Optimization control method and system suitable for SLCC high-voltage direct current system

Abstract

The invention discloses an optimal control method and system suitable for an SLCC high-voltage direct current system, and belongs to the technical field of power systems. The method comprises the following steps: determining topological structures and control strategies of converter stations at a rectification side and an inversion side of a multi-source self-adaptive commutation converter-high voltage direct current system SLCC-HVDC; based on the topological structure and the control strategy, detecting parameters of a converter transformer of the SLCC-HVDC system, and obtaining a detection result; and calculating the detection result to determine an SVG three-phase internal potential reference value of the LCC-HVDC system, and performing optimization control on the SLCC-HVDC system by taking the SVG three-phase internal potential reference value as an optimization control parameter. According to the method, the system is controlled by optimizing the control parameters, the recovery speed of the direct current power of the SLCC after the fault is improved, and the alternating current fault ride-through capability of the SLCC is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and more specifically, to an optimization control method and system suitable for a SLCC high voltage direct current system. Background Art

[0002] High-voltage direct current transmission technology based on line commutated converter (LCC) is mature and reliable, with large transmission capacity and low loss. It has been widely used in scenarios such as long-distance large-capacity transmission, power system networking and AC line capacity expansion and transformation. However, commutation failure is one of the common faults in DC systems. The transient change process of the reactive characteristics of the DC system during the fault will break the reactive balance between the converter station and the AC grid, and between the converter station and the new energy station, resulting in an increase in DC current and a decrease in transmission power. The converter valve will be affected by long-term excessive current and its service life will even be destroyed. With the increase of UHV DC capacity and the dense feeding of multiple DC lines, the problem of commutation failure will become more prominent.

[0003] Domestic and foreign scholars have conducted a lot of research on commutation failure suppression technology, which is mainly divided into two types of measures: optimizing control strategies and improving topology structures. However, optimizing control strategies can only reduce the risk of commutation failures, but cannot completely avoid commutation failures. In terms of improving topology structures, a multi-source adaptive commutation converter (self-adaption statcom and line commutation converter, SLCC) with composite voltage source and current source characteristics reduces the risk of commutation failure during faults and improves the reliability of equipment safe operation. At the same time, it can save the floor space of AC filters in conventional converter stations and has broad engineering application prospects.

[0004] Since its introduction, the high-voltage direct current transmission technology based on SLCC has rapidly attracted widespread attention at home and abroad, but there is still a lack of necessary research on the fault characteristics and power characteristics of SLCC. SLCC can only passively adjust the reactive power command according to the reactive power deviation of the grid connection point, and it is difficult to quickly track the reactive power demand of the DC system. Under severe faults, there are problems such as delay in command calculation value and slow reactive output response. Especially at the moment of fault occurrence and fault removal, due to the rapid change of reactive exchange, SVG control reacts slowly, reactive power output does not match actual demand, and there is still a large amount of reactive power exchange between systems, which is not conducive to the overall recovery of the power grid. Summary of the invention

[0005] In view of the above problems, the present invention proposes an optimization control method suitable for a SLCC high voltage direct current system, comprising:

[0006] Determine the topology and control strategy of the rectifier and inverter side converter stations of the multi-source adaptive commutation converter-high voltage direct current system SLCC-HVDC system;

[0007] Based on the topological structure and control strategy, the parameters of the converter transformer of the SLCC-HVDC system are detected to obtain the detection results;

[0008] The detection results are calculated to determine reference values ​​of the three-phase internal potential of the SVG of the LCC-HVDC system, and the three-phase internal potential reference values ​​of the SVG are used as optimization control parameters to optimize the control of the SLCC-HVDC system.

[0009] Optionally, the parameters of the converter transformer of the SLCC-HVDC system are detected, including:

[0010] The primary current and DC power of the converter transformer and the exchange reactive power between the converter transformer and the SLCC-HVDC system.

