Wind storage cooperative positive sequence impedance angle control method adaptive to directional element, medium and device

Abstract

The invention discloses a wind storage cooperative positive sequence impedance angle control method, medium and device adaptive to a directional element, and relates to the field of new energy power generation. The method comprises the following steps: acquiring wind storage grid-connected point data; calculating according to the wind storage grid-connected point data to obtain a positive sequence impedance angle, judging whether the positive sequence impedance angle meets a preset detection angle of a direction element or not, if not, calculating a real and imaginary part of an energy storage output positive sequence current based on the positive sequence impedance angle in combination with the obtained maximum reactive current support requirement when the grid-connected point fails, and outputting the positive sequence current; according to the real and imaginary parts of the energy storage output positive-sequence current, calculating to obtain an energy storage positive-sequence current output reference value; calculating an energy storage output positive sequence current according to the energy storage positive sequence current output reference value; and outputting a fault direction judgment result through a direction element according to the stored energy output positive sequence current. According to the invention, active and reactive output of the energy storage system can be autonomously distributed according to quadrant change of the positive sequence impedance angle, and dynamic adjustment of the positive sequence current phase is realized.

Description

Technical Field

[0001] This invention relates to the field of new energy power generation, specifically to a method, medium, and device for wind and energy storage coordinated positive sequence impedance angle control with adaptive directional elements. Background Technology

[0002] With the increasing integration of new energy sources into the power system, the parallel operation of wind farms and energy storage is becoming more common to overcome the volatility of these sources. In hybrid grid-connected scenarios involving both doubly-fed induction generators (DFIGs) and energy storage systems, the grid connection point current characteristics are significantly influenced by power electronic control. Especially during grid asymmetric faults, DFIGs typically employ a strategy to suppress stator negative-sequence current to avoid thermal stress on the stator windings caused by unbalanced currents. Under this control strategy, the phase angle of the DFIG stator positive-sequence current may span any quadrant. Simultaneously, the energy storage system operates based on a typical PQ control strategy, capable of regulating active and reactive currents within a four-quadrant range. The phase angle of its output current also varies from 0° to 360° depending on the charging / discharging and reactive power regulation states. In this scenario, the phase angle of the grid connection point positive-sequence current, formed by the vector superposition of the DFIG stator positive-sequence current and the energy storage positive-sequence current, no longer exhibits the predictable behavior of a traditional synchronous machine during faults, but may fall into any quadrant. Since the positive sequence impedance angle α⁺ measured by the directional element is determined by both the positive sequence voltage and current surges, the aforementioned uncertainty in this angle may lead to reduced sensitivity of the directional element or even incorrect direction determination. In hybrid renewable energy power stations combining DFIG and energy storage, maintaining the overall positive sequence impedance angle within a range that the directional element can correctly identify becomes a key issue in improving the reliability of relay protection in renewable energy power stations. Summary of the Invention

[0003] The purpose of this invention is to provide a method, medium, and device for wind-storage coordinated positive sequence impedance angle control adapted to directional elements. This improves the accuracy of directional element operation in renewable energy power plants by compensating for malfunctions in the positive sequence impedance angle when a storage current fault occurs.

[0004] To achieve the above objectives, the present invention is implemented using the following technical solution.

[0005] In a first aspect, the present invention provides a wind-storage coordinated positive sequence impedance angle control method for adaptive directional elements, comprising:

[0006] Acquire data from the wind and energy storage grid connection points to determine if a fault has occurred in the wind and energy storage grid connection lines.

[0007] In response to the aforementioned wind-storage grid connection line fault, the following correction operation is performed on the wind-storage coordinated positive sequence impedance angle:

[0008] S1: Calculate the positive sequence impedance angle based on the wind-storage grid connection point data, and determine whether the positive sequence impedance angle meets the preset detection angle of the directional element. If it does, proceed to step S2; otherwise, based on the quadrant position of the positive sequence impedance angle and combined with the maximum reactive current support requirement of the grid connection point, calculate the real and imaginary parts of the positive sequence current output by the energy storage, and then proceed to step S2.

[0009] S2, calculate the reference value of the positive sequence current output of the energy storage based on the real and imaginary parts of the positive sequence current output of the energy storage;

[0010] S3, calculate the energy storage output positive sequence current based on the energy storage positive sequence current output reference value;

[0011] S4, based on the positive sequence current output by the energy storage, output the fault direction judgment result through the directional element.

[0012] Optionally, the formula for calculating the positive sequence impedance angle based on the wind-storage grid connection point data is as follows:

[0013] (1)

[0014] in, Let represent the positive-sequence component, and Δ represent the phasor difference before and after the fault. It is the positive sequence impedance angle. The positive sequence current phasor difference before and after a fault at the grid connection point of the wind-storage system. The difference in positive sequence voltage phasors before and after a grid connection point fault. This is the phase angle symbol.

[0015] The data for the wind-storage grid connection point includes the positive sequence current output of the doubly-fed wind farm, the positive sequence current of the wind-storage system grid connection point, and the positive sequence voltage of the wind-storage system grid connection point. By defining the positive sequence impedance angle, the problem of the positive sequence impedance angle is transformed into an active control problem of the positive sequence current difference, so that the positive sequence impedance angle still falls stably within the effective operating range of the directional element under asymmetrical fault conditions. Through active coordinated control, the problem of directional element malfunction compensation in new energy power plants is realized, providing a brand-new control approach and ensuring the highest sensitivity of the directional element.

[0016] Optionally, based on the quadrant position of the positive sequence impedance angle and combined with the maximum reactive current support requirement during grid connection point faults, the real and imaginary parts of the positive sequence current output by the energy storage are calculated, including:

[0017] Based on the quadrant position of the positive sequence impedance angle, the adjustment conditions for the real and imaginary parts of the grid connection point current are determined.

