Power Converter Flywheel Duration Control
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Solution Overview
Problem
Existing power converters for electric rotating machines face challenges in maintaining reliable operation during transient states or unexpected changes, such as aged deterioration or temperature changes, leading to shifts in off-time and increased losses in rectification or backflow of current.
Innovation Solution
A power converter design with a switching circuit and controller that sets a constant current freewheeling duration by controlling the off-operation of upper and lower arms, eliminating the need for sensors to measure angular position and current, thereby reducing production costs and losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the off-time of MOS transistor is set based on on-time and electrical angle in feedforward mode, then the control is simple, but the off-time shifts during transient states or unexpected changes resulting in increased rectification loss or current backflow
Solution Approach 1:
The patent employs feedback control by detecting the actual off-time of the MOS transistor and comparing it with the target off-time. The controller adjusts the switching timing based on the detected deviation, ensuring accurate current freewheeling duration even during transient states or unexpected changes. This closed-loop feedback mechanism resolves the contradiction by maintaining reliability without significantly increasing system complexity.
Solution Approach 2:
The patent replaces sensor-based mechanical measurement systems with an electrical detection method. Instead of using angular position sensors and current sensors to determine off-time, the system uses electrical signal detection of the MOS transistor's switching state and voltage/current relationships to calculate and control the off-time. This substitution eliminates the need for additional sensors while maintaining control accuracy during transient conditions.
2Object-generated harmful factors
If the off-time is advanced to prevent current backflow, then current backflow is reduced, but rectification loss increases
Solution Approach 1:
The feedback control mechanism continuously monitors the actual off-time and adjusts the switching timing to achieve the precise target off-time. This ensures that the current freewheeling duration is optimized to prevent current backflow while avoiding excessive advancement that would cause increased rectification loss. The feedback loop dynamically balances these two opposing effects.
Solution Approach 2:
The patent dynamically adjusts the off-time parameter based on operating conditions such as electrical angle, speed, and load variations. By changing the off-time parameter adaptively rather than using a fixed value, the system optimizes the balance between preventing current backflow and minimizing rectification loss under different operating conditions.
3Loss of energy
If the off-time is delayed to reduce rectification loss, then rectification loss is reduced, but current backflow from power supply to windings occurs
Solution Approach 1:
The feedback control system detects when the off-time is insufficient to prevent current backflow and immediately adjusts the switching timing to extend the current freewheeling duration. This real-time adjustment ensures that the system maintains the minimum required off-time to prevent current backflow while minimizing rectification loss.
4Measurement precision
If sensors are used to measure angular position and current for accurate off-time control, then control precision is improved, but production cost increases
Solution Approach 1:
The patent replaces physical sensors (angular position sensors and current sensors) with an electrical detection system that uses voltage and current relationship analysis. The controller calculates the off-time based on electrical signal characteristics rather than direct sensor measurements, achieving accurate control without the cost and complexity of additional sensors.
Solution Approach 2:
The system uses its own existing electrical signals and components to determine the off-time. By analyzing the voltage and current relationships within the existing power converter circuitry, the system self-determines the appropriate switching timing without requiring external measurement devices, thereby reducing production costs while maintaining control precision.
Data Source
AI summary
A power converter for an electric rotating machine is provided which is designed to ensure a desired length of a current flywheel duration in which current is permitted to freewheel from the electric rotating machine even if the power converter is in a transient state or subjected to an unexpected change. The power converter is equipped with a controller and a switching circuit which is disposed between a power supply and windings of the electric rotating machine. The switching circuit has switches grouped into an upper and a lower arm. The controller works to control an off-operation of one of the switches of one of the upper and lower arm so as to produce a desired length of the current flywheel duration following turning off of the one of the switches, thereby minimizing a loss of rectification and avoiding the backflow of current from the power supply to the windings.