CN106655199A - VSC-HVDC power control method for improving voltage stability - Google Patents

VSC-HVDC power control method for improving voltage stability Download PDF

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CN106655199A
CN106655199A CN201710062867.3A CN201710062867A CN106655199A CN 106655199 A CN106655199 A CN 106655199A CN 201710062867 A CN201710062867 A CN 201710062867A CN 106655199 A CN106655199 A CN 106655199A
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vsc
hvdc
power
theta
voltage stability
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CN106655199B (en
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林章岁
胡臻达
黎萌
易杨
叶荣
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State Grid Corp of China SGCC
State Grid Fujian Electric Power Co Ltd
Economic and Technological Research Institute of State Grid Fujian Electric Power Co Ltd
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State Grid Corp of China SGCC
State Grid Fujian Electric Power Co Ltd
Economic and Technological Research Institute of State Grid Fujian Electric Power Co Ltd
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for AC mains or AC distribution networks
    • H02J3/12Circuit arrangements for AC mains or AC distribution networks for adjusting voltage in AC networks by changing a characteristic of the network load
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for AC mains or AC distribution networks
    • H02J3/12Circuit arrangements for AC mains or AC distribution networks for adjusting voltage in AC networks by changing a characteristic of the network load
    • H02J3/16Circuit arrangements for AC mains or AC distribution networks for adjusting voltage in AC networks by changing a characteristic of the network load by adjustment of reactive power
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for AC mains or AC distribution networks
    • H02J3/36Arrangements for transfer of electric power between AC networks via a high-tension DC link
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for AC mains or AC distribution networks
    • H02J3/36Arrangements for transfer of electric power between AC networks via a high-tension DC link
    • H02J2003/365Reducing harmonics or oscillations in HVDC
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30Reactive power compensation
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Electrical Variables (AREA)

Abstract

本发明涉及一种提高电压稳定性的VSC‑HVDC功率控制方法,对含VSC‑HVDC交直流混联电网电压稳定性问题,考虑VSC‑HVDC容量限制等约束条件,建立了基于电压稳定的交直流混合系统VSC‑HVDC有功功率、无功功率优化计算模型。通过求解拉格朗日函数,可以得到VSC‑HVDC最佳有功输送容量、无功出力以及交直流混联系统最大供电负荷等。本发明通过对VSC‑HVDC有功功率、无功出力优化,为交直流混合系统提高电压稳定性提供了一种可行的方法。

The invention relates to a VSC-HVDC power control method for improving voltage stability. For the voltage stability problem of a VSC-HVDC AC-DC hybrid power grid, considering constraints such as VSC-HVDC capacity limitations, a voltage-stabilized AC-DC method is established. Hybrid system VSC‑HVDC active power and reactive power optimization calculation model. By solving the Lagrangian function, the optimal active power transmission capacity, reactive power output and maximum power supply load of the AC-DC hybrid system can be obtained for VSC‑HVDC. The present invention provides a feasible method for improving voltage stability of an AC-DC hybrid system by optimizing the VSC-HVDC active power and reactive power output.

Description

一种提高电压稳定性的VSC-HVDC功率控制方法A VSC-HVDC Power Control Method for Improving Voltage Stability

技术领域technical field

本发明涉及电力系统分析和控制技术领域,特别是一种提高电压稳定性的VSC-HVDC功率控制方法。The invention relates to the technical field of power system analysis and control, in particular to a VSC-HVDC power control method for improving voltage stability.

背景技术Background technique

传统VSC-HVDC是自20世纪90年代发展起来的一种高压直流输电技术,其具有可对交流电网进行动态无功补偿,为受端系统提供电压支撑的优点。因此,VSC-HVDC成为一种改善交流系统电压稳定性的较有潜力的方案。The traditional VSC-HVDC is a high-voltage direct current transmission technology developed since the 1990s. It has the advantages of dynamic reactive power compensation for the AC grid and voltage support for the receiving end system. Therefore, VSC-HVDC becomes a more potential scheme to improve the voltage stability of AC system.

然而,在直流混联系统中VSC-HVDC向交流系统输送的有功功率和无功功率大小均对电压稳定有影响。一般地说,在无功功率不变前提下,输送的有功功率越大,电压稳定性越好;在有功功率不变前提下,输送的无功功率越大,电压稳定性越好。而受容量限制,VSC-HVDC向交流系统输送的有功功率和无功功率是相互制约的,因此在电压下降过程中,目前VSC-HVDC有功功率和无功功率控制方式可分为以下三种:一是通过减小有功出力为代价获得较大无功输出;二是以减小无功出力为代价来获得较大的有功输出;三是有功功率和无功功率同比例减小。应该采用何种控制方式对提高系统电压稳定最有利,以及如何根据交直流电网自身参数来计算基于提高电压稳定性的VSC-HVDC功率最佳控制值,现有的技术未能完全揭示。本发明针对上述问题,提出了一种以提高电压稳定水平为目标的VSC-HVDC功率控制方法,即考虑VSC-HVDC容量限制等约束条件,建立了基于电压稳定的交直流混合系统VSC-HVDC有功功率、无功功率优化计算模型,通过求解拉格朗日函数,得到VSC-HVDC最佳有功输送容量、无功出力以及交直流混联系统最大供电负荷等,用于提高交直流混联系统电压稳定性。However, in the DC hybrid system, both the active power and reactive power delivered by VSC-HVDC to the AC system have an impact on voltage stability. Generally speaking, under the premise of constant reactive power, the greater the active power transmitted, the better the voltage stability; under the premise of constant active power, the greater the reactive power transmitted, the better the voltage stability. However, limited by capacity, the active power and reactive power delivered by VSC-HVDC to the AC system are mutually restricted. Therefore, in the process of voltage drop, the current VSC-HVDC active power and reactive power control methods can be divided into the following three types: One is to obtain greater reactive output at the cost of reducing active output; the other is to obtain greater active output at the cost of reducing reactive output; third is to reduce active power and reactive power in the same proportion. What kind of control method should be adopted is the most beneficial to improve the system voltage stability, and how to calculate the optimal control value of VSC-HVDC power based on improving voltage stability based on the parameters of the AC and DC grid itself, the existing technology has not fully revealed. In view of the above problems, the present invention proposes a VSC-HVDC power control method aiming at improving the voltage stability level, that is, considering constraints such as VSC-HVDC capacity limitation, and establishing an AC-DC hybrid system VSC-HVDC active power based on voltage stability Power and reactive power optimization calculation model, by solving the Lagrangian function, the optimal active power transmission capacity of VSC-HVDC, reactive power output and the maximum power supply load of the AC-DC hybrid system are obtained, which are used to improve the voltage of the AC-DC hybrid system stability.

