Microgrid synchronization control method and microgrid power supply system

Abstract

Embodiments of the present application relate to the technical field of power supplies, and disclosed are a microgrid synchronization control method and a microgrid power supply system. In the embodiments of the present application, a central controller can directly send a phase difference between voltages on two sides of a grid-connected switch to a power converter in a microgrid, and the power converter directly performs phase compensation on a voltage between the power converter and the grid-connected switch instead of performing phase compensation on the voltage between the power converter and the grid-connected switch in a phase closed-loop control mode by the central controller. Compared with the phase closed-loop control mode, a direct phase compensation mode can quickly realize the phase synchronization of the voltages on the two sides of the grid-connected switch. Therefore, the microgrid synchronization control method provided by the embodiments of the present application can improve the speed of synchronization control.

Description

Microgrid synchronization control method and microgrid power supply system

[0001] This application claims priority to Chinese patent application No. 202410015876.7 filed on January 4, 2024, entitled “Microgrid Synchronization Control Method and Microgrid Power Supply System,” the entire contents of which are incorporated herein by reference. Technical Field

[0002] The embodiments of the present application relate to the field of power supply technology, and in particular to a microgrid synchronization control method and a microgrid power supply system. Background Art

[0003] A microgrid is a small power network that achieves a basic balance between internal power supply and consumption. During microgrid operation, if a circuit failure or a sudden loss of power generation results in insufficient energy supply, synchronization control is required to quickly connect the microgrid to the external grid to ensure power supply reliability. The purpose of synchronization control is to ensure that the difference in amplitude, phase, and frequency between the voltage on the microgrid and the external grid is less than a certain threshold. This means that the voltage on the microgrid and the external grid meet synchronization control conditions, thereby preventing system oscillation when the microgrid is connected to the external grid.

[0004] Summary of the Invention

[0005] The embodiments of the present application provide a synchronization control method and a microgrid power supply system, which can improve the speed of synchronization control. The technical solution is as follows:

[0006] In a first aspect, a microgrid synchronization control method is provided, which is applied to a microgrid power supply system. The microgrid power supply system includes a central controller, at least one power converter and a grid-connected switch, and the grid-connected switch is connected between at least one power converter and the power grid.

[0007] In the method, a central controller sends a phase difference between a first voltage and a second voltage to at least one power converter so that the at least one power converter compensates for the phase of the first voltage based on the phase difference, the first voltage is the voltage on the circuit between the at least one power converter and the grid-connected switch, and the second voltage is the voltage on the circuit between the power grid and the grid-connected switch; in response to the phase difference between the first voltage and the second voltage being less than a phase difference threshold, the frequency difference being less than a frequency difference threshold, and the amplitude difference being less than an amplitude difference threshold, the central controller controls the grid-connected switch to close so that the power grid supplies power to the at least one power converter through the grid-connected switch.

[0008] In an embodiment of the present application, a central controller can directly transmit the phase difference of the voltages on both sides of the grid-connected switch to a power converter in the microgrid, which then directly performs phase compensation on the voltage between the power converter and the grid-connected switch, rather than requiring the central controller to perform phase compensation on the voltage between the power converter and the grid-connected switch through phase closed-loop control. Compared to phase closed-loop control, direct phase compensation can quickly achieve phase synchronization of the voltages on both sides of the grid-connected switch. Therefore, the microgrid synchronization control method provided in an embodiment of the present application can improve the speed of synchronization control.

[0009] Based on the method provided in the first aspect, in one possible implementation, a central controller obtains a frequency difference between a first voltage and a second voltage; the central controller determines a reference active power based on a phase difference and a frequency difference; and the central controller sends the reference active power to at least one power converter, so that the at least one power converter adjusts the phase of the first voltage based on the reference active power. Based on the method provided in the first aspect, in one possible implementation, the central controller obtains an amplitude difference between the first voltage and the second voltage; the central controller determines a reference reactive power based on the phase difference and the amplitude difference; and the central controller sends the reference reactive power to at least one power converter, so that the at least one power converter adjusts the amplitude of the first voltage based on the reference reactive power.

[0010] In an embodiment of the present application, in order to achieve synchronous control accuracy while improving synchronous control speed, the central controller can also obtain the frequency difference between the first voltage and the second voltage, or obtain the amplitude difference between the first voltage and the second voltage. In this way, when the power converter subsequently compensates the phase of the first voltage through direct phase difference compensation, the central controller can also perform high-precision control of the phase difference or amplitude difference between the first voltage and the second voltage through closed-loop control based on reference active power or reference reactive power. In other words, the embodiment of the present application also provides a microgrid synchronous control solution that achieves both synchronous control accuracy and synchronous control speed.

[0011] Based on the method provided in the first aspect, in one possible implementation, the central controller collects voltage information of the first voltage and voltage information of the second voltage, where the voltage information indicates how the instantaneous voltage of the corresponding voltage changes over time; based on the voltage information of the first voltage and the voltage information of the second voltage, the central controller determines the phase difference.

[0012] In the above manner, the central controller can determine the phase difference through the voltage information collected in real time.

[0013] In a second aspect, a microgrid synchronization control method is provided, which is applied to a microgrid power supply system. The microgrid power supply system includes at least one power converter and a grid-connected switch, and the grid-connected switch is connected between at least one power converter and the power grid.

[0014] In this method, a power converter receives a phase difference from a central controller, where the phase difference is the difference between the phase of a first voltage and the phase of a second voltage, the first voltage being the voltage on the circuit between at least one power converter and a grid-connected switch, and the second voltage being the voltage on the circuit between the power grid and the grid-connected switch; the power converter compensates for the phase of the first voltage based on the phase difference.

[0015] In an embodiment of the present application, a central controller can directly transmit the phase difference of the voltages on both sides of the grid-connected switch to a power converter in the microgrid, which then directly performs phase compensation on the voltage between the power converter and the grid-connected switch, rather than requiring the central controller to perform phase compensation on the voltage between the power converter and the grid-connected switch through phase closed-loop control. Compared to phase closed-loop control, direct phase compensation can quickly achieve phase synchronization of the voltages on both sides of the grid-connected switch. Therefore, the microgrid synchronization control method provided in an embodiment of the present application can improve the speed of synchronization control.

[0016] Based on the method provided in the second aspect, in one possible implementation, the implementation process of the power converter compensating the phase of the first voltage based on the phase difference can be: superimposing the phase difference on the reference phase of the first voltage to obtain the compensated reference phase; and adjusting the phase of the first voltage through a closed-loop control method based on the compensated reference phase.

[0017] By directly superimposing the phase difference onto the reference phase of the first voltage, direct compensation of the reference phase of the first voltage can be achieved. Compared with adjusting the reference phase through closed-loop control, the scheme of directly compensating the reference phase can quickly adjust the phase of the first voltage.

[0018] Based on the method provided in the second aspect, in one possible implementation, the implementation process of the power converter compensating the phase of the first voltage based on the phase difference can be: dividing the phase difference into multiple phase differences; and compensating at least one of the multiple phase differences to the first voltage within at least one control cycle.

[0019] In order to improve the accuracy of synchronous control, when the power converter compensates the reference phase of the first voltage through the phase difference, it can also divide the phase difference into multiple parts, and then compensate the reference phase of the first voltage in different control cycles.

[0020] Based on the method provided in the second aspect, in a possible implementation, the process of dividing the phase difference into multiple molecular phase differences may be: if the phase difference exceeds a phase difference threshold, dividing the phase difference into multiple molecular phase differences.

[0021] In an embodiment of the present application, upon receiving a phase difference between a first voltage and a second voltage, the power converter may further determine the phase difference. If the phase difference exceeds a phase difference threshold, the phase difference is divided into multiple phase differences. Accordingly, if the phase difference does not exceed the phase difference threshold, the phase difference does not need to be divided. This avoids dividing the phase difference into multiple phase differences even when the phase difference is small, which could affect the synchronization control speed.

[0022] Based on the method provided in the second aspect, in one possible implementation, the power converter receives a reference active power from a central controller; the power converter adjusts the phase of the first voltage based on the reference active power. Based on the method provided in the second aspect, in one possible implementation, the power converter receives a reference reactive power from a central controller; the power converter adjusts the amplitude of the first voltage based on the reference reactive power.

