Storage battery converter control system, storage battery system, and storage battery system control method

Abstract

To achieve, in a storage battery system in which multiple charge / discharge lines each provided with a pair of converters and a storage battery are connected in parallel, a long life of the entire system while satisfying a charge / discharge amount instructed by an energy management system.SOLUTION: In a storage battery system 100, multiple charge / discharge lines 400 each provided with a pair of converters 4 and a storage battery 5 are connected in parallel. The storage battery system is provided with a control device 2 which receives a charge / discharge request from an energy management system 1, acquires a remaining life of each converter 4, and instructs charge / discharge electric power distributed according to the remaining life to each converter 4.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control system for a battery converter, a battery system, and a control method for a battery system. [Background technology]

[0002] Electric power systems are constructed by connecting power generation facilities and load facilities via power transmission and distribution facilities. There are various scales of electric power systems, from large-scale systems that connect multiple large-scale power plants with many factories, commercial facilities, and homes, to small-scale systems constructed within a specific facility. Regardless of the scale of the electric power system, an energy management system (EMS) is installed to manage the power supply and demand of the entire power system, and the energy management system balances the power supply from the power generation facilities and the power demand from the load facilities.

[0003] A storage battery system is connected to the power grid as described above and is used as one means of balancing the supply and demand of electricity. In the past, it was thought that storing large amounts of electricity was difficult, but the practical application of large-capacity storage batteries such as lithium-ion batteries and sodium-sulfur batteries has made it possible to store large amounts of electricity. By connecting a storage battery system equipped with such a storage battery to the power grid, when the supply of electricity is excessive compared to the demand, the excess electricity can be charged into the storage battery, and when the supply of electricity is insufficient compared to the demand, the shortage of electricity can be made up by discharging electricity from the storage battery.

[0004] One example of a suitable application of such a storage battery system is a combination with a power generation facility that utilizes natural energy such as solar or wind power. Power generation facilities that utilize natural energy are being widely introduced in response to the recent growing awareness of energy and environmental issues. However, power generation facilities that utilize natural energy have the disadvantage that they cannot provide a stable power supply because the generated power is easily affected by natural factors such as the season and weather. A storage battery system is a system that can compensate for this disadvantage, and by combining a storage battery system with a power generation facility that utilizes natural energy, a stable power supply can be provided.

[0005] When the storage battery system is connected to a power grid, the operation of the storage battery system is managed by the energy management system described above. The storage battery system includes an AC / DC converter connected to the storage battery. The converter has a function of converting AC power from the power grid to DC power to charge the storage battery, and a function of converting DC power from the storage battery to AC power to discharge the power to the power grid. FIG. 17 shows a storage battery system including multiple converters connected to a power grid, which is disclosed in Patent Document 1. A charge / discharge request is supplied from the energy management system to the converter, and the converter (referred to as a PCS in this document) operates according to the charge / discharge request, thereby achieving reception of power from the power grid to the storage battery, or discharge from the storage battery to the power grid. The charge / discharge request supplied from the energy management system to the converter is determined so as to balance the supply and demand of power in the entire power grid.

[0006] The converter is also called a PCS (power conditioner), and in the present invention, these are treated as synonyms, and will be referred to collectively below as a converter. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2016 / 067341 [Patent Document 2] JP 2018-191500 A Summary of the Invention [Problem to be solved by the invention]

[0008] Ensuring the reliability of storage batteries is of utmost importance in order to safely maintain the power grid. However, storage batteries have a limited lifespan, so the operation of the storage battery system must take this lifespan into consideration. Patent Document 1 discloses a control method for combining storage batteries with various life spans made by different manufacturers and using them for a long period of time. In a storage battery system consisting of multiple storage batteries, the control method detects the life span of each storage battery using a BMU (Battery Management Unit) and changes the charge / discharge amount command issued to the converter according to the life span of each storage battery. This makes it possible to provide a storage battery system that allows storage batteries with long life spans to perform more charging and discharging, and manages charging and discharging so that the replacement times of each storage battery are synchronized. This reduces the frequency of battery replacement, and makes it possible to reduce the maintenance and operating costs of the system.

[0009] Similarly, Patent Document 2 discloses a method for detecting deterioration of a storage battery in a storage battery system composed of multiple storage batteries and converters, specifically by grasping the internal temperature, and a control method for prioritizing charging and discharging in order to extend the life of the entire system. This method also aims to ensure the reliability of the power system and reduce operating costs.

