Variable-Speed Pumped Storage DC-Interruption Prevention
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Solution Overview
Problem
Existing variable-speed pumped storage power systems face challenges in quickly resuming operation after a grid system failure near the interconnection point, particularly due to the risk of DC-interruption by breakers, which can be damaged when the fault current's DC component exceeds the AC component, leading to potential equipment damage.
Innovation Solution
A variable-speed pumped storage power system equipped with a no-resistor short-circuit device capable of three-phase short-circuiting in the generator-motor secondary circuit, controlled by a DC-interruption avoidance device that detects voltage thresholds to prevent DC-interruption by ensuring the AC component can pass the zero point without resistor-induced attenuation, thereby maintaining system continuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If resistors are connected in series to the thyristor short-circuit device to rapidly attenuate fault current, then the fault current attenuation speed is improved, but the AC component attenuation becomes too rapid causing DC-interruption risk
Solution Approach 1:
The fault current attenuation function is divided into two stages: primary attenuation by resistors in the short-circuit device, and secondary attenuation by the exciter voltage reversal. This segmentation allows the resistors to quickly reduce current magnitude while the voltage reversal ensures AC component persistence, preventing DC-interruption of breakers.
Solution Approach 2:
The exciter voltage reversal is prepared and executed immediately after short-circuit device activation. By preliminarily establishing the voltage reversal mechanism, the system ensures that AC component attenuation is controlled even as resistors rapidly reduce fault current, maintaining breaker safety throughout the protection sequence.
2Reliability
If the overvoltage suppression device is activated to protect equipment, then equipment protection is improved, but the system operation continuity deteriorates due to extended shutdown time
Solution Approach 1:
The system implements periodic monitoring of voltage levels and fault conditions, allowing the overvoltage suppression device to be activated only when necessary. This periodic action enables quick deactivation once the fault is suppressed, minimizing shutdown duration and maintaining operation continuity while ensuring equipment protection.
Solution Approach 2:
The control system continuously monitors voltage levels, fault current magnitude, and system status to dynamically control the overvoltage suppression device activation and deactivation. This feedback mechanism ensures the device operates only when needed for protection, automatically deactivating to restore operation continuity, thus balancing equipment protection with productivity.
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 DC-interruptions and ensures safe operation by delaying AC component attenuation, allowing the system to maintain connection with the grid system during failures without damaging breakers, ensuring continuous operation and proper converter capacity.
Implementation Method 1
a no-resistor short-circuit device connected between the rotor winding and the AC exciter and capable of executing three-phase short-circuiting in the three-phase circuit
Implementation Method 2
a high-voltage side circuit voltage detector configured to detect a voltage of a high-voltage side circuit of the transformer
Implementation Method 3
a controller configured to cause the short-circuit device to execute three-phase short-circuiting on a condition that an output voltage of the high-voltage side circuit voltage detector becomes lower than a predetermined value
Data Source
Figure 1
Figure 2
Figure 3
AI summary
According to one embodiment, there is provided a variable-speed pumped storage power system (200), which includes a high-voltage side circuit voltage detector (104) configured to detect a voltage of a high-voltage side circuit of the transformer (M); a no-resistor short-circuit device (151) which is connected between the rotor winding and the AC exciter (3) and is capable of executing three-phase short-circuiting in the three-phase circuit; and a controller (153) configured to cause the short-circuit device (151) to execute three-phase short-circuiting on a condition that an output voltage of the high-voltage side circuit voltage detector (104) becomes lower than a predetermined value.