Feasible-region solving and reconstruction method and system for hybrid grid-following and grid-forming converter grid-tied system

Abstract

The present invention relates to a feasible-region solving and reconstruction method and system for a hybrid grid-following and grid-forming converter grid-tied system. The method comprises: acquiring hybrid converter grid-tied system parameters and alternating-current power grid parameters; by means of grouping and equivalent aggregation, simplifying a hybrid converter grid-tied system into a plurality of equivalent grid-following or grid-forming converters; theoretically determining a capacity feasible region satisfying overload capacity constraints and a static voltage stability feasible region satisfying static voltage stability constraints; discretizing an intersection of the capacity feasible region and the static voltage stability feasible region; determining, point by point, whether an operating condition satisfies wideband oscillation constraints, and if so, determining that the operating condition belongs to an operational feasible region of the hybrid converter grid-tied system, so as to finally obtain an operational feasible region of a hybrid grid-following and grid-forming converter grid-tied system; and expanding and reconstructing the operational feasible region by configuring grid-forming converters. The present invention considers the differences between different converters and all operating conditions that the converters may face, and can ensure the safe and stable operation of the converter grid-tied system.

Description

Feasibility domain solution, reconfiguration method and system for grid-connected hybrid converter systems Technical Field

[0001] This invention belongs to the field of power technology, and in particular relates to a feasible domain solution and reconfiguration method and system for grid-connected hybrid converter systems. Background Technology

[0002] Wind power and photovoltaic converters are connected to the AC grid via grid-connected or grid-connected converters. The randomness, volatility, and intermittency of new energy output lead to complex and variable operating conditions for these converters. As operating conditions change, the converter's operating characteristics (such as grid connection point voltage and oscillation characteristics) also change. Under certain operating conditions, the unit may face risks such as exceeding output current limits, port voltage not meeting grid connection requirements, or wide-frequency oscillation instability. These risks make it difficult for the converter-connected grid system to operate safely and stably, and in severe cases, may even lead to equipment damage or grid disconnection. Therefore, it is necessary to define the feasible operating domain of the converter-connected grid system to guide the system in avoiding risky operating conditions during operation, thereby ensuring the safe and stable operation of the system. However, existing research often treats hybrid converter grid-connected systems as equivalent to a single converter, ignoring the differences between different converters. Furthermore, when solving for the feasible operating domain, only a few typical operating conditions are analyzed, without fully considering all possible operating conditions that the converter may face. To ensure the safe and stable operation of the converter grid-connected system, it is necessary to study a method for solving the feasible operating domain that takes into account the differences between converters and all operating conditions. Summary of the Invention

[0003] The purpose of this invention is to provide a method and system for solving the feasible domain and reconfiguring a grid-connected hybrid converter system to solve the above-mentioned technical problems.

[0004] This invention provides

[0005] A method for solving and reconstructing the feasible region of a grid-connected system with a hybrid converter includes the following steps:

[0006] Step 1: Obtain the parameters of the hybrid converter grid-connected system and the AC grid parameters;

[0007] Step 2: The hybrid converter grid-connected system is simplified into multiple equivalent grid-connected or grid-connected converters by using the grouping method and the equivalent aggregation method.

[0008] Step 3: Theoretically solve the capacity feasible region that satisfies the overload capacity constraint and the static voltage stability feasible region that satisfies the static voltage stability constraint.

[0009] Step 4: Discretize the intersection of the capacity feasible region and the static voltage stability feasible region to obtain the discretized set;

[0010] Step 5: Determine whether the operating conditions within the discretized set satisfy the wideband oscillation constraint point by point. If they do, the operating condition belongs to the feasible operating region of the hybrid converter grid-connected system. Finally, the feasible operating region of the grid-connected hybrid converter system with and without grid connection is obtained.

[0011] Step 6: Expand and reconfigure the operational feasible domain by configuring the network converter.

[0012] Furthermore, the parameters of the hybrid converter grid-connected system mentioned in step 1 include the system circuit topology, the number of converters, the installation location of the grid-connected converters, the installation location of the grid-connected converters, the corresponding feeder impedance and step-up transformer impedance of each converter, the impedance model of the reactive power compensation device, and the impedance model of each converter; the AC grid parameters include the power supply amplitude range, the series resistance range, and the series reactance range.

[0013] Furthermore, the grouping method described in step 2 includes: classifying reactive power compensation devices as converters, grouping converters of the same model, with the same control parameters and geographical proximity into the same group, and by default, all converters in the group have the same active and reactive power outputs, and the same control strategies and parameters.

