Multi-level inverter bypass operation without extra switches
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Solution Overview
Problem
Medium voltage inverters without bypass switches for controlling bypass operations face increased DC-link voltage due to abnormal unit cells, leading to capacitor damage and operational failures.
Innovation Solution
A multi-level inverter design incorporating a first and second capacitor in series, with switches and diodes configured to allow for bypass operations without additional bypass switches, utilizing a controller to manage switch states for interrupting output voltage through predetermined bypass modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If no bypass switch is provided for controlling bypass operation in abnormal unit cells, then device complexity is reduced, but DC-link voltage increases beyond safe operating range causing capacitor damage
Solution Approach 1:
The normal unit cells automatically perform the bypass function for abnormal unit cells by controlling their switches to conduct, eliminating the need for separate bypass switches. The system uses its own operational components to handle failures, with the controller coordinating switch states to redirect current away from abnormal cells while maintaining DC-link voltage within safe ranges.
2Ease of manufacture
If bypass operation is implemented using existing switches and diodes without additional components, then ease of manufacture is improved, but control complexity increases
Solution Approach 1:
The existing switches and diodes in each unit cell are designed to perform both normal inverter operation and bypass operation. The same power switches that generate multi-level output voltages are also used to conduct current during bypass mode, eliminating the need for dedicated bypass components and simplifying manufacturing while the controller manages the dual functionality through coordinated switching sequences.
Data Source
AI summary
The present disclosure relates to a multi-level inverter capable of performing a bypass operation without adding any separate module. The multi-level inverter includes a first capacitor and a second capacitor coupled in series to each other, a plurality switches for generating a multi-level output voltage by using a voltage charged in the first capacitor and the second capacitor and a plurality of diodes respectively coupled in parallel to the plurality of switches, a first output terminal and a second output terminal for outputting the output voltage, and a controller for switching a state of each of the plurality of switches to an on or off state according to one of predetermined bypass modes, thereby interrupting the output of the output voltage through the first output terminal and the second output terminal.