Flexible direct-current engineering main control system, flexible direct-current engineering standby control system, flexible direct-current phase-locked loop redundancy synchronous control method and flexible direct-current phase-locked loop redundancy synchronous control device
By adopting the method of dynamic task execution cycle and phase angle compensation value in flexible DC engineering, the problem of phase angle deviation of phase locked loop caused by equipment differences is solved, and the high-precision synchronization and stable operation of the redundant control system are achieved.
Patent Information
- Application Number
- CN202510285120.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-11
- Publication Date
- 2025-06-24
AI Technical Summary
Due to the inherent differences in primary and secondary equipment of flexible DC engineering, the task execution cycles of the main and backup control systems are not fixed, which leads to a large deviation in the phase angle value of the phase locked loop output, affecting the synchronization and transient response characteristics of the redundant control system.
The dynamic task execution cycle is adopted, and the time error between adjacent task cycles of the same control system is reduced by taking the average of the measured values of the N consecutive task execution cycles before the current task execution cycle of the main and standby control systems as the current task execution cycle. At the same time, when the backup control system calculates the phase-locked loop output phase angle, it uses the positive sequence component integral of the q-axis grid voltage of the main control system, and calculates the phase-angle compensation value based on real-time communication delay.
The deviation of the phase angle value of the phase lock loop output of the main and standby control system is reduced, the accuracy of the phase angle value of the phase lock loop output is improved, the redundant system is ensured to switch without disturbance, and the transient response capability and system reliability and stability of the flexible DC system are improved.
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Figure CN120200301A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of grid phase-locked technology, and specifically relates to a main control system and a standby control system for a flexible DC project, a flexible DC phase-locked loop redundant synchronization control method and device. Background Art
[0002] For a flexible DC control system adopting grid-following control, in order to achieve the synchronization of converter control and the voltage of the AC system, a phase-locked loop function is configured in the converter control device. The input of the phase-locked loop uses the three-phase AC voltage measured at the grid side bus of the coupling transformer as the reference tracking object, and its output is a phase angle value based on time. To ensure the reliability of control, in a flexible DC project, the control system adopts a dual redundant configuration and operates in a "one main and one standby" mode. The grid-side voltage sampling devices of the main control system and the standby control system are independently set. The main control system participates in the real-time control of the flexible DC project, and the standby control system is in a hot standby state. The integral part of the positive sequence q-axis component of the grid voltage of its phase-locked loop follows the control system operating in the main mode in real time. As Figure 1 shown, the flexible DC control system uses the collected three-phase AC voltage on the grid side as the AC synchronous voltage, performs Clarke transformation on the three-phase AC voltage on the grid side to obtain the α-axis grid voltage Uα and the β-axis grid voltage Uβ in the two-phase stationary αβ coordinate system, respectively extracts the positive sequence components of Uα and Uβ to obtain the positive sequence component Uα of the α-axis grid voltage and the positive sequence component Uβ of the β-axis grid voltage in the two-phase stationary αβ coordinate system + and the positive sequence component Uβ of the β-axis grid voltage + , combines Uα + and Uβ + respectively perform trigonometric function operations with the sine value and cosine value of the phase angle output by the phase-locked loop to obtain the positive sequence component Uq of the q-axis grid voltage in the dq coordinate system + , then calculates the angular frequency error Δω through the phase-locked loop PI controller, adds the calculated angular frequency error to the reference angular frequency (the angular frequency of the previous task execution cycle) ω0 to obtain the current angular frequency, multiplies the current angular frequency by the fixed task execution cycle s (such as 50 us) of the control system to obtain the current phase angle θ output by the phase-locked loop. The phase angle θ is restricted by a 0-2π cycle, and this phase angle value is the reference phase angle of the flexible DC control system and is used to calculate the required arm reference voltage.