[0014] The equivalent aggregation method includes:

[0015] All units within the group are equivalently aggregated into a single grid-connected or grid-connected converter, and the equivalent converter is connected to the grid bus via a feeder. Three types of parameters are solved for the equivalent aggregation. The solution methods for each parameter include: 1) The impedance model of the equivalent converter is the same as that of the equivalent units within the group; 2) The active / reactive power output of the equivalent converter is the sum of the active / reactive power outputs of the equivalent units within the group; 3) The equivalent feeder impedance is solved based on the principle of consistent power loss.

[0016] Further, step 3 includes:

[0017] Suppose that there are m equivalent converters in the hybrid converter grid-connected system, and each converter is connected to the grid connection point via an equivalent feeder, and then connected to the AC grid; the operating conditions of the hybrid converter grid-connected system are expressed as: Ω0=[P1,Q1,…,P i Q i ,…,P m Q m ], i = 1, 2, ..., m

[0018] In the formula: P i Q i Let represent the active and reactive power outputs of the i-th equivalent converter; n is the total number of equivalent converters.

[0019] Capacity feasible range (Ω) for hybrid converter grid-connected systems I The solution method is as follows:

[0020] Static voltage stability feasible range (Ω) for hybrid converter grid-connected systems V Its expression is: Ω V ={(P1,Q1,…,P i Q i ,…,P m Q m )|0.9pu<V i <1.1pu,i=1,2,…,m}

[0021] In the formula: V i Let be the effective value of the high-voltage side voltage of the step-up transformer of the i-th equivalent converter. Let P be the voltage on the step-up transformer of the i-th equivalent converter, and both are related to the active power input P of the equivalent converter. i and no Q i The function;

[0022] Given the equivalent converter output power P i Q i When, use the following formula to solve.

[0023] In the formula: Z represents the output current of the i-th equivalent converter; the superscript * indicates the conjugate of the complex number; Z i Let be the equivalent feeder impedance of the i-th equivalent converter; R is the grid connection point voltage; g X g These are the equivalent resistance and equivalent reactance of the AC power grid, respectively.

[0024] Further, step 4 includes:

[0025] The set of operating conditions Ω for a hybrid converter grid-connected system that simultaneously meets overload capacity constraints, static voltage stability constraints, and inverter self-constraints. I ∩Ω V By uniformly dividing the Ω region, a finite number of operating points are obtained, which is Ω. I ∩Ω V Discretization of sets;

[0026] The discretized set is defined as Ω. VI The expression is: Ω VI ={(k P,1 ΔP,k P,1 ΔQ,…,k P,i ΔP,k Q,i ΔQ,…,k P,m ΔP,k Q,m ΔQ)∈(Ω I ∩ΩV )}

[0027] In the formula: ΔP and ΔQ are the active step size and reactive step size, respectively; k P,i k Q,i Let be the discrete coefficient of the i-th equivalent converter.

[0028] Furthermore, in step 5, if the damping of all oscillation modes is greater than zero, then the operating condition is determined to belong to the feasible operating domain of the hybrid converter grid-connected system.

[0029] The steps for solving the damping of the oscillation mode are as follows:

[0030] a) Aggregate the impedance models of each device in the system to obtain the aggregated system impedance Z. Σ ;

[0031] b) Solve for the determinant D of the system's pooling impedance. Σ D Σ (s)=R Σ +jX Σ =Z Σ11 (s)Z Σ22 (s)-Z Σ12 (s)Z Σ21 (s)

[0032] In the formula: Z Σ11 Z Σ12 Z Σ21 and Z Σ22 Z Σ The four elements; D Σ (s) The real part is defined as the equivalent resistance R. Σ The imaginary part is defined as the equivalent reactance X. Σ ;

[0033] c) Based on the equivalent resistance R Σ and equivalent reactance X Σ Solving for oscillation damping includes:

[0034] Equivalent reactance X Σ A zero-crossing point corresponds to an oscillation mode. Based on the properties of this zero-crossing point, the oscillation damping σ and oscillation frequency ω corresponding to this oscillation mode can be solved using the following expression:

[0035] In the formula: k R and k X R represents the slope of the equivalent resistance curve and the equivalent reactance curve, respectively. Σ ω is the equivalent resistance; r The frequency that crosses zero.

