Voltage Sag In Distribution System Research Articles

MITIGATION VOLTAGE SAG USING DVR WITH HYSTERESIS-ANN CONTROL ON DISTRIBUTION SYSTEM PUJON FEEDER LINE

This paper discusses the mitigation of voltage sag in distribution systems. Voltage sag often occurs due to a single line-to-ground short circuit fault. The fault has a major impact on load damage in the Pujon feeder line. Voltage sag can be mitigated by using Dynamic Voltage Restorer (DVR). DVR is one type of custom device that is effective in overcoming voltage sag. DVR requires control in regulating voltage recovery on the Pujon line. This research proposes DVR control using Hysteresis combined with ANN to mitigate voltage sag on Pujon line. Simulation results show that the Hysteresis-ANN control is able to recover the load voltage in phase R on average by 97% due to voltage sag that occurs on the Pujon feeder line.

Simulation-Based Comparison of PID with Sliding Mode Controller for Matrix-Converter-Based Dynamic Voltage Restorer under Variation of System Parameters to Alleviate the Voltage Sag in Distribution System

A constant power supply is a basic need for each consumer due to the increase in sensitive equipment day by day. As per IEEE standards, a 10% reduction in voltage from the supply voltage is not acceptable and may cause the failure of equipment. Previously, different techniques have been used to alleviate the voltage sag, such as STATCOM, DSTATCOM, SVC, and shunt capacitors, but these devices are connected in parallel, which compensates for the low value of voltage sag, and they have high maintenance costs involved. Compensation for the low and high values of voltage sag is possible through a series-connected device such as a dynamic voltage restorer. In this paper, a matrix converter is presented for DVR to convert AC to AC voltage directly and free from batteries, capacitors, and multiple conversions as needed in a voltage source inverter, resulting in a reduced cost of DVR topology. The DVR is meaningless in the absence of a controller, so it is necessary to select a suitable controller for the satisfactory operation of the DVR under a variation of system parameters. In this paper, the performance of a linear PID controller is analyzed and compared with a nonlinear controller, such as a sliding-mode controller, under variation of power system parameters inorder to select a robust controller that performs satisfactorily for DVR. Earlier trial-and-error methods were used to obtain the parameters of PID gains, but they require a large time to obtain the parameters of the PID gains and there is a chance of inaccuracy. A genetic algorithm was used to obtain the gain parameters, but it has more convergence time and the particle swarm optimization technique has involves less reliability. In this research paper, the sliding surface coefficient parameters such as and Ki for the PI sliding surface of SMC and PID gains are taken through an ant colony algorithm to obtain the robustness of the controllers. The purpose of this paper is to introduce the best DVR topology with reduced cost. MATLAB simulation software was utilized to analyze the performance of the DVR with PID and SMC controllers under different fault conditions and also the THD% of proposed controllers was analyzed through FFT.

Mitigation of voltage sag in a distribution system during start-up of water-pumping motors using superconducting magnetic energy storage: A case study

Voltage sag represents one of the most significant features of power quality in operation of distribution systems. The voltage sag throughout the distribution system caused by simultaneous start-up of water-pumping motors represents a problem, which negatively affects the power quality of the distribution system. The present research work investigates mitigation of voltage sag in a real Egyptian distribution system during simultaneous start-up of many connected water-pumping motors by using superconducting magnetic energy storage (SMES) unit. This calls for a transient analysis of the real distribution system using MATLAB package in order to follow up the temporal variation of the system voltage-profile during motors' start-up. A fuzzy-logic (FL) control strategy of SMES unit is adopted to compose of cascaded control a six-pulse pulse-width modulation (PWM) voltage source converter (VSC) and two-quadrant DC-DC chopper. The proposed fuzzy logic controller (FLC) of SMES unit employs the bus voltage variation and the variation of SMES current as input signals to control the power transfer between the distribution system and SMES. The effectiveness of the proposed FL-controlled SMES unit is validated in a case study of a real distribution feeder named Karot distribution feeder loaded by 16 water-pumps driven by induction motors as well as residential loads. The feeder is part of a distribution system serving the Unified Egyptian Electrical Network. The obtained results indicate that the SMES unit successfully mitigated the voltage sag in Karot distribution feeder due to simultaneous start-up of connected water-pumping motors where the voltage never drops below 0.9 pu.

Performance Analysis of Sliding Mode Controller for the Matrix Converter Based Dynamic Voltage Restorer to Mitigate the Voltage Sag in Distribution System

Performance Analysis of Sliding Mode Controller for the Matrix Converter Based Dynamic Voltage Restorer to Mitigate the Voltage Sag in Distribution System

Performance analysis of modified dynamic voltage restorer (DVR) employed to a grid connected solar PV system

Among various power quality problems, voltage sag and swell are dominant where loads are very sensitive to the voltage disturbances. Various custom power devices are introduced recently to overcome these voltage issues, dynamic voltage restorer (DVR) is one of them. It offers very cost effective solution for problems such as voltage sag, swell and harmonics by establishing the proper voltage level during voltage disturbances to protect sensitive loads. In this paper, performance of DVR to improve power quality is done for solar photovoltaic (PV) based generation system feeding the grid and the three phase linear load. Solar PV generation system is implemented with an incre-mental conductance (IC) maximum power point tracking (MPPT) technique. The DVR is connected in between solar PV system and load. The basic structure of DVR is modified by using the photovoltaic system as an alternative to DC source and in place of conventional 2-level voltage source converter (VSC) neutral point clamped (NPC) multi level inverter is used. The system performance is analyzed in the MATLAB/Simulink environment. The simulation results justified the efficiency of modified DVR in the mitigation of voltage sag in distri-bution system. Improvement of power quality by stabilizing voltage during fault and promoting renewable energy is the main framework of this work.

