JP6781637B2 - Control method of the cooperation system of storage battery and power converter, and power conditioning system - Google Patents

Description

The present invention relates to a power conversion device such as an inverter and a power conditioning system and a control method thereof.

With the recent increase in interest in renewable energy and the introduction of a power purchase system by the government, photovoltaic power generation systems using solar cells (PV: Photovoltaic) are rapidly becoming widespread. While the system can easily obtain power if there is sunlight, it is susceptible to fluctuations in power due to sunlight conditions and cannot generate electricity at night. Therefore, a solar cell-storage battery cooperation system has been proposed in which a storage battery capable of storing electric power and a solar cell are connected to cover the fluctuation of the electric power generated by the solar cell by charging and discharging the storage battery.

In particular, in areas where the system is vulnerable, such as inland areas far from remote islands and coastal power plants, or when the system is lost due to an accident or disaster, this cooperative system is a means to always secure power for important loads. Is expected as.

The key to the configuration of the solar cell-storage battery cooperation system is the power conditioning system (PCS) device, which is a type of power conversion device. The PCS is connected between the solar cell and the AC power line and between the storage battery and the AC power line, respectively, and optimizes the power generation conditions and performs charge / discharge operation. The PCSs are connected to each other on the AC side to supply and receive power between the PCSs and supply power to important loads. A plurality of PV-PCSs and a plurality of storage batteries-PCSs are connected to the AC side according to the scale of the cooperation system.

As a method of linking multiple PCSs when there is no system, a master-slave method in which one PCS is operated independently as a master and the remaining PCSs are operated in an interconnected manner as a slave, or all PCSs are coordinated. There is a parallel operation method for independent operation.

In the former, the master PCS establishes voltage and frequency throughout the system. Since the remaining slave PCS can specify the contribution power, the PV-PCS can pursue the maximum power, and the storage battery PCS can also be charged and discharged according to the charging rate of each. However, if the master PCS is stopped, the entire system including the remaining slave PCS must be stopped. Maintenance of the master PCS and its DC power supply (mainly storage batteries) becomes difficult, and the reliability of the system decreases.

On the other hand, as a technique for realizing the latter parallel operation, a technique called hanging control is described in Non-Patent Document 1 and Patent Document 1. In each PCS, the characteristics of dropping the frequency and the voltage according to the active power and the reactive power to be contributed are created in the PCS. A plurality of PCSs having drooping characteristics are driven in parallel as a master, and the drooping frequency and voltage are shared by each PCS to fairly share the load power. The reliability of the system is maintained for a long time because any PCS can be disconnected and re-parallelized without stopping the system for maintenance.

WO2014-098104 Japanese Unexamined Patent Publication No. 2014-207790

J. M. Guerror, et. al. , IEEE Trans on Industrial Electronics, vol. 55, No. 8, August 2008. P. 2485-2859.

In a system in which a plurality of storage batteries and PCS are connected, if charging and discharging are repeated, the charging rate of the storage battery of each PCS will vary. The reason for this is that it is caused by the variation in the characteristics of the storage battery itself, and the difference in the charging rate that occurs when the battery module is replaced by the maintenance of the storage battery or when the charge / discharge operation is temporarily stopped due to the maintenance of the PCS.

However, some storage batteries are equipped with a battery controller, and some are used to monitor the failure of the storage battery and grasp the charge rate. In that case, the variation among the storage cells constituting the storage battery is corrected by this controller. However, when viewed for each PCS, the variation between storage batteries cannot be eliminated.

In the droop control described above, the droop rate is determined according to the rating of the PCS, and the power is evenly distributed to the PCS of the same standard. On the contrary, the same applies when charging. In a system in which a plurality of storage batteries and a PCS are connected, if charging is performed with the same electric power in a state where the charging rates of the storage batteries are different, the storage battery-PCS having the highest charging rate must be stopped. In the case of discharge, the storage battery-PCS, which has the lowest charge rate, must be stopped. Therefore, the number of PCS that can be operated is reduced, and the reliability, which is an advantage of parallel operation, is reduced.

Not limited to hanging control, there is also a method of sending information on the charge rate of each storage battery to a centralized control device, collecting them into one, comparing them, and feeding them back to the charge / discharge control of each PCS to evenly operate each storage battery. It is published in 2. However, the PCS (inverter) used in these needs to be in a state in which the charge / discharge power of the storage battery can be controlled. Furthermore, since it is necessary to consolidate all charge rates, a dedicated control device is required, and the configuration also needs to be changed depending on the number of connected PCSs. That is, there are drawbacks in terms of maintaining reliability and realizing a flexible PCS configuration.

