Method for automatically improving response characteristics of static reactive power compensation device controller

Abstract

The invention belongs to the technical field of power transmission. The invention provides a method for automatically improving response characteristics of a static reactive power compensation device controller, which comprises the step of judging whether a power grid is operated in a large mode or a small mode according to a bus voltage value in a calculation result and an effective value and an average value of active power of line power flow. The bus voltage of the control target is detected in real time, and the line power flow of the control target is calculated in real time; the rapid response characteristic of SVG / SVC can be brought into full play, powerful dynamic reactive power support is provided when the power grid breaks down, and therefore the voltage stability of the receiving end power grid is improved. And meanwhile, the dynamic reactive compensation capability of the SVG / SVC is utilized to provide a forward damping effect for system power oscillation after fault recovery, and the pressure of system oscillation instability is relieved. The SVG / SVC is automatically switched to enter different control modes according to different operation modes of the power grid, so that the quick response characteristic of the SVG / SVC plays different roles in different operation modes of the power grid.

Description

Technical Field

[0001] The invention belongs to the technical field of power transmission, and in particular relates to a method for automatically improving the response characteristics of a controller of a static reactive power compensation device. Background Art

[0002] Static VAR compensation devices (SVG / SVC) are increasingly widely used in power systems, mainly for stabilizing grid voltage and providing necessary reactive power compensation. At present, the SVG / SVC control method in the transmission system generally uses a voltage regulator to adjust the system voltage, that is, the system voltage is compared with the reference voltage, and the difference is passed through the voltage regulator to obtain a control signal for adjusting the SVG / SVC reactive power, so that the system voltage accurately approaches the desired target curve.

[0003] With the gradual formation of AC / DC UHV and long-distance transmission networks in my country, the connection between regional power grids has become closer, the mutual influence has become more prominent, and the stability of the power grid has become more important. The traditional control method of SVG / SVC has played an extremely important role in regulating voltage and reactive power flow. In the design process of SVG / SVC controller, in order to ensure stable response characteristics, the gain of the voltage regulator is generally optimized in the weakest network state or in the most serious expected accident situation. This design method only ensures that SVG / SVC can obtain fast and stable response in this operating mode. When SVG / SVC is used in situations where the system short-circuit impedance varies greatly and operates at a large short-circuit capacity, if the gain of the SVG / SVC controller remains constant, the response will become very slow, making the power grid stability worse. Summary of the invention

[0004] In view of this, it is necessary to provide a method to automatically improve the response characteristics of the static VAR compensation device controller, and automatically adjust the control strategy of SVG / SVC in different operation modes of the power grid in large and small modes according to the power grid flow characteristics to improve the stability of the power grid.

[0005] A method for automatically improving the response characteristics of a static VAR compensation device controller comprises the following steps:

[0006] Step S1: Real-time detection of the bus voltage of the control target and real-time calculation of the line flow of the control target;

[0007] Step S2: judging whether the grid operation mode is large mode operation or small mode operation according to the effective value and average value of the bus voltage value and the active power of the line flow in the calculation result; if it is large mode operation, then executing the large mode control strategy; if it is small mode operation, then executing the small mode control strategy;

[0008] Step S3: When executing the large-scale control strategy, determine whether the bus voltage is too high. If it is too high, the action sequence of SVG / SVC includes the following steps:

[0009] Step S311: increasing inductive reactive power;

[0010] Step S312: exit the parallel capacitive branch;

[0011] Step S313: putting the parallel inductive branch into operation;

[0012] When executing the large-scale control strategy, if the bus voltage is not too high, then determine whether the bus voltage is too low. If it is too low, the action sequence of SVG / SVC includes the following steps:

[0013] Step S321: exit the parallel inductive branch;

[0014] Step S322: putting the parallel capacitive branch into operation;

[0015] Step S323: reducing inductive reactive power;

[0016] When executing the large-mode control strategy, if the target bus voltage is neither too high nor too low, the SVG / SVC will not act;

