Black start method of energy storage system and energy storage system

Abstract

The present invention provides a black start method and energy storage system, comprising the following steps: presetting the address numbers of each battery management system, setting one battery management system as the master, and the others as slaves; after each battery management system is powered on, each battery management system sends its own address number frame message; the host detects the address number frame message, and if no address number frame message is detected, the host controls the corresponding control switch to close; if an address number frame message is detected, the host designates one of the battery management systems to control the corresponding control switch to close. This invention solves the problem of backflow caused by the simultaneous power supply of multiple parallel battery clusters, preventing damage to electrical equipment due to excessive loop current.

Description

Technical Field

[0001] The present invention relates to the field of energy storage, and in particular to a black start method for an energy storage system and an energy storage system. Background Art

[0002] Household energy storage systems usually consist of battery packs, BMS (battery management system), PCS (energy storage inverter), photovoltaic panels or AC mains power. The PCS can start working through photovoltaic or mains power supply and send instructions to the BMS. The BMS controls the closure of the battery main circuit relay, thereby enabling photovoltaic or mains power to charge the battery and discharge the battery to household loads.

[0003] In an off-grid state with no photovoltaic power or mains electricity, the PCS has no power supply and cannot start working, so the battery cannot be used to power household loads. At this time, a black start operation is required to allow the BMS to control the battery main circuit relay to close, and the battery voltage output is used to power the PCS, so that the entire energy storage system can start and work normally.

[0004] Household energy storage systems have large capacity requirements and generally require multiple battery clusters to be connected in parallel. If there is a voltage difference between the battery clusters, after triggering a black start, when the BMS of each battery cluster actively closes the main circuit relay, the battery cluster with higher voltage will charge the battery cluster with lower voltage. In this charging circuit, the equivalent resistance is in the milliohm level, and the voltage difference between the battery clusters can reach tens of volts, resulting in excessive circuit current, even far exceeding the system's current capacity, damaging the battery and electrical equipment, and causing serious safety accidents. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a black start method and energy storage system for an energy storage system. After the black start is achieved, the main circuits of each cluster of parallel battery packs will not be connected at the same time, thereby solving the backflow problem caused by the pressure difference.

[0006] To achieve the above-mentioned objectives, the present invention provides a black start method for an energy storage system, comprising the following steps: presetting the address numbers of each battery management system, setting one of the battery management systems as a master and the other battery management systems as slaves, and setting the slaves to be controlled by the master; after each battery management system is powered on, a black start signal is triggered, and each battery management system sends its own address number frame message; the host detects the address number frame message, and if no address number frame message is detected, the host controls its corresponding control switch to close, thereby connecting the power supply circuit between the battery pack corresponding to the host and the energy storage inverter; if an address number frame message is detected, the host designates one of the battery management systems to control its corresponding control switch to close, thereby connecting the power supply circuit between the battery pack corresponding to the battery management system and the energy storage inverter.

[0007] Preferably, after being powered on, each battery management system automatically detects whether the corresponding battery pack has a fault. If a fault occurs, the corresponding control switch is not allowed to close.

[0008] Preferably, the host performs conflict detection on the detected address numbers, and if a conflict exists, prohibits the control switch corresponding to the conflicting battery management system from closing.

[0009] Preferably, the conflict detection includes detecting whether the address number is the same as the address number of the host itself, or detecting whether there are multiple identical address numbers.

[0010] Preferably, the host collects voltage data of all battery management systems, and designates one of the battery management systems to control the corresponding control switch to be closed according to the voltage data.

[0011] Preferably, the host compares the voltage data and specifies the battery management system with the highest voltage to control its corresponding control switch to close.

[0012] Preferably, after the power supply circuit is connected, the host detects whether communication is established with the energy storage inverter. If there is no communication, the host controls the closed control switch to open, thereby cutting off the power supply circuit.

