Voltage source inverter outer loop limiting method, device, equipment and medium

Abstract

The application belongs to the technical field of electric power automation, and discloses a voltage source inverter outer loop limiting method, device, equipment and medium; the method comprises the following steps: S1, obtaining three preset parameters; S2, calculating the d-axis current component i d and the q-axis current component i q of the VSC injected current i according to the three parameters; S3, judging whether the setting of the three parameters meets a preset condition according to the d-axis current component i d and the q-axis current component i q ; if yes, entering step S4, otherwise, modifying the three parameters and entering step S2; S4, calculating the boundary constraint of the voltage source inverter outer loop limiting according to the three parameters meeting the preset condition; S5, controlling the d-axis current component i d and the q-axis current component i q of the VSC injected current i to be within the boundary constraint. The application designs an improved VSC outer loop limiting strategy, which improves the stability of the VSC grid-connected system while modifying the limiting boundary as little as possible, so as to fully utilize the power electronic equipment and improve the transient stability of the VSC grid-connected system.

Description

Technical Field

[0001] This invention belongs to the field of power automation technology, and specifically relates to a method, device, equipment and medium for limiting the outer loop of a voltage source inverter. Background Technology

[0002] The proportion of renewable energy generation equipment using voltage source converters (VSCs) as grid-connected interfaces in power systems is increasing. VSC grid-connected systems rely on multi-timescale control mechanisms to achieve stable operation with the grid. When a large disturbance occurs in the power system, the control mechanism cannot accurately lock onto the actual state of the power system, leading to erroneous commands that cause renewable energy to disconnect from the grid, seriously jeopardizing the safety and stability of the power system. The controller's limiting mechanism is a crucial measure to prevent erroneous commands; it restricts the controller's command values ​​within a certain range, avoiding multi-stage instability caused by large fluctuations in command values.

[0003] Currently, research on the transient stability of VSC grid-connected systems mainly focuses on the tuning of control parameters and analysis of influencing factors in stages such as phase-locked loops, outer control loops, and inner control loops. Research and patent disclosures on the limiting stage and its impact on transient stability are scarce. Furthermore, the tuning and design of practical limiting stages are mostly based on engineering experience, making it difficult to guarantee their stability during transient processes. Summary of the Invention

[0004] The purpose of this invention is to provide a method, apparatus, device, and medium for limiting the outer loop of a voltage source inverter to improve the transient stability of a VSC grid-connected system.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] In a first aspect, the present invention provides an outer-loop limiting method for a voltage source inverter, comprising:

[0007] S1. Obtain the preset first parameter i lim1 The second parameter i lim2 and the third parameter i lim3 ;

[0008] S2, based on the first parameter i lim1 The second parameter i lim2 and the third parameter i lim3 Calculate the d-axis current component i of the VSC injection current i d and q-axis current component i q ;

[0009] S3. The d-axis current component i of the VSC injection current i obtained from step S2. dand q-axis current component i q Determine the first parameter i lim1 The second parameter i lim2 and the third parameter i lim3 Check if the settings meet the preset conditions; if they do, proceed to step S4; otherwise, modify the first parameter i. lim1 The second parameter i lim2 and the third parameter i lim3 Then proceed to step S2;

[0010] S4. Based on the first parameter i that meets the preset conditions lim1 The second parameter i lim2 and the third parameter i lim3 Calculate the boundary constraints for the outer loop limiting of the voltage source inverter;

[0011] S5, Controlling the d-axis current component i of the VSC injection current i d The q-axis current component of the VSC injected current i q Within the boundary constraints.

[0012] A further improvement of the present invention is that step S2 specifically includes:

[0013] The first parameter i lim1 The second parameter i lim2 and the third parameter i lim3 Substituting into formula (5), we can calculate the d-axis current component i of the VSC injection current i. d ; The q-axis current component of the VSC injected current i q ;

[0014]

[0015] A further improvement of the present invention is that step S3 specifically includes:

[0016] The d-axis current component i of the VSC injection current i obtained in step S2. d The q-axis current component of the VSC injected current i q Substitute into formulas (6) and (7) to determine whether the external preset conditions are met; the preset submission is the ring grid system in the neighborhood Ω of the SEP point. n The necessary and sufficient condition for asymptotic stability is determined; if satisfied, proceed to step S4; otherwise, modify the first parameter i. lim1 The second parameter i lim2 and the third parameter i lim3 Then proceed to step S2;

[0017] V(I)=I T QI (6)

[0018] In the formula, I is [i d -i d0 i q -i q0 Q is a positive definite symmetric matrix that satisfies P = J0 T Q+QJ0, where matrix P is a negative definite identity matrix and matrix J0 is the Jacobian matrix at point SEP;

[0019] V′(I)=f(I) T QI+I T Qf(I) (7)

[0020] In the formula, f(I)=[f1(I),f2(I)] T ;

[0021] Among them, the outer ring grid-connected system is in the neighborhood Ω of the SEP point. n The necessary and sufficient condition for asymptotic stability is:

[0022] 1) V(I) = 0, holds if and only if I = 0;

[0023] 2) V(I)>0, for Established;

[0024] 3) V′(I)<0, for Established.

