Optimal Dynamic Voltage Restorer Using Water Cycle Optimization Algorithm

This paper proposes a low complexity control scheme for voltage control of a dynamic voltage restorer(DVR)in a three-phase system.The control scheme employs the fractional order,proportional-integral-derivative(FOPID)controller to improve on the DVR performance in order to enhance the power quality in terms of the response time,steady-state error and total harmonic distortion(THD).The result obtained was compared with fractional order,proportionalintegral(FOPI),proportional-integral-derivative(PID)and proportional-integral(PI)controllers in order to show the effectiveness of the proposed DVR control scheme.A water cycle optimization algorithm(WCA)was utilized to find the optimal set for all the controller gains.They were used to solve four power quality issues;balanced voltage sag,balanced voltage swell,unbalanced voltage sag,and unbalanced voltage swell.It showed that one set of controller gain obtained from the WCA could solve all the power quality issues while the others in the literature needed an individual set of optimal gain for each power quality problem.To prove the concept,the proposed DVR algorithm was simulated in the MATLAB/Simulink software and the results revealed that the four optimal controllers can compensate for all the power quality problems.A comparative analysis of the results in various aspects of their dynamic response and%THD was discussed and analyzed.It was found that PID controller yields the most rapid performance in terms of average response time while FOPID controller yields the best performance in term of average%steady-state error.FOPI controller was found to provide the lowest THD percentage in the average%THD.FOPID did not differ much in average response from the PID and average%THD from FOPI;however,FOPID provided the most outstanding average steady-state error.According to the CBMA curve,the dynamic responses of all controllers fall in the acceptable power quality area.The total harmonic distortion(THD)of the compensated load voltage from all the controllers were within the 8%limit in accordance to the IEEE std.519-2014.

An Equivalent Fundamental and Odd Harmonic Resonators Controller for a Single-phase Dynamic Voltage Restorer

为提高单相动态电压恢复器（dynamic voltage restorer,DVR）的补偿性能,提出一种基于等效基波及奇次谐波谐振器组的数字控制方法。采用可等效为一组谐振器的延时模块,能够有效抑制电网基波和谐波扰动。给出一种包含两个控制参数和一组零相移陷波滤波器的结构及其设计方法,使系统在保证稳定性的同时,获得较大的谐振增益。其中,延时环节衰减系数可增加谐振器组鲁棒性;控制器比例增益可解决零相移陷波器中使用延时带来的问题;零相移陷波器组既能对消LC谐振峰,也能解决等效谐振器组高增益在高频处的稳定性问题。同时,引入电源电压和负载电流双前馈来保证响应速度,增加了对扰动的抑制能力。所提控制策略结构简单,谐波补偿能力强,动态响应快,易于实现。在2kW单相DVR实验装置上的实验结果验证了该控制方法的正确性。

New Control Algorithm for Capacitor Supported Dynamic Voltage Restorer

In this paper, a simple control algorithm for the dynamic voltage restorer (DVR) is proposed to mitigate the power quality problems in terminal voltage such as sag, swell, harmonics, unbalance etc. Two PI (proportional-integral) controllers are used each to regulate the dc bus voltage of DVR and the load terminal voltage respectively. The fundamental component of the terminal voltage is extracted using the synchronous reference frame theory. The control signal for the series connected DVR is obtained indirectly from the extracted reference load terminal voltage. The proposed DVR control strategy is validated through extensive simulation studies using MATLAB software with its Simulink and Sim-power system (SPS) block set tool boxes.

Low-voltage ride-through capability improvement of Type-3 wind turbine through active disturbance rejection feedback control-based dynamic voltage restorer

