A DC sending end voltage stabilization method for wind and fire bundle delivery system

Abstract

The present invention relates to the technical field of voltage stability of power systems, and proposes a method for stabilizing voltage at a DC sending end of a wind-fire bundled delivery system, comprising the following steps: S1: performing real-time voltage detection on a DC sending end of the system; S2: predicting whether the voltage at the DC sending end has a trend of rapid change based on the detected real-time voltage, and if so, intercepting a time window including the moment when the voltage at the DC sending end has a trend of rapid change, and executing step S3; otherwise, returning to executing step S1; S3: performing voltage stabilization control on the DC sending end based on the time window; S4: calculating a voltage recovery index of the DC sending end, and if the voltage recovery index meets a voltage stabilization control stop condition, stopping the voltage stabilization control; otherwise, moving the time window backward, and returning to executing step S3 based on the moved time window; the problem of control delay existing in the prior art is solved, and the purpose of effective voltage stabilization is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of power system voltage stabilization, and more specifically, to a DC sending-end voltage stabilization method for a wind-fire bundled delivery system. Background Art

[0002] my country has a huge amount of wind energy. As traditional fossil energy is becoming increasingly depleted, wind power will become an important source of energy in my country. However, my country's wind resources are mainly distributed in the northwest, north China and southeast coastal areas. The local power grids are relatively small and need to be transmitted and consumed through long-distance cross-regional transmission. There are two ways of regional interconnection: AC interconnection and DC interconnection. Among them, DC transmission has great advantages in long-distance and large-capacity transmission. At present, high-voltage DC transmission has become the only way to transmit and consume new energy.

[0003] When wind power is transmitted through a high-voltage direct current transmission system, it is easily affected by faults in the direct current transmission system, resulting in low voltage or overvoltage problems. When the direct current system fails to commutate on the inverter side and the AC short circuit occurs in the area near the sending end, the sending-end AC grid will first experience low voltage and then overvoltage, causing the wind turbine to first experience low voltage ride-through and then high voltage ride-through; when a direct current fault occurs in the direct current system, it will cause single / double-pole locking at the converter station, and the reactive power compensated by the sending-end AC filter fed into the sending-end AC grid will cause the sending-end AC grid voltage to rise sharply, causing the wind turbine to experience high voltage ride-through.

[0004] In order to deal with the low voltage / overvoltage problems in the power system, wind turbines need to have fault ride-through capabilities. However, the existing fault ride-through strategies usually only consider a single low voltage / overvoltage phenomenon, without considering the problem of low voltage first and then overvoltage, and may even aggravate the low voltage / overvoltage when facing such problems. In the existing fault ride-through strategies, in the reactive power control strategy, a control strategy is usually adopted to adjust the reactive output according to the degree of grid voltage drop / rise. However, due to the certain delay in the wind turbine control system, on the one hand, it is impossible to immediately adjust the reactive output to support the voltage when entering low voltage ride-through. On the other hand, some reactive output is still sent after exiting low voltage. When facing low voltage problems caused by faults such as commutation failure, it will aggravate the overvoltage problem after low voltage. In the active power control strategy, a fixed active current operation method is usually adopted to reduce the active power output. However, in the low voltage stage, a significant reduction in the active power output of the wind turbine will lead to a decrease in the terminal voltage of the wind turbine and worsen the transient low voltage. Summary of the invention

[0005] In order to overcome the defect of poor voltage stabilization effect in the above-mentioned prior art, the present invention provides a DC sending end voltage stabilization method for a wind and fire bundling delivery system which can effectively stabilize the voltage.

[0006] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0007] The wind-fired bundled delivery system includes a DC delivery terminal for delivering electricity to outside the system, and the DC delivery terminal includes a wind turbine and a thermal turbine for generating electricity;

[0008] The DC sending-end voltage stabilization method comprises the following steps:

[0009] S1: Performing real-time voltage detection on the DC sending end of the system;

[0010] S2: Based on the detected real-time voltage, predict whether the voltage at the DC sending end has a trend of rapid change. If so, intercept a time window including the moment when the voltage at the DC sending end has a trend of rapid change, and execute step S3; otherwise, return to execute step S1;

[0011] S3: performing voltage stabilization control on the DC sending end based on the time window;

[0012] S4: Calculate the voltage recovery index of the DC sending end. If the voltage recovery index meets the voltage stabilization control stop condition, stop the voltage stabilization control; otherwise, move the time window backward, and return to execute step S3 based on the moved time window.

[0013] The present invention also proposes a DC sending end voltage stabilization system for realizing the DC sending end voltage stabilization method for the wind-fire bundle delivery system. The system comprises:

[0014] A voltage detection module, used for performing real-time voltage detection on the DC sending end of the system;

[0015] A change trend prediction module is used to predict whether the voltage of the DC sending end has a trend of rapid change based on the detected real-time voltage. If so, a time window including the moment when the voltage of the DC sending end has a trend of rapid change is intercepted to execute the steps of the voltage stabilization control module; otherwise, the steps of the voltage detection module are returned to be executed;

[0016] A voltage stabilization control module, used for performing voltage stabilization control on the DC sending end based on the time window;

[0017] The index calculation module is used to calculate the voltage recovery index of the DC sending end. If the voltage recovery index meets the voltage stabilization control stop condition, the voltage stabilization control is stopped; otherwise, the time window is moved backward, and the steps of executing the voltage stabilization control module are returned based on the moved time window.