Therefore, an object of the present invention is a configuration of a storage battery-PCS that uniformly controls the charge rate of the storage battery among the plurality of PCSs while performing parallel control together with the plurality of storage batteries-PCS in a system in which the PV and the storage battery have no system. The purpose is to provide a control method and make the PCS as operable as possible to improve the reliability of the system.

One aspect of the present invention is a control method for a linked system of a storage battery and a power conversion device in which a storage battery and a power conversion device are connected one-to-one and a plurality of sets thereof are connected on the AC side. In this method, each of the power converters determines the charge / discharge rate of the storage battery according to the charge rate of the corresponding storage battery, and allocates the charge / discharge power of each of the power converters according to the charge / discharge rate. Then, the charge rate of the storage battery is controlled to be even.

Another aspect of the present invention is a cooperative system in which a storage battery block and a power conditioning system that connects to the storage battery block on a one-to-one basis constitute a storage battery-PCS pair, and a plurality of these pairs are connected on the AC side. , Power conditioning system. This power conditioning system consists of a switching element that converts direct current and alternating current between the storage battery block and the alternating current side, a power calculation unit that calculates active power from the alternating voltage and alternating current on the alternating current side, and a corresponding storage battery block. It includes an oscillator that generates a target frequency by reflecting the charge rate and active power, and a feedback control unit that feeds back the output of the oscillator to a switching element.

When controlling multiple storage batteries-PCS in parallel, the proportional division rate of charge / discharge power is changed according to the charge rate of each storage battery, so it is possible to correct variations in the charge rate and charge more power to the linked system. At the same time, more power can be discharged from the system.

The block diagram of the cooperation system of the storage battery block and the PV panel via PCS. The figure which shows the operation method of PCS in 1st Example. The block diagram of the storage battery block in 1st Example. The block diagram of the PCS in the 1st Example. The block diagram of the sagging rate calculation part in 1st Example. The graph which explains the characteristic of the drooping function in 1st Example. The graph which explains the characteristic of the drooping function in 1st Example. The graph which shows the drooping characteristic of PCS in parallel control which fixed drooping characteristic. The graph which shows the drooping characteristic of PCS in parallel control which fixed drooping characteristic. The graph which explains the electric power characteristic with respect to the droop rate in the 1st Example. The graph which explains the electric power characteristic with respect to the droop rate in the 1st Example. The graph which explains the electric power characteristic with respect to the droop rate in the 1st Example. The graph which explains the time change of the charge rate at the time of performing the fixed droop rate control. The graph which explains the time change of the charge rate in the 1st Example. The block diagram of the PCS in the 2nd Example. The block diagram of the rating value correction calculation part in 2nd Example. The graph which explains the characteristic of the rating value correction in the 2nd Example. The graph which explains the characteristic of the rating value correction in the 2nd Example. The graph which explains the electric power characteristic with respect to the rating value correction in 2nd Example. The graph which explains the electric power characteristic with respect to the rating value correction in 2nd Example. The graph which explains the electric power characteristic with respect to the rating value correction in 2nd Example. The block diagram of the PCS in the 3rd Example. The block diagram of the hanging rate calculation part in 4th Example.

Hereinafter, the present invention will be described with reference to Examples. This example is an example using the present invention, and the present invention is not limited to this example. In the following, in parallel control of a system in which a storage battery and a PCS are connected one-to-one and a plurality of them are connected in parallel, each PCS determines a droop rate according to the charge rate of the corresponding storage battery and is based on the droop rate. An example of charge / discharge control will be mainly described. In a more specific example, the storage battery-PCS is controlled to operate independently with a drooping characteristic, and the frequency drooping rate with respect to the active power is monotonically increased in the case of charging and monotonous in the case of discharging with respect to the charging rate of the storage battery. Set by the function of decrease.

In the configuration of the invention described below, the same reference numerals may be used in common among different drawings for the same parts or parts having similar functions, and duplicate description may be omitted.

FIG. 1A shows an example of a system configuration in which a solar cell and a storage battery cooperate with each other. Each of the solar cell (PV) panel 101 and the storage battery block 102 is connected to the critical load 103 and the system (for example, 200 V, 50 Hz) 104 via the PCS 100. The PCS100 serves as an interface between the DC side and the AC side and controls the direction and amount of electric power. In addition, the PCS synchronizes the frequency and voltage with the system. The PCS 100 controls charging / discharging of the storage battery block 102 depending on the direction of electric power. Further, the PCS 100 supplies the electric power generated by the PV panel 101 to the AC side by controlling, for example, maximum power point tracking (MPPT).

