Photovoltaic-storage-charging system and control method and control apparatus therefor

Abstract

The present invention provides a photovoltaic-storage-charging system and a control method and control apparatus therefor. The method comprises: acquiring the SOC of an energy storage battery of each energy storage cabinet in a system and output power of a PCS; acquiring the maximum SOC deviation on the basis of the maximum SOC value and the minimum SOC value, and determining whether the maximum SOC deviation exceeds a power level adjustment threshold; if yes, controlling the PCS to execute an SOC balancing strategy; if not, acquiring the maximum power deviation on the basis of the maximum power value and the minimum power value; determining whether the maximum power deviation exceeds a power adjustment threshold; and if yes, controlling the PCS to execute a power balancing strategy. In the present invention, SOC adjustment is used as an outer loop and power adjustment is used as an inner loop to perform SOC balancing on an energy storage battery of a photovoltaic-storage-charging system or power balancing, so as to solve the problem of an increasing SOC deviation that may be caused by long-term operation of a pure off-grid system. In addition, no additional electrical wiring and construction are required for the implementation of balancing adjustment, and the balancing adjustment is easy to implement and apply in existing photovoltaic-storage-charging systems.

Description

Photovoltaic energy storage and charging system and its control method and control device Technical Field

[0001] This invention relates to the field of new energy technology, specifically to a control method, a control device, and a photovoltaic-storage-charging system. Background Technology

[0002] Currently, for photovoltaic-storage-charging systems, a single PCS (Power Conversion System, energy storage inverter) operates in VF (Voltage / Frequency) mode when off-grid, while multiple PCSs operate in parallel off-grid using a non-communication drooping solution.

[0003] When PCS is operated in parallel off-grid, the power allocated to each PCS is significantly affected by the line impedance. Moreover, different internal control parameters need to be matched under different load conditions to achieve a good power sharing effect. Even if a good power sharing effect can be achieved, the State of Charge (SOC) between energy storage systems will gradually increase during long-term off-grid applications.

[0004] Therefore, ensuring SOC balance in the long-term operation of off-grid parallel systems has become a key issue restricting the reliability and operational profitability of photovoltaic-storage-charging systems. Technical issues

[0005] To solve the above-mentioned technical problems, the first objective of this invention is to propose a control method for an optical energy storage and charging system.

[0006] The second objective of this invention is to provide a control device for a photovoltaic energy storage and charging system.

[0007] The third objective of this invention is to provide an optical energy storage and charging system. Technical solutions

[0008] The technical solution adopted in this invention is as follows:

[0009] An embodiment of the first aspect of the present invention provides a control method for an optical energy storage and charging system.

[0010] Multiple energy storage cabinets, each including a power storage unit (PCS) and energy storage batteries, wherein when the PCS is in an off-grid state, the method includes the following steps: obtaining the state of charge (SOC) of the energy storage battery and the output power of the PCS in each energy storage cabinet of the photovoltaic-energy storage-charging system; obtaining the maximum SOC deviation based on the maximum and minimum SOC values, and determining whether the maximum SOC deviation exceeds a power regulation threshold; if the maximum SOC deviation exceeds the power regulation threshold, controlling the PCS to execute an SOC balancing strategy; if the maximum SOC deviation does not exceed the power regulation threshold, further obtaining the maximum power deviation based on the maximum and minimum output power values; determining whether the maximum power deviation exceeds a power regulation threshold; if the maximum power deviation exceeds the power regulation threshold, controlling the PCS to execute a power balancing strategy.

[0011] The control method for the photovoltaic energy storage and charging system proposed above in this invention may also have the following additional technical features:

[0012] According to an embodiment of the present invention, the power balancing strategy includes the following steps: obtaining the PCS with the highest power and the PCS with the lowest power; controlling the PCS with the highest power to reduce its output power by adjusting the off-grid control parameters; and controlling the PCS with the lowest power to increase its output power by adjusting the off-grid control parameters.