[0010] On the other hand, converters in battery storage systems also have a lifespan. There are many types of converters, including those that convert power from DC to DC and change the voltage level, those that convert power from AC to DC, and those that combine these. The power conversion of converters is achieved by the switching operation of power semiconductors. In the switching operation of power semiconductors, the temperature repeatedly rises and falls due to the power loss that occurs, which causes fatigue degradation of the solder and wire bonds that connect the power semiconductors. Because this fatigue degradation phenomenon also gives the converter section a lifespan, it is important to consider the converter section's lifespan in order to extend the lifespan of a battery storage system.

[0011] Therefore, the present invention aims to achieve a long life for the entire system in a storage battery system in which multiple charge / discharge lines each having a pair of converters and a storage battery are connected in parallel, while satisfying the charge / discharge amount commanded by an energy management system. [Means for solving the problem]

[0012] In order to solve the above-mentioned problems, the control system for a storage battery converter of the present invention is characterized in that it includes a control device that receives charge / discharge requests from an energy management system for a plurality of charge / discharge lines each having a pair of converters and a storage battery, obtains the remaining life of each of the converters, and instructs each of the converters to allocate charge / discharge power according to the remaining life.

[0013] The battery system of the present invention is characterized in that it comprises a plurality of charge / discharge lines each having a pair of converters and a storage battery, and a control device that receives a charge / discharge request from an energy management system for the charge / discharge lines, obtains the remaining life of each of the converters, and instructs each of the converters to allocate charge / discharge power according to the remaining life.

[0014] The control method for a storage battery system of the present invention is characterized in that a control device of a storage battery system in which multiple charge / discharge lines each having a pair of converters and a storage battery are connected in parallel includes the steps of receiving a charge / discharge request from an energy management system, acquiring the remaining life of each of the converters, and instructing the converter to allocate charge / discharge power according to the remaining life of each of the converters. Other means will be described in the description of the embodiment of the invention. Effect of the Invention

[0015] According to the present invention, in a storage battery system in which multiple charge / discharge lines each having a pair of converters and a storage battery are connected in parallel, it is possible to achieve a long life for the entire system while satisfying the charge / discharge amount commanded by the energy management system. [Brief description of the drawings]

[0016] [Figure 1] 1 is a configuration diagram of a storage battery system according to a first embodiment. [Diagram 2] FIG. 2 is an internal circuit diagram of a converter. [Figure 3A] FIG. 4 is a diagram illustrating a charging and discharging operation of a converter. [Figure 3B] FIG. 4 is a diagram illustrating a charging and discharging operation of a converter. [Figure 4] 1 is a diagram illustrating power loss and ΔTj occurring in a power semiconductor during charging and discharging operations of a converter. [Diagram 5] FIG. 2 is a diagram for explaining a power cycle life curve of a power semiconductor. [Figure 6] FIG. 2 is a schematic cross-sectional view of a power semiconductor. [Figure 7] 13 is a flowchart of a remaining life index calculation process performed by a converter. [Figure 8] 10 is a time chart showing duty ratio control of the gate of a DC-DC power converter in response to a charge / discharge power command. [Figure 9]11 is a graph illustrating a correlation between a charge / discharge power command value and a duty ratio. [Figure 10] 1 is a graph illustrating a relationship between the number of power cycles of a power semiconductor and a charge / discharge power command. [Figure 11] 4 is a flowchart of a control process of the storage battery system. [Figure 12] FIG. 13 is a diagram showing an example of a breakdown of the charge / discharge power ratio of each converter according to the remaining life index of each converter. [Figure 13] 1 is a graph illustrating the power conversion efficiency of a converter. [Figure 14] FIG. 2 is a diagram illustrating a timing chart of a control method according to the first embodiment. [Figure 15] FIG. 11 is a configuration diagram of a storage battery system according to a second embodiment. [Figure 16] 1 is a graph showing a power cycle life curve of a power semiconductor. [Figure 17] 1 is a graph illustrating a cycle life curve of a storage battery. [Figure 18] FIG. 11 is a configuration diagram of a storage battery system according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. First Embodiment FIG. 1 is a configuration diagram of a storage battery system 100 according to the first embodiment. The storage battery system 100 shown in Fig. 1 is connected to a transmission line 7 of a power system. In addition to the transmission line 7, the power system includes a power generation facility (not shown) connected to the transmission line 7, and a load facility (not shown) connected to the transmission line 7. The storage battery system 100 is connected to a remote energy management system 1 via a network. The energy management system 1 manages the power supply and demand of the power system, such as the amount of power generated by the power generation facility, the amount of charge and discharge of the storage battery system 100, and the amount of power received by the load facility.

