Direct-current sending end voltage stabilizing method for wind-thermal bundling sending-out system

Abstract

The invention relates to the technical field of voltage stabilization of an electric power system, and provides a direct-current sending end voltage stabilization method for a wind-thermal bundled sending-out system, and the method comprises the following steps: S1, carrying out the real-time voltage detection of a direct-current sending end of the system; s2, on the basis of the detected real-time voltage, predicting whether the voltage of the direct current sending end has a rapid change trend or not, if yes, intercepting a time window including the moment when the voltage of the direct current sending end has the rapid change trend, and executing the step S3; otherwise, returning to execute the step S1; s3, performing voltage stabilization control on the direct current sending end based on the time window; s4, calculating a voltage recovery index of the direct current sending end, and if the voltage recovery index meets a voltage stabilization control stop condition, stopping voltage stabilization control; otherwise, moving the time window backwards, and returning to execute the step S3 based on the moved time window; the problem of control delay 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 particularly to a method for stabilizing the DC sending-end voltage of a wind-fire bundled transmission system. Background Art

[0002] Against the backdrop of my country's dual-carbon strategic goals of "carbon peak and carbon neutrality," vigorously developing renewable energy power generation and establishing a new power system are becoming the general trend. my country has a huge total amount of wind energy, and as traditional fossil energy sources are becoming increasingly depleted, wind power will become a major source of energy for the country. However, my country's wind resources are mainly distributed in the northwest, north China, and southeast coastal areas. Local power grids are relatively small, necessitating long-distance, interregional transmission for external transmission and consumption. Interregional interconnection methods include AC and DC interconnection. DC transmission offers significant advantages in long-distance, large-capacity transmission. Currently, high-voltage DC transmission has become the only way to transmit and consume new energy.

[0003] When wind power is transmitted via a high-voltage direct current (HVDC) transmission system, it is susceptible to faults in the DC transmission system, leading to low voltage or overvoltage. When a commutation failure on the inverter side of the DC system occurs, as does an AC short circuit near the sending end, the sending AC grid experiences low voltage followed by overvoltage, triggering wind turbines to experience low voltage ride-through followed by high voltage ride-through. When a DC fault occurs in the DC system, it can cause single-pole or double-pole blocking at the converter station. Reactive power compensated by the sending AC filter is fed into the sending AC grid, causing a sudden voltage surge in the sending AC grid and triggering high voltage ride-through for wind turbines.

[0004] To cope with low voltage and overvoltage issues in the power system, wind turbines need to have fault ride-through capabilities. However, existing fault ride-through strategies typically only consider the single low voltage and overvoltage phenomenon, failing to account for the possibility of a low voltage followed by an overvoltage. These scenarios may even exacerbate the low voltage and overvoltage. Existing fault ride-through strategies typically employ reactive power control strategies that adjust reactive output based on the extent of the grid voltage dip or rise. However, due to the time delay inherent in wind turbine control systems, reactive power output cannot be immediately adjusted to support voltage upon entering low voltage ride-through. Furthermore, some reactive power may still be generated after exiting low voltage, exacerbating overvoltage issues caused by faults such as commutation failure. Active power control strategies typically employ fixed active current operation, reducing active power output. However, significantly reducing wind turbine active power output during low voltage phases can lead to lower turbine terminal voltage and exacerbate transient low voltage conditions. Summary of the Invention

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

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

[0007] The wind-fired bundled transmission system includes a DC transmission end for transmitting electricity to outside the system, and the DC transmission end 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 of the DC sending end has a trend of rapid change. If so, intercept a time window including the moment when the voltage of 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 implementing the above-mentioned DC sending end voltage stabilization method for the wind-fire bundled delivery system. The system includes:

[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, configured to predict, based on the detected real-time voltage, 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 the steps of the voltage stabilization control module; otherwise, return to executing the steps of the voltage detection module;

[0016] A voltage stabilization control module, configured to perform voltage stabilization control on the DC sending end based on the time window;