[0013] The present invention also provides an energy storage system, comprising an energy storage inverter, a black start device, and n clusters of parallel battery packs, wherein the n clusters of battery packs correspond to n battery management systems and n control switches, the battery packs are connected to a DC bus via the control switches, the DC bus is connected to the energy storage inverter, the battery management system controls the on and off of the control switches, the n battery management systems are connected via a CAN bus, one of which serves as a host and is connected to the energy storage inverter via the CAN bus; the battery management system is provided with an address module for setting an address number, the black start device is connected to the battery management system, and when the energy storage inverter is powered off, the battery management system is powered on, the black start device sends a black start signal to the battery management system, one of which controls the corresponding control switch to close, and the battery pack corresponding to the battery management system supplies power to the energy storage inverter.

[0014] Preferably, the control switch is a relay, and the battery management system is connected to the relay to control the on and off of the relay.

[0015] Compared with the existing technology, the technical solution of the present invention has the following advantages: by controlling only one battery pack's main power supply circuit to be closed to supply power to the energy storage inverter after a black start, the problem of backflow caused by simultaneous power supply of multiple parallel battery packs is solved, thereby avoiding damage to electrical equipment due to excessive loop current. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 1. It is a schematic diagram of the steps of an embodiment of a black start method for an energy storage system of the present invention;

[0017] Figure 2 is a further schematic diagram of an embodiment of a black start method for an energy storage system of the present invention;

[0018] Figure 3 Schematic diagram of an embodiment of the energy storage system of the present invention. DETAILED DESCRIPTION

[0019] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention is not limited to these embodiments and covers any substitution, modification, equivalent method and solution made within the spirit and scope of the present invention.

[0020] In order to make the public have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, but those skilled in the art can also fully understand the present invention without description of these details.

[0021] The present invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the drawings are simplified and not to exact proportions, and are only used for the purpose of conveniently and clearly illustrating the embodiments of the present invention.

[0022] Please refer to Figure 1 , is a schematic diagram of the steps of an embodiment of a black start method for an energy storage system of the present invention, wherein the steps are as follows:

[0023] S10: Preset the address number of each BMS, set the master and slave, and set the slave to be controlled by the master.

[0024] S20: After each BMS is powered on, a black start signal is triggered, and each BMS sends its own address number frame message.

[0025] S30: The host detects whether there is an address number frame message. If not, the host controls the corresponding control switch to close; if so, the host designates one of the BMSs to control the corresponding control switch to close.

[0026] The host detects all address number frame messages. If no address number frame message is detected and it is determined that there is no slave machine, the host controls the corresponding control switch to close, connects the power supply circuit between the battery pack corresponding to the host and the PCS, and enables the PCS to start working; if an address number frame message is detected and it is determined that there is a slave machine, one of the BMSs is designated to control the corresponding control switch to close, connects the power supply circuit between the corresponding battery pack and the PCS, and the battery pack supplies power to the PCS, so that the entire energy storage system can start working normally.

[0027] In this embodiment, the address numbers of each BMS are set as 1#, 2#, 3#, ... n#, and the corresponding battery packs and control switches are also 1#, 2#, 3#, ... n#, respectively. BMS #1 is set as the master, and the other BMSs are set as slaves. When the PCS is off-grid and unable to start, no instructions are sent to the BMS. In this case, the BMS is manually powered on, and a black start signal is triggered. The black start signal can be triggered manually by operating the black start device or automatically when the BMS is powered on. When each BMS receives the black start signal, the slave BMS does not automatically close its corresponding control switch, but waits for instructions from BMS #1, the master. At this point, each BMS sends its own address number frame message to the CAN bus. BMS #1 retrieves the address number frame message from the CAN bus for detection. If no address number frame message is detected, it is determined that the energy storage system has only a single battery pack or a fault in the BMS of another battery pack. BMS #1 controls the 1# control switch to close, connecting the power supply circuit between battery pack #1 and the PCS. If BMS #1 detects address number information, it determines that there are multiple battery packs in parallel, and BMS #1 designates one of the BMSs to control the corresponding control switch to close. Therefore, in the black start method of the present invention, only one battery pack supplies power to the PCS, and no backflow problem will occur after the black start. The black start method of the present invention is applicable to both single-cluster and multi-cluster battery storage systems.