A Multi-objective Approach for Optimized Monitoring of Voltage Sags in Distribution Systems

Voltage sags are among the most relevant power quality disturbances. Furthermore, they also have high occurrence rates. Their stochastic nature makes monitoring difficult and causes significant losses to power utilities and customers. This paper presents an approach to overcome the problem of allocating power quality monitors. To do so, our approach accounts for topological coverage, unmonitored voltage sags, and the total cost of required equipment. We used NSGA-II to build our approach due to its efficiency in dealing with combinatorial problems. We also used the Monte Carlo simulation method to model the time series in our approach due to the random nature of power quality disturbances. To evaluate our approach, we simulated the IEEE 13-, 34- and 37-bus distribution systems using the DigSILENT Power Factory 15.1 software. The evaluation results show that our approach supported cost reduction associated with the installation of power quality monitors, both in terms of identifying adequate number and position of the performance monitors.

Analysis and Design of a DSTATCOM Based on Sliding Mode Control Strategy for Improvement of Voltage Sag in Distribution Systems

Voltage sag is considered to be the most serious problem of power quality. It is caused by faults in the power system or by the starting of large induction motors. Voltage sag causes about 80% of the power quality problems in power systems. One of the main reasons for voltage sag is short circuit fault, which can be compensated for by a distribution static compensator (DSTATCOM) as an efficient and economical flexible AC transmission system (FACTS) device. In this paper, compensation of this voltage sag using DSTATCOM is reviewed, in which a sliding mode control (SMC) technique is employed. The results of this control system are compared with a P+Resonant control system. It will be shown that this control system is able to compensate the voltage sag over a broader range compared to other common control systems. Simulation results are obtained using PSCAD/EMTDC software and compared to that of a similar method.

A New Estimation Model to Control DVR for Mitigating Voltage Sags in Distribution Systems

In this study proposed, for voltage sag mitigation an estimation method based on Extended Kalman Filter (EKF) is suggested. The suggested EKF based estimation technique is applied to help the control algorithm for producing reference signals of Voltage Source Converter (VSC) of DVR. DVR offers the compensation voltage as output which is inserted in the connected line. With this estimation method, voltage sag issues are found out with precision and faster performance to revoke out the sag appearance in sensitivity load connected distribution systems. The presentation of the suggested estimation technique is examined in terms of presenting the fundamental sinusoidal waveform to the nonlinear sensitive load. The confirmation of the suggested estimation algorithm is carried out on MATLAB working platform. Simulation effects are inspected and suggested one is compared with Linear Kalman Filter (LKF).

Modelling of Dynamic Voltage Restorer against Balanced and Unbalanced Voltage Sags in Distribution systems

The Dynamic Voltage Restorer (DVR) is used to regulate the voltage at the load terminals from various power quality problems like sag, swell, harmonics, unbalance etc. in supply voltage. This paper presents modelling aspects of several types of Dynamic Voltage Restorer (DVR) working against various voltage sags by simulation. Dynamic voltage restorers (DVRs) are used to protect sensitive loads from the effects of voltage sags on the distribution feeder. Significant simulation results show that these several types of the modelled device can work very well against balanced and/or unbalanced voltages caused by faults in a distribution system. Detailed analyses illustrate that with suitable parameter setting these devices can deal with different levels of voltage sag severity. In addition, appropriate ways to obtain a good quality output voltage by a DVR during voltage sag is also presented. It then provides analyses of working performance of the device, including capability and quality of compensation. Index Terms- Dynamic Voltage Restorer (DVR), Balanced and unbalanced faults, Compensation capability, Power quality sag severity, voltage sag.

Voltage Sag Mitigation in a Three-Phase Induction Motor using DSTATCOM and DVR

Voltage sag in distribution system is one of the most frequently occurring power quality problem, There are many solutions to mitigate voltage sag. This paper describes one such technique to mitigate voltage sag occurring during the starting of three-phase induction motor by using power electronic devices called Dynamic Voltage Restorer (DVR) and Distribution Static Compensator (DSTATCOM). This paper is organized with a brief introduction of voltage sag and its characteristics, structure and control principles of DSTATCOM and DVR. The performance of both DSTATCOM and DVR to mitigate voltage sag caused by starting of three phase induction motor is observed and compared. The simulation models of both the devices are analyzed and results are shown.

Voltage Control and Active Power Management of Hybrid Fuel-Cell/Energy-Storage Power Conversion System Under Unbalanced Voltage Sag Conditions

This paper concentrates on the control of hybrid fuel-cell (FC)/energy-storage distributed generation (DG) systems under voltage sag in distribution systems. The proposed control strategy makes hybrid DG system work properly when a voltage disturbance occurs in distribution system, and it stays connected to the main grid. To distribute the power between dc power sources and stabilize the dc-link power, a Lyapunov-based neuro-fuzzy control strategy has been developed. This controller determines the supercapacitor power that should be generated according to the amount of available energy in dc-link. Also, current control strategies for the FC converter (boost) and supercapacitor converter (buck-boost converter) are designed by proportional-integral and sliding-mode control consequently. Moreover, a complementary control strategy for voltage source converter based on positive and negative symmetrical components is presented to investigate the voltage sag ride-through and voltage control capability. The hybrid system is studied under unbalance voltage sag condition. Simulation results are given to show the overall system performance including active power control and voltage sag ride-through capability of the hybrid DG system.