Steady voltage control method and system for reducing transient voltage instability risk of new energy collection station

Abstract

The present application relates to the technical field of power system stability control, and is a steady-state voltage control method and system for reducing transient voltage instability risk of a new energy collection station, the method comprising: establishing a new energy collection station bus transient voltage model of a new energy sending end power grid after a DC bipolar blocking fault; setting a new energy collection station transient voltage instability limit of the new energy sending end power grid after the DC bipolar blocking fault; and setting a steady-state voltage control threshold for reducing the transient voltage instability risk of the new energy collection station bus based on the new energy collection station bus transient voltage model. The present application can achieve the purpose of reducing transient voltage instability risk by controlling the steady-state operating voltage of a high-proportion new energy sending end power grid without increasing dynamic reactive power compensation equipment. The present application is used to solve the problem of transient voltage instability caused by new energy off-grid of a new energy collection station of a DC sending end power grid after a DC fault due to excessively high transient voltage caused by excessively high steady-state operating voltage of the power grid.

Description

Technical Field

[0001] This invention relates to the field of power system stability control technology, and in particular to a steady-state voltage control method and system for reducing the risk of transient voltage instability at new energy collection stations. Background Technology

[0002] With the increasing proportion of renewable energy connected to the ultra-high voltage direct current (UHVDC) grid, the safe and stable operation of the system faces severe challenges. Renewable energy units have relatively weak disturbance rejection capabilities, and the UHVDC system is closely coupled with the AC system. When a fault such as bipolar blocking occurs in the DC system, the sending-end AC grid is highly susceptible to severe transient overvoltages. If this phenomenon is not effectively controlled, it will directly cause the voltage at the renewable energy collection station to exceed the high-voltage ride-through capability of the renewable energy units, triggering a chain reaction of grid disconnection. This chain reaction worsens the system operating conditions, leading to transient voltage instability and load tripping. However, existing control strategies mostly focus on emergency response after a fault, lacking a systematic understanding of the correlation between steady-state operating voltage and transient voltage instability risk, making it difficult to effectively reduce such risks in advance by adjusting steady-state voltage operating control values.

[0003] This invention provides a steady-state voltage control method and system for reducing the risk of transient voltage instability at renewable energy collection stations. It can reduce the risk of transient voltage instability by controlling the steady-state operating voltage of renewable energy collection stations at high-proportion renewable energy DC transmission grids without adding dynamic reactive power compensation equipment. Summary of the Invention

[0004] This invention provides a steady-state voltage control method and system for reducing the risk of transient voltage instability at renewable energy collection stations. It overcomes the shortcomings of the prior art and can effectively solve the problem of transient voltage instability caused by renewable energy disconnection at renewable energy collection stations in the DC sending-end power grid due to excessively high transient voltage after a DC fault caused by the grid's steady-state operating voltage being too high.

[0005] To address the above problems, one of the technical solutions of this invention is achieved through the following method: a steady-state voltage control method for reducing the risk of transient voltage instability at the bus of a new energy collection station in a new energy DC transmission grid, comprising the following steps: Establish a transient voltage model of the new energy collection station bus of the new energy sending-end power grid after a bipolar blocking fault occurs in DC. Set the transient voltage instability limit for the new energy receiving station of the new energy sending-end power grid after a DC bipolar blocking fault. Based on the transient voltage model of the new energy collection station bus, a steady-state voltage control threshold is set to reduce the risk of transient voltage instability of the new energy collection station bus. Calculate the difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit after a DC bipolar blocking fault, and determine whether the difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit is greater than or equal to zero. Therefore, it is determined that the new energy collection station is at risk of transient voltage instability, that is, the new energy collection station may experience transient voltage instability after a bipolar blocking fault occurs in the DC power supply. The steady-state voltage control threshold is used as the steady-state voltage of the new energy collection station and substituted into the transient voltage model of the new energy collection station bus. The difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit after a bipolar blocking fault occurs in DC is calculated. It is then determined whether the difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit after the fault is less than zero. Therefore, it is determined that there is no risk of transient voltage instability at the new energy collection station, meaning that the risk of transient voltage instability at the new energy collection station is reduced after the steady-state control voltage threshold control is adopted.

