Grid-connected converter power optimization control method and system based on improved VOC

Abstract

The invention discloses an improved VOC-based grid-connected converter power optimization control method and system, and relates to the technical field of grid-connected converter control, and the method comprises the steps: obtaining the output voltage, current and angular frequency of a three-phase grid-connected converter in real time; according to the output voltage and the output current, a current deviation value is obtained through calculation, and after current scaling, the current deviation value is multiplied by a self-adaptive rotation angle matrix to obtain a current source and a voltage source; wherein according to the output voltage and the output angular frequency, the rotation angle is adaptively and dynamically adjusted to change the variation trend of the voltage and the angular frequency, and the active power and the reactive power are decoupled; a current source and a voltage source are input into a virtual oscillation controller, inductive current and capacitive voltage are output, voltage regulation values are obtained after voltage scaling, a converter switch control signal is obtained through PWM modulation, and stable control over the output power of the converter is achieved. Accurate tracking of the voltage and frequency of the grid-connected point and the output power of the grid-connected converter can be ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of grid-connected converter control, and in particular to a grid-connected converter power optimization control method and system based on improved VOC. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] With the aggravation of environmental pollution and the depletion of fossil energy, clean and renewable energy such as solar energy and wind energy have received widespread attention, and the proportion of new energy access to the power grid has gradually increased. However, since distributed generation is mostly located in remote areas, the transmission lines are long and there are many transformers, the power grid exhibits weak grid characteristics, and as the proportion of distributed generation increases, multiple converters are often operated in parallel to meet the load requirements. Under this condition, the equivalent grid impedance of a single converter increases, and the weak grid characteristics of the power grid are significant. Wind abandonment, solar abandonment and power grid failures caused by weak grids occur frequently. In addition, high-penetration new energy generation is intermittent, random and has output fluctuations. The grid impedance and grid strength often fluctuate greatly, which seriously threatens the safe and stable operation of the power grid and new energy power generation systems. To this end, grid-connected converters and their control strategies are introduced in new energy power generation systems such as micro energy, distributed generation, energy storage, AC / DC microgrids, etc. to achieve stable system operation.

[0004] Traditional grid-connected converters mainly adopt grid-following control or grid-forming control. Grid-following control adjusts the output of active and reactive power based on the grid phase, which is suitable for strong grids, but the stability margin is reduced in weak grids, which may cause harmonic resonance or even instability; grid-forming control directly adjusts the output power by controlling the output voltage vector phase, which is more stable in weak grids, but unstable in strong grids. That is, the traditional grid-following control or grid-forming control has poor stability in weak grids and strong grids, respectively, and it is difficult to adapt to the variable grid strength working conditions. In addition, the traditional grid-forming control also has power tracking problems, which may lead to a decrease in the efficiency of the new energy grid-connected system.

[0005] In the prior art, there is a virtual oscillator control (VOC) control strategy for grid-connected converters of renewable energy generation under large fluctuations in grid strength and high penetration, which is based on the dynamic characteristics of the Andronov-Hopf oscillator (AHO) to provide stable voltage and frequency output in both strong and weak grids. However, this method mainly adopts static parameter design with a fixed rotation angle, which leads to inherent coupling between active and reactive power regulation, and cannot achieve independent tracking of power instructions. It may cause a significant deviation between the actual output power of the converter and the reference instruction, causing chain hazards such as frequency / voltage instability, reduced power generation revenue, and limited new energy consumption, and cannot achieve system control with both stability and economy. Summary of the invention

[0006] In order to solve the deficiencies of the above-mentioned prior art, the present invention provides a power optimization control method and system for a grid-connected converter based on an improved VOC, establishes a converter control architecture based on a virtual oscillator, and designs a power optimization control method based on an adaptive rotation angle on the basis of the architecture, which can achieve fast and smooth correction when the converter output power deviates from the reference. At the same time, according to the droop characteristics of VOC, the changing trends of voltage and frequency are directly adjusted based on the adaptive rotation angle, thereby controlling the converter output power, ensuring accurate tracking of the grid-connected point voltage and frequency, and the output power of the grid-connected converter, and taking into account both system stability and grid-connected output efficiency.