发明内容Contents of the invention

本发明的目的在于提供一种提高电压稳定性的VSC-HVDC功率控制方法,以克服现有技术中存在的缺陷。The object of the present invention is to provide a VSC-HVDC power control method for improving voltage stability, so as to overcome the defects in the prior art.

为实现上述目的,本发明的技术方案是:一种提高电压稳定性的VSC-HVDC功率控制方法,其流程图如图1所示,包括如下步骤:In order to achieve the above object, the technical solution of the present invention is: a VSC-HVDC power control method for improving voltage stability, the flow chart of which is shown in Figure 1, including the following steps:

步骤S1:输入交流、直流电网参数数据,形成节点导纳矩阵;Step S1: Input AC and DC power grid parameter data to form a node admittance matrix;

步骤S2:计算交流系统戴维南等值模型参数;Step S2: Calculate the Thevenin equivalent model parameters of the AC system;

步骤S3:计算VSC-HVDC有功和无功运行范围;Step S3: Calculate the VSC-HVDC active and reactive operating range;

步骤S4:建立含VSC-HVDC的有功电压关系式;Step S4: Establishing an active voltage relational expression including VSC-HVDC;

步骤S5:计算基于提高电压稳定的VSC-HVDC最佳功率值;Step S5: Calculate the optimal power value of VSC-HVDC based on improving voltage stability;

步骤S6:进行VSC-HVDC功率控制。Step S6: Perform VSC-HVDC power control.

进一步地,在所述步骤S1中,所述交流电网参数数据包括:输电线路的首端、末端节点编号,变压器变比、阻抗,串联电阻、电抗以及并联电导、电纳;所述直流网络参数包括:VSC-HVDC桥臂电抗器阻抗,换流变容量、阻抗,换流器调制比以及最大允许电流IlimFurther, in the step S1, the AC power grid parameter data includes: the head end and end node numbers of the transmission line, transformer ratio, impedance, series resistance, reactance, parallel conductance, and susceptance; the DC network parameters Including: VSC-HVDC bridge arm reactor impedance, converter variable capacity, impedance, converter modulation ratio and maximum allowable current I lim .

进一步地,在所述步骤S2中,获取交流系统与VSC-HVDC等值电路,如图2所示,记VSC-HVDC换流站所接入交流母线为交流电网的第i个节点,其电压相量为换流器输出的基波电压相量为换流器与交流母线i之间的等值连接阻抗为Z1∠θ1=R1+jX1,且根据该第i节点确定的系统等值阻抗Z2∠θ2=R2+jX2,戴维南等值阻抗R2和X2可通过PSD-BPA计算软件获取交流系统。Further, in the step S2, the AC system and the VSC-HVDC equivalent circuit are obtained, as shown in Figure 2, the AC bus connected to the VSC-HVDC converter station is the i-th node of the AC grid, and its voltage Phasor is The fundamental wave voltage phasor output by the converter is The equivalent connection impedance between the converter and the AC bus i is Z 1 ∠θ 1 =R 1 +jX 1 , and the system equivalent impedance Z 2 ∠θ 2 =R 2 +jX 2 determined according to the i-th node , Thevenin equivalent impedance R 2 and X 2 can be obtained by PSD-BPA calculation software for AC systems.

进一步地,在所述步骤S3中,获取交流系统与VSC-HVDC系统等值电路,根据该交流系统与VSC-HVDC系统等值电路,计算直流侧功率:Further, in the step S3, the equivalent circuit of the AC system and the VSC-HVDC system is obtained, and the DC side power is calculated according to the equivalent circuit of the AC system and the VSC-HVDC system:

其中:Pdc、Qdc分别为VSC-HVDC注入节点i的有功与无功功率,δik=δik=δ-δk为节点i与节点k的电压相角差;M为换流器调制比,Ud为换流器直流侧电压,μ是PWM直流电压利用率;Where: P dc and Q dc are the active and reactive power injected into node i by VSC-HVDC respectively, and δ ikik =δ-δ k is the voltage phase angle difference between node i and node k; M is the modulation ratio of the converter, U d is the DC side voltage of the converter, μ is the utilization rate of the PWM DC voltage;

由上述两式可推得:From the above two formulas, it can be deduced that:

其中,VSC向交流系统输出无功时,Qdc为正;in, When VSC outputs reactive power to the AC system, Q dc is positive;

VSC-HVDC运行时最大允许电流限制:Maximum allowable current limit during VSC-HVDC operation:

其中,Ilim为VSC-HVDC最大允许电流。Among them, I lim is the maximum allowable current of VSC-HVDC.

进一步地,在所述步骤S4中,基于潮流方程建立P与Pdc、Qdc、U的关系方程式。根据该交流系统与VSC-HVDC系统等值电路中的交流支路,计算交流侧功率:Further, in the step S4, a relationship equation between P and P dc , Q dc , U is established based on the power flow equation. According to the AC branch in the equivalent circuit of the AC system and the VSC-HVDC system, calculate the AC side power:

其中,Pac、Qac分别为交流支路注入节点i的有功与无功功率,分别为交流支路两端电压,δij=δij=δ;Among them, P ac and Q ac are the active and reactive power injected into node i by the AC branch respectively, with are the voltages at both ends of the AC branch, δ ij = δ i - δ j = δ;

则可得:Then you can get:

其中, in,

再根据Pac+Pdc=P,Qac+Qdc=Q,ZD=RD+jXD经推导,可得P与Pdc、Qdc、U、RD、XD的关系方程式(交直流混联系统负荷功率计算公式):Then according to P ac +P dc =P, Q ac +Q dc =Q, Z D =R D +jX D , After derivation, the relational equations of P and P dc , Q dc , U, R D , X D can be obtained (calculation formula of load power of AC/DC hybrid system):

式中:P、Q分别为交直流混联电网供电的负荷有功功率和无功功率;ZD、RD和XD为交直流混联电网供电负荷的等值阻抗、等值电阻和等值电抗。In the formula: P and Q are the active power and reactive power of the load supplied by the AC-DC hybrid grid respectively; Z D , R D and X D are the equivalent impedance, equivalent resistance and equivalent value of the load supplied by the AC-DC hybrid grid Reactance.

