WO2022148074A1 - 基于阀侧电流时序特征的换流阀状态与阀电流的求解方法 - Google Patents

基于阀侧电流时序特征的换流阀状态与阀电流的求解方法 Download PDF

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Publication number
WO2022148074A1
WO2022148074A1 PCT/CN2021/122020 CN2021122020W WO2022148074A1 WO 2022148074 A1 WO2022148074 A1 WO 2022148074A1 CN 2021122020 W CN2021122020 W CN 2021122020W WO 2022148074 A1 WO2022148074 A1 WO 2022148074A1
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Prior art keywords
valve
bypass
phase
current
converter
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PCT/CN2021/122020
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English (en)
French (fr)
Inventor
李晓华
殷珊珊
李洁雯
刘对
李�昊
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华南理工大学
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Priority to US18/036,537 priority Critical patent/US20230396143A1/en
Publication of WO2022148074A1 publication Critical patent/WO2022148074A1/zh

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0012—Control circuits using digital or numerical techniques
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H1/00—Details of emergency protective circuit arrangements
    • H02H1/0007—Details of emergency protective circuit arrangements concerning the detecting means
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0009—Devices or circuits for detecting current in a converter
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
    • H02M7/68—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters
    • H02M7/72—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/75—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
    • H02M7/757—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
    • H02M7/7575—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only for high voltage direct transmission link
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/145—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
    • H02M7/155—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
    • H02M7/162—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only in a bridge configuration
    • H02M7/1623—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only in a bridge configuration with control circuit
    • H02M7/1626—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only in a bridge configuration with control circuit with automatic control of the output voltage or current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/505—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
    • H02M7/515—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Definitions

  • the invention relates to the technical field of electric power systems and automation thereof, in particular to a method for solving the state of a converter valve and valve current based on the timing characteristics of valve side current.
  • the converter valve is the core equipment of the LCC-HVDC DC project, which undertakes the function of mutual conversion between AC and DC.
  • AC failure can easily lead to commutation failure of the converter valve, the current distribution of each converter valve is uneven, and the valve with commutation failure is in an overcurrent or overheated state for a long time, which is extremely detrimental to the safety of the valve equipment, and will cause the equipment to burn out or use. Consequences of reduced life expectancy. From the safety point of view of the converter valve, accurately obtaining the valve state and valve current of the whole operation process is the precondition for protecting the valve equipment and controlling the coordination.
  • the purpose of the present invention is to solve the above-mentioned defects in the prior art, and at the same time to reduce the dependence on voltage, to provide a method for solving the state of the converter valve and the valve current based on the timing characteristics of the valve side current.
  • the state and valve current can provide strong support for fault analysis, control and protection optimization of DC engineering, etc.
  • a method for solving a converter valve state and a valve current based on the timing characteristics of the valve side current comprising the following steps:
  • A is the valve current coefficient matrix
  • i is the valve current vector
  • y is the current vector at both ends of the valve side
  • i VTm is the current of the six converter valves
  • step S3 According to the trigger pulses FP 1 , FP 2 , FP 3 , FP 4 , FP 5 , and FP 6 of the converter valve obtained in step S1, when the rising edge of the trigger pulse of the converter valve is detected, the The number m is latched into the register;
  • step S4 according to the trigger pulses FP 1 , FP 2 , FP 3 , FP 4 , FP 5 , FP 6 of the converter valve obtained in step S1 , the amplitude characteristics of the alternating current and the characteristics of the alternating current variation, conduct the valve state conduction and cut-off judgment, obtain the valve states s VT1 , s VT2 , s VT3 , s VT4 , s VT5 , and s VT6 of the six converter valves;
  • step S5 According to the valve state obtained in step S4, construct the valve state matrix S:
  • s VT1 , s VT2 , s VT3 , s VT4 , s VT5 , and s VT6 are the valve states of the six converter valves;
  • valve bypass states Sa , Sb , and Sc of each phase are:
  • S a represents the valve bypass state of phase a
  • S b represents the valve bypass state of phase b
  • S c the valve bypass state of phase c
  • Sk 1 means bypass
  • k is the serial number of a, b, c three-phase
  • S total represents the number of bypass phases in abc three-phase
  • step S4 process is as follows:
  • of the alternating current of the phase where the converter valve numbered m is located is greater than the fixed value of the alternating current, i.e.
  • i k is the three-phase alternating current of a, b and c, and I set3 is the constant value of alternating current;
  • I set4 is the cut-off current threshold value
  • I set5 is the change threshold value
  • the single-phase bypass pair judgment condition is: DC current
  • the maximum value of the maximum value minus the absolute value of the AC current is greater than the commutation failure threshold setting, and the maximum value of the absolute value of the AC current is less than the single-phase bypass pair threshold setting value, namely:
  • I set1 is the commutation failure threshold setting
  • I set2 is the single-phase bypass pair threshold setting
  • step S44 When the AC and DC currents satisfy the formula (G7) of step S43, the converter valve operates as a single-phase bypass pair, wherein the valve state judgment condition of the single-phase bypass pair is:
  • step S8 process is as follows:
  • step S81 According to the number of bypass phases obtained in step S7, when the number of bypass phases S total ⁇ 1, the converter valve operates without a bypass pair or a single-phase bypass pair, and there is no need to construct a bypass circuit voltage at this time. Equation, skip to step S91, otherwise, go to step S82;
  • step S9 process is as follows:
  • i [i VT1 i VT2 i VT3 i VT4 i VT5 i VT6 ] T .
  • i [i VT1 i VT2 i VT3 i VT4 i VT5 i VT6 ] T
  • p is the serial number of the bypass phase
  • E is the coefficient matrix composed of the coefficient matrix A and the coefficient matrix C p
  • z is the vector composed of the current vector y and the constant vector D p at both ends of the valve side.
  • FP m (t) is the trigger pulse signal of the converter valve numbered m at time t
  • FP m (t- ⁇ t) is the trigger pulse signal of the converter valve numbered m at time (t- ⁇ t)
  • t is the time at a certain moment
  • ⁇ t is the sampling time interval.
  • the present invention has the following advantages and effects:
  • the present invention can not only accurately calculate the valve current, but also real-time Distinguish the on and off state of the converter valve.
  • the monitoring of valve state and the accurate calculation of valve current are particularly important for existing theoretical research in practical engineering applications, and are of great significance to the protection and control of reconfigured converter valves.
