Hybrid grid-connected control method, system, device, medium and product for a cascade photovoltaic energy storage grid-connected inverter system

Abstract

The present application relates to the technical field of power grid system control, and particularly relates to a hybrid network construction control method, system, device, medium and product of a cascaded photovoltaic energy storage grid-connected inverter system. The method implements differentiated collaborative control on photovoltaic modules and energy storage modules in the cascaded photovoltaic energy storage grid-connected inverter; the fundamental frequency phase angle of the grid-connected current flowing through the series branch from each photovoltaic voltage control inverter forms a unified output voltage phase reference, realizing coordinated output of multiple photovoltaic modules without relying on high-speed synchronous communication between modules. The grid frequency is used to correct the system active power instruction, and the difference between the system target power and the photovoltaic active power is determined as the total active power instruction of the energy storage, and then the energy storage output is distributed according to the state of charge of each energy storage unit, thereby improving the operation stability, module expandability and fault tolerance capability of the system.

Description

Technical Field

[0001] This invention relates to the field of power grid system control technology, and in particular to a hybrid grid control method, system, equipment, medium and product for a cascaded photovoltaic energy storage grid-connected inverter system. Background Technology

[0002] With the rapid development of new energy power systems, the penetration rate of photovoltaic power generation continues to increase. However, its inherent intermittency, volatility, and undispatchability pose severe challenges to the stable operation of the power grid. Integrating energy storage with photovoltaics can effectively mitigate power fluctuations, improve controllability, and provide grid ancillary services.

[0003] Cascaded photovoltaic-energy storage inverter systems boost output voltage through modular series connection, reducing reliance on large-capacity transformers and high-power centralized converters, offering significant advantages in medium- and high-voltage grid-connected scenarios. However, existing control schemes mostly employ centralized architectures, relying on high-bandwidth communication, resulting in high system complexity, low reliability, and poor modularity and scalability. While distributed control can reduce communication dependence, research on power coordination, lack of communication synchronization, frequency support, and MPPT compatibility is insufficient, making it difficult to simultaneously meet the requirements of balanced energy storage output, high-efficiency photovoltaic power generation, and stable system operation. Summary of the Invention

[0004] In view of this, in order to solve the above-mentioned technical problems, the present invention provides a hybrid grid control method, system, equipment, medium and product for a cascaded photovoltaic energy storage grid-connected inverter system.

[0005] The first aspect of this invention provides a hybrid grid control method for a cascaded photovoltaic energy storage grid-connected inverter system, the method comprising:

[0006] Obtain the common coupling point voltage and grid frequency corresponding to each energy storage current control inverter, and obtain the DC side voltage, output active power, and grid-connected current flowing through the multiple photovoltaic voltage control inverters.

[0007] The DC side voltage reference value is determined based on the maximum power point of the photovoltaic unit corresponding to each photovoltaic voltage control inverter. The active power reference value is determined based on the deviation between the DC side voltage and the DC side voltage reference value. The output voltage amplitude command of each photovoltaic voltage control inverter is determined based on the deviation between the active power reference value and the output active power.

[0008] The fundamental frequency phase angle is extracted from the grid-connected current. The output voltage phase angle command of each photovoltaic voltage control inverter is determined according to the fundamental frequency phase angle. Based on the output voltage amplitude command and the output voltage phase angle command, each photovoltaic voltage control inverter is controlled to output AC voltage in the form of a voltage source.

[0009] The system active power command is corrected according to the grid frequency, and the total active power command of energy storage is determined according to the corrected system active power command and the active power reference value of each photovoltaic voltage control inverter.

[0010] The total active power command of energy storage is allocated according to the state of charge of each energy storage unit to obtain the current amplitude command of each energy storage current control inverter. The current phase angle command of each energy storage current control inverter is determined according to the phase angle of the common coupling point voltage, so as to control each energy storage current control inverter to output AC current in the form of a current source according to the current amplitude command and the current phase angle command.

[0011] In one example, the process of determining a DC-side voltage reference value based on the maximum power point of the photovoltaic unit corresponding to each photovoltaic voltage-controlled inverter, determining an active power reference value based on the deviation between the DC-side voltage and the DC-side voltage reference value, and determining the output voltage amplitude command of each photovoltaic voltage-controlled inverter based on the deviation between the active power reference value and the output active power, includes:

[0012] Maximum power point tracking is performed based on the photovoltaic side voltage and photovoltaic side current of the photovoltaic unit corresponding to each photovoltaic voltage control inverter to obtain the DC side voltage reference value corresponding to the maximum power point of the photovoltaic unit;

[0013] The deviation between the DC-side voltage and the DC-side voltage reference value is adjusted proportionally and integrally to obtain the active power reference value of the corresponding photovoltaic voltage control inverter.

[0014] The output voltage amplitude feedforward is determined based on the active power reference value, the fundamental frequency amplitude of the grid-connected current, and the preset power factor angle, and the output voltage amplitude correction is determined based on the deviation between the active power reference value and the output active power.

[0015] The output voltage amplitude feedforward and the output voltage amplitude correction are superimposed to obtain the output voltage amplitude command of the corresponding photovoltaic voltage control inverter.

[0016] In one example, the step of extracting the fundamental frequency phase angle from the grid-connected current, determining the output voltage phase angle command of each photovoltaic voltage control inverter based on the fundamental frequency phase angle, and controlling each photovoltaic voltage control inverter to output AC voltage in the form of a voltage source based on the output voltage amplitude command and the output voltage phase angle command includes:

[0017] Each photovoltaic voltage-controlled inverter extracts the fundamental frequency component of the locally collected grid-connected current to obtain the fundamental frequency phase angle of the grid-connected current;

[0018] The fundamental frequency phase angle of the grid-connected current is superimposed with the preset power factor angle to obtain the output voltage phase angle command of the corresponding photovoltaic voltage control inverter;

[0019] An AC voltage reference value is generated based on the output voltage amplitude command and the output voltage phase angle command;

[0020] The AC voltage reference value is compared with the actual output voltage of the corresponding photovoltaic voltage control inverter to obtain the output voltage deviation. The output voltage deviation is then adjusted through the voltage outer loop to obtain the AC current reference value.

[0021] The AC current reference value is compared with the actual output current of the corresponding photovoltaic voltage control inverter to obtain the output current deviation, and the output current deviation is adjusted through the current inner loop to obtain the voltage modulation signal.

[0022] The voltage modulation signal is pulse-width modulated to generate a switching drive signal for the H-bridge inverter circuit in the photovoltaic voltage control inverter, so that the actual output voltage of the photovoltaic voltage control inverter tracks the AC voltage reference value and outputs AC voltage in the form of a voltage source.

[0023] In one example, the step of correcting the system active power command based on the grid frequency, and determining the total active power command for energy storage based on the corrected system active power command and the active power reference values ​​of each photovoltaic voltage-controlled inverter, includes:

[0024] Determine the frequency deviation between the power grid frequency and the rated power grid frequency, as well as the rate of change of the power grid frequency over time;

[0025] The damping power correction amount is determined based on the frequency deviation and the preset damping coefficient, and the inertia power correction amount is determined based on the rate of change of the power grid frequency over time and the preset virtual inertia coefficient.

[0026] The system active power command at the rated frequency is corrected by using the damping power correction amount and the inertia power correction amount to obtain the corrected system active power command.

[0027] The active power reference values ​​of each photovoltaic voltage-controlled inverter are summed to obtain the total photovoltaic active power reference value, and the power difference between the corrected system active power command and the total photovoltaic active power reference value is determined as the total energy storage active power command.

