SLCC dynamic adaptive harmonic compensation control method, system, device and medium

Abstract

The invention discloses an SLCC dynamic self-adaptive harmonic compensation control method, system and equipment and a medium. The method comprises the following steps: acquiring a three-phase alternating current on a common coupling point of a commutation converter and a static var filter device, a three-phase alternating current on a bridge arm branch of the static var filter device and a fundamental frequency control voltage of a fundamental frequency reactive power control loop; based on the number of converter valve pulses, extracting the three-phase alternating current on the common coupling point and the three-phase alternating current on the bridge arm branch to obtain a specified subharmonic suppression current instruction and a specified subharmonic suppression voltage; calculating based on the specified subharmonic suppression voltage and the fundamental frequency control voltage to obtain a bridge arm modulation voltage of the static var filter device; harmonic compensation is carried out on the multi-source self-adaptive commutation direct current sending-out system based on the bridge arm modulation voltage; the harmonic current generated by the common point can be eliminated through extraction and suppression of the harmonic current of the common point, the power quality of grid connection of the direct-current converter valve is remarkably improved, and the precision and stability of harmonic compensation are improved.

Description

Technical Field

[0001] The present application relates to the field of direct current transmission technology, and in particular to a SLCC dynamic adaptive harmonic compensation control method, system, device and medium. Background Art

[0002] With the development of power grid construction and new technologies, high-voltage direct current transmission is a necessary means to assist the construction of new power systems. Conventional high-voltage direct current (LCC-HVDC) technology is mature and has low construction costs. It is the main force for large-scale long-distance power transmission at this stage. However, LCC converter valves are highly dependent on AC commutation voltage and there is a risk of continuous commutation failure. The impact of commutation failure and even DC locking is increasing, posing a serious threat to the safe and stable operation of the power grid.

[0003] Static Var Generator (SVG) is widely used in the export side of wind farms / photovoltaic power stations due to its good reactive output characteristics, fast action response speed, and low working loss. It is used to adjust the power factor of the power grid, suppress the unbalanced voltage at the common connection point, and the low voltage ride-through capability of new energy power stations. SVG is similar to VSC converter valve in topology and working principle, and the main difference is the way the command current is generated. When the capacity is met, based on a certain control strategy, SVG can track reactive power commands and current commands at the same time to achieve the purpose of taking into account reactive power compensation and harmonic suppression. SVG's flexible and efficient reactive power compensation and harmonic suppression capabilities just make up for the technical shortcomings of LCC-HVDC systems, but existing projects and research have not yet found the perfect combination of SVG and LCC-HVDC systems, and cannot give full play to the technical potential of SVG.

[0004] Taking the back-to-back interconnection project as an example, although the solution of configuring SVG on the grid side of the converter transformer can provide reactive power support and reduce the harmonic content of the grid-side current, it is difficult to solve the problem of reduced life caused by the vibration and noise caused by the long-term flow of harmonic current in the converter transformer. If SVG with sufficient capacity is configured on the valve side of the converter transformer of the LCC-HVDC system, and a new converter valve of SVG-LCC (referred to as SLCC) is constructed, the reactive power shortage of the system can be supplemented, the grid voltage can be stabilized, the acceptance capacity of the sending-end system for weak grids can be improved, and the probability of commutation failure in the receiving-end system can be reduced. It can also eliminate the harmonic current flowing through the converter transformer, reduce the loss, temperature rise and vibration of the converter transformer, and improve the life of the equipment. It is a feasible solution to solve the large-scale transmission of new energy at this stage.

[0005] The UHV DC converter valve is the core equipment of the UHV DC transmission project and the core functional unit for realizing AC / DC power conversion. Figure 1As shown. Each bridge arm of the UHV converter is a single valve (valve arm). For application scenarios corresponding to different voltage levels, 6-pulse converters and 12-pulse converters can be used, and the corresponding valve tower structure can be a double valve structure or a quadruple valve structure.

[0006] The thyristor level is the basic unit of the electrical structure of the DC commutation valve, including thyristors, damping absorption circuits, gate units, etc. Among them, the damping absorption circuit is used to suppress circuit oscillations during valve turn-on and turn-off processes, and to achieve voltage equalization distribution of the valve chain structure. The gate unit is the conversion center between the primary circuit and the valve base electronic equipment, and is used to realize triggering, monitoring and protection of the thyristor level, etc. A typical schematic diagram of the thyristor level away from the structure is as Figure 2 shown. In the figure, Thy is the thyristor; R dc is the voltage equalizing resistor; R d is the damping resistor; C d is the damping capacitor.

[0007] The SVG structure is similar to the flexible DC commutation valve and is designed with a full-bridge cascaded chain structure. Figure 3 is a schematic diagram of the main circuit topology of the three-phase module SVC. In the figure, L is the connection reactance; SM is the full-bridge sub-module.

[0008] Different from the structure of the MMC commutation valve where each phase contains upper and lower two bridge arms, each phase of the SVG has only one bridge arm. Each bridge arm is composed of multiple independently controlled sub-modules connected in series. Each sub-module is equivalent to a controlled two-level voltage source. By selecting the number of conducting sub-modules, different voltage values can be generated. Therefore, each bridge arm can be equivalent to a controlled multi-level voltage source. The outer loop characteristic of the SVG is the characteristic of the voltage source converter, which can operate in four quadrants and can flexibly control the reactive power generation and absorption. The SVG can independently control an active electrical quantity and a reactive electrical quantity at the same time. Among them, the active physical quantities include DC voltage, DC current and AC frequency, and the reactive physical quantities include reactive power and AC voltage. The common basic control modes of the commutation station mainly include three types: constant power (PQ) control, constant DC voltage control and voltage droop control, as Figure 4 shown. In the figure, U dc is the DC voltage, and P dc is the active power.