FIG. 1B is a table showing an example of an operation method of the PCS100 by comparing this embodiment with the master-slave method. As shown in FIG. 1B, in the master-slave system, one of the storage battery blocks 102-PCS100 operates independently as the master PCS, and the PV panel 101-PCS100 operates in an interconnected manner. In this embodiment, the plurality of storage battery blocks 102-PCS100 all perform independent operation, and parallel control is performed among the plurality of PCS. Therefore, unlike the master-slave method, stopping the master does not affect the entire system. Whether or not the PV panel 101-PCS100 participates in parallel operation in independent operation is not limited in this embodiment.

FIG. 1C shows a configuration example of the storage battery block 102. As shown in FIG. 1C, the storage battery block 102 is composed of one or a plurality of assembled batteries 107 and a battery controller 106 for monitoring the assembled batteries 107. The assembled battery 107 has a configuration obtained by connecting a storage battery cell 105, which is the smallest unit of a storage battery, in series, in parallel, or a combination thereof. FIG. 1C shows a configuration with only series connection.

The battery controller 106 monitors the state (voltage, current and temperature) of each storage battery cell 105, and determines whether the assembled battery 107 is normal or deteriorated. At the same time, the charge rate of each storage battery cell 105 is estimated from the monitored state quantity. In the case of a simple controller, the average value of the charge rates of each storage battery cell 105 is taken as the charge rate of the assembled battery 107. In a multifunctional controller, when there is a variation in the charging rate among the storage battery cells 105, a mechanism for partially discharging or charging only a specific storage battery cell 105 is used to reduce the variation in the assembled battery 107 and average the variation. Let the value be the charge rate of the assembled battery. The estimated charge rate is output from the storage battery block 102. Further, the stored electric power is supplied via the PCS.

FIG. 2 shows the configuration of the PCS 100 connected to the storage battery block 102 in the first embodiment of the present invention. The PCS100 is composed of a main circuit 210 and a control block 220. The main circuit 210 performs a desired orthogonal flow conversion between the AC side and the DC side (PV panel 101 or storage battery block 102 side) under the control of the control block 220. The control block 220 is a block that performs various calculations and processes for control, and can take the form of an information processing device including an input device, an output device, a processing device, and a storage device. In the information processing device, the processing device executes the program stored in the storage device to realize each block that processes the data input from the input device, and outputs the processing result from the output device. Equivalent functions can also be configured with hardware such as FPGA (Field-Programmable gate array).

The direct current is pulse-width modulated by the switching action of the semiconductor element 211 of the main circuit 210, and the harmonics are removed by the reactor 212, resulting in, for example, 50 Hz / 60 Hz alternating current. After that, it reaches the AC side via the transformer 213.

The control block 220 includes a voltage feedback control unit 221 and a voltage compensation control unit 222 as a configuration for carrying out independent operation control. Here, the main circuit 210 is controlled so as to generate an AC voltage with reference to the rated voltage (for example, 200 V) and the rated frequency (for example, 50 Hz). The AC voltage sensor 214 monitors the voltage on the AC side, and the voltage feedback control unit 221 controls the voltage so that it becomes the rated voltage. Since the voltage may drop due to the current flowing through the reactor 212, the current sensor 215 monitors it, inputs the AC voltage and AC current values to the voltage compensation unit 222, and compensates for the voltage drop in the voltage compensation unit 222. To do. Further, as a mechanism for dropping the rated frequency and the rated voltage, the AC side voltage is input to the oscillator 223, and the output phase of the oscillator 223 is controlled so as to match the phase with the AC on the PCS side.

Further, as a mechanism for dropping the rated frequency and the rated voltage, there is a hanging control unit 225. By obtaining the inner and outer products from the voltage and current on the AC side measured by the power calculation unit 224, the amount of power (active power and ineffective power) supplied by the PCS to the load side (local system) can be calculated. According to these amounts, the droop control unit 225 reduces the rated frequency and the rated voltage value so as to have a predetermined droop rate. At this time, the fixed droop control that reduces the droop rate by applying a fixed value so as to have a droop rate from the rated value can be configured in the same manner as the parallel control configuration of Non-Patent Document 1, for example.