[0018] The battery system 100 includes a pair of converters 4, a battery 5, and a battery monitoring device 6. The battery system 100 includes a configuration in which a plurality of charge / discharge lines 400a, 400b including the converters 4 are connected in parallel, and a control device 2. The battery system 100 further includes the control device 2 that commands the converters 4 to charge and discharge power.

[0019] The storage battery system 100 includes a plurality of converters 4. For ease of explanation, a pair of groups each consisting of a converter 4, a storage battery 5 connected to the converter 4, and a storage battery monitoring device 6 is referred to as a charge / discharge line 400. Since the basic configurations of the charge / discharge lines 400a and 400b are similar, the charge / discharge line 400a will be mainly illustrated here. Note that although two charge / discharge lines 400a and 400b are shown in FIG. 1, the number of charge / discharge lines 400 may be three or more.

[0020] The storage battery 5 is connected to the battery monitoring device 6 via a signal line. The battery monitoring device 6 is connected to the control device 2 via a network. In Fig. 1, one battery monitoring device 6 is connected to one storage battery 5, but this is just one example. One battery monitoring device 6 may be connected to multiple storage batteries 5 connected in series, and one battery monitoring device 6 may also be connected to multiple storage batteries 5 connected in parallel.

[0021] The battery monitoring device 6 monitors the state of the storage battery 5. Specifically, the battery monitoring device 6 includes a current sensor, a voltage sensor, and a temperature sensor as means for measuring the state quantities of the storage battery 5. The battery monitoring device 6 constantly monitors the storage battery 5 using these sensors, and transmits information about the storage battery 5 obtained by measurements using each sensor to the control device 2.

[0022] The control device 2 includes a memory including, for example, a ROM and a RAM, an interface for inputting and outputting various information, and a processor capable of executing various calculation processes based on the various information. The control device 2 is connected to the energy management system 1, the converters 4 of the charge / discharge lines 400a and 400b, and the battery monitoring device 6 via a network.

[0023] The control device 2 plays the role of a command center that issues charge / discharge commands to the converters 4 of each charge / discharge line 400a, 400b. As an example, the control device 2 receives a charge / discharge request transmitted from the energy management system 1 and storage battery information transmitted from the storage battery monitoring device 6. The charge / discharge request includes a request regarding the power to be charged / discharged by each converter 4. The control device 2 determines a charge / discharge command (corresponding to the charge / discharge amount [kW]) for each converter 4 based on the charge / discharge request, the storage battery information, and the remaining life information of the converter 4 of the present invention, and transmits the command to each converter 4. It also has a function of outputting a shutoff command to each converter 4 in the event of an abnormality, etc.

[0024] The converter 4 is connected to the power transmission line 7 via the transformer 3. The converter 4 has a charging function of converting AC power to DC power and charging the storage battery 5, and a discharging function of converting the DC power of the storage battery 5 to AC power and discharging it to the power grid. The amount of power charged to each storage battery 5 and the amount of power discharged from each storage battery 5 are adjusted by the converter 4. The amount of power charged and discharged by the converter 4 is adjusted according to a charge / discharge instruction received from the control device 2. In the present invention, the converter 4 of each charge / discharge line 400a, 400b transmits remaining life information generated by undergoing the operation of each power conversion to the control device 2.

[0025] FIG. 2 is an internal circuit diagram of the converter 4. Next, the operating principle and mechanism of the remaining life of converter 4 according to the present invention will be described. Fig. 2 is an internal circuit diagram of converter 4 which controls the charging and discharging function of storage battery 5. Converter 4 is composed of DC-DC power conversion unit 41 and DC-AC power conversion unit 42, and power conversion is performed by switching operations of power semiconductors 44, 45 arranged inside. Storage battery 5 is connected to DC-DC power conversion unit 41, and the power system is connected to DC-AC power conversion unit 42. The operation of discharging from storage battery 5 to the power system and the operation of storing power from the power system to storage battery 5 are realized by this converter 4.