[0009] In addition, the SVG controller can directly track the grid-side harmonics and send out corresponding harmonic currents to reduce the harmonic pollution of the AC power grid during the LCC commutation process.

[0010] The multi-source adaptive commutation converter (Statcom and Line Commutation Converter, SLCC) technology connects a static var filter (Stataic Var Filter, SVF) between a six-pulse (or twelve-pulse) line commutation converter (LCC) and a commutation transformer. The SVF compensates for the reactive power consumed by the LCC and the harmonic current generated by the LCC, and can replace the AC filter / parallel capacitor bank in conventional DC transmission, saving the floor area of the converter station and reducing the noise and losses of the commutation transformer. The SVF is connected to the valve side of the commutation transformer through a reactor. The topology of the SVF is a three-phase star connection without grounding or a delta connection, and its commutation chain is composed of multiple links (sub-modules) connected in series. The structure of the sub-module is an H-shaped full-bridge structure.

[0011] Currently, the large-capacity active filter devices applied in DC converter stations basically use current harmonics as the control target. The device detects the amplitude and phase of the harmonic load current generated by the commutation valve branch, and the control device emits harmonics with the same amplitude and opposite phase, and tries to control the harmonic current at the control point to the minimum as much as possible to reduce the harmonic current content at the common point. However, with the changes in the operation mode and power flow of the LCC, the harmonic current content at each harmonic of the control point will change at any time. When the real-time change rate is large, the open-loop control method with phase inversion has problems such as difficult parameter setting of the compensation link, slow dynamic adjustment response, and poor compensation effect.

[0012] The patent application with the application number CN118432119A and the name "A Method, Medium, Control Device and System for SLCC Reactive Power Control" solves the technical problem in the prior art that under the same working conditions, the change amount of the valve side voltage of the SLCC commutation transformer is larger than that of the conventional LCC, which may cause the tap changer to repeatedly act on two adjacent gears after the commutation transformer increases or decreases the power, resulting in an increase in the failure rate of the commutation transformer. However, it does not propose a specific control method for suppressing the harmonic current generated by the LCC.

[0013] The patent application with the application number CN109193658B and the name "A Method for Compensating Harmonic Current Using an Active Power Filter" reduces the device component losses during the harmonic compensation process. However, this method is only applicable to the AC network side and cannot achieve the same harmonic compensation effect on the valve side of the commutation transformer. Moreover, it adds a DCDC boost transient wave circuit, increasing the device cost and floor area.

[0014] Insensitive harmonic compensation will directly bring problems such as fluctuations in the losses of the commutation transformer and unstable AC power quality after the commutation valve inversion. Large fluctuations in the harmonic content will also cause fluctuations in the noise and losses of other primary equipment in the converter station, which is not conducive to the selection and design of primary equipment.

[0015] Therefore, how to improve the harmonic compensation accuracy and stability is an urgent problem to be solved at present. Summary of the Invention

[0016] In order to solve the problem of how to improve the harmonic compensation accuracy and stability in the prior art, this application proposes a SLCC dynamic adaptive harmonic compensation control method, including:

[0017] Collect the three-phase AC currents at the common coupling point of the phase-commutated converter and the static var filter in the multi-source adaptive phase-commutated HVDC transmission system, the three-phase AC currents on the arm branches of the static var filter, and the fundamental frequency control voltage of the fundamental frequency reactive power control loop;

[0018] Based on the number of commutation valve pulses of the phase-commutated converter, extract the three-phase AC currents at the common coupling point and the three-phase AC currents on the arm branches to obtain the specified harmonic suppression current command and the specified harmonic suppression voltage;

[0019] Calculate the arm modulation voltage of the static var filter based on the specified harmonic suppression voltage and the fundamental frequency control voltage;

[0020] Perform harmonic compensation on the multi-source adaptive phase-commutated HVDC transmission system based on the arm modulation voltage of the static var filter.

[0021] Preferably, the step of extracting the three-phase AC currents at the common coupling point and the three-phase AC currents on the arm branches based on the number of commutation valve pulses of the phase-commutated converter to obtain the specified harmonic suppression current command and the specified harmonic suppression voltage includes:

[0022] Based on the number of commutation valve pulses of the phase-commutated converter, extract the three-phase AC currents at the common coupling point to obtain the specified harmonic suppression current command;

[0023] Calculate the specified harmonic suppression voltage by combining the specified harmonic current component extracted from the three-phase AC currents on the arm branches with the specified harmonic suppression current command.

[0024] Preferably, the step of extracting the three-phase AC currents at the common coupling point based on the number of commutation valve pulses of the phase-commutated converter to obtain the specified harmonic suppression current command includes:

[0025] Determine the harmonic current order based on the number of commutation valve pulses of the phase-commutated converter;

[0026] Extract the harmonic current component of the specified order from the three-phase AC currents at the common coupling point based on the harmonic current order;

[0027] After comparing the specified sub-harmonic current component with the zero current, a specified sub-harmonic suppression current command is generated through a PI controller;

[0028] Based on the specified sub-harmonic suppression current command, a corresponding harmonic modulation wave is generated for harmonic suppression.

[0029] Preferably, the extraction of the three-phase alternating current at the common coupling point based on the harmonic current order to obtain the specified sub-harmonic current component includes:

[0030] After performing a synchronous rotating coordinate transformation of the corresponding harmonic current order on the three-phase alternating current at the common coupling point, the alternating current after the synchronous rotating coordinate transformation is obtained;

[0031] The alternating current after the synchronous rotating coordinate transformation is extracted using a low-pass filter to obtain the specified sub-harmonic current component.

