WO2016157632A1 - 太陽電池－蓄電池連携システムおよび電力変換制御装置 - Google Patents

太陽電池－蓄電池連携システムおよび電力変換制御装置 Download PDF

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WO2016157632A1
WO2016157632A1 PCT/JP2015/084670 JP2015084670W WO2016157632A1 WO 2016157632 A1 WO2016157632 A1 WO 2016157632A1 JP 2015084670 W JP2015084670 W JP 2015084670W WO 2016157632 A1 WO2016157632 A1 WO 2016157632A1
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Prior art keywords
frequency
power
droop
droop rate
rate
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PCT/JP2015/084670
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English (en)
French (fr)
Japanese (ja)
Inventor
古田　太
俊祐 松永
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株式会社日立産機システム
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Priority to JP2017509169A priority Critical patent/JP6300256B2/ja
Priority to CN201580077744.6A priority patent/CN107509391B/zh
Publication of WO2016157632A1 publication Critical patent/WO2016157632A1/ja

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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/66—Regulating electric power
    • G05F1/67—Regulating electric power to the maximum power available from a generator, e.g. from solar cell
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/44—Methods for charging or discharging
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/34—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering
    • H02J7/35—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering with light sensitive cells
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a solar cell-storage battery cooperation system and a power conversion control device, and more particularly to a technique effective for stabilizing power supply in cooperation between a solar battery and a storage battery.
  • a problem peculiar to solar power generation is power fluctuation due to changes in solar radiation conditions. Therefore, a solar battery-storage battery cooperative system has been proposed in which a storage battery capable of storing electric power and a solar battery are connected and the excess and deficiency of the electric power generated by the solar battery is covered by charging / discharging of the storage battery.
  • PCS power conditioner system
  • Interconnected operation is an operation that is established when the AC side of the power conditioner system is connected to the grid and the AC frequency and AC voltage are guaranteed from the grid. Only the amount of power supplied (or absorbed) to the grid is the target value. Control to match.
  • the power conditioner system (hereinafter referred to as PV-PCS) connected to the solar cell on the DC side is a “maximum power point tracking” (MPPT) control that generates maximum active power from the solar cell and supplies it to the system. "Is also implemented (see, for example, Non-Patent Document 1).
  • power control is performed by a charge / discharge command from an external control device.
  • the autonomous operation is a state where the AC side of the power conditioner system is disconnected from the power system and only the load is connected, and the power conditioner system itself establishes and controls the AC frequency and voltage. .
  • the inverter system controls only the frequency and voltage to the target values. For this reason, the power supplied to the load cannot be specified and depends on the load itself. PV-PCS generates only the electric power consumed by the load, and the excess solar radiation is discarded as heat in the solar cell panel.
  • the voltage will drop and operation will stop.
  • the storage battery-PCS discharges as much as it can supply power to the load and maintain the voltage. If the battery charge is insufficient, the operation is stopped due to a voltage drop.
  • This type of solar cell-storage battery cooperation system has a configuration having a plurality of PV-PCSs and storage battery-PCSs. And in each power conditioner system, the solar cell or the storage battery is connected to the direct current side, and it connects and cooperates in the alternating current side of the power conditioner system.
  • a storage battery-PCS is usually selected as the master inverter system.
  • other power conditioner systems are connected as a slave in a linked operation.
  • the power conditioner system to be a slave can be both storage battery-PCS and PV-PCS.
  • the storage battery-PCS supplies a certain amount of power in response to an external charge / discharge command.
  • the PV-PCS performs MPPT control and supplies maximum power.
  • a large-capacity storage battery that allows for power fluctuations is connected to the master power conditioner system. If control is not possible, the local system voltage and frequency deviate from the allowable range. From the viewpoint of safety, the power conditioner system stops operating one after another, making it difficult to supply power.
  • This technology can reduce the burden on the power conditioner system due to individual independent operation by distributing power fluctuations and load fluctuations.
  • the load power sharing between the inverters uses a drooping characteristic mounted on the inverter.
  • the drooping characteristics of a synchronous generator are simulated by an inverter.
  • the AC frequency is changed according to the amount of active power output from the inverter, and the AC voltage is changed according to the amount of reactive power output.
  • Non-Patent Document 2 also discloses a technique for setting the drooping characteristics in accordance with the characteristics of the power generator connected to the inverter.
