A flexible DC control link delay compensation method and system

Abstract

The present invention relates to a flexible direct current control link delay compensation method and system, which collects the simulated grid-side three-phase grid voltage by setting a primary electrical circuit simulation device, a secondary control protection device, and a secondary valve control device, and calculates the delay phase difference of the control link according to the three-phase grid voltage, converts it into the delay angle of the flexible direct current control link, and then performs corresponding angle compensation on the phase-locked loop. The technical solution provided by the present invention calculates the actual delay phase difference of the control link by transforming and inversely transforming the coordinate system of the three-phase grid voltage, and converts it into the delay angle of the flexible direct current control link, and then performs corresponding angle compensation on the phase-locked loop, which has the characteristics of real-time and high stability, can ensure the normal and stable operation of the AC power grid system and the flexible direct current transmission system, thereby improving the stability and reliability of the flexible direct current transmission system.

Description

Technical Field

[0001] This invention relates to the field of flexible DC transmission technology, and in particular to a method and system for delay compensation of flexible DC control links. Background Technology

[0002] High-voltage direct current (VSC-HVDC) transmission systems based on voltage source converters have the advantages of not requiring AC voltage compensation, eliminating commutation failure issues, providing power to passive systems, simultaneously and independently regulating active power and AC voltage, exhibiting low harmonic levels, and being suitable for constructing multi-terminal DC systems. With the rapid development of clean energy power generation technologies such as wind power and solar power, VSC-HVDC, as a new type of power transmission technology, is being widely used in current practical engineering projects.

[0003] In the VSC-HVDC system, the secondary control and protection device performs closed-loop control by acquiring electrical signals from the primary system and outputting reference values ​​for the voltage of each bridge arm to the valve control system. Then, it sends switching commands for the power modules of each bridge arm to the converter valve in pulse form, completing the closed-loop control function of the flexible DC system. In the entire system control loop, there is inevitably a link delay issue in the control command calculation; therefore, how to test and compensate for link delay is a crucial technical problem that needs to be solved in flexible DC control systems. Summary of the Invention

[0004] Based on the above-mentioned situation of the prior art, the purpose of the present invention is to provide a flexible DC control link delay compensation method and system. By using a control link delay detection system, the delay time of the control link is determined, converted into the delay angle of the flexible DC control link, and then the phase-locked loop is compensated accordingly.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for delay compensation of a flexible DC control link is provided, comprising the steps of:

[0006] S1, Simulated three-phase grid voltage on the grid side;

[0007] S2. Collect the simulated three-phase grid voltage U on the grid side. a U b U c Perform phase-locked loop (PLL) calculations to ensure that the PLL output phase θ is related to U. a Phase synchronization; where the positive-sequence q-axis component u q+ The control quantity is 0, and the preset phase compensation angle is 0.

[0008] S3. Perform coordinate transformation on the three-phase grid voltage to obtain the positive and negative sequence dq axis components u in the synchronous rotating coordinate system.d+ u q+ u d- u q- ;

[0009] S4. Perform an inverse coordinate transformation using the positive and negative sequence dq axis components to obtain the three-phase reference voltage V of the converter valve. a V b V c ;

[0010] S5, based on the three-phase reference voltage V of the converter valve a V b V c The voltage reference value V of the lower bridge arm of the converter valve was calculated. an V bn V cn ;

[0011] S6. Based on the voltage reference value V of the lower bridge arm of the converter valve. an V bn V cn The number N of the power modules switched on the lower arm was calculated. an N bn N cn ;

[0012] S7. Based on the number N of power modules switched on the lower arm. an N bn N cn The actual voltage value V′ of the lower bridge arm was calculated. an V′ bn V′ cn ;

[0013] S8. Based on the actual value of the A-phase voltage of the lower bridge arm, calculate the delay phase difference Δω of the control link:

[0014] Δω=2πfΔt

[0015] Where Δt is the simulated grid-side A-phase grid voltage U. a The time difference between the calculated zero-crossing point of phase A voltage in the lower arm of the converter valve and the measured value, where f is the rated frequency of the three-phase grid voltage on the grid side;

[0016] S9. Use the delayed phase difference Δω as the phase compensation angle in step S3 to perform phase compensation.