[0036] Further, step 6 includes:

[0037] If all operating conditions within the discretized set do not satisfy the condition that the oscillation mode damping is greater than zero, then the proportion of grid-connected converters is increased until the discretized set coincides with the feasible operating region of the hybrid converter grid-connected system; the steps for increasing the proportion of grid-connected converters are as follows:

[0038] (a) Select the node where the grid-connected converter is located, which is the farthest from the grid connection point in terms of electrical distance, and replace it with the grid-connected converter;

[0039] (b) Solve step 2 through step 4 in sequence to obtain the discretized set Ω. VI ;

[0040] (c) Solve for the feasible operating domain Ω of the hybrid converter grid-connected system according to step 5;

[0041] (d) Determine the discretized set Ω VI If the feasible region Ω of the grid-connected system with the hybrid converter overlaps, the optimal number and location of the grid-connected converters are obtained; if they do not overlap, steps (a) to (c) are repeated.

[0042] This invention also provides a feasible region solution and reconfiguration system for a grid-connected hybrid converter system, comprising:

[0043] The input unit is used to input the parameters of the hybrid converter grid-connected system and the AC grid parameters;

[0044] Equivalent aggregation unit is used to simplify a hybrid converter grid-connected system into multiple equivalent grid-connected or grid-forming converters through grouping and equivalent aggregation methods.

[0045] Capacity and static voltage feasible region solution unit, used to theoretically solve the capacity feasible region that satisfies overload capacity constraints and the static voltage stability feasible region that satisfies static voltage stability constraints;

[0046] The feasible region discretization unit is used to discretize the intersection of the capacity feasible region and the static voltage stability feasible region to obtain the discretized set.

[0047] The feasible region solution unit is used to determine point by point whether the operating conditions within the discretized set meet the wideband oscillation constraint. If they do, the operating condition belongs to the feasible region of the hybrid converter grid-connected system, and finally the feasible region of the grid-connected hybrid converter system with and without grid connection is obtained.

[0048] The operational feasible domain reconfiguration unit is used to expand and reconfigure the operational feasible domain by configuring the network converter;

[0049] The output unit is used to output the operational feasibility domain of the hybrid converter grid-connected system and the configuration results of the grid-connected converter.

[0050] The present invention also provides a non-transitory computer-readable storage medium that stores computer instructions, which, when executed by a processor, implement the feasible domain solution and reconfiguration method of the grid-connected hybrid converter system.

[0051] The present invention also provides an electronic device, comprising:

[0052] The system includes a memory and a processor, which are interconnected. The memory stores computer instructions, and the processor executes these computer instructions to perform the feasible domain solution and reconfiguration method for the grid-connected hybrid converter system.

[0053] By employing the above scheme, through the solution of the feasible domain of the grid-connected system of the hybrid converter, the reconstruction method and system, and considering the differences between different converters and all the operating conditions that the converters may face, the safe and stable operation of the grid-connected system of the converter can be guaranteed.

[0054] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0055] Figure 1 is a circuit topology of a converter grid-connected system in one embodiment of the invention;

[0056] Figure 2 is an equivalent circuit topology of a new energy grid-connected system in one embodiment of the invention;

[0057] Figure 3 is a flowchart of the feasible domain solution and reconfiguration method for the grid-connected system of the invention and the hybrid converter.

[0058] Figure 4 is a schematic diagram of the feasible domain solution and reconfiguration system of the grid-connected hybrid converter system of the invention;

[0059] Figure 5 is a schematic diagram of the structure of an electronic device. Detailed Implementation

[0060] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0061] The grid topology of the converter grid-connected system is shown in Figure 1. The converter control modes include two types: grid-connected and grid-connected. Therefore, this system is also called a hybrid grid-connected and grid-connected converter grid-connected system. Figure 1 shows a total of n converters. Each converter is connected to a feeder via a 0.69 / 35kV step-up transformer, and then connected to the AC grid via the feeder, Z1, Z2, ..., Z... nThese represent the feeder impedances corresponding to each converter; the AC power grid is equivalent to an infinite power source with series impedance, where the power source amplitude is V. g The series resistance is R g The series reactance is X g To improve system voltage stability, reactive power compensation devices are typically installed in the system, including but not limited to SVG and STATCOM.

[0062] The combination of active power P and reactive power Q at the converter output represents a certain operating condition. Therefore, any operating condition Ω0 of the system can be expressed as Ω0 = [P1, Q1, ..., P i Q i ,…,P n Q n ], i = 1, 2, ..., n (1)

[0063] In the formula: P i Q i Let represent the active and reactive power outputs of the i-th converter; n is the total number of converters.

[0064] During the operation of a hybrid converter grid-connected system, it is necessary to meet the converter overload capacity constraints, static voltage stability constraints, and wideband oscillation stability constraints to ensure the safe and stable operation of the system.

