Pdf voltage sag mitigation using static var compensator. Design of ac voltage sag compensators ieee conference. The basic function of the system is the compensation of voltage and current disturbances. The advantages of the dvr are fast response, ability to compensate for a voltage sag and a voltage phase shift using an inverter system. A voltage sag is a shortterm reduction in, or complete loss of, nominal voltage. A voltage sag happens when the rms voltage decreases between 10 and 90 percent of nominal voltage for onehalf cycle to one minute. Voltage sag swell compensator with phase shifter function.
As shown in figure 1, the voltage sag compensator consist of three phase voltage source inverter and coupling load transformer for serial connection of the system. Voltage sag is the major power quality problem and receives wide attention. This paper overviews the methods proposed for the compensation of. Moreover, to avoid saturation under all conditions, the injection transformer must be sized to handle at least twice the normal. Key benefits continuous protection from common utility voltage problems. Dvc is engineered to deliver power supply at constant voltage whenever there is a voltage dips at the main line, even complete momentary power. The voltage sag compensator comes into the picture when sag occurs. The duration of a voltage sag event, by definition, is less than 1 min and more than 8 msec, or a half cycle of 60hz electrical power. Pdf this paper represents analysis and performance of an improvement device for compensation of voltage sag perturbation. Dynamic voltage restorer dvr and distribution static compensator dstatcom are normally employed as voltage sag mitigation devices. Voltage sag is created by connecting an additional load in parallel with the existing load. In various companies voltage sag may affect many manufactures and introduce sufficient losses in the power system.
Transformer inrush current mitigation for series voltage sag. A simplified schematic diagram of the proposed voltage compensator for correcting sag swell and control of voltage phase angle is shown in fig. Analysis and design of a new voltage sag compensator for critical loads in electrical power distribution systems article pdf available in ieee transactions on industry applications 394. Voltage sags are commonly caused by lig design of ac voltage sag compensators ieee conference publication. Threephase acac converter for voltage sagswell compensator.
After detecting a voltage sag or interruption a load is disconnected from grid power supply. Voltage sag is thus, short duration reduction in r. An inrush mitigation technique is proposed and implemented in a synchronous reference frame sag compensator controller. The ratings and power requirements of a lowpower voltage sag compensator, also known as dynamic voltage restorer dvr are derived, as well as its deadbeat control algorithm implemented in a digital signal processor dsp. This paper describes a control scheme of fault current limiter by series voltage injection. Three phase fault is created via the three phase rl load. Sag detection techniques a voltage sag detection technique detects the occurrence of the sag, the start point, the end point, sag depth magnitude to be restored and phase shift. Voltage sag compensation using dynamic voltage restorer.
Voltage sag compensation of point of common coupling. There is a little more to it than just lowering the supply voltage until a machine fails. This study proposes a controller for a single and a threephase pulse width modulation pwm voltage sag compensator. Aug 08, 2002 a voltage sag generator is used to simulate voltage sags fig. It responds instantly to power quality problems such as sags and swells, providing continuous regulation of voltage. This over current may damage the inrush protection of the series connected. The voltage sag swell can be effectively compensatedusing a dynamic voltage restorer, series active filter upqc, etc. When voltage sags occur, the voltage sag compensator injects the required compensation voltage through the coupling transformer to protect sensitive loads from being interrupted by sags. This paper incorporates the functional performance of dvr during voltage sag in the power system. The dvr is a series connected device whose function is to protect a sensitive industrial load from voltage sags 5. Non linear loads need both magnitude as well as phase angle compensation.
Analysis and design of a new voltage sag compensator for. It is also very effective in damping out power oscillations and. In this paper the statcom and upfc are used to mitigate voltage sag at bus 6, with use of these devices the power flow in the system are also improved. Cooling system online and no abnormal flow or temperature conditions interlocks in ready state primary voltage measurement system synchronized and ready switches in closed position clc ready and synchronized. According the data of korea electric power corporationkepco, sag happens 5070 times a year and average economic losses due to the sag a year in korea is krw650,000musd 600m. The disturbance in power system is unavoidable situation. A threephase fault is created at point x via a resistance of 0. A voltage sag is a temporary reduction of the voltage rms below a speci. The most common compensator for voltage sag is dynamic voltage restorer dvr. The primary difference is that its injected voltage is not related to the line intensity and can be managed. Jul 16, 2015 in a large power system voltage sag is considered to be the most common and critical power quality pq issue. Voltage sag mitigation in ieee 6 bus system by using statcom.
