Sensorless PMSM Drive with LC Filter Using Adaptive Observer
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Solution Overview
Problem
Existing PMSM drives equipped with an LC filter face challenges in determining rotor speed and position without additional sensors, as they require measurements from the motor side, which can be complicated by the filter dynamics, especially at low speeds and in high-speed applications.
Innovation Solution
The method employs an adaptive full-order observer combined with pulsating high-frequency signal injection, allowing for accurate determination of rotor speed and position without additional measurements, using only the voltage of the intermediate circuit and output current of the inverter, thus eliminating the need for mechanical sensors and additional wiring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an LC filter is added to the inverter output, then the output voltage becomes nearly sinusoidal and voltage stresses are reduced, but the filter dynamics complicate the determination of motor terminal quantities for vector control
Solution Approach 1:
An adaptive full-order observer is introduced as an intermediary system that estimates the motor terminal quantities (voltages and currents) based on inverter output measurements and the known filter parameters. This observer acts as a mediator between the filtered inverter output and the vector control algorithm, providing the necessary motor terminal quantities without requiring direct measurements at the motor terminals.
Solution Approach 2:
The patent replaces mechanical measurement systems (voltage and current sensors at the motor terminals) with an electronic estimation system (adaptive full-order observer). This substitution uses mathematical models and signal processing to estimate the motor terminal quantities, thereby simplifying the hardware configuration while maintaining control accuracy.
2Measurement precision
If additional voltage or current sensors are installed on the motor side to measure terminal quantities, then accurate vector control is achieved, but hardware modifications and additional wiring are required
Solution Approach 1:
The adaptive full-order observer serves as an intermediary that computes motor terminal quantities from available inverter output measurements. This eliminates the need for additional physical sensors on the motor side, as the observer mathematically reconstructs the terminal quantities based on the known system model and measured inverter outputs.
Solution Approach 2:
Instead of directly measuring motor terminal quantities with additional sensors, the system creates a computational copy (estimate) of these quantities using the adaptive observer. This virtual copy is sufficiently accurate for vector control purposes and avoids all hardware modifications associated with physical sensing.
3Device complexity
If sensorless control is implemented in PMSM drives with LC filters, then mechanical sensors are eliminated, but accurate determination of rotor speed and position becomes challenging due to filter dynamics
Solution Approach 1:
The adaptive full-order observer employs feedback mechanisms where the estimated motor terminal quantities are continuously compared with actual measurements, and the estimation parameters are adjusted accordingly. This feedback loop ensures accurate rotor speed and position estimation despite the presence of the LC filter dynamics.
Solution Approach 2:
The observer is designed to be adaptive, meaning its parameters can dynamically adjust to account for the filter dynamics and operating conditions. This dynamic adaptation allows the sensorless control to maintain high accuracy in rotor speed and position estimation across varying operational scenarios, effectively compensating for the filter's influence.
Data Source
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AI summary
A method and a system in connection with a speed and position sensorless permanent magnet synchronous machine equipped with an output filter (26) and driven by an inverter (29), which method comprises the steps of forming a speed-adaptive full-order observer (25) based on the dynamic model of the combination of the permanent magnet synchronous machine (PMSM) and the output filter (26), measuring the inverter output current (iA), estimating inverter output current (îA), determining the estimate for the electrical angular speed (ω̂m) using the estimated and measured inverter output currents (îA, iA) in an adaptation law, injecting a voltage signal (uc) into the inverter voltage reference (uA,ref 0) to obtain a modified voltage reference (uA, ref ), detecting an error signal (ε) from the measured inverter output current (iA), and calculating the speed correction term (ωε) used in the adaptation of the observer from the error signal (ε).