Three-phase power supply conversion system, energy storage equipment, energy storage system and energy distribution method

Abstract

A three-phase power conversion system comprises a power conversion module, the first end of which is used for connecting a photovoltaic cell and a battery, and the second end of which is used for connecting to a power grid through a three-phase AC bus; the first load port and the second load port are sequentially connected to a three-phase alternating current bus between the power supply conversion module and a power grid; the three-phase alternating current bus between the second load port and the power grid is used for being connected to an electricity meter; the first current sensor is arranged at the alternating current output end of the power supply conversion module; the second current sensor is arranged at the first load port; and the controller is connected with the power supply conversion module, the electric meter, the first current sensor and the second current sensor.

Description

Technical Field

[0001] This application relates to the field of photovoltaic power generation and energy storage technology, specifically to a three-phase power conversion system, energy storage device, energy storage system, and energy distribution method. Background Technology

[0002] In a three-phase power conversion system (PCS), the three phases may carry different loads, thus requiring different power outputs from each phase, necessitating power distribution. This is particularly relevant in scenarios where users have installed additional photovoltaic (PV) inverters on top of an existing PV inverter. In this case, the output of the existing PV inverters is connected to the output of the three-phase PCS, which then manages the power output to the grid connection.

[0003] Therefore, it is an urgent problem to be solved to take into account the energy distribution of the three-phase PCS in both scenarios with and without an external photovoltaic inverter. Summary of the Invention

[0004] This application provides a three-phase power conversion system, energy storage device, energy storage system, and energy distribution method, which can save system costs while taking into account energy distribution in two scenarios of three-phase PCS, thereby improving economic efficiency.

[0005] In a first aspect, this application provides a three-phase power conversion system, comprising: a power conversion module, a first end of which is used to connect a photovoltaic cell and a battery, and a second end of which is used to connect to the power grid via a three-phase AC bus; a first load port and a second load port, which are sequentially connected to the three-phase AC bus; and the three-phase AC bus between the second load port and the power grid is used to connect to an electricity meter; a first current sensor and a second current sensor, the first current sensor being disposed at the AC output end of the power conversion module, and the second current sensor being disposed at the first load port; and a controller connected to the power conversion module, the electricity meter, the first current sensor, and the second current sensor. Attached Figure Description

[0006] The features, advantages, and technical effects of exemplary embodiments of this application will now be described with reference to the accompanying drawings.

[0007] Figure 1 This is a schematic diagram of the three-phase power conversion system provided in this application; Figure 2 One of the flowcharts illustrating the energy distribution method provided in this application; Figure 3 The second flowchart illustrating the energy distribution method provided in this application; Figure 4The third flowchart illustrating the energy distribution method provided in this application; Figure 5 The fourth flowchart illustrating the energy distribution method provided in this application; Figure 6 Fifth flowchart illustrating the energy distribution method provided in this application; Figure 7 The sixth flowchart illustrating the energy distribution method provided in this application; Figure 8 The seventh flowchart illustrating the energy distribution method provided in this application; Figure 9 The eighth flowchart illustrating the energy distribution method provided in this application.

[0008] The accompanying drawings are not necessarily drawn to scale. Detailed Implementation

[0009] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are some embodiments of this application, but not all embodiments.

[0010] In a three-phase power conversion system (PCS), the three phases may carry different loads, thus requiring different power outputs from each phase. The PCS needs to manage this power distribution appropriately. This is especially important in scenarios where users have installed additional photovoltaic (PV) inverters on top of existing ones. In this case, the output of the existing PV inverters is connected to the output of the three-phase PCS, which then manages the power output to the grid connection.

[0011] In scenarios where a PCS is connected to external photovoltaic (PV) systems, dual current transformer (CT) meters are typically used to simultaneously measure the power output of the PCS and the power generated by the external PV system, serving as the basis for energy allocation. Alternatively, two single-CT meters can be used for power acquisition, communicating between the two meters to the PCS controller for subsequent energy allocation. Another option is to not separately acquire the power generated by the external PV system.

[0012] However, these solutions all have certain limitations. For the dual-CT meter solution, it results in wasted costs when the PCS is not connected to external solar power. For the two single-CT meters solution, it also results in wasted costs when the PCS is not connected to external solar power (i.e., not an ACCouple scenario), and requires communication processing for both meters, which may lead to program incompatibility risks. For solutions that do not separately collect power generated by external solar power, if the PCS is connected to external solar power (i.e., an ACCouple scenario), the external solar power cannot be rationally allocated, resulting in wasted power and loss of economic benefits.

[0013] Based on this, this application provides a three-phase power conversion system, energy storage device, energy storage system and energy distribution method, which can save system costs while taking into account energy distribution in both non-AC Couple and AC Couple scenarios of three-phase PCS, thereby improving economic efficiency.

[0014] The three-phase power conversion system (PCS) of this application will be described below. Figure 1 As shown, a three-phase PCS may include: The power conversion module 101 has a first terminal for connecting the photovoltaic 300 and the battery 400, and a second terminal for connecting to the power grid via a three-phase AC bus. Understandably, the first terminal of the power conversion module 101 is connected to a DC power source, and the second terminal is connected to an AC power source.

[0015] The first load port 102 and the second load port 103 are sequentially connected to the three-phase AC bus between the power conversion module 101 and the power grid 600, and the three-phase AC bus between the second load port 103 and the power grid 600 is used to connect to the electricity meter 200.

[0016] A first current sensor 104 and a second current sensor 105 are used. The first current sensor 104 is located at the AC output terminal of the power conversion module 101, and the second current sensor 105 is located at the first load port 102. Optionally, the first current sensor 104 and the second current sensor 105 can be current sensors or current transformers.

[0017] The controller 106 is connected to the power conversion module 101, the meter 200, the first current sensor 104, and the second current sensor 105.

[0018] The first terminal of the power conversion module 101 can be used to connect to a DC power source (e.g., photovoltaic 300 and battery 400), and the second terminal of the power conversion module 101 can be connected to the power grid 600 via a three-phase AC bus. The power conversion module 101 can perform energy transfer and power conversion between DC and AC power. The power conversion module 101 can operate in inverter mode and rectification mode. In inverter mode, the power conversion module 101 can convert the DC power output from the photovoltaic 300 and / or battery 400 into AC power and supply power to the load through the first load port 102 and the second load port 103, and / or inject it into the power grid 600 via the three-phase AC bus. In rectification mode, the power conversion module 101 can convert AC power obtained from the power grid 600 and / or the external photovoltaic inverter 500 into DC power to charge the battery 400.

[0019] It is understandable that the PV300 and 400 cells can be used as external components of the three-phase PCS, and do not belong to the three-phase PCS itself.

[0020] The first load port 102 and the second load port 103 can be connected sequentially to the three-phase AC bus between the power conversion module 101 and the power grid 600. That is, both the first load port 102 and the second load port 103 can include three-phase ports, and each phase port can be used to connect a load, and the load is powered through the power grid 600 and / or the power conversion module 101.

[0021] The first load port 102 is closer to the power conversion module 101, and the second load port 103 is closer to the power grid 600. Accordingly, the load connected to the first load port 102 is referred to as the internal load, and the load connected to the second load port 103 is referred to as the external load. The second load port 102 can also be used to connect to an external photovoltaic inverter 500.

[0022] The meter 200 can be used as an external component of the three-phase PCS, connected to the three-phase AC bus between the second load port 103 and the power grid 600. In other words, the meter 200 is connected to the power grid 600 through the grid connection point on the three-phase AC bus between the second load port 103 and the power grid 600, and can be used to measure the electrical energy exchanged between the three-phase PCS and the power grid, and monitor power flow.

[0023] The first current sensor 104 is located at the AC output terminal of the power conversion module 101, and can collect the output current of each phase output terminal of the three-phase PCS, thereby calculating the output power of each phase. The second current sensor 105 is located at the first load port 102, and can collect the current of the internal load of each phase, thereby calculating the power of the internal load of each phase.

[0024] In non-AC Couple (i.e., without an external PV inverter connected) scenarios, the power of each phase's internal load and the power on meter 200 can be subtracted from the output power of each phase to obtain the power of the external load in each phase. In AC Couple (i.e., with an external PV inverter connected) scenarios, the power of each phase's internal load and the power on meter 200 can be subtracted from the output power of each phase to obtain the sum of the power of the external load and the power of the external PV inverter 500. This allows for power monitoring in both non-AC Couple and AC Couple scenarios of the three-phase PCS, facilitating subsequent energy distribution. It can be understood that the output power of each phase refers to the output power of each phase of the three-phase PCS.

[0025] The controller 106 can be connected to the power conversion module 101, the meter 200, the first current sensor 104, and the second current sensor 105 to achieve centralized control. For example, the controller can control the operating mode of the power conversion module 101 to be either rectification mode or inverter mode based on the photovoltaic power generation, battery charge, load demand, and grid conditions. Optionally, the controller 106 can also acquire sensor data to adjust power flow and ensure efficient and stable system operation, such as entering rectification mode to charge the battery when the grid electricity price is low, and entering inverter mode to discharge when the grid electricity price is high. Additionally, the controller can also perform functions such as fault detection.