Sag compensator r oxygen, thanks to a suitable sizing of the power components and a remarkable response speed sag of the grid voltage of a maximum duration of one minute. Cooling system online and no abnormal flow or temperature conditions interlocks in ready state primary voltage measurement system synchronized and ready. The compensator is bypassed by the thyristors when the grid operates normally for high efficiency. Among the available power quality enhancement devices, the upqc has better sag swell compensation capability 2. Mitigation voltage sag in power system by static synchronous. Generally voltage sag happens when the nominal voltage decreases between 10 and 90 percent of nominal voltage for onehalf cycle to one minute. The voltage reduction magnitude is between 10% and 90% of the normal root mean square rms voltage at 60 hz. In such cases, controlled series compensation helps effectively. Fixed series compensation has long been the preferred solution for optimizing performance in very large bulk transmission corridors.
Voltage sags arrives from the utility, but most of the time sags are generated inside a building. Voltage sag results in decrease in efficiency of the systems which affect the manufacturers in terms of losses related to money and credibility. Faculty of engineering, abhar branch, islamic azad. Voltage sag compensation using dynamic voltage restorer 647 transformer winding and the control algorithm adopted are dependent on the stepdown transformer winding in the distribution system. Static synchronous series compensator sssc is a modern power quality facts device that employs a voltage source converter connected in series to a transmission line through a transformer. Power quality, dstatcom, voltage sag, igbt, matlabsimulink, energy storage system, artificial neural network 1. The controller comprises a combination of a new sag detection technique namely phase angle analysis and a pwm voltage controller. Typically, voltage sag generation devices feature precise timing and phase angle control, enabling the simulation of sags with durations from 0. Although wavelet analysis works well for detecting voltage sag features, the existence of noise can reduce the advantages of wavelet method or even make it ineffective. The instantaneous voltage sag may give rise to serious problems in computer systems or electronic equipments. The voltage sag during the fault is proportional to the short circuit current. It is a series connected custom power device, which is considered to be cost effective compared to other alternative voltage sag compensation devices. The basic operation of the dvr is based on injection a compensation voltage with required magnitude, phase angle and frequency in series with sensitive electric distribution feeder 7, 8. Research on voltage sag detection has also grown up and it is an essential part of the voltage sag compensator.
This paper presents a low cost alternative for voltage sag. The dvr is a voltage sag compensator based on a voltage source inverter vsi. Therefore, precise and fast voltage detection is an essential part of the voltage sag and swell supporter. Dip voltage compensator manufacturer korea dvc features. The voltage sag occurs at bus 6 due to the overloading condition. Voltage sag compensation using dynamic voltage restorer 651 fig. Threephase crossphase voltage sag compensator to compensate balancedunbalanced voltage sags and phase outages in distribution systems ebrahim babaei mohammad farhadi kangarlu faculty of electrical and computer engineering, university of tabriz, tabriz, iran epec 2011. Voltage sag mitigation using static var compensator s. English or voltage dip british english is a short duration reduction in rms voltage which can be caused by a short circuit, overload or starting of electric motors. A cost effective voltage sag compensator for distribution. Voltage sags are caused by short circuit faults on the system, transformer energizing, overloads and starting of large motors.
Considering the sag and short outage compensation to be the target tasks, three different configurations have been selected. Configuration of a voltage sag compensator by use of a microa. Technique to mitigate inrush current of load transformer. Dvr saves energy through voltage injections that can affect the phase and waveshape of the power being supplied devices used for dvr include static var devices, which are.
Voltage sag is defined as a sudden reduction in supply voltage to between 90% and. The function of the series inverter is to compensate the voltage, when there are supply side disturbances, such as voltage sag, swell and unbalance. Synchronous frame control for voltage sag swell compensator. Installing a capacitive reactance in series in a long typically more than 200 km transmission line reduces both the angular deviation and the voltage drop, which increases the loadability and stability of the line. Generally, the sag compensator is rated for compensating all threephase voltages down to 50% of nominal grid voltage. After developing a prototype 100 kw, 400 v compensator awarded at the nasa contest 20, we are now developing a prototype of high power 1 mw medium voltage 6 kv compensator.
Batteryless, therefore no replacement and maintenance costs or hazardous waste. The converters used in the compensator structure are called crossphase direct converters. These are a problem because spikes consume power and sags reduce efficiency of some devices. The sssc operates like a controllable series capacitor and series inductor. Voltage sag, voltage sag detection, voltage sag compensator, rms detection, peak detection. Dynamic voltage restorer dvr system for compensation of. In pre sag compensation technique, dvr provides the difference between pre sag and sag voltage therefore restoring the voltage magnitude as well as the phase angle to that of the pre sag value. Some references defines the duration of a sag for a period of 0. Voltage sag compensation of point of common coupling pcc. Series compensation technique for voltage sag mitigation.