通常情况下,负荷功率因数短时间内变化不大,可假定为常数,经推导,可得P与Pdc、Qdc、U的关系方程式:Normally, the load power factor Little change in a short period of time, it can be assumed that is a constant, after derivation, the relationship equation between P and P dc , Q dc , U can be obtained:

进一步地,在所述步骤S5中,P为关于Pdc、Qdc、U、RD、XD的函数,即Further, in the step S5, P is a function about P dc , Q dc , U, R D , X D , namely

记拉格朗日函数L(Pdc,Qdc,U,RD,XD)为:Write down the Lagrangian function L(P dc , Q dc , U, R D , X D ) as:

式中,为约束条件;In the formula, as a constraint;

对上式求偏导,可得方程组Taking the partial derivative of the above formula, we can get the system of equations

求解上述6个方程可得6个未知数Pdc、Qdc、U、RD、XD和λ,代入方程P=f(Pdc,Qdc,U,RD,XD)可解得在约束条件下的最大负荷功率P,而Pdc、Qdc即为基于提高电压稳定水平的VSC-HVDC最佳功率设置。Solving the above 6 equations can get 6 unknowns P dc , Q dc , U, RD , X D and λ, and substituting them into the equation P=f(P dc , Q dc , U, R D , X D ) can be solved in The maximum load power P under the constraint conditions, and P dc and Q dc are the optimal power settings of VSC-HVDC based on improving the voltage stability level.

进一步地,在所述步骤S6中,VSC-HVDC采用传统的功率外环、dq解耦电流内环控制方式;受端逆变侧采用定有功功率Pdc和定无功功率Qdc控制。Further, in the step S6, the VSC-HVDC adopts the traditional power outer loop and dq decoupling current inner loop control mode; the inverter side of the receiving end adopts constant active power P dc and constant reactive power Q dc control.

正常运行情况下,设VSC-HVDC按照系统需求,将有功功率参考值Pref和无功功率参考值Qref分别设定为Pref0和Qref0,即:Under normal operation, it is assumed that the VSC-HVDC sets the active power reference value P ref and the reactive power reference value Q ref as P ref0 and Q ref0 respectively according to the system requirements, namely:

Pref=Pref0,Qref=Qref0P ref = P ref0 , Q ref = Q ref0 ;

当交流系统处于电压失稳过程,即VSC-HVDC所接交流母线i的电压幅值U小于越限值Ulim且持续时间大于tlim(tlim按避开故障切除时间等进行设定),VSC-HVDC受端的控制系统切换进入提高电压稳定性的VSC-HVDC功率控制模式。When the AC system is in the process of voltage instability, that is, the voltage amplitude U of the AC bus i connected to the VSC-HVDC is less than the limit value U lim and the duration is longer than t lim (t lim is set according to the time to avoid the fault, etc.), The control system at the receiving end of the VSC-HVDC switches into a VSC-HVDC power control mode that improves voltage stability.

该模式下,首先根据步骤S1和步骤S2计算得到的网络等值参数,以及步骤S5的计算方法,计算得出此刻负荷功率下VSC-HVDC的最佳功率设置Pdc、QdcIn this mode, first, according to the network equivalent parameters calculated in step S1 and step S2, and the calculation method in step S5, the optimal power settings P dc and Q dc of VSC-HVDC under the load power at the moment are calculated;

其次,为减小VSC-HVDC有功功率和无功功率的调节对系统的冲击,将VSC-HVDC有功功率参考值Pref和无功功率参考值Qref分别由原设定值Pref0和Qref0,通过步进方式过渡到其最佳功率设置Pdc、Qdc,使功率参考值最终设置为:Secondly, in order to reduce the impact of VSC-HVDC active power and reactive power adjustment on the system, the VSC-HVDC active power reference value P ref and reactive power reference value Q ref are respectively changed from the original set values P ref0 and Q ref0 , transition to its optimal power setting P dc , Q dc in a step-by-step manner, so that the power reference value is finally set to:

Pref=Pdc,Qref=QdcP ref = P dc , Q ref = Q dc ;

最后,分别经有功和无功功率外环PI控制器输出产生d、q轴电流参考值idref和iqref,并传入电流内环控制;经调制和触发后,VSC-HVDC输出功率将以步进方式逐渐过渡至Pdc、Qdc,即为提高电压稳定水平的VSC-HVDC最佳功率。Finally, the d and q axis current reference values i dref and i qref are generated by the output of the active and reactive power outer loop PI controllers respectively, and passed into the current inner loop control; after modulation and triggering, the VSC-HVDC output power will be The stepping method gradually transitions to P dc and Q dc , which is the optimal power of VSC-HVDC to improve the voltage stability level.

相较于现有技术,本发明具有以下有益效果:本发明提出的一种提高电压稳定性的VSC-HVDC功率控制方法,通过VSC-HVDC有功功率、无功出力优化为交直流混合系统的提高电压稳定性提供了一种可行的方法。为含VSC-HVDC的交直流混合系统电压稳定性改善和运行控制奠定基础。Compared with the prior art, the present invention has the following beneficial effects: A VSC-HVDC power control method for improving voltage stability proposed by the present invention optimizes VSC-HVDC active power and reactive output to improve the AC-DC hybrid system Voltage stabilization offers one possible approach. It lays the foundation for the voltage stability improvement and operation control of the AC-DC hybrid system containing VSC-HVDC.

附图说明Description of drawings

图1为本发明中一种提高电压稳定性的VSC-HVDC功率控制方法流程图。FIG. 1 is a flowchart of a VSC-HVDC power control method for improving voltage stability in the present invention.

图2为本发明中含VSC-HVDC交直流混联系统的等值电路。Fig. 2 is an equivalent circuit of the VSC-HVDC AC/DC hybrid system in the present invention.

图3为本发明中典型的PV曲线。Fig. 3 is a typical PV curve in the present invention.