The control block 220 of this embodiment basically follows the configuration of parallel control. However, in this embodiment, the drooping characteristic is not fixed, but is controlled based on the charge rate and the active power of the storage battery. That is, as shown in FIG. 2, the frequency droop rate is determined by the droop rate calculation unit 226 based on the magnitude of the charge rate output from the storage battery block 102 and the code of the active power calculated by the power calculation unit 224. decide.

FIG. 3 shows the configuration of the droop rate calculation unit 226. The code information of the active power output from the power calculation unit 224 is extracted by the code extraction unit 301. This is used to determine whether the current operation of the PCS 100 is a charging operation or a discharging operation. On the other hand, the charge rate information from the storage battery block 102 is input to the discharge hanging function unit 302 or the charging hanging function unit 303. Each is converted into a droop rate, and the droop rate according to the charge / discharge operation is selected by the selection unit 304 based on the code information described above.

FIG. 4 shows an example of the drooping function. In this embodiment, a monotonous increasing function as shown in FIG. 4A is used as the charging function, and a monotonous decreasing function as shown in FIG. 4B is used as the discharging drooping function. The horizontal axis shows the charge rate of the storage battery, and the vertical axis shows the droop rate. In the charging function, the larger the charging rate, the larger the drooping rate and the lower the output. The opposite is true for the discharge function. In each case, the operating range of the storage battery is determined by the charge rate, the maximum droop rate M _MAX and the minimum droop rate M _MIN are determined, and the battery is operated at M, _M'etc. within the range.

In addition to explaining the parallel control using the variable droop rate of this embodiment, first, the parallel control using the fixed droop rate will be described.

FIG. 5A is a diagram illustrating a drooping characteristic of one PCS in parallel control. As the physical quantity to be hung, the frequency f is selected for the active power P and the AC voltage V is selected for the reactive power Q by simulating the characteristics of the synchronous generator. FIG. 5A shows a diagram showing a change in frequency with respect to active power. In the following, active power and frequency will be mainly described as examples, but changes in AC voltage with respect to reactive power can also be described in the same manner. The frequency is lowered by a certain ratio with respect to the output active power. This ratio is called the drooping rate. The droop rate is the amount of decrease per electric power and corresponds to the slope θ. Normally, the frequency drop (hanging amount) is set to be within an allowable range with respect to the rated (maximum specification) power value of the PCS.

FIG. 5B shows the behavior when two PCSs having this drooping characteristic are connected on the AC side to supply active power to the load. The relationship between the active power and the frequency of each PCS moves so that the frequencies match on both sides, and the active power is automatically shared. If both have the same droop rate, the active power is evenly shared. If the ratings are different, the slope of the straight line of the hanging characteristics will be different, so the sharing ratio will be adjusted accordingly. Therefore, it is possible to share the power according to the rated active power of each PCS. The sharing of reactive power can be similarly explained by dropping the AC voltage.

This embodiment has a feature that the power distribution is changed for each PCS by making the drop rate of this active power variable according to the charge rate of the storage battery block. Specifically, the fixed hanging characteristics shown in FIGS. 5A and 5B are made variable by controlling the hanging rate based on the active power and the charging rate shown in FIG.

FIG. 6A shows the drooping characteristics of one PCS when the drooping rate is changed. Have an initial droop M ₀ and rating (maximum Usage) power value P _N the rated droop M _N which is set as reduction in the frequency falls within a range that allows to droop rate within that range is variable , The drooping rate M is determined according to the increase / decrease in the charging rate. The rated frequency is f _N, and the decrease in the allowable frequency is defined as the rated droop (Δf) _N.

More specifically, according to the charge rate and droop rate characteristics of FIG. 4A, the higher the charge rate is, the higher the droop rate is set during charging. On the other hand, according to the charge rate and droop rate characteristics of FIG. 4B, the higher the charge rate is, the lower the droop rate is set at the time of discharging. Hereinafter, a case where two PCSs are operated in parallel in this state will be considered.

In FIG. 6B, the storage battery block 1-PCS1 having this hanging characteristic and the storage battery block 2-PCS2 having this hanging characteristic are connected on the AC side, and both PCS receive the electric power (charging power) obtained by another means. It is a figure which shows the behavior of the case. When the charge rates of both storage battery blocks are the same, the droop rate is the same between PCS1 and PCS2 as shown in FIG. 5B, the power is evenly distributed, and the charge is evenly performed.