[0011] Optionally, calculating the detection result to determine a reference value of the three-phase internal potential of the SVG of the LCC-HVDC system includes:

[0012] Based on the detection result, the commutation angle, power factor angle, reactive power consumed and reactive power consumed by the converter valve are calculated; based on the commutation angle, power factor angle, reactive power consumed and reactive power consumed by the converter valve, the reactive demand of the converter valve and the converter transformer is calculated, and a proportional integral operation is performed on the exchange reactive power to obtain the operation result, the reactive demand of the converter valve and the converter transformer and the operation result are summed to obtain the SVG reactive reference value, the average voltage of the H-bridge module capacitor and the SVG reactive reference value are proportionally integrated to obtain the SVG output current reference value in the dq coordinate system, the SVG output current reference value in the dq coordinate system is proportionally integrated, and Park inverse transformation and Clark inverse transformation are performed to obtain the SVG three-phase internal potential reference value.

[0013] Optionally, based on the detection result, the commutation angle, power factor angle, reactive power consumed by the converter valve and reactive power consumed by the converter transformer are calculated, including:

[0014] Based on the detection results, the effective value of the three-phase current is calculated, and based on the effective value of the three-phase current, the commutation angle, power factor angle, consumed reactive power of the converter valve and the reactive power consumed by the converter transformer are calculated.

[0015] Optionally, the method also includes: calculating the upper and lower limits of the reactive power demand of the converter valve, and the calculated reactive power demand of the converter valve meets the upper and lower limits of the reactive power demand of the converter valve.

[0016] Optionally, the SVG output current reference value in the dq coordinate system includes: an active current reference value and a reactive current reference value.

[0017] Optionally, a proportional integral operation is performed on the SVG output current reference value in the dq coordinate system to obtain the SVG internal potential reference value, and a Park inverse transformation and a Clark inverse transformation are performed on the SVG internal potential reference value to obtain the SVG three-phase internal potential reference value.

[0018] On the other hand, the present invention also proposes an optimization control system suitable for a SLCC high voltage direct current system, comprising:

[0019] An initial unit for determining the topology and control strategy of the converter stations on the rectifier and inverter sides of the multi-source adaptive commutation converter-high voltage direct current system SLCC-HVDC system;

[0020] A detection unit, used to detect parameters of a converter transformer of the SLCC-HVDC system based on the topology structure and the control strategy, and obtain a detection result;

[0021] A calculation and control unit is used to calculate the detection result to determine the reference value of the three-phase internal potential of the SVG of the LCC-HVDC system, and optimize the control of the SLCC-HVDC system by taking the reference value of the three-phase internal potential of the SVG as the optimization control parameter.

[0022] Optionally, the detection unit detects parameters of the converter transformer of the SLCC-HVDC system, including:

[0023] The primary current and DC power of the converter transformer and the exchange reactive power between the converter transformer and the SLCC-HVDC system.

[0024] Optionally, the calculation and control unit calculates the detection result to determine the reference value of the three-phase internal potential of the SVG of the LCC-HVDC system, including:

[0025] Based on the detection result, the commutation angle, power factor angle, reactive power consumed and reactive power consumed by the converter valve are calculated; based on the commutation angle, power factor angle, reactive power consumed and reactive power consumed by the converter valve, the reactive demand of the converter valve and the converter transformer is calculated, and a proportional integral operation is performed on the exchange reactive power to obtain the operation result, the reactive demand of the converter valve and the converter transformer and the operation result are summed to obtain the SVG reactive reference value, the average voltage of the H-bridge module capacitor and the SVG reactive reference value are proportionally integrated to obtain the SVG output current reference value in the dq coordinate system, the SVG output current reference value in the dq coordinate system is proportionally integrated, and Park inverse transformation and Clark inverse transformation are performed to obtain the SVG three-phase internal potential reference value.

[0026] Optionally, the calculation and control unit calculates the commutation angle, power factor angle, reactive power consumed by the converter valve and reactive power consumed by the converter transformer based on the detection result, including:

[0027] Based on the detection results, the effective value of the three-phase current is calculated, and based on the effective value of the three-phase current, the commutation angle, power factor angle, consumed reactive power of the converter valve and the reactive power consumed by the converter transformer are calculated.

[0028] Optionally, the calculation and control unit is also used to: calculate the upper and lower limits of the reactive power demand of the converter valve, and the calculated reactive power demand of the converter valve meets the upper and lower limits of the reactive power demand of the converter valve.

[0029] Optionally, the SVG output current reference value in the dq coordinate system includes: an active current reference value and a reactive current reference value.

[0030] Optionally, the calculation and detection unit performs proportional integral operation on the SVG output current reference value in the dq coordinate system to obtain the SVG internal potential reference value, and performs Park inverse transformation and Clark inverse transformation on the SVG internal potential reference value to obtain the SVG three-phase internal potential reference value.

