A method, system and medium for active voltage support control of flexible DC system

Abstract

This invention relates to the field of DC power transmission and transformation technology, and particularly to a method, system, and medium for active voltage support control of flexible DC systems. The method includes setting reactive power support reference values ​​and AC voltage reference values ​​as control targets; obtaining reactive power error and AC voltage error based on actual measurements at the AC grid connection point and the control targets; processing these errors to obtain reactive power support control signals and AC voltage support control signals; optimizing and adjusting the reactive power support control signals and AC voltage support control signals using a fuzzy logic controller; and obtaining the control result using a proportional-integral controller; and superimposing the control result with the virtual excitation terminal voltage target value of a virtual synchronous machine to obtain the target control quantity for active voltage support of the flexible DC system. This invention combines AC voltage fluctuations and fuzzy membership coefficients to achieve precise active support control of AC grid voltage, thereby improving the stability of the power system.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current power transmission and transformation, and in particular to a method, system and medium for active voltage support control of a flexible direct current system. Background Art

[0002] In the rapid development process of the power industry, the widespread application of new energy is gradually changing the structure of the power system. With the continuous increase in the installed capacity of new energy, the stability of the local power grid has gradually weakened, which has brought new challenges to the stable operation of the power system. In the face of such changes, traditional flexible DC grid control has exposed a series of problems, especially wide-band oscillation problems and small signal interference stability problems. These problems have seriously affected the stability and reliability of the power system.

[0003] As an emerging technical means, flexible DC grid control has become an important way to improve the stability of access to weak power grids and build a new power system with new energy as the main body. Among them, droop control and virtual synchronous generator control based on the simulation of the operation mechanism of synchronous generators have been widely used in flexible DC grid control. However, although these control strategies have improved the stability of the system to a certain extent, they still face some problems that are difficult to ignore in actual operation. The networked converter station of the flexible DC system usually adopts AC voltage control mode or reactive power control mode in reactive control. According to the habit of grid dispatching management, the converter station usually actually operates in reactive power control mode. However, this control method makes the flexible DC converter station unable to directly respond to the system voltage demand, thereby limiting its role in voltage support. In addition, the existing flexible DC grid control outer loop usually adopts droop control superimposed on virtual excitation control. Although this control method improves the stability of the system to a certain extent, it does not fully consider the problem of grid voltage support from the perspective of grid demand, resulting in the converter station's dynamic response capability in the face of grid voltage disturbances. It is difficult to fully exert, which further limits the potential of the flexible DC system in voltage support.

[0004] In summary, the existing flexible DC system control strategy has obvious limitations when dealing with challenges such as the increase in new energy installed capacity and weakening of local power grids. Therefore, there is an urgent need to provide a more efficient and flexible flexible DC system voltage active support control method to improve the stability and reliability of the power system. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method, system and medium for active voltage support control of a flexible DC system.

[0006] In a first aspect, the present invention provides a method for active voltage support control of a flexible DC system, the method comprising the following steps:

[0007] According to the dispatching requirements of the flexible DC system, the reactive power support reference value and the AC voltage reference value are set as control targets;

[0008] Compare the actual measurement value of the AC grid connection point collected in real time with the control target to obtain a reactive power error and an AC voltage error; the actual measurement value of the AC grid connection point includes a reactive power output value and an AC voltage measurement value of the AC grid connection point;

[0009] The AC voltage active support control mode is started according to the three-phase effective value of the AC bus voltage of the flexible DC system, and the reactive power error and the AC voltage error are processed to obtain the corresponding reactive power support control signal and the AC voltage support control signal;

[0010] Based on the degree of AC voltage fluctuation, the reactive power support control signal and the AC voltage support control signal are optimized and adjusted by using a fuzzy logic controller to obtain a comprehensive control signal, and the comprehensive control signal is used as an input to obtain a control result by using a proportional-integral controller;

[0011] The control result is superimposed on the target value of the virtual excitation terminal voltage of the virtual synchronous machine to obtain the target control amount of active support of the flexible DC system voltage, and the target control amount is used to actively support the AC power grid voltage.

[0012] In a further embodiment, the step of comparing the actual measured value of the AC power grid connection point collected in real time with the control target to obtain the reactive power error and the AC voltage error includes:

[0013] Collect reactive power output value and AC voltage measurement value of AC power grid connection point in real time, compare the reactive power support reference value with the reactive power output value, and obtain reactive power error;

[0014] The AC voltage reference value is compared with the AC voltage measurement value to obtain an AC voltage error.