[0026] The DC-DC power converter 41 is composed of power semiconductors 44, 45 arranged on upper and lower arms, an inductor 43, a capacitor 46, a gate driver 47, and a sensing circuit 48. The upper arm power semiconductor 44 is provided with a temperature sensor 441. The lower arm power semiconductor 45 is provided with a temperature sensor 451. These temperature sensors 441, 451 are sensed by a sensing circuit 48. Although the description of the DC-AC power conversion unit 42 is omitted in this drawing, it is composed of a power semiconductor and a temperature sensor similar to the DC-DC power conversion unit 41.

[0027] The power semiconductors 44, 45 are generally a combination of an IGBT (Insulated Gate Bipolar Transistor) and a diode connected inversely in parallel, which allows a current to flow in the forward direction when the gate bias is applied and a current to flow constantly in the reverse direction, enabling bidirectional current operation. Note that instead of a combination of an IGBT and a diode, a MOSFET or a reverse conducting IGBT may be used, but in this drawing, a combination of an IGBT and a diode is shown.

[0028] The gate driver 47 receives charge / discharge commands from the control device 2 of the storage battery system 100, converts them into gate signals, and drives the gates of the upper arm power semiconductor 44 and the lower arm power semiconductor 45. The gate signals of the upper and lower arms are complementary, and when the gate signal of the upper arm is on, the gate signal of the lower arm is off, and are programmed in the control device 2 so that they are not turned on at the same time to create a short circuit. The gate signals output from the gate driver 47 turn the upper and lower arm power semiconductors 44, 45 on and off, so that energy moves from the inductor 43 to the capacitor 46 during discharging, and energy moves from the capacitor 46 to the inductor 43 during charging, thereby realizing the charge / discharge operation in the converter 4.

[0029] FIG. 3A is a diagram illustrating the discharging operation of converter 4. As shown in FIG. In the discharge operation, as shown in the left diagram, current flows alternately in the forward direction through the power semiconductor 45 of the lower arm of the DC-DC power converter 41 and in the reverse direction through the power semiconductor 44 of the upper arm at a set duty ratio. This operation is controlled by a gate signal generated by a gate driver 47. This operation transfers a certain amount of energy from the inductor 43 to the capacitor 46, and power flows from the storage battery 5 to the power grid via the DC-AC power converter 42.

[0030] FIG. 3B is a diagram illustrating the charging operation of converter 4. As shown in FIG. In charging operation, current flows alternately in the forward direction through power semiconductor 44 of the upper arm of DC-DC power converter 41 and in the reverse direction through power semiconductor 45 of the lower arm at a set duty ratio. This operation is also controlled by a gate signal generated by gate driver 47.

[0031] This operation causes a certain amount of energy to move from capacitor 46 to inductor 43, and then power flows from the power grid to storage battery 5 via DC-AC power converter 42. As described above, the gate signal generated by gate driver 47 and the resulting on / off operation of power semiconductors 44, 45 cause converter 4 to pass current in both directions, thereby achieving charging and discharging of storage battery 5.

[0032] Here, the charging and discharging operation of converter 4 causes power loss, which gives rise to the concept of the lifespan of the converter.

[0033] Figure 4 shows the power loss and ΔT j FIG. 4 is a schematic diagram showing power loss that occurs in power semiconductors 44, 45 when converter 4 repeats a stop operation, a discharge operation, a stop operation, a charge operation, and a charge / discharge operation. Here, the explanation is given for power semiconductor 44 arranged in the upper arm of DC-DC power conversion unit 41, but similar power loss occurs in power semiconductor 45 arranged in the lower arm and in the power semiconductor of DC-AC power conversion unit 42 during the charge / discharge operation of converter 4.

[0034] During the shutdown operation, no current flows, so no power loss occurs. Next, when the discharge operation begins in response to a gate signal from the gate driver 47, the power semiconductors arranged in the upper arm generate a conduction loss (Von) due to forward current, as well as a turn-on switching loss (Eon) and a turn-off switching loss (Eoff) caused by changes in voltage and current that occur during switching.

[0035] Power losses due to these operations occur steadily during the discharging operation of converter 4. Furthermore, during charging operation, the power semiconductors in the upper arm generate conduction losses (VF) due to reverse current flow, and recovery switching losses (Err) caused by changes in voltage and current that occur during switching. Power losses due to these operations also occur steadily during the charging operation of converter 4. These steadily occurring power losses and the thermal resistance that exists between the power semiconductors and the atmosphere cause the junction temperature of the power semiconductors in the upper arm to repeatedly rise and fall. Here, the amount of change in junction temperature, ΔT j and power loss P and thermal resistance R of the power semiconductor th The relationship between them satisfies the following equation (1):

number

[0036] R th is a value determined by the material and is considered to be constant, so ΔT jis generated in proportion to the power loss P. As shown in the figure, when the converter 4 repeats the normal charging and discharging operations of stopping, discharging, stopping, charging, and so on, the power loss in the power semiconductor causes the temperature to rise and fall.

