Mitigation of Transients in Capacitor Coupled Substations Using Traditional RLC Filter Techniques

This article presents an extensive examination and modeling of Capacitor Coupled Substations (CCS), noting some of their inherent constraints. The underlying implementation of a CCS is to supply electricity directly from high-voltage (HV) transmission lines to low-voltage (LV) consumers through coupling capacitors and is said to be cost-effective as compared to conventional distribution networks. However, the functionality of such substations is susceptible to various transient phenomena, including ferroresonance and overvoltage occurrences. To address these challenges, the study uses simulations to evaluate the effectiveness of conventional resistor-inductor-capacitor (RLC) filter in mitigating hazardous overvoltage resulting from transients. The proposed methodology entails using standard RLC filter to suppress transients and its associated overvoltage risks. Through a series of MATLAB/Simulink simulations, the research emphasizes the practical effectiveness of this technique. The study examines the impact of transients under varied operational scenarios, including no-load switching conditions, temporary short-circuits, and load on/off events. The primary aim of the article is to assess the viability of using an established technology to manage system instabilities upon the energization of a CCS under no-load circumstances or in case of a short-circuit fault occurring on the primary side of the CCS distribution transformer. The findings underscore the effectiveness of conventional RLC filters in suppressing transients induced by the CCS no-load switching.

Mathematical Modeling and Control Algorithm Development for Bidirectional Power Flow in CCS-CNT System

As the demand for more efficient and adaptable power distribution systems intensifies, especially in rural areas, innovative solutions like the Capacitor-Coupled Substation with a Controllable Network Transformer (CCS-CNT) are becoming increasingly critical. Traditional power distribution networks, often limited by unidirectional flow capabilities and inflexibility, struggle to meet the complex demands of modern energy systems. The CCS-CNT system offers a transformative approach by enabling bidirectional power flow between high-voltage transmission lines and local distribution networks, a feature that is essential for integrating renewable energy sources and ensuring reliable electrification in underserved regions. This paper presents a detailed mathematical representation of power flow within the CCS-CNT system, emphasizing the control of both active and reactive power through the adjustment of voltage levels and phase angles. A control algorithm is developed to dynamically manage power flow, ensuring optimal performance by minimizing losses and maintaining voltage stability across the network. The proposed CCS-CNT system demonstrates significant potential in enhancing the efficiency and reliability of power distribution, making it particularly suited for rural electrification and other applications where traditional methods fall short. The findings underscore the system's capability to adapt to varying operational conditions, offering a robust solution for modern power distribution challenges.

Mathematical Modeling of Multiple Capacitor Coupled Substations (CCS) Impact on Transmission Lines and Approaches for Ferroresonance Suppression

Rural electrification remains a critical challenge in achieving equitable access to electricity, a cornerstone for poverty alleviation, economic growth, and improved living standards. Capacitor Coupled Substations (CCS) offer a promising solution for delivering cost-effective electricity to these underserved areas. However, the integration of multiple CCS units along a transmission network introduces complex interactions that can significantly impact voltage, current, and power flow. This study presents a detailed mathematical model to analyze the effects of varying distances and configurations of multiple CCS units on a transmission network, with a focus on voltage stability, power quality, and reactive power fluctuations. Furthermore, the research addresses the phenomenon of ferroresonance, a critical issue in networks with multiple CCS units, by developing and validating suppression strategies to ensure stable operation. Through simulation and practical testing, the study provides insights into optimizing CCS deployment, ultimately contributing to more reliable and efficient rural electrification solutions.

Simulation Study on Series Capacitor Compensation to Improve the Voltage Quality of Rural Power Distribution Network

In order to improve the voltage quality of rural power distribution network, the series capacitor in distribution lines is proposed. The principle of series capacitor compensation technology to improve the quality of rural power distribution lines voltage is analyzed. The real rural power distribution network simulation model is established by Power System Power System Analysis Software Package (PSASP). Simulation analysis the effect of series capacitor compensation technology to improve the voltage quality of rural power distribution network, The simulation results show that the series capacitor compensation can effectively improve the voltage quality and reduce network losses and improve the transmission capacity of rural power distribution network.