[0015] In a further implementation scheme, the steps of starting the AC voltage active support control mode according to the three-phase effective value of the AC bus voltage of the flexible DC system, and processing the reactive power error and the AC voltage error to obtain the corresponding reactive power support control signal and AC voltage support control signal include:

[0016] Detecting the three-phase effective value of the AC bus voltage of the flexible DC system to obtain a first three-phase effective value, and judging whether the AC voltage is in a normal state according to the first three-phase effective value and a preset AC voltage dead zone range;

[0017] When the effective values ​​of the first three phases are not within the preset AC voltage dead zone and the duration reaches the preset duration threshold, it is determined that the AC voltage is in an abnormal state, the AC voltage active support control mode is started, and the AC voltage active support coefficient is output;

[0018] Determine a reactive support proportional gain, and use the reactive support proportional gain to amplify the reactive power error to obtain a reactive support control signal;

[0019] The AC voltage error is amplified using the AC voltage active support coefficient to obtain an AC voltage support control signal.

[0020] In a further implementation scheme, when the first three-phase effective values ​​are within a preset AC voltage dead zone, the AC voltage is determined to be in a normal state, at which time the AC voltage active support control mode is not started and the AC voltage active support coefficient is set to zero.

[0021] In a further embodiment, the step of optimizing and adjusting the reactive power support control signal and the AC voltage support control signal by using a fuzzy logic controller based on the AC voltage fluctuation degree to obtain a comprehensive control signal comprises:

[0022] After starting the AC voltage active support control mode, the three-phase effective value of the AC bus voltage of the flexible DC system is detected again to obtain a second three-phase effective value;

[0023] Calculate the difference between the second three-phase effective value and the AC voltage reference value to obtain the AC voltage fluctuation degree;

[0024] According to the AC voltage fluctuation degree, the fuzzy membership coefficient of reactive power support and the fuzzy membership coefficient of AC voltage support are determined by using the fuzzy logic controller;

[0025] According to the reactive power support fuzzy membership coefficient and the AC voltage support fuzzy membership coefficient, the reactive power support control signal and the AC voltage support control signal are optimized and adjusted to obtain the reactive power support control adjustment signal and the AC voltage support control adjustment signal;

[0026] The reactive power support control adjustment signal and the AC voltage support control adjustment signal are superimposed to obtain a comprehensive control signal.

[0027] In a further embodiment, the step of determining the reactive power support fuzzy membership coefficient and the AC voltage support fuzzy membership coefficient using a fuzzy logic controller according to the AC voltage fluctuation degree comprises:

[0028] According to the AC voltage fluctuation degree, the reactive support fuzzy membership function constructed in advance is used to calculate the initial value of the reactive support fuzzy membership coefficient;

[0029] According to the AC voltage fluctuation degree, the initial value of the AC voltage support fuzzy membership coefficient is calculated using a pre-constructed AC voltage support fuzzy membership function;

[0030] The reactive power support fuzzy membership coefficient initial value and the AC voltage support fuzzy membership coefficient initial value are normalized to obtain the corresponding reactive power support fuzzy membership coefficient and AC voltage support fuzzy membership coefficient.

[0031] In a further embodiment, the mathematical expressions of the reactive power support fuzzy membership function and the AC voltage support fuzzy membership function are respectively:

[0032]

[0033]

[0034] In the formula, is the fuzzy membership function of AC voltage support; is the degree of AC voltage fluctuation; a is the sensitivity adjustment factor of the flexible DC system to AC voltage fluctuation; b is the AC voltage support basic coefficient; is the fuzzy membership function of reactive support; x is the response speed adjustment factor of reactive support control; y is the stability adjustment factor of the flexible DC system for reactive support.

[0035] In a further embodiment, the sum of the reactive power support fuzzy membership coefficient and the AC voltage support fuzzy membership coefficient is equal to 1.

[0036] In a second aspect, the present invention provides a flexible DC system voltage active support control system, the system comprising:

[0037] A target determination module is used to set a reactive support reference value and an AC voltage reference value as control targets according to the dispatching requirements of the flexible DC system;

[0038] An error analysis module is used to compare the actual measurement value of the AC grid connection point collected in real time with the control target to obtain a reactive power error and an AC voltage error; the actual measurement value of the AC grid connection point includes a reactive power output value and an AC voltage measurement value of the AC grid connection point;

[0039] A signal generation module is used to start the AC voltage active support control mode according to the three-phase effective value of the AC bus voltage of the flexible DC system, and process the reactive power error and the AC voltage error to obtain the corresponding reactive power support control signal and AC voltage support control signal;

[0040] An optimization control module is used to optimize and adjust the reactive power support control signal and the AC voltage support control signal based on the AC voltage fluctuation degree by using a fuzzy logic controller to obtain a comprehensive control signal, and use the comprehensive control signal as an input to obtain a control result by using a proportional-integral controller;

[0041] The support control module is used to superimpose the control result with the target value of the virtual excitation terminal voltage of the virtual synchronous machine to obtain the target control amount of active support of the flexible DC system voltage, and use the target control amount to actively support the AC power grid voltage.

