DSP Based Controller for Unity Power Factor Front-End PWM Regenerative Converter

Abstract

Solid state ac-dc conversion of electric power is widely used in adjustable-speed drives, switch-mode power supplies, uninterrupted power supplies, and utility interface with non conventional energy sources such as solar PV, etc., battery energy storage systems, in process technology such as electroplating, welding units, etc., battery charging for electric vehicles, and power supplies for telecommunication systems, measurement and test equipments. Conventionally, ac-dc converters, which are also called rectifiers, are developed using diodes and thyristors to provide controlled and uncontrolled dc power with unidirectional and bidirectional power flow. They have the demerits of poor power quality in terms of injected current harmonics, caused voltage distortion and poor power factor at input ac mains and slow varying rippled dc output at load end, low efficiency and large size of ac and dc filters. In light of their increased applications, a new breed of rectifiers has been developed using new solid state self commutating devices such as MOSFETs, insulated gate bipolar transistors, gate turn-off thyristors. The report of major project is based on the performance comparison of single phase diode bridge rectifier and the proposed front-end converter in terms of the Total harmonic distortion (% THD) of the line current, power factor of the system and ability of energy saving of the converter by reverse power flow action. The parameters of the voltage control loop for proposed converter are derived by two methods named Unity Modulus (Magnitude Optimum) Method and Ziegler-Nichols method. The parameters obtained from both the methods are compared by the mathematical model for forward and reverse power flow mode of operation. The model is generated in simulink (MATLAB) and results are obtained for steady state, transient and dynamic conditions. It is observed that the unity power factor is maintained during all the conditions for various loads. Drastic reduction in %THD of input current waveform is obtained in proposed front-end converter with an added advantage of regenerative capability. For comparison of control loops results a programming file is also generated in MATLAB (M-file) and from the same step response and Nyquist plots are obtained for system control loops. The fabrication of IGBT based gate driver circuit and dead band circuit is performed. The gate driver circuit results are obtained after the fabrication of the PCB. The results are obtained for the normal working condition and also for the fault condition. The obtained results show the required performance of the gate driver circuit and the dead band circuit. To understand the circuit in proper manner all the components are tested and the results for the same are obtained as per requirement. The PWM signals for the prototype front-end converter are generated with the help of the MICRO-2407 DSP trainer kit. The results for the generated signal show the PWM signals as per the requirement for the both converters.