CN111509315A - Digital battery module management unit and management system thereof - Google Patents
Digital battery module management unit and management system thereof Download PDFInfo
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- CN111509315A CN111509315A CN202010352144.9A CN202010352144A CN111509315A CN 111509315 A CN111509315 A CN 111509315A CN 202010352144 A CN202010352144 A CN 202010352144A CN 111509315 A CN111509315 A CN 111509315A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/44—Methods for charging or discharging
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
- H02J7/0031—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits using battery or load disconnect circuits
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0047—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with monitoring or indicating devices or circuits
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0063—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with circuits adapted for supplying loads from the battery
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0068—Battery or charger load switching, e.g. concurrent charging and load supply
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Charge And Discharge Circuits For Batteries Or The Like (AREA)
Abstract
A digital battery module management unit and a management system thereof comprise a positive electrode interface and a negative electrode interface which are connected with a battery string, switching devices K1 and K2, a positive electrode port and a negative electrode port of the digital battery module, and a battery management unit BMU; the positive electrode port of the digital battery module is led out from the midpoint of the switch half-bridge, and the negative electrode port of the digital battery module is led out from a negative electrode interface connected with the battery string; according to the management unit and the management system of the digital battery module, the number of the digital battery modules which actually work in the system can be changed by controlling the on-off of the switching devices of the digital battery modules in the charging and discharging processes, and the total voltage of the ports of the management system of the battery modules is adjusted, so that the energy storage conversion system connected with the management unit always works in the optimal performance interval, and the working efficiency of the energy storage conversion system is improved.
Description
Technical Field
The invention belongs to the technical field of battery management of energy storage systems, and particularly relates to a digital battery module management unit and a management system thereof.
Background
At present, in the application field of electrochemical energy storage systems, a battery cluster is generally formed by serially connecting battery modules consisting of a plurality of battery strings and a battery management unit BMU, a selection switch is not arranged in each battery module, and the battery cluster formed by serially connecting the battery modules without the selection switch has the following defects:
(1) the total voltage of the battery cluster can not be actively controlled and adjusted, and can only be passively increased and decreased along with the charging and discharging processes. The voltage of the battery cluster has a wide variation range when the battery cluster is fully charged and when the battery cluster is discharged, so that an energy storage conversion system connected with the battery cluster cannot always work in the optimal performance range.
(2) The fault redundancy of the single cells in the battery module cannot be realized. When the single batteries in the battery modules in the battery cluster are in failure, the whole battery cluster cannot work continuously, so that the reliability of the battery cluster is greatly reduced.
(3) Active equalization among the battery modules cannot be realized, and only active or passive equalization of single batteries in the modules or passive equalization among the modules can be realized. The passive equalization among the modules is energy consumption type equalization, the equalization capability is weak, and the requirements of high-frequency charge and discharge circulation of a battery cluster in energy storage application are difficult to adapt. The capacity of the battery cluster is caused to exhibit a "barrel effect" phenomenon, i.e., the total capacity of charging and discharging thereof will be determined by the battery string of the battery module having the smallest capacity. Therefore, the battery modules with inconsistent nominal parameters of the batteries cannot be connected in series to form a cluster, or the battery modules with consistent nominal parameters of the batteries and inconsistent SOH (state of health) of the batteries cannot be connected in series to form a cluster, i.e. the secondary utilization of the batteries in the echelon is not well adapted.
(4) In the normal charging and discharging process, the online diagnosis of the battery modules in the battery cluster cannot be realized.
Disclosure of Invention
The present invention is directed to overcome the disadvantages of the battery module managed by the conventional battery module management unit and the battery management system formed by connecting the battery modules in series, and provides a management unit and a management system for a digital battery module to solve the above problems.