[0023] In an embodiment of the present application, in order to achieve synchronous control accuracy while improving synchronous control speed, the central controller can also obtain the frequency difference between the first voltage and the second voltage, or obtain the amplitude difference between the first voltage and the second voltage. In this way, when the power converter subsequently compensates the phase of the first voltage through direct phase difference compensation, the central controller can also perform high-precision control of the phase difference or amplitude difference between the first voltage and the second voltage through closed-loop control based on reference active power or reference reactive power. In other words, the embodiment of the present application also provides a microgrid synchronous control solution that achieves both synchronous control accuracy and synchronous control speed.

[0024] In a third aspect, a microgrid power supply system is provided. The microgrid power supply system includes a central controller, at least one power converter and a grid-connected switch, wherein the grid-connected switch is connected between the at least one power converter and the power grid.

[0025] The central controller is configured to send a phase difference between a first voltage and a second voltage to at least one power converter, the first voltage being a voltage on a circuit between the at least one power converter and the grid-connected switch, and the second voltage being a voltage on a circuit between the grid and the grid-connected switch;

[0026] a power converter configured to receive the phase difference and compensate the phase of the first voltage based on the phase difference;

[0027] The central controller is further configured to control the grid-connected switch to close in response to a current phase difference between the first voltage and the second voltage being less than a phase difference threshold, a current frequency difference being less than a frequency difference threshold, and a current amplitude difference being less than an amplitude difference threshold, so that the grid supplies power to at least one power converter through the grid-connected switch.

[0028] Based on the system provided in the third aspect, in one possible implementation, the central controller is further used to obtain the frequency difference between the first voltage and the second voltage, determine the reference active power based on the phase difference and the frequency difference, and send the reference active power to at least one power converter; the power converter is further used to receive the reference active power and adjust the phase of the first voltage based on the reference active power.

[0029] Based on the system provided in the third aspect, in one possible implementation, the central controller is further used to obtain the amplitude difference between the first voltage and the second voltage, determine the reference reactive power based on the phase difference and the amplitude difference, and send the reference reactive power to at least one power converter; the power converter is used to receive the reference reactive power and adjust the amplitude of the first voltage based on the reference reactive power.

[0030] Based on the system provided in the third aspect, in one possible implementation, the central controller is also used to: collect voltage information of the first voltage and voltage information of the second voltage, the voltage information indicating how the instantaneous voltage of the corresponding voltage changes over time; and determine the phase difference based on the voltage information of the first voltage and the voltage information of the second voltage.

[0031] Based on the system provided in the third aspect, in one possible implementation, the power converter is used to: superimpose the phase difference on the reference phase of the first voltage to obtain a compensated reference phase; and adjust the phase of the first voltage through a closed-loop control method based on the compensated reference phase.

[0032] Based on the system provided in the third aspect, in one possible implementation, the power converter is used to: divide the phase difference into multiple phase differences; and compensate at least one of the multiple phase differences to the first voltage within at least one control cycle.

[0033] Among them, the technical effects of the system provided by the third aspect can refer to the technical effects of the microgrid synchronization control method provided by the first aspect or the second aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG1 is a schematic diagram of the architecture of a microgrid provided in an embodiment of the present application;

[0035] FIG2 is a schematic diagram of an application scenario of synchronization control provided by an embodiment of the present application;

[0036] FIG3 is a schematic diagram of another application scenario of synchronization control provided by an embodiment of the present application;

[0037] FIG4 is a schematic diagram of the architecture of a microgrid power supply system provided in an embodiment of the present application;

[0038] FIG5 is a schematic diagram of the architecture of another microgrid power supply system provided in an embodiment of the present application;

[0039] FIG6 is an exemplary schematic diagram of a microgrid power supply system shown in FIG5 provided in an embodiment of the present application;

[0040] FIG7 is a flow chart of a microgrid synchronization control method provided in an embodiment of the present application;

[0041] FIG8 is a flow chart of another microgrid synchronization control method provided in an embodiment of the present application;

[0042] FIG9 is a flow chart of another microgrid synchronization control method provided in an embodiment of the present application;

[0043] FIG10 is a schematic diagram of a synchronization control flow based on the microgrid power supply system shown in FIG6 according to an embodiment of the present application;

[0044] FIG11 is a schematic diagram of a phase jump and instantaneous voltage jump based on the microgrid power supply system shown in FIG6 according to an embodiment of the present application;

[0045] FIG12 is a schematic structural diagram of a controller provided in an embodiment of the present application. DETAILED DESCRIPTION

[0046] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the implementation methods of the present application will be further described in detail below with reference to the accompanying drawings.

[0047] Before explaining the embodiments of the present application, the concepts and application scenarios involved in the embodiments of the present application are first explained.

[0048] Microgrid: This includes distributed generation equipment, power loads, monitoring / protection devices, and automation devices. In some scenarios, it can also include energy storage devices. A microgrid is a small power network that can achieve a basic balance of internal power. A microgrid can operate in parallel with an external power grid (hereinafter referred to as the external grid), that is, powered by the external grid, or operate independently (also known as island operation) off the grid, that is, powered by its own power generation equipment. A microgrid can also be simply called a microgrid.

[0049] Synchronous: The voltages on both sides of the switch have essentially the same amplitude, frequency, and phase.

[0050] Power conversion system (PCS): In an electrochemical energy storage system, a converter connected between the battery system and the grid, and / or between the battery system and the electrical load to achieve bidirectional conversion of electrical energy.

[0051] Point of common coupling (PCC): The point where multiple electrical loads are connected in a microgrid.

[0052] Microgrid central controller (MGCC): A controller used to control a microgrid.

[0053] Virtual synchronous generator (VSG): A virtual synchronous generator whose port characteristics behave as a generator.

[0054] FIG1 is a schematic diagram of the architecture of a microgrid provided in an embodiment of the present application. As shown in FIG1 , the microgrid includes distributed power generation equipment, energy storage equipment, and power loads. When the switch between the microgrid and the external grid is disconnected, the microgrid is in an off-grid operation state, also known as island operation, in which the distributed power generation equipment and / or energy storage equipment within the microgrid supplies power to the power loads. When the switch between the microgrid and the external grid is closed, the microgrid is in a grid-connected operation state, in which the external grid supplies power to the power loads in the microgrid.

[0055] When a circuit failure or a sudden loss of power generation causes insufficient energy supply in the microgrid shown in Figure 1, it is necessary to quickly connect to the external network through synchronous control to transfer power loads to ensure power supply reliability.

[0056] Figure 2 is a schematic diagram of an application scenario for synchronization control provided by an embodiment of the present application. Figure 2 includes a microgrid and an external network, with a circuit breaker configured between the microgrid and the external network. The microgrid in this scenario can be referred to as a grid-connected microgrid. Before the circuit breaker between the microgrid and the external network is closed, the microgrid operates in an isolated manner, meaning that its own photovoltaic and other power generation equipment supplies power to the load.

[0057] As shown in Figure 2, when a microgrid is operating in an isolated state and its photovoltaic and other power generation equipment suddenly loses some power, the energy storage equipment in the microgrid needs to supply power to all loads. However, because the energy storage equipment cannot meet the needs of all loads, the energy storage equipment temporarily supplies power to critical loads, while non-critical loads are temporarily shut down to maintain power balance within the microgrid. In Figure 2, critical loads are referred to as critical loads, and non-critical loads are referred to as non-critical loads. The microgrid performs synchronous control. After synchronous control is completed, the circuit breaker is closed (i.e., switched on) to connect the microgrid to the external network, quickly restoring power to all loads.