[0031] In yet another aspect, the present invention further provides a computing device, comprising: one or more processors;

[0032] a processor for executing one or more programs;

[0033] When the one or more programs are executed by the one or more processors, the above-described method is implemented.

[0034] In yet another aspect, the present invention further provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed, the method described above is implemented.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The present invention provides an optimization control method applicable to a SLCC high-voltage direct current system, including: determining the topology and control strategy of the converter stations on the rectifier and inverter sides of a multi-source adaptive commutation converter-high-voltage direct current system SLCC-HVDC system; based on the topology and control strategy, detecting the parameters of the converter transformer of the SLCC-HVDC system and obtaining the detection results; calculating the detection results to determine the reference value of the three-phase internal potential of the SVG of the LCC-HVDC system, and optimizing and controlling the SLCC-HVDC system by using the reference value of the three-phase internal potential of the SVG as the optimization control parameter. The present invention controls the system by optimizing the control parameters, thereby improving the recovery speed of the SLCC DC power after a fault, and effectively improving the AC fault ride-through capability of the SLCC. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a flow chart of the method of the present invention;

[0038] Figure 2 is a flow chart of an embodiment of the present invention;

[0039] Figure 3 A topological diagram of a high-voltage direct current transmission system based on SLCC provided by the present invention;

[0040] Figure 4 A single-pole topological structure diagram of the SLCC provided by the present invention;

[0041] Figure 5 A strategy diagram of an optimization control method based on a SLCC high voltage direct current system provided by the present invention;

[0042] Figure 6 af is a comparison diagram of response waveforms before and after SLCC optimization under a three-phase fault near the receiving power grid provided by the present invention (0.29pu);

[0043] Figure 7 af is a comparison diagram of response waveforms before and after SLCC optimization under a three-phase fault at the remote end of the receiving power grid provided by the present invention (0.61pu);

[0044] Figure 8 It is a structural diagram of the system of the present invention. DETAILED DESCRIPTION

[0045] Now, exemplary embodiments of the present invention are described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely and to fully convey the scope of the present invention to those skilled in the art. The terms used in the exemplary embodiments shown in the accompanying drawings are not intended to limit the present invention. In the accompanying drawings, the same units / elements are marked with the same reference numerals.

[0046] Unless otherwise specified, the terms (including technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is understood that the terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0047] Embodiment 1:

[0048] The present invention proposes an optimization control method suitable for SLCC high voltage direct current system. Figure 1 As shown, including:

[0049] Step 1, determine the topology and control strategy of the rectifier and inverter side converter stations of the multi-source adaptive commutation converter-high voltage direct current system SLCC-HVDC system;

[0050] Step 2: Based on the topology structure and control strategy, detect the parameters of the SLCC-HVDC system converter transformer and obtain the detection results;

[0051] Step 3: Calculate the detection results to determine a reference value of the three-phase internal potential of the SVG of the LCC-HVDC system, and use the reference value of the three-phase internal potential of the SVG as an optimization control parameter to optimize the control of the SLCC-HVDC system.

[0052] Among them, the parameters of the converter transformer of the SLCC-HVDC system are detected, including:

[0053] The primary current and DC power of the converter transformer and the exchange reactive power between the converter transformer and the SLCC-HVDC system.

[0054] The detection results are calculated to determine the reference value of the three-phase internal potential of the SVG of the LCC-HVDC system, including:

[0055] Based on the detection result, the commutation angle, power factor angle, reactive power consumed and reactive power consumed by the converter valve are calculated; based on the commutation angle, power factor angle, reactive power consumed and reactive power consumed by the converter valve, the reactive demand of the converter valve and the converter transformer is calculated, and a proportional integral operation is performed on the exchange reactive power to obtain the operation result, the reactive demand of the converter valve and the converter transformer and the operation result are summed to obtain the SVG reactive reference value, the average voltage of the H-bridge module capacitor and the SVG reactive reference value are proportionally integrated to obtain the SVG output current reference value in the dq coordinate system, the SVG output current reference value in the dq coordinate system is proportionally integrated, and Park inverse transformation and Clark inverse transformation are performed to obtain the SVG three-phase internal potential reference value.

