Power Control Devices Research Articles

A Novel Mixture Solid-State Switch Based on IGCT With High Capacity and IGBT With High Turn-off Ability for Hybrid DC Breakers

Hybrid dc circuit breakers (HCBs) usually require a large number of insulated-gate bipolar transistors (IGBTs) with high turn- off capability for series and parallel connections. This requirement entails excessive cost. Compared with IGBTs, integrated gate-commutated thyristors (IGCTs) are another kind of fully controlled power device with high surge current and voltage capability but are low cost. However, the weak turn- off capability of IGCTs hinders their application to high-powered HCBs. On the basis of the complementary advantages of IGBTs and IGCTs, this paper proposes a mixture solid-state switch (MSS) for HCBs that uses the switching action of several IGBTs to create a low-current condition that favors the turning off of large-scale series-connected IGCTs. The MSS topology can significantly reduce cost while maintaining the excellent performance of traditional solid-state switches. This study also introduces two different turn- off modes for MSS, namely, single oscillation and multiple oscillations. Finally, 25 kV/20 kA prototypes in both modes are developed to verify the effectiveness of the MSS topology.

Status evaluation of smart substation measurement and control device

In power system, measurement and control device plays an important role in maintaining an ideal level of reliability. Therefore, the reliability of the measurement and control device should be evaluated to fully understand the cause of its failure. A new evaluation model is proposed, which relates the fault of measurement and control system with the four main reasons of device hardware fault, software fault, auxiliary equipment fault and human fault. In addition, the model can also comprehensively consider other aspects of the measurement and control system, such as human error in testing and software upgrade, effectiveness of daily operation monitoring, degree of dependence on self-inspection, local backup and misoperation. These studies have a lot of significance to the reliability of the control system, and also can effectively improve the stability of the system.

Принципы построения трансформаторных датчиков для измерения постоянных, переменных и импульсных токов

Power electronics includes a number of key elements without which it is impossible to construct static electric energy converters. A current sensor is one of such elements. An ideal current sensor must have a number of features: it must provide galvanic isolation; it must have good linearity, and it must be able to operate in a wide range of temperatures. It must be able to measure direct, alternating, and impulse current with arbitrary shape, and have the maximally wide pass band. The most widely used technologies do not make it possible to construct a device that would satisfy all these requirements. In this connection, it is necessary to find alternative ways of solving this problem. The lack of domestically produced current sensors with galvanic isolation that are permitted for use in special-purpose devices and able to measure direct and alternating current with arbitrary shape is a state-scale problem. In addition, the task of ensuring the replacement of imported components for electric power control, conversion, and distribution devices has been set forth. The article proposes two versions of transformer current sensors, presents the functional diagrams, computer models, and simulation results confirming the correctness of the theoretical device operation principles.

Voltage quality in delta Egypt network and its impact in oil industry

The electrical energy is transmitted from the generating stations to the consumers through a transmission network. The effectiveness of improving voltage profile yields high transmission network efficiency and increase the capacity of transmission lines, also decrease power losses, voltage drop and unplanned shut down in the big industrial and strategic loads like (oil refining industry). This paper objective presents the suggested solutions for improving voltage profile in electrical network of delta Egypt to achieve a voltage quality. The methodology of suggested solutions are applied on delta Egypt network with voltage levels (66, 11, 6.6, 0.4) kV, the simulations were performed using digital simulation and electrical network calculation (DIgSILENT power factory software) to study the voltage profile. The validation of results was performed by comparing the voltage profile of proposed four different scenarios: 1st: power flow in normal operation (without using any voltage improving devices), 2nd: using Automatic Tap Changer (ATC) of transformers, 3rd: installing a Static Volt Ampere Reactive (VAR) System(SVS) with (ATC), 4th: installing a (SVS), (ATC) and shunt reactive power compensation devices (parallel capacitor / inductor). The best voltage profile achieved by using scenario 4, which supported and improved the voltage profile of all system and brings the magnitudes of all buses in permissible voltage level from (0.79-0.99 P.U.) at normal operation (scenario 1) to (0.9-1.04 P.U.) at (scenario 4). So the system can be operated with more efficiently, stability and improving the capacity of the network after applying the solution stated in scenario 4. • This paper studied the voltage profile in delta Egypt network. • A relation between voltage quality and catastrophic events in oil refining industry. • High quality grid must have voltage stability with in accepted levels at each bus. • Network construction was performed by (DIgSILENT power factory software). • The voltage profile was performed by proposed four different scenarios. Scenario 1: power flow (PF) study in normal operation (base case). Scenario 2: (PF) study using automatic tap changer (ATC). Scenario 3: (PF) study using (ATC)& static Var system (SVS). Scenario 4: (PF) study using (ATC), (SVS) and shunt reactive power control devices. • A comparison between all scenarios results have done to get the optimum solution. • The best voltage profile had achieved by using scenario 4.

