Self-adaptive virtual resistance control method and device for voltage source converter

Abstract

The invention discloses a self-adaptive virtual resistance control method and device for a voltage source converter in the technical field of power electronics, and the method comprises the steps: building a system simplification model and a droop control model of the converter based on a voltage amplitude adjustment strategy; acquiring a transmission power function and a droop control function based on the system simplification model and the droop control model; quantitatively analyzing a limit power angle based on the transmission power function and the droop control function, and acquiring a system critical reference voltage based on the limit power angle; when the converter has voltage drop and the voltage drop is greater than the critical reference voltage of the system, adding adaptive virtual resistance control; the self-adaptive virtual resistor control comprises the following steps of: adding a self-adaptive virtual resistor between a voltage and current double-closed-loop control module and a droop control module by considering an influence rule of a resistor at a grid-connected part on voltage when a power grid absorbs or releases active power to a converter; the transient stability of the converter can be realized through the control strategy.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to an adaptive virtual resistance control method and device for a voltage source converter. Background Art

[0002] In order to reduce carbon emissions and meet the growing demand for energy, the penetration of renewable energy in the power system continues to rise. Usually, renewable energy interacts with the grid through power electronic converters with current source characteristics, which are called grid-connected converters. The increasing capacity of grid-connected converters poses challenges to the control and stable operation of power systems. Due to its voltage source characteristics, voltage source converters can support grid operation like synchronous generators and provide voltage and frequency support for the grid. Therefore, voltage source converters can well solve the problems of grid-connected converters and are an effective way to achieve large-scale friendly grid connection of new energy. However, when a large disturbance occurs, the voltage source converter may lose its stability point and lose synchronization with the grid. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide an adaptive virtual resistance control method and device for a voltage source converter to solve the technical problem that the voltage source converter may lose its stability point and lose synchronization with the power grid when a large disturbance occurs.

[0004] To achieve the above object, the present invention is implemented by adopting the following technical solutions: In a first aspect, the present invention provides an adaptive virtual resistance control method for a voltage source converter, comprising: Based on the voltage amplitude regulation strategy, a simplified system model and droop control model of the converter are established; Acquire a transmission power function and a droop control function based on the simplified system model and the droop control model; quantitatively analyzing a limit power angle based on the transmission power function and the droop control function, and acquiring a system critical reference voltage based on the limit power angle; When a voltage drop occurs in the converter, and the voltage drop is greater than the critical reference voltage of the system, an adaptive virtual resistance control is added; the adaptive virtual resistance control includes: Considering the influence of the grid-connected resistance on the voltage when the grid absorbs or releases active power to the converter, an adaptive virtual resistor is added between the voltage and current dual closed-loop control module and the droop control module.

[0005] Optionally, the transmission power function is obtained based on the simplified model of the system, and its expression is: ; In the formula, is the AC side voltage and active power of the converter, is the grid voltage, is the phase difference between the converter and the grid, are the grid resistance and grid reactance; The droop control function is obtained based on the droop control model, and its expression is: ; ; In the formula, is the grid angular frequency, is the droop gain of active power control and reactive power control, is the AC side reference voltage and reference active power of the converter, is the system reference voltage, is the AC side reactive power of the converter and the reference reactive power.

[0006] Optionally, the quantitatively analyzing the limit power angle based on the transmission power function and the droop control function includes: In the critical stable state, let the maximum value of the AC side active power of the converter be equal to its reference active power, and obtain the limit power angle: ; ; In the formula, The maximum active power on the AC side Equal to its reference active power The corresponding limit power angle is, The maximum active power on the AC side Equal to its reference active power The corresponding limit power angle is, They are The maximum active power on the AC side at They are The maximum value of the AC side reference active power at ; Obtaining a system critical reference voltage according to the limit power angle and the transfer function: ; ; ; ; ; In the formula, They are The corresponding system critical reference voltage.

[0007] Optionally, the method for adaptively determining the value of the virtual resistance includes: when When adding a virtual resistor We can get: ; ; In the formula, is the power angle after adding the virtual resistance; Setting the resistance Starting from 0 and increasing gradually, we get Follow Varying curve; according to Curve determination The resistance corresponding to the maximum value , and then calculate the virtual resistance ; when When adding a virtual resistor We can get: ; Setting the resistance Starting from 0 and increasing gradually, we get Follow Varying curve; according to Curve determination The resistance corresponding to the maximum value , and then calculate the virtual resistance .

