Induction Machine Parallel with Power Electronics for Fault Current
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Solution Overview
Problem
Conventional power distribution systems face challenges in effectively triggering protection devices like fuses and circuit breakers due to differing fault current characteristics between synchronous generators and Power Electronics (PE) interfaces, leading to inadequate fault clearance times and increased costs with existing solutions.
Innovation Solution
Incorporating an Induction Machine (IM) connected in parallel with a PE interface in the power distribution system, which acts as an asynchronous motor during regular operation and provides a fault current similar to a synchronous generator, enabling faster fault clearance without additional mechanical energy exchange.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a PE interface is used to interface renewable energy sources or energy storage systems to the distribution grid, then the conversion efficiency and controllability are improved, but the fault current capability deteriorates causing protection devices to fail to operate as intended
Solution Approach 1:
A synchronous compensator is introduced as an intermediary device between the PE interface and the distribution grid. This compensator provides the necessary fault current capability while allowing the PE interface to maintain its high conversion efficiency and controllability for normal power conversion operations.
Solution Approach 2:
The invention merges the functions of the PE interface and the synchronous compensator into a hybrid system. The PE interface handles efficient power conversion while the synchronous compensator contributes fault current, creating a combined system that achieves both high conversion efficiency and adequate fault current capability.
2Reliability
If the rating or size of the inverter of the PE interface is increased to improve fault current capability, then the fault current capability is improved, but the cost and space requirements increase
Solution Approach 1:
The fault current capability is segmented between two components: the PE interface maintains its original smaller size for efficient power conversion, while the synchronous compensator provides the additional fault current capability. This segmentation avoids the need to oversize the inverter.
Solution Approach 2:
The synchronous compensator serves multiple functions: it provides fault current capability during faults, and during normal operation it can provide voltage control and power factor correction. This multi-functionality justifies its inclusion without requiring the PE interface to be oversized.
3Reliability
If synchronous compensators or diesel generators are operated online to provide fault current, then the fault current capability is improved, but the additional cost, space, and operating losses increase
Solution Approach 1:
The synchronous compensator operates continuously online, providing not only fault current capability when needed but also continuous voltage control and power factor correction during normal operation. This continuous useful action justifies the operating losses by providing multiple beneficial functions throughout system operation.
Solution Approach 2:
The synchronous compensator dynamically adjusts its operating parameters (reactive power output, voltage level) to match system conditions. During normal operation it provides voltage support and power factor correction, and during faults it switches to providing fault current, optimizing its contribution at each moment.
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 approach allows for efficient and economical fault current enhancement, enabling protection devices to clear faults within a reduced time frame, comparable to synchronous generator systems, while minimizing costs and maintenance.
Implementation Method 1
An Induction Machine (IM) is connected in parallel with a Power Electronics (PE) interface... provides a fault current similar to a synchronous generator
Implementation Method 2
The Induction Machine will act or is configured to act as a motor, in particular as an asynchronous motor, during regular operation
Data Source
AI summary
The present invention is concerned with a fault current enhancement for triggering a protection device, such as a fuse or circuit breaker or protection relay used in protecting a distribution line of a power distribution network in an efficient and economical way. An Induction Machine (IM) is operated in parallel with an energy source connected to the distribution line via a Power Electronics (PE) interface, to provide a fault current characteristic of the composite PE interface and IM similar to that of a synchronous generator. Comparable fault currents enable a same protection device to be provided for protecting the distribution line irrespective of a kind of interface used to source energy to the distribution line.