Flexible DC converter station reactive voltage coordination control method

Abstract

The invention provides a reactive voltage coordination control method for a flexible DC converter station, and belongs to the field of automatic voltage control of a power system. The method comprises the following steps: taking a converter stage of an AC / DC coupling transformer of the flexible DC converter station as an equivalent generator, and establishing a control model of an AVC secondary control zone corresponding to a 500kV flexible DC converter station area; when each control cycle arrives, if the bus voltage at the high-voltage side of the flexible DC converter station is out of limit, constructing a quadratic programming optimization model for eliminating the out-of-limit of the bus voltage of the flexible DC converter station, and eliminating the out-of-limit by utilizing reactive power resources of the flexible DC converter station; and if the voltage of the high-voltage side bus of the flexible DC converter station does not exceed the limit, constructing a quadratic programming optimization model of the voltage of the pilot bus in the flexible DC converter station region, and realizing reactive voltage coordination control by using reactive resources of the flexible DC converter station and the near-region plant station. According to the method, the regional bus voltage qualification rate of the flexible DC converter station and the reactive spinning reserve and voltage stability margin of the flexible DC converter station can be effectively improved, and the regional voltage stability is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of automatic voltage control of power system, and particularly relates to a reactive power and voltage coordinated control method for a flexible direct current converter station. BACKGROUND

[0002] An automatic voltage control (AVC) system is an important means for realizing safe (improving voltage stability margin), economic (reducing network loss), and high-quality (improving voltage qualification rate) operation of a power grid. The basic principle of the automatic voltage control system is to realize reasonable distribution of reactive power and voltage in the power grid by coordinately controlling reactive power output of a generator, a transformer tap, and a reactive power compensation device.

[0003] So far, there are three modes of mainstream automatic voltage control in the world.

[0004] The first mode is represented by a two-level control of RWE Power Company in Germany, and there is no so-called zonal control. An optimal power flow (OPF) optimization result is directly sent to a one-level voltage controller of each power plant for control. However, the OPF model has a large amount of calculation and a long calculation time. When a large disturbance, a steep load rise, or a steep load drop occurs in the system, if the OPF is completely relied on, the response speed of the AVC is not enough, and the dynamic quality of the control is difficult to guarantee.

[0005] The second mode is represented by a three-level voltage control mode of EDF in France, which has experienced more than thirty years of research, development, and application since the 1970s and is currently considered as the most advanced voltage control system in the world. The control mode has been well applied, but the mode still has shortcomings. This is because the two-level voltage control (SVC) of a region is developed based on the locality of reactive power and voltage of a power system, and the reactive power and voltage between regions are coupled. Therefore, the quality of the control system fundamentally depends on the coupling degree of the reactive power and voltage control between regions. However, with the development of the power system and real-time changes of the operation condition, the region considered to be relatively decoupled at the design time is not fixed, and the control sensitivity in the form of fixed control parameters also changes in real time with the operation condition. Therefore, the region controller fixed in the form of hardware is difficult to adapt to the continuous development of the power system and the large changes of the real-time operation condition, and thus it is difficult to persistently guarantee a good control effect.

[0006] The third is a three-level voltage control mode based on "soft zoning" proposed by the dispatching automation laboratory of the Department of Electrical Engineering of Tsinghua University, which is described by Sun Hongbin, Zhang Boming and Guo Qinglai in "Design of Global Voltage Optimization Control System Based on Soft Zoning" (Power System Automation, 2003, Vol. 27, No. 8, pp. 16-20). The mode overcomes the shortcomings of hard zoning in EDF three-level voltage control through soft zoning and has been widely used in more than 20 regional power grids and provincial power grids in China and successfully promoted to voltage control in the North American PJM power grid. The three-level control is the optimal power flow (OPF) for global reactive power optimization, which gives the coordinated voltage optimization control target of the whole network. The two-level control is the decoupled control strategy calculation, which takes the optimization control target of the hub bus in each subarea given by the three-level control as the input, considers the reactive power regulation devices such as power plants in the subarea, calculates the control strategy of various reactive power resources in the subarea, and issues the control strategy to power plants and substations. The substation AVC device at the plant and station end completes the one-level control, receives and executes the control strategy issued by the dispatching master station.

