Method and device for constructing multi-inverter grid-connected model based on bidirectional coordinate transformation

Abstract

The application provides a multi-converter grid-connection model construction method and device based on bidirectional coordinate transformation, which comprises the following steps: in a grid-connection system comprising multiple public connection points of multiple converters, three-phase voltage of the public connection point of the parallel connection of the converters is converted to an alpha-beta coordinate system by establishing a grid-side static alpha-beta coordinate system; the grid-side voltage of the public connection point of the parallel connection of the converters in the alpha-beta coordinate system is converted to a dq coordinate system; based on the voltage conversion result, a converter control link model is constructed in the dq coordinate system; based on the converter control link model, the grid-side current of the public connection point of the parallel connection of the converters is converted from the dq coordinate system to the alpha-beta coordinate system, and then the grid-side voltage of each public connection point in the alpha-beta coordinate system is obtained. The model established by the application supports the parallel connection of multiple converters, has a clear structure, and is convenient for engineering calculation and theoretical analysis.

Description

Technical Field

[0001] This invention belongs to the field of power system and new energy power electronics technology, and relates to a dynamic modeling method for power electronic converters. In particular, it relates to a method and device for constructing a multi-converter grid-connected model based on bidirectional coordinate transformation, which is applicable to scenarios such as small disturbance stability analysis, synchronous stability mechanism research, oscillation mechanism analysis and linearization analysis. Background Technology

[0002] In power grids with a high proportion of renewable energy integration, the voltage source converter (VSC), serving as the grid connection interface, is dynamically influenced by the controller, filters, grid impedance, and the phase angle difference with the grid. In weak grid and multi-machine coupled scenarios, traditional modeling methods that convert to a synchronous rotating coordinate system or a phase-locked loop output angular velocity rotating coordinate system have the following problems:

[0003] 1) Ignoring the phase angle difference of the PLL (phase-locked loop) between multiple VSCs leads to the weakening or incorrect modeling of the critical synchronization coupling relationship.

[0004] 2) The true phase coupling characteristics of multi-machine power exchange are weakened or mistakenly eliminated, causing the linearization model to become distorted.

[0005] 3) When multiple converters are connected in parallel, the modeling method is complex and not conducive to the coupling analysis between multiple converters.

[0006] Existing technologies generally lack a system modeling method that facilitates the parallel connection of multiple converters and includes dynamic phase angle differences. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies and propose a method and apparatus for constructing a multi-converter grid-connected model based on bidirectional coordinate transformation. The model established by this invention supports multiple VSCs in parallel, has a clear structure, and facilitates engineering calculations and theoretical analysis.

[0008] The first aspect of this invention proposes a method for constructing a multi-converter grid-connected model based on bidirectional coordinate transformation, comprising:

[0009] In a grid-connected system containing multiple converters and multiple points of common coupling, the three-phase voltage of the points of common coupling of the converters connected in parallel is converted to the αβ coordinate system by establishing a grid-side static αβ coordinate system.

[0010] The grid-side voltage at the common connection point of the parallel converters in the αβ coordinate system is converted to the dq coordinate system.

[0011] Based on the voltage transformation results, a converter control loop model is constructed in the dq coordinate system;

[0012] Based on the converter control loop model, the grid-side current of the common connection point of the parallel converter is transformed from the dq coordinate system to the αβ coordinate system, thereby obtaining the grid-side voltage of each common connection point in the αβ coordinate system.

[0013] In a specific embodiment of the present invention, the step of converting the three-phase voltage at the common connection point of the parallel converters to the αβ coordinate system includes:

[0014] The three-phase voltage at the m-th common coupling point of the parallel converters is transformed to the αβ coordinate system as follows:

[0015]

[0016] in, , Let be the voltages at the m-th common connection point in the αβ coordinate system; , , Let be the voltages at the m-th common connection point in the abc coordinate system;

[0017] T αβ Here is the Clarke transformation matrix:

[0018] .

[0019] In a specific embodiment of the present invention, the step of converting the grid-side voltage of the common connection point of the parallel converters in the αβ coordinate system to the dq coordinate system includes:

[0020] The rotation angle is generated by the k-th converter at the m-th common connection point using its own phase-locked loop. The grid-side voltage of the k-th converter at the m-th common connection point in the αβ coordinate system. and Transform to the dq coordinate system:

[0021]

[0022] in, , Let represent the d-axis and q-axis voltages at the k-th converter at the m-th common point, respectively; The transformation matrix αβ → dq at the k-th converter at the m-th common point is shown in the following equation:

[0023] .

[0024] In one specific embodiment of the present invention, constructing the converter control loop model includes:

[0025] 1) Construct the differential equations of the phase-locked loop (PLL):

[0026]

[0027]

[0028] in, This represents the q-axis voltage at the k-th converter grid connection point at the m-th common point; The synchronous angular velocity of the power grid; This refers to the state variable introduced in the PLL control of the k-th converter at the m-th common point. Let be the differential term of the intermediate state variable of the PLL control of the k-th converter at the m-th common point. The PLL output phase-locked phase of the k-th converter at the m-th common point is... for The differential term, , These are the proportional and integral parameters of the k-th converter PLL at the m-th common point, respectively.