In order to achieve the purpose, the invention adopts the following technical scheme:
a digital battery module management unit comprises a positive electrode interface and a negative electrode interface which are connected with a battery string, switching devices K1 and K2, a positive electrode port and a negative electrode port of a digital battery module, and a battery management unit BMU; the switching devices K1 and K2 are connected in series to form a switch half bridge and are connected in parallel between a positive electrode port and a negative electrode port which are connected with the battery string; the positive electrode port of the digital battery module is led out from the positive electrode port connected with the battery string, and the negative electrode port of the digital battery module is led out from the midpoint of the switch half-bridge; or the positive electrode port of the digital battery module is led out from the midpoint of the switch half-bridge, and the negative electrode port of the digital battery module is led out from the positive electrode port connected with the battery string; the control terminals of the switching devices K1 and K2 are connected to the battery management unit, the on/off of which is controlled by the battery management unit BMU.
Further, the switch half-bridge can be replaced by a switch full-bridge, and in the switch full-bridge, the switch devices are K1, K2, K3 and K4; the switching devices K1 and K2 are connected in series to form a switching half bridge, the switching devices K3 and K4 are connected in series to form another switching half bridge, the two switching half bridges are connected in parallel between a positive electrode interface and a negative electrode interface which are connected with the battery string, and the two switching half bridges are equivalent to a switching full bridge which is connected in parallel between the positive electrode interface and the negative electrode interface which are connected with the battery string; the positive electrode port of the digital battery module is led out from the midpoint of one switch half-bridge, and the negative electrode port of the digital battery module is led out from the midpoint of the other switch half-bridge; the control terminals of the switching devices K1, K2, K3 and K4 are connected to the battery management unit, the on/off of which is controlled by the battery management unit BMU.
Further, the switching devices K1, K2, K3 and K4 are any one of bidirectional conduction switching devices of a MOSFET, an IGBT with an anti-parallel diode or a relay.
Furthermore, the number of the single batteries of the battery string connected with the battery string port of the digital battery module management unit is more than or equal to 2; the single battery is any one of a ternary lithium battery, a lithium iron phosphate battery, a lithium manganate battery, a lithium cobaltate battery, a lithium titanate battery, a graphene lithium battery or a super capacitor; be provided with collection interface and communication interface on the BMU, the BMU gathers the parameter of the battery cell in the battery string through its collection interface, and the parameter includes one or several of voltage, electric current, temperature, pressure, PH value of this battery, and BMU's communication interface is CAN, RS485, one of Ethernet wired communication interface, or Wi-Fi, bluetooth, zigBee wireless communication interface.
Further, the switching on and off of the switching device in the BMU control switch half bridge is specifically: when a battery string managed by the digital battery module management unit is selected to be added, the switch device between the positive electrode port and the negative electrode port of the digital battery module is disconnected, and the other switch device is closed; when the battery string managed by the digital battery module management unit is selected to exit, the switch device between the positive electrode port and the negative electrode port of the digital battery module is closed, and the other switch device is disconnected; when the connection between the positive and negative electrode ports of the digital battery module and the battery string is selected to be cut off, so that the digital battery module port is in an open-circuit high-resistance state, the two switching devices are disconnected; the two switching devices cannot be closed simultaneously, and the danger caused by short circuit of the battery string is prevented.
Further, the on/off of the switch in the BMU control switch full bridge is specifically: when a battery string managed by the digital battery module management unit is selected to be added, a switching device between an anode port of the digital battery module and an anode interface of the battery string and a switching device between a cathode port of the digital battery module and a cathode interface of the battery string are closed, and the other two switching devices are disconnected to prevent two switching devices of the same switch half-bridge from being closed to short-circuit the battery string; when the battery string managed by the digital battery module management unit is selected to exit, two switching devices between the positive electrode port and the negative electrode port of the digital battery module and the positive electrode interface of the battery string are closed, or two switching devices between the positive electrode port and the negative electrode port of the battery module and the negative electrode interface of the battery string are closed, and the other two switching devices are disconnected to prevent the two switching devices of the same switch half-bridge from being closed to short-circuit the battery string; when the connection between the positive and negative electrode ports of the digital battery module and the battery string is selected to be cut off, so that the digital battery module port is in an open-circuit high-resistance state, all four switching devices are switched off or any three switching devices in the four switching devices are switched off; two switching devices of any one half bridge in the switch full bridge cannot be closed at the same time, and the danger caused by short circuit of the battery string is prevented.