[0003] When all the primary and secondary equipment of the flexible DC project is in an ideal state, the task execution period of the control system remains fixed. As a result, within the current task execution period, the positive sequence component of the q-axis grid voltage, the integral of the positive sequence component of the q-axis grid voltage, the angular frequency error, and the reference angular frequency of the two sets of control system phase-locked loops are the same. This enables the phase angle values output by the standby control system and the primary control system to be synchronized, thus achieving the synchronous control of the redundant control system phase-locked loop. However, in actual flexible DC projects, due to the inherent differences in the primary and secondary equipment of the flexible DC project, and the crystal oscillator of the primary and secondary equipment determines the accuracy of the task execution period. Therefore, neither the task execution period of the primary control system nor the task period of the standby control system is fixed. The non-fixed task execution period results in different reference angular frequencies in the actual primary and standby control systems, and thus different calculated angular frequency errors. Then, the current angular frequency calculated based on the angular frequency error and the reference angular frequency will also deviate, causing a large deviation in the phase angle values output by the two sets of control system phase-locked loops. Furthermore, this leads to a large deviation in the calculated arm reference voltage of the two sets of control systems. The redundant two sets of control systems cannot achieve complete synchronization, and there will inevitably be a large disturbance during the primary and standby control system switchover, affecting the transient response characteristics of the flexible DC project. Moreover, based on the existing deviation, the longer the control time, the larger the phase angle deviation accumulated by the phase-locked loop may become, affecting the stable operation of the flexible DC system. Summary of the Invention
[0004] The purpose of the present invention is to provide a primary control system and a standby control system for a flexible DC project, a flexible DC phase-locked loop redundant synchronization control method and device, to solve the problem of large deviation in the phase angle values output during the switchover of the primary and standby control systems of the flexible DC phase-locked loop with a fixed task execution period due to the inherent differences in the primary and secondary equipment.
[0005] The present invention provides a flexible DC phase-locked loop redundant synchronization control method to solve the above technical problems, including:
[0006] Taking the average value of the measured values of the continuous N task execution periods before the current task execution period of the primary control system as the current task execution period of the primary control system, and taking the average value of the measured values of the continuous N task execution periods before the current task execution period of the standby control system as the current task execution period of the standby control system;
[0007] When the primary control system operates normally, calculating the phase angle value output by the primary control system based on the positive sequence component of the q-axis grid voltage of the primary control system, the angular frequency of the previous task execution period, and the current task execution period of the primary control system;
[0008] When the primary control system runs abnormally and switches to the standby control system, the phase angle value output by the standby control system is calculated based on the integral of the positive sequence component of the q-axis grid voltage of the primary control system, the proportional quantity of the positive sequence component of the q-axis grid voltage of the standby control system, the angular frequency of the previous task execution cycle, and the current task execution cycle of the standby control system.
[0009] Further, when the primary control system runs normally and at the moment when the primary control system switches to the standby control system, the phase angle value used in the phase-locked loop calculation of the standby control system is determined based on the phase angle value output by the primary control system.
[0010] Further, when the primary control system runs normally and at the moment when the primary control system switches to the standby control system, the phase angle value used in the phase-locked loop calculation of the standby control system is the phase angle value output by the primary control system.
[0011] Further, when the primary control system runs normally and at the moment when the primary control system switches to the standby control system, the phase angle value used in the phase-locked loop calculation of the standby control system is the sum of the phase angle value output by the primary control system and the phase angle compensation value, and the phase angle compensation value is determined based on the real-time communication delay between the primary control system and the standby control system.
[0012] Further, the phase angle compensation value is calculated based on the following formula:
[0013]
[0014] where Δθ is the phase angle compensation value, π is 180°, t is the detected real-time communication delay between the primary and standby control systems, and T is the three-phase AC voltage period on the grid side.
[0015] The beneficial effects of the above technical solutions are as follows: The present invention is an improved invention. For the flexible DC project with primary and standby redundant control, a dynamic task execution cycle is adopted. The current task execution cycle is determined based on the average value of the measured values of multiple consecutive task execution cycles before the current task execution cycle. The task execution cycle of the corresponding control system is calculated with multiple consecutive task execution cycles as a sliding time window, which greatly reduces the time error between adjacent task cycles of the same control system, and further reduces the deviation of the phase angle difference between adjacent task cycles of the same control system. Since the integral of the positive sequence component of the q-axis grid voltage of the primary control system is used when the standby control system calculates the phase angle output by the phase-locked loop, the deviation between the phase angle output by the standby control system and the phase angle output by the primary control system is also reduced, thereby improving the accuracy of the phase angle value output by the phase-locked loop of the flexible DC control system, solving the problem that the phase angle deviation accumulated by the phase-locked loop may become larger and larger as the control time increases, ensuring seamless switching of the redundant system, and improving the transient response ability and system reliability and stability of the flexible DC system.