[0018] Based on the adjustment conditions of the real and imaginary parts of the grid connection point current and the maximum reactive current support requirements, the real and imaginary parts of the positive sequence current of the energy storage output are calculated.

[0019] By determining the adjustment conditions for the real and imaginary parts of the grid-connected current based on the quadrant position of each positive sequence impedance angle, the accuracy of the calculation of the real and imaginary parts of the positive sequence current of the energy storage output is ensured.

[0020] Optionally, based on the adjustment conditions of the real and imaginary parts of the grid connection point current and the maximum reactive current support requirement, the real and imaginary parts of the positive sequence current output by the energy storage are calculated, including:

[0021] Based on the adjustment conditions of the real and imaginary parts of the grid connection point current, a calculation formula for the real and imaginary parts of the positive sequence current of the energy storage output is constructed.

[0022] The wind-storage grid connection point data and the obtained positive sequence current of the doubly fed wind farm output are input into the calculation formula of the real and imaginary parts of the positive sequence current of the energy storage output to obtain the initial positive sequence current of the energy storage output.

[0023] Based on the real and imaginary parts of the initial energy storage output positive sequence current and the wind-storage grid connection point data, the energy storage demand is calculated, and it is determined whether the obtained energy storage capacity meets the energy storage demand. If it does, the real and imaginary parts of the energy storage output positive sequence current are calculated based on the initial energy storage output positive sequence current. If it does not, the positive sequence current output by the doubly-fed wind farm is scaled by a preset scaling factor, and the real and imaginary parts of the energy storage output positive sequence current are calculated.

[0024] By accurately determining the real part of the energy storage current and adjusting the imaginary part based on reactive capacity constraints, active positive sequence impedance angle correction across quadrants is achieved, realizing deep collaboration between the control side and the relay protection side. By introducing a scaling factor to reduce the output positive sequence current of the doubly-fed wind farm, the space for energy storage compensation is released, and the applicability of the wind-storage collaborative positive sequence impedance angle control method with adaptive directional elements is improved.

[0025] Optionally, the adjustment conditions for the real and imaginary parts of the grid connection point current include:

[0026] The real part of the grid connection point current satisfies the following: the sum of the real part of the reference value of the positive sequence current output by the energy storage after the fault and the real part of the component of the positive sequence current output by the doubly fed wind farm is equal to the real part of the positive sequence current at the grid connection point before the fault.

[0027] The imaginary part of the grid connection point current satisfies the following condition: the sum of the imaginary part of the reference value of the positive sequence current output by the energy storage after the fault and the imaginary part of the positive sequence current component output by the doubly fed wind farm is greater than the imaginary part of the positive sequence current at the grid connection point before the fault.

[0028] Based on the compensation target of positive sequence impedance angle, the positive sequence current output of energy storage is accurately calculated by means of the relationship between the positive sequence current output of energy storage, the positive sequence current output of doubly fed wind farm, and the positive sequence current at the grid connection point, thus ensuring the compensation efficiency and accuracy of positive sequence impedance angle.

[0029] Optionally, the quadrant position of the positive sequence impedance angle includes the first quadrant, the second quadrant, the third quadrant, and the fourth quadrant;

[0030] When the quadrant position of the positive sequence impedance angle is in the first quadrant or the second quadrant, the adjustment conditions for the real and imaginary parts of the grid connection point current include:

[0031] Formula for calculating the real part of the positive sequence current of energy storage output, based on the adjustment condition of the real part of the grid connection point current:

[0032] Re[I+ es] = Re[I0] - Re[I+ D] (2)

[0033] Formula for calculating the imaginary part of the positive sequence current output of energy storage, based on the imaginary part adjustment condition of the grid connection point current:

[0034] Im[I+ es] = I Q - Im[ΔI + (3)

[0035] When the positive sequence impedance angle is located in the third or fourth quadrant, the adjustment conditions for the real and imaginary parts of the grid connection point current include:

[0036] Formula for calculating the real part of the positive sequence current of energy storage output, based on the adjustment condition of the real part of the grid connection point current:

[0037] Re[I+ es] = Re[I+ 0] - Re[I+ D] (4)

[0038] Formula for calculating the imaginary part of the positive sequence current output of energy storage, based on the imaginary part adjustment condition of the grid connection point current:

[0039] Im[I+ es] = I Q - Im[I+ 0] + Im[I+ D](5)

[0040] Where Re[I+ es] represents the real part of the corrected post-fault energy storage output positive-sequence current reference value, and Im[I+ es] represents the imaginary part of the corrected post-fault energy storage output positive-sequence current reference value, I Q Represents the maximum reactive power capacity, Re[I+0] represents the real part of the positive sequence current at the grid connection point before the fault, Im[I+0] represents the imaginary part of the positive sequence current at the grid connection point before the fault, Re[I+D] represents the real part of the positive sequence current component of DFIG after the fault, and Im[I+D] represents the imaginary part of the positive sequence current component of DFIG after the fault.

[0041] By employing different formulas for calculating the positive sequence current of the energy storage output for different quadrant positions with varying positive sequence impedance angles, the accuracy of the calculated real and imaginary parts of the positive sequence current of the energy storage output is ensured.

[0042] Optionally, when the positive sequence impedance angle meets the preset detection angle of the directional element, the reference value of the positive sequence current output is calculated based on the real and imaginary parts of the energy storage output positive sequence current, using the following formula:

[0043] (6)

[0044] Where j represents the imaginary number sign, and I*+es represents the reference value of the positive sequence current output after a fault. This represents the real part of the positive sequence current reference value of the energy storage output after a fault. This represents the imaginary part of the positive sequence current reference value of the energy storage output after a fault.