[0007] Flexible DC has strong bidirectional reactive power regulation capability, and each converter station can be regarded as an SVG device. Therefore, the flexible DC converter station (referred to as flexible DC converter station) can be used as a dynamic reactive power compensation device to participate in the steady-state voltage regulation of the power grid. At present, the flexible DC converter station has not been included in the AVC control, and manual voltage regulation is required by the dispatcher, and there is a lack of coordinated control with the nearby AC plant and substation, resulting in frequent over-limit of the bus voltage in the flexible DC nearby power grid and unreasonable flow of reactive power between plants and substations, increasing the difficulty of voltage regulation, and the safety and economy indicators of the power grid need to be improved. SUMMARY

[0008] The purpose of the present application is to overcome the shortcomings of the prior art and provide a flexible DC converter station reactive voltage coordinated control method. In the reactive voltage automatic control, the converter stage of the AC-DC coupling transformer of the flexible DC converter station is modeled as an equivalent generator, and it is included in the global reactive power optimization and two-level voltage control of the AVC system of the power grid dispatching center, realizing the overall coordinated control of the flexible DC converter station and other reactive power resources in the power grid.

[0009] The embodiment of the present application provides a flexible DC converter station reactive voltage coordinated control method, which comprises the following steps:

[0010] The converter stage of the AC-DC coupling transformer of the flexible DC converter station is modeled as an equivalent generator, and the control model of the AVC two-level control subarea corresponding to the 500kV flexible DC converter station area is established;

[0011] Based on the control model, when each control cycle arrives, if the high-voltage side bus voltage of the HVDC converter station is out of limit, a quadratic programming optimization model for eliminating the out-of-limit of the bus voltage of the HVDC converter station is constructed, and the out-of-limit is eliminated by using the reactive power resource of the HVDC converter station itself; if the high-voltage side bus voltage of the HVDC converter station is not out of limit, a quadratic programming optimization model for the bus voltage of the HVDC converter station region is constructed, and the reactive power voltage coordinated control is realized by using the reactive power resource of the HVDC converter station and the nearby power station.

[0012] In one specific embodiment of the present application, further comprising:

[0013] The control model of the AVC secondary control partition corresponding to the 500kV HVDC converter station region is denoted as:

[0014] Z 500 ={V p , V h , Q g}

[0015] Wherein, V p represents the bus voltage in the region, V h represents the high-voltage side bus voltage of the HVDC converter station in the region, and Q g represents the equivalent generator reactive power of the HVDC converter station in the region.

[0016] In one specific embodiment of the present application, further comprising:

[0017] 1) constructing a quadratic programming optimization model for eliminating the out-of-limit of the bus voltage of the HVDC converter station;

[0018] The optimization objective of the quadratic programming optimization model is:

[0019]

[0020] Wherein:

[0021]

[0022] The constraint conditions of the quadratic programming optimization model include:

[0023]

[0024] Wherein, C hg is the sensitivity matrix of the equivalent generator reactive power adjustment of the HVDC converter station to the high-voltage side bus voltage; Q g , and respectively represent the current reactive power, the lower limit of the reactive power and the upper limit of the reactive power of the equivalent generator of the HVDC converter station; ΔQ g represents the equivalent generator reactive power adjustment of the HVDC converter station; V h , and These represent the current voltage, lower voltage limit, upper voltage limit, and maximum allowable single-step adjustment of the high-voltage side bus of the flexible DC converter station, respectively; parameter Θ g This is the target portion for balancing the reactive power output of equivalent generators within the flexible DC converter station area; W p1 W q1 These are the target weighting coefficients for voltage control and reactive power source balancing control under over-limit conditions, respectively. This represents the correction value for the high-voltage side bus voltage of the flexible DC converter station; δ h Dead zone for voltage correction;

[0025] 2) Solve the quadratic programming optimization model established in step 1) to obtain the equivalent generator reactive power regulation ΔQ of the flexible DC converter station. g ;

[0026] Using ΔQ g Calculate the voltage increment ΔV on the high-voltage side bus of the flexible DC converter station. h =C hg ΔQ g High-voltage side bus voltage setting value of the Herou DC converter station

[0027] 3) Make a judgment based on the results of step 2):

[0028] If |ΔQ g |>δ g Then, the reactive power resources of the flexible DC converter station are adjusted, and a voltage target command is issued to the flexible DC converter station. And the preset dead zone ε0, using the reactive power of the flexible DC converter station itself to eliminate voltage over-limit, where δ g To establish a dead zone for reactive power measurement of the unit, ensuring that the voltage on the high-voltage side bus of the flexible DC converter station meets the requirements after adjustment.