A Power Electronic Conditioner Using Ultracapacitors to Improve Wind Turbine Power Quality

The large variability in wind output power can adversely impact local loads that are sensitive to poor power quality. To mitigate large swings in power, the wind turbine output power can be conditioned by using a small energy buffer. A power conditioner is developed to smooth the wind power output by utilizing the energy of an electrochemical capacitor, or ultracapacitor. The conditioner is based on a single phase voltage source inverter connected between the grid inter-connection point and the ultracapacitor. The VSI shunt inverter injects or absorbs active power from the line to smooth the wind power output by utilizing the short term storage capabilities of the ultracapacitor. The ultracapacitor is connected to the DC link through a bidirectional DC-DC converter. The bidirectional DC-DC converter and VSI are constructed and field tested on a Skystream 3.7 wind turbine installed at the Missouri University of Science & Technology.

A Study on the Conducted Interference of Capacitor Charging Power Supply

In this paper, a mathematical analysis of the EMI (Electromagnetic Interference) for a 20 kHz/10 kV capacitor charging power supply in frequency-domain is presented, and a related circuit model considering the transient switching interference is proposed. Due to the high working frequency and the device-switching transitions, the conducted EMI caused by the charging circuit which includes the harmonics of grid frequency, working frequency and device-switching transition frequencies. Thus under certain working situations or loads parallel power supply, the interference may cause charging failure. To solve this problem, a high frequency transformer modeled with stray capacitances and an approximation of the device-switching transition is applied in the Spice-based simulation model, and a mathematical analysis in frequency-domain is presented.

High-Power and Ultralong-Life Aqueous Zinc-Ion Hybrid Capacitors Based on Pseudocapacitive Charge Storage

Rechargeable aqueous zinc-ion hybrid capacitors and zincion batteries are promising safe energy storage systems.In this study,amorphous RuO2·H2O for the first time was employed to achieve fast and ultralong-life Zn2+storage based on a pseudocapacitive storage mechanism.In the RuO2·H2O||Zn zinc-ion hybrid capacitors with Zn(CF3SO3)2 aqueous electrolyte,the RuO2·H2O cathode can reversibly store Zn2+in a voltage window of 0.4-1.6 V(vs.Zn/Zn2+),delivering a high discharge capacity of 122 mAh g?1.In particular,the zinc-ion hybrid capacitors can be rapidly charged/discharged within 36 s with a very high power density of 16.74 kW kg?1 and a high energy density of 82 Wh kg?1.Besides,the zinc-ion hybrid capacitors demonstrate an ultralong cycle life(over 10,000 charge/discharge cycles).The kinetic analysis elucidates that the ultrafast Zn2+storage in the RuO2·H2O cathode originates from redox pseudocapacitive reactions.This work could greatly facilitate the development of high-power and safe electrochemical energy storage.

Optimal Sizing of Capacitor Bank for Increasing Substation Capacity of Mamou

In order to increase the available power of the electrical energy distribution station and improve the voltage profile of the distribution lines, the use of shunt capacitor banks is indicated. The main results obtained during this study are: a reduction in subscribed power from 14913.978 kVA to 14010.100 kVA, a reduction in the transformer load rate from 99.4% to 93.4%, a reduction in reactive power called from 5481.729 kVAr to 481.729 kVAr, an increase in the active power transported by the substation from 8505.062 kW to 8962.323 kW, a reduction in the voltage drop from 4.8% to 3.9%, an increase in the power available at the secondary of the transformer station at full load from 13950 kW to 14700 kW and an annual electrical energy saving of 339943.48 kWh of electrical energy, therefore fuel savings and a reduction in CO2 and SO2 emissions due to this energy saving will be achieved. The installation of capacitor banks for optimization of reactive energy allowed a reduction in the current called therefore a reduction in the absorbed power: 14153.061 kVA, i.e. a reduction of 903.876 kVA. It is therefore essential that energy players are convinced of the need to install capacitors to reduce or even eliminate their reactive energy bill. This is necessarily accompanied by an investment by Electricité De Guinée by setting up active and reactive energy meters but also by implementing pricing in line with the reduction in the transfer of reactive energy in the network.