Further, a digital battery module management system comprises a plurality of digital battery modules and a system management module, wherein the plurality of digital battery modules are connected in series to form a digital battery cluster and are connected with the system management module; the digital battery module consists of a plurality of battery strings and a digital battery module management unit; the system management module is used for acquiring parameters and states of the battery cluster, communicating with the digital battery modules through the communication interface I, managing each digital battery module in the digital battery cluster, acquiring parameters and states of the digital battery modules and downloading control parameters and instructions; and the system management module is communicated with equipment outside the system through a communication interface II.
Furthermore, the system management module changes the number of actually working battery strings in the system by controlling the on and off of a switching device of the digital battery module in the charging and discharging processes, and adjusts the total port voltage of the digital battery cluster; and controlling the alternate rest working mode of the battery string according to the charge state SOC of each digital battery module in the digital battery cluster.
Further, the system management module performs online diagnosis on the state of health (SOH) of each battery string in the digital battery cluster, and selects the battery string with the bad exit state by controlling a switching device of the battery module management unit.
Further, when the system management module controls the digital battery modules to selectively add or withdraw from working, the system management module controls the magnitude of charging and discharging current in the transient process by controlling the widths of the on-off time of the switching devices of the digital battery modules in the system, namely controlling the pulse width.
Compared with the prior art, the invention has the following technical effects:
the invention can be used in all application occasions, such as the field of battery energy storage, in which a plurality of single batteries are required to be connected in series into a battery string and managed to form a battery module, and the battery module is required to be connected in series into a battery cluster and managed. According to the management unit and the management system of the digital battery module, the number of the digital battery modules which actually work in the system can be changed by controlling the on-off of the switching devices of the digital battery modules in the charging and discharging processes, and the total voltage of the ports of the management system of the battery modules is adjusted, so that the energy storage conversion system connected with the management unit always works in the optimal performance interval, and the working efficiency of the energy storage conversion system is improved.
In the charging process, the system management module can control the switching device to selectively add or withdraw the battery strings in the digital battery modules according to the state of charge (SOC) (state of charge) of the battery strings in each digital battery module until all the digital battery modules are fully charged; when discharging, the system management module can control the digital battery modules with more SOCs (states of charge) to discharge more until all the digital battery modules are discharged, so that even if the SOCs of the battery strings in the digital battery cluster are inconsistent, the energy storage capacity of the battery strings in the digital battery modules can be fully utilized.
Through the online diagnosis of each digital battery module in the system, the potential fault module is timely found, and the switch device of the potential fault module is controlled to selectively exit the module, so that the reliability of the system is improved.
Drawings
FIG. 1 is a schematic diagram of a digital battery module management unit solution according to the present invention;
FIG. 2 is another schematic diagram of a digital battery module management unit according to another embodiment of the present invention;
FIG. 3 is a schematic diagram of a second embodiment of a management unit of the digital battery module according to the present invention;
fig. 4 is a schematic diagram of an embodiment of a digital battery module formed by a digital battery module management unit and a battery string according to the present invention;
fig. 5 is a schematic structural diagram of a management system formed by connecting a plurality of digital battery modules in series according to the present invention.
Fig. 6 is another schematic diagram of a management system according to another embodiment of the present invention, in which a plurality of digital battery modules are connected in series.
FIG. 7 is a schematic diagram of an embodiment of a management system structure formed by connecting a plurality of digital battery modules in series according to the present invention;
FIG. 8 is an equivalent circuit schematic diagram of the addition or withdrawal of a string of digitized battery modules in a battery cluster
Fig. 9 is a timing diagram of a Q1 control signal during a string-adding process of a digital battery module, and a corresponding plot of a battery cluster current and a PCS dc-side voltage.
