Yuttana Kumsuwan

A Carrier-Based Unbalanced PWM Method for Four-Leg Voltage Source Inverter Fed Unsymmetrical Two-Phase Induction Motor

This paper presents a carrier-based unbalanced pulsewidth-modulated method for a two-phase four-leg voltage source inverter (VSI) and its realization for an unsymmetrical two-phase induction motor. A modulation strategy is developed to synthesize unbalanced two-phase output voltage waveforms based on the unipolar modulation technique with open-loop V/f control. The proposed control scheme allows independent magnitude controllability and quadrature phase angle for unbalanced two-phase output voltages. Thus, the modulation algorithm makes the four-leg VSI inequitable with unbalanced two-phase loads. Simulation and experimental results confirm the feasibility of the control method for the inverter.

A phase-shifted carrier-based PWM technique for cascaded h-bridge inverters application in standalone PV system

A phase-shifted carrier-based pulse width modulation strategy of two single-phase cascaded H-bridge inverters with separated solar photovoltaic sources, for standalone applications, is proposed in this paper. These functions are derived from a conventional unipolar modulation method with two phase-shifted triangular carrier waves, which can be easily implemented. The modulation strategy was developed to provide a five-level output waveform with a non unity power factor load. The possibility of the proposed technique has been verified though computer simulations and experimental results.

Control of single-phase cascaded H-bridge multilevel inverter with modified MPPT for grid-connected photovoltaic systems

This paper presents a control technique of cascaded H-bridge multilevel voltage source inverter (CHB-MLI) for a grid-connected photovoltaic system (GCPVS). The proposed control technique is the modified ripple-correlation control maximum power point tracking (MRCC-MPPT). This algorithm has been developed using the mean function concept to continuously correct the maximum power point (MPP) of power transferring from each PV string and to speedily reach the MPP in rapidly shading irradiance. Additionally, It can reduce a PV voltage harmonic filter in the dc-link voltage controller. In task of injecting the quality current to the utility grid, the current control technique based-on the principle of rotating reference frame is proposed. This method can generate the sinusoidal current and independently control the injection of active and reactive power to the utility grid. Simulation results for two H-bridge cells CHB-MLI 4000W/220V/50Hz GCPVS are presented to validate the proposed control scheme.

An improvement of synchronously rotating reference frame based voltage sag detection for voltage sag compensation applications under distorted grid voltages

An improvement of synchronously rotating reference frame based voltage sag detection for voltage sag compensation applications under distorted grid voltages is proposed. The voltage sag detection is the one of important parts in the voltage sag compensation processes. In the past, the conventional synchronously rotating reference frame (CSRRF) based voltage sag detection is widely used in the voltage sag compensation applications. Its disadvantage is a long delay of detection time. This means the next process initiation of voltage sag compensation is also delayed, and then the load voltage can be affected from voltage sag. The modified synchronously rotating reference frame (MSRRF) based voltage sag detection is able to detect the voltage sag in a short delay of detection time by differentiator employment. However, its operation under the distorted grid voltages condition is unavailable because of the sensitivity of differentiator action to the high frequency components that caused by voltage harmonic. This paper proposed the improvement of MSRRF based voltage sag detection under distorted grid voltages. The operation of proposed improved MSRRF, MSRRF, and CSRRF based voltage sag detections are investigated via computer simulation to verify the advantage of proposed voltage sag detection.

Implementation of shunt active power filter using source voltage and source current detection

This paper presents the implementation of shunt active power filter using source voltage and source current detection. The harmonic current and reactive power compensation of shunt active power filter controller is based on the digital signal processing (DSP) to control its operation. First, the signal quality of the designed prototype was tested with the simulation program. Then, the prototype for experiment has been setup for verifying the performance of system. It was found that reactive power could be compensated and harmonic current could be reduced, compared to the results of an active power filter with the load current detection. Since the source current detection used less controlling devices and its structure was simple, so it is more attractive.

