Wind power plant AVC substation and coordination control device and method for dynamic reactive voltage control

Abstract

The invention provides a wind power plant AVC substation and a coordination control device and method for dynamic reactive voltage control, and belongs to the field of new energy power generation, and the device comprises an AVC voltage control logic module, a dynamic voltage regulation control logic module, an AVC function soft pressing plate, a dynamic voltage regulation soft pressing plate, and a soft pressing plate switching module. A target voltage value is respectively input into the AVC voltage control logic module and the dynamic voltage regulation control logic module, an output signal of the AVC function soft pressing plate is respectively input into the AVC voltage control logic module and the soft pressing plate switching module, and an output signal of the dynamic voltage regulation soft pressing plate is input into the soft pressing plate switching module. The soft pressing plate switching module outputs a signal to the dynamic voltage regulation control logic module after performing logic combination operation, operates the AVC voltage control logic module or the dynamic voltage regulation control logic module, calculates a reactive power remote regulation total instruction, sends the reactive power remote regulation total instruction to the reactive power distribution strategy and algorithm module, calculates reactive power needing to be compensated, and outputs the reactive power through a remote regulation output port; and the steady-state operation capability of the wind power plant is improved by utilizing the reactive power regulation capability of the wind turbine generator.

Description

Technical Field

[0001] The present invention relates to the technical field of renewable energy power generation, and in particular to a coordinated control device and method for an AVC substation of a wind farm and dynamic reactive voltage control. Background Art

[0002] Wind power and photovoltaic power generation will enter a stage of high-quality leapfrog development. The high proportion of new energy access to the power system will inevitably increase the instability of the grid frequency and voltage, and the security of the power system will face serious threats.

[0003] At present, the grid voltage is mainly regulated by the automatic voltage control (AVC) system to achieve safe and economic optimization and control of the steady-state voltage of the grid. Traditional AVC does not take into account the transient process after a grid fault, does not have the function of improving the safety and stability of the transient voltage of the grid, and is insufficient to meet the voltage control challenges faced by the current power system. The paper "Dynamic Automatic Voltage Control System for AC / DC Hybrid Grids with a High Proportion of Renewable Energy: Design and Application" (Ge Huaichang et al., Department of Electrical Engineering and Applied Electronics Technology, Tsinghua University, Proceedings of the CSEE, 2020.8.20) designed and developed a dynamic automatic voltage control system for AC / DC hybrid grids with a high proportion of renewable energy. It improves the transient voltage safety and stability of AC / DC hybrid power systems with a high proportion of renewable energy as a whole, solves the voltage control problems faced by my country's power grid at this stage, and realizes the transition of grid voltage control from static to dynamic. At present, the wind farm AVC has incorporated the converter into the station reactive power source, but due to the lag of the converter technology itself and the time lag of the wind farm monitoring system communication, the wind farm converter cannot quickly release reactive power, so the wind farm currently needs to rely on the static var generator (SVG) to complete dynamic voltage support. SVG adopts centralized busbar compensation. Due to the investment of primary equipment, the initial construction cost of the wind farm increases. At the same time, SVG has the disadvantages of high failure rate, high loss, low safety, etc. Due to the use of centralized compensation, the reliability of wind farm reactive support is low.

[0004] Compared with traditional reactive power compensation devices, wind turbines have stronger power controllability and rapid response characteristics. Relying on converter control, they can achieve decoupling of active and reactive output and provide real-time voltage support for the power grid. However, at present, most wind farms still only invest in reactive power compensation devices to control the voltage at the grid connection point, and fail to fully utilize the reactive power regulation capabilities of wind turbines. Summary of the invention

[0005] The technical problem to be solved by the present invention is how to fully utilize the reactive power regulation capability of wind turbines to improve the steady-state operation capability of wind farms.

[0006] The present invention solves the above technical problems through the following technical solutions: a coordinated control device for an AVC substation and dynamic reactive voltage control in a wind farm, comprising an AVC voltage control logic module, a dynamic voltage regulation control logic module, an AVC functional soft pressure plate, a dynamic voltage regulation soft pressure plate, a soft pressure plate throw-in / out module, a reactive power distribution strategy and algorithm module, and a remote control output port; the target voltage values ​​are respectively input into the AVC voltage control logic module and the dynamic voltage regulation control logic module; the output signals of the AVC functional soft pressure plate are respectively input into the AVC voltage control logic module and the soft pressure plate throw-in / out module; the output signals of the dynamic voltage regulation soft pressure plate are input into the soft pressure plate throw-in / out module; the soft pressure plate throw-in / out module performs a logical combination operation and then outputs a signal to the dynamic voltage regulation control logic module, and selects to run the AVC voltage control logic module or the dynamic voltage regulation control logic module; when the AVC voltage control logic module or the dynamic voltage regulation control logic module is running, the total reactive power remote control instruction is calculated and sent to the reactive power distribution strategy and algorithm module; the reactive power required to be compensated is calculated by the reactive power distribution strategy and algorithm module, and outputted through the remote control output port.

