Hybrid simulation of power systems with SVC dynamic phasor model

A novel hybrid method for simulation of power systems equipped with static var compensators (SVC) is suggested in this paper, where dynamic phasor theory is applied for SVC, and traditional electromechanical transient models are used for ac subsystem. A detailed single-phase dynamic phasor-based SVC model is derived first, and an interface algorithm between the SVC dynamic phasor model and the ac subsystem is proposed next. Test results on the 9-bus and the New England 39-bus test power systems show clearly that the single-phase SVC dynamic phasor model has very good accuracy as compared with its electromagnetic transient model. The proposed hybrid-model simulation method provides a new approach for dynamic simulation of large-scale power systems including SVCs.     

含统一潮流控制器装置的电力系统动态混合仿真接口算法研究

提出了一种新的含UPFC装置的电力系统动态混合仿真接口算法，算法中对UPFC采用动态相量建模，对电力系统网络则采用成熟的机电暂态仿真。仿真中UPFC并联侧采用定交流母线电压控制和定直流电容电压控制，串联侧采用定线路潮流控制。文中推导了UPFC的动态相量模型，讨论了与网络机电暂态模型的接口算法。研究分析和算例仿真表明：使用动态相量建模可精确地仿真UPFC的电磁暂态（EMT）过程，且仿真速度快；文中所提混合仿真方案能保证较快的仿真速度和优良的仿真精度，具有较好的收敛性，且可用于含UPFC等FACTS装置的系统发生不对称故障时的暂态稳定分析。     

基于NETOMAC软件的直流输电系统混合仿真计算及参数优化

基于ＮＥＴＯＭＡＣ软件的混合仿真功能,建立了直流输电系统的混合仿真计算模,该模型能在对交流网络进行机电暂态计算的同时,对直流网络进行电磁暂态计算,因而能较精确地考察暂态过程中直流线路的动态行为,并可对任意对称的交流系统故障,直流线路的故障以及故障后直流输电系统的恢复等过程进行仿真的验证的且所需仿真时间较短,针对ＣＩＧＲＥ标准测试系统的仿真结果表明了该方法的优越性。此外,还应用ＮＥＴＯＭＡＣ软件的优     

统一潮流控制器的动态相量建模与仿真

为适应系统快速、精确仿真和分析、控制的需要，运用一种新的建模方法——基于时变傅里叶级数的动态相量法对统一潮流控制器(UPFC)进行建模和仿真。该方法通过忽略系统状态变量所对应的傅里叶级数中那些不重要的项而对原系统进行简化，并且可以有效地将系统中的连续事件和离散开关事件结合起来。在建模过程中可以根据研究需要提取出UPFC暂态模型中的直流分量和需要考虑的各次交流谐波分量。通过与详细时域模型仿真计算结果的比较，证明了UPFC的动态相量模型是精确而有效的，并且可以大大节省计算时间。     

含直流馈入的弱受端电网暂态电压稳定预防控制

远距离跨区直流输电(HVDC)的大规模应用给电力系统安全稳定运行带来了新的挑战.针对HVDC馈入后弱受端交流电网面临的暂态电压稳定问题,提出一种暂态电压稳定预防控制方法.建立以改善弱受端电网暂态电压恢复指标为目标函数,以火电机组有功出力、机端电压、直流输送功率为控制变量的暂态电压稳定预防控制优化模型.基于改进差分进化算...     

高压直流建模研究的相关问题

总结了电力系统稳定性分析中高压直流输电系统的一般性建模方法;讨论了直流模型的分类及模型的适用性;分析了常用商用电力系统分析软件中的直流模型,建议开发商适当增加内置直流模型与用户自定义模块间的接口,以拓展直流模型的适用范围;重点分析了基于采样数据建模方法和动态相量理论对直流换流器准稳模型的改进。认为采样数据建模方法建立了适合于电力系统次同步振荡研究的换流器小信号模型,但不能用于电力系统暂态稳定仿真计算中;动态相量法推导了换流器的大信号模型,但仍不能正确反映换相失败现象和不对称工作条件下高压直流系统的动态行为。认为在大规模交直流电力系统的暂态稳定性研究中,机电-电磁混合仿真思路较有潜力,而其关键问题在于各种扰动下电磁暂态仿真范围的合理确定。     

Dynamics of an HVDC system in the presence of unbalanced AC transmission line faults and a stabilization scheme

The introduction of an HVDC system into the trunk power supply system requires transmitting as much dc power as possible for improving the whole ac/dc system stability. The continued operation scheme of an HVDC system which makes it possible to operate even under very low commutation bus voltage is adopted to cope with such system requirement. Further stability improvement can be achieved by adding damping control which modulates converter active and/or reactive power. To take full advantage of these control effects, it is essential that the HVDC system can maintain stable operation during the ac system faults and reclosing. Particular attention should be given to a repetitive commutation failure following the unbalanced ac transmission line faults. This paper discusses first the cause of the repetitive commutation failure when supplied with unbalanced ac system voltage based on an experiment using the CRIEPI AC-DC Power System Simulator. Then a stabilization control scheme with an on-line extinction angle estimation is proposed and the effect is verified by digital simulation.     