[0056] Among them, based on the detection results, the commutation angle, power factor angle, reactive power consumed by the converter valve and reactive power consumed by the converter transformer are calculated, including:

[0057] Based on the detection results, the effective value of the three-phase current is calculated, and based on the effective value of the three-phase current, the commutation angle, power factor angle, consumed reactive power of the converter valve and the reactive power consumed by the converter transformer are calculated.

[0058] The method further includes: calculating the upper and lower limits of the reactive power demand of the converter valve, and the calculated reactive power demand of the converter valve meets the upper and lower limits of the reactive power demand of the converter valve.

[0059] The SVG output current reference value in the dq coordinate system includes an active current reference value and a reactive current reference value.

[0060] The proportional integral operation is performed on the SVG output current reference value in the dq coordinate system to obtain the SVG internal potential reference value, and the SVG internal potential reference value is subjected to Park inverse transformation and Clark inverse transformation to obtain the SVG three-phase internal potential reference value.

[0061] The present invention is further described below in conjunction with specific implementation cases:

[0062] Real-time case flow such as Figure 2 As shown, including:

[0063] (1) Determine the topology and control strategy of the converter stations on the rectifier and inverter sides of the SLCC-HVDC system;

[0064] (2) Detect the primary current, DC power, and reactive power exchanged with the system, and use the detection results in subsequent calculations;

[0065] (3) Calculate the commutation angle and power factor angle of the corresponding converter valve respectively

[0066] (4) Calculate the real-time reactive power demand of the converter valve and converter transformer, perform proportional integral operation on the exchange reactive power, and the sum of the three is the total SVG reactive power reference value;

[0067] (5) Proportional integration operation is performed on the average voltage of the H-bridge module capacitor and the SVG reactive power reference value, and the results are the SVG output current reference values ​​in the dq coordinate system;

[0068] (6) Perform proportional integral operation on the previous result and perform Park and Clark inverse transformation to obtain the reference value of the three-phase internal potential of SVG.

[0069] Preferably, the step (1) comprises:

[0070] The topology and control strategy of the HVDC system's transmitter-receiver converter station are studied. Conventional DC uses a true bipolar connection form, and the inverter side uses an SLCC topology, that is, a group of SVG is put between the unipolar converter valve and the converter transformer to provide dynamically controllable reactive power, replacing the AC filter on the original inverter side bus. In steady state, the rectifier side operates in a constant current control mode, and the inverter side operates in a constant voltage control mode.

[0071] Preferably, the step (2) comprises:

[0072] The primary current, DC power and reactive power exchanged with the system of the converter transformer are detected in real time, and the detection results are used for subsequent calculations.

[0073] Calculate the three-phase current effective value I based on formula 1 rms :

[0074]

[0075] In the formula, I base is the AC current reference value, I n (n=A, B, C) is the instantaneous value of three-phase current.

[0076] Preferably, the step (3) comprises:

[0077] Step 301: Calculate the commutation angle μ of the converter valve based on equation 2:

[0078]

[0079] Where, γ0 is the initial value of the arc extinction angle on the inverter side; a and b are constants; U diN is the rated DC voltage; U d is the line DC voltage; I diN is the rated DC current; I d is the line DC current; α is the trigger angle on the inverter side.

[0080] Step 302: Calculate the power factor angle of the converter valve using equation 3

[0081]

[0082] Step 303: Calculate the reactive power Q consumed by the converter valve based on equation 4: val.ref :

[0083]

[0084] Step 304: Calculate the reactive power Q consumed by the commutation transformer based on equation 5 trans.ref :

[0085]

[0086] Where, X T is the equivalent impedance of the commutation transformer.

[0087] Preferably, the step (4) comprises:

[0088] Step 401: Calculate reactive power reference value Q based on equation 6 sys.ref :

[0089] Q sys.ref =K p Q sys +K i ∫Q sys (6)

[0090] In the formula, K p , K i is the proportional adjustment coefficient and the integral adjustment coefficient; Q sys is the reactive power exchange amount.

[0091] Step 402: To avoid the saturation integral caused by Q in step 401 sys.ref Exceeding the actual hardware capability, resulting in the subsequent current inner loop I qref Hard to keep up with Q sys.ref , Q needs to be calculated based on Equation 7 sys.ref The upper and lower limits Q' UP.Limit , Q' DN.Limit :

[0092]

[0093] In the formula, Q UP.Limit , Q DN.Limit It is the upper and lower limits of the original SLCC reactive outer loop integral.

