Watcharin Srirattanawichaikul

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.

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.

A carrier-based PWM strategy for three-level neutral-point-clamped voltage source inverters

This paper present a modified modulation strategy based on a triangular carrier wave for the three-level neutral-point-clamped (NPC) voltage source inverter (VSI). The switch states of each leg are determined by comparison between the modulation signals and a triangular carrier wave, which is used only of one triangular carrier wave for generate the gating pulses in three-level NPC VSI. The feasibility of the proposed modulation technique is verified by simulation and experimental results. These results show that a proposed carrier-based PWM technique can be easily implemented are provided to verify the proposed modulation strategy.

A space vector modulation strategy for three-level operation based on dual two-level voltage source inverters

This paper presents a space vector modulation (SVM) technique for a three-level operation based on dual two-level voltage source inverter (VSI). This inverter topology uses two standard two-level VSI placed in parallel using a three-phase transformer to connect them together. This paper proposes a general modulation algorithm for dual two-level VSI based on the basic two-level SVM technique. The proposed inverter produces five-level line-to-line voltage waveforms, which is able to generate voltage levels similar to a three-level inverter. The practicality and performance of the modulation strategy for the proposed inverter topology has been verified via simulation and experiment.

Static series-connected compensator with load-side connected shunt converter based on single-phase VSI for voltage sag mitigation

This paper presents an improvement of the voltage restoration from voltage sags using the static series power quality compensator based on load-side connected shunt converter. The proposed topology is divided in two portions, which consists of the series and shunt configurations. The series converter is connected to the supply-side based on separated three sets single-phase voltage source inverters. The shunt converter uses a three-phase diode rectifier, which maintains the energy for the injection voltages with the dc-link capacitor. The algorithm technique of voltage sag detection and control method for compensation is based on the synchronously phase detection and the rotating reference frame transformation, which are independently controlled in each phase voltage. The performance of the proposed topology from the laboratory prototype is verified through experimental results.

Modified single-carrier-based modulation technique for grid-connected three-level NPC converters

This paper presents a modified carrier-based modulation technique for the grid-connected three-level neutral-point-clamped (NPC) converter system. The proposed carrier-based modulation technique uses the single triangular carrier signal in generating the gate signals for three-level NPC converter. The control method of the grid-connected system is applied for the voltage oriented control scheme, which provides independent control active and reactive power flow into the utility grid and maintain the dc-link voltage constant. The feasibility of the developed proposed modulation technique for the grid-connected three-level NPC converter system is confirmed with experiment results, which is validated the performance and effectiveness of the presented method.