[0065] The set of operating conditions that satisfy the overload capacity constraint is defined as the capacity feasible region Ω. I Ω I The definition can be based on either the converter's output power or the converter's output current. The specific expressions for these two methods are as follows:

[0066] In the formula: S max This refers to the allowable overload capacity of the converter.

[0067] In the formula: I max For the allowable overload current of the converter; I i Let I be the output current of the i-th converter. i Regarding the active power output P of the generator set i and no Q i The function.

[0068] The set of operating conditions that satisfy the static voltage stability constraint is defined as the static voltage stability feasible region Ω. V Its expression is:

[0069] In the formula: V i V is the effective value of the voltage on the high-voltage side of the step-up transformer of the i-th converter. i Regarding the active power output P of the generator seti and no Q i The function; V max V min These are the maximum and minimum effective voltage values ​​that the converter port can withstand, respectively.

[0070] The set of operating conditions that satisfy the broadband oscillation stability constraint is defined as the broadband oscillation feasible region Ω. σ Its expression is:

[0071] In the formula: σ j Let σ be the oscillation damping corresponding to the j-th oscillation mode of the hybrid converter grid-connected system. j Given the active and reactive power outputs of all converters, the system has a total of l oscillation modes.

[0072] The feasible operating region Ω of a hybrid converter grid-connected system represents the set of all operating conditions that satisfy overload capacity constraints, static voltage stability constraints, and wideband oscillation stability constraints; that is, the feasible operating region Ω is the same as the feasible capacity region Ω. I Static voltage stability feasible range (Ω) V and wideband oscillation feasible region Ω σ The intersection of these two points can be represented as Ω=Ω I ∩Ω V ∩Ω σ (6)

[0073] Referring to Figure 3, the steps for solving the feasible region and reconfiguring the grid-connected system of the hybrid converter are as follows:

[0074] Step S1: Obtain the parameters of the hybrid converter grid-connected system and the AC grid parameters. Wherein:

[0075] AC power grid parameters include power supply amplitude V g Range, series resistance R g Interval, series reactance X g Intervals, etc.

[0076] The parameters of a hybrid converter grid-connected system include the system circuit topology, the number of converters n, the installation locations of the grid-connected converters, the installation locations of the grid-connected converters, and the corresponding feeder impedances (Z1, Z2, ..., Z...). n ) and boost transformer impedance (Z T1 Z T2 ... Z Tn Impedance models of reactive power compensation devices, impedance models of various converters, etc.

[0077] Step S2 simplifies the hybrid converter grid-connected system into multiple equivalent grid-connected or grid-connected converters using the grouping method and the equivalent aggregation method.

[0078] Hybrid converter grid-connected systems often contain dozens or even hundreds of converters. Considering the potential operating conditions of all converters would make the solution extremely difficult. To improve computational efficiency, it is necessary to simplify the hybrid converter grid-connected system by equivalent means. This step first divides the hybrid converter grid-connected system into m groups containing different numbers of units. Then, all units within a single group are equivalently aggregated into a single grid-connected or grid-connected converter. Therefore, this step simplifies the hybrid converter grid-connected system to m grid-connected or grid-connected parallel converters, as shown in Figure 2. The grouping and equivalent aggregation methods are described below.

[0079] (a) Clustering method

[0080] Reactive power compensation devices such as SVG and STATCOM are also classified as converters. Converters of the same model, with the same control parameters, and geographically close (connected to the same or adjacent grid bus) are grouped together. After grouping, by default, all converters within a group have the same active and reactive power outputs, and the same control strategies and parameters. A larger number of groups, m, results in higher equivalent accuracy but lower computational efficiency; conversely, a smaller m results in lower equivalent accuracy but higher computational efficiency. Therefore, a trade-off between equivalent accuracy and computational efficiency is necessary when selecting m.

[0081] (c) Equivalence aggregation method

[0082] Equivalent aggregation is used to aggregate all units within a group into a single grid-connected or grid-connected converter, which is then connected to the grid bus via a feeder. Equivalent aggregation requires solving for three types of parameters, and the methods for solving each parameter include, but are not limited to: 1) The impedance model of the equivalent converter is the same as that of the units being equivalent within the group; 2) The active / reactive power output of the equivalent converter is the sum of the active / reactive power outputs of the units being equivalent within the group; 3) The equivalent feeder impedance can be solved based on the principle of consistent power loss.

[0083] Step S3: Theoretically solve for the feasible capacity region Ω that satisfies the overload capacity constraint. I The static voltage stability feasible region Ω that satisfies the static voltage stability constraint V .

