Renewable Power Plant Voltage Control for Weak Grid Oscillations
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Solution Overview
Problem
Existing methods struggle to effectively reduce oscillations and fluctuations in active and reactive power output from wind power plants connected to weak power networks, leading to instability and potential disconnection during grid faults.
Innovation Solution
A method involving a power plant controller that identifies network conditions, measures active power output, and adjusts voltage levels using a look-up table to maintain a natural voltage level, incorporating adaptive control modes to stabilize the grid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If voltage control mode is used to reduce oscillations in weak grid interconnections, then voltage stability is improved, but the method fails to effectively reduce oscillations in certain scenarios such as after grid faults
Solution Approach 1:
The patent implements adaptive control that dynamically switches between different control modes (power factor control mode and voltage control mode) based on real-time grid conditions. The controller monitors grid strength indicators and automatically adjusts the control strategy, transitioning from static voltage control to dynamic adaptive control that responds to changing grid conditions, thereby resolving the limitation of fixed voltage control mode in certain scenarios
Solution Approach 2:
The patent changes the control parameter from fixed voltage setpoint to adaptive power factor based on grid conditions. By calculating grid strength indicators and comparing them against thresholds, the system dynamically adjusts the power factor parameter to optimize performance. This parameter transformation allows the system to achieve better oscillation reduction reliability across varying grid conditions
2Stability of the object's composition
If reactive power is exchanged to control voltage at a given set point, then voltage oscillations are reduced in some scenarios, but further reduction of oscillations is desired in other scenarios
Solution Approach 1:
The patent implements a feedback mechanism where the controller continuously monitors grid strength indicators and compares them against predefined thresholds. Based on this feedback, the system automatically adjusts the control mode and power factor settings. This closed-loop feedback control enables the system to achieve further oscillation reduction by responding to actual grid conditions rather than operating with fixed parameters
3Stability of the object's composition
If the interconnection between remote wind power plant and power network is weak, then small changes in reactive/active power exchange result in large voltage oscillations, but increasing grid strength is not always feasible
Solution Approach 1:
The patent transforms the control approach by changing from direct voltage control to power factor control based on grid strength indicators. This parameter transformation simplifies the control logic while maintaining effectiveness in weak grid conditions. The system calculates a grid strength indicator and adjusts the power factor accordingly, providing a simpler yet effective solution compared to complex voltage control mechanisms
Data Source
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AI summary
There is provided a method of operating a renewable power plant that is connected to a wider power network by a bus. The method comprises: identifying a predetermined voltage condition of the renewable power plant or of the bus; controlling the renewable power plant to maintain zero reactive power exchange at the bus for a first period; calculating an average voltage level of the bus that was achieved during the first period; and controlling the renewable power plant to maintain the voltage output at a set voltage level for a second period, the set voltage level being substantially equal to the calculated average voltage level. The method ensures that voltage oscillations due to a push-pull phenomenon between a power plant controller and the power network do not upset the stability of the grid.