[0025] A further improvement of the present invention is that step S4 specifically includes:

[0026] The first parameter i that meets the preset conditions lim1 The second parameter i lim2 and the third parameter i lim3 Substituting into formula (8), the boundary constraints of the outer loop limiting of the voltage source inverter are calculated:

[0027]

[0028] In the formula, I max This is the current limit value.

[0029] A further improvement of the present invention is that: the first parameter i lim1 >0; the second parameter i lim2 <i lim3 The second parameter i lim2 Greater than the steady-state d-axis current i d0 .

[0030] Secondly, the present invention provides an outer-loop limiting device for a voltage source inverter, comprising:

[0031] The acquisition module is used to obtain the preset first parameter i. lim1 The second parameter ilim2 and the third parameter i lim3 ;

[0032] The current calculation module is used to calculate the current based on the first parameter i. lim1 The second parameter i lim2 and the third parameter i lim3 Calculate the d-axis current component i of the VSC injection current i d and q-axis current component i q ;

[0033] The judgment module is used to determine the d-axis current component i of the calculated VSC injection current i. d and q-axis current component i q Determine the first parameter i lim1 The second parameter i lim2 and the third parameter i lim3 Does the setting meet the preset conditions? If the preset conditions are met, the first parameter i that meets the preset conditions will be... lim1 The second parameter i lim2 and the third parameter i lim3 Send to the boundary constraint calculation module; otherwise, modify the first parameter i. lim1 The second parameter i lim2 and the third parameter i lim3 Then it is sent to the current calculation module;

[0034] The boundary constraint calculation module is used to calculate the first parameter i that meets the preset conditions. lim1 The second parameter i lim2 and the third parameter i lim3 Calculate the boundary constraints for the outer loop limiting of the voltage source inverter;

[0035] The limiting module is used to control the d-axis current component i of the VSC injected current i. d The q-axis current component of the VSC injected current i q Within the boundary constraints.

[0036] A further improvement of this invention is that the current calculation module calculates the first parameter i. lim1 The second parameter i lim2 and the third parameter i lim3 Substituting into formula (5), we can calculate the d-axis current component i of the VSC injection current i. d ; The q-axis current component of the VSC injected current i q ;

[0037]

[0038] The determination module will determine the d-axis current component i of the VSC injection current i. dThe q-axis current component of the VSC injected current i q Substitute into formulas (6) and (7) to determine whether the external preset conditions are met; the preset submission is the ring grid system in the neighborhood Ω of the SEP point. n The necessary and sufficient condition for asymptotic stability; the first parameter i that satisfies the preset condition when the preset condition is met. lim1 The second parameter i lim2 and the third parameter i lim3 Send to the boundary constraint calculation module; otherwise, modify the first parameter i. lim1 The second parameter i lim2 and the third parameter i lim3 Then it is sent to the current calculation module;

[0039] V(I)=I T QI (6)

[0040] In the formula, I is [i d -i d0 i q -i q0 Q is a positive definite symmetric matrix that satisfies P = J0 T Q+QJ0, where matrix P is a negative definite identity matrix and matrix J0 is the Jacobian matrix at point SEP;

[0041] V′(I)=f(I) T QI+I T Qf(I) (7)

[0042] In the formula, f(I)=[f1(I),f2(I)] T ;

[0043] Among them, the outer ring grid-connected system is in the neighborhood Ω of the SEP point. n The necessary and sufficient condition for asymptotic stability is:

[0044] 1) V(I) = 0, holds if and only if I = 0;

[0045] 2) V(I)>0, for Established;

[0046] 3) V′(I)<0, for Established;

[0047] The first parameter i lim1 >0; the second parameter i lim2 <i lim3 The second parameter i lim2 Greater than the steady-state d-axis current i d0 .

[0048] A further improvement of this invention is that: the boundary constraint calculation module will use the first parameter i that satisfies the preset conditions. lim1 The second parameter i lim2 and the third parameter i lim3 Substituting into formula (8), the boundary constraints of the outer loop limiting of the voltage source inverter are calculated:

[0049]

[0050] In the formula, I max This is the current limit value.

[0051] Thirdly, the present invention provides an electronic device including a processor and a memory, the processor being used to execute a computer program stored in the memory to implement the aforementioned voltage source inverter outer loop limiting method.

[0052] Thirdly, the present invention provides a computer-readable storage medium storing at least one instruction that, when executed by a processor, implements the voltage source inverter outer loop limiting method.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] This invention provides an outer-loop limiting method, device, equipment, and medium for voltage source inverters (VSCs). An improved VSC outer-loop limiting strategy is designed to improve the stability of the VSC grid-connected system while minimizing modifications to the limiting boundary, ensuring full utilization of power electronic equipment and enhancing the transient stability of the VSC grid-connected system.

