Network construction type SVG control method based on capacitor voltage and active power switching

Abstract

The invention relates to the technical field of power systems, and aims to provide a network construction type SVG control method based on capacitor voltage and active power switching. Continuously monitoring the total capacitor voltage of the direct current side of the SVG equipment, and when the total capacitor voltage drops to a set low threshold value, switching to capacitor voltage-frequency droop control to charge a direct current side capacitor; when charging reaches a set high threshold value, switching to active power-frequency control; if the threshold value is between the two threshold values, the original control strategy is kept unchanged; and the phase angles generated by the two control strategies are used for SVG control, and direct current side total capacitance voltage stability and output active power adjustment are maintained. According to the invention, automatic switching control of the active power-frequency unit and the capacitor voltage-frequency unit can be realized; the SVG equipment can always keep the stability of the total capacitor voltage at the direct current side, and the overshoot and over-discharge conditions of the capacitor at the direct current side are avoided; the operation stability of the network-forming SVG can be improved, the operation service life of the capacitor is prolonged, and the use cost of equipment is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a grid-type SVG control method based on capacitor voltage and active power switching. Background Art

[0002] With the continuous growth of electricity demand in production and life, higher requirements are placed on the stability and efficiency of the power grid. However, traditional power systems have revealed some problems when facing challenges such as increasingly complex load changes, new energy access, and large-scale industrial electricity consumption. In practical applications, traditional reactive power compensators have limitations in response speed, accuracy, and adaptability. Due to a certain lag in reactive power compensation, when the system voltage changes rapidly, conventional reactive power compensators are not only difficult to suppress transient voltage changes, but also have reactive power reverse regulation, which further worsens the voltage stability problem and cannot fully meet the needs of today's complex power systems.

[0003] Static VAR compensation equipment (SVG) is an application derived from grid-building technology. Its main function is to maintain the stability of the internal potential amplitude. When the voltage on the system side is disturbed, SVG can provide natural and delay-free reactive support. In addition, if equipped with a short-term energy storage device, SVG can also provide a certain inertia support for the large power grid. In summary, grid-building SVG can improve system response speed, reduce harmonic pollution, optimize power supply quality, and combine with intelligent distribution networks to achieve a comprehensive improvement in system stability and efficiency.

[0004] However, although the grid-type SVG can provide inertia support and damping capabilities to the power grid, it also increases the control requirements for the total capacitor voltage on the DC side. Existing grid-type SVGs usually use virtual synchronous machine control, which can balance the DC side phase-to-phase and intra-phase capacitor voltages, but cannot maintain the stability of the total capacitor voltage on the DC side, which can easily lead to problems such as capacitor overshoot and overdischarge, affecting the capacitor life.

[0005] Therefore, it is necessary to propose new solutions to solve the above problems. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a grid-type SVG control method based on capacitor voltage and active power switching.

[0007] To solve the technical problem, the solution of the present invention is:

[0008] A grid-type SVG control method based on capacitor voltage and active power switching is provided, which alternately performs active power-frequency control and capacitor voltage-frequency droop control during the operation of a static reactive power compensation device SVG, and specifically includes the following steps:

[0009] The total DC side capacitor voltage V of the SVG device is continuously monitored in each control cycle. DC ;

[0010] The DC side capacitor is charged and discharged in the following manner: When the total DC side capacitor voltage V DC falls to the set low threshold V DC , min When the active power-frequency control is switched to capacitor voltage-frequency droop control, the DC side capacitor of the SVG device is charged by the grid; when the total DC side capacitor voltage V DC Charges to the set high threshold V DC , max When the total capacitor voltage V DC If it is between two thresholds, the original control strategy remains unchanged;

[0011] The phase angle δ generated by active power-frequency control or capacitor voltage-frequency droop control is combined with the output voltage amplitude reference value E obtained by reactive power-voltage droop control. m , and finally generates a switching signal through the processing of virtual impedance voltage control, AC current inner loop control, Park transformation and intra-phase and inter-phase voltage balancing in sequence; by controlling the on and off of the internal switching devices of the SVG equipment, the total capacitor voltage on the DC side is kept stable and the output active power is regulated.

