Patent Application
20130154569
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2011-276672, filed on Dec. 19, 2011, the entire contents of which are incorporated herein by reference.
Embodiments of the present invention relate to an electric energy storage system having a plurality of battery modules and a method of maintaining the same.
In large-scale solar power generation equipments, for example, electric energy storage systems using a lot of battery cells in order to suppress the output power variation thereof are used. That is, in the electric energy storage system of this kind, a plurality of battery cells are connected in series and/or in parallel to thereby compose a battery module, and a plurality of the battery modules are further connected to thereby compose a battery unit.
In the battery unit, it is required that the capacities and voltages and so on of all the battery modules are balanced. In case that the battery modules are not balanced, they can not sufficiently exercise the battery performances, and in addition, they are at risk for fire caused by the overcharge or overdischage and so on. For the reason, generally, in a battery module, a cell monitoring unit called a CMU (Cell Monitoring Unit) is provided for the purpose of monitoring a charge and discharge current and a voltage of each of the battery cells and controlling the charge and discharge operation thereof. In addition, a battery management unit called a BMU (Battery Management Unit) is provided in the battery unit in order to monitor and control each of the battery modules.
In the electric energy storage system like this, in case that even one battery module in the battery unit has broken down, basically, the whole battery unit should be replaced. However, the replacement of the whole battery unit results in a high cost, and thereby it will impose a heavy burden on a user.
On the other hand, when it is tried to replace the battery module alone for reducing the replacement cost, the following problem will occur. That is, in the state in which the battery modules in the battery unit are balanced with the capacity of 80% and the voltage of 26 V, if a replacement battery module at the time of shipment of new one has the capacity of 50% and the voltage of 20 V, it is necessary to conform the capacity and the voltage of the replacement battery module to those of the battery modules during use.
However, since balance adjustment operation between the battery modules after replacement is difficult and requires a long time, the decrease in system availability and the increase in maintenance cost occur.
An electric energy storage system and a method of maintaining the same of the present embodiments is characterized by including the following configuration.
A method of maintaining the electric energy storage system described above using the maintenance connector and the charge and discharge control unit for a replacement module is also an embodiment of the present invention.
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in
The battery unit 2 has a plurality of battery modules 5a-5c, and a battery management unit (BMU) 6 to manage these battery modules 5a-5c. In the present embodiment, the number of the battery modules has been made 3, but the number of the battery modules is not limited to this.
Each of the battery modules 5a-5c has a secondary cell line which is composed by connecting a plurality of battery cells and a cell monitoring unit (CMU) 7. The cell monitoring unit 7 has a function to monitor a voltage and temperature of each of the battery cells composing the secondary cell line, to transmit the data to the battery management unit 6, and to equalize the cell voltages of the respective battery cells.
The battery management unit 6 and the respective cell monitoring units 7 of the battery modules 5a-5c are connected by a communication line 30, and the information of the charge and discharge state of each of the battery modules 5a-5c, such as the temperature, output current, voltage and capacity thereof is inputted to the battery management unit 6 through the communication line 30. In addition, the battery management unit 6 is connected to the DC/DC converter 3 for charge and discharge control through the communication line 30, and has a function to transmit the information of the charge and discharge state from each of the battery modules 5a-5c to the DC/DC converter 3 for charge and discharge control and to perform the charge and discharge control for each of the battery modules 5a-5c based on a charge and discharge command from the DC/DC converter 3 for charge and discharge control.
The DC/DC converter 3 for charge and discharge control is provided with a charge and discharge control unit 8 for a replacement module. The information of the charge and discharge state of each of the battery modules 5a-5c is inputted to the charge and discharge control unit 8 for a replacement module from the battery management unit 6 through the communication line 30. A display unit 9 is provided in the charge and discharge control unit 8 for a replacement module so as to display the charge and discharge state (the capacity and voltage, for example) of each of the battery modules 5a-5c in graph form and so on as shown in
A maintenance connector 10 for connecting a replacement battery module 5d is provided in the electric energy storage system 1. The power line 20 for charge and discharge extending from the DC/DC converter 3 for charge and discharge control, and the communication line 30 extending from the charge and discharge control unit 8 for a replacement module are connected to the maintenance connector 10.
Changeover switches 40b, 40a are provided in the power line 20 connecting the DC/DC converter 3 for charge and discharge control and the battery unit 2, and the power line 20 connecting the DC/DC converter 3 for charge and discharge control and the maintenance connector 10, respectively. These changeover switches 40a, 40b operate as follows. When it is detected that the replacement battery module 5d is connected to the maintenance connector 10, the changeover switch 40a at the maintenance connector 10 side is turned ON, and the changeover switch 40b at the battery unit 2 side is turned OFF.