[0029] 2) Construct the outer loop control equations:

[0030]

[0031]

[0032]

[0033] in, Let d be the d-axis current component injected into the grid side by the k-th converter at the m-th common point; Let q be the q-axis current component injected into the grid side by the k-th converter at the m-th common point. This represents the actual power injected into the grid side by the k-th converter at the m-th common point. This represents the reference power of the k-th converter at the m-th common point. , These are the proportional and integral coefficients, respectively, of the active power control element of the k-th converter at the m-th common point. Let be the reference value of the d-axis current output by the active power control loop of the k-th converter at the m-th common point. The state variable introduced for the PI control loop of the active power control loop of the k-th converter at the m-th common point;

[0034] 3) Construct the inner-loop control equation for the current:

[0035]

[0036]

[0037]

[0038]

[0039] in, , These are the actual d-axis and q-axis current values ​​output by the k-th converter at the m-th common point, respectively. , These are the proportional and integral coefficients of the PI element controlling the d-axis current of the k-th converter inner loop at the m-th common point. , These are the proportional and integral coefficients of the PI element in the inner loop control of the k-th converter's q-axis current at the m-th common point. , These are the state variables introduced by the d-axis and q-axis PI control of the inner loop current control link of the k-th converter at the m-th common point, respectively. , These are the output voltages of the d-axis and q-axis of the inner loop current control element of the k-th converter at the m-th common point, respectively. , Let L be the d-axis and q-axis voltages of the k-th converter grid-connected node at the m-th common point. f,m,k The grid-connected filter inductance of the k-th converter at the m-th common point;

[0040] 4) Construct the dq current differential equation for the filter:

[0041]

[0042] .

[0043] In one specific embodiment of the present invention, it further includes:

[0044] Transform the grid-side current at the common coupling point of the parallel converters from the dq coordinate system to the αβ coordinate system:

[0045]

[0046] in, , The actual output current of the k-th converter at the m-th common point in the αβ coordinate system;

[0047] For grid-side impedance R g + jωL g :

[0048]

[0049]

[0050] in, , These are the grid-side current values ​​at the m-th common point in the αβ coordinate system. , These are the grid-side voltage values ​​in the αβ coordinate system, respectively. , These are the voltage values ​​at the m-th common connection point in the αβ coordinate system;

[0051] The voltage at the m-th common connection point is superimposed by the injected current:

[0052]

[0053]

[0054] Among them, z g = R g + jωL g Thus, the grid-side voltage of the common connection point in the αβ coordinate system is obtained.

[0055] A second aspect of the present invention provides a device for constructing a multi-converter grid-connected model based on bidirectional coordinate transformation, comprising:

[0056] The first voltage conversion module is used to convert the three-phase voltage of the common connection point of the converters in a grid-connected system with multiple converters and multiple common connection points to the αβ coordinate system by establishing a grid-side static αβ coordinate system;

[0057] The second voltage conversion module is used to convert the grid-side voltage of the common connection point of the parallel converters in the αβ coordinate system to the dq coordinate system.

[0058] The control model building module is used to build a converter control loop model in the dq coordinate system based on the voltage transformation results.

[0059] The voltage calculation module is used to transform the grid-side current of the common connection point of the parallel converter from the dq coordinate system to the αβ coordinate system based on the converter control loop model, and then obtain the grid-side voltage of each common connection point in the αβ coordinate system.

[0060] In a specific embodiment of the present invention, the step of converting the three-phase voltage at the common connection point of the parallel converters to the αβ coordinate system includes:

[0061] The three-phase voltage at the m-th common coupling point of the parallel converters is transformed to the αβ coordinate system as follows:

[0062]

[0063] in, , Let be the voltages at the m-th common connection point in the αβ coordinate system; , , Let be the voltages at the m-th common connection point in the abc coordinate system;

[0064] T αβ Here is the Clarke transformation matrix:

[0065] .

[0066] In a specific embodiment of the present invention, the step of converting the grid-side voltage of the common connection point of the parallel converters in the αβ coordinate system to the dq coordinate system includes:

[0067] The rotation angle is generated by the k-th converter at the m-th common connection point using its own phase-locked loop. The grid-side voltage of the k-th converter at the m-th common connection point in the αβ coordinate system. and Transform to the dq coordinate system:

[0068]

[0069] in, , Let represent the d-axis and q-axis voltages at the k-th converter at the m-th common point, respectively; The transformation matrix αβ → dq at the k-th converter at the m-th common point is shown in the following equation:

[0070] .

