Matrix Converter AC Machine Control Eliminates Capacitors
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Solution Overview
Problem
Conventional induction motor drives and power transformers require substantial energy storage devices like large capacitors, which are bulky, unreliable, and cause inrush currents, and efficiency is reduced due to multiple conversion stages, especially at high temperatures with electronic switching devices.
Innovation Solution
An AC machine control system using matrix converters at each end of open-ended windings to transfer AC power without intermediate energy storage, eliminating common mode voltage and injecting zero sequence voltages, thereby achieving higher motor voltage capability and torque output without increasing flux or current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large storage capacitor is used to store DC power, then the motor control system can operate, but the system becomes bulky, unreliable, and causes inrush currents
Solution Approach 1:
The patent removes the large storage capacitor from the conventional AC-DC-AC conversion system. Instead of converting AC to DC and storing energy in a capacitor, the system directly converts AC power from the utility to AC power for the motor using a matrix converter, eliminating the capacitor entirely and resolving the contradiction between reliability and weight.
Solution Approach 2:
The matrix converter acts as an intermediary device that directly transforms AC power from the utility to AC power for the motor without requiring DC link capacitors. This intermediary conversion process eliminates the need for energy storage devices while maintaining system operation.
2Power
If multiple conversion stages are used (AC to DC, DC to HF AC, HF AC to DC, DC to AC), then power conversion is achieved, but efficiency is reduced
Solution Approach 1:
The matrix converter enables continuous AC to AC power conversion in a single stage, maintaining continuous useful action without the intermittent DC link charging/discharging cycles of multi-stage converters. This continuous operation reduces energy losses and improves efficiency while maintaining full power conversion capability.
Solution Approach 2:
The patent extracts and eliminates the intermediate DC conversion stages from the power conversion chain. By implementing direct AC to AC conversion through the matrix converter, the system reduces multiple conversion stages to a single stage, minimizing energy losses at each conversion interface.
3Power
If a conventional power transformer is used, then power transformation is achieved, but size and weight increase due to low operating frequency
Solution Approach 1:
The matrix converter changes the operating parameters by using high-frequency AC conversion instead of low-frequency transformer operation. This parameter change from low-frequency magnetic transformation to high-frequency electronic conversion dramatically reduces the size and weight of the power transformation device while maintaining full power capability.
4Ease of operation
If two-level inverters are used to drive open-ended induction motor, then motor control is achieved, but common mode voltage induces circulating currents
Solution Approach 1:
The matrix converter converts the harmful common mode voltage issue into a benefit by providing independent control of common mode voltages at both motor terminals. The system intentionally injects zero sequence voltages to cancel common mode voltages, transforming what was previously a harmful effect into a controllable feature that improves motor operation.
Data Source
AI summary
An AC machine control system for an AC machine (motor, generator, transformer, etc.) having open-ended windings, the control system comprising a drive circuit configured to transfer AC power between a first set of voltages and each end of the open-ended windings without the use of a substantial energy storage device, while eliminating common mode voltage and/or injecting zero sequence voltages.