SVG (Static Var Generator) control method under network construction type application

Abstract

The invention relates to a power system technology, and aims to provide an SVG control method under network construction type application. Comprising the following steps: respectively obtaining an initial d-axis active current given value, an initial q-axis reactive current given value and d-axis and q-axis voltage given values; through voltage and current double closed-loop control and proportional control of a current inner loop, feedback regulation of actual d-axis current and q-axis current of the SVG is realized, and then a modulation wave signal used for controlling the output voltage of the SVG is obtained. And comparing the modulated wave signal with a carrier signal to generate a switching signal of each sub-module in the SVG, and realizing compensation of the reactive power and the harmonic current of the SLCC by controlling on and off of a switching device. According to the method, the problem that active current and reactive current are mutually coupled under a dq rotating coordinate system when the current of the valve side of the converter transformer is oriented by the bus voltage can be solved only by introducing four arithmetic operations with few steps, and the influence on the overall calculation burden of a control system can be ignored.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a method for controlling active, reactive and harmonic currents of an SVG in a grid-forming application. Background Art

[0002] With the deepening of the green transformation of energy, the power system presents the "double high" characteristics of a high proportion of renewable energy and a high proportion of power electronic equipment. As the operation center of light and heavy industries, the AC power grid bears an increasing power load with the development of industry. The DC transmission system has gradually become the core channel for large-capacity power transmission due to its strong power transmission capacity, relatively economical overall engineering cost and smaller operating loss compared with the AC transmission system. According to the type of switching devices inside its converter valve, high-voltage DC transmission technology can be divided into traditional DC transmission technology (LCC) based on half-controlled thyristors and flexible DC transmission technology (VSC) based on fully controlled IGBTs. However, due to their own operating losses, fault ride-through capability, investment costs and other practical engineering limitations, both cannot be well applied to the "double high" new power system. Therefore, DC transmission technology based on new converter topology has become a major research hotspot in the field of power industry today.

[0003] As a DC transmission technology based on a new converter topology, the self-adaption statcom and line commutation converter (SLCC) commutation technology has attracted the attention of many researchers since its introduction. Among them, SVG (static reactive power compensation device) replaces the AC filter field of the traditional LCC (line-commuted converter) to compensate for reactive power and harmonic current, and the overall SLCC converter can effectively reduce the non-active current stress borne by the converter transformer and improve the response capability of the converter station under fault conditions; and thanks to the development of the grid-type technology, the application prospect of SVG in SLCC commutation technology will be further improved. However, the compensation position of SVG is on the valve side of the converter transformer, which will cause the reactive current and active current in the dq coordinate system to be coupled when the valve side current of the converter transformer is transformed with the bus voltage as the orientation, which will cause the conventional detection algorithm to be unable to obtain the d-axis and q-axis current given values ​​required by SVG in SLCC commutation technology.

[0004] Therefore, it is necessary to propose new solutions to solve the above problems. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a method for controlling active and reactive power and harmonic current of SVG in a grid-forming application.

[0006] To solve the technical problem, the solution of the present invention is:

[0007] A SVG control method for a grid-type application is provided, which controls a static reactive power compensation device SVG applied to a DC multi-source adaptive commutation converter SLCC through the following steps:

[0008] Detect the converter valve current, converter transformer grid-side current, converter transformer valve-side current and the average value of the capacitor voltage of each sub-module inside the SVG;

[0009] Subtract the average capacitor voltage of all submodules in the SVG from the rated capacitor voltage, and then perform PI calculation to obtain the initial d-axis active current given value;

[0010] The virtual current value on the grid side of the converter transformer is calculated using the converter valve current and the current reduction matrix, and then Parker transformation and low-pass filtering are performed to obtain the q-axis reactive current of the converter valve; the grid-side current of the converter transformer is subjected to Parker transformation and low-pass filtering to obtain the q-axis reactive current of the converter transformer; the q-axis reactive current of the converter transformer is summed with the q-axis reactive current of the converter valve after PI operation to obtain the initial q-axis reactive current given value;

[0011] The valve-side current of the converter transformer is transformed into the harmonic rotating coordinate system by using a multi-synchronous rotating coordinate transformation matrix, and multiple groups of d-axis and q-axis current components are obtained; and then multiple groups of initial d-axis and q-axis harmonic current given values ​​are obtained after low-pass filtering and PI operation respectively.

[0012] The initial d-axis active current given value is multiplied by two d-axis current conversion coefficients respectively, and the initial q-axis reactive current given value is multiplied by two q-axis current conversion coefficients respectively; then the coaxial currents are added to obtain the d-axis current given value and the q-axis current given value required for realizing SVG control;

[0013] Using a multi-synchronous rotating coordinate transformation matrix, the multiple groups of initial d-axis and q-axis harmonic current given values ​​are respectively inversely transformed into a dq rotating coordinate system, and then the coaxial voltages are added to obtain the d-axis voltage given value and the q-axis voltage given value required to realize SVG control;

[0014] By using the obtained d-axis and q-axis current and voltage given values, the actual d-axis current and q-axis current of SVG are feedback-regulated through voltage and current dual closed-loop control and proportional control of the current inner loop, thereby obtaining a modulated wave signal for controlling the output voltage of SVG. The modulated wave signal is compared with the carrier signal to generate switching signals for each sub-module inside SVG, and the compensation of SLCC reactive power and harmonic current is achieved by controlling the on and off of the switching devices.