[0032] Preferably, the specified sub-harmonic suppression voltage is obtained by calculating the specified sub-harmonic current component extracted based on the three-phase alternating current on the bridge arm branch in combination with the specified sub-harmonic suppression current command, including:

[0033] Based on the harmonic current order, the three-phase alternating current on the bridge arm branch is extracted to obtain the specified sub-harmonic current component;

[0034] Based on the result of comparing the specified sub-harmonic current component with the specified sub-harmonic suppression current command, after passing through a correction controller, a synchronous rotating coordinate inverse transformation is performed to obtain the specified sub-harmonic suppression voltage.

[0035] Preferably, the calculation of the bridge arm modulation voltage of the static var filtering device based on the specified sub-harmonic suppression voltage and the fundamental frequency control voltage includes:

[0036] The total harmonic suppression voltage is obtained by adding the specified sub-harmonic suppression voltages;

[0037] The bridge arm modulation voltage of the static var filtering device is obtained by adding the total harmonic suppression voltage and the fundamental frequency control voltage.

[0038] Based on the concept of the same application, the present application also proposes a SLCC dynamic adaptive harmonic compensation control system, including:

[0039] A current extraction module for collecting the three-phase alternating current at the common coupling point of the phase-shifting converter and the static var filtering device in a multi-source adaptive phase-shifting and commutation DC transmission system, the three-phase alternating current on the bridge arm branch of the static var filtering device, and the fundamental frequency control voltage of the fundamental frequency reactive power control loop;

[0040] A harmonic current suppression module, which is used to extract the three-phase AC current at the common coupling point and the three-phase AC current on the arm branch based on the number of commutation valve pulses of the commutation converter to obtain a specified harmonic suppression current command and a specified harmonic suppression voltage;

[0041] A modulation voltage generation module, which is used to calculate based on the specified harmonic suppression voltage and the fundamental frequency control voltage to obtain the arm modulation voltage of the static var filter device;

[0042] A harmonic compensation module, which is used to perform harmonic compensation on the multi-source adaptive commutation converter DC transmission system based on the arm modulation voltage of the static var filter device.

[0043] Preferably, the harmonic current suppression module includes:

[0044] A harmonic current suppression sub-module, which is used to extract the three-phase AC current at the common coupling point based on the number of commutation valve pulses of the commutation converter to obtain a specified harmonic suppression current command;

[0045] A harmonic suppression voltage generation sub-module, which is used to calculate based on the harmonic current component of the specified order extracted from the three-phase AC current on the arm branch and combine the specified harmonic suppression current command to obtain a specified harmonic suppression voltage.

[0046] Preferably, the harmonic current suppression sub-module includes:

[0047] A harmonic current order determination unit, which is used to determine the harmonic current order based on the number of commutation valve pulses of the commutation converter;

[0048] A harmonic current extraction unit, which is used to extract the three-phase AC current at the common coupling point based on the harmonic current order to obtain a harmonic current component of the specified order;

[0049] An instruction generation unit, which is used to generate a specified harmonic suppression current command through a PI controller after comparing the harmonic current component of the specified order with zero current;

[0050] A harmonic suppression unit, which is used to generate a corresponding harmonic modulation wave based on the specified harmonic suppression current command for harmonic suppression.

[0051] Preferably, the harmonic current extraction unit is specifically used for:

[0052] After performing a synchronous rotating coordinate transformation of the corresponding harmonic current order on the three-phase AC current at the common coupling point, the AC current after the synchronous rotating coordinate transformation is obtained;

[0053] The AC current after the synchronous rotational coordinate transformation is extracted by a low-pass filter to obtain the harmonic current component of a specified order.

[0054] Preferably, the harmonic suppression voltage generation sub-module is specifically configured to:

[0055] Extract the three-phase AC currents on the arm branches based on the harmonic current order to obtain the harmonic current component of a specified order;

[0056] Based on the result of comparing the harmonic current component of the specified order with the specified order harmonic suppression current command, perform an inverse synchronous rotational coordinate transformation through a correction controller to obtain the specified order harmonic suppression voltage.

[0057] Preferably, the modulation voltage generation module is specifically configured to:

[0058] Add the specified order harmonic suppression voltages to obtain the total harmonic suppression voltage;

[0059] Add the total harmonic suppression voltage and the fundamental frequency control voltage to obtain the arm modulation voltage of the static var filter device.

[0060] On the other hand, the present application also proposes an electronic device, including: at least one processor and a memory; the memory and the processor are connected through a bus;

[0061] The memory is used to store one or more programs;

[0062] When the one or more programs are executed by the at least one processor, the above-mentioned SLCC dynamic adaptive harmonic compensation control method is implemented.

[0063] On the other hand, the present application also proposes a readable storage medium, on which an execution program is stored, and when the execution program is executed, the above-mentioned SLCC dynamic adaptive harmonic compensation control method is implemented.

[0064] Compared with the prior art, the beneficial effects of the present application are:

[0065] A SLCC dynamic adaptive harmonic compensation control method, system, device and medium, including: collecting three-phase AC currents at the common coupling point of the phase-shifting converter and the static var filter device in the multi-source adaptive phase-shifting DC transmission system, three-phase AC currents on the bridge arm branch of the static var filter device, and the fundamental frequency control voltage of the fundamental frequency reactive power control loop; extracting the specified harmonic suppression current command and the specified harmonic suppression voltage from the three-phase AC currents at the common coupling point and the three-phase AC currents on the bridge arm branch based on the number of converter valve pulses of the phase-shifting converter; calculating based on the specified harmonic suppression voltage and the fundamental frequency control voltage to obtain the bridge arm modulation voltage of the static var filter device; performing harmonic compensation on the multi-source adaptive phase-shifting DC transmission system based on the bridge arm modulation voltage of the static var filter device; the extraction and suppression of harmonic currents at the common point in this application can eliminate the harmonic currents generated by the LCC converter valve at the common point, significantly improve the power quality of the DC converter valve connected to the grid, and improve the accuracy and stability of harmonic compensation;