[0045] By calculating the real and imaginary parts of the positive sequence current of the energy storage output, the reference value of the positive sequence current output is obtained, which efficiently and accurately compensates for the offset of the positive sequence impedance angle when a fault occurs.

[0046] Optionally, when the positive sequence impedance angle does not meet the preset detection angle of the direction element, the reference value of the positive sequence current output is calculated based on the real and imaginary parts of the energy storage output positive sequence current, using the following formula:

[0047] (7)

[0048] Where j represents the imaginary number sign, I*+ es represents the reference value of the positive sequence current output of the energy storage after the fault, Re[I+ es] represents the real part of the corrected reference value of the positive sequence current output of the energy storage after the fault, and Im[I+ es] represents the imaginary part of the corrected reference value of the positive sequence current output of the energy storage after the fault.

[0049] In a second aspect, the present invention provides a computer device, comprising:

[0050] Memory, used to store computer programs;

[0051] A processor for executing the computer program to implement the steps of the wind-storage coordinated positive sequence impedance angle control method for the adaptive directional element as described in any of the first aspects above.

[0052] Thirdly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the wind-storage coordinated positive sequence impedance angle control method for adaptive directional elements as described in any of the first aspects above.

[0053] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0054] This invention compensates for maloperation of the positive sequence impedance angle during wind-storage grid-connected line faults by calculating the positive sequence current output of energy storage, and improves the sensitivity of the directional element, ensuring the accuracy of the directional element's judgment results. By calculating the quadrant position of the positive sequence impedance angle, the accuracy of the calculated positive sequence current output of energy storage is improved. This invention achieves active positive sequence impedance angle correction across quadrants, enabling deep collaboration between the control side and the relay protection side. Through active collaborative control, it solves the problem of directional element maloperation in new energy power plants. Attached Figure Description

[0055] Figure 1 The diagram shows a topology of a wind power grid-connected system with energy storage.

[0056] Figure 2 The diagram shows the current compensation amount when the positive sequence impedance angle is in the first quadrant.

[0057] Figure 3 The diagram shows the current compensation amount when the positive sequence impedance angle is in the second quadrant.

[0058] Figure 4 The diagram shows the current compensation amount when the positive sequence impedance angle is in the third quadrant.

[0059] Figure 5 The diagram shows the current compensation amount when the positive sequence impedance angle is in the fourth quadrant.

[0060] Figure 6 The diagram shows the flow chart of wind-storage coordinated positive sequence impedance angle control.

[0061] Figure 7 The diagram shown is a schematic of the judgment result of the directional element at the wind-storage grid connection point after a single-phase ground fault according to the present invention.

[0062] Figure 8 The diagram shown is a schematic of the judgment result of the directional element at the wind-storage grid connection point after a two-phase short-circuit fault according to the present invention. Detailed Implementation

[0063] It should be noted that in wind power grid-connected systems with energy storage, the change in the positive sequence impedance angle α⁺ directly affects the accuracy and selectivity of the positive sequence directional element. When a forward fault occurs in the system, the positive sequence directional element should operate within the forward operating range (0~180°), and its operation is most accurate when α⁺=90°. However, the positive sequence impedance angle often deviates from 90°, leading to maloperation of the directional element. When a reverse fault occurs, since α⁺ is not affected by the wind farm and energy storage control but is determined by the opposite grid, satisfying α⁺=-90°, the directional element will operate accurately in the reverse direction. Therefore, the control objective of this invention is to coordinate the control of the DFIG and the energy storage system to make the positive sequence impedance angle actually measured by the directional element at the grid connection point as close as possible to 90° when the system experiences a forward fault.

[0064] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations thereof. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0065] The term "and / or" simply describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. Additionally, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0066] Example 1

[0067] This embodiment introduces a wind-storage coordinated positive sequence impedance angle control method for adaptive directional elements, such as... Figure 6 As shown, the specific steps include:

[0068] Acquire data from the wind and energy storage grid connection point, and use directional elements to determine if a fault has occurred in the wind and energy storage grid connection line; for example... Figure 1 As shown, the data for the wind-storage grid connection point includes the positive sequence current output of the doubly fed wind farm, the positive sequence current output of the doubly fed wind farm, the positive sequence current of the wind-storage system grid connection point, and the positive sequence voltage of the wind-storage system grid connection point.

[0069] In response to the aforementioned wind-storage grid connection line fault, the following adjustment operation is performed on the wind-storage coordinated positive sequence impedance angle:

[0070] S1: Calculate the positive sequence impedance angle based on the wind-storage grid connection point data, and determine whether the positive sequence impedance angle meets the preset detection angle of the directional element. If it does, proceed to step S2; otherwise, based on the quadrant position of the positive sequence impedance angle and combined with the maximum reactive current support requirement during grid connection point faults, calculate the real and imaginary parts of the positive sequence current output by the energy storage, and then proceed to step S2.

[0071] S2, calculate the reference value of the positive sequence current output of the energy storage based on the real and imaginary parts of the positive sequence current output of the energy storage;

[0072] S3, calculate the energy storage output positive sequence current based on the energy storage positive sequence current output reference value;

[0073] S4, based on the positive sequence current output by the energy storage, output the fault direction judgment result through the directional element.

[0074] The formula for calculating the positive sequence impedance angle from the wind-storage grid connection point data is as follows:

[0075] (1)

[0076] in, Let represent the positive-sequence component, and Δ represent the phasor difference before and after the fault. It is the positive sequence impedance angle. The positive sequence current phasor difference before and after a fault at the grid connection point of the wind-storage system. The difference in positive sequence voltage phasors before and after a grid connection point fault. The sign for the phase angle is given. Starting from the definition of the positive sequence impedance angle, the problem of adjusting the positive sequence impedance angle is transformed into adjusting the positive sequence current difference ΔI. + The problem of active phase angle control. Ensuring the positive sequence impedance angle remains stably within the effective operating range of the steering element under asymmetrical fault conditions, active coordinated control addresses the issue of steering element malfunction compensation in new energy power plants, providing a novel control approach and ensuring maximum sensitivity of the steering element.

