A method for grid-connected power scheduling synchronization of an inverter parallel system

Abstract

The application discloses a kind of methods for inverter parallel system grid-connected power scheduling synchronization, comprising the following steps: S1: energy management system periodically sends target power instruction to multiple inverters, and the target power instruction includes target power and corresponding index value;S2: after each the target power instruction in the inverter received the target power instruction, detect whether the index value in each phase is consistent, if consistent, generate comparison index value corresponding to index value, and send the comparison index value generated to all other inverters except itself;S3: each the inverter communicates with each other, each the inverter respectively confirms whether the comparison index value of all other inverters except itself is consistent with the comparison index value of itself;If yes, each the inverter synchronously executes the target power instruction corresponding to the comparison index value.The application makes the parallel system more stable to adjust target power.

Description

Technical Field

[0001] This invention relates to the field of energy storage system technology, and in particular to a method for grid-connected power scheduling and synchronization of an inverter parallel system. Background Technology

[0002] With the rapid development of the energy storage industry, residential energy storage products are becoming increasingly popular, and more and more users are using energy storage inverters to provide energy for their home loads. Against this backdrop, the application of off-grid and parallel operation is also becoming increasingly widespread. In off-grid mode, the control of the equipment is entirely handled by the PCS (Power Conversion System, inverter) control unit; while in grid-connected mode, the system needs to collect a large amount of data and communicate, typically with the grid-connected target power being issued by the control module of a dedicated EMS (Energy Management System), which is then executed by the PCS.

[0003] However, in grid-connected scenarios, when the EMS issues target power commands to multiple PCS units, communication delays or other reasons may prevent the PCS units from receiving the target power commands simultaneously, leading to asynchronous execution. This asynchrony can negatively impact the EMS's adjustment of target power, ranging from affecting user experience to potentially causing grid tripping and threatening system safety.

[0004] The above background information is provided only to aid in understanding the concept and technical solution of this invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above information was disclosed on the filing date of this patent application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0005] To address the risk of instantaneous power fluctuations caused by asynchronous execution of grid-connected power commands from multiple inverters, this invention proposes a method for grid-connected power scheduling synchronization in parallel systems, enabling the parallel systems to adjust target power more stably.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention discloses a method for grid-connected power scheduling and synchronization of an inverter parallel system, comprising the following steps:

[0008] S1: The energy management system periodically sends target power commands to multiple inverters, and the target power command contains the target power and the corresponding index value;

[0009] S2: After receiving the target power command, each inverter checks whether the index values ​​in the target power command of each phase are consistent. If they are consistent, it generates a comparison index value corresponding to the index value and sends the generated comparison index value to all other inverters except itself.

[0010] S3: Each inverter communicates with each other, and each inverter confirms whether the comparison index values ​​of all other inverters except itself are consistent with its own comparison index value; if so, each inverter synchronously executes the target power command corresponding to the comparison index value.

[0011] Preferably, S2 further includes: if the index values ​​of the target power commands of each phase are inconsistent, then continue to wait until the index values ​​of the target power commands of all phases are the same, generate a comparison index value corresponding to the same index value, and send the generated comparison index value to all other inverters except itself.

[0012] Preferably, S2 further includes: when any of the inverters receives the target power command corresponding to the new index value, a timer is started; if no target power command corresponding to the new index value is received within a first preset time, the corresponding abnormal situation is fed back to the energy management system.

[0013] Preferably, the first preset time is 1 / 3 to 2 / 3 of the minimum adjustment time of the energy management system, and the minimum adjustment time of the energy management system is 0.1s to 50s.

[0014] Preferably, S3 further includes: if an inverter confirms that the comparison index values ​​of all other inverters besides itself are not consistent with its own comparison index value, it continues to wait until all inverters confirm that the comparison index values ​​of all other inverters besides itself are consistent with its own comparison index value, and then each inverter synchronously executes the target power command corresponding to the consistent comparison index value.

[0015] Preferably, S3 further includes: when any inverter receives a comparison index value from another inverter besides itself, a timer is started; if, within a second preset time, an inverter still has not received a comparison index value from another inverter besides itself, the corresponding abnormal situation is reported back to the energy management system.

[0016] Preferably, the second preset time is 1 / 3 to 2 / 3 of the minimum adjustment time of the energy management system, and the minimum adjustment time of the energy management system is 0.1s to 50s.