[0084] The hybrid converter grid-connected system contains m equivalent converters, each connected to the grid connection point via an equivalent feeder, and then connected to the AC power grid. The operating conditions of the hybrid converter grid-connected system can be expressed as: Ω0=[P1,Q1,…,P i Q i ,…,P m Q m ], i = 1, 2, ..., m (7)

[0085] In the formula: P i Q iLet be the active and reactive power outputs of the i-th equivalent converter; n is the total number of equivalent converters.

[0086] Capacity feasible range (Ω) for hybrid converter grid-connected systems I The solution method is as follows:

[0087] Static voltage stability feasible range (Ω) for hybrid converter grid-connected systems V Its expression is:

[0088] In the formula: V i Let be the effective value of the high-voltage side voltage of the step-up transformer of the i-th equivalent converter. Let P be the voltage on the step-up transformer of the i-th equivalent converter, and both are related to the active power input P of the equivalent converter. i and no Q i The function.

[0089] Given the equivalent converter output power P i Q i When this happens, the following formula can be used to solve it.

[0090] In the formula: Z represents the output current of the i-th equivalent converter; the superscript * indicates the conjugate of the complex number; Z i Let be the equivalent feeder impedance of the i-th equivalent converter; R is the grid connection point voltage; g X g These are the equivalent resistance and equivalent reactance of the AC power grid, respectively.

[0091] Step S4, expand the feasible region Ω I and the feasible domain of static voltage stability Ω V Discretize the intersection of the given elements to obtain the discretized set Ω. VI .

[0092] set Ω I ∩Ω V This refers to the set of operating conditions for a hybrid converter grid-connected system that simultaneously meets overload capacity constraints, static voltage stability constraints, and inverter self-constraints. Geometrically, this set Ω... I ∩Ω V It contains countless operating conditions. Analyzing the oscillation stability of a massive number of operating conditions would be extremely time-consuming; therefore, the set Ω can be... I ∩Ω V By uniformly dividing the Ω region, a finite number of operating points are obtained, which is Ω. I ∩Ω V Discretization of the set. The discretized set is defined as Ω. VIThe expression is:

[0093] In the formula: ΔP and ΔQ are the active step size and reactive step size, respectively; k P,i k Q,i Let be the discrete coefficient of the i-th equivalent converter.

[0094] Step S5: Determine the discretized set Ω point by point. VI If the internal operating condition meets the wideband oscillation constraint, then the operating condition belongs to the feasible operating domain Ω of the hybrid converter grid-connected system, and finally the feasible operating domain Ω of the grid-connected hybrid converter system with and without grid connection is obtained.

[0095] This step will determine Ω point by point. VI Does the internal operating condition satisfy the wideband oscillation constraint? If it does, then the operating condition belongs to the feasible operating region Ω; otherwise, the operating condition does not belong to the feasible operating region Ω.

[0096] For any hybrid converter grid-connected system operating conditions [P1,Q1,…,P] i Q i ,…,P m Q m For i = 1, 2, ..., m, given the equivalent converter parameters (operating conditions, control strategy, parameters), equivalent feeder impedance, and AC grid parameters (equivalent impedance, grid topology), the oscillation damping σ for all oscillation modes of the renewable energy grid-connected system can be calculated. j (j = 1, 2, ..., l, where l represents the existence of l oscillation modes in the system). If the damping of all oscillation modes is greater than zero, then the operating condition belongs to the feasible region. Ω is determined point by point. VI Whether all operating conditions within the system belong to the feasible operating region is determined, and the feasible operating region Ω of the hybrid converter grid-connected system is finally obtained.

[0097] The steps for solving oscillation damping are briefly described here:

[0098] a) Aggregate the impedance models of each device in the system to obtain the aggregated system impedance Z. Σ ;

[0099] b) Solve for the determinant D of the system's pooling impedance. Σ D Σ (s)=R Σ +jX Σ =Z Σ11 (s)Z Σ22 (s)-Z Σ12 (s)Z Σ21 (s) (12)

[0100] In the formula: Z Σ11 ZΣ12 Z Σ21 and Z Σ22 Z Σ The four elements; D Σ (s) The real part is defined as the equivalent resistance R. Σ The imaginary part is defined as the equivalent reactance X. Σ .

[0101] c) Based on the equivalent resistance R Σ and equivalent reactance X Σ Solve for the oscillation damping.