However, as shown in FIG. 6B, when the charging rate of the storage battery block 1 is smaller than the charging rate of the storage battery block 2, the hanging rate M1 of the PCS1 is set to be smaller than the hanging rate M2 of the PCS2. Therefore, of the charging power, the power allocated to the PCS1 is larger than the power allocated to the PCS2, so that the charging of the storage battery block 1 proceeds from the storage battery block 2. This state of different power distribution continues until there is no difference in the charge rates of both storage batteries, so that the charge rates of both storage batteries are finally the same. Therefore, even charging of the storage battery block can be realized.

On the other hand, in FIG. 6C, the storage battery block 1-PCS1 having this hanging characteristic and the storage battery block 2-PCS2 having this hanging characteristic are connected on the AC side, and both PCSs load the electric power (discharge power) stored in the storage battery. It is a figure which shows the behavior at the time of output to. When the charge rates of both storage battery blocks are the same, the droop rate is the same between the PCS1 and the PCS2 as shown in FIG. 5B, the power is evenly distributed, and the discharge is evenly performed.

However, as shown in FIG. 6C, when the charge rate of the storage battery block 1 is larger than the charge rate of the storage battery block 2, the droop rate of the PCS 1 is set to be smaller than that of the PCS 2. Therefore, of the discharge power, the power distributed to the PCS 1 is larger than the power distributed to the PCS 2, and the discharge of the storage battery block 1 proceeds from the storage battery block 2. This state of different power distribution continues until there is no difference in the charge rates of both storage batteries, so that the charge rates of both storage batteries are finally the same. Therefore, uniform discharge of the storage battery block can be realized.

By having a mechanism that changes the power distribution according to the charge rate as described above, the charge rate of the storage battery block connected to each PCS can be made equal. Returning to FIG. 2, the droop rate calculation unit 226 for changing the power distribution according to the charge rate is involved in the system from the power calculation unit 224 to the oscillation unit 223, which suspends the frequency by the active power. Active power is generated by exchanging power between the AC side and the storage battery block 102. On the other hand, reactive power is generated between the AC side and the reactance and capacitance constituting the PCS100. Since it is the active power that is involved in the charging / discharging of the storage battery block 102, only the active power side may be used, and the reactive power side may be the conventional fixed hanging control.

FIG. 7A is an image of a time change of the charging rate in the charging operation of the storage battery block 102. Since the charging power is even, the variation in the charging rate that occurs at the initial stage develops over time as it is, and cannot be eliminated. The storage battery block that has reached full charge first has to be stopped.

FIG. 7B is an image of the time change of the charging rate in the charging operation in this embodiment. The power distribution changes according to the variation in the charging rate that occurs at the beginning. The PCS of the battery block with a low charge rate charges more power, and the PCS of the battery block with a high charge rate charges less power, so that the operation continues until the charge rates match. Therefore, parallel operation can be continued until both PCSs are fully charged.

Furthermore, the following merits can be expected in continuously changing the power distribution according to the charging rate. Depending on the type of battery, such as a lithium-ion battery, a longer life can be expected. Not limited to parallel operation, even in the conventional technology, the charging rate can be made uniform by turning the PCS ON / OFF while observing the charging rate. However, the operation of turning on / off the charge / discharge operation imposes a burden on the battery electrode of a battery whose electrode structure changes in the charge / discharge operation such as a Li ion battery. The burden can be reduced by continuously changing the charge / discharge power as in this example. As a result, deterioration of the battery is prevented, which leads to a longer battery life.

The following operations can be expected by combining a PCS or power supply having other drooping characteristics with the storage battery block-PCS of this example. By setting the droop rate so that the minimum power required to maintain the operation of the PCS is required when the storage battery block is fully charged, the charging power can be suppressed to almost 0 while continuing the operation of the PCS. Can be done. Therefore, in the prior art, the PCS had to be stopped when the storage battery block was fully charged, but the operation can be continued while suppressing the charging. Therefore, it is not necessary to stop the PCS, and reliability in parallel operation can be maintained.

FIG. 8 shows the configuration of the PCS 100-2 connected to the storage battery block 102 in the second embodiment of the present invention. In this PCS, the rated frequency value is variable, not the frequency droop rate is variable with respect to the charge rate. The surroundings of the main circuit 210 and its control are the same as those in the first embodiment, and the control block 220 of this example substantially follows the configuration of the self-sustaining operation of the first embodiment. Further, as a mechanism for carrying out parallel control, a drooping characteristic is added to the above-mentioned independent operation control.

The hanging control block 225 of this embodiment also substantially follows the configuration of the parallel control shown in FIG. However, in this embodiment, the rated value of the frequency is not fixed as shown in FIG. 2, but the corrected value output from the rated value correction calculation unit 826 is added as shown in FIG. This correction value is determined based on the magnitude of the charge rate and the code of the active power.

