Common DC Bus Inverter Reconnection Without In-Rush Current
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Solution Overview
Problem
Existing drive systems with a common DC bus face challenges in reconnecting an inverter without causing in-rush currents, which can be damaging, especially when the inverter has been offline for maintenance or repair, and require dedicated pre-charge circuits for each inverter, leading to complex and costly designs.
Innovation Solution
A drive system with a single pre-charge circuit that connects to multiple local DC buses, allowing the capacitor network of an inverter to be pre-charged before reconnecting it to the common DC bus, thereby mitigating in-rush currents and eliminating the need for dedicated pre-charge circuits for each inverter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dedicated pre-charge circuit is provided for each inverter, then in-rush current damage is prevented, but device complexity and cost increase
Solution Approach 1:
The patent merges multiple dedicated pre-charge circuits into a single shared pre-charge circuit that serves multiple inverters. The pre-charge bus connects the single pre-charge circuit to multiple inverter DC buses, allowing any inverter to be pre-charged through the shared circuit. This reduces component count and system complexity while maintaining the protective function against in-rush currents.
Solution Approach 2:
The single pre-charge circuit is designed with universal functionality to serve multiple inverters. It can pre-charge any inverter's DC bus independently through the pre-charge bus and switching mechanisms, making the pre-charge resource shared and multi-functional rather than dedicated to a single inverter.
2Device complexity
If inverters are reconnected to the common DC bus without pre-charging, then system simplicity is maintained, but in-rush currents cause damage
Solution Approach 1:
The system performs preliminary pre-charging action through the shared pre-charge circuit before connecting inverters to the common DC bus. The pre-charge switches control the timing to ensure capacitors are charged to the appropriate voltage level before main connection, preventing harmful in-rush currents while maintaining operational simplicity.
Solution Approach 2:
The pre-charge bus acts as an intermediary between the single pre-charge circuit and multiple inverter DC buses. It provides a controlled intermediate connection path that enables pre-charging without direct connection to the common DC bus, thereby preventing in-rush currents while maintaining system simplicity.
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
The system operates fault-tolerantly without service interruptions to other inverters, is simpler and less expensive, and effectively manages inverter reconnection without in-rush currents, enhancing reliability and reducing component count.
Implementation Method 1
a capacitor network connected to the local DC bus
Data Source
AI summary
A system includes: a pre-charge circuit configured to produce direct current (DC) electrical power; a common DC bus; and a plurality of inverters, each inverter including: a local DC bus; a capacitor network connected to the local DC bus; an electrical network connected to the local DC bus, the electrical network configured to generate an alternating current (AC) drive signal; and a plurality of switching assemblies, each switching assembly being associated with one of the inverters, and each switching assembly configured to control whether the local DC bus and the capacitor network of the associated inverter are electrically connected to the common DC bus or to the pre-charge circuit.