Adaptive Active Power Control for Weak Grid Stability
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Solution Overview
Problem
Renewable energy power plants, particularly those connected to weak grids, face challenges in maintaining stability during fault recovery due to large voltage oscillations caused by small changes in active power exchange, which conventional solutions like predetermined ramp rates may not adequately address.
Innovation Solution
A method for operating renewable energy power plants in adaptive active power mode, where the thermal capacity of chopper resistors is determined to set a limit on the rate of change of active power output, ensuring slow and stable recovery of voltage levels without exceeding thermal limits, thereby maintaining grid stability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If active power is ramped up quickly after fault recovery, then productivity is improved, but voltage oscillations increase causing grid instability
Solution Approach 1:
The patent applies dynamics by making the active power ramp rate adaptive rather than fixed. The control system continuously adjusts the ramp rate based on real-time grid conditions, specifically monitoring voltage stability and modifying the power increase speed accordingly. This dynamic adjustment allows the system to recover productivity quickly when conditions permit while preventing voltage oscillations when the grid is vulnerable.
Solution Approach 2:
The patent implements feedback control by monitoring grid voltage stability and using this information to adjust the active power ramp rate. The control system receives feedback about voltage oscillations and modifies the power recovery trajectory in response, creating a closed-loop control mechanism that balances productivity recovery with grid stability maintenance.
2Stability of the object's composition
If active power is ramped up slowly to maintain grid stability, then voltage oscillations are reduced, but the time to recover pre-fault power levels increases
Solution Approach 1:
The system dynamically adjusts the ramp rate based on real-time grid conditions rather than using a fixed slow rate. When voltage stability is confirmed, the ramp rate increases to reduce recovery time. This dynamic approach eliminates the need to consistently use slow ramping, thereby reducing time loss while maintaining stability when necessary.
Solution Approach 2:
The patent changes the operational parameter of ramp rate from a static value to a variable that adapts to grid conditions. By modifying the ramp rate parameter based on voltage stability assessments, the system optimizes the balance between recovery speed and stability, avoiding unnecessary time delays while preventing harmful oscillations.
3Ease of operation
If predetermined ramp rates are used for active power recovery, then ease of operation is improved, but adaptability to different grid conditions deteriorates
Solution Approach 1:
The control system performs self-service by automatically adjusting the ramp rate based on its own monitoring of grid conditions. Rather than requiring external intervention or complex manual adjustments, the system autonomously adapts its operation to match current grid state, maintaining ease of operation while achieving high adaptability.
Solution Approach 2:
The system implements parameter changes by automatically modifying the ramp rate parameter in response to detected grid conditions. This automated parameter adaptation eliminates the need for multiple predetermined rate settings while maintaining operational simplicity, as the system self-adjusts based on real-time feedback.
4Reliability
If chopper resistor thermal capacity is utilized to limit power ramp rate, then generator safety is improved, but the maximum achievable power output is reduced
Solution Approach 1:
The system dynamically adjusts the power ramp rate within the thermal limits of the chopper resistor rather than operating at a fixed reduced rate. By continuously monitoring and adapting the ramp rate, the system maximizes power output within safety constraints, achieving the highest possible power delivery without exceeding thermal capacity and compromising generator safety.
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 approach effectively balances stability and safety by allowing slow active power changes, reducing voltage oscillations, and ensuring compliance with grid requirements, even in weak grid interconnections, by using the thermal capacity of chopper resistors to manage active power output.
Implementation Method 1
determining a thermal capacity of a chopper resistor of the renewable energy generator; calculating, based upon the determined thermal capacity, a limit level of rate of change of active power output that may be implemented by the renewable energy generator
Data Source
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AI summary
A method (200) for operating a renewable energy power plant comprising a plurality of renewable energy generators. The method comprises: identifying (202) a predetermined condition of the renewable energy power plant, of the grid, or of the connection between the renewable energy power plant and the grid, the predetermined condition indicating a weak grid interconnection between the renewable energy power plant and the grid; and controlling (206) each renewable energy generator in an adaptive active power mode in response to recovery of the grid from a voltage deviation. The adaptive active power mode comprises: determining (210) a thermal capacity of a chopper resistor of the renewable energy generator; calculating (212), based upon the determined thermal capacity, a limit level of rate of change of active power output that may be implemented by the renewable energy generator; and operating (214) the renewable energy generator to output active power at the calculated rate of change limit level.