Single-Stage Buck-Boost Inverter Without DC Link Capacitors
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Solution Overview
Problem
Existing power conversion technologies for grid-connected applications, particularly for low voltage inputs, often require multiple stages of power conversion, leading to switching losses, bulky capacitors, and unidirectional energy flow issues, which result in inefficiencies, increased costs, and potential waveform distortion at light-load or on-load conditions.
Innovation Solution
A single-stage buck-boost inverter with step modulation and bidirectional energy flow capabilities, utilizing wide bandgap power devices and eliminating the need for DC link capacitors, allowing for efficient conversion of low and variable DC voltages to a fixed AC voltage with improved system efficiency and reduced footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple stages of power conversion are used for low voltage inputs, then voltage conversion capability is improved, but switching losses increase and system efficiency deteriorates
Solution Approach 1:
The patent combines multiple power conversion stages into a single integrated stage that can handle both buck and boost operations. The inverter circuit integrates the functionality of multiple converters into one unified structure, eliminating the need for separate conversion stages and their associated switching losses while maintaining full voltage conversion capability.
Solution Approach 2:
The inverter is designed with universal functionality to perform both buck conversion (when input voltage exceeds output voltage) and boost conversion (when input voltage is below output voltage) within a single circuit architecture. This multi-functional design eliminates the need for separate circuits for different voltage conditions, reducing overall switching losses.
2Stability of the object's composition
If DC link capacitors are used in multi-stage inverter topologies, then energy storage and voltage stabilization are improved, but device footprint and cost increase
Solution Approach 1:
The patent removes the DC link capacitor from the circuit topology by designing a capacitorless inverter architecture. The circuit uses alternative energy storage and voltage stabilization mechanisms inherent in the inductive and switching elements, eliminating the need for bulky electrolytic capacitors and their associated footprint and reliability issues.
Solution Approach 2:
The patent introduces coupled inductors as intermediary energy storage elements that replace the traditional DC link capacitor. These inductors provide the necessary energy buffering and voltage stabilization functions without requiring large capacitive components, thereby reducing device footprint while maintaining voltage stability.
3Device complexity
If unidirectional configuration is used, then circuit simplicity is improved, but energy flow flexibility and waveform quality deteriorate
Solution Approach 1:
The patent inverts the traditional unidirectional energy flow approach by implementing bidirectional switches and coupled inductors that enable energy to flow in both directions. This inversion allows the circuit to adapt to different operating modes (buck and boost) and maintain waveform quality across varying load conditions while adding minimal complexity through symmetric circuit design.
Data Source
AI summary
Disclosed is a novel and innovative class of buck-boost bidirectional inverters achieve ultra high efficiency in applications requiring converting of one or more low and variable DC voltages of one or more power sources (which may include a battery, a low-voltage DC source, or a set of PV solar panels) to an AC voltage (e.g., connected to a grid) through a single-stage power conversion with step modulation.