Abstract : This paper introduces the basic working principle and control method of a new cascade middle-voltage high-power inverter with transformer coupling. Keywords : transformer coupling; middle-voltage high-power; inverter 0 Introduction In the past 20 years, industrialized countries, especially Japan, France, and Germany, have attached great importance to the development and research of energy-saving technologies. On the one hand , they have far surpassed others in the research and application of high-performance, high-capacity AC motor drive technology; on the other hand, they have vigorously expanded the market for speed regulation technology and continuously broadened its application scope, making motor speed regulation technology a powerful industrial sector. Medium-power frequency converters are already widely available on the market and are used in high-performance systems such as electric locomotives, ship electric propulsion, steel rolling, and papermaking. In addition, the other 70% of electric motors also employ various speed-regulating and energy-saving technologies, applied in various fields, such as the drives of fans, pumps, compressors, hoists, conveyors, crushers, mills, rolling mills, textile machines, winding machines, and air conditioning units. These technologies are prevalent in metallurgy, chemical industry, power generation, machinery, building materials, petroleum, transportation, textiles, papermaking, coal, agriculture, and defense sectors, significantly reducing unit power consumption and achieving substantial improvements in product quality, output, and environmental benefits. [b][align=center]For more details, please click: A New Type of Transformer-Coupled Series Medium-Voltage High-Power Frequency Converter[/align][/b]