JP5906458B2 - Power conditioner and power generation system including the same - Google Patents

Description

  The present invention relates to a power conditioner and a power generation system including the same.

  Conventionally, a technique for extracting DC power from a plurality of solar cells and converting it to AC power is known (see, for example, Patent Document 1).

JP 2000-1161010 A

  FIG. 8 shows control signals input to a plurality of DC boost circuits (DC / DC converter devices) and inductor current waveforms in the device disclosed in Patent Document 1. In the figure, it is assumed that four solar cell panels and a DC booster circuit are connected. A rectangular wave pulse signal is input as a control signal to the gate of the switching element constituting the DC booster circuit, and a triangular wave inductor current is output by switching of the switching element. However, in each booster circuit, when the signal input to the gate is switched from off to on and from on to off, a switching surge occurs, causing conduction noise and radiation noise.

  The control signal for the DC booster circuit is generated by the control circuit. In the conventional power conditioner, the ON / OFF timing of the control signal input to each DC booster circuit is not particularly linked. Therefore, as shown in FIG. 8, if the ON timings or the OFF timings overlap each other in each DC booster circuit, a surge occurs simultaneously in each DC booster circuit, causing a large noise. The same applies to the case where the on timing of one of the DC boost circuits overlaps with the off timing of another DC boost circuit.

  The present invention has been made to solve the above-described problem, and an object of the present invention is to provide a power conditioner that can avoid the occurrence of surges simultaneously in each DC booster circuit and reduce noise generated by the surges. And

In order to achieve the above object, a power conditioner according to the present invention includes a plurality of DC voltage conversion units that convert a DC voltage input from a solar cell into a predetermined DC voltage, and output terminals of the plurality of DC voltage conversion units. A DC / AC converter connected to each other and connected to an input terminal thereof for converting DC power input to the input terminal into AC power, and a switching controller for controlling switching of the plurality of DC voltage converters. In the power conditioner, the switching control unit shifts the switching phase of each DC voltage conversion unit to switch the plurality of DC voltage conversion units at a constant switching frequency, and performs the maximum power point tracking control. the switching of on-duty of the DC voltage converter controls individually switching the plurality of DC voltage converters In which the ON period of the controls to overlap.

In this invention, it is preferable that the switching control unit shifts the switching phase so that the switching on timings of the DC voltage converting units are equally spaced .

In this invention, it is preferable that the switching control unit shifts the switching phase so that an interval of switching ON timing of each of the DC voltage conversion units is maximized .

In this invention, it is preferable that the switching control unit controls the switching ON timing so that the switching ON timing and the OFF timing of each DC voltage converter do not overlap .

Another power conditioner of the present invention includes a first DC voltage converter that converts a DC voltage input from a solar battery into a predetermined DC voltage, and converts a DC voltage input from the solar battery into a predetermined DC voltage. The second DC voltage converter, the output terminals of the first DC voltage converter and the second DC voltage converter are connected to each other and connected to the input terminal, and the DC power input to the input terminal is In a power conditioner including a DC / AC converter that converts AC power, and a switching controller that controls switching of the first DC voltage converter and the second DC voltage converter, the switching controller includes: The switching phases of the first DC voltage converter and the second DC voltage converter are shifted to switch the first DC voltage converter and the second DC voltage converter at a constant switching frequency. And separately controlling the on-duty of switching of the first DC voltage conversion unit and the second DC voltage conversion unit so as to perform the maximum power point tracking control, and the first DC voltage conversion unit and the second DC voltage conversion unit Control is performed so that the ON periods of switching of the DC voltage converter are overlapped.

  According to the power conditioner of the present invention, it is possible to avoid the occurrence of a surge in each booster circuit at the same time, and to reduce the noise generated by the surge.

