Voltage-sourced hvdc system with modulation function

Abstract

A voltage-sourced High-Voltage Direct Current (HVDC) apparatus, which converts 3-phase AC voltage from a 3-phase AC power source into high voltage DC through a rectifier including switching elements, is provided. In the apparatus, a rectifier controller receives detected 3-phase currents, apparent power, and active power and generates D and Q-axis signals. A D/Q controller receives the signals and generates active power D-axis signal and apparent power Q-axis signal. A PWM unit generates PWM on/off signals for turning on/off the switching elements based on output signals from the D/Q controller. The D/Q controller includes a rotary converter to convert the D and Q-axis signals into AC signals and D and Q-axis order units coupled thereto, and generates the D and Q-axis signals through the order units. The PWM unit converts the D and Q-axis signals into 3-phase AC signals and compares them with 3-phase triangular waves to generate on/off signals for turning on/off the switching elements.