[0102] Equivalent reactance X Σ A zero-crossing point corresponds to an oscillation mode. Based on the properties of this zero-crossing point, the oscillation damping σ and oscillation frequency ω corresponding to this oscillation mode can be solved, and the expression is:

[0103] In the formula: k R and k X R represents the slope of the equivalent resistance curve and the equivalent reactance curve, respectively. Σ ω is the equivalent resistance; r The frequency that crosses zero.

[0104] Step S6: Expand and reconstruct the feasible operating domain by configuring the grid converter (configure the grid converter to expand and reconstruct the feasible operating domain Ω of the hybrid converter grid-connected system to ΩVI).

[0105] If all operating conditions within the discretized set ΩVI do not satisfy the condition that the oscillation mode damping is greater than zero, then the proportion of grid-connected converters is increased until the discretized set ΩVI coincides with the feasible operating region Ω of the hybrid converter grid-connected system. The steps for increasing the proportion of grid-connected converters are as follows:

[0106] a) Select the node where the grid-connected converter is located, which is the farthest from the grid connection point in terms of electrical distance, and replace it with the grid-connected converter;

[0107] b) Solve step S2 to S4 sequentially to obtain the discretized set Ω. VI ;

[0108] c) Solve for the feasible operating domain Ω of the hybrid converter grid-connected system according to step S5;

[0109] d) Determine the discretized set Ω VI If the feasible region Ω of the grid-connected system with the hybrid converter overlaps, the optimal number and location of the grid-connected converters are obtained; if not, steps a) to c) are repeated.

[0110] The proposed method for solving the feasible domain and reconfiguring the grid-connected system of hybrid converters takes into account the differences between different converters and all the operating conditions that the converters may face, thus ensuring the safe and stable operation of the grid-connected system.

[0111] Referring to Figure 4, this embodiment also includes a feasible domain solution and reconfiguration system for a grid-connected hybrid converter system, comprising:

[0112] Input unit 310 is used to input the hybrid converter grid-connected system parameters and AC grid parameters. The inputs to this unit include: 1) external inputs, namely the initial hybrid converter grid-connected system parameters and AC grid parameters; and 2) the grid-connected converter configuration results and reconfigured hybrid converter grid-connected system parameters from unit 360. The parameters from unit 360 update the initial parameters from the external inputs.

[0113] The equivalent aggregation unit 320 is used to simplify a hybrid converter grid-connected system into multiple equivalent grid-connected or grid-connected converters using grouping and equivalent aggregation methods. It achieves grouping and equivalent aggregation of the hybrid converter grid-connected system, simplifying it into multiple equivalent grid-connected / grid-connected converters. Its input signal comes from unit 310, and its output signal includes equivalent converter parameters, equivalent system parameters, etc.

[0114] Capacity and static voltage feasible region solution unit 330 is used to theoretically solve the capacity feasible region satisfying overload capacity constraints and the static voltage stability feasible region satisfying static voltage stability constraints. Its input signal comes from unit 320, and its output signal is Ω. I and Ω V .

[0115] The feasible region discretization unit 340 is used to discretize the intersection of the capacity feasible region and the static voltage stability feasible region, obtaining a discretized set. The intersection Ω of the capacity feasible region and the static voltage feasible region... I ∩Ω V Discretization yields a set Ω containing only a finite number of operating points. VI Its input signal comes from unit 330, and its output signal is Ω. VI .

[0116] The feasible region solution unit 350 is used to determine point-by-point whether the operating conditions within the discretized set satisfy the wideband oscillation constraint. If they do, the operating condition belongs to the feasible region of the hybrid converter grid-connected system, ultimately obtaining the feasible region of the grid-connected hybrid converter system. The feasible region Ω of the grid-connected hybrid converter system is solved. Its input signal comes from unit 340, and the output signal is Ω. VI .

[0117] The feasible region reconfiguration unit 360 is used to expand and reconfigure the feasible region by configuring the network converter. This unit is disabled when the system is only required to solve for the feasible region. This unit is used to expand and reconfigure the feasible region Ω into Ω. VI This enables optimized configuration of the capacity and installation location of the grid-connected converter. Its input signal comes from unit 350, and its output signals include the feasible operating domain Ω, the grid-connected converter configuration result, and the reconfigured hybrid converter grid-connected system parameters.

[0118] Output unit 370 is used to output the operational feasible domain and grid-connected converter configuration results of the hybrid converter grid-connected system. When the system is required to only solve the operational feasible domain, this unit is used to output the operational feasible domain Ω from unit 350; when the device is required to solve the operational feasible domain and reconfigure, this unit is used to output the operational feasible domain Ω and grid-connected converter configuration results from unit 360.

