DPWM Transition Interval Control for Common-Mode Oscillation
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Solution Overview
Problem
Traditional discontinuous pulse-width modulation (DPWM) strategies in three-phase converters cause significant common-mode voltage and current oscillations, leading to increased power loss, hardware cost, and reduced efficiency due to the difficulty in selecting appropriate common-mode suppressor units and the need for isolation circuits.
Innovation Solution
A discontinuous pulse-width modulation method that introduces a transition interval and calculates a target zero-sequence component to slow down the change rate of modulation waves, reducing oscillations and stress on common-mode suppressor units by defining a transition interval and setting the target zero-sequence component in the non-transition interval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional discontinuous pulse-width modulation (DPWM) strategy is adopted, then power loss reduction and efficiency improvement are achieved, but significant common-mode voltage and current oscillations occur causing increased hardware cost and reduced reliability
Solution Approach 1:
The patent modifies the modulation strategy by introducing a transition interval that changes the zero-sequence component parameters. Instead of abrupt switching between DPWM sectors, the zero-sequence component is adjusted gradually within the transition interval, changing the temporal parameters of the modulation wave to reduce common-mode voltage oscillations while maintaining the discontinuous conduction mode for efficiency.
Solution Approach 2:
The transition interval acts as an intermediary mechanism between different DPWM sectors. By introducing this intermediate time period with controlled zero-sequence component adjustment, the patent mediates the abrupt transitions that cause common-mode oscillations, allowing smooth switching between modulation sectors while maintaining the benefits of DPWM.
2Productivity
If traditional DPWM modulation strategy is used, then system efficiency is improved, but big common-mode voltage causes need for isolation circuits increasing device complexity
Solution Approach 1:
The patent changes the zero-sequence component parameters within a transition interval to control the common-mode voltage amplitude. By adjusting the duration and magnitude of the zero-sequence component during sector transitions, the common-mode voltage is kept within acceptable limits, eliminating the need for additional isolation circuits while maintaining high system efficiency through discontinuous conduction mode operation.
3Power
If traditional DPWM strategy is adopted, then power conversion is achieved, but common-mode current oscillation aggravates converter loss reducing overall efficiency
Solution Approach 1:
The patent ensures continuous and smooth adjustment of the zero-sequence component during transition intervals, avoiding abrupt changes that cause common-mode current oscillations. This continuous modulation approach maintains effective power conversion while eliminating the harmful current oscillations that would otherwise increase converter losses and reduce overall efficiency.
Data Source
AI summary
The present invention discloses a discontinuous pulse width modulation method, including: shifting an obtained first three-phase modulation wave upwards and downwards to obtain an upward-shifted three-phase modulation wave, a down-shifted three-phase modulation wave, an upward-shifted zero-sequence component and a down-shifted zero-sequence component; calculating a start time-point of a transition interval, a target zero-sequence component within a transition interval and an end time-point of a transition interval based on the above modulation wave and its zero-sequence component; adding the first three-phase modulation wave and the target zero-sequence component together to obtain a target three-phase modulation wave. The discontinuous pulse width modulation method of the present invention can slow down a modulation wave change within the transition interval, effectively abate the voltage and current oscillation of the common-mode suppressor unit and decrease the stress of the common-mode suppressor unit device.