  • Fig. 1 is the flow chart of valve state discrimination and valve current calculation in the present invention
  • clockVT represents the symbol of the register
  • t_end represents the running end time
  • ia , ib , ic , idH and idN are the access ports for collecting current on the valve side of the converter, FP 1 , FP 2 , FP 3.
  • FP 4 , FP 5 , FP 6 are the acquisition and access ports of the trigger pulse of the converter valve
  • s VT1 , s VT2 , s VT3 , s VT4 , s VT5 , s VT6 are the output ports of the valve status signal
  • i VT1 , i VT2 , i VT3 , i VT4 , i VT5 , i VT6 are the output ports of the valve current calculation;
  • FIG. 3 is a schematic diagram of a converter valve for high-voltage direct current transmission in the present invention, wherein i a , ib , and ic are the a-phase, b -phase, and c -phase of the three-phase alternating current, idH is the high-voltage side direct current current, and idN is the low-voltage side Side DC current, i VT1 , i VT2 , i VT3 , i VT4 , i VT5 , i VT6 are valve currents, and the direction indicated by the arrow in the figure is positive current;
  • Fig. 5 is the trigger pulse of 6 converter valves of HVDC power transmission of the present invention, and FP 1 , FP 2 , FP 3 , FP 4 , FP 5 , and FP 6 are the trigger pulses of the 6 converter valves;
  • Fig. 6 is the current loop diagram of the state judgment of the bypass of the converter valve in the present invention.
  • Fig. 7 is the valve state judging flow chart of 6 pulses in the present invention.
  • Fig. 8 is the valve state discrimination flow chart of the converter valve numbered 1 in the present invention.
  • Fig. 9 is the flow chart of by-pass to state discrimination in the present invention.
  • Fig. 10 is a valve state waveform diagram based on the variation characteristics of the alternating current in the present invention, in which s VT1 , s VT2 , s VT3 , s VT4 , s VT5 and s VT6 are valve state signals;
  • Fig. 11 is the flow chart of supplementary bypass equation in the present invention.
  • valve current waveform diagram based on valve state calculation in the present invention, in which i VT1 , i VT2 , i VT3 , i VT4 , i VT5 , i VT6 are valve current signals;
  • FIG. 13 is a valve state waveform diagram considering the one-way conductivity correction of the valve in the present invention, in which s VT1 , s VT2 , s VT3 , s VT4 , s VT5 and s VT6 are valve state signals;
  • valve current waveform diagram calculated based on the corrected valve state in the present invention, in which i VT1 , i VT2 , i VT3 , i VT4 , i VT5 , and i VT6 are valve current signals.
  • the invention discloses a method for solving the converter valve state and valve current based on the timing characteristics of valve side current.
  • the working conditions of the converter valve after the AC fault change differently.
  • this embodiment takes the three-phase fault of the 6-pulse inverter side commutator bus as an example. 1 and 2 illustrate the present invention in further detail.
  • FIG. 3 The commutation topology of this embodiment is shown in Figure 3.
  • the six valve arms are numbered in the order in which they are normally opened.
  • VT1 represents the converter valve numbered 1
  • VT2 represents the converter valve numbered 2
  • VT3 represents the number VT4 represents the converter valve numbered 4
  • VT5 represents the converter valve numbered 5
  • VT6 represents the converter valve numbered 6
  • valve VT4 valve VT6
  • valve VT2 constitute the upper bridge arm
  • the valve VT1, the valve VT3, and the valve VT5 constitute the lower bridge arm.
  • A is the valve current coefficient matrix
  • i is the valve current vector
  • y is the current vector at both ends of the valve side
  • i VTm are the currents of the six converter valves
  • FP m (t) is the trigger pulse signal of the converter valve number m at time t
  • FP m (t- ⁇ t) is the trigger pulse signal of the converter valve numbered at (t- ⁇ t) time
  • t is the time at a certain moment
  • ⁇ t is the sampling time interval
  • step S4 in conjunction with step S1 and step S3, according to the trigger pulse of the converter valve and the amplitude characteristics of the alternating current and the characteristics of the alternating current change amount, carry out the conduction and cut-off discrimination of the valve state, and obtain the valve states s VT1 , s VT2 , s VT3 , s VT4 , s VT5 , s VT6 .
  • the valve state judgment of this method mainly uses the amplitude characteristics of the AC current, but when the converter valve only has the same-phase upper and lower bridge arms conducting to form a single-phase bypass pair, as shown in Figure 6, the three-phase AC current is 0, the AC and DC are completely isolated, and the valve state cannot be judged by the AC current, so the valve state of the single-phase bypass pair needs to be judged separately.
  • the flow chart of the total valve state determination is shown in Fig. 7, which includes the sub-module of valve state determination of 6 converter valves and the sub-module of single-phase bypass pair state determination.
  • the sub-module for judging the valve state of the six converter valves takes valve VT1 as an example, and the flowchart is shown in Figure 8.
  • the sub-module of single-phase bypass pair status judgment is shown in Figure 9.
  • the 6 valve state waveforms obtained based on the change characteristics of the AC current are shown in Figure 10, and s VT1 , s VT2 , s VT3 , s VT4 , s VT5 , and s VT6 respectively represent the six commutation the valve status of the valve;
  • step S4 specifically includes the following steps:
  • the conduction criterion of the converter valve is: the amplitude
  • i a is the a-phase alternating current
  • I set3 is the constant value of the alternating current.
  • the cut-off criterion of the converter valve is: the amplitude
  • I set4 is the cut-off current threshold value
  • I set5 is the change threshold value
  • step S43 when only the single-phase upper and lower valves are conducting, the converter valve operates as a single-phase bypass pair, and the two valves of the bypass pair are judged to be conducting.
  • the single-phase bypass pair judgment condition is: the maximum value of the DC current minus the maximum value of the absolute value of the AC current is greater than the commutation failure threshold setting, and the maximum value of the absolute value of the AC current is less than the single-phase bypass pair threshold setting.