一种单电源九开关二倍升压九电平逆变器

针对现有九电平逆变器存在使用器件较多且调制策略复杂的问题,提出1种新型的开关电容九电平逆变器,其拓扑仅需1个直流电源、9个开关、2个电容和2个二极管即可输出九电平,同时实现二倍升压。该逆变器具有电容电压自平衡的能力,无需复杂的控制算法和外部均压电路来维持电容电压平衡。采用多载波层叠调制策略对该逆变器进行调制,逆变器中4对开关的工作状态互补,可以使用非门逻辑电路来降低调制策略的复杂度。首先对该逆变器的拓扑结构和工作原理进行理论分析;其次,对调制策略进行了详细介绍,并将所提拓扑与其他九电平拓扑进行比较,介绍了该拓扑的优点;最后,搭建的仿真电路和实验平台验证了所提拓扑及调制策略的可行性和有效性。

模块化多电平中压直流变换器的高可靠自供电架构研究

随着大容量中压直流配电技术的迅速发展,模块化多电平直流变换器受到工业界和学术界的广泛关注。然而,实现高可靠的辅助供电是实现直流变换器在中压直流配电场景中应用的关键技术瓶颈之一。为此,提出一种面向模块化多电平中压直流变换器的高可靠自供电系统架构。该架构实现主控制器、子模块等辅电系统的中压直联馈电,从而无需额外低压直流电源,并且大幅提升系统启动速度。基于此架构设计,模块化多电平直流变换器的子模块控制器和旁路开关辅助供电均实现3倍冗余,提高系统容错运行的能力。在子模块电容预充电阶段,提出一种基于辅助电源自主控制的子模块电容均压方法,保证模块化多电平直流变换器可靠预充电。最终通过实验验证所提辅助供电系统架构的可行性。

Effect of Switching Devices on Power Quality and Transient Voltage Suppression Using Capacitor Bank Model

The main purpose of the electrical power system is to transport and distribute energy generated by the central power plants in a safe and reliable manner to the customer premises. Most of the electrical equipment is exposed within the open which suggests they can be vulnerable to lightning strikes, road dwindling, windstorms, and a few engineering activities with the potential of causing different degrees of damage to the electrical equipment. One of the ways to guard the equipment is to deploy switching devices. However, the operations of most of these switching devices produce oscillatory transient in the electrical transmission and distribution systems which result in voltage, current, and frequency fluctuations in the load. This paper investigates the effect of switching devices on power quality and proposes a positive sequence voltage power transient suppression technique that can spontaneously improve the distorted voltage at the instant of capacitor switching using the capacitor line model as a case study. MATLAB/Simulink software was utilized for the analysis on an electrical network model with bus voltages of 69 kV/12.47 kV and 480 V. The results showed that, during switching operations, the positive sequence voltage power detector block produces ripple-free accurate results.