[0119] This embodiment also provides a non-transitory computer-readable storage medium that stores computer instructions. When the computer instructions are executed by a processor, they implement the feasible domain solution and reconfiguration method of the grid-connected hybrid converter system.

[0120] Referring to Figure 5, this embodiment also provides an electronic device, including:

[0121] The system includes a memory 201 and a processor 202, which are interconnected. The memory 201 stores computer instructions, and the processor 202 executes the computer instructions to solve and reconstruct the feasible domain of the grid-connected hybrid converter system.

[0122] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for solving and reconstructing the feasible region of a grid-connected hybrid converter grid-connected system, characterized in that, Includes the following steps: Step 1: Obtain the parameters of the hybrid converter grid-connected system and the AC grid parameters; Step 2: The hybrid converter grid-connected system is simplified into multiple equivalent grid-connected or grid-connected converters by using the grouping method and the equivalent aggregation method. Step 3: Theoretically solve the capacity feasible region that satisfies the overload capacity constraint and the static voltage stability feasible region that satisfies the static voltage stability constraint. Step 4: Discretize the intersection of the capacity feasible region and the static voltage stability feasible region to obtain the discretized set; Step 5: Determine whether the operating conditions within the discretized set satisfy the wideband oscillation constraint point by point. If they do, the operating condition belongs to the feasible operating region of the hybrid converter grid-connected system. Finally, the feasible operating region of the grid-connected hybrid converter system with and without grid connection is obtained. Step 6: Expand and reconfigure the operational feasible domain by configuring the network converter.

2. The method of claim 1, wherein the method is characterized by: The parameters of the hybrid converter grid-connected system mentioned in step 1 include the system circuit topology, the number of converters, the installation location of the grid-connected converters, the installation location of the grid-connected converters, the corresponding feeder impedance and step-up transformer impedance of each converter, the impedance model of the reactive power compensation device, and the impedance model of each converter; the AC grid parameters include the power supply amplitude range, the series resistance range, and the series reactance range.

3. The method of claim 2, wherein the method is characterized by: The grouping method described in step 2 includes: classifying reactive power compensation devices as converters, grouping converters of the same model, with the same control parameters and geographical proximity into the same group, and by default, all converters in the group have the same active and reactive power outputs, and the same control strategies and parameters. The equivalent aggregation method includes: All units within the group are equivalently aggregated into a single grid-connected or grid-connected converter, and the equivalent converter is connected to the grid bus via a feeder. Three types of parameters are solved for the equivalent aggregation. The solution methods for each parameter include: 1) The impedance model of the equivalent converter is the same as that of the equivalent units within the group; 2) The active / reactive power output of the equivalent converter is the sum of the active / reactive power outputs of the equivalent units within the group; 3) The equivalent feeder impedance is solved based on the principle of consistent power loss.

4. The method of claim 3, wherein the method is characterized by: Step 3 includes: Suppose that there are m equivalent converters in the hybrid converter grid-connected system, and each converter is connected to the grid connection point via an equivalent feeder, and then connected to the AC power grid; the operating conditions of the hybrid converter grid-connected system are represented as follows: Ω0= [P1, Q1,..., P i Q i ,..., P m Q m ], i = 1, 2,..., m where: P i , Q i are the active and reactive output of the i-th equivalent converter; n is the total number of equivalent converters. Hybrid converter grid-connected system capacity feasible region Ω I The solving method is: Static voltage stability feasible region Ω of hybrid converter grid-connected system V whose expression is: Ω V = {(P1, Q1,..., P i , Q i ,..., P m , Q m ) | 0.9pu < V i < 1.1pu, i = 1, 2,..., m} wherein: V i is the effective value of the voltage on the high-voltage side of the step-up transformer of the i-th equivalent current transformer, VH(i) = VHV(i) - VHV(i-1) (1) VHV(i) = VHV(i) + VHV(i-1) (2) where VHV(i) is the voltage on the high voltage side of the step-up transformer of the ith equivalent converter, both being functions of the active P i and reactive Q i power at the input of the equivalent converter. It is known that the power P output by the converter is equal to i , Q i When this is the case, the following formula is used to solve for In the formulae: Ii is the output current of the ith equivalent current source; the superscript * indicates the conjugate of a complex number; Z i Zi is the equivalent feeder impedance of the ith equivalent current source; for the grid point voltage; R g , X g are the equivalent resistance and the equivalent reactance of the alternating current grid, respectively.

