Power grid transient voltage coordination control method under distributed wind storage high permeability working condition

Abstract

The invention discloses a power grid transient voltage coordination control method under a distributed wind storage high permeability working condition, and the method comprises the steps: detecting the voltage change condition of a grid-connected point where a distributed wind power station is located, combining the grid-connected point where the distributed wind power station is located with the short-circuit ratio of a collection point, and carrying out the estimation calculation of the reactive compensation amount needed near the grid-connected point where a key point is located; and through a wind storage cooperative control strategy, energy storage and doubly-fed fan reactive power compensation capability are developed, smooth processing of output power is realized, and improvement of transient voltage stability of a grid-connected point is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of power systems, and more specifically, relates to a method for coordinated control of transient voltage of a power grid under high penetration rate conditions of distributed wind energy storage. Background Art

[0002] In recent years, the development of distributed doubly-fed wind turbines has shown a trend of large-scale contiguous development and cluster grid-connected. With the continuous increase in the penetration rate of distributed wind turbines, the randomness and volatility of their output will have a significant impact on the safe and stable operation of the power grid. Especially when a power grid fails, if a distributed wind turbine is disconnected from the grid unplannedly, it will further aggravate the energy imbalance of the main power grid and may even cause voltage collapse.

[0003] Traditional methods of coordinated control of transient voltage by distributed wind and energy storage usually adopt local control strategies, such as droop control or power factor control, and mainly rely on local information of wind turbine systems and energy storage devices for voltage regulation. However, the coordination between wind turbines and energy storage devices is poor, which may lead to non-optimal resource scheduling or conflict with each other, reducing the overall efficiency of the system. In this technical context, energy storage systems can not only play an important role in voltage regulation, but also smooth the fluctuations of wind turbine power generation and compensate for the randomness of wind turbine power generation. At the same time, distributed wind storage coordinated control can achieve dynamic and stable regulation of regional power grids by combining local control with global optimization, thereby enhancing the safety and stability of the power grid. Therefore, the voltage regulation technology of coordinated control of distributed wind and energy storage has become an important direction for the development of modern power grid technology, which can not only improve the acceptance capacity of distributed power generation systems, but also enhance the adaptability of power grids to uncertainty and volatility. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for coordinated control of transient voltage of a power grid under high penetration conditions of distributed wind energy storage. The method combines a distributed wind turbine power generation system with an energy storage system, utilizes the fast reactive power compensation response capability of the energy storage system and the improved reactive power compensation capability of the doubly-fed wind turbine to jointly adjust the voltage and power balance.

[0005] To achieve the above-mentioned purpose, the present invention provides a method for coordinated control of transient voltage of a distributed wind power storage high-penetration working condition power grid, characterized in that it comprises the following steps:

[0006] (1) Collect the wind speed parameters of each distributed wind power station. Assume that the wind speed parameters of each wind turbine in the same wind power station are the same. The wind speed parameter of the i-th wind power station is S i , i=1,2,…,n, n is the number of wind turbine power stations;

[0007] (2) Select key points in the distributed wind power stations and group each distributed wind power station according to the key points and wind speed parameters;

[0008] (3) Prioritize the wind power stations in each group after grouping;

[0009] (4) Calculate the total amount of reactive power required to maintain voltage stability at key points when the grid is in a transient state;

[0010] (5) According to the total reactive power demand, the reactive power compensation mode of the energy storage system and wind power station included in each grid connection point is switched in the order of GP1, GP2, GP3, and GP4;

[0011] (6) The active power of each wind power station is compensated through the energy storage system, thereby stabilizing the grid voltage.

[0012] The object of the invention of the present invention is achieved in this way:

[0013] The present invention discloses a method for coordinated control of transient voltage of power grid under high penetration rate working condition of distributed wind energy storage. By detecting the voltage change of the grid connection point where the distributed wind power station is located, combined with the short-circuit ratio of the grid connection point and the collection point where the distributed wind power station is located, the reactive power compensation required near the grid connection point at the key point is estimated and calculated; then, the reactive power compensation capability of energy storage and doubly-fed wind turbine is developed through the coordinated control strategy of wind energy storage and the smooth processing of its output power is realized, so as to improve the transient voltage stability of the grid connection point.