[0017] Furthermore, the coordinate system transformation of the three-phase power grid voltage includes αβ transformation, extraction of positive and negative sequence αβ components, and dq transformation.

[0018] Furthermore, the inverse coordinate system transformation using the dq axis components includes employing both the inverse dq transformation and the inverse αβ transformation.

[0019] Furthermore, the three-phase reference voltage V of the converter valve... a V b V c The voltage reference value V of the lower bridge arm of the converter valve was calculated. an V bn V cn include:

[0020]

[0021]

[0022]

[0023] Among them, U dc This is the rated DC voltage.

[0024] Furthermore, the voltage reference value V of the lower bridge arm of the converter valve is used. an V bn V cn The number N of the power modules switched on the lower arm was calculated. an N bn N cn include:

[0025]

[0026]

[0027]

[0028] Among them, U sm This refers to the rated voltage of the power module.

[0029] Furthermore, the number N of power modules switched according to the lower arm... an N bn N cn The actual voltage value V′ of the lower bridge arm was calculated. an V′ bn V′ cn include:

[0030] V′ an =N an *U sm

[0031] V′ bn =N bn *U sm

[0032] V′ cn =N cn*U sm

[0033] According to a second invention of the present invention, a flexible DC control link delay compensation system is provided, comprising a primary electrical circuit simulation device, a secondary control and protection device, and a secondary valve control device; wherein,

[0034] The primary electrical circuit simulation device is used to simulate the three-phase grid voltage on the grid side; and based on the number of lower arm switching power modules input by the secondary valve control device, it calculates the actual voltage value of the lower arm, and then calculates the delay phase difference of the control link.

[0035] The secondary control and protection device is connected to the primary electrical circuit simulation device to collect the simulated three-phase grid voltage on the grid side, and to calculate based on the three-phase grid voltage to generate the phase of the A-phase grid voltage and calculate the voltage reference value of the lower bridge arm of the converter valve.

[0036] The secondary valve control device is connected to the secondary control and protection device and the primary electrical circuit simulation device respectively. It is used to calculate the number of power modules to be switched on the lower bridge arm based on the voltage reference value of the lower bridge arm of the converter valve, and output it to the primary electrical circuit simulation device.

[0037] Furthermore, the secondary control and protection device includes an electrical quantity acquisition module, a phase-locked loop control module, inner and outer loop control modules, and a bridge arm voltage reference value calculation module; wherein,

[0038] The electrical quantity acquisition module is used to acquire the simulated grid-side three-phase grid voltage and perform coordinate system transformation on the three-phase grid voltage to obtain the positive and negative sequence dq axis components in the synchronous rotating coordinate system.

[0039] The phase-locked loop control module is used to perform phase-locked loop calculations and output the phase angle θ and U. a Phase synchronization; where the positive-sequence q-axis component u q+ The control quantity is 0, and the preset phase compensation angle is 0.

[0040] The inner and outer loop control modules are used to perform coordinate system inverse transformation using positive and negative sequence dq axis components to obtain the three-phase reference voltage of the converter valve.

[0041] The bridge arm voltage reference value calculation module is used to calculate the voltage reference value of the lower bridge arm of the converter valve based on the three-phase reference voltage of the converter valve.

[0042] Furthermore, the primary electrical circuit simulation device calculates the delay phase difference of the control link based on the number of lower bridge arm switching power modules input by the secondary valve control device, including:

[0043] The actual voltage value of the lower bridge arm is calculated based on the number of power modules switched on the lower bridge arm.

[0044] Based on the actual voltage value of the lower bridge arm, the delay phase difference Δω of the control link is calculated:

[0045] Δω=2πfΔt

[0046] Where Δt is the measured time difference between the simulated grid-side A-phase grid voltage and the zero-crossing point of the converter valve lower arm A-phase voltage, and f is the rated frequency of the grid-side three-phase grid voltage.

