Active Crowbar Circuit for DFIG Fault Ride-Through
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Solution Overview
Problem
Doubly fed induction generators are sensitive to power grid faults, leading to control challenges and converter damage due to rapid current rises, and existing active crowbar circuits face issues with high voltage spikes and reduced service life.
Innovation Solution
A power grid fault ride-through device with a crowbar circuit comprising a switch circuit of full-controlled power electronic devices, connected between the du/dt inductance and generator-side converter, which includes a detection circuit, energy consumption resistance, and filter circuit to manage voltage spikes and extend the service life of the active crowbar circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passive crowbar circuit with half-controlled power electronic devices is used, then the converters are protected from overcurrent damage, but the devices cannot be switched off before the generator rotor energy is depleted, preventing continuous operation
Solution Approach 1:
The patent changes the control parameter from passive (half-controlled devices) to active (full-controlled devices), enabling bidirectional control of current flow. This allows the crowbar circuit to be switched off when rotor energy is depleted, restoring continuous operation capability while maintaining converter protection through controlled activation during faults.
Solution Approach 2:
The patent introduces dynamic control capability to the crowbar circuit by using full-controlled power electronic devices that can be activated and deactivated based on real-time system conditions. This dynamic behavior allows the system to adapt between protection mode during faults and normal operation mode, resolving the contradiction between protection and continuous operation.
2Duration of action of moving object
If an active crowbar circuit is used to enable continuous operation, then the generator can provide reactive power support during faults, but high voltage spikes occur when the crowbar circuit is switched off, threatening device safety
Solution Approach 1:
The patent applies beforehand cushioning by introducing an absorption circuit with parallel connection of resistance and capacitance. This circuit is pre-configured to absorb and suppress voltage spikes that occur when the crowbar circuit is switched off, protecting the full-controlled power electronic devices from damage while enabling continuous operation capability.
Solution Approach 2:
The absorption circuit acts as an intermediary element between the crowbar circuit and the power electronic devices. It mediates the harmful voltage spikes by providing a controlled discharge path, allowing the crowbar circuit to be switched off safely while protecting the connected devices from overvoltage damage.
3Reliability
If the crowbar circuit is connected between the du/dt inductance and rotor winding, then it protects the converter during faults, but high voltage generated by du/dt inductance when switched off can break through the power electronic device
Solution Approach 1:
The patent introduces the absorption circuit as an intermediary protective element between the du/dt inductance and the power electronic device. When the crowbar circuit is switched off, the absorption circuit absorbs the high voltage generated by the du/dt inductance, preventing it from breaking through and damaging the power electronic device, thus resolving the contradiction between protection function and device strength.
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 solution effectively prevents damage from high voltage spikes and prolongs the service life of the active crowbar circuit, enhancing its reliability and enabling continuous operation during power grid faults by managing voltage pulses and current flows.
Implementation Method 1
the passive crowbar circuit 30 is composed of a three-phase uncontrolled rectifier bridge, which is composed of diodes 31, and an energy consumption resistance 32
Data Source
AI summary
The invention discloses a power grid fault ride-through device and a method for a doubly fed induction generator. The device comprises a controller and a crowbar circuit, the controller is in controlled connection with a generator-side converter and a grid-side converter of the doubly fed induction generator and the crowbar circuit, a three-phase input end of the crowbar circuit is connected with a connection end of a du/dt inductance and the generator-side converter, the crowbar circuit comprises a switch circuit and a drive circuit which is in driving connection with the switch circuit, the controller is in controlled connection with the drive circuit, the switch circuit comprises a bridge circuit comprising full-controlled power electronic devices as constituent elements, and a three-phase input end of the switch circuit is connected to the three-phase input end of the crowbar circuit; and with the device, the method comprises the following steps of closing the generator-side converter and triggering the conduction of the switch circuit in case that a power grid dips to the condition that rotor current is equal to or larger than a conduction threshold value, and switching off the switch circuit in case that rotor current is equal to or smaller than a switch-off threshold value. The invention prolongs the service life of the crowbar circuit and improves the working reliability of the crowbar circuit, and has simple structure and easy implementation.