Lucas Giuliani Scherer

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.

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.

Supervisory and control system development applied to distributed generation using Web tools

This paper proposes a system of control and data acquisition (SCADA) to be applied in a distributed generation system. This system was developed with low-cost technology and it is based in wireless communication to perform the exchange of information between generation system and SCADA. The implementation of the proposed system contributes to operation, monitoring and maintenance of systems named smart grids, allowing the management of different generation sources, such as hydro, solar, wind, and others, through conventional monitoring systems like mobile devices, employing Web tools. Experimental results are presented in order to demonstrate the applicability of the system developed.

Hybrid topology and PRD controller applied in three-phase system based on induction generator

This paper deals with a control system for voltage regulation in stand-alone generation systems based on self-excited induction generators (SEIG). It is considered a three-wire hybrid topology composed by switchable capacitor banks and distribution static compensator (DSTATCOM). While the switchable capacitor banks supply the most part of the reactive power for voltage regulation, the DSTATCOM is controlled in order to supply the difference of reactive power, balance induction generation (IG) currents and compensate harmonics of load currents. To accomplish that, it is proposed the use of proportional-resonant-derivative (PRD) controllers in association to proportional-integral (PI) controllers to control the compensation currents processed by DSTATCOM. The proposed method of voltage regulation using DSTATCOM-switchable capacitors is implemented on an IG prototype system and the test results are presented to demonstrate its performance.

Voltage regulation of stand-alone micro-generation SEIG based system under nonlinear and unbalanced load

This study deals with a control system for voltage regulation of stand-alone generation systems based on self-excited induction generators (SEIG). It is considered a four-wire hybrid topology composed by switchable capacitor banks and distribution static compensator (DSTATCOM). While the switchable capacitor banks supply the most part of the reactive power for voltage regulation, the DSTATCOM is controlled in order to supply the difference of reactive power, to balance IG currents and compensate harmonics of load currents. To accomplish that, it is proposed the use of proportional-resonant-derivative (PRD) controllers in association to proportional-integral (PI) controllers to control the compensation currents processed by DSTATCOM. The proposed method of voltage regulation using DSTATCOM-switchable capacitors is simulated in software Simulink/Matlab® and the results are presented to demonstrate its performance.

Discrete-time adaptive control applied to voltage regulation of induction generator based systems

This paper deals with the development of an adaptive control system applied to voltage regulation of a standalone distributed power generation system, fed by self-excited induction generator. The generation system considers a four wire three-phase grid, composed by three phases plus neutral conductor, fed by three-phase three wires induction generator. The neutral conductor is created from the neutral point of star connection of excitation capacitors. The four-wire configuration allows the connection of three-phase loads in star or delta configuration, as well as single-phase loads. The voltage regulation is performed through a four-legs distribution static compensator (DSTATCOM) shunt connected to the AC bus. The adaptive controller proposed offers suitable voltage regulation in conditions of systems parameters variations such as, load connection and disconnection, and changes in induction generators unmodeled parameters. The proposed generating system was simulated in MATLAB, where simulation results were obtained to show the good performance of the voltage regulation control system during the connection and disconnection of three-phase loads. Additionally, some preliminary experimental results are presented as well.

Synchronization method and frequency tracking applied on voltage converters

This paper proposes a new closed-loop synchronization method for single-phase voltage converters. It presents a good performance under highly distorted grid voltages. Moreover, it has a good performance in terms of distortions in the synchronization signals and it has a good transient performance due amplitude, frequency and angle disturbances. In addition, a frequency adaptation algorithm is proposed for applications where large frequency variations are expected, such as in weak grids. This method can be extended for three-phase systems, applied in three-phase PWM converters. Experimental results using a DSP are given to demonstrate the good performance of the proposed synchronization method.

New hybrid topology of voltage regulation applied in three-phase four-wire system based on induction generator

This paper deals with the development of a new hybrid topology for voltage regulation in micro hydro power station using self-excited induction generator applied in three-phase four-wire systems. The proposed topology is a combination of a three-phase four legs static VAR compensator (SVC) and capacitor banks connected in parallel to the AC voltage bar. It is considered a three wires generator with no accessible neutral point being the neutral terminal for the load created through the neutral terminal of the excitation capacitor and the fourth leg of SVC, which provides the choice to connect the loads either star or delta configurations. A control algorithm and a project for the variable capacitors are proposed based on the specifications of the SVC. The proposed generating system is modeled and simulated in MATLAB. Simulation results and preliminary experimental results are presented to demonstrate the performance of the proposed new hybrid method for the voltage regulation of the self-excited induction generator. In the sequence, simulation results are presented in order to demonstrate the capability of the proposed system for feeding three-phase and single-phase balanced and unbalanced loads, with no distortion of the generated voltages.