Resistive Braking for Grid Fault Ride-Through
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Solution Overview
Problem
Small generator sets with low moments of inertia connected to an electric grid face challenges in maintaining synchronization and power supply during grid faults, as they tend to trip offline due to voltage drops, which is undesirable as the penetration of these sets increases, necessitating a method to ride through faults and continue supplying power.
Innovation Solution
A power generation system with a resistive braking system comprising a mechanical switch and a resistor connected in parallel, controlled by a controller that redirects current to the resistor during grid events and partially or fully switches off the engine's ignition to manage power delivery, ensuring the generator remains synchronized with the grid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If small generator sets trip offline during voltage drops, then they protect themselves from damage, but they fail to meet grid code requirements for fault voltage ride-through
Solution Approach 1:
A mechanical switch is introduced as an intermediary component to redirect current from the generator during fault conditions. The switch acts as a mediator between the generator and the grid, enabling the generator to ride through voltage drops without direct exposure to fault conditions, thus achieving fault voltage ride-through capability while maintaining system protection
Solution Approach 2:
The mechanical switch is pre-configured and ready to activate immediately upon detection of voltage drops. The system performs preliminary preparation by having the switch mechanism in place and the control logic predetermined, allowing rapid response to faults without requiring complex real-time decision-making systems
2Reliability
If small generator sets remain on line during low voltage conditions, then they maintain synchronization with the grid, but they risk loss of synchronism due to low moments of inertia
Solution Approach 1:
The mechanical switch serves as a protective intermediary that isolates the generator from severe voltage drops while allowing it to remain connected to the grid. This enables the generator to maintain synchronization during mild low voltage conditions without exposing it to harmful fault conditions that could cause loss of synchronism
Solution Approach 2:
The system applies partial protection by using the mechanical switch to redirect current only during significant voltage drops, while allowing the generator to operate normally during mild fluctuations. This selective approach maintains synchronization during acceptable conditions while protecting against severe faults
3Device complexity
If a mechanical switch is used to redirect current during faults, then the system structure is simplified, but the switch may remain closed too long causing excessive arcing
Solution Approach 1:
A controller continuously monitors the mechanical switch position and grid conditions, providing feedback to determine when to open or close the switch. This feedback mechanism ensures the switch operates only when necessary and opens promptly when fault conditions clear, preventing excessive arcing while maintaining system simplicity
Solution Approach 2:
The mechanical switch operates in periodic cycles - closing during detected faults to redirect current, then opening when faults clear. This periodic operation pattern, controlled by fault detection and clearance timing, prevents the switch from remaining closed too long and causing excessive arcing
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
Enables small generator sets to ride through grid faults by decelerating the rotor and maintaining synchronization, preventing loss of synchronism and allowing continued power supply after the fault is cleared, thus meeting grid code requirements for fault voltage ride-through.
Implementation Method 1
a resistor to absorb power from the generator during a grid fault condition
Data Source
Figure 1
Figure 2
Figure 3(a)~3(g)
AI summary
A power generation system 40 includes a generator 42 operatively coupled to an engine 60 for generating electrical power and supplying the electrical power to a grid 44. Further, the power generation system 40 includes a resistive braking system 40 operatively coupled between the generator 42 and the grid 44. The resistive braking system 46 includes a mechanical switch 54 connected in parallel with a resistor 52, and a controller 56 for, in response to a grid event, controlling power from the engine 60 and operating the mechanical switch 54 to redirect current between the mechanical switch 54 and the parallel connected resistor 52