An efficient switched-reactor-based static VAr compensator

A new static VAr compensator is presented in this paper. To overcome the problems of large low-order harmonics and slow response associated with conventional thyristor-controlled-reactor based compensators, a pulse-width-modulated (PWM) AC converter is used to control the reactances of switched reactors. Yet unlike the PWM static VAr compensators previously reported in the literature, the proposed compensator has a simpler structure and its gating signals are easier to implement. Moreover, it does not require synchronization with the AC mains. The proposed concept was verified through a 1 kVAr prototype and the measured experimental results prove that either leading or lagging reactive power can be achieved through simply duty cycle control     

Design considerations for the Eddy County static VAr compensator

This paper describes the steps for the design of the static VAr compensator at (SVC) Eddy County. The specified system requirements on operating range, loss evaluation and harmonic performance led to an SVC configuration which contains one thyristor switched capacitor (TSC) branch, one thyristor controlled reactor (TCR) branch for continuous reactive power control and two double tuned filter branches. The system voltage of the SVC secondary bus was optimized to 8.5 kV based on thyristor equipment capabilities. The paper shows the voltage and current stresses of the thyristor valves taking into account system faults for the TCR branch and misfiring effects on the TSC branch. The approach for filter design considering the harmonic performance requirements and resulting component ratings are shown. The Eddy County SVC commenced commercial operation in April 1992     

Detailed modeling of an actual static VAr compensator forelectromagnetic transient studies

The authors present a detailed model of a static VAr compensator (SVC) for digital simulation of electromagnetic transients. It is also demonstrated that this model can adequately reproduce SVC transient behavior as verified in transient network analyzer studies carried out with a replica of the SVC control system. The SVC control system is described, with emphasis on some special blocking schemes needed to meet particular requirements of the power system transient performance. The complete system and SVC data are also included     

Discussion of “Using a static VAr compensator to balance adistribution system”

In the paper by J.-H. Chen et al. on `Using a static VAr compensator to balance a distribution system' (see ibid. vol.35, p.298-304, 1999), the authors have made a positive contribution to balancing an unbalanced system. However, the author makes several comments and shares his experience with compensators consisting of a thyristor switched inductor (TSI). The author discusses the harmonics and resonance of a TSI     

An optimal location of static VAr compensator based on Gramian critical energy for damping oscillations in power systems

The increase in the scale and complexity of interconnected power systems leads to multiple electromechanical oscillations. Therefore, the electric network needs to be made more stable. One type of Flexible alternating current transmission systems (FACTS) devices, namely the static VAr compensator (SVC), can be installed at buses to increase the stability margins and dampen the power system oscillations by exchanging capacitive and/or inductive load to maintain and/or control specific parameters of electrical power systems. The efficiency and performance of the SVC depend on its optimal location. Consequently, seeking the optimal placement for SVC has become a key issue. In this paper, we propose a novel method to find the optimal location for the SVC based on a two‐step approach. First, an energetic approach based on the combination of the controllability Gramian critical energy analysis with the balanced realization reduction technique is used to search for several feasible locations; then the transient stability is analyzed to compare and determine an optimal location through various test cases. The effectiveness of the proposed method has been demonstrated on the IEEE 39‐bus England power system and compared with the modal controllability index. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Converter configurations and switching frequency for a GTO reactivepower compensator

This paper compares two converter configurations for a multi-10 MVA gate-turn-off (GTO) reactive power compensator (STATCOM) from the viewpoints of converter connection and switching frequency. One is a single-bridge system consisting of a three-phase bridge converter unit and a transformer. Its pulsewidth modulation (PWM) frequency varies from 450 to 1800 Hz, and its line frequency is 50 Hz. The other is a multiconnected converter system consisting of plural, single-, or three-phase converter units and transformers. Its switching frequencies are chosen to be the lowest possible. The evaluated items are harmonic distortion, power loss, GTO utilization factor, and control response. Our simulation study shows that the multiconnected converter system with the lowest switching frequency is superior to the single-bridge system with the higher switching frequency in every case, even when there are severe line faults requiring very quick response. A new control strategy is adopted for obtaining quick response     

谐振引起的牵引变电所无功动补投切故障分析

某牵引变电所TCR型动态无功补偿装置在进行设备投运时,发生2次谐波放大现象,导致牵引变电所继电保护装置频繁跳闸.结合SVC投切试验现象,对投切故障进行了分析.在工频频率下,SVC滤波支路的容抗远大于系统感抗.不会产生并联谐振.但对谐波频率而言,系统感抗大幅增加而滤波支路容抗大幅减小.当电力系统短路容量过小时,系统阻抗和...     