[0026] The three-phase power conversion system provided in this application employs two current sensors and a meter to measure the internal load power, as well as the external load power and / or the power of the external photovoltaic inverter. It is compatible with both non-AC Couple and AC Couple scenarios, enabling coordinated management of photovoltaics, batteries, the grid, the load, and / or the external photovoltaic inverter, providing the hardware foundation for dynamic power allocation. Thus, while saving system costs, it can simultaneously consider energy distribution in both three-phase PCS scenarios, improving economic efficiency.

[0027] In some optional examples, such as Figure 1 As shown, a first relay K1 is provided between the output port of the power conversion module 101 and the first load port 102, and a second relay K2 is provided between the first load port 102 and the second load port 103.

[0028] When the three-phase PCS fails, or when the three-phase PCS is not required to supply power to the load, the first relay K1 can be disconnected and the second relay K2 can be connected to supply power to the loads connected to the first load port 102 and the second load port 103 through the power grid 600.

[0029] If a fault occurs at the first load port 102, the first relay K1 and the second relay K2 can be disconnected. At this time, the load connected to the second load port 103 can be powered through the power grid 600, and the load connected to the first load port 102 will be in a power-off state.

[0030] It is understandable that if the second load port 103 is also connected to the external photovoltaic inverter 500, then the external photovoltaic inverter 500 and the grid 600 can be used to supply power together.

[0031] When the power grid 600 stops supplying power or a fault occurs at the second load port 103, the second relay K2 can be disconnected and the first relay K1 can be connected. At this time, the load connected to the first load port 102 can be powered by the photovoltaic 300 of the three-phase PCS, while the load connected to the second load port 103 is in a power-off state.

[0032] In this way, the first relay isolates the power conversion module from the first load port, which can prevent the spread of local faults. The second relay isolates the first load port from the second load port. While preventing the spread of local faults, it can also supply power to the internal load through the photovoltaic of the three-phase PCS when the power grid stops supplying power, thus improving the flexibility of the three-phase PCS system.

[0033] Optionally or additionally, such as Figure 1 As shown, a third relay K3 is also provided between the first load port 102 and the second load port 103. That is, two relays are provided between the first load port 102 and the second load port 103, namely the second relay K2 and the third relay K3.

[0034] In this way, by adding a third relay to enhance the isolation level between the first and second load ports, short circuits or interference between the grid and the photovoltaic and / or battery systems of the three-phase PCS are effectively prevented when power is switched from the grid to the three-phase PCS's photovoltaic and / or battery systems. Furthermore, by using two relays, arcing can be distributed between the two contacts, extending the relay's lifespan and improving the overall system reliability. Additionally, the dual relays allow for maintenance or replacement of one relay without causing the entire system to go offline.

[0035] Optionally or additionally, such as Figure 1 As shown, the power conversion module 101 may include: DC / AC converter 1011, the first terminal of DC / AC converter 1011 is connected to the power grid via a three-phase AC bus; A first DC / DC converter 1012, the first terminal of the first DC / DC converter 1012 is connected to the second terminal of the DC / AC converter 1011, and the second terminal of the first DC / DC converter 1012 is used to connect to the photovoltaic 300. The second DC / DC converter 1013 has a first terminal connected to the second terminal of the DC / AC converter 1011, and the second terminal of the second DC / DC converter 1013 is used to connect the battery 400.

[0036] The first terminal of the DC / AC converter 1011 is connected to the power grid 600 via a three-phase AC bus, and the second terminal of the DC / AC converter 1011 is connected to the first DC / DC converter 1012 and the second DC / DC converter 1013. The DC / AC converter 1011 is used to convert the DC power from the photovoltaic 300 and / or the battery 400 into three-phase AC power to enable interaction with the power grid 600.

[0037] The first terminal of the first DC / DC converter 1012 is connected to the second terminal of the DC / AC converter 1011, and the second terminal of the first DC / DC converter 1012 is used to connect to the photovoltaic 300. The first DC / DC converter 1012 is used to regulate the DC voltage generated by the photovoltaic 300 to match system requirements. For example, the output voltage of the photovoltaic 300 fluctuates with changes in light intensity and temperature, and the first DC / DC converter 1012 boosts and pulls the variable DC voltage to a stable DC voltage for use by the DC / AC converter 1011.

[0038] The first terminal of the second DC / DC converter 1013 is connected to the second terminal of the DC / AC converter 1011, and the second terminal of the second DC / DC converter 1013 is used to connect the battery 400. The second DC / DC converter 1013 is used to regulate the output voltage of the battery 400 or the voltage input to the battery 400 to match the system DC bus. The voltage of the battery 400 changes during charging and discharging, and the second DC / DC converter 1013 converts the battery voltage to a voltage compatible with the DC bus.

[0039] In this way, the architecture combining DC / AC converters and dual DC / DC converters supports independent input and decoupled control of photovoltaics and batteries, so as to adapt to different energy characteristics such as photovoltaic volatility and battery charging and discharging strategies.

[0040] Based on the three-phase power conversion system described above, this application also provides an energy storage device, which may include: As described above regarding the three-phase power conversion system and battery, the battery is connected to the first terminal of the power conversion module in the three-phase power conversion system. In some alternative examples, the battery may be connected to the second terminal of the second DC / DC converter in the power conversion module.

[0041] The specific connection relationships and working principles of energy storage devices have been described above and will not be repeated here.

[0042] Based on the energy storage device described above, this application also provides an energy storage system, which may include: As described above, the energy storage device and the electricity meter are used to connect the second load port in the energy storage device to the three-phase AC bus between the grid and the power grid.

[0043] In some optional examples, the energy storage system may also include an external photovoltaic inverter; An external photovoltaic inverter is connected to a three-phase AC bus.

[0044] The specific connection relationships and working principles of the energy storage system have been described above and will not be repeated here.

[0045] Based on the energy storage system described above, this application also provides an energy distribution method, such as... Figure 2 As shown, the method may include: Step 201: Determine the total power of each phase based on the power of each phase of the first load port and the power of each phase of the second load port; Step 202: Determine the total load power based on the total power of each phase; Step 203: In response to the case where the total load power is greater than 0, determine the total grid feed power based on the total load power, photovoltaic power, and battery power; Step 204: Based on the total power of each phase and the power limit of each phase, determine the corresponding power generation capacity; Step 205: Allocate the total power to the feeder grid based on the corresponding power generation capacity to obtain the corresponding initial power allocation value.

[0046] In this context, the phase power of the first load port can be defined as the power consumed by the internal load of each phase. For the phase power of the second load port: in a non-AC Couple scenario, the phase power of the second load port is the power consumed by the external load of each phase; in an AC Couple scenario, the phase power of the second load port is the sum of the power consumed by the external load of each phase and the output power of each phase of the external photovoltaic inverter. In the AC Couple scenario, this application denotes the output power of each phase of the external photovoltaic inverter as a negative value.

[0047] Optionally or additionally, such as Figure 3 As shown, before determining the total power of each phase based on the power of each phase at the first load port and the power of each phase at the second load port, the method may further include: Step 301: Obtain the corresponding first electrical signal in the first current sensor, the corresponding second electrical signal in the second current sensor, and the corresponding power of the meter in the meter. Step 302: Determine the power of each phase of the first load port based on the corresponding second electrical signals in the second current sensor; Step 303: Determine the phase power of the second load port based on the corresponding first electrical signal in the first current sensor, the power of the meter, and the phase power of the first load port. The power of each phase of the second load port includes the power of the load connected to the second load port, or the power of each phase of the second load port includes the output power of the external photovoltaic inverter and the power of the load connected to the second load port.

[0048] The controller in the three-phase PCS is connected to the electricity meter, the first current sensor, and the second current sensor, respectively, and can then acquire the corresponding first electrical signal from the first current sensor, the corresponding second electrical signal from the second current sensor, and the corresponding electricity power from the electricity meter.

[0049] Based on the corresponding second electrical signals from the second current sensor, the power of each phase at the first load port is determined. For example, taking the second electrical signal as a current signal, the controller can calculate the power consumed by the load inside each phase, i.e., the power of each phase at the first load port, based on the current signals of each phase collected by the second current sensor and the voltage signals collected by the power conversion module.

[0050] Furthermore, the power of each phase of the second load port can be determined based on the corresponding first electrical signal in the first current sensor, the power of the meter, and the power of each phase of the first load port. For example, taking the first electrical signal as a current signal, the controller can calculate the output power of each phase of the AC output terminal of the power conversion module based on the current signals of each phase collected by the first current sensor and the voltage signals collected by the power conversion module.

[0051] Then, based on the output power of each phase of the AC output terminal of the power conversion module, the power of each phase of the first load port, and the power of the meter, the power of each phase of the second load port can be calculated. The calculation formula is shown in formula (1): Wherein, PloadExA, PloadExB, and PloadExC are the phase power of the second load port, PbackloadA, PbackloadB, and PbackloadC are the phase power of the first load port, PinvA, PinvB, and PinvC are the output power of each phase of the AC output terminal of the power conversion module, and PmeterA, PmeterB, and PmeterC are the power of the corresponding meters.

[0052] In this way, by combining two current sensors and meter data, the power of each phase at the first load port and the power of each phase at the second load port can be decoupled, providing a reliable input for subsequent energy distribution.

