Medium-Voltage Drive Assembly Using Series Two-Level Converters
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Solution Overview
Problem
Existing medium voltage variable speed drive (VSD) technologies face limitations in optimizing electric machine design due to high switching losses in thyristor-based semiconductors, leading to suboptimal pole number selection, reduced torque production, and increased system costs.
Innovation Solution
A medium voltage variable speed assembly is designed with a rotating electric machine optimized for specific speed and power requirements by selecting the number of poles without frequency limitations, using a power supply configuration with multiple converter arrangements connected in series, each comprising a two-level converter unit with IGBTs or MOSFETs, and splitting the stator winding into separate systems for improved torque production and reduced mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If thyristor-based semiconductors are used in medium voltage VSD, then high voltage capability is achieved, but switching losses increase and switching frequency is limited
Solution Approach 1:
The patent segments the medium voltage power conversion into multiple lower voltage converter units connected in series. Each unit operates at a voltage level suitable for modern IGBTs/MOSFETs, enabling high switching frequencies while achieving overall medium voltage output through series connection of multiple units.
Solution Approach 2:
The patent changes the voltage parameter distribution by using multiple converter units with lower individual DC link voltages (suitable for IGBTs/MOSFETs) connected in series, rather than using a single high-voltage converter. This allows operation at higher switching frequencies with modern semiconductors while achieving the required medium voltage output.
2Power
If higher number of poles is used in electric machine, then rotor volume and torque production are maximized, but mechanical bending modes limit the operation speed range
Solution Approach 1:
The patent applies dynamics by using variable speed drive with high-frequency switching converters to dynamically control the motor operating point. This allows the system to operate efficiently across a wide speed range, compensating for the speed limitations imposed by mechanical bending modes through electronic control rather than mechanical design changes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach maximizes rotor volume and torque production per volume, reduces mechanical stress during short circuits, and avoids the need for a block transformer, leading to a more efficient, cost-effective, and optimized electric machine design.
Implementation Method 1
a power supply configuration for supplying alternating current power to the electric machine 2
Data Source
AI summary
A medium voltage variable speed assembly including an electric machine, and a power supply configuration for supplying alternating current power to the electric machine. The electric machine includes a plurality of stator winding systems. The power supply configuration includes a supply converter system having a two-level direct current input and an alternating current output connected to the plurality of stator winding systems. The supply converter system includes a plurality of converter arrangements connected in series such that each of the converter arrangements includes at least one two-level converter unit having a DC link whose nominal voltage is low enough for IGBTs, MOSFETs or similar components. Characteristics of the electric machine such as a number of machine phases, a number of stator poles, a number of stator winding systems and a number of stator slots are selected in a specific way.