最优最小开关损耗SVPWM地板水暖变频调速系统

为了提高地板水暖系统的整体性能,除了考虑管道系统的设计和水泵本身机械特性,还要考虑水泵电机变频调速系统的效率.针对提高电机变频调速系统效率的问题,在分析电压源逆变器多解性的基础上,分析几种最小开关损耗电压空间矢量脉冲宽度调制策略,提出一种最优化的解决方案,并应用于永磁同步电机-变频调速地板水暖系统,给出相应的开关损耗计...     

Four-wire three-phase load balancing with Static VAr Compensators

Static VAr Compensators (SVCs) can balance the phase currents of three-wire three-phase loads and compensate their reactive power. Thus, the SVC-load set becomes a balanced load with any desired power factor. This paper proposes a method to use SVCs with four-wire three-phase loads which still perform those functions: load balancing and reactive power compensation. As a result, any load connected to a three-(or-four-)wire three-phase system can be transformed into a balanced load with unity power factor, even if it is a single-phase load. Other properties that appear in particular cases are also analyzed.     

Analysis of a dynamic voltage compensator with reduced switch-count and absence of energy storage system

The utilization of dynamic voltage restorers to protect sensitive loads against short-term voltage disturbances has been proven to be a competitive solution in medium- and high-power applications. For low-power applications further cost reductions are required to make the technology even more competitive, although just a few numbers of studies have already been conducted in this area. This paper discusses the design and operation of a three-phase dynamic voltage compensator, including control strategies for the converters. The proposed topology and control strategies are evaluated through simulation studies based on measured data, selected by the IEEE Power Quality Task Force for the characterization of power quality events and device performance evaluation, along with disturbances recorded in a steel plant, in Minas Gerais State, Brazil. An experimental implementation of the compensator is developed to allow a better evaluation of specific and critical operating modes, such as the forced commutation of the bypass thyristors and inverter operation.     

AI approach to optimal VAr control with fuzzy reactive loads

This paper presents an artificial intelligence (AI) approach to the optimal reactive power (VAr) control problem. The method incorporates the reactive load uncertainty in optimizing the overall system performance. The artificial neural network (ANN) enhanced by fuzzy sets is used to determine the memberships of control variables corresponding to the given load values. A power flow solution determines the corresponding state of the system. Since the resulting system state may not be feasible in real-time, a heuristic method based on the application of sensitivities in an expert system is employed to refine the solution with minimum adjustments of control variables. Test cases and numerical results demonstrate the applicability of the proposed approach. Simplicity, processing speed and ability to model load uncertainties make this approach a viable option for online VAr control     

Indirect matrix converter drives for unity displacement factor and minimum switching losses

With sinusoidal input currents and no dc-link capacitor, a matrix converter offers remarkable advantages over other alternatives in applications requiring improved utility interaction and critical weight/volume reduction. Lately, indirect matrix converter topologies have also been investigated, leading to possibility of reduced switch number and multi-drive applications. However, due to off-line input current regulation of the converters, the input displacement factor varies with LC input filters and load conditions. This fact results in non-unity displacement factor and increased reactive power flow. In this paper, a novel on-line input current control strategy is proposed based on a closed-loop control in the synchronous reference frame. The approach allows independent control of two input current components (active and reactive), yielding zero reactive components. In addition, this paper specifies a relationship of input current phase angle and switching losses in semiconductors. Based on the specification, it is proved that the indirect matrix converter has minimum switching losses with the input currents in phase with the input voltages. Thus, the proposed control algorithm yields minimum switching losses and no reactive power flow. The feasibility of the proposed technique has been verified in the paper.     