[0016] To solve the above problems, the present invention also provides a main control system for a flexible DC project. The main control system is used to interact with the standby control system of the flexible DC project, and send its operating state and the integral of the positive sequence component of the q-axis grid voltage to the standby control system. When operating normally, the main control system calculates the phase angle value output by the main control system based on the positive sequence component of the q-axis grid voltage of the main control system, the angular frequency of the previous task execution cycle, and the current task execution cycle of the main control system, and performs real-time control of the flexible DC project based on the phase angle value output by the main control system; the current task execution cycle of the main control system is the average value of the measured values of the continuous N task execution cycles before the current task execution cycle of the main control system.
[0017] To solve the above problems, the present invention also provides a standby control system for a flexible DC project. The standby control system is used to interact with the main control system of the flexible DC project, receive the operating state sent by the main control system and the integral of the positive sequence component of the q-axis grid voltage of the main control system. When the main control system malfunctions and switches to the standby control system, the standby control system calculates the phase angle value output by the standby control system based on the integral of the positive sequence component of the q-axis grid voltage of the main control system, the proportional quantity of the positive sequence component of the q-axis grid voltage of the standby control system, the angular frequency of the previous task execution cycle, and the current task execution cycle of the standby control system, and performs real-time control of the flexible DC project based on the phase angle value output by the standby control system; the current task execution cycle of the standby control system is the average value of the measured values of the continuous N task execution cycles before the current task execution cycle of the standby control system.
[0018] Further, the standby control system also receives the phase angle value output by the main control system; when the main control system operates normally and at the moment when the main control system switches to the standby control system, the phase angle value used by the standby control system in the phase-locked loop calculation is the phase angle value output by the main control system.
[0019] Further, the standby control system also receives the phase angle value output by the main control system; when the main control system operates normally and at the moment when the main control system switches to the standby control system, the phase angle value used by the standby control system in the phase-locked loop calculation is the sum of the phase angle value output by the main control system and the phase angle compensation value, and the phase angle compensation value is determined based on the real-time communication delay between the main control system and the standby control system.
[0020] To solve the above technical problems, the present invention also provides a redundant synchronization control device for a flexible DC phase-locked loop, including a primary control system and a standby control system for a flexible DC project. The primary control system and the standby control system for the flexible DC project implement redundant synchronization control of the flexible DC phase-locked loop by using the flexible DC phase-locked loop redundant synchronization control method introduced above.
[0021] The beneficial effects of the above technical solution are as follows: The present invention is an improved invention. For a flexible DC project with primary and standby redundant control, a dynamic task execution cycle is adopted. The current task execution cycle is determined according to the average value of the measured values of a continuous plurality of task execution cycles before the current task execution cycle. The task execution cycle of the corresponding control system is calculated with a continuous plurality of task execution cycles as a sliding time window, which greatly reduces the time error between adjacent task cycles of the same control system, and further reduces the deviation of the phase angle difference between adjacent task cycles of the same control system. Since the integral component of the positive sequence of the q-axis grid voltage of the primary control system is used when the standby control system calculates the output phase angle of the phase-locked loop, the deviation between the phase angle output by the standby control system and the phase angle output by the primary control system is also reduced, thereby improving the accuracy of the output phase angle value of the phase-locked loop of the flexible DC control system, solving the problem that the phase angle deviation accumulated by the phase-locked loop may become larger and larger as the control time increases, ensuring seamless switching of the redundant system, and improving the transient response ability and system reliability and stability of the flexible DC system. Description of the Drawings
[0022] Figure 1 is a schematic diagram of the phase-locked loop control principle of a redundant control system in the prior art;
[0023] Figure 2 is a schematic diagram of the phase-locked loop control principle of the primary control system in an embodiment of the redundant synchronization control device for a flexible DC phase-locked loop of the present invention;
[0024] Figure 3 is a schematic diagram of the phase-locked loop control principle of the standby control system in an embodiment of the redundant synchronization control device for a flexible DC phase-locked loop of the present invention. Detailed Embodiments
[0025] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following further illustrates the detailed embodiments of the present invention with reference to the drawings.
