The PLL control is phase synchronization control that synchronizes the phase of the output current with the phase of the system voltage.

The target current calculation unit 52 calculates the target current (inverter target current) I _{inv_est} of the inverter 13 from the output current (inverter output current) I _{inv_out} of the inverter 13 acquired from the output current sensor 32.
The correction voltage calculation unit 53 calculates the correction voltage V ^PI _n of the inverter 13 from the correction current amount ΔI ^sq _n acquired from the correction current amount calculation unit 51 and the inverter target current I _{inv_est} acquired from the target current calculation unit 52. To do. For example, the correction voltage calculation unit 53 calculates the correction voltage V ^PI _n by performing PI processing on the difference between the correction current amount ΔI ^sq _n and the inverter target current I _{inv_est} and further performing upper and lower limit processing.

The target voltage calculation unit 54 includes the inverter output current I _{inv_out} acquired from the output current sensor 32, the basic output current I _{inv_ref} acquired from the mixer 49, and the correction voltage V ^PI _n acquired from the correction voltage calculation unit 53. The target voltage V _inv of the inverter 13 is calculated. For example, the target voltage calculation unit 54 calculates a basic output voltage from the inverter output current I _{inv_out} and the basic output current I _{inv_ref,} and the target voltage V _{inv of the} inverter 13 from the basic output voltage and the correction voltage V ^PI _n. Is calculated.

The PWM calculation unit 55 calculates a pattern of PWM control to the first to fourth switching elements 13e to 13h so that the target voltage V _inv acquired from the target voltage calculation unit 54 is obtained. The pattern is a combination pattern of on / off of the first to fourth switching elements 13e to 13h, a pattern of on / off time (duty), or the like. The PWM calculation unit 55 transmits the calculated PWM control pattern to the inverter 13 for control.

Next, the operation of the grid interconnection device 10 described above will be described with reference to FIGS. First, a case where the frequency of the system voltage is reduced will be described with reference to FIG. At time t1, the frequency of the system voltage decreases from f (m) to f (m−1). Until the time t1, the system voltage and the output current have the same frequency (f (m)) and the same phase. Time t1 is a zero cross timing. In the period from time t0 is a timing of the last zero crossing to time t1 (the predetermined period), the area ^I sum_PLL _n actual current waveform and the area ^I sum_base _n of the ideal current waveform are identical area, the area difference DC component is not generated. That is, the area difference (integral value difference) I ^sq _n is 0, and the correction current amount ΔI ^sq _n is 0. Therefore, the output current is not corrected from time t1 to time t2.

At time t2, which is the next zero crossing timing, the area difference in the period (predetermined period) from time t1 to time t2 is calculated. At this time, the area S1 of the system voltage is larger than the area S2 of the output current. A value ΔS (= S1−S2) obtained by subtracting the area S2 of the output current from the area S1 of the system voltage is larger than zero. The area S1 is an area I ^sum_base _n of an ideal current waveform. The area S2 is the area I ^sum_PLL _n of the actual current waveform. ΔS is the integral value difference I ^sq _n .
At this time, the output current is output following the phase of the system voltage, but if the phase is delayed, the direct current component is included in the current output due to the accuracy of the sensor or timer. This DC component is the integral value difference I ^sq _n .

Further, at time t2, the correction current amount ΔI ^sq _n is calculated. Then, from the time t2 to the next zero crossing timing, the output current (indicated by a broken line) is corrected so as to be reduced by the correction current amount ΔI ^sq _n . Thereby, the zero cross timing of the system voltage and the zero cross timing of the output current can be synchronized, and the generated DC component can be canceled.

Next, a case where the frequency of the system voltage is increased will be described with reference to FIG. At time t11, the frequency of the system voltage increases from f (m) to f (m + 1). Until time t11, the system voltage and the output current have the same frequency (f (m)) and the same phase. Time t11 is a zero-cross timing. In the period from time t0 is a timing of the last zero-crossing to the time t11 (the predetermined period), the area ^I sum_PLL _n actual current waveform and the area ^I sum_base _n of the ideal current waveform are identical area, the area difference DC component is not generated. That is, the area difference (integral value difference) I ^sq _n is 0, and the correction current amount ΔI ^sq _n is 0. Therefore, the output current is not corrected from time t11 to time t12.