[0014] At the same time, the method for coordinated control of transient voltage of power grid under high permeability conditions of distributed wind storage in the present invention also has the following beneficial effects:

[0015] (1) When a power grid failure causes a voltage drop at a renewable energy grid connection point, the distributed energy storage and wind power stations output reactive power compensation through priority grouping as the main means of voltage regulation to achieve high voltage control efficiency and reduce unnecessary power fluctuations.

[0016] (2) After the transient voltage is initially restored, active power coordination control of energy storage is added. On the one hand, this makes the power at the grid connection point smoother and reduces voltage fluctuations. On the other hand, the active power output of the energy storage is used as an indirect means of voltage regulation to increase the voltage stability on the load side and better serve the user side.

[0017] (3) After the voltage stability of the grid-connected point of the distributed wind power station is improved, the DC transient voltage stability can be further improved through interactive coupling between the distributed wind power station and the DC cross-voltage level. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a flow chart of a method for coordinated control of transient voltage of a power grid under high permeability conditions of distributed wind storage according to the present invention;

[0019] Figure 2 This is a topological diagram of a power grid including distributed wind storage according to an embodiment of the present application;

[0020] Figure 3 It is a comparison diagram of the key nodes of the example provided in the embodiment of the present application and the results before and after the DC bus voltage regulation; DETAILED DESCRIPTION

[0021] The specific implementation of the present invention is described below in conjunction with the accompanying drawings so that those skilled in the art can better understand the present invention. It should be noted that in the following description, when the detailed description of known functions and designs may dilute the main content of the present invention, these descriptions will be omitted here.

[0022] Example

[0023] In this embodiment, if Figure 2 As shown in the figure, the power grid system with distributed wind energy storage mainly includes DC bus, AC grid, wind power station, energy storage system and related inverters. Figure 2 In the power grid shown, wind power stations are mostly connected to the end of the network, and the energy storage system is usually installed at the same node as the wind power station. The relevant parameters are shown in Table 1 below:

[0024]

[0025] Before specific implementation, the wind speed change conditions of the wind turbine operating environment are simulated and set, and a random short time period is selected to verify the transient voltage of wind-storage coordinated control.

[0026] Next we combine Figure 2 A method for coordinated control of transient voltage of power grid under high permeability conditions of distributed wind energy storage is described in detail. Figure 1 As shown, the specific steps include:

[0027] (1) Collect parameters of each distributed wind power station;

[0028] Collect the wind speed parameters of each distributed wind power station. Assume that the wind speed parameters of each wind turbine in the same wind power station are the same. The wind speed parameter of the i-th wind power station is S i , i=1,2,…,n, n is the number of wind power stations;

[0029] In this embodiment, if Figure 2 As shown, the nodes containing wind power stations and energy storage are: 2, 3, 5, 6, 7, 10, 12, 13. The collected ambient wind speed data is shown in Table 1:

[0030]

[0031]

[0032] Table 1

[0033] (2) Grouping each distributed wind power station;

[0034] According to the inherent differences in the reactive power capacity of wind turbines in different wind power stations and the time-varying nature caused by the external environment, the reactive power compensation capabilities of different wind power stations are ranked and grouped as follows:

[0035] (2.1) Traverse the wind speed parameters of each distributed wind power station and convert the wind speed parameter S i Satisfy 12m / s≤S i Wind power stations with a speed of ≤15 m / s are marked as a priority group, and the remaining wind power stations are marked as alternative groups. In this embodiment, the priority groups are: 6, 7, 10, 12, 13; the alternative groups are: 2, 3, 5.