[0018] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0019] The DC sending end of the system is subjected to real-time voltage detection. When it is predicted that the voltage at the DC sending end has a trend of rapid change, the system is judged to be in a non-voltage-stabilized state, a time window including the moment when the voltage at the DC sending end has a trend of rapid change is intercepted, and voltage stabilization control is performed on the DC sending end based on the time window to solve the control delay problem existing in the prior art. At the same time, an effective voltage recovery index is proposed, which can effectively evaluate the voltage stabilization effect and stop the voltage stabilization control at an appropriate time to achieve the purpose of effective voltage stabilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a flow chart of the DC sending end voltage stabilization method for the wind-fire bundle delivery system proposed in Example 1;

[0021] Figure 2 This is a schematic diagram of the air-fire bundling and delivery system proposed in Example 2;

[0022] Figure 3 This is a start-up criterion record table diagram proposed in Example 2;

[0023] Figure 4 This is a control status information table diagram proposed in Example 2;

[0024] Figure 5 This is a control instruction information table diagram proposed in Example 2;

[0025] Figure 6 This is a schematic diagram of the active power instruction of the wind turbine generator set proposed in Example 2;

[0026] Figure 7 This is a schematic diagram of reactive power instructions for wind turbines proposed in Example 2;

[0027] Figure 8 This is a table and diagram of the voltage recovery index calculation results proposed in Example 2;

[0028] Fig. 9 This is a schematic diagram of the sending-end commutation bus voltage proposed in Example 2;

[0029] Fig.10 This is an overall framework diagram of a DC sending-end voltage stabilization system proposed in Example 3. DETAILED DESCRIPTION

[0030] The accompanying drawings are only used for illustrative purposes and should not be construed as limiting the present embodiment;

[0031] In order to better illustrate the present embodiment, some parts in the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product;

[0032] It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0033] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0034] Example 1

[0035] This embodiment proposes a DC sending end voltage stabilization method for a wind-fire bundle delivery system. Figure 1 It is a flow chart of the DC sending end voltage stabilization method for the wind-fire bundle delivery system of this embodiment;

[0036] In this embodiment, a DC sending end voltage stabilization method for a wind-fire bundled transmission system is proposed. The wind-fire bundled transmission system includes a DC sending end for transmitting electric power to outside the system. The DC sending end includes a wind turbine and a thermal turbine for generating electricity.

[0037] The DC sending-end voltage stabilization method comprises the following steps:

[0038] S1: Performing real-time voltage detection on the DC sending end of the system;

[0039] S2: Based on the detected real-time voltage, predict whether the voltage at the DC sending end has a trend of rapid change. If so, intercept a time window including the moment when the voltage at the DC sending end has a trend of rapid change, and execute step S3; otherwise, return to execute step S1;

[0040] S3: performing voltage stabilization control on the DC sending end based on the time window;

[0041] S4: Calculate the voltage recovery index of the DC sending end. If the voltage recovery index meets the voltage stabilization control stop condition, stop the voltage stabilization control; otherwise, move the time window backward, and return to execute step S3 based on the moved time window.

[0042] In the specific implementation process, real-time voltage detection is performed on the DC sending end of the system. When it is predicted that the voltage at the DC sending end has a trend of rapid change, the system is judged to be in a non-voltage-stabilized state, and a time window including the moment when the voltage at the DC sending end has a trend of rapid change is intercepted. Based on the time window, voltage stabilization control is performed on the DC sending end to control the system, thereby solving the control delay problem existing in the prior art; the voltage recovery index is used to stop the voltage stabilization control at the appropriate time to achieve the purpose of effective voltage stabilization.

[0043] In an optional embodiment, the step of performing real-time voltage detection on the DC sending end and predicting whether the voltage of the DC sending end has a trend of rapid change based on the detected real-time voltage includes:

[0044] Assume the current sampling time is t, with sampling rate f s Yes q , t], sampling the real-time voltage of the DC sending end, and storing the sampled voltage data in a first sampling information matrix O, wherein the matrix O is a row matrix;

[0045] When the first sampling information matrix O meets the voltage stabilization control start condition, it is determined that the voltage at the DC sending end has a trend of rapid change;

[0046] The expression of the voltage stabilization control start condition includes:

[0047]

[0048] b m =1+(m-1) 2 Δt / 100

[0049] o′ 1,j-1 =o 1,j -o 1,j-1 ,j>1

[0050] In the formula, o 1,j represents the element in the 1st row and the jth column in the first sampling information matrix O, and also represents [tt q , t] within the time range of the jth sampling point corresponding to the real-time voltage of the DC sending end; b m represents the mth transform coefficient under v-order transform; v represents a preset positive integer value, m represents a positive integer less than or equal to v; Δt represents the sampling time interval; K d1 represents the preset first voltage margin factor; |·| represents the absolute value symbol; K m,set K m,j Corresponding start criterion setting value; K set K m+1,j The corresponding start criterion setting value.

