Novel transformer active filters
Novel transformer active filters are proposed to obtain high attenuation of voltage or current ripple without deteriorating the transient response of the system considered. Experimental results show that the scheme gives good steady-state performance of the power supply. >
Utility Friendly Magnet-Load Power Supply
In order to meet the input and output requirements of an ac-dc converter used for magnet loads, a single-phase two-stage cascade switch-mode rectifier topology for a magnet load power supply is proposed. The first stage is a single switch boost rectifier to shape the input current in phase with the supply voltage. Second stage consists of a dc chopper, which satisfies the steady state and dynamic requirements of such kind of power supply. Judicious use of feedback and feedforward loops enhances the steady state and dynamic performance of the second stage. Novel circuit topology reduces the overall component count, system cost and offers a simple control
Performance Analysis of a Novel Microprocessor-Based Controller for a Phase-Controlled Rectifier Connected to a Weak AC System
The performance analysis of a novel fast-response micro-processor-based firing and control scheme for a phase-controlled rectifier is presented. Controller performance and stability analysis are emphasized, particularly when the converter operates in a closed loop fed by a weak ac system. The firing angle control scheme, which relies on real-time projection of the firing delay angle, has been implemented and tested. In this implementation the controller responds within 20¿s its to a change in the desired output voltage. The controller is synchronized to the line through a software phase-locked loop (PLL), which adapts to large variations in the line frequency. With this controller the bridge rectifier can operate properly, with a constant steady-state open-loop gain, even when a weak ac system with unregulated frequency feeds the converter. The operation and performance of the microprocessor-based converter with a current feedback loop are described. Two simple stability analyses, one based on system function simplification and the other based on exact system representation, are discussed and experimentally verified. The generation of subharmonics caused by the line inductance and the reference zero-crossing detection circuit is also studied. Experimental results are reported.