[0007] The present invention adds a dynamic reactive voltage control module on the basis of the AVC substation function, switches the AVC voltage control logic module and the dynamic voltage regulation control logic module through the logical combination operation of the soft pressure plate throw-in / out module, and utilizes the rapidity of dynamic reactive voltage control to improve the voltage control performance of the wind farm. Within the allowable voltage range of the wind farm, the dynamic reactive voltage control assists the AVC substation to complete rapid and precise control, reduces the voltage fluctuation amplitude within seconds, and when the station voltage exceeds the allowable range, the dynamic reactive voltage control can quickly pull the voltage back to the allowable operating range, reduces the voltage over-limit operating time, and the rapid response of the dynamic reactive voltage control can reduce the probability of the wind farm entering a transient state and reduce the probability of the wind farm being disconnected from the grid.

[0008] Preferably, the target voltage value is obtained by parsing a voltage curve instruction, and the voltage curve instruction includes a local curve voltage instruction and a remote dispatching voltage instruction issued by an AVC dispatching master station.

[0009] Preferably, the input of the AVC voltage control logic module also includes fixed values ​​and signal logic, and the input of the dynamic voltage regulation control logic module also includes fixed values, signal logic and newly added fixed values. The fixed values ​​include the maximum single voltage regulation amount of the master station, the voltage regulation dead zone, the voltage adjustment coefficient, the AVC single regulation cycle, the AVC single voltage regulation amount, and the AVC single maximum reactive power regulation amount. The newly added fixed values ​​include the voltage change rate threshold, the transient action return time and the absolute value of the transient action voltage change.

[0010] Preferably, the soft pressure plate activation and deactivation module comprises a NOT gate and an AND gate, the output end of the AVC function soft pressure plate is connected to the input end of the NOT gate, the output end of the NOT gate and the output end of the dynamic voltage regulation soft pressure plate are respectively connected to the input end of the AND gate, and the output end of the AND gate is connected to the input end of the dynamic voltage regulation control logic module.

[0011] Preferably, the coordination control device collects the voltage and current of the grid-connected point bus through a voltage sensor PT and a current sensor CT.

[0012] The present invention also provides a control method based on the wind farm AVC substation and the coordinated control device of dynamic reactive voltage control, comprising the following steps:

[0013] Step 1: Control the output signals of the AVC function soft pressure plate and the dynamic voltage regulation soft pressure plate, run the AVC voltage control logic module or the dynamic voltage regulation control logic module, and when running the dynamic voltage regulation control logic module, monitor the bus voltage in real time and obtain the actual measured value of the bus voltage U0, and calculate the target voltage value U t The voltage difference dU with the measured value of bus voltage U0, dU = U t -U0, calculate the voltage change rate dU / dt;

[0014] Step 2: Determine whether the voltage change rate dU / dt is greater than the voltage change rate threshold or whether the bus voltage measured value U0 is greater than the target voltage value U t If yes, go to step 3, if no, go to step 4;

[0015] Step 3: Start transient control, calculate reactive power regulation quantity ΔQ, and calculate and send reactive power remote regulation total instruction Q based on reactive power regulation quantity ΔQ, and then proceed to step 5;

[0016] Step 4: Start steady-state control. When the measured value of the bus voltage U0 is within the range of the high blocking threshold and the low blocking threshold, calculate the reactive adjustment amount ΔQ, constrain the reactive adjustment step, calculate and send the total reactive remote adjustment instruction Q based on the reactive adjustment amount ΔQ, and proceed to step 5.

[0017] Step 5: The reactive power distribution strategy and algorithm module receives the reactive power remote control total instruction, calculates the reactive power to be compensated according to the reactive power remote control total instruction, and outputs it through the remote control output port.

[0018] Preferably, in step 1, the output signals of the AVC function soft pressure plate and the dynamic voltage regulation soft pressure plate are controlled, and the output signals of the AVC function soft pressure plate are respectively input into the AVC voltage control logic module and the NOT gate, and the output signals of the NOT gate and the dynamic voltage regulation soft pressure plate are input into the AND gate, and the output signal of the AND gate is input into the dynamic voltage regulation control logic module. When the AVC function soft pressure plate is put into operation and the dynamic voltage regulation soft pressure plate is exited, the AVC voltage control logic module is run, and when the AVC function soft pressure plate is exited and the dynamic voltage regulation soft pressure plate is put into operation, the dynamic voltage regulation control logic module is run.