[0013] According to an embodiment of the present invention, the SOC equalization strategy includes the following steps: calculating the total load power of the photovoltaic-storage-charging system based on the output power of all PCS; determining the charging and discharging direction of the load based on the total load power, wherein the total load power is the sum of the photovoltaic output power and the power consumed by the electrical load; calculating the maximum allowable power deviation ΔPmax based on the maximum SOC deviation; and adjusting the power of the PCS of the largest SOC energy storage cabinet and the PCS of the smallest SOC energy storage cabinet based on the charging and discharging direction of the load and the maximum allowable power deviation ΔPmax.

[0014] According to one embodiment of the present invention, power adjustment is performed on the PCS of the largest SOC energy storage cabinet and the PCS of the smallest SOC energy storage cabinet based on the charging and discharging direction of the load and the maximum allowable power deviation ΔPmax. Specifically, this includes: if it is determined that the PCS is discharging to the load, determining whether the discharge power of the PCS of the largest SOC energy storage cabinet exceeds a discharge power threshold; if it does not exceed the discharge power threshold, further determining whether the power deviation between the PCS of the largest SOC energy storage cabinet and the PCS of the smallest SOC energy storage cabinet exceeds the maximum allowable power deviation ΔPmax; if it does not exceed the maximum allowable power deviation ΔPmax, reducing the virtual impedance of the PCS of the largest SOC energy storage cabinet and performing virtual impedance limiting. The virtual impedance of the PCS in the minimum SOC energy storage cabinet is increased and virtual impedance is limited. If it is determined that the PCS is charging the load, it is determined whether the power of the PCS in the minimum SOC energy storage cabinet exceeds the charging power threshold. If the power of the PCS in the minimum SOC energy storage cabinet does not exceed the charging power threshold, it is further determined whether the power deviation between the PCS in the maximum SOC energy storage cabinet and the PCS in the minimum SOC energy storage cabinet exceeds the maximum allowable power deviation ΔPmax. If it does not exceed the maximum allowable power deviation ΔPmax, the virtual impedance of the PCS in the maximum SOC energy storage cabinet is increased and virtual impedance is limited, and the virtual impedance of the PCS in the minimum SOC energy storage cabinet is decreased and virtual impedance is limited.

[0015] A second aspect of the present invention provides a control device for a photovoltaic-storage-charging system. The photovoltaic-storage system includes multiple energy storage cabinets connected in parallel on the same AC bus. Each energy storage cabinet includes a power storage unit (PCS) and an energy storage battery. The control device includes: a first acquisition module, configured to acquire the state of charge (SOC) of the energy storage battery and the output power of the PCS in each energy storage cabinet of the photovoltaic-storage-charging system when the PCS is in an off-grid state; a first judgment module, configured to acquire a maximum SOC deviation based on the maximum and minimum SOC values, and determine whether the maximum SOC deviation exceeds a power regulation threshold; a first execution module, configured to control the PCS to execute a SOC balancing strategy when the maximum SOC deviation exceeds the power regulation threshold; a second acquisition module, configured to further acquire a maximum power deviation based on the maximum and minimum output power values ​​when the maximum SOC deviation does not exceed the power regulation threshold; a second judgment module, configured to determine whether the maximum power deviation exceeds a power regulation threshold; and a second execution module, configured to control the PCS to execute a power balancing strategy when the maximum power deviation exceeds the power regulation threshold.

[0016] The control device for the photovoltaic energy storage and charging system described above in this invention also has the following additional technical features:

[0017] According to one embodiment of the present invention, the second execution module performs the power balancing strategy by employing the following steps: obtaining the PCS with the highest power and the PCS with the lowest power; controlling the PCS with the highest power to reduce its output power by adjusting the off-grid control parameters; and controlling the PCS with the lowest power to increase its output power by adjusting the off-grid control parameters.