[0077] Based on the above formula, in order to make α⁺=90° and ensure the highest sensitivity of the directional element, ΔI should be used at this time. + The real part should be strictly equal to zero, and the imaginary part should be positive, that is: Re[ΔI] + ] = 0, Im[ΔI + ] > 0, where Re[ΔI + ] represents ΔI + The real part, Im[ΔI + ] represents ΔI + The imaginary part.

[0078] The positive sequence current at the grid connection point satisfies: I + poc = I + D + I + es and ΔI + = I+ poc – I+ 0, where I+ poc is the positive sequence current at the grid connection point of the wind-storage system after the fault, I+ D is the positive sequence current component of the doubly fed wind farm output in I+ poc, I+ es is the positive sequence current component of the energy storage output in I+ poc, and I+ 0 is the positive sequence current at the grid connection point before the fault. The subscript poc indicates the grid connection point, and the subscript 0 indicates the period before the fault.

[0079] To ensure that the real and imaginary parts of the grid connection point current Re[ΔI] are equal... + ] = 0 and Im[ΔI + If the value is greater than 0, the operating conditions of the directional element, namely the adjustment conditions of the real and imaginary parts of the grid connection point current, are satisfied. These conditions include: the real part of the grid connection point current satisfies that the sum of the real part of the reference value of the positive-sequence current output by the energy storage after the fault and the real part of the component of the positive-sequence current output by the doubly-fed wind farm is equal to the real part of the positive-sequence current at the grid connection point before the fault; the imaginary part of the grid connection point current satisfies that the sum of the imaginary part of the reference value of the positive-sequence current output by the energy storage after the fault and the imaginary part of the component of the positive-sequence current output by the doubly-fed wind farm is greater than the imaginary part of the positive-sequence current at the grid connection point before the fault. Based on the compensation target of the positive-sequence impedance angle, the positive-sequence current output by the energy storage is accurately calculated through the relationship between the positive-sequence current output by the energy storage, the positive-sequence current output by the doubly-fed wind farm, and the positive-sequence current at the grid connection point, ensuring the compensation efficiency and accuracy of the positive-sequence impedance angle.

[0080] After an energy storage fault, the output current must satisfy Re[I+ es] = Re[I+ 0] - Re[I+ D] and Im[I+ es] + Im[I+ 0] - Im[I+ D] > 0. Here, Re[I+ es] represents the real part of the corrected positive-sequence current reference value after the fault, Im[I+ es] represents the imaginary part of the corrected positive-sequence current reference value after the fault, Re[I+ 0] is the real part of I+ 0, Im[I+ 0] is the imaginary part of I+ 0, and Re[I+ D] is the real part of I+ 0. The real part, Im[I+D] is The imaginary part. As can be seen from the above equation, the post-fault current output I+es of the energy storage system plays a dual role in this scheme, accurately determining the real part and flexibly adjusting the imaginary part. Its output current angle will directly determine the imaginary part. Whether it can be controlled to the expected quadrant.

[0081] Furthermore, the imaginary part control condition for the maximum reactive current support demand at the grid connection point can be written as: Im[I+ es] + Im[ΔI + ] = I Q Thus, we obtain the expression for the imaginary part: Im[I+es] = IQ - Im[ΔI] + Among them, I Q This is to meet the maximum reactive current support requirements at the grid connection point. When the energy storage capacity is insufficient, a DFIG current scaling factor λ is introduced to reduce the current amplitude, thereby releasing the energy storage compensation space and ensuring that the above conditions can still be achieved within the current capacity limit.

[0082] Because energy storage systems have both charging and discharging capabilities, the angle of I+es can drift in any quadrant. Since I+D and I+es are independent, the angle of I+poc can also drift in any quadrant, leading to ΔI... + It may drift in any quadrant, so it is analyzed and calculated separately in four quadrants. Based on the quadrant position of the positive sequence impedance angle, the adjustment conditions for the real and imaginary parts of the grid connection point current are determined; based on the adjustment conditions for the real and imaginary parts of the grid connection point current and the maximum reactive current support requirement, the real and imaginary parts of the energy storage output positive sequence current are calculated. By determining the adjustment conditions for the real and imaginary parts of the grid connection point current for each positive sequence impedance angle quadrant position, the accuracy of the calculation of the real and imaginary parts of the energy storage output positive sequence current is ensured. The specific steps include:

[0083] (1) α⁺ is located in the first quadrant (0°~90°)

[0084] like Figure 2 As shown, when the positive sequence impedance angle α⁺ falls into the first quadrant, it indicates that ΔI + The phase angle is close to the desired value, but due to the potential for significant drift in both the DFIG current and the energy storage current under asymmetrical fault conditions, the real and imaginary parts still need precise adjustment to ensure that α⁺ ultimately reaches 90°. In this quadrant, ΔI + The imaginary part of the energy storage current is usually positive, and its magnitude can be changed simply by adjusting the reactive current without sign flipping. According to the fundamental constraints of this invention, the real part of the energy storage current should satisfy:

[0085] Re[I+ es] = Re[I0] - Re[I+ D] (2)

[0086] The imaginary part is supported by the maximum reactive current demand I. Q limit:

[0087] Im[I+ es] = I Q - Im[ΔI + (3)

[0088] When the energy storage capacity is sufficient, this formula can directly yield the reactive current output by the energy storage system; if the energy storage capacity is insufficient, assuming the rated current of the energy storage system is only 30% of the grid connection point current, then:

[0089]