[0028] refer to Figure 2 , is a further schematic diagram of an embodiment of the black start method of the energy storage system of the present invention. Specifically, in step S20, the following steps are included:

[0029] S21: The BMS is powered on, triggering a black start signal, and the BMS performs a self-test on the battery pack.

[0030] S22: If there is a fault, the control switch corresponding to the faulty battery pack is prohibited from closing.

[0031] S23: If there is no fault, the BMS of the battery pack without fault sends its own address number frame message.

[0032] Each BMS first performs fault detection on the battery pack, and only the battery pack without fault is allowed to close the main circuit control switch to protect the electrical equipment.

[0033] Specifically, such as Figure 2 As shown, step S30 includes the following steps:

[0034] S31: The host detects whether there is an address number frame message. 1# BMS receives all address number frame messages and performs detection.

[0035] S32: If there is no slave, the host controls the corresponding control switch to close. If BMS 1# does not detect the address number frame message, it determines that there is no slave, and then connects the power supply circuit between battery pack 1# and the PCS.

[0036] S33: If there is a slave, check whether there is a conflicting address number. 1# BMS detects an address number frame message and determines that there is a slave, then checks all address numbers for repeated conflicts.

[0037] S34: If there is a conflict, the control switch corresponding to the conflicting BMS is prohibited from closing. For example, if address number 1 is detected, which conflicts with the host's own address number, the host prohibits the detected 1#BMS and its corresponding control switch from closing. Or if two 3#BMSs are detected, the host prohibits the control switches corresponding to both 3#BMSs from closing. This prevents the main power supply circuits of two battery clusters from being connected simultaneously when the host designates 3#BMS to control the corresponding control switch to close, thereby causing backflow problems.

[0038] S35: The host collects the voltage data of the non-conflicting BMS. BMS #1 collects the voltage data of all non-conflicting BMSs and compares the data.

[0039] S36: Designate one of the slaves based on the voltage data to control the corresponding control switch to close. In this embodiment, BMS #1 first collects and compares the voltage data collected by all BMSs, then designates the battery cluster with the highest voltage data (i.e., the largest battery capacity) to supply power. After this battery cluster has supplied power for a period of time and its voltage data drops, BMS #1 redesignates another battery cluster with the largest capacity to supply power, thereby balancing the capacity states of the battery clusters.

[0040] Please refer to Figure 3, is a schematic diagram of the energy storage system of the present invention, including an energy storage inverter PCS, a black start device (not shown), and n parallel battery packs. The n battery packs correspond to n BMSs and n relays k serving as control switches. That is, battery pack 1 corresponds to BMS 1 and relay 1, and battery pack 2 corresponds to BMS 2 and relay 2. The battery packs are connected to a DC bus L via relay K. The DC bus L is connected to the PCS. The BMS controls the on / off of relay K. When relay K is closed, the corresponding battery pack supplies power to the PCS via the DC bus L, or photovoltaic or AC mains power charges the battery pack via the PCS and the DC bus. The N BMSs are connected via a CAN2 bus so that they can communicate with each other. BMS #1 serves as a host and is connected to the PCS via a CAN1 bus. BMS #1 establishes communication with the PCS and receives relevant instructions from the PCS. All BMSs are equipped with an address module (not shown in the figure) for setting address numbers. BMS #1 distinguishes each slave based on the address number and issues instructions in a targeted manner. The black start device is connected to the BMS. When the PCS is powered off, all BMSs are powered on. The black start device sends a black start signal to the BMSs. BMS #1 sends an instruction to one of the BMSs to control the corresponding relay K to close. The battery pack corresponding to the BMS supplies power to the PCS.

