Investigation of Interline Dynamic Voltage Restorer with Virtual Impedance Injection

The inter-line dynamic voltage restorer （IDVR） consists of several voltage source inverters connected to different independent distribution feeders with common dc bus. When one of the inverters compensates for voltage sag that appears in its feeder （voltage control mode）, the other inverters pump the required power into the dc bus （power control mode）. Each inverter will have both voltage and power controllers; only one controller is in use during the abnormal conditions according to its feeder state. The voltage controller uses one of the dynamic voltage restoration techniques. In this paper, the in-phase technique is applied and two types of loads are considered （constant impedance and three phase induction motor）. Since the voltage restoration process may need real power injection into the distribution system, the power controller injects this power via voltage injection. This voltage injection is simulated by voltage drop across series virtual impedance. A new scheme is proposed to select the impedance value. The impedance value is selected such that the power consumed by this impedance represents the required power to be transferred without perturbing the load voltage. The performance of this system is also studied during voltage swell. A scheme for operation of multi-feeder IDVR system is proposed in this paper. Simulation results substantiate the proposed concept.

Realization of Unified Power Quality Conditioner for Mitigating All Voltage Collapse Issues

This paper proposes about a powerful control mechanism of UPQC (Unified Power Quality Conditioner) work on voltage source inverter which can effectively compensate source current harmonics and also mitigate all voltage collapse such as dip, swell, voltage unbalances and harmonics. The consolidation of series and parallel active power filters sharing mutual DC bus capacitor forms UPQC. PI (Proportional Integral) controller is mainly used in order to maintain continual DC voltage along with the hysteresis current controller. The parallel and series power filters were designed using 3-phase voltage source inverter. The reference signals for shunt and series active power filters were obtained by Synchronous Reference Frame (SRF) theory and Power Reactive (PQ) theory respectively. By using these theories, reference signals were obtained which was fed to the controllers for generating switching pulses for parallel and series active filters. The UPQC dynamic performance is obtained through testing terms like the compensation of voltage, current harmonics and all voltage distortion associated with 3-phase 3-wire power system which is simulated using MATLAB-Simulink software.

Dynamic Voltage Restorer with Active Disturbance Rejection Control

Power quality is one of the major concerns among consumers and electric utility companies. CUPS （custom power systems） devices are used to improve the quality of power and enhance the reliability of the power supply in the distribution networks. The DVR （dynamic voltage restorer） is an important CUPS device used to mitigate voltage sag/swell and imbalances. Various control techniques have been implemented to control the DVR, among which the PID （proportional-integral-derivative） controller is dominant because of its model independent property and its error driven technique. In this paper, a new controller based on the ADRC （active disturbance rejection control） concept is developed, and its performance is compared to that of the PID controller. The model of the DVR and its ADRC and PID controllers were developed under the MATLAB （matrix laboratory）/Simulink environment. The simulation results demonstrated the effectiveness of the ADRC over the PID controller.

Fuzzy Controlled Ultra-Capacitor Based DVR (UCAP-DVR) for Power Quality Enhancement

In recent years, a rapid decrease in the cost of various energy storage technologies and their integration into grid becomes a reality with the advent of smart grid. The Dynamic Voltage Restorer (DVR) is a custom power device that has an excellent dynamic capability used to provide voltage sag, swell compensation in distribution systems. Among the energy storage devices, Ultra-Capacitors (UCAP) have ideal characteristics such as high power and low energy density essential for the compensation of voltage sag and swell, which require high power for short interval of time. This paper presents an integration of rechargeable UCAP with DVR. This UCAP-DVR presents a modular, flexible system configuration that will have an active power capability and also provide deep, extended mitigation for power quality problems. The DVR is integrated into UCAP via bidirectional DC-DC converter which supports a rigid dc-link voltage for DVR and also helps in compensating temporary voltage sag and swell. FUZZY LOGIC Controller is used to enhance the performance of UCAP-DVR. The simulation model for the proposed system has been developed in MAT-LAB and the performance over conventional DVR is compared with the results obtained.