[0028] In one example, the process of allocating the total active power command of energy storage according to the state of charge of each energy storage unit to obtain the current amplitude command of each energy storage current control inverter, and determining the current phase angle command of each energy storage current control inverter according to the phase angle of the common coupling point voltage, so as to control each energy storage current control inverter to output AC current in the form of a current source according to the current amplitude command and the current phase angle command, includes:

[0029] Determine the proportion of the state of charge of each energy storage unit to the sum of the states of charge of all energy storage units, and allocate the total active power command of energy storage according to the proportion to obtain the active power allocation value of each energy storage current control inverter.

[0030] Based on the active power allocation value, the amplitude of the common coupling point voltage, and the preset power factor angle, determine the current amplitude command for the corresponding energy storage current control inverter;

[0031] The difference between the phase angle of the common coupling point voltage and the preset power factor angle is determined as the current phase angle command for the corresponding energy storage current control inverter.

[0032] Generate the corresponding AC current reference value for the energy storage current control inverter based on the current amplitude command and the current phase angle command;

[0033] The AC current reference value is compared with the actual output current of the corresponding energy storage current control inverter to obtain the current tracking deviation, and the current tracking deviation is adjusted by a proportional resonant controller to obtain a current modulation signal.

[0034] The current modulation signal is sinusoidally pulse-width modulated to generate a switching drive signal for the H-bridge inverter circuit in the corresponding energy storage current control inverter, so that the actual output current tracks the AC current reference value and controls the energy storage current control inverter to output AC current in the form of a current source.

[0035] In one example, determining the proportion of the state of charge of each energy storage unit to the sum of the states of charge of all energy storage units, and allocating the total active power command of energy storage according to the proportion to obtain the active power allocation value of each energy storage current control inverter, includes:

[0036] Calculate the sum of the states of charge of all energy storage units;

[0037] Determine the ratio of the state of charge of each energy storage unit to the sum of the states of charge;

[0038] The total active power command for energy storage is allocated according to the ratio corresponding to each energy storage unit, thereby obtaining the active power allocation value of each energy storage current control inverter.

[0039] Secondly, the present invention also provides a hybrid grid-connected control system for a cascaded photovoltaic energy storage grid-connected inverter system, the system comprising:

[0040] The data acquisition module is used to acquire the common coupling point voltage and grid frequency corresponding to each energy storage current control inverter, and to acquire the DC side voltage, output active power and grid-connected current flowing through the multiple photovoltaic voltage control inverters.

[0041] The voltage command generation module is used to determine the DC side voltage reference value based on the maximum power point of the photovoltaic unit corresponding to each photovoltaic voltage control inverter, determine the active power reference value based on the deviation between the DC side voltage and the DC side voltage reference value, and determine the output voltage amplitude command of each photovoltaic voltage control inverter based on the deviation between the active power reference value and the output active power.

[0042] The inverter voltage control module is used to extract the fundamental frequency phase angle from the grid-connected current, determine the output voltage phase angle command of each photovoltaic voltage control inverter according to the fundamental frequency phase angle, and control each photovoltaic voltage control inverter to output AC voltage in the form of a voltage source according to the output voltage amplitude command and the output voltage phase angle command.

[0043] The power command generation module is used to correct the system active power command according to the grid frequency, and to determine the total active power command of energy storage according to the corrected system active power command and the active power reference value of each photovoltaic voltage control inverter.

[0044] The inverter current control module is used to allocate the total active power command of energy storage according to the state of charge of each energy storage unit, obtain the current amplitude command of each energy storage current control inverter, and determine the current phase angle command of each energy storage current control inverter according to the phase angle of the common coupling point voltage, so as to control each energy storage current control inverter to output AC current in the form of a current source according to the current amplitude command and the current phase angle command.

[0045] Thirdly, the present invention also provides an electronic device, the electronic device including a memory and a processor, the memory storing a computer program, the computer program being executed by the processor causing the processor to perform the steps of the hybrid grid control method for the cascaded photovoltaic energy storage grid-connected inverter system as described in the first aspect.

[0046] Fourthly, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed, implements the steps of the hybrid grid control method for the cascaded photovoltaic energy storage grid-connected inverter system as described in the first aspect.

[0047] Fifthly, the present invention also provides a computer program product, the computer program product comprising a computer program stored on a non-transitory computer-readable storage medium, the computer program comprising program instructions, wherein, when the program instructions are executed by a computer, the computer performs the steps of the hybrid grid control method for a cascaded photovoltaic energy storage grid-connected inverter system as described in the first aspect.

[0048] As can be seen from the above technical solutions, this invention implements differentiated and coordinated control of the photovoltaic modules and energy storage modules in a cascaded photovoltaic energy storage grid-connected inverter. This enables the photovoltaic voltage control inverter to generate an active power reference value based on the DC-side voltage reference value corresponding to the maximum power point, and adjust the output voltage amplitude accordingly, thereby balancing the maximum photovoltaic power utilization and DC-side voltage stability. Simultaneously, each photovoltaic voltage control inverter extracts the fundamental frequency phase angle from the grid-connected current flowing through the series branches, forming a unified output voltage phase reference. This allows multiple photovoltaic modules to coordinate their output without relying on high-speed synchronous communication between modules. Furthermore, the system active power command is corrected using the grid frequency, and the difference between the system target power and the photovoltaic active power is determined as the total active power command for energy storage. Energy storage output is then allocated according to the state of charge of each energy storage unit, enabling the energy storage modules to both compensate for photovoltaic power variations and provide active power support during grid frequency fluctuations. Thus, this scheme achieves maximum photovoltaic power output, inter-module synchronization without communication, energy storage coordinated output according to state, and dynamic balance of photovoltaic and energy storage power within the same control chain. It reduces the cascaded system's dependence on centralized control and high-speed communication links, improves the problems of photovoltaic and energy storage being difficult to coordinate, power fluctuations being difficult to smooth, and insufficient frequency support under the existing decentralized control methods, and enhances the system's operational stability, module scalability, and fault tolerance. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 An application environment diagram of a hybrid grid control method for a cascaded photovoltaic energy storage grid-connected inverter system provided in an embodiment of the present invention;

[0051] Figure 2 This is a schematic diagram of a grid-connected cascaded photovoltaic-energy storage inverter system.

[0052] Figure 3A flowchart of a hybrid grid control method for a cascaded photovoltaic energy storage grid-connected inverter system provided in an embodiment of the present invention;

[0053] Figure 4 This is the control block diagram for the i-th photovoltaic voltage-controlled inverter;

[0054] Figure 5 This is the control block diagram for the i-th energy storage current-controlled inverter;

[0055] Figure 6a A schematic diagram of the power factor angle variation curves for each stage of the inverter unit;

[0056] Figure 6b A schematic diagram showing the change curves of active power output from each stage of the inverter unit;

[0057] Figure 7 A schematic diagram of the experimental results under power grid frequency offset;

[0058] Figure 8a This is a schematic diagram of the output voltage and current waveforms of the inverter unit.

[0059] Figure 8b A schematic diagram showing the change curve of the output active power of each inverter unit;

[0060] Figure 9 This is a schematic diagram of the hybrid grid control system of a cascaded photovoltaic energy storage grid-connected inverter system provided in an embodiment of the present invention;

[0061] Figure 10 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0062] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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.

