Capacitor-Less PMSM Drive Control for Bus Overvoltage Suppression
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Solution Overview
Problem
The use of thin-film capacitors in electrolytic capacitor-less driving systems for permanent magnet synchronous motors results in low capacitance values, leading to bus voltage overcharging during upwind starting and rapid frequency changes, which can damage driving system components.
Innovation Solution
A control method that corrects the coordinate transformation angle based on bus voltage and reference values to maintain bus voltage stability, using controllers to adjust q-axis and d-axis currents to prevent overvoltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thin-film capacitors are used in electrolytic capacitor-less driving systems, then the system structure is simplified and reliability is improved, but the capacitance value is low causing bus voltage overcharging during upwind starting and rapid frequency changes
Solution Approach 1:
The patent changes the control parameters by introducing a coordinate transformation angle correction based on bus voltage deviations. The controller adjusts the q-axis reference current according to the voltage deviation and electrical angular velocity, transforming the control strategy to actively regulate bus voltage during transient states like upwind starting and rapid frequency changes, thereby preventing overcharging without requiring high capacitance
2Device complexity
If thin-film capacitors are used in electrolytic capacitor-less driving systems, then the system structure is simplified, but bus voltage overcharging occurs during upwind starting and rapid frequency changes which can damage components
Solution Approach 1:
The patent implements a feedback control mechanism where the controller continuously monitors the bus voltage and compares it with a reference value. When voltage deviation is detected during upwind starting or rapid frequency changes, the system feeds back the voltage deviation information to adjust the coordinate transformation angle and q-axis reference current, forming a closed-loop control that actively suppresses bus voltage overcharging while maintaining the simplified capacitor-less structure
3Device complexity
If conventional control methods are used without coordinate transformation angle correction, then the control system is simple, but bus voltage stability cannot be maintained during transient operations
Solution Approach 1:
The patent introduces dynamic adjustment of the coordinate transformation angle based on real-time bus voltage conditions. During transient operations like upwind starting and rapid frequency changes, the controller dynamically corrects the angle using the voltage deviation and electrical angular velocity, making the control system adaptive to changing conditions and maintaining bus voltage stability without requiring overly complex control architecture
Data Source
AI summary
An electrolytic capacitor-less motor driving system includes a motor, a frequency converter and a controller. The controller is configured to: correct a coordinate transformation angle according to an electrical angular velocity of the motor, a bus voltage and a bus voltage reference value to obtain a corrected coordinate transformation angle, the coordinate transformation angle being an included angle between a current vector direction and a positive direction of an α axis, and the corrected coordinate transformation angle is configured to cause an included angle between the current vector direction and a positive direction of a d axis to be zero; and determine the pulse width modulation signal according to a three-phase current output by the frequency converter, a d-axis reference current, a q-axis reference current and the corrected coordinate transformation angle, and input the pulse width modulation signal to the frequency converter.