[0015] As a preferred solution of the present invention, the SVG is connected in parallel to the valve side of the converter transformer in the SLCC, and the converter transformer as a whole is a star-star topology structure or a star-delta topology structure; each phase of the SVG is composed of a bridge arm filter inductor L and N full-bridge sub-modules with the same electrical structure and parameters in series, and the switching device in the full-bridge sub-module is an IGBT or IGCT.

[0016] As a preferred solution of the present invention, the active current, reactive current and harmonic current are all controlled in a dq rotating coordinate system, and the d-axis of the dq rotating coordinate system is oriented according to the detected bus voltage.

[0017] As a preferred solution of the present invention, the initial d-axis active current given value is calculated according to the following formula:

[0018] i sd1 =k p3 (u dc_ref -u dc_ave )+k i3 ∫(u dc_ref -u dc_ave )

[0019] In the formula, i sd1 is the initial d-axis active current given value; k p3 k is the proportional coefficient of the active current PI operation link; i3 is the integral coefficient of the active current PI operation link; u dc_ref is the rated voltage of all submodule capacitors inside SVG; u dc _ ave It is the average value of the capacitor voltage of all sub-modules inside the SVG.

[0020] As a preferred solution of the present invention, the current reduction matrix is ​​specifically shown in the following formula:

[0021]

[0022] Wherein, k is the ratio m / n of the number of turns m of the valve-side winding of the converter transformer to the number of turns n of the grid-side winding; the corresponding matrix form is selected according to the winding connection type of the converter transformer in the SLCC.

[0023] As a preferred solution of the present invention, the initial q-axis reactive current given value is calculated by the following method:

[0024] First, the virtual current value on the grid side of the converter transformer is obtained by the following conversion formula:

[0025]

[0026] In the formula, i a_1 '、ib_1 '、i c_1 ' is the virtual current value of the converter transformer grid side, i va 、i vb 、i vc is the converter valve current; A is the current reduction matrix;

[0027] Then, for the virtual current value i a_1 '、i b_1 '、i c_1 'Perform Parker transformation and low-pass filtering to obtain the q-axis reactive current of the converter valve; a_1 、i b_1 、i c_1 Perform Park transformation and low-pass filtering to obtain the q-axis reactive current of the converter transformer; sum the q-axis reactive current of the converter transformer with the q-axis reactive current of the converter valve after PI operation to obtain an initial q-axis reactive current given value;

[0028] The specific formula is as follows:

[0029] i sq1 =k p1 i q_1 +k i1 ∫i q_1 +i q_1 '

[0030] In the formula, i sq1 is the initial q-axis reactive current given value; k p1 k is the proportional coefficient of the reactive current PI operation link; i1 is the integral coefficient of the reactive current PI operation link; i q_1 ' is the q-axis reactive current of the converter valve; i q_1 is the q-axis reactive current of the converter transformer.

[0031] As a preferred solution of the present invention, the initial d-axis and q-axis harmonic current given values ​​are calculated by the following method:

[0032] First, the valve-side current i of the converter transformer is transformed into a_2 、i b_2 、i c_2 Transformed to the harmonic rotating coordinate system, multiple groups of d-axis and q-axis current components are obtained;

[0033] Then, each group of current components is subjected to low-pass filtering and PI operation processing to obtain the initial d-axis and q-axis harmonic current given values;

[0034] The specific formula is as follows:

[0035]

[0036] In the formula, i sdn and i sqn are the initial d-axis and q-axis harmonic current given values, i d_2_n and i q_2_n is the current value of the dq axis current component after filtering, n = 5, 7, 11, 13...; k p2 k is the proportional coefficient of the harmonic current PI operation link; i2 It is the integral coefficient of the harmonic current PI operation link.

[0037] As a preferred solution of the present invention, the two d-axis current conversion coefficients are m d_d 、m d_q , respectively represent the conversion coefficients required to convert the initial d-axis active current given value into the partial components of the d-axis and q-axis current given values ​​required by SVG; the two q-axis current conversion coefficients are m q_d 、m q_q , respectively represent the conversion coefficients required to convert the initial q-axis reactive current given value into another component of the d-axis and q-axis current given values ​​required by SVG;

[0038] Specifically, the respective values ​​are confirmed in the following ways:

[0039] When the winding connection type of the converter transformer is a star-delta topology, m d_d The value is -3 / (2k), m d_q The value is m q_d The value is m q_q The value is 3 / (2k);

[0040] When the winding connection type of the converter transformer is a star-star topology, m d_d The value is -1 / k, m d_q The value is 0; m q_d The value is 0, m q_q The value is 1 / k;

[0041] Wherein, k refers to the ratio m / n of the number of turns m of the valve-side winding of the converter transformer to the number of turns n of the grid-side winding.

[0042] The present invention further provides a device for implementing an SVG control method in a network-building application, comprising: an active current processing module, a reactive current processing module, a harmonic current processing module, an SVG given value generation module and an SVG control module; wherein:

[0043] The active current processing module uses the voltage average value of all submodules in the SVG to calculate the initial d-axis active current given value; specifically, it includes: subtracting the capacitor voltage average value of all submodules in the SVG from the rated voltage of the capacitor, and then performing PI operation to obtain the initial d-axis active current given value;

[0044] The reactive current processing module uses the converter valve current and the converter transformer grid-side current to calculate the initial q-axis reactive current given value; specifically includes: using the converter valve current and the current reduction matrix to calculate the virtual current value on the converter transformer grid side, and then performing Parker transformation and low-pass filtering to obtain the converter valve q-axis reactive current; performing Parker transformation and low-pass filtering on the converter transformer grid-side current to obtain the converter transformer q-axis reactive current; summing the converter transformer q-axis reactive current with the converter valve q-axis reactive current after PI operation to obtain the initial q-axis reactive current given value;