[0042] In a third aspect, the present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and the computer program implements the steps of the above method when executed by a processor.

[0043] The present invention provides a method, system and medium for active voltage support control of a flexible direct current system. The method sets a reactive support reference value and an alternating current voltage reference value as control targets according to the dispatching requirements of the flexible direct current system; compares the actual measurement value of the alternating current grid connection point collected in real time with the control target to obtain a reactive power error and an alternating current voltage error; starts an active alternating current voltage support control mode according to the three-phase effective value of the alternating current bus voltage of the flexible direct current system, processes the reactive power error and the alternating current voltage error to obtain corresponding reactive support control signals and alternating current voltage support control signals; optimizes and adjusts the reactive support control signals and the alternating current voltage support control signals based on the degree of alternating current voltage fluctuation using a fuzzy logic controller to obtain a comprehensive control signal, uses the comprehensive control signal as input, and obtains a control result using a proportional integral controller; superimposes the control result with a target value of the virtual excitation terminal voltage of a virtual synchronous machine to obtain a target control amount of active voltage support of the flexible direct current system, and uses the target control amount to perform active support control on the alternating current grid voltage. Compared with the existing technology, this method combines the actual fluctuation of AC voltage and fuzzy membership coefficient, dynamically adjusts the control strategy of reactive power support and AC voltage support, and realizes precise regulation of active support of AC grid voltage to improve the stability and reliability of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic flow chart of a method for active voltage support control of a flexible DC system provided by an embodiment of the present invention;

[0045] Figure 2 It is a schematic diagram of an active voltage support control architecture of a flexible DC system provided by an embodiment of the present invention;

[0046] Figure 3 It is a schematic diagram of the process flow for determining the active support coefficient of AC voltage provided by an embodiment of the present invention;

[0047] Figure 4 is a schematic diagram of a curve showing the relationship between the AC voltage fluctuation degree and the AC voltage support fuzzy membership coefficient provided by an embodiment of the present invention;

[0048] Figure 5 is a schematic diagram of a curve showing the relationship between the AC voltage fluctuation degree and the reactive power support fuzzy membership coefficient provided in an embodiment of the present invention;

[0049] Figure 6 It is a block diagram of a flexible DC system voltage active support control system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0050] The following specifically illustrates the implementation mode of the present invention in conjunction with the accompanying drawings. The embodiments are provided for illustrative purposes only and cannot be understood as limiting the present invention. The accompanying drawings are provided for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0051] refer to Figure 1 The embodiment of the present invention provides a method for actively supporting voltage control of a flexible DC system. Figure 1 As shown, the method comprises the following steps:

[0052] S1. Set the reactive power support reference value and AC voltage reference value as control targets according to the dispatching requirements of the flexible DC system.

[0053] S2. Compare the actual measurement values ​​of the AC grid connection point collected in real time with the control target to obtain reactive power error and AC voltage error; the actual measurement values ​​of the AC grid connection point include reactive power output value and AC voltage measurement value of the AC grid connection point.

[0054] In this embodiment, the step of comparing the actual measurement value of the AC power grid connection point collected in real time with the control target to obtain the reactive power error and the AC voltage error includes:

[0055] Collect reactive power output value and AC voltage measurement value of AC power grid connection point in real time, compare the reactive power support reference value with the reactive power output value, and obtain reactive power error;

[0056] The AC voltage reference value is compared with the AC voltage measurement value to obtain an AC voltage error.

[0057] Specifically, Figure 2 As shown, in this embodiment, the reactive power support reference value that the flexible DC system needs to achieve is first set according to the dispatching requirements of the flexible DC system. and AC voltage reference As the control target, the present embodiment collects the reactive power output value of the AC grid connection point in real time through sensors. and AC voltage measurements , and use the signal comparator to convert the reactive support reference value and reactive output value These two measured values ​​are compared with the control target. Specifically, this embodiment compares the reactive support reference value Reactive output value Compare and get the reactive power error ; Set the AC voltage reference value With AC voltage measurement Compare and get the AC voltage error ; and the calculated reactive power error and AC voltage error are input into the control link as control signals for processing. Through real-time collection and comparative analysis, this embodiment can timely discover deviations in power grid operation and generate accurate control signals, thereby reducing voltage fluctuations and reducing power grid losses.