[0047] Furthermore, the primary electrical circuit simulation device outputs the delayed phase difference Δω to the phase-locked loop control module, so as to use the delayed phase difference Δω as the phase compensation angle for phase compensation.

[0048] In summary, this invention provides a method and system for delay compensation in flexible DC control links. By setting up a primary electrical circuit simulation device, a secondary control and protection device, and a secondary valve control device, the simulated three-phase grid voltage is collected. The delay phase difference of the control link is calculated based on this three-phase grid voltage, converted into the delay angle of the flexible DC control link, and then correspondingly compensated for the angle of the phase-locked loop (PLL). The technical solution provided by this invention, through coordinate system transformation and inverse transformation of the three-phase grid voltage, calculates the actual delay phase difference of the control link and converts it into the delay angle of the flexible DC control link, thereby performing corresponding angle compensation for the PLL. This method features high real-time performance and stability, ensuring the normal and stable operation of both the AC grid system and the flexible DC transmission system, thus improving the stability and reliability of the flexible DC transmission system. Attached Figure Description

[0049] Figure 1 This is a flowchart of the flexible DC control link delay compensation method of the present invention;

[0050] Figure 2 This is a block diagram of the flexible DC control link delay compensation system of the present invention. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0052] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings. According to one embodiment of the present invention, a method for delay compensation of a flexible DC control link is provided, the flowchart of which is shown below. Figure 1 As shown, it includes the following steps:

[0053] S1, Simulated three-phase grid voltage on the grid side;

[0054] S2. Collect the simulated three-phase grid voltage U on the grid side. a U b U c Perform phase-locked loop (PLL) calculations to ensure that the PLL output phase θ is related to U. a Phase synchronization; where the positive-sequence q-axis component u q+ The control quantity is 0, and the preset phase compensation angle is 0.

[0055] S3. Perform coordinate transformation on the three-phase grid voltage to obtain the positive and negative sequence dq axis components u in the synchronous rotating coordinate system. d+ u q+ u d- u q- The simulated three-phase grid voltage U on the grid side was collected. a U b U c Furthermore, a coordinate system transformation is performed on the three-phase grid voltage to obtain the positive and negative sequence dq axis components u in the synchronous rotating coordinate system. d+ u q+ u d- u q- The coordinate system transformation can be achieved through methods such as αβ transformation, extraction of positive and negative αβ components, and dq transformation. In this embodiment, the positive and negative dq axis components can be calculated using the following formula:

[0056]

[0057]

[0058] The output phase angle θ is obtained from S2.

[0059] S4. Perform an inverse coordinate transformation using the positive and negative sequence dq axis components to obtain the three-phase reference voltage V of the converter valve. a V b V c Inverse coordinate system transformation can be achieved using methods such as inverse dq transformation and inverse αβ transformation. In this embodiment, the inverse coordinate system transformation can be performed according to the following formula:

[0060]

[0061] S5, based on the three-phase reference voltage V of the converter valve a V b V c The voltage reference value V of the lower bridge arm of the converter valve was calculated. an V bn V cn ;

[0062]

[0063]

[0064]

[0065] Among them, U dc This is the rated DC voltage.

[0066] S6. Based on the voltage reference value V of the lower bridge arm of the converter valve. an V bn U cn The number N of the power modules switched on the lower arm was calculated. an N bn N cn ;

[0067]

[0068]

[0069]

[0070] Among them, U sm This refers to the rated voltage of the power module.

[0071] S7. Based on the number N of power modules switched on the lower arm. an N bn N cn The actual voltage value V′ of the lower bridge arm was calculated. an V′ bn V′ cn include:

[0072] V′ an =N an *U sm

[0073] V′ bn =N bn *U sm

[0074] V′ cn =N cn *U sm

[0075] S8. Based on the actual value of phase A voltage of the lower bridge arm, compare it with the grid voltage U of phase A on the grid side. a The calculated voltage V′ of phase A of the lower bridge arm of the converter valve an The delay phase difference Δω of the control link is calculated as follows:

[0076] Δω=2πfΔt

[0077] Where Δt is the simulated grid-side A-phase grid voltage U. a The calculated voltage V′ of phase A of the lower bridge arm of the converter valve an The time difference measurement at the zero crossing point, where f is the rated frequency of the three-phase grid voltage on the grid side;

[0078] S9. Use the delayed phase difference Δω as the phase compensation angle in step S3 to perform phase compensation.