[0071] In one specific embodiment of the present invention, constructing the converter control loop model includes:

[0072] 1) Construct the differential equations of the phase-locked loop (PLL):

[0073]

[0074]

[0075] in, This represents the q-axis voltage at the k-th converter grid connection point at the m-th common point; The synchronous angular velocity of the power grid; This refers to the state variable introduced in the PLL control of the k-th converter at the m-th common point. Let be the differential term of the intermediate state variable of the PLL control of the k-th converter at the m-th common point. The PLL output phase-locked phase of the k-th converter at the m-th common point is... for The differential term, , These are the proportional and integral parameters of the k-th converter PLL at the m-th common point, respectively.

[0076] 2) Construct the outer loop control equations:

[0077]

[0078]

[0079]

[0080] in, Let d be the d-axis current component injected into the grid side by the k-th converter at the m-th common point; Let q be the q-axis current component injected into the grid side by the k-th converter at the m-th common point. This represents the actual power injected into the grid side by the k-th converter at the m-th common point. This represents the reference power of the k-th converter at the m-th common point. , These are the proportional and integral coefficients, respectively, of the active power control element of the k-th converter at the m-th common point. Let be the reference value of the d-axis current output by the active power control loop of the k-th converter at the m-th common point. The state variable introduced for the PI control loop of the active power control loop of the k-th converter at the m-th common point;

[0081] 3) Construct the inner-loop control equation for the current:

[0082]

[0083]

[0084]

[0085]

[0086] in, , These are the actual d-axis and q-axis current values ​​output by the k-th converter at the m-th common point, respectively. , These are the proportional and integral coefficients of the PI element controlling the d-axis current of the k-th converter inner loop at the m-th common point. , These are the proportional and integral coefficients of the PI element in the inner loop control of the k-th converter's q-axis current at the m-th common point. , These are the state variables introduced by the d-axis and q-axis PI control of the inner loop current control link of the k-th converter at the m-th common point, respectively. , These are the output voltages of the d-axis and q-axis of the inner loop current control element of the k-th converter at the m-th common point, respectively. , Let L be the d-axis and q-axis voltages of the k-th converter grid-connected node at the m-th common point. f,m,k The grid-connected filter inductance of the k-th converter at the m-th common point;

[0087] 4) Construct the dq current differential equation for the filter:

[0088]

[0089] .

[0090] In one specific embodiment of the present invention, it further includes:

[0091] Transform the grid-side current at the common coupling point of the parallel converters from the dq coordinate system to the αβ coordinate system:

[0092]

[0093] in, , The actual output current of the k-th converter at the m-th common point in the αβ coordinate system;

[0094] For grid-side impedance R g + jωL g :

[0095]

[0096]

[0097] in, , These are the grid-side current values ​​at the m-th common point in the αβ coordinate system. , These are the grid-side voltage values ​​in the αβ coordinate system, respectively. , These are the voltage values ​​at the m-th common connection point in the αβ coordinate system;

[0098] The voltage at the m-th common connection point is superimposed by the injected current:

[0099]

[0100]

[0101] Among them, z g = R g + jωL g Thus, the grid-side voltage of the common connection point in the αβ coordinate system is obtained.

[0102] A third aspect of the present invention provides an electronic device comprising:

[0103] At least one processor; and a memory communicatively connected to said at least one processor;

[0104] The memory stores instructions that can be executed by the at least one processor, and the instructions are configured to execute the above-described method for constructing a multi-converter grid-connected model based on bidirectional coordinate transformation.

[0105] A fourth aspect of the present invention provides a computer-readable storage medium storing computer instructions for causing the computer to execute the above-described method for constructing a multi-converter grid-connected model based on bidirectional coordinate transformation.

[0106] The features and beneficial effects of this invention are as follows:

[0107] 1) In this invention, each VSC adopts an independent dq coordinate system and establishes a unified bidirectional transformation link with the network-side αβ coordinate system, which can preserve the dynamic characteristics of the phase angle difference of each grid-connected VSC.

[0108] 2) This invention supports multiple VSCs connected in parallel.

[0109] 3) This invention supports steady-state solutions and linearization (the Jacobian matrix can be directly calculated).

[0110] 4) The model structure established by this invention is clear, which facilitates engineering calculations and theoretical analysis. Attached Figure Description

[0111] Figure 1 This is a diagram of a multi-VSC and multi-PCC grid-connected structure in a specific embodiment of the present invention.

[0112] Figure 2 This is an overall flowchart of a method for constructing a grid-connected multi-converter model based on bidirectional coordinate transformation according to an embodiment of the present invention.

[0113] Figure 3 This is a structural diagram of the PI control loop in a specific embodiment of the present invention.