5. The method of claim 4, wherein the method is characterized by: Step 4 includes: The grid-connected system of the hybrid converter meets the operation condition set Ω of overload capability constraint, static voltage stability constraint and inverter self-constraint simultaneously I ∩Ω V The operation condition set Ω is discretized by uniform segmentation, i.e. I ∩Ω V The set is discretized; The discretized set is defined as Ω VI The expression is: Ω VI = {(k P,1 ΔP,k P,1 ΔQ,…,k P,i ΔP,k Q,i ΔQ,…,k P,m ΔP,k Q,m ΔQ)∈(Ω I ∩Ω V )} In the formula: ΔP, ΔQ are active step, reactive step; k P,i , k Q,i is the discrete coefficient of the ith equivalent converter.

6. The method of claim 5, wherein the method is characterized by: In step 5, if the damping of all oscillation modes is greater than zero, then the operating condition is determined to be within the feasible operating range of the hybrid converter grid-connected system. The steps for solving the damping of the oscillation mode are as follows: a) aggregating the impedance models of the devices within the system to obtain a system aggregated impedance Z Σ ; b) solving the determinant D of the system of aggregated impedances Σ D Σ (s) = R Σ + jX Σ = Z Σ11 (s) Z Σ22 (s) - Z Σ12 (s) Z Σ21 (s) wherein: Z Σ11 , Z Σ12 , Z Σ21 , and Z Σ22 are the four elements of Z Σ ; D Σ (s) is defined as the equivalent resistance R Σ , and the imaginary part is defined as the equivalent reactance X Σ ; c) solving for the oscillation damping, including: Σ and the equivalent reactance X Σ solving for the oscillation damping, including: Equivalent reactance X Σ The zero-crossing corresponds to an oscillation mode, the oscillation damping σ and the oscillation frequency ω of which are solved depending on the properties of the zero-crossing, the expression being: where: k R and k X are the slopes of the equivalent resistance and equivalent reactance curves, respectively; R Σ is the equivalent resistance; and ω r is the frequency of the zero crossing.

7. The method of claim 6, wherein the method is characterized by: Step 6 includes: If all operating conditions within the discretized set do not satisfy the condition that the oscillation mode damping is greater than zero, then the proportion of grid-connected converters is increased until the discretized set coincides with the feasible operating region of the hybrid converter grid-connected system; the steps for increasing the proportion of grid-connected converters are as follows: (a) Select the node where the grid-connected converter is located, which is the farthest from the grid connection point in terms of electrical distance, and replace it with the grid-connected converter; (b) sequentially solving for the discretized set Ω according to steps 2 through 4 VI ; (c) Solve for the feasible operating domain Ω of the hybrid converter grid-connected system according to step 5; (d) judging the discretized set Ω VI whether the operation feasible region Ω of the grid-connected system with hybrid converters coincides, if coincides, the optimal configuration number and configuration position of the grid-connected converter are obtained, if not coincides, repeating steps (a)-(c).

8. A grid-connected hybrid converter grid-connected system feasible region solving and reconstructing system, characterized in that, include: The input unit is used to input the parameters of the hybrid converter grid-connected system and the AC grid parameters; Equivalent aggregation unit is used to simplify a hybrid converter grid-connected system into multiple equivalent grid-connected or grid-forming converters through grouping and equivalent aggregation methods. Capacity and static voltage feasible region solution unit, used to theoretically solve the capacity feasible region that satisfies overload capacity constraints and the static voltage stability feasible region that satisfies static voltage stability constraints; The feasible region discretization unit is used to discretize the intersection of the capacity feasible region and the static voltage stability feasible region to obtain the discretized set. The feasible region solution unit is used to determine point by point whether the operating conditions within the discretized set meet the wideband oscillation constraint. If they do, the operating condition belongs to the feasible region of the hybrid converter grid-connected system, and finally the feasible region of the grid-connected hybrid converter system with and without grid connection is obtained. The operational feasible domain reconfiguration unit is used to expand and reconfigure the operational feasible domain by configuring the network converter; The output unit is used to output the operational feasibility domain of the hybrid converter grid-connected system and the configuration results of the grid-connected converter.

9. A non-transitory computer-readable storage medium, comprising: The non-transitory computer-readable storage medium stores computer instructions, which, when executed by a processor, implement the feasible domain solution and reconfiguration method for a grid-connected hybrid converter system as described in any one of claims 1-7.

10. An electronic device, comprising: include: The system includes a memory and a processor, which are interconnected. The memory stores computer instructions, and the processor executes the computer instructions to perform the feasible domain solution and reconfiguration method for a grid-connected hybrid converter system as described in any one of claims 1-7.

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