[0058] FIG3 is a schematic diagram of another application scenario of synchronous control provided by an embodiment of the present application. FIG3 includes a plurality of sub-microgrids (hereinafter referred to as sub-microgrids) running in parallel and an external network. These plurality of sub-microgrids constitute a microgrid group. FIG3 takes two sub-microgrids as an example, and these two sub-microgrids are marked as sub-microgrid 1 and sub-microgrid 2, respectively. Each sub-microgrid is connected to the external network through a transformer, and a bus tie switch is connected between adjacent sub-microgrids. For sub-microgrid 1, when transformer 1 between sub-microgrid 1 and the external network is currently cut off due to a fault, that is, sub-microgrid 1 cannot be supplied with power by the external network, the energy storage device in sub-microgrid 1 needs to supply power to all power loads. However, since the energy storage device cannot meet the needs of all power loads, sub-microgrid 1 temporarily supplies power to the critical power loads by the energy storage device, and the non-critical power loads are temporarily shut down, and fast synchronization is performed. After the synchronization control is completed, the bus tie switch is closed to connect with the adjacent sub-microgrid 2, thereby accessing the external network through the adjacent sub-microgrid 2 to quickly restore the power supply process of all power loads in sub-microgrid 1.

[0059] For the convenience of subsequent explanation, the side where the circuit breaker in Figure 2 is connected to the PCC of the microgrid or the bus tie switch in Figure 3 is connected to the PCC of the sub-microgrid is called the "microgrid side", and the side where the circuit breaker in Figure 2 or the bus tie switch in Figure 3 is connected to the external grid is called the "external grid side".

[0060] In the scenarios shown in Figure 2 or Figure 3, to ensure that the system voltage does not experience significant overshoot and oscillation during the closing process, synchronization control must ensure that when synchronization control is completed, the amplitude, frequency, and phase difference of the voltage on both sides of the circuit breaker or bus tie switch to be closed are adjusted to a very small range, that is, to achieve high-precision synchronization control.

[0061] For microgrids using PCS as a grid-forming power source, during synchronization, the voltage amplitude, frequency, and phase at the PCC on the microgrid side are regulated by the PCS, which is uniformly controlled by the MGCC. This synchronizes the voltage amplitude, frequency, and phase between the microgrid and the external grid. The MGCC regulates the amplitude, frequency, and phase of the voltage output by the PCS through closed-loop control. Due to the inertia and damping provided by the PCS, achieving large frequency changes and rate of change of frequency (RoCoF) in a short period of time during closed-loop control is difficult, resulting in slow synchronization control.

[0062] Based on this, an embodiment of the present application provides a microgrid synchronization control method, which can realize that when a microgrid suddenly suffers a large power generation loss or failure, resulting in the power generation capacity being unable to meet the needs of the local power load, the originally isolated microgrid can be merged into the external network through synchronization control technology to achieve rapid transfer of power load, that is, to increase the speed of synchronization control, thereby reducing the power outage time of the power load in the microgrid, and thus ensuring the power supply reliability of the microgrid.

[0063] The following explains the microgrid power supply system, microgrid synchronization control method and related products provided in the embodiments of the present application.

[0064] Figure 4 is a schematic diagram of the architecture of a microgrid power supply system provided in an embodiment of the present application. As shown in Figure 4, the system includes a central controller 10, at least one power converter 20, and a grid-connected switch 30. The grid-connected switch 30 is connected between the at least one power converter 20 and the power grid, which is also the aforementioned external power grid, and is labeled as the external grid in Figure 4. In addition, Figure 4 uses three power converters as an example for illustration, and the embodiments of the present application do not limit the number of power converters in the microgrid power supply system.

[0065] The power converter 20 is illustratively connected between the energy storage device and the electrical load in the microgrid shown in FIG1 to control the power supply from the energy storage device to the electrical load.

[0066] In addition, the central controller 10 is connected to at least one power converter 20 to send control instructions to each power converter, thereby adjusting the output voltage of the power converter 20. The central controller 10 is also connected to the grid-connected switch 30 to control the grid-connected switch 30 to close or open.

[0067] For example, the central controller 10 is configured to adjust the voltage between the at least one power converter 20 and the grid-connected switch 30 in a scenario where the at least one power converter 20 needs to be powered by the grid, thereby achieving synchronous control of the voltages on both sides of the grid-connected switch 30. When the voltages on both sides of the grid-connected switch 30 meet the synchronization control conditions, the central controller 10 controls the grid-connected switch 30 to close, so that the grid supplies power to the at least one power converter 20.

[0068] In the microgrid power supply system provided in the embodiments of the present application, the central controller 10 can directly transmit the phase difference of the voltages on both sides of the grid-connected switch 30 to at least one power converter 20, and the power converter 20 directly performs phase compensation on the voltage between the power converter 20 and the grid-connected switch 30, rather than the central controller performing phase compensation on the voltage between the power converter 20 and the grid-connected switch 30 through phase closed-loop control. Compared to the phase closed-loop control method, the direct phase compensation method can quickly achieve phase synchronization of the voltages on both sides of the grid-connected switch. Therefore, the synchronization control method provided in the embodiments of the present application can improve the speed of synchronization control.

[0069] The central controller 10 and the at least one power converter 20 may be components of the microgrid in the scenario shown in FIG2 , and the grid-connected switch 30 may be the circuit breaker in FIG2 . Alternatively, the central controller 10 and the at least one power converter 20 may be components of the sub-microgrid in the scenario shown in FIG3 , and the grid-connected switch 30 may be the bus tie switch in FIG3 .

[0070] It should be noted that the central controller 10 and the power converter 20 in FIG. 4 may be integrated into the same device, or alternatively, may be distributedly deployed in different devices, which is not limited in the embodiment of the present application.

[0071] In addition, in some embodiments, as shown in FIG. 5 , each power converter 20 includes a converter controller 201 and an energy storage converter 202 .

[0072] The input of the energy storage converter 202 is connected to the energy storage device in the microgrid power supply system. The output of the energy storage converter 202 is connected to the grid-connected switch 30. The control terminal of the energy storage converter 202 is connected to the output of the converter controller 201. The input of the converter controller 201 is connected to the central controller 10. The connection between the converter controller 201 and the energy storage converter 202 is not shown in FIG5 .

[0073] In the power supply system shown in Figure 5, the central controller 10 can directly send the phase difference of the voltage on both sides of the grid-connected switch 30 to the converter controller 201, and the converter controller 201 directly performs phase compensation on the voltage between the energy storage converter 202 and the grid-connected switch 30, instead of the central controller performing phase compensation on the voltage between the energy storage converter 202 and the grid-connected switch 30 through phase closed-loop control.

[0074] The energy storage converter 202 may be a PCS, and the converter controller 201 may be a PCS local controller.

[0075] Figure 6 is a schematic diagram of an example microgrid power supply system shown in Figure 5, provided in an embodiment of the present application. As shown in Figure 6, the microgrid power supply system includes an MGCC, one or more PCS modules, one or more power loads, and a grid-connected switch. The MGCC serves as the central controller shown in Figure 5.

[0076] As shown in Figure 6 , each PCS module includes a PCS local controller, a PCS, and an energy storage device (the energy storage device is labeled as "energy storage" in Figure 6 ). In Figure 6 , the PCSs in each PCS module are labeled PCS1 through PSCn, and the PCS local controllers in each PCS module are labeled PCS1 local controller through PSCn local controller.

[0077] Among them, the control end of the PCS in each PCS module is connected to the PCS local controller, the input end of the PCS is connected to the energy storage device, and the output end of the PCS is connected to one or more power loads, which are marked as load 1 to load k in Figure 6, where k is greater than or equal to 1.

[0078] As shown in Figure 6, loads 1 through k are connected to the output of each PCS, respectively, to power loads 1 through k through one or more PSC modules. The connection point between loads 1 through k and the output of each PCS is referred to as a PCC.

[0079] As shown in Figure 6, grid-connected switches are deployed between loads 1 through k and the external grid. The area between the grid-connected switch and the PCC is referred to as the microgrid side of the grid-connected switch, and the area between the grid-connected switch and the external grid is referred to as the external grid side of the grid-connected switch.

[0080] In the microgrid power supply system shown in Figure 6, when the MGCC determines that synchronization control is currently required, it can collect the voltage signal on the external grid side of the grid-connected switch (labeled as the external grid-side voltage sampling signal in Figure 6) and the voltage signal on the microgrid side of the grid-connected switch (labeled as the microgrid-side voltage sampling signal in Figure 6). Based on the difference between these two voltage signals, it sends a PCS control instruction to the PCS local controller to adjust the amplitude, frequency, and phase of the voltage at the PCS output, that is, the amplitude, frequency, and phase of the voltage at the PCC. As shown in Figure 6, the MGCC sends the PCS1 control instruction to the PCS1 local controller, ..., and sends the PCSn control instruction to the PCSn local controller, so that each PCS local controller adjusts the voltage at the corresponding PCS output.

