Sensorless PMSM Control Using Hybrid Observer Gain
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Solution Overview
Problem
Conventional sensorless control systems for permanent magnet synchronous machines face challenges in maintaining superior performance across both low and high speed regions due to insufficient voltage information at low speeds, leading to degraded performance.
Innovation Solution
A sensorless control system that includes a counter electromotive force estimation unit configured to estimate the counter electromotive force using phase current and voltage references, and a speed estimation unit to estimate angular velocity and electrical angle, employing a hybrid observer gain that switches between low-speed and high-speed configurations based on weighted values to ensure accurate estimation across all speed ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sensorless control systems are used, then system cost and volume are reduced by eliminating position sensors, but performance is degraded at low speeds due to insufficient voltage information
Solution Approach 1:
The observer gain is made dynamic by switching between high-speed and low-speed gains based on speed detection. The system detects rotor speed and selectively applies appropriate observer gains to maintain accurate counter electromotive force estimation across the entire speed range, resolving the low-speed performance degradation while preserving sensorless operation benefits
Solution Approach 2:
The system changes the observer gain parameter based on operating conditions. By detecting speed and switching between different gain values (high-speed gain and low-speed gain), the system adapts the estimation algorithm to maintain accuracy across varying speed conditions, directly addressing the low-speed estimation inaccuracy problem
2Measurement precision
If rotor speed and position detectors such as encoders or resolvers are used, then absolute position detection accuracy is improved for precise torque control, but system cost and volume increase and reliability is degraded
Solution Approach 1:
The system uses its own operational parameters (phase voltages and currents) to estimate rotor position and speed through counter electromotive force observation. This self-service approach eliminates the need for external position sensors, reducing system complexity and cost while maintaining the capability for precise torque control through accurate position estimation
Solution Approach 2:
The patent replaces mechanical position sensors (encoders or resolvers) with an electronic estimation system based on electrical measurements. By substituting the mechanical sensing system with an electronic observer-based estimation system, the patent reduces device complexity while achieving the same position detection function
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves robust performance by accurately estimating counter electromotive force and rotor position/speed at both low and high speeds, enhancing the reliability and efficiency of the control system.
Implementation Method 1
a counter electromotive force estimation unit configured to estimate a counter electromotive force of a permanent magnet synchronous machine using a phase current, which is applied from an inverter to the permanent magnet synchronous machine, and a phase voltage reference, which is applied to the inverter
Data Source
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AI summary
Disclosed is a sensorless control system for a permanent magnet synchronous machine. The sensorless control system includes a counter electromotive force estimation unit (6) configured to estimate a counter electromotive force using a phase voltage reference applied to an inverter (8) and a phase current applied from the inverter to the permanent magnet synchronous machine (9), and a speed estimation unit (5) configured to estimate an angular velocity and an electrical angle of a rotor of the permanent magnet synchronous machine, and the counter electromotive force estimation unit according to one embodiment of the present disclosure may maintain robust performance at a low speed by modifying some portion of a conventional Luenberger observer.