  • I set1 is the commutation failure threshold setting
  • I set2 is the single-phase bypass pair threshold setting
  • step S44 when the AC and DC currents satisfy the formula (4) of step S43, the converter valve operates as a single-phase bypass pair. Show. The valve state of the single-phase bypass pair is judged as:
  • step S5 According to the valve state obtained in step S4, construct the valve state matrix S:
  • s VT1 , s VT2 , s VT3 , s VT4 , s VT5 , and s VT6 are the valve states of the six converter valves;
  • step S6 by calculating the product of the upper and lower valve states of each phase, it is judged whether there is a bypass state for each phase, and the bypass states Sa , Sb and Sc of each phase are:
  • S a represents the valve bypass state of phase a
  • S b represents the valve bypass state of phase b
  • S c the valve bypass state of phase c
  • Sk 1 means bypass
  • k refers to a, b, c three phases
  • step S6 summing the valve bypass states of the three phases to determine the number of bypass phases.
  • S total represents the number of bypass phases in abc three-phase
  • step S8 specifically includes the following steps:
  • step S81 According to the number of bypass phases obtained in step S7, when the number of bypass phases S total ⁇ 1, there is no need to construct a bypass loop voltage equation at this time, and skip to step S91. Otherwise, go to step S82;
  • C abc is the coefficient matrix of the bypass circuit voltage equation when the abc phase is bypassed
  • D abc is the constant vector of the bypass circuit voltage equation when the abc phase is bypassed.
  • step S9 the converter valve current i VTm is solved to obtain the valve currents i VT1 , i VT2 , i VT3 , i VT3 , and i VT4 , i VT5 , i VT6 , compare the calculated valve current with the simulated value in the DC engineering, the waveform is shown in Figure 12, it is found that there is a significant difference between the calculated value and the simulated value, and the calculated value of the valve current is as follows: In the case of negative values, the calculation results need to be corrected;
  • step S9 specifically includes the following steps:
  • AS is the coefficient matrix
  • i [i VT1 i VT2 i VT3 i VT4 i VT5 i VT6 ] T .
  • i [i VT1 i VT2 i VT3 i VT4 i VT5 i VT6 ] T
  • p ab
  • E ab is a coefficient matrix composed of a coefficient matrix A and a coefficient matrix C ab
  • za ab is a vector composed of a current vector y at both ends of the valve side and a constant vector D ab .
  • the current of the internal converter valve can only be a positive value