[0051] In an optional embodiment, the step of performing voltage stabilization control on the DC sending end based on the time window includes:

[0052] Sampling and recording the DC sending end commutation bus voltage, wind turbine generator set terminal voltage, wind turbine generator set active power, wind turbine generator set rated capacity, thermal power generator set active power, thermal power generator set reactive power and thermal power generator set rated capacity within the time window;

[0053] Predicting a change trend of the voltage at the DC sending end based on the DC sending end commutation bus voltage, and formulating a voltage stabilization control instruction based on the change trend and the wind turbine generator terminal voltage;

[0054] The voltage stabilization control instruction is corrected based on the wind turbine active power, the rated capacity of the wind turbine, the active power of the thermal power unit, the reactive power of the thermal power unit and the rated capacity of the thermal power unit, and the corrected voltage stabilization control instruction is executed.

[0055] In this optional embodiment, based on the voltage prediction information and change trend information, the operating status of the wind turbine is divided more finely, and appropriate control instructions are issued according to the status information to achieve the purpose of effective voltage stabilization.

[0056] In an optional embodiment, the step of sampling and recording the DC sending-end commutation bus voltage within the time window includes:

[0057] Intercept[t 1 -t r1 , t 1 +t r2 ] as the time window, where t 1 Indicates the moment when the voltage at the DC sending end has a rapid change trend, t r1 and t r2 All are preset values;

[0058] With sampling rate f r Sample and record the DC sending end commutation bus voltage within the time window, and record the sampled voltage data as a matrix R 1 , where the matrix R 1 The element in the i-th row and j-th column of is denoted by r 1,i,j , r 1,i,j The DC sending-end commutation bus voltage corresponding to the i×j-th sampling point in the time window is recorded;

[0059] The step of predicting the change trend of the voltage at the DC sending end based on the DC sending end commutation bus voltage comprises:

[0060] Based on the matrix R 1 Calculate the first voltage prediction information matrix R 1 ' and the second voltage prediction information matrix R 1 ″;

[0061] Among them, the matrix R 1 ' and R 1 " includes:

[0062]

[0063] h 2 ≥h 1

[0064] In the formula, r' 1,i,j Represents the matrix R 1 'The element in the i-th row and j-th column; r"1,i,j Represents the matrix R 1 "The element in the i-th row and j-th column of "; Represents the matrix R 1 The i-th row and the j+h 1 Column elements; Represents the matrix R 1 The i-th row and the j+h 2 Column element; k 1 , k 2 , k 3 and k 4 represent the preset first, second, third and fourth transformation factors respectively; h 1 and h 2 Respectively represent the preset first and second transformation orders; u represents the matrix R 1 The total number of elements also represents the total number of sampling points in the time window;

[0065] like Then, it is determined that the voltage has an upward trend; at this time, if and Then, it is determined that the voltage has a trend of rapid increase, otherwise, it is determined that the voltage does not have a trend of rapid increase; where u set3 and u set4 represent the preset third and fourth voltage thresholds respectively;

[0066] like Then, it is determined that the voltage has a downward trend; at this time, if and Then, it is determined that the voltage has a trend of rapidly decreasing; otherwise, it is determined that the voltage does not have a trend of rapidly decreasing.

[0067] As an example, the matrix R 1 is a row matrix.

[0068] In an optional embodiment, the voltage stabilization control instruction formulated based on the change trend and the terminal voltage of the wind turbine generator set includes: an active power control instruction and a reactive power control instruction of the wind turbine generator set;

[0069] The active power control instruction of the wind turbine group is used to set the active power of the i-th wind turbine in the wind turbine group at the current moment to the maximum power c′ of the i-th wind turbine at the current wind speed. 1,i,j , where j represents the number of the current moment, and also represents the sampling point number within the time window;

[0070] The reactive power control instruction is used to divide the voltage change trend of the DC sending end into several states, and set the reactive power of the i-th wind turbine in the wind turbine group at the current moment to the reactive power value c′ corresponding to the state. 2,i,j ;

[0071] When the current voltage is less than the first voltage threshold, if the voltage has an upward trend, the voltage change trend of the DC sending end is regarded as state 1. At this time, c' 2,i,j =c q1 (u set1 -r 2,i,j ), if the voltage has a downward trend, then the voltage change trend of the DC sending end is regarded as state 2. At this time, c' 2,i,j =c q2 (u set1 -r 2,i,j ), where r 2,i,j represents the terminal voltage of the i-th wind turbine corresponding to the j-th sampling point in the time window, c q1 and c q2 Respectively represent the preset first and second reactive power control coefficients; u set1 represents a preset first voltage threshold;

[0072] When the current voltage is greater than or equal to the first voltage threshold and less than or equal to the second voltage threshold, if the voltage has a rapid rising trend, the voltage change trend of the DC sending end is regarded as state 3. At this time, If the voltage has a rapid downward trend, the voltage change trend of the DC sending end is considered to be state 4. At this time, Otherwise, the voltage variation trend of the DC sending end is considered to be state 5. At this time, c′ 2,i,j =c′ 2,i,j-1 , where c q3 and c q4 Respectively represent the preset third and fourth reactive power control coefficients;

[0073] When the current voltage is greater than the second voltage threshold, if the voltage has an upward trend, the voltage change trend of the DC sending end is considered to be state 6. At this time, c' 2,i,j =c q2 (u set2 -r 2,i,j ), if the voltage has a downward trend, then the voltage change trend of the DC sending end is regarded as state 7. At this time, c′ 2,i,j =c q1 (u set2 -r 2,i,j ), where u set2 Indicates a preset second voltage threshold.

