Hysteretic Voltage Drive System for Low Distortion Output
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Solution Overview
Problem
Conventional voltage drive systems employing deterministic controllers face challenges in synthesizing medium voltage phased output signals using H-bridges, resulting in significant distortion and high switching losses due to fixed switching rates, especially at high frequencies, which limits their ability to meet stringent acoustic specifications and efficiency requirements.
Innovation Solution
A voltage drive system utilizing a hysteretic non-deterministic controller that adjusts switching rates based on phase current errors and reference signals, increasing switching frequency at high slew rate portions and decreasing it at low slew rate portions to reduce distortion and switching losses, while maintaining waveform quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a deterministic controller switches H-bridges at constant time intervals, then the switching rate is fixed and simple to control, but the output waveform quality deteriorates at high frequencies due to fixed switching rate not adapting to slew rate variations
Solution Approach 1:
The patent transforms the fixed switching rate control into a dynamic switching rate control by using a hysteretic comparator that continuously adjusts the switching frequency based on the instantaneous phase current error. This allows the switching rate to adapt automatically to varying slew rate conditions, improving waveform quality without sacrificing control simplicity.
Solution Approach 2:
The patent implements feedback control by using the phase current error as a feedback signal to the hysteretic comparator. This feedback mechanism enables the controller to automatically adjust the switching rate according to the actual system state, resolving the contradiction between simple control and high waveform quality.
2Manufacturing precision
If the switching frequency is increased to improve output waveform quality, then the bandwidth and waveform quality improve, but the switching losses increase significantly
Solution Approach 1:
The hysteretic comparator dynamically adjusts the switching frequency based on the phase current error magnitude. When the error is large, the switching frequency increases to improve waveform quality; when the error is small, the switching frequency decreases to reduce switching losses. This dynamic adaptation resolves the contradiction between waveform quality and energy efficiency.
3Device complexity
If a fixed switching rate is used to simplify control, then the controller design is straightforward, but distortion increases at high frequencies due to inability to track reference voltage slew rate
Solution Approach 1:
The patent uses feedback control through the hysteretic comparator that continuously monitors the phase current error and adjusts the switching rate accordingly. This feedback mechanism enables automatic tracking of reference voltage slew rate without complex control algorithms, resolving the contradiction between simple controller design and low distortion output.
4Loss of energy
If the switching rate is decreased to reduce switching losses, then the energy efficiency improves, but the output waveform quality deteriorates due to insufficient switching frequency
Solution Approach 1:
The hysteretic comparator creates a dynamic switching rate that automatically scales with the phase current error. This ensures sufficient switching frequency is maintained when needed for waveform quality, while allowing the switching rate to decrease when the error is small, thereby reducing switching losses. This dynamic behavior resolves the contradiction between energy efficiency and waveform quality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The hysteretic non-deterministic controller effectively reduces distortion and switching losses, improves waveform quality, and eliminates clearly defined tones in the output signal spectrum, enhancing the system's ability to handle high-frequency operations and meet stringent acoustic specifications.
Implementation Method 1
A voltage drive system utilizing a hysteretic non-deterministic controller that adjusts switching rates based on phase current errors and reference signals
Data Source
AI summary
A voltage drive system is provided having a plurality of modulators and a plurality of cascaded switching circuits which collectively generate a single-phase output signal to a load. Each modulator receives a phase current error and has an adder which generates a modulated phase current error based on the phase current error and based on a signal having a phase. For each respective modulator, the phase of the respective signal is different. Each respective modulator changes a respective gate input when the respective modulated phase current error changes from being within a predetermined current range to being outside of the predetermined current range. Each respective switching circuit receives the respective gate input and generates a respective output terminal voltage based on the respective gate input. The change in the respective gate input effectively causes a switching event of the respective switching circuit.