[0017] When executing the small mode control strategy, it is determined whether the control target bus voltage is too high. If it is too high, the action sequence of SVG / SVC includes the following steps:

[0018] Step S331: SVG / SVC reactive power adjustment;

[0019] Step S332: exit the parallel capacitive branch;

[0020] Step S333: putting the parallel inductive branch into operation;

[0021] When executing the small mode control strategy, if the target bus voltage is not too high, then determine whether the target bus voltage is too low. If it is too low, the action sequence of SVG / SVC includes the following steps:

[0022] Step S341: SVG / SVC reactive power adjustment;

[0023] Step S342: exit the parallel inductive branch;

[0024] Step S343: putting the parallel capacitive branch into operation;

[0025] If the target bus voltage is neither too high nor too low, the SVG / SVC will not operate.

[0026] Beneficial effects: The method of dynamically improving the response characteristics of the controller of the static reactive power compensation device of the present invention can give full play to the rapid response characteristics of SVG / SVC, and provide powerful dynamic reactive power support when a fault occurs in the power grid, thereby improving the voltage stability of the receiving-end power grid, increasing the stable limit power, and enhancing the ability to resist major power grid accidents. At the same time, the dynamic reactive power compensation capability of SVG / SVC is used to provide a positive damping effect for the system power oscillation after the fault is restored, thereby reducing the pressure of system oscillation instability. By detecting and calculating the system flow, the SVG / SVC is automatically switched to different control modes according to the different operation modes of the power grid, so that the rapid response characteristics of SVG / SVC play different roles under different operation modes of the power grid, thereby better utilizing the functions of SVG / SVC and making the power grid more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the schematic diagram of the automatic switching of SVG / SVC control mode.

[0028] Figure 2 This is the block diagram of the SVG / SVC control principle under large-scale operation.

[0029] Figure 3 It is the reactive power curve of SVG / SVC when the power grid fails under large-scale operation.

[0030] Figure 4 This is the block diagram of the SVG / SVC control principle for small mode operation. DETAILED DESCRIPTION

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0032] Please see Figure 1 The method for automatically improving the response characteristics of a static VAR compensation device controller comprises the following steps:

[0033] Step S1: Real-time detection of the bus voltage of the control target and real-time calculation of the line flow of the control target;

[0034] Step S2: judging whether the grid operation mode is large mode operation or small mode operation according to the effective value of the bus voltage and the average value of the active power of the line flow; if it is large mode operation, then executing the large mode control strategy; if it is small mode operation, then executing the small mode control strategy;

[0035] The control principle of SVG / SVC in the large mode is: when the voltage is low, the shunt capacitor branch and the shunt reactor branch are activated first, and then the SVG / SVC is activated. When the voltage is high, the SVG / SVC is activated first and then the branch is activated. The regulation of SVG / SVC adopts a hierarchical regulation method. In this mode, the initial working point of SVG / SVC is required to be inductive reactive power, and its excess inductive reactive output is balanced and offset by the shunt capacitor branch. The specific process is as follows: step S311, step S312, step S313, step S321, step S322, step S323.

[0036] Step S3: When executing the large-scale control strategy, it is determined whether the control target bus voltage is too high. If it is too high, the action sequence of SVG / SVC includes the following steps:

[0037] Step S311: increasing inductive reactive power;

[0038] Step S312: exit the parallel capacitive branch;

[0039] Step S313: putting the parallel inductive branch into operation;

[0040] If the target bus voltage is not too high, then determine whether the target bus voltage is too low. If it is too low, the action sequence of SVG / SVC includes the following steps:

[0041] Step S321: exit the parallel inductive branch;

[0042] Step S322: putting the parallel capacitive branch into operation;

[0043] Step S323: reducing inductive reactive power;

[0044] If the target bus voltage is neither too high nor too low, the SVG / SVC will not operate;

[0045] In actual situations, the line voltage fluctuates. If it fluctuates within the allowable range, the line is operating normally. Otherwise, the line voltage needs to be corrected to quickly return to normal. If the effective value of the bus voltage is higher than the upper limit of the voltage threshold when the bus voltage is operating normally, it means that the bus voltage is too high; if the effective value of the bus voltage is lower than the lower limit of the voltage threshold when the bus voltage is operating normally, it means that the bus voltage is too low.