含废旧矿井抽蓄电站的源-荷-储协同控制调频研究

针对新能源在电网中渗透率不断提高导致系统调频容量和频率响应能力不足的问题,提出一种含废旧矿井抽蓄电站的源-荷-储协同控制调频方法。首先,建立了电解铝工业负荷、废旧矿井抽蓄电站和超级电容频率响应模型。然后,基于模型预测控制理论,以系统状态量和控制量的加权函数最小为目标,设计区域信息互动的分布式模型预测控制器,并提出含废旧矿井抽蓄电站的源-荷-储协同控制调频方法。最后,将分布式模型预测控制器应用在所提源-荷-储协同控制方法中,并在改进的IEEE标准两区域LFC模型中进行仿真。结果表明所提方法可以缩短频率恢复时间,减小最大频差值,改善系统调频动态性能。

功率型储能技术与应用综述

大规模可再生能源发电并网给电力系统安全稳定运行带来了新的挑战,储能技术是解决这一问题的重要手段。为了满足新型电力系统应用场景的多样化需求,储能技术呈现百花齐放、多元化发展新态势。其中,功率型储能技术具有功率密度高、响应速度快、循环寿命长等优势,在新型电力系统的电力调频、平滑新能源波动、负荷跟踪等领域应用具有重要的应用价值。剖析了电化学电容器、飞轮储能、超导磁储能等功率型储能的技术原理和性能特征,梳理了各类功率型储能技术未来发展规划,总结了功率型储能在新型电力系统的应用技术研究工作,同时列举了目前国内外功率型储能的工程示范应用典型案例。最后针对各类功率型储能未来在电力系统应用面临的挑战进行了分析,提出未来功率型储能技术未来发展方向,旨在为功率型储能技术研究和产业发展提供参考。

基于光储协同的改进型低压穿越控制策略

针对光伏发电系统低压穿越过程中传统控制策略引起的逆变器直流电压泵升,以及储能装置参与协调过程中存在的调节被动和响应滞后问题,提出一种基于光储协同的改进型低压穿越控制策略。首先,揭示不平衡功率在逆变器直流侧堆积是电压泵升的关键原因;其次,以并网点电压支撑与不平衡功率抑制为双重目标,构建逆变器参考电流自适应生成模块,通过优化逆变器低压穿越期间的电流指令抑制不平衡功率的产生。在此基础上,设置直接功率控制的超级电容储能,使其依据光伏与逆变器输出的实时功率差值主动协同消纳超出抑制能力的不平衡功率。仿真结果表明,改进型低压穿越控制策略在保证并网点电压支撑的前提下,通过分级调控获得更快的响应和调节速度,有效解决了逆变器直流侧电压升高问题。

模块化多电平矩阵换流器接入下的工频故障特性分析

基于模块化多电平矩阵换流器(M3C)的柔性低频输电系统在中远海风电外送、异步电网互联等方面优势突出。然而,有别于模块化多电平换流器(MMC)等其他电力电子换流设备,M3C的控制策略将导致系统故障特性发生显著变化。现有将电力电子设备负序部分等效为开路的故障等值与响应特性计算方法无法适用。文中计及M3C正序定电容电压总平均值控制、负序电流注入控制以及环流控制分层构成的桥臂电容电压均衡策略,推导了工频侧线路故障以后,M3C输入输出功率均衡、桥臂功率均衡(电容电压均衡的必要条件)与正负序电压电流间的映射关系,由此构建了工频侧线路故障(不对称、对称)后的M3C输出电压电流响应特性的等效模型。在此基础上,提出了M3C接入下工频侧线路故障后电压电流响应特性的精确计算方法。最后,基于PSCAD/EMTDC仿真平台,搭建了海上风电柔性低频送出系统仿真模型,通过大量仿真算例充分验证了所提故障特性分析方法的正确性和精确性。

基于比例重复控制的MMC-SST子模块电容纹波电压抑制策略

基于模块化多电平变换器的固态变压器(modular multilevel converter based solid state transformer,MMC-SST)是实现交直流混合配电网柔性互联及能量多向流动的关键装备。针对固态变压器输入级MMC子模块电容纹波电压过大,导致装置的体积和成本增加的问题,提出一种基于比例重复控制的MMC-SST改进纹波电压抑制策略。首先利用基于比例重复控制的电容电压闭环得到调整后的功率移相角。然后,通过双有源桥变换器将子模块电容纹波功率传递到低压直流母线,从而有效抑制MMC子模块的各频次纹波电压,达到减小电容值的目的。最后,仿真结果表明在网侧电压对称或不对称工况下,基于比例重复控制的MMC-SST子模块电容纹波电压抑制策略均具有良好的纹波电压抑制能力。

