Modeling Method for Blocking of Modular Multilevel Converter Based on Real-time Digital Simulator

Abstract

The invention belongs to the technical field of power system operation and control, and relates to a blocking modeling method of a modular multilevel converter based on a real-time digital simulator. It includes: establishing an equivalent model of the bridge arm of the converter, including N cascaded sub-modules and a bridge arm reactance, and using two switch groups containing diodes to control the locking and unlocking of the bridge arm. The integral algorithm of the bridge arm reactor adopts the backward Euler algorithm, and the equivalent of the diode is the model of the variable resistance parallel RC damping circuit, and according to the steady-state error, transient error and error caused by the diode delay action of the equivalent model of the diode Calculate the parameters of the capacitor and resistor in the RC damper circuit. The invention effectively suppresses the numerical oscillation problem generated by the trapezoidal integral algorithm adopted by the RTDS, reduces the voltage waveform distortion caused by the delayed action of the diode caused by the fixed RTDS simulation step size and cannot use the interpolation algorithm, and ensures the blocking of the MMC converter Correctness and accuracy of state simulation.

Description

technical field [0001] The invention belongs to the technical field of power system operation and control, and relates to a blocking modeling method of a modular multilevel converter based on a real-time digital simulator. Background technique [0002] Modular Multilevel Converter (MMC) has been widely used because of its high output level, low harmonic content, and independent control of active power and reactive power. Real-Time Digital Simulator (RTDS) is a device specially used to study electromagnetic transient phenomena in power systems, and is widely used in power system simulation real-time simulation research. Users can develop the bridge arm model of MMC converter in the Cbuilder tool provided by RTDS for the simulation research of the dynamic characteristics of MMC-HVDC. The latched state of the MMC is an abnormal working state, which is used to charge the sub-module capacitor when the MMC is started, or to bypass the sub-module capacitor when the MMC is faulty. ...

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Problems solved by technology

This method usually uses R ON / R OFF Two-value resistors simulate switching elements such as diodes. Since RTDS is a real-time simulation device that cannot be calculated backwards, it can neither use the backward interpolation algorithm nor change the simulation step size during the simulation process. This method exists when simulating the MMC locked state. The following two problems: 1. Because RTDS uses the trapezoidal integral algorithm, it will cause numerical oscillation when the diode operates; 2. Since RTDS is a fixed-step simulation platform and does not provide an interpolation algorithm, the diode can only be A state change occurs at an integer multiple of a long time, resulting in a delay in the switching action of the diode, resulting in an unreal distortion of the voltage and current waveforms

For the real-time simulation of MMC, some studies have used the interpolation prediction method to compensate the error caused by the single-step delay to a certain extent, but it still cannot solve the problem of waveform distortion caused by numerical oscillation and diode switching delay in the real-time simulation of the MMC locked state. question

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