[0045] The harmonic current processing module uses the valve-side current of the converter transformer to calculate the initial d-axis and q-axis harmonic current given values; specifically, it includes: using a multi-synchronous rotating coordinate transformation matrix to transform the valve-side current of the converter transformer into a harmonic rotating coordinate system to obtain multiple groups of d-axis and q-axis current components; and then after low-pass filtering and PI operation, multiple groups of initial d-axis and q-axis harmonic current given values ​​are obtained;

[0046] The SVG given value generation module uses the calculation results of the above three modules to calculate the d-axis and q-axis current given values, as well as the d-axis voltage given value and the q-axis voltage given value required for SVG control;

[0047] The initial d-axis active current given value is multiplied by two d-axis current conversion coefficients respectively, and the initial q-axis reactive current given value is multiplied by two q-axis current conversion coefficients respectively; then the coaxial currents are added to obtain the d-axis current given value and the q-axis current given value required for realizing SVG control; using a multi-synchronous rotating coordinate transformation matrix, the multiple groups of initial d-axis and q-axis harmonic current given values ​​are respectively inversely transformed to the dq rotating coordinate system, and then the coaxial voltages are added to obtain the d-axis voltage given value and the q-axis voltage given value required for realizing SVG control;

[0048] The SVG control module uses the calculated results to control the SVG in a meshing application. Specifically, the module uses the obtained d-axis and q-axis current and voltage given values ​​to feedback-regulate the actual d-axis current and q-axis current of the SVG through voltage and current dual closed-loop control and proportional control of the current inner loop, thereby obtaining a modulation wave signal for controlling the output voltage of the SVG; the modulation wave signal is compared with the carrier signal to generate switching signals for each submodule inside the SVG, and the compensation of the SLCC reactive power and harmonic current is achieved by controlling the on and off of the switching devices.

[0049] As a preferred solution of the present invention, the active current processing module calculates and obtains the initial d-axis active current given value according to the following formula:

[0050] i sd1 =k p3 (u dc_ref -u dc_ave )+k i3 ∫(u dc_ref -u dc_ave )

[0051] In the formula, i sd1 is the initial d-axis active current given value; k p3 k is the proportional coefficient of the active current PI operation link; i3 is the integral coefficient of the active current PI operation link; u dc_ref is the rated voltage of all submodule capacitors inside SVG; u dc _ ave It is the average value of the capacitor voltage of all sub-modules inside the SVG.

[0052] As a preferred solution of the present invention, the current reduction matrix used by the reactive current processing module is specifically shown in the following formula:

[0053]

[0054] Wherein, k is the ratio m / n of the number of turns m of the valve-side winding of the converter transformer to the number of turns n of the grid-side winding; the corresponding matrix form is selected according to the winding connection type of the converter transformer in the SLCC.

[0055] As a preferred solution of the present invention, the reactive current processing module calculates and obtains the initial q-axis reactive current given value by the following method:

[0056] First, the virtual current value on the grid side of the converter transformer is obtained by the following conversion formula:

[0057]

[0058] In the formula, i a_1 '、i b_1 '、i c_1 ' is the virtual current value of the converter transformer grid side, i va 、i vb 、i vc is the converter valve current; A is the current reduction matrix;

[0059] Then, for the virtual current value i a_1 '、i b_1 '、i c_1'Perform Parker transformation and low-pass filtering to obtain the q-axis reactive current of the converter valve; a_1 、i b_1 、i c_1 Perform Park transformation and low-pass filtering to obtain the q-axis reactive current of the converter transformer; sum the q-axis reactive current of the converter transformer with the q-axis reactive current of the converter valve after PI operation to obtain an initial q-axis reactive current given value;

[0060] The specific formula is as follows:

[0061] i sq1 =k p1 i q_1 +k i1 ∫i q_1 +i q_1 '

[0062] In the formula, i sq1 is the initial q-axis reactive current given value; k p1 k is the proportional coefficient of the reactive current PI operation link; i1 is the integral coefficient of the reactive current PI operation link; i q_1 ' is the q-axis reactive current of the converter valve; i q_1 is the q-axis reactive current of the converter transformer.

[0063] As a preferred solution of the present invention, the harmonic current processing module calculates and obtains the initial d-axis and q-axis harmonic current given values ​​by the following method:

[0064] First, the valve-side current i of the converter transformer is transformed into a_2 、i b_2 、i c_2 Transformed to the harmonic rotating coordinate system, multiple groups of d-axis and q-axis current components are obtained;

[0065] Then, each group of current components is subjected to low-pass filtering and PI operation processing to obtain the initial d-axis and q-axis harmonic current given values;

[0066] The specific formula is as follows:

[0067]

[0068] In the formula, i sdn and i sqn are the initial d-axis and q-axis harmonic current given values, i d_2_n and i q_2_n is the current value of the dq axis current component after filtering, n = 5, 7, 11, 13...; k p2 k is the proportional coefficient of the harmonic current PI operation link; i2It is the integral coefficient of the harmonic current PI operation link.