The block diagram which shows the structure of the electric power generation system by one Embodiment of this invention. The block diagram which shows the structure of the power conditioner by one Embodiment of this invention. The figure which shows the waveform of the control signal which a control circuit each inputs into each DC booster circuit, and the waveform of the inductor current of each DC booster circuit. The figure which shows the waveform of the modification of the control signal which a control circuit inputs into each DC booster circuit, respectively, and the waveform of the inductor current of each DC booster circuit. The figure which shows the waveform of another modification of the control signal which a control circuit each inputs into each DC boost circuit, and the waveform of the inductor current of each DC boost circuit. The figure which shows the waveform of another modification of the control signal which a control circuit each inputs into each DC boost circuit, and the waveform of the inductor current of each DC boost circuit. The figure which shows the waveform of another modification of the control signal which a control circuit each inputs into each DC boost circuit, and the waveform of the inductor current of each DC boost circuit. The figure which shows the waveform of the control signal each input into each DC booster circuit, and the inductor current waveform of each DC booster circuit in the conventional power conditioner.

  A power conditioner according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration of a power generation system including a power conditioner. The power generation system 100 includes a plurality of systems of solar battery panels (DC power input units) 50a, 50b, 50c, 50d, a power conditioner 1, a distribution board 60, and the like.

  Solar cell panels 50a, 50b, 50c, and 50d are installed on the roof of a building or the like and output DC power. The power conditioner 1 converts the DC power generated by the solar cell panels 50a, 50b, 50c, and 50d into AC power and outputs the AC power to the distribution board 60. The distribution board 60 is connected to a load 65, a system power supply, and the like. The load 65 is, for example, an electric device such as a home appliance, and the system power supply is a commercial power system. The distribution board 60 supplies the AC power input from the power conditioner 1 to the load 65. When the AC power input from the power conditioner 1 is larger than the power consumption of the load 65, the distribution board 60 reversely flows surplus power to the system power supply via a power sale meter (not shown). Note that a storage battery may be connected to the distribution board 60 via a converter / inverter as necessary.

  The power conditioner 1 includes a plurality of DC boosting circuits (DC voltage conversion units) 2a, 2b, 2c, 2d, an inverter circuit 3, a control circuit (switching control unit) 4, and the like.

  DC boosting circuits 2a, 2b, 2c and 2d are connected to solar cell panels 50a, 50b, 50c and 50d, respectively. The DC booster circuit is provided according to the number of systems (number of strings) of the solar battery panel. That is, by increasing / decreasing the number of DC boosting circuits, it is possible to cope with the case where the number of systems of solar battery panels is different. The output terminals of the DC boost circuits 2a, 2b, 2c, and 2d are connected in parallel to each other (see FIG. 2) and connected to the input terminal of the inverter circuit 3. The DC boosting circuits 2a, 2b, 2c, 2d boost-convert the DC voltage input from the solar battery panels 50a, 50b, 50c, 50d into a predetermined DC voltage. For example, the DC boosting circuits 2a, 2b, 2c, and 2d boost the input voltage DC250V to the output voltage DC320V.

  The inverter circuit 3 converts the DC power output from the DC boosting circuits 2a, 2b, 2c, and 2d into AC power. The output end of the inverter circuit 3 is connected to the input end of the distribution board 60 via a grid interconnection unit (not shown) constituted by a relay or the like.

  The control circuit 4 controls the DC boost circuits 2a, 2b, 2c, 2d, the inverter circuit 3, and a relay (not shown). For example, the control circuit 4 controls the on-duty of the switching elements constituting the DC boost circuits 2a, 2b, 2c, 2d based on the output voltages of the DC boost circuits 2a, 2b, 2c, 2d.

  FIG. 2 shows the configuration of the power conditioner 1. The DC booster circuit 2a is a booster chopper circuit that includes a capacitor C, an inductor L, a switching element S such as an FET, a diode D, and the like. The switching element S performs a switching operation according to the gate signal input from the control circuit 4. In the power conditioner 1 performing the maximum power point tracking control, the DC voltage (input voltage) input from the solar cell panel 50a to the DC booster circuit 2a is the specification of the solar cell panel constituting the solar cell panel 50a (P -V characteristics) and the number of connected in series. On the other hand, the DC voltage (output voltage) output from the DC booster circuit 2 a to the inverter circuit 3 is set so as to correspond to the specifications of the inverter circuit 3. The control circuit 4 drives the switching element S with an on-duty calculated from the input voltage and the output voltage.