图4为本发明中基于提高电压稳定性的VSC-HVDC最佳功率控制过程流程图。FIG. 4 is a flow chart of the VSC-HVDC optimal power control process based on improving voltage stability in the present invention.

图5为本发明一实施例中含VSC-HVDC交直流混联系统示意图。Fig. 5 is a schematic diagram of an AC/DC hybrid system including a VSC-HVDC in an embodiment of the present invention.

具体实施方式detailed description

下面结合附图,对本发明的技术方案进行具体说明。The technical solution of the present invention will be specifically described below in conjunction with the accompanying drawings.

本发明提供一种提高电压稳定性的VSC-HVDC功率控制方法,如图1所示,包括以下步骤:The present invention provides a VSC-HVDC power control method for improving voltage stability, as shown in Figure 1, comprising the following steps:

(1)输入交直流电网参数,形成节点导纳矩阵。其中交流电网参数数据包括:输电线路的首端、末端节点编号,变压器变比、阻抗,串联电阻、电抗以及并联电导、电纳;直流网络参数包括:VSC-HVDC桥臂电抗器阻抗,换流变容量、阻抗,换流器调制比以及最大允许电流Ilim(1) Input AC and DC grid parameters to form a node admittance matrix. Among them, the AC grid parameter data includes: the head end and terminal node number of the transmission line, the transformer ratio, impedance, series resistance, reactance, parallel conductance, and susceptance; the DC network parameters include: VSC-HVDC bridge arm reactor impedance, commutation current Variable capacity, impedance, converter modulation ratio and maximum allowable current I lim .

(2)计算交流系统戴维南等值模型参数。获取交流系统与VSC-HVDC等值电路,如图2所示,记VSC-HVDC换流站所接入交流母线为交流电网的第i个节点,其电压相量为换流器输出的基波电压相量为换流器与交流母线i之间的等值连接阻抗为Z1∠θ1=R1+jX1,且根据该第i节点确定的系统等值阻抗Z2∠θ2=R2+jX2,在本实施例中,戴维南等值阻抗R2和X2通过PSD-BPA计算软件获取交流系统。(2) Calculate the Thevenin equivalent model parameters of the AC system. Obtain the equivalent circuit of the AC system and VSC-HVDC, as shown in Figure 2, note that the AC bus connected to the VSC-HVDC converter station is the i-th node of the AC grid, and its voltage phasor is The fundamental wave voltage phasor output by the converter is The equivalent connection impedance between the converter and the AC bus i is Z 1 ∠θ 1 =R 1 +jX 1 , and the system equivalent impedance Z 2 ∠θ 2 =R 2 +jX 2 determined according to the i-th node , in this embodiment, the Thevenin equivalent impedance R 2 and X 2 are obtained by the PSD-BPA calculation software for the AC system.

(3)计算VSC-HVDC有功和无功运行范围(3) Calculate the active and reactive operating range of VSC-HVDC

根据图2,可得直流侧功率方程式:According to Figure 2, the DC side power equation can be obtained:

式中:Pdc、Qdc分别为VSC-HVDC注入节点i的有功与无功功率,δik=δik=δ-δk为节点i与节点k的电压相角差;M为换流器调制比,Ud为换流器直流侧电压,μ是PWM直流电压利用率;In the formula: P dc and Q dc are the active and reactive power injected into node i by VSC-HVDC respectively, and δ ikik =δ-δ k is the voltage phase angle difference between node i and node k; M is the modulation ratio of the converter, U d is the DC side voltage of the converter, μ is the utilization rate of the PWM DC voltage;

由式(1)、(2)可推得From formulas (1) and (2), it can be deduced that

其中,VSC向交流系统输出无功时,Qdc为正。in, When VSC outputs reactive power to the AC system, Q dc is positive.

同时,考虑VSC-HVDC运行时最大允许电流限制,即:At the same time, consider the maximum allowable current limit during VSC-HVDC operation, namely:

式中,Ilim为VSC-HVDC最大允许电流。In the formula, I lim is the maximum allowable current of VSC-HVDC.

进一步的,一般情况下VSC-HVDC运行约束中,尤其电压下降过程中,式(4)约束将起到关键作用。Furthermore, in general, in the operation constraints of VSC-HVDC, especially in the process of voltage drop, the constraint of formula (4) will play a key role.

(4)建立含VSC-HVDC的有功(P)电压(U)关系式。(4) Establish the relational expression of active power (P) and voltage (U) including VSC-HVDC.

为常数的情况下,含VSC-HVDC的有功(P)电压(U)关系式可以描述成以下形式:exist In the case of a constant, the active (P) voltage (U) relationship including VSC-HVDC can be described as the following form:

P=f(Pdc,Qdc,U) (5)P=f(P dc ,Q dc ,U) (5)

式中:P为负荷有功功率。对图2的电路可通过功率方程式推演PV关系式,具体如下。In the formula: P is the load active power. For the circuit in Figure 2, the PV relationship can be deduced through the power equation, as follows.

对图2中的交流支路,可列出交流侧功率方程式:For the AC branch in Figure 2, the AC side power equation can be listed:

其中,Pac、Qac分别为交流支路注入节点i的有功与无功功率,分别为交流支路两端电压,δij=δij=δ;。Among them, P ac and Q ac are the active and reactive power injected into node i by the AC branch respectively, with are the voltages at both ends of the AC branch, δ ij = δ i - δ j = δ;.

根据式(6)和(7)可得:According to formulas (6) and (7), we can get:

其中, in,

本实施例中,考虑负荷功率因数短时间内变化不大,即假定为常数,并根据Pac+Pdc=P,Qac+Qdc=Q,经推导,可得P与Pdc、Qdc、U的关系方程式:In this example, considering the load power factor Little change in a short period of time, that is, assuming is a constant, and according to P ac +P dc =P, Q ac +Q dc =Q, after derivation, the relationship equation between P and P dc , Q dc , U can be obtained:

式中:P、Q分别为交直流混联电网供电的负荷有功功率和无功功率。In the formula: P and Q are the active power and reactive power of the load supplied by the AC-DC hybrid grid, respectively.

根据式(9),可得交直流混联电网典型的PV曲线,如图3所示。According to formula (9), the typical PV curve of the AC/DC hybrid power grid can be obtained, as shown in Figure 3.