[0029] If |ΔQ g |≤δ g Then, a voltage target command is issued to the flexible DC converter station. With a preset large dead zone ε1, reactive power resources from nearby substations are used to assist in voltage regulation, ensuring that the voltage on the high-voltage side bus of the flexible DC converter station meets the requirements after regulation.

[0030] In one specific embodiment of the present invention, it further includes:

[0031] 1) Construct a quadratic programming optimization model for the central bus voltage in the flexible DC converter station area;

[0032] The optimization objective of the quadratic programming optimization model is:

[0033]

[0034] The constraints include:

[0035]

[0036] Among them, V p and These represent the current voltage and the optimized target voltage of the central bus, respectively. and These represent the lower and upper limits of the central bus voltage, respectively; C g ΔQ is the sensitivity matrix of the reactive power regulation of the equivalent generator at the flexible DC converter station to the central bus voltage; g This represents the reactive power regulation of the equivalent generator in the flexible DC converter station; parameter Θ g This is the target portion for balancing the reactive power output of equivalent generators within the flexible DC converter station area; W p2 W q2 These are the target weighting coefficients for voltage control and reactive power source balancing control under the condition of no limit exceedance, respectively.

[0037] 2) Solve the quadratic programming optimization model established in step 1) to obtain the equivalent generator reactive power regulation ΔQ of the flexible DC converter station. g ;

[0038] Using ΔQ g Calculate the voltage increment ΔV on the high-voltage side bus of the flexible DC converter station. h =C hg ΔQ g Herou DC converter station bus high voltage side line voltage setting value

[0039] 3) Make a judgment based on the results of step 2):

[0040] If satisfied And Q g <0, or satisfying And Q g A value greater than 0 indicates that the voltage regulation direction is consistent with the reactive power zeroing direction of the flexible DC converter station, adjusting the reactive power resources of the flexible DC converter station and issuing a voltage target command to the flexible DC converter station. And the preset dead zone ε0, the voltage of the high-voltage side bus of the flexible DC converter station after adjustment meets the requirements. This brings the central bus voltage close to the optimization target.

[0041] If satisfied And Q g >0, or satisfy or And Q g If the value is less than 0, it indicates that the voltage regulation direction is inconsistent with the reactive power zeroing direction of the flexible DC converter station, and a voltage target command is issued to the flexible DC converter station. and preset large dead zone ε1, using the reactive power resource of the near area power station to assist voltage regulation, and after regulation, the high voltage side bus voltage of the flexible direct current conversion station meets so that the central bus voltage approaches the optimization target

[0042] The characteristics and benefits of the present application are that:

[0043] The flexible direct current conversion station reactive voltage coordinated control method provided by the present application first obtains power grid network structure data from a power grid dispatching center, takes the conversion stage of the AC / DC coupling transformer of the flexible direct current conversion station as an equivalent generator in the AVC control model, and establishes a control model of an AVC secondary control partition of a flexible direct current conversion station area. When the control period arrives, if the high voltage side bus voltage of the flexible direct current conversion station is out of limit, a quadratic programming optimization model for eliminating the out-of-limit of the bus voltage of the flexible direct current conversion station is constructed, and the reactive power resource of the flexible direct current conversion station itself is used to quickly eliminate the out-of-limit. If the high voltage side bus voltage of the flexible direct current conversion station is not out of limit, a quadratic programming optimization model of the central bus voltage of the flexible direct current conversion station area is constructed, and according to the voltage regulation direction and the reactive power zero direction of the flexible direct current conversion station, the reactive power of the near area AC power station is used preferentially to replace the reactive power resource of the flexible direct current conversion station, and the dynamic reactive power rotating reserve of the flexible direct current conversion station is maximally reserved. The present application can effectively improve the bus voltage qualification rate of the flexible direct current conversion station area, the reactive power rotating reserve of the flexible direct current conversion station, and the voltage stability margin, reduce manual voltage regulation of the operation personnel, and improve the voltage stability of the area by equivalent modeling of the flexible direct current conversion station and incorporating the flexible direct current conversion station into the reactive voltage control module of the power grid dispatching center monitoring system. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 is a flowchart of a flexible direct current conversion station reactive voltage coordinated control method according to an embodiment of the present application. DETAILED DESCRIPTION

[0045] The present application provides a flexible direct current conversion station reactive voltage coordinated control method, which is described in further detail below in combination with the drawings and specific embodiments.