[0053] Furthermore, based on the phase power of the first load port and the phase power of the second load port, the total phase power is determined. That is, the total phase power can be the sum of the phase power of the first load port and the phase power of the second load port. The formula for calculating the total phase power is shown in formula (2): Wherein, PloadA, PloadB, and PloadC can be the total power of each phase, PbackloadA, PbackloadB, and PbackloadC can be the power of each phase of the first load port, and PloadExA, PloadExB, and PloadExC can be the power of each phase of the second load port.

[0054] Understandably, in a non-AC Coupled scenario, the total power of each phase is the sum of the power consumed by the internal and external loads of each phase. For example, if the power corresponding to the internal load of phase A is 1 kW and the power corresponding to the external load of phase A is 2 kW, then the total power of phase A is 1 + 2 = 3 kW. In an AC Coupled scenario, the total power of each phase is the sum of the power consumed by the internal and external loads of each phase, and the power output by the external photovoltaic inverter. For example, if the power corresponding to the internal load of phase A is 1 kW, the power corresponding to the external load of phase A is 2 kW, and the power output by the external photovoltaic inverter of phase A is 4 kW, that is, the power corresponding to the external photovoltaic inverter of phase A is -4 kW, then the total power of phase A is 1 + 2 + (-4) = -1 kW.

[0055] The sum of the total power of each phase can be calculated to obtain the total load power PloadAll. The calculation formula is shown in formula (3): Understandably, in a non-AC Couple scenario, the power of each phase at the first load port and the power of each phase at the second load port are both positive, so the total load power is also positive. In an AC Couple scenario, the external photovoltaic inverter outputs power, not consumes power; that is, the power value of the external photovoltaic inverter is recorded as negative. Therefore, the power of each phase at the second load port may be negative, and the total power of each phase may also be negative. Consequently, the final calculated total load power may also be negative.

[0056] When the total load power is positive, the DC power from the photovoltaic (PV) system and / or batteries needs to be converted to AC power for the load or injected into the grid; that is, the three-phase PCS operates in inverter mode. Further, it is determined whether the total load power PloadAll is greater than the PV power Ppv. If PloadAll < Ppv, it means the PV power Ppv can meet the load's power consumption, the PV supplies power to the load, and the remaining energy can charge the batteries. If PloadAll > Ppv, it means the PV power Ppv is insufficient to meet the load's power consumption; in this case, the batteries need to discharge, and both the PV and batteries jointly supply power to the load.

[0057] When the total load power is negative, it means that the external photovoltaic inverter has surplus energy while meeting the load consumption. At this time, the three-phase PCS can work in rectification mode so that it can obtain AC power from the external photovoltaic inverter and convert it into DC power through the power conversion module (such as DC / AC converter) to charge the battery.

[0058] Optionally or additionally, when the total load power is greater than 0, the controller can control the three-phase PCS to be in inverter mode and determine the total grid feed power based on the total load power, photovoltaic power and battery power.

[0059] The photovoltaic power can be the power output of the photovoltaic system in the three-phase PCS, and the battery power can be the power output of the battery in the three-phase PCS. It is understood that in this application, if the battery of the three-phase PCS is in a charging state, the battery power will be a negative value.

[0060] The formula for calculating the total feeder power is shown in formula (4): Where PrefAll is the total grid power, PloadAll is the total load power, Ppv is the photovoltaic power, and Pbat can be the battery power.

[0061] Furthermore, based on the total power of each phase and the power limit of each phase, the corresponding power generation capacity is determined. For example, the power limit of each phase can be calculated based on the voltage signal and the limiting current of each phase. The limiting current can be obtained from the configuration information of the three-phase PCS (such as the product manual, user manual, etc. of the three-phase PCS). The calculation formula for the corresponding power generation capacity can be as shown in formula (5): Where PabltA, PabltB, and PabltC represent the corresponding power generation capacity, PlimitA, PlimitB, and PlimitC represent the power limits of each phase, and PloadA, PloadB, and PloadC represent the total power of each phase, which is the sum of the power of each phase at the first load port and the power of each phase at the second load port.

[0062] The total power of the feeder grid can be allocated based on the corresponding generating capacity to obtain the corresponding initial power allocation value. For example, the total power of the feeder grid can be allocated according to the proportion of the corresponding generating capacity to obtain the corresponding initial power allocation value. Alternatively, the corresponding generating capacities can be sorted by size, and the power can be allocated to each phase in ascending order to obtain the corresponding initial power allocation value.

[0063] Understandably, the power of each phase at the first load port, the power of each phase at the second load port, the total power of each phase, the total load power, the photovoltaic power, the battery power, the total grid power, and the corresponding initial power allocation values ​​can all be active power.

[0064] In this way, the controller can switch the working mode of the three-phase PCS based on the positive or negative value of the total load power. When the total load power is greater than 0, the PCS feeds the grid and distributes the grid power according to the power generation capacity of each phase, avoiding single-phase overload. This improves system stability while ensuring efficiency and energy utilization.

[0065] Understandably, grid feeding refers to the transmission of electrical energy from a three-phase power generation system (PCS) to the grid. After the photovoltaic (PV) and / or battery cells of the three-phase PCS supply power to the load, if there is any remaining electrical energy (i.e., total grid feeding power), this remaining energy can be transmitted back to the grid. If the output power of the PV and / or battery cells of a certain phase of the three-phase PCS is less than the total power consumed by the load in that phase, then that phase also needs to draw power from the grid to supply power to its load; that is, the grid feeding power of that phase is negative. When an external PV inverter is also connected to the second load port of the three-phase PCS, in addition to the PV and / or battery cells of the three-phase PCS transmitting electrical energy to the grid, the external PV inverter may also transmit electrical energy to the grid.

[0066] Optionally or additionally, such as Figure 4 As shown, the total grid power is allocated based on the corresponding generation capacity to obtain the corresponding initial power allocation values, which may include: Step 401: Divide the total power of the feeder into three phases to obtain the average power of the first feeder. Step 402: In response to the first feeder average power being less than or equal to the first corresponding generation capacity, determine the initial power allocation value for each corresponding value as the first feeder average power. The first corresponding generation capacity is the minimum value among the corresponding generation capacities.

[0067] The corresponding power generation capacities are sorted by size, with the first corresponding power generation capacity being the minimum among all corresponding power generation capacities.

[0068] The total feeder power can be divided equally among the three phases to obtain the average power of the first feeder. That is, the average power of the first feeder is PrefAll / 3. Further, the average power of the first feeder PrefAll / 3 is compared with the first corresponding power generation capacity (assuming it is PabltA). If the average power of the first feeder is less than or equal to the first corresponding power generation capacity, that is, PrefAll / 3 ≤ PabltA, then the initial power allocation value of each corresponding value can be determined as the average power of the first feeder. That is, the expression of the initial power allocation value of each corresponding value can be shown in formula (6): Where Gridref1_A, Gridref1_B, and Gridref1_C are the corresponding initial power allocation values, and PrefAll / 3 is the average power of the first feeder.

[0069] The energy distribution method mentioned above will be illustrated with a specific example below.

[0070] Example 1: In this example, the photovoltaic power Ppv can be 15kW; the power limits of each phase PlimitA, PlimitB, and PlimitC can all be 5kW; the power of each phase at the first load port: PbackloadA can be 2kW, PbackloadB can be 3kW, and PbackloadC can be 5kW; the power of each phase at the second load port: PloadExA can be -1kW, PloadExB can be -1kW, and PloadExC can be -2kW.

[0071] The total power of each phase (i.e., the sum of the power of each phase at the first load port and the power of each phase at the second load port) is calculated as follows: PloadA is 2 + (-1) = 1 kW, PloadB is 3 + (-1) = 2 kW, and PloadC is 5 + (-2) = 3 kW; the total load power PloadAll is 1 + 2 + 3 = 6 kW. Since 0 < PloadAll < Ppv, the three-phase PCS is in inverter mode at this time, and the battery is charging. Since the battery charging limit is 6 kW, the battery power Pbat is -6 kW.

[0072] The total feeder power PrefAll is calculated to be Ppv + Pbat - PloadAll = 3kW. The corresponding generating capacities (i.e., the difference between the power limit of each phase and the total power of each phase) are: PabltA = 5 - 1 = 4kW, PabltB = 5 - 2 = 3kW, and PabltC = 5 - 3 = 2kW. Therefore, the minimum generating capacity of the three phases is 2kW. Since the average power of the first feeder PrefAll / 3 = 1kW < 2kW, the initial power allocation value for each phase is the average power of the first feeder, i.e., Gridref1_A, Gridref1_B, and Gridref1_C are all 1kW. At this point, each phase of the three-phase PCS can transmit 1kW of electricity to the grid.

[0073] In this way, the first phase with the weakest power generation capacity is used as the allocation benchmark. When the average power of the first feeder of the three phases does not exceed the power generation capacity of that phase, the equal distribution strategy is directly adopted. This avoids overload of the output power of each phase, simplifies the calculation, improves the allocation efficiency, and reduces problems such as harmonics and neutral point offset caused by three-phase imbalance, thereby improving the power quality of the grid and the life of the equipment.