  • a method for solving the state of the converter valve and the valve current based on the timing characteristics of the valve side current uses the trigger pulse signal of the converter valve and the change characteristics of the AC current amplitude to discriminate the valve state; Based on the valve state, the valve current is solved by combining the topological relationship between the AC and DC current and the valve current. Considering the one-way conductivity of the valve, correct the valve state, and calculate the valve current again, so as to obtain the valve state and valve current of the whole operation process. According to FIG. 14 , the calculated value of the valve current is consistent with the simulated value in the actual DC power grid, which verifies the effectiveness of the method of the present invention. This method can be applied to practical engineering, and is very important for engineering fault analysis and control coordination.

Abstract

一种基于阀侧电流时序特征的换流阀状态与阀电流的求解方法，过程如下：采集直流输电系统换流器阀侧三相交流电流、直流电流和换流阀触发脉冲；建立交直流电流与阀电流的节点电流方程；当检测到换流阀触发脉冲的上升沿时，将换流阀的编号进行锁存；根据换流阀的触发脉冲和交流电流的幅值特征以及交流电流变化量的特征进行阀状态的导通和截止判别，求取阀状态；构造阀状态矩阵；判断每相是否存在旁通的状态；通过求三相的阀旁通状态之和，判断旁通相的数量；增补旁通回路电压方程；对换流阀电流进行求解；当计算得到阀电流的值为负时，根据换流阀的单向导电性修正阀状态为截止，否则不修正；再次重复以上步骤计算阀电流。

Description

基于阀侧电流时序特征的换流阀状态与阀电流的求解方法 技术领域
本发明涉及电力系统及其自动化技术领域，具体涉及一种基于阀侧电流时序特征的换流阀状态与阀电流的求解方法。
背景技术
换流阀是LCC-HVDC直流工程的核心设备，承担交流和直流相互转换的功能。交流故障容易导致换流阀发生换相失败，各个换流阀的电流分布不均匀，换相失败的阀长时间处于过流或过热状态对阀设备的安全极为不利，会造成设备烧坏或使用寿命降低的后果。从换流阀的安全角度考虑，准确获取运行全过程的阀状态和阀电流是保护阀设备和控制协调的前提条件。
由于设备散热、绝缘等工艺设计的原因，实际电网直流工程的换流阀内部无法安装测量元件直接测量阀电流，只能利用换流阀外部的电流互感器测量得到的直流电气量和交流电气量间接表示换流阀的电流导通情况和换流阀的运行状态。正常运行时同相的上、下桥臂不会同时导通，根据电流从高电位阀流入、从低电位流出的工作规律，通过测量到的交流电流的极性特征可以计算得到阀电流和阀状态。然而，当发生交流故障时，同相的上、下桥臂可能会同时导通，换流阀出现单相旁通或多相旁通的运行情况，此时仅仅利用交流电流的极性特征无法求取换流阀电流和阀状态。
发明内容
本发明的目的是为了解决现有技术中的上述缺陷，同时为减小对电压的依赖，提供一种基于阀侧电流时序特征的换流阀状态与阀电流的求解方法，此方法得到的阀状态与阀电流可对直流工程的故障分析、控制保护优化等提供有力的支撑。
本发明的目的可以通过采取如下技术方案达到：
一种基于阀侧电流时序特征的换流阀状态与阀电流的求解方法，所述求解方法包括以下步骤：
S1、采集直流输电系统换流器阀侧三相交流电流i a、i b、i c和直流电流i dH、i dN，换流阀触发脉冲FP 1、FP 2、FP 3、FP 4、FP 5、FP 6；
S2、根据直流输电系统换流器的拓扑结构，建立阀侧三相交流电流i a、i b、i c、直流电流i dH、i dN与阀电流i VTm的节点电流方程Ai＝y；
Figure PCTCN2021122020-appb-000001
其中，
Figure PCTCN2021122020-appb-000002
A为阀电流系数矩阵， i为阀电流向量，y为阀侧两端电流向量，i VTm分别为6个换流阀的电流，m为6个换流阀的编号，m＝1、2、3、4、5、6；
S3、根据步骤S1得到的换流阀的触发脉冲FP 1、FP 2、FP 3、FP 4、FP 5、FP 6，当检测到换流阀的触发脉冲的上升沿时，将换流阀的编号m锁存到寄存器中；
S4、根据步骤S1得到的换流阀的触发脉冲FP 1、FP 2、FP 3、FP 4、FP 5、FP 6和交流电流的幅值特征以及交流电流变化量的特征进行阀状态的导通和截止判别，求取6个换流阀的阀状态s VT1、s VT2、s VT3、s VT4、s VT5、s VT6；
S5、根据步骤S4得到的阀状态，构造阀状态矩阵S：
Figure PCTCN2021122020-appb-000003
式中：s VT1、s VT2、s VT3、s VT4、s VT5、s VT6为6个换流阀的阀状态；
S6、通过求每相上、下两阀状态的乘积，判断每相是否存在旁通的状态，每相的阀旁通状态S a、S b、S c为：
Figure PCTCN2021122020-appb-000004
式中：S a表示a相的阀旁通状态，S b表示b相的阀旁通状态，S c表示c相的阀旁通状态，S k＝1表示旁通，S k＝0表示不旁通，k为a、b、c三相的序号；
S7、对三相的阀旁通状态进行求和，判断旁通相的数量，其中，旁通相的数量S total表示如下：S total＝∑(S a+S b+S c)  (G4)；
式中：S total表示abc三相中旁通相的数量；
S8、根据步骤S7中求得的旁通相的数量与对应相，增补旁通回路电压方程C pi＝D p；其中：C p为旁通回路电压方程的系数矩阵，i为阀电流向量，D p为常数向量，p为旁通相的序号；
S9、根据步骤S2和S8，并结合步骤S4对换流阀电流i VTm进行求解；
S10、当步骤S9计算的阀电流i VTm＜0时，考虑换流阀的单向导电性，修正阀状态，将阀状态修正为截止s VTm＝0，否则，不修正；
S11、重复步骤S5-步骤S10，直至计算得到的阀电流i VTm≥0。
进一步地，所述步骤S4过程如下：
S41、当步骤S1中检测到换流阀的触发脉冲是高电平且满足换流阀的导通判据时，置位阀状态s VTm＝1，其中，换流阀的导通判据是：编号为m的换流阀所在相的交流电流的幅值|i k|大于交流电流定值，即|i k|＞I set3  (G5)
式中：i k为a、b、c三相交流电流，I set3为交流电流定值；
S42、当编号为m的换流阀为导通状态s VTm＝1时，若交流电流满足截止判据，则编号为m的换流阀为截止状态s VTm＝0；否则，编号为m的换流阀继续保持导通状态s VTm＝1；其中，换流阀的截止判据是：编号为m的换流阀所在相的交流电流的幅值|i k|小于截止电流门槛定值，且交流电流变化率小于变化量门槛定值，即：|i k|＜I set4且
Figure PCTCN2021122020-appb-000005
式中：I set4为截止电流门槛定值，I set5为变化量门槛定值；
