Patent Application
20160187431
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2014-266179, filed Dec. 26, 2014; the entire contents of which are incorporated herein by reference.
An embodiment described herein relates to a storage battery, a storage-battery evaluating device, and a storage-battery evaluating method.
In electric vehicles and stationary battery systems, when used products are traded for secondary use or effective maintenance is performed, a technique for accurately and promptly evaluating the deterioration of the operating secondary batteries thereof has been demanded.
For example, to evaluate the deterioration of a secondary battery, a technique of estimating the performance of the secondary battery by analyzing the change in a charge/discharge curve that is precisely measured based on the material characteristics of the secondary battery has been considered.
Furthermore, for a secondary battery module constituted by a large number of battery cells, a technique of evaluating the performance of the entire module by analyzing and evaluating the change in a charge/discharge curve that is electrically synthesized has been also considered.
However, when the performance of the secondary battery module is deteriorated, it is difficult to determine whether all the battery cells are deteriorated substantially uniformly or the deterioration is caused by the influence of the characteristics of a small number of the battery cells the deterioration progresses of which have been advanced.
Similarly, when the performance of an entire battery string that is obtained by connecting a plurality of secondary battery modules in series is deteriorated, it is difficult to determine whether all the modules are deteriorated substantially uniformly or the deterioration is caused by the influence of the characteristics of a small number of the modules the deterioration progresses of which have been advanced.
According to one embodiment, a storage battery including: a plurality of power storage devices that are arranged in series; and a plurality of switching circuits that are each arranged between adjacent power storage devices.
Each of the switching circuits includes
The input terminal Si is electrically connected to the output terminal So of the switching circuit adjacent via the one of the adjacent power storage devices and the output terminal So is electrically connected to the input terminal Si of the switching circuit adjacent via the other of the adjacent power storage devices.
Hereinafter, the detailed explanation will be described with the accompanying drawings.
An ESS 100 is connected to a power system (hereinafter, referred to as “system”) 121. A load 122 is connected to the system. The ESS 100 performs charge/discharge (at least either charge or discharge) in accordance with an instruction from the system 121 so that power in the system 121 is leveled and the power quality is ensured. All or a part of power discharged from the ESS 100 may be supplied to the load 122 connected to the system. When the load 122 is a energy storage device, an inner energy storage device 105 may be charged by supply of power from the energy storage device. The ESS 100 may be separated from the system 121 and be connected to an independent specific load 123. In this case, the ESS 100 may charge/discharge the specific load 123.
A connected/independent-operation switching relay (hereinafter, referred to as “relay”) 101 switches the connection destination of the ESS 100 between the system side and the specific-load side in accordance with an instruction from a controller 106.
A bidirectional AC/DC inverter 102 converts AC power supplied from the system side or the specific-load side to DC power and outputs the DC power to a bidirectional DC/DC converter 103. The bidirectional AC/DC inverter 102 converts DC power supplied from the inner energy storage device 105 via the bidirectional DC/DC converter 103 to AC power and outputs the AC power to the system side or the specific-load side via the relay 101. When the specific load 123 is driven by DC power, an inverter that converts AC power to DC power or DC power to AC power may be arranged at the specific-load side.
The bidirectional DC/DC converter 103 performs DC-DC conversion of the voltage of DC power supplied from the bidirectional AC/DC inverter 102 to generate constant voltage and outputs the power having the generated constant voltage to a battery management system (BMS) 104. The bidirectional DC/DC converter 103 converts the voltage of DC power supplied from the energy storage device 105 to voltage corresponding to the bidirectional AC/DC inverter 102 and outputs the power having the converted voltage to the bidirectional AC/DC inverter 102. The bidirectional DC/DC converter 103 may be omitted in some embodiments.
The BMS 104 is connected to the energy storage device 105 and performs charge/discharge control to the energy storage device 105 in accordance with an instruction from the controller 106. In the embodiment illustrated in
The operations of the relay 101, the bidirectional AC/DC inverter 102, the bidirectional DC/DC converter 103, and the BMS 104, which are connected to the controller 106, are controlled by the controller 106.
