Energy storage converter, energy management system and energy storage system

Abstract

The invention discloses an energy storage converter, an energy management system and an energy storage system, the energy storage converter comprises a plurality of energy storage converters, and the alternating current ends of all the energy storage converters are connected together; all the energy storage converters are in communication connection with one another or the energy storage system further comprises an energy management system in communication connection with all the energy storage converters; the host is configured to determine an energy storage converter in a shutdown state in the energy storage system when a resonance phenomenon of the energy storage system is identified; issuing a switching instruction to at least one energy storage converter in a shutdown state, so that the at least one energy storage converter is switched from the shutdown state to a zero power state; determining whether the resonance phenomenon of the energy storage system is eliminated; and if the resonance phenomenon of the energy storage system is not eliminated, continuing to issue an instruction to at least one energy storage converter in a shutdown state. According to the invention, the THD standard exceeding of voltage / current caused by higher harmonics generated by resonance between the parallel modules is reduced, the risk of module failure is reduced, and the maintenance cost is reduced.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to an energy storage converter, an energy management system, and an energy storage system. Background Technology

[0002] With the rapid development of renewable energy and the increasing demand for flexibility in power systems, string energy storage converters are widely used due to their high power density, high efficiency, and modularity, and their importance in power systems is becoming increasingly prominent. However, in actual use, because the modules are directly connected in parallel on the AC side for expansion, LC resonance can occur between the parasitic parameters of the parallel modules under certain combinations and operating conditions. High-frequency resonance can cause the THD (Total Harmonic Distortion) of the grid voltage / current to exceed the standard, affecting the operation of other machines or equipment. At the same time, high-frequency resonance can also significantly increase the magnetic losses of the magnetic components on the AC side of the module itself, leading to overheating and failure. Summary of the Invention

[0003] This application provides an energy storage converter, an energy management system, and an energy storage system to solve the resonance phenomenon between parallel modules in the energy storage system.

[0004] This application provides an energy storage system, including multiple energy storage converters, with the AC terminals of all the energy storage converters connected together;

[0005] All the energy storage converters are interconnected, with one of the energy storage converters acting as the master and the other energy storage converters acting as slaves; or, the energy storage system further includes an energy management system that is interconnected with all the energy storage converters, with the energy management system acting as the master and all the energy storage converters acting as slaves.

[0006] The host is configured to, upon detecting a resonance phenomenon in the energy storage system, identify the energy storage converters in the energy storage system that are in a shutdown state; issue a switching command to at least one of the energy storage converters in the shutdown state, so that the at least one energy storage converter in the shutdown state switches from the shutdown state to the zero-power state; confirm whether the resonance phenomenon of the energy storage system has been eliminated; if the resonance phenomenon of the energy storage system has not been eliminated, continue to issue commands to at least one of the energy storage converters in the shutdown state.

[0007] In another aspect, this application provides an energy storage converter, which together with other energy storage converters forms an energy storage system, and the energy storage converter forms the host of the energy storage system;

[0008] The AC terminals of all the energy storage converters in the energy storage system are connected together and all the energy storage converters are interconnected.

[0009] The energy storage converter is configured to, upon detecting a resonance phenomenon in the energy storage system, identify the energy storage converters in the energy storage system that are in a shutdown state; issue a switching command to at least one of the energy storage converters in the shutdown state, so that the at least one energy storage converter in the shutdown state switches from the shutdown state to a zero-power state; confirm whether the resonance phenomenon of the energy storage system has been eliminated; if the resonance phenomenon of the energy storage system has not been eliminated, continue to issue commands to at least one energy storage converter in the shutdown state.

[0010] In another aspect, this application provides an energy management system that is communicatively connected to all energy storage converters in an energy storage system, wherein the AC terminals of all the energy storage converters in the energy storage system are connected together.

[0011] The energy management system is configured to, upon detecting a resonance phenomenon in the energy storage system, identify the energy storage converters in the energy storage system that are in a shutdown state; issue a switching command to at least one of the energy storage converters in the shutdown state, so that the at least one energy storage converter in the shutdown state switches from the shutdown state to a zero-power state; confirm whether the resonance phenomenon of the energy storage system has been eliminated; if the resonance phenomenon of the energy storage system has not been eliminated, continue to issue commands to at least one energy storage converter in the shutdown state.