[0066] It is realized through the static var filter device SVF in the SLCC DC transmission system, replacing the filters and capacitor banks on the AC side of the conventional DC converter valve, without increasing the system construction cost and greatly saving the floor area of the converter station. Brief Description of the Drawings

[0067] Figure 1 It is the principle structure diagram of the UHV converter valve of this application;

[0068] Figure 2 It is the electrical schematic diagram of the thyristor level of this application;

[0069] Figure 3 It is the schematic diagram of the main circuit topology of the SVG of this application;

[0070] Figure 4 It is the schematic diagram of the common basic control mode of the VSC-HVDC converter station of this application;

[0071] Figure 5 It is the flowchart of a SLCC dynamic adaptive harmonic compensation control method of this application;

[0072] Figure 6 It is the flowchart of the harmonic compensation control method of this application;

[0073] Figure 7 It is the topology diagram of a SLCC DC transmission system of this application;

[0074] Figure 8 It is the topology diagram of a SLCC DC transmission system of this application;

[0075] Figure 9 It is the schematic diagram of the specified harmonic current extraction module of this application;

[0076] Figure 10 Schematic diagram of the designated sub-harmonic current suppression module for this application;

[0077] Figure 11 Schematic diagram of the designated sub-harmonic suppression voltage generation module for this application;

[0078] Figure 12 Schematic diagram of the modulation voltage generation module for this application;

[0079] Figure 13 Schematic diagram of the simulation waveform at the grid connection point before harmonic current compensation for this application;

[0080] Figure 14 Schematic diagram of the simulation waveform at the grid connection point after harmonic current compensation for this application;

[0081] Figure 15 Structural diagram of a SLCC dynamic adaptive harmonic compensation control system for this application;

[0082] Figure 16 Schematic diagram of a SLCC dynamic adaptive harmonic compensation control system for this application;

[0083] Figure 17 Diagram of an electronic device for this application. Detailed implementation manners

[0084] To ensure the stability and reliability of the connection between the SLCC DC transmission system and the AC power grid, as well as the safety of the converter station equipment operation, a SLCC dynamic adaptive harmonic compensation control method, system, device, and medium are proposed to improve the harmonic compensation accuracy and stability, and effectively enhance the power quality performance of the SLCC grid-connected operation. To better understand this application, the content of this application will be further described below in conjunction with the specification drawings and embodiments.

[0085] Embodiment 1:

[0086] A SLCC dynamic adaptive harmonic compensation control method, the specific process is as Figure 5 shown, including:

[0087] Step 1, collect the three-phase AC current at the common coupling point of the phase converter and the static var filter in the multi-source adaptive phase-converting DC transmission system, the three-phase AC current on the bridge arm branch of the static var filter, and the fundamental frequency control voltage of the fundamental frequency reactive power control loop;

[0088] Step 2, based on the number of thyristor pulses of the phase converter, extract the designated sub-harmonic suppression current command and the designated sub-harmonic suppression voltage from the three-phase AC current at the common coupling point and the three-phase AC current on the bridge arm branch;

[0089] Step 3: Calculate based on the specified sub - harmonic suppression voltage and the fundamental - frequency control voltage to obtain the arm modulation voltage of the static var filter device.

[0090] Step 4: Perform harmonic compensation on the multi - source adaptive commutation - based HVDC transmission system based on the arm modulation voltage of the static var filter device.

[0091] The following Figure 6 illustrates this embodiment in detail with reference to the flowchart of the harmonic compensation control method shown below.

[0092] In Step 1, collect the three - phase AC currents at the common coupling point of the commutation converter and the static var filter device in the multi - source adaptive commutation - based HVDC transmission system, the three - phase AC currents on the arm branches of the static var filter device, and the fundamental - frequency control voltage of the fundamental - frequency reactive - power control loop. Specifically, it includes:

[0093] As Figure 7 and Figure 8 shown, the SLCC HVDC transmission system includes a conventional DC LCC commutation valve, a static var filter valve SVF, a converter transformer, and an AC system connected. The SVF is connected in parallel on the valve side of the converter transformer. The LCC is a six - pulse commutation valve composed of thyristors, which transmits electrical energy to the connected AC system through the converter transformer; the SVF is a three - phase star - connected non - grounded valve composed of full - bridge fully - controlled device modules, which compensates the commutation reactive - power gap during the transmission process of the LCC commutation valve and the characteristic sub - harmonics generated by the LCC valve during the stable operation stage. When the SLCC HVDC transmission system is in steady - state operation, due to the inherent characteristics of the thyristor commutation valve, a large amount of characteristic sub - harmonic currents will be injected into the common coupling point. The harmonic components flowing directly into the converter transformer will lead to increased noise and losses of the converter transformer. By using an optical CT to collect and process the three - phase AC currents at the common point, the dynamic harmonic current compensation control method of this application can effectively reduce the harmonic current components flowing through the converter transformer. In the figure, U sa / U sb / U sc are the phase voltages of the three - phase AC system; A / B / C are the three - phase names of the AC system; n is the neutral point of the AC system; Cell is the full - bridge sub - module; SVF Valve is the single - phase SVF valve arm; L d is the DC filter reactance; P is the active power transmitted by the DC system; i d is the DC current; T1 / T2 / T3 / T4 / T5 / T6 are the LCC thyristor commutation valve arms; i sa / i sb / i sc are the LCC AC - side output line currents; U d is the LCC pole - to - pole DC voltage; A, / B, / C, are the three - phase corresponding terminals on the LCC AC side.