[0055] The outer ring limiting link has a certain effect on improving the stability of the VSC grid-connected system. A reasonable limiting strategy can switch the system operating point to a trajectory with lower transient energy, which helps to dissipate the transient energy accumulated during the fault.

[0056] The VSC grid-connected system always automatically breaks free from the limiting link constraint at the fixed cut-out point. If the fixed cut-out point is located within the stability domain of the original autonomous system, the VSC grid-connected system under the limiting link constraint will not become unstable.

[0057] This invention proposes an improved outer-loop limiting strategy based on C-UCE, which determines the fixed cut-off point of the VSC grid-connected system by a limiting boundary based on a cubic function. This method improves the stability of the VSC grid-connected system while minimizing modifications to the limiting boundary, allowing for full utilization of power electronic equipment. A case study based on a real VSC grid-connected system verifies the effectiveness of the proposed improved limiting strategy. Attached Figure Description

[0058] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0059] Figure 1 This is a schematic diagram of a VSC grid-connected system model;

[0060] Figure 2 This is a schematic diagram of the outer loop limiting method for a voltage source inverter according to the present invention;

[0061] Figure 3 For the equipotential surface and stability region under amplitude limiting constraints;

[0062] Figure 4 A schematic diagram illustrating the limiting range of the C-UCE limiting strategy;

[0063] Figure 5 This is a comparative diagram of the C-UCE clipping strategy and the traditional clipping strategy.

[0064] Figure 6 This is a flowchart illustrating an outer loop limiting method for a voltage source inverter according to the present invention.

[0065] Figure 7 This is a final structural block diagram of the outer loop limiting of a voltage source inverter according to the present invention;

[0066] Figure 8 This is a structural block diagram of an electronic device according to the present invention. Detailed Implementation

[0067] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0068] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this invention is for describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0069] Example 1

[0070] This invention establishes as follows Figure 1 The VSC grid-connected system model shown is illustrated; the grid side is represented by an infinite power source, and the grid voltage U... g The voltage is an infinite supply voltage; u is the voltage at the VSC sampling point. The VSC collects the voltage vector at this point to achieve grid-following control; u cX is the VSC terminal voltage; i is the VSC injected current into the system; L For grid-connected reactors, R L For grid connection resistors.

[0071] Please see Figure 2 As shown, the present invention provides an outer loop limiting method for a voltage source inverter, comprising:

[0072] Step 1: Establish a VSC grid-connected system model that takes into account the outer ring limit.

[0073] Establish a VSC grid-connected system model that takes into account the outer ring limit:

[0074]

[0075] The variables are as follows:

[0076]

[0077]

[0078]

[0079] In the formula, i d This represents the d-axis current component of the VSC injected current i; i q The q-axis current component represents the VSC injected current i; the active power outer loop is used to track the active power command value P. ref Its output serves as the d-axis current reference value i for the VSC injection system. dref The reactive power outer loop is used to track the reactive power command value Q. ref Its output serves as the q-axis current reference value i for the VSC injection system. qref k p1 The proportional gain of the active power outer loop, k i1 k is the integral coefficient of the active outer loop; p2 The proportional coefficient of the reactive power outer loop, k i2 The integral coefficient of the reactive power outer loop; δ represents the grid voltage U. g The angle between the voltage u at the VSC sampling point and the angle between the voltage u and the VSC sampling point, cosδ is a mathematical operation of the trigonometric cosine function.

[0080] Step 2: Calculate the fixed tangent point

[0081] Define the shape parameters of the outer ring limiting boundary: First parameter i lim1 The third parameter i lim3 The q-axis current threshold and d-axis current threshold respectively determine the switching of the operating point from circular limiting to cubic function limiting; the second parameter i lim2 This determines the zero-crossing points of a cubic function. The fixed point of tangency can be calculated using the following formula:

[0082]

[0083] Step 3: Stability Region Calculation

[0084] Please see Figure 3 As shown, the alternative quadratic Lyapunov function is defined as follows:

[0085] V(I)=I T QI (6)

[0086] In the formula, V(I) represents the numerical value of the transient energy; I is [i d -i d0 i q -i q0 Let Q be a positive definite symmetric matrix given by an individual, satisfying P = J0. T Q+QJ0, where matrix P is a negative definite identity matrix and matrix J0 is the Jacobian matrix at the SEP point. To test the concavity / convexity of the candidate Lyapunov function, its derivative with respect to time is calculated as follows:

[0087] V′(I)=f(I) T QI+I T Qf(I) (7)

[0088] In the formula, f(I)=[f1(I),f2(I)] T As shown in equation (1). According to Lyapunov's second theorem, the outer ring grid-connected system in the neighborhood Ω of the SEP point... n The necessary and sufficient condition for asymptotic stability is:

[0089] 1) V(I) = 0, holds if and only if I = 0;

[0090] 2) V(I)>0, for Established;

[0091] 3) V′(I)<0, for Established.

