Energy storage converter parallel operation method, system and equipment and storage medium

Abstract

The invention relates to an energy storage converter parallel operation method, system and device and a storage medium, and belongs to the technical field of energy storage converter parallel operation, and the method comprises the steps: collecting three-phase voltage and current data of an energy storage converter side and a power grid side; according to the collected voltage and current data, actual active power and actual reactive power are obtained through calculation; calculating an output voltage and an output frequency according to the actual active power and the actual reactive power; carrying out DQ conversion on the output voltage, and converting the output voltage into a voltage given value under a DQ coordinate; the virtual impedance of the output line is calculated according to the voltage given value, the calculated virtual impedance is superposed to the voltage given value, and the final voltage input quantity is obtained; carrying out double closed-loop control of a voltage and current loop on the given value of the input voltage to generate a modulation wave; and generating a PWM signal of the switching tube according to the generated modulation wave, and controlling the conduction of the switching tube by the PWM signal so as to control the output power of the energy storage converter.

Description

Technical Field

[0001] The present invention relates to the technical field of parallel operation of energy storage converters, and in particular to a method, system, device and storage medium for parallel operation of energy storage converters. Background Art

[0002] Energy storage systems are generally composed of energy storage converters and batteries, where the battery is directly or indirectly connected to the DC bus through a DC / DC unit, and the energy storage converter is an inverter module composed of single-phase or three-phase bridge arms, which connects the DC bus and the AC grid or load to realize the battery charging and discharging function. With the development of energy storage systems, the demand for power and capacity of energy storage systems is increasing, but the rated power of the switching devices of energy storage converters is often limited by technical or economic factors. Therefore, multiple energy storage converters are usually used in parallel to increase system capacity.

[0003] There are many ways to operate multiple energy storage converters in parallel in current projects, which can be mainly divided into the following types: 1. Centralized: An external controller is used as the upper control unit of the multi-energy storage converter. The energy storage converter sends the operation information to the external controller, which then performs power distribution and current regulation based on the current power demand. 2. Master-slave type: There is no external controller. Any energy storage converter is selected as the master, and the other energy storage converters are used as slaves. The selected energy storage converter distributes power to the slaves in the form of a voltage source and provides a reference voltage. The slaves exist in the form of a current source. The master and slaves work together to supply power to the load or the grid. 3. Distributed: Each energy storage converter is equivalent to a host, and a communication network is established between multiple energy storage converters. Each energy storage converter obtains information from other energy storage converters through the communication network, and calculates the average power and average current of multiple energy storage converters to determine its own output power. 4. Droop control: The energy storage converter simulates the external characteristics of the synchronous generator to change the power. When the energy storage system changes, each energy storage converter can dynamically adjust its own power output according to the droop curve. By adjusting its own output voltage amplitude and frequency, the entire energy storage system moves from the original operating point to a new steady-state operating point.

[0004] Among the above methods, centralized, master-slave and decentralized methods all require the use of external controllers or external communication systems to transmit operating information in real time when realizing power and current distribution of parallel machines. In actual engineering applications, there are problems such as complex structure, increased cost and limited application scenarios. In addition, when problems occur in the external controller or external communication system, the energy storage system will not work properly. However, droop control does not rely on the assistance of external communication systems or external controllers, is simple and effective, saves costs, and is a good parallel machine solution.

[0005] However, the traditional droop control method uses a fixed power curve for change, and there is an impedance inconsistency problem in the energy storage converter, which will cause uneven power distribution in the energy storage converter. Summary of the invention

[0006] The object of the present invention is to provide a method, system, device and storage medium for parallel operation of energy storage converters to solve the above-mentioned technical problems.

[0007] In order to achieve the above object, the present invention provides the following technical solutions: In a first aspect, a method for parallel operation of an energy storage converter is provided, the method comprising: Step S1: Collecting three-phase voltage and three-phase current data on the grid side; Step S2: Calculate the actual active power and the actual reactive power on the grid side according to the collected three-phase voltage and three-phase current data on the grid side; Step S3: Calculate the output voltage and the output angular frequency of the grid side according to the actual active power and the actual reactive power of the grid side; Step S4: performing DQ transformation on the output voltage of the grid side, and transforming the output voltage of the grid side into a voltage given value under the DQ coordinate of the grid side; Step S5: Calculate the virtual impedance of the output line on the grid side according to the voltage given value under the DQ coordinate of the grid side, and superimpose the calculated virtual impedance of the output line on the grid side on the voltage given value under the DQ coordinate to obtain the final input voltage under the DQ coordinate of the grid side; Step S6: performing dual closed-loop control of the voltage and current loops on the final input voltage under the DQ coordinates on the grid side to generate a modulation wave; Step S7: Generate a PWM signal according to the generated modulation wave, and adjust the conduction of the switch tube of the energy storage converter by the PWM signal, so as to control the output power of the energy storage converter and realize the parallel operation of the energy storage converter.