(5)基于电压稳定的VSC-HVDC最佳功率值计算(5) Calculation of optimal power value of VSC-HVDC based on voltage stability

P为关于Pdc、Qdc、U、RD、XD的函数,即P is a function about P dc , Q dc , U, R D , X D , namely

定义拉格朗日函数L(Pdc,Qdc,U,RD,XD)为Define the Lagrange function L(P dc ,Q dc ,U,R D ,X D ) as

式中,为约束条件。In the formula, as constraints.

对式(11)求偏导,可得方程组Taking the partial derivative of formula (11), we can get the equation system

求解上述6个方程可得6个未知数Pdc、Qdc、U、RD、XD和λ,代入方程P=f(Pdc,Qdc,U,RD,XD)可解得在约束条件下的最大负荷功率P,而Pdc、Qdc即为基于提高电压稳定水平的VSC-HVDC最佳功率设置。Solving the above 6 equations can get 6 unknowns P dc , Q dc , U, RD , X D and λ, and substituting them into the equation P=f(P dc , Q dc , U, R D , X D ) can be solved in The maximum load power P under the constraint conditions, and P dc and Q dc are the optimal power settings of VSC-HVDC based on improving the voltage stability level.

(6)功率控制实现(6) Realization of power control

VSC-HVDC采用传统的功率外环、dq解耦电流内环控制方式;受端逆变侧采用定有功功率Pdc和定无功功率Qdc控制。正常情况下,设VSC-HVDC按照系统需求,将有功功率参考值Pref和无功功率参考值Qref分别设定为Pref0和Qref0,即:VSC-HVDC adopts the traditional power outer loop and dq decoupling current inner loop control mode; the inverter side of the receiving end adopts constant active power P dc and constant reactive power Q dc control. Under normal circumstances, it is assumed that the VSC-HVDC sets the active power reference value P ref and the reactive power reference value Q ref as P ref0 and Q ref0 respectively according to the system requirements, namely:

Pref=Pref0,Qref=Qref0P ref = P ref0 , Q ref = Q ref0 ;

如图4所示,当交流系统处于电压失稳过程,即VSC-HVDC所接交流母线i的电压幅值U小于越限值Ulim且持续时间大于tlim(tlim按避开故障切除时间等进行设定),VSC-HVDC受端的控制系统切换进入提高电压稳定性的VSC-HVDC功率控制模式。As shown in Figure 4, when the AC system is in the process of voltage instability, that is, the voltage amplitude U of the AC bus i connected to the VSC-HVDC is less than the limit value U lim and the duration is greater than t lim (t lim is the time to avoid the fault etc.), the control system at the VSC-HVDC receiving end switches into the VSC-HVDC power control mode to improve voltage stability.

该模式下,首先根据步骤(1)和步骤(2)计算得到的网络等值参数,以及步骤(5)中的计算方法,计算得出此刻负荷功率下VSC-HVDC的最佳功率设置Pdc、QdcIn this mode, firstly, according to the network equivalent parameters calculated in step (1) and step (2), and the calculation method in step (5), the optimal power setting P dc of VSC-HVDC under the load power at the moment is calculated , Q dc ;

其次,为减小VSC-HVDC有功功率和无功功率的调节对系统的冲击,将VSC-HVDC有功功率参考值Pref和无功功率参考值Qref分别由原设定值Pref0和Qref0通过步进方式过渡到其最佳功率设置Pdc、Qdc,使功率参考值最终设置为:Secondly, in order to reduce the impact of VSC-HVDC active power and reactive power adjustment on the system, the VSC-HVDC active power reference value P ref and reactive power reference value Q ref are respectively changed from the original set values P ref0 and Q ref0 Transition to its optimal power setting P dc , Q dc in a step-by-step manner, so that the power reference value is finally set to:

Pref=Pdc,Qref=QdcP ref = P dc , Q ref = Q dc ;

最后,分别经有功和无功功率外环PI控制器输出产生d、q轴电流参考值idref和iqref,并传入电流内环控制;经调制和触发后,VSC-HVDC输出功率将以步进方式逐渐过渡至Pdc、Qdc,即为提高电压稳定水平的VSC-HVDC最佳功率。基于提高电压稳定性的VSC-HVDC最佳功率控制过程如图4所示。Finally, the d and q axis current reference values i dref and i qref are generated by the output of the active and reactive power outer loop PI controllers respectively, and passed into the current inner loop control; after modulation and triggering, the VSC-HVDC output power will be The stepping method gradually transitions to P dc and Q dc , which is the optimal power of VSC-HVDC to improve the voltage stability level. The optimal power control process of VSC-HVDC based on improving voltage stability is shown in Fig. 4.

下面结合实例对本发明进行详细的说明。Below in conjunction with example the present invention is described in detail.

以图5所示的含VSC-HVDC的交直流混联输电系统为例进行说明,利用该发明所提供的方法对该系统的电压稳定性进行分析,具体包括以下步骤:Taking the AC/DC hybrid power transmission system containing VSC-HVDC shown in Figure 5 as an example for illustration, the voltage stability of the system is analyzed by using the method provided by the invention, which specifically includes the following steps:

1.计算交直流系统等值电路参数1. Calculate the equivalent circuit parameters of AC and DC systems

图5算例中,柔性直流输电系统主要参数见表1,其送端采用定直流电压Ud、定交流无功功率Q控制;受端采用定有功功率P、交流无功功率Q控制。受端最高负荷1998MW,功率因数最大运行方式受端交流电网等值阻抗R2=1.587Ω,X2=5.766Ω,交流系统等值电势Es=1.1pu(基准电压230kV)。In the calculation example in Figure 5, the main parameters of the flexible HVDC system are shown in Table 1. The sending end is controlled by constant DC voltage U d and constant AC reactive power Q; the receiving end is controlled by constant active power P and AC reactive power Q. The maximum load at the receiving end is 1998MW, and the power factor In the maximum operation mode, the equivalent impedance of the AC grid at the receiving end is R 2 =1.587Ω, X 2 =5.766Ω, and the equivalent potential of the AC system E s =1.1pu (reference voltage 230kV).