[0092] Step 4: Outer Ring Width Limiting Design

[0093] This invention proposes an inverter outer-loop limiting method to improve the stability of the fault recovery process. This method is based on circular limiting and uses a cubic function as the limiting boundary near the x-axis. The reason for using a cubic function boundary is that a cubic function has i around its zero-crossing point. d ′≠0,i qThe property that ′=0 ensures that the operating point has a velocity pointing towards the stable equilibrium point in the horizontal direction and a velocity close to 0 in the vertical direction. Furthermore, by designing the shape of the cubic function limiting boundary, the fixed cut-out point can be guaranteed to be located within the stable region, thereby improving the stability of the VSC grid-connected system. The proposed circular and cubic function (C-UCE) limiting strategy is as follows: Figure 4 As shown, its boundary constraints are:

[0094]

[0095] In the formula, I max The current limit value is determined for equipment safety; the circular limiting boundary section retains the original limiting boundary, ensuring safety requirements. The limiting boundary of the cubic function is determined by the first parameter i of the form. lim1 The second parameter i lim2 and the third parameter i lim3 Determined. Wherein, the first parameter i lim1 The third parameter i lim3 These parameters determine the q-axis current threshold and d-axis current threshold, respectively, when the operating point switches from circular limiting to cubic function limiting. To fully utilize the device's current-carrying capacity, the first parameter i... lim1 It is usually a positive number close to 0; the third parameter i lim3 Usually close to I max For positive numbers, it is necessary to ensure that i lim2 lim3 To switch it to a lower energy orbital as much as possible; the second parameter i lim2 The zero-crossing point of the cubic function is determined. To ensure the existence of a stable equilibrium point in the VSC grid-connected system, its value should be greater than the steady-state d-axis current i. d0 and as close to i as possible d0 This ensures that the fixed cut-out point is located within the stable region.

[0096] Example 2

[0097] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following description is provided in conjunction with... Figure 5 The embodiments of the present invention will be further described in detail below. Here, the illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0098] S01: As Figure 1 As shown, a VSC grid-connected system model considering the outer ring limiting is established:

[0099]

[0100] The variables are as follows:​

[0101]

[0102]

[0103]

[0104] In the formula, i d This represents the d-axis current component of the VSC injected current i; i q The q-axis current component represents the VSC injected current i; the active power outer loop is used to track the active power command value P. ref Its output serves as the d-axis current reference value i for the VSC injection system. dref The reactive power outer loop is used to track the reactive power command value Q. ref Its output serves as the q-axis current reference value i for the VSC injection system. qref k p1 k i1 For the PI parameters of the active outer loop; k p2 k i2 The PI parameters are for the reactive outer loop.

[0105] S02: Fixed cut-out point calculation.

[0106] As can be seen from formula (5), if the traditional clipping strategy is used, the fixed cut-off point is D1. If the improved C-UCE clipping strategy of this invention is used, the fixed cut-off point is D2.

[0107] like Figure 5 As shown, the trajectory of the running point under weak systems with high initial transient energy using the C-UCE limiting strategy and the typical limiting strategy is compared and analyzed. An autonomous system S1 with a certain initial transient energy starts from point A and runs along the autonomous trajectory to point B1. Due to the action of the circular limiting element, the autonomous system switches from S1 to S2, and the running point will move along the circular limiting boundary B1H.

[0108] If a traditional circular limiting circuit is used, the operating point continues to move along the circular limiting boundary after passing point H until it reaches the fixed cut-out point D1 and leaves the limiting circuit. Finally, it converges to the intersection of the circular limiting boundary and the x-axis. The actual power generated by the VSC grid-connected system cannot follow the power command value, and the VSC grid-connected system becomes unstable.

[0109] If the C-UCE limiting strategy of this invention is adopted, after the running point reaches point H, it will switch to autonomous system S4 and continue to move along the univariate cubic function limiting boundary until it reaches the fixed cut-out point D2, leaving the univariate cubic limiting boundary and switching back to the original autonomous system S1. The position of the fixed cut-out point D2 can be obtained by simultaneously solving the state equations of the univariate cubic limiting boundary and autonomous system S1:

[0110]

[0111] The improved limiting strategy proposed in this invention ensures that the fixed cut-out point is located within the stability domain of the original autonomous system S1, so that the operating point has a speed that tends towards the stable equilibrium point. Under the premise of ensuring the safety of power electronic equipment, the limiting boundary is modified as little as possible, which improves the stability of the VSC grid-connected system and allows the power electronic equipment to be fully utilized.

[0112] S03: Stability Domain Calculation

[0113] Based on formulas (6) and (7), the stability domain of the VSC grid-connected system is calculated as follows: Figure 5 The shaded area is shown by the diagonal line. If the three necessary and sufficient conditions of formulas (6) and (7) are satisfied, then it is inside the stability region.