[0018] According to an embodiment of the present invention, the first execution module performs the SOC balancing strategy by employing the following steps: calculating the total load power of the photovoltaic-storage-charging system based on the output power of all PCS; determining the charging and discharging direction of the load based on the total load power, wherein the total load power is the sum of the photovoltaic output power and the power consumed by the electrical load; calculating the maximum allowable power deviation ΔPmax based on the maximum SOC deviation; and adjusting the power of the PCS of the largest SOC energy storage cabinet and the PCS of the smallest SOC energy storage cabinet based on the charging and discharging direction of the load and the maximum allowable power deviation ΔPmax.

[0019] According to an embodiment of the present invention, the first execution module is further configured to: if it is determined that the PCS discharges to the load, determine whether the discharge power of the PCS of the largest SOC energy storage cabinet exceeds a discharge power threshold; if it does not exceed the discharge power threshold, further determine whether the power deviation between the PCS of the largest SOC energy storage cabinet and the PCS of the smallest SOC energy storage cabinet exceeds the maximum allowable power deviation ΔPmax; if it does not exceed the maximum allowable power deviation ΔPmax, reduce the virtual impedance of the PCS of the largest SOC energy storage cabinet and perform virtual impedance limiting, and increase the virtual impedance of the PCS of the smallest SOC energy storage cabinet and perform virtual impedance limiting. Virtual impedance limiting is applied; if it is determined that the PCS is charging the load, it is determined whether the power of the PCS of the smallest SOC energy storage cabinet exceeds the charging power threshold. If the power of the PCS of the smallest SOC energy storage cabinet does not exceed the charging power threshold, it is further determined whether the power deviation between the PCS of the largest SOC energy storage cabinet and the PCS of the smallest SOC energy storage cabinet exceeds the maximum allowable power deviation ΔPmax. If it does not exceed the maximum allowable power deviation ΔPmax, the virtual impedance of the PCS of the largest SOC energy storage cabinet is increased and virtual impedance limiting is applied, and the virtual impedance of the PCS of the smallest SOC energy storage cabinet is decreased and virtual impedance limiting is applied.

[0020] A third aspect of the present invention provides an optical energy storage and charging system, including the control device for the optical energy storage and charging system described in the second aspect of the present invention above. Beneficial effects

[0021] The beneficial effects of this invention are:

[0022] This invention uses SOC regulation as the outer loop and power regulation as the inner loop to perform SOC or power equalization on the energy storage batteries of the photovoltaic-storage-charging system. This solves the problem that the SOC deviation may become larger and larger during long-term operation of a pure off-grid system, improves the reliability of off-grid operation of the photovoltaic-storage-charging system, increases operational efficiency, and the equalization regulation does not require communication between PCS, nor does it require additional electrical wiring and construction, making it easy to implement and apply in existing photovoltaic-storage-charging systems. Attached Figure Description

[0023] Figure 1 is a flowchart of a control method for a photovoltaic energy storage and charging system according to a first embodiment of the present invention;

[0024] Figure 2 is a schematic diagram of a photovoltaic energy storage and charging system according to an embodiment of the present invention;

[0025] Figure 3 is a flowchart of a control method for a photovoltaic energy storage and charging system according to a second embodiment of the present invention;

[0026] Figure 4 is a flowchart of a control method for a photovoltaic energy storage and charging system according to a third embodiment of the present invention;

[0027] Figure 5 is a flowchart of a control method for a photovoltaic energy storage and charging system according to a fourth embodiment of the present invention;

[0028] Figure 6 is a block diagram of the control device of an optical energy storage and charging system according to an embodiment of the present invention. The best embodiment of the present invention

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Figure 1 is a flowchart of a control method for a photovoltaic-storage-charging system according to a first embodiment of the present invention. As shown in Figure 2, the photovoltaic-storage-charging system includes: multiple energy storage cabinets (ESS Cabinet) connected in parallel to the same AC bus, loads mounted on the AC bus, and an EMS (Energy Management System). The loads include electrical loads (Load), photovoltaic arrays (PV Panels), which are mounted on the AC bus via photovoltaic inverters (PV Inverters). Each ESS Cabinet consists of energy storage batteries, a storage inverter (PCS), and a local controller (LC). The LC acts as a data forwarding unit, responsible for forwarding data reported by the PCS to the EMS and forwarding data or commands issued by the EMS to the PCS. The EMS acts as a data aggregation unit, collecting key information such as the SOC percentage and PCS output power reported by each ESS Cabinet and then distributing it uniformly to all ESS Cabinet units. Alternatively, the LC in the energy storage cabinet can be omitted, with the PCS communicating directly with the EMS. If the LC is omitted, the EMS will also function as the LC.