[0046] When the power grid is running in a large mode, the power flow on the hydropower / thermal power / new energy transmission channel is large. At this time, a fault may cause an accident of UHV disconnection. Therefore, SVG / SVC needs to reserve more capacitive reactive power to improve the stability of the power grid. At this time, SVG / SVC is adjusted in a hierarchical control mode (SVG / SVC is divided into several discrete reactive power points within the adjustable range. According to the voltage regulation requirements of the steady-state system, the output power point is adjusted at a speed of minutes, and reactive power reserves are guaranteed). SVG / SVC is made to maintain a large output of inductive reactive power while taking into account the voltage regulation function, so as to reserve a large capacitive reactive power. When a system fault occurs, SVG / SVC responds at a speed of milliseconds, quickly releases the reserved capacitive reactive power, and helps the grid voltage to recover quickly. At an appropriate time after the system fault is restored, it returns to normal. The control system will perform dynamic reactive power regulation according to the voltage and flow characteristics of the grid at this time, give full play to the positive damping effect of SVG / SVC, and reduce system power oscillation. The control method under the large mode can not only enable SVG / SVC to take into account the steady-state voltage regulation function, but also significantly improve the stable limit power of the power grid, suppress system oscillation, and improve the stability of the power grid.

[0047] The key point of large-scale operation is to ensure that SVG / SVC is at a higher operating point as possible, so as to ensure a larger capacitive reactive power as the capacitive reactive power reserve of the power grid. When the power grid is operating normally, SVG / SVC focuses on its steady-state voltage regulation function. When the voltage is low, SVG / SVC will first automatically withdraw from the parallel inductive branch. When all parallel inductive branches within the control range are withdrawn, if the voltage is still low, SVG / SVC will automatically invest in the parallel capacitive branch within the control range. If the voltage is still low after all capacitive branches are invested, SVG / SVC will stabilize the system voltage by reducing inductive power or outputting a certain capacitance. Conversely, when the voltage is high, SVG / SVC will first increase the inductive reactive power output. If the voltage is still high after the inductive operating point of SVG / SVC has reached the maximum, SVG / SVC will then withdraw from the parallel capacitive branch. If the voltage is still high after all parallel capacitive branches are withdrawn, SVG / SVC will automatically invest in the parallel inductive branch.

[0048] SVG / SVC adopts a hierarchical regulation control mode, and makes SVG / SVC operate at a higher inductive reactive power, thereby reserving a large amount of capacitive reactive power for the system. In order to reserve sufficient capacitive reactive power, the control system tries to make SVG / SVC maintain a large output of inductive reactive power while taking into account steady-state voltage regulation. When a power grid fault occurs, the control system quickly detects and starts the transient strong compensation function of SVG / SVC within milliseconds, making full use of the fast regulation characteristics of SVG / SVC to instantly release sufficient capacitive reactive power and reduce the pressure of power grid instability. When the fault is removed, the control system uses the dynamic regulation of the voltage link and the power link to make SVG / SVC provide positive damping for system oscillation, thereby suppressing system oscillation and helping the system quickly enter a steady state after the fault.

[0049] The control principle of SVG / SVC in large mode is as follows Figure 2 As shown in the figure, the dynamic regulation of SVG / SVC is realized through the voltage link and the power link, and the steady-state regulation is controlled by adjusting the SVG / SVC series. The voltage link and the power link are respectively realized by the DC isolation link, the phase shift link and the proportional coefficient.

[0050] If a fault occurs in the power grid, the control system determines whether to start the transient strong compensation link according to the voltage drop condition. After the transient strong compensation link is started, the SVG / SVC quickly outputs the maximum capacitive reactive power. When the transient strong compensation ends, the dynamic reactive power regulation process of the voltage link and the power link plays a positive damping role to help suppress the oscillation process of the power grid. When a fault occurs in the power grid, the reactive power curve of the TCR branch of the SVC is as follows: Figure 3 As shown, the Figure 3 The process of SVC transient strong compensation and the dynamic reactive power regulation process after the transient strong compensation are completed can be seen in the figure.