FIG. 9 shows the configuration of the rated value correction calculation unit 826. The code information of the active power output from the power calculation unit 224 is extracted by the code extraction unit 901. This is used to determine whether the current operation of the PCS100-2 is a charging operation or a discharging operation. On the other hand, the charge rate information from the storage battery block 102 is input to the discharge correction function unit 902 or the charge correction function unit 903. Each is converted into a frequency correction value, and a correction value according to the charge / discharge operation is selected by the selection unit 904 based on the code information described above.

FIG. 10 shows an example of the correction function. In this example, a monotonous increase function as shown in FIG. 10A is used as the discharge correction function, and a monotonous decrease function as shown in FIG. 10B is used as the charge correction function. The horizontal axis shows the charge rate of the storage battery, and the vertical axis shows the frequency. In the discharge correction function, the larger the charge rate, the more the frequency to be added to the rated frequency and the more the output. The opposite is true for the charging correction function. In each case, the operating range of the storage battery is determined by the charge rate, the corresponding maximum frequency f _MAX and the minimum frequency f _MIN are determined, and the battery is operated at f, _f'etc. within that range. As described above, this embodiment has a feature of modifying the rated value of the frequency according to the charge rate of the storage battery block.

FIG. 11A shows the drooping characteristics of one PCS when the frequency rated value (rated frequency) is changed. Compared with FIG. 6 of the first embodiment, the slope of the droop rate _MN is fixed, but the rated frequency is changed. Initial frequency rated value f _N, and rated as decrease in the frequency range of allowable relative power value P _N (maximum Usage) fits, has a lowest frequency rated value set rated droop (Delta] f) _N The frequency rating value f ₀ is variable within that range, and the frequency rating value is determined according to the increase or decrease in the charging rate. More specifically, according to the charge rate and frequency rated value characteristics of FIG. 10A, the frequency rated value is set to increase as the charge rate increases during discharging. On the other hand, according to the charging rate and frequency rated value characteristics of FIG. 10B, the higher the charging rate is, the lower the frequency rated value is set during charging.

Consider a case where two PCSs are operated in parallel with reference to FIG. 11B. In FIG. 11B, the storage battery block 1-PCS1 having this hanging characteristic and the storage battery block 2-PCS2 having this hanging characteristic are connected on the AC side, and both PCS receive the electric power (charging power) obtained by another means. It is a figure which shows the behavior of the case. When the charge rates of both storage battery blocks are the same, the droop rate is the same between PCS1 and PCS2 as shown in FIG. 5B, the power is evenly distributed, and the charge is evenly performed.

However, as shown in FIG. 11B, when the charge rate of the storage battery block 1 is smaller than the charge rate of the storage battery block 2, the amount of hanging of the PCS 1 must be smaller than that of the PCS 2. Therefore, the frequency rated value f1 of the PCS1 is made larger than the frequency rated value f2 of the PCS2. In this way, even if the droop rate _MN is fixed, the power allocated to the PCS1 out of the charging power is larger than the power allocated to the PCS2, so that the charging of the storage battery block 1 proceeds from the storage battery block 2. This state of different power distribution continues until there is no difference in the charge rates of both storage batteries, so that the charge rates of both storage batteries are finally the same. Therefore, even charging of the storage battery block can be realized.

FIG. 11C shows a case where the storage battery block 2-PCS2 having the same hanging characteristic as the storage battery block 1-PCS1 having the hanging characteristic is connected on the AC side and both PCS receive the electric power (discharge power) stored in the storage battery. It is a figure which shows the behavior. When the charge rates of both storage battery blocks are the same, the droop rate is the same between the PCS1 and the PCS2 as shown in FIG. 5B, the power is evenly distributed, and the discharge is evenly performed.

However, as shown in FIG. 7A, when the charge rate of the storage battery block 1 is larger than the charge rate of the storage battery block 2, the drooping amount of the PCS 1 must be set to be smaller than that of the PCS 2. Therefore, the frequency rated value f1 of the PCS1 is made larger than the frequency rated value f2 of the PCS2. In this way, even if the droop rate _MN is fixed, the power allocated to the PCS1 out of the discharge power is larger than the power distributed to the PCS2, so that the discharge of the storage battery block 1 proceeds from the storage battery block 2. Since this state of different power distribution continues until there is no difference in the charge rates of both storage batteries, the charge rates of both storage batteries will eventually be the same. Therefore, even charging of the storage battery block can be realized.