[0069] As a preferred solution of the present invention, when the SVG given value generation module calculates the given values ​​of the d-axis and q-axis currents, the two d-axis current conversion coefficients are m d_d 、m d_q , respectively represent the conversion coefficients required to convert the initial d-axis active current given value into the partial components of the d-axis and q-axis current given values ​​required by SVG; the two q-axis current conversion coefficients are m q_d 、m q_q , respectively represent the conversion coefficients required to convert the initial q-axis reactive current given value into another component of the d-axis and q-axis current given values ​​required by SVG;

[0070] Specifically, the respective values ​​are confirmed in the following ways:

[0071] When the winding connection type of the converter transformer is a star-delta topology, m d_d The value is -3 / (2k), m d_q The value is m q_d The value is m q_q The value is 3 / (2k);

[0072] When the winding connection type of the converter transformer is a star-star topology, m d_d The value is -1 / k, m d_q The value is 0; m q_d The value is 0, m q_q The value is 1 / k;

[0073] Wherein, k refers to the ratio m / n of the number of turns m of the valve-side winding of the converter transformer to the number of turns n of the grid-side winding.

[0074] The present invention also provides a computer device, comprising: at least one processor, and a memory communicatively 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 so that the at least one processor executes the aforementioned SVG control method under the networking application.

[0075] 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 SVG control method under the networking application.

[0076] Compared with the prior art, the present invention has the following beneficial effects:

[0077] 1. Compared with conventional control methods, the control method proposed in the present invention only introduces a few steps of four arithmetic operations, which can solve the problem of mutual coupling between active and reactive currents in the dq rotating coordinate system when the valve-side current of the converter transformer is oriented with the bus voltage.

[0078] 2. The present invention can achieve accurate solution of the actual d-axis and q-axis current given values ​​required by SVG in SLCC commutation technology through an additional current reduction step; the entire calculation process introduces only a few steps of four arithmetic operations compared to the conventional SVG control method, and the impact on the overall calculation burden of the control system is negligible.

[0079] 3. The present invention solves the problem of mutual coupling between active and reactive currents obtained when the valve-side current of the converter transformer is subjected to Park transformation with the bus voltage as the orientation in the dq coordinate system; it realizes the precise compensation of reactive power and harmonic current in the SLCC commutation system, and at the same time ensures that SVG absorbs a certain amount of active power to maintain the voltage stability of its own sub-modules. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 A schematic diagram of the topological structure of an exemplary SLCC.

[0081] Figure 2 The topology diagram of an example SVG is shown in FIG.

[0082] Figure 3 It is the electrical schematic diagram of the grid / valve side winding of the YY type converter transformer.

[0083] Figure 4 It is the electrical schematic diagram of the network / valve side winding of the Y-△ type converter transformer.

[0084] Figure 5 Schematic diagram of the topology of the SLCC six-pulse converter composed of Y-△ type converter transformer.

[0085] Figure 6 It is a flow chart of the SVG control method implemented in the present invention.

[0086] Figure 7 The calculation logic diagram of each module provided for the example of the present invention.

[0087] Figure 8 The figure is a schematic diagram of an SVG control process used as an example in the implementation of the present invention.

[0088] Fig. 9 This is the current variation curve of the converter transformer valve side before SVG compensation in the implementation of the present invention.

[0089] Fig.10 This is the curve of the current change on the valve side of the converter transformer after SVG compensation in the implementation of the present invention. DETAILED DESCRIPTION

[0090] The present invention will be further described in detail below with reference to the accompanying drawings.

[0091] First of all, it should be explained that the present invention relates to 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 software programming skills to implement the present invention. The aforementioned software function modules include but are not limited to: active current processing module, reactive current processing module, harmonic current processing module, SVG given value generation module, SVG 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.

[0092] The SVG under the grid-type application described in the present invention is to connect a static reactive power compensation device SVG to the valve side of the converter transformer of the traditional phase-commutating converter LCC, replacing the passive filter field to compensate for reactive power and harmonic current. Specifically, the SVG is connected in parallel to the valve side of the converter transformer in the SLCC, and the converter transformer as a whole is a star-star topology structure or a star-delta topology structure; each phase of the SVG is composed of a bridge arm filter inductor L and N full-bridge sub-modules with the same electrical structure and parameters in series, and the switch device in the full-bridge sub-module can be IGBT or IGCT.

[0093] Figure 1-5 In the figure, the topological diagrams of the multi-source adaptive commutation converter SLCC and the static reactive power compensation device SVG as application examples are given, as well as the schematic diagrams of the converter transformer network / valve side winding in different forms. The SVG control method of the present invention can be well applied to these existing devices, and thus has universal adaptability. Figure 3 , 4 In the figure, the electrical connection diagrams of the grid / valve side windings of the YY type and Y-△ type converter transformers are shown respectively; Figure 5 The figure shows a schematic diagram of the SLCC six-pulse converter topology consisting of a Y-△ type converter transformer, in which the SVG is responsible for compensating the reactive power required by the converter valve during the AC / DC conversion process, filtering out the high-order harmonic currents generated in this process, and maintaining its own voltage stability.

[0094] The technical solution of the present invention relates to how to implement SVG control in the above application scenarios. As an example, Figure 6 The process of implementing the SVG control method is shown. The relevant calculation logic of active current, reactive current and harmonic current involved in this process is as follows Figure 7As shown, all are implemented in a dq rotating coordinate system, and the d-axis of the dq rotating coordinate system is oriented according to the detected bus voltage.

[0095] 1. The SVG control method for the networking application of the present invention comprises the following steps:

[0096] 1. Check the operating parameters of converter valves, converter transformers and other equipment in SLCC and the power grid.

[0097] Detect bus voltage v a 、v b 、v c , converter valve current i va 、i vb 、i vc , the grid-side current i of the converter transformer a_1 、i b_1 、i c_1 and valve side current i a_2 、i b_2 、i c_2 , the average voltage of all SVG submodules u dc_ave ; Each parameter value will be used in subsequent calculations.