[0079] According to another embodiment of the present invention, a flexible DC control link delay compensation system is provided, the block diagram of which is shown below. Figure 2 As shown, it includes a primary electrical circuit simulation device, a secondary control and protection device, and a secondary valve control device.

[0080] The primary electrical circuit simulation device is used to simulate the three-phase grid voltage on the grid side; and based on the number of lower arm switching power modules input by the secondary valve control device, it calculates the actual voltage value of the lower arm, and then calculates the delay phase difference of the control link. Specifically, this includes:

[0081] The actual voltage value of the lower bridge arm is calculated based on the number of power modules switched on the lower bridge arm.

[0082] Based on the actual voltage value of the lower bridge arm, the delay phase difference Δω of the control link is calculated:

[0083] Δω=2πfΔt

[0084] Where Δt is the simulated grid-side A-phase grid voltage U. a The calculated voltage V′ of phase A of the lower bridge arm of the converter valve an The time difference measurement at the zero crossing point, where f is the rated frequency of the three-phase grid voltage on the grid side;

[0085] The primary electrical circuit simulation device outputs the delayed phase difference Δω to the phase-locked loop control module, so as to use the delayed phase difference Δω as the phase compensation angle for phase compensation.

[0086] This primary electrical circuit simulation device, for example, can be implemented using real-time digital simulation (RTDS) or RTLAB devices. It has the function of simulating the primary electrical circuit of a flexible DC system and has a complete optical / electrical interface, which can realize the conversion of different communication protocols and the input and output of electrical quantities.

[0087] The secondary control and protection device is connected to the primary electrical circuit simulation device to acquire the simulated three-phase grid voltage on the grid side. Based on this voltage, calculations are performed to generate the phase of the A-phase grid voltage and to calculate the voltage reference value of the lower arm of the converter valve. This secondary control and protection device has complete flexible DC secondary control and protection functions, enabling the control and protection of flexible DC systems. It also features an optical / electrical interface for converting between different communication protocols and for data input / output.

[0088] The secondary valve control device is connected to both the secondary control and protection device and the primary electrical circuit simulation device. It calculates the number of power modules to be switched on the lower bridge arm based on the voltage reference value of the lower bridge arm of the converter valve and outputs this calculation to the primary electrical circuit simulation device. This secondary valve control device has a voltage equalization function for each bridge arm power module, calculating the number of power modules to be switched on the lower bridge arm from the lower bridge arm voltage reference value and issuing switching pulses for the lower bridge arm power modules.

[0089] Furthermore, the secondary control and protection device includes an electrical quantity acquisition module, a phase-locked loop control module, inner and outer loop control modules, and a bridge arm voltage reference value calculation module.

[0090] The electrical quantity acquisition module is used to acquire the simulated three-phase grid voltage and perform coordinate transformation on the three-phase grid voltage to obtain the positive and negative sequence dq axis components in a synchronous rotating coordinate system. This electrical quantity acquisition module has either a dielectric acquisition port or an optical dielectric acquisition port, and mainly completes the acquisition of grid-side voltage electrical quantity signals, performing functions such as analog-to-digital conversion, per-unit conversion, positive and negative sequence extraction, and dq transformation. The converted digital signals are then sent to the phase-locked loop control and inner / outer loop control modules via the PCIe high-speed backplane bus.