[0058] S3. Start the AC voltage active support control mode according to the three-phase effective value of the AC bus voltage of the flexible DC system, and process the reactive power error and the AC voltage error to obtain the corresponding reactive power support control signal and AC voltage support control signal.

[0059] In this embodiment, the steps of starting the AC voltage active support control mode according to the three-phase effective value of the AC bus voltage of the flexible DC system, and processing the reactive power error and the AC voltage error to obtain the corresponding reactive power support control signal and AC voltage support control signal include:

[0060] Detecting the three-phase effective value of the AC bus voltage of the flexible DC system to obtain a first three-phase effective value, and judging whether the AC voltage is in a normal state according to the first three-phase effective value and a preset AC voltage dead zone range;

[0061] When the effective values ​​of the first three phases are not within the preset AC voltage dead zone and the duration reaches the preset duration threshold, it is determined that the AC voltage is in an abnormal state, the AC voltage active support control mode is started, and the AC voltage active support coefficient is output;

[0062] Determine a reactive support proportional gain, and use the reactive support proportional gain to amplify the reactive power error to obtain a reactive support control signal;

[0063] The AC voltage error is amplified using the AC voltage active support coefficient to obtain an AC voltage support control signal.

[0064] Specifically, in this embodiment, the three-phase effective value of the flexible DC AC bus voltage is detected to obtain the first three-phase effective value , and determine whether the AC voltage is within the normal range. Specifically, Figure 3 As shown, in this embodiment, the AC voltage sets the AC voltage dead zone range, and the upper limit of the AC voltage dead zone range is set to , the lower limit of the AC voltage dead zone range is set to , when the first three-phase effective value is within the preset AC voltage dead zone, that is, when the first three-phase effective value The value of and When the AC voltage is between , it is determined that the AC voltage is in a normal state. At this time, the AC voltage active support control mode is not started, and the AC voltage active support coefficient is set to zero; if the first three-phase effective value The value is lower than the lower limit of the AC voltage dead zone range , and the first three-phase effective value The value is lower than the lower limit of the AC voltage dead zone range The duration of the , it is determined that the AC system voltage is reduced and the AC voltage is in an abnormal state. At this time, the AC voltage active support control mode needs to be started. The AC voltage active support coefficient Normal output; if the first three-phase effective value The value is higher than the upper limit of the AC voltage dead zone range , and the first three-phase effective value The value is higher than the upper limit of the AC voltage dead zone range The duration of the , it is determined that the AC system voltage is increased and the AC voltage is in an abnormal state. At this time, it is necessary to start the AC voltage active support control. At this time, the AC voltage active support coefficient Normal output.

[0065] S4. Based on the degree of AC voltage fluctuation, the reactive power support control signal and the AC voltage support control signal are optimized and adjusted using a fuzzy logic controller to obtain a comprehensive control signal, and the comprehensive control signal is used as input to obtain a control result using a proportional-integral controller.

[0066] In this embodiment, the step of optimizing and adjusting the reactive power support control signal and the AC voltage support control signal by using a fuzzy logic controller based on the AC voltage fluctuation degree to obtain a comprehensive control signal includes:

[0067] After starting the AC voltage active support control mode, the three-phase effective value of the AC bus voltage of the flexible DC system is detected again to obtain a second three-phase effective value;

[0068] Calculate the difference between the second three-phase effective value and the AC voltage reference value to obtain the AC voltage fluctuation degree;

[0069] According to the AC voltage fluctuation degree, the fuzzy membership coefficient of reactive power support and the fuzzy membership coefficient of AC voltage support are determined by using the fuzzy logic controller;

[0070] According to the reactive support fuzzy membership coefficient and the AC voltage support fuzzy membership coefficient, the reactive support control signal and the AC voltage support control signal are optimized and adjusted to achieve optimized control of the reactive support and the AC voltage support, and the reactive support control adjustment signal and the AC voltage support control adjustment signal are obtained;

[0071] The reactive power support control adjustment signal and the AC voltage support control adjustment signal are superimposed to obtain a comprehensive control signal.