  • the master power conditioner system (storage battery-PCS) is required to continue operation because it serves as a reference for frequency and voltage.
  • the master power conditioner system is controlled by independent operation and cannot be charged / discharged, maintenance such as charge / discharge management of the storage battery must be performed periodically, and therefore the power conditioner system must be stopped. There is.
  • Patent Document 3 describes a technique for changing the drooping characteristic with respect to a fluctuating DC power supply, but is not intended for cooperation with other power conditioner systems.
  • the object of the present invention is to implement parallel control together with a power conditioner system connected to another storage battery in a PV / storage battery cooperation system without an electric power system, and to extract the maximum power in the solar radiation from the solar battery. To provide technology.
  • the representative solar cell-storage battery cooperation system of the embodiment includes a first power conversion control device and a second power conversion control device.
  • a solar cell is connected to the direct current side, and autonomous operation control is performed.
  • a storage battery is connected to the direct current side, and the alternating current side of the first power conversion control device is connected in parallel to the alternating current side.
  • the first power conversion control device has a main circuit unit, a drooping control unit, and an operation control unit.
  • the main circuit unit converts the DC voltage generated by the solar cell into an AC voltage based on a PWM (Pulse Width Modulation) signal.
  • the droop control unit calculates a frequency droop amount and a voltage droop amount.
  • the operation control unit corrects and outputs the PWM signal from the frequency droop amount and the voltage droop amount calculated by the droop control unit.
  • the drooping control unit changes the frequency drooping rate indicating the ratio of reducing the frequency with respect to the active power output from the AC side of the first power conversion control device based on the change in the active power, and the changed frequency.
  • the frequency droop amount is calculated by multiplying the droop rate by the active power.
  • the droop control unit searches for the frequency droop rate so that the active power is maximized or the frequency droop rate is maximized in a region where the active power does not change with respect to the change of the frequency droop rate.
  • the power generated by the solar cell can be used efficiently.
  • FIG. 3 is an explanatory diagram showing an example of a configuration in a solar cell-storage battery cooperation system according to Embodiment 1. It is explanatory drawing which shows an example of a structure in the power conditioner system which the solar cell-storage battery cooperation system of FIG. 1 has. It is explanatory drawing which shows an example of a structure in the droop rate calculation part which the power conditioner system of FIG. 2 has. It is explanatory drawing which shows an example of the drooping characteristic for one power conditioner system in the parallel control which this inventor examined.
  • FIG. 5 is an explanatory diagram showing an example of behavior when two power conditioner systems having the drooping characteristics shown in FIG. 4 are connected on the AC side to supply active power to a load.
  • FIG. 10 is an explanatory diagram showing an example of a configuration in a power conditioner system included in a solar cell-storage battery cooperation system according to a fourth embodiment. It is explanatory drawing which shows an example of a structure in the droop rate calculation part which the power conditioner system of FIG. 13 has. It is explanatory drawing which shows an example of the estimation of the electric power condition estimated by the power conditioner system of FIG.
  • FIG. 10 is an explanatory diagram illustrating an example of a configuration in a power conditioner system according to a sixth embodiment. It is explanatory drawing which shows the mode of load sharing at the time of connecting the power conditioner system of FIG. 18, and the power conditioner system to which the storage battery was connected.
  • FIG. 10 is an explanatory diagram showing an example of a configuration in a power conditioner system according to a seventh embodiment.
  • the constituent elements are not necessarily indispensable unless otherwise specified and apparently essential in principle. Needless to say.
  • FIG. 1 is an explanatory diagram showing an example of the configuration of the solar cell-storage battery cooperation system according to the first embodiment.
  • the solar battery-storage battery cooperation system includes power conditioner systems 100 1 to 100 4 , solar batteries 101 1 and 101 2 , storage batteries 102 1 and 102 2 , and an operation panel 103.
  • Solar cells 101 1 and 101 2 are connected to the direct current sides of power conditioner systems 100 1 and 100 2 serving as first power conversion control devices, respectively.
  • Storage batteries 102 1 and 102 2 are connected to the direct current sides of the power conditioner systems 100 3 and 100 4 serving as second power conversion control devices, respectively.
  • a power system PW provided from a load LD and an electric power company is connected to the AC side of the power conditioner systems 100 1 to 100 4 .
