Voltage Sag Compensation Research Articles

Performance Analysis of Dynamic Voltage Restorer for Voltage Sag and Swell Compensation in Distribution System

Performance Analysis of Dynamic Voltage Restorer for Voltage Sag and Swell Compensation in Distribution System

Compensating Voltage Sag in Distribution Systems Using Single Phase Quasi-Z-Source AC/AC Converter

The utilization of a single-phase Quasi-Z-source AC/AC converter for voltage sag mitigation is introduced in this paper. The suggested topology can compensate voltage sag up to 50%, which is an advantage in comparison with traditional structure, as most voltage sags are not more than 50%. The suggested topology has superior characteristics compared to the conventional topologies and has the following specifications: using the same ground for sharing output and input voltages; functioning in the continuous current mode; employing direct AC/AC converter; applying safe-commutation scheme; the ability to expand of the output voltage range increasing reliability and reducing the harmonics in the output voltage. Because of using safe commutation strategy, as shown in results, no ripple and spike exist in the output voltage. The hardware prototype of the offered structure has magnificently been developed to obtain the experimental results. The experimental results were obtained based on the resistive and inductive loads for a few different sags in the input voltage. The results presented showed good performance despite the simplicity in the control scheme. Moreover, they confirm the good performance of the proposed topology.

A Novel Dual-DC-Port Dynamic Voltage Restorer With Reduced-Rating Integrated DC–DC Converter for Wide-Range Voltage Sag Compensation

A novel dual-dc-port dynamic voltage restorer (DDP-DVR) is proposed. One low-voltage dc port is directly connected to the energy storage, while the other high-voltage dc port is connected to the intermediate dc bus. An integrated dc-dc converter is interfaced with these two dc ports which is aimed at providing a high-dc-link voltage and maintaining the voltage injection capability even if the energy-storage voltage is lower than the peak value of the injected ac-line voltage. Compared with the traditional DVR that uses the dc-dc converter for all voltage sag compensation, the proposed DDP-DVR can compensate shallow voltage sags without using the dc-dc converter, and for deep voltage sags, only partial active power needs to be processed by the dc-dc converter. Therefore, the power rating of the dc-dc converter can be reduced significantly. Meanwhile, much lower power losses can be achieved by the proposed DDP-DVR due to reduced power conversion stages. The operation principles, modulation strategies, and characteristics of the proposed DDP-DVR are analyzed in detail and verified with experimental results.

Experimental Investigation of a High Temperature Superconducting Pancake Consisted of the REBCO Composite Cable for Superconducting Magnetic Energy Storage System

High temperature superconducting magnetic energy storage system (HT SMES) can be utilized to compensate voltage sag caused by grid-connected renewable energy power generation and can address power fluctuation while the fault occurs in electric power system, which effectively improves stability of power grid and quality of power supply. With the recent increased capacity requirements of SMES, improving the ampacity becomes a core for its application in renewable power grids. Therefore, a novel 100 m high temperature superconducting twisted stacked-tape in tube (TSTT) composite cable with inner spiral cooling channel is proposed and is manufactured for constructing a 3 MJ toroidal SMES in China Electric Power Research Institute. A prototype pancake using this 100 m TSTT cable is constructed. An experimental set up and critical properties measurement systems are built including a 3000 A dc current power supply, a closed-loop cooling system with LN2 and a high-precision data acquisition system of national instruments based on LABVIEW. The characteristics of critical current for the pancake under an operating temperature of 77 K are investigated in this paper. The experimental results have validated the feasibility of this TSTT composite cable for the MJ-class energy storage magnet. It provides a valuable reference to the large-scale HT SMES applied in the power grids based on a high temperature superconducting composite cable technology.

Validation of Control Platform Using TMS320F28027F for Dynamic Voltage Restorer to Improve Power Quality

A real-time control platform progressed for the power quality (PQ) change in a conveyance framework has been displayed in this paper. A DSP-based control platform is demonstrated for voltage sag compensation for dynamic voltage restorer in conjunction with a voltage source inverter (VSI) to enhance PQ. The output of VSI is controlled by activating IGBTs by SPWM control technique. A driver circuit is developed along with a filter circuit to compensate load voltage when sag occurs in a distribution system supplying a sensitive load of single-phase induction motor. The developed control platform has been asserted with a DSP processor TMS320F28027F, and its effectiveness has been shown by carrying a few experiments.

