N-level AC-DC Converter Reduces Filter Size
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Solution Overview
Problem
Traditional conversion devices face challenges in reducing size and cost, particularly in high-power applications, due to the use of high-voltage semiconductor devices with low operating frequencies, leading to increased filter size and cost, and inefficiencies at light or half loads.
Innovation Solution
The proposed conversion device employs an N-level AC-DC converter with semiconductor devices connected in series, allowing for higher switching frequencies and a more efficient filter design, along with a controller for dynamic power management and a DC circuit breaker for fault handling, integrated with a medium-voltage DC micro-grid architecture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-voltage semiconductor devices are used in traditional conversion devices, then the device can handle high-power applications, but the operating frequency is low leading to increased filter size and cost
Solution Approach 1:
The patent divides the high-voltage power conversion task into multiple lower-voltage stages (N-level converter architecture). Instead of using a single high-voltage semiconductor device, the system segments the voltage into N levels, with each semiconductor device handling only a portion of the total voltage. This segmentation enables higher switching frequencies while maintaining high-power capability, thereby reducing filter size.
Solution Approach 2:
The patent changes the voltage parameter distribution across semiconductor devices. By configuring multiple semiconductor devices in series within each bridge arm and using N-level voltage synthesis, the system transforms the operating voltage parameter from a single high-voltage value to multiple lower voltage levels, enabling higher switching frequencies and reduced filter requirements.
2Device complexity
If traditional AC-DC converter architecture is used, then the system is simple, but efficiency decreases at light or half loads
Solution Approach 1:
The patent introduces dynamic power management capability to the converter system. The controller can dynamically adjust the operating state of the N-level AC-DC converter based on load conditions, switching between different operational modes to maintain high efficiency across varying load levels. This dynamic adaptation resolves the contradiction between architectural simplicity and efficiency under varying conditions.
Solution Approach 2:
The patent implements partial operation capability where the converter can operate with a subset of its full capacity. At light or half loads, the system activates only the necessary portion of the N-level converter stages, avoiding the energy losses associated with operating all components at partial load. This partial action approach maintains efficiency without requiring complete architectural redesign.
3Volume of stationary object
If N-level AC-DC converter with series-connected semiconductor devices is used, then switching frequency increases and filter size reduces, but device complexity increases
Solution Approach 1:
The patent designs the N-level AC-DC converter with multi-functional bridge arms that can operate in different configurations. Each bridge arm is designed to handle multiple voltage levels and can be selectively activated based on operating conditions. This universal design approach reduces the overall system complexity compared to having separate converters for each voltage level, while still achieving the benefits of high switching frequency and reduced filter size.
Data Source
AI summary
A conversion device includes: an inductor electrically connected to the AC power grid; a first-stage converter configured to output a bus voltage according to the AC power grid, wherein the first-stage converter includes an N-level alternating current-direct current (AC-DC) converter, and the N-level AC-DC converter includes a plurality of switch bridge arms, wherein both an upper bridge arm and a lower bridge arm of each of the plurality of switch bridge arms of the N-level AC-DC converter include a plurality of semiconductor devices connected in series, and a rated withstand voltage Vsemi of each of the semiconductor devices is greater than or equal to (Vbus*δ)/((N−1)*Nseries*λ); and a second-stage converter configured to convert the bus voltage into an output voltage to supply energy to the load.