  The DC booster circuits 2b, 2c, and 2d are also equivalent to the DC booster circuit 2a, and thus description thereof is omitted. Usually, solar cell panels of the same specification and number are applied to the solar cell panels 50a, 50b, 50c, 50d of each system. Therefore, the on-duties of the gate signals input from the control circuit 4 to the switching elements S of the respective DC boost circuits 2a, 2b, 2c, and 2d are equal. Hereinafter, a case where an equivalent on-duty gate signal is input to the switching element S of the DC booster circuits 2a, 2b, 2c, and 2d will be described. In addition, when the solar cell panel of a different specification is applied to the solar cell panels 50a, 50b, 50c, 50d of each system, it is input to the switching element S of each DC booster circuit 2a, 2b, 2c, 2d. The on-duty of the gate signal is a value calculated individually. Further, even when the number of solar cell panels constituting the solar cell panels 50a, 50b, 50c, 50d of each system is different, the signals are input to the switching elements S of the DC boosting circuits 2a, 2b, 2c, 2d. The on-duty of the gate signal is a value calculated individually.

  In the present embodiment, the control circuit 4 outputs control signals for the switching elements S of the respective DC boosting circuits 2a, 2b, 2c, and 2d so that the switching timing does not overlap. Therefore, independent signal lines are provided at the gates of the switching elements S from the control circuit 4 to the DC boosting circuits 2a, 2b, 2c, and 2d.

  FIG. 3 shows waveforms of control signals input to the DC boost circuits 2a, 2b, 2c, and 2d by the control circuit 4 and inductor current waveforms of the DC boost circuits 2a, 2b, 2c, and 2d in this embodiment. . In each DC booster circuit 2a, 2b, 2c, 2d, a rectangular wave pulse (gate signal) is input to the gate of the switching element S. The frequencies (switching frequencies) of the gate signals input to the DC boost circuits 2a, 2b, 2c, and 2d are equal to F0.

  In the control shown in FIG. 3, the control circuit 4 shifts the phases of the gate signals input to the DC boost circuits 2a, 2b, 2c, and 2d, respectively. That is, the phase (switching phase) of the gate signal is shifted so that the timing at which the gate signal is switched from OFF to ON (rising of the pulse: ON timing) differs for each DC booster circuit 2a, 2b, 2c, 2d. Yes. Accordingly, the timing at which the gate signal switches from on to off (pulse fall: off timing) also differs for each DC booster circuit 2a, 2b, 2c, 2d.

  Further, in the DC boosting circuits 2a, 2b, 2c, and 2d, the phase of the gate signal is shifted so that the ON timing of the switching element S is equally spaced in one cycle. That is, a gate signal delayed by time ΔT is input to the DC booster circuit 2b with respect to the DC booster circuit 2a. Similarly, a gate signal delayed by time ΔT with respect to the DC boost circuit 2b is input to the DC boost circuit 2c, and a gate signal delayed by time ΔT with respect to the DC boost circuit 2c is input to the DC boost circuit 2c. Entered.

  As described above, the on-duty of the gate signal input to the switching element S of the DC boost circuits 2a, 2b, 2c, 2d depends on the input voltage and the output voltage of the DC boost circuits 2a, 2b, 2c, 2d. It is calculated and is equivalent between each DC booster circuit. Therefore, the on-timing and off-timing of the switching element S of each DC booster circuit 2a, 2b, 2c, 2d can be calculated according to the frequency F0 of the switching element S. Thus, by appropriately setting the frequency F0 of the switching element S, the ON timings overlap, the OFF timings overlap, and the ON timings and OFF timings overlap between the DC boost circuits 2a, 2b, 2c, 2d. Can be prevented. Even when the on-duty of the gate signal is different between the DC boost circuits, the control circuit 4 determines the ON timing of the switching elements S of the DC boost circuits 2a, 2b, 2c, and 2d from the on-duty and the switching frequency F0. In addition, the off timing can be calculated. Therefore, the control circuit 4 does not cause the ON timings to overlap between the DC boosting circuits 2a, 2b, 2c, and 2d, the OFF timings to overlap, and the ON timings to the OFF timings so as not to overlap. The frequency F0 is set.