Detailed Description
The invention is further described below with reference to the accompanying drawings:
referring to fig. 1, a digital battery module Management unit includes a positive interface BS + and a negative interface BS-, switching devices Q1 and Q2 for connecting a battery string, a positive port BM + and a negative port BM-, and a battery Management unit bmu (battery Management unit). The switching devices K1 and K2 are connected in series to form a switch half bridge and are connected in parallel between a positive electrode interface BS + and a negative electrode interface BS-which are connected with the battery string; the positive electrode port BM + of the digital battery module is led out from the midpoint of the switch half-bridge, and the negative electrode port BM-of the digital battery module is led out from a negative electrode interface connected with the battery string; the BMU is connected with corresponding interfaces of the battery string through the acquisition interfaces, acquires parameters of each single battery in the battery string, judges the states of the single batteries and the battery string according to the acquired parameters, then transmits the acquired parameters and states of the single batteries and the battery string to the system management module through the communication interfaces, and receives parameters and control instructions from the system management module; the BMU can control the on-off of the switching devices in the switch half bridge according to the received control instruction of the system management module, and can also control the on-off of the switching devices in the switch half bridge according to the detected battery parameters and states in the battery string. When the K1 is closed and switched on and the K2 is switched off, the voltage of the BM port is the managed voltage of the battery string, and the battery string can be charged and discharged; when the K1 is disconnected and cut off and the K2 is closed and conducted, the voltage of the BM port is 0V, namely the managed battery string is bypassed, and the battery string is not charged or discharged; when K1 and K2 are disconnected, the BM port is in an open-circuit high-resistance state outwards, and the managed battery string cannot be charged and discharged; it is kept in mind that K1 and K2 cannot be closed to conduction at the same time, which would otherwise bring a risk of shorting the battery string.
Referring to fig. 2, it is similar to fig. 1, except that the positive and negative terminals of the digital battery module are different, that is, the negative terminal BM-of the digital battery module is led from the midpoint of the half-bridge switch, and the positive terminal BM + of the digital battery module is led from the positive terminal connected to the battery string, and the rest is completely the same, so fig. 2 is referred to as another form of a schematic diagram of the management unit of the digital battery module according to the present invention. When K1 is closed and conducted and K2 is opened and cut off, the voltage of the BM port is 0V, namely the managed battery string is bypassed, and the battery string is not charged and discharged; when the K1 is disconnected and cut off and the K2 is closed and conducted, the voltage of the BM port is the managed voltage of the battery string, and the battery string can be charged and discharged; when K1 and K2 are disconnected, the BM port is in an open-circuit high-resistance state outwards, and the managed battery string cannot be charged and discharged; it is kept in mind that K1 and K2 cannot be closed to conduction at the same time, which would otherwise bring a risk of shorting the battery string.
Referring to fig. 3, a digital battery module management unit includes a positive electrode interface and a negative electrode interface for connecting a battery string, switching devices K1, K2, K3, and K4, a positive electrode port and a negative electrode port of the digital battery module, and a battery management unit BMU. The switching devices K1 and K2 are connected in series to form a switching half bridge, the switching devices K3 and K4 are connected in series to form another switching half bridge, and the two switching half bridges are connected in parallel between a positive electrode interface and a negative electrode interface connected with the battery string, namely equivalent to a switching full bridge connected in parallel between the positive electrode interface and the negative electrode interface connected with the battery string; the positive electrode port of the digital battery module is led out from the midpoint of one switch half-bridge, and the negative electrode port of the digital battery module is led out from the midpoint of the other switch half-bridge; the BMU is connected with the battery string through the acquisition interface, acquires parameters of each single battery in the battery string, judges the states of the single batteries and the battery string according to the acquired parameters, then transmits the acquired parameters and states of the single batteries and the battery string to the system management module through the communication interface, and receives parameters and control instructions from the system management module; the BMU can control the on-off of the switching devices in the switch half bridge according to the received control instruction of the system management module, and can also control the on-off of the switching devices in the switch half bridge according to the detected battery parameters and states in the battery string. When K1 and K4 are closed and turned on, and K2 and K3 are opened and turned off, the voltage of the BM port is the managed voltage of the battery string, and the battery string can be charged and discharged; when K1 and K3 are closed and conducted, K2 and K4 are opened and cut off, or when K2 and K4 are closed and conducted, and K1 and K3 are opened and cut off, the voltage of the BM port is 0V, namely the managed battery string is bypassed, and the battery string is not charged and discharged; when the K1, the K2, the K3 and the K4 are all disconnected or three of the switching devices are disconnected, the BM port is in an open-circuit high-resistance state outwards, and the managed battery string cannot be charged and discharged; in another embodiment, when the switches K2 and K3 are turned on and K1 and K4 are turned off, the voltage at the BM port is a negative string voltage, i.e., the string is deserialized at the positive and negative terminals of the digital battery module.