[0094] The control method of this application relies on the SLCC DC converter. Without adding additional equipment such as filter banks and capacitor compensator banks, it can solve the commutation reactive power gap and harmonic governance problems of the LCC converter valve simultaneously, without increasing the construction cost of the SLCC DC transmission system.

[0095] When the SLCC DC transmission system is in steady-state operation, collect the three-phase AC current i at the common coupling point of the LCC on the valve side of the converter transformer and the SVF. pcc and the three-phase AC current i of the SVF bridge arm branch var .

[0096] In step 2, based on the number of pulses of the converter valve of the phase-shifting converter, extract the three-phase AC current at the common coupling point and the three-phase AC current on the bridge arm to obtain the specified harmonic suppression current command and the specified harmonic suppression voltage, which specifically includes:

[0097] According to the number of pulses of the LCC converter valve, extract and suppress the harmonic components of i pcc to generate the specified harmonic suppression current command i href_n :

[0098] According to the number of pulses of the LCC converter valve, determine the characteristic harmonic current orders that need to be suppressed, and select the harmonic current suppression and extraction module corresponding to the harmonic current orders; input the measured common point current i pcc into the corresponding harmonic current suppression and extraction module to extract the harmonic current component of the specified order in the current i pccc . After comparing this component with the zero current, generate the corresponding harmonic suppression current command i href_n through a PI controller.

[0099] Extract the harmonic components of i var and generate the specified harmonic suppression voltage U href according to the command current i href_n :

[0100] Input the measured SVF bridge arm current i var into the harmonic current extraction module of the harmonic current order selected in the second step to extract the harmonic current component of the specified order in the current i var i var _n; after comparing this component with the corresponding harmonic suppression current command i href_n obtained in the second step, generate the specified harmonic suppression voltage U href_n after passing through a correction controller and then through an inverse synchronous rotating coordinate transformation.

[0101] The specified sub - harmonic current extraction includes: inputting the alternating current into the corresponding harmonic current extraction module. After the synchronous rotating coordinate transformation of the corresponding - order harmonics, the harmonic current component of the specified order in the alternating current is transformed into a direct - current component, and the harmonic current component is extracted through a low - pass filter.

[0102] As Figure 9 shown, according to the number of pulses of the LCC converter valve, calculate the harmonic current order to be suppressed. For example, for a six - pulse thyristor converter valve, n is the number of six - pulse thyristor converters, and the main harmonic current orders h on the AC side are h = 6n ± 1, and the main current harmonic orders are the 5th and 7th harmonics; for a twelve - pulse thyristor converter valve, n = 2, and the main current harmonic orders are the 11th and 13th harmonics. By calculating the harmonic current order to be suppressed, a harmonic current extraction module corresponding to the harmonic current order is generated. As Figure 10 shown, input the collected common - point current i PCC and the SVF bridge - arm current i SVF into the harmonic current extraction module. After the above - mentioned current undergoes the specified - order synchronous rotating coordinate transformation, the specified - order harmonic current component is transformed into a DC component, and the remaining current components are still AC components. Then, the DC components of the active and reactive parts of the aforementioned specified - order harmonics are extracted through a low - pass filter. After comparing the specified - order harmonic DC component obtained in the harmonic current extraction module with the zero current, through a PI controller, a harmonic current command of the specified order is generated. In the figure, I d_pcc_hn is the active part of the specified - order harmonic current at the PCC point; I q_pcc_hn is the reactive part of the specified - order harmonic current at the PCC point; I d_SVF_hn is the active part of the specified - order harmonic current of the SVF; I q_SVF_hn is the reactive part of the specified - order harmonic current of the SVF; LPF is the filter; SHS h is the harmonic order; θ is the phase angle of the PCC point; I d_ref_hn is the specified active part of the specified - order harmonic current; I q_ref_hn is the specified reactive part of the specified - order harmonic current; U ref_hn is the specified - order harmonic suppression voltage.

[0103] As Figure 11 shown, compare the harmonic current command of the specified order with the DC component of the harmonic of the corresponding - order bridge - arm current. Through a correction controller, generate the DC component of the harmonic suppression voltage in the corresponding synchronous rotating coordinate system. Finally, after the inverse transformation of the corresponding - order synchronous rotating coordinate, obtain the specified - order harmonic suppression voltage in the three - phase coordinate system; perform the same operation on all harmonic current components to be suppressed to obtain the corresponding specified - order harmonic suppression voltages.

[0104] In step 3, based on the specified sub - harmonic suppression voltage and the fundamental - frequency control voltage, calculate the bridge - arm modulation voltage of the static var filter device, specifically including:

[0105] Based on the above - mentioned specified sub - harmonic suppression voltage, generate a total harmonic suppression voltage, and superimpose it on the fundamental - frequency control voltage to generate the modulation voltage \(U\) of each bridge - arm of the SVF m_a / b / c :

[0106] Add up the specified sub - harmonic suppression voltages generated in the third step to obtain the total harmonic suppression voltage \(U\) href , and superimpose this quantity on the fundamental - frequency control voltage of the fundamental - frequency reactive - power control loop to generate the modulation voltage \(U\) of each phase bridge - arm of the SVF m_a / b / c .