[0019] Preferably, the calculation formula of the total reactive power remote regulation instruction Q in step 3 and step 4 is:

[0020] Q=Q0-ΔQ

[0021] ΔQ=k q (U0-U d )

[0022] Among them, Q0 is the reactive output value of the wind farm before control, U0 is the measured value of the bus voltage, and U d is the dynamic voltage regulation dead zone, k q is the voltage regulation coefficient.

[0023] Preferably, in step 4, when the measured value U0 of the bus voltage reaches a high locking threshold as it is higher or reaches a low locking threshold as it is lower, the steady-state voltage control is locked.

[0024] Preferably, the reactive power distribution strategy and algorithm module in step 5 calculates the reactive power to be compensated according to the total reactive power remote control instruction, and the calculation method adopts equal power factor distribution method, equal reactive power margin distribution method, equal reactive power capacity distribution method, or equal reactive power output distribution method.

[0025] The advantages provided by the present invention are:

[0026] (1) The present invention adds a dynamic reactive voltage control module on the basis of the AVC substation function, switches the AVC voltage control logic module and the dynamic voltage regulation control logic module through the logical combination operation of the soft pressure plate throw-in / out module, and utilizes the rapidity of dynamic reactive voltage control to improve the voltage control performance of the wind farm. Within the allowable voltage range of the wind farm, the dynamic reactive voltage control assists the AVC substation to complete rapid and precise control, reducing the voltage fluctuation amplitude within seconds. When the station voltage exceeds the allowable range, the dynamic reactive voltage control can quickly pull the voltage back to the allowable operating range, reducing the voltage over-limit operation time. The rapid response of the dynamic reactive voltage control can reduce the probability of the wind farm entering a transient state and reduce the probability of the wind farm being disconnected from the grid.

[0027] (2) The present invention adds three new constants: voltage change rate threshold, transient action return time and transient action voltage change absolute value, which will more finely control the dynamic regulation process of voltage and improve the stability and regulation efficiency of the power grid.

[0028] (3) In the coordinated control method of the present invention, when the reactive dynamic voltage regulation control logic module is running, whether the voltage change rate dU / dt is greater than the voltage change rate threshold or whether the bus voltage measured value U0 is greater than the target voltage value U t When the transient control process begins, the calculated reactive power is not limited by the maximum single reactive power regulation amount. Within the available range of reactive power resources, the adjustable reactive power resources can be fully utilized to complete the voltage callback control at the hundred millisecond level.

[0029] (4) When the voltage is greatly depressed, the AVC control cannot restore the station voltage to 90% of the rated voltage within the specified time, and the grid disconnection phenomenon will still occur. The present invention can quickly respond to the voltage depression by switching to the dynamic reactive voltage control logic module. Through multiple actions, the probability of the reactive source entering transient support can be reduced, the time for the wind farm to enter the grid disconnection can be delayed, and the probability of the wind farm being disconnected from the grid can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of a wind farm AVC substation and a coordinated control device for dynamic reactive voltage control provided by an embodiment of the present invention;

[0031] Figure 2 A schematic diagram of the deployment of a wind farm AVC substation and a coordinated control device for dynamic reactive voltage control provided by an embodiment of the present invention;

[0032] Figure 3 A flow chart of the coordinated control method of the wind farm AVC substation and dynamic reactive voltage control provided by the embodiment of the present invention switching to dynamic reactive voltage control;

[0033] Figure 4 A curve diagram of the total reactive remote regulation instruction Q in the coordinated control method for the wind farm AVC substation and dynamic reactive voltage control provided by the embodiment of the present invention;

[0034] Figure 5 A schematic diagram showing a comparison between the coordinated control method for wind farm AVC substation and dynamic reactive voltage control provided by an embodiment of the present invention and the current standard AVC control during the process of dispatching voltage increase action;

[0035] Figure 6 A schematic diagram showing a comparison between the coordinated control method for wind farm AVC substation and dynamic reactive voltage control provided by an embodiment of the present invention and the current standard AVC control during the dispatching voltage down-regulation process;

[0036] Figure 7 A schematic diagram of the automatic adjustment process principle of the coordinated control method for wind farm AVC substation and dynamic reactive voltage control provided by the embodiment of the present invention;

[0037] Figure 8 A diagram showing the response effect of the coordinated control method for wind farm AVC substation and dynamic reactive voltage control provided by the embodiment of the present invention and the current standard AVC control in the face of frequent voltage fluctuations;