[0008] Furthermore, in step S2, the actual active power and the actual reactive power of the grid side are calculated based on the collected three-phase voltage and three-phase current data of the grid side, including: Step S21: performing Clarke transformation and Park transformation on the collected three-phase voltage and three-phase current on the grid side to obtain the voltage and current components of the three-phase voltage and three-phase current on the grid side in DQ coordinates; The Clarke transformation formula is: ,

[0009] In the formula, Indicates the collected phase a voltage on the grid side. Indicates the collected b-phase voltage on the grid side. Indicates the collected c-phase voltage on the grid side, Indicates the collected a-phase current on the grid side, Indicates the collected b-phase current on the grid side, Indicates the collected c-phase current on the grid side, It represents the voltage component of the three-phase voltage on the grid side under the α-axis in the stationary coordinate system, It represents the voltage component of the three-phase voltage on the grid side under the β axis in the stationary coordinate system, It represents the voltage component of the three-phase voltage on the grid side under the 0 axis in the stationary coordinate system. It represents the current component of the three-phase current on the grid side under the α-axis in the stationary coordinate system, It represents the current component of the three-phase current on the grid side under the β axis in the stationary coordinate system, It represents the current component of the three-phase current on the grid side under the 0 axis in the stationary coordinate system; The formula for the Park transform is: ,

[0010] In the formula, It represents the voltage component of the three-phase voltage on the grid side under the d-axis in the rotating coordinate system, It represents the voltage component of the three-phase voltage on the grid side under the q-axis in the rotating coordinate system. It represents the voltage component of the three-phase voltage on the grid side under the 0 axis in the rotating coordinate system. It represents the current component of the three-phase current on the grid side under the d-axis in the rotating coordinate system, It represents the current component of the three-phase current on the grid side under the q-axis in the rotating coordinate system, It represents the current component of the three-phase current on the grid side under the 0 axis in the rotating coordinate system. is the actual angular frequency on the grid side; Step S22: Calculate the actual active power and actual reactive power on the grid side. The calculation formula is:

[0011] In the formula, Indicates the actual active power on the grid side, Indicates the actual reactive power on the grid side.

[0012] Furthermore, in step S3, the output voltage and output angular frequency of the grid side are calculated according to the actual active power and the actual reactive power of the grid side, including: Step S31: Calculate the active power deviation on the grid side, the calculation formula is:

[0013] In the formula, Indicates the active power deviation on the grid side. Indicates the actual active power on the grid side. Indicates the expected active power on the grid side; Step S32: Calculate the reactive power deviation on the grid side, the calculation formula is:

[0014] In the formula, Indicates the reactive power deviation on the grid side, Indicates the actual reactive power on the grid side, represents the expected reactive power on the grid side; Step S33: calculating the output voltage of the grid side and the output angular frequency of the grid side based on the reactive power deviation of the grid side and the active power deviation of the grid side; The calculation formula of the output angular frequency on the grid side is: ,

[0015] In the formula, represents the output angular frequency on the grid side, Indicates the output frequency on the grid side, Indicates the given frequency on the grid side, represents the frequency adjustment coefficient, Represents the proportional coefficient of the output frequency in PI control, Indicates the integral coefficient of the output frequency in PI control, represents the complex variable in the Laplace transform, Indicates the actual frequency on the grid side, Indicates the given frequency on the grid side; Calculate the output voltage on the grid side:

[0016] In the formula, Indicates the output voltage on the grid side, Indicates the given voltage on the grid side, represents the voltage regulation coefficient, Represents the proportional coefficient of the output voltage in PI control, Represents the integral coefficient of the output voltage in PI control, Indicates the average value of the output reactive power on the grid side.

[0017] Further, step S4: performing DQ transformation on the output voltage of the grid side, transforming the output voltage of the grid side into a voltage given value under the DQ coordinate of the grid side, includes: Construct the DQ transformation matrix, the DQ transformation matrix is:

[0018] in, is the voltage given value under the d-axis in the DQ coordinate on the grid side, is the voltage given value under the q axis in the DQ coordinate on the grid side, It is the voltage given value at the 0 axis in the DQ coordinate on the grid side.