[0114] Figure 4 This is a schematic diagram of the dual-coordinate transformation of the VSC grid-connected model in a specific embodiment of the present invention. Detailed Implementation

[0115] This invention proposes a method and apparatus for constructing a multi-converter grid-connected model based on bidirectional coordinate transformation, which will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0116] The first aspect of this invention proposes a method for constructing a multi-converter grid-connected model based on bidirectional coordinate transformation, comprising:

[0117] In a grid-connected system containing multiple converters and multiple points of common coupling, the three-phase voltage of the points of common coupling of the converters connected in parallel is converted to the αβ coordinate system by establishing a grid-side static αβ coordinate system.

[0118] The grid-side voltage at the common connection point of the parallel converters in the αβ coordinate system is converted to the dq coordinate system.

[0119] Based on the voltage transformation results, a converter control loop model is constructed in the dq coordinate system;

[0120] Based on the converter control loop model, the grid-side current of the common connection point of the parallel converter is transformed from the dq coordinate system to the αβ coordinate system, thereby obtaining the grid-side voltage of each common connection point in the αβ coordinate system.

[0121] In one specific embodiment of the present invention, the multi-VSC multi-PCC (point of common connection) grid-connected structure is as follows: Figure 1 As shown, the system contains multiple VSCs and their control systems; for the m-th group and the k-th converter VSC m,k Its control system is filtered by the corresponding filter inductor L. f,m,k Connect to the m-th PCC point, T m,k For the corresponding transformer, L g,m R g,m V represents the inductance and resistance between the m-th PCC point and the grid side, respectively. g P is the equivalent power supply voltage on the grid side. in,k This represents the injected power of the k-th converter.

[0122] In this embodiment, the overall process of the method for constructing a multi-converter grid-connected model based on bidirectional coordinate transformation is as follows: Figure 2 As shown, the method includes the following steps;

[0123] 1) By establishing a grid-side stationary αβ coordinate system, the three-phase voltages at the common connection point of the VSCs in parallel are transformed to the αβ coordinate system.

[0124] In this embodiment, the three-phase voltage of the m-th common connection point of the VSC in parallel is... Transform to the αβ coordinate system, denoted as The corresponding expression is as follows:

[0125]

[0126] in, , Let be the voltages at the m-th common connection point in the αβ coordinate system; , , Let be the voltages at the m-th common connection point in the abc coordinate system.

[0127] T αβ Here is the Clarke transformation matrix:

[0128]

[0129] In this embodiment, the grid-side current, impedance, and voltage are all uniformly represented using the αβ coordinate system.

[0130] 2) Based on the results of step 1), the grid-side voltage of the PCC point connected in parallel with VSC in the αβ coordinate system is transformed to the dq coordinate system.

[0131] In this embodiment, the rotation angle is generated by the k-th converter at the m-th common connection point using its own PLL. The grid-side voltage of the k-th converter at the m-th common connection point in the αβ coordinate system. , Transform to the dq coordinate system:

[0132]

[0133] in, , Let represent the d-axis and q-axis voltages at the k-th converter at the m-th common point, respectively; Let αβ → dq be the coordinate transformation matrix at the m-th common point and the k-th converter, and its form is shown in the following equation:

[0134]

[0135] It should be noted that the core of this step lies in the dq transformation angle of different VSCs. The differences can reflect the dynamics of phase angle difference (weak network characteristics).

[0136] 3) Based on the results of step 2), construct the converter control loop model. The specific steps are as follows:

[0137] 3-1) Construct the PLL differential equation.

[0138] A structural diagram of the PI control loop in a specific embodiment of the present invention is shown below. Figure 3 As shown, the process involves converting the three-phase voltage u a u b uc The dq-axis voltage u is obtained through Park transformation. d u q The angle value used for the park transformation is taken from the phase-locked phase θ output by the PLL. pll Based on the q-axis voltage as the input to the PI element in the PLL, the deviation Δω of the coordinate rotation angular velocity is obtained. Combined with the grid synchronization angular velocity ω0, the output speed ω of the phase-locked loop can be obtained. pll After studying ω pll Integrating θ, we can obtain θ. pll 1 / s is the integral symbol.

[0139] In this embodiment, based on the overall structure of the PLL, the differential equation of the PLL is constructed:

[0140]

[0141]

[0142] in, This represents the q-axis voltage at the k-th converter grid connection point at the m-th common point; This refers to the state variable introduced in the PLL control of the k-th converter at the m-th common point. Let be the differential term of the intermediate state variable of the PLL control of the k-th converter at the m-th common point. The PLL output phase-locked phase of the k-th converter at the m-th common point is... for The differential term, , These are the proportional and integral parameters of the k-th converter PLL at the m-th common point, respectively.

[0143] 3-2) Construct the outer loop control equations:

[0144]

[0145]

[0146]

[0147] in, Let d be the d-axis current component injected into the grid side by the k-th converter at the m-th common point; Let q be the q-axis current component injected into the grid side by the k-th converter at the m-th common point. This represents the actual power injected into the grid side by the k-th converter at the m-th common point. This represents the reference power of the k-th converter at the m-th common point. , These are the proportional and integral coefficients, respectively, of the active power control element of the k-th converter at the m-th common point. Let be the reference value of the d-axis current output by the active power control loop of the k-th converter at the m-th common point. The state variable is introduced into the PI control loop of the active power control loop of the k-th converter at the m-th common point.