At time t12, which is the next zero-cross timing, the area difference in the period (predetermined period) from time t11 to time t12 is calculated. At this time, the area S1 of the system voltage is smaller than the area S2 of the output current. A value ΔS (= S1−S2) obtained by subtracting the area S2 of the output current from the area S1 of the system voltage is smaller than zero. The area S1 is an area I ^sum_base _n of an ideal current waveform. The area S2 is the area I ^sum_PLL _n of the actual current waveform. ΔS is the integral value difference I ^sq _n .
At this time, the output current is output following the phase of the system voltage, but if the phase is delayed, the direct current component is included in the current output due to the accuracy of the sensor or timer. This DC component is the integral value difference I ^sq _n .

Further, at time t12, the correction current amount ΔI ^sq _n is calculated. Then, from the time t12 to the next zero crossing timing, the output current (indicated by a broken line) is corrected so as to be increased by the correction current amount ΔI ^sq _n . Thereby, the zero cross timing of the system voltage and the zero cross timing of the output current can be synchronized, and the generated DC component can be canceled.

  As is clear from the above description, the grid interconnection device 10 of the distributed power source generates a DC power and can be linked to the grid power source 20, and the DC from the fuel cell 11. An inverter 13 that converts electric power into AC power and outputs it to the system power source 20 side, a converter 12 that boosts DC power from the fuel cell 11 and outputs it to the inverter 13, and a system voltage that detects the AC voltage of the system power source 20 A detection circuit 33 (first voltage detection unit), a current sensor 32 (current detection unit) that detects an output current of the inverter 13, and a voltage sensor 31 (second voltage detection unit) that detects a DC output voltage of the converter 12. And a control device 16 for controlling the inverter 13. The control device 16 calculates an ideal current integration value that calculates, from the AC voltage of the system power supply 20 detected by the system voltage detection circuit 33, the integration value of the first current related to the system power supply 20 as a first integration value over a predetermined period. Based on the output current of the inverter 13 detected by the calculation unit 45 (first integration value calculation unit) and the current sensor 32, an integrated value of the second current related to the output current of the inverter 13 over a predetermined period is obtained as a second integral value. PLL current integral value computing unit 46 (second integral value computing unit), first integral value computed by ideal current integral value computing unit 45, and second integral computed by PLL current integral value computing unit 46 An integral value difference computing unit 50 that computes the difference from the value as an integral value difference, and a DC component that flows out to the output current of the inverter 13 from the integral value difference computed by the integral value difference computing unit 50 A correction current amount calculation unit 51 for calculating a positive current amount, and a.

  According to this, the correction current amount calculation unit 51 includes the first integrated value (the integrated value of the first current related to the system power supply 20) calculated over a predetermined period from the AC voltage of the system power supply 20 and the inverter 13. Output of the inverter 13 based on the second integrated value calculated over the predetermined period (the integrated value of the second current related to the output current of the inverter 13) and the integrated value difference calculated from the output current of A correction current amount equal to the direct current component flowing into the current is calculated. As a result, the target voltage of the inverter 13 can be calculated using this correction current amount. Therefore, the target voltage of the inverter 13 can be appropriately set at a predetermined period, and as a result, the direct current component generated by an external factor can be reduced.

Further, the predetermined period is a half cycle of the AC voltage of the system power supply 20 from the time when the AC voltage of the system power supply 20 detected by the system voltage detection circuit 33 changes from negative to positive or from positive to negative (zero cross timing). Or it is set to a period of one cycle.
According to this, the calculation of the target voltage of the inverter 13 can be started at an appropriate timing and can be performed for an appropriate period, and as a result, the correction current amount can be calculated accurately and accurately.
In particular, when the predetermined period is set to a period corresponding to a half cycle, the direct current component flowing out to the system power supply 20 side can be reduced with high responsiveness. Further, when the predetermined period is set to a period corresponding to one cycle, the calculation volume can be reduced, and the calculation speed can be improved. Further, when the fluctuation of the system voltage is stable, the correction current amount can be calculated more accurately.