[0072] Specifically, after starting the AC voltage active support control mode, this embodiment detects the three-phase effective value of the flexible DC AC bus voltage again to obtain the second three-phase effective value , the second three-phase effective value With AC voltage reference By comparing, the degree of AC voltage fluctuation is obtained, and the fuzzy membership coefficients of reactive power support control and AC voltage support control are determined according to the degree of AC voltage fluctuation. and , reactive support fuzzy membership coefficient It reflects the current system's demand for reactive power support and the AC voltage support fuzzy membership coefficient. It reflects the current system's demand for AC voltage support. Specifically, when the AC voltage fluctuation is lower than the preset fluctuation threshold, according to the system dispatch management habits, this embodiment takes reactive power support as the main goal; and when the AC voltage fluctuation is greater than the preset fluctuation threshold, this embodiment takes AC voltage support as the main goal according to system demand. The greater the AC voltage fluctuation, the greater the support demand. Based on this demand principle, this embodiment sets the fuzzy membership function and At the same time, this embodiment takes into account that both reactive power support and AC voltage support are reactive type support, and the support capacity has a limited boundary, and the initial value of the fuzzy membership coefficient of the AC voltage support corresponding to the AC voltage fluctuation degree is and initial value of fuzzy membership coefficient of reactive support Perform normalization processing to obtain the reactive support fuzzy membership coefficient and AC voltage support fuzzy membership coefficient In this embodiment, the step of determining the reactive power support fuzzy membership coefficient and the AC voltage support fuzzy membership coefficient by using a fuzzy logic controller according to the AC voltage fluctuation degree includes:

[0073] According to the AC voltage fluctuation degree, the initial value of the AC voltage support fuzzy membership coefficient is calculated using the pre-constructed AC voltage support fuzzy membership function At the same time, according to the degree of fluctuation of the AC voltage, the initial value of the reactive support fuzzy membership coefficient is calculated using the pre-constructed reactive support fuzzy membership function ; The mathematical expressions of the reactive power support fuzzy membership function and the AC voltage support fuzzy membership function are respectively:

[0074]

[0075]

[0076] in,

[0077]

[0078] In the formula, is the fuzzy membership function of AC voltage support; is the degree of AC voltage fluctuation; a is the sensitivity adjustment factor of the flexible DC system to AC voltage fluctuation; b is the AC voltage support basic coefficient; is the fuzzy membership function of reactive support; x is the response speed adjustment factor of reactive support control; y is the stability adjustment factor of the flexible DC system for reactive support; Figure 4 It is a schematic diagram of the relationship between the AC voltage fluctuation degree and the AC voltage support fuzzy membership coefficient. Figure 5 The relationship curve between the AC voltage fluctuation degree and the fuzzy membership coefficient of reactive power support is shown in Figure 4 , Figure 5 middle, The value is 1.2. The value is 0.1. The value is 3. The value is -0.95.

[0079] The initial value of the reactive power support fuzzy membership coefficient and the initial value of the AC voltage support fuzzy membership coefficient are normalized to obtain the corresponding reactive power support fuzzy membership coefficient and AC voltage support fuzzy membership coefficient; in this embodiment, the sum of the reactive power support fuzzy membership coefficient and the AC voltage support fuzzy membership coefficient is equal to 1, and the mathematical expressions of the reactive power support fuzzy membership coefficient and the AC voltage support fuzzy membership coefficient are respectively:

[0080]

[0081]

[0082] In the formula, is the fuzzy membership coefficient of reactive support; is the fuzzy membership coefficient of AC voltage support; is the initial value of the fuzzy membership coefficient of the AC voltage support; is the initial value of the fuzzy membership coefficient of reactive support.

[0083] S5. Superimpose the control result with the target value of the virtual excitation terminal voltage of the virtual synchronous machine to obtain the target control amount of active support of the flexible DC system voltage, and use the target control amount to actively support and control the AC grid voltage.

[0084] Specifically, this embodiment determines the proportional coefficient of reactive support control according to the requirements of flexible DC control response performance. , the proportional coefficient of voltage control and the integration time constant The control parameters such as s are complex numbers. These control parameters will affect the dynamic response and stability of the control system. They need to be selected according to the actual system characteristics and control requirements. Then the control parameters and the comprehensive control signal are input into the proportional-integral controller ( ), the proportional-integral controller is used to obtain the control result to improve the dynamic response and stability of the control system. Finally, the control result output by the proportional-integral controller is compared with the target value of the virtual excitation terminal voltage of the virtual synchronous machine. The target control quantity of the active voltage support of the flexible DC system is obtained by superposition, and the target control quantity is connected to the subsequent DC control program as an input quantity. The corresponding control signal is output by the flexible DC system to realize the active support control of the voltage of the flexible DC system. Through the above method, this embodiment can dynamically adjust the control strategy of reactive power support and AC voltage support according to the actual needs of the power grid and the actual fluctuation of AC voltage to realize stable voltage control and meet the system's demand for voltage stability.

