Controlling an inverter device of a high voltage DC system for supporting an AC system

摘要

A method of controlling an inverter device, a control device, an inverter device and a direct current power transmission system are provided. The direct current power transmission system is provided for connection to an AC voltage bus of an AC power system and includes the control device and the inverter device that converts between DC power and AC power. The control device receives measurements of the voltage (VAC) at the AC voltage bus and controls the inverter device to provide a constant AC voltage on the bus.

主权项

1. A method of controlling a capacitor commutated inverter device being connected to an AC voltage bus of an AC power system and converting between DC power and AC power, the inverter device including a number of converter valves in a 6-pulse valve bridge, and the method comprising:
receiving measurements of a measured AC voltage (UAC) at the AC voltage bus; applying the measured AC voltage in a proportional control branch for obtaining an AC voltage dependent control factor (αMAX—UAC) that increases or decreases a maximum limitation signal (αMAX) in order to provide a constant AC voltage; determining a commutation margin based control factor (αMAX—γ′), based on a commutation margin, as a firing angle calculated for a given commutation margin reference (γref); combining the AC voltage dependent control factor and the commutation margin based control factor through selecting the lower of the commutation margin based control factor and the AC voltage dependent control factor as the maximum limitation signal (αMAX); and controlling the inverter device to provide a constant AC voltage on the AC voltage bus based on the received measurements through:
providing the maximum limitation signal to a maximum output limitation terminal (max lim) of a DC current controller amplifier that determines a fire angle order based on a direct current control and being forced against a maximum limitation; andcontrolling the firing angle (α) of the converter valves using the fire angle order (αorder) at an output of the DC current control amplifier for generating reactive power to or absorbing reactive power from the AC voltage bus.