[0046] The present application provides a flexible direct current conversion station reactive voltage coordinated control method, which is described in further detail below in combination with the drawings and specific embodiments.

[0047] The conversion stage of the AC / DC coupling transformer of the flexible direct current conversion station is taken as an equivalent generator, and a control model of an AVC secondary control partition corresponding to a 500kV flexible direct current conversion station area is established;

[0048] Based on the control model, when each control cycle arrives, if the high-voltage side bus voltage of the HVDC converter station is out of limit, a quadratic programming optimization model for eliminating the out-of-limit of the bus voltage of the HVDC converter station is constructed, and the out-of-limit is eliminated by using the reactive power resource of the HVDC converter station itself; if the high-voltage side bus voltage of the HVDC converter station is not out of limit, a quadratic programming optimization model for the bus voltage of the HVDC converter station region is constructed, and the reactive power voltage coordinated control is realized by using the reactive power resource of the HVDC converter station and the nearby power station.

[0049] In a specific embodiment of the present application, in the automatic voltage control system of the power grid dispatching center, the control cycle T (generally 5 minutes), the bus voltage control small dead zone ε0 (generally 0.5 kV) and the control large dead zone ε1 (generally 10 kV) are set in advance, and the reactive power voltage coordinated control method of the HVDC converter station has the overall process as shown in the figure, which includes the following steps: Figure 1

[0050] 1) The network structure data of the power grid is obtained from the power grid dispatching center monitoring system, the converter stage of the HVDC converter station connected with the AC / DC transformer is taken as an equivalent generator in the AVC control model, so that a 500 kV HVDC converter station region is taken as the control model of the AVC secondary control partition, and is recorded as Z 500 , Z 500 ={V p , V h , Q g}, wherein V p represents the bus voltage in the region, V h represents the high-voltage side bus voltage of the HVDC converter station in the region, and Q g represents the reactive power of the equivalent generator of the HVDC converter station in the region.

[0051] In the embodiment, the reactive power Q g of the equivalent generator of the HVDC converter station is taken as the reactive power of the converter stage, and the upper limit and the lower limit of the adjustable reactive power are sent in real time by the AVC substation of the HVDC converter station.

[0052] 2) When the control cycle arrives, it is determined:

[0053] If the high-voltage side bus voltage of the HVDC converter station is out of limit, i.e. or Step 3) is entered to perform the reactive power voltage coordinated control of the HVDC converter station under the out-of-limit condition.

[0054] If the high-voltage side bus voltage of the HVDC converter station is not out of limit, i.e. Step 4) is entered to perform the reactive power voltage coordinated control of the HVDC converter station under the non-out-of-limit condition.

[0055] wherein, and​ These represent the lower and upper voltage limits of the high-voltage side bus of the flexible DC converter station, respectively; V h This indicates the voltage of the high-voltage side bus of the flexible DC converter station.

[0056] 3) Based on control model Z 500 The specific steps for coordinated reactive voltage control of the flexible DC converter station under over-limit conditions are as follows:

[0057] 3-1) Construct a quadratic programming optimization model for eliminating bus voltage over-limit in flexible DC converter stations.

[0058] The optimization objective of this quadratic programming optimization model is:

[0059]

[0060] in:

[0061]

[0062] The constraints of this quadratic programming optimization model include:

[0063]

[0064] Among them, C hg Q represents the sensitivity matrix of the reactive power regulation of the equivalent generator in the flexible DC converter station to the voltage on the high-voltage side bus. g , and These represent the current reactive power, lower reactive power limit, and upper reactive power limit of the equivalent generator at the flexible DC converter station, respectively; ΔQ g V represents the reactive power regulation of the equivalent generator in a flexible DC converter station. h , and These represent the current voltage, lower voltage limit, upper voltage limit, and maximum allowable single-step adjustment of the high-voltage side bus of the flexible DC converter station, respectively. Parameter Θ g For the reactive power balance target part of each equivalent generator in the flexible DC converter station area, W p1 W q1 These are the target weighting coefficients for voltage control and reactive power source balancing control under over-limit conditions (W). p1 The value is generally greater than W. q1 ).

[0065] This represents the correction value for the high-voltage side bus voltage of the flexible DC converter station. δ h For voltage correction dead zone, 0.5 to 1.0 kV can be used for 500 kV busbars.