[0091] The phase-locked loop (PLL) control module is used to perform PLL calculations using the positive-sequence q-axis component of the three-phase grid voltage, with a preset phase compensation angle of 0, to generate the phase of the A-phase grid voltage. This PLL control module uses the positive-sequence q-axis component of the grid voltage as the reference synchronization voltage for phase locking. It calculates the grid voltage tracking angular frequency error through a PLL-controlled PI controller, compensates for the sampling delay using PLL phase compensation, and sends the phase information to the electrical quantity acquisition module and the inner and outer loop control modules via the PCIe high-speed backplane bus.

[0092] The inner and outer loop control modules are used to perform inverse coordinate transformation using the positive and negative sequence dq axis components to obtain the three-phase reference voltage of the converter valve. These modules are also used to calculate the inner loop current control reference value required for the inner loop current control by outputting the outer loop power control calculation. The inner loop current control is decoupled from the inner loop current PI controller, calculates the three-phase reference voltage of the converter valve, and sends it to the bridge arm voltage reference value calculation module via the PCIe high-speed backplane bus.

[0093] The bridge arm voltage reference value calculation module is used to calculate the voltage reference value of the lower bridge arm of the converter valve based on the three-phase reference voltage of the converter valve. This module calculates the lower bridge arm voltage reference value of the converter valve by modulating the three-phase reference voltage, and simultaneously sends the control and protection interlocking signals to the secondary valve control device via a high-speed optical fiber.

[0094] The other specific processes by which each module in the device performs its function are the same as the steps of the fault location method in the first embodiment of the present invention, and will not be repeated here.

[0095] In summary, this invention relates to a method and system for delay compensation in a flexible DC control link. By setting up a primary electrical circuit simulation device, a secondary control and protection device, and a secondary valve control device, the simulated three-phase grid voltage is collected. The delay phase difference of the control link is calculated based on this three-phase grid voltage, converted into the delay angle of the flexible DC control link, and then correspondingly compensated for the angle of the phase-locked loop (PLL). The technical solution provided by this invention, through coordinate system transformation and inverse transformation of the three-phase grid voltage, calculates the actual delay phase difference of the control link and converts it into the delay angle of the flexible DC control link, thereby performing corresponding angle compensation for the PLL. This method features high real-time performance and stability, ensuring the normal and stable operation of both the AC grid system and the flexible DC transmission system, thus improving the stability and reliability of the flexible DC transmission system.

[0096] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0097] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0098] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0099] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the invention.

Claims

1. A method for compensating delay of a flexible DC control link, characterized in that: Includes steps: S1, simulate the three-phase grid voltage on the grid side; S2, collect the simulated grid-side three-phase grid voltage U a , U b , U c , perform phase-locked loop calculation so that the phase-locked loop output phase θ is equal to U a Phase synchronization; where the positive sequence q-axis component u q+ The control amount is 0, and the preset phase compensation angle is 0; S3, transform the coordinate system of the three-phase grid voltage to obtain the positive and negative sequence dq axis components u in the synchronous rotating coordinate system d+ 、u q+ 、u d- 、u q- ; S4. Use the positive and negative sequence dq axis components to perform inverse coordinate transformation to obtain the three-phase reference voltage V of the converter valve. a 、V b 、V c ; S5, according to the three-phase reference voltage V a 、V b 、V c , calculate the voltage reference value V of the lower bridge arm of the converter valve an 、V bn 、V cn ; S6, according to the voltage reference value V of the lower bridge arm of the converter valve an 、V bn 、V cn , calculate the number of lower arm switching power modules N an 、N bn 、N cn ; S7, according to the number N of power modules switched on and off in the lower bridge arm an 、N bn 、N cn , calculate the actual voltage value V' of the lower bridge arm an 、V' bn 、V' cn ; S8. According to the actual value of the A-phase voltage of the lower bridge arm, the delay phase difference Δω of the control link is calculated: Δω=2πfΔt Among them, Δt is the simulated grid-side A phase grid voltage U a The measured value of the time difference between the calculated zero-crossing point of the A-phase voltage of the lower bridge arm of the converter valve, and f is the rated frequency of the three-phase grid voltage on the grid side; S9, using the delayed phase difference Δω as the phase compensation angle in step S3 to perform phase compensation.