[0148] 3-3) Construct the inner loop control equation for the current.

[0149] In this embodiment, the controller output (voltage before modulation) is expressed as follows:

[0150]

[0151]

[0152]

[0153]

[0154] in, , These are the actual d-axis and q-axis current values ​​output by the k-th converter at the m-th common point, respectively. , These are the proportional and integral coefficients of the PI element controlling the d-axis current of the k-th converter inner loop at the m-th common point. , These are the proportional and integral coefficients of the PI element in the inner loop control of the k-th converter's q-axis current at the m-th common point. , These are the state variables introduced by the d-axis and q-axis PI control of the inner loop current control link of the k-th converter at the m-th common point, respectively. , These are the output voltages of the d and q axes of the inner loop current control loop of the converter at the m-th common point, respectively, which are also the voltages before PWM modulation. , Let L be the d-axis and q-axis voltages of the k-th converter grid-connected node at the m-th common point. f,m,k Let be the grid-connected filter inductor of the k-th converter at the m-th common point.

[0155] 3-4) Construct the dq current differential equation for the filter.

[0156] In this embodiment, the grid-connected inductor L f The dynamic characteristics can be described by the following differential equation:

[0157]

[0158]

[0159] 4) Based on the results of step 3), the grid-side current of the common connection point of the parallel converters is transformed from the dq coordinate system to the αβ coordinate system.

[0160] In this embodiment, the grid-connected current of the k-th converter at the m-th common point is transformed from its dq rotating coordinate system to the global αβ coordinate system, as expressed below:

[0161]

[0162] in, , It is the actual current output by the k-th converter at the m-th common point in the αβ coordinate system.

[0163] 5) Based on the results of step 4), calculate the grid-side voltage in the αβ coordinate system.

[0164] In this embodiment, the grid impedance R on the grid side is... g + jωL g :

[0165]

[0166]

[0167] in, , These are the grid-side current values ​​at the m-th common point in the αβ coordinate system. , These are the grid-side voltage values ​​in the αβ coordinate system, respectively. , These are the voltage values ​​at the m-th common connection point in the αβ coordinate system.

[0168] The voltage at the m-th common connection point is superimposed by the injected current:

[0169]

[0170]

[0171] Among them, z g = R g + jωL g .

[0172] Thus, the voltage under αβ is solved.

[0173] Figure 4 This is a schematic diagram of the dual-coordinate transformation of the VSC grid-connected model in a specific embodiment of the present invention. According to... Figure 4The process shown, using the method described in this embodiment, first obtains the voltage V in the αβ coordinate system of the PCC point through the change of the grid-side voltage. pcc,αβ The voltage V in the dq coordinate system on the VSC side is further obtained by Clarke transformation. pcc,dq The VSC grid-connected current i in the dq coordinate system can be obtained through model solving of the converter control loop. VSC,dq Further back-calculation yields the grid-connected current i in the αβ coordinate system. VSC, αβ Based on this process, a multi-VSC grid-connected model can be constructed. By combining the voltage and current dual-coordinate changes and the grid-side equations, the characteristics of a multi-converter system that retains the essential interaction between the VSC and the grid can be calculated.

[0174] To implement the above embodiments, a second aspect of the present invention proposes a multi-converter grid-connected model construction device based on bidirectional coordinate transformation, comprising:

[0175] The first voltage conversion module is used to convert the three-phase voltage of the common connection point of the converters in a grid-connected system with multiple converters and multiple common connection points to the αβ coordinate system by establishing a grid-side static αβ coordinate system;

[0176] The second voltage conversion module is used to convert the grid-side voltage of the common connection point of the parallel converters in the αβ coordinate system to the dq coordinate system.

[0177] The control model building module is used to build a converter control loop model in the dq coordinate system based on the voltage transformation results.

[0178] The voltage calculation module is used to transform the grid-side current of the common connection point of the parallel converter from the dq coordinate system to the αβ coordinate system based on the converter control loop model, and then obtain the grid-side voltage of each common connection point in the αβ coordinate system.

[0179] In a specific embodiment of the present invention, the step of converting the three-phase voltage at the common connection point of the parallel converters to the αβ coordinate system includes:

[0180] The three-phase voltage at the m-th common coupling point of the parallel converters is transformed to the αβ coordinate system as follows:

[0181]

[0182] in, , Let be the voltages at the m-th common connection point in the αβ coordinate system; , , Let be the voltages at the m-th common connection point in the abc coordinate system;

[0183] T αβ Here is the Clarke transformation matrix:

[0184] .

