Multi-Phase Inverter Overmodulation for Accurate High-Index Output
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Solution Overview
Problem
Existing multi-phase inverter technologies fail to achieve optimal control of output voltage accuracy, particularly at high modulation index values, leading to suboptimal power output and increased harmonic distortion.
Innovation Solution
A method for overmodulating a multi-phase inverter that involves determining hardware limitations to calculate specific hold and clamp angles, allowing for a constant duty cycle and maximum voltage clamping, respectively, using algorithms that consider hardware constraints to optimize voltage accuracy and reduce harmonic distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional PWM methods are used for inverter control, then the control is simple to implement, but the output voltage accuracy deteriorates at high modulation index values
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the duty cycle based on the modulation index value. When the modulation index exceeds a predetermined threshold, the system transitions from conventional PWM to overmodulation mode, changing the control parameters to maintain voltage accuracy. This involves calculating compensation values and adjusting switching duty cycles to counteract the voltage droop that occurs at high modulation indices.
2Power
If the modulation index is increased to maximize power output, then the energy provision is improved, but the voltage accuracy and harmonic distortion worsen
Solution Approach 1:
The patent implements feedback control by continuously monitoring the modulation index and comparing it against predetermined thresholds. Based on this feedback, the system automatically adjusts the duty cycle and switches between different modulation modes (conventional PWM and overmodulation) to maintain optimal voltage accuracy across the full power range. The feedback mechanism ensures that voltage errors are compensated in real-time.
Solution Approach 2:
The system dynamically adapts its control strategy based on operating conditions. The modulation mode is not fixed but changes dynamically with the modulation index, transitioning between linear PWM region and overmodulation region. This dynamic adaptation allows the system to maximize power output while maintaining voltage accuracy by selecting the optimal control mode for each operating point.
3Use of energy by moving object
If overmodulation is applied to maximize voltage output, then the energy provision is improved, but the harmonic distortion increases
Solution Approach 1:
The patent applies local quality by implementing different control strategies for different regions of the modulation index range. In the linear region (below threshold), conventional PWM is used for clean waveforms. In the overmodulation region (above threshold), a specialized control algorithm is applied to manage harmonic content. This localized approach allows the system to maximize energy provision in the overmodulation region while minimizing harmonic distortion through region-specific optimization.
Data Source
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AI summary
The invention relates to a method (100) for overmodulating a multi-phase inverter that is configured to convert a DC input voltage to an AC output voltage, comprising: - determining (110) at least one hardware limitation of the multi-phase inverter, - calculating (120) a hold angle (210), for which a duty cycle (230) of the inverter is kept at a constant level, - calculating (130) a clamp angle (220), for which the AC output voltage is clamped to one half of the DC input voltage, wherein calculating (120, 130) the hold angle (210) and/or the clamp angle (220) is specific for the at least one hardware limitation of the inverter. The invention further relates to a computer program product and a multi-phase inverter.