Disconnections due to voltage drops in the grid cannot be permitted if wind turbines(WTs)contribute significantly to electricity pro-duction,as this increases the risk of production loss and destabilizes the grid.To mitigate the negative effects of these occurrences,WTs must be able to ride through the low-voltage conditions and inject reactive current to provide dynamic voltage support.This paper investigates the low-voltage ride-through(LVRT)capability enhancement of a Type-3 WT utilizing a dynamic voltage restorer(DVR).During the grid voltage drop,the DVR quickly injects a compensating voltage to keep the stator voltage constant.This paper proposes an active disturbance rejection control(ADRC)scheme to control the rotor-side,grid-side and DVR-side converters in a wind–DVR integrated network.The performance of the Type-3 WT with DVR topology is evaluated under various test conditions using MATLAB®/Simulink®.These simulation results are also compared with the experimental results for the LVRT capability performed on a WT emulator equipped with a crowbar and direct current(DC)chopper.The simulation results demonstrate a favourable transient and steady-state response of the Type-3 wind turbine quantities defined by the LVRT codes,as well as improved reactive power support under balanced fault conditions.Under the most severe voltage drop of 95%,the stator currents,rotor currents and DC bus voltage are 1.25 pu,1.40 pu and 1.09 UDC,respectively,conforming to the values of the LVRT codes.DVR controlled by the ADRC technique significantly increases the LVRT capabilities of a Type-3 doubly-fed induction generator-based WT under symmetrical voltage dip events.Although setting up ADRC controllers might be challenging,the proposed method has been shown to be extremely effective in reducing all kinds of internal and external disturbances.

中压并联型DVR链式变流器主电路及参数设计

中压并联型动态电压恢复器(DVR)由快速开关(HSS)和并联电压源变流器组成。电网发生故障时HSS关断,并联变流器转入负荷电压控制运行模式,并联变流器内置的超级电容器向负荷释放能量。此处对并联链式变流器主电路进行分析与比较,设计了链式变流器功率模块直流侧滤波电路,给出了滤波电路参数设计方法,并通过仿真和实验验证了直流侧滤波电路滤波效果,给出了链式变流器并网运行实验结果。

Energy-saving Superconducting Magnetic Energy Storage(SMES)Based Interline DC Dynamic Voltage Restorer

The fast-response feature from a superconducting magnetic energy storage(SMES)device is favored for suppressing instantaneous voltage and power fluctuations,but the SMES coil is much more expensive than a conventional battery energy storage device.In order to improve the energy utilization rate and reduce the energy storage cost under multiple-line power distribution conditions,this paper investigates a new interline DC dynamic voltage restorer(IDC-DVR)scheme with one SMES coil shared among multiple compensating circuits.In this new concept,an improved current-voltage(I/V)chopper assembly,which has a series of input/output power ports,is introduced to connect the single SMES coil with multiple power lines,and thereby satisfy the independent energy exchange requirements of any line to be compensated.Specifically,if two or more power lines have simultaneous compensating demands,the SMES coil can be selectively controlled to compensate the preferable line according to the priority order of the line.The feasibility of the proposed scheme is technically verified to maintain the transient voltage stability in multiple-line voltage swell and sag cases caused by either output voltage fluctuations from external power sources or power demand fluctuations from local sensitive loads.The simulation results provide a technical basis to develop a cost-effective SMES-based IDC-DVR for use in various DC distribution networks.

Double-loop Control Structure Using Proportional Resonant and Sequence-decoupled Resonant Controllers in Static Coordinates for Dynamic Voltage Restorer

Among incidents on grids,the sag/swell voltage is considered as the most frequent incident.To solve this problem,custom power devices are used.In particular,the dynamic voltage restorer(DVR)is a modern and efficient customer device.DVRs are used to mitigate voltage sag/swells and harmonics on the load bus,thus protecting the sensitive loads.The DVR is a serial compensator that applies a voltage to the point of common coupling to maintain the voltage of sensitive load at the nominal value.To improve the performance of DVRs,in this study,the control strategy of the two-stage loop circuit is implemented.The external voltage control loop uses a sequence-decoupled resonant(SDR)controller,and the inner current-control loop uses the proportional resonant(PR)controller implemented in the stationary frameαβ.

Application of Dynamic Voltage Restorer in Fault Ride-Through of Grid-Connected Photovoltaic Storage System

Problems in power quality such as temporary drops in grid voltage and flickers have been caught attention with the increasing capacity of the new energy grid-connected systems, such as photovoltaic(PV) and photovoltaic storage. To solve these problems, a dynamic voltage restorer(DVR) for fault ride-through of photovoltaic energy storage systems is presented. We select the appropriate DVR topology and compensation strategy for PV energy storage systems which are used as energy supply equipment for DVR. It proves to be energy-saving and solves the instability of photovoltaic output effectively. The intelligent algorithm that optimized the controller parameter of dynamic voltage restorer is used and the effectiveness of the controller strategy proposed has been assessed by time-domain simulations in the MATLAB/Simulink platform.