[0098] 2. Calculate the given values ​​of the initial d-axis and q-axis active current, reactive current and axis harmonic current.

[0099] (1) The average capacitor voltage of all submodules in SVG is u dc _ ave With the rated voltage u of the capacitor dc_ref Then perform PI operation to obtain the initial d-axis active current given value i sd1 ; The specific formula is as follows:

[0100] i sd1 =k p3 (u dc_ref -u dc_ave )+k i3 ∫(u dc_ref -u dc_ave )

[0101] In the formula, i sd1 is the initial d-axis active current flow given value; k p3 k is the proportional coefficient of the active current PI operation link; i3 is the integral coefficient of the active current PI operation link; u dc_ref is the rated voltage of all submodule capacitors inside SVG; u dc _ ave It is the average value of the capacitor voltage of all sub-modules inside the SVG.

[0102] (2) First, use the converter valve current i va 、i vb 、i vc The virtual current value of the converter transformer grid side is obtained by conversion:

[0103]

[0104] In the formula, i a_1 '、i b_1 '、i c_1 ' is the virtual current value of the converter transformer grid side, i va 、i vb 、i vc is the converter valve current;

[0105] A is the current reduction matrix, which is shown in the following formula:

[0106]

[0107] Wherein, k is the ratio m / n of the number of turns m of the valve-side winding of the converter transformer to the number of turns n of the grid-side winding; the corresponding matrix form is selected according to the winding connection type of the converter transformer in the SLCC.

[0108] According to the winding turns m and n on the valve side and grid side of the converter transformer obtained in advance, m is divided by n to obtain the ratio k:

[0109]

[0110] Then, for the virtual current value i a_1 '、i b_1 '、i c_1 'Perform Parker transformation and low-pass filtering to obtain the q-axis reactive current i of the converter valve q_1 '; For the grid-side current i of the converter transformer a_1 、i b_1 、i c_1 Perform Park transformation and low-pass filtering to obtain the q-axis reactive current i of the converter transformer q_1 ; Convert the q-axis reactive current i of the converter transformer q_1 After PI calculation, the q-axis reactive current i of the converter valve is q_1 'Sum and get the initial q-axis reactive current given value i sq1 ;

[0111] The specific formula is as follows:

[0112] i sq1 =k p1 i q_1 +k i1 ∫i q_1 +i q_1 '

[0113] In the formula, i sq1 is the initial q-axis reactive current given value; k p1 k is the proportional coefficient of the reactive current PI operation link; i1 is the integral coefficient of the reactive current PI operation link; i q_1 ' is the q-axis reactive current of the converter valve; i q_1 is the q-axis reactive current of the converter transformer.

[0114] (3) First, the valve-side current i of the converter transformer is transformed into a_2 、i b_2 、i c_2 Transformed to the harmonic rotating coordinate system, multiple groups of d-axis and q-axis current components are obtained;

[0115] Then, each group of current components is low-pass filtered and PI operation is performed to obtain the initial d-axis and q-axis harmonic current given values ​​i sdn and i sqn ;

[0116] The specific formula is as follows:

[0117]

[0118] In the formula, i sdn and i sqn are the initial d-axis and q-axis harmonic current given values, i d_2_n and i q_2_n is the current value of the dq axis current component after filtering, n = 5, 7, 11, 13...; k p2 k is the proportional coefficient of the harmonic current PI operation link; i2 It is the integral coefficient of the harmonic current PI operation link.

[0119] 3. Calculate the d-axis and q-axis current given values ​​required by SVG based on the initial d-axis active current given value and the initial q-axis reactive current given value; calculate the d-axis and q-axis voltage given values ​​required by SVG based on the initial d-axis and q-axis harmonic current given values.

[0120] (1) multiplying the initial d-axis active current given value by the two d-axis current conversion coefficients respectively, and multiplying the initial q-axis reactive current given value by the two q-axis current conversion coefficients respectively;

[0121] The conversion factor of the two d-axis currents is m d_d 、m d_q , respectively represent the conversion coefficients required when the initial d-axis active current given value is converted into the partial components of the d-axis and q-axis current given values ​​required by SVG; the two q-axis current conversion coefficients are m q_d 、mq_q , respectively represent the conversion coefficients required when the initial q-axis reactive current given value is converted into the other components of the d-axis and q-axis current given values ​​required by SVG.

[0122] Specifically, refer to Table 1 to confirm the respective values:

[0123] Table 1

[0124]

[0125] In Table 1, Y-△ type indicates that the winding connection type of the converter transformer is a star-delta topology; YY type indicates that the winding connection type of the converter transformer is a star-star topology. k refers to the ratio m / n of the number of turns m of the valve-side winding of the converter transformer to the number of turns n of the grid-side winding.

[0126] Then the coaxial currents are added to obtain the d-axis current given value and the q-axis current given value i required to realize SVG control. sd_ref with i sq_ref :

[0127]

[0128] (2) Using a multi-synchronous rotating coordinate transformation matrix, the multiple groups of initial d-axis and q-axis harmonic current given values ​​are respectively transformed back to the dq rotating coordinate system, and then the coaxial voltages are added to obtain the d-axis voltage given value u required to realize SVG control dn and q-axis voltage given value u qn .

[0129] 4. Use the d-axis and q-axis current given values ​​and the d-axis and q-axis voltage given values ​​to perform SVG control.