[0090] The above equation becomes the constraint boundary. To avoid energy storage overload, this invention introduces a scaling factor λ, which scales the positive sequence current of the DFIG proportionally with λ. This ensures that the maximum current circle of energy storage and the compensation equation hold simultaneously. Under the scaling condition, we have:

[0091] Re[I+ es] = Re[I+ 0] - λRe[I+ s]

[0092] Im[I+ es] = I Q - Im[I+ 0] - λIm[I+ s]

[0093] By combining the maximum current circle equation, ensuring the energy storage current vector falls within the allowable region, and simultaneously maintaining the positive sequence impedance angle precisely adjusted to 90°, the following solution can be obtained:

[0094]

[0095] Among them, variables a, b, and c satisfy a = Re[I + D], b = Im[I + D], c = Re[I + 0], and d = Im[I + 0], respectively. Substituting λ, we can obtain Re[I + es] and Im[I + es].

[0096] (2) α⁺ is located in the second quadrant (90°~180°)

[0097] like Figure 3 As shown, when the positive sequence impedance angle α⁺ is located in the second quadrant, although ΔI + The phase angle has exceeded 90°, but its imaginary part is still positive. Therefore, the compensation mechanism used is mathematically identical to that in the first quadrant. At this point, the main factor affecting α⁺ is ΔI. + The real part of the energy storage current deviates from the zero axis. Since its positive offset would cause α⁺ to exceed 90°, this invention still precisely specifies the real part of the energy storage current:

[0098] Re[I+ es] = Re[I0] - Re[I+ D] (2)

[0099] ΔI + The real part is pulled back to zero, bringing it back to the optimal orientation path of the orientation element. The imaginary part remains I. Q Restriction, through

[0100] Im[I+ es] = I Q - Im[ΔI + (3)

[0101] The reactive power support level at the grid connection point is adjusted to ensure that the final angle of α⁺ falls back to the target value. Since the second quadrant is more prone to insufficient compensation of the imaginary part of energy storage compared to the first quadrant, this invention utilizes the same scaling mechanism, namely, introducing a scaling factor λ to the DFIG current, so that the energy storage vector can satisfy both real part compensation and imaginary part limitation conditions within the maximum current circle. During this process, the energy storage performs the following continuous constraints:

[0102]

[0103] And simultaneously satisfying the aforementioned real and imaginary part equations, so that α⁺ is strictly pulled back to 90°, achieving active stabilization control in the second quadrant, the solution can be obtained as follows:

[0104]

[0105] Substituting λ, we can obtain Re[I+ es] and Im[I+ es].

[0106] (3) α⁺ is located in the third quadrant (180°~270°)

[0107] like Figure 4 As shown, when α⁺ enters the third quadrant, ΔI + The phase has crossed 180°, at which point its imaginary part may be negative or close to zero, making the direction element extremely prone to reverse misjudgment. This can be addressed by analyzing ΔI. + Based on the structural characteristics, it was found that the imaginary part in this quadrant must be significantly enhanced to restore the discriminative ability of α⁺. The mathematical constraints of the third quadrant become:

[0108] Im[I+ es] + Im[I+ 0] - Im[I+ D] = I Q

[0109] That is, energy storage must be achieved by injecting a sufficient positive imaginary part to make ΔI + The imaginary part becomes positive again and enters the direction-discriminating range of the directional element. At this time, the real part of the energy storage current still follows:

[0110] Re[I+ es] = Re[I+ 0] - Re[I+ D] (4)

[0111] The formula for calculating the imaginary part is:

[0112] Im[I+ es] = I Q - Im[I+ 0] + Im[I+ D](5)

[0113] Because the conditions in the third quadrant are more demanding than in the first two quadrants, energy storage is more prone to imaginary capacity insufficiency. Therefore, this invention again uses a scaling factor λ to reduce the DFIG current, thereby releasing more reactive energy storage capacity. After scaling, we have:

[0114] Re[I+ es] = Re[I+ 0] - λRe[I+ D]

[0115] Im[I+ es] = I Q - Im[I+0] - λIm[I+D]

[0116] The solution is:

[0117]

[0118] Substituting λ, we can obtain Re[I+ es] and Im[I+ es].

[0119] (4) α⁺ is located in the fourth quadrant (270°~360°)

[0120] like Figure 5 As shown, when α⁺ is in the fourth quadrant, its phase angle is close to 360°, similar to the third quadrant, ΔI + The imaginary part is negative, and the grid connection point exhibits a severe reversal of direction. At this point, the aforementioned unified framework is still used, enabling energy storage to undertake the dual tasks of boosting the imaginary part and offsetting the real part, and ensuring that ΔI... + The real and imaginary parts of the current re-satisfy the requirements of the directional element. Mathematically, the stored current satisfies:

[0121] Re[I+ es] = Re[I+ 0] - Re[I+ D] (4)

[0122] as well as

[0123] Im[I+ es] = I Q - Im[I+ 0] + Im[I+ D](5)

[0124] When the energy storage capacity is sufficient, the optimal vector of the energy storage current can be directly obtained from the above two equations; when the energy storage capacity is insufficient, the scaling factor λ ensures that:

[0125]

[0126] and combined

[0127] Re[I+ es] = Re[I+ 0] - λRe[I+ D]

[0128] Im[I+ es] = I Q - Im[I+0] - λIm[I+D]

[0129] The solution is:

[0130]

[0131] Substituting λ, we can obtain Re[I+ es] and Im[I+ es].