[0008] In a second aspect, the present invention provides an adaptive virtual resistance control device for a voltage source converter, comprising: A model building module is configured to build a system simplified model and a droop control model of the converter based on a voltage amplitude regulation strategy; A function generation module, configured to obtain a transmission power function and a droop control function based on the system simplified model and the droop control model; a critical analysis module, configured to quantitatively analyze a limit power angle based on the transmission power function and the droop control function, and obtain a system critical reference voltage based on the limit power angle; The judgment control module is configured to add adaptive virtual resistance control when a voltage drop occurs in the converter and the voltage drop is greater than the critical reference voltage of the system; the adaptive virtual resistance control includes: Considering the influence of the grid-connected resistance on the voltage when the grid absorbs or releases active power to the converter, an adaptive virtual resistor is added between the voltage and current dual closed-loop control module and the droop control module.

[0009] Optionally, the quantitatively analyzing the limit power angle based on the transmission power function and the droop control function includes: In the critical stable state, let the maximum active power of the AC side of the converter be equal to its reference active power, and obtain the limit power angle: ; ; In the formula, The maximum active power on the AC side Equal to its reference active power The corresponding limit power angle is, The maximum active power on the AC side Equal to its reference active power The corresponding limit power angle is They are The maximum active power on the AC side at They are The maximum value of the AC side reference active power at ; Obtaining a system critical reference voltage according to the limit power angle and the transfer function: ; ; ; ; ; In the formula, They are The corresponding system critical reference voltage.

[0010] Optionally, the method for adaptively determining the value of the virtual resistance includes: when When adding a virtual resistor We can get: ; ; In the formula, is the power angle after adding the virtual resistance; Setting the resistance Starting from 0 and increasing gradually, we get Follow Varying curve; according to Curve determination The resistance corresponding to the maximum value , and then calculate the virtual resistance ; when When adding a virtual resistor We can get: ; Setting the resistance Starting from 0 and increasing gradually, we get Follow Varying curve; according to Curve determination The resistance corresponding to the maximum value , and then calculate the virtual resistance .

[0011] In a third aspect, the present invention provides an electronic device, including a processor and a storage medium; The storage medium is used to store instructions; The processor is used to operate according to the instructions to execute the steps according to the above method.

[0012] In a fourth aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, which implements the steps of the above method when executed by a processor.

[0013] In a fifth aspect, the present invention provides a computer program product, comprising a computer program / instruction, which implements the steps of the above method when executed by a processor.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides an adaptive virtual resistance control method and device for a voltage source converter. According to the influence of voltage control parameters on active power, factors affecting the transient stability of the voltage source converter, such as voltage, power angle and grid resistance, are quantitatively analyzed. An adaptive virtual resistance is added between the voltage and current dual closed-loop module and the droop control module, thereby affecting the voltage amplitude and improving the transient stability of the system, so that the converter remains stable under large disturbances, and there is no need to connect any additional power circuit components. The invention has a good impact prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic diagram of a control structure of a voltage source converter provided by an embodiment of the present invention; Figure 2is a flow chart of an adaptive virtual resistance control method for a voltage source converter provided by an embodiment of the present invention; Figure 3 is a structural diagram of a simplified system model of a converter provided by an embodiment of the present invention; Figure 4 is a structural diagram of a P-ω droop control method provided by an embodiment of the present invention; Figure 5 is a structural diagram of a QV droop control method provided by an embodiment of the present invention; Figure 6 It is a structural diagram of a simplified system model of a converter with virtual resistance added provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0016] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0017] Embodiment 1:

[0018] The voltage source converter consists of a DC voltage source, a three-phase full-bridge inverter and a low-pass output LC filter. Figure 1 As shown, the control structure of the voltage source converter includes a multi-loop control structure of an active power loop, a reactive power loop, an inner current loop and an outer voltage loop. The active power loop can obtain the phase angle of the system, the reactive power loop can obtain the reference voltage of the system, and the active power loop and the reactive power loop can adopt droop control. The voltage loop and the current loop can use traditional proportional integral controllers respectively. This embodiment introduces an adaptive virtual resistor into the above control structure to achieve the transient stability of the enhanced converter, so that the voltage source converter can still be stable when the grid voltage drops.

