DC Power Terminal Pairing for Oscillation Damping
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Solution Overview
Problem
Multiterminal DC (MTDC) grids face increased complexity in power oscillation damping due to numerous combinations of active power distribution among terminals, making it challenging to efficiently damp interarea oscillations between power generating machines in different regions of an AC power system.
Innovation Solution
A method involving a DC power system with multiple terminals, where terminals are paired based on dynamic models of the power system and AC power system regions to modulate active and reactive power, ensuring a selected power difference criteria is met, thereby damping oscillations without relying on primary controls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple terminals are used in MTDC grids to convey power between locations, then power transmission capability and adaptability are improved, but device complexity and control difficulty increase due to numerous combinations of active power distribution
Solution Approach 1:
The patent segments the complex MTDC grid into multiple terminal pairs, where each pair is independently controlled for power oscillation damping. By dividing the overall control task into smaller terminal-specific control units, the system manages complexity while maintaining the ability to damp oscillations across the entire grid. Each terminal pair operates with its own controller that modulates active power based on local oscillation conditions.
2Reliability
If active power modulation is applied at terminals to damp interarea oscillations, then oscillation damping effectiveness is improved, but power distribution stability deteriorates due to imbalances among terminals
Solution Approach 1:
The patent merges the oscillation damping function with the primary power distribution control by implementing a coordinated control strategy. The active power modulation for damping is combined with the primary control signals in a unified control framework, ensuring that damping actions do not create power imbalances. The controllers at each terminal pair coordinate their power modulation to maintain overall power distribution stability while achieving effective oscillation damping.
Solution Approach 2:
The patent implements feedback mechanisms where controllers at each terminal pair monitor oscillation conditions and adjust active power modulation accordingly. The feedback loop detects oscillations and automatically modulates power to damp them, while also monitoring power distribution to prevent imbalances. This closed-loop control ensures both oscillation damping effectiveness and power distribution stability are maintained simultaneously.
3Productivity
If terminals are paired and controlled independently for oscillation damping, then damping efficiency is improved, but direct voltage variations increase within the DC power system
Solution Approach 1:
The patent applies counterbalancing control where terminal pairs modulate their active power in opposite directions to damp oscillations. When one terminal in a pair increases power output, the other terminal decreases it by a corresponding amount, creating a counterbalancing effect. This anti-weight approach allows efficient oscillation damping while maintaining overall DC voltage stability, as the net power injection variation is minimized.
Data Source
AI summary
Embodiments disclose using a pairing or pairings of terminals in a DC power system including a plurality of terminals to implement power oscillation damping (POD), where the DC power system is connectable to at least one AC power system. The active and/or reactive power of the terminals in the pairing may be controlled or modulated in a similar manner such that no power imbalance in the DC power system is created. For example, POD may be implemented by means of active and/or reactive power modulation by pairing two terminals in the DC power system) such that their active and/or reactive powers are controlled or modulated in the same or substantially the same manner or identically but with the opposite sign.