[0132] Finally, based on the previously calculated Re[I+ es] and Im[I+ es], the reference value for the positive sequence current output of the energy storage after a fault, which satisfies the adaptability of the directional element, can be obtained:

[0133] When the positive sequence impedance angle meets the preset detection angle of the directional element, the reference value of the positive sequence current output is calculated based on the real and imaginary parts of the energy storage output positive sequence current, using the following formula:

[0134] (6)

[0135] Where j represents the imaginary number sign, and I*+es represents the reference value of the positive sequence current output after a fault. This represents the real part of the positive sequence current reference value of the energy storage output after a fault. This represents the imaginary part of the positive sequence current reference value of the energy storage output after a fault.

[0136] When the positive sequence impedance angle does not meet the preset detection angle of the direction element, the reference value of the positive sequence current output is calculated based on the real and imaginary parts of the energy storage output positive sequence current, using the following formula:

[0137] (7)

[0138] Where j represents the imaginary number sign, I*+ es represents the reference value of the positive sequence current output of the energy storage after the fault, Re[I+ es] represents the real part of the corrected reference value of the positive sequence current output of the energy storage after the fault, and Im[I+ es] represents the imaginary part of the corrected reference value of the positive sequence current output of the energy storage after the fault.

[0139] Once a fault is detected, the reference value I*+es for the positive sequence current output of the energy storage is input to the control module of the energy storage to correct the positive sequence current I+es. By adjusting I+es, the positive sequence impedance angle α at the grid connection point is achieved. + The target of 90° means that the correct operation of the positive sequence components is ensured through the coordinated control of the wind farm by energy storage.

[0140] In summary, based on the adjustment conditions of the real and imaginary parts of the grid connection point current, a calculation formula for the real and imaginary parts of the positive sequence current of the energy storage output is constructed. The wind-storage grid connection point data and the acquired positive sequence current of the doubly-fed wind farm output are input into the calculation formula for the real and imaginary parts of the positive sequence current of the energy storage output to obtain the initial positive sequence current of the energy storage output. Furthermore, based on the real and imaginary parts of the initial positive sequence current of the energy storage output and the wind-storage grid connection point data, the energy storage demand is calculated, and it is determined whether the acquired energy storage capacity meets the energy storage demand. If it does, the real and imaginary parts of the positive sequence current of the energy storage output are calculated based on the initial positive sequence current of the energy storage output. If it does not, the positive sequence current of the doubly-fed wind farm output is scaled by a preset scaling factor, and the real and imaginary parts of the positive sequence current of the energy storage output are then calculated.

[0141] By accurately determining the real part of the energy storage current and adjusting the imaginary part based on reactive capacity constraints, active positive sequence impedance angle correction across quadrants is achieved, realizing deep collaboration between the control side and the relay protection side. By introducing a scaling factor to reduce the output positive sequence current of the doubly-fed wind farm, the space for energy storage compensation is released, and the applicability of the wind-storage collaborative positive sequence impedance angle control method with adaptive directional elements is improved.

[0142] Example 2

[0143] Based on the same inventive concept as Embodiment 1, this embodiment introduces a wind-storage cooperative positive sequence impedance angle control device adapted to the directional element, used to test the wind-storage cooperative positive sequence impedance angle control method adapted to the directional element in Embodiment 1, specifically including:

[0144] like Figure 1 As shown, a simulation model of a wind farm based on a DFIG and energy storage system was constructed to verify the impedance angle adjustment process under asymmetrical fault conditions. The system structure includes a 2 MW doubly-fed induction generator (DFIG) and an energy storage system accounting for 30% of the total capacity, both connected to the 35 kV grid through a grid connection point. The energy storage system uses bidirectional converter control and has four-quadrant current output capability; the DFIG adopts a traditional grid-following control strategy, and a current scaling factor λ is introduced in this invention to achieve coordinated regulation. Various faults can occur on the wind-storage grid connection line; different faults are applied to the system below to test this scheme.

[0145] (a) A single-phase ground fault (phase A grounded) is applied to the system at 0.5s. After the fault occurs, the positive sequence voltage and current at the grid connection point are first extracted, and the sudden change ΔU before and after the fault is calculated. + With ΔI + Thus, the positive-sequence impedance angle α⁺ is obtained. In the initial stage of the fault, due to the DFIG suppressing the negative-sequence current, the stator current phase shifts, and α⁺ momentarily deviates to approximately 55°, entering the non-optimal operating range of the directional element. According to the control strategy of this invention, the quadrant in which α⁺ is located is first determined, and the required energy storage positive-sequence current compensation amount to return α⁺ to 90° is calculated. Under this operating condition, the energy storage system has the current capability to meet the compensation requirements; therefore, there is no need to trigger DFIG current scaling. The corresponding reactive current compensation amount is directly output from the energy storage system, making ΔI... + The real and imaginary parts satisfy a preset phase relationship.

[0146] Subsequently, the energy storage system quickly adjusts its output current according to the compensation command, so that the grid connection point ΔI + The phase angle gradually approaches the theoretical value. Simulation results show that within approximately 0.2 seconds after the fault, the positive sequence impedance angle α⁺ is pulled back to near 90° and remains stable, with a steady-state value of approximately 90.15°. Figure 7 As shown.

[0147] (b) A two-phase short-circuit fault (AB short circuit) is applied to the system at 0.5s. After the fault occurs, the positive sequence voltage at the grid connection point drops significantly, and the phase of the DFIG current shifts rapidly, causing the positive sequence impedance angle α⁺ to drop from 90° before the fault to about 30°, which is far from the effective operating range of the directional element.