The controller 106 includes a feedback controller 107, a sequencer 108, an interface 109, and a control power supply 110. The controller 106 is referred to as a PCS (Power Conditioning System) in some cases.
The control power supply 110 supplies operation power of the controller 106.
The interface 109 is a communication interface that performs wired or wireless communication with the outside via a communication network. The interface 109 communicates with an external device such as SCADA (Supervisory Control And Data Acquisition) to receive an instruction for charge/discharge. The interface 109 may transmit to an external device information about the operation state in the ESS 100, the state of electric power stored in the energy storage device 105, or the like.
The sequencer 108 converts the instruction for charge/discharge from the SCADA or the like to an operation instruction (a control sequence) for the BMS 104 and transmits the operation instruction to the BMS 104.
The feedback controller 107 performs control to stabilize the operations of the bidirectional AC/DC inverter 102 and the bidirectional DC/DC converter 103. For example, the feedback controller 107 performs control to stabilize the step-up/step-down operation of the bidirectional DC/DC converter 103. The feedback controller 107 performs control to stabilize the amplitude, the frequency, or the like of AC power generated by the bidirectional AC/DC inverter 102. The feedback controller 107 may receive information for specifying the specific contents of control from an external device such as SCADA and perform control based on the information.
The energy storage device 105 is a energy storage device that can charge/discharge electric power. The energy storage device 105 includes one or more arbitrary secondary batteries. Examples of the arbitrary secondary battery include a lithium ion battery, a lithium ion polymer battery, a lead storage battery, a nickel-cadmium battery, and a nickel-hydrogen battery. In the present embodiment, the energy storage device 105 is used for the ESS. However, the energy storage device 105 may be provided in other types of a device or system such as a portable electronic device and an electronic vehicle. The energy storage device 105 includes an evaluating device 111 that evaluates the deterioration of storage batteries. The evaluating device 111 may be arranged not inside the energy storage device 105 but outside the energy storage device 105 to be externally connected to the energy storage device 105.
The energy storage device 105 here includes two types of cells that are the cell A and the cells B. However, the energy storage device 105 may include only one type of cells or may include three or more types of cells. The battery A and the batteries B can be connected to and disconnected from the bidirectional AC/DC inverter by the switches 104A, 104B, 104C, and 104D, respectively. However, in some embodiment, the battery A and the batteries B may be fixedly connected to the bidirectional AC/DC inverter while omitting these switches. In other embodiments, the bidirectional DC/DC converters 103A to 103D may be omitted, as described above. The present embodiment has a characteristic in which the deterioration of the cells, the battery modules, or the batteries is evaluated by the outside, even when the energy storage device 105 is operating. For example, even when the switch 104A is in an on state, the deterioration of each cell 12 of the battery A is measured and evaluated by the outside.
Each of the switching circuits includes an input terminal Si and an output terminal So, an input terminal I and an output terminal O, and an input terminal Mi and an output terminal Mo. The input terminal Si and the output terminal So are used to bypass an arbitrary cell in the series connection of the cells. The input terminal I and the output terminal O are used to connect adjacent cells to each other. The input terminal Mi and the output terminal Mo are used to set a route for connecting the arbitrary cell to a charge/discharge inspecting device 202. Each of the switching circuits includes seven switches for setting the connection among the terminals.
The output terminal So is connected to the input terminal Si and the input terminal I via respective switches. The output terminal O is connected to the input terminal Si, the input terminal I, and the input terminal Mi via respective switches. The output terminal Mo is connected to the input terminal I and the input terminal Mi via respective switches.
Broken lines and solid lines connecting the terminals in blocks, which represent the switching circuits, represent switches. The broken lines indicate switches that are off (open). The solid lines indicate switches that are on (closed). The positive electrode of a cell is connected to the input terminal I of the switching circuit at the positive electrode side of the cell. The negative electrode of a cell is connected to the output terminal O of the switching circuit at the negative electrode side of the cell. However, since no switching circuit is provided at the positive electrode side of the cell (Bn+2) that is the top of the positive electrode side and no switching circuit is provided at the negative electrode side of a cell that is the end of the negative electrode side, the above connections do not exist there.