[0038] FIG9(a) is a transient control process of the coordinated control method for wind farm AVC substation and dynamic reactive voltage control provided by an embodiment of the present invention when the adjustable resources are sufficient and the voltage exceeds the limit;

[0039] Figure 9(b) shows the transient control process when the voltage exceeds the limit when the adjustable resources are insufficient;

[0040] Fig.10 A coordinated control method for wind farm AVC substation and dynamic reactive voltage control provided by an embodiment of the present invention and a response effect diagram of the current standard AVC control voltage under low penetration conditions;

[0041] In the figure: 10 AVC voltage control logic module, 20 dynamic voltage regulation control logic module, 30 AVC function soft pressure plate, 40 dynamic voltage regulation soft pressure plate, 50 soft pressure plate activation and deactivation module, 51 NOT gate, 52 AND gate, 60 reactive power distribution strategy and algorithm module, 70 remote control output port. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the technical solution of the present invention is clearly and completely described below in combination with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Example 1

[0044] like Figure 1As shown, this embodiment provides a coordinated control device for wind farm AVC substation and dynamic reactive voltage control, including an AVC voltage control logic module 10, a dynamic voltage regulation control logic module 20, an AVC functional soft pressure plate 30, a dynamic voltage regulation soft pressure plate 40, a soft pressure plate throw-in / out module 50, a reactive power distribution strategy and algorithm module 60, and a remote adjustment output port 70. The target voltage value is respectively input into the AVC voltage control logic module 10 and the dynamic voltage regulation control logic module 20, and the output signal of the AVC functional soft pressure plate 30 is respectively input into the AVC voltage control logic module 10 and the soft pressure plate throw-in / out module 50. The output signal of the dynamic voltage regulation soft pressure plate 40 is input into the soft pressure plate throw-in / out module 50. After performing a logic combination operation, the soft pressure plate throw-in / out module 50 outputs a signal to the dynamic voltage regulation control logic module 20, and selects to run the AVC voltage control logic module 10 or the dynamic voltage regulation control logic module 20. When the AVC voltage control logic module 10 or the dynamic voltage regulation control logic module 20 is running, the total reactive power remote regulation instruction is calculated and sent to the reactive power distribution strategy and algorithm module 60. The reactive power required to be compensated is calculated by the reactive power distribution strategy and algorithm module 60, and outputted through the remote regulation output port 70.

[0045] Target voltage value U t The voltage curve instructions are obtained by parsing the voltage curve instructions, which include remote dispatching voltage instructions and local curve voltage instructions. The fixed value, signal logic, and the analyzed target voltage value are respectively transmitted in parallel to the AVC voltage control logic module 10 and the dynamic voltage regulation control logic module 20 through the input port. The fixed value includes the maximum single voltage regulation amount of the master station (over-limit lockout), voltage regulation dead zone (action start threshold), voltage adjustment coefficient, AVC single adjustment cycle, AVC single voltage adjustment amount, and AVC single maximum reactive power adjustment amount. Among them, the maximum single voltage regulation amount of the master station limits the maximum single voltage regulation amount of the master station to ensure that the regulation process is within a safe range. The voltage regulation dead zone sets the sensitive area of ​​voltage regulation. The voltage adjustment coefficient in the on-site test evaluation reflects the accuracy of voltage regulation. The AVC single maximum reactive power adjustment amount reflects the impact of actual characteristics on the voltage regulation process. The above fixed values ​​are respectively input into the AVC voltage control logic module 10 and the dynamic voltage regulation control logic module 20. The dynamic voltage regulation control logic module 20 input fixed values ​​also includes newly added fixed values. The newly added fixed values ​​include the voltage change rate threshold, the transient action return time and the transient action voltage change absolute value. These newly added fixed values ​​will more finely control the dynamic regulation process of the voltage and improve the stability and regulation efficiency of the power grid. The present invention takes the rated voltage of 220kV as an example. The fixed values ​​and newly added fixed values ​​are shown in Table 1, and the signal logic is shown in Table 2.

[0046] Table 1 Dynamic voltage regulation control logic constant enumeration

[0047] Table 2 Dynamic voltage regulation control signal logic adjustment

[0048]

[0049] The soft pressure plate throw-in and throw-out module 50 includes a NOT gate 51 and an AND gate 52. The output end of the AVC function soft pressure plate 30 is connected to the input end of the NOT gate 51. The output end of the NOT gate 51 and the output end of the dynamic voltage regulation soft pressure plate 40 are respectively connected to the input end of the AND gate 52. The output end of the AND gate 52 is connected to the input end of the dynamic voltage regulation control logic module 20. By controlling the AVC function soft pressure plate 30 and the dynamic voltage regulation soft pressure plate 40 to be thrown in or out, the AVC voltage control function and the dynamic voltage regulation control function can be switched. When the AVC function soft pressure plate 30 is thrown in and the dynamic voltage regulation soft pressure plate 40 is out, the AVC voltage control function is executed, that is, the current standard AVC control strategy. When the AVC function soft pressure plate 30 is out and the dynamic voltage regulation soft pressure plate 40 is thrown in, the dynamic voltage regulation control function is executed. When the AVC function soft pressure plate 30 and the dynamic voltage regulation soft pressure plate 40 are both out, the voltage control function is exited. The throw-in and throw-out logic function table of the soft pressure plate throw-in and throw-out module 50 is shown in Table 3.

