Converter-Controlled Generator Grid Support via Oscillation Damping
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Solution Overview
Problem
Directly coupled synchronous generators in electricity supply grids are prone to oscillatory excitations during grid faults, which can lead to instability and potential disruption of the grid, and decentralized generators may inadvertently exacerbate these oscillations.
Innovation Solution
A method involving a converter-controlled generation unit that selects between normal and support control functions based on grid stability, using grid frequency and voltage as state variables to feed active and reactive power, with the support control function specifically designed to counteract synchronous generator oscillations by adjusting power infeed in response to measured frequency gradients and oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If decentralized generators feed additional power into the electricity supply grid during grid faults, then grid support and stability are improved, but oscillatory excitation of synchronous generators is worsened
Solution Approach 1:
The control function continuously monitors grid frequency and voltage as state variables, and adjusts the active and reactive power infeed accordingly. During grid faults, the system detects frequency deviations and oscillations, then modulates the power output to counteract these deviations while avoiding excitation of synchronous generators. This closed-loop feedback mechanism enables the decentralized generator to provide grid support without causing harmful oscillations.
Solution Approach 2:
The control function dynamically switches between normal operation mode and grid support mode based on real-time grid conditions. During grid faults, the system transitions to a dynamic response where power infeed is continuously adjusted according to measured frequency gradients and oscillation characteristics. This dynamic adaptation allows the system to respond rapidly to grid disturbances while avoiding the fixed, potentially harmful infeed patterns that could excite synchronous generators.
2Productivity
If converter-controlled generation units rapidly increase active power infeed following grid faults, then grid support effectiveness is improved, but oscillatory excitation of synchronous generators is worsened
Solution Approach 1:
The control function applies periodic modulation to the active power infeed based on detected oscillation frequency and characteristics. When synchronous generator oscillations are detected, the system superimposes a counter-phase periodic power adjustment that opposes the oscillation frequency. This periodic action rapidly counteracts oscillations while maintaining effective grid support, as the modulation frequency is specifically tailored to match and cancel the harmful oscillations.
Solution Approach 2:
The control function dynamically changes power infeed parameters including active power magnitude, reactive power level, and modulation depth based on real-time grid conditions. Following grid faults, the system adjusts these parameters to provide rapid support while monitoring for oscillatory patterns. When oscillations are detected, the parameters are further modified to dampen the oscillations, thus achieving both rapid response and oscillation avoidance through continuous parameter optimization.
Data Source
AI summary
A method for exchanging or feeding electric power into an electricity supply grid that has a grid frequency using a converter-controlled generator at a grid connection point is provided. The method includes feeding in electric power depending on a control function, where the electric power may comprise active and reactive power, and the control function controls the power depending on at least one state variable of the grid. It is possible to select between a normal control function and a support control function, different from the normal control function, as the control function. The normal control function is selected when it has been detected that the grid is operating stably and the support control function is selected when a grid problem, grid fault or an end of the grid fault has been detected. The support control function controls the fed-in power to counteract an oscillation in the grid.