基于光伏储能的DVR分数阶PI控制策略

动态电压恢复器(dynamic voltage restorer,DVR)是设备侧有效治理电压暂降故障的装置,目前DVR的控制设计基本采用比例积分(proportional-integral,PI)控制器,但是DVR为非线性系统,传统PI控制器并不能达到理想的控制效果。为改善DVR的控制效果,提出一种新型电压电流双闭环分数阶PI(fractional order PI,FOPI)控制策略。首先,以光伏储能系统为DVR直流侧能量源,并建立相应的三相逆变器前馈解耦数学模型;其次,设计光伏储能系统与逆变器的双闭环PI控制策略,并进行参数整定;之后,将整数阶控制策略推广到分数阶来改善控制效果,并采用增益变化时的鲁棒性准则对FOPI控制器进行参数校正;最后,搭建不同控制策略下的DVR仿真模型,仿真结果验证了FOPI控制器应用于DVR系统的可行性,且相对于传统PI控制器其具备更好的动态响应速度与抗干扰性能。

非理想条件下MMC-DVR的Lyapunov控制策略研究

动态电压调节器(DVR)与模块化多电平转换器(MMC)组合的MMC-DVR可用于解决中高电压的动态电压补偿问题。目前MMC-DVR基本采用PID等线性控制方法,而MMC-DVR为非线性系统,因而其控制效果并不能令人满意。为此,提出了针对非理想条件下MMC-DVR系统的非线性李雅普诺夫(Lyapunov)控制方法来解决此问题。首先,建立MMV-DVR的数学建模。接着,设计了非理想条件下正、负序MMC-DVR的Lyapunov控制系统。最后,通过实验验证了所提的Lyapunov控制方法用于MMC-DVR的正确性和有效性。与传统PID控制相比,Lyapunov控制方法的电压在理想、非理想的多种不同工况下都能得到很好的补偿,且系统的动态响应更快、鲁棒性更强。

基于负荷电压的DVR补偿策略分析方法及最小能量控制

动态电压恢复器(dynamic voltage restorer,DVR)的补偿策略对于补偿效果有很大影响。针对传统分析方法的不足,提出一种基于暂降前负荷电压的相量图分析方法,该方法物理概念清晰,确定DVR补偿范围时简洁方便,在分析复杂电压暂降的补偿策略时具有很大优势,且可适用于负荷不平衡情形。给出该分析方法的基本思路与过程,并以三单相桥共用直流母线型DVR为例,对其补偿策略进行研究,通过该方法实现在发生不平衡电压暂降且负荷不平衡时最小能量的补偿策略,并给出实现零有功补偿的条件,有效地延长了DVR补偿时间。仿真结果验证了该方法的正确性。

线电压补偿型动态电压调节器(DVR)的原理与实现

该文提出了基于线电压补偿的三相动态电压补偿器拓扑结构。给出了补偿算法及控制方式。解决了锁相、电压不平衡补偿、电压有效利用、低通滤波、电压泵升等技术问题。通过动态电压波动补偿示例,说明论文所实现的DVR样机的有效性。

DVR的不平衡浪涌和过电压控制

讨论无串联隔离变压器的动态电压调节器(DVR)在不平衡电压浪涌或过电压情况下的补偿问题。使用不可控整流为直流侧电容充电的DVR,在补偿时只允许其向系统注入有功功率。在浪涌或过电压发生时,DVR可能发生从系统吸收有功功率的情况,如果仍然使用传统的同相或相位不变电压注入控制方法,将导致直流侧电容电压迅速升高,可能损坏开关器件或储能单元。利用最小能量补偿控制方法也不能完全解决该问题,因而提出一种单向功率流动控制算法。该算法通过将参考电压旋转一定的角度,使DVR无论在3相平衡与不平衡浪涌或过电压的情况下,都不从配电系统吸收有功,同时能将负荷电压补偿为3相平衡且达到正弦的额定值。该算法加入对DVR最大补偿极限的考虑,以确保注入补偿电压不超过DVR的补偿极限。文中对直流母线电压不可避免的泵升问题提出了缓冲控制策略。最后,仿真结果验证了算法的正确性及有效性。