[0148] First, α⁺ is calculated in real time based on the voltage and current differences ΔU⁺ and ΔI⁺ before and after the fault. The controller determines that α⁺ falls into the first quadrant and calculates the theoretical energy storage compensation current according to the method of this invention. However, since the rated current of the energy storage system is low, the amplitude of the theoretical compensation amount significantly exceeds its maximum capacity. At this time, forcibly outputting this compensation current will cause energy storage overload, so it is necessary to enable the DFIG scaling factor λ proposed in this invention. To release the compensation space of energy storage, the positive sequence current of the DFIG is scaled according to λ:

[0149] The scaled DFIG current has a lower amplitude compared to the pre-fault state, reducing the compensation required by the energy storage system to within its capacity. In this embodiment, λ≈0.72 is obtained. This means the DFIG positive-sequence current needs to be scaled to approximately 72% of its original amplitude. Subsequently, the energy storage system outputs a compensation current that meets the constraints, and the DFIG outputs the scaled positive-sequence current. These two currents are superimposed at the grid connection point to form a new ΔI⁺, thereby gradually correcting the impedance angle.

[0150] Simulation results are as follows Figure 8 As shown, after the λ scaling mechanism is enabled, the positive sequence impedance angle α⁺ rises rapidly from the initial 30° and is pulled back to nearly 90° approximately 0.2 seconds after a fault; its steady-state value is approximately 89.53°, significantly improving the stability and reliability of the directional element. Without λ scaling, insufficient energy storage compensation will cause α⁺ to fail to return to positive, resulting in directional element failure.

[0151] The results show that when the energy storage system cannot independently bear the required compensation, the λ scaling strategy introduced in this invention can effectively coordinate DFIG and energy storage output, keeping the positive sequence impedance angle within a controllable range, thereby ensuring that the directional protection can still be reliably executed under severe asymmetric faults.

[0152] In summary, this invention starts from the relationship between the DFIG positive-sequence current, the energy storage positive-sequence current, and the grid connection point positive-sequence current, systematically derives the current compensation condition for α⁺ drift in the four quadrants, and constructs corresponding energy storage current compensation control logic and DFIG scaling logic in each of the four quadrants. By accurately determining the real part of the energy storage current, adjusting the imaginary part based on reactive power capacity constraints, and introducing a unified scaling factor λ to the DFIG current when capacity is insufficient, this invention achieves active α⁺ return across quadrants, enabling deep collaboration between the control side and the relay protection side.

[0153] Example 3

[0154] Based on the same inventive concept as Embodiment 2, this embodiment introduces a computer storage medium that can be located in a server to store at least one instruction, at least one program, code set, or instruction set for implementing the method embodiments. The at least one instruction, the at least one program, the code set, or the instruction set is loaded and executed by the processor to implement the steps of the wind-storage coordinated positive sequence impedance angle control method for adaptive directional elements as described in either Method Embodiment 1 or 2.

[0155] Optionally, in embodiments of the present invention, the storage medium may be located at at least one of a plurality of network servers in a computer network. Optionally, in embodiments of the present invention, the storage medium may include, but is not limited to, various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0156] As can be seen from the technical solutions provided in the embodiments of this specification above, in this embodiment, based on the quadrant position of the positive sequence impedance angle, the adjustment conditions of the real and imaginary parts of the grid-connected current are determined, and a calculation formula for the real and imaginary parts of the energy storage output positive sequence current is constructed; the wind-storage grid-connected data and the obtained doubly-fed wind farm output positive sequence current are input into the calculation formula for the real and imaginary parts of the energy storage output positive sequence current to obtain the initial energy storage output positive sequence current; based on the real and imaginary parts of the initial energy storage output positive sequence current and the wind-storage grid-connected data, the energy storage demand is calculated, and it is determined whether the obtained energy storage capacity meets the energy storage demand. If it does, the real and imaginary parts of the energy storage output positive sequence current are calculated based on the initial energy storage output positive sequence current; if it does not, the real and imaginary parts of the energy storage output positive sequence current are calculated after scaling the doubly-fed wind farm output positive sequence current by a preset scaling factor. By accurately determining the real part of the energy storage current, adjusting the imaginary part based on the reactive capacity constraint, and introducing a uniform scaling factor λ to the DFIG current when the capacity is insufficient, this invention achieves active positive sequence impedance angle correction across quadrants, enabling deep collaboration between the control side and the relay protection side.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for wind-storage coordinated positive sequence impedance angle control adapting to directional elements, characterized in that, include: Acquire data from the wind and energy storage grid connection points to determine if a fault has occurred in the wind and energy storage grid connection lines. In response to the aforementioned wind-storage grid connection line fault, the following correction operation is performed on the wind-storage coordinated positive sequence impedance angle: S1: Calculate the positive sequence impedance angle based on the wind-storage grid connection point data, and determine whether the positive sequence impedance angle meets the preset detection angle of the directional element. If it does, proceed to step S2; otherwise, based on the quadrant position of the positive sequence impedance angle and combined with the maximum reactive current support requirement of the grid connection point, calculate the real and imaginary parts of the positive sequence current output by the energy storage, and then proceed to step S2. S2, calculate the reference value of the positive sequence current output of the energy storage based on the real and imaginary parts of the positive sequence current output of the energy storage; S3, calculate the energy storage output positive sequence current based on the energy storage positive sequence current output reference value; S4, based on the positive sequence current output by the energy storage, output the fault direction judgment result through the directional element.

2. The wind-storage coordinated positive sequence impedance angle control method for adaptive directional elements according to claim 1, characterized in that, The formula for calculating the positive sequence impedance angle based on the wind-storage grid connection point data is as follows: （1） in, Let represent the positive-sequence component, and Δ represent the phasor difference before and after the fault. It is the positive sequence impedance angle. The positive sequence current phasor difference before and after a fault at the grid connection point of the wind-storage system. The difference in positive sequence voltage phasors before and after a grid connection point fault. This is the phase angle symbol.