[0074] Optionally or additionally, such as Figure 4 As shown, the method may also include: Step 403: In response to the fact that the average power of the first feeder is greater than the first corresponding power generation capacity, the initial power allocation value of the first corresponding is determined to be the first corresponding power generation capacity. Step 404: Divide the remaining feeder power into two phases to obtain the second feeder average power; the remaining feeder power is the difference between the total feeder power and the corresponding power generation capacity of the first feeder. Step 405: In response to the second feeder average power being less than or equal to the second corresponding power generation capacity, determine that the initial power allocation value of the second corresponding value and the initial power allocation value of the third corresponding value are both the second feeder average power; the power generation capacity of the second corresponding value is the smaller value among the power generation capacities of the remaining two corresponding values.

[0075] If the average power of the first feeder is greater than the corresponding generating capacity (assumed to be PabltA), the initial power allocation value of the first corresponding feeder can be determined to be the corresponding generating capacity. That is, if PrefAll / 3 > PabltA, then the initial power allocation value Gridref1_A of the first corresponding feeder can be PabltA.

[0076] The difference between the total feeder power and the corresponding generating capacity of the first feeder is further divided into two equal parts to obtain the second feeder average power. That is, the second feeder average power is (PrefAll - PabltA) / 2.

[0077] Further, the average power of the second feeder network (PrefAll-PabltA) / 2 is compared with the corresponding power generation capacity (assuming it is PabltB). If the average power of the second feeder network is less than or equal to the corresponding power generation capacity, i.e. (PrefAll-PabltA) / 2≤PabltB, then the initial power allocation value of the second corresponding network and the initial power allocation value of the third corresponding network are both determined to be the average power of the second feeder network. At this time, the expression for each corresponding initial power allocation value can be shown in formula (7): Where Gridref1_A, Gridref1_B, and Gridref1_C are the corresponding initial power allocation values, PabltA is the first corresponding power generation capacity, and (PrefAll-PabltA) / 2 is the second average power of the feeder grid.

[0078] In this way, when the first phase cannot handle the power distribution, it is prioritized to allocate as much power as possible to the grid. That is, the first phase feeds power to the grid according to its corresponding generating capacity. Then, the remaining grid power is divided equally between the remaining two phases. The generating capacity of the second weakest phase is used as a benchmark for the remaining two phases. If the average power of the second phase fed to the grid does not exceed the generating capacity of the second phase, then the equal distribution strategy is adopted between the remaining two phases. This approach can overcome the limitations of the three-phase equal distribution strategy in scenarios where the generating capacities of each phase are asymmetrical, maximizing the total grid power output while ensuring that the output power of each phase is not overloaded.

[0079] Optionally or additionally, such as Figure 4 As shown, the method may also include: Step 406: In response to the fact that the average power of the second feeder is greater than the second corresponding power generation capacity, the initial power allocation value of the second corresponding power generation capacity is determined to be the second corresponding power generation capacity. Step 407: Based on the remaining feeder power and the second corresponding power generation capacity, determine the third corresponding initial power allocation value.

[0080] Furthermore, if the average power of the second feeder is greater than the second corresponding generating capacity (assumed to be PabltB), the initial power allocation value of the second corresponding feeder can be determined to be the second corresponding generating capacity. That is, if (PrefAll-PabltA) / 2>PabltB, then the initial power allocation value of the second corresponding feeder, Gridref1_B, can be PabltB.

[0081] The difference between the remaining feeder power and the second corresponding generating capacity can be used as the initial power allocation value for the third corresponding power allocation. That is, the expression for each corresponding initial power allocation value can be shown in formula (8): Where Gridref1_A, Gridref1_B, and Gridref1_C are the corresponding initial power allocation values, PabltA is the first corresponding power generation capacity, PabltB is the second corresponding power generation capacity, and PrefAll-PabltA can be the remaining feeder power.

[0082] The energy distribution method mentioned above will be illustrated with a specific example below.

[0083] Example 2: In this example, the photovoltaic power Ppv can be 20kW; the power limits of each phase PlimitA, PlimitB, and PlimitC can all be 5kW; the power of each phase at the first load port: PbackloadA can be 9kW, PbackloadB can be 5kW, and PbackloadC can be 3kW; the power of each phase at the second load port: PloadExA can be -1kW, PloadExB can be -1kW, and PloadExC can be -2kW.

[0084] The total power of each phase (i.e., the sum of the power of each phase at the first load port and the power of each phase at the second load port) is calculated as follows: PloadA is 9 + (-1) = 8 kW, PloadB is 5 + (-1) = 4 kW, and PloadC is 3 + (-2) = 1 kW; the total load power PloadAll is 8 + 4 + 1 = 13 kW. Since 0 < PloadAll < Ppv, the three-phase PCS is in inverter mode at this time, and the battery is charging. Since the battery charging limit is 6 kW, the battery power Pbat is -6 kW.

[0085] The total grid power PrefAll is calculated to be Ppv + Pbat - PloadAll = 1 kW. The corresponding generating capacities (i.e., the difference between the power limit of each phase and the total power of each phase) are: PabltA = 5 - 8 = -3 kW, PabltB = 5 - 4 = 1 kW, and PabltC = 5 - 1 = 4 kW. Therefore, the minimum generating capacity of the three phases is -3 kW.

[0086] Since the average power of the first feeder grid, PrefAll / 3 = 1 / 3 kW > -3 kW, the initial power allocation value Gridref1_A corresponding to A can be PabltA = -3 kW. Continuing to calculate the average power of the second feeder grid, (PrefAll - PabltA) / 2 = 2 kW. Since the average power of the second feeder grid, (PrefAll - PabltA) / 2 > 1 kW, the initial power allocation value Gridref1_B corresponding to B can be PabltB = 1 kW, and the initial power allocation value Gridref1_C corresponding to C is PrefAll - PabltA - PabltB = 3 kW. At this point, phase A of the three-phase PCS draws 3 kW of electricity from the grid, phase B supplies 1 kW of electricity to the grid, and phase C supplies 3 kW of electricity to the grid.

[0087] In this way, when the second phase with the weakest power generation capacity cannot withstand the secondary power sharing, it is given priority to allocate as much power to the grid as possible, so that the second phase feeds power to the grid according to its corresponding power generation capacity. Then, all the remaining power to the grid is allocated to the third phase with the strongest power generation capacity. This can cover the situation where the power generation capacity of each phase of the three-phase PCS is severely unbalanced. While maximizing the total power output of the grid, it ensures that the output power of each phase is not overloaded, thus ensuring the safe operation of the system.

[0088] In some optional examples, such as Figure 5 As shown, the method may also include: Step 501: Based on the corresponding initial power allocation values ​​and the total power of each phase, determine the total energy absorption and the corresponding absorption capacity. Step 502: Allocate the total absorbed energy based on the corresponding absorption capacity to obtain the corresponding absorption power allocation value; Step 503: Based on the corresponding initial power allocation value and the corresponding absorption power allocation value, determine the corresponding secondary power allocation value.

[0089] Understandably, for non-AC Couple scenarios, since there is no external photovoltaic inverter interfering with the power allocation value of each phase, the power can be fed to the grid according to the corresponding initial power allocation value.

[0090] However, in AC-coupled scenarios, there may be excess power remaining in one phase of the external photovoltaic inverter after supplying power to its corresponding load. This excess power will feed back into the grid, interfering with the grid feed power of the three-phase PCS. Therefore, to ensure a reasonable allocation of grid feed power in both AC-coupled and non-AC-coupled scenarios, the grid feed power can be redistributed based on the initial power allocation values. This allows the three-phase PCS to absorb or absorb the excess energy generated by the external photovoltaic inverter. The excess energy is the portion of the power fed into the grid by one phase of the external photovoltaic inverter that exceeds its initial power allocation value, thus maintaining the power balance of the entire system.

[0091] Specifically, such as Figure 6 As shown, the process of a three-phase PCS absorbing or consuming excess energy generated by an external photovoltaic inverter can include the following steps: Step 601: In response to the fact that the sum of the initial power allocation value of each corresponding phase and the total power of each phase is less than 0, the absorption energy of each corresponding phase is determined to be the absolute value of the sum of the initial power allocation value of each corresponding phase and the total power of each phase, and the absorption capacity of each corresponding phase is 0. Step 602: In response to the sum of the initial power allocation value of each corresponding phase and the total power of each phase being greater than or equal to 0, determine that the energy absorbed by each corresponding phase is 0, and the absorption capacity of each corresponding phase is the sum of the initial power allocation value of each corresponding phase and the total power of each phase. Step 603: The sum of the corresponding absorption energies is determined as the total absorption energy.

[0092] As mentioned above, the total power of each phase may be negative in an AC Couple scenario. When the total power of a certain phase is negative, it can be assumed that the output power of the external photovoltaic inverter in that phase is greater than the total power consumed by all loads in that phase. The excess output power of the external photovoltaic inverter in that phase will be fed into the grid. It is understandable that the power fed into the grid by the external photovoltaic inverter is not controlled by the three-phase PCS.

[0093] Furthermore, if the sum of the initial power allocation value of each corresponding phase and the total power of each phase is less than 0, that is, if the sum of the initial power allocation value of a certain corresponding phase and the total power of that phase is still negative, it can be considered that the power delivered to the grid by the external photovoltaic inverter of that phase exceeds the grid power originally allocated to that phase. The excess portion is the energy that needs to be absorbed by that phase. The energy that needs to be absorbed by that phase can be defined as the absorption energy of that corresponding phase.