The positive electrode of the cell (Bn+2) that is the top of the positive electrode side is electrically connected to the output terminal Mo of the switching circuit (SWn+2) at the negative electrode side of the cell (Bn+2). The negative electrode of the cell (B1) that is the end of the negative electrode side is electrically connected to the input terminal Mi of the switching circuit (SW2) at the positive electrode side of the cell (B1). The measuring terminals of the charge/discharge inspecting device 202 are connected respectively to the both ends of a row formed of the cells and switching circuits that are alternately arranged in series. More specifically, one of the measuring terminals is electrically connected to the positive electrode of the cell (Bn+2) that is the top of the positive electrode side and the output terminal Mo of the switching circuit (SWn+2) at the negative electrode side of the cell (Bn+2). The other of the measuring terminals is electrically connected to the negative electrode of the cell (B1) that is the end of the negative electrode side and the input terminal Mi of the switching circuit (SW2) at the positive electrode side of the cell (B1).
In this way, in the storage battery, by employing a plurality of switching circuits arranged between the adjacent cells, it is possible to selectively set any one of a plurality of patters to electrically separate each one of the plurality of cells connected in series from other cells of the plurality of cells excluding the one cell and electrically connect the other cells in series.
In
The charge/discharge evaluation controller 201 selects a cell (a target cell) to be measured and evaluated and controls the switches in each switching circuit in such a way that the target cell is electrically separated from the other cells and the other cells are connected in series (in such a way that the both adjacent cells of the target cell are connected with each other by bypassing the target cell). The charge/discharge evaluation controller 201 controls the switches in each switching circuit in such a way that the target cell is connected to the charge/discharge inspecting device and the other cells are electrically separated from the charge/discharge inspecting device 202.
In the embodiment illustrated in
That is, in the switching circuit (SWn) at the negative electrode side of the cell Bn, the switch between the input terminal Si and the output terminal So and the switch between the input terminal Si and the output terminal O are turned off (open) to open the input terminal Si. The switch between the input terminal I and the output terminal So is turned on (closed) to connect these terminals. The switch between the input terminal Mi and the output terminal O is turned on to connect these terminals. Both of the switch between the input terminal I and the output terminal O and the switch between the input terminal I and the output terminal Mo are turned off and the switch between the input terminal Mi and the output terminal Mo is turned off. The switch setting and connection state among the terminals as described above is referred to as “Status I”.
In the switching circuit (SWn+1) at the positive electrode side of the cell Bn, the switch between the input terminal Si and the output terminal O is turned on to connect these terminals. The switch between the input terminal I and the output terminal Mo is turned on to connect these terminals. Both of the switch between the input terminal Mi and the output terminal O and the switch between the input terminal Mi and the output terminal Mo are turned off to open the input terminal Mi. The other switches than the above switches are all turned off. The switch setting and connection state among the terminals as described above is referred to as “Status B”.
In each of the other switching circuits than the switching circuits (SWn and SWn+1), the switch between the input terminal Si and the output terminal So is turned on to connect these terminals (or the input terminal Si may be opened in some embodiments). The switch between the input terminal I and the output terminal O is turned on to connect these terminals. The switch between the input terminal Mi and the output terminal Mo is turned on to connect these terminals. The other switches than the above switches are all turned off. The switch setting and connection state among the terminals as described above is referred to as “Status R”.
The above control of the switches in the switching circuits causes the cells excluding the cell Bn to be connected in series, as indicated by the line L1 in
The charge/discharge inspecting device 202 charges/discharges (at least either charges or discharges) a target cell for measurement (see
The deterioration evaluator 203 acquires measurement data (such as current, voltage, power, and a temperature) that is obtained by measuring the target cell at a fixed sampling rate during the charge/discharge and stores the acquired measurement data in the monitor-value storage 204 (see
For example, the deterioration evaluator 203 generates a charge/discharge curve (also referred to as “QV curve”) from the acquired measurement data group and calculates a feature amount from the generated charge/discharge curve or a curve (a dQdV curve) that is obtained by differentiating the charge/discharge curve by using a calculation algorithm that is determined in advance. Data (such as a function and a table) associating the feature amount and the performance (such as the capacity value and the internal resistance value) of a cell is stored in the battery evaluation DB 205. The deterioration evaluator 203 calculates the cell performance from the data in the battery evaluation DB 205 by using the calculated feature amount. The deterioration evaluator 203 also sequentially selects the other cells, charges/discharges, measures, and evaluates the cells to calculate the performance of each cell.