[0114] S04: Outer Ring Brake Limiting Design

[0115] The circular-univariate cubic equation (C-UCE) limiting strategy proposed in this invention is as follows: Figure 4 As shown, its boundary constraints are:

[0116]

[0117] In the formula, I max The current limit value is determined for equipment safety; the circular limiting boundary section retains the original limiting boundary, ensuring safety requirements. The limiting boundary of the cubic function is determined by the first parameter i of the form. lim1 The second parameter i lim2 and the third parameter i lim3 Determined. Wherein, the first parameter i lim1 The third parameter i lim3 These parameters determine the q-axis current threshold and d-axis current threshold, respectively, when the operating point switches from circular limiting to cubic function limiting. To fully utilize the device's current-carrying capacity, the first parameter i... lim1 It is usually a positive number close to 0; the third parameter i lim3 Usually close to I max For positive numbers, it is necessary to ensure that i lim2 lim3 To switch it to a lower energy orbital as much as possible; the second parameter i lim2 The zero-crossing point of the cubic function is determined. To ensure the existence of a stable equilibrium point in the VSC grid-connected system, its value should be greater than the steady-state d-axis current i. d0 and as close to i as possible d0 This ensures that the fixed cut-out point is located within the stable region.

[0118] ​If the traditional outer loop limiting strategy is adopted, the operating point will move along the trajectory of AB1HD1, and the VSC grid-connected system cannot achieve constant power control. If the C-UCE outer loop limiting strategy proposed in this invention is adopted, the operating point is obtained by formula (1); the operating point will move along the trajectory of AB1HB2D2S, and the operating point will eventually return to the stable equilibrium point, and the VSC grid-connected system can achieve constant power control.

[0119] Example 3

[0120] Please see Figure 6 As shown, the present invention provides an outer loop limiting method for a voltage source inverter, comprising the following steps:

[0121] S1. Obtain the preset first parameter i lim1 The second parameter i lim2 and the third parameter i lim3 From formulas (1)-(4), the d-axis current component i of the VSC injection current i is obtained. d q-axis current component i q The mathematical relationship with other parameters; substituting formula (1) into formulas (6) and (7), we obtain all d-axis current components i d q-axis current component i q The corresponding V value and V' value;

[0122]

[0123] The variables are as follows:

[0124]

[0125]

[0126]

[0127] In the formula, i d This represents the d-axis current component of the VSC injected current i; i q The q-axis current component represents the VSC injected current i; the active power outer loop is used to track the active power command value P. ref Its output serves as the d-axis current reference value i for the VSC injection system. dref The reactive power outer loop is used to track the reactive power command value Q. ref Its output serves as the q-axis current reference value i for the VSC injection system. qref k p1 The proportional gain of the active power outer loop, k i1 k is the integral coefficient of the active outer loop; p2 The proportional coefficient of the reactive power outer loop, k i2 The integral coefficient of the reactive power outer loop; δ represents the grid voltage U. gThe angle between the voltage u at the VSC sampling point and the angle between the voltage u and the VSC sampling point, cosδ is a mathematical operation of the trigonometric cosine function.

[0128] V(I)=I T QI (6)

[0129] In the formula, V(I) represents the numerical value of the transient energy; I is [i d -i d0 i q -i q0 Let Q be a positive definite symmetric matrix given by an individual, satisfying P = J0. T Q+QJ0, where matrix P is a negative definite identity matrix and matrix J0 is the Jacobian matrix at the SEP point. To test the concavity / convexity of the candidate Lyapunov function, its derivative with respect to time is calculated as follows:

[0130] V′(I)=f(I) T QI+I T Qf(I) (7)

[0131] In the formula, f(I)=[f1(I),f2(I)] T As shown in equation (1).

[0132] S2, the first parameter i obtained lim1 The second parameter i lim2 and the third parameter i lim3 Substituting into formula (5), we can calculate the d-axis current component i of the VSC injection current i. d ; The q-axis current component of the VSC injected current i q ;

[0133]

[0134] S3. Calculate the d-axis current component i of the VSC injection current i. d The q-axis current component of the VSC injected current i q Substitute these values ​​into formulas (6) and (7) to determine the V and V' values ​​at this point. Determine whether the V and V' values ​​at this point satisfy the condition of the outer ring grid-connected system in the neighborhood of the SEP point Ω. n The necessary and sufficient condition for asymptotic stability is met; if the condition is met, proceed to step S4 to calculate the required amplitude limit boundary; otherwise, modify the first parameter i. lim1 The second parameter i lim2 and the third parameter i lim3 Then proceed to step S2;

[0135] V(I)=I T QI (6)

[0136] In the formula, I is [i d -id0 i q -i q0 Q is a positive definite symmetric matrix that satisfies P = J0 T Q+QJ0, where matrix P is a negative definite identity matrix and matrix J0 is the Jacobian matrix at the SEP point; to test the concavity and convexity of the candidate Lyapunov function, its derivative with respect to time is calculated as follows:

[0137] V′(I)=f(I) T QI+I T Qf(I) (7)

[0138] In the formula, f(I)=[f1(I),f2(I)] T ;

[0139] Among them, the outer ring grid-connected system is in the neighborhood Ω of the SEP point. n The necessary and sufficient condition for asymptotic stability is:

[0140] 1) V(I) = 0, holds if and only if I = 0;

[0141] 2) V(I)>0, for Established;

[0142] 3) V′(I)<0, for Established;

[0143] S4, will satisfy the outer ring grid connection system in the neighborhood of SEP point Ω n The first parameter i of the necessary and sufficient condition for asymptotic stability lim1 The second parameter i lim2 and the third parameter i lim3 Substituting into formula (8), the boundary constraints of the outer loop limiting of the voltage source inverter are calculated:

[0144]

[0145] In the formula, I max The current limit value is determined for equipment safety; the circular limiting boundary section retains the original limiting boundary, ensuring safety requirements; the cubic function limiting boundary is determined by the first morphological parameter i. lim1 The second parameter i lim2 and the third parameter i lim3 Determined; where the first parameter i lim1 The third parameter i lim3 These parameters determine the q-axis current threshold and d-axis current threshold, respectively, when the operating point switches from circular limiting to cubic function limiting. To fully utilize the device's current-carrying capacity, the first parameter i... lim1 It is usually a positive number close to 0; the third parameter i lim3 Usually close to Imax For positive numbers, it is necessary to ensure that i lim2 lim3 To switch it to a lower energy orbital as much as possible; the second parameter i lim2 The zero-crossing point of the cubic function is determined. To ensure the existence of a stable equilibrium point in the VSC grid-connected system, its value should be greater than the steady-state d-axis current i. d0 and as close to i as possible d0 This ensures that the fixed cut-out point is located within the stable region;

[0146] S5, Controlling the d-axis current component i of the VSC injection current i d The q-axis current component of the VSC injected current i q Within the boundary constraints.

[0147] Example 4

[0148] Please see Figure 7 As shown, the present invention provides an outer loop limiting device for a voltage source inverter, comprising:

[0149] The acquisition module is used to obtain the preset first parameter i. lim1 The second parameter i lim2 and the third parameter i lim3 ;

[0150] The current calculation module is used to calculate the current based on the first parameter i. lim1 The second parameter i lim2 and the third parameter i lim3 Calculate the d-axis current component i of the VSC injection current i d and q-axis current component i q ;

[0151] The judgment module is used to determine the d-axis current component i of the calculated VSC injection current i. d and q-axis current component i q Determine the first parameter i lim1 The second parameter i lim2 and the third parameter i lim3 Does the setting meet the preset conditions? If the preset conditions are met, the first parameter i that meets the preset conditions will be... lim1 The second parameter i lim2 and the third parameter i lim3 Send to the boundary constraint calculation module; otherwise, modify the first parameter i. lim1 The second parameter i lim2 and the third parameter i lim3 Then it is sent to the current calculation module;

[0152] The boundary constraint calculation module is used to calculate the first parameter i that meets the preset conditions. lim1 ​The second parameter i lim2 and the third parameter i lim3 Calculate the boundary constraints for the outer loop limiting of the voltage source inverter;

[0153] The limiting module is used to control the d-axis current component i of the VSC injected current i. d The q-axis current component of the VSC injected current i q Within the boundary constraints.

[0154] In one specific implementation, the current calculation module will use the first parameter i lim1 The second parameter i lim2 and the third parameter i lim3 Substituting into formula (5), we can calculate the d-axis current component i of the VSC injection current i. d ; The q-axis current component of the VSC injected current i q ;

[0155]

[0156] The determination module will determine the d-axis current component i of the VSC injection current i. d The q-axis current component of the VSC injected current i q Substitute into formulas (6) and (7) to determine whether the external preset conditions are met; the preset submission is the ring grid system in the neighborhood Ω of the SEP point. n The necessary and sufficient condition for asymptotic stability; the first parameter i that satisfies the preset condition when the preset condition is met. lim1 The second parameter i lim2 and the third parameter i lim3 Send to the boundary constraint calculation module; otherwise, modify the first parameter i. lim1 The second parameter i lim2 and the third parameter i lim3 Then it is sent to the current calculation module;

[0157] V(I)=I T QI (6)

[0158] In the formula, I is [i d -i d0 i q -i q0 Q is a positive definite symmetric matrix that satisfies P = J0 T Q+QJ0, where matrix P is a negative definite identity matrix and matrix J0 is the Jacobian matrix at point SEP;

[0159] V′(I)=f(I) T QI+I T Qf(I) (7)

[0160] In the formula, f(I)=[f1(I),f2(I)] T ;

[0161] Among them, the outer ring grid-connected system is in the neighborhood Ω of the SEP point. n The necessary and sufficient condition for asymptotic stability is:

[0162] 1) V(I) = 0, holds if and only if I = 0;

[0163] 2) V(I)>0, for Established;

[0164] 3) V′(I)<0, for Established;

[0165] The first parameter i lim1 >0; the second parameter i lim2 <i lim3 The second parameter i lim2 Greater than the steady-state d-axis current i d0 .