[0006] The above-mentioned model establishes a transient voltage model of the new energy collection station bus in the new energy sending-end power grid after a bipolar blocking fault occurs in DC; including: The transient voltage model of the DC rectifier station after a bipolar blocking fault is established as follows: , , In the formula, This refers to the transient voltage of the AC bus of the DC rectifier station. This refers to the steady-state voltage of the AC bus of the DC rectifier station. This represents the transient voltage increment of the AC bus of the DC rectifier station after DC bipolar blocking. This refers to the reactive power fed back to the AC grid after DC bipolar blocking. This refers to the transient short-circuit capacity of the AC bus of the DC rectifier station after DC bipolar blocking. The transient voltage model of the new energy cluster station after a bipolar blocking fault in DC power is established as follows: , , , In the formula, The reactive power sent to the cluster station, The active power sent to the cluster station, The reactance from the rectifier station to the cluster station; For reactive power sent to the collection station, The active power of the collecting station, For the reactive power of the AC main grid, To exchange the active power of the main network, This refers to the active power supplied from the rectifier station to the trunking station. This refers to the transient voltage of the AC bus of the DC rectifier station. This refers to the transient voltage of the busbar at the cluster station. The reactive power supplied from the rectifier station to the cluster station; The transient voltage model of the new energy collection station after a bipolar blocking fault occurs in DC is established as follows: , , In the formula, This refers to the transient voltage at the renewable energy collection station after the bipolar blocking of the ultra-high voltage direct current (UHVDC) at the renewable energy sending-end power grid. This refers to the transient voltage increment at the renewable energy collection station after the bipolar blocking of the ultra-high voltage direct current (UHVDC) at the renewable energy sending-end power grid. The steady-state voltage of the renewable energy collection station before the bipolar blocking of the ultra-high voltage direct current transmission line at the renewable energy sending end of the power grid. The reactance of the AC line from the cluster station to the collection station.

[0007] The above-mentioned limits for transient voltage instability at the renewable energy collection station in the renewable energy sending-end grid after a DC bipolar blocking fault include: The calculation method for transient voltage instability limits is as follows: , In the formula, This is the limit for transient voltage instability. This refers to the rated voltage of the busbar at the collection station.

[0008] The aforementioned steady-state voltage control threshold, based on the transient voltage model of the new energy aggregation station bus, is used to reduce the risk of transient voltage instability at the new energy aggregation station bus; including: The steady-state voltage control threshold is calculated as follows: , In the formula, The steady-state voltage control threshold, Voltage margin reserved for the safe operation of the power grid This is the lower limit of the allowable steady-state voltage range for the collection station.

[0009] The above calculation of the difference between the expected transient voltage and the transient voltage instability limit of the new energy collection station bus after a bipolar blockage of DC transmission includes: The expected transient voltage of the new energy collection station bus after DC bipolar blocking is calculated as follows: , In the formula, This represents the expected transient voltage value of the new energy collection station after a bipolar blocking fault occurs in the DC transmission line. This refers to the upper limit of the allowable steady-state voltage range of the collection station. This refers to the transient voltage of the busbar at the cluster station. The reactive power sent to the cluster station, The active power sent to the cluster station, Reactance of the AC line from the cluster station to the collection station; The difference between the expected transient voltage and the transient voltage instability limit of the new energy collection station bus after DC bipolar blocking is calculated as follows: , In the formula, This is the difference between the expected transient voltage and the transient voltage instability limit of the new energy collection station. This represents the expected transient voltage value of the new energy collection station after a bipolar blocking fault occurs in the DC transmission line. This is the limit for transient voltage instability.