[0185] In a specific embodiment of the present invention, the step of converting the grid-side voltage of the common connection point of the parallel converters in the αβ coordinate system to the dq coordinate system includes:

[0186] The rotation angle is generated by the k-th converter at the m-th common connection point using its own phase-locked loop. The grid-side voltage of the k-th converter at the m-th common connection point in the αβ coordinate system. and Transform to the dq coordinate system:

[0187]

[0188] in, , Let represent the d-axis and q-axis voltages at the k-th converter at the m-th common point, respectively; The transformation matrix αβ → dq at the k-th converter at the m-th common point is shown in the following equation:

[0189] .

[0190] In one specific embodiment of the present invention, constructing the converter control loop model includes:

[0191] 1) Construct the differential equations of the phase-locked loop (PLL):

[0192]

[0193]

[0194] in, This represents the q-axis voltage at the k-th converter grid connection point at the m-th common point; The synchronous angular velocity of the power grid; This refers to the state variable introduced in the PLL control of the k-th converter at the m-th common point. Let be the differential term of the intermediate state variable of the PLL control of the k-th converter at the m-th common point. The PLL output phase-locked phase of the k-th converter at the m-th common point is... for The differential term, , These are the proportional and integral parameters of the k-th converter PLL at the m-th common point, respectively.

[0195] 2) Construct the outer loop control equations:

[0196]

[0197]

[0198]

[0199] in, Let d be the d-axis current component injected into the grid side by the k-th converter at the m-th common point; Let q be the q-axis current component injected into the grid side by the k-th converter at the m-th common point. This represents the actual power injected into the grid side by the k-th converter at the m-th common point. This represents the reference power of the k-th converter at the m-th common point. , These are the proportional and integral coefficients, respectively, of the active power control element of the k-th converter at the m-th common point. Let be the reference value of the d-axis current output by the active power control loop of the k-th converter at the m-th common point. The state variable introduced for the PI control loop of the active power control loop of the k-th converter at the m-th common point;

[0200] 3) Construct the inner-loop control equation for the current:

[0201]

[0202]

[0203]

[0204]

[0205] in, , These are the actual d-axis and q-axis current values ​​output by the k-th converter at the m-th common point, respectively. , These are the proportional and integral coefficients of the PI element controlling the d-axis current of the k-th converter inner loop at the m-th common point. , These are the proportional and integral coefficients of the PI element in the inner loop control of the k-th converter's q-axis current at the m-th common point. , These are the state variables introduced by the d-axis and q-axis PI control of the inner loop current control link of the k-th converter at the m-th common point, respectively. , These are the output voltages of the d-axis and q-axis of the inner loop current control element of the k-th converter at the m-th common point, respectively. , Let L be the d-axis and q-axis voltages of the k-th converter grid-connected node at the m-th common point. f,m,k The grid-connected filter inductance of the k-th converter at the m-th common point;

[0206] 4) Construct the dq current differential equation for the filter:

[0207]

[0208] .

[0209] In one specific embodiment of the present invention, it further includes:

[0210] Transform the grid-side current at the common coupling point of the parallel converters from the dq coordinate system to the αβ coordinate system:

[0211]

[0212] in, , The actual output current of the k-th converter at the m-th common point in the αβ coordinate system;

[0213] For grid-side impedance R g + jωL g :

[0214]

[0215]

[0216] in, , These are the grid-side current values ​​at the m-th common point in the αβ coordinate system. , These are the grid-side voltage values ​​in the αβ coordinate system, respectively. , These are the voltage values ​​at the m-th common connection point in the αβ coordinate system;

[0217] The voltage at the m-th common connection point is superimposed by the injected current:

[0218]

[0219]

[0220] Among them, z g = R g + jωL g Thus, the grid-side voltage of the common connection point in the αβ coordinate system is obtained.

[0221] To implement the above embodiments, a third aspect of the present invention provides an electronic device, comprising:

[0222] At least one processor; and a memory communicatively connected to said at least one processor;

[0223] The memory stores instructions that can be executed by the at least one processor, and the instructions are configured to execute the above-described method for constructing a multi-converter grid-connected model based on bidirectional coordinate transformation.

[0224] To implement the above embodiments, a fourth aspect of the present invention provides a computer-readable storage medium storing computer instructions for causing the computer to execute the above-described method for constructing a multi-converter grid-connected model based on bidirectional coordinate transformation.

[0225] It should be noted that the computer-readable medium described in this disclosure can be a computer-readable signal medium or a computer-readable storage medium, or any combination thereof. A computer-readable storage medium can be, for example,—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In this disclosure, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in connection with an instruction execution system, apparatus, or device. In this disclosure, a computer-readable signal medium can include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A computer-readable signal medium can be any computer-readable medium other than a computer-readable storage medium, which can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium can be transmitted using any suitable medium, including but not limited to: wires, optical fibers, RF (radio frequency), etc., or any suitable combination thereof.

