DC Rail Capacitor Backup for Selective Fault Isolation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electric power systems, particularly in ships, face challenges in providing sufficient fault current quickly enough to effectively isolate faulty components during a fault situation, leading to potential incomplete separation of the faulty portion from the rest of the system.
Innovation Solution
The introduction of a capacitor system connected to the direct voltage rail via a second over-current protector, which can supply fault current to switch the first over-current protectors into a non-conductive state, ensuring selective protection by mitigating voltage drops and providing sufficient fault current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If supply-converters are designed with basic components (inductor coil, controllable switch, diode) for voltage conversion, then device complexity is reduced and cost effectiveness is improved, but fault current supply capability within sufficient time is insufficient
Solution Approach 1:
The capacitor system is pre-charged during normal operation from the direct voltage rail, storing energy in advance. When a fault occurs, this pre-stored energy is immediately discharged through the second over-current protector to provide sufficient fault current for rapid fuse operation, eliminating the need for complex active fault current injection circuits in the supply-converters.
Solution Approach 2:
The capacitor system acts as an intermediary energy storage device between the direct voltage rail and the fault location. It mediates the fault current supply by being charged from the healthy portions of the system during normal operation and then discharging to assist fault clearing, decoupling the fault current supply function from the supply-converter design.
2Reliability
If fuses or over-current protectors are installed at each supply-converter and load-converter for selective protection, then fault isolation capability is improved, but fault current magnitude within sufficient time is insufficient to reliably operate protectors
Solution Approach 1:
The capacitor system is pre-charged during normal operation from the direct voltage rail, storing energy in advance. When a fault occurs, this pre-stored energy is immediately discharged through the second over-current protector to provide sufficient fault current for rapid fuse operation, eliminating the need for complex active fault current injection circuits in the supply-converters.
3Reliability
If additional means are added to supply-converters to provide sufficient fault current quickly, then fault current supply capability is improved, but device complexity and cost increase significantly
Solution Approach 1:
The capacitor system acts as an intermediary energy storage device between the direct voltage rail and the fault location. It mediates the fault current supply by being charged from the healthy portions of the system during normal operation and then discharging to assist fault clearing, decoupling the fault current supply function from the supply-converter design.
Solution Approach 2:
The capacitor system automatically charges itself from the direct voltage rail during normal operation and automatically discharges during faults without requiring complex control circuits or active management in the supply-converters. This self-service mechanism provides fault current support while keeping the supply-converter design simple and cost-effective.
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 enables rapid and effective isolation of faulty components by ensuring sufficient fault current is available to trigger the over-current protectors, thereby maintaining system integrity and operational reliability.
Implementation Method 1
a capacitor system connected to the direct voltage rail via a second over-current protector and comprising one or more capacitors, the capacitor system being capable of supplying fault current for switching one of the first over-current protectors into a non-conductive state
Data Source
Figure 1a
Figure 1b
AI summary
An electric power system comprises a direct voltage rail (101), battery elements (102-104) connected with supply-converters (105-107) to the direct voltage rail, and load-converters (111-113) for converting direct voltage of the direct voltage rail into voltages suitable for loads of the electric power system, where the supply-converters and the load-converters are connected with over-current protectors (108-110, 114-116) to the direct voltage rail. The electric power system further comprises a capacitor system (117) connected to the direct voltage rail and capable of supplying fault current for switching an over-current protector into a non-conductive state in response to a fault causing a voltage drop at an electrical node connected to the direct voltage rail via the over-current protector. The capacitor system may comprise one or more high-capacitance electric double layer capacitors. The fault current available from the capacitor system enables a selective protection.