[0031] According to an embodiment of the present invention, as shown in FIG1, the EMS can implement a control method for an optical storage and charging system using the following steps:

[0032] S1, obtain the SOC and PCS output power of the energy storage battery in each energy storage cabinet of the photovoltaic energy storage and charging system.

[0033] S2: Obtain the maximum SOC deviation based on the maximum and minimum SOC values, and determine whether the maximum SOC deviation exceeds the power regulation threshold.

[0034] Specifically, the SOC of the energy storage batteries in all energy storage cabinets can be sorted, the maximum and minimum values ​​can be selected, the energy storage cabinet numbers corresponding to the maximum and minimum values ​​can be recorded, and the difference between the maximum and minimum SOC values ​​can be calculated as the maximum SOC deviation.

[0035] S3, if the maximum SOC deviation exceeds the power regulation threshold, control the PCS to execute the SOC balancing strategy.

[0036] S4. If the maximum SOC deviation does not exceed the power regulation threshold, then the maximum power deviation is further obtained based on the maximum and minimum output power values.

[0037] Specifically, the PCS output power of all energy storage cabinets can be sorted, the maximum and minimum values ​​can be selected, the energy storage cabinet numbers corresponding to the maximum and minimum values ​​can be recorded, and the difference between the maximum and minimum output power can be calculated as the maximum power deviation.

[0038] S5 determines whether the maximum power deviation exceeds the power regulation threshold.

[0039] S6, if the maximum power deviation exceeds the power regulation threshold, control the PCS to execute the power balancing strategy.

[0040] Specifically, SOC balancing is first performed based on the actual SOC, and then power balancing is performed based on the actual output power. Thus, SOC regulation is used as the outer loop and power regulation as the inner loop to perform SOC balancing or power balancing on the energy storage batteries of the photovoltaic-storage-charging system. This solves the problem that the SOC deviation may become larger and larger due to long-term operation of the pure off-grid system, improves the reliability of the photovoltaic-storage-charging system off-grid operation, increases operational efficiency, and the balancing adjustment does not require communication between PCS, nor does it require additional electrical wiring and construction, making it easy to implement and apply in existing photovoltaic-storage-charging systems.

[0041] As a specific example of the present invention, as shown in Figure 3, the power equalization strategy includes the following steps:

[0042] S11, obtain the PCS with the highest power and the PCS with the lowest power.

[0043] S12, by adjusting the off-grid control parameters, controls the PCS with the highest power to reduce its output power.

[0044] S13, by adjusting the off-grid control parameters, increases the output power of the PCS with the lowest control power.

[0045] Specifically, power regulation is performed simultaneously on the two PCS units with the highest and lowest power outputs to ensure that their output power is approximately equal. Off-grid control parameters may include virtual impedance. Controlling the output power of the PCS with the highest power can be achieved by increasing the virtual impedance and limiting it; similarly, controlling the output power of the PCS with the lowest power can be achieved by decreasing its virtual impedance and limiting it. Virtual impedance limiting restricts the magnitude of the virtual impedance. When increasing the virtual impedance, the increase stops if it reaches the maximum virtual impedance magnitude threshold; similarly, when decreasing the virtual impedance, the decrease stops if it reaches the minimum virtual impedance magnitude threshold.

[0046] As a specific example of the present invention, as shown in Figure 4, the SOC balancing strategy includes the following steps:

[0047] S21. Calculate the total load power of the photovoltaic-storage-charging system based on the output power of all PCS, and determine the charging / discharging direction of the load based on the total load power. The total load power is the sum of the photovoltaic output power and the power consumed by the electrical load.