含静止无功补偿器的电力系统混合仿真新算法研究

传统的机电暂态仿真对HVDC和其它FACTS电力电子装置采用准稳态模型,因而不能仿真它们的瞬变电压、电流特性.而电磁暂态仿真程序(例如EMTP)受计算规模的限制,一般要对研究对象的外部电力系统进行等值化简,因此不能反映系统机电暂态过程对电磁暂态过程的影响.本文介绍的混合仿真算法为弥补上述两种方法的不足,对电力网络采用准稳态模型,而对待研究的电力电子装置(例如SVC)使用电磁暂态模型,两种仿真的结合使用了本文发展的考虑系统频率偏移影响的接口技术.本文介绍的混合仿真算法为研究HVDC和FACTS等电力电子装置及其控制系统的动态性能提供了一种有力的工具.     

基于PSASP的直流系统用户自定义建模

针对大规模交直流电力系统机电暂态仿真时采用程序缺省的直流输电模型不能有效描述实际直流输电特性的问题，以实际直流系统为参考，利用PSASP用户自定义建模环境，采用注入功率法建立高压直流用户自定义模型。此自定义直流模型由潮流模型和稳定模型2部分组成，稳定模型涵盖实际直流控制器的主要控制功能模型以及变压器分接头控制、无功控制等辅助功能模型。以EPRI-7节点系统为例，研究在不同工作状态下自定义直流模型系统的特性，仿真结果证明了模型的合理性。     

电压源型直流输电的动态相量建模与仿真

为适应电力系统快速精确仿真和分析控制的需要,采用了一种新的建模方法—基于时变傅立叶级数的动态相量法,对电压源型直流输电(VSC-HVDC)进行建模和仿真。该方法通过保留与系统状态变量相对应的时变傅立叶级数中的重要项对原系统进行简化,首先建立用开关函数描述的VSC-HVDC换流站详细时域模型,在此基础上,给出VSC-HVDC动态相量模型的详细推导过程。在对VSC-HVDC进行动态相量建模的过程中,换流站的开关函数考虑直流分量和基频分量,直流传输线路只考虑直流分量,从而大大简化高频开关过程,在保证仿真精度的同时,大大缩短了仿真时间。通过MATLAB仿真软件用动态相量模型与详细时域电磁暂态(EMT)模型分别对VSC-HVDC进行仿真比较的结果表明,动态相量模型精确而有效,不仅可以精确描述VSC-HVDC的暂态变化过程,而且可以大大节省仿真计算时间。     

电力系统仿真软件PSS/E的直流系统模型及其仿真研究

简要介绍了电力系统仿真软件(PSS/E)动态仿真的基本原理.PSS/E中的直流模型可以分为两类:一类考虑直流线路电感暂态过程和高频控制器动态特性,另一类不考虑以上动态特性.文章分析了这些直流模型的有效性和适用性,并通过准稳态直流动态模型CDC4进行了仿真研究,仿真结果表明PSS/E直流模型能够满足大规模交/直流系统仿真的要求.     

含逆变器的微电网动态相量模型

微电网作为一种分布式可再生能源并网的有效途径,是传统电力系统的重要补充。然而,微电网中含有大量的并网逆变器、机端负荷和线路,其电磁暂态过程给微电网的建模、分析和控制带来了巨大的挑战。以并网逆变器、线路和机端负荷的动态相量模型为基础,建立含并网逆变器的微电网动态相量模型。最后,在电磁暂态综合分析程序PSCAD/EMTDC中建立一个含有多台并网逆变器的微电网模型,并在Matlab/Simulink中建立其动态相量模型。仿真试验的结果验证了所提微电网动态相量模型的正确性和有效性,为并网逆变器和微电网的建模、分析和控制提供了一种新方法。     

A nonlinear emergency control strategy for HVDC transmission systems

A novel nonlinear emergency control method for HVDC transmission systems is presented in this paper. First, an observation-decoupled state space model of AC and DC interconnected power systems, which allows estimation or computation of the state components from local measurements, is developed. Secondly, the nonlinear control rules of HVDC links are derived using optimal-variable-aim strategy, which not only improves the first-swing stability, but also effectively damps the subsequent power oscillation. Finally, the simulation results of a three-machine six-bus system show that the proposed method can enough use the capabilities of fast response and short-time overload of HVDC links to improve the transient stability of power systems.     