[0074] In an optional embodiment, the voltage stabilization control instruction formulated based on the change trend includes: an active power control instruction and a reactive power control instruction of the wind turbine generator set;

[0075] The active power control instruction of the wind turbine group is used to set the active power of the i-th wind turbine in the wind turbine group at the current moment to the maximum power c′ of the i-th wind turbine at the current wind speed. 1,i,j , where j represents the number of the current moment, and also represents the sampling point number within the time window;

[0076] The reactive power control instruction is used to set the reactive power of the i-th wind turbine in the wind turbine group at the current moment to c′ 2,i,j ;

[0077] The expression for correcting the voltage stabilization control instruction based on the wind turbine active power, the wind turbine rated capacity, the thermal power active power, the thermal power reactive power and the thermal power rated capacity includes:

[0078]

[0079] In the formula, c″ 1,i,j represents the corrected c′ 1,i,j ;c″ 2,i,j represents the corrected c′ 2,i,j ; r 3,i,j represents the active power of the i-th wind turbine corresponding to the j-th sampling point in the time window; r 8,i,1 represents the rated capacity of the i-th thermal power plant corresponding to the j-th sampling point in the time window; r 5,i,j and r 6,i,j They represent the active power and reactive power of the i-th thermal power plant corresponding to the j-th sampling point in the time window respectively; z represents the total number of thermal power plants in the thermal power plant group; r 7,i,1 represents the rated capacity of the i-th wind turbine; l represents the total number of wind turbines in the wind turbine group.

[0080] In an optional embodiment, the expression of the voltage recovery index of the DC sending end includes:

[0081]

[0082] Where S(d) represents the voltage recovery index of the DC sending end in the dth cycle; u represents the total number of sampling points in the time window, j represents the number of the current moment, and also represents the sampling point number in the time window. When j=u, x 1,j =x 1,u And x 2,j =x 2,u ;u bus1，j represents the sending-end commutation bus voltage corresponding to the jth sampling point; u set1 and u set2 Respectively represent the preset first and second voltage thresholds.

[0083] In an optional embodiment, the expression of the voltage stabilization control stop condition includes:

[0084]

[0085] Wherein, d represents the current voltage regulation control cycle number, the initial value of d is 1, and the time window moves backward once, the value of d increases by 1; d min represents the preset minimum number of voltage stabilization control cycles; S(e) represents the voltage recovery index of the DC sending end corresponding to the e-th voltage stabilization control cycle.

[0086] In an optional embodiment, the time range of the time window is [t 1 -t r1 , t 1 +t r2 ], where t 1 Indicates the moment when the voltage at the DC sending end has a rapid change trend, t r1 and t r2 All are preset values;

[0087] When the time window is moved backward, let t 1 =t 1 +t r2 , and get the time window after moving.

[0088] Example 2

[0089] This embodiment is based on the DC sending end voltage stabilization method for the wind-fire bundle delivery system proposed in Embodiment 1, and proposes the following implementation examples:

[0090] The wind turbine is marked as WG(i), the synchronous turbine is marked as G(i), i is the corresponding number of the turbine. Figure 2 Schematic diagram of the wind and fire bundling delivery system proposed in this embodiment; Figure 2 As shown in FIG. 1 , an AC fault occurs at the receiving end AC bus at 0.5s, and the fault is cleared at 0.6s.

[0091] Step 1: Real-time detection of the commutation bus voltage u at the sending end bus , stored in the first sampling information matrix O, and the first voltage start information matrix O' is calculated, and the second voltage start information matrix O'' is calculated according to the first voltage start information matrix, and the size relationship between the second voltage start information and the start criterion setting value is judged, and whether to start the next action is determined based on the judgment.

[0092] Step 11: Assume that the current sampling time is t, and take time t as the zero time, and the sampling rate is f s Transmission end commutation bus voltage u bus Perform real-time detection and capture the time window [tt q, t], the detected wind turbine terminal voltage u w Stored in the first sampling information matrix O, as time t moves forward, the matrix O can be updated in real time.

[0093] O=[u bus，1 u bus2 u bus，3 … u bus,n ] 1×n

[0094] Where n is the number of sampling points, n = t q f s +1. In this embodiment, select t q =0.05s, sampling rate f s =200kHz, sampling interval Δt=0.5ms, then n=101.

[0095] Step 12: Transform the matrix O according to the following formula to obtain the first voltage start-up information matrix O'.

[0096] o′ 1,j-1 =o 1,j -o 1,j-1 ,j>1

[0097] O'=[o' 1,1 o' 1,2 o' 1,3 … o' 1,n-1 ] 1×(n-1)

[0098] In the formula, o i,j represents the element in the i-th row and j-th column of matrix O, o' i,j Represents the element in the i-th row and j-th column of the matrix O'.

[0099] Step 13: Calculate and obtain the second voltage startup information matrix O'' according to the following formula.

[0100]

[0101] b m =1+(m-1) 2 Δt / 100

[0102]

[0103] In the formula, K m,j is the element in the mth row and jth column of the matrix, m is the transformation order of the second voltage startup information, b m is the transformation coefficient under the m-th order transformation, K d1 is the first voltage margin factor. In this embodiment, a fourth-order transformation is adopted, then b1 =1, b 2 =1.005, b 3 =1.02, b 4 =1.045, define K d1 =0.005.

[0104] Step 14: Determine the second voltage startup information and the startup criterion setting value K m,set , K set If the following relationship is satisfied, the time that satisfies the start criterion is recorded as the start time t 1 , go to step 2, otherwise return to step 11.