[0048] S22, the maximum allowable power deviation ΔPmax is calculated based on the maximum SOC deviation.

[0049] S23, adjust the power of the PCS of the maximum SOC energy storage cabinet and the PCS of the minimum SOC energy storage cabinet according to the charging and discharging direction of the load and the maximum allowable power deviation ΔPmax.

[0050] Furthermore, according to an embodiment of the present invention, as shown in FIG5, power adjustment is performed on the PCS of the maximum SOC energy storage cabinet and the PCS of the minimum SOC energy storage cabinet based on the charging and discharging direction of the load and the maximum allowable power deviation ΔPmax, specifically including:

[0051] If it is determined that the PCS is discharging to the load, it is determined whether the discharge power of the PCS of the largest SOC energy storage cabinet exceeds the discharge power threshold (S231-232). If it does not exceed the discharge power threshold, it is further determined whether the power deviation between the PCS of the largest SOC energy storage cabinet and the PCS of the smallest SOC energy storage cabinet exceeds the maximum allowable power deviation ΔPmax (S233). If it does not exceed the maximum allowable power deviation ΔPmax, the virtual impedance of the PCS of the largest SOC energy storage cabinet is reduced and virtual impedance is limited, and the virtual impedance of the PCS of the smallest SOC energy storage cabinet is increased and virtual impedance is limited (S234).

[0052] If it is determined that the PCS is charging the load, it is determined whether the power of the PCS of the smallest SOC energy storage cabinet exceeds the charging power threshold (S235-S236). If the power of the PCS of the smallest SOC energy storage cabinet does not exceed the charging power threshold, it is further determined whether the power deviation between the PCS of the largest SOC energy storage cabinet and the PCS of the smallest SOC energy storage cabinet exceeds the maximum allowable power deviation ΔPmax (S237). If it does not exceed the maximum allowable power deviation ΔPmax, the virtual impedance of the PCS of the largest SOC energy storage cabinet is increased and virtual impedance is limited, and the virtual impedance of the PCS of the smallest SOC energy storage cabinet is decreased and virtual impedance is limited (S238).

[0053] Specifically, power regulation is performed simultaneously on the two energy storage cabinets with the highest and lowest SOCs. The goal is to reduce charging in the cabinet with the highest SOC and increase charging in the cabinet with the lowest SOC. For equipment requiring increased charging power, it is necessary to determine whether its output power reaches the charging power threshold and whether its power deviation reaches the maximum allowable power deviation. If it does not reach the charging power threshold and does not exceed the maximum allowable power deviation ΔPmax, then the virtual impedance of the PCS of the energy storage cabinet with the highest SOC is increased, and the virtual impedance of the PCS of the energy storage cabinet with the lowest SOC is decreased. This achieves SOC balancing of the energy storage cabinets.

[0054] In summary, the control method of the photovoltaic-storage-charging system according to the embodiments of the present invention uses SOC regulation as the outer loop and power regulation as the inner loop to perform SOC balancing or power balancing on the energy storage batteries of the photovoltaic-storage-charging system. This solves the problem that the SOC deviation may become increasingly large during long-term operation of a pure off-grid system, improves the reliability of off-grid operation of the photovoltaic-storage-charging system, increases operational efficiency, and the balancing regulation does not require communication between PCS, nor does it require additional electrical wiring and construction, making it easy to implement and apply in existing photovoltaic-storage-charging systems.

[0055] Corresponding to the control method of the aforementioned photovoltaic energy storage and charging system, this invention also proposes a control device for the photovoltaic energy storage and charging system. Since the device embodiments of this invention correspond to the method embodiments described above, details not disclosed in the device embodiments can be found in the method embodiments described above, and will not be repeated here.