基于无阻尼谐振调节器的DVR控制策略研究

文章针对电网电压的不平衡跌落情况,采用了三相全桥的主电路结构,研究了静止坐标系中基于无阻尼谐振调节器的三相DVR控制方案,不仅实现了DVR输出电压的无差跟踪,而且使系统获得强鲁棒性;为了实现对变流器的限流控制,采用了滤波电感电流反馈结合DVR输出电压反馈的双环控制结构,并运用DVR输出电压和直流电压的前馈补偿使系统获得了较好的动态响应。最后,通过样机实验验证了理论分析的正确性。

DVR和逆变式微电源配合补偿微电网中电压暂降问题的研究

对电压暂降原理和动态电压恢复器的补偿范围进行理论分析,提出利用PWM逆变式微电源配合DVR补偿微电网中电压暂降的策略。DVR储能容量的大小直接决定装置的成本,为在储能容量一定的前提下提高DVR的补偿能力,在补偿过程中让逆变式微电源相应多注入一些功率,分担DVR的有功注入,从而增大DVR的电压补偿范围。对发生电压暂降后DVR单独不能满足全相补偿的情况,采用PSCAD/EMTDC对逆变式微电源输入功率变化前后DVR的补偿能力进行仿真验证,结果表明通过增加PWM逆变式微电源的输出,能有效增大DVR的补偿能力,减轻暂降给负荷带来的影响。

基于最小能量法的DVR控制算法

考虑动态电压恢复器(DVR)在不同的补偿方式下对装置的能量要求不同,针对如何实现DVR最小能量补偿进行研究,将电压补偿情况分为7种(5种为电压暂降情况,2种为电压突升情况),并根据每种情况的各自幅值、相角特点,计算DVR输出的补偿电压的幅值和相角,并给出最小能量补偿的依据。同时,在DVR传统结构上进行改进,以最新的三单相独立补偿取代传统的三相同时补偿,形成3个独立的充电电路、储能电容和输出补偿电路,提高了DVR的响应速度和精度,而且增加了抑制电压突升的功能。在Matlab/Simulink仿真软件下进行的单相电压跌落补偿试验,仿真结果显示,所提的补偿算法在不同电压突变情况下,均可对系统进行恰当的电压补偿,并能保证DVR消耗的能量最小。

DVR在风电机组LVRT中的应用及其无功补偿能力

针对动态电压补偿器(DVR)在风电机组低电压穿越(LVRT)的应用进行了讨论。为了提高DVR的动态响应能力,设计了双闭环控制策略,并引入电网电压前馈项,以避免补偿电压的过冲;电压外环采用了谐振控制器,可在静止坐标系下实现无静差跟踪,省略了坐标变换以及锁相环节。同时详细分析了DVR在正常运行与跌落情况下无功补偿能力,通过对其补偿方式的分类与比较,指出了其无功补偿能力受到限制的原因。在Matlab/SIMULINK中构建仿真模型,仿真结果表明,所设计的控制策略能够迅速精准地补偿定子电压,减小了定子电流冲击,平稳地实现了机组的低电压穿越。最后在110 kW的电机平台上进行了实验验证。

一种补偿电网电压凹陷的DVR优化补偿策略

针对电网中敏感负荷引起的电压凹陷问题,以及提高动态电压恢复器(DVR)的补偿质量,提出了一种优化的综合补偿策略。首先,详细分析了DVR三种基本控制策略的补偿电压与功率流动,推导出最大跌落支持时间;然后,提出了一种跌落前补偿向最小能量补偿过渡的优化综合补偿策略,利用一次过渡曲线将跌落前补偿的电压幅值与相角逐渐过渡到最小能量补偿的值,物理意义明确,减小电压相位跳变的同时增加补偿时间。算例分析结果表明,该法较单一补偿方法显著增加了DVR的补偿时间。仿真结果验证了该方法的有效性。

动态电压恢复器(DVR)研究现状与发展综述

动态电压恢复器(DVR)是一种串联型补偿装置,其良好的动态性能和很高的性价比使得它成为治理动态电压问题,特别是电压凹陷的最经济、有效的手段。首先介绍了动态电压恢复器(DVR)的功能、组成及其特点,然后就目前国内外有关DVR研究的现状、存在的问题进行了详细的阐述和分析,最后讨论了DVR的发展趋势。