[0105]

[0106] In this embodiment, K 1,set =0.0040, K 2,set =0.0045, K 3,set =0.0050, K 4,set =0.0055, K set =0.0240.

[0107] Figure 3 The start-up criteria record table diagram proposed in this embodiment; Figure 3 It can be seen that at t = 0.5285s, the start criterion is met, so the start time t is recorded. 1 =0.5285s, record the current control period d=1, and go to step 2.

[0108] Step 2: Cut the time window to [t 1 -t r1 , t 1 +t r2 ], record the bus voltage u at the sending end within the time window bus , each wind turbine terminal voltage u w , Active power P w , reactive power Q w , active power P of each synchronous unit g , reactive power Q g , the voltage prediction information of the sending-end commutation bus, the margin coefficient of each wind turbine unit and the control margin information of each wind turbine unit are calculated.

[0109] Step 21: Cut the time window to [t 1 -t r1 , t 1 +t r2 ], set the sampling rate to f r , the sending-end commutation bus voltage u bus , each wind turbine terminal voltage uw , Active power P w , reactive power Q w , active power P of each synchronous unit g , reactive power Q g The sampling data are recorded as matrix R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , record the rated capacity of each wind turbine as matrix R 7 , the rated capacity of each synchronous unit is the matrix R 8 Specifically, the terminal voltage u of wind turbine WG(i) is w , Active power P w , reactive power Q w , Rated capacity S w Stored in matrix R 2 , R 3 , R 4 , R 7 The i-th row of the synchronous generator G(i) is g , reactive power Q g , Rated capacity S G Stored in matrix R 5 , R 6 , R 8 The i-th row.

[0110] R 1 =[u bus1,1 u bus1,2 u bus1,3 … u bus1,u ] 1×u

[0111]

[0112]

[0113] Where u is the time window [t 1 -t r1 , t 1 +t r2 ], u=(t r1 +t r2 )f r +1. In this embodiment, t r1 =0.002s, t r2 =0.008s, then u = 2001. l is the number of wind turbines, and z is the number of synchronous units.

[0114] Step 22: Matrix R1 Transform according to the following formula to obtain the first voltage prediction information matrix R 1 ', the second voltage prediction information matrix R 1 ”.

[0115]

[0116] In the formula, r 1,i,j Represents the matrix R 1 The element in row i and column j in r' 1,i,j Represents the matrix R 1 'The element in row i and column j, k 1 is the first transformation factor, k 2 is the second transformation factor, k 3 is the third transformation factor, k 4 is the fourth transformation factor, h 1 is the first transformation order, h 2 is the second transform order, h 2 ≥h 1 In this embodiment, k is defined 1 =-0.95, k 2 =1, k 3 =-0.95, k 4 =1,h 1 =10,h 2 =20.

[0117] Step 23: Calculate the margin coefficient matrix R of each wind turbine generator set according to the following formula.

[0118]

[0119] In the formula, r i,1 is the element in row i and column 1 of R, r 7,i,1 is the matrix R 7 The element at row i and column 1 in .

[0120] Step 24: Calculate the control margin matrix R' of each wind turbine generator set according to the following formula.

[0121]

[0122] In the formula, r' i,j is the element in the i-th row and j-th column of the matrix R', r 3,i,j is the matrix R 3 The element in row i and column j in 8,i,1 is the matrix R 8 The element in row i and column 1, r 5,i,j is the matrix R 5 The element in row i and column j in 6,i,jis the matrix R 6 The element at row i and column j in .

[0123] Step 3: Based on the voltage prediction information obtained in step 2, the control state information of the wind turbine is obtained by looking up the table, different control instructions are obtained according to different control states, and the control instructions are corrected according to the control margin information of the wind turbine. The active and reactive control instruction information of the wind turbine is sent to each wind turbine.

[0124] Step 31: According to the voltage conversion information matrix R obtained in step 2 1 '、R 1 ”, Figure 4 The control state information table diagram proposed in this embodiment is based on Figure 4 The control state information matrix C is obtained, and the matrix C is shown in the following formula.

[0125]

[0126] In the table, u set,1 ,u set,2 ,u set,3 ,u set,4 are the first, second, third and fourth voltage thresholds respectively. In this embodiment, u set,1 =0.9,u set,2 =1.1,u set,3 =0.0002,u set,4 =0.005, c 1,j is the element in the 1st row and the jth column of the matrix C.

[0127] Step 32: Figure 5 This is a control instruction information table diagram proposed in this embodiment; according to Figure 3 Transform the control state information matrix C to obtain the first control instruction matrix C' 1 , C' 2 .

[0128]

[0129] In the table, c' 1,i,j is the matrix C' 1 The element in row i and column j in 2,i,j is the matrix C' 2 The element in the i-th row and j-th column of iv is the maximum power of the wind turbine at the current wind speed, c q1 is the first reactive power control coefficient, c q2 is the second reactive power control coefficient, r 2,i,j is the matrix R 2 In this embodiment, take c q1=1.5, c q2 =2.25, c q3 =1.5.

[0130] Step 33: Based on the control margin matrix R' obtained in step 2, the first control command matrix C' is calculated as follows: 1 , C' 2 Make corrections to obtain the second control instruction matrix C" 1 , C” 2 .