  In the above-described embodiment, the start time of the predetermined period is set to the zero-cross timing, but may be set to a time when the reactive power phase changes by a predetermined angle or more. In this case, a reactive power phase change determination unit may be provided instead of the zero-cross determination unit 42. As described above, the reactive power phase change determination unit can calculate the reactive power phase α from the active power P, the current effective value I, and the voltage effective value E. The reactive power phase change determination unit determines whether or not the calculated reactive power phase α is equal to or greater than a predetermined angle. The result is output to the ideal current integral value calculation unit 45 and the PLL current integral value calculation unit 46.

That is, the predetermined period may be set to a period corresponding to a half cycle or one cycle of the AC voltage of the system power supply 20 from the time when the reactive power phase changes by a predetermined angle or more.
According to this, the calculation of the target voltage of the inverter 13 can be started at an appropriate timing and can be performed for an appropriate period, and as a result, the correction current amount can be calculated accurately and accurately.

  In the above-described embodiment, the predetermined period is set to a period corresponding to a half cycle of the system voltage. However, the predetermined period is not set to a half period, but set to a period corresponding to one period of the system voltage. Also good.

Moreover, in embodiment mentioned above, it can respond also when changing a power factor. In this case, the start point of the predetermined period is as described above, but the end point of the predetermined period is a phase considering the phase difference to be adjusted, that is, the power factor improving current phase. The power factor correction current phase can be calculated from the target output current instantaneous value I ^Peak_lim _n .

  DESCRIPTION OF SYMBOLS 10 ... Grid connection apparatus, 11 ... Fuel cell (power generation device), 12 ... Converter, 13 ... Inverter, 14 ... Smoothing circuit, 14a, 14b ... Reactor, 14c ... Capacitor, 15 ... Disconnection relay (switch), 16 ... Control device, 31 ... Voltage sensor (second voltage detection unit), 32 ... Current sensor (current detection unit), 33 ... System voltage detection circuit (first voltage detection unit), 41 ... Voltage phase calculation unit, 42 ... Zero cross Determining unit, 43 ... target output current instantaneous value calculating unit, 44 ... current phase calculating unit, 45 ... ideal current integrated value calculating unit (first integrated value calculating unit), 46 ... PLL current integrated value calculating unit (second integrated value) Calculation unit) 47 ... PLL phase calculation unit 48 ... Reference sine wave calculation unit 49 ... Mixer 50 ... Integral value difference calculation unit 51 ... Correction current amount calculation unit 52 ... Target current calculation unit 53 ... Correction Voltage calculation unit, 54 ... target voltage Calculation unit, 55 ... PWM calculation section.

Claims (3)

A generator that generates direct-current power and can be connected to a system power supply;
An inverter that converts the DC power from the power generator into AC power and outputs the AC power to the system power supply side;
A converter that boosts the DC power from the power generation device and outputs the boosted DC power to the inverter;
A first voltage detector for detecting an AC voltage of the system power supply;
A current detector for detecting an output current of the inverter;
A second voltage detector for detecting a DC output voltage of the converter;
A control device for controlling the inverter,
The control device includes:
A first integral value computing unit that computes an integral value of a first current related to the system power supply as a first integral value over a predetermined period from the AC voltage of the system power supply detected by the first voltage detection unit;
A second integrated value calculation unit that calculates an integral value of a second current related to the output current of the inverter over the predetermined period from the output current of the inverter detected by the current detection unit;
An integral value difference computing unit that computes a difference between the first integral value computed by the first integral value computing unit and the second integral value computed by the second integral value computing unit as an integral value difference;
A correction current amount calculation unit that calculates a correction current amount equal to a direct current component flowing into the output current of the inverter from the integral value difference calculated by the integral value difference calculation unit;
A distributed power grid interconnection device comprising:   The predetermined period is a half period or one period of the AC voltage of the system power supply from the time when the AC voltage of the system power supply detected by the first voltage detector changes from negative to positive or from positive to negative. The system interconnection apparatus of the distributed power supply according to claim 1, which is set for a period.   2. The distributed power grid interconnection according to claim 1, wherein the predetermined period is set to a period corresponding to a half cycle or one cycle of the AC voltage of the grid power supply from the time when the reactive power phase changes by a predetermined angle or more. apparatus.

Images