A new hybrid DC circuit breaker topology

Being advantageous for long-distance power transmission and new energy connection, DC system has wide range of applications in many scenarios. As the capacity of DC power grids increases, the fault current is more difficult to interrupt. And the DC circuit breaker which is very important for protecting DC grid attracts more and more attention of researchers. In this paper, a new hybrid DC circuit breaker topology based on the technique of thyristor forced current zero is proposed. The breaker is able to interrupt the fault current in several milliseconds, and the mechanical switch can be cut off at zero current. In addition, no extra power supply and control devices are needed, the pre-charging capacitor can obtain energy from DC grid directly. Therefore, the control process is simpler and the reliability is greatly improved. The operating principle of the proposed circuit breaker is analyzed in detail, and then the simulation is carried out in PSCAD/EMTDC which verifies the correctness of the theoretical analysis and the feasibility of the breaker.

Three‐phase qZ‐source inverter with fault tolerant capability

The requirement of three-phase inverters with high reliability capability is considered important in several applications. Most of the adopted fault-tolerant solutions use classical three-phase voltage source inverters (VSI) with redundant controlled power devices or modified control strategies for acceptably degraded performance in the event of a failure yielding the loss of devices. This work proposes the use of a fault-tolerant converter based on the quasi-Z-source inverter (qZSI). This inverter presents important features such as boost capability and not requires dead time circuits. These features associated to the proposed topology results in a converter with high reliability and fault-tolerant capability. The proposed topology is designed to allow the reconfiguration of the converter after a power switch failure, using only two legs in the faulty mode. Additionally, this topology avoids extra inductors, capacitors and active power switches for the fault-tolerant condition. A current controller associated to a vectorial voltage modulator is used to control the proposed topology, which results in three-phase balanced AC currents with reduced total harmonic distortion even in faulty condition. The performance of this solution is confirmed through experimental results obtained from a laboratory prototype.

The Power Characteristic Results According to the Superconducting Magnet Coil Load Tests of the Motor Generator System

When the poloidal field (PF) magnet power supplies (MPSs) of 11 units are operated, maximum power of 200 MVA is required to achieve long pulse operation of Korea superconducting tokamak advanced research (KSTAR). Motor generator (MG) system was installed to resolve the power shortage because the available grid power is only 100 MVA at the National Fusion Research Institute site. MG system is composed of mechanical devices (stator, rotor, bearings, etc.), power control devices (variable voltage variable frequency and exciter), power facilities (transformers, switchboard, uninterruptible power system, filter, dynamic brake, etc.), utilities (cooling water pump, heat exchangers, cooling fans, oil circulation pump, mechanical brake, etc.), and control systems. MG system supplies power to the PF MPS of 11 units. And we configure the reactive power compensator (RPC) and harmonic filter (HF) system to stabilize the MG power system. After installing the MG system, individual tests and dummy coil tests were conducted to determine the safety and performance of MG system. And we completed the commissioning of the MG system by carrying out the superconducting magnet coil load tests for the 2014 KSTAR experiment. MG system was operated up to 150 MVA of PF MPS with the RPC and HF system. And the maximum operating duration was about 100 s. In this paper, we discuss about the power characteristic results of the MG system according to the superconducting magnet coil load tests.