[0017] Preferably, the energy management system communicates with each of the inverters via wired or wireless means, and the inverters communicate with each other via wired means, wherein the wired means include CAN, SCI or SPI, and the wireless means include Bluetooth or WIFI.

[0018] Preferably, the index value corresponding to the target power instruction is generated based on an incrementing sequence number or a hash value.

[0019] In a second aspect, the present invention discloses a computer-readable storage medium storing a computer program, wherein the computer program is configured to be run by a processor to perform the grid-connected power scheduling and synchronization method for inverter parallel systems described in the first aspect.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: The method for grid-connected power scheduling synchronization of the parallel system disclosed in the present invention, by attaching a corresponding index value when the EMS issues the target power, firstly, each inverter determines whether the index values ​​of each phase are the same. If they are the same, a corresponding comparison index value is generated. Then, each inverter determines whether the comparison index values ​​of other inverters are consistent with its own. Only if they are consistent is the target power executed. Through the index value verification and secondary comparison mechanism, it is ensured that all inverters reach a consensus on the same instruction, avoiding the misexecution of some devices due to communication delays or losses. This enables the parallel system to synchronously execute the target power issued by the EMS module under grid-connected conditions, thereby eliminating instantaneous load spikes in the power grid and enabling the parallel system to adjust the target power more stably.

[0021] Other beneficial effects of the embodiments of the present invention will be further described below. Attached Figure Description

[0022] Figure 1 This is a flowchart of a method for grid-connected power scheduling and synchronization of an inverter parallel system disclosed in a preferred embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the communication topology of an inverter parallel system in a specific example;

[0024] Figure 3 This is a schematic diagram showing the target power executed by each inverter and the overall output power of the system during delayed response;

[0025] Figure 4 This is a schematic diagram of the target power sent by EMS at various times;

[0026] Figure 5 This is a flowchart of the grid-connected power scheduling and synchronization method for an inverter parallel system in a specific embodiment of the present invention;

[0027] Figure 6Each time, the EMS sends the target power and its corresponding index value to the inverter;

[0028] Figure 7 This is a schematic diagram illustrating the steps involved in determining the target power received by each inverter.

[0029] Figure 8 This is a schematic diagram illustrating the communication between two inverters. Detailed Implementation

[0030] The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary and not intended to limit the scope and application of the present invention.

[0031] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as "connected to" another component, it can be directly connected to or indirectly connected to that other component. Furthermore, a connection can be used for both fixing and circuit / signal connectivity.

[0032] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0033] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0034] like Figure 1 As shown, a preferred embodiment of the present invention discloses a method for grid-connected power scheduling and synchronization of an inverter parallel system, comprising the following steps:

[0035] S1: The Energy Management System (EMS) periodically sends target power commands to multiple inverters (PCS), and the target power command contains the target power and the corresponding index value;

[0036] The index value corresponding to the target power command is generated based on an incrementing sequence number or a hash value. That is, within the same cycle, the index value of the target power command sent by the energy management system to each inverter is the same; however, in different cycles, the index value of the target power command sent by the energy management system to each inverter is different, specifically generated based on an incrementing sequence number or a hash value. In other words, the index value is a logical marker that uniquely identifies the target power command.

[0037] The energy management system communicates with each inverter via wired or wireless means. Wired means include CAN (Controller Area Network), SCI (Serial Communication Interface), or SPI (Serial Peripheral Interface), while wireless means include Bluetooth (BLE) or WIFI.

[0038] S2: After receiving the target power command, each inverter checks whether the index values ​​in the target power command of each phase are consistent. If they are consistent, it generates a comparison index value corresponding to the index value and sends the generated comparison index value to all other inverters except itself.

[0039] In step S2, each inverter checks whether the index values ​​in the target power command of each phase are consistent. If they are consistent, the inverter generates a comparison index value corresponding to the index value and sends the generated comparison index value to all other inverters except itself. If the index values ​​of the target power command of each phase are inconsistent, the inverter continues to wait until the index values ​​in the target power command of all its phases are the same, generates a comparison index value corresponding to the same index value, and sends the generated comparison index value to all other inverters except itself.

[0040] Step S2 further includes: when any inverter receives a target power command corresponding to the new index value, a timer is started; if no target power commands corresponding to the new index value are received within a first preset time, the corresponding abnormal situation is reported to the energy management system. The first preset time is 1 / 3 to 2 / 3 of the minimum adjustment time of the energy management system, for example, half of the minimum adjustment time of the energy management system; the minimum adjustment time of the energy management system is 0.1s to 50s.