[0019] like Figure 2 As shown, the present invention provides an adaptive virtual resistance control method for a voltage source converter, comprising the following steps: Step S1: Based on the voltage amplitude regulation strategy, a simplified system model and a droop control model of the converter are established.

[0020] The simplified system model of the converter is as follows: Figure 3 As shown in Figure 2, the droop control model includes the active power loop and the reactive power loop, as shown in Figure 4 and Figure 5 shown.

[0021] Step S2: acquiring a transmission power function and a droop control function based on the simplified system model and the droop control model.

[0022] The transmission power function is obtained based on the simplified system model, and its expression is: ; In the formula, is the AC side voltage and active power of the converter, is the grid voltage, is the phase difference between the converter and the grid, are the grid resistance and grid reactance; The droop control function is obtained based on the droop control model, and its expression is: ; ; In the formula, is the grid angular frequency, is the droop gain of active power control and reactive power control, is the AC side reference voltage and reference active power of the converter, is the system reference voltage, is the AC side reactive power of the converter and the reference reactive power.

[0023] Step S3: quantitatively analyzing the limit power angle based on the transmission power function and the droop control function, and obtaining the system critical reference voltage based on the limit power angle. The specific process includes: In the critical stable state, let the maximum value of the AC side active power of the converter be equal to its reference active power, and obtain the limit power angle: ; ; In the formula, The maximum active power on the AC side Equal to its reference active power The corresponding limit power angle is, The maximum active power on the AC side Equal to its reference active power The corresponding limit power angle is, They are The maximum active power on the AC side at They are The maximum value of the AC side reference active power at ; When the converter voltage drops, if the system has a balance point, the system is stable, and if the system does not have a balance point, the system is unstable. Therefore, there will be a critical voltage. If the voltage drop is greater than the critical voltage, the system is stable, and if the voltage drop is less than the critical voltage, the system is unstable. If the voltage drop is less than the critical voltage, it means that the system is unstable and an adaptive virtual resistor needs to be added to increase the stability of the system.

[0024] Obtain the system critical reference voltage based on the limit power angle and transfer function: ; ; ; ; ; In the formula, They are The corresponding system critical reference voltage.

[0025] Step S4: When the converter voltage drops and the voltage drop is greater than the critical reference voltage of the system, adaptive virtual resistance control is added; the adaptive virtual resistance control includes: Considering the influence of the grid-connected resistance on the voltage when the grid absorbs or releases active power to the converter, an adaptive virtual resistor is added between the voltage and current double closed-loop control module and the droop control module, such as Figure 6 shown.

[0026] The adaptive value selection method of the virtual resistance includes: (1) When When the grid absorbs active power from the converter, a virtual resistor is added. We can get: ; ; In the formula, is the power angle after adding the virtual resistance; Setting the resistance Starting from 0 and increasing gradually, we get Follow Varying curve; according to Curve determination The resistance corresponding to the maximum value , and then calculate the virtual resistance ; make , can be obtained ; when , ,at this time Follow When , ,at this time Follow Increase and decrease. hour, Maximum, then .

[0027] (2) When When adding a virtual resistor We can get: ; Follow The increase is first negative and then positive.

[0028] Setting the resistance Starting from 0 and increasing gradually, we get Follow Varying curve; according to Curve determination The resistance corresponding to the maximum value , and then calculate the virtual resistance .

[0029] In order to verify the superiority of the control method provided by the present invention, simulation analysis is carried out in MATLAB / simulink, and the system parameters are shown in Table 1.

[0030] Table 1: System parameters

[0031] Simulation results: When no adaptive virtual resistance is added, after the voltage drops, the waveforms of the converter voltage Vg, active power Pg, and system frequency ωg all oscillate, and the system becomes unstable; when an adaptive virtual resistance is added, after the voltage drops, the active power Pg stabilizes again after a short oscillation, and ωg can also reach a new stable state after a short oscillation, and the system stabilizes again after a short oscillation.

