PWM Inverter Phase Error Compensation via Digital Advance
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Solution Overview
Problem
Conventional PWM inverters experience significant phase errors in generating PWM signals due to the delay in transmitting the amplitude and phase of the signal wave, particularly when the carrier wave frequency is not substantially higher than the signal wave frequency, leading to inaccuracies in AC output voltage control.
Innovation Solution
A PWM inverter with a phase adjusting section that advances the phase of the signal wave by adding a phase delay component, synchronized with digital control cycles, and utilizing carrier waves such as triangular or sawtooth waves, or adjusting the carrier wave frequency to prevent phase errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital control is used to generate signal wave from amplitude and phase data using trigonometric function, then control precision is improved, but phase error occurs due to quantization delay
Solution Approach 1:
The patent applies preliminary action by advancing the phase of the signal wave a1 before comparison with the carrier wave. Specifically, the phase advancing section adds a phase delay component (corresponding to half the control period) to the signal wave in advance, so that when the PWM signal is generated through comparison, the phase error caused by digital control quantization is compensated. This ensures accurate transmission of amplitude A and phase θ without requiring the carrier wave frequency to be much higher than the signal wave frequency.
2Manufacturing precision
If carrier wave frequency is increased to reduce phase error, then phase accuracy is improved, but device complexity and switching losses increase
Solution Approach 1:
The patent applies parameter changes by modifying the phase parameter of the signal wave rather than changing the carrier wave frequency. The phase advancing section adjusts the phase of the signal wave a1 by adding a phase delay component that corresponds to half the control period. This parameter adjustment achieves phase error compensation without increasing the carrier wave frequency, thereby avoiding increased device complexity and switching losses while maintaining accurate AC output voltage control.
3Manufacturing precision
If carrier wave frequency is increased to reduce phase error, then phase accuracy is improved, but energy loss increases
Solution Approach 1:
The patent applies parameter changes by modifying the phase parameter of the signal wave rather than increasing the carrier wave frequency. The phase advancing section adds a phase delay component to the signal wave, which compensates for the phase error introduced by digital control quantization. This approach achieves accurate phase transmission without requiring high-frequency switching, thereby reducing switching losses and energy consumption while maintaining control precision.
Data Source
AI summary
There is provided a PWM inverter capable of preventing a phase error from occurring in generating a PWM signal even in the case where a carrier wave frequency is not sufficiently higher than a signal wave frequency. A PWM signal generating section (2) includes a phase adjusting section (11) configured to advance a phase of the signal wave by adding, to a signal wave, a delay component of the PWM signal with respect to the signal wave, the phase delay component being involved by digital control. Furthermore, in a case where the carrier wave frequency is changed, the phase delay component with respect to the signal wave is updated in synchronism with the timing of change of the carrier wave frequency.