Multi-Level Bridge Power Converter for Wind Turbines
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Solution Overview
Problem
Power converters in power generation systems face limitations in achieving high voltage, low distortion, and high efficiency with variable frequency output, often requiring large and costly passive filters and restrictive voltage limitations due to the use of single Insulated Gate Bipolar Transistors (IGBTs).
Innovation Solution
A multi-level bridge circuit power converter with multiple series of switches and a voltage divider configuration, allowing for selective connection of switches across voltage level points to generate variable frequency waveforms, reducing switching losses and filtering requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If single IGBTs are used in power converters, then the voltage is restricted, but the device complexity is reduced
Solution Approach 1:
The power converter circuit is divided into multiple bridge legs, each containing multiple IGBTs arranged in series. This segmentation allows the system to achieve high voltage capability by distributing the voltage stress across multiple switching devices while maintaining a modular and manageable circuit structure.
Solution Approach 2:
The patent transitions from a single-level bridge topology to a multi-level bridge topology by adding series-connected IGBTs and intermediate voltage levels. This dimensional change in the circuit architecture enables higher voltage operation without proportionally increasing circuit complexity, as the additional components are organized in a structured multi-level framework.
2Manufacturing precision
If multiple IGBTs are used to create high quality waveform, then the waveform quality is improved, but the device complexity increases
Solution Approach 1:
The bridge circuit is segmented into multiple legs with multiple IGBTs each, allowing independent control of each switching device. This segmentation enables precise waveform synthesis by independently modulating each IGBT pair, achieving high waveform quality while keeping the control of individual components manageable.
Solution Approach 2:
The patent employs dynamic pulse width modulation (PWM) control where the switching patterns of multiple IGBTs are dynamically adjusted to synthesize high-quality waveforms. This dynamic control allows the system to maintain waveform quality across varying operating conditions without requiring a static increase in circuit complexity.
3Manufacturing precision
If passive filters are used to reduce distortion, then the waveform quality is improved, but the device size and cost increase
Solution Approach 1:
The patent extracts the waveform quality improvement function from the passive filter and relocates it to the active switching network of multiple IGBTs. By using multi-level PWM switching to directly synthesize high-quality waveforms at the source, the need for large passive filters is eliminated, reducing both size and cost while maintaining waveform quality.
Solution Approach 2:
The patent replaces the mechanical/passive filter system with an active electronic switching system. Instead of using large inductors and capacitors to filter distortion, the system uses dynamically controlled IGBT switches to actively synthesize clean waveforms, substituting a compact electronic solution for bulky passive components.
4Reliability
If mechanical valves and bypass are used for power conversion, then the reliability is improved, but the efficiency deteriorates
Solution Approach 1:
The patent replaces mechanical valves and bypass mechanisms with solid-state IGBT switching devices. This substitution eliminates mechanical wear and reliability issues associated with moving parts while maintaining high conversion efficiency through electronic switching, achieving both reliability and efficiency improvements over mechanical systems.
Solution Approach 2:
The system uses periodic PWM switching of IGBTs to control power flow, replacing continuous mechanical valve operation. This periodic electronic switching achieves reliable power conversion with minimal energy loss, as the solid-state switches can be turned on and off rapidly with very low conduction losses compared to mechanical systems.
Data Source
AI summary
The present subject matter is directed to apparatus and methods for producing a variable frequency output waveform from a power converter for use in a power generation system, such as a wind turbine power generation system. A voltage divider is employed to provide plural voltage levels to which a multi-level bridge circuit employing selectively activated switches in pairs of switches is coupled. The switches are operated in such a fashion as to produce a generally sinusoidal waveform that may be easily filtered by low cost filters due to the plural voltage levels to produce a generally smooth sine wave from the converter. Such converters may be used in various environments including in pairs in multi-phase power converters.