[0056] Figure 6 is a block diagram of a control device for a photovoltaic energy storage and charging system according to an embodiment of the present invention. The photovoltaic energy storage system includes multiple energy storage cabinets connected in parallel on the same AC bus. Each energy storage cabinet includes a PCS and an energy storage battery. As shown in Figure 6, the device includes: a first acquisition module 100, a first judgment module 200, a first execution module 300, a second acquisition module 400, a second judgment module 500, and a second execution module 600.

[0057] The system comprises the following modules: a first acquisition module 100, which acquires the SOC of the energy storage battery and the output power of the PCS in each energy storage cabinet of the photovoltaic energy storage and charging system when the PCS is in an off-grid state; a first judgment module 200, which acquires the maximum SOC deviation based on the maximum and minimum SOC values ​​and determines whether the maximum SOC deviation exceeds the power regulation threshold; a first execution module 300, which controls the PCS to execute an SOC balancing strategy when the maximum SOC deviation exceeds the power regulation threshold; a second acquisition module 400, which acquires the maximum power deviation based on the maximum and minimum output power values ​​when the maximum SOC deviation does not exceed the power regulation threshold; a second judgment module 500, which determines whether the maximum power deviation exceeds the power regulation threshold; and a second execution module 600, which controls the PCS to execute a power balancing strategy when the maximum power deviation exceeds the power regulation threshold.

[0058] According to one embodiment of the present invention, the second execution module 600 performs a power balancing strategy by employing the following steps: obtaining the PCS with the highest power and the PCS with the lowest power; controlling the PCS with the highest power to reduce its output power by adjusting the off-grid control parameters; and controlling the PCS with the lowest power to increase its output power by adjusting the off-grid control parameters.

[0059] According to an embodiment of the present invention, the first execution module 300 performs the SOC balancing strategy by adopting the following steps: calculating the total load power of the photovoltaic energy storage and charging system based on the output power of all PCS; determining the charging and discharging direction of the load based on the total load power, wherein the total load power is the sum of the photovoltaic output power and the power consumed by the electrical load; calculating the maximum allowable power deviation ΔPmax based on the maximum SOC deviation; and adjusting the power of the PCS of the energy storage cabinet with the maximum SOC and the PCS of the energy storage cabinet with the minimum SOC based on the charging and discharging direction of the load and the maximum allowable power deviation ΔPmax.

[0060] According to one embodiment of the present invention, the first execution module 300 is further configured to: if it is determined that the PCS discharges to the load, determine whether the discharge power of the PCS of the largest SOC energy storage cabinet exceeds the discharge power threshold; if it does not exceed the discharge power threshold, further determine whether the power deviation between the PCS of the largest SOC energy storage cabinet and the PCS of the smallest SOC energy storage cabinet exceeds the maximum allowable power deviation ΔPmax; if it does not exceed the maximum allowable power deviation ΔPmax, reduce the virtual impedance of the PCS of the largest SOC energy storage cabinet and perform virtual impedance limiting, and increase the virtual impedance of the PCS of the smallest SOC energy storage cabinet and perform virtual impedance limiting. Virtual impedance limiting: If it is determined that the PCS is charging the load, it is determined whether the power of the PCS of the smallest SOC energy storage cabinet exceeds the charging power threshold. If the power of the PCS of the smallest SOC energy storage cabinet does not exceed the charging power threshold, it is further determined whether the power deviation between the PCS of the largest SOC energy storage cabinet and the PCS of the smallest SOC energy storage cabinet exceeds the maximum allowable power deviation ΔPmax. If it does not exceed the maximum allowable power deviation ΔPmax, the virtual impedance of the PCS of the largest SOC energy storage cabinet is increased and virtual impedance limiting is applied, and the virtual impedance of the PCS of the smallest SOC energy storage cabinet is decreased and virtual impedance limiting is applied.

[0061] In summary, the control device for the photovoltaic-storage-charging system according to the embodiments of the present invention uses SOC regulation as the outer loop and power regulation as the inner loop to perform SOC balancing or power balancing on the energy storage batteries of the photovoltaic-storage-charging system. This solves the problem that the SOC deviation may become increasingly large during long-term operation of a pure off-grid system, improves the reliability of off-grid operation of the photovoltaic-storage-charging system, increases operational efficiency, and the balancing regulation does not require communication between PCS, nor does it require additional electrical wiring and construction, making it easy to implement and apply in existing photovoltaic-storage-charging systems.