[0094] In other words, at this point, the absolute value of the sum of the corresponding initial power allocation value and the total power of the phase can be used as the corresponding energy absorption.

[0095] For example, if the power of phase A at the first load port is 1 kW, the power of phase A at the second load port is -4 kW, and the calculated initial power allocation value for phase A is 1 kW, then the total power of phase A is 1 + (-4) = -3 kW. The sum of the initial power allocation value for phase A and the total power of phase A is 1 + (-3) = -2 kW. In this case, the absolute value of 2 kW can be taken as the energy absorbed by phase A.

[0096] Since the actual feed power of this phase has exceeded the allocated feed power, meaning that there is energy in this phase that needs to be absorbed, and this phase, as the object to be absorbed, cannot help other phases absorb energy, the absorption capacity of this phase is 0.

[0097] Conversely, if the sum of the initial power allocation value of each corresponding phase and the total power of each phase is greater than or equal to 0, it can be considered that the power fed to the grid by the external photovoltaic inverter of that phase does not exceed the original grid-feed power allocated to that phase, and it is capable of helping other phases absorb the excess energy generated by the external photovoltaic inverter. In this case, the absorption capacity of that phase is the sum of the initial power allocation value of that phase and the total power of that phase. And since there is no energy that needs to be absorbed in that phase, the absorption capacity of that phase is 0.

[0098] The sum of the corresponding absorption energies can be determined as the total absorption energy. The formula for calculating the total absorption energy is shown in formula (9): Among them, PabsorpA, PabsorpB, and PabsorpC can be the corresponding absorption energies, and PabsorpAll can be the total absorption energy.

[0099] This defines a mutually exclusive relationship between energy absorption and absorption capacity: when a phase has energy that needs to be absorbed, its ability to help other phases absorb energy is zero; conversely, when a phase can help absorb energy from other phases, the energy that phase needs to absorb is zero. This explicit quantification of the absorption gap or redundant capacity of each phase provides accurate input data for allocation, improving system reliability.

[0100] The total absorbed energy can be allocated based on the corresponding absorption capacity to obtain the corresponding absorption power allocation value.

[0101] Optionally or additionally, the total absorbed energy can be allocated according to the proportion of each corresponding absorption capacity to obtain the corresponding absorption power allocation value. Alternatively, the corresponding absorption capacities can be sorted by size, and the absorption power can be allocated to each phase in ascending order to obtain the corresponding absorption power allocation value.

[0102] The corresponding secondary power allocation value can be determined based on the corresponding initial power allocation value and the corresponding absorption power allocation value. For example, the calculation formula for the corresponding secondary power allocation value can be shown in formula (10): Wherein, Gridref1_A, Gridref1_B, and Gridref1_C are the corresponding initial power allocation values, Gridref2_A, Gridref2_B, and Gridref2_C are the corresponding absorption power allocation values, and Gridref1_A, Gridref1_B, and Gridref1_C are the corresponding secondary power allocation values.

[0103] The three-phase PCS can feed power to the grid according to the corresponding secondary power distribution values.

[0104] In this way, the problem of external photovoltaic inverters supplying more power to the grid than the initial power allocation value is solved by secondary allocation, so as to absorb the excess energy generated by external photovoltaic inverters, improve the rationality of power allocation of each phase of the three-phase PCS feeder network, ensure system power balance, and further improve system stability.

[0105] In some optional examples, such as Figure 7 As shown, the total absorbed energy is allocated based on the corresponding absorption capacity to obtain the corresponding absorption power allocation value, which may include: Step 701: Divide the total absorbed energy equally among the three phases to obtain the first average absorbed power; Step 702: In response to the first average absorption power being less than or equal to the first corresponding absorption capacity, determine the absorption power allocation value of each corresponding power as the first average absorption power; the absorption capacity of the first corresponding power is the minimum value among the absorption capacities of each corresponding power.

[0106] In this example, the corresponding absorption capacities are sorted by size. The absorption capacity of the first corresponding capacity is the minimum value among all corresponding capacities.

[0107] The total absorbed energy can be divided equally among the three phases to obtain the first average absorbed power. That is, the first average absorbed power can be PabsorpAll / 3.

[0108] Further comparing the first average absorption power PabsorpAll / 3 with the first corresponding absorption capacity (assumed to be PabsA), if the first average absorption power is less than or equal to the first corresponding absorption capacity, i.e., PabsorpAll / 3 ≤ PabsA, then the corresponding absorption power allocation value can be determined as the first average absorption power. That is, the expression for the corresponding absorption power allocation value can be shown in formula (11): Among them, Gridref2_A, Gridref2_B, and Gridref2_C can be the corresponding power absorption allocation values, and PabsorpAll / 3 can be the first average power absorption.

[0109] The energy absorption and distribution method mentioned above will be illustrated with a specific example below.

[0110] As mentioned in Example 1 above, the total power of each phase is calculated to be: 1kW for PloadA, 2kW for PloadB, and 3kW for PloadC; the corresponding initial power allocation values ​​are: 1kW for each of Gridref1_A, Gridref1_B, and Gridref1_C.

[0111] Since Gridref1_A + PloadA = 2kW > 0, it is clear that phase A has no energy to be absorbed. Therefore, the absorption energy PabsorpA corresponding to phase A is 0, and the absorption capacity PabsA corresponding to phase A is 2kW. Since Gridref1_B + PloadB = 3kW > 0, it is clear that phase B has no energy to be absorbed. Therefore, the absorption energy PabsorpB corresponding to phase B is 0, and the absorption capacity PabsB corresponding to phase B is 3kW. Since Gridref1_C + PloadC = 4kW > 0, it is clear that phase C also has no energy to be absorbed. Therefore, the absorption energy PabsorpC corresponding to phase C is 0, and the absorption capacity PabsC corresponding to phase C is 4kW. Therefore, the minimum absorption capacity among the three phases is 2kW.

[0112] The calculated PabsorpAll is PabsorpA + PabsorpB + PabsorpC = 0 kW. Since PabsorpAll / 3 = 0 < 2 kW, the corresponding power absorption allocation value is the first average power absorption, that is, Gridref2_A, Gridref2_B and Gridref2_C are all 0 kW.

[0113] The final calculated secondary power distribution values ​​are: Gridref_A = 1 - 0 = 1 kW, Gridref_B = 1 - 0 = 1 kW, Gridref_C = 1 - 0 = 1 kW. At this point, each of the three phases of the three-phase PCS supplies 1 kW of power to the grid.

[0114] In this way, the first phase with the weakest absorption capacity is used as the allocation benchmark. When the average absorption power of the first phase does not exceed the absorption capacity of the first phase, the equal distribution strategy is directly adopted to avoid overload, ensure system safety, prevent equipment damage or grid fluctuations caused by excessive absorption power, simplify calculations, improve allocation efficiency, and reduce problems such as harmonics and neutral point offset caused by three-phase imbalance, thereby improving grid stability.

[0115] Optionally or additionally, such as Figure 7 As shown, the method may also include: Step 703: In response to the first average power absorption being greater than the first corresponding absorption capacity, determine the first corresponding power absorption allocation value as the first corresponding absorption capacity; Step 704: Divide the remaining absorption energy equally between the two phases to obtain the second absorption average power; the remaining absorption energy is the difference between the total absorption energy and the absorption capacity corresponding to the first phase. Step 705: In response to the second average absorption power being less than or equal to the second corresponding absorption capacity, determine that the absorption power allocation value of the second corresponding power and the absorption power allocation value of the third corresponding power are both the second average absorption power; the absorption capacity of the second corresponding power is the smaller value among the absorption capacities of the remaining two corresponding power.

[0116] If the first average power absorbed is greater than the first corresponding absorption capacity (assumed to be PabsA), the first corresponding absorption power allocation value can be determined to be the first corresponding absorption capacity. That is, if PabsorpAll / 3 > PabsA, then the first corresponding absorption power allocation value Gridref2_A can be PabsA.

[0117] Furthermore, the difference between the total absorbed energy and the corresponding absorbed capacity in the first phase can be divided equally between the two phases to obtain the second average absorbed power. That is, the second average absorbed power can be (PabsorpAll-PabsA) / 2.

[0118] The second average absorption power (PabsorpAll-PabsA) / 2 can be compared with the second corresponding absorption capacity (assumed to be PabsB). If the second average absorption power is less than or equal to the second corresponding absorption capacity, i.e., (PabsorpAll-PabsA) / 2≤PabsB, then it can be determined that the second corresponding absorption power allocation value and the third corresponding absorption power allocation value are both the second average absorption power. That is, the expression for each corresponding absorption power allocation value can be shown in formula (12): Where Gridref2_A, Gridref2_B, and Gridref2_C are the corresponding absorption power allocation values, PabsA is the first corresponding absorption capacity, and (PabsorpAll-PabsA) / 2 is the second absorption average power.

[0119] The energy distribution method mentioned above will be illustrated with a specific example below.

