Rotary Machine Rotor Position Estimation via PWM Voltage Integration
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Solution Overview
Problem
Conventional rotary machine control methods using voltage command values for rotor position estimation lead to torque and power pulsations due to estimation errors, which adversely affect mechanical and power systems.
Innovation Solution
A rotary machine control device comprising a voltage applicator, current detector, controller, pulse width modulator, voltage integrator, and position estimator, which applies a stator voltage of a rectangular waveform and uses voltage integration values to estimate the rotor position, reducing estimation errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If voltage command values are used for rotor position estimation, then the control system is simple, but torque and power pulsations occur due to estimation errors
Solution Approach 1:
The patent introduces an intermediary component (voltage integrator) that processes the voltage command values before they are used for position estimation. This intermediary transforms the voltage command values into integrated values, which serve as a more accurate basis for rotor position estimation, thereby reducing estimation errors and the resulting torque and power pulsations without significantly increasing system complexity
Solution Approach 2:
The patent changes the parameter used for position estimation from raw voltage command values to integrated voltage values. This parameter transformation improves the accuracy of rotor position estimation by accounting for the temporal accumulation of voltage effects, thereby reducing estimation errors and eliminating torque and power pulsations while maintaining relatively simple control system architecture
2Measurement precision
If high-frequency signals are applied to estimate rotor position, then position estimation accuracy is improved, but torque pulsation and noise occur
Solution Approach 1:
The patent replaces the high-frequency signal injection method with an alternative approach using integrated voltage command values for position estimation. This substitution eliminates the need for high-frequency electrical signals while achieving accurate rotor position estimation through mathematical integration of voltage commands, thereby avoiding torque pulsation and noise generation
Solution Approach 2:
The patent changes the estimation method from high-frequency signal-based measurement to integration-based calculation. By transforming the estimation parameter from instantaneous high-frequency responses to accumulated voltage effects over time, the system achieves accurate position estimation without introducing harmful torque pulsations and noise
Data Source
AI summary
A control device includes: a current detector that detects a stator current flowing between a voltage applicator and a stator winding of a rotary machine; a controller that computes a voltage command value based on the stator current and a rotor position, the voltage command value being a command value of a stator voltage applied to the stator winding; a PWM modulator that generates a gate signal such that a value obtained by smoothing the stator voltage matches the voltage command value, and to use this gate signal to control turning on and off of switching elements provided in the voltage applicator; a voltage integrator that computes a voltage integration value by integrating the gate signal; and a position estimator that estimates the rotor position based on the voltage integration value and the stator current.