[0051] If the power grid is normal, the control system controls the dynamic output of the voltage link and the power link according to the voltage and line active power, and adjusts the operation level of the SVG / SVC according to the bus voltage. It should be noted that in order to ensure that the SVG / SVC is at a higher inductive operation level as much as possible, the prerequisite for adjusting the SVG / SVC level here is that the action priority of the SVG / SVC is effective, that is, when the voltage is high, the SVG / SVC can first increase the inductive reactive level, and when the voltage is low, the inductive operation level of the SVG / SVC can be reduced only after all parallel inductive branches are completely withdrawn and all parallel capacitive branches are fully put into operation. At this time, the inductive reactive power actually output by the SVG / SVC is jointly determined by the voltage link, the power link and the level link. Among them, the voltage link and the power link reflect the dynamic reactive power regulation process, and the level link reflects the steady-state voltage regulation process.

[0052] The control principle of SVG / SVC in the small mode is: no matter the voltage is high or low, SVG / SVC will be activated first, and the branch will be activated when the output of SVG / SVC reaches the limit. The regulation of SVG / SVC adopts a stepless smooth regulation method, that is, SVG / SVC is adjusted in real time according to the difference between the grid voltage and the set voltage. The specific process is as follows: steps S331, S332, S333 and S341, S342, S343.

[0053] When executing the small mode control strategy, it is determined whether the bus voltage is too high. If it is too high, the action sequence of SVG / SVC includes the following steps:

[0054] Step S331: SVG / SVC reactive power adjustment;

[0055] Step S332: exit the parallel capacitive branch;

[0056] Step S333: putting the parallel inductive branch into operation;

[0057] If the bus voltage is not too high, then determine whether the target bus voltage is too low. If it is too low, the action sequence of SVG / SVC includes the following steps:

[0058] Step S341: SVG / SVC reactive power adjustment;

[0059] Step S342: exit the parallel inductive branch;

[0060] Step S343: putting the parallel capacitive branch into operation;

[0061] If the target bus voltage is neither too high nor too low, the SVG / SVC will not operate.

[0062] When the inductive output of SVG / SVC reaches the maximum, if the voltage is still high, SVG / SVC will automatically exit the capacitive branch. If the voltage is still high after the capacitive branch is exited, SVG / SVC will automatically switch to the inductive branch. Conversely, when the output of SVG / SVC reaches the maximum capacitive output, if the voltage is still low, SVG / SVC will automatically exit the inductive branch. If the voltage is still low after the inductive branch is exited, SVG / SVC will automatically switch to the capacitive branch. The control principle of SVG / SVC in small mode is as follows: Figure 4 As shown in the figure, the control system adjusts the reactive power output of SVG / SVC in real time according to the voltage changes.

[0063] In the small mode, the control system automatically switches to the SVG / SVC stepless regulation control mode, with steady-state voltage regulation as the primary control target, making full use of the smooth adjustment characteristics of SVG / SVC, so that the bus voltage of the control target can quickly, smoothly and accurately track the target voltage.

[0064] The method for automatically improving the response characteristics of the controller of the static var compensation device of the present invention can give full play to the fast response characteristics of SVG / SVC, provide strong dynamic reactive power support when the power grid fails, thereby improving the voltage stability of the receiving-end power grid, increasing the stable limit power, and enhancing the ability to withstand major power grid accidents. At the same time, the dynamic reactive power compensation ability of SVG / SVC is used to provide a positive damping effect for the system power oscillation after the fault recovery, reducing the pressure of system oscillation instability.

[0065] The control system calculates the system power flow and automatically switches SVG / SVC to different control modes according to different power grid operation modes, so that the fast response characteristics of SVG / SVC play different roles under different power grid operation modes, thereby bringing the functions of SVG / SVC into full play.

