Polyphase PWM Control for Converter Nonlinearity and Voltage Balance
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Solution Overview
Problem
Current power converter control algorithms, particularly PWM, restrict switching durations below minimum semiconductor conduction or blocking times, leading to non-linearity zones that cause voltage distortion and unbalanced output voltages, resulting in reduced converter performance and harmonic distortions.
Innovation Solution
A method for a polyphase power converter that modifies control parameters associated with non-linearity zones to align with linearity zones, using corrective values to adjust drive setpoint values or pulse durations, ensuring balanced voltage output by determining and applying differences to move control parameters into linearity zones, thereby optimizing converter operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PWM control algorithms prohibit switching duration less than minimum semiconductor conduction time, then semiconductor destruction is prevented, but non-linearity zones cause voltage distortion and unbalanced output voltages
Solution Approach 1:
The patent modifies control parameters (drive setpoint values or pulse durations) that fall within non-linearity zones by adding or subtracting predefined corrective values. This shifts the parameters into linearity zones where the relationship between control input and output voltage is proportional, thereby eliminating voltage distortion and imbalance while preserving the minimum conduction time requirement for semiconductor protection.
2Reliability
If control value is modified to ensure minimum conduction duration, then semiconductor reliability is improved, but converter performance deteriorates due to non-linear operation zones
Solution Approach 1:
The patent applies parameter transformation by correcting drive setpoint values or pulse durations through addition or subtraction of predefined values. This moves control parameters from non-linear zones (where converter performance degrades) to linear zones (where performance is optimal), while maintaining the constraint that ensures minimum semiconductor conduction duration for reliability.
3Duration of action of moving object
If drive setpoint value is corrected using predefined values, then minimum conduction time is ensured, but output voltage distortion increases
Solution Approach 1:
The patent employs a two-stage parameter correction approach: first, predefined values are added or subtracted from drive setpoint values to ensure minimum conduction duration; second, the corrected parameters are verified to fall within linearity zones where the control-to-output relationship remains proportional. This dual correction eliminates both conduction time violations and output voltage distortion.
Data Source
AI summary
A method of controlling of a polyphase power converter driven by an algorithm of the pulse width modulation type, in which a control parameter comprising a drive setpoint value or a pulse duration associated with a value of drive setpoint of at least one phase, situated in a non-linearity zone of a chart, is modified by modifying the value of said parameter so that it is in a linearity zone of the chart. The control parameter of each of the phases is modified in the same manner.