[0010] The above-mentioned steady-state voltage control threshold is used as the steady-state voltage of the new energy collection station and substituted into the transient voltage model of the new energy collection station bus. The difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit after the fault is calculated, including: The transient voltage of the new energy collection station after a bipolar blocking fault in DC power is calculated as follows: , In the formula, The steady-state voltage control threshold, The reactive power sent to the cluster station, The active power sent to the cluster station, For the AC line reactance from the cluster station to the collection station, This refers to the transient voltage at the new energy collection station after a bipolar blocking fault occurs in the DC power supply. This refers to the transient voltage of the busbar at the cluster station. The difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit of the new energy collection station after applying steady-state voltage control threshold control is calculated as follows: , In the formula, This is the difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit of the new energy collection station after applying steady-state voltage control threshold control.

[0011] The second technical solution of this invention is achieved through the following means: a steady-state voltage control system for reducing the risk of transient voltage instability in new energy collection stations, using a steady-state voltage control method for reducing the risk of transient voltage instability in new energy collection stations, comprising: The voltage model establishment unit establishes a transient voltage model of the new energy collection station bus of the new energy sending-end power grid after a bipolar blocking fault occurs in DC. Voltage instability limit setting unit, sets the transient voltage instability limit of the new energy sending end grid new energy collection station after DC bipolar blocking fault; The voltage control threshold setting unit sets a steady-state voltage control threshold based on the transient voltage model of the new energy collection station bus to reduce the risk of transient voltage instability of the new energy collection station bus. The steady-state voltage control difference calculation unit calculates the difference between the expected transient voltage and the transient voltage instability limit of the new energy collection station bus after DC bipolar blocking, and determines whether the difference between the expected transient voltage and the transient voltage instability limit of the new energy collection station bus is greater than or equal to zero. The transient voltage instability risk assessment unit responds by determining that the new energy collection station has a transient voltage instability risk, that is, after a bipolar blocking fault occurs in the DC power supply, the new energy collection station may experience transient voltage instability. The steady-state voltage control difference calculation unit takes the steady-state voltage control threshold as the steady-state voltage of the new energy collection station and inputs it into the transient voltage model of the new energy collection station bus. It calculates the difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit after a DC bipolar blocking fault occurs, and determines whether the difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit after the fault is less than zero. The transient voltage instability risk reduction judgment unit responds, and then determines that there is no transient voltage instability risk at the new energy collection station, that is, the transient voltage instability risk of the new energy collection station is reduced after the steady-state control voltage threshold control is adopted.

[0012] Compared with the prior art, the present invention has the following advantages: This invention discloses a steady-state voltage control method for reducing the risk of transient voltage instability at the bus of a renewable energy collection station in a renewable energy DC sending-end power grid. First, a transient voltage model of the bus of the renewable energy collection station in the renewable energy sending-end power grid is established after a bipolar blocking fault occurs in the DC power grid. Second, a limit value for transient voltage instability at the renewable energy collection station in the renewable energy sending-end power grid is set after a bipolar blocking fault. Then, a steady-state voltage control threshold for reducing the risk of transient voltage instability at the bus of the renewable energy collection station is set. Based on this, the risk of transient voltage instability at the bus of the renewable energy collection station is calculated. Finally, the control effect of using the steady-state voltage control threshold on the risk of transient voltage instability at the bus of the renewable energy collection station is verified to confirm the reduction of instability risk. Therefore, this invention can reduce the risk of transient voltage instability by controlling the steady-state operating voltage of a high-proportion renewable energy sending-end power grid without adding dynamic reactive power compensation equipment. It is used to solve the problem of transient voltage instability caused by renewable energy disconnection at the renewable energy collection station in the DC sending-end power grid due to excessively high transient voltage after a DC fault caused by an excessively high steady-state operating voltage in the power grid. This method provides a reference for improving the safe and stable operation of the new energy DC transmission grid under extreme conditions, and has guiding significance for improving the safe and stable operation of the high-proportion new energy UHVDC transmission grid. Attached Figure Description

[0013] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0014] Figure 1 This is a flowchart of the method in Embodiment 1 of the present invention.

[0015] Figure 2 This is an equivalent schematic diagram of the new energy collection station of the new energy DC transmission grid in Embodiment 1 of the present invention.

[0016] Figure 3 This is a system block diagram of Embodiment 2 of the present invention.