[0012] As a preferred solution of the present invention, according to the total rated voltage V of the DC side capacitor of the SVG device DC , rated To determine the low threshold V DC , min and high threshold V DC , max The value of; Among them, the low threshold V DC , min The value is not higher than 0.7V DC , rated , high threshold V DC , max The value is not less than 0.9V DC , rated .

[0013] As a preferred solution of the present invention, the active power-frequency control is realized based on the active power-frequency link in the virtual synchronous mechanism network control; by adding the rotor motion equation in the control link to simulate the synchronous generator, the system is given inertia and damping characteristics; the rotor motion equation is expressed by the following formula:

[0014]

[0015] Where, J represents the inertia coefficient of VSG control, D represents the damping coefficient of VSG control, and P m Represents mechanical power, P e represents electromagnetic power, ω represents VSG output angular velocity, ω s represents the grid voltage angular velocity, and δ represents the virtual power angle.

[0016] As a preferred solution of the present invention, the capacitor voltage-frequency droop control is based on the similarity between the dynamics of the DC capacitor and the dynamics of the generator rotor to simulate the synchronous characteristics of the synchronous machine; the transfer function used is as follows:

[0017]

[0018] In the formula, G PS (s) is the transfer function of the square difference of the total capacitance voltage on the DC side-frequency; s is the complex variable in the transfer function; K J is the inertia simulation coefficient; K D is the damping coefficient.

[0019] As a preferred solution of the present invention, the angular frequency ω is obtained based on the capacitor voltage-frequency droop control or the active power-frequency control, and the phase angle δ is obtained by integral calculation; then the phase angle δ and the output voltage amplitude reference value E obtained by the reactive power-voltage droop control are used as the reference value. m As input for virtual impedance voltage control.

[0020] As a preferred solution of the present invention, the SVG device is based on a cascaded H-bridge star topology or a triangle topology; each phase in the SVG device is composed of a filter inductor and N sub-modules with the same electrical structure and parameters in series; each sub-module is composed of a capacitor and 4 switching tubes forming an H-bridge, and the switching tube is an IGBT or IGCT.

[0021] The present invention further provides a device for implementing a grid-type SVG control method based on capacitor voltage and active power switching, the device comprising a capacitor voltage monitoring module, a control strategy switching module and an SVG device control module;

[0022] The capacitor voltage monitoring module continuously monitors the total capacitor voltage V on the DC side of the SVG device in each control cycle. DC ;

[0023] The control strategy switching module realizes the charging and discharging operation of the DC side capacitor by switching the control strategy, specifically including: when the total DC side capacitor voltage V DC falls to the set low threshold V DC , minWhen the active power-frequency control is switched to capacitor voltage-frequency droop control, the DC side capacitor of the SVG device is charged by the grid; when the total DC side capacitor voltage V DC Charges to the set high threshold V DC , max When the total capacitor voltage V DC If it is between two thresholds, the original control strategy remains unchanged;

[0024] The SVG equipment control module uses the phase angle δ generated by active power-frequency control or capacitor voltage-frequency droop control, combined with the output voltage amplitude reference value E obtained by reactive power-voltage droop control m , and finally generates a switching signal through the processing of virtual impedance voltage control, AC current inner loop control, Park transformation and intra-phase and inter-phase voltage balancing in sequence; by controlling the on and off of the internal switching devices of the SVG equipment, the total capacitor voltage on the DC side is kept stable and the output active power is regulated.

[0025] As a preferred solution of the present invention, the control strategy switching module is based on the total rated voltage V of the DC side capacitor of the SVG device. DC , rated To determine the low threshold V DC , min and high threshold V DC , max The value of; Among them, the low threshold V DC , min The value is not higher than 0.7V DC , rated , high threshold V DC , max The value is not less than 0.9V DC , rated .

[0026] As a preferred solution of the present invention, the control strategy switching module is implemented based on the active power-frequency link in the virtual synchronous mechanism network control when executing active power-frequency control; by adding the rotor motion equation in the control link to imitate the synchronous generator, the system is given inertia and damping characteristics; the rotor motion equation is expressed by the following formula:

[0027]

[0028] Where, J represents the inertia coefficient of VSG control, D represents the damping coefficient of VSG control, and P m Represents mechanical power, P e represents electromagnetic power, ω represents VSG output angular velocity, ω s represents the grid voltage angular velocity, and δ represents the virtual power angle.