[0107] As Figure 12 shown, add up multiple specified sub - harmonic suppression voltages to obtain the total harmonic suppression voltage, and then superimpose it on the fundamental - frequency control voltage to generate the bridge - arm modulation voltage of the SVF. In this application, the harmonic current extraction and suppression module suppresses the harmonic current at the common point, can eliminate the harmonic current generated by the LCC converter valve at the common point, and significantly improve the power quality of the electric energy flowing from the SLCC converter valve into the AC system connected to the converter transformer. In the figure, \(Q\) PCC is the reactive power at the PCC point; \(Q\) ref is the target reactive power; \(V\) dc_ref is the target DC voltage of the module; \(V\) dc_实测 is the measured DC voltage of the module; \(U\) ref_fc is the fundamental - frequency control voltage; SHS5 is the specified harmonic order; \(U\) ref_hc is the total harmonic suppression voltage; \(U\) ref_abc is the bridge - arm modulation voltage of the SVF

[0108] As Figure 13 shown is the simulation waveform at the common point before harmonic current suppression. There are harmonic currents mainly with 5 / 7 times at the common point, and also contain certain 11 / 13 harmonics. After Fourier analysis, the 5 - th harmonic content is 36%, the 7 - th harmonic content is 26%, the 11 - th harmonic content is 16%, and the 13 - th harmonic content is 14%, which does not meet the standard requirements. Using the harmonic current compensation control method proposed in this application, suppress the 5 / 7 / 11 / 13 - th harmonic currents. The simulation results after suppression are as Figure 14As shown, it can be seen that the harmonic current at the common point is significantly reduced. After Fourier analysis, the 5th harmonic content is 0.3%, the 7th harmonic content is 0.2%, the 11th harmonic content is 0.3%, and the 13th harmonic content is 0.3%, meeting the power quality requirements. In the figure, Inverter, SVF:Graphs is the simulation waveform diagram of the grid connection point before harmonic current compensation; Uac230 is the valve side voltage of the converter transformer; Iac21I is the valve side current of the converter transformer; I_SVF is the SVF bridge arm current; sec is the unit of the horizontal axis coordinate in seconds; I S152 maga is the Fourier decomposition waveform diagram of the valve side current of the converter transformer; Man:Gaphs is the simulation waveform diagram of the grid connection point after harmonic current compensation; BCO is the output current of the LCC converter valve; BCH is the valve side current of the converter transformer; svf is the SVF bridge arm current.

[0109] In step 4, harmonic compensation is performed on the multi-source adaptive phase-shifting converter DC transmission system based on the bridge arm modulation voltage of the static var filter device, which specifically includes:

[0110] Based on the modulation voltage U of each phase bridge arm of the SVF m_a / b / c Harmonic compensation is carried out.

[0111] This application proposes a harmonic current dynamic compensation control method for the multi-source adaptive phase-shifting converter DC transmission system, suppresses the characteristic sub-harmonic current on the valve side of the converter transformer, significantly reduces the total harmonic current distortion rate, the suppression rate of the characteristic sub-harmonic current is above 95%, and some times can reach 99%, meeting the power quality requirements for the grid connection of the DC converter valve, significantly reducing the noise and loss of the converter transformer, and improving the safety and stability of the operation of the primary equipment of the converter station.

[0112] This application is realized through the static var filter device SVF in the SLCC DC transmission system, replaces the filters and capacitor banks on the AC side of the conventional DC converter valve, does not increase the system construction cost and greatly saves the floor area of the converter station.

[0113] Embodiment 2:

[0114] A SLCC dynamic adaptive harmonic compensation control system has a structure as Figure 15 shown, including:

[0115] A current extraction module, which is used to collect the three-phase AC current at the common coupling point of the phase-shifting converter and the static var filter device in the multi-source adaptive phase-shifting converter DC transmission system, the three-phase AC current on the bridge arm branch of the static var filter device, and the fundamental frequency control voltage of the fundamental frequency reactive power control loop;

[0116] A harmonic current suppression module, which is used to extract the three-phase AC current at the common coupling point and the three-phase AC current on the arm branch based on the number of commutation valve pulses of the commutation converter to obtain a specified harmonic suppression current command and a specified harmonic suppression voltage;

[0117] A modulation voltage generation module, which is used to calculate based on the specified harmonic suppression voltage and the fundamental frequency control voltage to obtain the arm modulation voltage of the static var filter device;

[0118] A harmonic compensation module, which is used to perform harmonic compensation on the multi-source adaptive commutation converter DC transmission system based on the arm modulation voltage of the static var filter device.

[0119] Combined with Figure 16 The schematic diagram of the SLCC dynamic adaptive harmonic compensation control system shown in the figure is used to introduce this embodiment in detail:

[0120] The current extraction module is used to collect the three-phase AC current at the common coupling point of the LCC on the valve side of the commutation transformer and the SVF and the three-phase AC current of the SVF arm branch when the SLCC DC transmission system is in steady-state operation;

[0121] The harmonic current suppression module includes:

[0122] A sub-module for suppressing harmonic current, which is used to extract the three-phase AC current at the common coupling point based on the number of commutation valve pulses of the commutation converter to obtain a specified harmonic suppression current command;

[0123] A sub-module for generating harmonic suppression voltage, which is used to calculate based on the harmonic current component of the specified order extracted from the three-phase AC current on the arm branch and combine with the specified harmonic suppression current command to obtain the specified harmonic suppression voltage.

[0124] The sub-module for suppressing harmonic current includes:

[0125] A harmonic current order determination unit, which is used to determine the harmonic current order based on the number of commutation valve pulses of the commutation converter;

[0126] A harmonic current extraction unit, which is used to extract the three-phase AC current at the common coupling point based on the harmonic current order to obtain the harmonic current component of the specified order;

[0127] An instruction generation unit, which is used to generate a specified harmonic suppression current command through a PI controller after comparing the harmonic current component of the specified order with zero current;

[0128] A harmonic suppression unit, which is used to generate a corresponding harmonic modulation wave based on the specified harmonic suppression current command for harmonic suppression.