[0130] Using the current and voltage given values ​​of the d-axis and q-axis obtained in step 3, the actual d-axis current and q-axis current of the SVG are feedback-regulated through dual closed-loop voltage and current control and proportional control of the current inner loop, thereby obtaining a modulation wave signal for controlling the output voltage of the SVG; the modulation wave signal is compared with the carrier signal to generate switching signals for each submodule inside the SVG, and the compensation of the SLCC reactive power and harmonic current is achieved by controlling the on and off of the switching devices, while maintaining the stability of the voltage of all submodules inside the SVG. For the control process of this part, please refer to Figure 8 .

[0131] 2. To implement the above control method, the present invention provides a device for obtaining the current and voltage set values ​​required for SVG control under grid-type applications, including: an active current processing module, a reactive current processing module, a harmonic current processing module, an SVG set value generation module and an SVG control module; wherein, the active current processing module calculates the initial d-axis active current set value using the voltage average value of all sub-modules inside the SVG according to the above operation; the reactive current processing module calculates the initial q-axis reactive current set value using the converter valve current and the grid-side current of the converter transformer according to the above operation; the harmonic current processing module calculates the initial d-axis and q-axis harmonic current set values ​​using the converter transformer according to the above operation; the SVG set value generation module calculates the d-axis and q-axis current set values ​​required for SVG control, as well as the d-axis voltage set value and the q-axis voltage set value according to the above operation using the calculation results of the above three modules; the SVG control module uses the calculation results of the SVG set value generation module to obtain the modulation wave signal and generate the switching signals of each sub-module inside the SVG through the voltage and current dual closed-loop control and proportional control of the current inner loop. The calculation logic diagram of some modules is shown as follows: Figure 7 shown.

[0132] Furthermore, the present invention also provides corresponding computer equipment and computer-readable storage media, which implement the various steps in the SVG control method under the networking application as described above by executing the stored computer program.

[0133] Effect verification experiment:

[0134] The topology and control model of the SLCC six-pulse converter composed of Y-△ type converter transformers was constructed in the PSCAD / EMTDC simulation software to verify the specific feasibility and corresponding technical effects of the present invention.

[0135] Based on the electromagnetic transient simulation results, it can be seen that when applied to SLCC commutation, the converter valve current i va 、i vb 、i vc (i.e. the converter transformer valve side current i before compensation a_2 、i b_2 、i c_2 ) is approximately a square wave, and the result is as follows Fig. 9 Then, after using the SVG control method proposed in the present invention, it can be found that the converter valve side current i a_2 、i a_2 、i a_2 The current is compensated to a standard sine wave current, and the current distortion rate is extremely small, which can well meet the needs of the AC power grid. The results are as follows Fig.10 shown.

Claims

1. A SVG control method for a networking application, characterized in that: The static reactive power compensation device SVG used in the DC multi-source adaptive commutation converter SLCC is controlled through the following steps: Detect the converter valve current, converter transformer grid-side current, converter transformer valve-side current and the average value of the capacitor voltage of each sub-module inside the SVG; Subtract the average capacitor voltage of all submodules in the SVG from the rated capacitor voltage, and then perform PI calculation to obtain the initial d-axis active current given value; The virtual current value on the grid side of the converter transformer is calculated using the converter valve current and the current reduction matrix, and then Parker transformation and low-pass filtering are performed to obtain the q-axis reactive current of the converter valve; the grid-side current of the converter transformer is subjected to Parker transformation and low-pass filtering to obtain the q-axis reactive current of the converter transformer; the q-axis reactive current of the converter transformer is summed with the q-axis reactive current of the converter valve after PI operation to obtain the initial q-axis reactive current given value; The valve-side current of the converter transformer is transformed into a harmonic rotating coordinate system by using a multi-synchronous rotating coordinate transformation matrix to obtain multiple groups of d-axis and q-axis current components. After low-pass filtering and PI operation, multiple groups of initial d-axis and q-axis harmonic current given values ​​are obtained; The initial d-axis active current given value is multiplied by two d-axis current conversion coefficients respectively, and the initial q-axis reactive current given value is multiplied by two q-axis current conversion coefficients respectively; then the coaxial currents are added to obtain the d-axis current given value and the q-axis current given value required for realizing SVG control; Using a multi-synchronous rotating coordinate transformation matrix, the multiple groups of initial d-axis and q-axis harmonic current given values ​​are respectively inversely transformed into a dq rotating coordinate system, and then the coaxial voltages are added to obtain the d-axis voltage given value and the q-axis voltage given value required to realize SVG control; By using the obtained d-axis and q-axis current and voltage given values, the actual d-axis current and q-axis current of SVG are feedback-regulated through voltage and current dual closed-loop control and proportional control of the current inner loop, thereby obtaining a modulated wave signal for controlling the output voltage of SVG. The modulated wave signal is compared with the carrier signal to generate switching signals for each sub-module inside SVG, and the compensation of SLCC reactive power and harmonic current is achieved by controlling the on and off of the switching devices.

2. The SVG control method according to claim 1, characterized in that: The SVG is connected in parallel to the valve side of the converter transformer in the SLCC, and the converter transformer as a whole is a star-star topology structure or a star-delta topology structure; each phase of the SVG is composed of a bridge arm filter inductor L and N full-bridge sub-modules with the same electrical structure and parameters in series, and the switching device in the full-bridge sub-module is an IGBT or IGCT.

3. The SVG control method according to claim 1, characterized in that: The active current, reactive current and harmonic current are all controlled in a dq rotating coordinate system, and the d-axis of the dq rotating coordinate system is oriented according to the detected bus voltage.