[0085] An embodiment of the present invention provides a method for active voltage support control of a flexible DC system, the method setting a reactive support reference value and an AC voltage reference value as control targets according to the scheduling requirements of the flexible DC system; comparing the actual measurement value of the AC power grid connection point collected in real time with the control target to obtain a reactive power error and an AC voltage error; starting an AC voltage active support control mode according to the three-phase effective value of the AC bus voltage of the flexible DC system, and processing the reactive power error and the AC voltage error to obtain corresponding reactive support control signals and AC voltage support control signals; optimizing and adjusting the reactive support control signal and the AC voltage support control signal based on the degree of AC voltage fluctuation by using a fuzzy logic controller to obtain a comprehensive control signal, and using the comprehensive control signal as input to obtain a control result by using a proportional-integral controller; superimposing the control result with the target value of the virtual excitation terminal voltage of the virtual synchronous machine to obtain a target control amount of active voltage support of the flexible DC system, and using the target control amount to perform active support control on the AC power grid voltage. Compared with the existing technology, this method combines the actual fluctuation of AC voltage and fuzzy membership coefficient, dynamically adjusts the control strategy of reactive power support and AC voltage support, and realizes precise regulation of active support of AC grid voltage to improve the stability and reliability of the power system.

[0086] It should be noted that the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0087] In one embodiment, Figure 6 As shown, an embodiment of the present invention provides a flexible DC system voltage active support control system, the system comprising:

[0088] A target determination module 101 is used to set a reactive power support reference value and an AC voltage reference value as control targets according to a dispatching requirement of the flexible DC system;

[0089] The error analysis module 102 is used to compare the actual measurement value of the AC grid connection point collected in real time with the control target to obtain a reactive power error and an AC voltage error; the actual measurement value of the AC grid connection point includes a reactive power output value and an AC voltage measurement value of the AC grid connection point;

[0090] The signal generating module 103 is used to start the AC voltage active support control mode according to the three-phase effective value of the AC bus voltage of the flexible DC system, and process the reactive power error and the AC voltage error to obtain the corresponding reactive power support control signal and AC voltage support control signal;

[0091] The optimization control module 104 is used to optimize and adjust the reactive power support control signal and the AC voltage support control signal based on the AC voltage fluctuation degree by using a fuzzy logic controller to obtain a comprehensive control signal, and use the comprehensive control signal as an input to obtain a control result by using a proportional integral controller;

[0092] The support control module 105 is used to superimpose the control result with the target value of the virtual excitation terminal voltage of the virtual synchronous machine to obtain the target control amount of active support of the flexible DC system voltage, and use the target control amount to actively support the AC grid voltage.

[0093] In this embodiment, the error analysis module 102 is specifically used for:

[0094] Collect reactive power output value and AC voltage measurement value of AC power grid connection point in real time, compare the reactive power support reference value with the reactive power output value, and obtain reactive power error;

[0095] The AC voltage reference value is compared with the AC voltage measurement value to obtain an AC voltage error.

[0096] For the specific definition of a flexible DC system voltage active support control system, please refer to the above-mentioned definition of a flexible DC system voltage active support control method, which will not be repeated here. A person of ordinary skill in the art will appreciate that the various modules and steps described in conjunction with the embodiments disclosed in this application can be implemented in hardware, software, or a combination of both. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0097] The embodiment of the present invention provides a flexible DC system voltage active support control system, wherein a target determination module of the system sets a reactive support reference value and an AC voltage reference value as control targets according to the scheduling requirements of the flexible DC system; an error analysis module compares the actual measurement value of the AC power grid connection point collected in real time with the control target to obtain a reactive power error and an AC voltage error; a signal generation module starts an AC voltage active support control mode according to the three-phase effective value of the AC bus voltage of the flexible DC system, and processes the reactive power error and the AC voltage error to obtain corresponding reactive support control signals and AC voltage support control signals; an optimization control module optimizes and adjusts the reactive support control signal and the AC voltage support control signal based on the degree of AC voltage fluctuation using a fuzzy logic controller to obtain a comprehensive control signal, and uses the comprehensive control signal as input to obtain a control result using a proportional integral controller; a support control module superimposes the control result with the target value of the virtual excitation terminal voltage of the virtual synchronous machine to obtain a target control amount of the flexible DC system voltage active support, and uses the target control amount to perform active support control on the AC power grid voltage. Compared with the existing technology, this system combines the actual fluctuation of AC voltage and fuzzy membership coefficient to dynamically adjust the control strategy of reactive support and AC voltage support, and realizes active support and precise regulation of AC grid voltage to improve the stability and reliability of the power system.