2. The method according to claim 1, characterized in that The coordinate system transformation of the three-phase grid voltage includes adopting αβ transformation, positive and negative sequence αβ component extraction, and dq transformation.

3. The method according to claim 2, characterized in that The inverse transformation of the coordinate system using the dq axis components includes using dq inverse transformation and αβ inverse transformation.

4. The method according to claim 3, characterized in that The three-phase reference voltage V of the converter valve a 、V b 、V c , calculate the voltage reference value V of the lower bridge arm of the converter valve an 、V bn 、V cn include: Among them, U dc is the DC voltage rating.

5. The method according to claim 4, characterized in that The voltage reference value V of the lower bridge arm of the converter valve an 、V bn 、V cn , calculate the number of lower arm switching power modules N an 、N bn 、N cn include: Among them, U sm is the power module voltage rating.

6. The method according to claim 5, characterized in that The number N of power modules switched on and off according to the lower bridge arm an 、N bn 、N cn , calculate the actual voltage value V' of the lower bridge arm an 、V' bn 、V' cn include: V′ an =N an *U sm V′ bn =N bn *U sm V′ cn =N cn *U sm 。 7. A flexible DC control link delay compensation system for implementing the flexible DC control link delay compensation method according to any one of claims 1 to 6, characterized in that: It includes a primary electrical circuit simulation device, a secondary control protection device, and a secondary valve control device; wherein, The primary electrical circuit simulation device is used to simulate the three-phase grid voltage on the grid side; and according to the number of the lower bridge arm switching power modules input by the secondary valve control device, the actual voltage value of the lower bridge arm is calculated, and then the delay phase difference of the control link is calculated; The secondary control protection device is connected to the primary electrical circuit simulation device, and is used to collect the simulated grid-side three-phase grid voltage, and perform calculations based on the three-phase grid voltage to generate the phase of the A-phase grid voltage and calculate the voltage reference value of the lower bridge arm of the converter valve; The secondary valve control device is connected to the secondary control protection device and the primary electrical circuit simulation device respectively, and is used to calculate the number of power modules switched on and off in the lower bridge arm according to the voltage reference value of the lower bridge arm of the converter valve, and output it to the primary electrical circuit simulation device.

8. The system according to claim 7, characterized in that The secondary control protection device includes an electrical quantity acquisition module, a phase-locked loop control module, an inner and outer loop control module, and a bridge arm voltage reference value calculation module; wherein, The electrical quantity acquisition module is used to acquire the simulated grid-side three-phase grid voltage and perform coordinate system transformation on the three-phase grid voltage to obtain positive and negative sequence dq axis components in a synchronous rotating coordinate system; The phase-locked loop control module is used to perform phase-locked loop calculations to complete the output phase angle θ and U a Phase synchronization; where the positive sequence q-axis component u q+ The control amount is 0, and the preset phase compensation angle is 0; The inner and outer loop control modules are used to perform inverse coordinate transformation using positive and negative sequence dq axis components to obtain a three-phase reference voltage for the converter valve; The bridge arm voltage reference value calculation module is used to calculate the voltage reference value of the lower bridge arm of the converter valve according to the three-phase reference voltage of the converter valve.

9. The system according to claim 8, characterized in that The primary electrical circuit simulation device calculates the delay phase difference of the control link according to the number of lower bridge arm switching power modules input by the secondary valve control device, including: According to the number of power modules switched on and off in the lower bridge arm, the actual voltage value of the lower bridge arm is calculated; According to the actual voltage value of the lower bridge arm, the delay phase difference Δω of the control link is calculated: Δω=2πfΔt Wherein, Δt is the measured value of the time difference between the simulated grid-side A-phase grid voltage and the zero-crossing point of the A-phase voltage of the lower bridge arm of the converter valve, and f is the rated frequency of the grid-side three-phase grid voltage.

10. The system according to claim 9, characterized in that The primary electrical circuit simulation device outputs the delayed phase difference Δω to the phase-locked loop control module, so as to use the delayed phase difference Δω as a phase compensation angle for phase compensation.

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