[0029] As a preferred solution of the present invention, when the control strategy switching module performs capacitor voltage-frequency droop control, it simulates the synchronous characteristics of the synchronous machine based on the similarity between the dynamics of the DC capacitor and the dynamics of the generator rotor; the transfer function used is as follows:

[0030]

[0031] In the formula, G PS (s) is the transfer function of the square difference of the total capacitance voltage on the DC side-frequency; s is the complex variable in the transfer function; K J is the inertia simulation coefficient; K D is the damping coefficient.

[0032] As a preferred solution of the present invention, the control strategy switching module uses the angular frequency ω obtained by capacitor voltage-frequency droop control or active power-frequency control, and then obtains the phase angle δ through integral calculation; the SVG device control module converts the output voltage amplitude reference value E obtained by reactive power-voltage droop control m Combined with the phase angle δ, they serve as the input for virtual impedance voltage control.

[0033] The present invention also provides a computer device, comprising: at least one processor, and a memory connected to the at least one processor in communication, wherein the memory stores instructions to be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor executes the aforementioned grid-type SVG control method based on capacitor voltage and active power switching.

[0034] The present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer instructions, and the computer instructions are used to enable the computer to execute the aforementioned grid-type SVG control method based on capacitor voltage and active power switching.

[0035] Compared with the prior art, the advantages of the present invention are:

[0036] 1. The present invention realizes automatic switching control of active power-frequency unit and capacitor voltage-frequency unit by real-time monitoring of the total capacitor voltage on the DC side; the meshed SVG can always maintain the stability of the total capacitor voltage on the DC side, avoiding the occurrence of overshoot and over-discharge of the DC side capacitor.

[0037] 2. The present invention switches and controls capacitor voltage and active power, so that the grid-type SVG can effectively adjust the output active power while maintaining the stability of the total capacitor voltage on the DC side, solving the problem that the traditional virtual synchronous machine control method can only control the output active power but cannot maintain the total capacitor voltage on the DC side, and the DC side total capacitor voltage-frequency control can maintain the stability of the total capacitor voltage on the DC side but cannot directly control the output active power. By monitoring the threshold of the total capacitor voltage on the DC side and cleverly using simple switching operations, the advantages of the two control strategies can be used simultaneously in the entire control operation process and their respective technical disadvantages can be avoided.

[0038] 3. The present invention can improve the operational stability of the mesh-type SVG, while extending the operational life of the capacitor and reducing the cost of equipment use. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the topological structure of the meshed SVG main circuit based on the cascaded H-bridge in an embodiment of the present invention;

[0040] Figure 2 It is a control block diagram of the switching between the capacitor voltage and active power of the grid-type SVG in an embodiment of the present invention;

[0041] Figure 3 1 is a waveform diagram of the total capacitor voltage on the DC side in an embodiment of the present invention. DETAILED DESCRIPTION

[0042] First of all, it should be explained that the present invention relates to the field of circuit control technology, which is an application of computer technology in the field of electronic circuit technology. In the process of implementing the present invention, the application of multiple software function modules will be involved. The applicant believes that after carefully reading the application documents and accurately understanding the implementation principle and purpose of the present invention, in combination with the existing known technology, those skilled in the art can fully use their mastered software programming skills to implement the present invention. The aforementioned software function modules include but are not limited to: capacitor voltage monitoring module, control strategy switching module and SVG device control module, etc. All those mentioned in the application documents of the present invention belong to this category, and the applicant will not list them one by one.

[0043] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0044] In the present invention, the SVG device can be optionally based on a cascaded H-bridge star topology or a triangle topology; each phase in the SVG device is composed of a filter inductor and N sub-modules with the same electrical structure and parameters in series; each sub-module is composed of a capacitor and 4 switching tubes that form an H-bridge, and the switching tube is an IGBT or IGCT. Figure 1The main circuit topology of a meshed SVG based on a cascaded H-bridge is shown in FIG. 1 . The SVG consists of three phases (a, b, c) connected in a star configuration.