[0032] Embodiment 2: An embodiment of the present invention provides an adaptive virtual resistance control device for a voltage source converter, comprising: A model building module is configured to build a system simplified model and a droop control model of the converter based on a voltage amplitude regulation strategy; A function generation module is configured to obtain a transmission power function and a droop control function based on a simplified system model and a droop control model; A critical analysis module is configured to quantitatively analyze the limit power angle based on the transmission power function and the droop control function, and obtain a system critical reference voltage based on the limit power angle; The judgment control module is configured to add adaptive virtual resistance control when a voltage drop occurs in the converter and the voltage drop is greater than the critical reference voltage of the system; the adaptive virtual resistance control includes: Considering the influence of the grid-connected resistance on the voltage when the grid absorbs or releases active power to the converter, an adaptive virtual resistor is added between the voltage and current dual closed-loop control module and the droop control module.

[0033] Specifically, the transmission power function is obtained based on the simplified system model, and its expression is: ; In the formula, is the AC side voltage and active power of the converter, is the grid voltage, is the phase difference between the converter and the grid, are the grid resistance and grid reactance.

[0034] Specifically, the droop control function is obtained based on the droop control model, and its expression is: ; ; In the formula, is the grid angular frequency, is the droop gain of active power control and reactive power control, is the AC side reference voltage and reference active power of the converter, is the system reference voltage, is the AC side reactive power of the converter and the reference reactive power.

[0035] Specifically, the quantitative analysis of the limit power angle based on the transmission power function and the droop control function includes: In the critical stable state, let the maximum active power of the AC side of the converter be equal to its reference active power, and obtain the limit power angle: ; ; In the formula, The maximum active power on the AC side Equal to its reference active power The corresponding limit power angle is The maximum active power on the AC side Equal to its reference active power The corresponding limit power angle is They are The maximum active power on the AC side at They are The maximum value of the AC side reference active power at ; Obtain the system critical reference voltage based on the limit power angle and transfer function: ; ; ; ; ; In the formula, They are The corresponding system critical reference voltage.

[0036] Specifically, the adaptive value determination method of the virtual resistance includes: when When adding a virtual resistor We can get: ; ; In the formula, is the power angle after adding the virtual resistance; Setting the resistance Starting from 0 and increasing gradually, we get Follow Varying curve; according to Curve determination The resistance corresponding to the maximum value , and then calculate the virtual resistance ; when When adding a virtual resistor We can get: ; Setting the resistance Starting from 0 and increasing gradually, we get Follow Varying curve; according to Curve determination The resistance corresponding to the maximum value , and then calculate the virtual resistance .

[0037] Embodiment three: Based on the adaptive virtual resistance control method provided in the first embodiment, an embodiment of the present invention provides an electronic device, including a processor and a storage medium; The storage medium is used to store instructions; The processor is used to operate according to the instructions to execute the steps according to the above method.

[0038] Embodiment 4:

[0039] Based on the adaptive virtual resistance control method provided in the first embodiment, an embodiment of the present invention provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the steps of the above method are implemented.

[0040] Embodiment five:

[0041] Based on the adaptive virtual resistance control method provided in the first embodiment, an embodiment of the present invention provides a computer program product, including a computer program / instruction, which implements the steps of the above method when executed by a processor.

[0042] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0043] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0044] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0045] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An adaptive virtual resistance control method for a voltage source converter, characterized in that: include: Based on the voltage amplitude regulation strategy, a simplified system model and droop control model of the converter are established; Acquire a transmission power function and a droop control function based on the simplified system model and the droop control model; quantitatively analyzing a limit power angle based on the transmission power function and the droop control function, and acquiring a system critical reference voltage based on the limit power angle; When a voltage drop occurs in the converter, and the voltage drop is greater than the critical reference voltage of the system, an adaptive virtual resistance control is added; The adaptive virtual resistance control comprises: Considering the influence of the grid-connected resistance on the voltage when the grid absorbs or releases active power to the converter, an adaptive virtual resistor is added between the voltage and current dual closed-loop control module and the droop control module.

