S. Senthil Kumar

Major methods of steady-state analysis of three-phase SEIGs - A summary

Through an elaborate survey of the papers published so far, a summary of three major methods of performance analysis of Self-Excited Induction Generators (SEIGs) has been presented. Among the various methods, the optimization approach has been shown to be the best in handling the variation in the generator and load parameters. The comparative study presented herein would be useful for any researcher as a starting platform, for further investigations in this field of wind energy electric conversion systems.

A voltage controller in photo-voltaic system without battery storage for Stand-Alone Applications

The paper proposes the new voltage controller in photo-voltaic system for Stand-Alone Applications without battery energy storage. The output of the PV array is unregulated DC supply due to change in weather conditions. The maximum power is tracked with respect to temperature and irradiance levels by using DC-DC converter. The perturbation and observes algorithm is applied for maximum power point tracking (MPPT) purpose. This algorithm is selected due to its ability to withstand against any parameter variation and having high efficiency. The output of DC-DC converter is converted to AC voltage by using inverter. The AC output voltage and frequency are regulated. A closed loop voltage control for inverter is done by using unipolar sine wave pulse width modulation (SPWM). The regulated AC voltage is fed to AC standalone loads or grid integration. The overall system is designed, developed and validated by using MATLAB-SIMULINK. The simulation results demonstrate the effective working of MPPT algorithm and voltage controller with SPWM technique for inverter in AC standalone load applications.

A Dual DC Output Power Supply for a Stand-alone Photovoltaic System

Abstract This article presents a dual DC power output for easy integration of renewable energy sources and battery banks at a low-voltage DC bus. The low-voltage loads are connected to the low-voltage DC bus directly (across the battery banks), obviating an additional conversion stage. Such low-voltage loads are LED-based lighting, computers, laptop chargers, etc. The proposed system consists of a photovoltaic array, DC-DC converters, a maximum power point tracker, and a storage medium (battery) targeted for low-voltage (24 V) and high-voltage (110 V) DC loads. The maximum value of photovoltaic power is extracted using the buck DC-DC converter along with the effective incremental conductance maximum power point tracking technique to control the power transfer to the low-voltage DC grid. The DC-DC boost converter is designed to operate at a constant voltage of 110 V DC load. The proportional-integral-derivative control parameters for voltage mode closed-loop control of the boost converter are chosen by using the genetic algorithm technique. A prototype system has been built in the laboratory, and its satisfactory working has been demonstrated experimentally for the different shading and loading conditions; experimental results are provided.

Performance predetermination of variable speed wind-driven grid connected SEIGs

A Self Excited Induction Generator (SEIG) system has been proposed for supplying power to the grid through a combination of a three-phase semi-converter (SC) and a line commutated inverter. This system is capable of operating at variable speed to enable maximum power, proportional to the cube of the wind speed, to be extracted from the wind. The method of analysing the system has been explained by deriving the relevant expressions for the various performance quantities. The different control schemes to be adopted for the SC to suit the various speed ranges of the generator has been described with an example along with the predetermined performance characteristics of the system, following cube law power curve. The simulated waveforms of voltage and current at the various stages of the proposed system are also presented.

A simple analog voltage controller for three-phase single switch boost rectifier

A voltage controller for the operation of three-phase single switch boost rectifier is proposed using low cost op-amps. The controller automatically adjusts the pulse width of the boost rectifier to maintain a constant dc load voltage of desired level, despite the variations in the load and source voltage. Methods have been proposed for calculating the duty ratio to obtain the desired dc load voltage for given input voltage and other parameters of the boost rectifier operating in continuous conduction mode. Further, MATLAB simulations have also been carried out and the simulated waveforms are found to coincide with the theoretical calculations. The analog controller has been tested in steady-state and dynamic conditions. The experimental waveforms along with the simulated results show the working and usefulness of the low cost op-amp based voltage controller for three-phase boost rectifier applications.

Investigation of PWM current mode controllers for UPF three phase - Rectifier with split DC bus based on the Scott transformer

In this paper, the unity power factor isolated three phase rectifier based on the Scott transformer is analyzed. This topology presents a Scott transformer for galvanic isolation and uses instantaneous current control. The various current control schemes like PI control, Hysteresis control and One cycle control are tested. The use of the Scott transformer makes a split dc-bus voltage possible and the rectifier operates with unity power factor. The proposed approach draws sinusoidal input current at unity power factor and has output voltage regulation capability. Using only two active switches, the rectifier is able to generate symmetrical currents in the line and a balanced split dc-bus output voltage, which is necessary in several applications. The control technique is independent for each boost that integrates the rectifier. Therefore, it makes possible with two single-phase boosts to obtain a unity power factor three-phase rectifier. This rectifier is particularly attractive when galvanic isolation and minimum number of active switches is required. Pulse width modulation and instantaneous average current control are used. There are two voltage controls that regulate the output voltage and the split dc-bus voltage. Complete simulation results under closed loop operation are presented.