[0063] The hybrid grid control method for cascaded photovoltaic energy storage grid-connected inverter systems provided in this application can be applied to, for example... Figure 1In the application environment shown, terminal 101 communicates with server 102 via a network. A data storage system can store the data that server 102 needs to process. The data storage system can be integrated onto server 102 or placed on a cloud or other network server. Terminal 101 or server 102 executes a hybrid grid control method for a cascaded photovoltaic energy storage grid-connected inverter system. This method includes: acquiring the common coupling point voltage and grid frequency corresponding to each energy storage current control inverter; acquiring the DC-side voltage, output active power, and grid-connected current flowing through multiple photovoltaic voltage control inverters for each photovoltaic voltage control inverter; determining a DC-side voltage reference value based on the maximum power point of the photovoltaic unit corresponding to each photovoltaic voltage control inverter; determining an active power reference value based on the deviation between the DC-side voltage and the DC-side voltage reference value; and determining the output voltage amplitude command for each photovoltaic voltage control inverter based on the deviation between the active power reference value and the output active power; extracting the fundamental frequency phase angle from the grid-connected current; and determining the output voltage amplitude command based on the fundamental frequency phase angle. The system generates output voltage phase angle commands for each photovoltaic voltage-controlled inverter and controls each inverter to output AC voltage as a voltage source based on the output voltage amplitude commands and output voltage phase angle commands. It also corrects the system active power command based on the grid frequency and determines the total active power command for energy storage based on the corrected system active power command and the active power reference values ​​of each photovoltaic voltage-controlled inverter. Furthermore, it distributes the total active power command for energy storage based on the state of charge of each energy storage unit, obtaining the current amplitude commands for each energy storage current-controlled inverter. Finally, it determines the current phase angle commands for each energy storage current-controlled inverter based on the phase angle of the common coupling point voltage, and controls each inverter to output AC current as a current source based on the current amplitude commands and current phase angle commands.

[0064] Terminal 101 can be, but is not limited to, various personal computers, laptops, smartphones, and tablets.

[0065] Server 102 can be a standalone physical server, a server cluster or distributed system consisting of multiple physical servers, or a cloud server that provides cloud computing services.

[0066] In this embodiment, as Figure 2As shown, the cascaded photovoltaic energy storage grid-connected inverter system includes n inverter units. The first to m-th inverter units are energy storage current-controlled inverters, and the (m+1)-n-th inverter units are photovoltaic voltage-controlled inverters. The AC output terminals of the multiple energy storage current-controlled inverters are connected in parallel, ensuring that each inverter has the same AC output voltage. The branch currents output by each inverter are combined to form the system grid-connected current. The AC output terminals of the multiple photovoltaic voltage-controlled inverters are connected in series, allowing all inverters to share the grid-connected current.

[0067] The DC side of the energy storage current-controlled inverter is connected to the corresponding energy storage unit. Its AC side includes an H-bridge inverter circuit and a filter circuit, and is controlled by a local current controller. The DC side of the photovoltaic voltage-controlled inverter is connected to the corresponding photovoltaic unit. Its DC bus is equipped with a DC-side capacitor, and its AC side includes an H-bridge inverter circuit and a filter circuit, and is controlled by a local voltage controller. The point of common coupling (PLL) is the location where the cascaded photovoltaic energy storage grid-connected inverter system is connected to the grid. The PLL voltage is used to characterize the actual grid-connected voltage of the system.

[0068] The "hybrid grid control" referred to in this embodiment mainly refers to the following: the energy storage inverter controls its output current in a current source manner, the photovoltaic inverter controls its output voltage in a voltage source manner, and a common phase reference is established among the photovoltaic voltage-controlled inverters using the grid-connected current flowing through the photovoltaic series branches. This forms a hybrid control structure that combines current-controlled inverters and voltage-controlled inverters.

[0069] like Figure 3 As shown, this application provides a hybrid grid control method for a cascaded photovoltaic energy storage grid-connected inverter system, which is applied to... Figure 1 Taking terminal 101 or server 102 as an example, the explanation includes the following steps S1 to S5. Wherein:

[0070] Step S1: Obtain the common coupling point voltage and grid frequency corresponding to each energy storage current control inverter, and obtain the DC side voltage, output active power, and grid-connected current flowing through multiple photovoltaic voltage control inverters.

[0071] Specifically, for the i-th energy storage current control inverter, the voltage at the common coupling point is obtained through a voltage sampling unit located at the common coupling point, and the fundamental frequency phase tracking of the common coupling point voltage is performed through a phase-locked loop to obtain the voltage amplitude V at the common coupling point. p Common coupling point voltage phase angle θ p and grid angular frequency .

[0072] A phase-locked loop (PLL) can construct orthogonal signals, calculate phase errors, and perform loop filtering on the sampled common coupling point voltage, and update the output phase angle in real time based on the phase error. When different energy storage current-controlled inverters are all connected to the same common coupling point, the obtained common coupling point voltage is in principle the same. However, each energy storage current-controlled inverter can obtain the corresponding voltage phase angle and grid frequency through local sampling and local PLL, without relying on high-speed communication to transmit synchronization commands.

[0073] Each energy storage current control inverter also acquires the state of charge (SoC) of the corresponding energy storage unit. i and actual output current i i (t). Among them, the state of charge can be provided by the battery management system of the energy storage unit based on the results of current integration, voltage correction or model estimation, and is used to characterize the proportion of the current remaining available power of the corresponding energy storage unit to its rated capacity.

[0074] For k photovoltaic voltage-controlled inverters, the photovoltaic side voltage V of the corresponding photovoltaic unit is obtained through the local sampling unit. pv,k Photovoltaic side current Ip v,k DC side voltage V dc,k AC side output voltage u k (t) and the grid-connected current i of the series branch. g (t).

[0075] Each photovoltaic voltage-controlled inverter is connected in series. Therefore, ignoring sampling errors and branch parasitic currents, each photovoltaic voltage-controlled inverter carries the same grid-connected current, which is the result of the combined output current of each parallel energy storage current-controlled inverter.

[0076] Step S2: Determine the DC side voltage reference value based on the maximum power point of the photovoltaic unit corresponding to each photovoltaic voltage control inverter; determine the active power reference value based on the deviation between the DC side voltage and the DC side voltage reference value; and determine the output voltage amplitude command of each photovoltaic voltage control inverter based on the deviation between the active power reference value and the output active power.

[0077] The maximum power point tracking (MPPT) stage adjusts the DC-side voltage reference value based on the output power changes before and after the photovoltaic (PV) side operating voltage changes, so that the operating point of the PV unit gradually approaches the maximum power point under the current light intensity and temperature conditions.

[0078] Maximum power point tracking (MPPT) can be achieved using perturbation observation, incremental conductance, or other methods that determine the maximum power point based on the photovoltaic (PV) side voltage and current. This embodiment does not limit the specific MPPT algorithm; the output of the MPPT stage is the DC-side voltage reference value for the corresponding PV voltage-controlled inverter.

[0079] Preferably, each photovoltaic unit is controlled as a self-synchronizing voltage source. The reference value of the DC side voltage corresponding to the maximum power point of each photovoltaic unit is generated by the MPPT algorithm. The active power reference value is generated by the DC voltage outer loop based on the DC side voltage deviation. The output voltage amplitude of the inverter is then adjusted by the power regulator. At the same time, the output voltage phase angle is generated by using the common current fundamental frequency phase angle of the cascaded system as the synchronization phase reference. Thus, the photovoltaic unit can achieve self-synchronizing operation, DC side voltage stability and maximum power output under conditions without communication.

