Sensorless PMSM Startup via Dynamic High Frequency Injection
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Solution Overview
Problem
Sensorless Permanent Magnet Synchronous Motor (PMSM) systems face challenges in starting and controlling motors at low speeds due to unreliable speed and position estimation methods, particularly in commercial fan and blower applications, where large inertia and natural wind forces complicate rotor movement and stability.
Innovation Solution
The implementation of a robust closed-loop startup control system using dynamic high frequency injection (DHFI) and a universal dqController, which decouples high frequency injection signals from stator current responses, allowing for reliable speed estimation and motor control across a wide speed range without open-loop control methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensorless PMSM systems use flux-based speed estimation methods, then reliability is improved at normal operating speeds, but measurement precision deteriorates at zero or low speeds
Solution Approach 1:
The system dynamically switches between different speed estimation methods based on operating conditions. At normal speeds, flux-based estimation is used; at zero or low speeds, the system transitions to open-loop voltage control with back-EMF detection, adapting the estimation approach to match the current speed regime and maintaining reliability across the full speed range.
Solution Approach 2:
The system changes the control parameters and estimation methodology based on speed thresholds. When speed drops below a threshold, the system switches from closed-loop flux-based estimation to open-loop control with adjusted voltage commands, allowing accurate speed estimation to be maintained despite the change in operating conditions.
2Ease of operation
If open-loop control methods are used for startup, then ease of operation is improved, but reliability deteriorates due to rotor oscillations and inability to handle wind-run forces
Solution Approach 1:
The system implements feedback through back-EMF detection during the startup phase. By monitoring the back-EMF generated during open-loop voltage ramping, the system can detect rotor position and speed, providing feedback that enables a smooth transition to closed-loop control, thereby maintaining reliability while preserving the simplicity of open-loop startup.
Solution Approach 2:
The system performs preliminary open-loop voltage ramping to bring the motor to a detectable speed range before engaging closed-loop control. This preliminary action prepares the system for reliable closed-loop operation by ensuring the rotor is moving at a speed where back-EMF can be detected, thus preventing rotor oscillations and handling wind-run forces effectively.
3Reliability
If back-EMF startup methods are used, then reliability is improved for position estimation, but measurement precision deteriorates when back-EMF is indistinguishable from noise at zero or low speeds
Solution Approach 1:
The system uses periodic voltage ramping commands during startup to generate detectable back-EMF signals. By applying periodic excitation voltages and monitoring the resulting back-EMF at specific intervals, the system can distinguish the back-EMF signal from noise even at low speeds, maintaining both reliability and measurement precision during the transition to closed-loop control.
4Measurement precision
If signal injection methods are used for startup, then measurement precision is improved for position tracking, but device complexity increases due to high frequency signal injection and spatial saliency analysis
Solution Approach 1:
The system extracts position information from the back-EMF signal generated during normal voltage ramping operations, rather than injecting separate high-frequency signals. By taking out the position estimation function from a dedicated signal injection system and integrating it into the existing voltage control framework, the system maintains measurement precision while reducing device complexity.
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
Enables reliable and stable motor startup and operation from zero to high speeds, maintaining closed-loop control throughout, even in the presence of wind-run forces, improving reliability and efficiency in commercial fan and blower applications.
Implementation Method 1
a motor controller selectively coupled to the stator and configured to generate the three-phase voltages
Implementation Method 2
Back-EMF startup methods estimate the back-EMF generated by rotation of the motor under fundamental excitation for position and speed estimation
Data Source
AI summary
A robust starting system and method for an interior permanent magnet synchronous motor, suitable for commercial fan and blower drive applications. A comprehensive starting control process is provided that utilizes control flags to implement closed-loop control accounting for any pre-existing rotor movement, controlling the motor speed from an initial speed to a destination speed. A universal dqController provides selective configurability for collecting information regarding the initial state of the motor, as well as starting and operational motor control. Dynamic high frequency injection enables the use of HFI outside the normal standstill motor speeds by intelligently decoupling the high frequency and rotor movement portions of the stator current response.