[0081] In an embodiment of the present application, the PCS control instruction sent by the MGCC to the PCS local controller carries the phase difference between the microgrid-side voltage and the external grid-side voltage, so that the PCS local controller can directly perform phase compensation on the voltage output by the PSC based on the phase difference, thereby improving the speed of synchronization control.

[0082] When the MGCC detects that the voltage signal on the external grid side of the grid-connected switch and the voltage signal on the microgrid side of the grid-connected switch meet the synchronization control condition, the MGCC sends a grid-connected switch control instruction to the grid-connected switch to control the grid-connected switch to close.

[0083] The microgrid synchronization control method provided in the embodiment of the present application is explained below.

[0084] FIG7 is a flow chart of a microgrid synchronization control method provided by an embodiment of the present application. The method is applied to the central controller shown in FIG4 or FIG5, and is exemplarily applied to the MGCC shown in FIG6. As shown in FIG6, the method includes the following steps.

[0085] Step 701: The central controller sends a phase difference between a first voltage and a second voltage to at least one power converter, so that the at least one power converter compensates for the phase of the first voltage based on the phase difference, where the first voltage is the voltage on the circuit between the at least one power converter and the grid-connected switch, and the second voltage is the voltage on the circuit between the grid and the grid-connected switch.

[0086] Step 702: In response to the phase difference between the first voltage and the second voltage being less than the phase difference threshold, the frequency difference being less than the frequency difference threshold, and the amplitude difference being less than the amplitude difference threshold, the central controller controls the grid-connected switch to close so that the grid supplies power to at least one power converter through the grid-connected switch.

[0087] In an embodiment of the present application, a central controller can directly transmit the phase difference of the voltages on both sides of the grid-connected switch to a power converter in the microgrid, which then directly performs phase compensation on the voltage between the power converter and the grid-connected switch, rather than requiring the central controller to perform phase compensation on the voltage between the power converter and the grid-connected switch through phase closed-loop control. Compared to phase closed-loop control, direct phase compensation can quickly achieve phase synchronization of the voltages on both sides of the grid-connected switch. Therefore, the microgrid synchronization control method provided in an embodiment of the present application can improve the speed of synchronization control.

[0088] Figure 8 is a flow chart of another microgrid synchronization control method provided by an embodiment of the present application. This method is applied to the power converter shown in Figure 4 or Figure 5, and is illustratively applied to any PCS local controller in the microgrid shown in Figure 6. As shown in Figure 8, this method includes the following steps.

[0089] Step 801: The power converter receives a phase difference from a central controller, where the phase difference is the difference between the phase of a first voltage and the phase of a second voltage. The first voltage is the voltage on the circuit between the power converter and the grid-connected switch, and the second voltage is the voltage on the circuit between the grid and the grid-connected switch.

[0090] Step 802: The power converter compensates the phase of the first voltage based on the phase difference.

[0091] In an embodiment of the present application, a central controller can directly transmit the phase difference of the voltages on both sides of the grid-connected switch to a power converter in the microgrid, which then directly performs phase compensation on the voltage between the power converter and the grid-connected switch, rather than requiring the central controller to perform phase compensation on the voltage between the power converter and the grid-connected switch through phase closed-loop control. Compared to phase closed-loop control, direct phase compensation can quickly achieve phase synchronization of the voltages on both sides of the grid-connected switch. Therefore, the microgrid synchronization control method provided in an embodiment of the present application can improve the speed of synchronization control.

[0092] FIG9 is a flow chart of another microgrid synchronization control method provided in an embodiment of the present application. The method is applied to the microgrid power supply system shown in any of FIG4 to FIG6. As shown in FIG9, the method includes the following steps.

[0093] Step 901: The central controller sends a phase difference between a first voltage and a second voltage to at least one power converter, where the first voltage is the voltage on the circuit between at least one power converter and the grid-connected switch, and the second voltage is the voltage on the circuit between the grid and the grid-connected switch.

[0094] In some embodiments, before sending the phase difference between the first voltage and the second voltage to the power converter, the central controller may also obtain the phase difference between the first voltage and the second voltage in response to the synchronization control instruction.

[0095] The synchronization control command can be triggered by an operator through a specified operation on the central controller. For example, in certain scenarios, such as testing, when the operator needs to supply power to the microgrid's loads from the grid, the operator can trigger the synchronization control command through the user interface provided by the central controller.

[0096] In other embodiments, the central controller can also detect the actual power of the electrical load in the microgrid in real time. When it is detected that the actual power of the electrical load in the microgrid does not reach the rated power of the electrical load in the microgrid, it can automatically execute the operation of obtaining the phase difference between the first voltage and the second voltage.

[0097] In addition, in some embodiments, the central controller can collect voltage information of the first voltage and voltage information of the second voltage, where the voltage information indicates how the instantaneous voltage of the corresponding voltage changes over time; based on the voltage information of the first voltage and the voltage information of the second voltage, the central controller determines the phase difference.

[0098] For example, based on the voltage information of the first voltage and the voltage information of the second voltage, the central controller can determine the phase difference by: processing the voltage information of the first voltage and the voltage information of the second voltage through a phase-locked loop (PLL) circuit respectively to obtain the phase of the first voltage and the phase of the second voltage; based on the phase of the first voltage and the phase of the second voltage, determining the phase difference between the first voltage and the second voltage.

[0099] Among them, the PLL circuit is a circuit that uses feedback technology to achieve frequency and phase control. Therefore, the PLL circuit can also be called a PLL integrator. The phase determined by the PLL circuit has high accuracy.

[0100] The principle of determining the phase of a certain voltage through a PLL circuit is as follows: the voltage is used as a reference signal, and then the phase difference between the input signal of the PLL circuit and the reference signal is compared. The frequency and phase of the output signal of the PLL circuit are adjusted through feedback control to synchronize the output signal with the reference signal. The phase of the output signal after such adjustment is the phase of the voltage.

[0101] As another example, based on the voltage information of the first voltage and the voltage information of the second voltage, the central controller can determine the phase difference by performing Clarke transform on the voltage information of the first voltage and the voltage information of the second voltage, respectively, to obtain a first Clarke transform result and a second Clarke transform result; based on the first Clarke transform result and the second Clarke transform result, calculating the phase difference between the first voltage and the second voltage.

[0102] Considering that the PLL circuit's feedback control response is slow, thus affecting the synchronization control speed, embodiments of the present application also provide a phase difference calculation method based on the instantaneous voltage Clarke transform. In this method, there is no need to determine the phase difference through feedback control, so the phase difference is determined more quickly. Therefore, this method is more conducive to improving the synchronization control speed.

[0103] For example, use u grid-α 、u grid-β They represent the components of the second voltage instantaneous value in the αβ coordinate system, and u PCC-α 、u PCC-β Respectively represent the components of the first voltage instantaneous value in the αβ coordinate system, with V grid 、V PCC Represent the instantaneous amplitude of the second voltage and the first voltage respectively, and use θ grid ,θ PCC Represent the phase of the second voltage and the first voltage respectively. The relationship between these parameters can be expressed by the following formula. In the following formula, the first and second rows are the results of the second Clarke transform, and the third and fourth rows are the results of the first Clarke transform:

[0104] The phase difference between the first voltage and the second voltage can be obtained by the above formula. The phase difference is expressed as Δθ, and Δθ can be expressed by the following formula:

[0105] In the above formula, atan2() is a function that comes with the C language function library. The parameters A and B can be expressed by the following formula:

[0106] In the above formula for determining the first Clarke transform result and the second Clarke transform result, there is no need to assume that the voltage amplitudes of the first voltage and the second voltage are equal, so the calculation accuracy is higher. Therefore, this phase difference calculation method is more conducive to improving the speed of synchronous control.

[0107] It should be noted that the above two implementation methods are used to illustrate how to determine the phase difference between the first voltage and the second voltage. The embodiments of the present application do not limit the implementation method of how to determine the phase difference between the first voltage and the second voltage, and will not be illustrated one by one here.