[0037] This ΔT j As a result, the metal wires and solder that make up the power semiconductor expand and contract, causing fatigue degradation. j The lifespan of a power semiconductor is defined as the number of power cycles corresponding to the power supply voltage.

[0038] FIG. 5 is a diagram for explaining the power cycle life curve of a power semiconductor. The upper right of this curve is the destructive range, where metal wires or solder joints melt and fall outside the guaranteed characteristics. The lower left of this curve is the non-destructive range (normal range), and use within this non-destructive range is within the guaranteed characteristics of power semiconductors.

[0039] FIG. 6 is a schematic cross-sectional view of a power semiconductor. The power semiconductor chip 93 is bonded onto a metal patterned substrate 91 via solder 92. Metal wires 94 are electrically connected to the power semiconductor chip 93.

[0040] Fatigue resistance of the metal wire 94 and solder 92 connecting the power semiconductor chip 93, ΔT that can be guaranteed j The power cycle life curve is determined by the number of cycles. j The smaller the axial length, the smaller the amount of expansion and contraction, resulting in a smaller degree of fatigue and an increased number of power cycles that can be guaranteed.

[0041] The remaining life of a power semiconductor can be quantified by counting the cumulative number of times it is actually operated against the power cycle life curve. ΔT j The remaining life is calculated from the difference between the accumulated number of times and the guaranteed power cycle life curve. Here, ΔT jIn order to quantify the number of power cycles that differ for each test, it is possible to quantify it using the cumulative fatigue damage index D. Here, ΔT j For example, n1, n2, n3, ... are specified in units of 1°C, or in other units that make it easy to count the number of operations. j Let N1, N2, N3, . . . be the cumulative number of operations per unit time and N1, N2, N3, . . . be the guaranteed number of power cycle lifespans. The cumulative fatigue damage index D is calculated by the following equation (2).

number

[0042] When this cumulative fatigue damage index D reaches 1, it means that the power semiconductor's lifespan has expired, and the difference between them is an index of the remaining lifespan. The remaining lifespan index E is calculated using the following formula (3).

number

[0043] From the above, it has been shown that the bonding material of the internal power semiconductor deteriorates due to the charge and discharge operation of the converter 4, and the remaining life can be quantified from the power cycle life by the remaining life index. The converter 4 of the storage battery system 100 of the present invention monitors the remaining life, which is defined as the deterioration due to the operation of the constituent power semiconductors.

[0044] FIG. 7 is a flowchart of the remaining life index calculation process performed by the converter 4. The sensing circuit 48 of the converter 4 detects the ΔT j and its ΔT j and calculates a remaining life index determined from the power cycle life curve (step S10). Next, the sensing circuit 48 determines the smallest remaining life index among the remaining life indexes of the multiple power semiconductors as the remaining life index of the converter 4 (step S11) and transmits it to the control device 2 (step S12), and the remaining life index calculation process of FIG. 7 is terminated.

[0045] Here, the sensing circuit 48 detects the ΔT jis acquired through the gate wiring of the element or the power semiconductor by a dedicated thermistor or thermocouple provided in close proximity to the power semiconductor, or by other methods. In the present invention, at the timing when the charge / discharge operation is switched by a command from the energy management system 1, the control device 2 obtains a power command value based on the remaining life and provides it to the converter 4. Therefore, the sensing circuit 48 obtains ΔT j The sensing circuit 48 includes a calculator for calculating the remaining life index and a ΔT j The sensing circuit 48 includes a storage device that accumulates the data, and an interface unit that communicates the data with the control device 2. The sensing circuit 48 includes, for example, a microcomputer, a Field Programmable Gate Array (FPGA), or a dedicated integrated circuit, and realizes these functions.

[0046] Next, a life extension operation for extending the remaining life by adjusting the charge / discharge command of converter 4 will be described. FIG. 8 is a time chart showing the duty ratio control of the gate of the DC-DC power converter 41 in response to a charge / discharge power command.