S43、当只有单相的上、下两阀导通时，换流阀形成单相旁通对运行，旁通对的两 阀判别为导通状态，单相旁通对判别条件是：直流电流的最大值减去交流电流绝对值的最大值大于换相失败门槛定值，且交流电流绝对值的最大值小于单相旁通对门槛定值，即：
Figure PCTCN2021122020-appb-000006
式中：I set1为换相失败门槛定值，I set2为单相旁通对门槛定值；
S44、当交直流电流满足步骤S43的公式(G7)时，换流阀为单相旁通对运行，其中，单相旁通对的阀状态判别条件为：
1)当所有阀的旁通状态标志s bypass_m＝0时，若步骤S3的寄存器信号等于m，则编号为m的换流阀所在相为旁通相，置位旁通相两阀的旁通状态标志等于1，保持旁通相两阀都为导通状态，即：s bypass_m＝1和s bypass_(mod(m+3,6))＝1，s VTm＝1和s VT(mod(m+3,6))＝1；
2)当编号为m的换流阀所在相的旁通状态标志s bypass_m＝1或s bypass_(mod(m+3,6))＝1时，保持编号为m的换流阀所在相两阀都为导通状态。
进一步地，所述步骤S8过程如下：
S81、根据步骤S7中得到的旁通相的数量，当旁通相的数量S total≤1时，换流阀无旁通对或单相旁通对运行，此时不需要构造旁通回路电压方程，跳到步骤S91，否则，转到步骤S82；
S82、当旁通相的数量S total＝2时，表明换流阀两相旁通运行，增补旁通回路电压方程C pi＝D p，跳到步骤S92，否则，转到步骤S83；其中，
1)若S a＝S b，则存在以下关系：i VT1+i VT4＝i VT3+i VT6  (G8)
增补旁通回路电压方程C abi＝D ab，其中：C ab＝[1 0 -1 1 0 -1]，D ab＝[0]，p＝ab，C ab为ab相旁通时旁通回路电压方程的系数矩阵，D ab为ab相旁通时旁通回路电压方程的常数向量；
2)若S a＝S c，则存在以下关系：i VT1+i VT4＝i VT2+i VT5  (G9)
增补旁通回路电压方程C aci＝D ac，其中：C ac＝[1 -1 0 1 -1 0]，D ac＝[0]，p＝ac，C ac为ac相旁通时旁通回路电压方程的系数矩阵，D ac为ac相旁通时旁通回路电压方程的常数向量；
3)若S b＝S c，则存在以下关系：i VT2+i VT5＝i VT3+i VT6  (G10)
增补旁通回路电压方程C bci＝D bc中，C bc＝[0 1 -1 0 1 -1]，D bc＝[0]，p＝bc，C bc为bc相旁通时旁通回路电压方程的系数矩阵，D bc为bc相旁通时旁通回路电压方程的常数向量；
S83、当旁通对工况S total＝3时，表明换流阀三相旁通对运行，增补旁通回路电压方程C pi＝D p，跳到步骤S92；同时，存在以下关系：
Figure PCTCN2021122020-appb-000007
增补旁通回路电压方程C abci＝D abc，其中：
Figure PCTCN2021122020-appb-000008
D abc＝[0 0] T，p＝abc，C abc为abc相旁通时旁通回路电压方程的系数矩阵，D abc为abc相旁通时旁通回路电压方程的常数向量；
所述步骤S9过程如下：
S91、构造基于阀状态特征的状态方程ASi＝y，对系数矩阵求逆计算阀电流i VTm：
i＝(AS) -1×y  (G12)
式中：i＝[i VT1 i VT2 i VT3 i VT4 i VT5 i VT6] T。
S92、将Ai＝y与C pi＝D p联立，结合阀状态特征S构造状态方程ESi＝z，对系数矩阵求逆，计算阀电流i VTm：i＝(ES) -1×z  (G13)
式中：i＝[i VT1 i VT2 i VT3 i VT4 i VT5 i VT6] T，
Figure PCTCN2021122020-appb-000009
p为旁通相的序号，E为系数矩阵A和系数矩阵C p组成的系数矩阵，z为阀侧两端电流向量y和常数向量D p组成的向量。
进一步地，所述步骤S3中当检测到换流阀的触发脉冲的上升沿FP m(t)-FP m(t-Δt)＝1时，将换流阀的编号m锁存到寄存器中；其中：FP m(t)是编号为m的换流阀在t时刻的触发脉冲信号，FP m(t-Δt)是编号为m的换流阀在(t-Δt)时刻的触发脉冲信号，t为某一时刻的时间，Δt为采样时间间隔。
本发明相对于现有技术具有如下的优点及效果：
高压直流输电系统中，基于换流阀电流为基础所做的理论研究偏多，如换相失败检测等。然而，阀电流不可直接测量且无合适的计算方法，使得研究成果不能直接应用于实际直流工程，只能停留在理论研究阶段。本发明根据换流阀两端的交流电流、直流电流以及换流阀触发脉冲可以测量得到的信号，通过节点电流方程和换流阀的单向导电性，不但可以准确计算阀电流，而且还能实时判别换流阀的导通和关断状态。阀状态的监控和阀电流的精确计算对已有的理论研究在实际工程应用尤为重要，且对重构换流阀的保护与控制具有重要意义。
附图说明
图1是本发明中阀状态判别和阀电流计算的流程图，clockVT表示寄存器的符号，t_end表示运行结束时间；
图2是本发明中阀状态和阀电流计算模型示意图，其中i a、i b、i c、i dH、i dN为换流器阀侧采集电流的接入端口，FP 1、FP 2、FP 3、FP 4、FP 5、FP 6为换流阀触发脉冲的采集接入端口，s VT1、s VT2、s VT3、s VT4、s VT5、s VT6为阀状态信号的输出端口；i VT1、i VT2、i VT3、i VT4、i VT5、i VT6为阀电流计算的输出端口；
图3是本发明中高压直流输电换流阀示意图，其中i a、i b、i c为三相交流电流的a相、b相、c相，i dH为高压侧直流电流，i dN为低压侧直流电流，i VT1、i VT2、i VT3、i VT4、i VT5、i VT6为阀电流，图中箭头指示方向为正电流；
图4是本发明中换流阀阀侧三相交流电流i a、i b、i c和直流电流i dmax的波形，直流电流i dmax是高压侧直流电流i dH和低压侧直流电流i dN的最大值，即i dmax＝max(i dH,i dN)；
图5是本发明的高压直流输电6个换流阀的触发脉冲，FP 1、FP 2、FP 3、FP 4、FP 5、FP 6为6个换流阀的触发脉冲；
图6是本发明中换流阀旁通对状态判别的电流回路图；
图7是本发明中6脉波的阀状态判别流程图；
图8是本发明中编号为1的换流阀的阀状态判别流程图；
图9是本发明中旁通对状态判别的流程图；
图10是本发明中基于交流电流的变化特征判别的阀状态波形图，图中s VT1、s VT2、s VT3、s VT4、s VT5、s VT6为阀状态信号；
图11是本发明中增补旁通方程的流程图；
图12是本发明中基于阀状态计算的阀电流波形图，图中i VT1、i VT2、i VT3、i VT4、i VT5、 i VT6为阀电流信号；
图13是本发明中考虑阀的单向导电性修正的阀状态波形图，图中s VT1、s VT2、s VT3、s VT4、s VT5、s VT6为阀状态信号；
图14是本发明中基于修正后阀状态计算的阀电流波形图，图中i VT1、i VT2、i VT3、i VT4、i VT5、i VT6为阀电流信号。