[0108] Alternatively, other devices may collect voltage information of the first voltage and the second voltage, determine the phase difference between the first voltage and the second voltage, and then send the phase difference to the central controller, thereby reducing the data processing pressure of the central controller.

[0109] In addition, in an embodiment of the present application, in order to achieve synchronous control accuracy while improving synchronous control speed, the central controller can also obtain the frequency difference between the first voltage and the second voltage, and / or obtain the amplitude difference between the first voltage and the second voltage. In this way, when the power converter subsequently compensates the phase of the first voltage through direct phase difference compensation, the central controller can also perform high-precision control of the amplitude difference, frequency difference, and phase difference between the first voltage and the second voltage through closed-loop control. Therefore, an embodiment of the present application also provides a synchronous control scheme that achieves both synchronous control accuracy and synchronous control speed.

[0110] For example, in the microgrid power supply system shown in FIG6 , the MGCC receives and stores the instantaneous sampling value of the first voltage (i.e., the voltage on the microgrid side of the grid-connected switch) and the instantaneous sampling value of the second voltage (i.e., the voltage on the external grid side of the grid-connected switch), i.e., the voltage information of the first voltage and the voltage information of the second voltage. For the convenience of subsequent description, the voltage information of the first voltage is represented as v PCC (k), the voltage information of the second voltage is expressed as v grid (k).

[0111] MGCC uses PLL circuit, based on v PCC (k) and v grid (k) Calculate the phase of the first voltage and the phase of the second voltage at the current moment respectively, and express the phase of the first voltage as θ PCC (k), the phase of the second voltage is expressed as θ grid (k). MGCC uses PLL circuit or discrete Fourier transform (DFT) circuit and other technologies based on v PCC (k) and v grid (k) Calculate the frequency of the first voltage and the frequency of the second voltage at the current moment respectively, and express the frequency of the first voltage as f PCC (k), the frequency of the second voltage is expressed as f grid(k). MGCC uses root mean square (RMS) and other algorithms based on v PCC (k) and v grid (k) Calculate the amplitude of the first voltage and the amplitude of the second voltage at the current moment respectively, and express the amplitude of the first voltage as V PCC (k), the amplitude of the second voltage is expressed as V grid (k).

[0112] Based on the above calculation results, MGCC calculates the phase difference, frequency difference, and amplitude difference between the first voltage and the second voltage at the current moment, respectively. The phase difference is expressed as Δθ(k), the frequency difference is expressed as Δf(k), and the amplitude difference is expressed as ΔV(k). The phase difference, frequency difference, and replication fork can be expressed by the following formulas:

[0113] The above methods of determining the frequency difference and the amplitude difference are for illustration only and are not limited to these in the embodiments of the present application.

[0114] Furthermore, based on the above, the central controller can also obtain the frequency difference between the first voltage and the second voltage. In this scenario, the central controller determines a reference active power based on the phase difference and the frequency difference. The central controller then transmits the reference active power to at least one power converter, causing the at least one power converter to adjust the phase of the first voltage based on the reference active power. This means adjusting the phase of the first voltage in a closed-loop manner.

[0115] In addition, based on the above, it can be seen that the central controller can also obtain the amplitude difference between the first voltage and the second voltage. In this scenario, the central controller determines a reference reactive power based on the phase difference and the amplitude difference; the central controller sends the reference reactive power to at least one power converter, so that the at least one power converter adjusts the amplitude of the first voltage based on the reference reactive power. In other words, the amplitude of the first voltage is adjusted in a closed-loop manner.

[0116] The following description will be made by taking the microgrid power supply system shown in FIG6 as an example.

[0117] The MGCC performs phase closed-loop control, frequency closed-loop control, and amplitude closed-loop control of the first voltage based on the calculated phase difference, frequency difference, and amplitude difference between the first and second voltages, respectively, and combines the output results of each closed-loop control into active power and reactive power, which are transmitted to the PCS local controller.

[0118] The phase closed-loop control, frequency closed-loop control, and amplitude closed-loop control of the first voltage can be implemented using proportional-integral controllers, respectively. The inputs of the proportional-integral controller are the phase difference Δθ(k), frequency difference Δf(k), and amplitude difference ΔV(k) between the first voltage and the second voltage at the current moment, respectively. The output of the proportional-integral controller after executing the phase closed-loop control is expressed as P θ (k), the output of the proportional-integral controller after executing the frequency closed-loop control is expressed as P f (k), the output of the proportional-integral controller after performing amplitude closed-loop control is expressed as Q V (k), the closed-loop control process can be expressed by the following formula:

[0119] Among them, T s-MGCC is the control period of MGCC, K p-θ , K i-θ are the proportional and integral coefficients of phase closed-loop control, K p-f , K i-f are the proportional and integral coefficients of frequency closed-loop control, K p-V , K i-V are the proportional and integral coefficients of amplitude closed-loop control respectively.

[0120] The MGCC can determine the reference active power and reference reactive power using the following formula and transmit the reference active power and reference reactive power to the PCS local controller, so that the PCS local controller uses the received reference active power and reference reactive power as the active power reference value and reactive power reference value for the PCS VSG control at the current moment:

[0121] Among them, P ref (k) represents the reference active power, Q ref (k) represents the reference reactive power.

[0122] It should be noted that the above method is used to illustrate the method for determining the reference active power and the reference reactive power. The embodiment of the present application does not limit the method for determining the reference active power and the reference reactive power, and will not be illustrated one by one here.

[0123] FIG10 is a schematic diagram of a synchronous control process based on the microgrid power supply system shown in FIG6 according to an embodiment of the present application. As shown in FIG10 , the MGCC includes a phase / frequency / amplitude difference calculation module, a phase closed-loop control module, a frequency closed-loop control module, and an amplitude closed-loop control module, all of which are software modules. The phase / frequency / amplitude difference calculation module is used to obtain the voltage information v of the first voltage collected by the voltage sensor on the microgrid side. PCC(k), and the voltage information v of the second voltage collected by the voltage sensor on the external network side grid Based on the two voltage information, a phase difference Δθ(k), a frequency difference Δf(k), and an amplitude difference ΔV(k) between the first voltage and the second voltage are determined.

[0124] After obtaining the phase difference Δθ(k), the phase / frequency / amplitude difference calculation module sends the phase difference Δθ(k) to the PCS local controller, so that the PCS local controller directly compensates the phase of the first voltage based on the phase difference Δθ(k).

[0125] In addition, the phase / frequency / amplitude difference calculation module also sends the phase difference Δθ(k), frequency difference Δf(k) and amplitude difference ΔV(k) to the phase closed-loop control module, frequency closed-loop control module and amplitude closed-loop control module respectively. The phase closed-loop control module performs phase closed-loop control based on the phase difference Δθ(k), the frequency closed-loop control module performs frequency closed-loop control based on the frequency difference Δf(k), and the amplitude closed-loop control module performs amplitude closed-loop control based on the amplitude difference ΔV(k). The output results of the phase closed-loop control module and the frequency closed-loop control module are combined to form the reference active power P ref (k) is sent to the PCS local controller, and the output result of the amplitude closed-loop control module is used as the reference reactive power Q ref (k) Delivered to the PCS local controller.

[0126] Step 902: The power converter receives the phase difference from the central controller.

[0127] For example, in the microgrid power supply system shown in FIG5 , the converter controller receives the phase difference.

[0128] For example, in the microgrid power supply system shown in FIG6 , the PCS local controller in each PCS module receives the phase difference.

[0129] Step 903: The power converter compensates the phase of the first voltage based on the phase difference.

[0130] In some embodiments, the power converter may compensate for the phase of the first voltage based on the phase difference by superimposing the phase difference on the reference phase of the first voltage to obtain a compensated reference phase; and adjusting the phase of the first voltage through closed-loop control based on the compensated reference phase.

[0131] For example, for the system shown in Figure 6, the MGCC outputs the calculated phase difference between the first voltage and the second voltage to each PCS local controller. The PCS local controller adjusts the reference phase of the PCS output voltage based on the received phase difference and controls the PCS output voltage according to the adjusted reference phase.