The image of correcting the variation in the charge rate between the storage battery blocks under the control of this embodiment is the same as that of FIG. 7B of the first embodiment. In addition, the advantages of extending the life of the storage battery and continuing parallel operation when the storage battery block is fully charged, as described in Example 1, can be expected in this example as well.

FIG. 12 shows the configuration of the PCS 100-3 connected to the storage battery block 102 in the third embodiment of the present invention. This example is a method of changing the frequency droop rate according to the change of the charge rate as in the first embodiment. However, in this embodiment, the charge rate is not input from the storage battery block 102, but the voltage on the DC side is acquired by the voltage sensor 1216, converted into the charge rate by the charge rate estimation unit 1217, and the charge rate is dropped. Input to the rate calculation unit 1226. The charge rate estimation unit 1217 prepares in advance a table showing the relationship between the DC voltage of the battery to be used and the charge rate. The charge rate is estimated from the voltage through the table.

This embodiment is applied to the case of a low-budget simple block in which the battery controller is not mounted on the storage battery block 102. In this case, the system configuration of the storage battery block-PCS is only the assembled battery 107 to which the storage battery cell 105 is connected, the PCS 100, and the DC wiring between them. Other operations are the same as in the first embodiment. Further, the same charge rate estimation method can be applied to the case of modifying the rated value of the second embodiment.

FIG. 13 shows the configuration of the droop rate calculation unit 1326 in the fourth embodiment of the present invention. The droop rate calculation unit 1326 can be used in place of, for example, the droop rate calculation unit 226 of FIG. This example is a method of changing the frequency droop rate according to the change of the charge rate as in the first embodiment. In the first embodiment, the algorithms of the droop rate calculation unit 226 of each PCS100 are assumed to be the same. However, in this embodiment, the drooping function can be selected according to the type of the battery of the connected storage battery block 102. Prepare a set of drooping functions for charging and discharging 1226 _{1 to} 1226 _N according to the type and number of batteries. Based on the battery information (type and number) of the storage battery, an appropriate droop function set is obtained from the selection unit 1201 and used as the droop rate.

The battery information is acquired from the storage battery block 102 together with the charge rate. Alternatively, it may be held separately as data. With this configuration, the portion depending on the storage battery block 102 is collected in the storage battery block, and the PCS100 has an advantage that the same one can be applied. Other operations are the same as in the first embodiment. Further, the same configuration can be applied to the case of modifying the rated value of the second embodiment.

In the fifth embodiment of the present invention, an example is shown in which the portion for calculating the droop rate according to the charge rate is mounted on a PLC (Program Logic Controller) instead of the control block. Generally, the PCS includes a PLC as a mechanism for controlling operation. Therefore, by incorporating this embodiment into the PLC, uniform charging / discharging can be realized without modifying the PCS.

As described in the above examples, when the storage battery-PCS is controlled in parallel, the charge / discharge power proportional division rate is changed according to the charge rate of each storage battery, so that the variation in the charge rate can be corrected. Specifically, when charging, a large amount of electric power is allocated to the storage battery-PCS having a lower charge rate. When discharging, a large amount of power is contributed from the storage battery-PCS having a higher charge rate. By this operation, the variation in the charge rate of each storage battery becomes small. Therefore, more electric power can be charged to the linked system, and more electric power can be discharged from the system.

In this way, in the parallel control of a system in which a plurality of storage batteries-PCS are connected in parallel, the power to be charged / discharged in the system is distributed according to the charge / discharge rate determined by the PCS. As a result, even in parallel control, it is possible to prevent the entire system from being depleted due to the exhaustion of the charge of one storage battery, and stable control can be performed.

The present invention is not limited to the above-described embodiment, and includes various modifications. For example, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add / delete / replace the configurations of other examples with respect to a part of the configurations of each embodiment.