  • the power system PW has, for example, a three-phase of about 200 V and a frequency of about 50 Hz.
  • Storage battery 102 1, 102 2 together with the solar cell 101 1, 101 2 to charge too much electric power generated, the power to the power system PW discharges when the power generation amount of the solar cell 101 1, 101 2 is insufficient Supply.
  • the power conditioner systems 100 1 and 100 2 to which the solar cells 101 1 and 101 2 are connected convert the DC voltage generated by the solar cells 101 1 and 101 2 into an AC voltage, and the AC voltage is converted into the power system PW. To match the voltage and frequency.
  • the power conditioner systems 100 3 and 100 4 to which the storage batteries 102 1 and 102 2 are connected control charging / discharging of the storage batteries 102 1 and 102 2 based on a charge / discharge command from the outside.
  • the inverter systems 100 1 to 100 4 themselves establish AC frequencies and voltages and perform control operations.
  • the operation panel 103 includes, for example, an input unit and a display unit (not shown), and inputs operation status display and various setting information in the solar cell-storage battery cooperation system.
  • FIG. 1 shows an example of a solar cell-storage battery cooperation system. Therefore, the number of the power conditioner systems to which the solar cells are connected and the number of the power conditioner systems to which the storage batteries are connected are not particularly limited, and may be one or more.
  • FIG. 1 the solar cell of FIG. 1 - an explanatory view showing an example of the configuration in the power conditioner system 100 1 included in the battery cooperation system.
  • power conditioner system 100 1 of the configuration will be described, the same applies to the configuration of the power conditioner system 100 2 solar cell 101 2 is connected.
  • a main circuit 210 serving as a main circuit unit includes a semiconductor element 211, a reactor 212, and a transformer 213.
  • the semiconductor element 211 is made of a switching transistor, on the basis of the PWM signal output from the voltage compensator 222, performs pulse width modulation by switching a DC voltage supplied from the solar cell 101 1.
  • the reactor 212 removes harmonics of the signal that has been pulse width modulated by the semiconductor element 211. Thereby, for example, an alternating current of 50 Hz / 60 Hz is generated. This AC signal is converted into a desired voltage by the transformer 213 and output to the power system PW side.
  • the control unit 200 includes an operation control unit 220 and a drooping control unit 225.
  • the operation control unit 220 is a block that controls the independent operation, generates an AC voltage based on a rated voltage (for example, about 200 V) and a rated frequency (for example, about 50 Hz), and controls the main circuit 210.
  • the operation control unit 220 includes a voltage feedback control unit 221, a voltage compensation unit 222, an oscillation unit 223, and adders 227 and 228.
  • the adder 227 adds the rated frequency to the frequency droop amount described later, and outputs it as a frequency command value.
  • the adder 228 adds the rated voltage to a voltage droop amount described later, and outputs the result as a voltage command value.
  • Voltage feedback control unit 221 performs a voltage feedback control such that the voltage on the AC side of the power conditioner system 100 1 detected by the AC voltage sensor 214 matches the voltage command value from the adder 228.
  • the AC voltage sensor 214 is provided on the AC output side of the power conditioner system 100 1, detects the voltage value of the AC voltage output from the power conditioner system 100 1.
  • the amplitude value of the input AC voltage is extracted, the voltage command value input by the amplitude value is subtracted, and an appropriate transfer function is applied. This is a new amplitude value A ′. Further, the AC signal A ′ ⁇ sin ( ⁇ ) is calculated together with the phase ⁇ which is the phase command value input from the oscillating unit 223, and is set as the output value of the voltage feedback control unit 221.
  • the transfer function is not specified here because it is not relevant here.
  • the voltage compensation unit 222 compensates for a voltage drop caused by a current flowing through the reactor 212.
  • the current amplitude I is extracted from the AC current detected by the current sensor 215, and the voltage amplitude V is extracted from the AC voltage detected by the AC voltage sensor 214.
  • a compensation value VR + j ⁇ L ⁇ I is calculated from the impedance ⁇ L of the reactor and added to the AC signal from the voltage feedback control unit 221.
  • For the current sensor 215 is also provided to the AC output side of the power conditioner system 100 1, for detecting a current flowing in the electric power system PW side of the power conditioner system 100 1.