[0045] As an example, Figure 2 The process of implementing the control method of meshed SVG is demonstrated. The SVG control method realizes the automatic switching control of active power-frequency unit and capacitor voltage-frequency unit by real-time monitoring of the total capacitor voltage on the DC side of the SVG device, so that the meshed SVG can control the stability of the total capacitor voltage on the DC side and effectively adjust the output active power.

[0046] 1. Grid-type SVG control method based on capacitor voltage and active power switching

[0047] For ease of understanding, a control cycle is used as an example for explanation. The control block diagram of this method is as follows: Figure 2 As shown, the specific steps include:

[0048] (1) Real-time monitoring of the total DC side capacitor voltage V of the SVG device DC ,

[0049] (2) Charge and discharge the DC side capacitor in the following manner:

[0050] First, according to the total rated voltage V of the DC side capacitor of the SVG device DC , rated The value of the low threshold V DC , min and high threshold V DC , max The value of; Among them, the low threshold V DC , min The value is not higher than 0.7V DC , rated , high threshold V DC , max The value is not less than 0.9V DC , rated .

[0051] When the total capacitor voltage V DC falls to the set low threshold V DC , min When the active power-frequency control is switched to the capacitor voltage-frequency droop control, a modulation wave is finally generated based on the capacitor voltage-frequency droop control, and the DC side capacitor of the SVG device is charged by the power grid.

[0052] The principle of active power-frequency control is to add the rotor motion equation to the control link to simulate the synchronous generator, giving the system inertia and damping characteristics; the rotor motion equation can be expressed as follows:

[0053]

[0054] Among them, P m Represents mechanical power, P e represents electromagnetic power, J represents the inertia coefficient of VSG control, D represents the damping coefficient of VSG control, ω represents the VSG output angular velocity, ω s represents the grid voltage angular velocity, and δ represents the virtual power angle. From the rotor motion equation, we can get Figure 2 Contents recorded in the active power-frequency control block diagram.

[0055] Capacitor voltage-frequency droop control is also based on the similarity between the dynamics of DC capacitors and the dynamics of generator rotors, which simulates the synchronous generator and brings inertia and damping characteristics to the system. This control strategy can refer to the existing technology. The transfer function of capacitor voltage to frequency is:

[0056]

[0057] In the formula, G PS (s) is the transfer function of the square difference of the total capacitance voltage on the DC side-frequency; s is the complex variable in the transfer function; K J is the inertia simulation coefficient; K D is the damping coefficient.

[0058] When the total capacitor voltage V DC Charges to the set high threshold V DC , max When the active power-frequency control is used, the control mode is switched from capacitor voltage-frequency droop control back to active power-frequency control; a modulation wave is finally generated based on the active power-frequency control, and the SVG device outputs active power to the grid; the active power-frequency control is implemented based on the active-frequency link in the virtual synchronous mechanism network control, and this control strategy belongs to the traditional technology.

[0059] If the total capacitor voltage V DC If it is between the two thresholds, the original control strategy remains unchanged.

[0060] Based on the capacitor voltage-frequency droop control or active power-frequency control strategy, the angular frequency ω is obtained respectively; and then the phase angle δ is obtained through the calculation of the integrator;

[0061] (3) The output voltage amplitude reference value E obtained by combining the phase angle δ with the reactive power-voltage droop control mAs input, it goes through virtual impedance voltage control, AC current inner loop control, Park transformation and intra-phase and inter-phase voltage balancing to finally generate a switching signal; by controlling the SVG device; the on and off of the internal switching devices, the total capacitor voltage on the DC side is kept stable and the output active power is regulated.

[0062] 2. To implement the above control method, the present invention provides a device for implementing a grid-type SVG control method based on capacitor voltage and active power switching, the device comprising a capacitor voltage monitoring module, a control strategy switching module and an SVG device control module. The capacitor voltage monitoring module is used to continuously monitor the total capacitor voltage V on the DC side of the SVG device in each control cycle. DC ; The control strategy switching module compares the total DC side capacitor voltage V DC Compared with the case of two preset thresholds, the charging and discharging operations of the DC side capacitors are realized by switching the control strategy, and the phase angle δ is generated respectively. The SVG equipment control module combines the phase angle δ and the output voltage amplitude reference value E obtained by the reactive power-voltage droop control m , and finally generates switch signals for each submodule inside the SVG device and realizes the control of the SVG device.