Sag is momentary voltage drop phenomenon within one second. Technique to mitigate inrush current of load transformer by. Thus, the authors have already proposed an instantaneous voltage sag swell compensator utilizing singlephase matrix converter1. However, certain detection time typically within 4ms is required by the sag compensator controller to identify the sag event. A voltage sag is a momentary decrease in the root mean square rms voltage between 0. The best known disturbances of the voltage waveform are voltage sags and swells, harmonics, interharmonics and voltage imbalances. Mitigation of inrush current of transformer using voltage. The voltage sag swell on the system is oneof the most important power quality problems. Voltage sag compensation in multiline distribution system using. The current limiter proposed in this study is based on the use of a smes.
First, natural reason such as lightning, storms, snow, heavy winds, or damage by wild animal and plant. The vbc series is an active voltage conditioner designed to solve voltage problems by shizuki smart backup system. In this paper, a new voltage sag compensator for powering critical loads in electric distribution systems is discussed. Static var compensator svc plant control the svc can only be energized if the status of critical systems is confirmed such as.
Ac operated electronic equipment are vulnerable to momentary losses of ac voltage, which are known as voltage sags. Analysis and design of a new voltage sag compensator for critical. Due to the large amount of compensator topologies it is important to establish the set of the most suitable ones for a given functional feature. The voltage sag during the fault is proportional to the short. Artificial neural network controller based distribution. In a large power system voltage sag is considered to be the most common and critical power quality pq issue. Introduction sag detection is important as it determines the dynamic performance of a voltage sag compensator. With the advent of powersemiconductor devices many pq devices came into existence. The magnitude of output voltage determines the behavior of hysteresis voltage control method and the starting moment of compensation. Threephase crossphase voltage sag compensator to compensate. Mitigation of inrush current of transformer using voltage sag.
A transformer inrush may occur at the start of sag compensator. Voltage sags are an important power quality problem for which the dynamic voltage restorer dvr is known as an effective device to mitigate them. Introduction voltage sag and voltage harmonics are the most important power quality pq problems that many industries and utilities face it. The voltage sag compensator is based on three phase voltage source inverter and a coupling transformer for serial connection. A new voltage sag and swell compensator switched by. Faculty of engineering, university of urmia, urmia, iran s. Transient performance and design issues for a parallel. Plant engineering voltage sags and what to do about them.
The compensator is monitoring the voltage of the grid. Bulletin 1608 power quality products rockwell automation. Mitigation of inrush current in load transformer for. Pdf analysis and design of a new voltage sag compensator. The voltage sag compensator, a transformercoupled arrangement associated voltage source inverter, is among the most savvy arrangement against voltage sags. A sag is a deep voltage decrease and is shorter in duration than a voltage regulation problem brownout. Voltage detection is important because it determines the dynamic performance of voltage compensator. Pdf on jul 1, 2006, fernando ortiz martinz and others published a low power voltage sag compensator find, read and cite all. Secondly artificial reason which is manly about input voltage drops by electrical overloading due to peripheral equipment usage.
Generally voltage sag happens when the residual voltage decreases between 10 and 90 percent of nominal voltage for onehalf cycle to one minute. Allenbradley dysc voltage sag protector the solution to voltage sags allenbradley dynamic sag correctors dysc from rockwell automation are unique and exclusive industrial power quality solutions that protect against voltage sags and momentary outages that account for a signifi cant amounts of manufacturing downtime and damaged equipment. From an electric utility perspective, a fault on the transmission system can produce a sag to electricity users downstream of that location, and depending on the system topology. Voltage sags are a 10% to 90% reduction in the supply voltage of nominal voltage. Voltage sagswell compensation using dynamic voltage. Review of voltage sag compensation techniques ijareeie. The closed loop pi, pid and fl controlled systems are modelled and. Phase angle analysis for pwmswitched autotransformer voltage. Capacitor rating selection for voltage sag compensation in. Voltage sag sell is most important power quality problems challenging the utility industry can be compensated and power is injected into the distribution system. To improve the compensating performance of the system, twodegreeoffreedom voltage control is.
There are several possible solutions to voltage sag problems. The compensation against voltage sags is achieved by adding the voltage conditioned by the. The dynamic voltage restorer dvr has been proposed to protect sensitive loads from such voltage sags. Pdf voltage sag compensation by using dynamic voltage. Voltage sag mitigation using static var compensator. A transition to ups mode requires that these auxiliary controls be disabled within a few milliseconds of opening the electronic switch. Transition time for the fault is considered from 0. In each phase of the proposed compensator there is a direct converter, a lowpass lc filter, an injection transformer and a bypass switch. The proposed scheme employs a pulsewidthmodulation acac converter four insulated gate bipolar transistors per phase along with. Transformer inrush current mitigation for series voltage. Dynamics of the sag compensator the dynamics of the sag compensator can be represented by an equivalent circuit in fig. Transient performance and design issues for a parallelconnected voltage sag and outage compensator leon voss epe 99 lausanne p. Voltage sag is defined as a decrease of rms voltage from 0.
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