  • a drooping control unit 225 as a mechanism for drooping the rated frequency and the rated voltage.
  • the frequency droop against real power power conditioner system 100 1 outputs, the fraction in lowering frequencies.
  • the droop control unit 225 includes a power calculation unit 224, a droop rate calculation unit 226, and multipliers 229 and 230.
  • Power calculation unit 224, the power from the voltage value and current value AC voltage sensor 214 and current sensor 215 detects consists active and reactive power power conditioner system 100 1 is supplied to the load side (local systems) Each amount is calculated.
  • the droop control unit 225 calculates the frequency droop rate based on the magnitude of the active power calculated by the power calculation unit 224. Therefore, the frequency droop rate is determined based on the magnitude of the active power, not a fixed value.
  • the multiplier 230 multiplies the preset voltage droop rate by the reactive power calculated by the power calculator 224 and outputs the result to the adder 228 as a voltage droop amount.
  • Figure 3 is an explanatory diagram showing an example of the configuration of the hanging ratio calculator 226 included in the power conditioner system 100 1 of FIG.
  • a power change calculation unit 301 a power difference value evaluation unit 302, a droop rate difference value generation unit 303, a droop rate increase / decrease counter 304, an initial value storage unit 305, and a rated limit value storage unit 306.
  • the active power value P calculated by the power calculator 224 shown in FIG. 2 is input to the power change calculator 301.
  • the power change calculation unit 301 outputs the difference value ⁇ P using the input active power value P.
  • the power difference value evaluation unit 302 evaluates the difference value ⁇ P together with the difference value ⁇ M of the previous frequency droop rate, and outputs an increase / decrease command value as the evaluation result.
  • the droop rate difference value generation unit 303 receives the increase / decrease command value output from the power difference value evaluation unit 302, generates a new frequency droop rate difference value, and outputs the difference value to the droop rate increase / decrease counter 304.
  • the droop rate increase / decrease counter 304 determines the frequency droop rate M from the difference value of the received frequency droop rates.
  • Limit information which is an initial count value and a maximum count value necessary for the count operation, is input from the operation panel 103 shown in FIG. 1 before driving.
  • the initial value input from the operation panel 103 is stored in the initial value storage unit 305, and the limit information is stored in the rated limit value storage unit 306. These pieces of information stored in the initial value storage unit 305 and the rated limit value storage unit 306 are input to the droop rate increase / decrease counter 304 for the first time during operation, that is, only during initialization.
  • FIG. 4 is an explanatory diagram showing an example of drooping characteristics for one power conditioner system in parallel control studied by the present inventors.
  • a frequency is selected for active power and a voltage is selected for reactive power by simulating the characteristics of a synchronous generator.
  • FIG. 4 shows a change in frequency with respect to active power.
  • the frequency droop rate is set so that the decrease in frequency is within the allowable range for the rated power that is the maximum in the specifications of the power conditioner system.
  • FIG. 5 shows the behavior when two power conditioner systems (shown as PCS1 and PCS2 in the figure) having the drooping characteristics shown in FIG. 4 are connected on the AC side and active power is supplied to the load. It is explanatory drawing which showed an example.
  • the relationship between the active power and the frequency of each power conditioner system moves so that the frequencies coincide with each other, and the active power is automatically shared.
  • the active power is equally shared.
  • the slope of the straight line of the drooping characteristic is different, so that the sharing ratio is set accordingly.
  • FIG. 6 is an explanatory diagram showing an example of the drooping characteristic of the power conditioner system.
  • FIG. 6A shows the drooping characteristics for one power conditioner system when the frequency droop rate is varied.
  • the rated droop rate M N which is a frequency droop rate set so that the decrease in frequency is within the allowable range with respect to the initial rated droop rate M 0 that is the initially set frequency droop rate and the maximum rated power value in the specification. In this range, the frequency droop rate is variable.
  • the rated droop rate is stored in the rated limit value storage unit 306 as the limit information described above.
  • M N By setting the rated droop rate M N , it is possible to limit the power output from the power conditioner system, so that it is possible to prevent abnormal power from being output, and the semiconductor element 211 shown in FIG. And the reactor 212 can be protected.
  • the frequency droop rate is determined according to the increase or decrease of the active power at that time. More specifically, the frequency droop rate M value is searched so that the power conditioner system can share the maximum power within the rated power.