Referring to fig. 1 to 3, the switching devices K1, K2, K3 and K4 are any one of a MOSFET, an IGBT (with an anti-parallel diode) or a relay for bidirectional conduction; the communication interface of the BMU CAN be a wired communication interface such as CAN, RS485, Ethernet and the like or a wireless communication interface such as Wi-Fi, Bluetooth, ZigBee and the like; the number of the single batteries of the battery string connected with the digital battery module management unit is more than or equal to 2; the single battery can be any one of a ternary lithium battery, a lithium iron phosphate battery, a lithium manganate battery, a lithium cobaltate battery, a lithium titanate battery, a graphene lithium battery and a super capacitor; the BMU acquires parameters of the single batteries in the battery string through an acquisition interface of the BMU, wherein the parameters are one or more of voltage, current, temperature, pressure and PH value of the batteries; the BMU has the function of keeping the voltage deviation of each single battery in the battery string within an expected range, thereby ensuring that each single battery keeps the same state when in normal use, and avoiding the occurrence of overcharge and overdischarge, namely the battery balancing function.
Referring to fig. 4, a digital battery module composed of a management unit and a battery string of the digital battery module is shown in an embodiment
The battery string is formed by connecting 15 lithium iron phosphate single batteries in series, the serial numbers of the batteries are BC1, BC2 and … … BC15 respectively, the voltage and the temperature at two ends of each single battery are connected to a detection port of the battery string through leads, and the nominal total voltage of the battery string is 48V;
q1 and Q2 in the digital battery module management unit are both MOSFET switching tubes, a BMU connects a detection port of a battery string with a BMU acquisition interface through a signal line, acquires the voltage and temperature of the single batteries in the battery string, and realizes voltage equalization on the single batteries in the battery string through passive equalization, so that the voltages of the single batteries in the battery string are consistent;
the BMU communication interface is a high-speed CAN communication interface, and is communicated with the system management module through the wired communication interface, receives parameters and control instructions from the system management module, and transmits the voltage and temperature parameters of the single batteries of the battery string, the SOC and SOH parameters of the battery module and the on-off state of the MOS tube to the system management module.
The BMU can be switched on by controlling the Q1 and switched off by controlling the Q2, and can be selectively added into the battery string, namely, the voltage between the ports BM + and BM-is the total voltage of the battery string, and the battery string can be charged and discharged; the Q1 can be controlled to be cut off, the Q2 can be controlled to be switched on, and the battery string can be bypassed, namely the voltage between the ports BM + and BM-is 0V, so that the battery string cannot be charged and discharged; the connection between the port of the digital battery module and a power loop of the battery string can be cut off by controlling the cut-off of Q1 and the cut-off of Q2, so that an open circuit is formed between the ports BM + and BM-, namely, the high-resistance state is formed between the ports BM + and BM-; however, it is said that Q1 and Q2 cannot be controlled to both conduct, causing a danger of short-circuiting the battery string.
Referring to fig. 5, a schematic diagram of a management system structure formed by connecting a plurality of digital battery modules in series includes n (n > ═ 2) digital battery modules formed by battery strings and digital battery module management units, and a system management module SMM. The n digital battery modules are connected in series to form a digital battery cluster, wherein a negative port BM 1-of a first digital battery module DBM1 is connected to a system management module SMM, a positive port BM1+ of the DBM1 is connected to a negative port BM 2-of a second digital battery module DBM2, and so on until the nth digital battery module DBMN negative port BMn-, DBMN positive port BMn + is connected to the system management module SMM. The SMM manages each digital battery module in the cluster through the communication interface by communicating parameters, states and instructions. In addition, the SMM has another communication interface II, which can communicate with a device outside the battery system.