电力系统仿真软件PSS/E中柔性直流输电系统模型及其仿真研究

柔性直流输电系统(voltage sourced converters high voltage direct current，VSC-HVDC)因其快速灵活的可控性在电力工业中将有越来越广泛的应用，研究其在复杂电力网络中的动态性能具有工程实际意义，应用电力系统仿真软件PSS/E可模拟柔性直流输电的准稳态响应。介绍了PSS/E动态仿真的基本原理；分析了柔性直流输电模型VSCDCT的有效性和适用性，并基于实际系统对准稳态直流动态模型VSCDCT进行了仿真研究，仿真结果表明 PSS/E直流模型能够满足大规模交/直流系统仿真的要求。     

New techniques for enhancing accuracy of EMTP/TSP hybrid simulation

This paper proposes a new hybrid approach, which integrates the simulation of electromagnetic transient program (EMTP) for waveform solutions to concerned electrical components, such as FACTS devices and HVDC etc. and the simulation of transient stability program (TSP) for phasor solutions to the rest of power systems. In the interface between the two simulations, new techniques considering the effect of frequency deviation due to disturbances are proposed for improving accuracy of the hybrid simulation. A case study is performed on the IEEE 10-generator New England systems. The results show that simulation accuracy of conventional EMTP/TSP hybrid methods has been evidently improved. The proposed new method would thus provide an efficient tool in the design and analysis of behaviors of FACTS devices in power system dynamics.     

Integration of HVDC control dynamics into transient energy functions

A common approximation used in the formulation of transient energy functions (TEFs) for ac/dc power systems involves the omission of dc control dynamics. The differential equations representing the dc system dynamics are used to track the fault-on trajectory, but not to derive the TEF. This approach leads to an error in TEF-based stability prediction. In this paper, a method is presented to derive the TEF with dc system dynamics explicitly integrated. By using this comprehensive transient energy function, the accuracy of the stability prediction in ac/dc systems is improved. In addition, because differential equations representing dc dynamics are included directly in the TEF, the calculation of the post-fault equilibrium point is done only once. This leads to a considerable reduction in CPU time. The method is validated by comparing results from 12-bus and 30-bus ac/dc test systems with those obtained from time simulation.     

交直流电力系统非线性鲁棒直流调制控制器设计

随着“西电东送、全国联网”战略的实施,大区之间通过交直流并列运行输电系统实现电网互联。性能优良的直流调制控制器可以快速有效地调节直流联络线的输送功率,减轻交流输电系统的暂态输电压力,以提高交流系统的动态性能。以交直流并列电力系统为研究对象,采用基于扩张状态观测器的动态反馈线性化方法,将系统的非线性数学模型动态补偿为一个伪线性系统,然后利用线性鲁棒H∞理论进行控制器综合。仿真试验表明,当交流联络线发生三相短路故障时,给出的控制器能够有效抑制两侧交流系统的功角振荡,且对于系统不确定性表现出良好的鲁棒性,从而使整个交直流电力系统的暂态稳定性得到改善。与基于精确反馈线性化方法的非线性控制器相比,具有更为优越的动态品质。     

直流孤岛系统低次谐波稳定性仿真研究

针对南方电网牛从和普侨两个直流输电工程孤岛运行状态下的低次谐波稳定性问题,在PSCAD/EMTDC中搭建了详细的时域仿真模型并进行仿真研究。首先,使用测试信号法在一定频率范围内扫描直流输电系统直流回路阻抗和交流并联阻抗。其次,通过分析比较低次谐波频率下直流回路阻抗与交流并联阻抗之间的大小关系,对直流系统的低次谐波稳定性进行初步判断。最后,用时域仿真法对可能出现低次谐波振荡的工况进行校核。计算结果表明,在孤岛运行方式下,交流系统短路比的变化对直流回路阻抗和交流并联阻抗的阻抗频率特性有一定影响,随着短路比减小,阻抗频率特性向左上方偏移。此外,在所考虑的孤岛运行方式与故障情况下,直流系统均不会发生低次谐波不稳定现象。     

应对多馈入直流换相失败的综合防御研究

随着多馈入直流格局的形成,系统安全稳定控制难度也随之增大。发生严重交直流故障时,存在多直流同时换相失败使系统失去稳定的风险,因此避免直流换相失败和维持受端电压稳定,是目前多馈入直流受端系统控制措施需要解决的重要问题。研究了多馈入直流换相失败的电网特性和影响因素,从三道防线角度研究提出应对多馈入直流换相失败导致的电压失稳的控制策略。基于实际电网进行仿真验证,所提出的控制策略可降低多馈入直流换相失败风险、提高受端电网电压稳定水平。     

Multi-task control for VSC–HVDC power and frequency control

A robust control strategy for a VSC–HVDC transmission scheme between two ac networks is presented. The VSC converters at both ends of the dc line are equipped with a multi-task controller that facilitates: power management between the two ac systems, provision of independent reactive power control at the point of common couplings (PCCs) and frequency regulation at the sending-end side. The paper investigate the utilization of VSC–HVDC system to provide frequency regulation to an ac network; this is useful for networks with high penetration of renewables (e.g. wind), and nuclear generation. The proposed control strategies for the VSCs are presented in detail, investigating further the tuning method for the proper operation of the inner controllers. The robustness of the control system is tested under large disturbances. The study is conducted in Matlab/Simulink and results that substantiate the dynamic performance of the VSC–HVDC with the proposed control are thoroughly discussed.