[0132] By directly superimposing the phase difference onto the reference phase of the first voltage, direct compensation of the reference phase of the first voltage is achieved. Compared with adjusting the reference phase through closed-loop control, the scheme of directly compensating the reference phase can achieve rapid adjustment of the phase of the first voltage.

[0133] For ease of understanding, the principles of the PCS local controller are explained here. In the embodiment of the present application, as shown in Figure 10, the PCS local controller includes a phase compensation calculation module, a VSG control module, and a PCS voltage control loop module. These three modules are all software modules.

[0134] The VSG control module is used to determine the reference phase and reference amplitude of the first voltage based on the received reference active power and reference reactive power. As shown in FIG10 , the reference phase before phase difference compensation, that is, the reference phase output by the VSG control module, is marked as θ VSG , mark the reference amplitude output by the VSG control module as V ref The phase compensation calculation module is used to determine the current compensation amount required to compensate the reference phase, as shown in Figure 10, and the compensation amount is marked as θ comp (k), the reference phase after phase difference compensation is marked as θ ref , where θ ref =θ VSG +θ comp (k) The PCS voltage control loop module is used to adjust the control pulses of each device in the PCS through closed-loop control so that the output voltage of the PSC meets the reference amplitude V ref and the compensated reference phase θ ref .

[0135] In addition, in order to improve the accuracy of synchronous control, the power converter can also divide the phase difference into multiple parts when compensating the reference phase of the first voltage through the phase difference, and then compensate the reference phase of the first voltage respectively in different control cycles.

[0136] Based on this, for example, the implementation method of the power converter compensating the phase of the first voltage based on the phase difference can be: dividing the phase difference into multiple phase differences; and compensating at least one of the multiple phase differences to the first voltage within at least one control cycle.

[0137] For the microgrid power supply system shown in Figure 6, the above control cycle refers to the control cycle of the PCS local controller. In the i-th control cycle after receiving the phase difference, the received reference active power and reference reactive power are converted into the reference phase θ by the VSG control module. VSG and reference amplitude V ref, then the reference phase θ VSG Superimposed with the phase difference of the i-th molecule, the reference phase θ after compensation in the current control cycle is obtained ref The reference phase after compensation θ ref And the reference amplitude V ref Input to the PCS voltage control loop module, the PCS voltage control loop module according to the compensated reference phase θ ref and reference amplitude V ref The control pulses of each device in the PCS are adjusted by closed-loop control so that the output voltage of the PSC meets the compensated reference phase θ ref and reference amplitude V ref .

[0138] For example, assuming that the number of phase compensations is N (N=1, 2, 3, ...), the compensation amount θ of the reference phase of the first voltage in each control cycle is comp (i) (i.e., the sub-phase difference) can be determined according to the following formula, T s Indicates the control cycle of the PCS local controller:

[0139] The input reference phase to the PCS voltage control loop module can be determined by the following formula: ref (k) = θ comp (k)+θ VSG (k)

[0140] Among them, θ comp (k) represents the reference phase after compensation in the current control cycle, θ VSG (k) represents the reference phase output by the VSG control module in the current control cycle.

[0141] In addition, in an embodiment of the present application, upon receiving a phase difference between the first voltage and the second voltage, the power converter may further determine the phase difference. If the phase difference exceeds a phase difference threshold, the phase difference is divided into multiple phase differences. Accordingly, if the phase difference does not exceed the phase difference threshold, the phase difference does not need to be divided. This avoids dividing the phase difference into multiple phase differences even when the phase difference is small, which may result in a decrease in synchronization control speed.

[0142] Through the method provided in the embodiment of the present application, when the power converter receives the phase difference, it can compensate the reference phase of the first voltage once or multiple times using the phase difference.

[0143] In addition, based on step 901, it can be known that the power converter can also receive reference active power from the central controller. In this scenario, the power converter can also adjust the phase of the first voltage based on the reference active power.

[0144] In addition, based on step 901, it can be known that the power converter can also receive a reference reactive power from the central controller. In this scenario, the power converter can also adjust the amplitude of the first voltage based on the reference reactive power.

[0145] Among them, the power converter adjusts the phase of the first voltage based on the reference active power, and the power converter adjusts the amplitude of the first voltage based on the reference reactive power. The functions of the VSG control module and the PCS voltage control loop module in Figure 10 can be referred to and will not be described in detail here.

[0146] Step 904: In response to the phase difference between the first voltage and the second voltage being less than the phase difference threshold, the frequency difference being less than the frequency difference threshold, and the amplitude difference being less than the amplitude difference threshold, the central controller controls the grid-connected switch to close so that the grid supplies power to at least one power converter through the grid-connected switch.

[0147] The grid supplying power to the at least one power converter via the grid-connected switch may be understood as the grid supplying power to the power load connected to the at least one power converter via the grid-connected switch.

[0148] In addition, the phase difference threshold, the frequency difference threshold, and the amplitude difference threshold may be the same threshold, or may be three thresholds configured independently, which is not limited in the embodiment of the present application.

[0149] For example, in the microgrid power supply system shown in FIG6 , the MGCC obtains voltage information of the first voltage and the second voltage from the voltage sampling device, calculates and determines whether the absolute value of the current phase difference, the current frequency difference, and the current amplitude difference between the first voltage and the second voltage are less than a set threshold value; if so, it determines that the synchronization control is completed and sends a closing command to the grid-connected switch; if not, it returns to step 901 to continue executing the synchronization control.

[0150] For example, the phase difference threshold is expressed as ε θ , the frequency difference threshold is expressed as ε f , the amplitude difference threshold is expressed as ε V , then the synchronous control condition can be expressed by the following formula: (|Δθ(k)|<ε θ )and(|Δf(k)|<ε f )and(|ΔV(k)|<ε V )

[0151] It should be noted that step 903 is executed once in each control cycle of the power converter. If it is determined that the synchronous control is not completed, step 901 is executed again in the next control cycle.

[0152] In summary, in the embodiments of the present application, the central controller can directly transmit the phase difference of the voltages on both sides of the grid-connected switch to the power converter in the microgrid, and the power converter can directly perform phase compensation on the voltage between the power converter and the grid-connected switch, rather than the central controller performing phase compensation on the voltage between the power converter and the grid-connected switch through phase closed-loop control. Compared to the phase closed-loop control method, the direct phase compensation method can quickly achieve phase synchronization of the voltages on both sides of the grid-connected switch. Therefore, the synchronization control method provided in the embodiments of the present application can improve the speed of synchronization control.

[0153] In addition, it should be noted that since the power converter directly compensates for the phase of the first voltage through the phase difference, the reference phase of the first voltage will jump during the synchronous control process through the method provided in the embodiment of the present application, and accordingly, the instantaneous voltage waveform of the first voltage will also jump during the synchronous control process.

[0154] Figure 11 is a schematic diagram of a phase change and transient voltage according to an embodiment of the present application, based on the microgrid power supply system shown in Figure 6. As shown in Figure 11, after the PCS local controller receives the phase difference and compensates the reference phase output by the VSG control module based on the phase difference, the reference phase input to the PCS voltage control loop module undergoes a jump.

[0155] As shown in Figure 11, due to a jump in the reference phase input to the PCS voltage control loop module, the waveform of the first voltage also changes after closed-loop control of the PCS voltage control loop, becoming a continuous sine wave instead of a continuous sine wave. It should be noted that the first voltage is a three-phase voltage, and the waveform of the first voltage in Figure 11 represents one phase. The waveforms of the other phase voltages also change after the PCS local controller compensates for the reference phase, but this is not shown in Figure 11.

[0156] In summary, in the embodiments of the present application, the central controller can directly transmit the phase difference of the voltages on both sides of the grid-connected switch to the power converter in the microgrid, and the power converter can directly perform phase compensation on the voltage between the power converter and the grid-connected switch, rather than the central controller performing phase compensation on the voltage between the power converter and the grid-connected switch through phase closed-loop control. Compared to the phase closed-loop control method, the direct phase compensation method can quickly achieve phase synchronization of the voltages on both sides of the grid-connected switch. Therefore, the microgrid synchronization control method provided in the embodiments of the present application can improve the speed of synchronization control.

