Demercil de Souza Oliveira

A Three-Phase High-Frequency Semicontrolled Rectifier for PM WECS

This paper proposes the use of a three-phase high-frequency semicontrolled rectifier for wind energy conversion systems based on permanent magnet generators. The main advantages of the topology are: simplicity, since all active switches are connected to a common point, robustness, as short-circuit through a leg is not possible, and high efficiency due to reduced number of elements. As a disadvantage, higher but acceptable total harmonic distortion of the generator currents results. The complete operation of the converter and theoretical analysis are presented. Additionally, a single-phase pulsewidth modulation inverter is also employed in the grid connection. Experimental results on 5-kW prototype are presented and discussed.

A variable speed wind energy conversion system connected to the grid for small wind generator

The wind energy system presented in this paper uses a permanent magnet generator connected to a three- phase semi-controlled rectifier. Although an acceptable THD and power factor result, the proposed converter is simple, cheaper, and robust. Additionally, a single-phase PWM inverter is also employed in the grid connection. The inverter uses a double hysteresis in the control of the current injected in the grid, what implies reduced switching losses. Analysis and partial experimental results are presented for a 5 kW prototype. At the final version of this paper, a more detailed theoretical analysis, simulation results, as well as experimental results at rated power are supposed to be presented.

High frequency isolation on-line UPS system for low power applications

In this paper, a new high frequency isolation on-line uninterruptible power supply (UPS) system is proposed as a viable solution for low power applications. Its composed by one half-bridge chopper that operates in open loop with fixed duty cycle, a step-up converter that operates in closed loop using the traditional average current mode control and a traditional full bridge voltage source inverter (VSI). The step-up converter control provides power factor correction to the system. The proposed circuit is suitable for the development of low power UPSs (less than 1 kVA) which few batteries are used. In such applications the battery bank voltage, can be 24 V, 36 V or 48 V. Principle of operation, as well as, experimental results for the UPS operating in both, grid and battery modes are presented. Accordingly to the experimental results for a 1 kVA assembled prototype, an efficiency of 81,3% is obtained for grid mode and 89,2% for the battery mode, confirming the effectiveness of the proposed configuration.

A novel three-phase rectifier with high power factor for wind energy conversion systems

In this paper it is proposed a new topology of three-phase controlled rectifier feasible for high power wind energy conversion systems (WECS). This rectifier is based on the bridgeless rectifier, uses six wires of the generator, and allows the operation with high power factor, increasing the generator efficiency. One cycle control (OCC), which avoids the need of sinusoidal reference signals, was used in the rectifier control. This study is then concerned with the operation principle and experimental results obtained from a 5 kVA prototype.

Five-level hybrid converter based on a Half-Bridge/ANPC cell

This work presents a novel five-level hybrid Half-Bridge/ANPC multilevel inverter. Along with the switching states possibilities, employed modulation techniques, conduction losses analysis, and simulation results from a three-phase topology, it is presented the experimental results from a monophasic structure, operating with 1020Hz switching frequency, output frequency of 60Hz, phase output voltage of 220Vrms, output power of 2.3kW and power factor of 0.92. From the presented results, it can be noticed the reduced losses and better harmonic content.

A DCM three-phase high frequency semi-controlled rectifier feasible for low power WECS based on a permanent magnet generator

This paper proposes the use of a three-phase high frequency semi-controlled rectifier operating in the discontinuous conduction mode, feasible for small wind energy conversion systems based on permanent magnet generator. The main advantages of the topology are: simple gate drive circuits, since all active switches of the rectifier are connected to a common point; robustness, as short circuit through a leg is not possible; high efficiency due to reduced number of elements; simplicity since the DCM operation avoid feedback circuits and sensors as well as it allows open loop control. As a disadvantage, higher but acceptable THD of the generator currents results. The complete operation of the converter and theoretical analysis are presented. Additionally, a conventional single-phase PWM inverter is also employed in the grid connection. Experimental results on 1.6 kW prototype are presented and discussed.

Steady-State Analysis of a ZVS Bidirectional Isolated Three-Phase DC–DC Converter Using Dual Phase-Shift Control With Variable Duty Cycle

This study presents the steady-state analysis and experimental results on a soft-switching bidirectional isolated three-phase dc–dc converter using DPS control with variable duty cycle. The topology uses three single H-bridges in the primary side and a three-phase inverter in the secondary side. High-frequency isolation is ensured by using three single-phase transformers connected in open delta-wye configuration. The variation of both phase-shift angles between the H-bridge legs and/or primary and secondary sides allows controlling the power flow, while reduced reactive power flow is possible. The variable duty cycle is used to ensure a constant voltage bus and/or zero voltage switching operation. A detailed analysis is presented considering a model based on the fundamental components for the voltages and currents in the transformer. A comparison between the fundamental and the actual models is carried out to validate the proposed model. Experimental results on a 96xa0V/350–400xa0V, 3.5xa0kW prototype are presented and discussed to validate the proposed approach.

Low cost and high efficiency static converter for small wind systems

This work introduces an innovative low cost topology for a wind conversion system with an efficient output power control in order to meet the battery charge requirements. The project is in accord with the specifications required at IFEC 2009 (the 2009 International Future Energy Challenge, sponsored by IEEE). The proposed topology is based on a high frequency discontinuous conduction mode three-phase semi-controlled rectifier associated with buck converter. The converter is controlled by a system composed of three loops, which limit the current and the voltage to the maximum values allowed by the batteries and the voltage over the DC bus. There is also a MPPT algorithm that intends to maximize the power extracted from the turbine/generator association.

Carrier-based PWM modulation for THD and losses reduction on multilevel inverters

This paper presents an adapted carrier-based PWM modulation technique to be applied on both NPC and FC structures of multilevel inverters. The proposed modulation leads to an improved performance of the output voltage THD and also reduces the total loss dissipation across the semiconductors devices, when compared to other conventional carrier-based PWM modulation techniques, such as PSPWM and LSPWM. The effectiveness of the proposed technique is demonstrated through experimental results of a three-phase, three-level, 6kW prototype.

Modelling of nonisolated high-voltage gain boost converters using the PWM switch model

This paper presents the small-signal models for nonisolated dc–dc boost converters based on the three-state switching cell (3SSC) and voltage multiplier cells (VMCs) by using the concept of pulse-width modulation switch introduced by Vorpérian. Two possible topologies are analysed in the study using one multiplier cell (VMC = 1) and two multiplier cells (VMC = 2). The models are validated by properly comparing the theoretical curves with those obtained in simulation tests. Besides, conventional average current-mode control is implemented in practice for the topology with VMC = 2. An experimental prototype rated at 1 kW is evaluated so that it can be seen that the control system is stable and the dynamic response of the converter is satisfactory.