[0166] In one specific implementation, the boundary constraint calculation module will calculate the first parameter i that satisfies the preset conditions. lim1 The second parameter i lim2 and the third parameter i lim3 Substituting into formula (8), the boundary constraints of the outer loop limiting of the voltage source inverter are calculated:

[0167]

[0168] In the formula, I max This is the current limit value.

[0169] Example 5

[0170] Please see Figure 8 As shown, the present invention also provides an electronic device 100 for implementing the outer loop limiting method of a voltage source inverter; the electronic device 100 includes a memory 101, at least one processor 102, a computer program 103 stored in the memory 101 and executable on the at least one processor 102, and at least one communication bus 104.

[0171] The memory 101 can be used to store the computer program 103. The processor 102 implements the steps of the voltage source inverter outer loop limiting method described in Embodiments 1, 2, or 3 by running or executing the computer program stored in the memory 101 and calling the data stored in the memory 101. The memory 101 may mainly include a program storage area and a data storage area. The program storage area may store the operating system, at least one application program required for a function (such as sound playback function, image playback function, etc.), etc.; the data storage area may store data created according to the use of the electronic device 100 (such as audio data), etc. In addition, the memory 101 may include non-volatile memory, such as hard disk, memory, plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, at least one disk storage device, flash memory device, or other non-volatile solid-state storage device.

[0172] The at least one processor 102 may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The processor 102 may be a microprocessor or any conventional processor. The processor 102 is the control center of the electronic device 100, connecting various parts of the electronic device 100 via various interfaces and lines.

[0173] The memory 101 in the electronic device 100 stores multiple instructions to implement a voltage source inverter outer loop limiting method, and the processor 102 can execute the multiple instructions to achieve the following:

[0174] S1. Obtain the preset first parameter i lim1 The second parameter i lim2 and the third parameter i lim3 ;

[0175] S2, based on the first parameter i lim1 The second parameter i lim2 and the third parameter i lim3 Calculate the d-axis current component i of the VSC injection current i d and q-axis current component iq ;

[0176] S3. The d-axis current component i of the VSC injection current i obtained from step S2. d and q-axis current component i q Determine the first parameter i lim1 The second parameter i lim2 and the third parameter i lim3 Check if the settings meet the preset conditions; if they do, proceed to step S4; otherwise, modify the first parameter i. lim1 The second parameter i lim2 and the third parameter i lim3 Then proceed to step S2;

[0177] S4. Based on the first parameter i that meets the preset conditions lim1 The second parameter i lim2 and the third parameter i lim3 Calculate the boundary constraints for the outer loop limiting of the voltage source inverter;

[0178] S5, Controlling the d-axis current component i of the VSC injection current i d The q-axis current component of the VSC injected current i q Within the boundary constraints.

[0179] Specifically, the specific implementation method of the processor 102 for the above instructions can be referred to the description of the relevant steps in Embodiment 3, and will not be repeated here.

[0180] Example 6

[0181] If the modules / units integrated in the electronic device 100 are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, and a read-only memory (ROM).

[0182] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0183] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0184] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0185] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0186] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A voltage source inverter outer loop limiting method, characterized in that, include: Step S1: Obtain the preset first parameter i lim1 Second parameter i lim2 and the third parameter i lim3 First parameter i lim1 Third parameter i lim3 The second parameter determines the q-axis current threshold and d-axis current threshold values ​​for switching the operating point from circular limiting to cubic function limiting; i lim2 It determines the zero-crossing points of a cubic function; the first parameter i lim1 >0; second parameter i lim2 < i lim3 ; second parameter i lim2 Greater than steady-state d-axis current i d0 ; Step S2: Based on the first parameter i lim1 Second parameter i lim2 and the third parameter i lim3 Calculate the d-axis current component of the VSC injected current i and q-axis current component ; Step S3: Calculate the d-axis current component of the VSC injection current i obtained in step S2. and q-axis current component Determine the first parameter i lim1 Second parameter i lim2 and the third parameter i lim3 Does the setting meet the preset conditions? If the preset conditions are met, proceed to step S4; otherwise, modify the first parameter. i lim1 Second parameter i lim2 and the third parameter i lim3 Then proceed to step S2; Step S4: Based on the first parameter that meets the preset conditions i lim1 Second parameter i lim2 and the third parameter i lim3 Calculate the boundary constraints for the outer loop limiting of the voltage source inverter; Step S5: Control the d-axis current component of the VSC injection current i q-axis current component of VSC injected current i Within the boundary constraints; Step S2 specifically includes: The first parameter i lim1 Second parameter i lim2 and the third parameter i lim3 Substituting into formula (5), the d-axis current component of the VSC injection current i is calculated. ; q-axis current component of VSC injected current i ; (5)； Step S3 specifically includes: The d-axis current component of the VSC injection current i obtained in step S2. q-axis current component of VSC injected current i Substitute into formulas (6) and (7) to determine whether the preset conditions are met; the preset conditions are that the ring-connected system in the neighborhood Ω of the SEP point. n The necessary and sufficient conditions for asymptotic stability are determined; if satisfied, proceed to step S4; otherwise, modify the first parameter. i lim1 Second parameter i lim2 and the third parameter i lim3 Then proceed to step S2; (6) In the formula, I for[ i d - i d0 , i q - i q0 ], Q It is a positive definite symmetric matrix that satisfies P = J 0 T Q + QJ 0, where the matrix P For a negative definite identity matrix, the matrix J 0 represents the Jacobian matrix at the SEP point; (7) In the formula, f ( I ) = [ f 1( I ), f 2( I )] T ; in, (1) The outer ring grid-connected system in the neighborhood Ω of the SEP point n The necessary and sufficient condition for asymptotic stability is: 1) V ( I ) = 0, if and only if I = 0 condition; 2) V ( I )>0, for I Ω n 0 is true; 3) V ( I )<0, for I Ω n \{0} is true.