[0094] Step 403: Calculate the total reactive power reference value Q based on equation 8 ref :

[0095] Q ref =Q val.ref +Q trans.ref +Q sys.ref (8)

[0096] Preferably, the step (5) comprises:

[0097] Step 501: Calculate the active current reference value i using equation 9 dref :

[0098] i dref =K p (V cref -V cavg )+K i ∫(V cref -V cavg) (9)

[0099] In the formula, K p , K i is the proportional adjustment coefficient and the integral adjustment coefficient; V cref K is the rated voltage of the H-bridge module capacitor; i is the average voltage of the H-bridge module capacitor.

[0100] Step 502: Calculate the reactive current reference value i using equation 10 qref :

[0101] i qref =K p (Q ref -Q svg )+K i ∫(Q ref -Q svg ) (10)

[0102] In the formula, K p , K i is the proportional adjustment coefficient and the integral adjustment coefficient; Q svg Contribute to SVG reactive power.

[0103] Preferably, the step (6) comprises:

[0104] Step 601: Obtain the reference value U of the internal potential of the SVG in the dq rotating coordinate system based on equation 11: dref , U qref :

[0105]

[0106] In the formula, K p , K i is the proportional adjustment coefficient and the integral adjustment coefficient; i d 、i q is the SVG output current in the dq rotating coordinate system.

[0107] Step 602: The result of step 601 is subjected to Park inverse transformation and Clark inverse transformation to obtain the SVG three-phase internal potential reference value U aref , U bref , U cref .

[0108] The above steps are specifically as follows:

[0109] (1) Determine the topology and control strategy of the converter stations on the rectifier and inverter sides of the SLCC-HVDC system

[0110] 1) The topology of SLCC HVDC transmission system is as follows Figure 3As shown in the figure, conventional DC uses a true bipolar connection form. The inverter side uses the SLCC topology, that is, a set of SVG is added between the unipolar converter valve and the converter transformer to provide dynamic controllable reactive power, replacing the AC filter on the original inverter side bus. In steady state, the rectifier side operates in constant current control mode, and the inverter side operates in constant voltage control mode. The topology of SVG is shown in the figure. Figure 4 As shown, a single bridge arm is composed of a cascaded H bridge and a bridge arm inductor in series, and the bridge arm voltage and output reactive power are changed by controlling the number of conducting sub-modules.

[0111] (2) The original SLCC strategy indirectly meets the reactive power demand of DC line equipment by limiting the busbar exchange reactive power. Although the real-time reactive power consumption of converter valves and converter transformers is difficult to detect directly, it can be obtained by measuring electrical quantities and calculating. The present invention directly implements additional feedforward control based on DC power, and provides a reactive feedforward strategy such as Figure 5 shown.

[0112] 1) Based on formula 1, real-time detection and calculation of the effective value of the primary current of the commutation transformer I rms ;

[0113] 2) Measure the DC power and exchange reactive power with the system for subsequent calculations.

[0114] (3) Calculate the commutation angle μ and power factor angle of the single-pole converter valve in turn The real-time reactive power demand Q of the converter valve and converter transformer is obtained by using equations 4 and 5. val.ref and Q trans.ref , where X T is the equivalent impedance of the commutation transformer.

[0115] (4) In order to ensure the dynamic adjustment performance of the optimization strategy, the PI link is retained.

[0116] 1) To avoid saturation integration in the PI link, which causes the reactive reference value to exceed the actual hardware capability and leads to loss of control of the subsequent current inner loop, it is necessary to calculate the variable limit Q' based on the previous calculation result based on formula 7 UP.Limit , Q' DN.Limit ;

[0117] 2) Perform proportional integral operation on the exchange reactive power to obtain Q sys.ref The sum of the above three reference values ​​is the total SVG reactive power reference value.

[0118] (5) Use equations 9 and 10 to calculate the SVG output active current reference value i dref , reactive current reference value i qref .

[0119] (6) Using equation 11 to perform proportional integration on the previous result, we can obtain the reference value of the internal potential of SVG in the dq rotating coordinate system:dref , U qref .

