PWM Controller Adaptive Zero-Voltage Periods for Power Converter
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Solution Overview
Problem
Conventional power converting apparatuses face challenges in reducing switching losses and suppressing dead time while maintaining efficient voltage output, particularly in adjusting periods of zero and non-zero voltage in PWM signals based on voltage commands.
Innovation Solution
A power converter system that includes a controller generating PWM signals with adjustable periods of zero and non-zero voltage, allowing one first period and one or more second periods within an updating cycle of the voltage command, to optimize switching operations and reduce losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If carrier frequency is reduced to reduce switching loss, then switching loss is reduced, but output voltage distortion increases
Solution Approach 1:
The patent applies dynamics by making the PWM signal structure adaptive and variable. The controller dynamically adjusts the number of zero-voltage periods and non-zero voltage periods within each voltage command updating cycle based on the magnitude of the voltage command. This dynamic restructuring allows the system to optimize between switching loss reduction and voltage distortion suppression under different operating conditions, resolving the contradiction between these two parameters.
Solution Approach 2:
The patent changes the structural parameters of the PWM signal by varying the number of first periods (zero voltage) and second periods (non-zero voltage) within the updating cycle. When the voltage command magnitude is small, the controller increases the proportion of zero-voltage periods to reduce switching frequency and loss. When the voltage command magnitude is large, the controller adjusts to maintain voltage quality. This parameter change approach directly addresses the contradiction between switching loss and output voltage distortion.
2Measurement precision
If PWM switching frequency is increased to improve voltage control precision, then voltage control precision is improved, but switching loss increases
Solution Approach 1:
The system dynamically adjusts the PWM signal structure based on the voltage command magnitude. For small voltage commands, the controller configures more zero-voltage periods which reduces the effective switching frequency and thus switching loss, while still maintaining adequate voltage control precision through the optimized distribution of non-zero voltage periods. This dynamic adaptation resolves the contradiction between precision and loss.
Solution Approach 2:
The patent utilizes periodic action by organizing the PWM signal into repeating patterns of first periods (zero voltage) and second periods (non-zero voltage) within each voltage command updating cycle. By carefully designing the number and duration of these periodic segments, the system achieves both precise voltage control during the non-zero periods and reduced switching activity during zero-voltage periods, thereby resolving the contradiction between control precision and switching loss.
3Reliability
If dead time is increased to prevent switching conflicts, then switching reliability is improved, but current control responsiveness deteriorates
Solution Approach 1:
The patent extracts and eliminates unnecessary dead time from the PWM signal structure by optimizing the transition between switching states. Through intelligent arrangement of the first periods and second periods, the controller minimizes the time when switching elements are in indeterminate states, thereby reducing dead time while maintaining switching reliability. This extraction of excessive dead time improves current control responsiveness without compromising reliability.
Solution Approach 2:
The patent applies skipping by rapidly transitioning through critical switching states in the optimized PWM sequence. By carefully designing the timing and sequence of the first and second periods, the controller rushes through the switching transitions with minimal dead time, maintaining reliability through proper state sequencing while improving responsiveness. This skipping approach reduces the time spent in non-productive dead time periods.
Data Source
AI summary
A power converting apparatus is provided. The power converting apparatus includes a power converter configured to output a voltage to a load, and a controller configured to output a PWM signal which is generated in response to a voltage command to the power converter. The power converter includes a plurality of switching elements driven based on the PWM signal. The controller is configured to generate the PWM signal such that a first period during which a zero voltage is outputted and a second period during which a non-zero voltage is outputted are adjusted according to the voltage command. The controller is allowed to output the PWM signal which is set such that one first period and one or more second periods exist within an updating cycle of the voltage command, to the power converter.