4. The SVG control method according to claim 1, characterized in that: The initial d-axis active current given value is calculated according to the following formula: and sd1 =k p3 (in dc_ref -in dc_ave )+k i3 ∫(in dc_ref -in dc_ave ) In the formula, i sd1 is the initial d-axis active current given value; k p3 k is the proportional coefficient of the active current PI operation link; i3 is the integral coefficient of the active current PI operation link; u dc_ref is the rated voltage of all submodule capacitors inside SVG; u dc _ ave It is the average value of the capacitor voltage of all sub-modules inside the SVG.

5. The SVG control method according to claim 1, characterized in that: The current reduction matrix is ​​specifically shown in the following formula: Wherein, k is the ratio m / n of the number of turns m of the valve-side winding of the converter transformer to the number of turns n of the grid-side winding; the corresponding matrix form is selected according to the winding connection type of the converter transformer in the SLCC.

6. The SVG control method according to claim 1, characterized in that: The initial q-axis reactive current given value is calculated by the following method: First, the virtual current value on the grid side of the converter transformer is obtained by the following conversion formula: In the formula, i a_1 '、i b_1 '、i c_1 ' is the virtual current value of the converter transformer grid side, i va 、i vb 、i vc is the converter valve current; A is the current reduction matrix; Then, for the virtual current value i a_1 '、i b_1 '、i c_1 'Perform Parker transformation and low-pass filtering to obtain the q-axis reactive current of the converter valve; a_1 、i b_1 、i c_1 Perform Park transformation and low-pass filtering to obtain the q-axis reactive current of the converter transformer; sum the q-axis reactive current of the converter transformer with the q-axis reactive current of the converter valve after PI operation to obtain an initial q-axis reactive current given value; The specific formula is as follows: i sq1 =k p1 i q_1 +k i1 ∫i q_1 +i q_1 ' In the formula, i sq1 is the initial q-axis reactive current given value; k p1 k is the proportional coefficient of the reactive current PI operation link; i1 is the integral coefficient of the reactive current PI operation link; i q_1 ' is the q-axis reactive current of the converter valve; i q_1 is the q-axis reactive current of the converter transformer.

7. The SVG control method according to claim 1, characterized in that: The initial d-axis and q-axis harmonic current given values ​​are calculated by the following method: First, the valve-side current i of the converter transformer is transformed into a_2 、i b_2 、i c_2 Transformed to the harmonic rotating coordinate system, multiple groups of d-axis and q-axis current components are obtained; Then, each group of current components is subjected to low-pass filtering and PI operation processing to obtain the initial d-axis and q-axis harmonic current given values; The specific formula is as follows: In the formula, i sdn and i sqn are the initial d-axis and q-axis harmonic current given values, i d_2_n and i q_2_n is the current value of the dq axis current component after filtering, n = 5, 7, 11, 13...; k p2 k is the proportional coefficient of the harmonic current PI operation link; i2 It is the integral coefficient of the harmonic current PI operation link.

8. The SVG control method according to claim 1, characterized in that: The two d-axis current conversion coefficients are m d_d 、m d_q , respectively represent the conversion coefficients required to convert the initial d-axis active current given value into the partial components of the d-axis and q-axis current given values ​​required by SVG; the two q-axis current conversion coefficients are m q_d 、m q_q , respectively represent the conversion coefficients required to convert the initial q-axis reactive current given value into another component of the d-axis and q-axis current given values ​​required by SVG; Specifically, the respective values ​​are confirmed by the following methods: When the winding connection type of the converter transformer is a star-delta topology, m d_d The value is -3 / (2k), m d_q The value is m q_d The value is m q_q The value is 3 / (2k); When the winding connection type of the converter transformer is a star-star topology, m d_d The value is -1 / k, m d_q The value is 0; m q_d The value is 0, m q_q The value is 1 / k; Wherein, k refers to the ratio m / n of the number of turns m of the valve-side winding of the converter transformer to the number of turns n of the grid-side winding.

9. A device for implementing an SVG control method in a networking application, characterized in that: include: Active current processing module, reactive current processing module, harmonic current processing module, SVG given value generation module and SVG control module; wherein, The active current processing module uses the voltage average value of all submodules in the SVG to calculate the initial d-axis active current given value; specifically, it includes: subtracting the capacitor voltage average value of all submodules in the SVG from the rated voltage of the capacitor, and then performing PI operation to obtain the initial d-axis active current given value; The reactive current processing module uses the converter valve current and the converter transformer grid-side current to calculate the initial q-axis reactive current given value; specifically includes: using the converter valve current and the current reduction matrix to calculate the virtual current value on the converter transformer grid side, and then performing Parker transformation and low-pass filtering to obtain the converter valve q-axis reactive current; performing Parker transformation and low-pass filtering on the converter transformer grid-side current to obtain the converter transformer q-axis reactive current; summing the converter transformer q-axis reactive current with the converter valve q-axis reactive current after PI operation to obtain the initial q-axis reactive current given value; The harmonic current processing module uses the valve-side current of the converter transformer to calculate the initial d-axis and q-axis harmonic current given values; specifically, it includes: using a multi-synchronous rotating coordinate transformation matrix to transform the valve-side current of the converter transformer into a harmonic rotating coordinate system to obtain multiple groups of d-axis and q-axis current components; and then after low-pass filtering and PI operation, multiple groups of initial d-axis and q-axis harmonic current given values ​​are obtained; The SVG given value generation module uses the calculation results of the above three modules to calculate the d-axis and q-axis current given values, as well as the d-axis voltage given value and the q-axis voltage given value required for SVG control; The initial d-axis active current given value is multiplied by two d-axis current conversion coefficients respectively, and the initial q-axis reactive current given value is multiplied by two q-axis current conversion coefficients respectively; then the coaxial currents are added to obtain the d-axis current given value and the q-axis current given value required for realizing SVG control; using a multi-synchronous rotating coordinate transformation matrix, the multiple groups of initial d-axis and q-axis harmonic current given values ​​are respectively inversely transformed to the dq rotating coordinate system, and then the coaxial voltages are added to obtain the d-axis voltage given value and the q-axis voltage given value required for realizing SVG control; The SVG control module uses the calculated results to control the SVG in a meshing application. Specifically, the module uses the obtained d-axis and q-axis current and voltage given values ​​to feedback-regulate the actual d-axis current and q-axis current of the SVG through voltage and current dual closed-loop control and proportional control of the current inner loop, thereby obtaining a modulation wave signal for controlling the output voltage of the SVG; the modulation wave signal is compared with the carrier signal to generate switching signals for each submodule inside the SVG, and the compensation of the SLCC reactive power and harmonic current is achieved by controlling the on and off of the switching devices.