[0080] Step S3: Extract the fundamental frequency phase angle from the grid-connected current, determine the output voltage phase angle command of each photovoltaic voltage control inverter based on the fundamental frequency phase angle, and control each photovoltaic voltage control inverter to output AC voltage in the form of a voltage source according to the output voltage amplitude command and the output voltage phase angle command.

[0081] Since the AC output terminals of each photovoltaic voltage-controlled inverter are connected in series, all photovoltaic voltage-controlled inverters share the same grid-connected current. Each photovoltaic voltage-controlled inverter can collect the grid-connected current through its local current sampling unit and extract the fundamental frequency of the collected grid-connected current to obtain the fundamental frequency phase angle of the grid-connected current.

[0082] Preferably, utilizing the physical characteristic that each inverter module in the cascaded structure carries the same grid-connected current, the AC side current is locally acquired by each inverter module, and the phase angle of the grid-connected current fundamental frequency component is obtained through the fundamental frequency extraction stage. The phase angle is used as a common synchronization phase reference. Each photovoltaic voltage control inverter generates the output voltage phase angle based on the common synchronization phase reference and the rated power factor angle, and generates the output AC voltage in combination with the voltage amplitude command. It also controls each photovoltaic voltage control inverter to output AC voltage in the form of a voltage source. Thus, without the need for communication transmission of phase angle, frequency or synchronization commands, the cascaded photovoltaic voltage control inverters can achieve self-synchronization operation and maintain coordinated grid connection with the energy storage current control inverter.

[0083] Step S4: Correct the system active power command according to the grid frequency, and determine the total active power command of energy storage based on the corrected system active power command and the active power reference value of each photovoltaic voltage control inverter.

[0084] Since the grid frequency changes dynamically, the system active power command can be corrected by the primary frequency regulation stage based on the grid frequency deviation. Based on the corrected system active power command and the active power reference values ​​of each photovoltaic voltage control inverter, the total active power command of the energy storage system can be determined, thereby enabling the energy storage system to provide active power support when the grid frequency deviates and changes rapidly.

[0085] Step S5: Allocate the total active power command of energy storage according to the state of charge of each energy storage unit to obtain the current amplitude command of each energy storage current control inverter, and determine the current phase angle command of each energy storage current control inverter according to the phase angle of the common coupling point voltage, so as to control each energy storage current control inverter to output AC current in the form of a current source according to the current amplitude command and the current phase angle command.

[0086] Based on the remaining available capacity of each energy storage unit, the total active power command is allocated proportionally. Energy storage units with larger remaining capacities receive higher active power command values, while those with smaller remaining capacities receive lower values. This ensures a balanced state of charge across all energy storage units and prevents overcharging and over-discharging in some units. After obtaining the active power command for each energy storage current-controlled inverter, the current amplitude command and current phase angle command for each inverter can be calculated by combining the phase angle of the common coupling point voltage. Finally, the local current controller tracks the commands and controls the energy storage current-controlled inverter to output AC current with corresponding amplitude and phase angle as a current source, achieving stable active power output.

[0087] The hybrid grid control method for the cascaded photovoltaic energy storage grid-connected inverter system described above implements differentiated and coordinated control of the photovoltaic modules and energy storage modules in the cascaded photovoltaic energy storage grid-connected inverter. This allows the photovoltaic voltage control inverter to generate an active power reference value based on the DC-side voltage reference value corresponding to the maximum power point, and adjust the output voltage amplitude accordingly, thereby balancing the maximum photovoltaic power utilization and DC-side voltage stability. Simultaneously, each photovoltaic voltage control inverter extracts the fundamental frequency phase angle from the grid-connected current flowing through the series branches, forming a unified output voltage phase reference. This enables coordinated output from multiple photovoltaic modules without relying on high-speed synchronous communication between modules. Furthermore, the system active power command is corrected using the grid frequency, and the difference between the system target power and the photovoltaic active power is determined as the total active power command for energy storage. Energy storage output is then allocated according to the state of charge of each energy storage unit, enabling the energy storage modules to both compensate for photovoltaic power variations and provide active power support during grid frequency fluctuations. Thus, this scheme achieves maximum photovoltaic power output, inter-module synchronization without communication, energy storage coordinated output according to state, and dynamic balance of photovoltaic and energy storage power within the same control chain. It reduces the cascaded system's dependence on centralized control and high-speed communication links, improves the problems of photovoltaic and energy storage being difficult to coordinate, power fluctuations being difficult to smooth, and insufficient frequency support under the existing decentralized control methods, and enhances the system's operational stability, module scalability, and fault tolerance.

[0088] In some embodiments, a DC-side voltage reference value is determined based on the maximum power point of the photovoltaic unit corresponding to each photovoltaic voltage-controlled inverter; an active power reference value is determined based on the deviation between the DC-side voltage and the DC-side voltage reference value; and an output voltage amplitude command for each photovoltaic voltage-controlled inverter is determined based on the deviation between the active power reference value and the output active power. This includes: performing maximum power point tracking based on the photovoltaic-side voltage and photovoltaic-side current of the photovoltaic unit corresponding to each photovoltaic voltage-controlled inverter to obtain the DC-side voltage reference value corresponding to the maximum power point of the photovoltaic unit; performing proportional-integral adjustment on the deviation between the DC-side voltage and the DC-side voltage reference value to obtain the active power reference value of the corresponding photovoltaic voltage-controlled inverter; determining the output voltage amplitude feedforward based on the active power reference value, the fundamental frequency amplitude of the grid-connected current, and a preset power factor angle; and determining the output voltage amplitude correction based on the deviation between the active power reference value and the output active power; and superimposing the output voltage amplitude feedforward and the output voltage amplitude correction to obtain the output voltage amplitude command for the corresponding photovoltaic voltage-controlled inverter.

[0089] For the k-th photovoltaic voltage-controlled inverter, local control is achieved by locally acquiring the photovoltaic side voltage, photovoltaic side current, DC side capacitor voltage, AC side output voltage, and common AC current. The maximum power point tracking (MPPT) stage is based on the photovoltaic side voltage u. i and current i g Generate the DC-side voltage reference value V corresponding to the maximum power point. dci,ref This is to ensure that the photovoltaic unit can operate at its maximum power point under various environmental conditions.

[0090] Subsequently, as Figure 4 As shown, the actual DC side voltage V is then... dc,i DC side voltage reference value V dci,ref The comparison is performed, and an active power reference value is generated through a DC voltage proportional-integral regulator. :

[0091]

[0092] Where k vdc,p and k vdc,I These are the proportional-integral controller parameters for the DC side voltage of the i-th voltage-controlled inverter.

[0093] When the actual DC side voltage V dc,i Higher than V dci,ref When the DC input power is greater than the AC output power, the controller increases its power output, causing the inverter to output more active power to the AC side to reduce the DC voltage; conversely, when the DC input power is less than the AC output power, the controller reduces the AC active power output, thereby lowering the DC voltage. dc,i Tracking V dci,ref .

[0094] Subsequently, the power regulator adjusts the active power reference value. With actual output active power P i The deviation between the values ​​generates an AC output voltage amplitude command. Simultaneously, based on the active power reference value... The fundamental frequency amplitude of the grid-connected current and preset power factor Angle determines the feedforward amount of output voltage amplitude:

[0095]

[0096] Then, the output voltage amplitude correction amount is determined based on the deviation between the active power reference value and the output active power. Then, by combining the output voltage amplitude feedforward and the output voltage amplitude correction, the output voltage amplitude command for the corresponding photovoltaic voltage control inverter is obtained as follows:

[0097]

[0098] In the formula, The output voltage amplitude of photovoltaic voltage-controlled inverter i.

