Inverter Frequency Control for Grid Stability
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Solution Overview
Problem
The stability of AC voltage grids is challenging due to the high penetration of converter-based power generation systems, which lack inertia, leading to difficulties in controlling frequency fluctuations and grid stability during disruptions, especially when conventional power plants are not available.
Innovation Solution
A method for operating power generation systems with photovoltaic generators and inverters that adjust active and reactive power based on instantaneous frequency and voltage changes, allowing for quick and effective frequency stabilization by reducing active power input and feeding it back as DC power when frequency deviations exceed certain limits, thereby simulating inertia in the grid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If converter-based power generation plants are used to displace synchronous generators, then renewable energy penetration is increased, but grid inertia and frequency stability are reduced
Solution Approach 1:
The patent implements a feedback mechanism where the inverter continuously monitors grid frequency and dynamically adjusts active power output accordingly. When frequency deviation exceeds a threshold, the inverter reduces or stops active power feed-in, creating a closed-loop control system that stabilizes grid frequency without requiring synchronous generators or energy storage
Solution Approach 2:
The converter-based power generation plant performs frequency stabilization autonomously through built-in frequency-dependent active power control. The system self-regulates its active power output based on real-time frequency measurements, eliminating the need for external conventional power plants to provide inertia and frequency stability
2Reliability
If frequency-dependent active power reduction is implemented, then frequency stability is improved, but power generation output is reduced
Solution Approach 1:
The patent applies partial action by implementing frequency-dependent active power reduction only when frequency deviation exceeds a predefined threshold. Under normal frequency conditions, the power generation plant operates at full capacity, while frequency stabilization measures are activated only when necessary, minimizing impact on overall power generation output
3Reliability
If immediate shutdown of power generation plants is used to prevent grid collapse, then grid stability is protected, but revenue loss and restart problems occur
Solution Approach 1:
The patent implements preliminary anti-action by proactively reducing active power feed-in when frequency deviation thresholds are exceeded, preventing grid instability before it develops into a catastrophic failure. This preventive approach avoids the need for immediate shutdowns and subsequent restart operations, eliminating revenue loss while maintaining grid stability
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
This method enables rapid and predictable contribution to frequency stabilization, even in grids with high renewable energy penetration, by utilizing the dynamic response of inverters to frequency and voltage changes, ensuring grid stability without significant energy storage and minimizing disruptions.
Implementation Method 1
An inverter is connected to an AC grid. Electrical power is transferred between the inverter and the AC grid. The transferred electrical power comprises active power and reactive power.
Implementation Method 2
the active power fed into the AC grid by the inverter is reduced to a value less than zero in the second operating mode, so that active power is drawn from the AC grid by the inverter, and the active power thus drawn is rectified by the inverter and fed back into the photovoltaic generator as DC power
Data Source
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AI summary
The invention relates to a method for operating an energy generating system comprising a photovoltaic generator and an inverter. Electric power is transferred between the inverter and the alternating current grid, and the transferred electric power has an active power (P) and a reactive power (Q). The photovoltaic generator is operated using the inverter in a first operating mode at a point of maximal active power (MPP). The method according to the invention is characterized in that in a second operating mode, the active power (P) is set depending on a current grid frequency value (f) and a grid frequency change rate (df/dt), and in the second operating mode, the reactive power (Q) is set depending on a current grid voltage value (U) and a grid voltage change rate (dU/dt). An inverter according to the invention for an energy generating system comprising a photovoltaic generator is designed to carry out the method.