Wound Field Synchronous Machine Rotor Position Detection
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Solution Overview
Problem
Conventional sensorless motor control methods for wound field synchronous machines are inadequate at low angular rotor velocity or standstill, particularly due to the 180-degree rotor position anomaly, and there is a need for improved reliability, complexity, and cost-effectiveness.
Innovation Solution
The system employs a high frequency rotating transformer with a generator control unit that includes a position and velocity decoder, synchronous filters, and an extended rotor flux estimator to estimate rotor position and velocity, eliminating the need for mechanical shaft sensors and improving control in both motoring and generating modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If back EMF based method is used for sensorless motor control, then implementation is easy and it works well at high angular rotor velocity, but it is inadequate for low velocity or standstill
Solution Approach 1:
The system dynamically switches between back EMF based control at high velocities and signal injection control at low velocities/standstill. The controller adapts the control method based on rotor velocity conditions, ensuring reliable operation across the entire velocity range while maintaining ease of implementation through a unified control architecture.
Solution Approach 2:
The system changes the control parameters and methodology based on operating conditions. At high velocities, back EMF parameters are used; at low velocities and standstill, signal injection parameters take over. This parameter switching resolves the contradiction by optimizing control reliability for each velocity regime while maintaining overall system ease of operation.
2Reliability
If signal injection method is used for sensorless motor control, then it can operate at low angular rotor velocity or standstill, but it is more difficult to implement and subject to 180 degree rotor position anomaly
Solution Approach 1:
The system uses feedback from rotor position detection to identify and correct the 180-degree anomaly. By monitoring the detected rotor position and comparing it with expected position based on control signals, the system can detect when the anomaly occurs and apply corrective transformations to the control parameters, eliminating the positioning error while maintaining low-velocity operational capability.
Solution Approach 2:
The controller acts as an intermediary that processes signal injection responses and transforms them into accurate rotor position information. It mediates between the raw signal injection data and the control system, applying algorithms to resolve the 180-degree ambiguity and provide accurate position feedback, thereby reducing implementation complexity while maintaining reliability.
3Measurement precision
If mechanical shaft sensors are used for rotor position detection, then accurate position sensing is achieved, but system cost and complexity increase
Solution Approach 1:
The system replaces mechanical shaft sensors with sensorless control methods using back EMF detection and signal injection techniques. These electrical methods provide sufficient position sensing accuracy for the application while eliminating mechanical components, thereby reducing system complexity, cost, and maintenance requirements while maintaining measurement precision needed for effective motor control.
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 solution enhances system reliability, complexity, and cost-effectiveness by providing accurate position sensing, damping rotor oscillations, and maintaining power density, while improving dynamic performance and stability.
Implementation Method 1
a transformer secondary winding operatively connected to the transformer primary winding to form a rotating transformer. The transformer secondary winding is connected in parallel to the main field winding.
Implementation Method 2
Each synchronous filter can also be operatively connected to receive sine and cosine signals from a quadrature generator and to output first and second filtered two phase voltage signals phase-shifted by 90 electrical degrees that contain rotor position information.
Data Source
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AI summary
An electrical machine (100) includes a stator (102) having a main armature winding (104), an exciter field winding (105), and a transformer primary winding (106). A rotor (108) is operatively connected to rotate relative to the stator (102), wherein the rotor (108) includes an exciter armature winding (107) operatively connected to the exciter field winding (105) for field excitation therebetween, a main field winding (109) operatively connected to the main armature winding (104) for field excitation therebetween, and a transformer secondary winding (110) operatively connected to the transformer primary winding (106) to form a rotating transformer. A generator control unit (112) is operatively connected to the main armature winding (104), exciter field winding (105), and transformer primary winding (106) to control the main armature (104) and exciter field windings (105) based on excitation in the primary winding (106) received from the transformer secondary winding (110).