[0036] (2.2) Add random disturbance to the grid connection point where the distributed wind power station is located, and select the grid connection point with the largest voltage fluctuation as the key point j. In this embodiment, node 2 is selected as the key point at the current moment;

[0037] The wind power stations 1 to j-1 between the key point j and the collection point O are classified as upstream units, and the wind power stations j to n between the key point j and the end of the line are classified as downstream units;

[0038] (2.3) Taking into account the inherent differences and environmental time-varying characteristics of different wind power stations, the wind power station in the downstream unit and in the priority group is marked as GP1; the wind power station in the upstream unit and in the priority group is marked as GP2; the wind power station in the downstream unit and in the alternative group is marked as GP3; the wind power station in the upstream unit and in the alternative group is marked as GP4;

[0039] In this embodiment, at the current moment, the nodes are grouped into: GP1 (6, 7, 10, 12, 13), GP2, GP3 (2, 3, 5), GP4.

[0040] (3) Prioritize the wind power plants in each group;

[0041] (3.1) Calculate the voltage sensitivity S between the grid connection point i and the key point j of each wind power station in each group ij ;

[0042]

[0043] Among them, U j Represents the transformer output voltage of the wind power station at key point j when the power grid is in steady state; R 1,i , X 1,i Respectively represent the line resistance and line reactance between the first grid connection point and the i-th grid connection point; R 1,j , R 1,jThey represent the line resistance and line reactance between the first grid connection point and the key point j respectively;

[0044] In this embodiment, assuming that the unit line impedance is (0.602+j0.232)Ω / km, according to the above formula, the voltage sensitivity moments of each node are respectively:

[0045] S 32 =[0.26378 0.13179]

[0046] S 52 =[0.28779 0.13067]

[0047] S 62 =[0.32473 0.13096]

[0048] S 72 =[0.34853 0.13432]

[0049] S 102 =[0.52107 0.14377]

[0050] S 122 =[0.77369 0.15594]

[0051] S 132 =[0.78534 0.15766]

[0052] (3.2), set the wind power station corresponding to key point j to have the highest priority, and note that the wind power station corresponding to node 2 has the highest priority;

[0053] According to the voltage sensitivity, the wind power plants with greater voltage sensitivity in the same group have higher priority, that is, the higher the priority of enabling the reactive power compensation function of its inverter, so we classify the wind power plants in each group according to the voltage sensitivity S ij Arrange in descending order, and finally get the priority ranking of all wind power stations.

[0054] In this embodiment, the nodes containing the wind power station in the example are prioritized as follows: 2, 13, 12, 7, 6, 10, 5, 3.

[0055] (4) Calculate the total amount of reactive power required to maintain voltage stability at key point j when the grid is in a transient state;

[0056] (4.1) Calculate the reactive power impact factor K of the key point j on the grid connection point i of each distributed wind power station Q,ji ;

[0057]

[0058] Among them, x iorepresents the line reactance between the grid connection point i and the collection point O, x jo Indicates the line reactance from the key point j to the collection point O; ΔU i Indicates the voltage fluctuation value at the grid connection point i when the grid is in a transient state, ΔU j It represents the voltage fluctuation value at the key point j when the power grid is in transient state;

[0059] (4.2), calculate the short-circuit ratio SCR at the key point j and the collection point O j 、SCR O :

[0060]

[0061] Among them, S ac,j represents the short-circuit capacity at the key point j, S ac,O represents the short-circuit capacity at the collection point O, Q j represents the reactive power output by the wind power station at the key point j;

[0062] (4.3) Calculate the total amount of reactive power required to maintain voltage stability at key point j when the grid is in transient state;

[0063]

[0064] Among them, U N is the nominal voltage; E is the potential of the power grid system; It represents the transformer output voltage of the wind power station at the key point j when the power grid is in transient state;

[0065] In this embodiment, as the voltage exceeds the limit, when the voltage drops to 0.9 pu, the total reactive power required for the key node 2 to maintain voltage stability is:

[0066]

[0067] (5) According to the reactive power demand value required when the voltage fluctuates, the reactive power compensation mode of each wind power station is switched according to the priority of the GP1, GP2, GP3, and GP4 groups, that is, in the order of 2, 13, 12, 7, 6, 10, 5, and 3;

[0068] (5.1) First, the working modes of each energy storage in GP1 are switched according to the priority order;