[0012] The energy storage converter, energy management system, and energy storage system provided in this application automatically control the number of energy storage converters in the zero-power state in the energy storage system when resonance occurs, and change the resonance point of the resonance network to eliminate resonance. This reduces the high-order harmonics generated by resonance between parallel modules, which leads to excessive THD of voltage / current, reduces the risk of module failure caused by resonance between parallel modules, and lowers maintenance costs. Attached Figure Description

[0013] Figure 1 A schematic diagram of an energy storage system provided in an embodiment of this application;

[0014] Figure 2 This is a schematic diagram of an energy storage converter provided in an embodiment of this application;

[0015] Figure 3 This is a schematic diagram of the control flow of an energy storage system provided in an embodiment of this application;

[0016] Figure 4 This is another control flow diagram of the energy storage system provided in an embodiment of this application.

[0017] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0018] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer and more understandable, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the scope of this application.

[0019] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0020] like Figure 1 As shown in the figure, this application provides an energy storage system including multiple energy storage converters, such as PCS1 to PCSn in the figure.

[0021] The DC terminal of each energy storage converter (shown as BAT+ and BAT- in the diagram) is connected to the corresponding energy storage battery. For example, the DC terminal of PCS1 is connected to battery 1, the DC terminal of PCS2 is connected to battery 2, and so on, the DC terminal of PCSn is connected to battery n.

[0022] The AC terminals of each energy storage converter (shown as A1, B1, and C1 in the diagram) are connected to the AC terminals of other energy storage converters, that is, the AC terminals of all energy storage converters are connected together to form the AC terminals of the energy storage system (shown as A, B, and C in the diagram). The AC terminals of the energy storage system can be connected to the power grid.

[0023] All energy storage converters are interconnected, with one energy storage converter acting as the master and the others as slaves; or, the energy storage system may also include an energy management system (EMS in the figure, the communication connection can be seen by the dotted line in the figure) that is interconnected with all energy storage converters, with the energy management system acting as the master and all energy storage converters acting as slaves.

[0024] like Figure 2 As shown in one example, each energy storage converter includes an inverter (shown as DC / AC in the figure) and a temperature detection device (not shown in the figure). The DC terminal of the inverter is connected to the DC terminal of each energy storage converter (shown as BAT+ and BAT- in the figure) through a first switch K2. A soft-start circuit is connected in parallel across the two ends of the first switch K2. The soft-start circuit includes a third switch K1 and a soft-start resistor R1 connected in series. A DC bus capacitor is connected between the positive DC terminal and the negative DC terminal of the inverter, such as capacitors C1 and C2 shown in the figure.

[0025] The AC terminal of the inverter is connected to the AC terminal of each energy storage converter (shown as A1, B1, and C1 in the figure) through a first filter inductor L1, a first filter capacitor C3, a second switch K3, a second filter inductor L2, and a second filter capacitor C4 connected in sequence. The temperature detection device is used to detect the temperature of the second filter inductor L2, for example, to detect the temperature of the magnetic core of the second filter inductor L2.

[0026] The first switch K2 includes, but is not limited to, a DC contactor; the third switch K1 includes, but is not limited to, a relay; the inverter includes, but is not limited to, a three-level inverter topology; the first filter inductor L1, the first filter capacitor C3, and the second filter inductor L2 constitute the LCL filter on the AC side; the second filter capacitor C4 is the EMI filter capacitor for the AC port; and the second switch K3 includes, but is not limited to, a grid-connected relay.

[0027] In one example, the master is configured to issue charging commands to all slaves, causing the slaves to charge their respective energy storage batteries.

[0028] Specifically, when each energy storage converter receives a charging command, if the AC / DC side voltage is within the operating range, it first controls the soft-start circuit to start, that is, controls the third switch K1 to be turned on or closed, so as to realize the soft start of the DC bus capacitor. After the soft start is realized, the first switch K2 and the second switch K3 are turned on in sequence. That is, the first switch K2 is turned on first, and the inverter inverts the signal, and then the second switch K3 is turned on, thereby completing grid connection and realizing bidirectional energy flow between the battery and the grid.