[0047] The duty ratio is the ratio of the on-time given to the gate signal of the power semiconductor per period. For example, in discharging operation, the discharge current can be increased by increasing the duty ratio of the gate of the power semiconductor of the lower arm. Also, in charging operation, the charge current can be increased by increasing the duty ratio of the gate of the power semiconductor of the upper arm. In other words, the charge and discharge power of the converter 4 can be variably adjusted by adjusting the duty ratio of the gate signal on the control board. The power loss generated by the power semiconductor changes depending on the charge and discharge power, and the power loss increases as the charge and discharge power is set higher. In other words, the ΔT j can be adjusted by controlling the charge and discharge power.

[0048] Figure 9 shows the relationship between the charge / discharge power command value and ΔT j1 is a graph for explaining the correlation between the charge / discharge power command value and ΔT j This shows that. In this way, ΔT j increases in proportion to the charge / discharge power command value. j In order to reduce this, the charge / discharge power command value should be reduced.

[0049] FIG. 10 is a graph illustrating the relationship between the number of power cycles of a power semiconductor and a charge / discharge power command. The graph in FIG. 10 shows the magnitude of the guaranteed number of power cycles when the charge / discharge power command is changed with respect to the power cycle life curve of the power semiconductor. By reducing the charge / discharge power command of the converter 4, ΔT j The smaller the resistance, the lower the degree of fatigue of the power semiconductor junctions, and the higher the guaranteed number of power cycles, allowing for longer lifespans. For example, this shows that it is possible to extend the lifespan of a power semiconductor that has almost reached the end of its lifespan by issuing a command to reduce the charge / discharge power.

[0050] The configuration of the present invention, which utilizes the above-mentioned characteristics of the power semiconductor regarding its life span to enable the converter 4 to have a long life span, and its control method will be described.

[0051] FIG. 11 is a flowchart of a control process of the storage battery system 100. Upon receiving a new charge / discharge command from the energy management system 1, the control device 2 senses the remaining life index of the converter 4 in each charge / discharge line 400 from the converter 4. Then, the control device 2 determines the charge / discharge power of each converter 4 according to the remaining life index of each converter 4, and then issues a charge / discharge command to each converter 4. Here, it is assumed that the converters 4 have different remaining life indices due to past operations and replacement.

[0052] FIG. 12 shows a schematic example of a breakdown of the charge / discharge power ratio for each converter 4 according to the remaining life index of each converter 4. In FIG. For example, the breakdown is shown for a case where an energy storage system is composed of five charge / discharge lines, and the lifespan index of each converter 4 is as shown. A remaining lifespan index of 1.0 is for a brand new converter, and the smaller the value, the longer the converter's lifespan has been consumed. The lifespan considered here is the lifespan of the power semiconductor parts, as mentioned above. The total demand P from the energy management system 1 is calculated according to the ratio of these lifespan indexes. req The charge and discharge power is distributed to each converter 4. The converter life E of line x x For the charge / discharge power command value P x is given by the following equation (4).

number

[0053] As a result, the charge / discharge power of the converter 4 with a small life index, i.e., whose life has been consumed, is reduced to extend its life, and the converter 4 with a long life takes over, thereby extending the life of the entire system while generally satisfying the charge / discharge power requirements of the energy management system 1. In other words, the user can use the storage battery system 100 for a longer life.

[0054] FIG. 13 is a graph illustrating the power conversion efficiency of the converter 4. As shown in FIG. The power conversion efficiency of converter 4 depends on the charge / discharge power. In general, there is a dependency in which the efficiency decreases as the charge / discharge power is reduced. Lowering the power conversion efficiency results in wasted energy, so charging / discharging with low conversion efficiency should be avoided. Taking this tendency into account, a more efficient method is to command each charge / discharge line the charge / discharge power that can achieve the specified minimum power conversion efficiency, and then allocate the additional power according to the remaining life index of each converter 4. In this case, the converter life E of line x is x For the charge / discharge power command value P x is given by the following equation (5): min Let be the charge / discharge power that can achieve the specified minimum power conversion efficiency.

number

[0055] Here, the rated power of converter 4 is P rated Therefore, commands above the rated power should be avoided in order to ensure safe operation and life span of the converter 4. Therefore, it is necessary to confirm that the relationship in the following equation (6) holds.

number

[0056] If this relationship cannot be satisfied, a command value according to equation (1) is given.