[0098] In one embodiment, the present invention provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the above method are implemented.

[0099] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented by software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiment of the present invention is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from a website site, computer, server or data center to another website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line) or wireless (e.g., infrared, wireless, microwave, etc.) mode. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more available media integrated. The available medium can be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., an SSD), etc.

[0100] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing related hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods.

[0101] The above-mentioned embodiments only express several preferred implementation modes of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in the technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be regarded as the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be based on the protection scope of the claims.

Claims

1. A method for active voltage support control of a flexible DC system, characterized in that: The following steps are involved: According to the dispatching requirements of the flexible DC system, the reactive power support reference value and the AC voltage reference value are set as control targets; Compare the actual measurement value of the AC grid connection point collected in real time with the control target to obtain a reactive power error and an AC voltage error; the actual measurement value of the AC grid connection point includes a reactive power output value and an AC voltage measurement value of the AC grid connection point; The AC voltage active support control mode is started according to the three-phase effective value of the AC bus voltage of the flexible DC system, and the reactive power error and the AC voltage error are processed to obtain the corresponding reactive power support control signal and the AC voltage support control signal; Based on the degree of AC voltage fluctuation, the reactive power support control signal and the AC voltage support control signal are optimized and adjusted by using a fuzzy logic controller to obtain a comprehensive control signal, and the comprehensive control signal is used as an input to obtain a control result by using a proportional-integral controller; The control result is superimposed on the target value of the virtual excitation terminal voltage of the virtual synchronous machine to obtain the target control amount of active support of the voltage of the flexible DC system, and the target control amount is used to actively support the AC grid voltage; The steps of starting the AC voltage active support control mode according to the three-phase effective value of the AC bus voltage of the flexible DC system, and processing the reactive power error and the AC voltage error to obtain the corresponding reactive power support control signal and AC voltage support control signal include: Detecting the three-phase effective value of the AC bus voltage of the flexible DC system to obtain a first three-phase effective value, and judging whether the AC voltage is in a normal state according to the first three-phase effective value and a preset AC voltage dead zone range; When the first three-phase effective values ​​are not within the preset AC voltage dead zone range and the duration reaches the preset duration threshold, it is determined that the AC voltage is in an abnormal state, the AC voltage active support control mode is started, and the AC voltage active support coefficient is output; Determine a reactive support proportional gain, and use the reactive support proportional gain to amplify the reactive power error to obtain a reactive support control signal; The AC voltage error is amplified using the AC voltage active support coefficient to obtain an AC voltage support control signal.

2. A method for active voltage support control of a flexible DC system according to claim 1, characterized in that: The step of comparing the actual measurement value of the AC power grid connection point collected in real time with the control target to obtain the reactive power error and the AC voltage error includes: Collect reactive power output value and AC voltage measurement value of AC power grid connection point in real time, compare the reactive power support reference value with the reactive power output value, and obtain reactive power error; The AC voltage reference value is compared with the AC voltage measurement value to obtain an AC voltage error.

3. The method for active voltage support control of a flexible DC system according to claim 1, characterized in that: When the first three-phase effective values ​​are within the preset AC voltage dead zone, the AC voltage is determined to be in a normal state. At this time, the AC voltage active support control mode is not started, and the AC voltage active support coefficient is set to zero.

4. The method for active voltage support control of a flexible DC system according to claim 1, characterized in that: The step of optimizing and adjusting the reactive power support control signal and the AC voltage support control signal by using a fuzzy logic controller based on the AC voltage fluctuation degree to obtain a comprehensive control signal comprises: After starting the AC voltage active support control mode, the three-phase effective value of the AC bus voltage of the flexible DC system is detected again to obtain a second three-phase effective value; Calculate the difference between the second three-phase effective value and the AC voltage reference value to obtain the AC voltage fluctuation degree; According to the AC voltage fluctuation degree, the fuzzy membership coefficient of reactive power support and the fuzzy membership coefficient of AC voltage support are determined by using the fuzzy logic controller; According to the reactive power support fuzzy membership coefficient and the AC voltage support fuzzy membership coefficient, the reactive power support control signal and the AC voltage support control signal are optimized and adjusted to obtain the reactive power support control adjustment signal and the AC voltage support control adjustment signal; The reactive power support control adjustment signal and the AC voltage support control adjustment signal are superimposed to obtain a comprehensive control signal.