[0007] In a first aspect, the present invention provides a power optimization control method for a grid-connected converter based on improved VOC.

[0008] A power optimization control method for a grid-connected converter based on improved VOC, comprising: Obtain the output voltage, current and angular frequency of the three-phase grid-connected converter in real time; According to the output voltage and the output current, the current deviation value is calculated, and after the current deviation value is current scaled, it is multiplied by the adaptive rotation angle matrix to obtain the current source and the voltage source; wherein, according to the output voltage and the output angular frequency, the rotation angle is adaptively and dynamically adjusted to change the variation trend of the voltage and the angular frequency, and the active power and the reactive power are decoupled; The current source and the voltage source are input into the virtual oscillation controller, the inductor current and the capacitor voltage are output, and the voltage adjustment value is obtained after voltage scaling; PWM modulation is performed according to the voltage adjustment value to obtain the converter switch control signal, thereby achieving stable control of the converter output power.

[0009] A further technical solution is that the dynamic adjustment of the adaptive rotation angle is: The output voltage amplitude and the voltage amplitude reference value, the output angular frequency and the angular frequency reference value are respectively input into corresponding comparators, and a comparison result is output; wherein four different comparison results are generated according to the difference between the two sets of input values; Based on the comparison result output, according to the mapping relationship between the comparison result and the rotation angle value, the sine and cosine components of the rotation angle are calculated to complete the dynamic adjustment of the rotation angle.

[0010] In a second aspect, the present invention provides a power optimization control system for a grid-connected converter based on improved VOC.

[0011] A power optimization control system for a grid-connected converter based on improved VOC, comprising: A data acquisition module is used to obtain the output voltage, current and angular frequency of the three-phase grid-connected converter in real time; The voltage and current regulation module is used to calculate the current deviation value according to the output voltage and the output current. After the current deviation value is current scaled, it is multiplied by the adaptive rotation angle matrix to obtain the current source and the voltage source; wherein, according to the output voltage and the output angular frequency, the rotation angle is adaptively and dynamically adjusted to change the variation trend of the voltage and the angular frequency, and the active power and the reactive power are decoupled; A virtual oscillation adjustment module is used to input a current source and a voltage source into a virtual oscillation controller, output an inductor current and a capacitor voltage, and then obtain a voltage adjustment value after voltage scaling; The power optimization control module is used to perform PWM modulation according to the voltage adjustment value to obtain the converter switch control signal and realize stable control of the converter output power.

[0012] In a third aspect, the present invention further provides an electronic device, comprising: a memory for storing executable instructions; and a processor for implementing the above-mentioned grid-connected converter power optimization control method based on improved VOC when executing the executable instructions stored in the memory.

[0013] In a fourth aspect, the present invention further provides a computer-readable storage medium storing executable instructions for causing a processor to execute the executable instructions to implement the above-mentioned grid-connected converter power optimization control method based on improved VOC.

[0014] In a fifth aspect, the present invention also provides a computer program product, which includes executable instructions stored in a computer-readable storage medium; wherein, when a processor of an electronic device reads the executable instructions from the computer-readable storage medium and executes the executable instructions, the above-mentioned grid-connected converter power optimization control method based on improved VOC is implemented.

[0015] One or more of the above technical solutions have the following beneficial effects: 1. The present invention provides a power optimization control method and system for a grid-connected converter based on an improved VOC, establishes a converter control architecture based on a virtual oscillator, and designs a power optimization control method based on an adaptive rotation angle on the basis of the architecture, which can achieve fast and smooth correction when the converter output power deviates from the reference. At the same time, according to the droop characteristics of VOC, the voltage and frequency change trends are directly adjusted based on the adaptive rotation angle, thereby controlling the converter output power, ensuring accurate tracking of the grid-connected point voltage and frequency, and the grid-connected converter output power, and taking into account both system stability and grid-connected output efficiency.