[0057] FIG. 14 is a diagram illustrating a timing chart of the control method according to the first embodiment. Upon receiving a charge / discharge command from the energy management system 1, the control device 2 acquires a remaining life index from the converters 4 of the charge / discharge lines 400a, 400b, etc., and determines the charge / discharge power of each converter 4 based on the request value from the energy management system 1 and the above-mentioned relational expression. Then, the control device 2 transmits a charge / discharge command to each converter 4. The charge / discharge operation is continued until the request from the energy management system 1 is satisfied or until a specified SOC (State of Charge) is reached in the storage batteries 5 of each charge / discharge line 400a, 400b. The storage battery system 100 of the present invention is operated by repeating this series of processes.

[0058] When an abnormality signal is received from the battery monitoring device 6 during charging / discharging operation, or when the remaining life index of the converter 4 reaches a specified value, the charging / discharging operation or command operation of the corresponding charging / discharging line is stopped by an emergency stop signal from the control device 2. In addition, the abnormality is displayed on a display panel linked to the control device 2, and the operation manager is prompted to perform maintenance or replace parts.

[0059] Second Embodiment FIG. 15 is a configuration diagram of a storage battery system 200 according to the second embodiment. The battery system 200 shown in Fig. 15 includes a pair of converters 4, a storage battery 5, and a storage battery monitoring device 6, which are connected in parallel. The battery system 200 also includes a control device 2 that controls charge / discharge power commands for the converters 4. The battery system 200 also includes a connection unit 500 that switches connections between the multiple storage batteries 5 and the multiple converters 4. The connection unit 500 is communicatively connected to the control device 2 via a communication line (not shown).

[0060] The battery system 200 is also composed of a plurality of batteries 5 having different remaining lives. The remaining lives of the batteries 5 are communicated to the control device 2 via a battery monitoring device 6. The remaining life of the converter 4 is communicated to the control device 2 by a control board of the converter 4.

[0061] The connection unit 500 of the second embodiment of the present invention is characterized in that it connects the storage battery 5 and the converter 4 so that the ranking of the remaining life of the storage battery 5 and the ranking of the remaining life of the converter 4 match, and configures each charge / discharge line 400. This connection is established, for example, when a charge / discharge request from the energy management system 1 is completed and all the charge / discharge lines 400 stop operating. Note that, although two charge / discharge lines 400a, 400b are depicted in FIG. 15, there may be three or more charge / discharge lines.

[0062] The effects of the second embodiment of the present invention will be described below. Fig. 16 is a graph showing a power cycle life curve of a power semiconductor, and Fig. 17 is a graph explaining a cycle life curve of a storage battery.

[0063] In power semiconductors, lowering the charge / discharge power command reduces power loss and reduces ΔT j As already explained, the characteristic that the power cycle life is extended because the power consumption is reduced and fatigue deterioration of the joint members is improved. On the other hand, a similar tendency is observed in the storage battery 5, and it is known that the guaranteed number of charge / discharge cycles tends to increase as the charge / discharge power command decreases. This is because the heat generation of the resistance parts present inside the storage battery is suppressed, and the progress of deterioration of the joint parts is suppressed.

[0064] By utilizing these similar relationships between the charge / discharge power command values ​​and the number of guaranteed cycles and applying control that changes the charge / discharge power according to the remaining life of the converter 4, it is possible to suppress the charge / discharge power for the storage battery 5 with a short remaining life, suppress the progression of deterioration, and extend the life of the storage battery 5 together with the converter 4. In other words, the present invention makes it possible to provide a storage battery system 200 that can be used for a longer period of time as a whole system while satisfying the charge / discharge requests from the energy management system 1. In particular, even when applying an already deteriorated second-hand storage battery to the new storage battery system 200, the present invention allows it to be used for a longer period of time, contributing to efficient system operation.

[0065] Third Embodiment FIG. 18 is a configuration diagram of a storage battery system 300 according to the third embodiment. 18 includes a pair of converters 4, a storage battery 5, and a storage battery monitoring device 6, which are connected in parallel. Also includes a control device 2 that controls charge / discharge power commands for these converters 4.

[0066] The storage battery system 300 also includes a communication line 33 connecting the control device 2 and each converter 4. Here, the communication line 33 may be a wired optical line or wireless communication. The communication line 33 communicates charge / discharge power commands from the control device 2, and also communicates the remaining life index described in the first embodiment from each converter 4. Wireless communication is effective when the control device 2 is remotely separated from the converters 4 or when each charge / discharge line is remotely separated, and can eliminate wire congestion, making it possible to provide a storage battery system 300 that is easier to maintain.

