Dual Inverter Driving Device for Rotating Electric Machine
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Solution Overview
Problem
Existing driving devices for rotating electric machines face a trade-off between conduction losses and switching losses, with high-frequency switching in inverters leading to increased conduction losses due to the need for switching elements with small gate input capacitance and high switching speed.
Innovation Solution
A driving device configuration with two inverter units, where the first inverter unit operates at a higher switching frequency using switching elements with higher switching speed and lower ON resistance, and the second inverter unit operates at a lower switching frequency using switching elements with lower ON resistance, reducing conduction losses while minimizing switching loss increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high-frequency switching is performed in both inverter units, then AC voltage application to motor generator is achieved, but conduction losses increase significantly
Solution Approach 1:
The patent implements alternating periodic operation between the first and second inverter units. The first inverter unit operates during one half cycle of the motor generator's fundamental frequency, while the second inverter unit operates during the other half cycle. This periodic alternation allows the system to maintain high-frequency switching capability when needed while reducing overall conduction losses by utilizing the second inverter unit's low ON resistance elements during current conduction phases.
Data Source
AI summary
In a driving device for a rotating electric machine, a first inverter unit blocks and allows, for each winding of multi-phase windings of the rotating electric machine, current conduction on one side of the winding and a second inverter unit blocks and allows current conduction on the other side of the winding. A plurality of second switching elements forming the second inverter unit each have a lower ON resistance than a plurality of first switching elements forming the first inverter unit. A controller is configured to switch on and off the respective first switching elements at a switching frequency higher than an electric fundamental frequency and switch on and off the respective second switching elements at a switching frequency lower than the switching frequency at which to switch on and off the first switching elements.