[0129] The harmonic current extraction unit is specifically configured to:

[0130] After performing synchronous rotating coordinate transformation of the corresponding harmonic current order on the three-phase alternating current at the common coupling point, the alternating current after synchronous rotating coordinate transformation is obtained;

[0131] The alternating current after synchronous rotating coordinate transformation is extracted by using a low-pass filter to obtain the harmonic current component of the specified order.

[0132] Specifically, first, according to the number of pulses of the LCC converter valve, the harmonic current order to be suppressed is determined. The foregoing alternating current is input into the module. After synchronous rotating coordinate transformation of the harmonic of the corresponding order, the harmonic current component of the specified order in the foregoing alternating current is converted into a direct current component, and this direct current component is extracted through a low-pass filter.

[0133] The instruction generation unit specifically compares the obtained harmonic current component of the specified order with the zero current, and then generates a corresponding harmonic current instruction through a PI controller.

[0134] The harmonic suppression voltage generation sub-module is specifically configured to:

[0135] Extract the three-phase alternating current on the bridge arm branch based on the harmonic current order to obtain the harmonic current component of the specified order;

[0136] Based on the result of comparing the harmonic current component of the specified order with the harmonic suppression current instruction of the specified order, after passing through a correction controller, perform inverse synchronous rotating coordinate transformation to obtain the harmonic suppression voltage of the specified order.

[0137] Specifically, compare the harmonic current instruction with the harmonic component of the bridge arm current. After passing through a correction controller and then through inverse synchronous rotating coordinate transformation of the specified order, generate the harmonic suppression voltage of the specified order.

[0138] The modulation voltage generation module is specifically configured to:

[0139] Add the harmonic suppression voltages of the specified order to obtain the total harmonic suppression voltage;

[0140] Add the total harmonic suppression voltage and the fundamental frequency control voltage to obtain the bridge arm modulation voltage of the static var filter device.

[0141] Specifically, add the harmonic suppression voltages of the specified order to generate the total harmonic suppression voltage, and superimpose the total harmonic suppression voltage and the fundamental frequency control voltage to finally generate the modulation voltage of each phase valve branch of the SVF.

[0142] Embodiment 3:

[0143] As Figure 17As shown, the present invention also provides an electronic device, which may be a computer device, a single-chip microcomputer device, a smart mobile device, etc. The electronic device in this embodiment may include a processor, a memory, a transceiver component, etc. The memory, the processor, and the transceiver component are connected through a bus; the memory can be used to store an execution program, and an exemplary execution program may include instructions; the processor is used to execute the instructions stored in the memory. The memory can also be used to store data, and this data can be called and / or modified when the instructions are executed.

[0144] The processor may be a Central Processing Unit (CPU), or may also be other general-purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, and is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions in the storage medium to implement the corresponding method flow or corresponding function, so as to implement the steps of a SLCC dynamic adaptive harmonic compensation control method in the above embodiment.

[0145] Embodiment 4

[0146] Based on the same inventive concept, the present invention also provides a readable storage medium, specifically an electronic device-readable storage medium (Memory). The electronic device-readable storage medium is a memory device in the electronic device, and is used to store programs and data. It can be understood that the storage medium here can include both the built-in storage medium in the electronic device, and of course can also include the extended storage medium supported by the electronic device. The storage medium provides a storage space, and this storage space stores the operating system of the terminal. And, one or more instructions suitable for being loaded and executed by the processor are also stored in this storage space. These instructions can be one or more execution programs (including program codes). It should be noted that the storage medium here can be a high-speed RAM memory, or a non-volatile memory, such as at least one disk memory. By the processor loading and executing one or more instructions stored in the storage medium, the steps of a SLCC dynamic adaptive harmonic compensation control method in the above embodiment can be implemented.

[0147] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0148] The present application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for realizing the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or the combination of blocks.

[0149] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device that realizes the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or the combination of blocks.

[0150] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for realizing the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or the combination of blocks.

[0151] The above are only the embodiments of the present application and are not used to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application are included in the scope of the claims of the present application pending approval.

Claims

1. A SLCC dynamic adaptive harmonic compensation control method, characterized in that: include: Collect the three-phase AC current at the common coupling point between the phase-commutated converter and the static reactive power filter device in the multi-source adaptive phase-commutated DC transmission system, the three-phase AC current on the bridge arm branch of the static reactive power filter device, and the fundamental frequency control voltage of the fundamental frequency reactive power control loop; Based on the number of commutation valve pulses of the phase-commutation converter, extracting the three-phase AC current on the common coupling point and the three-phase AC current on the bridge arm branch to obtain a specified harmonic suppression current instruction and a specified harmonic suppression voltage; Calculating based on the specified subharmonic suppression voltage and the fundamental frequency control voltage to obtain a bridge arm modulation voltage of the static VAR filter device; Based on the bridge arm modulation voltage of the static reactive filter device, harmonic compensation is performed on the multi-source adaptive phase-commutated DC transmission system.

2. The method according to claim 1, characterized in that The method of extracting the three-phase AC current on the common coupling point and the three-phase AC current on the bridge arm branch based on the number of converter valve pulses of the phase-commutating converter to obtain a specified harmonic suppression current instruction and a specified harmonic suppression voltage includes: Based on the number of pulses of the commutation valve of the phase-commutation converter, the three-phase AC current at the common coupling point is extracted to obtain a specified harmonic suppression current instruction; The specified harmonic current component is extracted based on the three-phase alternating current on the bridge arm branch, and is calculated in combination with the specified harmonic suppression current instruction to obtain the specified harmonic suppression voltage.