[0131]

[0132] Step 34: Send the control command to the wind turbine and write the control command matrix C" 1 The i-th row of is set to the active power command value of wind turbine WG(i) in turn, and the C" 2 The i-th row is set to the reactive power command value of wind turbine WG(i) in sequence. Figure 6 This is a schematic diagram of the active power instruction of the wind turbine generator set proposed in this embodiment; Figure 7 Schematic diagram of reactive power command of wind turbine generator set proposed in this embodiment; active power command and reactive power command of wind turbine generator set are as follows: Figure 6 and Figure 7 shown.

[0133] Step 4: Preprocess the measured data of the sending-end commutation bus voltage within the time window, calculate the voltage recovery index S(d) within the current cycle, and determine whether to end the process based on the current control cycle number d and the calculated S(d) value.

[0134] Step 41: Preprocess the measured data of the sending-end commutation bus voltage within the time window and calculate the matrix R 1 Transform to get matrix X 1 , X 2 .

[0135]

[0136] X 1 =[x 1,1 x 1,2 … x 1,u ] 1×u

[0137] X 1 =[x 2,1 x 2,2 … x 2,u ] 1×u

[0138] Step 42: According to the matrix X 1 , X 2, calculate the voltage recovery index S(d) of the current cycle.

[0139]

[0140] Step 43: Determine whether to end the process based on the current control cycle number d and the calculated S(d) value. If the following equation is satisfied, end the process. Otherwise, set t 1 =t 1 +t r2 , d=d+1, return to step 2.

[0141]

[0142] Among them, d min To control the minimum number of cycles, t m To determine the shortest time required for voltage stabilization, is the rounding symbol. In this embodiment, let t m = 0.05s, then d min =5. Figure 8 This is a table of voltage recovery index calculation results proposed in this embodiment; Figure 8 As shown, at the 20th control cycle, it is satisfied, it is considered that the voltage has recovered to the normal operating level, and the process ends.

[0143] Fig. 9 Schematic diagram of the sending-end commutation bus voltage proposed in this embodiment; after commutation failure occurs, the sending-end commutation bus voltage using this strategy is as follows Fig. 9 As shown. Fig. 9 It can be seen that after a commutation failure occurs, the adoption of this strategy can significantly raise the low voltage and suppress the overvoltage, which has a good effect on maintaining voltage stability after the commutation failure.

[0144] In this embodiment, it can be seen that this method: 1) predicts and classifies the operating status of the power system based on historical voltage data, and enters the low voltage crossing stage in advance when a downward trend in voltage is detected, which solves the problem of control delay in the existing low voltage crossing strategy, and can immediately adjust the reactive power to support the voltage when entering the low voltage crossing; 2) increases reactive power support at the initial stage of low voltage crossing, and reduces reactive power support in advance at the rising edge of voltage in the low voltage stage, which can, on the one hand, effectively support the low voltage, and on the other hand, avoid the overvoltage problem caused by surplus reactive power during the low voltage crossing period caused by control delay; 3) in the process of low voltage crossing, on the basis of ensuring that the wind turbine has a certain reactive power support capacity, the active power output of the wind turbine is maintained to the greatest extent, which can avoid the deterioration of low voltage due to a sudden drop in active power output; 4) in the process of high voltage crossing, appropriately reduces the active power output of the wind turbine, which can make fuller use of the voltage regulation capability of the wind turbine and suppress overvoltage.

[0145] Example 3

[0146] This embodiment proposes a DC sending end voltage stabilization system, which is used to implement a DC sending end voltage stabilization method for a wind-fire bundling delivery system proposed in Embodiment 1.

[0147] Fig.10 Schematic diagram of the overall framework of the DC sending-end voltage stabilization system of this embodiment.

[0148] The DC sending-end voltage stabilization system comprises:

[0149] A voltage detection module, used for performing real-time voltage detection on the DC sending end of the system;

[0150] A change trend prediction module is used to predict whether the voltage of the DC sending end has a trend of rapid change based on the detected real-time voltage. If so, a time window including the moment when the voltage of the DC sending end has a trend of rapid change is intercepted to execute the steps of the voltage stabilization control module; otherwise, the steps of the voltage detection module are returned to be executed;

[0151] A voltage stabilization control module, used for performing voltage stabilization control on the DC sending end based on the time window;

[0152] The index calculation module is used to calculate the voltage recovery index of the DC sending end. If the voltage recovery index meets the voltage stabilization control stop condition, the voltage stabilization control is stopped; otherwise, the time window is moved backward, and the steps of executing the voltage stabilization control module are returned based on the moved time window.

[0153] This embodiment proposes a computer device, including a memory and a processor, wherein the memory stores computer-readable instructions, and when the computer-readable instructions are executed by the processor, the processor executes the steps of the DC sending end voltage stabilization method for the wind and fire bundling delivery system described in Example 1.

[0154] It can be understood that the DC sending end voltage stabilization system and computer device of this embodiment improve the method of embodiment 1, and the options in the above embodiment 1 are also applicable to this embodiment, so they will not be repeated here.