  • FIG. 6B shows a power conditioner system having a drooping characteristic with variable frequency droop rate (PCS2 in FIG. 6B) and a power conditioner system having a fixed frequency droop rate (PCS1 in FIG. 6B). ) Are connected on the AC side, and the behavior when the active power is supplied to the load is shown.
  • PCS2 variable frequency droop rate
  • PCS1 fixed frequency droop rate
  • the sharing rate of the PCS 2 can be increased, that is, the effective power shared by the PSC 2 can be increased.
  • the power sharing of each power conditioner system can be optimized. For example, when the PCS 2 is connected to a solar cell, the power sharing can be increased by reducing the frequency droop rate when the amount of solar radiation is large.
  • FIG. 7 is an explanatory diagram showing an example of a change in active power with respect to the frequency droop rate.
  • FIG. 8 is an explanatory diagram showing an example of the power characteristics of a solar cell using the DC voltage output from the solar cell as an operation variable. For comparison with general MPPT control (search), FIG. 8 shows the power characteristics of a solar cell using the DC voltage of the solar cell as an operating variable.
  • FIGS. 7A and 8A show the power characteristics when the amount of solar radiation is larger than the rated power.
  • FIGS. 7B and 8B show the amount of solar radiation more than the rated power. The power characteristic when there is little is shown.
  • the sharing ratio of the PCS 2 can be increased by lowering the droop rate M (releasing the slope).
  • the state with the power generation surplus is a state in which power limitation depending on the droop rate is applied.
  • the increase / decrease ⁇ P of the active power is evaluated with respect to the difference value ⁇ M of the frequency droop rate. If ⁇ P increases, the droop rate is further lowered to increase the share of power. Go. As shown in FIG. 8, when the frequency droop rate is lowered, the power limit value moves upward and the active power rises.
  • the frequency droop rate is continuously lowered, the maximum share will eventually be reached. If the amount of solar radiation is greater than the rated maximum value, as shown in FIG. 7 (a) and FIG. 8 (a), the active power also while leaving margin in generated power is the rated power value P N.
  • the frequency droop rate M is not set lower than the rated droop rate. Electricity assessment will continue.
  • the maximum shared amount is the maximum power point P MPP in the solar radiation amount at that time. This point is a point at which the power does not change with respect to the change in the frequency droop rate, as shown in FIG.
  • the operation of the frequency droop rate is switched from monotonous decrease to small round trips (stepping state), and the change in the electric energy is continuously evaluated. This is similar to the behavior near the top in the so-called general hill-climbing search method.
  • the point to be stepped on is the maximum point of the active power as shown in FIG. 7B, and is set so that the droop rate M becomes maximum.
  • the stepping can be realized by an operation of continuously increasing the droop rate when the active power does not change and increasing the frequency droop rate when the active power decreases.
  • the frequency droop rate can be made to follow the change in the amount of solar radiation. Since the amount of solar radiation when the drops below the rated power value P N, the active power is reduced, Reduce the power sharing amount by increasing the frequency droop rate. In this case, the search is performed so that the active power does not change and the maximum frequency droop rate is obtained.
  • the frequency droop rate is slightly decreased and the active power is increased in a stepped state, the amount of solar radiation is further increased and it is determined that there is power generation surplus, so the frequency droop rate is lowered again.
  • the active power decreases regardless of the increase or decrease of the frequency droop rate, it can be determined that the amount of solar radiation has decreased and the amount of power generation has decreased from the amount of power sharing, so increase the frequency droop rate and decrease the power sharing amount. . Even in this case, the search is performed so that the active power does not change and the maximum frequency droop rate is obtained.
  • the optimum frequency droop rate that is, the power sharing amount of the power conditioner systems 100 1 and 100 2 is determined.
  • the above operation can be realized by the droop rate calculation unit 226 shown in FIG.
  • FIG. 9 is a diagram for explaining the estimation of the frequency droop rate search state by the droop rate calculation unit 226 in FIG. 3, and FIG. 10 shows an example of the increase / decrease command value output by the power difference value evaluation unit 302 in FIG. It is explanatory drawing shown.
  • the power situation as shown in FIG. 9 is estimated from the active power difference value and the difference value of the current frequency droop rate. For example, when both the effective power and the frequency droop rate are increasing, it can be considered from FIG. 9 that the solar radiation increases near the maximum power point.