3. The method according to claim 2, characterized in that The method of extracting the three-phase AC current at the common coupling point based on the number of commutation valve pulses of the phase-commutation converter to obtain a specified harmonic suppression current instruction includes: Determining the harmonic current order based on the number of pulses of the commutation valve of the phase-commutation converter; Extracting the three-phase alternating current at the common coupling point based on the harmonic current order to obtain a harmonic current component of a specified order; After comparing the harmonic current component of the specified order with the zero current, a harmonic suppression current instruction of the specified order is generated through a PI controller; Based on the specified harmonic suppression current instruction, a corresponding harmonic modulation wave is generated to perform harmonic suppression.

4. The method according to claim 3, characterized in that The extracting of the three-phase alternating current at the common coupling point based on the harmonic current order to obtain a harmonic current component of a specified order includes: After performing synchronous rotating coordinate transformation of the three-phase alternating current at the common coupling point corresponding to the harmonic current order, an alternating current after synchronous rotating coordinate transformation is obtained; The alternating current after the synchronous rotating coordinate transformation is extracted by using a low-pass filter to obtain a harmonic current component of a specified order.

5. The method according to claim 3, characterized in that: The specified harmonic current component extracted based on the three-phase alternating current on the bridge arm branch is calculated in combination with the specified harmonic suppression current instruction to obtain the specified harmonic suppression voltage, including: Extracting the three-phase alternating current on the bridge arm branch based on the harmonic current order to obtain the harmonic current component of the specified order; Based on the result of comparing the harmonic current component of the specified order with the harmonic suppression current instruction of the specified order, a synchronous rotating coordinate inverse transformation is performed through a correction controller to obtain a harmonic suppression voltage of the specified order.

6. The method according to claim 1, characterized in that The method of calculating based on the specified subharmonic suppression voltage and the fundamental frequency control voltage to obtain the bridge arm modulation voltage of the static VAR filter device includes: Obtaining a total harmonic suppression voltage based on the addition of the specified harmonic suppression voltages; The bridge arm modulation voltage of the static reactive filter device is obtained based on the addition of the total harmonic suppression voltage and the fundamental frequency control voltage.

7. A SLCC dynamic adaptive harmonic compensation control system, characterized in that: include: A current extraction module is used to collect the three-phase AC current at the common coupling point between the phase-commutated converter and the static reactive power filter device in the multi-source adaptive phase-commutated DC transmission system, the three-phase AC current on the bridge arm branch of the static reactive power filter device, and the base frequency control voltage of the base frequency reactive power control loop; A harmonic current suppression module, for extracting the three-phase AC current on the common coupling point and the three-phase AC current on the bridge arm branch to obtain a specified harmonic suppression current instruction and a specified harmonic suppression voltage based on the number of converter valve pulses of the phase-commutating converter; A modulation voltage generation module, used for calculating based on the specified subharmonic suppression voltage and the fundamental frequency control voltage to obtain a bridge arm modulation voltage of a static VAR filter device; The harmonic compensation module is used to perform harmonic compensation on the multi-source adaptive phase-commutated DC transmission system based on the bridge arm modulation voltage of the static reactive filter device.

8. The system according to claim 7, characterized in that The harmonic current suppression module comprises: A harmonic current suppression submodule is used to extract the three-phase AC current at the common coupling point based on the number of converter valve pulses of the phase-commutating converter to obtain a specified harmonic suppression current instruction; The harmonic suppression voltage generating submodule is used to obtain the specified harmonic current component extracted based on the three-phase alternating current on the bridge arm branch, and calculate the specified harmonic suppression voltage in combination with the specified harmonic suppression current instruction.

9. The system according to claim 8, characterized in that The harmonic current suppression submodule comprises: A harmonic current order determination unit, used to determine the harmonic current order based on the number of pulses of the commutation valve of the phase-commutation converter; A harmonic current extraction unit, configured to extract the three-phase alternating current at the common coupling point based on the harmonic current order to obtain a harmonic current component of a specified order; An instruction generating unit, configured to generate a specified harmonic suppression current instruction through a PI controller based on the comparison between the specified harmonic current component and the zero current; The harmonic suppression unit is used to generate a corresponding harmonic modulation wave based on the specified harmonic suppression current instruction to perform harmonic suppression.

10. The system according to claim 9, characterized in that The harmonic current extraction unit is specifically used for: After performing synchronous rotating coordinate transformation of the three-phase alternating current at the common coupling point corresponding to the harmonic current order, an alternating current after synchronous rotating coordinate transformation is obtained; The alternating current after the synchronous rotating coordinate transformation is extracted by using a low-pass filter to obtain a harmonic current component of a specified order.

11. The system according to claim 9, characterized in that The harmonic suppression voltage generation submodule is specifically used for: Extracting the three-phase alternating current on the bridge arm branch based on the harmonic current order to obtain the harmonic current component of the specified order; Based on the result of comparing the harmonic current component of the specified order with the harmonic suppression current instruction of the specified order, a synchronous rotating coordinate inverse transformation is performed through a correction controller to obtain a harmonic suppression voltage of the specified order.

12. The font according to claim 7, characterized in that: The modulation voltage generating module is specifically used for: Obtaining a total harmonic suppression voltage based on the addition of the specified harmonic suppression voltages; The bridge arm modulation voltage of the static reactive filter device is obtained based on the addition of the total harmonic suppression voltage and the fundamental frequency control voltage.

13. An electronic device, characterized in that: include: at least one processor and memory; The memory and the processor are connected via a bus; The memory is used to store one or more programs; When the one or more programs are executed by the at least one processor, a SLCC dynamic adaptive harmonic compensation control method according to any one of claims 1 to 6 is implemented.

14. A readable storage medium, characterized in that: An execution program is stored thereon, and when the execution program is executed, a SLCC dynamic adaptive harmonic compensation control method according to any one of claims 1 to 6 is implemented.

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