Alexandre C. Oliveira

Improved Dead-Time Compensation for Sinusoidal PWM Inverters Operating at High Switching Frequencies

This paper proposes a technique to compensate the effects of dead time in sinusoidal pulsewidth-modulated voltage-source inverters. The compensation is implemented by adjusting the switching frequency to avoid unfeasible pulsewidths of the gating signals, as well as to minimize the total harmonic distortion of the inverter output voltage. The technique can be used at any switching frequency, but the best results are obtained in the high-frequency range. The experimental results of the proposed technique that is applied in a three-phase induction motor drive system are presented.

The Transformerless Single-Phase Universal Active Power Filter for Harmonic and Reactive Power Compensation

This paper presents a universal active filter for harmonic and reactive power compensation for single-phase systems applications. The proposed system is a combination of parallel and series active filters without transformer. It is suitable for applications where size and weight are critical factors. The model of the system is derived and it is shown that the circulating current observed in the proposed active filter is an important quantity that must be controlled. A complete control system, including pulse-width modulation (PWM) techniques, is developed. Comparisons between the structures are made from weighted total harmonic distortion (WTHD). The steady-state analysis is also presented in order to demonstrate the possibility to obtain an optimum voltage angle reducing the current amplitude of both series and parallel converters and, consequently, the total losses of the system. Simulated and experimental results validate the theoretical considerations.

Sensorless Control of a PMSM Synchronous Motor at Low Speed

This paper presents a self-sensing technique for a surface-mounted permanent-magnet synchronous machine (SM-PMSM) based on high frequency voltage injection. The reactances of the high frequency model vary as a function of rotor position and a simple method based on measured currents and voltages can be used to identify those reactances. Using the motor reactances, the rotor position and velocity are determined. The proposed technique is relatively independent of the machine parameters and it can be applied to any type of synchronous machine. The proposed technique has been tested experimentally for a commercial SM-PMSM machine. The experimental results have demonstrated the feasibility of the proposed technique

Transformerless Single-Phase Universal Active Filter With UPS Features and Reduced Number of Electronic Power Switches

This paper presents an universal active power filter for harmonic and reactive power compensation with uninterrupted power supplies (UPS) features. The configurations does not use transformer in the series part. Transformerless modern UPS systems have been rapidly replacing the old technology due to their performance and size attributes. Reducing the numbers of passive elements and/or switches in active power filters and UPS topologies not only reduces the cost of the whole system but also provides some advantages, such as great compactness, smaller weight, and higher reliability. However, the cost reduction requires the use of more complex control strategies. The model of the proposed system is derived and it is observed that the system can be reconfigurable to operate with four or three leg depending on the issue. A complete control system, including the pulsewidth modulation techniques, is developed and a comparison between the proposed filter and the standard one is done, as well. Simulated and experimental results validate the theoretical considerations.

Parameter and Speed Estimation for Implementing Low Speed Sensorless PMSM Drive System Based on an Algebraic Method

This paper presents a sensorless control scheme for a surface-mounted permanent-magnet synchronous machine (SM-PMSM) using the high frequency voltage signal injection method. The reactances of the high frequency model vary as a function of rotor position and a simple method based on measured high frequency currents and voltages is used to identify these reactances. Using such motor reactances, rotor position and velocity can be estimated. The proposed method is algebraic and does not require accurate knowledge of the initial value of the rotor position. The strategy was verified experimentally using a commercial SM-PMSM machine.

Comparison of HF signal injection methods for sensorless control of PM synchronous motors

This paper presents a comparative study of high-frequency (HF) voltage signal injections used for rotor position estimation in sensorless control of AC motors. This work reviews these methods and evaluates the performance under sensorless speed control applied to a surface permanent-magnet synchronous motor (PMSM). Theoretical analysis is verified by simulations and confirms the effectiveness of these methods. The experimental results of speed control using an industrial PMSM drive system are presented for each of the injection methods.

Hybrid multilevel inverter system for Open-End Winding (OEW) induction motor drive based on Double-Star Chopper-Cells (DSCC) converter

This paper proposes a hybrid multilevel topology for Open-End stator Winding (OEW) induction motor drive based on Modular Multilevel Cascade Inverter (MMCI) with Double-Star Chopper-Cells (DSCC) and 2-Level Voltage Source Inverter (2L-VSI). An efficient Voltage Reference Technique is proposed to generate the pole voltages of both inverters. As a result, the DSCC inverter is commanded in high-switching frequency, while the 2L-VSI operates at the fundamental frequency. A voltage-balancing control of the floating DC capacitors of the DSCC is presented to ensure the energy balance. At last, to investigate the proposed system and control strategy, experimental results are presented.

Single-Phase AC–AC Double-Star Chopper Cells (DSCC) Converter Without Common DC-Link Capacitor

This paper presents a single-phase AC-AC converter based on Modular Multilevel Cascade Converter (MMCC) with Double-Star Chopper-Cells (DSCC). This structure is composed by three DSCC-legs, the middle leg is shared, and also it does not present a common DC-link capacitor. It is suitable for regenerative low-power AC-AC conversion. The voltage-balancing control is presented to regulate the floating DC capacitor voltages. Furthermore, a grid current and terminal load voltage control is presented to correct the Power Factor (PF) and to ensure sinusoidal waveforms. Details about a designed 16-SM prototype are also presented. The experimental results allow validating the control strategies and the effectiveness of the proposed structure.

Cooperative control for active power compensators allocated in distributed networks

This paper proposes cooperative control of multiple active filters based on voltage detection and Total Harmonic Distortion (THD) computation for improve power quality. The time changing of loads, shunt capacitors, faults or others occurs in real Electric Power Systems (EPS). This dynamic scenarios require a distributed control, which, more than one Active Power Line Conditioner (APLC) reduce, cooperatively, harmonics from all Points of Common Coupling (PCC)s in the EPS. The harmonic reduction should satisfy IEEE-519 norm, which regulated that the THD value should be under 5%.

Hybrid Modular Multilevel DSCC Inverter for Open-End Winding Induction Motor Drives

This paper proposes a hybrid modular multilevel drive system based on a modular multilevel cascade inverter (MMCI) with double-star chopper cells (DSCC) and a two-level (2L) inverter to feed three-phase induction motors with open-end windings (OEWs). The proposed system is an alternative for high-speed motor drives based on a small-scale DSCC topology. A voltage reference technique is presented based on the analysis of the degrees of freedom of the system for generating the output voltage references, considering any voltage ratios of the dc links. The proposed system is evaluated in a symmetric scenario, in which the dc-link voltages are equal. Thus, the 2L inverter is set up to operate at the fundamental frequency, while the DSCC inverter synthesizes the output voltage references from high-quality waveform with a significant number of voltage levels. Experimental results obtained from a downscaled 10-kVA 380-V prototype driving a full loaded 3.7-kW OEW induction motor are provided to verify the viability of the proposed system.