  As described above, according to the power conditioner 1 of the present embodiment, it is possible to avoid the occurrence of a surge at each DC booster circuit 2a, 2b, 2c, 2d, and to disperse and average the noise generated by the surge. To be reduced.

  In particular, the control circuit 4 shifts the phases of the gate signals input to the DC boost circuits 2a, 2b, 2c, and 2d, respectively, so that the ON timings of the switching elements S are dispersed so as not to overlap. As a result, it is possible to avoid the occurrence of surges simultaneously at the ON timing in each booster circuit, and to reduce the noise generated by the surges. Moreover, since the switching elements S are distributed so that the off timings do not overlap, it is possible to avoid the occurrence of a surge at the time of the off timing in each booster circuit, and to reduce the noise generated by the surge.

  Further, in the DC boosting circuits 2a, 2b, 2c and 2d, the switching elements S are driven at the same switching frequency F0, and the ON timings of the switching elements S are equally spaced in one switching cycle. The phase is shifted. Thereby, the ON timings of the switching elements S can be distributed so as not to overlap each other, and it is possible to avoid the occurrence of a surge simultaneously at the ON timing in each booster circuit, and to reduce the noise generated by the surge.

  Further, since it is possible to prevent the ON timings between the DC boost circuits 2a, 2b, 2c, and 2d, the overlap between the OFF timings, and the overlap between the ON timing and the OFF timing, noise generated by a surge can be further reduced. it can.

  Note that, as shown in FIG. 3 and the like, the noise superimposed on the inductor current requires an appropriate time from its generation to convergence. Therefore, it is desirable that the timing overlap does not overlap in all the time required from the generation of noise to convergence. However, depending on the number of systems of the solar battery panel and the DC booster circuit constituting the power conditioner 1, it may not be possible to control the timing so as not to overlap in all the time required from the generation of noise to convergence. In such a case, it is also effective to control so that the above timing does not overlap in a part of time required from the generation of noise to convergence. This is because the noise superimposed on the inductor current can be partially dispersed.

  FIG. 4 shows a waveform of a modified example of the control signal input to each DC booster circuit 2a, 2b, 2c, 2d by the control circuit 4 and the inductor current of the DC booster circuits 2a, 2b, 2c, 2d in this embodiment. The waveform is shown. In this modification, the control circuit 4 shifts the phase of the gate signal so that the ON timing intervals of the DC booster circuits 2a, 2b, 2c, and 2d are maximized at equal intervals. That is, the control circuit 4 inputs a gate signal whose phase is shifted by 1 / 4F0 to each of the DC boosting circuits 2a, 2b, 2c, and 2d. When the number of systems of the solar battery panel and the DC booster circuit is n, if the control circuit 4 inputs a gate signal whose phase is shifted by 1 / nF0 to each DC booster circuit, switching of each DC booster circuit is performed. The on-timing interval is maximized at equal intervals.

  According to this modification, since the intervals of the switching on timing of each DC booster circuit are distributed so as to be maximized, the surge generated at the on timing in each booster circuit is dispersed, and the noise generated by the surge is reduced. Is done.

  FIG. 5 shows a waveform of another modified example of a control signal input to each DC booster circuit 2a, 2b, 2c, 2d by the control circuit 4 and the DC booster circuits 2a, 2b, 2c, 2d in this embodiment. The waveform of an inductor current is shown. In this modification, the switching frequency of the switching element S in each DC booster circuit 2a, 2b, 2c, 2d is shifted. In particular, in this modification, the control circuit 4 inputs gate signals having different switching frequencies F0, F1, F2, and F3 for the respective DC boosting circuits 2a, 2b, 2c, and 2d. The switching frequencies F0, F1, F2, and F3 in the DC boost circuits 2a, 2b, 2c, and 2d are fixed without fluctuation.