Adaptive soft starter for a three‐phase induction‐motor driving device using a multifunctional series compensator

This study proposes an adaptive soft starter control for induction motors using a multifunctional series compensator (MFSC). The proposed MFSC can operate in two modes: (i) the compensation mode for voltage sags and (ii) the virtual impedance mode for soft starting. Various MFSC functions are obtained by controlling the output characteristics of the series inverter. In the voltage sag compensation mode, a voltage is injected in series with the fault phase; as a result, the terminal voltage of the motor remains constant. In the soft-starter mode, the proposed converter injects adjustable virtual impedance in each phase; as a result, the starting current can be limited to the desired value. A novel control scheme and the optimal parameter selection of the MFSC are also presented. The design methodology of the proposed MFSC is verified using simulations conducted in MATLAB/Simulink software. Experimental results prove the capability and effectiveness of the proposed MFSC.

Compensation of Voltage Sag and Swell Using Smes Based Dynamic Voltage Restorer

Compensation of Voltage Sag and Swell Using Smes Based Dynamic Voltage Restorer

Development of a 10-kV regional compensation dynamic voltage restorer with multiple functions

ABSTRACTThe first 10-kV regional compensation dynamic voltage restorer (DVR) has been installed in a 110-kV substation in Shenzhen power grid, to protect plenty of sensitive loads in a wide area simultaneously from the disturbances caused by voltage sags. The location selection and performance indicators of the DVR are determined based on the voltage sag statistic results in recent years of Shenzhen power grid. The implementation schemes of main circuit elements, such as the energy storage unit, inverter and LC filter are presented. To further improve the DVR’s cost-effectiveness, a novel virtual impedance control strategy is proposed to provide the DVR with a function of a Fault Current Limiter (FCL) or a Series Compensator (SC) besides the function of voltage sag compensation. Simulation and field experimental results are provided to show the correctness and effectiveness of the main circuit design and control system development of the 10-kV DVR.

Enhancing Transient Voltage Quality in a Distribution Power System With SMES-Based DVR and SFCL

Conceptual design and performance evaluation of a voltage sag compensation scheme based on the superconducting fault current limiter (SFCL) and a MW-class dynamic voltage restorer (DVR) system integrated with superconducting magnetic energy storage (SMES) are presented and investigated. A pre-sag compensation strategy is introduced to lock the instantaneous magnitudes and phase angles of real-time line voltages for compensating the improper voltage components completely. A 0.3-H/1.76-kA SMES magnet is structurally designed for MW-class power exchange operations, and the SFCL's resistance is also estimated in detail. Various simulation cases with regard to voltage sag are carried out. The simulations have demonstrated that the proposed voltage sag compensation scheme is able to maintain the stabilizations of root-mean-square voltages, and mitigate the adverse effects of voltage sag on sensitive load. Furthermore, the compensated power injected to sensitive load by DVR is decreased owing to the additional voltage improvement provided by SFCL, thereby reducing the total capital costs of DVR.

DVR with Modified Y Source Inverter and MCFC

Power quality is a big challenge nowadays. Various disturbances present in the power system are voltage sag, voltage swell, harmonics, transients, interruptions, voltage collapse etc. To solve the problem of power quality, various custom power devices are generally used in a power system, dynamic voltage restorer (DVR) being one of them. DVR is used for the compensation of voltage sag and swell. In this paper, a model of DVR with molten carbonate fuel cell (MCFC) and Y source inverter is proposed. The proposed model is compared with the existing ones to check its performance characteristics. MATLAB/SIMULINK was been used to check and compare the performance of the proposed with existing models.

Voltage Sag Compensation Using Dynamic Voltage Restorer for DFIG Fed Distribution Network

This paper investigates compensation of voltage sag due to faults in distribution system for a doubly fed induction motor(DFIG) configuration using dynamic voltage restorer(DVR). Series compensation of terminal voltage during fault conditions using DVR is carried out by injecting voltage at the point of common coupling to the grid voltage to maintain constant DFIG stator voltage. However, the control of the DVR is crucial in order to improve the FRT capability in the DFIG-based wind turbines.wind turbine is controlled by pitch angle which controls the rotor and stator currents of induction generator under different wind speeds. DVR injects voltage in series using vector control which compensates voltage quality problems. The proposed work is verified using matlab/ Simulink software. Keywords: DFIG,DVR.Voltage sag,FRT DOI : 10.7176/ISDE/10-2-02

Compressed air energy storage powered dynamic voltage restorer for voltage compensation in three-phase distribution system

The steady supply of quality power from the distribution system is a major concern for the sensitive loads. The dynamic voltage restorer system is mainly used to compensate voltage sags and swells for uninterrupted reliable &quality power supply. Hence, this work proposes a novel combination of dynamic voltage restorer and compressed air energy storage for power quality enhancement. The main aim of this work is to replace the conventional battery powered dynamic voltage restorers with the compressed air energy storage powered dynamic voltage restorers. This article presents the design and modeling of a third generation compressed air energy storage system with zero greenhouse gas emission and high response time. Further, a compressed air energy storage powered dynamic voltage restorer (CAESPDVR) connected distribution system supplying a sensitive load is modeled and the voltage variations during various faults are analyzed. The behavior of the system with and without the compressed air energy storage powered dynamic voltage restorer is investigated. MATLAB/Simulink and SimulationX software are used for modeling and analysis.