[0017] Figure 4 This is a schematic diagram of the power grid wiring in Embodiment 3 of the present invention.

[0018] Figure 5 This is a transient voltage curve diagram in Embodiment 3 of the present invention.

[0019] Figure 6 This is a comparison curve of transient voltages in Embodiment 3 of the present invention. Detailed Implementation

[0020] The present invention is not limited to the following embodiments, and the specific implementation can be determined according to the technical solution of the present invention and the actual situation.

[0021] Example 1: As Figure 1 As shown in the figure, this invention discloses a steady-state voltage control method for reducing the risk of transient voltage instability at a new energy collection station, comprising the following steps: S101, Establish a transient voltage model of the new energy collection station bus of the new energy sending-end power grid after a bipolar blocking fault occurs in DC. S102, set the transient voltage instability limit of the new energy receiving station of the new energy sending end grid after a DC bipolar blocking fault. S103, based on the transient voltage model of the new energy collection station bus, sets a steady-state voltage control threshold to reduce the risk of transient voltage instability of the new energy collection station bus. S104, calculate the difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit after a DC bipolar blocking fault, and determine whether the difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit is greater than or equal to zero. S105, in response, it is determined that the new energy collection station has a risk of transient voltage instability, that is, after the DC bipolar blocking fault occurs, the new energy collection station may have transient voltage instability. S106, the steady-state voltage control threshold is used as the steady-state voltage of the new energy collection station and is substituted into the transient voltage model of the new energy collection station bus. The difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit after the DC bipolar blocking fault occurs is calculated, and it is determined whether the difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit after the fault is less than zero. S107, in response, it is determined that there is no risk of transient voltage instability at the new energy collection station, that is, the risk of transient voltage instability at the new energy collection station is reduced after the steady-state control voltage threshold control is adopted.

[0022] In step S101 above, such as Figure 2 As shown, a transient voltage model of the new energy collection station bus in the new energy sending-end power grid is established after a bipolar blocking fault occurs in the DC power grid; including: The transient voltage model of the DC rectifier station after a bipolar blocking fault is established as follows: , , In the formula, This refers to the transient voltage of the AC bus of the DC rectifier station. This refers to the steady-state voltage of the AC bus of the DC rectifier station. This represents the transient voltage increment of the AC bus of the DC rectifier station after DC bipolar blocking. This refers to the reactive power fed back to the AC grid after DC bipolar blocking. This refers to the transient short-circuit capacity of the AC bus of the DC rectifier station after DC bipolar blocking. The transient voltage model of the new energy cluster station after a bipolar blocking fault in DC power is established as follows: , , , In the formula, The reactive power sent to the cluster station, The active power sent to the cluster station, The reactance from the rectifier station to the cluster station; For reactive power sent to the collection station, The active power of the collecting station, For the reactive power of the AC main grid, To exchange the active power of the main network, This refers to the active power supplied from the rectifier station to the trunking station. This refers to the transient voltage of the AC bus of the DC rectifier station. This refers to the transient voltage of the busbar at the cluster station. The reactive power supplied from the rectifier station to the cluster station; The transient voltage model of the new energy collection station after a bipolar blocking fault occurs in DC is established as follows: , , In the formula, This refers to the transient voltage at the renewable energy collection station after the bipolar blocking of the ultra-high voltage direct current (UHVDC) at the renewable energy sending-end power grid. This refers to the transient voltage increment at the renewable energy collection station after the bipolar blocking of the ultra-high voltage direct current (UHVDC) at the renewable energy sending-end power grid. The steady-state voltage of the renewable energy collection station before the bipolar blocking of the ultra-high voltage direct current transmission line at the renewable energy sending end of the power grid. The reactance of the AC line from the cluster station to the collection station.

[0023] In step S102 above, a transient voltage instability limit is set for the renewable energy receiving station in the renewable energy sending-end power grid after a DC bipolar blocking fault; including: The calculation method for transient voltage instability limits is as follows: , In the formula, This is the limit for transient voltage instability. This refers to the rated voltage of the busbar at the collection station.