Alternatively, the deterioration evaluator 203 may apply a different estimating method. For example, the deterioration evaluator 203 calculates the internal resistance value of the target cell, generates measurement data including temperature-time distribution and current-time distribution and a deterioration characteristic map indicating the distribution of deterioration constant relative to the cell voltage and the temperature, and integrates the staying time on a cell voltage-temperature plane of the deterioration characteristic map. In this way, the deterioration evaluator 203 may estimate the deterioration amount of the target cell (Japanese Patent Laid-Open No. 2014-190763).
The deterioration evaluator 203 calculates the performance value of the battery module from the performance values of the cells that are calculated in the above way and returns the evaluation result based on the calculated performance value to the BMS via the charge/discharge evaluation controller 201. For example, the deterioration evaluator 203 may determine the worst value of the performance values of the cells as the evaluation result of the battery module or determine the statistic value such as the average value as the performance value of the battery module. Alternatively, the deterioration evaluator 203 may calculate the residual life of the battery module based on the data of the relation between performance values and residual lives and return the calculated residual life as the evaluation result. The deterioration evaluator 203 may return the evaluation result based on the performance value of each cell to the BMS via the charge/discharge evaluation controller 201. The evaluation result may be a performance value as it is or may be the residual life of a cell calculated from the evaluation result. The above methods of calculating the performances of the cells and the battery module are some examples among many. Any other calculating method can be applied as long as the respective performances are calculated from measurement data. For example, a value that is obtained by multiplying the feature amount calculated by the deterioration evaluator 203 by a fixed coefficient may be determined as the performance value of the cell.
To switch a target cell from Bn to Bn+1, it suffices that the status of each switching circuit is controlled in the following way. As shown in Table 1, when the cell Bn is selected, SWb, SWb+1, and the others are in the status I, the status B, and the status R, respectively. When the cell Bn is switched to the cell Bn+1, SWn+1, SWn+2, and the others enter the status I, the status B, and the status R, respectively. Accordingly, the cell Bn+1 is electrically separated from the battery module and the battery module excluding the cell Bn+1 starts to function. However, when the cell Bn+2 is selected in the embodiment in
When the charge/discharge evaluation controller 201 determines to start operations, the charge/discharge evaluation controller 201 selects one cell as a target cell and connects the other cells in series to bypass the target cell. That is, the switches in each switching circuit are set so as to achieve the above connection.
The charge/discharge evaluation controller 201 electrically connects the target cell to the charge/discharge inspecting device. More specifically, the switches in each switching circuit are set so as to electrically connect only the target cell to the chare/discharge inspecting device. This setting may be performed at Step 501. The charge/discharge inspecting device 202 charges/discharges the target cell. The charge/discharge evaluation controller 201 specifies a charging/discharging condition such as a charging rate based on the battery evaluation DB 205 and instructs the charge/discharge inspecting device 202 about the condition.
The deterioration evaluator 203 sequentially acquires measurement data that is output at a fixed sampling rate from the monitor device arranged corresponding to the target cell. For example, the measurement data includes information about voltage, the cell temperature, or the like. The acquired measurement data is stored in the monitor-value storage 204.
The deterioration evaluator 203 obtains the performance value (such as the capacity value and the internal resistance value) of a cell by evaluating the deterioration of the cell based on the measurement data stored in the monitor-value storage 204 and the battery evaluation DB 205.
After the charge/discharge for measurement of the target cell is completed, the charge/discharge inspecting device 202 adjusts the charged amount of the target cell after the deterioration evaluation so as to make the charged amount equal to that of an ESS cell (the battery module 300) that is being operated.
The charge/discharge evaluation controller 201 determines whether all the cells in the battery module have been measured. When a cell having not been measured exists (NO at Step 506), the operation returns to Step 501 and a next cell is selected.