具体实施方式
为使本发明实施例的目的、技术方案和优点更加清楚，下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。
实施例
本发明公开了一种基于阀侧电流时序特征的换流阀状态与阀电流的求解方法，利用此方法在实际电网工程里面进行阀状态判别和阀电流计算。交流故障后换流阀工况变化不尽相同，为了更能全面的囊括故障后的换流阀工况情况，本实施例以6脉波逆变侧换流母线的三相故障为例，按照图1和图2对本发明做进一步详细说明。
S1、首先对本发明涉及的换流器进行简要描述。本实施例的换流拓扑结构如图3所示，图中6个阀臂按正常开通的次序编号，VT1表示编号为1的换流阀，VT2表示编号为2的换流阀，VT3表示编号为3的换流阀，VT4表示编号为4的换流阀，VT5表示编号为5的换流阀，VT6表示编号为6的换流阀，阀VT4、阀VT6、阀VT2构成上桥臂，阀VT1、阀VT3、阀VT5构成下桥臂。采集直流输电系统图3换流器阀侧三相交流电流i a、i b、i c、高压侧直流电流i dH、高压侧直流电流i dN和换流阀触发脉冲FP 1、FP 2、FP 3、FP 4、FP 5、FP 6。根据采集的信号，得到故障前后阀侧三相交流电流和直流电流的电流波形如图4所示，6个换流阀的触发脉冲波形如图5所示；
S2、根据步骤S1中直流输电系统换流器的拓扑结构，根据基尔霍夫定律，建立阀侧三相交流电流i a、i b、i c、直流电流i dH、i dN与阀电流i VTm的节点电流方程Ai＝y；
Figure PCTCN2021122020-appb-000010
其中，
Figure PCTCN2021122020-appb-000011
A为阀电流系数矩阵，i为阀电流向量，y为阀侧两端电流向量，i VTm分别为6个换流阀的电流，m为6个换流阀的编号，m＝1、2、3、4、5、6；
S3、根据步骤S1中采集的换流阀的触发脉冲FP 1、FP 2、FP 3、FP 4、FP 5、FP 6，当检测到换流阀的触发脉冲的上升沿(FP m(t)-FP m(t-Δt)＝1)时，将换流阀的编号m锁存到寄存器中；其中：FP m(t)是编号为m的换流阀在t时刻的触发脉冲信号，FP m(t-Δt)是编号为m的换流阀在(t-Δt)时刻的触发脉冲信号，t为某一时刻的时间，Δt为采样时间间隔；例如：当检测到编号为1的换流阀的触发脉冲的上升沿时，寄存器中保存编号1；
S4、结合步骤S1和步骤S3，根据换流阀的触发脉冲和交流电流的幅值特征以及 交流电流变化量的特征进行阀状态的导通和截止判别，求取阀状态s VT1、s VT2、s VT3、s VT4、s VT5、s VT6。本方法的阀状态判别主要利用交流电流的幅值特征，但当换流阀只有同相上、下桥臂导通形成单相旁通对时，如图6所示，此时三相交流电流为0，交直流完全隔离，无法利用交流电流判别阀状态，故需要对单相旁通对的阀状态单独判别。其中，阀状态总判别的流程图如图7所示，图中包含6个换流阀的阀状态判别的子模块和单相旁通对状态判别的子模块。6个换流阀的阀状态判别的子模块以阀VT1为例，流程图如图8所示。单相旁通对状态判别的子模块如图9所示。根据流程图7、8、9基于交流电流的变化特征得到的6个阀状态波形如图10所示，s VT1、s VT2、s VT3、s VT4、s VT5、s VT6分别表示6个换流阀的阀状态；
本实施例中，结合图7阀状态判别的流程图，步骤S4具体包括以下几个步骤：
S41、根据步骤S1，以阀VT1为例，阀VT1的阀状态判别流程图如图8所示，当检测到阀VT1的触发脉冲是高电平且满足换流阀的导通判据时，置位阀状态s VT1＝1。其中，换流阀的导通判据是：阀VT1所在a相的交流电流的幅值|i a|大于交流电流定值。即：|i a|＞I set3  (2)
式中：i a为a相交流电流；I set3为交流电流定值。
S42、根据步骤S41，当阀VT1为导通状态(s VT1＝1)时，若交流电流满足截止判据，则阀VT1为截止状态(s VT1＝0)。否则，阀VT1继续保持导通状态(s VT1＝1)。其中，换流阀的截止判据是：阀VT1所在a相的交流电流的幅值|i a|小于截止电流门槛定值，且交流电流变化率小于变化量门槛定值。即：|i a|＜I set4且
Figure PCTCN2021122020-appb-000012
式中：I set4为截止电流门槛定值，I set5为变化量门槛定值。
S43、根据步骤S1、步骤S41和步骤S42，当只有单相的上、下两阀导通时，换流阀形成单相旁通对运行，旁通对的两阀判别为导通状态。单相旁通对判别条件是：直流电流的最大值减去交流电流绝对值的最大值大于换相失败门槛定值，且交流电流绝对值的最大值小于单相旁通对门槛定值。即：
Figure PCTCN2021122020-appb-000013
Figure PCTCN2021122020-appb-000014
式中：I set1为换相失败门槛定值，I set2为单相旁通对门槛定值。
S44、根据S1、步骤S3和步骤S43，当交直流电流满足步骤S43的公式(4)时，换流阀为单相旁通对运行，旁通对条件下状态判别的流程图如图9所示。单相旁通对的阀状态判别为：
1)当所有阀的旁通状态标志s bypass_m＝0时，若步骤S3中寄存器信号等于1或4，a相旁通对。则旁通状态标志s bypass_1＝1和s bypass_4＝1，阀状态s VT1＝1和s VT4＝1；否则：若步骤S3中寄存器信号等于3或6，b相旁通对。则s bypass_3＝1和s bypass_6＝1，s VT3＝1和s VT6＝1；否则：若步骤S3中寄存器信号等于2或5，c相旁通对。则s bypass_2＝1和s bypass_5＝1，s VT2＝1和s VT5＝1；
2)当旁通状态标志s bypass_1＝1或s bypass_4＝1时，保持a相两阀继续导通状态；否则： 当旁通状态标志s bypass_3＝1或s bypass_6＝1，保持b相两阀继续导通状态；否则：当旁通状态标志s bypass_2＝1或s bypass_5＝1，保持c相两阀继续导通状态。
S5、根据步骤S4得到的阀状态，构造阀状态矩阵S：
Figure PCTCN2021122020-appb-000015
式中：s VT1、s VT2、s VT3、s VT4、s VT5、s VT6为6个换流阀的阀状态；
S6、根据步骤S5，通过求每相上、下两阀状态的乘积，判断每相是否存在旁通的状态，每相的旁通状态S a、S b、S c为：
Figure PCTCN2021122020-appb-000016
式中：S a表示a相的阀旁通状态，S b表示b相的阀旁通状态，S c表示c相的阀旁通状态，S k＝1表示旁通，S k＝0表示不旁通，k指a、b、c三相；
S7、根据步骤S6，对三相的阀旁通状态进行求和，判断旁通相的数量。旁通相的数量S total表示如下：S total＝∑(S a+S b+S c)   (7)
式中：S total表示abc三相中旁通相的数量；
