Predictive DC Link Overvoltage Mitigation in Wind Turbine Converters
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Solution Overview
Problem
Conventional wind turbine power converter systems experience time delays in mitigating overvoltage conditions on the DC link due to grid transients, leading to potential damage from rapid voltage increases.
Innovation Solution
A method that predicts future voltage values on the DC link by processing voltage feedback signals and their rate of change, using filters and gain adjustments, to enable proactive control measures such as activating a crowbar circuit or shutting down the system before overvoltage occurs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional control functions (crowbar and software IOC protection) are used to mitigate overvoltage, then damage to converter hardware is prevented, but time delays due to finite task rates cause the mitigation to be too slow for rapid voltage increases
Solution Approach 1:
The system performs preliminary action by predicting future DC link voltage values based on current voltage feedback and rate of change calculations. This prediction enables the control system to take preventive action before the overvoltage condition actually occurs, eliminating the reactive time delay inherent in conventional protection schemes. The predictive approach allows the crowbar circuit to be activated in advance based on forecasted voltage excursions rather than waiting for threshold violations.
Solution Approach 2:
The system applies preliminary anti-action by using the predicted future voltage to trigger protective measures before the harmful overvoltage condition develops. The control system calculates the rate of change of DC link voltage and uses this information to anticipate future voltage levels, enabling preemptive activation of the crowbar circuit to counteract the impending overvoltage condition before it can cause damage.
2Object-affected harmful factors
If the control system waits for voltage threshold to be exceeded before activating protection, then false activations are avoided, but rapid voltage increases occur before mitigation can take effect
Solution Approach 1:
The control system performs preliminary action by predicting future voltage values using the current voltage feedback signal and its rate of change. This prediction capability allows the system to anticipate rapid voltage increases before they exceed damage thresholds, enabling proactive activation of protective measures. The system calculates dV/dt and uses this information to forecast future voltage levels, triggering protection in advance rather than reactively after thresholds are exceeded.
3Loss of time
If faster control execution is implemented to reduce time delays, then response speed improves, but system complexity and cost increase
Solution Approach 1:
The system applies parameter changes by utilizing the rate of change of voltage (dV/dt) as an additional parameter in the control algorithm. By incorporating this temporal derivative into the prediction calculation, the system achieves faster effective response without requiring hardware upgrades. The predictive voltage is calculated as V_future = V_current + (dV/dt × Δt), where Δt is the control cycle time, allowing standard controllers to achieve predictive protection capability through software algorithms alone.
Data Source
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AI summary
A system and method for mitigating overvoltage on a DC link (244) of a power converter (210) of an electrical power system (200) connected to a power grid (242) includes receiving a voltage feedback signal (404) from the DC link (244) for a predetermined time period. The method also includes determining a rate of change (420) of the voltage feedback signal (404) during the predetermined time period. Further, the method includes predicting a future voltage value (422) on the DC link (244) as a function of the voltage feedback signal (404) and the rate of change (420) of the voltage feedback signal (404). Moreover, the method includes controlling the electrical power system (200) based on the future voltage value (422).