[0024] In step S103 above, a steady-state voltage control threshold is set based on the transient voltage model of the new energy collection station bus to reduce the risk of transient voltage instability of the new energy collection station bus; including: The steady-state voltage control threshold is calculated as follows: , In the formula, The steady-state voltage control threshold, Voltage margin reserved for the safe operation of the power grid This is the lower limit of the allowable steady-state voltage range for the collection station.

[0025] In step S104 above, the calculation of the difference between the expected transient voltage and the transient voltage instability limit of the new energy collection station bus after the DC bipolar blocking occurs includes: The expected transient voltage of the new energy collection station bus after DC bipolar blocking is calculated as follows: , In the formula, This represents the expected transient voltage value of the new energy collection station after a bipolar blocking fault occurs in the DC transmission line. This refers to the upper limit of the allowable steady-state voltage range of the collection station. This refers to the transient voltage of the busbar at the cluster station. The reactive power sent to the cluster station, The active power sent to the cluster station, Reactance of the AC line from the cluster station to the collection station; The difference between the expected transient voltage and the transient voltage instability limit of the new energy collection station bus after DC bipolar blocking is calculated as follows: , In the formula, This is the difference between the expected transient voltage and the transient voltage instability limit of the new energy collection station. This represents the expected transient voltage value of the new energy collection station after a bipolar blocking fault occurs in the DC transmission line. This is the limit for transient voltage instability.

[0026] In step S106 above, the steady-state voltage control threshold is used as the steady-state voltage of the new energy collection station and substituted into the transient voltage model of the new energy collection station bus. The difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit after the fault is calculated, including: The transient voltage of the new energy collection station after a bipolar blocking fault in DC power is calculated as follows: , In the formula, The steady-state voltage control threshold, The reactive power sent to the cluster station, The active power sent to the cluster station, For the AC line reactance from the cluster station to the collection station, This refers to the transient voltage at the new energy collection station after a bipolar blocking fault occurs in the DC power supply. This refers to the transient voltage of the busbar at the cluster station. The difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit of the new energy collection station after applying steady-state voltage control threshold control is calculated as follows: , In the formula, This is the difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit of the new energy collection station after applying steady-state voltage control threshold control.

[0027] Among them, if If so, the new energy collection station does not have the risk of transient voltage instability, meaning that the transient voltage instability of the new energy collection station is reduced after adopting steady-state control voltage threshold control; if If the new energy collection station still faces the risk of transient voltage instability, manual intervention is required.

[0028] Example 2: As Figure 3 As shown, this embodiment of the invention discloses a steady-state voltage control system for reducing the risk of transient voltage instability in new energy collection stations, comprising: The voltage model establishment unit establishes a transient voltage model of the new energy collection station bus of the new energy sending-end power grid after a bipolar blocking fault occurs in DC. Voltage instability limit setting unit, sets the transient voltage instability limit of the new energy sending end grid new energy collection station after DC bipolar blocking fault; The voltage control threshold setting unit sets a steady-state voltage control threshold based on the transient voltage model of the new energy collection station bus to reduce the risk of transient voltage instability of the new energy collection station bus. The steady-state voltage control difference calculation unit calculates the difference between the expected transient voltage and the transient voltage instability limit of the new energy collection station bus after DC bipolar blocking, and determines whether the difference between the expected transient voltage and the transient voltage instability limit of the new energy collection station bus is greater than or equal to zero. The transient voltage instability risk assessment unit responds by determining that the new energy collection station has a transient voltage instability risk, that is, after a bipolar blocking fault occurs in the DC power supply, the new energy collection station may experience transient voltage instability. The steady-state voltage control difference calculation unit takes the steady-state voltage control threshold as the steady-state voltage of the new energy collection station and inputs it into the transient voltage model of the new energy collection station bus. It calculates the difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit after a DC bipolar blocking fault occurs, and determines whether the difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit after the fault is less than zero. The transient voltage instability risk reduction judgment unit responds, and then determines that there is no transient voltage instability risk at the new energy collection station, that is, the transient voltage instability risk of the new energy collection station is reduced after the steady-state control voltage threshold control is adopted.