[0099] Through the above control, the i-th photovoltaic voltage control inverter can maintain DC side voltage stability and achieve maximum photovoltaic power output, while using the phase angle of the common grid-connected current for self-synchronization, and output AC voltage with controllable amplitude and phase angle in the form of a voltage source.

[0100] Further, the fundamental frequency phase angle is extracted from the grid-connected current. Based on the fundamental frequency phase angle, the output voltage phase angle command for each photovoltaic voltage-controlled inverter is determined. Then, based on the output voltage amplitude command and the output voltage phase angle command, each photovoltaic voltage-controlled inverter is controlled to output AC voltage in the form of a voltage source. This includes: each photovoltaic voltage-controlled inverter extracting the fundamental frequency component of the locally acquired grid-connected current to obtain the fundamental frequency phase angle of the grid-connected current; superimposing the fundamental frequency phase angle of the grid-connected current with a preset power factor angle to obtain the output voltage phase angle command for the corresponding photovoltaic voltage-controlled inverter; generating an AC voltage reference value based on the output voltage amplitude command and the output voltage phase angle command; and converting the AC voltage... The reference value is compared with the actual output voltage of the corresponding photovoltaic voltage-controlled inverter to obtain the output voltage deviation. The output voltage deviation is adjusted through the voltage outer loop to obtain the AC current reference value. The AC current reference value is compared with the actual output current of the corresponding photovoltaic voltage-controlled inverter to obtain the output current deviation. The output current deviation is adjusted through the current inner loop to obtain the voltage modulation signal. Pulse width modulation is performed on the voltage modulation signal to generate the switching drive signal of the H-bridge inverter circuit in the corresponding photovoltaic voltage-controlled inverter, so that the actual output voltage of the photovoltaic voltage-controlled inverter tracks the AC voltage reference value and outputs AC voltage in the form of a voltage source.

[0101] like Figure 4 As shown, the photovoltaic voltage-controlled inverter extracts the fundamental frequency component of the locally collected grid-connected current to obtain the fundamental frequency phase angle θ of the grid-connected current. Ig The controller extracts the fundamental frequency phase angle from the common alternating current and combines it with a preset power factor angle. Superimpose the values ​​to generate the AC output voltage phase angle command. Subsequently, the output voltage amplitude command V will be sent. i and output voltage phase angle command Combined, forming the voltage phasor command V i ∠θ V,i And further generate an instantaneous reference value for the AC voltage. If V i If the effective value is used, then the AC voltage reference value can be expressed as:

[0102]

[0103] In the formula, This is the reference value of the AC output voltage that the i-th photovoltaic voltage control inverter needs to track.

[0104] The AC voltage reference value is compared with the actual output voltage of the corresponding photovoltaic voltage-controlled inverter to obtain the output voltage deviation. The output voltage deviation is then adjusted through a dual current-voltage closed loop. Specifically, the output voltage deviation is adjusted through the outer voltage loop to obtain the AC current reference value. This AC current reference value is then compared with the actual output current of the corresponding photovoltaic voltage-controlled inverter to obtain the output current deviation. The output current deviation is then adjusted through the inner current loop to obtain the voltage modulation signal.

[0105] Then, pulse width modulation is performed based on the voltage modulation signal to generate the switching drive signal for the H-bridge inverter, so that the actual output voltage of the photovoltaic voltage control inverter tracks the AC voltage reference value and outputs AC voltage as a voltage source. Thus, the photovoltaic module can achieve self-synchronization operation, DC-side voltage stability, and maximum power output even without communication.

[0106] In some embodiments, the system active power command is corrected according to the grid frequency, and the total active power command of energy storage is determined according to the corrected system active power command and the active power reference values ​​of each photovoltaic voltage-controlled inverter. This includes: determining the frequency deviation between the grid frequency and the rated grid frequency and the rate of change of the grid frequency over time; determining the damping power correction amount according to the frequency deviation and a preset damping coefficient, and determining the inertia power correction amount according to the rate of change of the grid frequency over time and a preset virtual inertia coefficient; correcting the system active power command at the rated frequency using the damping power correction amount and the inertia power correction amount to obtain the corrected system active power command; summing the active power reference values ​​of each photovoltaic voltage-controlled inverter to obtain the total photovoltaic active power reference value, and determining the power difference between the corrected system active power command and the total photovoltaic active power reference value as the total active power command of energy storage.

[0107] like Figure 5 As shown, the energy storage unit current-controlled inverter achieves local control by locally acquiring the AC side output voltage, output current, and energy storage unit state of charge. The phase-locked loop (PLL) obtains the phase angle and frequency information of the grid-connected voltage based on the AC side output voltage. The phase angle is used to generate the phase reference for the output current, and the frequency information is used to determine the grid frequency deviation and generate a frequency-supported power command. Specifically, to enable the energy storage current-controlled inverter to provide frequency support to the grid, the system active power command... It can be designed as:

[0108]

[0109] In the formula, The rated angular frequency of the power grid. For the power grid frequency, This represents the rated active power of the photovoltaic-energy storage system at the rated frequency (the system active power command at the rated frequency), where D and J are the damping coefficient and inertia coefficient, respectively.

[0110] Then, the active power reference values ​​of each photovoltaic voltage-controlled inverter are summed to obtain the total photovoltaic active power reference value, and the power difference between the corrected system active power command and the total photovoltaic active power reference value is determined as the total energy storage active power command.

[0111] In some embodiments, the total active power command for energy storage is allocated according to the state of charge of each energy storage unit to obtain the current amplitude command for each energy storage current control inverter, and the current phase angle command for each energy storage current control inverter is determined according to the phase angle of the common coupling point voltage, so as to control each energy storage current control inverter to output AC current in the form of a current source according to the current amplitude command and the current phase angle command. This includes: determining the proportion of the state of charge of each energy storage unit to the sum of the states of charge of all energy storage units, and allocating the total active power command for energy storage according to the proportion to obtain the active power allocation value for each energy storage current control inverter; determining the current of the corresponding energy storage current control inverter according to the active power allocation value, the amplitude of the common coupling point voltage and the preset power factor angle. The amplitude command is used to determine the current phase angle command of the corresponding energy storage current control inverter by the difference between the phase angle of the common coupling point voltage and the preset power factor angle. Based on the current amplitude command and the current phase angle command, an AC current reference value for the corresponding energy storage current control inverter is generated. The AC current reference value is compared with the actual output current of the corresponding energy storage current control inverter to obtain the current tracking deviation. The current tracking deviation is adjusted by a proportional resonant controller to obtain a current modulation signal. The current modulation signal is sinusoidally pulse-width modulated to generate a switching drive signal for the H-bridge inverter circuit in the corresponding energy storage current control inverter, so that the actual output current tracks the AC current reference value and controls the energy storage current control inverter to output AC current as a current source.

[0112] Specifically, the proportion of the state of charge (SBC) of each energy storage unit to the sum of the SBCs of all energy storage units is determined, and the total active power command for energy storage is allocated according to this proportion to obtain the active power allocation value for each energy storage current-controlled inverter. Based on the active power allocation value, the amplitude of the common coupling point voltage, and the preset power factor angle, the current amplitude command for the corresponding energy storage current-controlled inverter is determined.