[0063] The present invention also provides a computer device, comprising: at least one processor, and a memory connected to the at least one processor, wherein the memory stores instructions executed by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to execute the aforementioned grid-type SVG control method based on capacitor voltage and active power switching. The calculation logic diagram of some modules is as follows Figure 2 shown.

[0064] Furthermore, the present invention also provides corresponding computer equipment and computer-readable storage media, which implement the various steps in the aforementioned grid-type SVG control method based on capacitor voltage and active power switching by executing the stored computer program.

[0065] Effect verification experiment:

[0066] For ease of understanding, this embodiment constructs a cascaded H-bridge network-based SVG and control model in the PLECS simulation software, in order to verify the specific feasibility and corresponding technical effects of the present invention.

[0067] The grid voltage is set to 55V, the total capacitor voltage on the DC side is set to 120V, the grid-type SVG works under constant reactive conditions, and the output reactive power is -200Var.

[0068] The simulation results are as follows Figure 3As shown in the figure, when SVG works under active power-frequency control, the total capacitor voltage on the DC side will drop. When it drops to the set value of 62V, it switches to capacitor voltage-frequency droop control to charge the DC side capacitor. When it is charged to 120V, it switches back to active power-frequency control.

[0069] It can be seen that the control method of the present invention solves the problem that the traditional virtual synchronous machine control cannot control the DC side voltage. While ensuring that the traditional virtual synchronous machine control can control the active power output, the total capacitor voltage on the DC side can work under safe conditions. Since the problems of overcharge and over-discharge are avoided, the service life of the capacitor is extended and the operation stability of the grid-type SVG is enhanced.

Claims

1. A control method for a grid-type static reactive power compensation device SVG based on capacitor voltage and active power switching, characterized in that: Specifically include: The total capacitance voltage V of the DC side of the static VAR compensation device SVG is continuously monitored in each control cycle. DC ; When the total capacitor voltage V DC falls to the set low threshold V DC , min When the active power-frequency control is switched to capacitor voltage-frequency droop control, the DC side capacitor of the SVG device is charged by the grid; when the total DC side capacitor voltage V DC Charges to the set high threshold V DC , max When the total capacitor voltage V DC If it is between two thresholds, the original control strategy remains unchanged; The phase angle δ generated by active power-frequency control or capacitor voltage-frequency droop control is combined with the output voltage amplitude reference value E obtained by reactive power-voltage droop control. m , and finally generates a switching signal through the processing of virtual impedance voltage control, AC current inner loop control, Park transformation and intra-phase and inter-phase voltage balancing in sequence; by controlling the on and off of the internal switching devices of the SVG equipment, the total capacitor voltage on the DC side is kept stable and the output active power is regulated.

2. The method according to claim 1, characterized in that According to the total rated voltage V of the DC side capacitor of the SVG device DC , rated To determine the low threshold V DC , min and high threshold V DC , max The value of; Among them, the low threshold V DC , min The value is not higher than 0.7V DC , rated , high threshold V DC , max The value is not less than 0.9V DC , rated .

3. The method according to claim 1, characterized in that The active power-frequency control is realized based on the active power-frequency link in the virtual synchronous mechanism network control; by adding the rotor motion equation in the control link to simulate the synchronous generator, the system is given inertia and damping characteristics; the rotor motion equation is expressed by the following formula: Where, J represents the inertia coefficient of VSG control, D represents the damping coefficient of VSG control, and P m Represents mechanical power, P e represents electromagnetic power, ω represents VSG output angular velocity, ω s represents the grid voltage angular velocity, and δ represents the virtual power angle.

4. The method according to claim 1, characterized in that The capacitor voltage-frequency droop control is based on the similarity between the dynamics of the DC capacitor and the dynamics of the generator rotor to simulate the synchronous characteristics of the synchronous machine; the transfer function used is as follows: In the formula, G PS (s) is the transfer function of the square difference of the total capacitance voltage on the DC side-frequency; s is the complex variable in the transfer function; K J is the inertia simulation coefficient; K D is the damping coefficient.