100: PCS, 101: PV panel, 102: Storage battery block, 103: Important load, 104: System, 105: Power storage cell, 106: Battery controller, 107: Assembly battery, 210: Main circuit, 211: Switch element, 212 : Reactor, 213: Transformer, 214: AC voltage sensor, 215: AC current sensor, 220: Control block, 221: Voltage feedback control, 222: Voltage compensation control, 223: Oscillation unit, 224: Power calculation unit, 225: Drooping Control block, 226: droop rate calculation unit, 301: code extraction unit, 302: discharge droop function unit, 303: charging droop function unit, 304: droop rate switching unit, 726: rated value correction calculation unit, 802: charging Correction function for, 803: Correction function for discharge, 901: Charge rate estimation unit, 1226: Dripping function set for charge / discharge, 1201: Function set switching unit

Claims (10)

A cooperative system of a storage battery and a power converter , in which a storage battery and a power converter are connected one-to-one, a plurality of sets thereof are connected on the AC side, and each of the power converters is independently controlled by parallel operation. In the control method of
The drooping characteristic used for controlling the parallel operation is set so that the frequency is drooped according to the active power to be output in each of the power conversion devices, and the active power is automatically shared.
The drooping characteristic is a drooping rate, and by reflecting the charging rate of the storage battery connected to each power conversion device in the drooping rate,
Each of the power conversion devices determines the charge / discharge rate of the storage battery according to the charge rate of the corresponding storage battery.
By allocating the charge / discharge power of each of the power conversion devices according to the charge / discharge rate,
Control so that the charge rates of the storage batteries are even,
A control method for a system that links a storage battery and a power conversion device. The method of determining the previous Symbol drooping rate is different at the time of discharge and during charging of the battery,
The relationship between the magnitude of the charge rate and the droop rate is
At the time of the charging, the drooping rate monotonically increases with respect to the charging rate.
During said discharge, Ri the droop rate decreases monotonically der respect to the charging rate,
The charging rate is reflected by changing the slope of the monotonous increase or the monotonous decrease.
The method for controlling a system for linking a storage battery and a power conversion device according to claim 1, wherein the system is linked. The sagging characteristic can be represented by a graph showing the relationship between electric power and frequency, and the intercept of the coordinate axis indicating the frequency is fixed, and the sagging rate reflects the charge rate of the storage battery connected to each power conversion device. Let,
The method for controlling a system for linking a storage battery and a power conversion device according to claim 1, wherein the system is linked. The charge rate is associated with the storage battery and utilizes the output of a battery controller that monitors the voltage, current and temperature of the storage battery.
The method for controlling a system for linking a storage battery and a power conversion device according to claim 1, wherein the system is linked. The charge rate is estimated from the voltage of the storage battery.
The method for controlling a system for linking a storage battery and a power conversion device according to claim 1, wherein the system is linked. The power conditioning system in a cooperative system in which a storage battery-PCS pair is formed by a storage battery block and a power conditioning system connected to the storage battery block on a one-to-one basis, and the pair is connected to a plurality of sets on the AC side. ,
A switching element that converts direct current and alternating current between the storage battery block and the alternating current side,
A power calculation unit that calculates active power from the AC voltage and AC current on the AC side,
An oscillator that generates a target frequency by reflecting the charge rate of the corresponding storage battery block and the active power.
A feedback control unit that feeds back the output of the oscillator to the switching element,
It is provided with a droop rate calculation unit that inputs the charge rate and the active power.
The droop rate calculation unit
A code extraction unit that extracts the code information of the active power and determines whether the current operation is a charging operation or a discharging operation.
A charging drooping function unit that outputs a charging drooping rate corresponding to the charging rate,
A discharge function unit that outputs a discharge rate corresponding to the charge rate, and a discharge function unit.
A selection unit for outputting either the charging droop rate or the discharging droop rate based on the code information is provided.
Based on the output of the droop rate calculation unit, the rated frequency is drooped to generate the target frequency.
The rated frequency droop is set so as to control the frequency droop rate according to the voltage and current on the AC side in each of the power conditioning systems.
The relationship between the active power and frequency of each power conditioning system moves, and the active power is automatically shared.
Power conditioning system. A control unit that inputs the charge rate and the active power is provided.
The control unit determines a control value based on the charge rate and the active power.
The rated frequency is adjusted based on the control value to generate the target frequency.
The power conditioning system according to claim 6 . The control unit
The code of the active power is detected,
A different control value is determined based on the detected code.
The power conditioning system according to claim 7 . The power calculation unit calculates reactive power from the AC voltage and AC current on the AC side.
A voltage command value generation circuit for determining a voltage drop amount using the reactive power and generating a voltage command value based on the voltage drop amount is provided.
The feedback control unit feeds back the voltage command value to the switching element.
The power conditioning system according to claim 8 . The characteristics of the charging droop rate and the discharging droop rate can be represented by a graph showing the relationship between electric power and frequency, and the section of the coordinate axis indicating the frequency is fixed, and the charging rate of the storage battery block is set to the droop rate. To reflect,
The power conditioning system according to claim 7.

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