전압계측기반 CVR제어 알고리즘 개발 및 검증을 위한 RTDS-MATLAB 연동 시뮬레이션 환경 개발

CVR은 계통의 전압을 감소시켜 소비 전력을 줄이는 기술로, 과거 많은 실증과 연구가 진행되어 왔다. 최근, SCADA 기반 또는 AMI 기반의 VVC가 개발되면서 CVR이 중요한 운영 방식이 되었다. CVR은 다양한 계측기를 사용하여 폐루프 제어(closed loop control)방식으로 최적 VVC제어 지령치를 결정한다. 본 논문에서는 전압 계측기반 CVR제어 알고리즘 개발 및 검증을 위한 RTDS-MATLAB 연동 환경을 구현하였다. RTDS를 이용하여 배전 계통의 전압제어기기들을 모델링하고 MATLAB으로 RTDS의 모의 계통의 전압을 계측하고 제어할 수 있는 제어기를 구성하였다. 무효전력 제어기기인 캐패시터는 계통의 전압을 평탄화하고 계통의 전압 기반으로 OLTC의 탭 제어를 하여 계통의 전압을 낮추는 제어 알고리즘을 MATLAB을 통해 구현하였다. 시뮬레이션을 통해 제안한 시스템을 검증하였다. CVR is a technique for reducing power consumption by reducing the voltage of the system and many demonstrations and studies have been conducted in the past. Recently, SCADA-based or AMI-based VVC have been developed and the CVR is used as an important operation mode. Using a variety of instruments, CVR determines the optimal VVC control references by closed loop control. In this paper, we implemented RTDS-MATLAB integrated simulation environment for development and verification of CVR control algorithm based on voltage measurement. The voltage control device of distribution system was modeled using RTDS and MATLAB has constructed a controller that can measure and control the voltage of the simulation system of RTDS. After the capacitor, which is a reactive power control device, flattens the voltage of the system, the control algorithm reduces the voltage of the system by tap control of the OLTC based on the flatten voltage. The proposed system was verified by simulations.

Reactive power coordinated optimisation method with renewable distributed generation based on improved harmony search

The reactive power coordinated optimisation problem for distribution network (DN) with the integration of renewable distributed generation (DG) is investigated in this study. By actively participating in reactive power control together with an under-load tap changer and shunt capacitors, DG can operate more effectively in the DN. Non-dispatchable DG is considered in the coordinated optimisation method. The objective of the proposed reactive power coordinated optimisation method is to minimise active power loss and to decrease the number of switching device operations while maintaining the grid voltage within the allowable range. The optimisation problem is to solve a variable combination including integers and continuous variables, which will formulate a mixed integer non-linear programming (MINLP) problem. The control variable includes operations of traditional reactive power control devices and the reactive power adjustments of DGs. To solve the MINLP problem, a heuristic searching method, an improved harmony search algorithm is proposed with adaptive parameters process. Numerical tests on a standard 10-kV distribution system and a real distribution system demonstrate the applicability of the proposed reactive power coordinated optimisation method.

Assessment of actual power and electric power at construction sites

The article deals with issues connected with power supply of buildings and structures under construction. Due to nonlinear nature of electric power consumption at building industry enterprises, current and feeding voltage are distorted. This causes additional losses of actual power and energy, as well as inaccuracy and ambiguity in readings of power control devices and electric power metering. The article generalizes results of research on harmonic composition of electric power parameters of static converters and states recommendations on improvement of assessment and accounting of actual power and electric energy in electrical networks of building organizations.

Hierarchical Two-Level Voltage Controller for Large Power Systems

This paper proposes a two-level voltage controller for large-scale power systems. The aim of the controller is to maintain a near-optimal voltage profile in the transmission network by coordinating discrete reactive power (var) control devices in the system. The controller is targeted for implementation in electric power transmission utility companies where most of the voltage controls are coordinated by switching of discrete var devices such as shunt capacitor and reactor banks and transformer banks load tap changers (LTCs). By effectively dividing the controller responsibilities between local substation controls and a central coordinator at control center level, the design is aimed at voltage control of large-scale power systems. At local level, the substation controllers maintain their respective substation bus voltages by local power-flow-like computations using mostly local PMU measurements. The central coordinator computes and provides the voltage set-points to the substation controllers and also coordinates by enabling or disabling the local controllers as needed. The controller is being designed towards prototype implementation in Southern California Edison (SCE), starting with local controllers at specific substations in the first stage. It is tested on real-time dynamic models and large-scale power-flow simulations of SCE transmission network.

PLC(Programmable Logic Controller)와 공중통신망을 이용한 하천수위감시시스템 구축 사례 연구

A river water level monitoring system which prevents salt water damages and effectively excludes floods has been developed to contribute efficient operation of Nakdong river estuary barrage. The system can be used for monitoring upstream conditions more quickly and do appropriate responses over changes. Telemetry and telecontrols using PLCs have been built at the three sites that directly influence on the operation of barrage gates, and are linked to Nakdong river estuary barrage’s IOS (Integrated Operation System) through public communication networks. By using PLC, the system can achieve even higher reliability and versatility than before as well as easy management. By power control devices, we can remotely control the power of PLCs to treat the minor troubles instantly without going on-sites. The power control devices also save data in preparation for the cases of communication failures. The system uses ADSL (FTTH) as a main network between SCADA server and PLCs, and CDMA (M2M) as a secondary network. In order to compensate security vulnerabilities of public communication network, we have installed the VPNs for secure communication between center and the observation stations, just like a dedicated network. Generally, river water level observations have been used custom-manufactured remote terminals to suit their special goals. However, in this case, we have established a system with open architecture considering the interface between different systems, the ease of use and maintenance, security, price, etc.