5. The method according to claim 1, characterized in that Based on capacitor voltage-frequency droop control or active power-frequency control, the angular frequency ω is obtained, and then the phase angle δ is obtained through integral calculation; then the phase angle δ and the output voltage amplitude reference value E obtained by reactive power-voltage droop control are used as the reference value. m As input for virtual impedance voltage control.

6. The method according to claim 1, characterized in that The SVG device is based on a cascaded H-bridge star topology or a triangle topology; each phase in the SVG device is composed of a filter inductor and N submodules with the same electrical structure and parameters in series; each submodule is composed of a capacitor and four switching tubes forming an H-bridge, and the switching tubes are IGBTs or IGCTs.

7. A device for implementing a grid-type SVG control method based on capacitor voltage and active power switching, characterized in that: It includes capacitor voltage monitoring module, control strategy switching module and SVG equipment control module; The capacitor voltage monitoring module continuously monitors the total capacitor voltage V on the DC side of the SVG device in each control cycle. DC ; Control strategy switching module, when the total DC side capacitor voltage V DC falls to the set low threshold V DC , min When the active power-frequency control is switched to capacitor voltage-frequency droop control, the DC side capacitor of the SVG device is charged by the grid; when the total DC side capacitor voltage V DC Charges to the set high threshold V DC , max When the total capacitor voltage V DC If it is between two thresholds, the original control strategy remains unchanged; The SVG equipment control module uses the phase angle δ generated by active power-frequency control or capacitor voltage-frequency droop control, combined with the output voltage amplitude reference value E obtained by reactive power-voltage droop control m , and finally generates a switching signal through the processing of virtual impedance voltage control, AC current inner loop control, Park transformation and intra-phase and inter-phase voltage balancing; By controlling the on and off of the switching devices, the total capacitor voltage on the DC side of the SVG equipment is kept stable and the output active power is regulated.

8. The device according to claim 7, characterized in that The control strategy switching module is based on the total rated voltage V of the DC side capacitor of the SVG device. DC , rated To determine the low threshold V DC , min and high threshold V DC , max The value of; Among them, the low threshold V DC , min The value is not higher than 0.7V DC , rated , high threshold V DC , max The value is not less than 0.9V DC , rated .

9. The device according to claim 7, characterized in that The control strategy switching module is implemented based on the active power-frequency link in the virtual synchronous mechanism network control when executing active power-frequency control; the rotor motion equation is added to the control link to simulate the synchronous generator, giving the system inertia and damping characteristics; the rotor motion equation is expressed by the following formula: Where, J represents the inertia coefficient of VSG control, D represents the damping coefficient of VSG control, and P m Represents mechanical power, P e represents electromagnetic power, ω represents VSG output angular velocity, ω s represents the grid voltage angular velocity, and δ represents the virtual power angle.

10. The device according to claim 7, characterized in that When the control strategy switching module performs capacitor voltage-frequency droop control, it simulates the synchronous characteristics of the synchronous machine based on the similarity between the dynamics of the DC capacitor and the dynamics of the generator rotor; the transfer function used is as follows: In the formula, G PS (s) is the transfer function of the square difference of the total capacitance voltage on the DC side-frequency; s is the complex variable in the transfer function; K J is the inertia simulation coefficient; K D is the damping coefficient.

11. The device according to claim 7, characterized in that The control strategy switching module uses the angular frequency ω obtained by capacitor voltage-frequency droop control or active power-frequency control, and then obtains the phase angle δ through integral calculation; the SVG device control module converts the output voltage amplitude reference value E obtained by reactive power-voltage droop control m Combined with the phase angle δ, they serve as the input for virtual impedance voltage control.

12. A computer device, characterized in that: include: At least one processor, and a memory in communication with the at least one processor, wherein the memory stores instructions executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor executes the grid-type SVG control method based on capacitor voltage and active power switching according to any one of claims 1 to 6.

13. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable the computer to execute the grid-type SVG control method based on capacitor voltage and active power switching according to any one of claims 1 to 6.

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