[0066] 3-2) Solve the quadratic programming optimization model established in step 3-1).

[0067] In this embodiment, the solution of the quadratic programming problem can adopt the method introduced in the document "Research on Coordinated Two-level Voltage Control" (Power System Automation, 2005, 29(23): 19-23) by Guo Qinglai, Sun Hongbin, Zhang Boming, etc. to obtain the equivalent generator reactive power adjustment amount ΔQ g of the flexible AC transmission system station, and further to calculate the voltage increment ΔV h of the high-voltage side bus of the flexible AC transmission system station hg = C g ΔQ g and the voltage set value V

[0068] 3-3) Based on the result of step 3-2), make a judgment:

[0069] If the flexible AC transmission system station has reactive power adjustment capability, i.e., |ΔQ g | > δ g (the dead zone of the unit reactive power measurement), adjust the reactive power resource of the flexible AC transmission system station, issue the voltage target instruction V and the small dead zone ε0 to the flexible AC transmission system station, and use the reactive power of the flexible AC transmission system station itself to quickly eliminate the voltage overrun. In this embodiment, the high-voltage side bus voltage of the flexible AC transmission system station after adjustment should be within the ε0 dead zone of V , i.e., the high-voltage side bus voltage of the flexible AC transmission system station satisfies V .

[0070] If the flexible AC transmission system station has no reactive power adjustment capability, i.e., |ΔQ g | ≤ δ g , issue the voltage target instruction V and the large dead zone ε1 to the flexible AC transmission system station, use the reactive power resource of the conventional power plant in the vicinity to assist voltage regulation, and send the voltage adjustment instruction to the conventional power plant in the vicinity. In this embodiment, the high-voltage side bus voltage of the flexible AC transmission system station after adjustment should be within the ε1 dead zone of V , i.e., the high-voltage side bus voltage of the flexible AC transmission system station satisfies V

[0071] 4) Based on the control model Z 500 , perform the reactive power and voltage coordinated control of the flexible AC transmission system station under the non-overrun condition, and the specific steps are as follows:

[0072] 4-1) Construct the quadratic programming optimization model of the regional hub bus voltage of the flexible AC transmission system station.

[0073] The optimization objective of the quadratic programming optimization model is:

[0074]

[0075] The constraint conditions include:

[0076]

[0077] where, V p and represent the current voltage and the optimization target voltage of the central bus, respectively, and the optimization target value comes from the global reactive power optimization of the tertiary control. and represent the lower limit and the upper limit of the central bus voltage, respectively, and C g is the sensitivity matrix of the equivalent generator reactive power regulation of the HVDC converter station to the central bus voltage. W p2 , W q2 are the voltage control target weight coefficient and the reactive power source balance control target weight coefficient (W p2 ) under the condition of no over-limit. q2 ).

[0078] 4-2) Solving the quadratic programming optimization model established in step 4-1).

[0079] In this embodiment, the quadratic programming problem can be solved by using the method introduced in the literature “Research on Coordinated Two-level Voltage Control” (Power System Automation, 2005, 29(23): 19-23) by Guo Qinglai, Sun Hongbin, Zhang Boming, etc., to obtain the equivalent generator reactive power regulation of the HVDC converter station ΔQ g , and further to calculate the voltage increment of the high-voltage side bus of the HVDC converter station ΔV h = C hg ΔQ g and the voltage setting value of the high-voltage side bus of the HVDC converter station

[0080] 4-3) Making a judgment based on the result of step 4-2):

[0081] If the voltage regulation direction is consistent with the reactive power zero direction of the HVDC converter station, i.e. and Q g <0, or and Q g >0, then the reactive power resource of the HVDC converter station is adjusted, and the voltage target instruction and a small dead zone ε0are issued to the HVDC converter station. In this embodiment, the high-voltage side bus voltage of the HVDC converter station after adjustment should be within the ε0dead zone range, i.e., the high-voltage side bus voltage of the HVDC converter station satisfies ).

[0082] If the voltage regulation direction is inconsistent with the reactive power zero direction of the HVDC converter station, i.e. and Q g >0, or and Q g <0, then the voltage target instruction ​and a large dead zone ε1, using the near conventional station reactive power resources to assist voltage regulation, sending voltage adjustment instructions to the near conventional station. In this embodiment, the adjusted high voltage side bus voltage of the flexible AC transmission system station should be within the ε1 dead zone range, i.e., the high voltage side bus voltage of the flexible AC transmission system station satisfies

[0083] 5) Wait for the next control cycle to come, and then return to step 2).