[0029] Example 3: This example is based on a real regional power grid. The power grid wiring diagram is attached. Figure 4 As shown, the total output of new energy sources in this region's power grid is 16000MW, and the DC transmission power is 8000MW of the rated transmission capacity. Assume the rated voltage of "Ganguazhou 11" is... The normal operating voltage range of the "Ganguazhou 11" busbar is as follows: ,in, This refers to the upper limit of the allowable steady-state operating voltage range for the "Ganguazhou 11" busbar. This is the lower limit of the allowable steady-state operating voltage range for the "Ganzhou-Guazhou 11" busbar. At time t = 1.0s, a bipolar blocking fault occurred in the Ganzhou-Qilian-Lianhuan 71-Hunan-Zhuzhou 51 UHVDC transmission line.

[0030] Taking into account the reduction of transient voltage instability risk, the allowable operating range of the power grid, and the reserved safety margin, the voltage margin reserved for safe operation of the power grid is selected as follows: The steady-state voltage control threshold for the "Ganguazhou 11" busbar is then set as follows: Transient voltage instability limit for new energy collection stations .

[0031] The upper limit of the steady-state actual operating voltage of the "Ganguazhou 11" busbar. and lower limit value Simulation calculations were performed separately, and the simulation results are shown in Table 1. The transient voltage curves are attached. Figure 5 As shown.

[0032] Simulation results show that if the steady-state voltage of the "Ganzhou 11" busbar operates at the upper limit of the allowable range, a bipolar blocking fault will occur when the Ganzhou-Qilian-Lianyungang 71-Hunan-Zhuzhou 51 UHVDC line experiences this fault. The calculated result is clearly greater than 0, indicating that the substation is at risk of transient voltage instability. If the steady-state operating voltage of the bus is controlled within the lower limit of the allowable operating range, the transient voltage can be significantly reduced, thereby lowering the risk of transient voltage instability in the power grid.

[0033] The steady-state operating voltage of the "Ganguazhou 11" busbar is controlled according to the steady-state voltage threshold. A DC bipolar blocking fault simulation was performed, and the simulation results are shown in Table 2. The transient voltage comparison curves are attached. Figure 6 As shown.

[0034] From Table 2 and Appendix Figure 6 It can be seen that when the steady-state operating voltage of the "Ganguazhou 11" bus is controlled to the control threshold, the transient voltage after the DC bipolar blocking is reduced to... Now, we need to calculate again: , Verification conclusion: After the implementation of the method proposed in this invention, the transient voltage of the new energy collection station bus is less than the set transient voltage instability limit, thus eliminating the risk of transient voltage instability of the new energy collection station.

[0035] In summary, the steady-state voltage control method of this invention for reducing the risk of transient voltage instability at the bus of a new energy collection station in a new energy DC sending-end power grid first establishes a transient voltage model of the bus of the new energy collection station in the new energy sending-end power grid after a bipolar blocking fault occurs in the DC grid. Second, it sets a limit value for transient voltage instability at the new energy collection station in the new energy sending-end power grid after a bipolar blocking fault. Then, it sets a steady-state voltage control threshold to reduce the risk of transient voltage instability at the bus of the new energy collection station. Based on this, the risk of transient voltage instability at the bus of the new energy collection station is calculated. Finally, the control effect of using the steady-state voltage control threshold on the risk of transient voltage instability at the bus of the new energy collection station is verified to confirm the reduction of instability risk. Therefore, this invention can reduce the risk of transient voltage instability by controlling the steady-state operating voltage of a high-proportion new energy sending-end power grid without adding dynamic reactive power compensation equipment. It is used to solve the problem of transient voltage instability caused by the disconnection of new energy from the DC sending-end power grid's new energy collection station due to excessively high transient voltage after a DC fault caused by an excessively high steady-state operating voltage in the power grid. This method provides a reference for improving the safe and stable operation of the new energy DC transmission grid under extreme conditions, and has guiding significance for improving the safe and stable operation of the high-proportion new energy UHVDC transmission grid.

