A General-Purpose Microprocessor-Based Control Circuit for a Three-Phase Controlled Rectifier Bridge

A novel general-purpose microprocessor-based control circuit for a three-phase controlled rectifier is presented. The performance exhibited by the controller is superior to previously presented circuits. The firing angle is smoothly controlled in the range of 0 to 180/s=deg/ with a fast response and a constant open loop gain, even for the cases where the converter is fed by a weak ac system of unregulated frequency. The synchronization between the line and VCO is implemented by an efficient software-controlled PLL. The effect of source impedance in delaying the synchronization signal has been properly compensated for by the-control circuit. The implementation of the compensation circuit is also presented. The hardware and software control circuit implementation built around an 8086 microprocessor is discussed, and the experimental results are given.