Chopper Control Method for DC Bus Voltage Management
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Solution Overview
Problem
Wind turbine generators face performance issues during grid events like voltage dips, leading to transient currents and potential damage in Doubly Fed Induction Generators (DFIG) and power discharge limitations in full converter systems, with existing solutions like hysteresis control and PWM modulation being insufficient for quick response and requiring complex hardware.
Innovation Solution
A control method that manages a chopper in the DC bus by monitoring both DC bus voltage and current, allowing for predictive activation and deactivation based on voltage and current levels, enabling faster response times and maintaining DC bus voltage within normal ranges, similar to more advanced PWM systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If hysteresis control is used to activate or deactivate the chopper, then the control is simple, but the response is too slow to maintain DC bus voltage within normal operating range during grid transients
Solution Approach 1:
The control method predicts future DC bus voltage by calculating the rate of change (dVbus/dt) and extrapolating to a future time point. This preliminary action allows the system to activate the chopper before the voltage actually exceeds the threshold, enabling faster response compared to waiting for the voltage to actually reach the threshold level.
Solution Approach 2:
The control method dynamically adjusts the switching decision based on real-time voltage and current measurements, calculating the rate of change and using it to predict future voltage levels. This dynamic approach replaces the static hysteresis bands with adaptive, time-dependent control that responds faster to transient conditions.
2Reliability
If PWM modulation is used to control the chopper, then the DC bus voltage is maintained at desired level, but the hardware control becomes more complicated and expensive
Solution Approach 1:
The invention replaces complex PWM hardware control with a simpler control method that uses basic voltage and current sensors combined with a prediction algorithm. Instead of investing in expensive PWM modulation hardware, the system uses computationally simple voltage-rate-of-change calculation to achieve similar performance, effectively substituting cheap computational logic for expensive hardware.
Solution Approach 2:
The invention substitutes the mechanical/electronic PWM modulation system with a control method based on mathematical prediction of voltage behavior. By using the rate of change of voltage (dVbus/dt) and extrapolating future voltage levels, the system replaces complex hardware-based PWM control with a simpler predictive control algorithm that achieves the same voltage maintenance objective.
3Device complexity
If chopper is activated based on DC bus voltage threshold only, then the control is simple, but the system cannot predict sudden voltage variations during grid transients
Solution Approach 1:
The control method continuously monitors both the DC bus voltage and the current, calculating the rate of change of voltage (dVbus/dt). This feedback mechanism uses real-time measurements to predict future voltage levels, allowing the system to anticipate voltage excursions before they occur and activate the chopper proactively rather than reactively.
Data Source
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AI summary
Optimizes the operation and control of electric generators against events produced in the power grid, such as voltage dips or overvoltages, comprising the following steps: detecting that the DC bus voltage level (Vbus) (301) exceeds the maximum operating limit established in normal conditions; enabling activation permission of the chopper (201); activating the different operating states (304) of the chopper (201) according to the DC bus voltage level (Vbus) (301) and to the current entering the DC bus (Iin.bus) from the generator; detecting that the DC bus voltage level (Vbus) (301) is within the normal operating range; enabling deactivation permission of the chopper (201); deactivating the different operating states (304) of the chopper (201) according to the DC bus voltage level (Vbus) (301) and to the current entering the DC bus (Iin.bus) from the generator.