[0016] 2. In the present invention, according to the droop characteristics of VOC, the coordinated mapping relationship between output power and voltage and frequency is utilized to set the sine and cosine components of the rotation angle. By dynamically adjusting the rotation angle to change the changing trend of voltage and frequency, active and reactive power decoupling is achieved, thereby effectively improving the stability and economy of the grid-connected converter under the condition of grid strength fluctuation. The whole scheme is simple, effective and conducive to engineering implementation.

[0017] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0019] Figure 1 It is an overall flow chart of the power optimization control method of the grid-connected converter based on the improved VOC according to the embodiment of the present invention; Figure 2 It is a structural diagram of power optimization control of a grid-connected converter based on improved VOC in an embodiment of the present invention; Figure 3 FIG. 4 is a schematic diagram of an adaptive adjustment of a rotation angle according to an embodiment of the present invention. DETAILED DESCRIPTION

[0020] It should be noted that the following detailed descriptions are exemplary only, are intended to describe specific embodiments, are intended to provide further explanation of the present invention, and are not intended to limit exemplary embodiments according to the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those of ordinary skill in the art to which the present invention belongs. In addition, it should also be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0021] It should be clear that the existing virtual oscillator control strategy of the grid-connected converter is: based on a given power reference value and , combined with instantaneous current calculation, the output current reference value is obtained and The reference value is subtracted from the instantaneous current measurement value, and then scaled and added to the rotation angle matrix Multiply them together to get a set of input signals for the virtual oscillator and , the inductor current output after being processed by the virtual oscillator is scaled and PWM modulated to obtain the switch control signal of the grid-connected converter, thereby realizing the control of the converter. However, considering the above-mentioned existing grid-connected converter control strategy based on the virtual oscillation controller VOC, it adopts a constant rotation angle to couple active power and reactive power, that is, it is impossible to control active power and reactive power at the same time, which may cause a significant deviation between the actual output power of the converter and the reference instruction, causing chain hazards such as frequency and voltage instability, reduced power generation income, and limited new energy consumption. To solve this problem, the present invention proposes a power optimization control method for a grid-connected converter based on an improved virtual oscillation controller VOC, which utilizes the coordinated mapping relationship between output power and voltage and frequency, dynamically adjusts the rotation angle to change the change trend of voltage and frequency, realizes the decoupling of active and reactive power, and then controls the output power of the converter, thereby ensuring the accurate tracking of the voltage and frequency at the grid connection point and the output power of the grid-connected converter, taking into account the system stability and grid-connected output efficiency, and effectively improving the stability of the converter and the grid-connected power quality in the new energy grid-connected power generation system.

[0022] Embodiment 1 This embodiment provides a power optimization control method for a grid-connected converter based on improved VOC, such as Figure 1 As shown, the specific steps include: Step S1, obtaining the output voltage, current and angular frequency of the three-phase grid-connected converter in real time; Step S2, according to the output voltage and the output current, the current deviation value is calculated, and after the current deviation value is current scaled, it is multiplied by the adaptive rotation angle matrix to obtain the current source and the voltage source; wherein, according to the output voltage and the output angular frequency, the rotation angle is adaptively and dynamically adjusted to change the variation trend of the voltage and the angular frequency, and the active power and the reactive power are decoupled; Step S3, inputting the current source and the voltage source into the virtual oscillation controller, outputting the inductor current and the capacitor voltage, and then obtaining the voltage adjustment value after voltage scaling; Step S4: Perform PWM modulation according to the voltage adjustment value to obtain a converter switch control signal to achieve stable control of the converter output power.

[0023] The following content introduces the power optimization control method of the grid-connected converter based on the improved VOC proposed in this embodiment in more detail.