[0155] The same or similar reference numerals correspond to the same or similar components;

[0156] The terms used to describe the positional relationship in the drawings are only used for illustrative purposes and should not be construed as limiting the present embodiment;

[0157] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for stabilizing the voltage at the DC sending end of a wind and fire bundle delivery system, characterized in that: The wind-fired bundled delivery system includes a DC delivery terminal for delivering electricity to outside the system, and the DC delivery terminal includes a wind turbine and a thermal turbine for generating electricity; The DC sending-end voltage stabilization method comprises the following steps: S1: Performing real-time voltage detection on the DC sending end of the system; S2: Based on the detected real-time voltage, predict whether the voltage at the DC sending end has a trend of rapid change. If so, intercept a time window including the moment when the voltage at the DC sending end has a trend of rapid change, and execute step S3; otherwise, return to execute step S1; S3: performing voltage stabilization control on the DC sending end based on the time window; S4: Calculate the voltage recovery index of the DC sending end, and if the voltage recovery index meets the voltage stabilization control stop condition, stop the voltage stabilization control; otherwise, move the time window backward, and return to execute step S3 based on the moved time window; The step of performing voltage stabilization control on the DC sending end based on the time window comprises: Sampling and recording the DC sending end commutation bus voltage, wind turbine generator set terminal voltage, wind turbine generator set active power, wind turbine generator set rated capacity, thermal power generator set active power, thermal power generator set reactive power and thermal power generator set rated capacity within the time window; Predicting a change trend of the voltage at the DC sending end based on the DC sending end commutation bus voltage, and formulating a voltage stabilization control instruction based on the change trend and the wind turbine generator terminal voltage; Based on the wind turbine active power, the wind turbine rated capacity, the thermal power active power, the thermal power reactive power and the thermal power rated capacity, the voltage stabilization control instruction is corrected, and the corrected voltage stabilization control instruction is executed; The step of sampling and recording the DC sending-end commutation bus voltage within the time window includes: Intercept [t1-t r1 , t1+t r2 ] as the time window, where t1 represents the moment when the voltage at the DC sending end has a rapid change trend, and t r1 and t r2 All are preset values; With sampling rate f r Sample and record the DC sending end commutation bus voltage within the time window, and record the sampled voltage data as a matrix R1, where the element in the i-th row and j-th column of the matrix R1 is recorded as r 1,i,j , r 1,i,j The DC sending-end commutation bus voltage corresponding to the i×j-th sampling point in the time window is recorded; The step of predicting the change trend of the voltage at the DC sending end based on the DC sending end commutation bus voltage comprises: Calculate a first voltage prediction information matrix R1′ and a second voltage prediction information matrix R1″ based on the matrix R1; The expressions of the matrices R1' and R1'' include: h2 ≥ h1 In the formula, r' 1,i,j Represents the element in the i-th row and j-th column of the matrix R1'; r'' 1,i,j Represents the element in the i-th row and j-th column of the matrix R1''; Represents the element in the i-th row and j+h1-th column of the matrix R1; represents the element of the i-th row and j+h2-th column of the matrix R1; k1, k2, k3 and k4 represent the preset first, second, third and fourth transformation factors respectively; h1 and h2 represent the preset first and second transformation orders respectively; u represents the total number of elements of the matrix R1, and also represents the total number of sampling points in the time window; like Then, it is determined that the voltage has an upward trend; at this time, if and Then, it is determined that the voltage has a trend of rapid increase, otherwise, it is determined that the voltage does not have a trend of rapid increase; where u set3 and u set4 represent the preset third and fourth voltage thresholds respectively; like Then, it is determined that the voltage has a downward trend; at this time, if and Then, it is determined that the voltage has a trend of rapidly decreasing; otherwise, it is determined that the voltage does not have a trend of rapidly decreasing.

2. The DC sending end voltage stabilization method for the wind and fire bundling delivery system according to claim 1 is characterized in that: The step of predicting whether the voltage at the DC sending end has a trend of rapid change based on the detected real-time voltage includes: Assume the current sampling time is t, with sampling rate f s Yes q , t], sampling the real-time voltage of the DC sending end, and storing the sampled voltage data in a first sampling information matrix O, wherein the matrix O is a row matrix; When the first sampling information matrix O meets the voltage stabilization control start condition, it is determined that the voltage at the DC sending end has a trend of rapid change; The expression of the voltage stabilization control start condition includes: b m =1+(m-1) 2 Δt / 100 o' 1,j-1 =o 1,j -o 1,j-1 ,j>1 In the formula, o 1,j represents the element in the 1st row and the jth column in the first sampling information matrix O, and also represents [tt q , t] within the time range of the jth sampling point corresponding to the real-time voltage of the DC sending end; b m represents the mth transform coefficient under v-order transform; v represents a preset positive integer value, m represents a positive integer less than or equal to v; Δt represents the sampling time interval; K d1 represents the preset first voltage margin factor; |·| represents the absolute value symbol; K m,set K m,j Corresponding start criterion setting value; K set K m+1,j The corresponding start criterion setting value.