[0026] The present invention is directed to a flexible DC phase-locked loop control system including a primary and a standby. To reduce the influence of the differences between primary and secondary equipment, neither the primary nor the standby control system adopts a fixed task execution period. Instead, the principle of a sliding time window is used. The average value of the measured values of the continuous N task execution periods before the current task execution period is used as the current task execution period of the standby control system, thereby dynamically adjusting the task execution period. By averaging, the output phase angle deviation caused by different actual task execution periods is reduced, the accuracy of the phase-locked loop control output phase angle of the primary and standby control systems is improved, and thus the real-time synchronization of the phase-locked loop output phase angle values between redundant systems is achieved, ensuring seamless switching between redundant systems and improving the transient response ability and system reliability and stability of the flexible DC system.
[0027] Embodiment of a Flexible DC Phase-Locked Loop Redundant Synchronization Control Device
[0028] A flexible DC phase-locked loop redundant synchronization control device of the present invention includes a primary control system and a standby control system in a flexible DC project, and is used to implement a flexible DC phase-locked loop redundant synchronization control method. The implementation principle of the flexible DC phase-locked loop redundant synchronization control method is as Figure 2 and Figure 3 shown, and the following is a detailed description.
[0029] 1. The primary control system and the standby control system adopt a dynamic task execution period.
[0030] The average value of the measured values of the continuous N task execution periods before the current task execution period of the primary is used as the current task execution period of the primary control system, and the average value of the measured values of the continuous N task execution periods before the current task execution period of the standby control system is used as the current task execution period of the standby control system. The value range of N is generally 10 to 100 and can be set according to specific control requirements. In this embodiment, N is set to 20, and the average value of the measured values of 20 consecutive task execution periods is used as the current task execution period of the corresponding control system. The calculation formula is:
[0031]
[0032] where s d is the dynamic task execution period, and s t is the measured value of the t-th task execution period within 20 consecutive task execution periods before the current task execution period.
[0033] If the number of task execution periods before the current task execution period is less than N, that is, within the first N task execution periods, control is performed according to the average value of the measured values of all task execution periods before the current task execution period.
[0034] 2. Determine the positive sequence component of the α-axis grid voltage and the positive sequence component of the β-axis grid voltage in the two-phase stationary αβ coordinate system based on the three-phase AC voltage on the grid side. Calculate the positive sequence component of the q-axis grid voltage in the dq coordinate system according to the sine value and cosine value of the phase angle output by the phase-locked loop respectively for the positive sequence component of the α-axis grid voltage and the positive sequence component of the β-axis grid voltage.
[0035] The voltage sampling device of the primary control system collects the three-phase AC voltages Ua, Ub, and Uc on the grid side, performs Clarke transformation on the three-phase AC voltages on the grid side to obtain the α-axis grid voltage Uα and the β-axis grid voltage Uβ in the two-phase stationary αβ coordinate system, and extracts the positive sequence components of Uα and Uβ respectively to obtain the positive sequence component Uα of the α-axis grid voltage + and the positive sequence component Uβ of the β-axis grid voltage + , and perform trigonometric operations on Uα + and Uβ + respectively with the sine value and cosine value of the phase angle output by the phase-locked loop of the primary control system to obtain the positive sequence component Uq of the q-axis grid voltage of the primary control system in the dq coordinate system + .
[0036] The voltage sampling device of the standby control system collects the three-phase AC voltages on the grid side, and obtains the positive sequence component Uα of the α-axis grid voltage + and the positive sequence component Uβ of the β-axis grid voltage + in the two-phase stationary αβ coordinate system according to the above method. Perform trigonometric operations on Uα + and Uβ + respectively with the sine value and cosine value of the phase angle output by the phase-locked loop of the standby control system to obtain the positive sequence component Uq of the q-axis grid voltage of the standby control system in the dq coordinate system + .