[0084] The method described in this embodiment is further illustrated as follows in combination with two specific embodiments.

[0085] Embodiment 1:

[0086] In this embodiment, in the automatic voltage control system of the power grid dispatching center, the control cycle T is preset, the value is 5 minutes, the small dead zone ε0 of the bus voltage control is 0.5 kV, the large dead zone ε1 is 10 kV, and the flexible AC transmission system station reactive voltage coordination control method comprises the following steps.

[0087] 1) Obtain the power grid network structure data from the power grid dispatching center monitoring system, and take the converter stage of the AC coupling transformer of the flexible AC transmission system station as an equivalent generator in the AVC control model, so as to take a 500 kV flexible AC transmission system station area as the control model of the AVC secondary control partition, denoted as Z 500 , Z 500 ={V p , V h , Q g}, wherein V p represents the central bus voltage in the area, V h represents the high voltage side bus voltage of the flexible AC transmission system station in the area, and Q g represents the equivalent generator reactive power of the flexible AC transmission system station in the area.

[0088] In this embodiment, the equivalent generator reactive power Q g of the flexible AC transmission system station is taken as the converter stage reactive power, and the upper limit and the lower limit of the adjustable reactive power are real-time uploaded by the AVC substation of the flexible AC transmission system station.

[0089] 2) When the control cycle arrives, it is determined that:

[0090] If the high voltage side bus voltage of the flexible AC transmission system station is out of limit, i.e. then step 3) is entered to perform the flexible AC transmission system station reactive voltage coordination control under the out-of-limit condition.

[0091] 3) Based on the control model Z 500 , the flexible AC transmission system station reactive voltage coordination control under the out-of-limit condition is performed, and the specific steps are as follows:​

[0092] 3-1) Constructing a quadratic programming optimization model for eliminating over-limit of HVDC converter station bus voltage.

[0093] The optimization objective of the quadratic programming optimization model is:

[0094]

[0095] Wherein:

[0096]

[0097] The constraint conditions of the quadratic programming optimization model include:

[0098]

[0099] Wherein, C hg =||0.25|| is the sensitivity matrix of the equivalent generator reactive power regulation of the HVDC converter station to the HVDC converter station bus voltage; Q g , and are the current reactive power, lower limit of reactive power and upper limit of reactive power of the equivalent generator of the HVDC converter station; ΔQ g represents the reactive power regulation of the equivalent generator of the HVDC converter station; V h =542.5kV, and respectively represent the current voltage, lower limit of voltage, upper limit of voltage and allowed maximum adjustment of single step of the HVDC converter station bus; parameter Θ g is the reactive power output balancing objective part of each equivalent generator in the HVDC converter station area; W p1 takes value 1.0, W q1 takes value 0, which are respectively the voltage control objective weight coefficient and the reactive power source balancing control objective weight coefficient under over-limit condition.

[0100] represents the correction value of the HVDC converter station bus voltage; δ h is the dead zone of voltage correction, which takes 1kV.

[0101] In this embodiment:

[0102]

[0103] 3-2) Solving the quadratic programming optimization model established in step 3-1) to obtain the reactive power regulation ΔQ g =||-6|| of the equivalent generator of the HVDC converter station, and further calculating the HVDC converter station bus voltage increment ΔV h =C hg ΔQ g= 0.25 * -6 = -1.5 kV and the voltage setting value of the high-voltage side bus of the HVDC converter station

[0104] 3-3) Based on the result of step 3-2), a decision is made:

[0105] In this embodiment, the HVDC converter station has reactive power adjustable capability, that is, |-6|>0.5 (δ g is the reactive power measurement dead zone of the unit, and the value is 0.5 Mvar), the reactive power resource of the HVDC converter station is adjusted, the voltage target instruction 541.00 kV and the small dead zone 0.5 are issued to the HVDC converter station, and the voltage overrun is quickly eliminated by using the reactive power of the HVDC converter station itself; then step 5) is entered.

[0106] 5) Wait for the next control cycle to come, and then return to step 2) again.