[0036] Table 1. Transient voltage of the "Ganguazhou 11" new energy collection station at the upper and lower limits of the allowable steady-state operating voltage. Table 2 Comparison of transient voltage values ​​before and after applying steady-state voltage control method

Claims

1. A steady-state voltage control method for reducing the risk of transient voltage instability at a new energy collection station, characterized in that, Includes the following steps: Establish a transient voltage model of the new energy collection station bus of the new energy sending-end power grid after a bipolar blocking fault occurs in DC. Set the transient voltage instability limit for the new energy receiving station of the new energy sending-end power grid after a DC bipolar blocking fault. Based on the transient voltage model of the new energy collection station bus, a steady-state voltage control threshold is set to reduce the risk of transient voltage instability of the new energy collection station bus. Calculate the difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit after a DC bipolar blocking fault, and determine whether the difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit is greater than or equal to zero. Therefore, it is determined that the new energy collection station is at risk of transient voltage instability, that is, the new energy collection station may experience transient voltage instability after a bipolar blocking fault occurs in the DC power supply. The steady-state voltage control threshold is used as the steady-state voltage of the new energy collection station and substituted into the transient voltage model of the new energy collection station bus. The difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit after a bipolar blocking fault occurs in DC is calculated. It is then determined whether the difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit after the fault is less than zero. Therefore, it is determined that there is no risk of transient voltage instability at the new energy collection station, meaning that the risk of transient voltage instability at the new energy collection station is reduced after the steady-state control voltage threshold control is adopted.

2. The steady-state voltage control method for reducing the risk of transient voltage instability at new energy collection stations according to claim 1, characterized in that, The establishment of a transient voltage model for the new energy collection station bus in the new energy sending-end power grid after a bipolar blocking fault in DC transmission includes: The transient voltage model of the DC rectifier station after a bipolar blocking fault is established as follows: ， ， In the formula, This refers to the transient voltage of the AC bus of the DC rectifier station. This refers to the steady-state voltage of the AC bus of the DC rectifier station. This represents the transient voltage increment of the AC bus of the DC rectifier station after DC bipolar blocking. This refers to the reactive power fed back to the AC grid after DC bipolar blocking. This refers to the transient short-circuit capacity of the AC bus of the DC rectifier station after DC bipolar blocking. The transient voltage model of the new energy cluster station after a bipolar blocking fault in DC power is established as follows: ， ， ， In the formula, The reactive power sent to the cluster station, The active power sent to the cluster station, The reactance from the rectifier station to the cluster station; For reactive power sent to the collection station, The active power of the collecting station, For the reactive power of the AC main grid, To exchange the active power of the main network, This refers to the active power supplied from the rectifier station to the trunking station. This refers to the transient voltage of the AC bus of the DC rectifier station. This refers to the transient voltage of the busbar at the cluster station. The reactive power supplied from the rectifier station to the cluster station; The transient voltage model of the new energy collection station after a bipolar blocking fault occurs in DC is established as follows: ， ， In the formula, This refers to the transient voltage at the renewable energy collection station after the bipolar blocking of the ultra-high voltage direct current (UHVDC) at the renewable energy sending-end power grid. This refers to the transient voltage increment at the renewable energy collection station after the bipolar blocking of the ultra-high voltage direct current (UHVDC) at the renewable energy sending-end power grid. The steady-state voltage of the renewable energy collection station before the bipolar blocking of the ultra-high voltage direct current transmission line at the renewable energy sending end of the power grid. The reactance of the AC line from the cluster station to the collection station.

3. The steady-state voltage control method for reducing the risk of transient voltage instability at new energy collection stations according to claim 1, characterized in that, The set limit value for transient voltage instability at the new energy collection station of the new energy sending-end power grid after a DC bipolar blocking fault is set. include: The calculation method for transient voltage instability limits is as follows: ， In the formula, This is the limit for transient voltage instability. This refers to the rated voltage of the busbar at the collection station.