[0066] The power flow of the line of the present invention refers to the steady-state distribution of the node voltages and the active power on the line in the system.

[0067] Further, in step S1, the real-time calculation of the target line power flow is specifically as follows:

[0068] Calculate the active power transmitted by the line:

[0069]

[0070] In the formula, U A and U B are respectively the effective values of the voltages at both ends of the line, and are respectively the phase angles of the voltages at both ends of the line, and X is the line impedance;

[0071] Calculate the average values of the active power and reactive power at any point:

[0072]

[0073] In the formula, P is the active power, Q is the reactive power, U and I are respectively the effective values of the bus voltage and current, is the angle between the voltage and the current. Among them, the effective values of the bus voltage and current are respectively 0.707 times the instantaneous maximum value of the bus voltage and 0.707 times the instantaneous maximum value of the current.

[0074] When the average value of the line active power P > P0, the power grid operation mode is the large mode. When the average value of the line active power P < P0, the power grid operation mode is the small mode, where P0 is the set value of the line active power. Since the active powers of different power grid systems are different, the set values of the active power are different.

[0075] For example, during peak hours and seasons, the power system dispatch needs to ensure that there are enough generators online. In this case, the system usually has sufficient hot reserves. If a sudden load increase occurs, the hot reserves can be released to ensure system balance. In this case, the large mode is used.

[0076] During the Spring Festival or low-load periods, the capacity of the online generator sets is small. When the load increases, the generator sets cannot meet the power demand of the highest load, resulting in load shedding. In this case, the small mode is used for operation.

[0077] When the present invention is operated in a large mode, the control system automatically adjusts to take increasing the stable limit power of the power grid as the primary control target. SVG / SVC adopts a hierarchical regulation control method, and makes SVG / SVC operate at a relatively high inductive reactive power, thereby reserving a large capacity of capacitive reactive power for the system. In order to reserve sufficient capacitive reactive power, the control system tries to make SVG / SVC maintain a large output of inductive reactive power while taking into account steady-state voltage regulation. When a power grid fault occurs, the control system quickly detects and starts the transient reinforcement function of SVG / SVC within milliseconds, making full use of the rapid regulation characteristics of SVG / SVC to instantly release sufficient capacitive reactive power and reduce the pressure of power grid instability. When the fault is removed, the control system uses the dynamic regulation of the voltage link and the power link to enable SVG / SVC to provide a positive damping effect for the system oscillation, thereby suppressing the system oscillation and helping the system to quickly enter a steady state after the fault.

[0078] In the large-scale control mode, the action priority of SVG / SVC is as follows: when the voltage is high, the action priority of SVG / SVC, capacitive branch, and inductive branch is arranged from high to low. When the voltage is low, the action priority of inductive branch, capacitive branch, and SVG / SVC branch is arranged from high to low. After all actions at each priority level are completed, it automatically enters the next priority level.

[0079] In the large-scale control mode, the inductive reactive power output of SVG / SVC is determined by the voltage link, power link, steady-state operation level adjustment link and transient strong compensation link. Among them, the transient strong compensation link is used to increase the stable limit power of the power grid, the voltage link and power link provide positive damping for the system, and the steady-state operation level adjustment link is mainly used for steady-state voltage regulation needs.

[0080] In the small mode of the present invention, the control system automatically switches to the SVG / SVC stepless regulation control mode, takes steady-state voltage regulation as the primary control target, and makes full use of the smooth adjustment characteristics of SVG / SVC, so that the bus voltage of the control target can quickly, smoothly and accurately track the target voltage.

[0081] In the small mode control mode, the action priority of SVG / SVC is: when the voltage is high, the action priority of SVG / SVC branch, capacitive branch, and inductive branch is arranged from high to low. When the voltage is low, the action priority of SVG / SVC branch, inductive branch, and capacitive branch is arranged from high to low. After all the actions at each priority level are completed, it automatically enters the next priority level.

[0082] In the small-scale control mode, the reactive output of SVG / SVC depends on the control action of the voltage regulator. At this time, the reactive output of SVG / SVC will be adjusted in real time according to the difference between the bus voltage and the target voltage.