[0226] The aforementioned computer-readable medium may be included in the aforementioned electronic device; or it may exist independently and not assembled into the electronic device. The aforementioned computer-readable medium carries one or more programs, which, when executed by the electronic device, cause the electronic device to perform a method for constructing a multi-converter grid-connected model based on bidirectional coordinate transformation as described in the above embodiments.

[0227] Computer program code for performing the operations of this disclosure can be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, and C++, and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer can be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or can be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0228] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0229] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0230] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the function involved, as will be understood by those skilled in the art to which embodiments of this application pertain.

[0231] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which programs can be printed, because programs can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0232] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0233] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0234] Furthermore, the functional units in the various embodiments of this application can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0235] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of this application.

Claims

1. A method for constructing a grid-connected multi-converter model based on bidirectional coordinate transformation, characterized in that, include: In a grid-connected system containing multiple converters and multiple points of common coupling, the three-phase voltage of the points of common coupling of the converters connected in parallel is converted to the αβ coordinate system by establishing a grid-side static αβ coordinate system. The grid-side voltage at the common connection point of the parallel converters in the αβ coordinate system is converted to the dq coordinate system. Based on the voltage transformation results, a converter control loop model is constructed in the dq coordinate system; Based on the converter control loop model, the grid-side current of the common connection point of the parallel converter is transformed from the dq coordinate system to the αβ coordinate system, thereby obtaining the grid-side voltage of each common connection point in the αβ coordinate system.

2. The method according to claim 1, characterized in that, The process of converting the three-phase voltage at the common coupling point of the parallel converters to the αβ coordinate system includes: The three-phase voltage at the m-th common coupling point of the parallel converters is transformed to the αβ coordinate system as follows: in, , Let be the voltages at the m-th common connection point in the αβ coordinate system; , , Let be the voltages at the m-th common connection point in the abc coordinate system; T αβ Here is the Clarke transformation matrix: 。 3. The method according to claim 2, characterized in that, The process of converting the grid-side voltage of the common connection point of the parallel converters in the αβ coordinate system to the dq coordinate system includes: The rotation angle is generated by the k-th converter at the m-th common connection point using its own phase-locked loop. The grid-side voltage of the k-th converter at the m-th common connection point in the αβ coordinate system. and Transform to the dq coordinate system: in, , Let represent the d-axis and q-axis voltages at the k-th converter at the m-th common point, respectively; The transformation matrix αβ → dq at the k-th converter at the m-th common point is shown in the following equation: 。 4. The method according to claim 3, characterized in that, The construction of the converter control loop model includes: 1) Construct the differential equations of the phase-locked loop (PLL): in, This represents the q-axis voltage at the k-th converter grid connection point at the m-th common point; The synchronous angular velocity of the power grid; This refers to the state variable introduced in the PLL control of the k-th converter at the m-th common point. Let be the differential term of the intermediate state variable of the PLL control of the k-th converter at the m-th common point. The PLL output phase-locked phase of the k-th converter at the m-th common point is... for The differential term, , These are the proportional and integral parameters of the k-th converter PLL at the m-th common point, respectively. 2) Construct the outer loop control equations: in, Let d be the d-axis current component injected into the grid side by the k-th converter at the m-th common point; Let q be the q-axis current component injected into the grid side by the k-th converter at the m-th common point. This represents the actual power injected into the grid side by the k-th converter at the m-th common point. This represents the reference power of the k-th converter at the m-th common point. , These are the proportional and integral coefficients, respectively, of the active power control element of the k-th converter at the m-th common point. Let be the reference value of the d-axis current output by the active power control loop of the k-th converter at the m-th common point. The state variable introduced for the PI control loop of the active power control loop of the k-th converter at the m-th common point; 3) Construct the inner-loop control equation for the current: in, , These are the actual d-axis and q-axis current values ​​output by the k-th converter at the m-th common point, respectively. , These are the proportional and integral coefficients of the PI element controlling the d-axis current of the k-th converter inner loop at the m-th common point. , These are the proportional and integral coefficients of the PI element in the inner loop control of the k-th converter's q-axis current at the m-th common point. , These are the state variables introduced by the d-axis and q-axis PI control of the inner loop current control link of the k-th converter at the m-th common point, respectively. , These are the output voltages of the d-axis and q-axis of the inner loop current control element of the k-th converter at the m-th common point, respectively. , Let L be the d-axis and q-axis voltages of the k-th converter grid-connected node at the m-th common point. f,m,k The grid-connected filter inductance of the k-th converter at the m-th common point; 4) Construct the dq current differential equation for the filter: 。 5. The method according to claim 4, characterized in that, Also includes: Transform the grid-side current at the common coupling point of the parallel converters from the dq coordinate system to the αβ coordinate system: in, , The actual output current of the k-th converter at the m-th common point in the αβ coordinate system; For grid-side impedance R g + jωL g : in, , These are the grid-side current values ​​at the m-th common point in the αβ coordinate system. , These are the grid-side voltage values ​​in the αβ coordinate system, respectively. , These are the voltage values ​​at the m-th common connection point in the αβ coordinate system; The voltage at the m-th common connection point is superimposed by the injected current: Among them, z g = R g + jωL g Thus, the grid-side voltage of the common connection point in the αβ coordinate system is obtained.

