Power Converter Neutral Point Equalization for Motor Drive Fault Tolerance
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Solution Overview
Problem
Existing power converters face challenges in effectively controlling a motor when a winding failure occurs, as the neutral point of the failed inverter becomes floated, making it difficult to drive the motor efficiently in abnormal states.
Innovation Solution
A power converter design with a first and second inverter connected to opposite ends of n-phase windings, each with n legs of low-side and high-side switching elements, and a switching circuit to manage connection and disconnection between the inverters and the power supply, allowing for two-phase energization control by equalizing node potentials and using a predetermined duty ratio for switching operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a winding failure occurs and the neutral point of the failed inverter is used for energization, then motor operation can be maintained, but the neutral point becomes floated making it difficult to drive the motor
Solution Approach 1:
The patent introduces a neutral point potential equalization circuit as an intermediary mechanism. This circuit includes switching elements and resistors that actively regulate the neutral point potential of the failed inverter to match the neutral point potential of the normal inverter. By doing so, it eliminates the floating neutral point problem and enables effective two-phase energization control, thus resolving the control difficulty while maintaining motor operation continuity.
Solution Approach 2:
The patent changes the electrical parameter (potential) of the neutral point in the failed inverter from a floating state to a regulated state. By dynamically adjusting the neutral point potential to be equal to the normal inverter's neutral point potential through controlled switching operations, the system transforms an uncontrollable floating neutral point into a controllable reference point, enabling effective motor drive in abnormal conditions.
2Reliability
If two power converters are provided for one motor to achieve redundant design, then safety and continuous operation are improved, but device complexity increases
Solution Approach 1:
The patent makes the dual inverter system multi-functional by enabling it to operate in both normal three-phase mode and abnormal two-phase mode. The same hardware configuration (two inverters) serves multiple purposes: providing full three-phase power under normal conditions and providing fault-tolerant two-phase power when one inverter or winding fails. This universal design achieves redundancy and safety without requiring additional dedicated backup components, thus limiting the increase in device complexity.
3Power
If switching operations are performed on the first and second switching elements at a predetermined duty ratio, then two-phase windings can be effectively energized, but control complexity increases
Solution Approach 1:
The patent employs periodic switching operations on the first and second switching elements with a predetermined duty ratio. This periodic action creates controlled current flow through the two-phase windings, effectively energizing them despite the inverter failure. The regular, rhythmic switching pattern simplifies the control logic compared to complex adaptive control, as it uses fixed timing parameters rather than dynamic adjustment, thus achieving effective energization while limiting control complexity.
Data Source
AI summary
A power converter includes a first inverter, a second inverter, and a switching circuit including first and second switching elements. In a state in which, in the first inverter, potentials at a first node in a high side and a second node in a low side are equal to each other, and potentials at first ends of two-phase windings of n-phase windings with n being an integer of 2 or more are equal to each other, two-phase windings are energized using two legs connected to second ends of the two-phase windings of n legs of the second inverter while performing switching operations on the first and second switching elements of the switching circuit at a predetermined duty ratio.