Switching-Loss Balancing Circuit for Multilevel Inverters
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Solution Overview
Problem
In photovoltaic power generation systems, the switching losses in multilevel inverters are unevenly distributed between high-side and low-side switches, leading to concentrated heat generation and limited temperature operating conditions due to differential impedance between upper and lower switches.
Innovation Solution
A balancing circuit is introduced, comprising additional resistors connected to the voltage sensing unit of a power conversion device, which balances the impedance between high-side and low-side switches by connecting a second resistor to the (+) terminal and a fourth resistor to the (−) terminal, ensuring equal VDS voltage across all switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a differential amplifier is added to sense AC voltage at the output end, then the lower impedance is reduced and VDS voltage of switches (S1, S3) becomes DC-LINK voltage, but the switching loss is concentrated on S1 and S3 and upper switches generate more heat
Solution Approach 1:
The patent applies asymmetry by introducing different impedance paths for upper and lower switches through the balancing circuit. The differential amplifier configuration creates asymmetric impedance where the lower side has reduced impedance through the added resistor, while the upper side maintains higher impedance, thereby balancing the voltage distribution and switching losses across all switches.
2Measurement precision
If the VDS voltage of switches (S1, S3) becomes DC-LINK voltage due to reduced lower impedance, then voltage sensing is improved, but the use temperature condition is limited under the same switching loss condition
Solution Approach 1:
The patent changes the impedance parameter by adding a resistor to the lower side of the differential amplifier, which modifies the voltage distribution across switches. This parameter change balances the switching losses and heat generation, enabling operation at higher temperatures while maintaining accurate voltage sensing.
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 solution equalizes switching losses between high-side and low-side switches, reducing heat concentration and allowing the system to operate at higher temperature conditions by balancing impedance, thereby improving the overall efficiency and reliability of the power conversion device.
Implementation Method 1
a second resistor connected to the same node as that of a first resistor of a voltage sensing unit connected to a first terminal of an output end of a power conversion device; and a fourth resistor connected to the same node as that of a third resistor of the voltage sensing unit connected to a second terminal of the output end of the power conversion device
Data Source
AI summary
A balancing circuit according to an embodiment of the present invention comprises: a second resistor connected to the same node as that of a first resistor of a voltage sensing unit connected to a first terminal of an output end of a power conversion device; and a fourth resistor connected to the same node as that of a third resistor of the voltage sensing unit connected to a second terminal of the output end of the power conversion device, wherein the second resistor and the fourth resistor are connected to an upper switch of the power conversion device.