[0107] Embodiment 2:

[0108] In this embodiment, in the automatic voltage control system of the power grid dispatching center, the control period T is pre-set, the value is 5 minutes, the small dead zone ε0 of the bus voltage control is 0.5 kV, the large dead zone ε1 is 10 kV, and the HVDC converter station reactive power voltage coordination control method comprises the following steps:

[0109] 1) Obtain the power grid network structure data from the power grid dispatching center monitoring system, and in the AVC control model, the converter stage of the HVDC converter station connected transformer is taken as an equivalent generator, so that a 500 kV HVDC converter station area is taken as the control model of the AVC secondary control partition, and is recorded as Z 500 , Z 500 ={V p , V h , Q g}, wherein V p represents the central bus voltage in the area, V h represents the high-voltage side bus voltage of the HVDC converter station in the area, and Q g represents the equivalent generator reactive power of the HVDC converter station in the area.

[0110] In this embodiment, the reactive power Q g of the equivalent generator of the HVDC converter station is the reactive power of the converter stage, and the upper limit and the lower limit of the adjustable reactive power are sent in real time by the AVC substation of the HVDC converter station.

[0111] 2) When the control period comes, the following is obtained by decision:

[0112] The HVDC converter station bus voltage is not overrun, that is, Step 4) is entered for the HVDC converter station reactive power voltage coordination control under the condition of no overrun.

[0113] 4) Based on the control model Z 500 , the reactive power and voltage coordinated control of the HVDC converter station under the condition of no over-limit is carried out, and the specific steps are as follows:

[0114] 4-1) A quadratic programming optimization model of the voltage of the regional hub bus of the HVDC converter station is constructed.

[0115] The optimization objective of the quadratic programming optimization model is:

[0116]

[0117] The constraint conditions include:

[0118]

[0119] Wherein, V p = 540.0 kV and respectively represent the current voltage and the optimization target voltage of the hub bus, and the optimization target value is from the global reactive power optimization of the tertiary control. and respectively represent the lower limit and the upper limit of the hub bus voltage, C g = ||0.20|| is the sensitivity matrix of the equivalent generator reactive power regulation amount of the HVDC converter station to the hub bus voltage. W p2 and W q2 are respectively the voltage control target weight coefficient and the reactive power source balance control target weight coefficient under the condition of no over-limit.

[0120] 4-2) The quadratic programming optimization model established in step 4-1) is solved to obtain the equivalent generator reactive power regulation amount ΔQ g = ||-4|| of the HVDC converter station, and further the voltage increment ΔV h = C hg ΔQ g = 0.25*-4 =-1.0 kV and the set value of the high-voltage side bus voltage of the HVDC converter station

[0121] 4-3) Based on the result of step 4-2), the judgment is carried out:

[0122] In this embodiment, the voltage regulation direction is consistent with the reactive power zero direction of the HVDC converter station, that is, and Q g = 8.6 Mvar>0, the reactive power resource of the HVDC converter station is adjusted, the voltage target instruction and the small dead zone ε0=0.5 are issued to the nearby power station to send the flat regulation instruction.

[0123] 5) Wait for the next control cycle to come, and then return to step 2).

Claims

1. A method for coordinated reactive power and voltage control in a flexible DC converter station, characterized in that, include: Using the converter stage connected to the AC / DC connection transformer of the flexible DC converter station as an equivalent generator, a control model of the AVC secondary control zone corresponding to the 500kV flexible DC converter station area is established. Based on the control model, at the arrival of each control cycle, if the voltage of the high-voltage side bus of the flexible DC converter station exceeds the limit, a quadratic programming optimization model for eliminating the voltage exceedance of the flexible DC converter station bus is constructed, utilizing the reactive power resources of the flexible DC converter station itself to eliminate the limit exceedance; if the voltage of the high-voltage side bus of the flexible DC converter station does not exceed the limit, a quadratic programming optimization model for the voltage of the regional central bus of the flexible DC converter station is constructed, utilizing the reactive power resources of the flexible DC converter station and nearby power plants to achieve reactive power and voltage coordinated control.

2. The method according to claim 1, characterized in that, Also includes: The control model for the AVC secondary control zone corresponding to the 500kV flexible DC converter station area is denoted as: Z 500 ={V p ,V h ,Q g } Among them, V p This represents the voltage of the central bus in this area, V. h Q represents the voltage of the high-voltage side bus of the flexible DC converter station in this area. g This indicates the reactive power of the equivalent generator at the flexible DC converter station in this area.

