Voltage balancing of islanded microgrids using a time-domain technique

In this paper, voltage balancing and frequency control of converter-fed, islanded microgrids, using a novel time-domain technique which has not been applied for such applications is discussed in detail. In particular, the connection of single-phase loads to the islanded microgrid causes voltage unbalance and this is eliminated by supplying the negative-sequence component of the voltage from the converter. The negative sequence components of the voltage and current are extracted using the aforementioned time-domain technique. The simulations are carried out in RSCAD™ and experimental results are provided to validate the concept.     

微电网负荷控制装置设计方法研究

为维持微电网的电能质量和供用电平衡,提出了1种微电网负荷控制装置。对微电网负荷控制装置设计方法进行了研究,提出了微电网母线电压、频率以及它们的变化率,当发生频率、电压事故时相应的判断方法,实现微电网系统低频、低压、过频、过压控制功能,提高微电网的供电质量。     

考虑智能建筑特性的多微网端对端能量交易方法

针对当前分布式交易市场未充分考虑终端用户用能特性,且市场主体之间的博弈关系仍需进一步挖掘等问题,文中提出了考虑智能建筑特性的多微网端对端(P2P)能量交易方法.首先,以智能建筑作为终端负荷载体,提出了一种新的建筑热阻-热容热平衡模型,并构建了市场主体即微网的自治调度模型.其次,分别采用非合作博弈及主从博弈模型分析了P2...     

智能电网中清洁分布式能源的优化利用策略

智能电网是全球经济和技术发展的必然结果。为此,分析了智能电网中清洁能源大量使用的发展趋势,同时借助微电网模式对分布式能源进行管理,研究了智能电网中分布式能源最优化利用问题。提出了基于多代理系统(MAS)的控制框架。为了优化利用分布式能源,设计了协调控制策略。详细分析了各Agent的控制方法。MAS实现了对全网清洁分布式能源信息化、智能化的控制。仿真结果验证了MAS能够快速有效地对全网各电源进行协调控制,保证了各种状态下系统的安全稳定以及对清洁分布式能源的最优化利用。     

基于余弦平顶窗的谐波相量测量

In this paper, a Backstepping Global Integral Terminal Sliding Mode Controller (BGITSMC) with the view to enhancing the dynamic stability of a hybrid AC/DC microgrid has been presented. The proposed approach controls the switching signals of the inverter, interlinking the DC-bus with the AC-bus in an AC/DC microgrid for a seamless interface and regulation of the output power of renewable energy sources (Solar Photovoltaic unit, PMSG-based wind farm), and Battery Energy Storage System. The proposed control approach guarantees the dynamic stability of a hybrid AC/DC microgrid by regulating the associated states of the microgrid system to their intended values. The dynamic stability of the microgrid system with the proposed control law has been proved using the Control Lyapunov Function. A simulation analysis was performed on a test hybrid AC/DC microgrid system to demonstrate the performance of the proposed control strategy in terms of maintaining power balance while the system’s operating point changed. Furthermore, the superiority of the proposed approach has been demonstrated by comparing its performance with the existing Sliding Mode Control (SMC) approach for a hybrid AC/DC microgrid.     

直流微电网分布式控制的时滞稳定化设计

直流微电网中,大部分控制器在设计时未考虑通信延时对系统性能的影响,这可能会导致控制器在实际应用中失效甚至影响系统的稳定性.本文基于一种分布式控制策略,建立了直流微电网系统的时滞模型,重点研究了通信延时对系统稳定性的影响.结合Razumikhin稳定性理论,提出了一种针对时变时滞系统的全时滞稳定性判据.为了更加适用于实际系统,在另一种全时滞稳定性判据的基础上,对系统时滞相关稳定性进行分析,得到保证系统稳定的延时上界,进而给出了一种确定控制参数范围的方法.与传统的将通信延时处理为一阶惯性环节的分析方法相比,基于时滞系统的分析方法更切合实际,为系统的稳定运行提供了一个更宽的时滞范围,提高了系统的可靠性.仿真和实验结果表明本文提出的控制参数设计方法能保证系统在最大延时下的稳定运行.     

采用分布式单纯形法的微电网分散式动态经济调度

对含多种分布式电源的微电网,基于分布式单纯形法,提出了一种求解微电网动态经济调度问题的分散式优化算法。通过对目标函数进行线性化,建立了微电网动态经济调度的线性规划模型。将每个分布式电源均视为独立的智能体,从而将线性规划模型中的成本向量和约束方程系数矩阵按智能体进行分块,进而采用分布式单纯形法求解。每次迭代过程中,智能体通过通信网络传递当前解对应的最优基和成本向量。所提算法不需要中央控制器的参与,智能体间具有一定的信息保密性,且通信次数与通信网络的直径成线性增长的关系。最后,以某实际微电网为测试系统,验证了线性化模型的准确性和算法的有效性。     

Robustness of delayed multistable systems with application to droop-controlled inverter-based microgrids

Motivated by the problem of phase-locking in droop-controlled inverter-based microgrids with delays, the recently developed theory of input-to-state stability (ISS) for multistable systems is extended to the case of multistable systems with delayed dynamics. Sufficient conditions for ISS of delayed systems are presented using Lyapunov–Razumikhin functions. It is shown that ISS multistable systems are robust with respect to delays in a feedback. The derived theory is applied to two examples. First, the ISS property is established for the model of a nonlinear pendulum and delay-dependent robustness conditions are derived. Second, it is shown that, under certain assumptions, the problem of phase-locking analysis in droop-controlled inverter-based microgrids with delays can be reduced to the stability investigation of the nonlinear pendulum. For this case, corresponding delay-dependent conditions for asymptotic phase-locking are given.     

微电网并网逆变器的改进下垂控制策略研究

采用下垂法下垂系数的确定是个很大的难题。下垂系数很小,动态响应速度变慢;增大下垂系数可以改善动态响应,但是频率和电压幅值会大幅度偏离设定值,造成系统的不稳定,这种矛盾很难调和。本文提出了分段滞环的下垂控制策略,用三条斜率较大的下垂曲线代替一条斜率较小下垂曲线,使用此方法既可以解决动态响应的问题又可以增加功率输出范围而保持输出幅频不会变化太大。最后让此控制策略与传统的下垂控制策略相比较,比较结果证明了该策略的可行性和优越性。     

基于形态学梯度算法的微电网行波保护方案

针对交流微电网的故障特征和保护要求,提出一种基于形态学梯度算法的行波保护故障选线选相方案。首先,通过比较离散小波变换和形态学梯度算法对电流行波的提取结果,得出形态学梯度算法能更清晰地提取行波的结论。其次,设计适用于多种拓扑结构的微电网行波保护故障选线方案。然后,利用三相初始电流行波及其模分量设计一种故障类型判断和故障选相方案。最后,对行波保护的死区问题进行分析并提出相应的解决方案。利用PSCAD/EMTDC和Matlab软件进行仿真分析,仿真结果验证了所述保护方案的正确性和可行性。