3. The wind-storage coordinated positive sequence impedance angle control method for adaptive directional elements according to claim 1, characterized in that, Based on the quadrant position of the positive sequence impedance angle and combined with the maximum reactive current support requirement during grid connection point faults, the real and imaginary parts of the positive sequence current output by the energy storage are calculated, including: Based on the quadrant position of the positive sequence impedance angle, the adjustment conditions for the real and imaginary parts of the grid connection point current are determined. Based on the adjustment conditions of the real and imaginary parts of the grid connection point current and the maximum reactive current support requirements, the real and imaginary parts of the positive sequence current of the energy storage output are calculated.

4. The wind-storage coordinated positive sequence impedance angle control method for adaptive directional elements according to claim 3, characterized in that, Based on the adjustment conditions of the real and imaginary parts of the grid connection point current and the maximum reactive current support requirement, the real and imaginary parts of the positive sequence current output by the energy storage are calculated, including: Based on the adjustment conditions of the real and imaginary parts of the grid connection point current, a calculation formula for the real and imaginary parts of the positive sequence current of the energy storage output is constructed. The wind-storage grid connection point data and the obtained positive sequence current of the doubly fed wind farm output are input into the calculation formula of the real and imaginary parts of the positive sequence current of the energy storage output to obtain the initial positive sequence current of the energy storage output. Based on the real and imaginary parts of the initial energy storage output positive sequence current and the wind-storage grid connection point data, the energy storage demand is calculated, and it is determined whether the obtained energy storage capacity meets the energy storage demand. If it does, the real and imaginary parts of the energy storage output positive sequence current are calculated based on the initial energy storage output positive sequence current. If it does not, the positive sequence current output by the doubly-fed wind farm is scaled by a preset scaling factor, and the real and imaginary parts of the energy storage output positive sequence current are calculated.

5. The wind-storage coordinated positive sequence impedance angle control method for adaptive directional elements according to claim 4, characterized in that, The adjustment conditions for the real and imaginary parts of the grid connection point current include: The real part of the grid connection point current satisfies the following: the sum of the real part of the reference value of the positive sequence current output by the energy storage after the fault and the real part of the component of the positive sequence current output by the doubly fed wind farm is equal to the real part of the positive sequence current at the grid connection point before the fault. The imaginary part of the grid connection point current satisfies the following condition: the sum of the imaginary part of the reference value of the positive sequence current output by the energy storage after the fault and the imaginary part of the positive sequence current component output by the doubly fed wind farm is greater than the imaginary part of the positive sequence current at the grid connection point before the fault.

6. The wind-storage coordinated positive sequence impedance angle control method for adaptive directional elements according to claim 5, characterized in that, The quadrant positions of the positive sequence impedance angle include the first quadrant, the second quadrant, the third quadrant, and the fourth quadrant; When the quadrant position of the positive sequence impedance angle is in the first quadrant or the second quadrant, the adjustment conditions for the real and imaginary parts of the grid connection point current include: Formula for calculating the real part of the positive sequence current of energy storage output, based on the adjustment condition of the real part of the grid connection point current: Re[I+ es] = Re[I0] - Re[I+ D] (2) Formula for calculating the imaginary part of the positive sequence current output of energy storage, based on the imaginary part adjustment condition of the grid connection point current: Im[I+ es] = I Q - Im[ΔI + ](3) When the positive sequence impedance angle is located in the third or fourth quadrant, the adjustment conditions for the real and imaginary parts of the grid connection point current include: Formula for calculating the real part of the positive sequence current of energy storage output, based on the adjustment condition of the real part of the grid connection point current: Re[I+ es] = Re[I+ 0] - Re[I+ D] (4) Formula for calculating the imaginary part of the positive sequence current output of energy storage, based on the imaginary part adjustment condition of the grid connection point current: Im[I+ es] = I Q - Im[I+ 0] + Im[I+ D](5) Where Re[I+ es] represents the real part of the corrected post-fault energy storage output positive-sequence current reference value, and Im[I+ es] represents the imaginary part of the corrected post-fault energy storage output positive-sequence current reference value, I Q Represents the maximum reactive power capacity, Re[I+0] represents the real part of the positive sequence current at the grid connection point before the fault, Im[I+0] represents the imaginary part of the positive sequence current at the grid connection point before the fault, Re[I+D] represents the real part of the positive sequence current component of DFIG after the fault, and Im[I+D] represents the imaginary part of the positive sequence current component of DFIG after the fault.

7. The wind-storage coordinated positive sequence impedance angle control method for adaptive directional elements according to claim 1, characterized in that, When the positive sequence impedance angle meets the preset detection angle of the directional element, the reference value of the positive sequence current output is calculated based on the real and imaginary parts of the energy storage output positive sequence current, using the following formula: （6） Where j represents the imaginary number sign, and I*+es represents the reference value of the positive sequence current output after a fault. This represents the real part of the positive sequence current reference value of the energy storage output after a fault. This represents the imaginary part of the positive sequence current reference value of the energy storage output after a fault.

8. The wind-storage coordinated positive sequence impedance angle control method for adaptive directional elements according to claim 6 or 7, characterized in that, When the positive sequence impedance angle does not meet the preset detection angle of the direction element, the reference value of the positive sequence current output is calculated based on the real and imaginary parts of the energy storage output positive sequence current, using the following formula: （7） Where j represents the imaginary number sign, I*+ es represents the reference value of the positive sequence current output of the energy storage after the fault, Re[I+ es] represents the real part of the corrected reference value of the positive sequence current output of the energy storage after the fault, and Im[I+ es] represents the imaginary part of the corrected reference value of the positive sequence current output of the energy storage after the fault.

9. A computer device, characterized in that, include: Memory, used to store computer programs; A processor for executing the computer program to implement the steps of the wind-storage coordinated positive sequence impedance angle control method for adaptive directional elements as described in any one of claims 1 to 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the wind-storage coordinated positive sequence impedance angle control method for adaptive directional elements as described in any one of claims 1 to 8.

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