[0037] 3. When the primary control system is operating normally, calculate the phase angle value output by the primary control system based on the positive sequence component of the q-axis grid voltage of the primary control system, the angular frequency of the previous task execution cycle, and the current task execution cycle. This phase angle value is used as the reference phase angle of the flexible DC control system to calculate the dq inverse transformation of the arm reference voltage for real-time control of the flexible DC project.
[0038] Among them, the angular frequency of each task execution cycle is obtained by adding the angular frequency error obtained by performing PI control on the positive sequence component of the q-axis grid voltage of this task execution cycle to the angular frequency of the previous task execution cycle of this task execution cycle.
[0039] Currently, when the primary control system is normally participating in real-time control, the standby control system is in the hot standby state, and the integral part of its phase-locked loop (that is, the integral of the positive sequence component of the q-axis grid voltage in the PI controller )A control system that follows the main system in real time. To further improve the accuracy of the primary-backup redundancy synchronization control, in the present invention, when the main control system is operating normally and at the moment when the main control system switches to the backup control system, the backup control system performs a phase-locked loop calculation (which means performing trigonometric operations on Uα + and Uβ + respectively with the sine and cosine values of the phase angle to obtain the positive sequence component Uq of the grid voltage on the q-axis of the backup control system in the dq coordinate system + ). The phase angle value used is determined based on the phase angle value output by the main control system, that is, the phase angle value of the backup control system also follows the main control system in real time, so that the positive sequence component of the grid voltage on the q-axis of the backup control system calculated according to the phase angle value is more accurate.
[0040] In one embodiment, the output phase angle value of the main control system can be sent to the backup control system and directly used as the phase angle value for the backup control system to perform the phase-locked loop calculation.
[0041] Considering that there is a communication delay in the backup control system receiving the phase angle value of the main control system, and the accuracy of the task execution cycle of the control system is determined by the crystal oscillator of its own device, resulting in the communication delay between the primary and backup control systems not being fixed. Therefore, the method of increasing the real-time delay is used to compensate for the phase angle difference caused by the communication delay. In a preferred embodiment, when the main control system is operating normally and at the moment when the main control system switches to the backup control system, the phase angle value used by the backup control system for the phase-locked loop calculation is the sum of the phase angle value output by the main control system and the phase angle compensation value, and the phase angle compensation value is determined based on the real-time communication delay between the main and backup control systems.
[0042] The backup control system detects the time difference between the real-time transmission flag bit W0 and receiving the same flag bit W0 fed back by the main control system, and then divides it by 2 to obtain the real-time communication delay t (unit: ms). The backup control system converts the real-time communication delay t into a phase difference, compensates the phase angle value output by the phase-locked loop of the main control system, and uses the compensated phase angle value as the output phase angle value for the backup control system. The phase angle compensation value is calculated based on the following formula:
[0043]
[0044] where, Δθ is the phase angle compensation value, π is 180°, t is the detected real-time communication delay between the main and backup control systems, and T is the three-phase AC voltage period on the grid side.
[0045] The phase angle value θos used by the backup control system for the phase-locked loop calculation is calculated according to the following formula:
[0046] θos = Δθ + θo
[0047] Among them, θo is the phase angle value output by the received primary control system.
[0048] 4. When the primary control system of the flexible DC project runs abnormally and switches to the standby control system, the standby control system calculates the phase angle value output by the standby control system based on the integral of the positive sequence component of the q-axis grid voltage of the primary control system, the proportional amount of the positive sequence component of the q-axis grid voltage of the standby control system, the angular frequency of the previous task execution cycle, and the current task execution cycle of the standby control system, and uses the phase angle value output by the standby control system as the reference phase angle to control the flexible DC project. After the switch is completed, the standby control system no longer uses the integral of the positive sequence component of the q-axis grid voltage and the phase angle value sent by the primary control system for phase-locked loop calculation, but calculates the phase angle value output by the standby control system based on the integral of the positive sequence component of the q-axis grid voltage of the standby control system, the proportional amount, the angular frequency of the previous task execution cycle, and the current task execution cycle of the standby control system, and uses the output phase angle value as the reference phase angle to participate in the real-time control of the flexible DC project.