A Discrete-Time Control Method for Fast Transient Voltage-Sag Compensation in DVR

This paper presents a discrete-time domain control scheme for balanced voltage sag compensation using a Dynamic Voltage Restorer (DVR), which is recognized to be an appropriate and economical power electronic device with which to ameliorate these disturbances. The proposed control method is implemented in the synchronous reference frame (SRF), with two nested regulators, one of which includes an integral action. This algorithm has some advantages with respect to other control algorithms, such as the fact that the proposed methodology permits all the closed-loop poles of the DVR system to be placed in the desired locations in order to define the dynamical behavior with a reduction in the number of the electrical magnitudes to be measured and without the need for state observers, as occurs in traditional control methods. What is more, the well-known inner current loop implemented in other control schemes, which is employed to attenuate the resonance of the plant, is unnecessary. Furthermore, the unbalanced voltage sag compensation can be achieved by adding a “plug-in” controller and following the same methodology presented for balanced voltage sags to design the controller. The good performance of the proposed control scheme is validated by means of simulation and experimental results carried out with a 5 kW DVR laboratory prototype. The discrete-time control method is also compared with two control schemes previously proposed in literature.

Dual Resonant Voltage Droop Compensation for Bipolar Solid-State Marx Generator Topologies

This paper discusses a novel methodology to increase the voltage droop compensation range in generalized solid-state bipolar high-voltage Marx modulators with one resonant stage. To maintain the modularity characteristic of bipolar Marx modulators, the imbedding of additional resonant stages is not straightforward. Nevertheless, this paper proposes to add a second resonant stage to the already existing resonant-type voltage droop compensation stage. This second stage increases the voltage droop compensation percentage of a generalized solid-state bipolar Marx generator. The compensation of the bipolar pulse voltage droop is now achieved by adding two auxiliary synchronous compensation resonant voltages, to the output capacitive decaying voltage. Simulation and experimental results are presented for six Marx plus two resonant stages, 16% voltage droop, with 3-kV pulse amplitude, 100- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> pulsewidth, 40-ms relaxation time, and 10-Hz pulse repetition rate.

Improving of operation stability of frequency converters with active rectifiers in electric steel-making complex electrical equipment switching

Frequency converters with active rectifiers (FC-AR) are now used in rolling mill electric drives. Modern control systems of ARs are not adapted to voltage sags in power supply systems, which leads to converter tripping. The known methods of ensuring AR operation stability, such as kinetic buffering, correction signals based on negative sequence voltage and others, do not eliminate these emergency trips. As an additional measure the paper proposes the method of voltage sag compensation by using static var compensators (SVC) of electric arc furnaces (EAF) for parallel operation of frequency converters with active rectifiers and electric arc furnaces. However, it remains unknown how disturbances (such as overvoltages of switching of SVC harmonic filters (HF) and voltage sags during furnace transformer switching) affect operation stability of frequency converters with active rectifiers. All this makes it necessary to study the effect of these processes on the operation conditions of FC-AR and to improve the active rectifier control system. The authors used experimental arrays of instantaneous values of voltages and currents of the real-life complex «EAF-SVC» («Electric Arc Furnace – Statistic VAR Compensator») in this study. They also applied mathematical models of FC-AR with different PWM algorithms realized in Matlab-Simulink software. The main assumption of the model consists in using equivalent current sources modelling the operation of autonomous voltage invertors. An improved control system of AR has been developed. The main feature that distinguishes it from the known systems is the fact that it ensures operation stability during SVC harmonic filter and EAF transformer switching by using a signal conditioning unit for setting the active rectifier reactive current component as a function of power supply and AR input voltage difference. Implementation of the improved AR control system improves FC-AR stability during parallel operation with EAFs through reactive power consumption of the supply system. As a result, it reduces the amplitude of inrush current and voltage deviations in the DC-link of the FC-AR to the values lower than the setpoints of the AR protection system.