三元复合聚丙烯电介质材料性能调控研究进展

当前快速增长的能源需求要求电力设备具有更高运行电压、更大容量、更小体积,因此要求聚丙烯等介质材料实现电学、机械和热学等多种性能的协同提升的同时,兼顾加工性、环保性、经济性等优势。针对聚丙烯单一性能提升方面的研究取得了显著成效,而多性能协同提升成为了近年来的研究重点和难点,其中将共混改性和纳米复合改性两种方法结合,构筑三元复合聚丙烯的性能调控思路具有突出优势。文中基于电缆绝缘和电容器薄膜两个典型的聚丙烯应用场景,对“聚丙烯/有机物/纳米粒子”三元复合聚丙烯的研究进展进行了总结梳理,进一步阐明了三元复合聚丙烯绝缘性能与机械性能协同提升的机理,建立了三元复合聚丙烯储能密度与介电损耗平衡调控的演化模型,最后对三元复合聚丙烯未来的发展提出了展望。

基于等效阻抗的分数阶RLC_(α)串联谐振BD-WPT系统传输特性分析

针对谐振式无线电能传输系统中分数阶电感、电容元件的仿真实现困难的问题,采用等效阻抗实现分数阶电容的等效.基于分数阶电容的阻抗特性,给出了一种分数阶RLC_(α)串联谐振双向无线电能传输(bidirectional wireless power transfer,BD-WPT)系统结构,通过建立含分数阶电容的串联谐振式双向无线电能传输系统的电路模型,推导了其传输功率和效率关系.仿真实验结果表明,与整数阶串联谐振系统相比,系统的输出功率提升了7.82%,传输效率提升了0.58个百分点.

感应电能传输系统多并联拾取模块电流和输出功率均衡方法

大功率感应电能传输系统通常采用多并联拾取模块结构。然而,多并联拾取模块参数不一致,会导致各个拾取模块的电流和输出功率不均衡,从而降低系统效率,严重时会因模块过流而造成系统故障。为解决该问题,文中提出一种基于并联拾取模块补偿电容器的多并联拾取模块电流和输出功率均衡方法。首先,介绍了传统感应电能传输系统与所提出的感应电能传输系统拓扑的特性。然后,分别分析了互感、拾取线圈自感及内阻对电流分布和系统效率的影响。最后,通过4个并联拾取模块的感应电能传输系统实验平台验证了所提方法的有效性。实验结果表明,采用所提方法时多并联拾取模块的电流和输出功率基本一致,并且相比传统感应电能传输系统,系统效率最高提升了2.21%。

计及实时最大功率约束的高速磁浮列车再生制动能量存储利用

针对高速磁浮列车牵引供电系统结构及运行规则特殊性导致再生制动能量无法主动利用、能量回馈方式对局域网电压影响大的问题,在对高速磁浮列车牵引供电系统结构和能量流动机理进行分析的基础上,给出基于地面式超级电容储能的高速磁浮列车再生制动能量回收利用系统拓扑结构;考虑高速磁浮列车再生制动能量回收系统容量配置小、超级电容工作电压变化明显的特性,以高效回收再生制动能量为目标,将储能系统实时的可运行最大功率作为约束功率,制定相应的能量管理策略,实现系统不同工况下的能量管理,并通过分层控制策略实现整个再生制动能量利用系统的高效运行。通过仿真验证所提再生制动能量回收利用系统及控制策略的有效性,结果表明:所提方案可使高速磁浮列车牵引能耗降低21.83%;与储能系统采用固定功率约束的功率分配方式相比,再生制动能量利用率提高了11.9%。