Multi Bandwidth Voltage Control for Wind Power Plants
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Solution Overview
Problem
Wind power plants face challenges in providing voltage stability and meeting stringent grid code requirements, particularly when connected to weak grids, due to the need for advanced voltage support comparable to traditional synchronous machines.
Innovation Solution
Implementing a wind power plant with multiple bandwidth voltage controllers, where the wind turbine generator has a high bandwidth controller and the power plant controller has a low bandwidth controller, with adjustable ratios and gains based on short circuit ratio and X/R ratio, and optionally including a reactive power compensation unit with a third bandwidth controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single voltage controller is used in the wind power plant, then the control system is simple, but the voltage stability and response speed are insufficient to meet grid code requirements
Solution Approach 1:
The voltage control system is segmented into two independent controllers: a wind turbine generator-level voltage controller and a power plant-level voltage controller. Each controller operates with different bandwidths and control strategies, allowing the system to achieve superior voltage stability through distributed control while maintaining manageable complexity at each control level.
Solution Approach 2:
The control architecture transitions from a single-dimensional control approach to a two-dimensional control structure, where control actions occur at both the individual turbine level and the aggregate power plant level. This multi-layered control dimension enables comprehensive voltage support that satisfies stringent grid code requirements.
2Speed
If a high bandwidth controller is used for fast voltage response, then the voltage support capability is improved, but the control system becomes overly sensitive and unstable on weak grids
Solution Approach 1:
Different controllers are assigned different bandwidth characteristics according to their specific functions and operational contexts. The wind turbine generator-level controller operates with higher bandwidth for fast local voltage support, while the power plant-level controller uses lower bandwidth for stable aggregate control, optimizing performance for each control level's specific requirements.
Solution Approach 2:
The control system dynamically adjusts the effective bandwidth through hierarchical control, where the higher-level controller modulates the reference signals for the lower-level controller. This dynamic coordination allows the system to achieve fast response when needed while maintaining stability through the stabilizing influence of the lower-bandwidth power plant-level controller.
3Reliability
If multiple bandwidth controllers are implemented, then the voltage control performance is improved, but the control system complexity increases
Solution Approach 1:
The complex multi-bandwidth control problem is segmented into two manageable control levels, each with its own voltage controller operating at appropriate bandwidths. This segmentation reduces the overall system complexity by distributing control functions across hierarchical levels rather than requiring a single complex controller.
Solution Approach 2:
The control system merges the fast response capability of high-bandwidth turbine-level control with the stable aggregate control of lower-bandwidth power plant-level control. By combining these complementary control actions in a hierarchical structure, the system achieves superior voltage control performance while keeping individual controller designs relatively simple.
Data Source
AI summary
The present invention relates to a wind power plant, with at least one wind turbine generator, where each of the at least one wind turbine generator has a first voltage controller with a first bandwidth, arranged for controlling a voltage level, and where the wind power plant has a power plant controller with a second voltage controller with a second bandwidth also arranged for controlling the voltage level, the first bandwidth is larger than the second bandwidth. The invention also relates to a method for controlling the voltage level of a wind power plant, by using multi bandwidth voltage controllers.