[0157] In addition, it should be noted that the above method is described using a microgrid power supply system as an example. Optionally, the synchronous control scheme provided in this application can also be applied in other scenarios. For example, in a scenario where an energy storage power station supplies power to the grid, a switch is connected between the energy storage power station and the grid. Before the energy storage power station is restarted and connected to the grid, it is also necessary to ensure that the difference in amplitude, phase, and frequency of the voltage on both sides of the switch is less than a certain threshold. In this scenario, the method shown in Figure 9 can be used to achieve that the difference in amplitude, phase, and frequency of the voltage on both sides of the switch is less than a certain threshold. This will not be described in detail here.

[0158] In addition, referring to the microgrid power supply system shown in FIG4 , the functions of the various components in the microgrid power supply system are as follows.

[0159] wherein at least one central controller is configured to send a phase difference between a first voltage and a second voltage to at least one power converter, wherein the at least one first voltage is a voltage on a circuit between the at least one power converter and the at least one grid-connected switch, and the at least one second voltage is a voltage on a circuit between the power grid and the at least one grid-connected switch;

[0160] at least one power converter configured to receive the at least one phase difference and compensate for a phase of the at least one first voltage based on the at least one phase difference;

[0161] At least one central controller is further used to control at least one grid-connected switch to close in response to a current phase difference between at least one first voltage and at least one second voltage being less than a phase difference threshold, a current frequency difference being less than a frequency difference threshold, and a current amplitude difference being less than an amplitude difference threshold, so that at least one power grid supplies power to at least one power converter through the at least one grid-connected switch.

[0162] Optionally, the at least one central controller is further configured to obtain a frequency difference between the at least one first voltage and the at least one second voltage, determine a reference active power based on the at least one phase difference and the at least one frequency difference, and send the at least one reference active power to the at least one power converter;

[0163] The at least one power converter is further configured to receive at least one reference active power and adjust a phase of at least one first voltage based on the at least one reference active power.

[0164] Optionally, the at least one central controller is further configured to obtain an amplitude difference between the at least one first voltage and the at least one second voltage, determine a reference reactive power based on the at least one phase difference and the at least one amplitude difference, and send the at least one reference reactive power to the at least one power converter;

[0165] At least one power converter is configured to receive at least one reference reactive power and adjust the amplitude of at least one first voltage based on the at least one reference reactive power.

[0166] Optionally, the at least one central controller is further configured to:

[0167] collecting voltage information of at least one first voltage and voltage information of at least one second voltage, wherein at least one voltage information indicates how the instantaneous voltage of the corresponding voltage changes over time;

[0168] At least one phase difference is determined based on voltage information of at least one first voltage and voltage information of at least one second voltage.

[0169] Optionally, at least one power converter is configured to:

[0170] superimposing at least one phase difference onto a reference phase of at least one first voltage to obtain a compensated reference phase;

[0171] The phase of at least one first voltage is adjusted through closed-loop control based on the compensated reference phase.

[0172] Optionally, at least one power converter is configured to:

[0173] dividing at least one phase difference into multiple molecular phase differences;

[0174] At least one phase difference of at least one plurality of phase differences is compensated to at least one first voltage within at least one control cycle.

[0175] Optionally, the power converter is used to:

[0176] If the at least one phase difference exceeds a phase difference threshold, the at least one phase difference is divided into multiple phase differences.

[0177] The implementation of the functions of the various components in the above-mentioned microgrid power supply system can refer to the embodiment shown in Figure 9, and will not be repeated here.

[0178] In addition, an embodiment of the present application further provides a microgrid synchronization control device, which is deployed in a central controller in a microgrid power supply system. The microgrid power supply system also includes at least one power converter and a grid-connected switch, wherein the grid-connected switch is connected between the at least one power converter and the power grid; the device includes:

[0179] The first sending module is used to send the phase difference between the first voltage and the second voltage to at least one power converter, so that the at least one power converter compensates for the phase of the first voltage based on the phase difference, the first voltage is the voltage on the circuit between the at least one power converter and the grid-connected switch, and the second voltage is the voltage on the circuit between the power grid and the grid-connected switch; the specific implementation method can refer to step 901 in the embodiment of Figure 9.

[0180] The control module is configured to control the grid-connected switch to close in response to the phase difference between the first voltage and the second voltage being less than a phase difference threshold, the frequency difference being less than a frequency difference threshold, and the amplitude difference being less than an amplitude difference threshold, so that the grid supplies power to the at least one power converter via the grid-connected switch. For specific implementation, see step 904 in the embodiment of FIG. 9 .

[0181] Optionally, the device further comprises:

[0182] A first acquisition module, configured to acquire a frequency difference between the first voltage and the second voltage;

[0183] A first determining module, configured to determine a reference active power based on a phase difference and a frequency difference;

[0184] The second sending module is configured to send reference active power to at least one power converter, so that the at least one power converter adjusts the phase of the first voltage based on the reference active power.

[0185] Optionally, the device further comprises:

[0186] A second acquisition module, configured to acquire an amplitude difference between the first voltage and the second voltage;

[0187] A second determining module is used to determine a reference reactive power based on the phase difference and the amplitude difference;

[0188] The third sending module is configured to send reference reactive power to at least one power converter, so that the at least one power converter adjusts the amplitude of the first voltage based on the reference reactive power.

[0189] Optionally, the device further comprises:

[0190] an acquisition module, configured to acquire voltage information of the first voltage and voltage information of the second voltage, wherein the voltage information indicates how the instantaneous voltage of the corresponding voltage changes over time;

[0191] The third determining module is configured to determine a phase difference based on the voltage information of the first voltage and the voltage information of the second voltage.

[0192] In an embodiment of the present application, a central controller can directly transmit the phase difference of the voltages on both sides of the grid-connected switch to a power converter in the microgrid, which then directly performs phase compensation on the voltage between the power converter and the grid-connected switch, rather than requiring the central controller to perform phase compensation on the voltage between the power converter and the grid-connected switch through phase closed-loop control. Compared to phase closed-loop control, direct phase compensation can quickly achieve phase synchronization of the voltages on both sides of the grid-connected switch. Therefore, the microgrid synchronization control method provided in an embodiment of the present application can improve the speed of synchronization control.

[0193] It should be noted that the microgrid synchronization control device provided in the above embodiment is merely an example of the division of the above functional modules when performing synchronization control. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. In addition, the microgrid synchronization control device provided in the above embodiment and the microgrid synchronization control method embodiment are based on the same concept. The specific implementation process is detailed in the method embodiment and will not be repeated here.

[0194] In addition, an embodiment of the present application further provides a microgrid synchronization control device, which is deployed in a power converter in a microgrid power supply system. The microgrid power supply system includes at least one power converter and a grid-connected switch, and the grid-connected switch is connected between the at least one power converter and the power grid; the device includes:

[0195] The first receiving module is used to receive a phase difference from the central controller, where the phase difference is the difference between the phase of the first voltage and the phase of the second voltage, the first voltage is the voltage on the circuit between at least one power converter and the grid-connected switch, and the second voltage is the voltage on the circuit between the power grid and the grid-connected switch; for specific implementation methods, please refer to step 902 in the embodiment of Figure 9.

[0196] The compensation module is configured to compensate the phase of the first voltage based on the phase difference. For specific implementation, please refer to step 903 in the embodiment of FIG9 .

[0197] Optionally, the compensation module is used to:

[0198] superimposing the phase difference onto the reference phase of the first voltage to obtain a compensated reference phase;

[0199] The phase of the first voltage is adjusted through a closed-loop control method based on the compensated reference phase.

[0200] Optionally, the compensation module is used to:

[0201] Divide the phase difference into multiple molecular phase differences;

[0202] At least one phase difference among the plurality of phase differences is compensated to a first voltage within at least one control period.

[0203] Optionally, the compensation module is used to:

[0204] If the phase difference exceeds the phase difference threshold, the phase difference is divided into multiple molecular phase differences.

[0205] Optionally, the device further comprises:

[0206] A second receiving module is used to receive the reference active power from the central controller;

[0207] The first adjustment module is configured to adjust the phase of the first voltage based on the reference active power.

