Inverter Auxiliary Power Circuit Segmentation for Efficiency
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Solution Overview
Problem
Inverters used in photovoltaic grid-connected systems face low power conversion efficiency under light load states due to high voltage stress and hard switching features of conventional flyback converters, which are exacerbated by varying DC input voltages from photovoltaic modules.
Innovation Solution
The inverter design incorporates a DC-DC conversion circuit that generates auxiliary power for both itself and the inverting circuit, allowing the auxiliary power circuit to be implemented as a non-isolated DC-DC converter, reducing power loss by eliminating the need to supply power to the inverting circuit directly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flyback converter is used as the auxiliary power circuit, then the auxiliary power can be supplied to the inverting circuit, but the power conversion efficiency under light load state is low due to high voltage stress and hard switching
Solution Approach 1:
The patent divides the auxiliary power supply function into two separate circuits: a first auxiliary power circuit (flyback converter) that supplies power to the DC-DC conversion circuit, and a second auxiliary power circuit (non-isolated DC-DC converter) that supplies power to the inverting circuit. This segmentation allows each circuit to be optimized for its specific function, with the second circuit operating at lower voltage stress and achieving higher efficiency under light load conditions.
Solution Approach 2:
The patent introduces an intermediate DC-DC conversion circuit that acts as a mediator between the first auxiliary power circuit and the inverting circuit. Instead of directly supplying power from the high-voltage flyback converter to the inverting circuit, the DC-DC conversion circuit converts the high voltage to a lower voltage suitable for the inverting circuit, thereby reducing voltage stress and improving efficiency in the second auxiliary power circuit.
2Device complexity
If the auxiliary power circuit supplies power to both the DC-DC conversion circuit and the inverting circuit, then the structure is simple, but the power loss increases under light load conditions
Solution Approach 1:
The patent segments the auxiliary power supply into two dedicated circuits with distinct functions. The first auxiliary power circuit is responsible for powering the DC-DC conversion circuit, while the second auxiliary power circuit is responsible for powering the inverting circuit. This segmentation reduces power loss by allowing the second circuit to operate at lower voltage and with optimized switching characteristics suitable for light load conditions.
Solution Approach 2:
The patent applies different circuit topologies and design characteristics to different parts of the auxiliary power system. The first auxiliary power circuit uses a flyback converter topology suitable for high-voltage isolation applications, while the second auxiliary power circuit uses a non-isolated DC-DC converter topology optimized for low-voltage, high-efficiency operation. This local optimization of circuit quality reduces overall power loss.
3Adaptability or versatility
If the DC input voltage varies with sunlight intensity, then the inverter operates under different load states, but the power conversion efficiency deteriorates under light load state
Solution Approach 1:
The patent implements a dynamic auxiliary power supply system that can adapt to varying load conditions. The control circuitry monitors the operating state and adjusts the switching parameters of both auxiliary power circuits to optimize efficiency across different load conditions. The second auxiliary power circuit is specifically designed to maintain high efficiency under light load conditions when sunlight intensity is low.
Solution Approach 2:
The patent changes key operating parameters of the auxiliary power circuits based on load conditions. The second auxiliary power circuit operates with adjusted switching frequencies and duty cycles optimized for light load conditions, thereby maintaining high power conversion efficiency even when the DC input voltage varies due to changing sunlight intensity.
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
This configuration enhances power conversion efficiency, especially under light load conditions, by optimizing the auxiliary power circuit's design and reducing power loss, thereby maintaining system efficiency even during varying sunlight intensities.
Implementation Method 1
The isolation transformer has a primary winding, a first secondary winding and a second secondary winding, where the primary winding is coupled to the first switch circuit
Implementation Method 2
The rectifier and filter circuit is coupled between the isolation transformer and the inverting circuit, and is configured to rectify and filter outputs of the first and the second secondary windings
Data Source
AI summary
An inverter and a power supply method thereof and an application thereof are provided. The inverter includes a DC-DC conversion circuit, an inverting circuit and an auxiliary power circuit. The DC-DC conversion circuit converts a DC input voltage into a DC bus voltage. The inverting circuit is configured to convert the DC bus voltage into an AC output voltage. The auxiliary power circuit is enabled in response to the DC input voltage, and the auxiliary power circuit generates a first auxiliary power for enabling the DC-DC conversion circuit after being enabled. The DC-DC conversion circuit is enabled in response to the first auxiliary power, and the DC-DC conversion circuit generates a second auxiliary power for enabling the inverting circuit after being enabled, such that the inverting circuit is enabled in response to the second auxiliary power and generates the AC output voltage.