  • control logic for outputting an increase / decrease command value as shown in FIG. 10 is assembled in the power difference value evaluation unit 302, and the droop rate difference value generation unit 303 determines the frequency based on the increase / decrease command value.
  • a positive difference value ( ⁇ M) of the droop rate is determined.
  • control is performed so as to decrease the difference value of the frequency droop rate from FIG.
  • control is performed so as to increase the difference value of the frequency droop rate from FIG.
  • the power conditioner systems 100 1 and 100 2 can acquire the power corresponding to the solar radiation to the maximum within the rated range while performing the independent operation. In addition, since the power conditioner systems 100 1 and 100 2 are self-supporting, the operation can be continued even when other power conditioner systems are stopped.
  • the operation can be continued even when other inverter system is stopped by the independent operation. This means that even if there is only one power conditioner system to which the linked storage battery is connected and it is stopped due to maintenance, etc., if there is enough solar radiation to supply power, power supply can be continued without shutting off the system. .
  • the threshold setting of the part that recognizes that it is flat is likely to be affected by noise when detecting the boundary between the flat part where power does not change and the part that does not change. For this reason, it is easier to obtain the inflection point rather than the gradient ( ⁇ P / ⁇ M) of the power change with respect to the change in the frequency droop rate. Therefore, the second embodiment will describe another technique for detecting the maximum power point.
  • the frequency droop rate-power characteristic is different in the nature of the curve in the power change region and the constant region. Specifically, it is convex upward or not.
  • the drooping rate is lowered, the increase in power becomes gentle near the shoulder, and when it is further lowered, the power does not change.
  • FIG. 11 is an explanatory diagram illustrating an example of a configuration of the droop rate calculation unit 226 included in the power conditioner system according to the second embodiment.
  • the basic operation of the droop rate calculation unit 226 provided with the twice derivative calculation unit 307 performs a search by reducing the frequency droop rate and evaluating the power difference value, as in the first embodiment.
  • a droop rate difference command is set so as to obtain the extreme value. This is a typical hill-climbing search, and the technique disclosed in Non-Patent Document 1, for example, can be applied.
  • the frequency droop rate is determined by, for example, the droop rate calculation unit 226 of the hardware configuration shown in FIGS. 3 and 10, but in this third embodiment, the operation of the droop rate calculation unit 226 is performed.
  • the processing corresponding to is performed by software in a program format will be described.
  • the program is stored in, for example, a program storage memory (not shown) provided in the control unit 200 of FIG.
  • a CPU central processing unit
  • the control unit 200 of FIG. 2 executes processing based on software stored in the program storage memory.
  • FIG. 12 is a flowchart showing an example of a program process for determining the frequency droop rate according to the third embodiment.
  • FIG. 12A shows an example of processing by the frequency droop rate initialization program stored in the program storage memory
  • FIG. 12B shows an example of processing by the update program stored in the program storage memory. Show.
  • the frequency droop rate initialization program is a program that is read out and executed by the above-described CPU when the operation of the power conditioner system starts.
  • the update program is a program that is read periodically from the main program of the inverter system by timer interruption or the like (every m to several 100 ms interval) and is also executed by the CPU.
  • the voltage value and current value detected by the AC voltage sensor 214 and the current sensor 215, respectively, are A / D converted and then input to the CPU.
  • step S101 an initial value of the frequency droop rate and a temporary difference value are set. Then, in preparation for starting the next update program, the inner product of the obtained three-phase voltage and three-phase current is taken to obtain the active power P 0 (step S102).
  • the active power P (n is calculated by taking the inner product of the three-phase voltage (voltage value detected by the AC voltage sensor 214) obtained by the execution of the n-th update program and the three-phase current (current value detected by the current sensor 215). ) Is obtained (step S201).
  • steps S203 to S205 are processed so as to obtain the increase / decrease command value shown in FIG. 10 of the first embodiment. Based on this increase / decrease command value, a new frequency droop rate difference value ⁇ M (n) is set (steps S206 and S207), and a new frequency droop rate is determined (step S208).
  • the determined frequency droop rate is compared with the rated droop rate M N and is limited so as not to exceed this (step S209).
  • the rated droop rate M N is stored as limit information in the rated limit value storage unit 306 shown in FIG.