Please refer to fig. 6, which is similar to fig. 5, except that the serial connection sequence of the positive and negative ports of the plurality of digital battery modules is different, that is, the positive port BM1+ of the digital battery module DBM1 is connected to the system management module SMM, the negative port BM 1-of the DBM1 is connected to the positive port BM2+ of the second digital battery module DBM2, and so on, until the nth digital battery module DBMn positive port BMn +, the DBMn negative port BMn-is connected to the system management module SMM.
Referring to fig. 7, a schematic diagram of an embodiment of a management system structure formed by connecting 16 digital battery modules in series is shown. The digital battery module is the embodiment of the digital battery module shown in fig. 4. The positive port BM1+ of the digital battery module DBM1 is connected to the system management module SMM, the negative port BM1+ of the DBM1 is connected to the positive port BM2+ of the second digital battery module DBM2, and so on, until the 16 th digital battery module DBM16 positive port BM16+, DBM16 negative port BM 16-is connected to the system management module SMM. The main functions of the system management module SMM are as follows: (1) the SMM collects the current of the battery cluster and the total voltage of a battery cluster port, and monitors the insulation resistance of the positive electrode and the negative electrode of the battery cluster to the ground; (2) the method comprises the steps that the CAN communication interface I is communicated with each digital battery module to obtain the voltage, the temperature and the switching state of a single battery of the digital battery module, and control parameters and instructions are transmitted to each digital battery module according to the control strategy of the system; (3) the high-efficiency working range of the direct current side voltage of the power conversion system PCS is obtained through communication between the CAN communication interface II and the power conversion system PCS (power conversion system) outside the system.
Generally, the nominal voltage of a single lithium iron phosphate single battery is 3.2V, the working voltage range is 2.8V-3.6V (the voltage of 90% DOD of lithium iron phosphate current is 2.8V), then the nominal value of the port voltage of a digital battery module formed by connecting 15 lithium iron phosphate single batteries in series is 48V, the working voltage range is 42V-54V, the uncontrolled nominal voltage of a battery cluster formed by connecting 16 digital battery modules in series is 768V, the working voltage range is 672V-864V, and the working voltage range of the dc side of a PCS connected with the battery cluster is 600V-900V, and the high-efficiency and high-performance working voltage range is 650V-750V. Then the PCS is most of the time operating in the non-efficient high performance region without adjusting the port voltage for this cluster. The system management module can bypass 1 or 2 battery strings in the digital battery modules by controlling the on-off of the switch devices of the digital battery modules according to the characteristic of the PCS, so that the working voltage of the direct current side of the PCS is in a high-efficiency high-performance working interval, the PCS works in the high-efficiency high-performance working interval most of the time, and the performance and the economy of the energy storage system can be improved.
When the battery strings of the digital battery modules in the battery cluster are subjected to power cycles for many times or used for system construction, the gradient batteries are used, the parameter consistency of the battery strings of the digital battery modules in the battery cluster is poorer along with the continuous increase of the charge-discharge cycles of the batteries in the battery cluster, the capacity of the battery cluster is determined by the battery string with the minimum capacity in the battery cluster system which can not control the addition or the withdrawal of the battery string, the wooden barrel effect of the capacity is embodied, and the total energy storage capacity of the battery cluster is greatly reduced. For example, the SOC of 16 battery strings in a fully charged state is 75%, 73%, 65%, 77%, 76%, 75%, 74%, 76%, 75%, 72%, 76%, 77%, 71%, 74%, 73%, 75%, respectively. Since the SOC of the cell string in the 3 rd digital cell module is only 65% in the full-charge condition, the maximum charge-discharge capacity of the cell cluster is determined by the maximum SOC of the 3 rd cell string under the condition that the cell cluster is not controlled, namely 65%, and the digital cell module can control the switching device to enable all the cell strings to be fully charged and emptied, which is equivalent to adding the SOCs of all the cell strings and then averaging, namely the available SOC is 74%. The difference between the two can be seen to be more than 9%, so that the energy storage capacity of the battery strings in the digital battery module can be fully utilized by adopting the battery clusters formed by the digital battery module in series.
