Sensorless PMSM Controller for Battery-Limited Start-Up Acceleration
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Solution Overview
Problem
Battery-powered sensorless PMSM drives face start-up acceleration failures due to battery voltage drops, high torque demand, and prolonged rotor position estimation convergence times, leading to delays and potential dc-link under-voltage protection.
Innovation Solution
A controller with a battery capacity adjustment factor and a speed feedforward feature that adjusts flux and torque generating voltage references based on battery capacity, and includes a rotor position estimator with a speed feedforward term to mitigate voltage drops and accelerate convergence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high start-up acceleration rate is used to improve productivity, then start-up speed is improved, but battery voltage drops significantly due to excessive torque demand
Solution Approach 1:
The controller dynamically adjusts the voltage reference based on real-time battery voltage conditions. The voltage reference is scaled by a factor that varies with battery state, allowing the system to optimize acceleration performance while preventing voltage collapse during start-up transients
Solution Approach 2:
The system changes the voltage reference parameter dynamically during start-up based on measured battery voltage. When battery voltage drops below a threshold, the voltage reference is proportionally reduced to match available battery capacity, preventing protective shutdown while maintaining acceptable acceleration
2Ease of operation
If conventional PLL observer/estimator is used to estimate rotor position, then sensorless control is achieved, but position estimation convergence time is prolonged during start-up
Solution Approach 1:
The system applies preliminary voltage references based on estimated rotor position even before accurate position detection is achieved. This allows the motor to start rotating and generates back-EMF signals that enable the PLL observer to converge faster to the actual rotor position
Solution Approach 2:
The PLL observer continuously monitors the relationship between applied voltage and current response to refine rotor position estimates in real-time. The observer uses feedback from current measurements and voltage references to correct position estimation errors and accelerate convergence during start-up
3Speed
If steep load change occurs during operation, then response speed is improved, but dc-link voltage drops trigger under-voltage protection
Solution Approach 1:
The controller anticipates voltage drops during load transients by implementing proactive voltage reference adjustment. When voltage drop is detected, the system preemptively reduces voltage references to prevent the dc-link voltage from falling into the under-voltage protection threshold
Solution Approach 2:
The system continuously monitors dc-link voltage and uses this feedback to dynamically adjust voltage references. During load transients, the feedback loop rapidly detects voltage changes and modulates the voltage reference to maintain stable operation above the protection threshold
Data Source
AI summary
A controller for a battery-powered PMSM (permanent magnet synchronous motor) is described. In one embodiment, the controller includes: a first controller configured to generate a flux generating voltage reference for the PMSM; a second controller configured to generate a torque generating voltage reference for the PMSM; and a battery capacity adjustment factor configured to adjust the flux generating voltage reference and the torque generating voltage reference, based on capacity of the battery. In another embodiment, the controller includes: a rotor position estimator configured to estimate a rotor electrical angle and a rotor electrical speed of the PMSM, based on a flux generating voltage reference for the PMSM, a torque generating voltage reference for the PMSM, a flux generating current feedback for the PMSM, and a torque generating current feedback for the PMSM, the rotor position estimator including a speed feedforward term. The controller embodiments are not necessarily mutually exclusive.