  According to this modification, since the on-timing and off-timing between the DC boosting circuits 2a, 2b, 2c, 2d are distributed, the surge generated at the on-timing in each boosting circuit is dispersed and generated by the surge. Noise is reduced.

  FIG. 6 shows a waveform of another modified example of the control signal input to each DC booster circuit 2a, 2b, 2c, 2d by the control circuit 4 and the DC booster circuits 2a, 2b, 2c, 2d in this embodiment. The waveform of the output inductor current is shown. Also in this modification, the switching frequency of the switching element S in each DC booster circuit 2a, 2b, 2c, 2d is shifted. In particular, in the present modification, the control circuit 4 outputs the pulses of the switching frequencies F0, F1, F2, and F3 that fluctuate as gate signals in the DC boost circuits 2a, 2b, 2c, and 2d. The switching frequency is varied by, for example, frequency jitter control. The control circuit 4 varies the switching frequencies F0, F1, F2, and F3 at the same switching frequency for each of the DC boost circuits 2a, 2b, 2c, and 2d. The control circuit 4 varies the switching frequencies F0, F1, F2, and F3 so as to circulate periodically.

  That is, in the first switching, the control circuit 4 inputs a pulse having the switching frequency F0 as a gate signal to each of the DC boosters 2a, 2b, 2c, and 2d. Thereafter, the switching frequency of the gate signal input to each DC booster circuit 2a, 2b, 2c, 2d fluctuates as F1, F2, F3 for each switching, returns to F0, and circulates in the same manner. In each switching, the switching elements S of the DC boost circuits 2a, 2b, 2c, 2d operate at the same switching frequency, so that the DC boost circuits 2a, 2b, 2c, 2d are not overlapped with each other. The initial phase is shifted between.

  According to this modification, since the on-timing and off-timing between the DC boosting circuits 2a, 2b, 2c, 2d are distributed, the surge generated at the on-timing in each boosting circuit is dispersed and generated by the surge. Noise is reduced. Further, since the switching frequency of each DC booster circuit 2a, 2b, 2c, 2d varies, in each DC booster circuit 2a, 2b, 2c, 2d, noise of harmonic components having the switching frequency as a fundamental wave is reduced. Can do.

  FIG. 7 shows another modified example of the control signals input to the DC boost circuits 2a, 2b, 2c and 2d by the control circuit 4 and the DC boost circuits 2a, 2b, 2c and 2d in this embodiment. The waveform of an inductor current is shown. Also in this modification, the switching frequency of the switching element S in each DC booster circuit 2a, 2b, 2c, 2d is shifted. In particular, in the present modification, the control circuit 4 inputs, as gate signals, pulses of switching frequencies F0, F1, F2, and F3 that fluctuate in the DC boosting circuits 2a, 2b, 2c, and 2d. The switching frequency is varied by, for example, frequency jitter control. The control circuit 4 changes the switching frequencies F0, F1, F2, and F3 at different switching frequencies for each of the DC boost circuits 2a, 2b, 2c, and 2d. The control circuit 4 varies the switching frequencies F0, F1, F2, and F3 so as to circulate periodically.

  That is, in the first switching, the control circuit 4 inputs pulses of the switching frequencies F0, F1, F2, and F3 as gate signals to the DC boosters 2a, 2b, 2c, and 2d, respectively. In the next switching, the control circuit 4 inputs pulses of the switching frequencies F1, F2, F3, and F0 as gate signals to the DC boost circuits 2a, 2b, 2c, and 2d, respectively. Further, in the next switching, the control circuit 4 inputs pulses of the switching frequencies F2, F3, F0, and F1 as gate signals to the DC boosting circuits 2a, 2b, 2c, and 2d, respectively. Further, in the next switching, the control circuit 4 inputs pulses of the switching frequencies F3, F0, F1, and F2 as gate signals to the DC boosters 2a, 2b, 2c, and 2d, respectively. In the next switching, the control circuit 4 inputs pulses of the switching frequencies F0, F1, F2, and F3 as gate signals to the DC boosting circuits 2a, 2b, 2c, and 2d, respectively. The switching frequency of the gate signal input to the DC boosting circuits 2a, 2b, 2c and 2d by the control circuit 4 circulates in the same manner. In this modification, the first time, the fifth time, the ninth time. . . In this switching, it is desirable that the initial phase is shifted between the DC boosting circuits 2a, 2b, 2c, and 2d so that the ON timings do not overlap.