[0050] Table 3 Soft pressure plate throw and throw logic function table

[0051] AVC function soft pressure plate Dynamic pressure regulating soft pressure plate Implementation plan Investment / Current standard AVC substation functions quit Investment Dynamic voltage regulation control function quit quit Voltage control function exits

[0052] The coordinated control device of the wind farm AVC substation and dynamic reactive voltage control of the present invention is deployed as a reactive control device in the wind farm AVC and dynamic voltage system, such as Figure 2 As shown, the whole system adopts the hardware deployment mode of "AVC dispatching master station-reactive power control device-wind turbine and reactive power compensation device". The AVC dispatching master station is a computer system and software installed in power dispatching institutions at all levels, which can automatically analyze the voltage conditions in the power grid, including voltage level, voltage stability, etc. Based on the analysis results, the AVC dispatching master station can generate optimized control and adjustment instructions to achieve accurate control of the power grid voltage. The present invention adds a dynamic reactive voltage control module 20 on the basis of the current standard AVC substation function, so that the reactive power control device has the AVC substation function and the dynamic reactive voltage control function. The AVC voltage control logic module 10 and the dynamic voltage regulation control logic module 20 are both provided with independent functional soft pressure plates. The two functions are switched through the logic combination operation of the soft pressure plate investment and withdrawal module 50. The rapidity of dynamic reactive voltage control is used to supplement the AVC substation control means, improve the accuracy of steady-state voltage control of the wind farm and the high and low voltage crossing time, and thus improve the steady-state operation capability of the wind farm.

[0053] Example 2

[0054] Based on the coordinated control device for wind farm AVC substation and dynamic reactive voltage control of embodiment 1, this embodiment provides a coordinated control method for wind farm AVC substation and dynamic reactive voltage control, including the following steps:

[0055] Step 1: Control the output signals of the AVC function soft pressure plate 30 and the dynamic voltage regulation soft pressure plate 40, and run the AVC voltage control logic module 10 or the dynamic voltage regulation control logic module 20. When the dynamic voltage regulation control logic module 20 is run, the bus voltage is monitored in real time and the measured value of the bus voltage U0 is obtained, and the target voltage value U0 is calculated. t The voltage difference dU with the measured value of bus voltage U0, dU = U t -U0, calculate the voltage change rate dU / dt.

[0056] In step 1, the output signals of the AVC function soft pressure plate 30 and the dynamic voltage regulation soft pressure plate 40 are controlled. The output signal of the AVC function soft pressure plate 30 is respectively input into the AVC voltage control logic module 10 and the NOT gate 51. The output signals of the NOT gate 51 and the dynamic voltage regulation soft pressure plate 40 are input into the AND gate 52. The output signal of the AND gate 52 is input into the dynamic voltage regulation control logic module 20. When the AVC function soft pressure plate 30 is put into operation and the dynamic voltage regulation soft pressure plate 40 is withdrawn, the AVC voltage control logic module 10 is operated. When the AVC function soft pressure plate 30 is withdrawn and the dynamic voltage regulation soft pressure plate 40 is put into operation, the dynamic voltage regulation control logic module 20 is operated.

[0057] Step 2: Determine whether the voltage change rate dU / dt is greater than the voltage change rate threshold or whether the bus voltage measured value U0 is greater than the target voltage value U t If yes, go to step 3, if no, go to step 4;

[0058] Step 3: Start transient control, calculate reactive power regulation ΔQ, and calculate and send reactive power remote regulation total instruction Q based on reactive power regulation ΔQ, and then proceed to step 5;

[0059] Step 4: Start steady-state control. When the measured value of the bus voltage U0 is within the range of the high blocking threshold and the low blocking threshold, calculate the reactive adjustment amount ΔQ, constrain the reactive adjustment step, calculate and send the total reactive remote adjustment instruction Q based on the reactive adjustment amount ΔQ, and proceed to step 5.