[0208] Optionally, the device further comprises:

[0209] A third receiving module is used to receive a reference reactive power from the central controller;

[0210] The second adjustment module is configured to adjust the amplitude of the first voltage based on the reference reactive power.

[0211] In an embodiment of the present application, a central controller can directly transmit the phase difference of the voltages on both sides of the grid-connected switch to a power converter in the microgrid, which then directly performs phase compensation on the voltage between the power converter and the grid-connected switch, rather than requiring the central controller to perform phase compensation on the voltage between the power converter and the grid-connected switch through phase closed-loop control. Compared to phase closed-loop control, direct phase compensation can quickly achieve phase synchronization of the voltages on both sides of the grid-connected switch. Therefore, the microgrid synchronization control method provided in an embodiment of the present application can improve the speed of synchronization control.

[0212] It should be noted that the microgrid synchronization control device provided in the above embodiment is merely an example of the division of the above functional modules when performing synchronization control. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. In addition, the microgrid synchronization control device provided in the above embodiment and the microgrid synchronization control method embodiment are based on the same concept. The specific implementation process is detailed in the method embodiment and will not be repeated here.

[0213] 12 is a schematic diagram of the structure of a controller provided in an embodiment of the present application. The controller may be the aforementioned central controller or a converter controller in a power converter, such as an MGCC or a PCS local controller.

[0214] As shown in Figure 12, the controller 1200 includes a processing unit 1201 and a communication unit 1202. The communication unit 1202 is used to communicate with other components in the microgrid power supply system, and the processing unit 1201 is used to implement the functions of the aforementioned central controller or power converter.

[0215] In the above embodiments, all or part of the embodiments can be implemented by software, hardware, firmware, or any combination thereof. When implemented using software, all or part of the embodiments can be implemented in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via a wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) method. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or data center that includes one or more available media integrated therein. The available medium may be a magnetic medium (eg, a floppy disk, a hard disk, a magnetic tape), an optical medium (eg, a digital versatile disc (DVD)), or a semiconductor medium (eg, a solid state disk (SSD)).

[0216] Those skilled in the art will understand that all or part of the steps to implement the above embodiments may be accomplished by hardware, or by a program to instruct the relevant hardware, and the program may be stored in a computer-readable storage medium, which may be a read-only memory, a disk, or an optical disk, etc.

[0217] The above content is not intended to limit the embodiments of the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the embodiments of the present application should be included in the scope of protection of the embodiments of the present application.

Claims

1. A microgrid synchronization control method, characterized in that, The method is applied to a microgrid power supply system, which includes a central controller, at least one power converter, and a grid connection switch. The grid connection switch is connected between at least one of the power converters and the power grid. The method includes: The central controller sends the phase difference between a first voltage and a second voltage to at least one of the power converters, so that at least one of the power converters compensates the phase of the first voltage based on the phase difference. The first voltage is the voltage on the circuit between at least one of the power converters and the grid connection switch, and the second voltage is the voltage on the circuit between the power grid and the grid connection switch. In response to the phase difference between the first voltage and the second voltage being less than the phase difference threshold, the frequency difference being less than the frequency difference threshold, and the amplitude difference being less than the amplitude difference threshold, the central controller controls the grid connection switch to close, so that the power grid supplies power to at least one of the power converters through the grid connection switch.

2. The method according to claim 1, characterized in that, The method further includes: The central controller obtains the frequency difference between the first voltage and the second voltage. The central controller determines the reference active power based on the phase difference and the frequency difference. The central controller sends the reference active power to at least one of the power converters, so that at least one of the power converters adjusts the phase of the first voltage based on the reference active power.

3. The method according to claim 1 or 2, characterized in that The method further includes: The central controller obtains the amplitude difference between the first voltage and the second voltage. The central controller determines the reference reactive power based on the phase difference and the amplitude difference. The central controller sends the reference reactive power to at least one of the power converters, so that at least one of the power converters adjusts the amplitude of the first voltage based on the reference reactive power.

4. The method according to any one of claims 1-3, characterized in that The method further includes: The central controller collects the voltage information of the first voltage and the voltage information of the second voltage. The voltage information indicates the variation of the instantaneous voltage of the corresponding voltage with time. Based on the voltage information of the first voltage and the voltage information of the second voltage, the central controller determines the phase difference.

5. A microgrid synchronization control method, characterized in that, The method is applied to a microgrid power supply system, which includes at least one power converter and a grid connection switch. The grid connection switch is connected between at least one of the power converters and the power grid. The method includes: The power converter receives the phase difference from the central controller. The phase difference is the difference between the phase of a first voltage and the phase of a second voltage. The first voltage is the voltage on the circuit between at least one of the power converters and the grid connection switch, and the second voltage is the voltage on the circuit between the power grid and the grid connection switch. The power converter compensates the phase of the first voltage based on the phase difference.

6. The method according to claim 5, wherein The power converter compensating the phase of the first voltage based on the phase difference includes: Adding the phase difference to the reference phase of the first voltage to obtain the compensated reference phase. Adjusting the phase of the first voltage in a closed-loop control manner based on the compensated reference phase.

7. The method according to claim 5 or 6, characterized in that, The power converter compensates the phase of the first voltage based on the phase difference, including: Dividing the phase difference into multiple sub-phase differences; Compensating at least one of the multiple sub-phase differences to the first voltage within at least one control period respectively.

8. The method according to claim 7, characterized in that, The dividing the phase difference into multiple sub-phase differences includes: If the phase difference exceeds the phase difference threshold, dividing the phase difference into multiple sub-phase differences.

9. The method according to any one of claims 5 to 8, characterized in that, The method further includes: The power converter receives a reference active power from the central controller; The power converter adjusts the phase of the first voltage based on the reference active power.

10. The method according to any one of claims 5-9, characterized in that, The method further includes: The power converter receives a reference reactive power from the central controller; The power converter adjusts the amplitude of the first voltage based on the reference reactive power.

11. A microgrid power supply system, characterized in that, The microgrid power supply system includes a central controller, at least one power converter, and a grid connection switch, and the grid connection switch is connected between at least one of the power converters and the power grid; The central controller is configured to send the phase difference between the first voltage and the second voltage to at least one of the power converters, where the first voltage is the voltage on the circuit between at least one of the power converters and the grid connection switch, and the second voltage is the voltage on the circuit between the power grid and the grid connection switch; The power converter is configured to receive the phase difference and compensate the phase of the first voltage based on the phase difference; The central controller is further configured to control the grid connection switch to close in response to that the current phase difference between the first voltage and the second voltage is less than the phase difference threshold, the current frequency difference is less than the frequency difference threshold, and the current amplitude difference is less than the amplitude difference threshold, so that the power grid supplies power to at least one of the power converters through the grid connection switch.

12. The system according to claim 11, wherein The central controller is further configured to obtain the frequency difference between the first voltage and the second voltage, determine a reference active power based on the phase difference and the frequency difference, and send the reference active power to at least one of the power converters; The power converter is further configured to receive the reference active power and adjust the phase of the first voltage based on the reference active power.

13. The system according to claim 11 or 12, wherein The central controller is further configured to obtain the amplitude difference between the first voltage and the second voltage, determine a reference reactive power based on the phase difference and the amplitude difference, and send the reference reactive power to at least one of the power converters; The power converter is configured to receive the reference reactive power and adjust the amplitude of the first voltage based on the reference reactive power.

14. The system according to any one of claims 11-13, characterized in that, The central controller is further configured to: Collect the voltage information of the first voltage and the voltage information of the second voltage, where the voltage information indicates the change of the instantaneous voltage of the corresponding voltage over time; Determine the phase difference based on the voltage information of the first voltage and the voltage information of the second voltage.

15. The system according to any one of claims 11-14, characterized in that, The power converter is configured to: Superimpose the phase difference on the reference phase of the first voltage to obtain a compensated reference phase; Adjust the phase of the first voltage in a closed-loop control manner based on the compensated reference phase.

16. The system according to any one of claims 11-15, characterized in that, The power converter is configured to: Divide the phase difference into multiple sub-phase differences; Compensate at least one of the multiple sub-phase differences to the first voltage within at least one control period respectively.

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