Even, when the SOH of the battery string in the 3 rd digital battery module is found to be lower than 30% through online diagnosis along with the continuous charge-discharge cycle of the battery cluster, the switching device Q1 can be controlled to be opened, the switching device Q2 is controlled to be closed, the battery string is bypassed, the system management module is informed through communication, the remaining 15 battery strings can still continue to operate, the port voltage range of the battery cluster is 630V-810V, and the port voltage range is still in the direct current side operating range of the PCS, namely, the reliability of the battery system is improved.
When a battery string in a battery cluster is selected to be added or withdrawn, the voltage of a port of the battery string changes rapidly, and a direct current side of a PCS connected to the battery string is provided with a capacitive device, if the battery string is added or withdrawn, the impact current of the battery string is large due to small internal resistance of the battery string, if the battery string is not controlled, the battery string is added or withdrawn, fig. 8 is an equivalent circuit diagram drawn according to the addition or withdrawal of the battery string in the digital battery module, wherein an inductor L s represents the sum of conductors of the series-connected single batteries and the digital battery module in the battery cluster, and each single battery has a parasitic inductor itself, a resistor Rs represents the internal resistance of the battery cluster, and a Cpcs represents a capacitive device on the direct current side of the PCS, if the inductor L s represents the sum of the series-connected single batteries and the digital battery module, and each single battery itself has a parasitic inductor, the resistor Rs represents the internal resistance of the battery cluster, and the PCS 639 represents a steady-state in which the battery string is not started to be added to the battery string when the voltage of the PCS linearly increased or withdrawn, the PCS linearly increased voltage of the PCS is equal to.
Claims (10)
1. A digital battery module management unit is characterized by comprising a positive electrode interface and a negative electrode interface which are connected with a battery string, switching devices K1 and K2, a positive electrode port and a negative electrode port of a digital battery module, and a battery management unit BMU; the switching devices K1 and K2 are connected in series to form a switch half bridge and are connected in parallel between a positive electrode port and a negative electrode port which are connected with the battery string; the positive electrode port of the digital battery module is led out from the positive electrode port connected with the battery string, and the negative electrode port of the digital battery module is led out from the midpoint of the switch half-bridge; or the positive electrode port of the digital battery module is led out from the midpoint of the switch half-bridge, and the negative electrode port of the digital battery module is led out from the positive electrode port connected with the battery string; the control terminals of the switching devices K1 and K2 are connected to the battery management unit, the on/off of which is controlled by the battery management unit BMU.
2. The management unit of claim 1, wherein the switch half-bridge can be replaced by a switch full-bridge, and in the switch full-bridge, the switching devices are K1, K2, K3 and K4; the switching devices K1 and K2 are connected in series to form a switching half bridge, the switching devices K3 and K4 are connected in series to form another switching half bridge, the two switching half bridges are connected in parallel between a positive electrode interface and a negative electrode interface which are connected with the battery string, and the two switching half bridges are equivalent to a switching full bridge which is connected in parallel between the positive electrode interface and the negative electrode interface which are connected with the battery string; the positive electrode port of the digital battery module is led out from the midpoint of one switch half-bridge, and the negative electrode port of the digital battery module is led out from the midpoint of the other switch half-bridge; the control terminals of the switching devices K1, K2, K3 and K4 are connected to the battery management unit, the on/off of which is controlled by the battery management unit BMU.
3. The management unit of digital battery module as claimed in claim 2, wherein the switching devices K1, K2, K3 and K4 are any one of MOSFET, IGBT with anti-parallel diode or relay for bidirectional conduction.