[0041] S3: Each inverter communicates with each other, and each inverter confirms whether the comparison index values ​​of all other inverters are consistent with its own comparison index value; if so, each inverter synchronously executes the target power command corresponding to the comparison index value.

[0042] In step S3, each inverter checks whether the comparison index values ​​of all other inverters are consistent with its own comparison index value. If they are, each inverter synchronously executes the target power command corresponding to the comparison index value. If they are not consistent, they continue to wait until all inverters confirm that the comparison index values ​​of all other inverters are consistent with their own comparison index values. Then, each inverter synchronously executes the target power command corresponding to the consistent comparison index value.

[0043] Step S3 further includes: when any inverter receives a comparison index value from another inverter besides itself, a timer is started; if an inverter still has not received a comparison index value from another inverter besides itself within a second preset time, the corresponding abnormal situation is reported to the energy management system. The second preset time is 1 / 3 to 2 / 3 of the minimum adjustment time of the energy management system, for example, half of the minimum adjustment time of the energy management system; the minimum adjustment time of the energy management system is 0.1s to 50s.

[0044] The inverters communicate with each other via wired connections, including CAN, SCI, or SPI. Comparison index values ​​are transmitted between inverters via master-slave nodes or multicast to reduce redundant communication.

[0045] The preferred embodiment of the present invention discloses a method for grid-connected power scheduling and synchronization of an inverter parallel system. By using multiple index values ​​and related logic, the grid-connected power adjustment and synchronization of the parallel system is realized. It also provides corresponding processing for various complex and unexpected operating conditions, enabling the off-grid parallel system to execute the target power issued by the EMS module synchronously when connected to the grid.

[0046] The following detailed description, in conjunction with specific examples, provides a further explanation of the method for grid-connected power scheduling and synchronization of inverter parallel systems disclosed in the preferred embodiments of the present invention.

[0047] like Figure 2The diagram shows the communication topology of the inverter parallel system in this specific example. The inverters (Inverter INV1 and Inverter INV2) in the parallel system need to achieve microsecond-level communication. Specifically, the inverters (Inverter INV1 and Inverter INV2) communicate with each other via wired (CAN / SCI / SPI) communication. This allows for real-time interactive communication and control when off-grid, while only necessary information is sent when connected to the grid. The EMS needs to communicate with each inverter at the second level. Specifically, the EMS communicates with each inverter via wired (CAN / SCI) or wireless (BLE / WIFI) communication, enabling each inverter (Inverter INV1 and Inverter INV2) to receive and control the target power sent by the EMS via wired (CAN / SCI / SPI) communication. Each inverter has three phases: L1, L2, and L3.

[0048] by Figure 2 Taking an inverter parallel system as an example, assume that the L1 phase of INV1 is discharging to the grid, while the L1 phase of INV2 is in grid-connected standby mode; when the EMS schedules power according to the user scenario and interacts with the target power of INV1 and INV2, if INV2 responds to the discharge target power first at time t1, while INV1 delays responding to the standby target power until time t2, then... Figure 3 As shown, during this brief time difference of t1 to t2, the target power P_INV1 and P_INV2 will be superimposed, and the overall system output power P_GRID will spike, causing a sudden power surge that poses a potential threat to the user environment.

[0049] Based on the aforementioned problems, this specific embodiment proposes a method for grid-connected power scheduling and synchronization of an inverter parallel system. The following example illustrates the solution of this specific embodiment using the most complex scenario: the EMS wirelessly transmits the target power to the inverter, and the target powers of L1 / L2 / L3 are not in the same frame, requiring multiple transmissions. An example of this transmission is shown below. Figure 4 As shown, at time T1, the EMS sends the target power of phases L1, L2, and L3 to INV1 and INV2 respectively: L1T1 target power, L2T1 target power, and L3T1 target power; at time T2, the EMS sends the target power of phases L1, L2, and L3 to INV1 and INV2 respectively: L1T2 target power, L2T2 target power, and L3T2 target power; at time T3, the EMS sends the target power of phases L1, L2, and L3 to INV1 and INV2 respectively: L1T3 target power, L2T3 target power, and L3T3 target power.