[0019] Further, step S5: calculating the virtual impedance of the output line on the grid side according to the voltage given value under the DQ coordinate of the grid side, superimposing the calculated virtual impedance of the output line on the grid side to the voltage given value under the DQ coordinate, and obtaining the final input voltage under the DQ coordinate of the grid side, including: Step S51: Calculate the virtual impedance of the output line on the grid side, the calculation formula is:

[0020] In the formula, Represents the virtual impedance of the output line on the grid side, Represents the impedance of the output line on the grid side, Indicates the inductive reactance of the output line on the grid side, represents a complex variable in the Laplace transform; Step S52: superimpose the virtual impedance of the output line on the grid side onto the voltage given value on the d-axis under the DQ coordinate on the grid side , and obtain the voltage given value under the d-axis in the DQ coordinate after adding the virtual impedance of the output line on the grid side , that is, the final input voltage under the d-axis under the DQ coordinate on the grid side, and its expression is:

[0021] in, is the virtual impedance of the output line on the grid side, is the proportional coefficient of PI control, is the integral coefficient of PI control, is the output reactive power given value on the grid side; Step S53: superimpose the virtual impedance of the output line on the grid side onto the voltage given value on the q axis in the DQ coordinate , and obtain the voltage given value under the q axis in the DQ coordinate after adding the virtual impedance of the output line on the grid side , that is, the final input voltage under the q-axis in the DQ coordinate on the grid side, and its expression is:

[0022] in, is the proportional coefficient of PI control, is the integral coefficient of PI control.

[0023] In a second aspect, a parallel operation system of an energy storage converter is provided, the system comprising: A sensor unit, used to collect three-phase voltage and three-phase current data on the grid side; The PQ calculation unit is used to calculate the actual active power and the actual reactive power on the grid side according to the collected three-phase voltage and three-phase current data on the grid side; The droop controller is used to calculate the output voltage and the output angular frequency of the grid side according to the actual active power and the actual reactive power of the grid side; A DQ conversion unit, used for performing DQ conversion on the output voltage of the grid side, and converting the output voltage of the grid side into a voltage given value under the DQ coordinate of the grid side; An adaptive virtual impedance controller is used to calculate the virtual impedance of the output line on the grid side according to the voltage given value under the DQ coordinate of the grid side, and superimpose the calculated virtual impedance of the output line on the grid side to the voltage given value under the DQ coordinate to obtain the final input voltage under the DQ coordinate of the grid side; A dual closed-loop control unit is used to perform dual closed-loop control of the voltage and current loops on the final input voltage under the DQ coordinates on the grid side to generate a modulation wave; The PWM modulation controller is used to generate a PWM signal from the generated modulation wave, and the conduction of the switch tube of the energy storage converter is adjusted by the PWM signal, so as to control the output power of the energy storage converter and realize the parallel operation of the energy storage converter.

[0024] Furthermore, the sensor unit includes a voltage sensor and a current Hall sensor.

[0025] Furthermore, the PWM modulation controller adopts SPWM or SVPWM.

[0026] According to a third aspect, a terminal is provided, the terminal comprising: processor; A memory for storing execution instructions of the processor; The processor is configured to execute the methods described in the above aspects. In a fourth aspect, a computer-readable storage medium storing a computer program is provided, wherein when the program is executed by a processor, the methods described in the above aspects are implemented.

[0027] The beneficial effects of the invention are as follows: the output voltage and angular frequency of the grid side are calculated according to the active power and reactive power, and then the subsequent processing is performed, so that the voltage and frequency of the grid side can be better controlled to meet the requirements of parallel operation, and the reliability and adaptability of the system are improved. The virtual impedance of the output line on the grid side is calculated and superimposed on the voltage set value, which helps to enhance the stability of the system, overcome the problem of inconsistent impedance and reduce the problem of circulating current, and improve the overall efficiency and reliability of the parallel system; The use of dual closed-loop control of the voltage and current loop to process the final input voltage can improve the dynamic response and stability of the system, enable the output power of the energy storage converter to quickly and accurately track the given value, and enhance the system's anti-interference ability.

[0028] These and other objects, features and advantages of the present invention will be fully reflected in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of the grid-connected system structure of the energy storage converter parallel operation system of the present invention is shown.

[0030] Figure 2 The schematic diagram of the structure of the droop controller of the energy storage converter parallel operation system of the present invention is shown.