[0017] An 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 the voltage stabilization control module are returned to be executed 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] 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 an unregulated state. 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 stabilize the system, thereby solving 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 the 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 bundled delivery system proposed in Example 1;

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

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

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

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

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

[0026] Figure 7 This is a schematic diagram of the reactive power instruction of the wind turbine proposed in Example 2;

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

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

[0029] Figure 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 for illustrative purposes only and are not to be construed as limiting the present embodiment;

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

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

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

[0034] Example 1

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

[0036] This embodiment proposes a DC sending terminal voltage stabilization method for a wind-fired bundled power transmission system. The wind-fired bundled power transmission system includes a DC sending terminal for transmitting power to an outside of the system. The DC sending terminal includes a wind turbine and a thermal power unit 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 of the DC sending end has a trend of rapid change. If so, intercept a time window including the moment when the voltage of 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] During 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 an unregulated 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 and the system is controlled to solve 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 that the current sampling time is t, and the sampling rate is 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 of the DC sending end has a trend of rapid change;

[0046] The expression of the voltage stabilization control starting 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 jth column of the first sampling information matrix O, and also represents [tt q , t] within the time range of the jth sampling point corresponding to the DC sending end real-time voltage; b m represents the mth transform coefficient under the 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, the wind turbine generator set terminal voltage, the wind turbine generator set active power, the wind turbine generator set rated capacity, the thermal power generator set active power, the thermal power generator set reactive power and the 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 terminal voltage;

[0054] The voltage stabilization control instruction is corrected 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, 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 [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, t r1 and t r2 All are preset values;

[0058] At 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 Record the DC sending end commutation bus voltage corresponding to the i×j-th sampling point in the time window;

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

[0060] Calculate a first voltage prediction information matrix R1′ and a second voltage prediction information matrix R1″ based on the matrix R1;

[0061] The matrices R1' and R1" are expressed as follows:

[0062]

[0063] h2≥h1

[0064] Where 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 in 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 transform factors, respectively; h1 and h2 represent the preset first and second transform orders, respectively; u represents the total number of elements in the matrix R1, and 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 rapid rising trend, otherwise, it is determined that the voltage does not have a rapid rising trend; 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 R1 is a row matrix.

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

[0069] The active power control instruction of the wind turbine is used to set the active power of the vth wind turbine in the wind turbine at the current moment to the maximum power c' of the ith 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] Among them, when the current voltage is less than the first voltage threshold, if the voltage has an upward trend, then 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 considered to be state 2. At this time, c' 2,i,j =c q2 (u set1 -r2,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 considered to be 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 change 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 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.

[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 is used to set the active power of the i-th wind turbine in the wind turbine 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 unit active power, the thermal power unit reactive power and the thermal power unit rated capacity includes:

[0078]

[0079] Where 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 Respectively represent the active power and reactive power of the i-th thermal generator corresponding to the j-th sampling point in the time window; z represents the total number of thermal generators in the thermal power 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 j-th sampling point; u set1 and u set2 Represent the preset first and second voltage thresholds respectively.

[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 [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;

[0087] When the time window is moved backward, let t1 = t1 + 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 Example 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 This is a schematic diagram of the air-fire bundling and delivery system proposed in this embodiment; Figure 2 As shown in Figure 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 sending-end commutation bus voltage u bus , stored in the first sampling information matrix O, and the first voltage startup information matrix O' is calculated. The second voltage startup information matrix O'' is calculated based on the first voltage startup information matrix, and the size relationship between the second voltage startup information and the startup criterion setting value is judged. Based on the judgment, it is decided whether to start the next action.

[0092] Step 11: Assume that the current sampling time is t, and t is the zero time, and the sampling rate is f s Commutation bus voltage at the sending end 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 advances, 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 startup 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 the 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] Where 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, so b1=1, b2=1.005, b3=1.02, b4=1.045, and K is defined as 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 when the start criterion is satisfied is recorded as the start time t1, and the process goes to step 2; otherwise, it returns to step 11.

