Energy storage converter and multi-machine parallel system

Abstract

The invention discloses an energy storage converter and a multi-machine parallel system, the direct current side of the energy storage converter is connected with a corresponding energy storage battery, and the alternating current side of the energy storage converter is connected in parallel with the alternating current sides of other energy storage converters and then is connected with a power grid; the energy storage converter further comprises a first controller, and the first controller is configured to obtain standby flag bits of other energy storage converters; judging whether the number of all the set standby flag bits is the same as the parallel operation number or not; and when the number of all the set standby flag bits is the same as the parallel operation number, controlling the energy storage converter to synchronously enter a standby state along with other energy storage converters. According to the invention, loss of battery power can be reduced, and abnormity in an operation process is avoided.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to an energy storage converter and a multi-machine parallel system. Background Technology

[0002] Parallel energy storage converters are generally in standby mode during non-charging / discharging periods. In this state, the power switches of the energy storage converters, such as IGBTs, are in a blocked state, reducing battery power loss. However, in standby mode, the IGBTs do not operate, making it impossible to avoid abnormal situations through software methods such as modulation. This leads to other operational anomalies: When some parallel energy storage converters are in standby mode while others are still charging / discharging at low power, the standby converter may detect a certain amount of active power, causing the other converters to abnormally reverse-charge the battery by executing low-power charging / discharging commands. Simultaneously, filter capacitor overcurrent faults are prone to occur. The reverse charging is caused by the high AC harmonic content, leading to abnormal power control. The filter capacitor overcurrent is caused by some energy storage converters fully charging or discharging before entering standby mode. During standby, the AC / DC switches of the energy storage converters are still closed, and their LC filter capacitors remain connected to the grid. This increases the equivalent capacitance of the filter in the charging / discharging energy storage converter, creating a mismatch with the original control parameters and making it prone to failure. Summary of the Invention

[0003] This application provides an energy storage converter and a multi-machine parallel system to reduce battery power loss and avoid abnormalities during operation.

[0004] This application provides an energy storage converter, wherein the DC side of the energy storage converter is connected to a corresponding energy storage battery, and the AC side of the energy storage converter is connected in parallel with the AC sides of other energy storage converters and then connected to the power grid.

[0005] The energy storage converter also includes a first controller, which is configured to acquire the standby flag bits of other energy storage converters; determine whether the number of all set standby flag bits is the same as the number of parallel connections; and when the number of all set standby flag bits is the same as the number of parallel connections, control the energy storage converter to enter the standby state synchronously with other energy storage converters.

[0006] Another aspect of this application provides a multi-machine parallel system, which includes n energy storage batteries and n energy storage converters, where n≥2; the DC side of each energy storage converter is connected to a corresponding energy storage battery, and the AC side of each energy storage converter is connected in parallel with the AC sides of other energy storage converters and then connected to the power grid.

[0007] The multi-unit parallel system further includes a second controller that is communicatively connected to the n energy storage converters. The second controller is configured to acquire the standby flag bits of all the energy storage converters; determine whether the number of all set standby flag bits is the same as the number of parallel units; and when the number of all set standby flag bits is the same as the number of parallel units, control all the energy storage converters to synchronously enter the standby state.

[0008] The energy storage converter and multi-unit parallel system provided in this application, without adding hardware, avoid the battery power loss caused by the energy storage converter being in zero-power modulation mode for a long time, which may lead to over-discharge of the battery in severe cases; it also avoids the problem of some energy storage converters being in standby mode while others are still charging and discharging at low power, resulting in abnormal reverse charging of the battery by the charging and discharging energy storage converters; it also avoids the problem of some energy storage converters being fully charged or discharged in advance and entering standby mode due to the difference in the remaining energy of the battery at the end of the charging and discharging process, while others are still charging and discharging, leading to overcurrent failure of the filter capacitor. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of a multi-machine parallel system provided in an embodiment of this application;

[0010] Figure 2 A detailed circuit diagram of a multi-machine parallel system provided in the embodiments of this application;

[0011] Figure 3 This is a schematic diagram of the control process of a multi-machine parallel system provided in an embodiment of this application.

