Multi-Inverter Motor Control for Common Capacitor Ripple Suppression
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Solution Overview
Problem
Existing control systems for rotating electric machines with multiple power conversion circuits and a common capacitor face malfunctions due to unadjusted output periods of voltage vectors, leading to increased ripple current in the capacitor, especially when torque and rotation speed differences occur between the machines.
Innovation Solution
A control apparatus that adjusts the output modes of voltage vectors to rotating electric machines and performs switching operations to output these adjusted vectors, using a combination of 60-degree and 120-degree voltage vectors to synchronize and adjust the output periods, thereby reducing the ripple current in the capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the output periods of voltage vectors are not adjusted, then the control system is simple, but the ripple current in the capacitor increases causing malfunctions
Solution Approach 1:
The control apparatus dynamically adjusts the output periods of voltage vectors based on the operating conditions of the rotating electric machines. When torque and rotation speed differences occur between machines, the control apparatus modifies the voltage vector output periods to maintain system reliability and prevent capacitor malfunction, making the control system adaptive rather than static.
Solution Approach 2:
The control apparatus monitors the operating states of multiple rotating electric machines and uses this feedback information to adjust the voltage vector output periods. By detecting torque and rotation speed differences, the system implements closed-loop control to maintain optimal operation and prevent ripple current-induced malfunctions.
2Object-generated harmful factors
If the output periods of voltage vectors are adjusted to synchronize, then the ripple current in the capacitor is reduced, but the control process becomes more complex
Solution Approach 1:
The control apparatus applies periodic adjustment to the voltage vector output periods, synchronizing them to reduce ripple current in the capacitor. By implementing regular, rhythmic adjustments to the voltage vector timing, the system eliminates harmful current fluctuations while maintaining manageable control complexity through standardized periodic control cycles.
3Adaptability or versatility
If torque and rotation speed differences occur between machines, then the adaptability of the control system improves, but the ripple current increases causing malfunctions
Solution Approach 1:
The control apparatus dynamically adjusts the voltage vector output periods in response to varying torque and rotation speed conditions across multiple machines. This dynamic adaptation maintains system reliability by preventing ripple current-induced capacitor malfunctions while accommodating the full range of operational variations, achieving both adaptability and reliability simultaneously.
Data Source
AI summary
A control apparatus of a rotating electric machine is applicable to a control system that includes: a plurality of power conversion circuits that convert direct-current power from a direct-current power supply to alternating-current power and output the alternating-current power by switching operations; rotating electric machines that are provided in correspondence to the power conversion circuits and supplied with the alternating-current power outputted from the power conversion circuits; and a capacitor that is connected in parallel to the direct-current power supply, provided on an input side of the power conversion circuits, and common to the power conversion circuits. The control apparatus includes: an adjusting unit that performs an adjustment process in which output modes of voltage vectors to the rotating electric machines are adjusted and an operating unit that performs the switching operations of the power conversion circuits to output the voltage vectors adjusted by the adjusting unit.