Robinson F. de Camargo

Space vector modulation for voltage-source inverters: a unified approach

This paper presents a unified approach of the space vector modulation for voltage-source inverters. To demonstrate the proposed unified approach, five fundamental inverters topologies are analyzed: single-phase full-bridge, three-phase three-wire, three-phase four-wire, three-phase four-leg and three-phase three-level inverters. Switching vectors, separation and boundary planes in the inverter output space as well as decomposition matrices and possible switching sequences are derived for each one of these inverters. Experimental results are shown to validate the proposed unified approach.

Kalman Filter Based Synchronization Methods

This paper proposes single and three-phase synchronization methods based on the optimum filtering theory. The proposed methods incorporate, explicitly, in the problem formulation the presence of harmonics, voltage unbalance, measurement noise, transients and frequency variation, which can degrade the performance of many synchronization methods. The solution is based on the Kalman filter. Experimental results using a DSP TMS320F2812 are presented to show the performance of the proposed schemes.

Advances in the modeling and control of micro hydro power stations with induction generators

The interest in technologies related to microgeneration has increased over the last decade. Hydro, wind and solar power represent some of the technologies which had significant improvement. Among these technologies, micro hydro power stations with self-excited induction generators (IG) became an excellent choice for limited power generation in isolated areas, due basically to its robustness and low cost, compared to synchronous machine. This paper describes the controllers for micro hydro power stations for island operation based on nonlinear model of hydraulic turbine with a self-excited induction generators. Frequency control is obtained by a speed governor applied to the turbine feed system while constant voltage control is reached through reactive power control using a voltage source inverter (VSI). In order to reach effective frequency control, it is proposed the use of a motor flux estimation algorithm to obtain the measurement of instantaneous rotor speed without using a mechanical sensor applied on his shaft resulting in inherent cost reduction. Simulation results are given and they illustrate the transient behavior due step changes in load and frequency reference setting point.

Control of micro hydro power stations using nonlinear model of hydraulic turbine applied on microgrid systems

Over the last few years the interest in microgeneration has increased once it represents the nearest solution for the current problems faced in electricity generation filed. Among different technologies available in microsources field, micro hydro power stations with induction generators (IG) represent one interesting choice, mainly considering its application in isolated areas or connected to the grid. This paper presents an approach to full modeling and control of micro hydro power stations based on the nonlinear model of hydraulic turbine applied on induction generators. Constant frequency control is obtained by a speed governor applied to the turbine feed system while constant voltage control is reached through reactive power control using a voltage source inverter (VSI) connected in parallel to the grid. The proposed system is as well able to connect to the main utility grid being the synchronism previously established. Simulation results considering step changes in load and frequency reference setting have been considered. Grid connection and disconnection is as well established. Experimental results related to reactive power control and voltage regulation are presented and have shown satisfactory dynamic performance.

Hybrid method for control of voltage regulation applied in micro hydro power station

This paper deals with the development of a hybrid method of control for voltage regulation in micro hydro power station using self-excited induction generation. The proposed method performs the voltage regulation with the use of capacitor banks plus static VAR compensator. A considerable literature review was undertaken to identify the key control systems for voltage regulation applied to self-excited induction generator. A control algorithm and a project for the variable capacitors are proposed based on the resolution of normative procedures of Electricity Distribution in the National Electric System. Simulation and experimental results are presented to demonstrate the performance of the proposed hybrid method for the voltage regulation of the self-excited induction generator during variations of different types of load. Moreover, experimental results concerning the analysis of reactive power processed by the static VAR compensator during its operation in the hybrid method are obtained. These results are compared with the results obtained through the method that uses only the static VAR compensator, where the hybrid method has advantages in terms of reduction of the size of the static VAR compensator.

Estruturas de sincronismo monofásica e trifásica baseadas no filtro de Kalman

This paper proposes single-phase and three-phase synchronization methods based on the optimum filtering theory. The Kalman filter is used for the generation of the synchronization signals. The proposed methods incorporate, explicitly, in the problem formulation the presence of harmonics, voltage unbalance, measurement noise, transients and frequency deviation. These perturbations degrade the performance of many synchronization structures presented in literature. The formulation presented here makes the synchronization signals be less sensitive to these perturbations. It is also shown that the proposed methods can be helpfull to provide information about amplitude, instantaneous phase and frequency of the grid voltages, that can be usefull for purposes of power quality analysis. Furthermore, the Kalman filter provides a way to obtain a good compromise between transient response and measurement noise rejection for the synchronization signals. Experimental results using a DSP TMS320F2812 are presented to show the performance of the proposed schemes.

Modulação space vector para inversores alimentados em tensão: uma abordagem unificada

This paper presents a unified approach of the space vector modulation for voltage-source inverters. To demonstrate the proposed unified approach, five fundamental inverters topologies are analyzed, that are: single-phase full-bridge; three-phase three-wire; three-phase four-wire, three-phase four-leg and three-phase three-level inverters. Switching vectors, separation and boundary planes in the inverter output space as well as decomposition matrices and possible switching sequences are derived for each one of these inverters. Experimental results are shown to validate the proposed approach.

Impacto de métodos de sincronismo no desmpenho de geradores de indução auto-excitados

This paper analyzes digital sensorless control systems used to regulate the output voltages of a self-excited squirrel-cage induction generator. Different mechanical sensorless synchronization methods are evaluated and their performances are compared under several load conditions, including unbalanced and nonlinear loads. Simulation and experimental results are included to demonstrate the impact of distinct digital control systems on the output voltages distortion and the unbalance factor.

Closed loop selective harmonic elimination applied to a grid connected PWM converter with LCL filter

This paper presents the development and design of a control strategy applied to a three-phase grid connected PWM converter with Selective Harmonic Elimination (SHE). First, the transcendental equations of SHE are solved offline and then stored in a look-up table inside of the SHE-Modulator, which is implemented using a FPGA. Synchronism with the grid is obtained using a modified Digital PLL which includes the Modulator with SHE. A discrete model is obtained in dq synchronous frame for the converter with LCL-filter with passive damping and dq PI controllers are used to provide zero steady-state error of grid current. Finally, simulation results are presented to validate the proposed approach.

Frequency and voltage control of micro hydro power stations based on hydraulic turbine's linear model applied on induction generators

This paper presents an approach to full modeling and control of micro hydro power stations using linear model of hydraulic turbine applied on induction generators. Constant frequency control is obtained by a speed governor applied in turbine feed system while constant voltage control is reached through reactive power control by a voltage-source inverter (VSI). In order to reach effective frequency control it is proposed the use of motor flux estimation algorithm to obtain the measurement of instantaneous rotor speed without the necessity of mechanical sensor applied on his shaft, resulting in inherent cost reduction. Simulation results, considering step changes in load and frequency reference setting, have been considered. Experimental results related to reactive power control and voltage regulation are presented and have shown satisfactory dynamic performance.