[0031] Figure 3 The schematic diagram of the structure of the dual closed-loop control unit of the energy storage converter parallel operation system of the present invention is shown. DETAILED DESCRIPTION

[0032] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art can think of other obvious variations. The basic principles of the present invention defined in the following description can be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not deviate from the spirit and scope of the present invention.

[0033] It should be understood by those skilled in the art that, in the disclosure of the specification, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device including a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices. Therefore, the above terms should not be understood as limiting the present invention.

[0034] refer to Figures 1 to 3A method for parallel operation of an energy storage converter according to a preferred embodiment of the present invention will be described in detail below, wherein a method for parallel operation of an energy storage converter comprises steps S1 to S7: Step S1: Collect three-phase voltage and three-phase current data on the grid side.

[0035] Step S2: Calculate the actual active power and the actual reactive power on the grid side based on the collected three-phase voltage and three-phase current data on the grid side.

[0036] Step S3: Calculate the output voltage and the output angular frequency of the grid side according to the actual active power and the actual reactive power of the grid side.

[0037] Step S4: Perform DQ transformation on the output voltage on the grid side, and transform the output voltage on the grid side into a voltage given value under the DQ coordinates on the grid side.

[0038] Step S5: Calculate the virtual impedance of the output line on the grid side according to the voltage given value under the DQ coordinate on the grid side, and superimpose the calculated virtual impedance of the output line on the grid side on the voltage given value under the DQ coordinate to obtain the final input voltage under the DQ coordinate on the grid side.

[0039] Step S6: Perform dual closed-loop control of the voltage and current loops on the final input voltage under the DQ coordinates on the grid side to generate a modulation wave.

[0040] Step S7: Generate a PWM signal according to the generated modulation wave, and adjust the conduction of the switch tube of the energy storage converter by the PWM signal, so as to control the output power of the energy storage converter and realize the parallel operation of the energy storage converter.

[0041] The output voltage and angular frequency on the grid side are calculated based on the active power and reactive power, and subsequent processing can better control the voltage and frequency on the grid side to meet the requirements of parallel operation and improve the reliability and adaptability of the system.

[0042] Calculating the virtual impedance of the grid-side output line and adding it to the voltage setpoint helps to enhance system stability, reduce circulating current problems, and improve the overall efficiency and reliability of the parallel system.

[0043] The use of dual closed-loop control of the voltage and current loop to process the final input voltage can improve the dynamic response and stability of the system, enable the output power of the energy storage converter to quickly and accurately track the given value, and enhance the system's anti-interference ability.

[0044] Exemplarily, in step S2, the actual active power and the actual reactive power of the grid side are calculated based on the collected three-phase voltage and three-phase current data of the grid side, including: Step S21: Clarke transform and Park transform are performed on the collected three-phase voltage and three-phase current on the grid side to obtain the voltage and current components of the three-phase voltage and three-phase current on the grid side in DQ coordinates.

[0045] The Clarke transformation formula is: ,

[0046] In the formula, Indicates the collected a-phase voltage on the grid side. Indicates the collected b-phase voltage on the grid side, Indicates the collected c-phase voltage on the grid side, Indicates the collected a-phase current on the grid side, Indicates the collected b-phase current on the grid side, Indicates the collected c-phase current on the grid side, It represents the voltage component of the three-phase voltage on the grid side under the α-axis in the stationary coordinate system, It represents the voltage component of the three-phase voltage on the grid side under the β axis in the stationary coordinate system, It represents the voltage component of the three-phase voltage on the grid side under the 0 axis in the stationary coordinate system. It represents the current component of the three-phase current on the grid side under the α-axis in the stationary coordinate system, It represents the current component of the three-phase current on the grid side under the β axis in the stationary coordinate system, It represents the current component of the three-phase current on the grid side under the 0 axis in the stationary coordinate system.

[0047] The formula for the Park transform is: ,

[0048] In the formula, It represents the voltage component of the three-phase voltage on the grid side under the d-axis in the rotating coordinate system, It represents the voltage component of the three-phase voltage on the grid side under the q-axis in the rotating coordinate system. It represents the voltage component of the three-phase voltage on the grid side under the 0 axis in the rotating coordinate system. It represents the current component of the three-phase current on the grid side under the d-axis in the rotating coordinate system, It represents the current component of the three-phase current on the grid side under the q-axis in the rotating coordinate system, It represents the current component of the three-phase current on the grid side under the 0 axis in the rotating coordinate system. is the actual angular frequency on the grid side.