  • the droop rate difference value ⁇ M (n) is stored as a state variable ⁇ M (n ⁇ 1) because it is used in the next update program.
  • the frequency sag rate may be determined by obtaining a second derivative ( ⁇ 2 P / ⁇ M 2 ) with respect to the power sag rate, and the increase / decrease value thereof. In this case, it becomes a hill-climbing search of a differential value twice with respect to the frequency droop rate, and a known technique can also be used in the search algorithm.
  • the operation of the drooping rate calculation unit 226 can be performed by a program, the hardware configuration can be reduced. Thereby, the cost of the power conditioner system can be reduced.
  • FIG. 13 is an explanatory diagram showing an example of the configuration of the power conditioner system provided in the solar cell-storage battery cooperation system according to the fourth embodiment.
  • DC voltage sensor 216 is provided on the DC side of the solar cell is connected to the power conditioner system 100 1.
  • the DC voltage sensor 216 detects a DC voltage value output from the solar battery.
  • the DC voltage value detected by the DC voltage sensor 216 is input to the droop rate calculation unit 226 as described above.
  • Other connection configurations and operations are the same as those in FIG.
  • the fluctuation of the solar radiation power and the burden power is separated by reciprocating the frequency droop rate in small increments near the MPP point. Furthermore, to increase and decrease the load power, the frequency droop rate may be gradually increased while reciprocating.
  • the fourth embodiment it can be more easily separated by evaluating the voltage on the DC side of the power conditioner system.
  • the dotted line indicates the power characteristic when the amount of solar radiation is greater than the rated power
  • the solid line indicates the power characteristic when the amount of solar radiation is less than the rated power.
  • a decrease in power due to a decrease in solar power under a power limit (for example, M 'in the figure) is accompanied by a decrease in the DC voltage of the solar cell.
  • a power limit for example, M 'in the figure
  • the load power itself decreases this corresponds to a decrease in the limit value, and the DC voltage increases conversely.
  • FIG. 14 is an explanatory diagram showing an example of the configuration of the droop rate calculation unit 226 provided in the power conditioner system of FIG.
  • a DC voltage difference value calculation unit 308 is newly added to the configuration of the droop rate calculation unit 226 shown in FIG. 3 of the first embodiment.
  • a DC voltage value detected by the DC voltage sensor 216 shown in FIG. 13 is input to the DC voltage difference value calculation unit 308, and a DC voltage difference value is calculated from the DC voltage value detected by the DC voltage sensor 216. calculate.
  • the search when the load power does not change is as described in the first embodiment. Similarly, the frequency droop rate is decreased when there is power generation surplus, and the frequency droop rate is increased when the power does not change, and the same is applied to the maximum power point.
  • any change is reflected in the change in active power, but the cause depends on the direction of change in DC voltage. That is, when the frequency droop rate is increased in the stepped state to increase the active power and the DC voltage is increased, it is considered that the amount of solar radiation increases. For this reason, the frequency droop rate is further lowered to increase the amount of electric power shared. On the contrary, when the DC voltage decreases, it is considered that the state of the load has changed and the amount of active power to the load has increased.
  • the droop rate calculation unit 226 in FIG. 14 performs the above operation.
  • the power situation shown in FIG. 15 is estimated from the active power difference value and the current frequency droop rate difference value. For example, when the DC voltage difference value, the active power difference value, and the frequency droop rate difference value are all increasing, it can be considered from FIG. 15 that the solar radiation increases near the maximum power point.
  • control logic for outputting an increase / decrease command value as shown in FIG. 16 is assembled in the power difference value evaluation unit 302, and the droop rate difference value generation unit 303 is based on the increase / decrease command value.
  • ⁇ M a positive frequency difference value
  • the program is stored in, for example, a program storage memory (not shown) provided in the control unit 200 of FIG.
  • a CPU Central Processing Unit
  • the control unit 200 of FIG. 2 executes processing based on software stored in the program storage memory.
  • the programs stored in the program storage memory are the frequency droop rate initialization program and the update program as in the third embodiment.
  • FIG. 17 is a flowchart showing an example of a program process for determining the frequency droop rate according to the fifth embodiment.
  • the frequency droop rate initialization program is a program that is read out and executed by the above-described CPU when the operation of the power conditioner system starts.