[0105]

[0106] In this embodiment, K 1,set =0.0040, K 2,set =0.0045, K3,set =0.0050, K 4,set =0.0055, K set =0.0240.

[0107] Figure 3 This is the start-up criteria record chart proposed in this embodiment; Figure 3 It can be seen that at t=0.5285s, the start criterion is met, so the start time t1=0.5285s is recorded, the current control period d=1 is recorded, and step 2 is entered.

[0108] Step 2: Cut the time window to [t1-t r1 , t1+t r2 ], record the sending end commutation bus voltage u within the time window bus , terminal voltage of each wind turbine unit 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 [t1-t r1 , t1+t r2 ], set the sampling rate to f r , the sending-end commutation bus voltage u in the time window bus , terminal voltage of each wind turbine unit u w , 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 matrices R1, R2, R3, R4, R5, and R6 respectively, the rated capacity of each wind turbine is recorded as matrix R7, and the rated capacity of each synchronous turbine is recorded as matrix R8. Specifically, the terminal voltage u of wind turbine WG(i) is recorded as w , active power P w , reactive power Q w , Rated capacity S w Store them in the i-th row of matrices R2, R3, R4, and R7 respectively, and store the active power P of the synchronous unit G(i) g , reactive power Q g , Rated capacity S G Stored in the i-th row of matrices R5, R6, and R8 respectively.

[0110] R1=[u bus1,1 u bus1,2 ubus1,3 … u bus1,u ] 1×u

[0111]

[0112]

[0113] Where u is the time window [t1-t r1 , t1+t r2 ], u=(t r1 +t r2 )f r +1. In this embodiment, set 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 turbines.

[0114] Step 22: Transform the matrix R1 according to the following formula to obtain the first voltage prediction information matrix R1' and the second voltage prediction information matrix R1".

[0115]

[0116] Where 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', k1 is the first transformation factor, k2 is the second transformation factor, k3 is the third transformation factor, k4 is the fourth transformation factor, h1 is the first transformation order, h2 is the second transformation order, h2 ≥ h1. In this embodiment, k1 is defined as -0.95, k2 as 1, k3 as -0.95, k4 as 1, h1 as 10, and h2 as 20.

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

[0118]

[0119] Where r i,1 is the element in row i and column 1 of R, r 7,i,1 is the element in the i-th row and the first column of the matrix R7.

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

[0121]

[0122] Where r' i,j is the element in the i-th row and j-th column of the matrix R', r 3,i,jis the element in the i-th row and j-th column of the matrix R3, r 8,i,1 is the element in the i-th row and the first column of the matrix R8, r 5,i,j is the element in the i-th row and j-th column of the matrix R5, r 6,i,j is the element in the i-th row and j-th column of matrix R6.

[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: Based on the voltage conversion information matrix R1', R1", obtained in step 2 Figure 4 This is the control status information table proposed in this embodiment, according to Figure 4 The control state information matrix C is obtained, and the matrix C is shown in the following formula.

[0125] 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.

[0126] Step 32: Figure 5 This is the control instruction information table proposed in this embodiment; Figure 3 The control state information matrix C is transformed to obtain first control instruction matrices C'1 and C'2.

[0127]

[0128] In the table, c' 1,i,j is the element in the i-th row and j-th column of the matrix C'1, c' 2,i,j is the element in the i-th row and j-th column of the matrix C'2, P 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 element in the i-th row and j-th column of the matrix R2. In this embodiment, c q1 =1.5, c q2 =2.25, cq3 =1.5.

[0129] Step 33: Based on the control margin matrix R' obtained in step 2, the first control command matrices C'1 and C'2 are modified according to the following formula to obtain the second control command matrices C"1 and C"2.