[0049] Step S22: Calculate the actual active power and actual reactive power on the grid side. The calculation formula is:

[0050] In the formula, Indicates the actual active power on the grid side. Indicates the actual reactive power on the grid side.

[0051] For example, in combination Figure 2 In step S3, the output voltage and output angular frequency of the grid side are calculated according to the actual active power and actual reactive power of the grid side, including: Step S31: Calculate the active power deviation on the grid side, the calculation formula is:

[0052] In the formula, Indicates the active power deviation on the grid side. Indicates the actual active power on the grid side. Indicates the expected active power on the grid side.

[0053] Step S32: Calculate the reactive power deviation on the grid side, the calculation formula is:

[0054] In the formula, Indicates the reactive power deviation on the grid side, Indicates the actual reactive power on the grid side, represents the expected reactive power on the grid side; Step S33: Calculate the output voltage of the grid side and the output angular frequency of the grid side based on the reactive power deviation of the grid side and the active power deviation of the grid side.

[0055] The calculation formula of the output angular frequency on the grid side is: ,

[0056] In the formula, represents the output angular frequency on the grid side, Indicates the output frequency on the grid side, Indicates the given frequency on the grid side, represents the frequency adjustment coefficient, Represents the proportional coefficient of the output frequency in PI control, Indicates the integral coefficient of the output frequency in PI control, represents the complex variable in the Laplace transform, Indicates the actual frequency on the grid side, Indicates the given frequency on the grid side.

[0057] Calculate the output voltage on the grid side:

[0058] In the formula, Indicates the output voltage on the grid side, Indicates the given voltage on the grid side, represents the voltage regulation coefficient, Represents the proportional coefficient of the output voltage in PI control, Represents the integral coefficient of the output voltage in PI control, Indicates the average value of the output reactive power on the grid side.

[0059] It can be understood that the PI control in this embodiment refers to a PI controller.

[0060] Exemplarily, step S4: performing DQ transformation on the output voltage of the grid side to transform the output voltage of the grid side into a given voltage value under the DQ coordinate of the grid side includes: Construct the DQ transformation matrix, the DQ transformation matrix is:

[0061] in, is the voltage given value under the d-axis in the DQ coordinate on the grid side, is the voltage given value under the q axis in the DQ coordinate on the grid side, It is the voltage given value at the 0 axis in the DQ coordinate on the grid side.

[0062] Exemplarily, step S5: calculating the virtual impedance of the output line on the grid side according to the voltage given value under the DQ coordinate of the grid side, superimposing the calculated virtual impedance of the output line on the grid side to the voltage given value under the DQ coordinate, and obtaining the final input voltage under the DQ coordinate of the grid side, includes: Step S51: Calculate the virtual impedance of the output line on the grid side, the calculation formula is:

[0063] In the formula, Represents the virtual impedance of the output line on the grid side, Represents the impedance of the output line on the grid side, Indicates the inductive reactance of the output line on the grid side, represents a complex variable in the Laplace transform.

[0064] Step S52: superimpose the virtual impedance of the output line on the grid side onto the voltage given value on the d-axis under the DQ coordinate on the grid side , and obtain the voltage given value under the d-axis in the DQ coordinate after adding the virtual impedance of the output line on the grid side , that is, the final input voltage under the d-axis under the DQ coordinate on the grid side, and its expression is:

[0065] in, is the voltage given value under the d-axis in the DQ coordinate after adding the virtual impedance of the output line on the grid side, that is, the final input voltage under the d-axis in the DQ coordinate on the grid side, is the virtual impedance of the output line on the grid side, is the proportional coefficient of PI control, is the integral coefficient of PI control, It is the output reactive power given value on the grid side.

[0066] Step S53: superimpose the virtual impedance of the output line on the grid side onto the voltage given value on the q axis in the DQ coordinate , and obtain the voltage given value under the q axis in the DQ coordinate after adding the virtual impedance of the output line on the grid side , that is, the final input voltage under the q-axis in the DQ coordinate on the grid side, and its expression is:

[0067] in, is the voltage given value under the q-axis in the DQ coordinate after adding the virtual impedance of the output line on the grid side, that is, the final input voltage under the q-axis in the DQ coordinate on the grid side, is the proportional coefficient of PI control, is the integral coefficient of PI control.

[0068] The present invention also provides a parallel operation system of an energy storage converter, the system comprising: The sensor unit is used to collect the three-phase voltage and three-phase current data on the grid side.

[0069] The PQ calculation unit is used to calculate the actual active power and actual reactive power on the grid side according to the collected three-phase voltage and three-phase current data on the grid side.