[0062] In the description of this invention, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Any process or method description in the flowcharts or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logical functions or processes, and the scope of preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order according to the functions involved, as should be understood by those skilled in the art to which embodiments of the invention pertain.

[0063] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0064] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0065] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A control method for a photovoltaic energy storage and charging system, characterized in that, The photovoltaic-storage system includes multiple energy storage cabinets connected in parallel to the same AC bus. Each energy storage cabinet includes a power storage unit (PCS) and energy storage batteries. When the PCS is in an off-grid state, the method includes the following steps: Obtain the SOC and PCS output power of each energy storage cabinet in the photovoltaic energy storage and charging system; The maximum SOC deviation is obtained based on the maximum and minimum SOC values, and it is determined whether the maximum SOC deviation exceeds the power regulation threshold. If the maximum SOC deviation exceeds the power regulation threshold, the PCS is controlled to execute an SOC balancing strategy. If the maximum SOC deviation does not exceed the power regulation threshold, then the maximum power deviation is further obtained based on the maximum output power and the minimum output power. Determine whether the maximum power deviation exceeds the power adjustment threshold; If the maximum power deviation exceeds the power adjustment threshold, the PCS is controlled to execute a power equalization strategy.

2. The control method for the photovoltaic energy storage and charging system according to claim 1, characterized in that, The power equalization strategy includes the following steps: Obtain the PCS with the highest power and the PCS with the lowest power; By adjusting the off-grid control parameters, the output power of the PCS with the highest control power is reduced; By adjusting the off-grid control parameters, the output power of the PCS with the lowest control power is increased.

3. The control method for the photovoltaic energy storage and charging system according to claim 1, characterized in that, The SOC balancing strategy includes the following steps: The total load power of the photovoltaic-storage-charging system is calculated based on the output power of all PCS. The charging and discharging direction of the load is determined based on the total load power. The total load power is the sum of the photovoltaic output power and the power consumed by the electrical load. The maximum allowable power deviation ΔPmax is calculated based on the maximum SOC deviation. Power regulation is performed on the PCS of the largest SOC energy storage cabinet and the PCS of the smallest SOC energy storage cabinet based on the charging and discharging direction of the load and the maximum allowable power deviation ΔPmax.

4. The control method for the photovoltaic energy storage and charging system according to claim 3, characterized in that, Power regulation is performed on the PCS of the maximum SOC energy storage cabinet and the PCS of the minimum SOC energy storage cabinet based on the charging and discharging direction of the load and the maximum allowable power deviation ΔPmax. Specifically, this includes: If it is determined that the PCS discharges to the load, it is determined whether the discharge power of the PCS of the largest SOC energy storage cabinet exceeds the discharge power threshold. If it does not exceed the discharge power threshold, it is further determined whether the power deviation between the PCS of the largest SOC energy storage cabinet and the PCS of the smallest SOC energy storage cabinet exceeds the maximum allowable power deviation ΔPmax. If it does not exceed the maximum allowable power deviation ΔPmax, the virtual impedance of the PCS of the largest SOC energy storage cabinet is reduced and virtual impedance is limited, and the virtual impedance of the PCS of the smallest SOC energy storage cabinet is increased and virtual impedance is limited. If it is determined that the PCS is charging the load, it is determined whether the power of the PCS of the smallest SOC energy storage cabinet exceeds the charging power threshold. If the power of the PCS of the smallest SOC energy storage cabinet does not exceed the charging power threshold, it is further determined whether the power deviation between the PCS of the largest SOC energy storage cabinet and the PCS of the smallest SOC energy storage cabinet exceeds the maximum allowable power deviation ΔPmax. If it does not exceed the maximum allowable power deviation ΔPmax, the virtual impedance of the PCS of the largest SOC energy storage cabinet is increased and virtual impedance is limited, and the virtual impedance of the PCS of the smallest SOC energy storage cabinet is decreased and virtual impedance is limited.