基于成本最优的含储热光热电站与火电机组联合出力日前调度

含储热光热发电的优势体现为良好的出力可控性和可调度性,合理调度光热发电能够有效降低系统运行成本。以成本最优为目标,从光热电站的光电转换特性分析角度出发,在计及各项运行约束的基础上,提出含储热光热电站与火电机组联合出力调度策略。该策略综合考虑火电机组发电成本、光热发电并网消纳的环境效益和运行维护成本、系统旋转备用成本以及电网安全运行约束等因素,从而确定光热电站在既定储热容量下的最优出力调度策略。基于遗传算法,通过IEEE 30节点算例验证了所提方法的可行性与有效性。     

A multilevel voltage-source inverter with separate DC sources forstatic VAr generation

A new multilevel voltage-source inverter with separate DC sources is proposed for high-voltage, high-power applications, such as flexible AC transmission systems (FACTS) including static VAr generation (SVG), power-line conditioning, series compensation, phase shifting, voltage balancing, fuel cell, and photovoltaic utility systems interfacing, etc. The new M-level inverter consists of (M-1)/2 single-phase full bridges in which each bridge has its own separate DC source. This inverter can generate almost sinusoidal waveform voltage with only one time switching per cycle as the number of levels increases. It can solve the size-and-weight problems of conventional transformer-based multipulse inverters and the component-counts problems of multilevel diode-clamp and flying-capacitor inverters. To demonstrate the superiority of the new inverter, an SVG system using the new inverter topology is discussed through analysis, simulation, and experiment     

采用逆变高压电源的50MW脉冲调制器保护电路

介绍了合肥同步辐射光源50 Mw大功率速调管脉冲调制器的恒流逆变充电电源。分析了充电电源和脉冲形成网络连接时反向电压对电源高压输出电路的不利影响,使用数值模拟程序模拟计算了PFN电路中的反向电压,设计了充电电源保护电路并给出了实际运行中的工作波形。     

Thyristor voltage pulse shapers for controlling high-voltage switching electronic elements

The efficiency of using switching high-voltage electron-beam valves (EBVs) in power-supply systems of electrophysical and other high-power units is shown. The novelty of the scientific and engineering solutions applied to design EBVs with high electric parameters is emphasized. The rationale for using single-operation SCR thyristors for EBV control is provided. The principles of constructing thyristor voltage pulse shapers are analyzed and generalized.     

一种新型谐振软开关多路稳压电源拓扑研究

研究设计了一种新型基于谐振软开关的多路稳压输出电源拓扑.该拓扑主电路采用半桥结构.谐振电容在变压器高压侧,谐振电感在低压侧.在不增加任何辅助开关和辅助元件的情况下,主电路开关和输出各路调节开关都工作在完全谐振状态,自然实现零电流软开关.各路输出采用单独电压闭环调节,可以实现各路独立稳压输出并且具有较高的输出精度.由于各路输m的谐振电感相互耦合,所以各路的动态调节过程不会影响主电路谐振状态和其它各路的谐振状态.通过一台6路输出总功率400 W开关电源验证了理论分析的正确性和该方案的可行性.经测试,各路输出误差均在0.5%以内,效率可达93%以上.     

An improved topology of electronic ballast with wide dimming range,PFC and low switching losses using PWM-controlled soft-switching inverter

This paper presents a novel improved topology of voltage-fed soft-switching LC_rC_dc series–parallel quasi-resonant inverter with a constant-frequency for electronic ballast applications. This new topology introduces a low-cost solution to reduce switching losses to achieve high-efficiency ballast. A symmetrical pulse wide modulation (PWM) control scheme is implemented to regulate a wide range of output power. Switching losses effect on ballast efficiency is discussed through experimental point of view. In this discussion, an improved topology in which accomplishes soft-switching operation over a wide power regulation range is proposed. Energy consumption of this new circuit is decreased by using reverse recovery attribute. Additionally, a power-factor correction (PFC) circuit is employed to make the line current follow naturally the sinusoidal line voltage waveform.     

A static compensator model for use with electromagnetic transientssimulation programs

A static VAr compensator (SVC) model based on state variable techniques is presented. This model is capable of being interfaced to a parent (or host) electromagnetic transients program, and, in particular a stable method of interfacing to the EMTDC program is described. The model is primarily that of a thyristor-controlled reactor. (TCR) and a thyristor-switched capacitor (TSC). Capacitor switchings within the TSC have been handled in a novel way to simplify storage and computation time requirements. During thyristor switching, the child SVC model is capable of using a smaller timestep than the one used by the parent electromagnetic transients program; after the switching, the SVC model is capable of reverting back to a (larger) timestep compatible with the one used by the parent program. Other features considered include the modeling of a phase-locked-loop-based, valve firing system. An application of this model to the simulation of a SVC controlling the AC voltage of the inverter bus of a back-to-back HVDC (high-voltage direct current) tie is presented