[0060] In step 4, when the measured value U0 of the bus voltage reaches the high blocking threshold when it is higher or reaches the low blocking threshold when it is lower, the steady-state voltage control will be blocked, but the transient voltage control will not be blocked.

[0061] The calculation method of the total reactive power remote regulation command Q during transient control and steady-state control is the same. The difference is that during transient control, the calculated reactive power is not limited by the single maximum reactive power regulation amount. Within the available range of reactive power resources, the adjustable reactive power resources are fully utilized to complete the voltage callback control at the hundred millisecond level.

[0062] The calculation formula of total reactive power remote regulation command Q is:

[0063] Q=Q0-ΔQ

[0064] ΔQ=k q (U0-U d )

[0065] Among them, Q0 is the reactive output value of the wind farm before control, U0 is the measured value of the bus voltage, and U d is the dynamic voltage regulation dead zone, k q The dynamic voltage regulation control logic module 20 of the present invention implements a constant voltage closed-loop control function with a voltage regulation function according to the reactive power droop function. The dynamic voltage regulation droop curve function is as follows: Figure 4 As shown in the figure, U L is the dynamic voltage lower limit, U H is the upper limit of dynamic voltage.

[0066] Step 5: The reactive power distribution strategy and algorithm module 60 receives the reactive power remote control general instruction, calculates the reactive power to be compensated according to the reactive power remote control general instruction, and outputs it through the remote control output port 70. After executing one cycle, the system waits for the next control cycle and re-executes the control process from step 1.

[0067] In step 5, the reactive power distribution strategy and algorithm module 60 calculates the reactive power to be compensated according to the total reactive power remote adjustment instruction, and the calculation method adopts equal power factor distribution method, equal reactive power margin distribution method, equal reactive power capacity distribution method, or equal reactive power output distribution method. Among them, the equal power factor distribution method performs reactive power distribution of each controlled generator set according to the principle of the same power factor; the equal reactive power margin distribution method distributes according to the reactive power margin size of each generator set participating in voltage control, that is, the unit with more residual reactive power provides more reactive power, and the unit with less residual reactive power provides less reactive power; the equal reactive power capacity distribution method distributes according to the reactive power capacity size of each generator set participating in voltage control, that is, the unit with large capacity provides more reactive power, and the unit with small capacity provides less reactive power; the equal reactive power output distribution method distributes the total reactive power of the whole field evenly to each generator set participating in voltage control.

[0068] Case Study

[0069] In the power system, the working principle of typical actions is the key to ensuring the stable operation of the power grid. By comparing the action mechanism of the coordinated control method of the present invention with that of the current standard AVC control, the up and down adjustment of the dispatching voltage, the rapid and precise control of voltage fluctuations within seconds, the transient control strategy when the voltage exceeds the limit, and the action response of the station voltage in the case of high and low penetration are analyzed respectively.

[0070] Figure 5 This is a schematic diagram of the principle of the dispatching voltage increase action process. The current bus voltage is 220.0kV, the dispatching voltage instruction is 221.0kV, the voltage regulation dead zone of the current standard AVC control is 0.5kV, and the single regulation cycle is 20s. In the first regulation action, the AVC control adjusts the bus voltage from 220.0kV to 220.5kV, and in the second regulation action, the AVC control adjusts the bus voltage from 220.5kV to 221.0kV. In the coordinated control method of the present invention, the single voltage regulation amount of the dynamic voltage is 0.1kV, and the single regulation cycle is 0.5s.

[0071] Figure 6 This is a schematic diagram of the principle of the dispatching voltage reduction process. The current bus voltage is 222.0kV, and the dispatching voltage command is 221.0kV, which is consistent with the dispatching voltage increase. During the voltage reduction action, in the current standard AVC control, the voltage is reduced to the command voltage through two cycles. In the coordinated control method of the present invention, the dynamic voltage is adjusted to the command voltage through multiple cycles.

[0072] Figure 7 This is a schematic diagram of the principle of the automatic adjustment process. The current bus voltage is 222.1kV, and the dispatch voltage command is 222.0kV. The automatic adjustment function is applied to the process in which the dispatch voltage command does not change, but the wind farm voltage deviates from the dead zone voltage. When the bus voltage crosses the set voltage control dead zone, the maximum delayed action time is one adjustment cycle (the voltage has just completed an action before crossing the dead zone). The voltage starts to act when it crosses the dead zone, and automatically fine-tunes when it returns to the dead zone according to the size of the voltage difference, so as to maintain the bus voltage as close to the target voltage as possible. The degree of approximation depends on the accuracy of the reactive source response.