[0113] like Figure 5 As shown, the energy storage control law is based on the active power command P. ∗ The state of charge (SoC) of the i-th energy storage unit i The sum of the states of charge of all energy storage units and the voltage amplitude V at the point of common coupling. p and preset power factor angle Determine the current amplitude command for the i-th energy storage current control inverter. The current amplitude command can be expressed as:

[0114]

[0115] At the same time, the phase angle θ of the voltage at the common coupling point p With preset power factor angle By performing the subtraction, the current phase angle command of the i-th energy storage current control inverter is obtained. .

[0116] Then, the controller sends the current amplitude command. and current phase angle command Combined, an AC current reference value is generated. .when When the effective value is 0, the AC current reference value can be expressed as:

[0117]

[0118] Subsequently, the AC current reference value was set. With actual output current i i The current tracking error is obtained by comparison. This error is then input into the proportional resonant controller PR. The proportional resonant controller has high gain near the grid fundamental frequency, enabling it to track sinusoidal alternating current with zero or low steady-state error, and outputs a current modulation signal.

[0119] The current modulation signal is further input to the sinusoidal pulse width modulation (SPWM) stage. Based on the comparison between the current modulation signal and the carrier signal, the SPWM stage generates the switching drive signals d for each switching device in the H-bridge inverter circuit. i The H-bridge inverter circuit uses the switching drive signal d. i Under the control of L, its AC side output is adjusted. f and C f After filtering, the actual output current i is reduced. i Tracking AC current reference value This allows the i-th energy storage current-controlled inverter to output AC current as a controlled current source.

[0120] Furthermore, the proportion of the state of charge (SBC) of each energy storage unit to the sum of the SBCs of all energy storage units is determined, and the total active power command for energy storage is allocated according to the proportion to obtain the active power allocation value for each energy storage current-controlled inverter. This includes: calculating the sum of the SBCs of all energy storage units; determining the ratio of the SBC of each energy storage unit to the sum of the SBCs; and allocating the total active power command for energy storage according to the ratio corresponding to each energy storage unit to obtain the active power allocation value for each energy storage current-controlled inverter.

[0121] The sum of the states of charge (SOCs) of all energy storage units can be calculated by a unified power coordination controller based on the SOCs reported by each energy storage unit. Since the SOC is a slow time-varying state relative to the current control cycle, the SOC data can be transmitted at a lower update frequency than the voltage and current loops, and does not require the use of a high-speed communication link for phase synchronization.

[0122] For example, the current control cycle can be in the microsecond or sub-millisecond range, while the state of charge update cycle can be in the hundreds of milliseconds or seconds. Therefore, even if the state of charge of each energy storage unit is obtained through low-speed communication, it will not change the technical essence of this scheme, which uses grid-connected current to achieve communication-free phase synchronization of photovoltaic inverters.

[0123] To verify the ability of the method proposed in this application to adjust the power factor angle of each module, see Figures 6a-6b. Figure 6b As shown, the rated power factor angle The power factor angle jumps from 0 to 0.2 at t=0.6s. As shown in Figure 6a, the power factor angle of all modules can track the new rated power factor angle; meanwhile, as shown in Figure 6b, the active power of the four modules remains basically unchanged, approximately P1=1200 W, P2=1000 W, P3=1000 W, and P4=1000 W respectively. The above results show that the proposed control strategy can effectively achieve independent adjustment of the power factor angle.

[0124] Furthermore, to evaluate the dynamic adaptability of the proposed method under grid frequency disturbances, as shown in Figure 7, the grid frequency decreased from 50 Hz to 48 Hz during the period from 0.6 s to 1.1 s. During this process, the active power of each module was adjusted accordingly: the initial values ​​were approximately P1 = 1800 W, P2 = 1200 W, and P... 3,4 =2000 W, after adjustment, P1=1950W, P2=1300W and P 3,4 =2000 W. When the grid frequency drops, the active power output of the energy storage module increases proportionally to its state of charge. The above results show that the method proposed in this application can provide effective frequency support during grid frequency fluctuations.

[0125] To verify the power regulation capability of the method proposed in this application, under this operating condition, the energy storage unit needs to compensate for the power fluctuations of the photovoltaic unit to maintain a constant total active power injected into the grid. For example... Figures 8a-8bAs shown, at t=0.6s, the active power of the photovoltaic unit increased from P3=1000 W, P4=1000 W to P3=1200 W, P4=1400 W, respectively. Correspondingly, the output power of the energy storage unit was adjusted from P1=1200 W, P2=1800 W to P1=800 W, P2=1200 W, while the total output power remained constant at approximately 5 kW. Meanwhile, the experimental waveforms in Figure 8a show that the voltage and current of each module remained stable during the adjustment process. These results demonstrate that the method proposed in this application can effectively coordinate the output of the photovoltaic and energy storage units: the increase in photovoltaic output power is compensated by the decrease in energy storage output power, thereby maintaining a constant total active power injected into the grid.

[0126] Based on the same inventive concept, this application also provides a hybrid grid control system for a cascaded photovoltaic energy storage grid-connected inverter system for implementing the hybrid grid control method of the cascaded photovoltaic energy storage grid-connected inverter system mentioned above.

[0127] The solution provided by this system is similar to the solution described in the above method. Therefore, the specific limitations of the hybrid grid control system embodiment of one or more cascaded photovoltaic energy storage grid-connected inverter systems provided below can be found in the limitations of the hybrid grid control method for cascaded photovoltaic energy storage grid-connected inverter systems described above, and will not be repeated here.

[0128] like Figure 9 As shown in the figure, this application provides a hybrid grid control system for a cascaded photovoltaic energy storage grid-connected inverter system, the system comprising:

[0129] The data acquisition module 100 is used to acquire the common coupling point voltage and grid frequency of each energy storage current control inverter, and to acquire the DC side voltage, output active power and grid-connected current flowing through multiple photovoltaic voltage control inverters.

[0130] The voltage command generation module 200 is used to determine the DC side voltage reference value based on the maximum power point of the photovoltaic unit corresponding to each photovoltaic voltage control inverter, determine the active power reference value based on the deviation between the DC side voltage and the DC side voltage reference value, and determine the output voltage amplitude command of each photovoltaic voltage control inverter based on the deviation between the active power reference value and the output active power.

[0131] The inverter voltage control module 300 is used to extract the fundamental frequency phase angle from the grid-connected current, determine the output voltage phase angle command of each photovoltaic voltage control inverter according to the fundamental frequency phase angle, and control each photovoltaic voltage control inverter to output AC voltage in the form of a voltage source according to the output voltage amplitude command and the output voltage phase angle command.

[0132] The power command generation module 400 is used to correct the system active power command according to the grid frequency, and to determine the total active power command of energy storage according to the corrected system active power command and the active power reference value of each photovoltaic voltage control inverter.

[0133] The inverter current control module 500 is used to allocate the total active power command of energy storage according to the state of charge of each energy storage unit, obtain the current amplitude command of each energy storage current control inverter, and determine the current phase angle command of each energy storage current control inverter according to the phase angle of the common coupling point voltage, so as to control each energy storage current control inverter to output AC current in the form of a current source according to the current amplitude command and the current phase angle command.

[0134] In some embodiments, the voltage command generation module 200 is configured to:

[0135] Maximum power point tracking is performed based on the photovoltaic side voltage and photovoltaic side current of the photovoltaic unit corresponding to each photovoltaic voltage control inverter to obtain the DC side voltage reference value corresponding to the maximum power point of the photovoltaic unit;

[0136] The deviation between the DC-side voltage and the DC-side voltage reference value is adjusted proportionally and integrally to obtain the active power reference value of the corresponding photovoltaic voltage control inverter.