[0024] The core point of the method proposed in this embodiment is: based on the VOC control architecture, a power optimization control method based on adaptive rotation angle is designed to ensure accurate tracking of the grid connection point voltage / frequency and the grid-connected converter output power. Specifically, the grid-connected converter virtual oscillator control structure proposed in this embodiment is as follows: Figure 2 As shown, the physical part (i.e., the converter grid-connected physical system) includes a DC source , three-phase bridge PWM inverter, filter inductor And filter capacitor The LC filter and grid-side inductor and AC power grid, the main body of the control part is the AHO oscillator, and its virtual circuit model includes: (1) Inductor and capacitor The resonant LC circuit consists of a natural resonant frequency Equal to the grid angular frequency, ,inductance The current on the inductor is the inductor current ,capacitance The capacitor voltage on ; (2) Nonlinearly related preset voltage source and preset current source , , ,in, , , , are steady-state convergence speed and oscillation amplitude, respectively; (3) Input current source and input voltage source .

[0025] In addition, in the above virtual circuit model, the inductor After being connected in series with the preset voltage source and the output voltage source, the preset current source and the capacitor in parallel with the input current source.

[0026] On the basis of the above, firstly, the output voltage, output current and output angular frequency of the three-phase grid-connected converter are acquired in real time, and the instantaneous value of the output voltage, the instantaneous value of the output current and the instantaneous value of the output angular frequency can be acquired.

[0027] Second, define and They are Axis and The instantaneous value of the output voltage of the shaft, and are the output active power and output reactive power respectively, and Given active power reference value and reactive power reference value respectively, according to the instantaneous value of output voltage and active power reference value and reactive power reference value, calculate Axis and Output current reference value of the axis and .Depend on , calculate , The formula is: ; in, .

[0028] After that, the output current reference value , and Axis and Instantaneous current measurement of the shaft , Difference, we get Axis and Axis current deviation , .

[0029] Then, the current deviation value is current scaled, and the scaled result is multiplied by the adaptive rotation angle matrix to obtain a current source and a voltage source, which are used as the above-mentioned input current source and input voltage source. Specifically, define , are the voltage and current scaling factors, respectively, is the adaptive rotation angle, is the rotation angle matrix and , current deviation value , go through Scaling and multiplying with the rotation angle matrix gives , , and its calculation formula is: .

[0030] Furthermore, this embodiment provides a power optimization control method based on an adaptive rotation angle. The rotation angle adaptive adjustment framework is as follows: Figure 3 As shown, specifically, first set the output voltage amplitude With voltage amplitude reference value , output angular frequency With angular frequency reference value They are input into the corresponding comparators respectively and the comparison results are output. , , the differential of the output voltage amplitude is .in addition, is the natural resonant frequency, which is actually the angular frequency reference value .

[0031] Among them, four different comparison results are generated according to the difference between the two sets of input values ,for: .

[0032] Then, based on the comparison result output, according to the mapping relationship between the comparison result and the rotation angle value, the sine and cosine components of the rotation angle are calculated to complete the dynamic adjustment of the rotation angle. - Four different comparison results generated in the Calculation module The mapping relationship formed with a set of rotation angle values ​​is: a) ,make ; b) ,make ; c) ,make ; d) ,make ; Then, the sine and cosine components of the rotation angle are ; in, , , , , is the capacitance value.

[0033] When the output active power / output reactive power deviates from the power set value, and The sine and cosine components of the above adaptive rotation angle can be controlled to achieve , According to the above dynamic trend , Expressions can also be implemented , The algorithm proposed in this embodiment uses the coordinated mapping relationship between output power, voltage and frequency according to the droop characteristics of VOC, dynamically adjusts the rotation angle to change the change trend of voltage and frequency, realizes active and reactive power decoupling, and can effectively improve the stability and economy of the grid-connected converter under the condition of grid strength fluctuation. The whole solution is simple, effective and conducive to engineering implementation.

[0034] Finally, the current deviation value , Current scaling factor After scaling, the current source and voltage source are multiplied by the adaptive rotation angle matrix to obtain the input current source and input voltage source, which are input into the virtual oscillation controller to output the inductor current and capacitor voltage , and then through the voltage coefficient After voltage scaling, the voltage adjustment value is obtained , ; Perform PWM modulation according to the voltage adjustment value to obtain the converter switch control signal , to achieve stable control of the converter output power.