A Fuzzy-Multiagent Self-Healing Scheme for a Distribution System With Distributed Generations

In this paper, a new multi-agent control system (MACS) is proposed for smart distribution networks. It can: 1) eliminate the feeders' congestion, 2) globally correct voltage violations, and 3) coordinate the operation of reactive power control devices. In performing its functions, the MACS must prevent overstress on the substation voltage regulator tap changer under all operating conditions, and avoid selective active power curtailment from DG units. This can help to improve reliability, economic revenue, and power quality. A fuzzy rule-based system is employed for decision-making support in MACS. The proposed MACS can achieve the self-healing requirement of smart distribution network. It eliminates feeders' congestion by properly reconfiguring the distribution network. Meanwhile, it amends most of voltage violation problems by coordinated operation of voltage control devices in the distribution system. The MACS overcomes the severe voltage violation problems via distribution network reconfiguration. It is applied to the IEEE 33-bus test feeder. A full dynamic model is constructed using a parallel MATLAB-JADE simulation arrangement. Comparative performance evaluations of the MACS and other schemes are presented under various conditions.

Distributed Multiple Agent System Based Online Optimal Reactive Power Control for Smart Grids

Under high penetration of renewable energy resources, more and more reactive power control devices are integrated into power grids. The large-scale deployment of these devices requires upgrading existing reactive power control solutions. To improve energy efficiency and voltage profiles of the power grids under different operating conditions, this paper proposes a fully distributed multiple agent system based optimal reactive control solution. To update its control setting, a reactive controller only needs information measured locally or obtained from its neighboring buses. The updating rules of the subgradient based algorithm are derived under mild assumptions. The solution is able to provide comparable steady state performance as that of centralized optimization solutions. Due to the simplicity of communication topology and the reduced amount of data to process, the solution can provide timely response to changes of operating conditions. Simulation studies with power systems of different sizes demonstrate the effectiveness of proposed control solution.

실리콘 에피-웨이퍼 기반의 펄스감마선 검출센서 최적화 연구

본 연구에서는 전자장비 내방사화 기술의 새로운 효율적 접근방법인 전원제어형 방호장치에서 핵심 기능을 수행하는 고속 반도체 센서를 개발하고 그 특성을 분석하였다. 먼저, 펄스방사선에 의한 다이오드 내부에서의 생성 전하를 계산한 후 TCAD로 모델링하여 <TEX>$42{\mu}m$</TEX> 진성층의 실리콘 에피텍시 웨이퍼 기반의 고속 신호탐지용 PIN 다이오드 센서를 다양한 구조로 설계하였다. PAL의 Test LINAC의 전자빔 변환 감마방사선 4.88E8 rad(Si)/sec에 대한 실측시험에서 소자의 면적에 비례하는 광감도와 응답속도 증가 결과를 얻었으며 포화특성과 소자의 균일성을 기준으로 2mm직경의 센서를 최적으로 판단되었다. 선정 센서를 대상으로 한 펄스감마선 고출력 범위(2.47E8 rad(Si)/sec~6.21E8 rad(Si)/sec)로 선량률 가변시험에서는 개발한 소자가 시험장치의 고 선량률 영역에서 전원제어 신호처리에 충분한 60mA 이상의 광전류 피크값과 함께 350 ns 이하의 고속 응답특성을 가지는 선형적 센서임을 확인하였다. In this paper, we designed and fabricated a high-speed semiconductor sensor for use in power control devices and analyzed the characteristics with pulsed radiation tests. At first, radiation sensitive circular Si PIN diodes with various diameters(0.1 mm ~5.0 mm) were designed and fabricated using Si epitaxial wafer, which has a <TEX>$42{\mu}m$</TEX> thick intrinsic layer. The reverse leakage current of the diode with a radius of 2 mm at a reverse bias of 30 V was about 20.4 nA. To investigate the characteristic responses of the developed diodes, the pulsed gamma-radiation tests were performed with the intensity of 4.88E8 rad(Si)/sec. From the test results showing that the output currents and the rising speeds have a linear relationship with the area of the sensors, we decided that the optimal condition took place at a 2 mm diameter. Next, for the selected 2 mm diodes, dose rate tests with a range of 2.47E8 rad(Si)/sec to 6.21E8 rad(Si)/sec were performed. From the results, which showed linear characteristics with the radiation intensity, a large amount of photocurrent over 60mA, and a high speed response under 350ns without saturation, we can conclude that the our developed PIN diode can be a good candidate for the sensor of power control devices.