[0137] The output voltage amplitude feedforward is determined based on the active power reference value, the fundamental frequency amplitude of the grid-connected current, and the preset power factor angle, and the output voltage amplitude correction is determined based on the deviation between the active power reference value and the output active power.

[0138] The output voltage amplitude feedforward and output voltage amplitude correction are superimposed to obtain the output voltage amplitude command for the corresponding photovoltaic voltage control inverter.

[0139] In some embodiments, the inverter voltage control module 300 is used for:

[0140] Each photovoltaic voltage-controlled inverter extracts the fundamental frequency component of the locally collected grid-connected current to obtain the fundamental frequency phase angle of the grid-connected current;

[0141] The fundamental frequency phase angle of the grid-connected current is superimposed with the preset power factor angle to obtain the output voltage phase angle command of the corresponding photovoltaic voltage control inverter;

[0142] An AC voltage reference value is generated based on the output voltage amplitude command and the output voltage phase angle command;

[0143] The AC voltage reference value is compared with the actual output voltage of the corresponding photovoltaic voltage control inverter to obtain the output voltage deviation. The output voltage deviation is then adjusted through the voltage outer loop to obtain the AC current reference value.

[0144] The AC current reference value is compared with the actual output current of the corresponding photovoltaic voltage-controlled inverter to obtain the output current deviation. The output current deviation is then adjusted through the current inner loop to obtain the voltage modulation signal.

[0145] The voltage modulation signal is pulse-width modulated to generate the corresponding switching drive signal for the H-bridge inverter circuit in the photovoltaic voltage control inverter, so that the actual output voltage of the photovoltaic voltage control inverter tracks the AC voltage reference value and outputs AC voltage in the form of a voltage source.

[0146] In some embodiments, the power command generation module 400 is used for:

[0147] Determine the frequency deviation between the grid frequency and the rated grid frequency, as well as the rate of change of the grid frequency over time;

[0148] The damping power correction is determined based on the frequency deviation and the preset damping coefficient, and the inertia power correction is determined based on the rate of change of the grid frequency over time and the preset virtual inertia coefficient.

[0149] The system active power command at rated frequency is corrected by using damping power correction and inertia power correction to obtain the corrected system active power command.

[0150] The active power reference values ​​of each photovoltaic voltage-controlled inverter are summed to obtain the total photovoltaic active power reference value. The power difference between the corrected system active power command and the total photovoltaic active power reference value is determined as the total energy storage active power command.

[0151] In some embodiments, the inverter current control module 500 is used for:

[0152] Determine the proportion of the state of charge of each energy storage unit to the sum of the states of charge of all energy storage units, and allocate the total active power command of energy storage according to the proportion to obtain the active power allocation value of each energy storage current control inverter.

[0153] Based on the active power allocation value, the amplitude of the common coupling point voltage, and the preset power factor angle, determine the current amplitude command for the corresponding energy storage current control inverter;

[0154] The difference between the phase angle of the common coupling point voltage and the preset power factor angle is determined as the current phase angle command for the corresponding energy storage current control inverter.

[0155] Generate the corresponding AC current reference value for the energy storage current control inverter based on the current amplitude command and the current phase angle command;

[0156] The AC current reference value is compared with the actual output current of the corresponding energy storage current control inverter to obtain the current tracking deviation. The current tracking deviation is then adjusted by a proportional resonant controller to obtain the current modulation signal.

[0157] The current modulation signal is sinusoidally pulse-width modulated to generate the switching drive signal of the H-bridge inverter circuit in the corresponding energy storage current control inverter, so that the actual output current tracks the AC current reference value and controls the energy storage current control inverter to output AC current in the form of a current source.

[0158] In some embodiments, the inverter current control module 500 is used for:

[0159] Calculate the sum of the states of charge of all energy storage units;

[0160] Determine the ratio of the state of charge of each energy storage unit to the sum of its states of charge;

[0161] Based on the ratio corresponding to each energy storage unit, the total active power of the energy storage is allocated according to the command, and the active power allocation value of each energy storage current control inverter is obtained.

[0162] like Figure 10 As shown, this application provides an electronic device 10, which includes a memory 20 and a processor 30. The memory 20 stores a computer program. When the computer program is executed by the processor 30, the processor 30 performs the steps of the hybrid grid control method for the cascaded photovoltaic energy storage grid-connected inverter system as described in the above embodiment.

[0163] This application provides a computer-readable storage medium storing a computer program thereon. When the computer program is executed, it implements the steps of the hybrid grid control method for the cascaded photovoltaic energy storage grid-connected inverter system as described in the above embodiments.

[0164] This application provides a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium. The computer program includes program instructions, wherein when the program instructions are executed by a computer, the computer performs the steps of the hybrid grid control method for the cascaded photovoltaic energy storage grid-connected inverter system as described in the above embodiments.

[0165] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, electronic devices, computer storage media, and computer program products described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0166] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0167] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0168] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0169] In the several embodiments provided by this invention, it should be understood that the disclosed systems, electronic devices, computer storage media, computer program products, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, indirect coupling or communication connection between devices or units, and may be electrical, mechanical, or other forms.

[0170] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0171] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0172] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for executing all or part of the steps of the methods described in the various embodiments of the present invention through a computer device (which may be a personal computer, a server, or a network device, etc.). The aforementioned storage medium includes: USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, optical disks, and other media capable of storing program code.

[0173] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A hybrid grid control method for a cascaded photovoltaic energy storage grid-connected inverter system, characterized in that, The method includes: Obtain the common coupling point voltage and grid frequency corresponding to each energy storage current control inverter, and obtain the DC side voltage, output active power, and grid-connected current flowing through the multiple photovoltaic voltage control inverters. The DC side voltage reference value is determined based on the maximum power point of the photovoltaic unit corresponding to each photovoltaic voltage control inverter. The active power reference value is determined based on the deviation between the DC side voltage and the DC side voltage reference value. The output voltage amplitude command of each photovoltaic voltage control inverter is determined based on the deviation between the active power reference value and the output active power. The fundamental frequency phase angle is extracted from the grid-connected current. The output voltage phase angle command of each photovoltaic voltage control inverter is determined according to the fundamental frequency phase angle. Based on the output voltage amplitude command and the output voltage phase angle command, each photovoltaic voltage control inverter is controlled to output AC voltage in the form of a voltage source. The system active power command is corrected according to the grid frequency, and the total active power command of energy storage is determined according to the corrected system active power command and the active power reference value of each photovoltaic voltage control inverter. The total active power command of energy storage is allocated according to the state of charge of each energy storage unit to obtain the current amplitude command of each energy storage current control inverter. The current phase angle command of each energy storage current control inverter is determined according to the phase angle of the common coupling point voltage, so as to control each energy storage current control inverter to output AC current in the form of a current source according to the current amplitude command and the current phase angle command.

2. The hybrid grid control method for a cascaded photovoltaic energy storage grid-connected inverter system according to claim 1, characterized in that, The process of determining a DC-side voltage reference value based on the maximum power point of the photovoltaic unit corresponding to each photovoltaic voltage-controlled inverter, determining an active power reference value based on the deviation between the DC-side voltage and the DC-side voltage reference value, and determining the output voltage amplitude command of each photovoltaic voltage-controlled inverter based on the deviation between the active power reference value and the output active power includes: Maximum power point tracking is performed based on the photovoltaic side voltage and photovoltaic side current of the photovoltaic unit corresponding to each photovoltaic voltage control inverter to obtain the DC side voltage reference value corresponding to the maximum power point of the photovoltaic unit; The deviation between the DC-side voltage and the DC-side voltage reference value is adjusted proportionally and integrally to obtain the active power reference value of the corresponding photovoltaic voltage control inverter. The output voltage amplitude feedforward is determined based on the active power reference value, the fundamental frequency amplitude of the grid-connected current, and the preset power factor angle, and the output voltage amplitude correction is determined based on the deviation between the active power reference value and the output active power. The output voltage amplitude feedforward and the output voltage amplitude correction are superimposed to obtain the output voltage amplitude command of the corresponding photovoltaic voltage control inverter.

