Sensorless PMSM Startup Using Rotor Flux Projection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional sensorless field-oriented control (FOC) systems for permanent magnet synchronous motors (PMSMs) face challenges in smooth startup due to the lack of load information, leading to excessive torque application and potential motor stalling or over-speeding during the transition from a stopped state to closed-loop control.
Innovation Solution
The proposed method involves a load-adaptive smooth startup technique that uses rotor flux projection on the d- or q-axis to adjust the current reference, determining when sufficient torque is applied to spin the motor, and then transitions to closed-loop sensorless FOC control based on the estimated load angle difference, ensuring a smooth transition without excessive current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If excessive torque is applied during startup to ensure minimum speed for back-EMF generation, then the motor can achieve sufficient speed for sensorless control, but the motor may over-speed or stall
Solution Approach 1:
The patent applies dynamics by making the current reference adaptive during startup. Instead of using a fixed excessive current reference, the system dynamically adjusts the current reference based on the detected rotor flux projection. This allows the torque to be precisely controlled at the minimum level needed to overcome load and achieve back-EMF generation, preventing both over-speeding and stalling during the transition to closed-loop control.
Solution Approach 2:
The patent implements feedback by using the rotor flux projection (derived from back-EMF) as a feedback signal during startup. The control system continuously monitors the rotor flux projection and uses this information to adjust the current reference in real-time. This feedback mechanism enables the system to apply only the necessary torque to maintain minimum speed, avoiding the need for excessive torque that would cause instability.
2Device complexity
If a fixed current reference is used during startup, then the control system is simple to implement, but it cannot adapt to varying load conditions leading to excessive current application
Solution Approach 1:
The patent applies parameter changes by making the current reference a variable parameter that changes based on operating conditions. Specifically, the current reference is adjusted according to the rotor flux projection, which reflects the actual load on the motor. This allows the system to reduce current (and energy consumption) when load is light while maintaining sufficient current when load is heavy, eliminating the need for a fixed conservative current reference.
Solution Approach 2:
The patent implements self-service by enabling the motor control system to automatically determine its own operating parameters during startup. The system uses the rotor flux projection to self-adjust the current reference without external intervention or complex lookup tables. This self-service capability maintains simplicity while achieving load adaptability, as the system serves itself by using its own back-EMF signal to control its own current.
3Device complexity
If the transition from reference startup FOC to closed-loop sensorless FOC is made abruptly, then the control switching is simple, but the motor experience torque shocks and unstable operation
Solution Approach 1:
The patent applies preliminary action by preparing the system for smooth transition before the actual switching occurs. During the reference startup FOC phase, the system continuously tracks the rotor flux projection and uses this information to pre-calculate the appropriate current reference for closed-loop control. By the time the transition is initiated, the system is already prepared with the correct parameters, eliminating torque shocks and ensuring smooth handover to closed-loop sensorless FOC.
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
This approach reduces energy consumption and facilitates a smooth transition between startup and closed-loop control phases, preventing motor stalling and over-speeding by adapting the current reference to the motor's load conditions.
Implementation Method 1
The stator 102 includes a number of electrical windings 104 arranged to surround the rotor 108. During operation, electrical current through the windings 104 sets up a magnetic field within the air gap 110 between the rotor 108 and the stator 102, and the interaction between the magnets 106 and the magnetic field causes the rotor 108 to rotate, producing torque.
Implementation Method 2
lacking information regarding the load on the PMSM, the FOC control system may be designed to apply an excessive amount of torque during the transition to ensure that the motor achieves a minimum amount of speed to generate usable back-electromagnetic force (back-EMF) information.
Data Source
AI summary
A field oriented control (FOC) system and method provides smooth field-oriented startup for three-phase sensorless permanent magnet synchronous motors (PMSMs) despite the absence of load information. The system uses the rotor flux projection on the d- or q-axis to determine whether the stator flux current reference being applied during reference startup phase is sufficient to spin the PMSM, thereby providing smooth operation during the reference startup phase and saving energy relative to applying rated current. The system also determines a suitable initial value for the stator torque current reference to use at the start of closed-loop sensorless FOC control mode based on an angle difference between the reference and estimated angles. Since this angle difference is reflective of the load on the PMSM, the selected initial value allows the system to achieve a smooth transition from reference startup mode to closed-loop sensorless FOC control mode.