[0067] <<Variation>> The present invention is not limited to the above-described embodiment, and includes various modified examples. For example, the above-described embodiment has been described in detail to clearly explain the present invention, and is not necessarily limited to those having all of the configurations described. It is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is also possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

[0068] The above configurations, functions, processing units, processing means, etc. may be realized in part or in whole by hardware such as an integrated circuit. The above configurations, functions, etc. may be realized by software by a processor interpreting and executing a program that realizes each function. Information such as the program, table, file, etc. that realizes each function can be stored in a recording device such as a memory, a hard disk, or an SSD (Solid State Drive), or a recording medium such as a flash memory card or a DVD (Digital Versatile Disk).

[0069] In each embodiment, the control lines and information lines are those that are considered necessary for the explanation, and not all control lines and information lines in the product are necessarily shown. In reality, it may be considered that almost all components are connected to each other. [Explanation of symbols]

[0070] 1. Energy Management System 2. Control device 3. Transformer 4. Converter 5. Storage battery 6 Battery monitoring device 7. Power Lines 33 Communication Line 41 DC-DC power converter 42 DC-AC power converter 43 Inductor 44,45 Power semiconductors (switching elements) 46 Capacitor 47 Gate Driver 48 Sensing Circuit 91 Patterning Substrate 92 Solder 93 Power Semiconductor Chips 94 Metal Wire 100, 200, 300 Battery Storage System 400, 400a, 400b Charge / discharge lines 500 Connection

Claims

1. a control device that receives a charge / discharge request from an energy management system for a plurality of charge / discharge lines each including a pair of converters and a storage battery, acquires a remaining life of each of the converters, and commands each of the converters to allocate charge / discharge power in accordance with the remaining life; A control system for a storage battery converter comprising:

2. the control device allocates to each of the converters a larger charge / discharge power as the remaining life of each of the converters increases; 2. The battery converter control system according to claim 1 .

3. The control device derives a remaining life index from a cumulative fatigue damage index calculated based on a ratio of the number of junction life cycles of the multiple power semiconductors constituting each of the converters to the number of cumulative operation cycles for each amount of change in junction temperature caused by power loss during charging and discharging operations, and determines the remaining life of the converter based on the smallest remaining life index among the multiple power semiconductors constituting the converter.

2. The battery converter control system according to claim 1 .

4. The control device calculates a cumulative fatigue damage index by dividing the number of operation cycles for the amount of change in the junction temperature of each of the power semiconductors by the guaranteed number of power cycles and accumulating the result, and calculates a remaining life index by subtracting the cumulative fatigue damage index from 1.

4. The battery converter control system according to claim 3.

5. The control device determines power to be allocated to each of the converters based on a ratio of a remaining life index of each of the converters to a sum of the remaining life indexes of the converters.

2. The battery converter control system according to claim 1 .

6. The control device determines the power to be allocated to each of the converters by adding an amount exceeding the power that achieves a predetermined charge / discharge efficiency of the converter as an adjustment amount based on a ratio of the remaining life index of each of the converters.

2. The battery converter control system according to claim 1 .

7. A plurality of charge / discharge lines each including a pair of converters and a storage battery; a control device that receives a charge / discharge request from an energy management system for the charge / discharge line, acquires a remaining life of each of the converters, and commands each of the converters to allocate charge / discharge power in accordance with the remaining life; A storage battery system comprising:

8. Each of the storage batteries is provided with a storage battery monitoring device that monitors a remaining life of the storage batteries, a connection section for connecting the converters so as to match the order of remaining lives of the storage batteries; The battery system according to claim 7, further comprising:

9. The control device allocates the charge / discharge power to each of the converters so that the charge / discharge power is larger as the remaining life of each of the converters is longer, and adjusts the charge / discharge power to satisfy a charge / discharge request from an energy management system. The battery system according to claim 7 .

10. The control device and each of the converters are connected via a network by optical communication or wireless communication. The battery system according to claim 9 .

11. A control device of a storage battery system in which a plurality of charge / discharge lines, each including a pair of converters and a storage battery, are connected in parallel receives a charge / discharge request from an energy management system; obtaining a remaining life of each of the converters; instructing each of the converters to charge and discharge power allocated in accordance with the remaining life of the converter; A method for controlling a battery converter comprising:

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