[0120] 1) Perform Park inverse transformation to obtain the reference value U of the internal potential of SVG in the αβ stationary coordinate system αref , U βref ;

[0121] 2) Perform Clark inverse transformation to obtain the reference value U of the internal potential of SVG in the abc three-phase stationary coordinate system. aref , U bref , U cref .

[0122] In the PSD-PSModel electromechanical-electromagnetic hybrid simulation software independently developed by the China Electric Power Research Institute, the electromechanical transient model of the AC power grid at the sending and receiving ends and the electromagnetic transient model of the SLCC are built. The DC parameters of the SLCC are shown in Table 1, which verifies the rationality of the theoretical analysis of the present invention and the effectiveness of the control method.

[0123] Table 1

[0124]

[0125]

[0126] The SLCC control method with outer loop feedforward is adopted. The three-phase short-circuit faults in the near and far areas of the receiving AC power grid are simulated at 0.1s, and the faults are removed at 0.2s. The difference in transient performance of SLCC during fault period is compared before and after the optimization control method is adopted.

[0127] Figure 6 af is the comparison of the characteristics of SLCC before and after the optimization control under the proximal three-phase short-circuit fault. Figure 7 af is the comparison of the characteristics of SLCC before and after the optimization control under the remote three-phase short-circuit fault.

[0128] Since the essence of the strategy is still to control reactive power rather than voltage, it does not help to establish the bus AC voltage, and the bus voltage waveform remains basically the same during the fault. In the early stage of the fault, the DC current increases rapidly, and the reactive power demand of the converter valve increases dramatically. Limited by the hardware capacity and AC voltage drop, the reactive output of SVG is difficult to keep up with the reference value, and a large amount of reactive power is absorbed to the system side. The optimization strategy takes action in advance before the PI calculation link, which naturally has a lag, so the reference value reaches the limit value faster, reducing reactive power absorption. As the DC current decreases, the DC power continues to drop to 0. At this time, the reactive power demand decreases rapidly, and the optimization strategy gradually turns to be dominated by the PI link, quickly pressing down the reactive reference value while avoiding overshoot of the reference value. After a small amount of reactive power is sent out, the output immediately decreases. At the moment of fault recovery, the bus voltage is quickly established, which directly causes the reactive output of SVG to jump and send a large amount to the system side. In the case of a proximal fault, both strategies fail to commutate, and the DC voltage and DC power drop to zero. Under the optimization strategy, Q val.ref is negative, by reducing Q ref Limiting SVG output; before the strategy optimization, two commutation failures lasting a total of 0.048s occurred during the remote fault. The DC current increased and the reactive power of the converter valve was seriously insufficient. After the optimization, no commutation failure occurred, which successfully limited the large-scale exchange of reactive power with the system side. As the DC current increased, the DC power gradually recovered, and the internal conversion of the optimization strategy was dominated by the feedforward link, avoiding large-scale overshoot fluctuations of the SVG reactive power reference value. By removing the limitation of the VDCOL link on the current rise speed, the optimized DC power recovery speed is greatly improved at the same voltage level, and less transmission energy is lost in various fault conditions.

[0129] Embodiment 2:

[0130] The present invention also proposes an optimization control system 200 suitable for SLCC high voltage direct current system, such as Figure 8 As shown, including:

[0131] The initial unit 201 is used to determine the topology and control strategy of the rectifier and inverter side converter stations of the multi-source adaptive commutation converter-high voltage direct current system SLCC-HVDC system;

[0132] A detection unit 202, configured to detect parameters of a converter transformer of the SLCC-HVDC system based on the topology structure and the control strategy, and obtain a detection result;

[0133] The calculation and control unit 203 is used to calculate the detection result to determine the reference value of the three-phase internal potential of the SVG of the LCC-HVDC system, and use the reference value of the three-phase internal potential of the SVG as the optimization control parameter to optimize the control of the SLCC-HVDC system.

[0134] The detection unit 202 detects the parameters of the SLCC-HVDC system converter transformer, including:

[0135] The primary current and DC power of the converter transformer and the exchange reactive power between the converter transformer and the SLCC-HVDC system.

