Grid-Connected Inverter Control for Zero-Voltage Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional grid-connected inverters suffer from significant turn-on losses in switching transistors due to hard-switching control methods, hindering advancements in high-frequency and high-efficiency operations.
Innovation Solution
A grid-connected inverter control method that employs zero-voltage/valley-voltage switching of switching transistors by determining the switching period and duty ratio based on DC input voltage, grid voltage, and polarity of the grid-connected reference current, using a calculation rule that meets zero-voltage/valley-voltage switching conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional hard-switching control method is used, then the inverter can operate at utility frequency, but the switching transistor experiences significant turn-on loss
Solution Approach 1:
The patent applies preliminary action by ensuring that the switching transistor is turned on when the voltage across it is already at zero or valley level. This is achieved by calculating the switching period based on the resonant characteristics of the LC circuit, allowing the voltage to naturally oscillate to zero before the switching transistor is activated. This preliminary preparation of zero-voltage condition eliminates turn-on losses while enabling high-frequency operation.
Solution Approach 2:
The patent changes the operating parameters of the switching transistor by transitioning from conventional hard-switching to zero-voltage/valley-voltage switching. The switching period and duty ratio are dynamically adjusted based on the resonant frequency of the LC circuit, allowing the voltage across the switching transistor to reach zero or valley level before turn-on. This parameter change enables high-frequency operation with minimal losses.
2Loss of energy
If high-frequency switching operation is implemented, then efficiency can be improved, but turn-on loss of switching transistor increases significantly
Solution Approach 1:
The patent applies preliminary action by ensuring that the switching transistor is turned on when the voltage across it is already at zero or valley level. This is achieved by calculating the switching period based on the resonant characteristics of the LC circuit, allowing the voltage to naturally oscillate to zero before the switching transistor is activated. This preliminary preparation of zero-voltage condition eliminates turn-on losses while enabling high-frequency operation.
Solution Approach 2:
The patent changes the operating parameters of the switching transistor by transitioning from conventional hard-switching to zero-voltage/valley-voltage switching. The switching period and duty ratio are dynamically adjusted based on the resonant frequency of the LC circuit, allowing the voltage across the switching transistor to reach zero or valley level before turn-on. This parameter change enables high-frequency operation with minimal losses.
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The present application relates to a grid-connected inverter control method and a grid-connected inverter, wherein the method comprises: acquiring a DC input voltage, a grid voltage and a grid-connected reference current; determining a switching transistor operating at high frequency according to the polarity of the grid-connected reference current; determining the current working mode of the grid-connected inverter according to the grid voltage and the polarity of the grid-connected reference current; determining the switching period and the duty ratio of the switching transistor according to the DC input voltage, the grid voltage and a period calculation rule corresponding to the working mode; and controlling zero-voltage/valley-voltage switching of the switching transistor according to the switching period and the duty ratio of the switching transistor. Therefore, the zero-voltage/valley-voltage switching of the switching transistor for the grid-connected inverter is realized, which effectively reduces the loss caused by the turn-on process of the switching transistor.