[0130]

[0131]

[0132] Step 34: Send the control command to the wind turbine, set the i-th row of the control command matrix C"1 as the active power command value of the wind turbine WG(i), and set the i-th row of the control command matrix C"2 as the reactive power command value of the wind turbine WG(i). Figure 6 This is a schematic diagram of the active power instruction of the wind turbine proposed in this embodiment; Figure 7 This is a schematic diagram of the reactive power command of the wind turbine proposed in this embodiment; the active power command and reactive power command of the wind turbine 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 transform the matrix R1 to obtain matrices X1 and X2.

[0135]

[0136] Step 42: Calculate the voltage recovery index S(d) of the current cycle according to the matrices X1 and X2.

[0137]

[0138] 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 t1 = t1 + t r2 , d=d+1, return to step 2.

[0139]

[0140]

[0141] 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 showing the calculation results of the voltage recovery index 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.

[0142] Figure 9 This is a 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 Figure 9 As shown. Figure 9 It can be seen that after commutation failure occurs, the adoption of this strategy can significantly raise the low voltage and suppress overvoltage, which has a good effect on maintaining voltage stability after commutation failure.

[0143] In this embodiment, it can be seen that the method: 1) predicts and classifies the operating status of the power system based on historical voltage data, and enters the low voltage ride-through stage in advance when a downward trend in voltage is detected, which solves the problem of control delay in the existing low voltage ride-through strategy and can immediately adjust the reactive output to support the voltage when entering the low voltage ride-through; 2) increases reactive support in the early stage of low voltage ride-through, and reduces reactive support in advance at the voltage rising edge of the low voltage stage. On the one hand, it can effectively support the low voltage, and on the other hand, it can avoid the overvoltage problem caused by surplus reactive power during the low voltage ride-through period due to control delay; 3) during the low voltage ride-through process, on the basis of ensuring that the wind turbine has a certain reactive support capacity, the active 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 output; 4) during the high voltage ride-through process, appropriately reduces the active output of the wind turbine, which can more fully utilize the voltage regulation capability of the wind turbine and suppress overvoltage.

[0144] Example 3

[0145] This embodiment proposes a DC sending end voltage stabilization system, which is used to implement the DC sending end voltage stabilization method for the wind-fire bundled delivery system proposed in Example 1.

[0146] Figure 10 2 is an overall framework diagram of the DC sending-end voltage stabilization system of this embodiment.

[0147] The DC sending-end voltage stabilization system comprises:

[0148] A voltage detection module, used for performing real-time voltage detection on the DC sending end of the system;

[0149] a change trend prediction module, configured to predict, based on the detected real-time voltage, 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 the steps of the voltage stabilization control module; otherwise, return to executing the steps of the voltage detection module;

[0150] A voltage stabilization control module, configured to perform voltage stabilization control on the DC sending end based on the time window;

[0151] An 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 the voltage stabilization control module are returned to be executed based on the moved time window.

[0152] This embodiment proposes a computer device including a memory and a processor, wherein the memory stores computer-readable instructions. 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-fire bundle delivery system described in Example 1.

[0153] It can be understood that the DC sending-end voltage stabilization system and computer device of this embodiment improve the method of Example 1. The options in the above-mentioned Example 1 are also applicable to this embodiment, so they will not be repeated here.

[0154] The same or similar reference numerals correspond to the same or similar components;

[0155] The terms used in the drawings to describe positional relationships are for illustrative purposes only and should not be construed as limiting the present embodiment.

[0156] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection 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. 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.

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 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; 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.

4. The DC sending end voltage stabilization method for wind and fire bundling delivery system according to claim 3 is characterized in that: 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.

5. The DC sending end voltage stabilization method for wind and fire bundling delivery system according to claim 3 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 vth wind turbine in the wind turbine group at the current moment to the maximum power c' of the ith 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.

6. The DC sending end voltage stabilization method for wind and fire bundling delivery system according to claim 3 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.

7. 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: S(d)=1000×(x 1,u +x 1,u-1 +x 2,u +x 2,u-1 )Δt 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.

8. 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.

9. The DC sending end voltage stabilization method for wind and fire bundle delivery system according to any one of claims 1 to 7, 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.

10. 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 8, 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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