[0120] Example 3: In this example, the photovoltaic power Ppv can be 13kW; the power limits of each phase PlimitA, PlimitB, and PlimitC can all be 5kW; the power of each phase at the first load port: PbackloadA can be 5kW, PbackloadB can be 3kW, and PbackloadC can be 0kW; the power of each phase at the second load port: PloadExA can be -1kW, PloadExB can be -1kW, and PloadExC can be -2kW.

[0121] The total power of each phase (i.e., the sum of the power of each phase at the first load port and the power of each phase at the second load port) is calculated as follows: PloadA is 5 + (-1) = 4 kW, PloadB is 3 + (-1) = 2 kW, and PloadC is 0 + (-2) = -2 kW; the total load power PloadAll is 4 + 2 + (-2) = 4 kW. Since 0 < PloadAll < Ppv, the three-phase PCS is in inverter mode at this time, and the battery is charging. Since the battery charging limit is 6 kW, the battery power Pbat is -6 kW.

[0122] The total grid power PrefAll is calculated to be Ppv + Pbat - PloadAll = 3kW; the corresponding generating capacities (i.e., the difference between the power limit of each phase and the total power of each phase) are: PabltA = 5 - 4 = 1kW, PabltB = 5 - 2 = 3kW, and PabltC = 5 - (-2) = 7kW. Therefore, the minimum generating capacity of the three phases is 1kW.

[0123] Since the average power of the first feeder grid PrefAll / 3 = 1kW, the corresponding initial power allocation values ​​are the average power of the first feeder grid, that is, Gridref1_A, Gridref1_B and Gridref1_C are all 1kW.

[0124] Since Gridref1_A + PloadA = 5kW > 0, it is clear that there is no energy to be absorbed in phase A. Therefore, the energy absorbed by phase A, PabsorpA, is 0, and the absorption capacity PabsA is 5kW. Since Gridref1_B + PloadB = 3kW > 0, it is clear that there is no energy to be absorbed in phase B. Therefore, the energy absorbed by phase B, PabsorpB, is 0, and the absorption capacity PabsB is 3kW. Since Gridref1_C + PloadC = -1kW < 0, it is clear that the external photovoltaic inverter in phase C will supply an additional 1kW of power to the grid. This means that there is energy to be absorbed in phase C. Therefore, the energy absorbed by phase C, PabsorpC, is 1kW, and the absorption capacity PabsC is 0. Thus, the minimum absorption capacity among the three phases is 0kW.

[0125] The calculation yields PabsorpAll = PabsorpA + PabsorpB + PabsorpC = 1kW. Since PabsorpAll / 3 = 1 / 3kW > 0kW, the power absorption capacity corresponding to C is the absorption capacity corresponding to C, i.e., Gridref2_C = PabsC = 0kW.

[0126] Continue calculating the second average power absorption (PabsorpAll-PabsC) / 2 = 0.5 kW. Since the second average power absorption (PabsorpAll-PabsC) / 2 < 3 kW, the remaining two corresponding power absorption values ​​are assigned to the second average power absorption, that is, Gridref2_A and Gridref2_B are both 0.5 kW.

[0127] The final calculated secondary power distribution values ​​are: Gridref_A = 1 - 0.5 = 0.5 kW, Gridref_B = 1 - 0.5 = 0.5 kW, Gridref_C = 1 + 0 = 1 kW. At this point, phase A of the three-phase PCS supplies 0.5 kW of power to the grid, phase B supplies 0.5 kW of power to the grid, and phase C supplies 1 kW of power to the grid.

[0128] The grid port energy for phase A is the secondary power allocation value corresponding to phase A, which is 0.5 kW; the grid port energy for phase B is the secondary power allocation value corresponding to phase B, which is 0.5 kW; the grid port energy for phase C is the secondary power allocation value corresponding to phase C, plus the 1 kW of electricity supplied to the grid by the external photovoltaic inverter in phase C, totaling 2 kW. It can be understood that the grid port energy indicates the total electrical energy received by the grid from the three-phase PCS and / or the external photovoltaic inverter.

[0129] In this way, when the first phase cannot withstand the equally distributed power, it is prioritized to distribute as much power as possible. That is, the first phase is allocated its corresponding power distribution value according to its corresponding power absorption capacity. Then, the remaining power is evenly distributed between the remaining two phases. The power absorption capacity of the second phase, which has the weakest absorption capacity, is used as a benchmark for verification. If the average power absorption capacity of the remaining two phases does not exceed the absorption capacity of the second phase, then an even distribution strategy is adopted between the remaining two phases. This approach can overcome the limitations of the three-phase even distribution strategy in scenarios where the power absorption capacity of each phase is asymmetrical, ensuring that the power absorption capacity allocated to each phase is not overloaded, thereby achieving system power balance.

[0130] Optionally or additionally, such as Figure 7 As shown, the method may also include: Step 706: In response to the second average absorption power being greater than the second corresponding absorption capacity, determine the second corresponding absorption power allocation value as the second corresponding absorption capacity; Step 707: Based on the remaining absorption energy and the second corresponding absorption capacity, determine the third corresponding absorption power allocation value.

[0131] If the second average power absorption is greater than the second corresponding absorption capacity (assumed to be PabsB), the second corresponding power absorption allocation value can be determined to be the second corresponding absorption capacity. That is, if (PabsorpAll-PabsA) / 2>PabsB, then the second corresponding power absorption allocation value Gridref2_B can be PabsB.

[0132] The difference between the remaining absorbed energy and the second corresponding absorbed capacity can be used to determine the third corresponding absorbed power allocation value. That is, the expression for each corresponding absorbed power allocation value can be shown in formula (13): Among them, Gridref2_A, Gridref2_B, and Gridref2_C are the corresponding absorption power allocation values, PabsA is the first corresponding absorption capacity, PabsB is the second corresponding absorption capacity, and PabsorpAll-PabsA is the remaining absorption energy.

[0133] The energy distribution method mentioned above will be illustrated with a specific example below.

[0134] Example 4: In this example, the photovoltaic power Ppv can be 8kW; the power limits of each phase PlimitA, PlimitB, and PlimitC can all be 5kW; the power of each phase at the first load port: PbackloadA can be 6kW, PbackloadB can be 1kW, and PbackloadC can be 0kW; the power of each phase at the second load port: PloadExA can be -1kW, PloadExB can be 0kW, and PloadExC can be -5kW.

[0135] The total power of each phase (i.e., the sum of the power of each phase at the first load port and the power of each phase at the second load port) is calculated as follows: PloadA is 6 + (-1) = 5 kW, PloadB is 1 + 0 = 1 kW, PloadC is 0 + (-5) = -5 kW; the total load power PloadAll is 5 + 1 + (-5) = 1 kW. Since 0 < PloadAll < Ppv, the three-phase PCS is in inverter mode at this time, and the battery is charging. Since the battery charging limit is 6 kW, the battery power Pbat is -6 kW.

[0136] The total grid power PrefAll is calculated to be Ppv + Pbat - PloadAll = 1 kW; the corresponding generating capacities (i.e., the difference between the power limit of each phase and the total power of each phase) are: PabltA = 5 - 5 = 0 kW, PabltB = 5 - 1 = 4 kW, and PabltC = 5 - (-5) = 10 kW. Therefore, the minimum generating capacity of the three phases is 0 kW.

[0137] Since the average power of the first feeder grid PrefAll / 3 > 0 kW, the initial power allocation value corresponding to A is the power generation capacity corresponding to A, that is, Gridref1_A = PabltA = 0 kW.

[0138] Continue calculating the average power of the second feeder grid: (PrefAll - PabltA) / 2 = 0.5 kW. Since the average power of the second feeder grid (PrefAll - PabltA) / 2 < 4 kW, the corresponding initial power allocation values ​​for the remaining two grids are the average power of the second feeder grid, i.e., Gridref1_B and Gridref1_C are both 0.5 kW.

[0139] Since Gridref1_A + PloadA = 5kW > 0, it is clear that there is no energy to be absorbed in phase A. Therefore, the energy absorbed by phase A, PabsorpA, is 0, and the absorption capacity PabsA is 5kW. Since Gridref1_B + PloadB = 1.5kW > 0, it is clear that there is no energy to be absorbed in phase B. Therefore, the energy absorbed by phase B, PabsorpB, is 0, and the absorption capacity PabsB is 1.5kW. Since Gridref1_C + PloadC = -4.5kW < 0, it is clear that the external photovoltaic inverter in phase C will supply an additional 4.5kW of power to the grid. This means that there is energy to be absorbed in phase C. Therefore, the energy absorbed by phase C, PabsorpC, is 4.5kW, and the absorption capacity PabsC is 0. Thus, the minimum absorption capacity among the three phases is 0kW.

[0140] The calculation yields PabsorpAll = PabsorpA + PabsorpB + PabsorpC = 4.5 kW. Since PabsorpAll / 3 = 1.5 kW > 0 kW, the power absorption capacity corresponding to C is the absorption capacity corresponding to C, i.e., Gridref2_C = PabsC = 0 kW.

[0141] Continue calculating the second average power absorption (PabsorpAll-PabsC) / 2 = 2.25 kW. Since the second average power absorption (PabsorpAll-PabsC) / 2 > 1.5 kW, the power absorption allocation value Gridref2_B corresponding to B can be PabsB = 1.5 kW, and the power absorption allocation value Gridref2_A corresponding to A can be PabsorpAll-PabsC-PabsB = 3 kW.