[0049] Embodiment of the flexible DC phase-locked loop redundant synchronization control method
[0050] A flexible DC phase-locked loop redundant synchronization control method of the present invention, which is the flexible DC phase-locked loop redundant synchronization control method described in the above embodiment of the flexible DC phase-locked loop redundant synchronization control device, and will not be described in detail here.
[0051] Embodiment of the primary control system of the flexible DC project
[0052] A primary control system of a flexible DC project of the present invention, which is used to interact with the standby control system of the flexible DC project, send its operating state and the integral of the positive sequence component of the q-axis grid voltage to the standby control system, and is used to calculate the phase angle value output by the primary control system based on the positive sequence component of the q-axis grid voltage of the primary control system, the angular frequency of the previous task execution cycle, and the current task execution cycle of the primary control system when operating normally, and perform real-time control of the flexible DC project based on the phase angle value output by the primary control system; where the current task execution cycle of the primary control system is the average value of the measured values of the continuous N task execution cycles before the current task execution cycle of the primary control system.
[0053] Embodiment of the standby control system of the flexible DC project
[0054] A redundant control system for a flexible DC project of the present invention. The redundant control system is used to interact with the primary control system of the flexible DC project, receive the operating status sent by the primary control system and the integral of the positive sequence component of the q-axis grid voltage of the primary control system. When the primary control system fails and switches to the redundant control system, the redundant control system calculates the phase angle value output by the redundant control system based on the integral of the positive sequence component of the q-axis grid voltage of the primary control system, the proportional amount of the positive sequence component of the q-axis grid voltage of the redundant control system, the angular frequency of the previous task execution cycle, and the current task execution cycle of the redundant control system, and performs real-time control on the flexible DC project based on the phase angle value output by the redundant control system; the current task execution cycle of the redundant control system is the average value of the measured values of the continuous N task execution cycles before the current task execution cycle of the redundant control system.
[0055] In order to further reduce the deviation between the primary and redundant control systems, the redundant control system also receives the phase angle value output by the primary control system sent by the primary control system; when the primary control system is operating normally and at the moment when the primary control system switches to the redundant control system, the phase angle value used by the redundant control system in the phase-locked loop calculation is the phase angle value output by the primary control system.
[0056] Furthermore, when the primary control system is operating normally and at the moment when the primary control system switches to the redundant control system, the phase angle value used by the redundant control system in the phase-locked loop calculation is the sum of the phase angle value output by the primary control system and the phase angle compensation value, and the phase angle compensation value is determined based on the real-time communication delay between the primary control system and the redundant control system.
[0057] The present invention aims at the primary and redundant control systems in the flexible DC transmission project, adopts a dynamic task execution cycle, improves the accuracy of the phase angle output by the phase-locked loop control; adopts a dynamic phase angle value following control, converts the real-time detected communication delay between redundant control devices into a phase difference value, and compensates the phase angle value output by the phase-locked loop of the primary operating control system, so as to achieve real-time consistency of the phase angles of the redundant control systems. The present invention not only realizes the accuracy of the phase angle value output by the phase-locked loop of any control device, but also realizes the real-time synchronization of the phase angle values output by the phase-locked loops between redundant systems, thereby ensuring seamless switching between redundant systems, and improving the transient response ability and system reliability and stability of the flexible DC system.
Claims
1. A flexible DC phase-locked loop redundant synchronization control method, characterized in that: include: The average value of the actual measured values of N consecutive task execution cycles before the current task execution cycle of the active control system is used as the current task execution cycle of the active control system, and the average value of the actual measured values of N consecutive task execution cycles before the current task execution cycle of the standby control system is used as the current task execution cycle of the standby control system; When the main control system operates normally, the phase angle value output by the main control system is calculated based on the positive sequence component of the q-axis grid voltage of the main control system, the angular frequency of the previous task execution cycle and the current task execution cycle of the main control system; When the main control system operates abnormally and switches to the backup control system, the phase angle value of the backup control system output is calculated based on the integral of the positive-sequence component of the q-axis grid voltage of the main control system, the proportional component of the positive-sequence component of the q-axis grid voltage of the backup control system, the angular frequency of the previous task execution cycle, and the current task execution cycle of the backup control system.