[0136] The calculation and control unit 203 calculates the detection result to determine the reference value of the three-phase internal potential of the SVG of the LCC-HVDC system, including:

[0137] Based on the detection result, the commutation angle, power factor angle, reactive power consumed and reactive power consumed by the converter valve are calculated; based on the commutation angle, power factor angle, reactive power consumed and reactive power consumed by the converter valve, the reactive demand of the converter valve and the converter transformer is calculated, and a proportional integral operation is performed on the exchange reactive power to obtain the operation result, the reactive demand of the converter valve and the converter transformer and the operation result are summed to obtain the SVG reactive reference value, the average voltage of the H-bridge module capacitor and the SVG reactive reference value are proportionally integrated to obtain the SVG output current reference value in the dq coordinate system, the SVG output current reference value in the dq coordinate system is proportionally integrated, and Park inverse transformation and Clark inverse transformation are performed to obtain the SVG three-phase internal potential reference value.

[0138] The calculation and control unit 203 calculates the commutation angle, power factor angle, reactive power consumed by the converter valve and reactive power consumed by the converter transformer based on the detection result, including:

[0139] Based on the detection results, the effective value of the three-phase current is calculated, and based on the effective value of the three-phase current, the commutation angle, power factor angle, consumed reactive power of the converter valve and the reactive power consumed by the converter transformer are calculated.

[0140] The calculation and control unit 203 is further used to calculate the upper and lower limits of the reactive power demand of the converter valve, and the calculated reactive power demand of the converter valve meets the upper and lower limits of the reactive power demand of the converter valve.

[0141] The SVG output current reference value in the dq coordinate system includes an active current reference value and a reactive current reference value.

[0142] The calculation and detection unit 203 performs proportional integral operation on the SVG output current reference value in the dq coordinate system to obtain the SVG internal potential reference value, and performs Park inverse transformation and Clark inverse transformation on the SVG internal potential reference value to obtain the SVG three-phase internal potential reference value.

[0143] The present invention controls the system by optimizing control parameters, thereby improving the recovery speed of SLCC DC power after a fault, and effectively improving the AC fault ride-through capability of SLCC.

[0144] Embodiment 3:

[0145] Based on the same inventive concept, the present invention also provides a computer device, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding functions, so as to implement the steps of the method in the above embodiment.

[0146] Embodiment 4:

[0147] Based on the same inventive concept, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It is understandable that the computer-readable storage medium here can include both a built-in storage medium in a computer device and an extended storage medium supported by the computer device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by a processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of the method in the above embodiment.

[0148] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may 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.) containing computer-usable program codes. The schemes in the embodiments of the present invention may be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0149] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0150] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0151] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0152] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0153] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. An optimization control method applicable to a SLCC high voltage direct current system, characterized in that: include: Determine the topology and control strategy of the rectifier and inverter side converter stations of the multi-source adaptive commutation converter-high voltage direct current system SLCC-HVDC system; Based on the topological structure and control strategy, the parameters of the converter transformer of the SLCC-HVDC system are detected to obtain the detection results; The detection results are calculated to determine reference values ​​of the three-phase internal potential of the SVG of the LCC-HVDC system, and the three-phase internal potential reference values ​​of the SVG are used as optimization control parameters to optimize the control of the SLCC-HVDC system.

2. The optimization control method according to claim 1, characterized in that: The detection of the parameters of the SLCC-HVDC system converter transformer includes: The primary current and DC power of the converter transformer and the exchange reactive power between the converter transformer and the SLCC-HVDC system.

3. The optimization control method according to claim 1, characterized in that: The calculating of the detection results to determine the reference value of the three-phase internal potential of the SVG of the LCC-HVDC system includes: Based on the detection result, the commutation angle, power factor angle, reactive power consumed and reactive power consumed by the converter valve are calculated; based on the commutation angle, power factor angle, reactive power consumed and reactive power consumed by the converter valve, the reactive demand of the converter valve and the converter transformer is calculated, and a proportional integral operation is performed on the exchange reactive power to obtain the operation result, the reactive demand of the converter valve and the converter transformer and the operation result are summed to obtain the SVG reactive reference value, the average voltage of the H-bridge module capacitor and the SVG reactive reference value are proportionally integrated to obtain the SVG output current reference value in the dq coordinate system, the SVG output current reference value in the dq coordinate system is proportionally integrated, and Park inverse transformation and Clark inverse transformation are performed to obtain the SVG three-phase internal potential reference value.