[0035] The control method for the grid-connected converter proposed in this embodiment establishes a converter control architecture based on a virtual oscillator (Virtualoscillator control, VOC). On the basis of this architecture, a power optimization control method based on an adaptive rotation angle is designed to achieve accurate tracking of the grid-connected point voltage / frequency and the output power of the grid-connected converter, which can effectively improve the stability of the converter and the grid-connected power quality in the new energy grid-connected power generation system.

[0036] Embodiment 2 This embodiment provides a power optimization control system for a grid-connected converter based on an improved VOC, which specifically includes: A data acquisition module is used to obtain the output voltage, current and angular frequency of the three-phase grid-connected converter in real time; The voltage and current regulation module is used to calculate the current deviation value according to the output voltage and the output current. After the current deviation value is current scaled, it is multiplied by the adaptive rotation angle matrix to obtain the current source and the voltage source; wherein, according to the output voltage and the output angular frequency, the rotation angle is adaptively and dynamically adjusted to change the variation trend of the voltage and the angular frequency, and the active power and the reactive power are decoupled; A virtual oscillation adjustment module is used to input a current source and a voltage source into a virtual oscillation controller, output an inductor current and a capacitor voltage, and then obtain a voltage adjustment value after voltage scaling; The power optimization control module is used to perform PWM modulation according to the voltage adjustment value to obtain the converter switch control signal and realize stable control of the converter output power.

[0037] Embodiment 3 This embodiment provides an electronic device, including: a memory, used to store executable instructions; and a processor, used to implement the above method provided in this embodiment when executing the executable instructions stored in the memory.

[0038] Embodiment 4 This embodiment also provides a computer-readable storage medium storing executable instructions. When the executable instructions are executed by a processor, the processor will be caused to execute the above method provided in this embodiment.

[0039] Embodiment 5 This embodiment provides a computer program product, which includes an executable instruction, which is a computer instruction; the executable instruction is stored in a computer-readable storage medium. When a processor of an electronic device reads the executable instruction from the computer-readable storage medium and the processor executes the executable instruction, the electronic device executes the above method provided in this embodiment.

[0040] The steps involved in the above embodiments 2 to 5 correspond to the method embodiment 1. For the specific implementation, please refer to the relevant description part of embodiment 1. The term "computer-readable storage medium" should be understood as a single medium or multiple media including one or more instruction sets; it should also be understood to include any medium that can store, encode or carry an instruction set for execution by a processor and enable the processor to execute any method in the present invention.

[0041] Those skilled in the art should understand that the modules or steps of the present invention described above can be implemented by a general-purpose computer device, or alternatively, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. The present invention is not limited to any specific combination of hardware and software.

[0042] The above description is only a preferred embodiment of the present invention. Although the specific implementation mode of the present invention is described in conjunction with the accompanying drawings, it is not a limitation of the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative work are still within the protection scope of the present invention.

Claims

1. A power optimization control method for a grid-connected converter based on improved VOC, characterized in that: include: Obtain the output voltage, current and angular frequency of the three-phase grid-connected converter in real time; According to the output voltage and the output current, the current deviation value is calculated, and after the current deviation value is current scaled, it is multiplied by the adaptive rotation angle matrix to obtain the current source and the voltage source; wherein, according to the output voltage and the output angular frequency, the rotation angle is adaptively and dynamically adjusted to change the variation trend of the voltage and the angular frequency, and the active power and the reactive power are decoupled; The current source and the voltage source are input into the virtual oscillation controller, the inductor current and the capacitor voltage are output, and the voltage adjustment value is obtained after voltage scaling; PWM modulation is performed according to the voltage adjustment value to obtain the converter switch control signal, thereby achieving stable control of the converter output power.