[0041] Although the embodiments are described and explained separately above, some common technologies are involved. It is the opinion of ordinary technicians in this field that they can be replaced and integrated between the embodiments. If there is anything not clearly recorded in one of the embodiments, reference can be made to another recorded embodiment.

[0042] The above-described embodiments do not constitute a limitation on the scope of protection of this technical solution. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the above-described embodiments shall be included in the scope of protection of this technical solution.

Claims

1. A black start method for an energy storage system, comprising the following steps: Preset the address numbers of the battery management systems, set one of the battery management systems as a master, and the other battery management systems as slaves, and set the slaves to be controlled by the master; After each battery management system is powered on, a black start signal is triggered, and each battery management system sends its own address number frame message; The host detects the address number frame message. If no address number frame message is detected, the host controls the corresponding control switch to close, thereby connecting the power supply circuit between the battery pack corresponding to the host and the energy storage inverter. If an address number frame message is detected, the host designates one of the battery management systems to control the corresponding control switch to close, thereby connecting the power supply circuit between the battery pack corresponding to the battery management system and the energy storage inverter. The host collects voltage data of all battery management systems and designates one of the battery management systems to control the corresponding control switch to be closed according to the voltage data; The host compares the voltage data and designates the battery management system with the highest voltage to control the corresponding control switch to be closed. When the battery pack corresponding to the control switch supplies power for a period of time and the voltage data of the battery pack drops, the host again collects the voltage data of all battery management systems and redesignates the battery management system with the highest voltage to control the corresponding control switch to be closed. After the power supply circuit is connected, the host detects whether communication is established with the energy storage inverter. If no communication is established, the host controls the closed control switch to open, thereby cutting off the power supply circuit.

2. The black start method of the energy storage system according to claim 1, characterized in that: After being powered on, each battery management system automatically detects whether the corresponding battery pack has any faults. If a fault occurs, the corresponding control switch is not allowed to close.

3. The black start method of the energy storage system according to claim 1, characterized in that: The host performs conflict detection on the detected address numbers. If a conflict exists, the control switch corresponding to the conflicting battery management system is prohibited from closing.

4. The black start method of the energy storage system according to claim 3, characterized in that: The conflict detection includes detecting whether the address number is the same as the address number of the host itself, or detecting whether there are multiple identical address numbers.

5. An energy storage system comprising an energy storage inverter, a black start device, and n battery packs connected in parallel, wherein the n battery packs correspond to n battery management systems and n control switches, characterized in that: The battery pack is connected to a DC bus via a control switch, the DC bus is connected to the energy storage inverter, the battery management system controls the on and off of the control switch, and the n battery management systems are connected via a CAN bus, wherein one battery management system serves as a host and is connected to the energy storage inverter via the CAN bus; The battery management system is provided with an address module for setting an address number. The black start device is connected to the battery management system. When the energy storage inverter is powered off, the battery management system is powered on. The black start device sends a black start signal to the battery management system. One of the battery management systems controls the corresponding control switch to close, and the battery pack corresponding to the battery management system supplies power to the energy storage inverter. The host collects voltage data of all battery management systems and designates one of the battery management systems to control the corresponding control switch to be closed according to the voltage data; The host compares the voltage data and designates the battery management system with the highest voltage to control the corresponding control switch to be closed. When the battery pack corresponding to the control switch supplies power for a period of time and the voltage data of the battery pack drops, the host again collects the voltage data of all battery management systems and redesignates the battery management system with the highest voltage to control the corresponding control switch to be closed. After the power supply circuit is connected, the host detects whether communication is established with the energy storage inverter. If no communication is established, the host controls the closed control switch to open, thereby cutting off the power supply circuit.

6. The energy storage system according to claim 5, characterized in that: The control switch is a relay, and the battery management system is connected to the relay to control the on and off of the relay.

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