2. The flexible DC phase-locked loop redundant synchronization control method according to claim 1, characterized in that: When the main control system operates normally and at the moment when the main control system switches to the backup control system, the phase angle value used by the backup control system when performing phase-locked loop calculation is determined based on the phase angle value output by the main control system.
3. The flexible DC phase-locked loop redundant synchronization control method according to claim 2, characterized in that: When the main control system operates normally and at the moment when the main control system switches to the backup control system, the phase angle value used by the backup control system when performing phase-locked loop calculation is the phase angle value output by the main control system.
4. The flexible DC phase-locked loop redundant synchronization control method according to claim 2, characterized in that: When the main control system operates normally and at the moment when the main control system switches to the backup control system, the phase angle value used by the backup control system when performing phase-locked loop calculation is the sum of the phase angle value output by the main control system and the phase angle compensation value, and the phase angle compensation value is determined based on the real-time communication delay between the main control system and the backup control system.
5. The flexible DC phase-locked loop redundant synchronization control method according to claim 4, characterized in that: The phase angle compensation value is calculated based on the following formula: Among them, Δθ is the phase angle compensation value, π is 180°, t is the real-time communication delay of the detected main and standby control systems, and T is the three-phase AC voltage period on the grid side.
6. A main control system of a flexible DC project, the main control system is used to interact with the backup control system of the flexible DC project, and sends its operating status and the integral of the positive sequence component of the q-axis grid voltage to the backup control system, characterized in that: The main control system is used to calculate the phase angle value output by the main control system based on the positive sequence component of the q-axis grid voltage of the main control system, the angular frequency of the previous task execution cycle and the current task execution cycle of the main control system when operating normally, and to perform real-time control of the flexible DC project based on the phase angle value output by the main control system; the current task execution cycle of the main control system is the average value of the actual measured values of N consecutive task execution cycles before the current task execution cycle of the main control system.
7. A backup control system for a flexible DC project, the backup control system being used to interact with a main control system of the flexible DC project, receiving an operating status sent by the main control system and an integral of a positive sequence component of a q-axis grid voltage of the main control system, characterized in that: When the main control system operates abnormally and switches to the backup control system, the backup control system calculates the phase angle value output by the backup control system based on the integral of the positive-sequence component of the q-axis grid voltage of the main control system and the proportional amount of the positive-sequence component of the q-axis grid voltage of the backup control system, the angular frequency of the previous task execution cycle and the current task execution cycle of the backup control system, and performs real-time control of the flexible DC project based on the phase angle value output by the backup control system; the current task execution cycle of the backup control system is the average value of the actual measured values of N consecutive task execution cycles before the current task execution cycle of the backup control system.
8. The flexible DC engineering backup control system according to claim 7 is characterized in that: The backup control system also receives the phase angle value output by the main control system; when the main control system operates normally and the moment the main control system switches to the backup control system, the phase angle value used by the backup control system when performing phase-locked loop calculation is the phase angle value output by the main control system.
9. The flexible DC engineering backup control system according to claim 7 is characterized in that: The backup control system also receives the phase angle value output by the main control system; when the main control system operates normally and at the moment when the main control system switches to the backup control system, the phase angle value used by the backup control system when performing phase-locked loop calculation is the sum of the phase angle value output by the main control system and the phase angle compensation value, and the phase angle compensation value is determined based on the real-time communication delay between the main control system and the backup control system.
10. A flexible DC phase-locked loop redundant synchronous control device, comprising a main control system and a backup control system of a flexible DC project, characterized in that: The main control system and the backup control system of the flexible DC project adopt the flexible DC phase-locked loop redundant synchronization control method as described in any one of claims 1 to 5 to realize redundant synchronization control of the flexible DC phase-locked loop.