  • the update program is a program that is read periodically from the main program of the inverter system by timer interruption or the like (every m to several 100 ms interval) and is also executed by the CPU.
  • Conditional branching is performed based on the power difference value, voltage difference value, and frequency droop rate difference value ⁇ M (n ⁇ 1) determined in the previous call (steps 305 to S307, or steps S304, S310 to S312).
  • a branch by the voltage difference value by the process of step S304 is added.
  • steps S305 to S307, or the processes in steps S304 and S310 to S312 are processed so as to obtain the increase / decrease value command value shown in FIG.
  • control such as decreasing the frequency droop rate difference value is performed from FIG.
  • a new frequency droop rate difference value ⁇ M (n) is set (step S308, S309, or steps S313, S314) by branching in steps S305 to S307 or steps S304 and S310 to S312 and a new droop rate is determined. (Step S315).
  • the frequency droop rate is compared with the rated droop rate M N , is limited so as not to exceed this, and the update program ends (step S316).
  • the rated droop rate M N is stored in the rated limit value storage unit 306 shown in FIG. 3 as described in the first embodiment.
  • the frequency droop rate difference value ⁇ M (n) is stored in the state variable ⁇ M (n ⁇ 1) because it is used in the next update program.
  • the hardware configuration can be reduced, and the cost of the power conditioner system can be reduced.
  • the power conditioner system having the independent operation parallel control that can draw out the power of the solar cell as much as possible generates electric power that exceeds the load of the solar cell when a cooperative system with the power conditioner system connected to the storage battery is configured. And the surplus electric power shall be charged to a storage battery via the power conditioner system to which the storage battery is connected.
  • Figure 18 is an explanatory diagram showing an example of the configuration of the power conditioner system 100 1 according to the sixth embodiment.
  • the droop rate calculation unit 226 controls the frequency droop rate similarly to the fourth embodiment, but outputs a correction signal to the rating correction unit 231 when the load increases or decreases as shown in FIG.
  • This correction signal may be a binary digital signal indicating increase / decrease or an analog value indicating a specific increase / decrease value.
  • the rating correction unit 231 receives this correction signal, outputs a predetermined increase / decrease value, and outputs a rating correction command for correcting the value of the rated frequency.
  • FIG. 19 is an explanatory diagram showing a state of load sharing when the power conditioner system of FIG. 18 and the power conditioner system to which the storage battery is connected are connected.
  • PCS2 The solar cell is connected, shows the power conditioner system having a drooping characteristic to correct the rated frequency, that is, the power conditioner system 100 1 of the configuration shown in FIG. 18.
  • PCS1 shows storage batteries connected power conditioner system, etc. power conditioner system 100 3 shown for example in Figure 1 of the first embodiment.
  • the coordinated operation exceeds the rated frequency.
  • the operating point of PCS1 exists in a region where the active power is negative. This indicates that the amount of active power borne by the PCS 1 is charging power.
  • the difference in the shared power (absolute value) between PCS2 and PCS1 is the load power.
  • the surplus power of the solar battery can be charged to the storage battery, the power efficiency in the solar battery-storage battery cooperation system can be improved.
  • Embodiment 7 ⁇ Overview>
  • the above-described power conditioner system having the independent operation parallel control that can draw out the electric power of the solar cell to the maximum is not limited to use only in a system that does not have an electric power system. Therefore, this Embodiment 7 demonstrates a power conditioner system provided with the control structure which can perform an interconnection operation other than a self-sustained operation.
  • Figure 20 is an explanatory diagram showing an example of the configuration of the power conditioner system 100 1 according to the seventh embodiment.
  • the presence or absence of the power system it is possible to switch the operating mode.
  • switching from the voltage feedback control unit 221 to the current feedback control unit 234 is performed by switching the operation mode switching unit 233 to perform power control.
  • power control is switched from voltage feedback control to current feedback control.
  • the operation mode switching unit 232 blocks the frequency command value output from the adder 227. As a result, only the phase command value is input to the oscillation unit 223. In this case, it synchronizes with the phase and frequency of the system. With the above configuration, it is possible to participate in “interconnected operation” in the solar cell-storage battery cooperation system.
  • a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. .

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CN112421675B (zh) * 2020-10-10 2023-03-28 浙江大学 一种基于电流源下垂的输出功率控制方法

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