[0069] (5.1.1) In a distributed wind power station, each wind power station is equipped with an energy storage system. The energy storage system corresponding to the wind power station ranked first in GP1 is numbered i;

[0070] (5.1.2) When the power grid is in a transient state, the reactive output range of the converter of energy storage system i when switching from normal mode to reactive compensation mode is calculated as:

[0071]

[0072] Among them, S N is the rated apparent power of the converter of each energy storage system, P i , Q i is the active power and reactive power output by the converter of energy storage system i;

[0073] Take the maximum reactive power value Q output by the converter of the energy storage system within the reactive output range i,max , if Q i,max >Q' j , then the converter of energy storage system i provides reactive power to key point j, and then proceeds to step (6.1); if Q i,max ≤Q' j , then go to step (5.2);

[0074] (5.2) Calculate the total reactive power Q required to maintain voltage stability at key point j after energy storage system i provides reactive power to key point j” j =Q' j -Q i,max ;

[0075] (5.3) Taking the total reactive power Q” j As a benchmark, according to step (5.1), the energy storage systems in GP1, GP2, GP3, and GP4 are switched in working mode in order of priority. If the voltage at key point j cannot be maintained stable after the switching of each energy storage system is completed, then go to step (5.4);

[0076] (5.4) Calculate the total amount of reactive power required to maintain voltage stability at key point j after the energy storage systems are switched, recorded as Then the total reactive power Based on the above, the working modes of the wind power stations in GP1, GP2, GP3 and GP4 are switched in order of priority according to step (5.1).

[0077] In this embodiment, the energy storage system where the key node 2 is located is first dispatched. If the maximum reactive power provided by the key node 2 cannot stabilize the power grid (that is, the maximum reactive power is less than the total reactive power required for the stability of the power grid), the 13th node with the highest priority in GP1 is used to provide reactive power to the key node 2 first, and then the same process is repeated. Finally, reactive power is provided to the key node 2 in the order of priority 2, 13, 12, 7, 6, 10, 5, and 3.

[0078] If the voltage of key point 2 cannot be maintained stable after the switching of each energy storage system is completed, the wind power station where key node 2 is located will be dispatched. If the maximum reactive power provided by key node 2 cannot stabilize the power grid (that is, the maximum reactive power is less than the total reactive power required for the stability of the power grid), the reactive power will be provided to key node 2 through node 13 with the highest priority in GP1, and then by analogy, finally providing reactive power to key node 2 in the order of 2, 13, 12, 7, 6, 10, 5, and 3;

[0079] (6) Compensate each wind power station for its active power through the energy storage system;

[0080] (6.1) Calculate the reactive power Q provided by wind turbine station i to key point j D,out The line loss P line,i ;

[0081]

[0082] in, It indicates the transformer output voltage at the wind turbine power station i when the grid voltage is initially restored;

[0083] (6.2) Calculate the active power P provided by wind power station i to the grid when the grid voltage is in the initial recovery stage. Di Compared with the shortfall ΔP under normal operation Di ;

[0084] ΔP Di =P DiN -P Di

[0085] Among them, P DiN is the active power output of wind power station i to the grid under normal operation;

[0086] (6.3), energy storage system i provides equal active power compensation P to wind power station i C,i ;

[0087] P C,i =P line,i +ΔP Di

[0088] In summary, the present invention is not only applicable to the improvement of transient voltage at the grid-connected point of new energy, but also can further improve the stability of transient voltage at the DC voltage bus through interactive coupling between new energy and DC voltage levels: the improvement of voltage stability at the grid-connected point of distributed new energy has a positive impact on the transient voltage of the upper high-voltage DC bus, mainly in terms of reducing voltage fluctuations, accelerating system recovery, reducing voltage drops and overvoltage risks, reducing harmonics and oscillations, and suppressing chain reactions. This helps to improve the voltage stability and reliability of the entire power grid.