[0029] In one example, each energy storage converter controls the second switch K3 to open when the corresponding energy storage battery is fully charged, meaning that the energy storage converter is in a shutdown state when the corresponding energy storage battery is fully charged.

[0030] When all energy storage inverters begin charging their corresponding energy storage batteries, due to voltage differences, not all inverters can fully charge all batteries simultaneously. At the end of charging, some inverters' corresponding batteries are fully charged and they stop operating, while the remaining inverters (e.g., 1-2) are still charging their batteries. This situation can easily lead to resonance. The main reason is that the parasitic inductance of the cable between the second filter capacitor C4 of the inverter that has completed charging and is in a stopped state and the other parallel modules will cause LC resonance. When the resonance point is near the inverter's switching frequency, the resonant network generates a high-amplitude resonant current due to its low impedance, causing the THD of the AC side voltage / current to exceed the standard. Simultaneously, for the remaining charging inverters, the high-frequency resonant current will cause the core of their second filter inductor L2 to heat up. Continued heating can cause insulation failure, arcing, and ultimately, inverter failure. Based on this:

[0031] In one example, the host is configured to, upon detecting a resonance phenomenon in the energy storage system, identify all energy storage converters in the energy storage system that are in a shutdown state; issue a switching command to at least one of the energy storage converters in a shutdown state to switch the at least one energy storage converter from a shutdown state to a zero-power state; confirm whether the resonance phenomenon of the energy storage system has been eliminated; if the resonance phenomenon of the energy storage system has not been eliminated, continue to issue commands to at least one energy storage converter in a shutdown state.

[0032] Among them, at least one energy storage converter in the shutdown state controls the first switch K2 and the second switch K3 to turn on when it receives the switching command, thereby switching from the shutdown state to the zero power state.

[0033] After entering the zero-power state, at least one energy storage converter in the shutdown state will introduce the second filter inductor L2 and the first filter capacitor C3 into the parallel system, changing the size of the parasitic capacitance and parasitic inductance in the parallel system, thereby changing the resonance point of the LC resonance, making the resonance point far away from the switching frequency point of the inverter operation, thus reducing the impact of resonance.

[0034] In one example, the master is configured to receive alarm information uploaded by any slave and determine that the energy storage system has resonated based on the alarm information.

[0035] In one example, the slave device is configured to, upon receiving an alarm message from another slave device, determine that the other slave device is experiencing resonance and upload its own status information to the master device.

[0036] In one example, the slave device is configured to acquire the temperature of the second filter inductor L2 detected by the temperature detection device; when the temperature of the second filter inductor L2 exceeds a preset temperature threshold, an alarm message is generated and sent to other slave devices or uploaded to the host. For example, the preset temperature threshold is 105℃; if it exceeds 105℃, it is determined that resonance has occurred, thereby generating an alarm message and sending it to other slave devices or uploading it to the host.

[0037] The following uses an energy management system as the main unit and combines it with Figure 3 Explanation:

[0038] EMS establishes communication and data exchange with all PCS.

[0039] When PCSk (1≤k≤n) detects that the temperature of inductor L2 exceeds the threshold, it issues an alarm and uploads the alarm information to EMS.

[0040] The EMS receives an alarm message and identifies it as a resonance. The EMS confirms that there are m PCS in the parallel system that are in a stopped state, and issues a power-on command to the p-th PCS in the stopped state (the initial value of p is 1).

[0041] The p-th PCS will soon transition from a shutdown state to a zero-power state. Upon entering the zero-power state, the p-th PCS will introduce the second filter inductor L2 and the first filter capacitor C3 into the parallel system, changing the magnitude of the parasitic capacitance and inductance within the parallel system. This alters the resonant point of the LC resonance, moving it away from the inverter's operating switching frequency and thus reducing the impact of resonance.

[0042] EMS continues to evaluate the information received from each PCS to confirm whether the alarm has been cleared.

[0043] If the alarm is not cleared, the EMS continues to issue commands to the next PCS module in the shutdown state to switch from shutdown to zero power state, and repeats the above operation. If the alarm is cleared, the process ends.

[0044] The following uses one of the energy storage converters as the main unit and combines it with... Figure 4 Explanation:

[0045] All PCS establish communication and exchange data.

[0046] When PCSk (1≤k≤n) detects that the temperature of inductor L2 exceeds the threshold, it issues an alarm and sends the alarm information to other PCSs.