表1 VSC-HVDC系统主要参数Table 1 Main parameters of VSC-HVDC system

根据上述给定数据,将图5所示的含VSC-HVDC的交直流混联电网按照图2进行简化等值,等值电路各个参数见表2。表2中给出了参数有名值和标么值,为方便起见,以下计算均采用标么值进行。According to the given data above, the AC/DC hybrid power grid containing VSC-HVDC shown in Figure 5 is simplified and equivalent according to Figure 2, and the parameters of the equivalent circuit are shown in Table 2. Table 2 gives the parameter name value and standard unit value. For convenience, the following calculations are carried out with standard unit value.

表2电路参数计算结果Table 2 Calculation results of circuit parameters

注:基准值分别为,UB=230kV,SB=100MVA,ZB=529Ω。Note: The reference values are respectively, U B =230kV, S B =100MVA, Z B =529Ω.

2.基于电压稳定的VSC-HVDC最佳功率值计算2. Calculation of optimal power value of VSC-HVDC based on voltage stability

将表1和表2中的参数(标幺值)分别代入下式Substitute the parameters (per unit value) in Table 1 and Table 2 into the following formula

式中:In the formula:

(标幺值) (Pu)

对L(Pdc,Qdc,U)求偏导,可得方程组Taking the partial derivative of L(P dc ,Q dc ,U), we can get the equation system

解上述方程组,考虑Pdc、Qdc、U为大于0的实数解,可得一组有意义的实数解Solving the above equations, considering that P dc , Q dc , and U are real number solutions greater than 0, a set of meaningful real number solutions can be obtained

方程组解Pdc用有名值表示为554.6MW,即为提高电压稳定性的VSC-HVDC最佳有功功率值。The equation system solution P dc is expressed as 554.6MW with a famous value, which is the best active power value of VSC-HVDC to improve voltage stability.

将上述解代入f(Pdc,Qdc,U)中,可解得系统最大输送功率P为Substituting the above solution into f(P dc ,Q dc ,U), the maximum transmission power P of the system can be solved as

Pmax=f(Pdc,Qdc,U)=44.420P max = f(P dc , Q dc , U) = 44.420

Pmax用有名值表示为44420MW,即为交直流混联系统最大可输送功率。P max is expressed as 44420MW with a well-known value, which is the maximum transmittable power of the AC-DC hybrid system.

3.功率控制3. Power control

本实施例中,VSC-HVDC有功功率参考值Pref和无功功率参考值Qref初始值按系统需求分别设定为800MW和100Mvar;交流母线电压越限值设为0.9p.u.,持续时间越限值设为1s。当VSC-HVDC监测到所连交流母线电压幅值小于0.9p.u.且持续时间大于1s时,启动基于提高电压稳定性的功率控制,根据计算结果,其基于提高电压稳定性的最佳有功、无功功率值为554.6MW、518.0Mvar。VSC-HVDC自动将Pref、Qref通过步进方式过渡到其最佳有功、无功功率值554.6MW、518.0Mvar。经VSC-HVDC功率内外环控制后,VSC-HVDC输出有功功率也将以步进方式逐渐过渡至554.6MW、518.0Mvar,直至系统电压恢复。In this embodiment, the initial values of VSC-HVDC active power reference value P ref and reactive power reference value Q ref are set to 800MW and 100Mvar respectively according to system requirements; The value is set to 1s. When the VSC-HVDC monitors that the voltage amplitude of the connected AC bus is less than 0.9pu and lasts longer than 1s, it starts power control based on improving voltage stability. According to the calculation results, it is based on the best active and reactive power The power values are 554.6MW and 518.0Mvar. VSC-HVDC automatically transitions Pref and Q ref to its optimal active and reactive power values of 554.6MW and 518.0Mvar in a step-by-step manner. After being controlled by the inner and outer loops of VSC-HVDC power, the output active power of VSC-HVDC will gradually transition to 554.6MW and 518.0Mvar in a stepwise manner until the system voltage recovers.

以上是本发明的较佳实施例,凡依本发明技术方案所作的改变,所产生的功能作用未超出本发明技术方案的范围时,均属于本发明的保护范围。The above are the preferred embodiments of the present invention, and all changes made according to the technical solution of the present invention, when the functional effect produced does not exceed the scope of the technical solution of the present invention, all belong to the protection scope of the present invention.

Claims (7)

