Wind Turbine Active Rectifier Control for Circulating Current Suppression
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Solution Overview
Problem
The parallel connection of inverters in wind turbines using a hysteresis method for current control is prone to circulating currents, which can negatively affect current control, and the use of inductances to mitigate this issue is costly.
Innovation Solution
A method where active rectifiers control partial currents based on the total current, using a hysteresis method with a common tolerance band for the total current, eliminating the need for separate sensors and allowing for smaller inductances, and incorporating individual delay times and dynamic relationships to manage switching operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If sufficient inductance is used to keep circulating currents low, then circulating currents are reduced, but the cost increases due to expensive inductors
Solution Approach 1:
The invention extracts the circulating current component from the total current measurement and compensates for it in the control signal. By measuring the total current and subtracting the calculated circulating current portion, the control system obtains an accurate representation of the actual load current, eliminating the need for additional inductance to suppress circulating currents.
Solution Approach 2:
The control system introduces an intermediary calculation step that computes the circulating current component based on the parallel connection configuration and total current measurement. This intermediary value is then used to compensate the control signals sent to individual inverters, effectively eliminating circulating currents through control rather than passive components.
2Device complexity
If passive inverters (diode rectifiers) are used for inverting, then the system is simpler, but targeted control of the generator is improved by using active rectifiers
Solution Approach 1:
The control system automatically compensates for circulating currents by calculating them from the total current measurement and adjusting individual inverter control signals accordingly. This self-service approach eliminates the need for external passive components while maintaining system simplicity.
3Ease of manufacture
If multiple partial inverters are connected in parallel, then more cost-effective inverters can be used, but circulating currents occur due to parallel connection
Solution Approach 1:
The system uses feedback from the total current measurement to continuously adjust the control signals sent to each partial inverter. By measuring the total current and calculating the circulating current component, the control system provides real-time feedback compensation that eliminates circulating currents while maintaining the cost-effective parallel inverter configuration.
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 reduces circulating currents, minimizes the need for costly inductances, and ensures precise current control, thereby improving the efficiency and cost-effectiveness of inverter systems in wind turbines.
Implementation Method 1
In particular, the active rectifier works according to a hysteresis method, with a tolerance band with upper and lower band limits being specified for the total current
Data Source
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AI summary
The invention relates to a method for controlling a wind turbine (100), and the wind turbine comprises a generator (101) for generating a generator current with one or more generator current phases, and an active rectifier for rectifying and controlling the generator current, wherein the rectifier has several controllable partial rectifiers (201-203) for each generator current phase, each controllable partial rectifier (201-203) is characterized by a partial inductance (231-233), and each controllable partial rectifier (201-203) controls a partial current of the generator current phase, and each generator current phase forms a total current as the sum of all partial currents of the respective generator current phase, wherein the active rectifier is controlled such that the total current is detected for each generator current phase, and each controllable partial rectifier (201-203) of the respective current phase controls its partial current depending on the detected total current.