PMG Rotor Position Compensation Using Resolver Error Offsets
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Solution Overview
Problem
High power density PMG systems with multi-pole generators face accuracy issues in rotor angle detection due to mechanical misalignment, electrical characteristics, and conversion time errors, affecting the field-oriented control of active rectifiers in electric and hybrid-electric vehicles.
Innovation Solution
A method that involves obtaining PMG phase voltages and resolver output signals, filtering higher order harmonics, converting mechanical to electrical angles, aligning them with PMG fundamental phase voltage angles, and storing resolver error offset values in a DSP component to create compensation tables for accurate rotor position compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a frameless two-pole resolver is used with a high pole count PMG to achieve high power density, then power density is improved, but rotor angle detection accuracy deteriorates due to mechanical misalignment and electrical characteristics
Solution Approach 1:
The patent applies preliminary action by performing resolver error compensation before the PMG operates in the full speed range. A compensation table is pre-calculated and stored in the DSP, containing correction values for rotor angle measurements at different electrical angles. This pre-computed compensation data enables accurate angle detection throughout operation without real-time calculation delays.
Solution Approach 2:
The patent implements feedback by continuously monitoring the PMG phase voltages and comparing the resolver-measured electrical angle with the actual fundamental phase voltage angle. The difference (error) is used to retrieve appropriate compensation values from the pre-stored compensation table, which then corrects the resolver output signals. This closed-loop feedback ensures accurate angle measurement despite mechanical misalignment or electrical characteristics of the frameless resolver.
2Ease of operation
If resolver output signals are used directly for field oriented control, then control implementation is simplified, but control accuracy deteriorates over the entire speed range without error compensation
Solution Approach 1:
The patent introduces an intermediary compensation mechanism between the resolver and the field-oriented control system. The compensation table acts as a mediator that translates the inaccurate resolver signals into accurate electrical angle information. The DSP component serves as another intermediary, processing the PMG phase voltages to determine fundamental angles and retrieving appropriate compensation values from the table based on the electrical angle sector, thereby maintaining control simplicity while improving accuracy.
3Device complexity
If mechanical misalignment and electrical errors are not compensated, then system complexity is reduced, but field oriented control accuracy deteriorates
Solution Approach 1:
The patent reduces real-time computational complexity by performing error compensation preparation in advance. The compensation table is pre-calculated and stored in the DSP memory, containing correction values for all possible electrical angle positions. During operation, the system only needs to lookup the appropriate compensation value from the table based on the current electrical angle sector, rather than performing complex real-time calculations, thus maintaining low system complexity while achieving high accuracy.
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 method enhances the accuracy of rotor position information, compensates for positional and speed errors, and simplifies the error compensation process for frameless resolvers in high pole count PMG systems, ensuring precise control of the power generating system.
Implementation Method 1
feeding an excitation signal to a resolver rotor coil; feeding sinusoidal and cosine-shaped signals from respective coils of a resolver associated with a rotor of the PMG
Data Source
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AI summary
A method of compensating for rotor position error of a rotor (56) of a permanent magnet synchronous generator (PMG) (30) that provides electrical power to a direct current (DC) power generating system (20), the method including obtaining PMG phase voltages and resolver processed angular position output when the PMG (30) is driven by a prime mover (24). Once obtained, a PMG fundamental phase voltage waveform is selected by eliminating higher order harmonics. A mechanical angle of the rotor (56) is then converted into an electrical angle, then the electrical angle is aligned within the mechanical angle with a corresponding PMG fundamental phase voltage angle by adjusting offset to the electrical angle. After alignment, a plurality of resolver error offset values associated with the electrical angle are stored and additional values to the compensation table are added by interpolating data between two corresponding resolver error offset values of the plurality of resolver error offset values.