[0012] 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

[0013] 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 this application.

[0014] 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.

[0015] like Figure 1As shown in the figure, an embodiment of this application provides a multi-machine parallel system, which includes n energy storage batteries (energy storage battery 1 to energy storage battery n in the figure) and n energy storage converters (PCS1 to PCSn in the figure), where n≥2; the DC side of each energy storage converter is connected to a corresponding energy storage battery, for example, the DC side of PCS1 is connected to energy storage battery 1... the DC side of PCSn is connected to energy storage battery n, and the AC side of each energy storage converter is connected in parallel with the AC sides of other energy storage converters and then connected to the power grid.

[0016] In some examples, the AC side of each of the energy storage converters is connected in parallel with the AC side of the other energy storage converters, and then connected to the power grid through a grid-connected transformer T1.

[0017] In some examples, each of the energy storage converters includes a first controller for controlling the operation of each of the energy storage converters.

[0018] In some examples, the multi-machine parallel system also includes a second controller that is communicatively connected to the n energy storage converters (as shown by the dashed lines in the figure). The second controller may be an energy management system (EMS) or other similar unit.

[0019] like Figure 2 The diagram shown is a schematic of a multi-machine parallel system provided in this application embodiment.

[0020] In some examples, each of the energy storage converters (energy storage converters 1 to n in the figure) includes an inverter, such as the midpoint clamped three-level inverter (NPC inverter) shown in the figure. The DC terminal of the inverter is connected to a corresponding energy storage battery through a DC fuse and a DC switch. The positive DC terminal of the inverter is also connected to a soft-start circuit, which includes a soft-start resistor, a soft-start contactor, and a DC contactor. The AC terminal of the inverter is connected to the grid after being connected in parallel with the AC side of the other energy storage converters through an LC filter, an AC switch, and an AC surge protector.

[0021] It should be noted that the specific structure of each energy storage converter is not limited to the situation shown in the figure.

[0022] Based on the above multi-machine parallel system, in some examples, the first controller is configured to acquire the standby flag bits of other energy storage converters; determine whether the number of all set standby flag bits is the same as the number of parallel units; and when the number of all set standby flag bits is the same as the number of parallel units, control the energy storage converter to enter the standby state synchronously with the other energy storage converters.

[0023] The number of parallel units refers to the total number of energy storage converters connected in parallel on the AC side, such as the aforementioned n energy storage converters.

[0024] In some specific examples, the first controller is also configured to acquire the operating status of other energy storage converters; when other energy storage converters are in a charging / discharging state, if the energy storage converter meets the standby conditions, the energy storage converter is adjusted to a zero-power modulation mode, and the standby flag bit of the energy storage converter is set. For example, if the standby flag bit of the energy storage converter is a binary bit, the binary bit can be set to 1.

[0025] In some specific examples, the first controller is also configured to receive parameter settings for the number of parallel devices.

[0026] In some specific examples, the first controller is also configured to receive parameter settings for the parallel unit number; wherein the parallel unit number has a standby flag bit of the energy storage converter, and the minimum value of the parallel unit number is zero and the maximum value is the number of parallel units minus 1, for example, the maximum value is n-1.

[0027] Based on the above-mentioned multi-machine parallel system, in some other examples, the second controller is configured to acquire the standby flag bits of all the energy storage converters; determine whether the number of all set standby flag bits is the same as the number of parallel units; and when the number of all set standby flag bits is the same as the number of parallel units, control all the energy storage converters to synchronously enter the standby state.

[0028] The number of parallel units refers to the total number of energy storage converters connected in parallel on the AC side, such as the aforementioned n energy storage converters.

[0029] In other specific examples, the operating status of all the energy storage converters is obtained; when any one of the energy storage converters is in a charging / discharging state and the other energy storage converters meet the standby conditions, the other energy storage converters are controlled to adjust to zero-power modulation mode and the standby flag of the other energy storage converters is set. For example, the standby flag of the energy storage converter is a binary bit, which can be set to 1.