4. The digital battery module management unit according to claim 1, wherein the number of the single batteries of the battery string connected to the battery string port of the digital battery module management unit is greater than or equal to 2; the single battery is any one of a ternary lithium battery, a lithium iron phosphate battery, a lithium manganate battery, a lithium cobaltate battery, a lithium titanate battery, a graphene lithium battery or a super capacitor; be provided with collection interface and communication interface on the BMU, the BMU gathers the parameter of the battery cell in the battery string through its collection interface, and the parameter includes one or several of voltage, electric current, temperature, pressure, PH value of this battery, and BMU's communication interface is CAN, RS485, one of Ethernet wired communication interface, or Wi-Fi, bluetooth, zigBee wireless communication interface.
5. The digital battery module management unit of claim 1, wherein the switching devices in the BMU-controlled switching half-bridge are specifically configured to: when a battery string managed by the digital battery module management unit is selected to be added, the switch device between the positive electrode port and the negative electrode port of the digital battery module is disconnected, and the other switch device is closed; when the battery string managed by the digital battery module management unit is selected to exit, the switch device between the positive electrode port and the negative electrode port of the digital battery module is closed, and the other switch device is disconnected; when the connection between the positive and negative electrode ports of the digital battery module and the battery string is selected to be cut off, so that the digital battery module port is in an open-circuit high-resistance state, the two switching devices are disconnected; the two switching devices cannot be closed simultaneously, and the danger caused by short circuit of the battery string is prevented.
6. The digital battery module management unit of claim 2, wherein the on/off of the switch in the BMU control switch full bridge is specifically: when a battery string managed by the digital battery module management unit is selected to be added, a switching device between an anode port of the digital battery module and an anode interface of the battery string and a switching device between a cathode port of the digital battery module and a cathode interface of the battery string are closed, and the other two switching devices are disconnected to prevent two switching devices of the same switch half-bridge from being closed to short-circuit the battery string; when the battery string managed by the digital battery module management unit is selected to exit, two switching devices between the positive electrode port and the negative electrode port of the digital battery module and the positive electrode interface of the battery string are closed, or two switching devices between the positive electrode port and the negative electrode port of the battery module and the negative electrode interface of the battery string are closed, and the other two switching devices are disconnected to prevent the two switching devices of the same switch half-bridge from being closed to short-circuit the battery string; when the connection between the positive and negative electrode ports of the digital battery module and the battery string is selected to be cut off, so that the digital battery module port is in an open-circuit high-resistance state, all four switching devices are switched off or any three switching devices in the four switching devices are switched off; two switching devices of any one half bridge in the switch full bridge can not be closed at the same time, and the danger caused by short circuit of the battery string is prevented.
7. A digital battery module management system, which is characterized in that a digital battery module management unit based on any one of claims 1 to 6 comprises a plurality of digital battery modules and a system management module, wherein the plurality of digital battery modules are connected in series to form a digital battery cluster and are connected with the system management module; the digital battery module consists of a plurality of battery strings and a digital battery module management unit; the system management module is used for acquiring parameters and states of the battery cluster, communicating with the digital battery modules through the communication interface I, managing each digital battery module in the digital battery cluster, acquiring parameters and states of the digital battery modules and downloading control parameters and instructions; and the system management module is communicated with equipment outside the system through a communication interface II.
8. The digital battery module management system according to claim 7, wherein the system management module changes the number of battery strings actually operated in the system by controlling the on and off of the switching devices of the digital battery modules during the charging and discharging processes, and adjusts the total port voltage of the digital battery clusters; and controlling the alternate rest working mode of the battery string according to the charge state SOC of each digital battery module in the digital battery cluster.
9. The digital battery module management system according to claim 7, wherein the system management module performs online diagnosis of the state of health (SOH) of each battery string in the digital battery cluster, and controls the switching device of the battery module management unit to select the battery string with the bad exit state.
10. The digital battery module management system according to claim 7, wherein the system management module controls the magnitude of charging and discharging current in the transient process by controlling the width of on and off time of the switching device of each digital battery module in the system, that is, controlling the pulse width when the digital battery module is controlled to selectively add or withdraw from operation.
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