3. The hybrid grid control method for a cascaded photovoltaic energy storage grid-connected inverter system according to claim 1, characterized in that, The step of extracting the fundamental frequency phase angle from the grid-connected current, determining the output voltage phase angle command of each photovoltaic voltage control inverter based on the fundamental frequency phase angle, and controlling each photovoltaic voltage control inverter to output AC voltage in the form of a voltage source based on the output voltage amplitude command and the output voltage phase angle command includes: Each photovoltaic voltage-controlled inverter extracts the fundamental frequency component of the locally collected grid-connected current to obtain the fundamental frequency phase angle of the grid-connected current; The fundamental frequency phase angle of the grid-connected current is superimposed with the preset power factor angle to obtain the output voltage phase angle command of the corresponding photovoltaic voltage control inverter; An AC voltage reference value is generated based on the output voltage amplitude command and the output voltage phase angle command; The AC voltage reference value is compared with the actual output voltage of the corresponding photovoltaic voltage control inverter to obtain the output voltage deviation. The output voltage deviation is then adjusted through the voltage outer loop to obtain the AC current reference value. The AC current reference value is compared with the actual output current of the corresponding photovoltaic voltage control inverter to obtain the output current deviation, and the output current deviation is adjusted through the current inner loop to obtain the voltage modulation signal. The voltage modulation signal is pulse-width modulated to generate a switching drive signal for the H-bridge inverter circuit in the photovoltaic voltage control inverter, so that the actual output voltage of the photovoltaic voltage control inverter tracks the AC voltage reference value and outputs AC voltage in the form of a voltage source.

4. The hybrid grid control method for a cascaded photovoltaic energy storage grid-connected inverter system according to claim 1, characterized in that, The step of correcting the system active power command based on the grid frequency, and determining the total active power command for energy storage based on the corrected system active power command and the active power reference values ​​of each photovoltaic voltage-controlled inverter, includes: Determine the frequency deviation between the power grid frequency and the rated power grid frequency, as well as the rate of change of the power grid frequency over time; The damping power correction amount is determined based on the frequency deviation and the preset damping coefficient, and the inertia power correction amount is determined based on the rate of change of the power grid frequency over time and the preset virtual inertia coefficient. The system active power command at the rated frequency is corrected by using the damping power correction amount and the inertia power correction amount to obtain the corrected system active power command. The active power reference values ​​of each photovoltaic voltage-controlled inverter are summed to obtain the total photovoltaic active power reference value, and the power difference between the corrected system active power command and the total photovoltaic active power reference value is determined as the total energy storage active power command.

5. The hybrid grid control method for a cascaded photovoltaic energy storage grid-connected inverter system according to claim 1, characterized in that, The process of allocating the total active power command of energy storage according to the state of charge of each energy storage unit to obtain the current amplitude command of each energy storage current control inverter, and determining the current phase angle command of each energy storage current control inverter according to the phase angle of the common coupling point voltage, so as to control each energy storage current control inverter to output AC current in the form of a current source according to the current amplitude command and the current phase angle command, includes: Determine the proportion of the state of charge of each energy storage unit to the sum of the states of charge of all energy storage units, and allocate the total active power command of the energy storage according to the proportion to obtain the active power allocation value of each energy storage current control inverter. Based on the active power allocation value, the amplitude of the common coupling point voltage, and the preset power factor angle, determine the current amplitude command for the corresponding energy storage current control inverter; The difference between the phase angle of the common coupling point voltage and the preset power factor angle is determined as the current phase angle command for the corresponding energy storage current control inverter. Generate the corresponding AC current reference value for the energy storage current control inverter based on the current amplitude command and the current phase angle command; The AC current reference value is compared with the actual output current of the corresponding energy storage current control inverter to obtain the current tracking deviation, and the current tracking deviation is adjusted by a proportional resonant controller to obtain a current modulation signal. The current modulation signal is sinusoidally pulse-width modulated to generate a switching drive signal for the H-bridge inverter circuit in the corresponding energy storage current control inverter, so that the actual output current tracks the AC current reference value and controls the energy storage current control inverter to output AC current in the form of a current source.

6. The hybrid grid control method for a cascaded photovoltaic energy storage grid-connected inverter system according to claim 5, characterized in that, The process of determining the proportion of the state of charge (SBC) of each energy storage unit to the sum of the SBCs of all energy storage units, and allocating the total active power command of energy storage according to the proportion to obtain the active power allocation value for each energy storage current-controlled inverter, includes: Calculate the sum of the states of charge of all energy storage units; Determine the ratio of the state of charge of each energy storage unit to the sum of the states of charge; The total active power command for energy storage is allocated according to the ratio corresponding to each energy storage unit, thereby obtaining the active power allocation value of each energy storage current control inverter.

7. A hybrid grid control system for a cascaded photovoltaic energy storage grid-connected inverter system, characterized in that, The system includes: The data acquisition module is used to acquire the common coupling point voltage and grid frequency corresponding to each energy storage current control inverter, and to acquire the DC side voltage, output active power and grid-connected current flowing through the multiple photovoltaic voltage control inverters. The voltage command generation module is used to determine the DC side voltage reference value based on the maximum power point of the photovoltaic unit corresponding to each photovoltaic voltage control inverter, determine the active power reference value based on the deviation between the DC side voltage and the DC side voltage reference value, and determine the output voltage amplitude command of each photovoltaic voltage control inverter based on the deviation between the active power reference value and the output active power. The inverter voltage control module is used to extract the fundamental frequency phase angle from the grid-connected current, determine the output voltage phase angle command of each photovoltaic voltage control inverter according to the fundamental frequency phase angle, and control each photovoltaic voltage control inverter to output AC voltage in the form of a voltage source according to the output voltage amplitude command and the output voltage phase angle command. The power command generation module is used to correct the system active power command according to the grid frequency, and to determine the total active power command of energy storage according to the corrected system active power command and the active power reference value of each photovoltaic voltage control inverter. The inverter current control module is used to allocate the total active power command of energy storage according to the state of charge of each energy storage unit, obtain the current amplitude command of each energy storage current control inverter, and determine the current phase angle command of each energy storage current control inverter according to the phase angle of the common coupling point voltage, so as to control each energy storage current control inverter to output AC current in the form of a current source according to the current amplitude command and the current phase angle command.

8. An electronic device, characterized in that, The electronic device includes a memory and a processor. The memory stores a computer program. When the computer program is executed by the processor, the processor performs the steps of the hybrid grid control method for a cascaded photovoltaic energy storage grid-connected inverter system as described in any one of claims 1-6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed, it implements the steps of the hybrid grid control method for a cascaded photovoltaic energy storage grid-connected inverter system as described in any one of claims 1-6.

10. A computer program product, characterized in that, The computer program product includes a computer program stored on a non-transitory computer-readable storage medium, the computer program including program instructions, wherein when the program instructions are executed by a computer, the computer performs the steps of the hybrid grid control method for a cascaded photovoltaic energy storage grid-connected inverter system as described in any one of claims 1-6.

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