In the present embodiment, at the time of the operation of the electric energy storage system 1, the DC/DC converter for charge and discharge control outputs charge and discharge commands for the respective battery modules 5a-5c to the battery management unit 6 so that a DC voltage at the side of the AC/DC converter 4 for system interconnection falls within a prescribed range.
In addition, the cell management unit 7 of each of the battery modules 5a-5c receives, from the battery management unit 6, the information relating to the charge and discharge state including the SOC (State of Charge) and the life duration of each of the cells composing the secondary cell line, and controls the charge and discharge of each of the secondary cells based on the received data. As a result of this, in the state where the respective battery modules 5a-5c are normal, the capacities and the voltages of the respective battery modules 5a-5c are almost the same values (the capacity: 80%, the voltage: 26 V, in the example of
In this state, for example, it is assumed that the battery module 5c shown in
The replacement battery module 5d is charged, in its new state at the time of shipment, in the state of the capacity of 50% and the voltage of 20 V. In this state, these values thereof are not balanced with the capacity of 80% and the voltage of 26 V of each of the normal battery modules 5a, 5b connected to the battery unit 2. Consequently, the replacement battery module 5d is connected to the maintenance connector 10 provided in the electric energy storage system 1.
Then, when this connection is detected, the changeover switch 40a at the maintenance connector 10 side becomes ON and the changeover switch 40b at the battery unit 2 side becomes OFF. As a result, the battery modules 5a-5c at the battery unit 2 side are electrically disconnected from the DC/DC converter 3 for charge and discharge control, to cause the DC/DC converter 3 for charge and discharge control to stop performing the charge and discharge, and thereby the defective battery module 5c can be removed from the battery unit 2.
Even in the state in which the defective battery module 5c is removed, since the communication line 30 between the battery unit 2 and the DC/DC converter 3 for charge and discharge control is in the connected state, the charge and discharge control unit 8 for a replacement module obtains the states of the battery modules 5a, 5b in the battery unit 2 through the communication line 30. At the same time, the charge and discharge control unit 8 for a replacement module obtains the information such as the capacity and voltage and so on of the replacement battery module 5d from the cell monitoring unit 7 inside the replacement battery module 5dthrough the communication line 30 connected to the maintenance connector 10.
The charge and discharge control unit 8 for a replacement module performs the charge and discharge of the replacement battery module 5d, based on the information of each of the battery modules obtained like this, so that the normal battery modules 5a, 5b are balanced with the replacement battery module 5d. Specifically, the charge and discharge control unit 8 for a replacement module outputs a charge and discharge command to the DC/DC converter 3 for charge and discharge control, and thereby the DC/DC converter 3 for charge and discharge control charges the replacement battery module 5d connected to the maintenance connector 10, using the charge and discharge function for the battery modules 5a-5c inside the battery unit 2 which is provided as the original function of the electric energy storage system 1.
The information relating to the charged state (the capacity and voltage) of the replacement battery module 5dcaused by the DC/DC converter 3 for charge and discharge control is constantly transmitted to the charge and discharge control unit 8 for a replacement module through the communication line 30. As a result, the charge and discharge control unit 8 for a replacement module can detect that the replacement battery module 5d has come into the balanced state with the normal battery modules 5a, 5b in the battery unit 2. After they are in the balanced state, the replacement battery module 5d is removed from the maintenance connector 10 and is attached to the inside of the battery unit 2.
The present embodiment has the following effects.
The power line 20 of each of the battery modules 5a-5c is connected to the battery unit 2 by way of the terminal block 41a for the main circuit. The communication line 30 of each of the battery modules 5a-5c is connected to the battery unit 2 by way of the terminal block 41b for the communication circuit.
In the second embodiment, the power line 20 and the transmission line 30 of each of the battery modules 5a-5c can be connected to the battery unit 2 using the terminal blocks 41a, 41b, respectively. As a result, at the time of replacement of the battery module, the operation such as soldering and wire connection is made unnecessary. In addition, each of the terminal blocks 41a, 41b may be a terminal block on which a plurality of the battery modules are connected as shown in the drawing, or small-scale terminal blocks each of which connects a single battery module may be prepared by the number of the battery modules.
The present invention is not limited to the above-described embodiments, but includes other embodiments as in the following.
In the electric energy storage system 1, a case having a converter with any of the following configurations is included: the configuration including the AC/DC converter 4 for system interconnection and the DC/DC converter 3 for charge and discharge control as shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011276672 | Dec 2011 | JP | national |