[0050] Under the above conditions, the target power transmission may result in the following various operating conditions:

[0051] The first operating condition is: at time T1, INV1 and INV2 do not receive the target power simultaneously;

[0052] The second operating condition is: INV1 receives the target power at the corresponding time, while INV2 only receives the target power at time T1;

[0053] The third scenario is: only INV2 receives the comparison index value from INV1, while INV1 does not receive the comparison index value from INV2.

[0054] The above three are typical operating conditions, basically covering common energy dispatching problems in parallel operation. The following analysis of the above three operating conditions will introduce the solution provided by this specific embodiment.

[0055] For the first scenario, if INV1 and INV2 execute immediately upon receiving the target power, but the target power reception is not synchronized, the following will occur: Figure 3 The situation shown. As... Figure 5 As shown, this specific embodiment makes full use of the communication between INV1 and INV2. For example, when the EMS sends the target power, the target power calculated in each round is sent with the same index value (e.g., frame number). After the inverter receives the target power, it confirms with other INVs whether the received target power sequence number (comparison index value) is the same. If they are the same, it executes immediately; if they are different, it waits in place.

[0056] like Figure 6 As shown, each time the EMS sends the target power to each inverter, at time Tn, it sends the target power of L1Tn + index n, L2Tn + index n, and L3Tn + index n to INV1, and the target power of L1Tn + index n, L2Tn + index n, and L3Tn + index n to INV2. Here, index n is the index value attached when sending the target power at time Tn. That is, the index value sent each time is different within a certain period of time. Specifically, the index value can be generated based on an incrementing sequence number or a hash value.

[0057] like Figure 7 After each inverter receives the target power, it needs to determine whether the index values ​​corresponding to the target power are the same. If the index values ​​of the three-phase target power are the same, a comparison index value Pn is generated, and the comparison index value is the same as the index value corresponding to the received target power. If the index values ​​of the three-phase target power are different, it continues to wait until the index values ​​of the three-phase target power are the same. If two phases have the same index value and the third phase is always different, the previously different index value will be discarded when the next new target power is sent.

[0058] Inverters communicate with each other to confirm the comparison index values ​​of other inverters. If the comparison index value of an inverter is the same as that of all other inverters, it immediately executes the target power calculation. If the comparison index value is different from that of other inverters, it waits until the comparison index value is the same; that is, the target power calculation will not take effect if the comparison index values ​​are different. Alternatively, when a new comparison index value is received, the old one is discarded, and each inverter then determines whether its new comparison index value is the same as that of all other inverters. Specifically, as follows... Figure 8 INV1 currently receives the latest comparison index value P2n from INV2, and INV2 currently receives the latest comparison index value P1n from INV1. INV1 compares the received P2n with its own latest comparison index value P1n, and INV2 compares the received P1n with its own latest comparison index value P2n. If they are the same, the target power is executed immediately.

[0059] Using the above methods, even if the two inverters do not receive the target power simultaneously due to communication interference or delay, they can still execute the target power simultaneously using the index value.

[0060] In the second operating scenario, if INV2 does not receive the target power at time T2, it cannot generate the latest comparison index value. Therefore, the inverter continues to execute the target power at time T1 until INV2 receives the target power at time T2 or both INV1 and INV2 receive the target power at time T3. Simultaneously, the inverter needs to determine whether the target power reception timed out or was not received, and report this to the EMS so that the EMS can recognize the corresponding situation. The timeout judgment logic is as follows: upon receiving a target power with a new index value in any frame, a timer is started. If, within a certain period, all new index values ​​of target power are not received, this abnormal situation is reported to the EMS. Here, the timeout judgment time is half of the EMS's minimum adjustment time. After receiving the abnormality, the EMS retransmits the target power command for the current index value or switches to fault-tolerant mode to maintain the previous valid command. The adjustment time of parallel systems varies depending on the application scenario. The adjustment time of residential energy storage devices that are closer to ordinary users will be shorter, generally in the range of seconds or even hundreds of milliseconds. For example, in one instance, the minimum adjustment time of EMS is 0.1s to 50s, and the minimum adjustment time of EMS is more preferably 0.1s to 10s.

[0061] For the third operating condition, which is a communication anomaly between INV1 and INV2, INV2 needs to perform a timeout judgment. If it does not receive the comparison index value of other inverters within a certain period of time, it also needs to report the anomaly to EMS. Here, the timeout judgment time is also half of the minimum adjustment time of EMS.