1.一种提高电压稳定性的VSC-HVDC功率控制方法,其特征在于,包括如下步骤:1. a VSC-HVDC power control method that improves voltage stability, is characterized in that, comprises the steps: 步骤S1:输入交流、直流电网参数数据,形成节点导纳矩阵;Step S1: Input AC and DC power grid parameter data to form a node admittance matrix; 步骤S2:计算交流系统戴维南等值模型参数;Step S2: Calculate the Thevenin equivalent model parameters of the AC system; 步骤S3:计算VSC-HVDC有功和无功运行范围;Step S3: Calculate the VSC-HVDC active and reactive operating range; 步骤S4:建立含VSC-HVDC的有功电压关系式;Step S4: Establishing an active voltage relational expression including VSC-HVDC; 步骤S5:计算基于提高电压稳定的VSC-HVDC最佳功率值;Step S5: Calculate the optimal power value of VSC-HVDC based on improving voltage stability; 步骤S6:进行VSC-HVDC功率控制。Step S6: Perform VSC-HVDC power control. 2.根据权利要求1所述的一种提高电压稳定性的VSC-HVDC功率控制方法,其特征在于,在所述步骤S1中,所述交流电网参数数据包括:输电线路的首端、末端节点编号,变压器变比、阻抗,串联电阻、电抗以及并联电导、电纳;所述直流网络参数包括:VSC-HVDC桥臂电抗器阻抗,换流变容量、阻抗,换流器调制比以及最大允许电流Ilim2. A kind of VSC-HVDC power control method that improves voltage stability according to claim 1, is characterized in that, in described step S1, described AC grid parameter data comprises: the head end of transmission line, terminal node serial number, transformer ratio, impedance, series resistance, reactance and parallel conductance, susceptance; the DC network parameters include: VSC-HVDC bridge arm reactor impedance, converter variable capacity, impedance, converter modulation ratio and maximum allowable Current I lim . 3.根据权利要求1所述的一种提高电压稳定性的VSC-HVDC功率控制方法,其特征在于,在所述步骤S2中,获取交流系统与VSC-HVDC等值电路,记VSC-HVDC换流站所接入交流母线为交流电网的第i个节点,其电压相量为换流器输出的基波电压相量为换流器与交流母线i之间的等值连接阻抗为Z1∠θ1=R1+jX1,且根据该第i节点确定的系统等值阻抗Z2∠θ2=R2+jX2,戴维南等值阻抗R2和X2可通过PSD-BPA计算软件获取交流系统。3. A kind of VSC-HVDC power control method that improves voltage stability according to claim 1, it is characterized in that, in described step S2, obtain AC system and VSC-HVDC equivalent circuit, denote VSC-HVDC exchange The AC bus connected to the flow station is the i-th node of the AC grid, and its voltage phasor is The fundamental wave voltage phasor output by the converter is The equivalent connection impedance between the converter and the AC bus i is Z 1 ∠θ 1 =R 1 +jX 1 , and the system equivalent impedance Z 2 ∠θ 2 =R 2 +jX 2 determined according to the i-th node , Thevenin equivalent impedance R 2 and X 2 can be obtained by PSD-BPA calculation software for AC systems. 4.根据权利要求1所述的一种提高电压稳定性的VSC-HVDC功率控制方法,其特征在于,在所述步骤S3中,获取交流系统与VSC-HVDC系统等值电路,根据该交流系统与VSC-HVDC系统等值电路,计算直流侧功率:4. A kind of VSC-HVDC power control method that improves voltage stability according to claim 1, is characterized in that, in described step S3, obtains AC system and VSC-HVDC system equivalent circuit, according to this AC system Calculate the DC side power with the equivalent circuit of the VSC-HVDC system: PP dd cc == Uu kk Uu ii ZZ 11 cc oo sthe s (( θθ 11 ++ δδ ii kk )) -- Uu ii 22 ZZ 11 cosθcosθ 11 == Uu kk Uu ZZ 11 cc oo sthe s (( θθ 11 ++ δδ ii kk )) -- Uu 22 ZZ 11 cosθcosθ 11 ;; QQ dd cc == Uu kk Uu ii ZZ 11 sthe s ii nno (( θθ 11 ++ δδ ii kk )) -- Uu ii 22 ZZ 11 sinθsinθ 11 == Uu kk Uu ZZ 11 sthe s ii nno (( θθ 11 ++ δδ ii kk )) -- Uu 22 ZZ 11 sinθsinθ 11 ;; 其中:Pdc、Qdc分别为VSC-HVDC注入节点i的有功与无功功率,δik=δik=δ-δk为节点i与节点k的电压相角差;M为换流器调制比,Ud为换流器直流侧电压,μ是PWM直流电压利用率;Where: P dc and Q dc are the active and reactive power injected into node i by VSC-HVDC respectively, and δ ikik =δ-δ k is the voltage phase angle difference between node i and node k; M is the modulation ratio of the converter, U d is the DC side voltage of the converter, μ is the utilization rate of the PWM DC voltage; 由上述两式可推得:From the above two formulas, it can be deduced that: (( PP dd cc ++ Uu 22 GG 11 )) 22 ++ (( QQ dd cc -- Uu 22 BB 11 )) 22 == YY 11 22 Uu kk 22 Uu 22 ;; 其中,VSC向交流系统输出无功时,Qdc为正;in, When VSC outputs reactive power to the AC system, Q dc is positive; VSC-HVDC运行时最大允许电流限制:Maximum allowable current limit during VSC-HVDC operation: PP dd cc 22 ++ QQ dd cc 22 ≤≤ (( 33 UIUI limlim )) 22 其中,Ilim为VSC-HVDC最大允许电流。Among them, I lim is the maximum allowable current of VSC-HVDC. 5.根据权利要求1所述的一种提高电压稳定性的VSC-HVDC功率控制方法,其特征在于,在所述步骤S4中,基于潮流方程建立P与Pdc、Qdc、U的关系方程式。根据该交流系统与VSC-HVDC系统等值电路中的交流支路,计算交流侧功率:5. A kind of VSC-HVDC power control method that improves voltage stability according to claim 1, is characterized in that, in described step S4, establishes the relational equation of P and Pdc, Qdc , U based on power flow equation . According to the AC branch in the equivalent circuit of the AC system and the VSC-HVDC system, calculate the AC side power: PP aa cc == Uu ii Uu jj ZZ 22 cc oo sthe s (( θθ 22 ++ δδ ii jj )) -- Uu ii 22 ZZ 22 cosθcosθ 22 == UEUE sthe s ZZ 22 cc oo sthe s (( θθ 22 ++ δδ )) -- Uu 22 ZZ 22 cosθcosθ 22 ;; QQ aa cc == Uu ii Uu jj ZZ 22 sthe s ii nno (( θθ 22 ++ δδ ii jj )) -- Uu ii 22 ZZ 22 sinθsinθ 22 == UEUE sthe s ZZ 22 sthe s ii nno (( θθ 22 ++ δδ )) -- Uu 22 ZZ 22 sinθsinθ 22 ;; 其中,Pac、Qac分别为交流支路注入节点i的有功与无功功率,分别为交流支路两端电压,δij=δij=δ;Among them, P ac and Q ac are the active and reactive power injected into node i by the AC branch respectively, with are the voltages at both ends of the AC branch, δ ij = δ i - δ j = δ; 则可得:Then you can get: (( PP aa cc ++ Uu 22 GG 22 )) 22 ++ (( QQ aa cc -- Uu 22 BB 22 )) 22 == Uu 22 EE. sthe s 22 YY 22 22 ;; 其中, in, 再根据Pac+Pdc=P,Qac+Qdc=Q,ZD=RD+jXD经推导,可得P与Pdc、Qdc、U、RD、XD的关系方程式(交直流混联系统负荷功率计算公式):Then according to P ac +P dc =P, Q ac +Q dc =Q, Z D =R D +jX D , After derivation, the relational equations of P and P dc , Q dc , U, R D , X D can be obtained (calculation formula of load power of AC/DC hybrid system): PP == PP dd cc -- Uu 22 GG 22 ++ QQ dd cc Xx DD. RR DD. ++ Uu 22 BB 22 Xx DD. RR DD. ±± -- [[ QQ dd cc -- PP dd cc Xx DD. RR DD. ++ Uu 22 (( BB 22 ++ GG 22 Xx DD. RR DD. )) ]] 22 ++ YY 22 22 Uu 22 EE. sthe s 22 (( 11 ++ Xx DD. 22 RR DD. 22 )) 11 ++ Xx DD. 22 RR DD. 22 式中:P、Q分别为交直流混联电网供电的负荷有功功率和无功功率;ZD、RD和XD为交直流混联电网供电负荷的等值阻抗、等值电阻和等值电抗。