Dual-Buck AC–AC Converter With Inverting and Non-Inverting Operations

In this paper, a novel buck–boost ac–ac converter is proposed. The basic switching unit of the proposed converter is a unidirectional buck circuit; therefore, it has no shoot-through worries. It can achieve safe commutation without using RC snubbers or soft commutation strategies. It can be implemented with power MOSFETs without their body diodes conducting and, for current freewheeling external diodes, can be used to minimize the reverse recovery issues and related loss. It has a bipolar voltage gain with both inverting and non-inverting operations. The non-inverting operation can be used to compensate voltage sag, and inverting operation can be used to compensate voltage swell. Therefore, the proposed converter as a dynamic voltage restorer is capable of compensating for both voltage sag and swell in a wide range. The detailed theoretical analysis followed by detailed experimental results of a 300-W prototype converter is provided.

Mitigation Balanced/ Unbalanced Voltage Sag and Phase Jumping Using Unified Power Quality Conditioner UPQC with Three Voltage Compensation Methods

Semiconductors are extensively used in many industrial and residential applications that leads to drop in the quality of voltages and currents in distribution system. Faults causes balance or unbalance voltage sag and phase jumping. Sensitive loads effected not only by the voltage sag but also by the variation in phase angle specially the motor drive systems. Poor power quality may cause interruption of production and coasting a huge amount of money. New remedies that adopted in recent years are using active filters. UPQC is an active device used to enhance the quality of the load voltage as well as current of utility. Little attention is made in literature for comparing methods of injection voltage in the case of unbalance voltage and phase jumping. Three methods of voltage sag compensation based on the mode of injected voltage are adopted. A deep comparison between synchronous reference frame, quadrature injection voltage and pre-sag compensation methods based on the rating, total harmonic distortion, phase jumping mitigation point of view show that a proposed presage compensation method is more suitable for mitigation voltage sag. Abnormal voltages and currents are recovered simultaneously in all studied cases.&#x0D;

The Operation and Model of UPQC in Voltage Sag Mitigation Using EMTP by Direct Method

Nowdays, regarding to the great us of sensitive devices, the quality of the transmitted power, have become an important issue. One of the most important dimension of power quality is magnitude load terminal voltage. Different devices has been designed for voltage sag compensation or other distortions. UPQC is a compensator which is able to compensate all distortions, such as voltage sag, flicker, unbalance, harmonic and current distortions such as reactive, harmonic and unbalance. Several controllers have been designed to compensate the whole or a part of distortions. In this paper its going to introduce a kind of controller which is able to compensate voltage sag to direct and simple by UPQC. At the end, simulation and voltage sag mitigation is going to be performed by ATP-EMTP software.

Power quality improvement of radial feeders using an efficient method

In this paper, a voltage sag compensation of Point of Common Coupling (PCC) is provided using a suitable hybrid scheme composed of a Fault Current Limiter (FCL) and a Dynamic Voltage Restorer (DVR). Current limiting task is devolved to the FCL, which has a very simple structure, along with a fast and reliable performance, low on-state losses, and low cost. The FCL not only can preserve the short-circuit level of the Distributed Generation grid (DG-grid) in a safe level, but also compensates the voltage sag for the sensitive loads connected to the PCC. The PCC feeders are classified into high-sensitive, low-sensitive, and non-sensitive feeders. In this paper, by profiting from the collaboration of the FCL and DVR in non-sensitive and high-sensitive feeders, respectively, a suitable compensation with minimum cost is suggested. The proposed compensation scheme mitigates the voltage sag and phase angle jump at the PCC. Using this strategy, a cost-effective desirable power quality for the whole loads is assured. Analytical study supported by simulation and experimental results are presented to confirm the effectiveness of the proposed hybrid technique.

A Two Degrees of Freedom Resonant Control Scheme for Voltage-Sag Compensation in Dynamic Voltage Restorers

This paper presents a two degrees of freedom (2DOF) control scheme for voltage compensation in a dynamic voltage restorer (DVR). It commences with the model of the DVR power circuit, which is the starting point for the control design procedure. The control scheme is based on a 2DOF structure implemented in a stationary reference frame (α-β), with two nested controllers used to obtain a passband behavior of the closed-loop transfer function, and is capable of achieving both a balanced and an unbalanced voltage-sag compensation. The 2DOF control has certain advantages with regard to traditional control methods, such as the possibility of ensuring that all the poles of the closed-loop transfer function are chosen without the need for observers and reducing the number of variables to be measured. The use of the well-known double control-loop schemes that employ feedback current controllers to reduce the resonance of the plant is, therefore, unnecessary. A simple control methodology permits the dynamic behavior of the system to be controlled and completely defines the location of the poles. Furthermore, extensive simulations and experimental results obtained using a 5-kW DVR laboratory prototype show the good performance of the proposed control strategy.