S8、根据步骤S7中得到的旁通相的数量与对应相，当S total＞1时，换流阀存在2条及以上旁通对，直接根据式(1)换流阀的节点电流方程不可求解阀电流或方程解不唯一，故需要增补旁通回路电压方程C pi＝D p，判别增补流程图如图11所示，其中：C p为旁通回路电压方程的系数矩阵，i为阀电流向量，D p为常数向量，p为旁通相的序号；
本实施例中，增补旁通回路电压方程的流程图如图11所示，步骤S8具体包括以下几个步骤：
S81、根据步骤S7中得到的旁通相的数量，当旁通相的数量S total≤1时，此时不需要构造旁通回路电压方程，跳到步骤S91。否则，转到步骤S82；
S82、根据步骤S7和步骤S81，当旁通相的数量S total＝2时，表明换流阀两相旁通运行，跳到步骤S92。否则，转到步骤S83。
若：S a＝S b，则存在以下关系：i VT1+i VT4＝i VT3+i VT6  (8)
增补旁通回路电压方程C abi＝D ab中，C ab＝[1 0 -1 1 0 -1]，D ab＝[0]，C ab为ab相旁通时旁通回路电压方程的系数矩阵，D ab为ab相旁通时旁通回路电压方程的常数 向量；
当S a＝S c和S b＝S c的旁通情况下，公式(8)只需要修改对应的旁通相即可。
S83、根据步骤S7、步骤S81和步骤S82，当旁通对工况S total＝3时，表明换流阀三相旁通对运行，跳到步骤S92。则存在以下关系：
Figure PCTCN2021122020-appb-000017
增补旁通回路电压方程C abci＝D abc中，
Figure PCTCN2021122020-appb-000018
D abc＝[0 0] T，C abc为abc相旁通时旁通回路电压方程的系数矩阵，D abc为abc相旁通时旁通回路电压方程的常数向量。
S9、根据步骤S2和步骤S8，并结合步骤S4对换流阀电流i VTm进行求解，得到基于交流电流的变化特征得到的阀状态的基础上计算的阀电流i VT1、i VT2、i VT3、i VT4、i VT5、i VT6，将计算得到的阀电流与直流工程中的仿真值进行对比，波形如图12所示，发现计算值与仿真值存在明显差异，且存在阀电流的计算值有负值的情况，需要对计算结果进行修正；
本实施例中，结合图1和图11，步骤S9具体包括以下几个步骤：
S91、根据步骤S2、步骤S4和步骤S81，构造基于阀状态特征的状态方程ASi＝y，计算阀电流i VTm。其中：
Figure PCTCN2021122020-appb-000019
式中，
Figure PCTCN2021122020-appb-000020
AS为系数矩阵。
对系数矩阵AS求逆。计算阀电流i VTm：
i＝(AS) -1×y    (11)
式中：i＝[i VT1 i VT2 i VT3 i VT4 i VT5 i VT6] T。
S92、根据步骤S2、步骤S4、步骤S81和步骤S83，将Ai＝y与C pi＝D p的，结合阀状态特征S构造状态方程ESi＝z。对系数矩阵求逆，计算阀电流i VTm。
例如：当S a＝S b，结合式(1)和式(8)，构造状态方程E abSi＝z ab：
Figure PCTCN2021122020-appb-000021
式中，
Figure PCTCN2021122020-appb-000022
对系数矩阵E abS求逆，计算阀电流i VTm：
i＝(E abS) -1×z ab   (13)
式中：i＝[i VT1 i VT2 i VT3 i VT4 i VT5 i VT6] T，
Figure PCTCN2021122020-appb-000023
p＝ab，E ab为系数矩阵A和系数矩阵C ab组成的系数矩阵，z ab为阀侧两端电流向量y和常数向量D ab组成的向量。
其它旁通情况类似。
S10、根据步骤S9，当步骤S9中计算的阀电流i VTm＜0(m＝1,2,3,4,5,6)时，考虑换流阀的单向导电性，在规定的正方向内换流阀的电流只能为正值，修正此时的阀状态，将阀状态修正为截止s VTm＝0，否则，不修正；
S11、重复步骤S5-步骤S10，直至计算得到的阀电流i VTm＞0。考虑阀的单向导电性修正后的阀状态如图13所示，s VT1、s VT2、s VT3、s VT4、s VT5、s VT6为6个换流阀修正后的阀状态；基于修正后的阀状态的基础上再次计算的阀电流i VT1、i VT2、i VT3、i VT4、i VT5、i VT6，将阀状态修正后计算得到的阀电流与仿真值做对比，波形如图14所示，发现计算值与仿真值相吻合，表明此方法的有效性。
综上，本实施例提出的一种基于阀侧电流时序特征的换流阀状态与阀电流的求解方法，借助于换流阀的触发脉冲信号和交流电流幅值的变化特征对阀状态判别；基于阀状态的基础上，结合交直流电流与阀电流的拓扑关系求解阀电流。考虑阀的单向导电性修正阀状态，再次计算阀电流，从而得到运行全过程的阀状态和阀电流。根据图14，阀电流的计算值与实际直流电网中的仿真值相吻合，验证了本发明方法的有效性。此方法可以应用到实际工程中，对工程的故障分析及控制协调非常重要。
上述实施例为本发明较佳的实施方式，但本发明的实施方式并不受上述实施例的限制，其他的任何未背离本发明的精神实质与原理下所作的改变、修饰、替代、组合、简化，均应为等效的置换方式，都包含在本发明的保护范围之内。

Claims (4)

  1. 一种基于阀侧电流时序特征的换流阀状态与阀电流的求解方法，其特征在于，所述求解方法包括以下步骤：
    S1、采集直流输电系统换流器阀侧三相交流电流i a、i b、i c和直流电流i dH、i dN，换流阀触发脉冲FP 1、FP 2、FP 3、FP 4、FP 5、FP 6；
    S2、根据直流输电系统换流器的拓扑结构，建立阀侧三相交流电流i a、i b、i c、直流电流i dH、i dN与阀电流i VTm的节点电流方程Ai＝y；
    Figure PCTCN2021122020-appb-100001
    其中，
    Figure PCTCN2021122020-appb-100002
    A为阀电流系数矩阵，i为阀电流向量，y为阀侧两端电流向量，i VTm分别为6个换流阀的电流，m为6个换流阀的编号，m＝1、2、3、4、5、6；
    S3、根据步骤S1得到的换流阀的触发脉冲FP 1、FP 2、FP 3、FP 4、FP 5、FP 6，当检测到换流阀的触发脉冲的上升沿时，将换流阀的编号m锁存到寄存器中；
    S4、根据步骤S1得到的换流阀的触发脉冲FP 1、FP 2、FP 3、FP 4、FP 5、FP 6和交流电流的幅值特征以及交流电流变化量的特征进行阀状态的导通和截止判别，求取6个换流阀的阀状态s VT1、s VT2、s VT3、s VT4、s VT5、s VT6；
    S5、根据步骤S4得到的阀状态，构造阀状态矩阵S：
    Figure PCTCN2021122020-appb-100003
    式中：s VT1、s VT2、s VT3、s VT4、s VT5、s VT6为6个换流阀的阀状态；
    S6、通过求每相上、下两阀状态的乘积，判断每相是否存在旁通的状态，每相的阀 旁通状态S a、S b、S c为：
    Figure PCTCN2021122020-appb-100004
