Synchronous Machine Rotor Angle Detection via PWM Frequency Modulation
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Solution Overview
Problem
Existing methods for determining the rotor angle of synchronous machines, especially at low speeds, are inefficient and unreliable, often requiring additional voltage or current pulses and relying on encoders, which can disrupt smooth operation and increase measurement inaccuracies.
Innovation Solution
The method involves modifying pulse-width-modulated (PWM) drive signals by changing their frequencies to extend the duration of active voltage phasors, allowing for rotor angle determination without encoders, and using the differences in neutral point potentials to calculate the rotor angle, thereby enhancing robustness and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional voltage or current pulses are used to determine rotor angle, then measurement precision is improved, but device complexity and operational smoothness deteriorate
Solution Approach 1:
The system uses the existing PWM drive signals and neutral point voltage measurements to determine rotor angle, without requiring additional voltage or current pulses. The neutral point potential naturally contains rotor position information during normal operation, eliminating the need for separate measurement excitations.
Solution Approach 2:
The invention extracts rotor position information from the neutral point voltage that already exists during normal PWM operation. By analyzing the neutral point potential during active voltage phasor periods, the system separates position detection functionality from the main drive operation without adding measurement-specific excitations.
2Measurement precision
If encoder is used for rotor angle measurement, then measurement precision is improved, but reliability and smooth operation deteriorate
Solution Approach 1:
The invention replaces the mechanical encoder system with an electrical measurement approach using neutral point voltage analysis. This eliminates mechanical contactors and encoder-specific failure modes while maintaining measurement capability through electrical signal processing during normal operation.
Solution Approach 2:
The neutral point voltage measurement serves dual purposes: it provides information for rotor position determination while simultaneously being part of the normal inverter operation. This multi-functionality eliminates the need for separate measurement systems and improves overall system reliability.
3Duration of action of moving object
If PWM drive signals are modified to extend active voltage phasor duration, then time period for voltage phasor presence is increased, but device complexity increases
Solution Approach 1:
The system dynamically adjusts PWM drive signal frequencies to extend the duration of active voltage phasors during which neutral point voltage measurements can be performed. By making frequency adjustments based on operational requirements, the system increases measurement time windows without permanent structural changes.
Solution Approach 2:
The invention changes PWM drive signal parameters (frequencies) to optimize the duration of active voltage phasor periods. By modifying frequency parameters, the system extends the time window for reliable neutral point voltage measurement while maintaining normal drive functionality.
Data Source
AI summary
A method for determining the rotor angle of a synchronous machine. In one implementation, the method includes generating a multiplicity of pulse-width-modulated drive signals for the phases of an inverter feeding the synchronous machine depending on a voltage to be fed into the synchronous machine, changing the pulse width modulation frequency of at least one drive signal of the multiplicity of pulse-width-modulated drive signals, with the result that the duration of the switching states of the inverter in which an active voltage phasor is output is extended in order to generate a switching pattern for the phases of the inverter, driving the inverter with the generated switching pattern, determining one or more of neutral point potentials at the neutral point of the synchronous machine during driving of the inverter with the switching pattern, and calculating the rotor angle of the synchronous machine depending on the determined neutral point potentials.