2. The power optimization control method for grid-connected converter based on improved VOC according to claim 1, characterized in that: The dynamic adjustment of the adaptive rotation angle is: The output voltage amplitude and the voltage amplitude reference value, the output angular frequency and the angular frequency reference value are respectively input into corresponding comparators, and a comparison result is output; wherein four different comparison results are generated according to the difference between the two sets of input values; Based on the comparison result output, according to the mapping relationship between the comparison result and the rotation angle value, the sine and cosine components of the rotation angle are calculated to complete the dynamic adjustment of the rotation angle.

3. The power optimization control method for grid-connected converter based on improved VOC according to claim 2, characterized in that: The four different comparison results generated are: ； in, Indicates the output voltage amplitude, Indicates the voltage reference value, represents the output angular frequency, represents the angular frequency reference value, Indicates different comparison results.

4. The power optimization control method for grid-connected converter based on improved VOC according to claim 3, characterized in that: The mapping relationship between the four different comparison results and a set of rotation angle values ​​is: when season ; when season ; when season ; when season ; Then the sine and cosine components of the rotation angle are ; in, , , , , , Indicates the output voltage amplitude, and They are Axis and The instantaneous value of the output voltage of the shaft, Indicates the voltage amplitude reference value, , are the voltage and current scaling factors, respectively, is the steady-state convergence speed; represents the output angular frequency, is the natural resonant frequency, i.e. the angular frequency reference value ; and are the output active power and output reactive power respectively, and are given active power reference value and given reactive power reference value respectively, is the capacitance value.

5. The power optimization control method for grid-connected converter based on improved VOC according to claim 1, characterized in that: According to the output voltage and output current, the current deviation value is calculated, including: Calculating an output current reference value based on an output voltage instantaneous value and an active power reference value and a reactive power reference value; The output current reference value is subtracted from the output current instantaneous value to obtain the current deviation value.

6. The power optimization control method for grid-connected converter based on improved VOC according to claim 1, characterized in that: The virtual circuit model of the virtual oscillation controller is: The virtual circuit model includes an inductor and capacitor A resonant LC circuit composed of a nonlinearly related preset voltage source and a preset current source, an input current source and an input voltage source; Among them, the current source and voltage source obtained by multiplying the adaptive rotation angle matrix are used as the input current source and input voltage source, and the inductor After being connected in series with the preset voltage source and the output voltage source, the preset current source and the capacitor in parallel with the input current source.

7. A power optimization control system for grid-connected converter based on improved VOC, characterized in that: include: A data acquisition module is used to obtain the output voltage, current and angular frequency of the three-phase grid-connected converter in real time; The voltage and current regulation module is used to calculate the current deviation value according to the output voltage and the output current. After the current deviation value is current scaled, it is multiplied by the adaptive rotation angle matrix to obtain the current source and the voltage source; wherein, according to the output voltage and the output angular frequency, the rotation angle is adaptively and dynamically adjusted to change the variation trend of the voltage and the angular frequency, and the active power and the reactive power are decoupled; A virtual oscillation adjustment module is used to input a current source and a voltage source into a virtual oscillation controller, output an inductor current and a capacitor voltage, and then obtain a voltage adjustment value after voltage scaling; The power optimization control module is used to perform PWM modulation according to the voltage adjustment value to obtain the converter switch control signal and realize stable control of the converter output power.

8. An electronic device, characterized in that: include: A memory for storing executable instructions; The processor is used to implement the power optimization control method of the grid-connected converter based on improved VOC as described in any one of claims 1 to 6 when executing the executable instructions stored in the memory.

9. A computer-readable storage medium, characterized in that: Executable instructions are stored, which are used to cause the processor to execute the executable instructions to implement the power optimization control method of the grid-connected converter based on the improved VOC as described in any one of claims 1-6.

10. A computer program product, characterized in that The computer program product includes executable instructions stored in a computer-readable storage medium; When the processor of the electronic device reads the executable instructions from the computer-readable storage medium and executes the executable instructions, the power optimization control method for the grid-connected converter based on the improved VOC as described in any one of claims 1 to 6 is implemented.

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