In the formula: P and Q are the active power and reactive power of the load supplied by the AC-DC hybrid grid respectively; Z D , R D and X D are the equivalent impedance, equivalent resistance and equivalent value of the load supplied by the AC-DC hybrid grid Reactance. 由于负荷功率因数短时间内变化不大,记为常数,经推导,可得P与Pdc、Qdc、U的关系方程式:due to load power factor Little change in a short period of time, remember is a constant, after derivation, the relationship equation between P and P dc , Q dc , U can be obtained: 6.根据权利要求1所述的一种提高电压稳定性的VSC-HVDC功率控制方法,其特征在于,在所述步骤S5中,P为关于Pdc、Qdc、U、RD、XD的函数,即6. A kind of VSC-HVDC power control method that improves voltage stability according to claim 1, is characterized in that, in described step S5, P is about P dc , Q dc , U, R D , X D function, that is PP == ff (( PP dcdc ,, QQ dcdc ,, Uu ,, RR DD. ,, Xx DD. )) == PP dcdc -- Uu 22 GG 22 ++ QQ dcdc Xx DD. RR DD. ++ Uu 22 BB 22 Xx DD. RR DD. ±± -- [[ QQ dcdc -- PP dcdc Xx DD. RR DD. ++ Uu 22 (( BB 22 ++ GG 22 Xx DD. RR DD. )) ]] 22 ++ YY 22 22 Uu 22 EE. sthe s 22 (( 11 ++ Xx DD. 22 RR DD. 22 )) 11 ++ Xx DD. 22 RR DD. 22 记拉格朗日函数L(Pdc,Qdc,U,RD,XD)为:Write down the Lagrangian function L(P dc , Q dc , U, R D , X D ) as: 式中,为约束条件;In the formula, as a constraint; 对上式求偏导,可得方程组Taking the partial derivative of the above formula, we can get the system of equations 求解上述6个方程可得6个未知数Pdc、Qdc、U、RD、XD和λ,代入方程P=f(Pdc,Qdc,U,RD,XD)可解得在约束条件下的最大负荷功率P,而Pdc、Qdc即为基于提高电压稳定水平的VSC-HVDC最佳功率设置。Solving the above 6 equations can get 6 unknowns P dc , Q dc , U, RD , X D and λ, and substituting them into the equation P=f(P dc , Q dc , U, R D , X D ) can be solved in The maximum load power P under the constraint conditions, and P dc and Q dc are the optimal power settings of VSC-HVDC based on improving the voltage stability level. 7.根据权利要求1所述的一种提高电压稳定性的VSC-HVDC功率控制方法,其特征在于,在所述步骤S6中,VSC-HVDC采用功率外环、dq解耦电流内环控制方式;受端逆变侧采用定有功功率Pdc和定无功功率Qdc控制;7. A kind of VSC-HVDC power control method that improves voltage stability according to claim 1, is characterized in that, in described step S6, VSC-HVDC adopts power outer loop, dq decoupling current inner loop control mode ; The inverter side of the receiving end is controlled by constant active power P dc and constant reactive power Q dc ; 正常运行情况下,设VSC-HVDC按照系统需求,将有功功率参考值Pref和无功功率参考值Qref分别设定为Pref0和Qref0,即:Under normal operation, it is assumed that the VSC-HVDC sets the active power reference value P ref and the reactive power reference value Q ref to P ref0 and Q ref0 respectively according to the system requirements, namely: Pref=Pref0,Qref=Qref0P ref = P ref0 , Q ref = Q ref0 ; 当交流系统处于电压失稳过程,即VSC-HVDC所接交流母线i的电压幅值U小于越限值Ulim,且持续时间大于tlim,VSC-HVDC受端的控制系统切换进入提高电压稳定性的VSC-HVDC功率控制模式;When the AC system is in the process of voltage instability, that is, the voltage amplitude U of the AC bus i connected to the VSC-HVDC is less than the limit value U lim and the duration is longer than t lim , the control system at the receiving end of the VSC-HVDC switches to improve voltage stability VSC-HVDC power control mode; 该模式下,首先根据步骤S1和步骤S2计算得到网络等值参数,并利用步骤S5的计算方法,计算得出此刻负荷功率下VSC-HVDC的最佳功率设置Pdc、QdcIn this mode, first calculate the network equivalent parameters according to step S1 and step S2, and use the calculation method of step S5 to calculate the optimal power settings P dc and Q dc of the VSC-HVDC under the load power at the moment; 其次,为减小VSC-HVDC有功功率和无功功率的调节对系统的冲击,将VSC-HVDC有功功率参考值Pref和无功功率参考值Qref分别由原设定值Pref0和Qref0,通过步进方式过渡到其最佳功率设置Pdc、Qdc,使功率参考值最终设置为:Pref=Pdc,Qref=QdcSecondly, in order to reduce the impact of VSC-HVDC active power and reactive power regulation on the system, the VSC-HVDC active power reference value P ref and reactive power reference value Q ref are respectively changed from the original set values P ref0 and Q ref0 , transition to its optimal power settings P dc and Q dc in a step-by-step manner, so that the power reference value is finally set as: P ref =P dc , Q ref =Q dc ; 最后,分别经有功和无功功率外环PI控制器输出产生d、q轴电流参考值idref和iqref,并传入电流内环控制;经调制和触发后,VSC-HVDC输出功率将以步进方式逐渐过渡至Pdc、Qdc,即为提高电压稳定水平的VSC-HVDC最佳功率。Finally, the d and q axis current reference values i dref and i qref are generated through the output of the active and reactive power outer loop PI controllers respectively, and passed into the current inner loop control; after modulation and triggering, the VSC-HVDC output power will be The stepping method gradually transitions to P dc and Q dc , which is the optimal power of VSC-HVDC to improve the voltage stability level.
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