3. The DC sending end voltage stabilization method for wind and fire bundling delivery system according to claim 1 is characterized in that: The voltage stabilization control instructions formulated based on the change trend and the terminal voltage of the wind turbine generator set include: active power control instructions and reactive power control instructions of the wind turbine generator set; The active power control instruction of the wind turbine group is used to set the active power of the i-th wind turbine in the wind turbine group at the current moment to the maximum power c′ of the i-th wind turbine at the current wind speed. 1,i,j , where j represents the number of the current moment, and also represents the sampling point number within the time window; The reactive power control instruction is used to divide the voltage change trend of the DC sending end into several states, and set the reactive power of the i-th wind turbine in the wind turbine group at the current moment to the reactive power value c′ corresponding to the state. 2,i,j ; When the current voltage is less than the first voltage threshold, if the voltage has an upward trend, the voltage change trend of the DC sending end is regarded as state 1. At this time, c' 2,i,j =c q1 (u set1 -r 2,i,j ), if the voltage has a downward trend, then the voltage change trend of the DC sending end is regarded as state 2. At this time, c' 2,i,j =c q2 (u set1 -r 2,i,j ), where r 2,i,j represents the terminal voltage of the i-th wind turbine corresponding to the j-th sampling point in the time window, c q1 and c q2 Respectively represent the preset first and second reactive power control coefficients; u set1 represents a preset first voltage threshold; When the current voltage is greater than or equal to the first voltage threshold and less than or equal to the second voltage threshold, if the voltage has a rapid rising trend, the voltage change trend of the DC sending end is regarded as state 3. At this time, If the voltage has a rapid downward trend, the voltage change trend of the DC sending end is considered to be state 4. At this time, Otherwise, the voltage variation trend of the DC sending end is considered to be state 5. At this time, c′ 2,i,j =c′ 2,i,j-1 , where c q3 and c q4 Respectively represent the preset third and fourth reactive power control coefficients; When the current voltage is greater than the second voltage threshold, if the voltage has an upward trend, the voltage change trend of the DC sending end is considered to be state 6. At this time, c' 2,i,j =c q2 (u set2 -r 2,i,j ), if the voltage has a downward trend, then the voltage change trend of the DC sending end is considered to be state 7. At this time, c' 2,i,j =c q1 (u set2 -r 2,i,j ), where u set2 Indicates a preset second voltage threshold.

4. The DC sending end voltage stabilization method for the wind and fire bundling delivery system according to claim 1 is characterized in that: The voltage stabilization control instructions formulated based on the change trend include: active power control instructions and reactive power control instructions of the wind turbine generator set; The active power control instruction of the wind turbine group is used to set the active power of the i-th wind turbine in the wind turbine group at the current moment to the maximum power c′ of the i-th wind turbine at the current wind speed. 1,i,j , where j represents the number of the current moment, and also represents the sampling point number within the time window; The reactive power control instruction is used to set the reactive power of the i-th wind turbine in the wind turbine group at the current moment to c′ 2,i,j ; The expression for correcting the voltage stabilization control instruction based on the wind turbine active power, the wind turbine rated capacity, the thermal power active power, the thermal power reactive power and the thermal power rated capacity includes: In the formula, c″ 1,i,j represents the corrected c′ 1,i,j ;c″ 2,i,j represents the corrected c′ 2,i,j ; r 3,i,j represents the active power of the i-th wind turbine corresponding to the j-th sampling point in the time window; r 8,i,1 represents the rated capacity of the i-th thermal power plant corresponding to the j-th sampling point in the time window; r 5,i,j and r 6,i,j They represent the active power and reactive power of the i-th thermal power plant corresponding to the j-th sampling point in the time window respectively; z represents the total number of thermal power plants in the thermal power plant group; r 7,i,1 represents the rated capacity of the i-th wind turbine; l represents the total number of wind turbines in the wind turbine group.

5. The DC sending end voltage stabilization method for wind and fire bundling delivery system according to claim 1 is characterized in that: The expression of the voltage recovery index of the DC sending end includes: Where S(d) represents the voltage recovery index of the DC sending end in the dth cycle; u represents the total number of sampling points in the time window, j represents the number of the current moment, and also represents the sampling point number in the time window. When j=u, x 1,j =x 1,u And x 2,j =x 2,u ;u bus1，j represents the sending-end commutation bus voltage corresponding to the jth sampling point; u set1 and u set2 Respectively represent the preset first and second voltage thresholds.

6. The DC sending end voltage stabilization method for wind and fire bundling delivery system according to claim 1 is characterized in that: The expression of the voltage stabilization control stop condition includes: Wherein, d represents the current voltage regulation control cycle number, the initial value of d is 1, and the time window moves backward once, the value of d increases by 1; d min represents the preset minimum number of voltage stabilization control cycles; S(e) represents the voltage recovery index of the DC sending end corresponding to the e-th voltage stabilization control cycle.

7. The DC sending end voltage stabilization method for wind and fire bundle delivery system according to any one of claims 1 to 5, characterized in that: The time range of the time window is [t1-t r1 , t1+t r2 ], where t1 represents the moment when the voltage at the DC sending end has a rapid change trend, t r1 and t r2 All are preset values; When the time window is moved backward, let t1 = t1 + t r2 , and get the time window after moving.

8. A DC sending end voltage stabilization system, used to implement the DC sending end voltage stabilization method for wind and fire bundling delivery system as described in any one of claims 1 to 6, characterized in that: include: A voltage detection module, used for performing real-time voltage detection on the DC sending end of the system; A change trend prediction module, used to predict whether the voltage at the DC sending end has a trend of rapid change based on the detected real-time voltage, and if so, intercept a time window including the moment when the voltage at the DC sending end has a trend of rapid change, and execute the steps of the voltage stabilization control module; Otherwise, return to the step of executing the voltage detection module; A voltage stabilization control module, used for performing voltage stabilization control on the DC sending end based on the time window; The index calculation module is used to calculate the voltage recovery index of the DC sending end. If the voltage recovery index meets the voltage stabilization control stop condition, the voltage stabilization control is stopped; otherwise, the time window is moved backward, and the steps of executing the voltage stabilization control module are returned based on the moved time window.

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