Souvik Chattopadhyay

Digital implementation of a line current shaping algorithm for three phase high power factor boost rectifier without input voltage sensing

In this paper the implementation of a simple yet high performance digital current mode controller that achieves high power factor operation for three phase boost rectifier is described. The indicated objective is achieved without input voltage sensing and without transformation of the control variables into rotating reference frame. The controller uses the concept of resistance emulation for shaping of input current like input voltage in digital implementation. Two decoupled fixed frequency current mode controllers calculate the switching instants for equivalent single phase boost rectifiers. A combined switching strategy is developed in the form of space vectors to simultaneously satisfy the timing requirements of both the current mode controllers in a switching period. Conventional phase locked loop (PLL) is not required as converter switching is self-synchronized with the input voltage. Analytical formula is derived to obtain the steady state stability condition of the converter. A linear, low frequency, small signal model of the three phase boost rectifier is developed and verified by measurement of the voltage control transfer function. In implementation Texas Instrumentss DSP TMS320F240F is used as the digital controller. The algorithm is tested on a 10-kW, 700-V dc, three phase boost rectifier.

A single reset integrator based implementation of line current shaping controller for high power factor operation of flyback rectifier

The objective of this paper is to present a simple yet accurate implementation of a resistor emulator type line current shaping controller for high power factor operation of a flyback rectifier. The important feature is input voltage sensing is not required. In circuit realization of the controller no multiplier is used. Current shaping is performed directly on the input filter inductor current. The modulator uses only one reset integrator for the generation of duty ratio. The analysis presented in this paper shows the effect of input filter capacitance on discontinuous conduction mode (DCM) of operation of the flyback inductor. Design equations for selection of the input filter components are derived. A low frequency small signal model of the rectifier is developed and verified by measurement up to 1 kHz. The performance of the controller is first tested by SABER circuit simulator package. Then a 100 W, 110 V AC input, 50 V DC output, single phase flyback rectifier prototype is built for experimental verification.

A predictive switching modulator for current mode control of high power factor boost rectifier

In this paper, a new variation of current mode control for a high power factor boost rectifier is presented. The general features are: no input voltage sensing; no use of multiplier; and no inner current regulator. It therefore follows the same control structure as that of linear peak current mode control (LPCM) and nonlinear carrier control (NLC). However it implements a different equation for the modulator that extends the range of continuous conduction mode (CCM) of operation. The controller is predictive as the actual current equals the reference current at the end of each switch period.

Phase angle balance control for harmonic filtering of a three phase shunt active filter system

This paper proposes a new strategy for harmonic filtering of a three-phase shunt active filter system. The shunt harmonic filters control objective is defined as: balance the phase angle of the input current with the phase angle of the line frequency component of the load current. This objective is achieved in discreet implementation without sensing the input voltages. The controller uses a phase shifting method on the sensed input current and then applies the resistor emulator type input current shaping strategy on the phase-shifted current. In implementation Texas Instruments DSP based unit TMS320F240 EVM is used as the digital hardware platform. The control algorithm is computationally simple yet the harmonic filtering performance is high. The analysis, simulation and experimental results of a three-phase shunt active filter prototype on a 25A nonlinear load are presented.

Impedance emulation method for a single phase shunt active filter

A new strategy for harmonic elimination for single phase shunt active filter system is proposed in this paper. The control objective of the filter is defined as: shift the phase angle of the input current with the phase angle of the fundamental load current component. For discreet implementation the objective can be obtained without sensing the input voltage. The controller on the sensed input currents applies phase shifting method and a resistor emulator type input current shaping strategy is applied on the phase shifted current. The proposed control algorithm is computationally simple furthermore effective in filtering the harmonic currents. The simulation results for various kinds of nonlinear loads are presented in this paper.

A voltage sensorless control method to balance the input current of the boost rectifier under unbalanced input voltage condition

This paper proposes a control method that can balance the input current of the three phase, three wire, boost rectifier under unbalanced input voltage condition. The control objective is to operate the rectifier in the high power factor mode under normal operating condition but to give overriding priority to the current balance function in case of unbalance in the input voltages. The inner loop implements resistor emulator type input current shaping strategy. The outer control loop performs magnitude scaling and phase shifting operations on current of one axis to make it balanced with respect to the current on the other axis. The coefficients of scaling and shifting functions are determined by two closed loop PI controllers. The control method is input voltage sensorless. In implementation Texas Instruments DSP TMS320F240F is used as the digital controller.