Edison Roberto Cabral da Silva

Sensitive load voltage compensation with a suitable control method

This work proposes the usage of a repetitive-based control to dynamically restore the voltage applied to grid sensitive loads. The control is able to wipe off harmonic distortion and relies on simple transfer function. As a consequence, there is no need to apply harmonic selective filters. Moreover, the filter is able to work on sinusoid references and avoids employment of the dq transform. The design of the control parameters along with the system stability are discussed. A Simulink-based simulation has been built to verify the designed control performance. The experimental results are extracted from a setup of three-phase compensator which copes correctly with different scenarios of sagged and harmonic distorted voltages.

Dual input dual output single switch DC-DC converter for renewable energy applications

Normally, a photovoltaic energy generation system is composed of dc-dc converter, dc-ac converter, and their corresponding control circuits. This paper presents a two-input two-output single switch dc-dc converter with a reduced number of switches, drivers and controllers. The proposed converter performs independent energy flux control for each dc input while producing two symmetrical, automatically balanced, output voltages. A very simple MPPT technique, based on fractional voltage control technique, is employed to confirm the performance of proposal. Simulation and experimental results verify the proposed scheme feasibility.

A stationary stator reference frame control of DFIG under unbalanced voltage conditions

In this paper a control strategy of a wind turbine based on Doubly-Fed Induction Generator (DFIG) supply with unbalanced grid voltage is presented. In the proposed control strategy, the rotor side converter (RSC) is able to keep sinusoidal stator and rotor currents and also remove the pulsations in either stator active power or stator reactive power (this case eliminates the oscillation in electromagnetic torque). Unlike the other reported techniques, rotor currents scheme has been implemented in the stationary stator reference frame. These currents are regulated by a synchronous controller (similar to resonant type) without any positive or negative component decomposition. Simulation results are presented.

A hybrid two-four leg H-bridge inverter

This paper proposes a 5-level single-phase multilevel inverter topology with reduced number of components. In order to validate the proposed structure, simulation and experimental results are presented. In addition, the proposed topology is compared with an existing counterpart structure in terms of number of levels and number of devices and value of power supply.

Single-phase to three-phase generation system based on doubly-fed induction generator

This paper presents a single-phase to three-phase ac-dc-ac converter for a wind energy conversion system based on Doubly-Fed Induction Generator (DFIG). The ac-dc-ac converter has six-leg and is composed of three converters. The grid-side converter (GSC), which is responsible for power factor and dc-link voltage controls, the stator-side converter (SSC), which guarantees the control of the stator voltage, and the rotor-side converter (RSC), which is responsible for vector control of the generator. The GSC and SSC use an ac-dc-ac three-leg converter with a shared leg. The model system, pulse-width modulation (PWM) and control strategies are presented. Finally, simulation and experimental results are presented.

Wind energy conversion system based on DFIG with series grid side converter without transformer

In this paper a Wind Energy Conversion System based on Doubly Fed Induction Generator (DFIG) with an additional Series Grid Side Converter (SGSC) without transformer is proposed. Unbalanced stator voltages may be compensated by SGSC, thus eliminating unbalanced stator and rotor currents, active and reactive power oscillations, and shaft torque oscillations. Moreover, the control strategy of the proposed system keeps sinusoidal grid currents with a high power factor even during voltage sags. Simulation and experimental results are presented to evaluate the proposed system.

Dual input single switch DC-DC converter for renewable energy applications

Among the available renewable energy sources, the photovoltaic (PV) one is a fast growing market all over the world. Such renewable energy generation system is normally composed of dc-dc and dc-ac converters and correlated control circuits. Also, for medium and high power PV systems optimal operation, it is interesting to employ a decentralized maximum power point tracking (MPPT) control instead of a centralized one. This paper presents a two-input single switch dc-dc converter controlled by a single switch. The proposed converter performs independent energy flux control for each dc input while minimizing the number of switches and drivers. Maximum power point tracking technique is employed in order to confirm the performance of the proposed converter when applied to photovoltaic systems. Simulation and experimental results verify the proposed scheme feasibility.Among the available renewable energy sources, the photovoltaic (PV) one is a fast growing market all over the world. Such renewable energy generation system is normally composed of dc-dc and dc-ac converters and correlated control circuits. Also, for medium and high power PV systems optimal operation, it is interesting to employ a decentralized maximum power point tracking (MPPT) control instead of a centralized one. This paper presents a two-input single switch dc-dc converter controlled by a single switch. The proposed converter performs independent energy flux control for each dc input while minimizing the number of switches and drivers. Maximum power point tracking technique is employed in order to confirm the performance of the proposed converter when applied to photovoltaic systems. Simulation and experimental results verify the proposed scheme feasibility.

Voltage quality enhancement with minimum power injection

This work proposes the usage of a repetitive-based control to dynamically restore the voltage applied to sensitive and critical loads of power systems. Besides, sag and voltage swells, the proposed control can intrinsically mitigate harmonic distortions. Furthermore, the filter is able to work out on sinusoid references and, thus, avoids the need of employing the dq transform. A recursive least-squares is also included to the control system in order to assure the synchronization of the injected voltages to be restored. The design of the control parameters along with the system stability are discussed throughout the paper. Also, this work aims to analyze two different types of voltage insertion into the grid through the series compensator. In the first one, the voltage injection is in synchronization with the pre-faulted grid voltage, while the second injects the voltage in a manner that the compensator spends a minimum of active power. Both types produce reference voltages that are used by the repetitive control. Additionally, simulated and experimental results are presented and corroborate the method efficacy.

An APF-OCC Strategy for Common-Mode Current Rejection

This paper proposes a DSP-based one-cycle control (OCC) strategy for a shunt active power filter (APF), which is able to reject common-mode currents caused by common-mode voltages. The proposed strategy is based on an OCC rectifier control, which utilizes an input resistance control to set up dc-link voltage and achieve a unity power factor as well as a lead-lag compensator to average phase current. In this sense, the proposed APF strategy employs input resistance to control the power factor, while a lead-lag compensator is used to filter harmonics in phase current. Simulation and experimental results confirm the presented proposal.

Fault tolerant Active Neutral Point Clamped inverter: Short-circuit and open-circuit failures

This paper investigates the fault-tolerant capacity of a modified three-level Active Neutral Point Clamped (ANPC) inverter when its switches are submitted to open and short-circuit failures. The main change consists on adding a thyristor in parallel with each inverter switch. This improves the behavior of the converter when a switch fails. Fault detection and identification methods are presented together with configured schemes for ten types of failures. Simulation and experimental results validate the theoretical studies.