5. A method for active voltage support control of a flexible DC system according to claim 4, characterized in that: The step of determining the reactive power support fuzzy membership coefficient and the AC voltage support fuzzy membership coefficient by using a fuzzy logic controller according to the AC voltage fluctuation degree comprises: According to the AC voltage fluctuation degree, the reactive support fuzzy membership function constructed in advance is used to calculate the initial value of the reactive support fuzzy membership coefficient; According to the AC voltage fluctuation degree, the initial value of the AC voltage support fuzzy membership coefficient is calculated using a pre-constructed AC voltage support fuzzy membership function; The reactive power support fuzzy membership coefficient initial value and the AC voltage support fuzzy membership coefficient initial value are normalized to obtain the corresponding reactive power support fuzzy membership coefficient and AC voltage support fuzzy membership coefficient.

6. A method for active voltage support control of a flexible DC system as claimed in claim 5, characterized in that: The mathematical expressions of the reactive power support fuzzy membership function and the AC voltage support fuzzy membership function are respectively: In the formula, is the AC voltage support fuzzy membership function; is the degree of AC voltage fluctuation; a is the sensitivity adjustment factor of the flexible DC system to AC voltage fluctuation; b is the AC voltage support basic coefficient; is the fuzzy membership function of reactive support; x is the response speed adjustment factor of reactive support control; y is the stability adjustment factor of the flexible DC system for reactive support.

7. The method for active voltage support control of a flexible DC system according to claim 5, characterized in that: The sum of the reactive power support fuzzy membership coefficient and the AC voltage support fuzzy membership coefficient is equal to 1.

8. A flexible DC system voltage active support control system, characterized in that: The system comprises: A target determination module is used to set a reactive support reference value and an AC voltage reference value as control targets according to the dispatching requirements of the flexible DC system; An error analysis module is used to compare the actual measurement value of the AC grid connection point collected in real time with the control target to obtain a reactive power error and an AC voltage error; the actual measurement value of the AC grid connection point includes a reactive power output value and an AC voltage measurement value of the AC grid connection point; A signal generation module is used to start the AC voltage active support control mode according to the three-phase effective value of the AC bus voltage of the flexible DC system, and process the reactive power error and the AC voltage error to obtain the corresponding reactive power support control signal and AC voltage support control signal; An optimization control module is used to optimize and adjust the reactive power support control signal and the AC voltage support control signal based on the AC voltage fluctuation degree by using a fuzzy logic controller to obtain a comprehensive control signal, and use the comprehensive control signal as an input to obtain a control result by using a proportional-integral controller; A support control module is used to superimpose the control result with the target value of the virtual excitation terminal voltage of the virtual synchronous machine to obtain a target control amount of active support of the voltage of the flexible DC system, and use the target control amount to perform active support control on the AC grid voltage; Among them, starting the AC voltage active support control mode according to the three-phase effective value of the AC bus voltage of the flexible DC system, and processing the reactive power error and the AC voltage error to obtain the corresponding reactive power support control signal and AC voltage support control signal specifically include: Detecting the three-phase effective value of the AC bus voltage of the flexible DC system to obtain a first three-phase effective value, and judging whether the AC voltage is in a normal state according to the first three-phase effective value and a preset AC voltage dead zone range; When the first three-phase effective values ​​are not within the preset AC voltage dead zone range and the duration reaches the preset duration threshold, it is determined that the AC voltage is in an abnormal state, the AC voltage active support control mode is started, and the AC voltage active support coefficient is output; Determine a reactive support proportional gain, and use the reactive support proportional gain to amplify the reactive power error to obtain a reactive support control signal; The AC voltage error is amplified using the AC voltage active support coefficient to obtain an AC voltage support control signal.

9. A flexible DC system voltage active support control system as claimed in claim 8, characterized in that: The error analysis module is specifically used for: Collect reactive power output value and AC voltage measurement value of AC power grid connection point in real time, compare the reactive power support reference value with the reactive power output value, and obtain reactive power error; The AC voltage reference value is compared with the AC voltage measurement value to obtain an AC voltage error.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

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