[0062] Another preferred embodiment of the present invention discloses a computer-readable storage medium storing a computer program, wherein the computer program is configured to be run by a processor to perform the steps of the method for grid-connected power scheduling and synchronization of an inverter parallel system in the above preferred embodiment.

[0063] Optionally, the aforementioned computer-readable storage media may include, but are not limited to, various media capable of storing computer programs, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0064] The background section of this invention may include background information about the problems or circumstances surrounding the invention, rather than a description of prior art by others. Therefore, the content included in the background section is not an admission of prior art by the applicant.

[0065] The above description provides a further detailed explanation of the present invention in conjunction with specific / preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the concept of the present invention, and all such substitutions or modifications should be considered within the scope of protection of the present invention. In the description of this specification, the reference to terms such as "an embodiment," "some embodiments," "preferred embodiment," "example," "specific example," or "some examples," etc., indicates that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Furthermore, those skilled in the art can combine and integrate different embodiments or examples and features of different embodiments or examples described in this specification without contradiction. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made herein without departing from the scope defined by the appended claims.

Claims

1. A method for grid-connected power scheduling synchronization of an inverter-interconnected system, characterized in that, The method comprises the following steps: S1: the energy management system periodically sends target power instructions to multiple inverters, and the target power instructions contain target power and corresponding index values; S2: after each inverter receives the target power instructions, it detects whether the index values in the target power instructions of each phase are consistent, and if so, generates a comparison index value corresponding to the index values and sends the generated comparison index value to all other inverters except itself; S3: the inverters communicate with each other, and each inverter confirms whether the comparison index values of all other inverters except itself are consistent with its own comparison index value; if so, each inverter synchronously executes the target power instructions corresponding to the comparison index value.

2. The method of grid-connected power dispatch synchronization for a parallel inverter system of claim 1, wherein, S2 further comprises: if the index values in the target power instructions of each phase are detected to be inconsistent, continue to wait until the index values in the target power instructions of all phases are detected to be the same, generate a comparison index value corresponding to the same index value, and send the generated comparison index value to all other inverters except itself.

3. The method of grid-connected power dispatch synchronization for a parallel inverter system of claim 1, wherein, S2 further comprises: when any inverter receives the target power instructions containing a new index value, start timing, and if all target power instructions containing the new index value are not received within a first preset time, feed back the corresponding abnormal situation to the energy management system.

4. The method of grid-connected power scheduling synchronization for a parallel inverter system of claim 3, wherein, The first preset time is 1 / 3 to 2 / 3 of the minimum adjustment time of the energy management system, and the minimum adjustment time of the energy management system is 0.1s-50s.

5. The method of grid-connected power dispatch synchronization for a parallel inverter system of claim 1, wherein, S3 further comprises: if the comparison index values of all other inverters except itself are confirmed by the inverters to be inconsistent with its own comparison index value, continue to wait until all inverters confirm that the comparison index values of all other inverters except itself are consistent with its own comparison index value, and then each inverter synchronously executes the target power instructions corresponding to the consistent comparison index value.

6. The method of grid-connected power dispatch synchronization for a parallel inverter system of claim 1, wherein, S3 further comprises: when any inverter receives the comparison index values of other inverters except itself, start timing, and if any inverter still does not receive the comparison index values of other inverters except itself within a second preset time, feed back the corresponding abnormal situation to the energy management system.

7. The method of grid-connected power scheduling synchronization for a parallel inverter system of claim 6, wherein, The second preset time is 1 / 3 to 2 / 3 of the minimum adjustment time of the energy management system, and the minimum adjustment time of the energy management system is 0.1s-50s.

8. The method of grid-connected power dispatch synchronization for a parallel inverter system of claim 1, wherein, The energy management system and each inverter communicate through wired or wireless means, and the inverters communicate with each other through wired means. The wired means include CAN, SCI or SPI, and the wireless means include Bluetooth or WIFI.

9. The method of grid-connected power dispatch synchronization for a parallel inverter system of claim 1, wherein, The corresponding index values in the target power instructions are generated based on incremental serial numbers or hash values.

10. A computer-readable storage medium, characterized in that, The computer readable storage medium stores a computer program, wherein the computer program is arranged to be run by a processor to execute the method for grid-connected power dispatch synchronization of the inverter system according to any one of claims 1 to 9.

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