An Improvement in Synchronously Rotating Reference Frame-Based Voltage Sag Detection under Distorted Grid Voltages

This study proposed an improvement in synchronously rotating reference frame-based voltage sag detection under distorted grid voltages. In the past, the conventional synchronously rotating reference frame (CSRRF)-based voltage sag detection was generally used in the voltage sag compensation applications. Its disadvantage is a long delay of detection time. The modified synchronously rotating reference frame (MSRRF)-based voltage sag detection is able to detect the voltage sag with only a short delay in detection time. However, its operation under distorted grid voltage conditions is unavailable. This paper proposed the improvement of modified synchronously rotating reference frame (IMSRRF)-based voltage sag detection for use in distorted grid voltages with very fast operation of voltage sag detection. The operation of the proposed voltage sag detections is investigated via simulations and experimentations to verify the performance of the IMSRRF-based voltage sag detection.

Modified Unipolar Carrier-Based PWM Strategy for Three-Level Neutral-Point-Clamped Voltage Source Inverters

This paper presents a simple modified unipolar carrier-based pulsewidth modulation (CB- PWM) strategy for the three-level neutral-point-clamped (NPC) voltage source inverter (VSI). Analytical expressions for the relationship between modulation reference signals and output voltages are derived. The proposed modulation technique for the three-level NPC VSI includes the maximum and minimum of the three-phase sinusoidal reference voltages with zero-sequence voltage injection concept. The proposed modified CB-PWM strategy incorporates a novel method that requires only of one triangular carrier wave for generate the gating pulses in three-level NPC VSI. It has the advantages of being simplifying the algorithm with no need of complex two/multi-carrier pulsewidth modulation or space vector modulation (SVM) and its also simple to implement. The possibility of the proposed CB-PWM technique has been verified though computer simulation and experimental results.

Static series-connected compensator with control of load-side using three single-phase H-bridge inverters

In this paper, a static series-connected compensator with load-side connected shunt converter and a voltage sag detection control strategy are proposed. The proposed system uses three single-phase H-bridge inverters with the unipolar pulsewidth modulation technique. The control strategy for the series converter is based on the transport delay phase-locked loop for each phase in a three-phase system. The aim of this research is to improve the voltage restoration of static series-connected compensator, by which the voltage on the load-side can be restore under voltage sag condition as well as normal condition including symmetrical and asymmetrical voltage sags. The simulation results confirm the feasibility of the proposed system which was compared with the supply-side connected shunt converter of the static series-connected compensator for both symmetrical and asymmetrical voltage sag conditions.

A carrier-based unbalanced PWM method for four-leg voltage source inverter fed asymmetrical two-phase induction motor

This paper presents a carrier-based unbalanced PWM method for two-phase four-leg voltage source inverter and its realization for asymmetrical two-phase induction motor. A modulation strategy is developed to synthesize unbalanced two-phase output voltage waveforms based on the unipolar modulation technique with open-loop V/f control. The proposed control scheme allows independent magnitude controllability and quadrature phase angle for unbalanced two-phase output voltages. Thus, the modulation algorithm makes the four-leg voltage source inverter inequitable with unbalanced two-phase loads. Simulation and experimental results confirm the feasibility of the control method for the inverter.

Phase-shifted PWM strategy of a seven-level single-phase current source inverter for grid-connection systems

This paper presents a detailed analysis of a seven-level single-phase current source inverter for grid-connection systems. The aim of this research was to control high power factor operation, injecting a sinusoidal current flowing into the utility grid. The proposed two-stage power conversion strategies consisted of a dc-dc multilevel converter and a current source inverter, which operated with high switching and line frequency. A proposed topology is used to produce a seven-level current output with a phase-shifted PWM technique. A simple method is presented to improve the total harmonic distortion and power factor requirement. The feasibility of the proposed method was verified by simulation and experimental results.