2. The adaptive virtual resistance control method of a voltage source converter according to claim 1, characterized in that: The transmission power function is obtained based on the simplified model of the system, and its expression is: ； In the formula, is the AC side voltage and active power of the converter, is the grid voltage, is the phase difference between the converter and the grid, are the grid resistance and grid reactance; The droop control function is obtained based on the droop control model, and its expression is: ； ； In the formula, is the grid angular frequency, is the droop gain of active power control and reactive power control, is the AC side reference voltage and reference active power of the converter, is the system reference voltage, is the AC side reactive power of the converter and the reference reactive power.

3. The adaptive virtual resistance control method of a voltage source converter according to claim 2, characterized in that: The quantitative analysis of the limit power angle based on the transmission power function and the droop control function comprises: In the critical stable state, let the maximum value of the AC side active power of the converter be equal to its reference active power, and obtain the limit power angle: ； ； In the formula, The maximum active power on the AC side Equal to its reference active power The corresponding limit power angle is The maximum active power on the AC side Equal to its reference active power The corresponding limit power angle is, They are The maximum active power on the AC side at They are The maximum value of the reference active power on the AC side at ; Obtaining a system critical reference voltage according to the limit power angle and the transfer function: ； ； ； ； ； In the formula, They are The corresponding system critical reference voltage.

4. The adaptive virtual resistance control method of a voltage source converter according to claim 3, characterized in that: The method for adaptively determining the value of the virtual resistor includes: when When adding a virtual resistor We can get: ； ； In the formula, is the power angle after adding the virtual resistance; Setting the resistance Starting from 0 and increasing gradually, we get Follow Varying curve; according to Curve determination The resistance corresponding to the maximum value , and then calculate the virtual resistance ; when When adding a virtual resistor We can get: ； Setting the resistance Starting from 0 and increasing gradually, we get Follow Varying curve; according to Curve determination The resistance corresponding to the maximum value , and then calculate the virtual resistance .

5. An adaptive virtual resistance control device for a voltage source converter, characterized in that: include: A model building module is configured to build a system simplified model and a droop control model of the converter based on a voltage amplitude regulation strategy; A function generation module, configured to obtain a transmission power function and a droop control function based on the system simplified model and the droop control model; a critical analysis module, configured to quantitatively analyze a limit power angle based on the transmission power function and the droop control function, and obtain a system critical reference voltage based on the limit power angle; A judgment control module is configured to add adaptive virtual resistance control when a voltage drop occurs in the converter and the voltage drop is greater than the critical reference voltage of the system; The adaptive virtual resistance control comprises: Considering the influence of the grid-connected resistance on the voltage when the grid absorbs or releases active power to the converter, an adaptive virtual resistor is added between the voltage and current dual closed-loop control module and the droop control module.

6. The adaptive virtual resistance control device for a voltage source converter according to claim 5, characterized in that: The quantitative analysis of the limit power angle based on the transmission power function and the droop control function comprises: In the critical stable state, let the maximum value of the AC side active power of the converter be equal to its reference active power, and obtain the limit power angle: ； ； In the formula, The maximum active power on the AC side Equal to its reference active power The corresponding limit power angle is, The maximum active power on the AC side Equal to its reference active power The corresponding limit power angle is, They are The maximum active power on the AC side at They are The maximum value of the reference active power on the AC side at ; Obtaining a system critical reference voltage according to the limit power angle and the transfer function: ； ； ； ； ； In the formula, They are The corresponding system critical reference voltage.

7. The adaptive virtual resistance control device for a voltage source converter according to claim 5, characterized in that: The method for adaptively determining the value of the virtual resistor includes: when When adding a virtual resistor We can get: ； ； In the formula, is the power angle after adding the virtual resistance; Setting the resistance Starting from 0 and increasing gradually, we get Follow Varying curve; according to Curve determination The resistance corresponding to the maximum value , and then calculate the virtual resistance ; when When adding a virtual resistor We can get: ； Setting the resistance Starting from 0 and increasing gradually, we get Follow Varying curve; according to Curve determination The resistance corresponding to the maximum value , and then calculate the virtual resistance .

8. An electronic device, characterized in that: including processor and storage medium; The storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the steps of the method according to any one of claims 1 to 4.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 4 are implemented.

10. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by a processor, the steps of the method according to any one of claims 1 to 4 are implemented.

Images