    式中：S a表示a相的阀旁通状态，S b表示b相的阀旁通状态，S c表示c相的阀旁通状态，S k＝1表示旁通，S k＝0表示不旁通，k为a、b、c三相的序号；
    S7、对三相的阀旁通状态进行求和，判断旁通相的数量，其中，旁通相的数量S total表示如下：
    S total＝Σ(S a+S b+S c)    (G4)；
    式中：S total表示abc三相中旁通相的数量；
    S8、根据步骤S7中求得的旁通相的数量与对应相，增补旁通回路电压方程C pi＝D p；其中：C p为旁通回路电压方程的系数矩阵，i为阀电流向量，D p为常数向量，p为旁通相的序号；
    S9、根据步骤S2和S8，并结合步骤S4对换流阀电流i VTm进行求解；
    S10、当步骤S9计算的阀电流i VTm＜0时，考虑换流阀的单向导电性，修正阀状态，将阀状态修正为截止s VTm＝0，否则，不修正；
    S11、重复步骤S5-步骤S10，直至计算得到的阀电流i VTm≥0。
  2. 根据权利要求1所述的基于阀侧电流时序特征的换流阀状态与阀电流的求解方法，其特征在于，所述步骤S4过程如下：
    S41、当步骤S1中检测到换流阀的触发脉冲是高电平且满足换流阀的导通判据时，置位阀状态s VTm＝1，其中，换流阀的导通判据是：编号为m的换流阀所在相的交流电流的幅值|i k|大于交流电流定值，即：
    |i k|＞I set3    (G5)
    式中：i k为a、b、c三相交流电流，I set3为交流电流定值；
    S42、当编号为m的换流阀为导通状态s VTm＝1时，若交流电流满足截止判据，则编号为m的换流阀为截止状态s VTm＝0；否则，编号为m的换流阀继续保持导通状态s VTm＝1；其中，换流阀的截止判据是：编号为m的换流阀所在相的交流电流的幅值|i k| 小于截止电流门槛定值，且交流电流变化率小于变化量门槛定值，即：
    Figure PCTCN2021122020-appb-100005
    式中：I set4为截止电流门槛定值，I set5为变化量门槛定值；
    S43、当只有单相的上、下两阀导通时，换流阀形成单相旁通对运行，旁通对的两阀判别为导通状态，单相旁通对判别条件是：直流电流的最大值减去交流电流绝对值的最大值大于换相失败门槛定值，且交流电流绝对值的最大值小于单相旁通对门槛定值，即：
    Figure PCTCN2021122020-appb-100006
    式中：I set1为换相失败门槛定值，I set2为单相旁通对门槛定值；
    S44、当交直流电流满足步骤S43的公式(G7)时，换流阀为单相旁通对运行，其中，单相旁通对的阀状态判别条件为：
    1)当所有阀的旁通状态标志s bypass_m＝0时，若步骤S3的寄存器信号等于m，则编号为m的换流阀所在相为旁通相，置位旁通相两阀的旁通状态标志等于1，保持旁通相两阀都为导通状态，即：s bypass_m＝1和s bypass_(mod(m+3,6))＝1，s VTm＝1和s VT(mod(m+3,6))＝1；
    2)当编号为m的换流阀所在相的旁通状态标志s bypass_m＝1或s bypass_(mod(m+3,6))＝1时，保持编号为m的换流阀所在相两阀都为导通状态。
  3. 根据权利要求1所述的基于阀侧电流时序特征的换流阀状态与阀电流的求解方法，其特征在于，所述步骤S8过程如下：
    S81、根据步骤S7中得到的旁通相的数量，当旁通相的数量S total≤1时，换流阀无旁通对或单相旁通对运行，此时不需要构造旁通回路电压方程，跳到步骤S91，否则，转到步骤S82；
    S82、当旁通相的数量S total＝2时，表明换流阀两相旁通运行，增补旁通回路电压方程C pi＝D p，跳到步骤S92，否则，转到步骤S83；其中，
    1)若S a＝S b，则存在以下关系：
    i VT1+i VT4＝i VT3+i VT6    (G8)
    增补旁通回路电压方程C abi＝D ab，其中：C ab＝[10-110-1]，D ab＝[0]，p＝ab，C ab为ab相旁通时旁通回路电压方程的系数矩阵，D ab为ab相旁通时旁通回路电压方程的常数向量；
    2)若S a＝S c，则存在以下关系：
    i VT1+i VT4＝i VT2+i VT5    (G9)
    增补旁通回路电压方程C aci＝D ac，其中：C ac＝[1 -1 0 1 -1 0]，D ac＝[0]，p＝ac，C ac为ac相旁通时旁通回路电压方程的系数矩阵，D ac为ac相旁通时旁通回路电压方程的常数向量；
    3)若S b＝S c，则存在以下关系：
    i VT2+i VT5＝i VT3+i VT6    (G10)
    增补旁通回路电压方程C bci＝D bc中，C bc＝[0 1 -1 0 1 -1]，D bc＝[0]，p＝bc，C bc为bc相旁通时旁通回路电压方程的系数矩阵，D bc为bc相旁通时旁通回路电压方程的常数向量；
    S83、当旁通对工况S total＝3时，表明换流阀三相旁通对运行，增补旁通回路电压方程C pi＝D p，跳到步骤S92；同时，存在以下关系：
    Figure PCTCN2021122020-appb-100007
    增补旁通回路电压方程C abci＝D abc，其中：
    Figure PCTCN2021122020-appb-100008
    D abc＝[0 0] T，p＝abc，C abc为abc相旁通时旁通回路电压方程的系数矩阵，D abc为abc相旁通时旁通回路电压方程的常数向量；
    所述步骤S9过程如下：
    S91、构造基于阀状态特征的状态方程ASi＝y，对系数矩阵求逆计算阀电流i VTm：
    i＝(AS) -1×y    (G12)
    式中：i＝[i VT1 i VT2 i VT3 i VT4 i VT5 i VT6] T。
    S92、将Ai＝y与C pi＝D p联立，结合阀状态特征S构造状态方程ESi＝z，对系数矩阵求逆，计算阀电流i VTm：
    i＝(ES) -1×z    (G13)
    式中：i＝[i VT1 i VT2 i VT3 i VT4 i VT5 i VT6] T，
    Figure PCTCN2021122020-appb-100009
    p为旁通相的序号，E为系数矩阵A和系数矩阵C p组成的系数矩阵，z为阀侧两端电流向量y和常数向量D p组成的向量。
  4. 根据权利要求1所述的基于阀侧电流时序特征的换流阀状态与阀电流的求解方法，其特征在于，所述步骤S3中当检测到换流阀的触发脉冲的上升沿 FP m(t)-FP m(t-Δt)＝1时，将换流阀的编号m锁存到寄存器中；其中：FP m(t)是编号为m的换流阀在t时刻的触发脉冲信号，FP m(t-Δt)是编号为m的换流阀在(t-Δt)时刻的触发脉冲信号，t为某一时刻的时间，Δt为采样时间间隔。
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