Doubly Fed Asynchronous Generator Fault Ride-Through Control
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Solution Overview
Problem
Current control and protection systems for doubly fed asynchronous generators in wind turbines fail to effectively manage asymmetrical faults, leading to generator decoupling from the grid due to unregulated current oscillations and increased risk to converter components during symmetrical faults.
Innovation Solution
A comprehensive control and protection system that includes a central control unit, resistor branches for initial energy absorption, and PI regulators to dampen rotor currents and manage oscillations, ensuring safe operation during both symmetrical and asymmetrical faults by preventing over-voltages and maintaining generator control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the converter over-current protection causes the converter to disconnect during grid voltage dips, then the converter is protected from over-current damage, but the generator is disconnected from the grid and the BUS voltage increases putting converter components at risk
Solution Approach 1:
The crowbar circuit acts as an intermediary protective device that is activated during grid faults to short-circuit the rotor windings. This mediator prevents harmful currents from damaging the converter while avoiding the harmful effect of BUS voltage increase by providing a controlled discharge path for the intermediate circuit through the crowbar activation sequence
Solution Approach 2:
The system activates the crowbar circuit in advance before the fault conditions can cause damage to converter components. By detecting grid faults early and pre-activating the crowbar protection mechanism, the system cushions against the harmful effects of over-current and voltage transients before they can occur
2Reliability
If the generator is disconnected from the grid during asymmetrical faults, then the converter is protected from current oscillations, but the generator loses control and is finally decoupled from the grid
Solution Approach 1:
The control system continuously monitors grid conditions and provides feedback to determine whether to activate crowbar protection or maintain generator control. By using feedback from voltage and current sensors, the system can distinguish between symmetrical and asymmetrical faults and respond appropriately, maintaining productivity when possible while ensuring converter protection when necessary
Solution Approach 2:
The system dynamically adjusts its protection strategy based on the type of fault detected. For asymmetrical faults, the control system can maintain generator operation with adjusted parameters rather than immediate disconnection, allowing the generator to ride through the fault while the crowbar provides selective protection only when absolutely necessary
3Productivity
If control mechanisms are introduced to regulate generator power during asymmetrical faults, then generator control is maintained, but the system complexity increases
Solution Approach 1:
The existing converter control system is enhanced to perform multiple functions: normal power regulation, fault detection, crowbar control, and ride-through management. By making the control system universal and multi-functional, the patent avoids adding separate dedicated systems for each function, thereby limiting the increase in overall system complexity while maintaining generator regulation capability during asymmetrical faults
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 effectively protects the converter and maintains generator control during grid faults, preventing over-voltages and ensuring stable operation by dampening rotor currents and managing fault-induced oscillations, thus meeting stringent grid operation requirements.
Implementation Method 1
resistor branches for initial energy absorption
Implementation Method 2
PI regulators to dampen rotor currents and manage oscillations
Data Source
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AI summary
The invention relates to a system for controlling and protecting against symmetrical and asymmetrical faults for double-fed asynchronous-type generators, which, in the event of a symmetrical or asymmetrical fault, remains connected to the grid, absorbing the initial transient, and maintains control of the aerogenerator. In this way, the invention fulfils the requirements of the various different grid connection standards relating to the supply of active and reactive power in fault situations, which are intended to assist in the recovery of the grid.