[0047] When other PCS receive the alarm message, they identify that resonance has occurred and upload their own status information to the host. The host confirms that there are m PCS in the parallel system that are in a stopped state, and issues a power-on command to the p-th PCS in the stopped state (the initial value of p is 1).

[0048] The p-th PCS will soon transition from a shutdown state to a zero-power state. Upon entering the zero-power state, the p-th PCS will introduce the second filter inductor L2 and the first filter capacitor C3 into the parallel system, changing the magnitude of the parasitic capacitance and inductance within the parallel system. This alters the resonant point of the LC resonance, moving it away from the inverter's operating switching frequency and thus reducing the impact of resonance.

[0049] The host continues to evaluate the information received from each PCS to confirm whether the alarm has been cleared.

[0050] If the alarm is not cleared, the host continues to issue commands to the next PCS module in the shutdown state to switch from shutdown to zero power state, and repeats the above operation. If the alarm is cleared, the process ends.

[0051] Another embodiment of this application provides an energy storage converter, which together with other energy storage converters forms an energy storage system, and the energy storage converter forms the host of the energy storage system; for example, PCS1 and PCS2 to PCSn form an energy storage system, PCS1 forms the host of the energy storage system, and PCS2 to PCSn all form slaves of the energy storage system.

[0052] In the energy storage system, the AC terminals of all energy storage converters (e.g., PCS1 to PCSn) are connected together and all energy storage converters are interconnected.

[0053] The energy storage converter (e.g., the PCS1 that forms the host of the aforementioned energy storage system) is configured to, when a resonance phenomenon is detected in the energy storage system, identify all energy storage converters in the energy storage system that are in a shutdown state; issue a switching command to at least one energy storage converter in the shutdown state so that the at least one energy storage converter in the shutdown state switches from the shutdown state to the zero power state; confirm whether the resonance phenomenon of the energy storage system has been eliminated; if the resonance phenomenon of the energy storage system has not been eliminated, continue to issue commands to at least one energy storage converter in the shutdown state.

[0054] It should be noted that in this example, parts similar to those in the previous examples can be understood by referring to the aforementioned content.

[0055] Another embodiment of this application provides an energy management system. The energy management system (e.g., shown as EMS in the figure) is communicatively connected to all energy storage converters (e.g., PCS1 to PCSn) in the energy storage system, and the AC terminals of all energy storage converters in the energy storage system are connected together. The energy management system forms the host of the energy storage system, while PCS1 to PCSn all form slaves of the energy storage system.

[0056] The energy management system is configured to, upon detecting a resonance phenomenon in the energy storage system, identify all energy storage converters in the energy storage system that are in a shutdown state; issue a switching command to at least one energy storage converter in a shutdown state to switch that at least one energy storage converter in a shutdown state to a zero-power state; confirm whether the resonance phenomenon of the energy storage system has been eliminated; if the resonance phenomenon of the energy storage system has not been eliminated, continue to issue commands to at least one energy storage converter in a shutdown state.

[0057] It should be noted that in this example, parts similar to those in the previous examples can be understood by referring to the aforementioned content.

[0058] The preferred embodiments of this application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and spirit of this application shall be within the scope of the claims.

Claims

1. An energy storage system, characterized by, The energy storage system comprises a plurality of energy storage converters, AC terminals of all the energy storage converters being connected together; All the energy storage converters are connected in communication with each other, and one of the energy storage converters forms a master, and the others form slaves, or the energy storage system further comprises an energy management system connected in communication with all the energy storage converters, the energy management system forming a master, and all the energy storage converters forming slaves; The master is configured to, when identifying that resonance phenomenon occurs in the energy storage system, determine the energy storage converter in a shutdown state in the energy storage system, issue a switching instruction to at least one energy storage converter in the shutdown state, so that the at least one energy storage converter in the shutdown state is switched from the shutdown state to a zero-power state, and confirm whether the resonance phenomenon in the energy storage system is eliminated, and if the resonance phenomenon in the energy storage system is not eliminated, continue to issue an instruction to at least one energy storage converter in the shutdown state.

2. The energy storage system of claim 1, wherein, The master is configured to receive alarm information uploaded by any one of the slaves, and determine, according to the alarm information, that resonance phenomenon occurs in the energy storage system.