3. The method according to claim 2, characterized in that, Also includes: 1) Construct a quadratic programming optimization model for eliminating bus voltage over-limit in flexible DC converter stations; The optimization objective of the quadratic programming optimization model is: in: The constraints of the quadratic programming optimization model include: Among them, C hg Q represents the sensitivity matrix of the reactive power regulation of the equivalent generator in the flexible DC converter station to the voltage on the high-voltage side bus. g , and These represent the current reactive power, lower reactive power limit, and upper reactive power limit of the equivalent generator at the flexible DC converter station, respectively; ΔQ g V represents the reactive power regulation of the equivalent generator in a flexible DC converter station. h , and These represent the current voltage, lower voltage limit, upper voltage limit, and maximum allowable single-step adjustment of the high-voltage side bus of the flexible DC converter station, respectively; parameter Θ g This is the target portion for balancing the reactive power output of equivalent generators within the flexible DC converter station area; W p1 W q1 These are the target weighting coefficients for voltage control and reactive power source balancing control under over-limit conditions, respectively. This represents the correction value for the high-voltage side bus voltage of the flexible DC converter station; δ h Dead zone for voltage correction; 2) Solve the quadratic programming optimization model established in step 1) to obtain the equivalent generator reactive power regulation ΔQ of the flexible DC converter station. g ; Using ΔQ g Calculate the voltage increment ΔV on the high-voltage side bus of the flexible DC converter station. h =C hg ΔQ g High-voltage side bus voltage setting value of the Herou DC converter station 3) Make a judgment based on the results of step 2): If |ΔQ g |>δ g Then, the reactive power resources of the flexible DC converter station are adjusted, and a voltage target command is issued to the flexible DC converter station. And the preset dead zone ε0, using the reactive power of the flexible DC converter station itself to eliminate voltage over-limit, where δ g To establish a dead zone for reactive power measurement of the unit, ensuring that the voltage on the high-voltage side bus of the flexible DC converter station meets the requirements after adjustment. If |ΔQ g |≤δ g Then, a voltage target command is issued to the flexible DC converter station. With a preset large dead zone ε1, reactive power resources from nearby substations are used to assist in voltage regulation, ensuring that the voltage on the high-voltage side bus of the flexible DC converter station meets the requirements after regulation.

4. The method according to claim 2, characterized in that, Also includes: 1) Construct a quadratic programming optimization model for the central bus voltage in the flexible DC converter station area; The optimization objective of the quadratic programming optimization model is: The constraints include: Among them, V p and These represent the current voltage and the optimized target voltage of the central bus, respectively. and These represent the lower and upper limits of the central bus voltage, respectively; C g ΔQ is the sensitivity matrix of the reactive power regulation of the equivalent generator at the flexible DC converter station to the central bus voltage; g This represents the reactive power regulation of the equivalent generator in the flexible DC converter station; parameter Θ g This is the target portion for balancing the reactive power output of equivalent generators within the flexible DC converter station area; W p2 W q2 These are the target weighting coefficients for voltage control and reactive power source balancing control under the condition of no limit exceedance, respectively. 2) Solve the quadratic programming optimization model established in step 1) to obtain the equivalent generator reactive power regulation ΔQ of the flexible DC converter station. g ; Using ΔQ g Calculate the voltage increment ΔV on the high-voltage side bus of the flexible DC converter station. h =C hg ΔQ g Herou DC converter station bus high voltage side line voltage setting value 3) Make a judgment based on the results of step 2): If satisfied And Q g <0, or satisfying And Q g A value greater than 0 indicates that the voltage regulation direction is consistent with the reactive power zeroing direction of the flexible DC converter station, adjusting the reactive power resources of the flexible DC converter station and issuing a voltage target command to the flexible DC converter station. And the preset dead zone ε0, the voltage of the high-voltage side bus of the flexible DC converter station after adjustment meets the requirements. This brings the central bus voltage close to the optimization target. If satisfied And Q g >0, or satisfy or And Q g If the value is less than 0, it indicates that the voltage regulation direction is inconsistent with the reactive power zeroing direction of the flexible DC converter station, and a voltage target command is issued to the flexible DC converter station. With the preset large dead zone ε1, the reactive power resources of nearby substations are used to assist in voltage regulation, and the voltage of the high-voltage bus of the flexible DC converter station after regulation meets the requirements. This brings the central bus voltage close to the optimization target.

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