2. The voltage source inverter outer loop limiting method according to claim 1, characterized in that, Step S4 specifically includes: The first parameter that meets the preset conditions i lim1 Second parameter i lim2 and the third parameter i lim3 Substituting into formula (8), the boundary constraints for the outer loop limiting of the voltage source inverter are calculated: (8) In the formula, I max This is the current limit value.

3. An outer-loop limiting device for a voltage source inverter, characterized in that, include: The acquisition module is used to obtain the preset first parameter. i lim1 Second parameter i lim2 and the third parameter i lim3 First parameter i lim1 Third parameter i lim3 The second parameter determines the q-axis current threshold and d-axis current threshold values ​​for switching the operating point from circular limiting to cubic function limiting; i lim2 It determines the zero-crossing points of a cubic function; the first parameter i lim1 >0; second parameter i lim2 < i lim3 ; second parameter i lim2 Greater than steady-state d-axis current i d0 ; The current calculation module is used to calculate the current based on the first parameter. i lim1 Second parameter i lim2 and the third parameter i lim3 Calculate the d-axis current component of the VSC injected current i and q-axis current component ; The judgment module is used to determine the d-axis current component of the VSC injection current i obtained through calculation. and q-axis current component Determine the first parameter i lim1 Second parameter i lim2 and the third parameter i lim3 Does the setting meet the preset conditions? When the preset conditions are met, the first parameter that meets the preset conditions will be... i lim1 Second parameter i lim2 and the third parameter i lim3 Send to the boundary constraint calculation module; otherwise, modify the first parameter. i lim1 Second parameter i lim2 and the third parameter i lim3 Then it is sent to the current calculation module; The boundary constraint calculation module is used to calculate the first parameter that meets the preset conditions. i lim1 Second parameter i lim2 and the third parameter i lim3 Calculate the boundary constraints for the outer loop limiting of the voltage source inverter; The limiting module is used to control the d-axis current component of the VSC injected current i. q-axis current component of VSC injected current i Within the boundary constraints; The current calculation module will use the first parameter i lim1 Second parameter i lim2 and the third parameter i lim3 Substituting into formula (5), the d-axis current component of the VSC injection current i is calculated. ; q-axis current component of VSC injected current i ; (5) The determination module will determine the d-axis current component of the VSC injection current i. q-axis current component of VSC injected current i Substitute into formulas (6) and (7) to determine whether the preset conditions are met; The preset condition is that the ring-connected system is in the neighborhood Ω of the SEP point. n Necessary and sufficient conditions for asymptotic stability; When the preset conditions are met, the first parameter that meets the preset conditions will be... i lim1 Second parameter i lim2 and the third parameter i lim3 Send to the boundary constraint calculation module; otherwise, modify the first parameter. i lim1 Second parameter i lim2 and the third parameter i lim3 Then it is sent to the current calculation module; (6) In the formula, I for[ i d - i d0 , i q - i q0 ], Q It is a positive definite symmetric matrix that satisfies P = J 0 T Q + QJ 0, where the matrix P For a negative definite identity matrix, the matrix J 0 represents the Jacobian matrix at the SEP point; (7) In the formula, f ( I ) = [ f 1( I ), f 2( I )] T ; in, (1) The outer ring grid-connected system in the neighborhood Ω of the SEP point n The necessary and sufficient condition for asymptotic stability is: 1) V ( I ) = 0, if and only if I = 0 condition; 2) V ( I )>0, for I Ω n 0 is true; 3) V ( I )<0, for I Ω n \{0} is true.

4. The voltage source inverter outer loop limiting device according to claim 3, characterized in that, The boundary constraint calculation module will satisfy the first parameter of the preset conditions. i lim1 Second parameter i lim2 and the third parameter i lim3 Substituting into formula (8), the boundary constraints for the outer loop limiting of the voltage source inverter are calculated: (8) In the formula, I max This is the current limit value.

5. An electronic device, characterized in that, It includes a processor and a memory, the processor being used to execute a computer program stored in the memory to implement the voltage source inverter outer loop limiting method as described in any one of claims 1 to 2.

6. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores at least one instruction, which, when executed by a processor, implements the voltage source inverter outer loop limiting method as described in any one of claims 1 to 2.

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