  According to this modification, since the on-timing and off-timing between the DC boosting circuits 2a, 2b, 2c, 2d are distributed, the surge generated at the on-timing in each boosting circuit is dispersed and generated by the surge. Noise is reduced. Further, since the switching frequency of each DC booster circuit 2a, 2b, 2c, 2d varies, in each DC booster circuit 2a, 2b, 2c, 2d, noise of harmonic components having the switching frequency as a fundamental wave is reduced. Can do.

  The present invention is not limited to the configuration of the above embodiment. At least the control circuit 4 has a plurality of DC boosting circuits 2a, 2b, 2c, 2d. . . Of the DC boosting circuits 2a, 2b, 2c, 2d. . . What is necessary is just to be comprised so that switching of these may be controlled. The present invention can be further modified in various ways. For example, in the waveform of the modification shown in FIGS. 6 and 7, the switching frequency of each DC booster circuit 2a, 2b, 2c, 2d is not limited to a form that periodically circulates and fluctuates, and varies irregularly. It may be a form to do. Further, the DC power input unit is not limited to the solar battery panel, and may include a power generation device using renewable energy such as wind power, wave power / tidal power, running water / tide, geothermal heat, and the like. A storage battery may be used as the DC power input unit.

1 Power conditioner 2a, 2b, 2c, 2d DC booster circuit (DC voltage converter)
3 Inverter circuit (DC / AC converter)
4 Control circuit (switching control unit)
50a, 50b, 50c, 50d Solar panel (DC power input unit)
100 Power generation system

Claims (5)

A plurality of DC voltage converters for converting a DC voltage input from the solar cell into a predetermined DC voltage;
A plurality of DC voltage converters connected to each other and connected to their input terminals, and a DC / AC converter that converts DC power input to the input terminals into AC power;
In a power conditioner including a switching control unit that controls switching of the plurality of DC voltage conversion units,
The switching control unit shifts the switching phase of each DC voltage conversion unit to switch the plurality of DC voltage conversion units at a constant switching frequency, and performs the maximum power point tracking control. The on-duty of switching is controlled individually, and the switching on-periods of the plurality of DC voltage converters are controlled so as to overlap with each other . 2. The power conditioner according to claim 1, wherein the switching control unit shifts the switching phase so that switching on timings of the DC voltage conversion units are equally spaced . 3. 3. The power conditioner according to claim 2, wherein the switching control unit shifts the switching phase so that a switching ON timing interval of each of the DC voltage conversion units is maximized . 4. 2. The power conditioner according to claim 1 , wherein the switching control unit controls the on-timing of the switching so that the on-timing and off-timing of the switching of each of the DC voltage converters do not overlap each other . A first DC voltage converter that converts a DC voltage input from the solar cell into a predetermined DC voltage;
A second DC voltage converter that converts a DC voltage input from the solar cell into a predetermined DC voltage;
A DC / AC converter that connects the output terminals of the first DC voltage converter and the second DC voltage converter to each other and is connected to the input terminal, and converts the DC power input to the input terminal into AC power; ,
In a power conditioner including a switching control unit that controls switching of the first DC voltage conversion unit and the second DC voltage conversion unit,
The switching control unit shifts the switching phase of the first DC voltage converter and the second DC voltage converter to switch the first DC voltage converter and the second DC voltage converter at a constant switching frequency. The on-duty of switching of the first DC voltage converter and the second DC voltage converter is individually controlled so as to perform the maximum power point tracking control, and the first DC voltage converter and the second DC are controlled. A power conditioner that performs control so that the ON periods of switching of the voltage conversion unit overlap.

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