[0083] What is disclosed above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. A person skilled in the art can understand that all or part of the processes of the above embodiments and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for automatically improving the response characteristics of a static VAR compensation device controller, characterized in that: It includes the following steps: Step S1: Real-time detect the bus voltage of the control target and calculate the line power flow of the control target in real time; Step S2: According to the bus voltage value and the effective value and average value of the active power of the line power flow in the calculation result, judge whether the power grid operation mode is large mode operation or small mode operation; if it is large mode operation, then execute the large mode control strategy; if it is small mode operation, then execute the small mode control strategy; Step S3: When executing the large mode control strategy, judge whether the bus voltage is too high. If it is too high, the action sequence of SVG / SVC includes the following steps: Step S311: Increase inductive reactive power; Step S312: Disconnect the shunt capacitive branch; Step S313: Connect the shunt inductive branch; When executing the large mode control strategy, if the bus voltage is not too high, then judge whether the bus voltage is too low. If it is too low, the action sequence of SVG / SVC includes the following steps: Step S321: Disconnect the shunt inductive branch; Step S322: Connect the shunt capacitive branch; Step S323: Decrease inductive reactive power; When executing the large mode control strategy, if the target bus voltage is neither too high nor too low, then SVG / SVC does not act; When executing the small mode control strategy, judge whether the bus voltage of the control target is too high. If it is too high, the action sequence of SVG / SVC includes the following steps: Step S331: SVG / SVC reactive power adjustment; Step S332: Disconnect the shunt capacitive branch; Step S333: Connect the shunt inductive branch; When executing the small mode control strategy, if the target bus voltage is not too high, then judge whether the target bus voltage is too low. If it is too low, the action sequence of SVG / SVC includes the following steps: Step S341: SVG / SVC reactive power adjustment; Step S342: Disconnect the shunt inductive branch; Step S343: Connect the shunt capacitive branch; If the target bus voltage is neither too high nor too low, then SVG / SVC does not act.

2. The method for automatically improving the response characteristics of a static VAR compensation device controller according to claim 1, characterized in that: In step S1, the real-time calculation of the target line power flow is specifically as follows: Calculate the active power transmitted by the line: Where U A and U B are the effective values ​​of the voltage at both ends of the line, and are the phase angles of the voltages at both ends of the line, and X is the line impedance; Calculate the average value of the active power and reactive power at any point: Where P is active power, Q is reactive power, U and I are the effective values ​​of bus voltage and current respectively. is the angle between voltage and current, where the effective values ​​of the bus voltage and current are 0.707 times the instantaneous maximum value of the bus voltage and 0.707 times the instantaneous maximum value of the current, respectively.

3. The method for automatically improving the response characteristics of a static VAR compensation device controller according to claim 1, characterized in that: In step S2, when the average value of the line active power P > P0, the power grid operation mode is large mode, and when the average value of the line active power P < P0, the power grid operation mode is small mode, where P0 is the set value of the line active power.

4. The method for automatically improving the response characteristics of a static VAR compensation device controller according to claim 1, characterized in that: It can be used for the grid lines of the power transmission channels with hydropower, thermal power, wind power or solar power generation.

5. The method for automatically improving the response characteristics of a static VAR compensation device controller according to claim 1, characterized in that: When executing the large mode control strategy, if a serious fault occurs in the power grid system, after the control system detects the voltage change, it quickly activates the transient strong compensation function of SVG / SVC.

6. The method for automatically improving the response characteristics of a static VAR compensation device controller according to claim 1, characterized in that: When executing the large mode control strategy, if the power grid fault is removed, then the control system enables SVG / SVC to provide positive damping for the system oscillation through the dynamic regulation of the voltage link and the power link, thereby suppressing the system oscillation and helping the system to quickly enter the steady state after the fault.

7. The method for automatically improving the response characteristics of a static VAR compensation device controller according to claim 6, characterized in that: Both the voltage link and the power link are realized by the DC blocking link, the phase shift link and the proportional coefficient.

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