Synchronous Machine PWM Control for Accurate 1-Shunt Current Sensing
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Solution Overview
Problem
Existing methods for controlling synchronous machines, particularly in sensorless configurations, face challenges in accurately determining electrical phase currents due to noise issues caused by temporal jumps in switching signals during duty cycle changes, especially under high motor voltages and varying duty cycles.
Innovation Solution
The method involves generating center-centered or non-center-centered pulse width modulated switching signals for half-bridges to ensure a sufficient minimum measurement period, avoiding temporal jumps by shifting switching signal edges based on duty cycle ratios, allowing for noise-optimized 1-shunt current measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If center-centered PWM switching signals are used, then control simplicity is improved, but measurement precision deteriorates due to insufficient minimum measuring duration
Solution Approach 1:
The patent dynamically adjusts the PWM switching signal configuration based on operational conditions. When center-centered signals provide insufficient measurement duration, the system transitions to non-centered signals, making the control approach adaptive rather than static to maintain measurement precision across varying operating conditions
Solution Approach 2:
The patent changes the temporal parameters of the PWM switching signals by shifting switching edges to create non-centered configurations. This parameter modification extends the minimum measuring duration while maintaining effective current measurement capability, resolving the contradiction between control simplicity and measurement precision
2Measurement precision
If switching signal edges are shifted to provide minimum measuring duration, then measurement precision is improved, but noise increases due to temporal jumps in phase current curves
Solution Approach 1:
The patent applies preliminary anti-action by pre-calculating and compensating for potential temporal jumps in phase current curves. The switching signal configuration is designed in advance to avoid jumps at duty cycle transitions, preventing noise generation before it occurs while maintaining sufficient measurement duration
Solution Approach 2:
The system performs preliminary action by adjusting switching signal edges to predetermined positions that guarantee adequate measuring duration. These pre-positioned edges are configured to avoid temporal jumps during duty cycle changes, ensuring both measurement precision and noise-free operation
3Device complexity
If 1-shunt current measurement is implemented, then device complexity is reduced, but measurement precision deteriorates under high motor voltages with varying duty cycles
Solution Approach 1:
The patent changes the temporal parameters of switching signals (edge positions, duty cycle timing) to optimize measurement conditions for 1-shunt current measurement. By adjusting these parameters, the system maintains measurement precision across high motor voltages and varying duty cycles while retaining the hardware simplicity of single-shunt measurement
Data Source
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AI summary
The invention relates to a method for operating an electric synchronous machine, having the steps of: - generating centered pulse-width-modulated switching signals for switching elements (T1...T6) of half-bridges, wherein two switching elements (T1...T6) are connected to a respective half-bridge in each case; second switching elements (T4...T6) of each half-bridge are actuated in a complementary manner to the first switching elements (T1...T3) of each half-bridge if a sufficient minimum measurement duration (TM) is thereby provided during which the switching signals of switching elements (T1...T6) of two half-bridges lie at different potentials; - otherwise: - generating pulse-width-modulated switching signals for the switching elements (T1...T6) of the half-bridges, said switching signals deviating from the center at least to such a degree that a sufficient minimum measurement duration (TM) is provided, wherein - the switching signals of the switching elements (T1...T6) are designed such that temporal changes corresponding to the minimum measurement duration (TM) in the switching signals of the switching elements (T1...T6) are prevented; and - carrying out a 1-shunt current measurement within the provided minimum measurement duration TM).