[0070] The droop controller is used to calculate the output voltage and the output angular frequency of the grid side according to the actual active power and the actual reactive power of the grid side.

[0071] The DQ conversion unit is used to perform DQ conversion on the output voltage of the grid side, and convert the output voltage of the grid side into a voltage given value under the DQ coordinate of the grid side.

[0072] The adaptive virtual impedance controller is used to calculate the virtual impedance of the output line on the grid side according to the voltage given value under the DQ coordinate of the grid side, and superimpose the calculated virtual impedance of the output line on the grid side to the voltage given value under the DQ coordinate to obtain the final input voltage under the DQ coordinate of the grid side.

[0073] The dual closed-loop control unit is used to perform dual closed-loop control of the voltage and current loops on the final input voltage under the DQ coordinates on the grid side to generate a modulation wave. The dual closed-loop control unit adopts an existing dual closed-loop controller, which consists of a voltage outer loop and a current inner loop. For the final input voltage under the d-axis under the DQ coordinates on the grid side obtained by the adaptive virtual impedance controller, , the final input voltage under the q axis under the DQ coordinate on the grid side , the voltage outer loop formed by PI controller can be expressed by the following expression:

[0074] in is the current loop given value under the d-axis in the DQ coordinate, is the given value of the current loop under the q axis in the DQ coordinate, is the decoupling value of the reactor capacitance.

[0075] After the current loop given value is calculated by the voltage outer loop, the reference voltage of the dq axis modulation wave can be obtained by the following formula:

[0076] in is the component of the output modulation wave under the d-axis in the DQ coordinate, is the component of the output modulation wave under the q axis in the DQ coordinate, is the current sampling value of the energy storage converter under the d-axis in the DQ coordinate, is the current sampling value of the energy storage converter under the q axis in the DQ coordinate, is the inductance decoupling value of the reactor.

[0077] Then, according to the following dq inverse transformation formula, , Changes to the required PWM three-phase modulation wave , , .

[0078]

[0079] The dual closed-loop control unit consists of a voltage outer loop and a current inner loop. After the current loop output is superimposed with the feedforward, the switch tube modulation wave is obtained through the dq axis inverse transformation. , , It is the output PWM reference modulation wave.

[0080] The PWM modulation controller is used to generate a PWM signal from the generated modulation wave, and the conduction of the switch tube of the energy storage converter is adjusted by the PWM signal, so as to control the output power of the energy storage converter and realize the parallel operation of the energy storage converter.

[0081] Exemplarily, the sensor unit includes a voltage sensor and a current Hall sensor. The primary winding of the voltage sensor is connected in parallel to the three-phase power line on the grid side, and the secondary winding output signal of the voltage sensor is transmitted to the PQ calculation unit for calculation. The voltage sensor is used to obtain the three-phase voltage data on the grid side. The appropriate voltage sensor type is selected according to the range, accuracy requirements and working environment of the measured voltage. In this embodiment, a Hall effect voltage sensor is used. When in use, the primary winding of the voltage sensor is connected in parallel to the three-phase power line on the grid side. In this embodiment, the first end of the primary winding of the voltage sensor is connected to the phase line of the three-phase power line on the grid side, and the second end of the primary winding of the voltage sensor is connected to the neutral line of the three-phase power line on the grid side to measure the voltage on the three-phase power line on the grid side. Then, the secondary winding of the voltage sensor is connected to the PQ calculation unit for calculation.

[0082] The magnetic core sleeve of the current Hall sensor is arranged on the three-phase electric line on the grid side, and the signal output signal of the current Hall sensor is transmitted to the PQ calculation unit to participate in the calculation. The current Hall sensor is used to obtain the three-phase current data on the grid side. When in use, the current Hall sensor is installed in the three-phase circuit on the grid side. Specifically, the magnetic core sleeve of the current Hall sensor is arranged on the three-phase electric line on the grid side to realize contactless current measurement. An external power supply is provided to power the current Hall sensor. When in use, the external power supply is connected to the power pin of the current Hall sensor. At the same time, the signal output pin of the current Hall sensor is connected to the input port of the PQ calculation unit.

[0083] Exemplarily, the PWM modulation controller adopts SPWM or SVPWM.

[0084] The present invention also provides a terminal, comprising: processor; A memory for storing execution instructions of the processor; The processor is configured to execute the methods described in the above embodiments. The present invention also provides a computer-readable storage medium storing a computer program, which implements the methods described in the above embodiments when executed by a processor.