[0073] Figure 8 This is the response effect diagram of AVC and dynamic voltage control facing frequent voltage fluctuations. The instability of wind energy and the characteristics of the wind turbine itself lead to changes in output power, which in turn cause voltage fluctuations. Within the allowable voltage range, when the bus voltage fluctuates frequently, the voltage drops multiple times in a short period of time. AVC takes action. After processing the first voltage fluctuation, there is a 20-second adjustment cycle, which makes it difficult to respond quickly to the second voltage fluctuation. Compared with AVC, the adjustment time of dynamic voltage control is 0.5s. Dynamic reactive voltage control assists the AVC substation to complete fast and precise control and reduce the voltage fluctuation amplitude within seconds.

[0074] Figure 9(a) shows the transient control process when the voltage exceeds the limit when the adjustable resources are sufficient, and Figure 9(b) shows the transient control process when the voltage exceeds the limit when the adjustable resources are insufficient. The current bus voltage is 221.0 kV, the dispatch voltage command is 221.0 kV, and the voltage changes rapidly and drops to 0.95 pu. The intermittent and volatile nature of wind power output, the fluctuation of wind power during long-distance transmission through submarine cables, and load changes may all cause voltage to exceed the limit, causing the voltage in the power grid to deviate from the normal range, thereby affecting the stability of the power grid and the normal operation of the equipment. When the bus voltage deviates from the target voltage for a short time or the voltage change rate exceeds the set threshold, the dynamic voltage control algorithm starts transient control, and the calculated reactive power is not limited by the single maximum reactive power regulation. Within the available range of reactive resources, the adjustable reactive resources are fully utilized to complete the voltage callback control at the 100-millisecond level.

[0075] Fig.10 The AVC control and dynamic voltage control respond to the voltage low penetration respectively. Due to system failure, large-capacity motor start-up or external line failure, the current in the power grid suddenly increases, causing a short voltage drop. When the station voltage drops below 90% of the rated voltage, it is regarded as a voltage low penetration. When the voltage low penetration is large and lasts for a long time, the equipment may not be able to work normally for a long time and choose to disconnect from the grid for protection. The AVC control is activated in the case of a voltage low penetration at the station. When the voltage low penetration is large, the AVC control cannot restore the station voltage to 90% of the rated voltage within the specified time, and the grid disconnection phenomenon will still occur. The present invention can quickly respond to the voltage low penetration by switching to the dynamic reactive voltage control logic module. Through multiple actions, the probability of reactive source entering transient support can be reduced, the time for the wind farm to enter the grid disconnection can be delayed, and the probability of the wind farm being disconnected from the grid can be reduced.

[0076] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A coordinated control device for wind farm AVC substation and dynamic reactive voltage control, characterized by: The invention comprises an AVC voltage control logic module (10), a dynamic voltage regulation control logic module (20), an AVC function soft pressure plate (30), a dynamic voltage regulation soft pressure plate (40), a soft pressure plate throw-in / out module (50), a reactive power distribution strategy and algorithm module (60), and a remote adjustment output port (70). The target voltage value is respectively input into the AVC voltage control logic module (10) and the dynamic voltage regulation control logic module (20). The output signal of the AVC function soft pressure plate (30) is respectively input into the AVC voltage control logic module (10) and the soft pressure plate throw-in / out module (50). The output signal of the dynamic voltage regulation soft pressure plate (40) is respectively input into the AVC voltage control logic module (10) and the soft pressure plate throw-in / out module (50). The soft pressure plate throw-in / out module (50) is input, and the soft pressure plate throw-in / out module (50) performs a logic combination operation and then outputs a signal to the dynamic voltage regulation control logic module (20), and selects to run the AVC voltage control logic module (10) or the dynamic voltage regulation control logic module (20). When the AVC voltage control logic module (10) or the dynamic voltage regulation control logic module (20) is running, the total reactive power remote regulation instruction is calculated and sent to the reactive power distribution strategy and algorithm module (60), and the reactive power size to be compensated is calculated by the reactive power distribution strategy and algorithm module (60), and outputted through the remote regulation output port (70).

2. The coordinated control device for wind farm AVC substation and dynamic reactive voltage control according to claim 1, characterized in that: The target voltage value is obtained by parsing the voltage curve instruction, and the voltage curve instruction includes the local curve voltage instruction and the remote dispatching voltage instruction issued by the AVC dispatching master station.

3. The coordinated control device for wind farm AVC substation and dynamic reactive voltage control according to claim 1, characterized in that: The input of the AVC voltage control logic module (10) also includes fixed values ​​and signal logic, and the input of the dynamic voltage regulation control logic module (20) also includes fixed values, signal logic and newly added fixed values, the fixed values ​​include the maximum single voltage regulation amount of the master station, the voltage regulation dead zone, the voltage adjustment coefficient, the AVC single regulation cycle, the AVC single voltage regulation amount, and the AVC single maximum reactive power regulation amount, and the newly added fixed values ​​include the voltage change rate threshold, the transient action return time and the transient action voltage change absolute value.