4. The optimization control method according to claim 3, characterized in that: The method of calculating the commutation angle, power factor angle, reactive power consumed by the converter valve and reactive power consumed by the converter transformer based on the detection result includes: Based on the detection results, the effective value of the three-phase current is calculated, and based on the effective value of the three-phase current, the commutation angle, power factor angle, consumed reactive power of the converter valve and the reactive power consumed by the converter transformer are calculated.

5. The optimization control method according to claim 3, characterized in that: The method further includes: calculating the upper and lower limits of the reactive power demand of the converter valve, and the calculated reactive power demand of the converter valve meets the upper and lower limits of the reactive power demand of the converter valve.

6. The optimization control method according to claim 3, characterized in that: The SVG output current reference value in the dq coordinate system includes: an active current reference value and a reactive current reference value.

7. The optimization control method according to claim 3, characterized in that: A proportional integral operation is performed on the SVG output current reference value in the dq coordinate system to obtain the SVG internal potential reference value, and a Park inverse transformation and a Clark inverse transformation are performed on the SVG internal potential reference value to obtain the SVG three-phase internal potential reference value.

8. An optimization control system suitable for SLCC high voltage direct current system, characterized in that: include: An initial unit for determining the topology and control strategy of the converter stations on the rectifier and inverter sides of the multi-source adaptive commutation converter-high voltage direct current system SLCC-HVDC system; A detection unit, used to detect parameters of the SLCC-HVDC system converter transformer based on the topology structure and control strategy, and obtain detection results; A calculation and control unit is used to calculate the detection result to determine the reference value of the three-phase internal potential of the SVG of the LCC-HVDC system, and optimize the control of the SLCC-HVDC system by taking the reference value of the three-phase internal potential of the SVG as the optimization control parameter.

9. The optimization control system according to claim 8, characterized in that: The detection unit detects the parameters of the SLCC-HVDC system converter transformer, including: The primary current and DC power of the converter transformer and the exchange reactive power between the converter transformer and the SLCC-HVDC system.

10. The optimization control system according to claim 8, characterized in that: The calculation and control unit calculates the detection result to determine the reference value of the three-phase internal potential of the SVG of the LCC-HVDC system, including: Based on the detection result, the commutation angle, power factor angle, reactive power consumed and reactive power consumed by the converter valve are calculated; based on the commutation angle, power factor angle, reactive power consumed and reactive power consumed by the converter valve, the reactive demand of the converter valve and the converter transformer is calculated, and a proportional integral operation is performed on the exchange reactive power to obtain the operation result, the reactive demand of the converter valve and the converter transformer and the operation result are summed to obtain the SVG reactive reference value, the average voltage of the H-bridge module capacitor and the SVG reactive reference value are proportionally integrated to obtain the SVG output current reference value in the dq coordinate system, the SVG output current reference value in the dq coordinate system is proportionally integrated, and Park inverse transformation and Clark inverse transformation are performed to obtain the SVG three-phase internal potential reference value.

11. The optimization control system according to claim 10, characterized in that: The calculation and control unit calculates the commutation angle, power factor angle, reactive power consumed by the converter valve and reactive power consumed by the converter transformer based on the detection result, including: Based on the detection results, the effective value of the three-phase current is calculated, and based on the effective value of the three-phase current, the commutation angle, power factor angle, consumed reactive power of the converter valve and the reactive power consumed by the converter transformer are calculated.

12. The optimization control system according to claim 10, characterized in that: The calculation and control unit is also used to calculate the upper and lower limits of the reactive power demand of the converter valve, and the calculated reactive power demand of the converter valve meets the upper and lower limits of the reactive power demand of the converter valve.

13. The optimization control system according to claim 10, characterized in that: The SVG output current reference value in the dq coordinate system includes: an active current reference value and a reactive current reference value.

14. The optimization control system according to claim 10, characterized in that: The calculation and detection unit performs proportional integral operation on the SVG output current reference value in the dq coordinate system to obtain the SVG internal potential reference value, and performs Park inverse transformation and Clark inverse transformation on the SVG internal potential reference value to obtain the SVG three-phase internal potential reference value.

15. A computer device, characterized in that: include: one or more processors; a processor for executing one or more programs; When the one or more programs are executed by the one or more processors, the method according to any one of claims 1 to 7 is implemented.

16. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed, the method according to any one of claims 1 to 7 is implemented.

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