4. The steady-state voltage control method for reducing the risk of transient voltage instability at a new energy collection station according to claim 1, characterized in that, The steady-state voltage control threshold is set based on the transient voltage model of the new energy collection station bus to reduce the risk of transient voltage instability of the new energy collection station bus. include: The steady-state voltage control threshold is calculated as follows: ， In the formula, The steady-state voltage control threshold, Voltage margin reserved for the safe operation of the power grid This is the lower limit of the allowable steady-state voltage range for the collection station.

5. The steady-state voltage control method for reducing the risk of transient voltage instability at new energy collection stations according to claim 1, characterized in that, The calculation of the difference between the expected transient voltage and the transient voltage instability limit of the new energy collection station bus after DC bipolar blocking includes: The expected transient voltage of the new energy collection station bus after DC bipolar blocking is calculated as follows: ， In the formula, This represents the expected transient voltage value of the new energy collection station after a bipolar blocking fault occurs in the DC transmission line. This refers to the upper limit of the allowable steady-state voltage range of the collection station. This refers to the transient voltage of the busbar at the cluster station. The reactive power sent to the cluster station, The active power sent to the cluster station, Reactance of the AC line from the cluster station to the collection station; The difference between the expected transient voltage and the transient voltage instability limit of the new energy collection station bus after DC bipolar blocking is calculated as follows: ， In the formula, This is the difference between the expected transient voltage and the transient voltage instability limit of the new energy collection station. This represents the expected transient voltage value of the new energy collection station after a bipolar blocking fault occurs in the DC transmission line. This is the limit for transient voltage instability.

6. The steady-state voltage control method for reducing the risk of transient voltage instability at a new energy collection station according to claim 1, characterized in that, The step of substituting the steady-state voltage control threshold as the steady-state voltage of the new energy collection station into the transient voltage model of the new energy collection station bus to calculate the difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit after a fault includes: The transient voltage of the new energy collection station after a bipolar blocking fault in DC power is calculated as follows: ， In the formula, The steady-state voltage control threshold, The reactive power sent to the cluster station, The active power sent to the cluster station, For the AC line reactance from the cluster station to the collection station, This refers to the transient voltage at the new energy collection station after a bipolar blocking fault occurs in the DC power supply. This refers to the transient voltage of the busbar at the cluster station. The difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit of the new energy collection station after applying steady-state voltage control threshold control is calculated as follows: ， In the formula, This is the difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit of the new energy collection station after applying steady-state voltage control threshold control.

7. A steady-state voltage control system for reducing the risk of transient voltage instability at a renewable energy collection station, comprising the steady-state voltage control method for reducing the risk of transient voltage instability at a renewable energy collection station as described in any one of claims 1 to 6, characterized in that, include: The voltage model establishment unit establishes a transient voltage model of the new energy collection station bus of the new energy sending-end power grid after a bipolar blocking fault occurs in DC. Voltage instability limit setting unit, sets the transient voltage instability limit of the new energy sending end grid new energy collection station after DC bipolar blocking fault; The voltage control threshold setting unit sets a steady-state voltage control threshold based on the transient voltage model of the new energy collection station bus to reduce the risk of transient voltage instability of the new energy collection station bus. The steady-state voltage control difference calculation unit calculates the difference between the expected transient voltage and the transient voltage instability limit of the new energy collection station bus after DC bipolar blocking, and determines whether the difference between the expected transient voltage and the transient voltage instability limit of the new energy collection station bus is greater than or equal to zero. The transient voltage instability risk assessment unit responds by determining that the new energy collection station has a transient voltage instability risk, that is, after a bipolar blocking fault occurs in the DC power supply, the new energy collection station may experience transient voltage instability. The steady-state voltage control difference calculation unit takes the steady-state voltage control threshold as the steady-state voltage of the new energy collection station and inputs it into the transient voltage model of the new energy collection station bus. It calculates the difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit after a DC bipolar blocking fault occurs, and determines whether the difference between the transient voltage of the new energy collection station bus and the transient voltage instability limit after the fault is less than zero. The transient voltage instability risk reduction judgment unit responds, and then determines that there is no transient voltage instability risk at the new energy collection station, that is, the transient voltage instability risk of the new energy collection station is reduced after the steady-state control voltage threshold control is adopted.

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