When all the cells in the battery module have been measured (YES at Step 506), the charge/discharge evaluation controller 201 obtains the performance value of the battery module by aggregating the performance values of the cells. The charge/discharge evaluation controller 201 outputs an evaluation result based on the performance value of the battery module. Alternatively, the charge/discharge evaluation controller 201 may output an evaluation result for each cell based on the performance value thereof.
The charge/discharge evaluation controller 201 sets the switches in each switching circuit in such a way that the target cell is finally connected to the battery module again at Step 508. More specifically, the charge/discharge evaluation controller 201 sets all the switching circuits to the status R. Accordingly, all the cells in the battery module are connected in series.
In the present embodiment, a cell to be measured is sequentially switched while targeting the cells in the battery module. However, the unit for measurement may be not a cell but a power storage module. For example, in some embodiments, switching circuits are arranged among battery modules and measurement is performed by switching a battery module to be measured sequentially while targeting the battery modules in a battery string. In this case, measurement and performance evaluation are performed in battery-module unit and the evaluated performances of the battery modules are aggregated. Accordingly, the performance of the battery string can be evaluated.
In the present embodiment, each switching circuit includes the input terminal Mi and the output terminal Mo and the measuring terminals of the charge/discharge inspecting device are connected respectively to the both ends of the row formed of the cells and the switching circuits that are arranged alternately in series (see
As described above, according to the present embodiment, in the electric power storage module in which cells are connected in series, the electric power storage modules in operation can be evaluated from the outside. That is, the switching circuits are interposed among the cells connected in series and an arbitrary cell in the battery module is separated from the series connection of the cells by settings of the switching circuits. Cells before and after the separated cell are reconnected by settings of the switching circuits to bypass the separated cell. The separated cell can be electrically connected to the outside of the battery module freely. Thus, by independently connecting to the charge/discharge inspecting device, the separated cell can be charged/discharged for measurement and the deterioration of the separated cell can be evaluated.
At that time, owing to the separation of the cell, the voltage of the battery module is decreased by the voltage of one cell, and when the number of the cells is “h”, the decreased voltage is “1/h”. This decrease can be absorbed by the voltage change of a cell the voltage of which monotonically increases relative to the charged amount or by the DC/DC converter 103 that keeps the output voltage of the battery constant. Therefore, even when one cell is electrically separated from the battery module for measurement, the functions and performance of the battery module can be held equal to that before the separation.
Similarly, when the unit for measurement and evaluation is not a cell but a battery module, switching circuits are interposed among all battery modules connected in series so that an arbitrary battery module can be separated from the series connection of the battery modules by settings of the switching circuits. The separated battery module can be electrically connected to the outside of the battery module freely. Thus, the separated battery module independently connects to the charge/discharge inspecting device so that the separated battery module can be charged/discharged for measurement and the deterioration of the separated battery module can be evaluated. When a battery module is separated, the voltage decreases by voltage of one battery module. However, as in the above case, this voltage decrease can be absorbed by the DC/DC converter 103 that keeps the output voltage of the battery constant or the like. Therefore, even when one battery module is electrically separated from a battery string for measurement, the functions and performance of the battery string can be held equal to that before the separation.
The inputter 62 includes an input device such as a keyboard and a mouse. The display 63 includes a display such as an LCD (Liquid Crystal Display) and a CRT (Cathode Ray Tube). The communicator 64 includes wireless or wired communicating means and performs communication by a predetermined communication method.
The external storage 66 includes a storage medium such as an HDD, an SSD, a memory device, a CD-R, a CD-RW, a DVD-RAM, and a DVD-R. In the external storage 66, a program for causing the CPU 61 to execute the functions of the respective processing units in
The main storage 65 develops a control program stored in the external storage 66 under the control of the CPU 61 and stores data required for executing the program, data generated by execution of the program, and the like therein. The main storage 65 includes an arbitrary memory or storage such as a volatile memory (such as a DRAM and a SRAM) or a non-volatile memory (such as a NAND flush memory and a MRAM). The control program developed by the main storage 65 may be executed by the CPU 61 to perform the functions of the charge/discharge evaluation controller 201, the charge/discharge inspecting device 202, and the deterioration evaluator 203.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-266179 | Dec 2014 | JP | national |