[0089] After implementing the above-mentioned coordinated control method for transient voltage of the power grid under the condition of high penetration rate of distributed wind storage, a three-phase short circuit fault occurred in the 220kV DC near area of ​​the power system, resulting in a voltage drop condition, and the transient voltage of key nodes was observed under different external conditions. Figure 3 The transient voltage comparison diagram of the selected key node 2 and 220kV DC bus voltage before and after the grid transient voltage coordinated control method under the distributed wind storage high penetration rate working condition is shown in Table 2. A moment is randomly selected as the analysis and research time node, and the control method and traditional control are compared, and the DC bus voltage at 220kV is further tested. The relevant calculation results are shown in Table 2. At this time, the system short-circuit ratio is 2.472.

[0090] Depend on Figure 3 It can be seen that the grid connection point voltage of key node 2 under the control of this method does not have transient overvoltage during the recovery process. The recovery of 220kV DC bus voltage is faster and smoother overall; Table 2: Calculation results of the present invention and traditional control when the short circuit ratio is 2.472.

[0091] parameter Traditional Control The present invention controls Key node voltage drop / pu 0.849 0.836 Key node voltage recovery time / s 0.48 0.32 Transient overvoltage at key nodes / pu 1.038 1.000 DC bus voltage recovery time / s 0.4 0.37 DC bus voltage transient overvoltage / pu 1.08 1.03

[0092] Table 2

[0093] The results show that after the voltage of the key grid-connected point under coordinated control is subjected to voltage shock, the degree of transient overvoltage can be reduced by combining the relevant wind storage regulation capability, thereby reducing the impact on the upper high-voltage DC bus voltage, helping to reduce the transient voltage fluctuation time of the DC bus, improving the dynamic response performance of the system, and reducing the voltage overshoot phenomenon during the transient period.

[0094] Although the above describes the illustrative specific embodiments of the present invention to facilitate those skilled in the art to understand the present invention, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

Claims

1. A method for coordinated control of transient voltage of power grid under high penetration rate of distributed wind energy storage, characterized in that: The following steps are involved: (1) Collect the wind speed parameters of each distributed wind power station. Assume that the wind speed parameters of each wind turbine in the same wind power station are the same. The wind speed parameter of the i-th wind power station is S i , i=1,2,…,n, n is the number of wind power stations; (2) Select key points in the distributed wind power stations and group each distributed wind power station according to the key points and wind speed parameters; (3) Prioritize the wind power stations in each group after grouping; (4) Calculate the total amount of reactive power required to maintain voltage stability at key points when the grid is in a transient state; (5) According to the total reactive power demand, the reactive power compensation mode of the energy storage system and wind power station included in each grid connection point is switched in the order of GP1, GP2, GP3, and GP4; (6) The active power of each wind power station is compensated through the energy storage system, thereby stabilizing the grid voltage.

2. According to claim 1, a method for coordinated control of transient voltage of power grid under high penetration rate of distributed wind energy storage is characterized in that: The method for grouping distributed wind power stations is as follows: (2.1) Traverse the wind speed parameters of each distributed wind power station and convert the wind speed parameter S i Satisfy 12m / s≤S i Wind power stations with a speed of ≤15m / s are marked as the priority group, and the remaining wind power stations are marked as the alternative group; (2.2) Add random disturbances to the grid connection point where the distributed wind power station is located, and select the grid connection point with the largest voltage fluctuation as the key point j; The wind power stations 1 to j-1 between the key point j and the collection point O are classified as upstream units, and the wind power stations j to n between the key point j and the end of the line are classified as downstream units; (2.3) The wind power station in the downstream unit and in the priority group is marked as GP1; the wind power station in the upstream unit and in the priority group is marked as GP2; the wind power station in the downstream unit and in the alternative group is marked as GP3; the wind power station in the upstream unit and in the alternative group is marked as GP4.

3. The method for coordinated control of transient voltage of power grid under high penetration rate of distributed wind energy storage according to claim 1 is characterized in that: The method for prioritizing the wind power stations is as follows: (3.1) Calculate the voltage sensitivity S between the grid connection point i and the key point j of each wind power station in each group ij ; Among them, U j Represents the transformer output voltage of the wind power station at key point j when the power grid is in steady state; R 1,i , X 1,i Respectively represent the line resistance and line reactance between the first grid connection point and the i-th grid connection point; R 1,j , R 1,j They represent the line resistance and line reactance between the first grid connection point and the key point j respectively; (3.2) Set the priority of the wind power station corresponding to the key point j to be the highest, and the wind power stations in each group are classified according to the voltage sensitivity S ij Arrange in descending order, and finally get the priority ranking of all wind power stations.