5. A control device of a light storage and charge system characterized by comprising: The photovoltaic-storage system includes multiple energy storage cabinets connected in parallel to the same AC bus, each energy storage cabinet including a PCS and an energy storage battery, and the control device includes: The first acquisition module is used to acquire the SOC of the energy storage battery and the output power of the PCS of each energy storage cabinet in the photovoltaic energy storage and charging system when the PCS is in an off-grid state. The first judgment module is used to obtain the maximum SOC deviation based on the maximum SOC value and the minimum SOC value, and to determine whether the maximum SOC deviation exceeds the power adjustment threshold. The first execution module is used to control the PCS to execute a SOC balancing strategy when the maximum SOC deviation exceeds the power regulation threshold. The second acquisition module is used to further acquire the maximum power deviation based on the maximum output power and the minimum output power when the maximum SOC deviation does not exceed the power adjustment threshold. The second judgment module is used to determine whether the maximum power deviation exceeds the power adjustment threshold. The second execution module is used to control the PCS to execute a power equalization strategy when the maximum power deviation exceeds the power adjustment threshold.

6. The control device for the photovoltaic energy storage and charging system according to claim 5, characterized in that, The second execution module performs the power balancing strategy using the following steps: Obtain the PCS with the highest power and the PCS with the lowest power; By adjusting the off-grid control parameters, the output power of the PCS with the highest control power is reduced; By adjusting the off-grid control parameters, the output power of the PCS with the lowest control power is increased.

7. The control device for the photovoltaic energy storage and charging system according to claim 5, characterized in that, The first execution module executes the SOC balancing strategy using the following steps: The total load power of the photovoltaic-storage-charging system is calculated based on the output power of all PCS. The charging and discharging direction of the load is determined based on the total load power. The total load power is the sum of the photovoltaic output power and the power consumed by the electrical load. The maximum allowable power deviation ΔPmax is calculated based on the maximum SOC deviation. Power regulation is performed on the PCS of the largest SOC energy storage cabinet and the PCS of the smallest SOC energy storage cabinet based on the charging and discharging direction of the load and the maximum allowable power deviation ΔPmax.

8. The control device for the photovoltaic energy storage and charging system according to claim 7, characterized in that, The first execution module is further configured to: If it is determined that the PCS discharges to the load, it is determined whether the discharge power of the PCS of the largest SOC energy storage cabinet exceeds the discharge power threshold. If it does not exceed the discharge power threshold, it is further determined whether the power deviation between the PCS of the largest SOC energy storage cabinet and the PCS of the smallest SOC energy storage cabinet exceeds the maximum allowable power deviation ΔPmax. If it does not exceed the maximum allowable power deviation ΔPmax, the virtual impedance of the PCS of the largest SOC energy storage cabinet is reduced and virtual impedance is limited, and the virtual impedance of the PCS of the smallest SOC energy storage cabinet is increased and virtual impedance is limited. If it is determined that the PCS is charging the load, it is determined whether the power of the PCS of the smallest SOC energy storage cabinet exceeds the charging power threshold. If the power of the PCS of the smallest SOC energy storage cabinet does not exceed the charging power threshold, it is further determined whether the power deviation between the PCS of the largest SOC energy storage cabinet and the PCS of the smallest SOC energy storage cabinet exceeds the maximum allowable power deviation ΔPmax. If it does not exceed the maximum allowable power deviation ΔPmax, the virtual impedance of the PCS of the largest SOC energy storage cabinet is increased and virtual impedance is limited, and the virtual impedance of the PCS of the smallest SOC energy storage cabinet is decreased and virtual impedance is limited.

9. A photovoltaic energy storage and charging system, characterized in that, The system includes a control device for the photovoltaic energy storage and charging system according to any one of claims 5-8.

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