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.

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

The aim of this paper is to present a modulation technique to achieve highest voltage sag compensation using direct converter based dynamic voltage restorer (DVR). The DVR topology proposed in this paper, has a direct converter and a series transformer. The direct converter is fabricated using only two bi-directional switches. The DVR is designed to compensate the sag in a phase by taking power from the same phase. The direct converter is connected between the series transformer and the line in which sag compensation is to be achieved. Conventionally, the PWM pulses for the direct converters are produced by comparing the error signal with the carrier signal. The error signal is obtained by comparing the amplitude of voltage in the line with the amplitude of the reference voltage. If the amplitude of the carrier signal is kept constant and the actual amplitude of error signal is used for PWM generation, it is possible to achieve only 22% of voltage sag compensation. But if the error signal amplitude is modulated according to the amplitude of existing voltage sag in the line, 52% of the voltage sag can be compensated with the THD less than 5%. Simulation results are presented for validating the analysis.

/pdf/voltage-sag-compensation-using-direct-converter-based-dvr-by-1tf58fbdrx.pdf

Voltage sag compensation using direct converter based DVR by modulating the error signal

The aim of this paper is to achieve maximum voltage sag compensation of 52% using direct converter based DVR. The DVR topology has only two switches. The DVR is designed to compensate the voltage sag in a phase by taking power from the same phase. A direct converter is connected between the series transformer and the line in which sag compensation is to be achieved. If the actual amplitude of the error signal is used and the amplitude of carrier signal is kept at 1 unit, it is possible to achieve only 22% of sag compensation. If the amplitude of the carrier signal is modulated according to the percentage of existing sag, 52% of the sag is compensated through ordinary PWM technique with the THD less than 5%. Matlab Simulation results are presented for the validating the analysis.

http://ijece.iaescore.com/index.php/IJECE/article/download/21294/14075

Maximum voltage sag compensation using direct converter by modulating the carrier signal

Electric power aims to generate electrical energy and distribute to the end-user application at an acceptable voltage level. The quality of power will be affected by various factors like voltage sag, swell, harmonic and Power interruptions, etc. The major reason behind the deteriorations of the power quality is nonlinearity in loads which draws out harmonics. Due to this nonlinearity, all loads cause disturbances in the voltage waveform. In this paper, an Intrinsic Space Vector Transformation (ISVT) based solar fed Dynamic Voltage Restorer (DVR) is connected in series with the power grid to compensate for the reactive power. The operation of the proposed DVR model produces reactive power based on the voltage sag and voltage swell. The ISVT controller produces an appropriate pulse to the voltage source inverter (VSI), which delivers a suitable reactive power to compensate for the sag and swell voltages in the grid. Moreover, solar fed DVR reduces Total Harmonic Distortion (THD) value at the time of voltage sag mitigation. The performance of the proposed system is evaluated by analysing the power consumption and efficiency. Finally, the proposed system is compared with other existing methods. The simulation is carried out using MATLAB SIMULINK 2017b software.

A novel intrinsic space vector transformation based solar fed dynamic voltage restorer for power quality improvement in distribution system

This work deals with reducing major voltage flickering problems by using dynamic voltage restoration and SPWM technique it helps to improve the power quality of the system. Even though voltage swag and swell occurs in transmission as well as distribution side but the problem is resolved only at the distribution side. A systematic approach is made to assume the components needed to design the system. Voltage flickering is detected by using dqo theory and by using SPWM technique voltage is being controlled .Dynamic voltage restorer is attached in series that immediately detects the voltage flickering and reestablish high voltage to original value. This designed model also effectively clears the voltage flickering problem. Results are simulated using MATLAB Simulink, which explained the importance of the system.

Mitigation of Voltage Sag And Voltage Swell By Dynamic Voltage Restorer

The fast developments in power electronic technology have made it possible to mitigate voltage disturbances in power system. Among the voltage disturbances challenging the industry, the voltage sags are considered the most important problem to the sensitive loads. Dynamic voltage restorer (DVR) is a series connected power electronic based device that can quickly mitigate the voltage sags in the system and restore the load voltage to the prefault value. DVR is recognized to be the best effective solution to overcome this problem. The primary advantage of the DVR is keeping the users always on-line with high quality constant voltage maintaining the continuity of production. In this paper, the usefulness of including DVR in distribution system for the purpose of voltage sag and swell mitigation is described. The DVR presented here is based on the concept of dqo. The proposed control method is found very efficient for detecting and clearing any power quality disturbance in distribution systems. Results of simulation using Matlab-Simulink are demonstrated to prove the usefulness of this scheme.

Deepa Francis

Papers

Mitigation of voltage sag and swell using dynamic voltage restorer