10. The device according to claim 9, characterized in that The active current processing module calculates and obtains the initial d-axis active current given value according to the following formula: and sd1 =k p3 (in dc_ref -in dc_ave )+k i3 ∫(in dc_ref -in dc_ave ) In the formula, i sd1 is the initial d-axis active current given value; k p3 k is the proportional coefficient of the active current PI operation link; i3 is the integral coefficient of the active current PI operation link; u dc_ref is the rated voltage of all submodule capacitors inside SVG; u dc _ ave It is the average value of the capacitor voltage of all sub-modules inside the SVG.

11. The device according to claim 9, characterized in that The current reduction matrix used by the reactive current processing module is specifically shown in the following formula: Wherein, k is the ratio m / n of the number of turns m of the valve-side winding of the converter transformer to the number of turns n of the grid-side winding; the corresponding matrix form is selected according to the winding connection type of the converter transformer in the SLCC.

12. The device according to claim 9, characterized in that The reactive current processing module calculates the initial q-axis reactive current given value by the following method: First, the virtual current value on the grid side of the converter transformer is obtained by the following conversion formula: In the formula, i a_1 '、i b_1 '、i c_1 ' is the virtual current value of the converter transformer grid side, i va 、i vb 、i vc is the converter valve current; A is the current reduction matrix; Then, for the virtual current value i a_1 '、i b_1 '、i c_1 'Perform Parker transformation and low-pass filtering to obtain the q-axis reactive current of the converter valve; a_1 、i b_1 、i c_1 Perform Park transformation and low-pass filtering to obtain the q-axis reactive current of the converter transformer; sum the q-axis reactive current of the converter transformer with the q-axis reactive current of the converter valve after PI operation to obtain an initial q-axis reactive current given value; The specific formula is as follows: i sq1 =k p1 i q_1 +k i1 ∫i q_1 +i q_1 ' In the formula, i sq1 is the initial q-axis reactive current given value; k p1 k is the proportional coefficient of the reactive current PI operation link; i1 is the integral coefficient of the reactive current PI operation link; i q_1 ' is the q-axis reactive current of the converter valve; i q_1 is the q-axis reactive current of the converter transformer.

13. The device according to claim 9, characterized in that The harmonic current processing module calculates and obtains the initial d-axis and q-axis harmonic current given values ​​by the following method: First, the valve-side current i of the converter transformer is transformed into a_2 、i b_2 、i c_2 Transformed to the harmonic rotating coordinate system, multiple groups of d-axis and q-axis current components are obtained; Then, each group of current components is subjected to low-pass filtering and PI operation processing to obtain the initial d-axis and q-axis harmonic current given values; The specific formula is as follows: In the formula, i sdn and i sqn are the initial d-axis and q-axis harmonic current given values, i d_2_n and i q_2_n is the current value of the dq axis current component after filtering, n = 5, 7, 11, 13...; k p2 k is the proportional coefficient of the harmonic current PI operation link; i2 It is the integral coefficient of the harmonic current PI operation link.

14. The device according to claim 9, characterized in that When the SVG given value generation module calculates the given values ​​of the d-axis and q-axis currents, the two d-axis current conversion coefficients are m d_d 、m d_q , respectively represent the conversion coefficients required to convert the initial d-axis active current given value into the partial components of the d-axis and q-axis current given values ​​required by SVG; the two q-axis current conversion coefficients are m q_d 、m q_q , respectively represent the conversion coefficients required to convert the initial q-axis reactive current given value into another component of the d-axis and q-axis current given values ​​required by SVG; Specifically, the respective values ​​are confirmed by the following methods: When the winding connection type of the converter transformer is a star-delta topology, m d_d The value is -3 / (2k), m d_q The value is m q_d The value is m q_q The value is 3 / (2k); When the winding connection type of the converter transformer is a star-star topology, m d_d The value is -1 / k, m d_q The value is 0; m q_d The value is 0, m q_q The value is 1 / k; Wherein, k refers to the ratio m / n of the number of turns m of the valve-side winding of the converter transformer to the number of turns n of the grid-side winding.

15. A computer device, characterized in that: include: At least one processor, and a memory communicatively 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 so that the at least one processor executes the SVG control method for a meshed application as described in any one of claims 1 to 8.

16. 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 SVG control method for a meshing application according to any one of claims 1 to 8.

Images