Dynamic DC-link Voltage Selection for Wind Turbine Converters
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Solution Overview
Problem
Wind turbine converter systems face challenges in setting a stable reference DC-link voltage due to varying wind conditions and grid voltage fluctuations, leading to inefficiencies in power output and potential damage to converter components.
Innovation Solution
A method is introduced to determine a reference DC-link voltage by selecting the highest DC voltage demand value between the generator-side and grid-side inverters, with the master converter controller adjusting the net power flow to maintain this voltage within safe thresholds, ensuring maximum active/reactive power output while preventing component damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the reference DC-link voltage is set based on fixed thresholds, then the converter components are protected from damage, but the power output efficiency decreases due to conservative voltage limits
Solution Approach 1:
The patent implements dynamic reference voltage determination by continuously adjusting the reference DC-link voltage based on real-time demands from both generator-side and grid-side inverters. The master converter controller dynamically selects the highest demanded voltage value, allowing the system to adapt to varying operating conditions rather than using fixed conservative thresholds, thereby maximizing power output while maintaining component safety
Solution Approach 2:
The system employs feedback mechanisms where both generator-side and grid-side inverters communicate their DC voltage demands to the master converter controller. The controller receives feedback from both sides, compares the demanded voltage values, and adjusts the reference DC-link voltage accordingly. This closed-loop feedback ensures that the reference voltage reflects actual system needs rather than predetermined limits, optimizing both efficiency and safety
2Productivity
If the DC-link voltage is increased to maximize power output, then the active/reactive power output increases, but the risk of exceeding maximum admissible voltage and damaging components increases
Solution Approach 1:
The master converter controller proactively determines the reference DC-link voltage by evaluating demands from both inverters before voltage excursions can occur. By calculating the highest demanded voltage value in advance and setting the reference accordingly, the system prevents voltage surges before they happen rather than reacting after exceeding limits, thus maximizing power output while preventing component damage
Solution Approach 2:
The system changes the reference voltage parameter dynamically based on operating conditions. Instead of using a fixed maximum voltage limit, the reference DC-link voltage is adjusted according to the highest demand from generator-side or grid-side inverter, allowing optimal voltage levels that maximize power transfer while staying within safe operating boundaries for all components
3Adaptability or versatility
If separate DC voltage controls are used for generator-side and grid-side inverters, then each inverter can operate independently, but the DC-link voltage instability increases due to conflicting voltage demands
Solution Approach 1:
The patent merges the separate voltage control functions of generator-side and grid-side inverters into a unified reference voltage determination process. The master converter controller combines information from both sides, selects the highest demanded voltage value, and establishes a single common reference DC-link voltage. This unified approach maintains the adaptability of independent inverter operation while ensuring DC-link voltage stability by eliminating conflicting voltage demands
Data Source
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AI summary
A method of setting a reference DC-link voltage of a wind-turbine converter system is provided. At least at least one DC voltage demand from at least one generator-side inverter and at least one DC voltage demand are received from at least one grid-side inverter. A generator-side DC voltage demand value on the basis of the at least one DC voltage demand received from the at least one generator-side inverter. Also a grid-side DC voltage demand value is determined on the basis of the at least one DC voltage demand received from the at least one grid-side inverter. The highest DC voltage demand value out of the generator-side and grid-side DC voltage demand values is chosen. This chosen value corresponds to the set reference DC-link voltage.