3. The energy storage system of claim 1, wherein, The slave is configured to, when receiving alarm information sent by other slaves, determine, according to the alarm information, that resonance phenomenon occurs in other slaves, and upload state information of the slave to the master.

4. The energy storage system of claim 1, wherein, Each of the energy storage converters comprises an inverter and a temperature detection device, a DC terminal of the inverter is connected with a DC terminal of each of the energy storage converters through a first switch, an AC terminal of the inverter is connected with an AC terminal of each of the energy storage converters through a first filter inductor, a first filter capacitor, a second switch, a second filter inductor and a second filter capacitor connected in sequence, and the temperature detection device is used for detecting a temperature of the second filter inductor. The slave is configured to acquire the temperature of the second filter inductor detected by the temperature detection device. When the temperature of the second filter inductor exceeds a preset temperature threshold, alarm information is generated and sent to other slaves or uploaded to the master.

5. The energy storage system of claim 1, wherein, Each of the energy storage converters comprises an inverter and a temperature detection device, a DC terminal of the inverter is connected with a DC terminal of each of the energy storage converters through a first switch, an AC terminal of the inverter is connected with an AC terminal of each of the energy storage converters through a first filter inductor, a first filter capacitor, a second switch, a second filter inductor and a second filter capacitor connected in sequence, and the temperature detection device is used for detecting a temperature of the second filter inductor. The at least one energy storage converter in the shutdown state controls the first switch and the second switch to be conductive when receiving the switching instruction.

6. The energy storage system of claim 1, wherein, The master is configured to issue a charging instruction to all the slaves, so that the slaves charge the corresponding energy storage batteries.

7. The energy storage system of claim 6, wherein, Each of the energy storage converters comprises an inverter and a temperature detection device, a direct current end of the inverter is connected with a direct current end of each of the energy storage converters through a first switch, an alternating current end of the inverter is connected with an alternating current end of each of the energy storage converters through a first filter inductor, a first filter capacitor, a second switch, a second filter inductor and a second filter capacitor connected in sequence, and the temperature detection device is used for detecting a temperature of the second filter inductor. Each of the energy storage converters controls the first switch and the second switch to be turned on in sequence when receiving the charging instruction.

8. The energy storage system of claim 6, wherein, Each of the energy storage converters comprises an inverter and a temperature detection device, a direct current end of the inverter is connected with a direct current end of each of the energy storage converters through a first switch, an alternating current end of the inverter is connected with an alternating current end of each of the energy storage converters through a first filter inductor, a first filter capacitor, a second switch, a second filter inductor and a second filter capacitor connected in sequence, and the temperature detection device is used for detecting a temperature of the second filter inductor. Each of the energy storage converters controls the second switch to be turned off when the corresponding energy storage battery is fully charged.

9. An energy storage converter, characterized by The energy storage converter and other energy storage converters form an energy storage system, and the energy storage converter forms a host of the energy storage system. Alternating current ends of all the energy storage converters in the energy storage system are connected together, and all the energy storage converters are connected in communication with each other. The energy storage converter is configured to, when identifying that a resonance phenomenon occurs in the energy storage system, determine the energy storage converter in a shutdown state in the energy storage system, issue a switching instruction to at least one energy storage converter in the shutdown state, so that the at least one energy storage converter in the shutdown state is switched from the shutdown state to a zero-power state, confirm whether the resonance phenomenon of the energy storage system is eliminated, and if the resonance phenomenon of the energy storage system is not eliminated, continue to issue an instruction to at least one energy storage converter in the shutdown state.

10. An energy management system, characterized by The energy management system is connected in communication with all the energy storage converters in the energy storage system, and alternating current ends of all the energy storage converters in the energy storage system are connected together. The energy management system is configured to, when identifying that a resonance phenomenon occurs in the energy storage system, determine the energy storage converter in a shutdown state in the energy storage system, issue a switching instruction to at least one energy storage converter in the shutdown state, so that the at least one energy storage converter in the shutdown state is switched from the shutdown state to a zero-power state, confirm whether the resonance phenomenon of the energy storage system is eliminated, and if the resonance phenomenon of the energy storage system is not eliminated, continue to issue an instruction to at least one energy storage converter in the shutdown state.

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