[0142] The final calculated secondary power distribution values ​​are: Gridref_A = 0 - 3 = -3 kW, Gridref_B = 0.5 - 1.5 = -1 kW, Gridref_C = 0.5 - 0 = 0.5 kW. At this point, phase A of the three-phase PCS draws 3 kW of power from the grid, phase B draws 1 kW of power from the grid, and phase C supplies 0.5 kW of power back to the grid.

[0143] The grid port energy for phase A is the secondary power allocation value corresponding to phase A, which is -3kW; the grid port energy for phase B is the secondary power allocation value corresponding to phase B, which is -1kW; and the grid port energy for phase C is the secondary power allocation value corresponding to phase C, plus the 4.5kW of electricity supplied to the grid by the external photovoltaic inverter in phase C, totaling 5kW. It can be understood that the grid port energy indicates the total electrical energy received by the grid from the three-phase PCS and / or the external photovoltaic inverter.

[0144] In this way, when the second phase with the weakest absorption capacity also cannot withstand the secondary equal distribution of absorption power, it is given priority to distribute as much absorption power as possible. That is, the second phase absorbs the excess energy according to its corresponding absorption capacity, and then all the remaining absorption energy is distributed to the third phase with the strongest absorption capacity. This can cover the situation where the absorption capacity of each phase of the three-phase PCS is seriously unbalanced, ensuring that the absorption power distributed to each phase is not overloaded, so as to achieve system power balance and thus ensure that the system can operate safely.

[0145] Optionally or additionally, such as Figure 8 As shown, the method may also include: Step 801: In response to the total load power being less than 0, determine the rectified power based on the photovoltaic power and the battery power; Step 802: Allocate the rectified power based on the corresponding rectified power limits to obtain the corresponding rectified power allocation values.

[0146] As mentioned above, when the total load power is less than 0, the three-phase PCS can be considered to be in rectification mode. In this case, the rectified power can be determined based on the photovoltaic power and battery power. The formula for calculating the rectified power is shown in formula (14): Where PrefAll_pfc is the rectified power, Ppv is the photovoltaic power, and Pbat is the battery power.

[0147] The rectified power can be allocated based on the corresponding rectified power limits to obtain the corresponding rectified power allocation values. The corresponding rectified power limits can be calculated based on the voltage signals and rectified limit currents of each phase, and the rectified limit currents can be directly obtained from the configuration information of the three-phase PCS.

[0148] Optionally or additionally, the rectified power can be allocated according to the proportion of each corresponding rectified power limit to obtain each corresponding rectified power allocation value; alternatively, the corresponding rectified power limits can be sorted by size, and the rectified power can be allocated to each phase in ascending order to obtain each corresponding rectified power allocation value.

[0149] In this way, the operating mode of the three-phase PCS is switched based on the positive or negative value of the total load power. When the total load power is negative, the rectification mode is activated to charge the battery. The rectification power is distributed in combination with the rectification power limit of each phase to avoid single-phase overload and improve system stability.

[0150] In some optional examples, such as Figure 9 As shown, the rectified power is allocated based on the corresponding rectified power limits to obtain the corresponding rectified power allocation values, which may include: Step 901: Divide the rectified power equally among the three phases to obtain the first average rectified power; Step 902: In response to the first average rectified power being less than or equal to the first corresponding rectified power limit, determine the corresponding rectified power allocation value as the first average rectified power; the first corresponding rectified power limit is the minimum value among the corresponding rectified power limits.

[0151] The corresponding rectified power limits are sorted by size, with the first corresponding rectified power limit being the minimum value among all corresponding rectified power limits.

[0152] The rectified power can be evenly distributed across the three phases to obtain the first average rectified power. That is, the first average rectified power can be PrefAll_pfc / 3.

[0153] Compare the first average rectified power PrefAll_pfc / 3 with the first corresponding rectified power limit (assuming it is PrectA). If the first average rectified power is less than or equal to the first corresponding rectified power limit, i.e., PrefAll_pfc / 3 ≤ PrectA, then the corresponding rectified power allocation value can be determined as the first average rectified power. The expression for each corresponding rectified power allocation value can be shown in formula (15): Where Gridref_pfc_A, Gridref_pfc_B, and Gridref_pfc_C are the corresponding rectified power allocation values, and PrefAll_pfc / 3 is the first rectified average power.

[0154] In this way, the first phase with the weakest rectified power limit is used as the allocation benchmark. When the average rectified power of the three phases does not exceed the rectified power limit of that phase, the equal-sharing strategy is directly adopted. This avoids the rectified power of each phase from exceeding its corresponding rectified power limit, simplifies the calculation, improves the allocation efficiency, and reduces problems such as harmonics and neutral point offset caused by three-phase imbalance.

[0155] Optionally or additionally, such as Figure 9 As shown, the method may also include: Step 903: In response to the first average rectified power being greater than the first corresponding rectified power limit, determine the first corresponding rectified power allocation value as the first corresponding rectified power limit; Step 904: Divide the remaining rectified power equally between the two phases to obtain the second average rectified power; the remaining rectified power is the difference between the rectified power and the first corresponding rectified power limit; Step 905: In response to the second rectified average power being less than or equal to the second corresponding rectified power limit, determine that the second corresponding rectified power allocation value and the third corresponding rectified power allocation value are both the second rectified average power; the second corresponding rectified power limit is the smaller of the remaining two corresponding rectified power limits.

[0156] Specifically, the second corresponding rectified power limit is the smaller of the remaining two corresponding rectified power limits.

[0157] If the first average rectified power is greater than the first corresponding rectified power limit (let's assume it's PrectA), then the first corresponding rectified power allocation value can be determined to be the first corresponding rectified power limit. That is, if PrefAll_pfc / 3 > PrectA, then the first corresponding rectified power allocation value Gridref_pfc_A can be PrectA.

[0158] Next, the difference between the rectified power and the first corresponding rectified power limit is divided equally to obtain the second average rectified power. That is, the second average rectified power can be (PrefAll_pfc-PrectA) / 2.

[0159] Further comparing the second average rectified power (PrefAll_pfc-PrectA) / 2 with the second corresponding rectified power limit (assuming it is PrectB), if the second average rectified power is less than or equal to the second corresponding rectified power limit, i.e. (PrefAll_pfc-PrectA) / 2≤PrectB, then it can be determined that the second corresponding rectified power allocation value and the third corresponding rectified power allocation value are both the second average rectified power. That is, the expression for each corresponding rectified power allocation value can be shown in formula (16): Among them, Gridref_pfc_A, Gridref_pfc_B, and Gridref_pfc_C can be the corresponding rectified power allocation values, PrectA can be the first corresponding rectified power limit, and (PrefAll_pfc-PrectA) / 2 can be the second rectified average power.

[0160] In this way, when the first phase cannot bear the rectified power evenly, it is given priority to allocate as much rectified power as possible. That is, the first phase allocates its corresponding rectified power according to its corresponding rectified power limit. Then, the remaining rectified power is evenly divided between the remaining two phases. The remaining two phases are then checked again with the rectified power limit of the second phase with the weakest rectified power limit as the benchmark. This can overcome the limitations of the even distribution strategy and is compatible with the actual situation of inconsistent parameters of three-phase rectifier equipment.

[0161] Optionally or additionally, such as Figure 9 As shown, the method may also include: Step 906: In response to the second rectified average power being greater than the second corresponding rectified power limit, determine the second corresponding rectified power allocation value as the second corresponding rectified power limit; Step 907: Based on the remaining rectified power and the second corresponding rectified power limit, determine the third corresponding rectified power allocation value.

[0162] If the second average rectified power is greater than the second corresponding rectified power limit (assuming it is PrectB), then the second corresponding rectified power allocation value can be determined to be the second corresponding rectified power limit. That is, if (PrefAll_pfc-PrectA) / 2>PrectB, then the second corresponding rectified power allocation value Gridref_pfc_B can be PrectB.

[0163] The difference between the remaining rectified power and the second corresponding rectified power limit can be used as the third corresponding rectified power allocation value. That is, the expression for each corresponding rectified power allocation value can be shown in formula (17): Where Gridref_pfc_A, Gridref_pfc_B, and Gridref_pfc_C are the corresponding rectified power allocation values, PrectA is the first corresponding rectified power limit, PrectB is the second corresponding rectified power limit, and PrefAll_pfc-PrectA is the remaining rectified power.

[0164] In this way, when the second phase of the weakest rectifier power limit cannot withstand the secondary equalization of rectifier power, it is given priority to distribute as much rectifier power as possible, and then all the remaining rectifier power is distributed to the third phase of the strongest rectifier power limit. Even when the two-phase rectification capability is insufficient, the system power balance is still guaranteed and the system can operate safely.

[0165] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A three-phase power conversion system, characterized by, include: A power conversion module, wherein the first end of the power conversion module is used to connect photovoltaic and battery, and the second end of the power conversion module is used to connect to the power grid through a three-phase AC bus; A first load port and a second load port are connected sequentially to the three-phase AC bus, and the three-phase AC bus between the second load port and the power grid is used to connect to the electricity meter. A first current sensor and a second current sensor are provided. The first current sensor is located at the AC output terminal of the power conversion module, and the second current sensor is located at the first load port. The controller is connected to the power conversion module, the meter, the first current sensor, and the second current sensor.