[0030] In other specific examples, the second controller is also configured to receive parameter settings for the number of parallel devices.

[0031] In some other specific examples, the second controller is also configured to receive parameter settings for a parallel unit number; wherein the parallel unit number has a standby flag bit of the energy storage converter, and the minimum value of the parallel unit number is zero and the maximum value is the number of parallel units minus 1, for example, the maximum value is n-1.

[0032] The following combination Figure 3 Explanation:

[0033] First, a standby flag is added to the carrier synchronization communication of the energy storage converter, and the "parallel number" and "parallel position number" of the energy storage converter are set.

[0034] When any energy storage converter meets the conditions for entering standby, if the number of standby flag bits set to 1 is less than the number of parallel units, the energy storage converter that meets the conditions for entering standby will automatically adjust to zero-power modulation mode, and the corresponding bit of the standby flag of the parallel unit number of the energy storage converter that has been adjusted to zero-power modulation mode will be set to 1.

[0035] When the number of standby flag bits set to 1 equals the number of parallel connections, all parallel energy storage converters synchronously enter standby mode.

[0036] 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 converter, characterized in that, The DC side of the energy storage converter is connected to the corresponding energy storage battery, and the AC side of the energy storage converter is connected to the grid after being connected in parallel with the AC sides of other energy storage converters. The energy storage converter also includes a first controller, which is configured to acquire the standby flag bits of other energy storage converters; determine whether the number of all set standby flag bits is the same as the number of parallel connections; and when the number of all set standby flag bits is the same as the number of parallel connections, control the energy storage converter to enter the standby state synchronously with other energy storage converters.

2. The energy storage converter according to claim 1, characterized in that, The first controller is also configured to acquire the operating status of other energy storage converters; when other energy storage converters are in a charging / discharging state, if the energy storage converter meets the standby conditions, the controller will adjust the energy storage converter to a zero-power modulation mode and set the standby flag of the energy storage converter.

3. The energy storage converter according to claim 1, characterized in that, The first controller is also configured to receive parameter settings for the number of parallel units.

4. The energy storage converter according to claim 1, characterized in that, The first controller is also configured to receive parameter settings for a parallel grid position number; wherein the parallel grid position number has a standby flag bit of the energy storage converter.

5. The energy storage converter according to claim 4, characterized in that, The minimum value of the parallel unit number is zero and the maximum value is the number of parallel units minus 1.

6. A multi-machine parallel system, characterized in that, The multi-machine parallel system includes n energy storage batteries and n energy storage converters, where n≥2; the DC side of each energy storage converter is connected to a corresponding energy storage battery, and the AC side of each energy storage converter is connected in parallel with the AC sides of other energy storage converters and then connected to the power grid. The multi-unit parallel system further includes a second controller that is communicatively connected to the n energy storage converters. The second controller is configured to acquire the standby flag bits of all the energy storage converters; determine whether the number of all set standby flag bits is the same as the number of parallel units; and when the number of all set standby flag bits is the same as the number of parallel units, control all the energy storage converters to synchronously enter the standby state.

7. The multi-machine parallel system according to claim 6, characterized in that, Obtain the operating status of all the energy storage converters; when any one of the energy storage converters is in a charging / discharging state and the other energy storage converters meet the standby conditions, control the other energy storage converters to adjust to zero-power modulation mode and set the standby flag of the other energy storage converters.

8. The multi-machine parallel system according to claim 6, characterized in that, The second controller is also configured to receive parameter settings for the number of parallel units.

9. The multi-machine parallel system according to claim 6, characterized in that, The second controller is also configured to receive parameter settings for a parallel unit position number; wherein the parallel unit position number has a standby flag bit of the energy storage converter.

10. The multi-machine parallel system according to claim 9, characterized in that, The minimum value of the parallel unit number is zero and the maximum value is the number of parallel units minus 1.

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