4. The coordinated control device for wind farm AVC substation and dynamic reactive voltage control according to claim 1, characterized in that: The soft pressure plate throw-in / out module (50) comprises a NOT gate (51) and an AND gate (52); the output end of the AVC function soft pressure plate (30) is connected to the input end of the NOT gate (51); the output end of the NOT gate (51) and the output end of the dynamic voltage regulation soft pressure plate (40) are respectively connected to the input end of the AND gate (52); and the output end of the AND gate (52) is connected to the input end of the dynamic voltage regulation control logic module (20).

5. The coordinated control device for wind farm AVC substation and dynamic reactive voltage control according to claim 1, characterized in that: The coordination control device collects the voltage and current of the grid connection point bus through the voltage sensor PT and the current sensor CT.

6. A control method for a wind farm AVC substation and a coordinated control device for dynamic reactive voltage control based on any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: Control the output signals of the AVC function soft pressure plate (30) and the dynamic voltage regulation soft pressure plate (40), and run the AVC voltage control logic module (10) or the dynamic voltage regulation control logic module (20). When the dynamic voltage regulation control logic module (20) is run, the bus voltage is monitored in real time and the actual measured value u0 of the bus voltage is obtained, and the target voltage value u is calculated. t The voltage difference dU with the measured value u0 of the bus voltage, dU = U t -U0, calculate the voltage change rate dU / dt; Step 2: Determine whether the voltage change rate dU / dt is greater than the voltage change rate threshold or whether the bus voltage measured value U0 is greater than the target voltage value U t If yes, go to step 3, if no, go to step 4; Step 3: Start transient control, calculate reactive power regulation quantity ΔQ, and calculate and send reactive power remote regulation total instruction Q based on reactive power regulation quantity ΔQ, and then proceed to step 5; Step 4: Start steady-state control. When the measured value of the bus voltage U0 is within the range of the high blocking threshold and the low blocking threshold, calculate the reactive adjustment amount ΔQ, constrain the reactive adjustment step, calculate and send the total reactive remote adjustment instruction Q based on the reactive adjustment amount ΔQ, and proceed to step 5. Step 5: The reactive power allocation strategy and algorithm module (60) receives the reactive power remote adjustment total instruction, calculates the reactive power to be compensated according to the reactive power remote adjustment total instruction, and outputs it through the remote adjustment output port (70).

7. The coordinated control method for wind farm AVC substation and dynamic reactive voltage control according to claim 6 is characterized in that: In the step 1, the output signals of the AVC function soft pressure plate (30) and the dynamic voltage regulation soft pressure plate (40) are controlled, the output signal of the AVC function soft pressure plate (30) is respectively input into the AVC voltage control logic module (10) and the NOT gate (51), the output signals of the NOT gate (51) and the dynamic voltage regulation soft pressure plate (40) are input into the AND gate (52), and the output signal of the AND gate (52) is input into the dynamic voltage regulation control logic module (20); when the AVC function soft pressure plate (30) is put into operation and the dynamic voltage regulation soft pressure plate (40) is withdrawn, the AVC voltage control logic module (10) is operated, and when the AVC function soft pressure plate (30) is withdrawn and the dynamic voltage regulation soft pressure plate (40) is put into operation, the dynamic voltage regulation control logic module (20) is operated.

8. The coordinated control method for wind farm AVC substation and dynamic reactive voltage control according to claim 6, characterized in that: The calculation formula of the total reactive power remote regulation instruction Q in step 3 and step 4 is: Q=Q0-ΔQ ΔQ=k q (U0-U d ) Among them, Q0 is the reactive output value of the wind farm before control, U0 is the measured value of the bus voltage, and U d is the dynamic voltage regulation dead zone, k q is the voltage regulation coefficient.

9. The coordinated control method for wind farm AVC substation and dynamic reactive voltage control according to claim 6, characterized in that: In step 4, when the measured value U0 of the bus voltage reaches a high blocking threshold as it is higher or reaches a low blocking threshold as it is lower, the steady-state voltage control is blocked.

10. The coordinated control method for wind farm AVC substation and dynamic reactive voltage control according to claim 6, characterized in that: In step 5, the reactive power allocation strategy and algorithm module (60) calculates the reactive power to be compensated according to the reactive power remote adjustment total instruction, and the calculation method adopts equal power factor allocation method, equal reactive power margin allocation method, equal reactive power capacity allocation method, or equal reactive power output allocation method.

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