2. The three-phase power conversion system of claim 1, wherein, A first relay is provided between the power conversion module and the first load port, and a second relay is provided between the first load port and the second load port.

3. The three-phase power conversion system according to claim 2, characterized in that, A third relay is also provided between the first load port and the second load port.

4. The three-phase power conversion system according to any one of claims 1 to 3, characterized in that, The power conversion module includes: A DC / AC converter, wherein the first terminal of the DC / AC converter is connected to the power grid via a three-phase AC bus; A first DC / DC converter, wherein a first terminal of the first DC / DC converter is connected to a second terminal of the DC / AC converter, and the second terminal of the first DC / DC converter is used to connect to the photovoltaic cell; A second DC / DC converter, wherein a first terminal of the second DC / DC converter is connected to a second terminal of the DC / AC converter, and the second terminal of the second DC / DC converter is used to connect to the battery.

5. An energy storage device, characterized in that, include: The three-phase power conversion system as described in any one of claims 1 to 4; A battery, which is connected to the first end of the power conversion module.

6. An energy storage system, characterized in that, include: The energy storage device as described in claim 5; An electricity meter is connected to the three-phase AC bus between the second load port of the energy storage device and the power grid.

7. The energy storage system according to claim 6, characterized in that, The energy storage system includes an external photovoltaic inverter; The external photovoltaic inverter is connected to the three-phase AC bus.

8. An energy distribution method, applied to the energy storage system as described in claim 6 or 7, characterized in that, The method includes: The total power of each phase is determined based on the power of each phase at the first load port and the power of each phase at the second load port. Based on the total power of each phase, determine the total load power; In response to the total load power being greater than 0, the total grid feed power is determined based on the total load power, photovoltaic power, and battery power. Based on the total power of each phase and the power limit of each phase, the corresponding power generation capacity is determined; The total power of the feeder grid is allocated based on the corresponding power generation capacity to obtain the corresponding initial power allocation value.

9. The method according to claim 8, characterized in that, The allocation of the total grid power based on the corresponding power generation capacity to obtain corresponding initial power allocation values ​​includes: The total power of the feeder network is divided equally among the three phases to obtain the average power of the first feeder network; In response to the first feed grid average power being less than or equal to the first corresponding power generation capacity, the initial power allocation value of each corresponding is determined to be the first feed grid average power, and the first corresponding power generation capacity is the minimum value among the corresponding power generation capacities. or, In response to the first feeder average power being greater than the first corresponding power generation capacity, the first corresponding initial power allocation value is determined to be the first corresponding power generation capacity. The remaining feeder power is divided equally between the two phases to obtain the second average feeder power, whereby the remaining feeder power is the difference between the total feeder power and the corresponding generation capacity of the first feeder power. In response to the fact that the average power of the second feed grid is less than or equal to the power generation capacity of the second corresponding grid, the initial power allocation value of the second corresponding grid and the initial power allocation value of the third corresponding grid are both determined to be the average power of the second feed grid, and the power generation capacity of the second corresponding grid is the smaller value of the power generation capacity of the remaining two corresponding grids. or, In response to the first feeder average power being greater than the first corresponding power generation capacity, the first corresponding initial power allocation value is determined to be the first corresponding power generation capacity. The remaining feeder power is divided equally between the two phases to obtain the second average feeder power, whereby the remaining feeder power is the difference between the total feeder power and the corresponding generation capacity of the first feeder power. In response to the fact that the average power of the second feeder is greater than the corresponding generation capacity, the initial power allocation value of the second corresponding feeder is determined to be the corresponding generation capacity. Based on the remaining feeder power and the second corresponding power generation capacity, the third corresponding initial power allocation value is determined.

10. The method according to claim 8 or 9, characterized in that, The method further includes: Based on the corresponding initial power allocation values ​​and the total power of each phase, the total energy absorption and the corresponding absorption capacity are determined. The total absorbed energy is allocated based on the corresponding absorption capacity to obtain the corresponding absorption power allocation value; Based on the corresponding initial power allocation values ​​and the corresponding absorption power allocation values, the corresponding secondary power allocation values ​​are determined.

11. The method according to claim 10, characterized in that, The allocation of the total absorbed energy based on the corresponding absorption capacity to obtain corresponding absorption power allocation values ​​includes: The total absorbed energy is divided equally among the three phases to obtain the first average absorbed power; In response to the first average absorption power being less than or equal to the first corresponding absorption capacity, the absorption power allocation value of each corresponding power is determined to be the first average absorption power, and the first corresponding absorption capacity is the minimum value among the corresponding absorption capacities. or, In response to the first average power absorption being greater than the first corresponding absorption capacity, the first corresponding power absorption allocation value is determined to be the first corresponding absorption capacity. The remaining absorbed energy is divided equally between the two phases to obtain the second average absorbed power. The remaining absorbed energy is the difference between the total absorbed energy and the corresponding absorbed capacity of the first phase. In response to the second average absorption power being less than or equal to the second corresponding absorption capacity, it is determined that the second corresponding absorption power allocation value and the third corresponding absorption power allocation value are both the second average absorption power, and the second corresponding absorption capacity is the smaller value among the remaining two corresponding absorption capacities. or, In response to the first average power absorption being greater than the first corresponding absorption capacity, the first corresponding power absorption allocation value is determined to be the first corresponding absorption capacity. The remaining absorbed energy is divided equally between the two phases to obtain the second average absorbed power. The remaining absorbed energy is the difference between the total absorbed energy and the corresponding absorbed capacity of the first phase. In response to the second average power absorption being greater than the second corresponding absorption capacity, the second corresponding power absorption allocation value is determined to be the second corresponding absorption capacity. Based on the remaining absorption energy and the second corresponding absorption capacity, the third corresponding absorption power allocation value is determined.

12. The method according to claim 10 or 11, characterized in that, The determination of the total absorption energy and the corresponding absorption capacity based on the corresponding initial power allocation values ​​and the total power of each phase includes: In response to the fact that the sum of the corresponding initial power allocation value and the total power of each phase is less than 0, the absorption energy of each corresponding phase is determined to be the absolute value of the sum of the corresponding initial power allocation value and the total power of each phase, and the absorption capacity of each corresponding phase is 0. In response to the sum of the corresponding initial power allocation value and the total power of each phase being greater than or equal to 0, the energy absorption of each corresponding phase is determined to be 0, and the absorption capacity of each corresponding phase is the sum of the corresponding initial power allocation value and the total power of each phase. The sum of the corresponding absorption energies is determined as the total absorption energy.

13. The method according to any one of claims 8 to 12, characterized in that, The method further includes: In response to the total load power being less than 0, the rectified power is determined based on the photovoltaic power and the battery power; The rectified power is allocated based on the corresponding rectified power limits to obtain the corresponding rectified power allocation values.

14. The method according to claim 13, characterized in that, The allocation of rectified power based on corresponding rectified power limits to obtain corresponding rectified power allocation values ​​includes: The rectified power is divided equally among the three phases to obtain the first average rectified power; When the first average rectified power is less than or equal to the first corresponding rectified power limit, the corresponding rectified power allocation value is determined to be the first average rectified power, and the first corresponding rectified power limit is the minimum value among the corresponding rectified power limits. or, In response to the first average rectified power being greater than the first corresponding rectified power limit, the first corresponding rectified power allocation value is determined to be the first corresponding rectified power limit. The remaining rectified power is divided equally between the two phases to obtain a second average rectified power, wherein the remaining rectified power is the difference between the rectified power and the corresponding first rectified power limit. In response to the second rectified average power being less than or equal to the second corresponding rectified power limit, it is determined that both the second corresponding rectified power allocation value and the third corresponding rectified power allocation value are the second rectified average power, and the second corresponding rectified power limit is the smaller value among the remaining two corresponding rectified power limits; or, In response to the first average rectified power being greater than the first corresponding rectified power limit, the first corresponding rectified power allocation value is determined to be the first corresponding rectified power limit. The remaining rectified power is divided equally between the two phases to obtain a second average rectified power, wherein the remaining rectified power is the difference between the rectified power and the corresponding first rectified power limit. In response to the second average rectified power being greater than the second corresponding rectified power limit, the second corresponding rectified power allocation value is determined to be the second corresponding rectified power limit. Based on the remaining rectified power and the second corresponding rectified power limit, the third corresponding rectified power allocation value is determined.

15. The method according to any one of claims 8 to 14, characterized in that, Before determining the total power of each phase based on the power of each phase at the first load port and the power of each phase at the second load port, the method further includes: Acquire the first electrical signal corresponding to each of the first current sensors, the second electrical signal corresponding to each of the second current sensors, and the corresponding power of each of the meters; Based on the corresponding second electrical signals in the second current sensor, the power of each phase of the first load port is determined; Based on the corresponding first electrical signals in the first current sensor, the power of the meter, and the phase power of the first load port, the phase power of the second load port is determined. Wherein, the phase power of the second load port includes the power of the load connected to the second load port, or the phase power of the second load port includes the output power of the external photovoltaic inverter and the power of the load connected to the second load port.

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