A reflux power optimization method suitable for modular multilevel DC transformers

Abstract

The invention discloses a reflux power optimization method suitable for a modular multi-level DC transformer, wherein an MMC bridge arm and an H bridge form an MMC-H bridge type DC transformer, an MMCside is set to be a nearest level modulation strategy, the H bridge adopts an extended phase-shifting modulation with internal phase-shifting, and analyzes the operation characteristics of the DC transformer; According to MMC-H bridge type DC transformer topology and operation characteristics, transmission power expressions of the DC transformer based on the nearest approximation modulation strategy and extended phase-shift control are derived. For the derived power expression, the distribution of power with parameters is analyzed, the factors affecting the return power are summarized, and the optimal configuration of voltage regulation ratio, the boundary conditions of scouring zero return power and the optimal working interval of return power and the region of zero return power are discussed. By adjusting the internal and external phase shifting, DC transformer can work in the optimal working range of reflux power to reduce the reflux power and current stress. This method can reducethe reflux power and current stress.

Description

technical field [0001] The invention belongs to the field of modularized multilevel converters and direct current conversion, in particular to a modularized multilevel MMC direct current transformer. Background technique [0002] The extensive application of renewable energy power generation such as photovoltaics and wind power has become an important measure to achieve sustainable development and address climate change around the world. In 2017, the new installed capacity of wind power in my country reached 15.03 million kilowatts, and the cumulative installed capacity of wind power in the country was 164 million kilowatts. In 2017, the cumulative installed capacity of photovoltaic power generation in my country was 130 million kilowatts, and the annual power generation was about 305.7 billion kwh. The proportion of new energy power generation in total power generation continues to increase. [0003] Renewable energy power generation has the characteristics of random fluc...

AI Technical Summary

Problems solved by technology

However, the current control strategy of this topology is to use multiple or all sub-modules to be turned on at the same time, and the operating frequency is high, which is easy to generate a large dv / dt, which affects the stability of the circuit

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