4. The method for coordinated control of transient voltage of power grid under high penetration rate of distributed wind energy storage according to claim 1 is characterized in that: The method for calculating the total amount of reactive power required to maintain voltage stability at the key point is: (4.1) Calculate the reactive power impact factor K of the key point j on the grid connection point i of each distributed wind power station Q,ji ; Among them, x io represents the line reactance between the grid connection point i and the collection point O, x jo Indicates the line reactance from the key point j to the collection point O; ΔU i Indicates the voltage fluctuation value at the grid connection point i when the grid is in a transient state, ΔU j It represents the voltage fluctuation value at the key point j when the power grid is in transient state; (4.2), calculate the short-circuit ratio SCR at the key point j and the collection point O j 、SCR O : Among them, S ac,j represents the short-circuit capacity at the key point j, S ac,O represents the short-circuit capacity at the collection point O, Q j represents the reactive power output by the wind power station at the key point j; (4.3) Calculate the total amount of reactive power required to maintain voltage stability at key point j when the grid is in transient state; Among them, U N is the nominal voltage; E is the potential of the power grid system; It represents the transformer output voltage of the wind power station at key point j when the power grid is in transient state.

5. The method for coordinated control of transient voltage of power grid under high penetration rate of distributed wind energy storage according to claim 1 is characterized in that: The process of switching the reactive power compensation mode in step (5) is as follows: (5.1) First, the working modes of each energy storage system in GP1 are switched according to the priority order; (5.1.1) In the distributed wind power station, each wind power station is equipped with an energy storage system. The energy storage system corresponding to the wind power station ranked first in GP1 is numbered i; (5.1.2) When the power grid is in a transient state, the reactive output range of the converter of energy storage system i when switching from normal mode to reactive compensation mode is calculated as: Among them, S N is the rated apparent power of each energy storage system converter, P i , Q i is the active power and reactive power output by the converter of energy storage system i; Take the maximum reactive power value Q output by the converter of the energy storage system within the reactive output range i,max , if Q i,max >Q' j , then the converter of energy storage system i provides reactive power to key point j, and then proceeds to step (6.1); if Q i,max ≤Q' j , then go to step (5.2); (5.2) Calculate the total reactive power Q required to maintain voltage stability at key point j after energy storage system i provides reactive power to key point j” j =Q' j -Q i,max ; (5.3) Taking the total reactive power Q” j As a benchmark, according to step (5.1), the energy storage systems in GP1, GP2, GP3, and GP4 are switched in working mode in order of priority. If the voltage at key point j cannot be maintained stable after the switching of each energy storage system is completed, then go to step (5.4); (5.4) Calculate the total amount of reactive power required to maintain voltage stability at key point j after the energy storage systems are switched, recorded as Then the total reactive power Based on the above, the working modes of the wind power stations in GP1, GP2, GP3 and GP4 are switched in order of priority according to step (5.1).

6. The method for coordinated control of transient voltage of power grid under high penetration rate of distributed wind energy storage according to claim 1 is characterized in that: The method for the energy storage system to perform active power compensation on each wind power station is as follows: (6.1) Calculate the reactive power Q provided by wind power station i to key point j D,out The line loss P line,i ; in, It represents the transformer output voltage at wind power station i when the grid voltage is initially restored; (6.2) Calculate the active power P provided by wind power station i to the grid when the grid voltage is in the initial recovery stage. Di Compared with the shortfall ΔP under normal operation Di ; ΔP Di =P DiN -P Di Among them, P DiN is the active power output of wind power station i to the grid under normal operation; (6.3), energy storage system i provides equal active power compensation P to wind power station i C,i ; P C,i =P line,i +ΔP Di 。

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