Hybrid TCSC With Filter Switch for SSR Damping
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Solution Overview
Problem
Conventional series capacitors in power systems face issues with destabilization of torsional systems, sub-synchronous resonance, and electrical instability, which can cause damage to mechanical and electrical components, and existing solutions like passive damping filters and thyristor-controlled series capacitors (TCSCs) have limitations in mitigating these problems effectively.
Innovation Solution
A hybrid TCSC and passive damping filter circuit that coordinates the application of both technologies for improved SSR mitigation and power oscillation damping, employing a filter switch to selectively control the operation of the passive damping filter and thyristor-controlled circuit, allowing for coordinated damping of sub-synchronous series resonance and transient states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passive damping filter is used to damp sub-synchronous series resonance, then SSR mitigation is improved, but power dissipation increases due to continuous conduction through the filter resistor
Solution Approach 1:
The filter switch controls the filter resistor to conduct periodically rather than continuously. The switch opens during steady-state operation to block current and minimize power dissipation, then closes during transient conditions to provide damping when needed. This periodic switching action resolves the contradiction by providing SSR mitigation only when necessary while minimizing continuous power loss.
Solution Approach 2:
The damping filter circuit transitions from a static continuous conduction mode to a dynamic switched mode. The filter switch dynamically changes the circuit configuration based on operating conditions, allowing the system to adapt between minimal power dissipation during steady-state and active damping during transients, thus resolving the contradiction between continuous mitigation and energy loss.
2Adaptability or versatility
If a thyristor-controlled series capacitor (TCSC) is used to control conduction duration, then reactance control is improved, but conflicting control commands occur during transient states
Solution Approach 1:
The control system is segmented into two independent parts: the TCSC for steady-state reactance control and the filter switch for transient damping control. This segmentation allows each component to operate independently without conflicting commands, as the filter switch provides a dedicated transient response path that does not interfere with TCSC's continuous reactance modulation.
Solution Approach 2:
The filter circuit acts as an intermediary element that handles transient damping separately from the TCSC's primary reactance control function. By introducing this intermediate damping path with its own independent switch control, the system avoids the conflicting commands that would otherwise occur within the TCSC control system during transient states.
3Reliability
If the filter switch is closed to provide damping during transients, then power oscillation damping is improved, but steady-state conduction and power dissipation increase
Solution Approach 1:
The filter switch operates periodically, closing during transient oscillations to provide damping and opening during steady-state operation to minimize power dissipation. This periodic switching pattern ensures that the damping function is activated only when power oscillations are present, resolving the contradiction between providing oscillation damping and minimizing continuous energy loss.
4Temperature
If deionized water cooling is used for the thyristor valve, then thermal management is improved, but system complexity and maintenance requirements increase
Solution Approach 1:
The complex deionized water cooling system is extracted and replaced with a simpler air-cooling or natural convection cooling approach. By removing the water cooling subsystem entirely, the patent simplifies the thermal management system while still maintaining acceptable operating temperatures for the thyristor valve, thus reducing device complexity and maintenance requirements.
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 hybrid solution enhances SSR mitigation performance in both steady and transient states, reduces component damage, and minimizes power losses by enabling efficient damping of sub-synchronous resonance and transient torque amplification, while eliminating the need for cooling processes in the thyristor-controlled circuit.
Implementation Method 1
The filter resistor 122 damps the sub-synchronous series resonance caused by the main capacitor bank 110
Implementation Method 2
The capacitor 124 and the filter reactor 126 block current in resistor 122 at the synchronous frequency
Implementation Method 3
The capacitor 124 and the filter reactor 126 block current in resistor 122 at the synchronous frequency
Implementation Method 4
a thyristor valve reactor 220 serially connected with a thyristor valve 230 having a pair of anti-parallel connected thyristors which operate as a switching device
Data Source
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AI summary
Provided is a series compensation circuit (e.g., a hybrid thyristor-controlled series capacitor (TCSC) and passive damping circuit (300)) for controlling a flow of power on a transmission line (305). The circuit (300) includes a filter circuit (320) and a thyristor-controlled circuit (340). An interconnection and operation of the filter circuit (320) and the thyristor-controlled circuit (340) are performed, based on a coordination of control thereof, to connect to a series capacitor bank (310) on the transmission line (305).