Advanced control and communication scheme for aerospace applications

This article presents multiple channel estimation (MCE) that is a multi-sensor access wireless system model. An avionics wireless system needs a power control device to match the power received from the multiple sensors. Without a power control device, the aircraft control unit is unable to receive the signals from sensors due to signal reflections, refraction and transmission loss. The MCE system is designed to suppress multi-sensor signal noise and interference while a sensor, with lower power than the other sensors, is received. This article investigates overcome the power difference based on the MCE system. The performance of proposed MCE model is investigated and validated for a safe indoor avionics wireless system and it improves the overall performance of the wireless system to perfect power stability.

발전소용 유압 서보액추에이터의 쿠션 모델링 및 시뮬레이션

Turbine power control devices at a nuclear / thermoelectric power plant lead to failure by creating mechanical shocks and strong vibrations that are due to the strong elasticity of a spring and the inertia of the valve face during its rapid movement to block steam. To ensure durability of the turbine power control device, which is the main component in the power plant, it is necessary to develop a device that can prevent such vibrations. In this study, a cushion mechanism is added to the head of the hydraulic servo actuator, which is a turbine power control device. Moreover, the cushion mechanism, which includes various modifies shapes and orifices is investigated dynamically through modeling and simulations.

Modeling and Analysis of Voltage and Power Control Devices in Current Injections Load Flow Method

This article presents a developed method to improve the representation of a voltage-controlled bus in the current injection load flow method. This improvement is based on a hybrid current and power mismatches formulation, where the load bus equations are represented by current mismatches and voltage-controlled buses bus equations are based on power mismatches. In this method, the advantages of the Newton–Raphson method and current injection mismatches method are collected. The total number of equations is reduced, where only one equation is required for each voltage-controlled bus. This article also describes direct modeling of voltage/power control devices in the developed load flow method. The static synchronous compensator can be represented as a voltage-controlled bus node in terms of power mismatch. The static series synchronous compensator and unified power flow controller are modeled by series impedance and two current injections at the corresponding nodes. In the case of unified power flow controller, additional power injection is included at the sending-end node to represent the voltage-controlled node. This modeling reduces the complexities of the computer program codes and enhances the reusability by avoiding the modifications in the Jacobian matrix. The IEEE data as well as systems from literature are used to validate the developed method and flexible AC transmission systems models.

An IPM-CFAPSO based Hybrid Method for Multiple Objective Minimizations using TCPS

paper presents an Interior Pont Method (IPM) and vari- ant of Particle Swarm Optimization (CFAPSO) based hybrid method to solve optimal power flow in power system incorpo- rating Flexible AC Transmission Systems (FACTS) such as Thyristor Controlled Phase Shifter (TCPS) for minimization of multiple objectives. The proposed IPM-CFAPSO algorithm identifies the optimal values of generator active-power output and the adjustment of reactive power control devices. The proposed optimization process with IPM-CFAPSO is present- ed with case study example using IEEE 30-bus test system to demonstrate its applicability. The results are presented to show the feasibility and potential of this new approach.

Coordinated Reactive Power-Voltage Controller for Multimachine Power Plant

This paper presents a newly developed voltage and reactive power control device, the coordinated Q -V controller (CQVC), for a multimachine steam power plant (SPP). The requirements for the new controller are defined based on identified inadequacies of manual Q-V control. The controller uses a feed-forward correction signal based on the application of the sensitivity matrix at a power plant level. It is designed and its performance initially assessed using the Matlab/Simulink environment. The performed simulations show that all the primary design objectives are met. The Q-V controller maintains the voltage at the SPP busbar with a certain droop characteristic during slow voltage changes in the power system whilst also maintaining equal per unit reactive power sharing among the SPP generators. This ensures that the power system fully benefits from all generating units during system perturbations. The performance of the designed CQVC is validated by comparing simulation results with measured responses obtained from a real CQVC installed at a SPP.