6. A device for constructing a grid-connected multi-converter model based on bidirectional coordinate transformation, characterized in that, include: The first voltage conversion module is used to convert the three-phase voltage of the common connection point of the converters in a grid-connected system with multiple converters and multiple common connection points to the αβ coordinate system by establishing a grid-side static αβ coordinate system; The second voltage conversion module is used to convert the grid-side voltage of the common connection point of the parallel converters in the αβ coordinate system to the dq coordinate system. The control model building module is used to build a converter control loop model in the dq coordinate system based on the voltage transformation results. The voltage calculation module is used to transform the grid-side current of the common connection point of the parallel converter from the dq coordinate system to the αβ coordinate system based on the converter control loop model, and then obtain the grid-side voltage of each common connection point in the αβ coordinate system.

7. The apparatus according to claim 6, characterized in that, The process of converting the three-phase voltage at the common coupling point of the parallel converters to the αβ coordinate system includes: The three-phase voltage at the m-th common coupling point of the parallel converters is transformed to the αβ coordinate system as follows: in, , Let be the voltages at the m-th common connection point in the αβ coordinate system; , , Let be the voltages at the m-th common connection point in the abc coordinate system; T αβ Here is the Clarke transformation matrix: 。 8. The apparatus according to claim 7, characterized in that, The process of converting the grid-side voltage of the common connection point of the parallel converters in the αβ coordinate system to the dq coordinate system includes: The rotation angle is generated by the k-th converter at the m-th common connection point using its own phase-locked loop. The grid-side voltage of the k-th converter at the m-th common connection point in the αβ coordinate system. and Transform to the dq coordinate system: in, , Let represent the d-axis and q-axis voltages at the k-th converter at the m-th common point, respectively; The transformation matrix αβ → dq at the k-th converter at the m-th common point is shown in the following equation: 。 9. The apparatus according to claim 8, characterized in that, The construction of the converter control loop model includes: 1) Construct the differential equations of the phase-locked loop (PLL): in, This represents the q-axis voltage at the k-th converter grid connection point at the m-th common point; The synchronous angular velocity of the power grid; This refers to the state variable introduced in the PLL control of the k-th converter at the m-th common point. Let be the differential term of the intermediate state variable of the PLL control of the k-th converter at the m-th common point. The PLL output phase-locked phase of the k-th converter at the m-th common point is... for The differential term, , These are the proportional and integral parameters of the k-th converter PLL at the m-th common point, respectively. 2) Construct the outer loop control equations: in, Let d be the d-axis current component injected into the grid side by the k-th converter at the m-th common point; Let q be the q-axis current component injected into the grid side by the k-th converter at the m-th common point. This represents the actual power injected into the grid side by the k-th converter at the m-th common point. This represents the reference power of the k-th converter at the m-th common point. , These are the proportional and integral coefficients, respectively, of the active power control element of the k-th converter at the m-th common point. Let be the reference value of the d-axis current output by the active power control loop of the k-th converter at the m-th common point. The state variable introduced for the PI control loop of the active power control loop of the k-th converter at the m-th common point; 3) Construct the inner-loop control equation for the current: in, , These are the actual d-axis and q-axis current values ​​output by the k-th converter at the m-th common point, respectively. , These are the proportional and integral coefficients of the PI element controlling the d-axis current of the k-th converter inner loop at the m-th common point. , These are the proportional and integral coefficients of the PI element in the inner loop control of the k-th converter's q-axis current at the m-th common point. , These are the state variables introduced by the d-axis and q-axis PI control of the inner loop current control link of the k-th converter at the m-th common point, respectively. , These are the output voltages of the d-axis and q-axis of the inner loop current control element of the k-th converter at the m-th common point, respectively. , Let L be the d-axis and q-axis voltages of the k-th converter grid-connected node at the m-th common point. f,m,k The grid-connected filter inductance of the k-th converter at the m-th common point; 4) Construct the dq current differential equation for the filter: 。 10. The apparatus according to claim 9, characterized in that, Also includes: Transform the grid-side current at the common coupling point of the parallel converters from the dq coordinate system to the αβ coordinate system: in, , The actual output current of the k-th converter at the m-th common point in the αβ coordinate system; For grid-side impedance R g + jωL g : in, , These are the grid-side current values ​​at the m-th common point in the αβ coordinate system. , These are the grid-side voltage values ​​in the αβ coordinate system, respectively. , These are the voltage values ​​at the m-th common connection point in the αβ coordinate system; The voltage at the m-th common connection point is superimposed by the injected current: Among them, z g = R g + jωL g Thus, the grid-side voltage of the common connection point in the αβ coordinate system is obtained.

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