[0085] It should be understood by those skilled in the art that the embodiments of the present invention described above and shown in the accompanying drawings are only examples and do not limit the present invention. The advantages of the present invention have been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and explained in the embodiments, and the embodiments of the present invention may be deformed or modified in any way without departing from the principles.

Claims

1. A method for parallel connection of energy storage converters, characterized in that: The method comprises: Step S1: Collecting three-phase voltage and three-phase current data on the grid side; Step S2: Calculate the actual active power and the actual reactive power on the grid side according to the collected three-phase voltage and three-phase current data on the grid side; Step S3: Calculate the output voltage and the output angular frequency of the grid side according to the actual active power and the actual reactive power of the grid side; Step S4: performing DQ transformation on the output voltage of the grid side, and transforming the output voltage of the grid side into a voltage given value under the DQ coordinate of the grid side; Step S5: Calculate the virtual impedance of the output line on the grid side according to the voltage given value under the DQ coordinate of the grid side, and superimpose the calculated virtual impedance of the output line on the grid side on the voltage given value under the DQ coordinate to obtain the final input voltage under the DQ coordinate of the grid side; Step S6: performing dual closed-loop control of the voltage and current loops on the final input voltage under the DQ coordinates on the grid side to generate a modulation wave; Step S7: Generate a PWM signal according to the generated modulation wave, and adjust the conduction of the switch tube of the energy storage converter by the PWM signal, so as to control the output power of the energy storage converter and realize the parallel operation of the energy storage converter.

2. The method according to claim 1, characterized in that In step S2, the actual active power and the actual reactive power of the grid side are calculated based on the collected three-phase voltage and three-phase current data of the grid side, including: Step S21: performing Clarke transformation and Park transformation on the collected three-phase voltage and three-phase current on the grid side to obtain the voltage and current components of the three-phase voltage and three-phase current on the grid side in DQ coordinates; The Clarke transformation formula is: ， In the formula, Indicates the collected a-phase voltage on the grid side. Indicates the collected b-phase voltage on the grid side. Indicates the collected c-phase voltage on the grid side, Indicates the collected a-phase current on the grid side, Indicates the collected b-phase current on the grid side, Indicates the collected c-phase current on the grid side, It represents the voltage component of the three-phase voltage on the grid side under the α-axis in the stationary coordinate system, It represents the voltage component of the three-phase voltage on the grid side under the β axis in the stationary coordinate system, It represents the voltage component of the three-phase voltage on the grid side under the 0 axis in the stationary coordinate system. It represents the current component of the three-phase current on the grid side under the α-axis in the stationary coordinate system, It represents the current component of the three-phase current on the grid side under the β axis in the stationary coordinate system, It represents the current component of the three-phase current on the grid side under the 0 axis in the stationary coordinate system; The formula for the Park transform is: ， In the formula, It represents the voltage component of the three-phase voltage on the grid side under the d-axis in the rotating coordinate system, It represents the voltage component of the three-phase voltage on the grid side under the q-axis in the rotating coordinate system. It represents the voltage component of the three-phase voltage on the grid side under the 0 axis in the rotating coordinate system. It represents the current component of the three-phase current on the grid side under the d-axis in the rotating coordinate system, It represents the current component of the three-phase current on the grid side under the q-axis in the rotating coordinate system, It represents the current component of the three-phase current on the grid side under the 0 axis in the rotating coordinate system. is the actual angular frequency on the grid side; Step S22: Calculate the actual active power and actual reactive power on the grid side. The calculation formula is: In the formula, Indicates the actual active power on the grid side, Indicates the actual reactive power on the grid side.

3. The method according to claim 2, characterized in that In step S3, the output voltage and output angular frequency of the grid side are calculated according to the actual active power and actual reactive power of the grid side, including: Step S31: Calculate the active power deviation on the grid side, the calculation formula is: In the formula, Indicates the active power deviation on the grid side, Indicates the actual active power on the grid side, Indicates the expected active power on the grid side; Step S32: Calculate the reactive power deviation on the grid side, the calculation formula is: In the formula, Indicates the reactive power deviation on the grid side, Indicates the actual reactive power on the grid side, represents the expected reactive power on the grid side; Step S33: calculating the output voltage of the grid side and the output angular frequency of the grid side based on the reactive power deviation of the grid side and the active power deviation of the grid side; The calculation formula of the output angular frequency on the grid side is: ， In the formula, represents the output angular frequency on the grid side, Indicates the output frequency on the grid side, Indicates the given frequency on the grid side, represents the frequency adjustment coefficient, Represents the proportional coefficient of the output frequency in PI control, Indicates the integral coefficient of the output frequency in PI control, represents the complex variable in the Laplace transform, Indicates the actual frequency on the grid side, Indicates the given frequency on the grid side; Calculate the output voltage on the grid side: In the formula, Indicates the output voltage on the grid side, Indicates the given voltage on the grid side, represents the voltage regulation coefficient, Represents the proportional coefficient of the output voltage in PI control, Represents the integral coefficient of the output voltage in PI control, Indicates the average value of the output reactive power on the grid side.

