A Modeling Method for Equivalent Simulation Calculation of Modular Multilevel Converter

Abstract

The invention relates to a high-efficiency simulation modeling method of a modular multilevel converter. The modular multilevel converter is composed of six bridge arms, each two bridge arms are connected in series to form a phase unit, and each bridge arm is composed of cascaded sub-modules and bridge arm reactance L connected in series, and the sub-modules include insulating Gate bipolar thyristors IGBT1, IGBT2, diodes D1, D2 and capacitor C, each insulated gate bipolar thyristor and a diode are connected in reverse parallel to form a switching device branch. In the present invention, the sub-module and the bridge arm of the modularized multilevel converter are equivalent to the Dommel equivalent calculation model, and the conduction state of the switch tube in the blocking stage of the modularized multilevel converter is between two simulation times The problem of inter-changes is dealt with by additional switching devices. The invention reduces the calculation amount in the simulation operation by reducing the number of variable impedance branches in the electromagnetic transient simulation calculation, and makes the simulation of the modularized multilevel converter efficient. The calculation result of the invention is stable and reliable.

Description

technical field [0001] The invention relates to a high-efficiency simulation modeling method for a modular multilevel converter, belonging to the technical field of power transmission and distribution. Background technique [0002] For the sake of sustainable development, using renewable energy such as solar energy and wind energy to generate electricity has become the development direction of the future power system. These power generation methods have the characteristics of being far away from the main grid and fluctuating greatly over time. The flexible DC transmission system is based on Voltage Source Converter (Voltage Source Converter, VSC) and Pulse Width Modulation (Pulse Width Modulation, PWM) technology to invert DC voltage into AC voltage with controllable amplitude and phase, and can be independently and quickly controlled The transmitted active power and reactive power greatly enhance the flexibility of power transmission and become the most potential power tra...

AI Technical Summary

Problems solved by technology

It has been proposed in the literature that a controllable voltage source can be used to replace the output voltage of the sub-module in the modular multilevel converter, and a controllable current source can be used to connect the sub-module circuit. However, this method does not consider the delay problem in the numerical calculation. , the value used by the controllable voltage and current source in the decoupling method is not the calculated value in the current solution step but the calculated value obtained in the previous step, which will artificially make the voltage and current of the bridge arm equivalent circuit The solution of is decoupled in time, leading to model instability under dynamics

In some literature, the modular multilevel converter is equivalent to a capacitor with controllable output voltage and current, ignoring the difference in the capacitance of each sub-module, so this model cannot be used to verify the voltage balance algorithm

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