4. The method according to claim 3, characterized in that Step S4: performing DQ transformation on the output voltage of the grid side to transform the output voltage of the grid side into a voltage given value under the DQ coordinate of the grid side, including: Construct the DQ transformation matrix, the DQ transformation matrix is: in, is the voltage given value under the d-axis in the DQ coordinate on the grid side, is the voltage given value under the q axis in the DQ coordinate on the grid side, It is the voltage given value at the 0 axis in the DQ coordinate on the grid side.

5. The method according to claim 1, characterized in that Step S5: Calculate the virtual impedance of the output line on the grid side according to the voltage given value under the DQ coordinate of the grid side, and superimpose the calculated virtual impedance of the output line on the grid side on the voltage given value under the DQ coordinate to obtain the final input voltage under the DQ coordinate of the grid side, including: Step S51: Calculate the virtual impedance of the output line on the grid side, the calculation formula is: In the formula, Represents the virtual impedance of the output line on the grid side, Represents the impedance of the output line on the grid side, Indicates the inductive reactance of the output line on the grid side, represents a complex variable in the Laplace transform; Step S52: superimpose the virtual impedance of the output line on the grid side onto the voltage given value on the d-axis under the DQ coordinate on the grid side , and obtain the voltage given value under the d-axis in the DQ coordinate after adding the virtual impedance of the output line on the grid side , that is, the final input voltage under the d-axis under the DQ coordinate on the grid side, and its expression is: in, is the virtual impedance of the output line on the grid side, is the proportional coefficient of PI control, is the integral coefficient of PI control, is the output reactive power given value on the grid side; Step S53: superimpose the virtual impedance of the output line on the grid side onto the voltage given value on the q axis in the DQ coordinate , and obtain the voltage given value under the q axis in the DQ coordinate after adding the virtual impedance of the output line on the grid side , that is, the final input voltage under the q-axis under the DQ coordinate on the grid side, and its expression is: in, is the virtual impedance of the output line on the grid side, is the proportional coefficient of PI control, is the integral coefficient of PI control.

6. An energy storage converter parallel system, characterized in that: The system comprises: A sensor unit, used to collect three-phase voltage and three-phase current data on the grid side; The PQ calculation unit is used to calculate the actual active power and the actual reactive power on the grid side according to the collected three-phase voltage and three-phase current data on the grid side; The droop controller is used to calculate the output voltage and the output angular frequency of the grid side according to the actual active power and the actual reactive power of the grid side; A DQ conversion unit, used for performing DQ conversion on the output voltage of the grid side, and converting the output voltage of the grid side into a voltage given value under the DQ coordinate of the grid side; An adaptive virtual impedance controller is used to calculate the virtual impedance of the output line on the grid side according to the voltage given value under the DQ coordinate of the grid side, and superimpose the calculated virtual impedance of the output line on the grid side to the voltage given value under the DQ coordinate to obtain the final input voltage under the DQ coordinate of the grid side; A dual closed-loop control unit is used to perform dual closed-loop control of the voltage and current loops on the final input voltage under the DQ coordinates on the grid side to generate a modulation wave; The PWM modulation controller is used to generate a PWM signal from the generated modulation wave, and the conduction of the switch tube of the energy storage converter is adjusted by the PWM signal, so as to control the output power of the energy storage converter and realize the parallel operation of the energy storage converter.

7. The system according to claim 6, characterized in that The sensor unit includes a voltage sensor and a current Hall sensor.

8. The system according to claim 7, characterized in that The PWM modulation controller adopts SPWM or SVPWM.

9. A terminal, characterized in that: The terminal comprises: processor; A memory for storing execution instructions of the processor; The processor is configured to execute the method according to any one of claims 1 to 5.

10. A computer-readable storage medium storing a computer program, characterized in that: When the program is executed by a processor, the method according to any one of claims 1 to 5 is implemented.

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