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Optimized load sharing control by means of thermal reliability management

Optimized load sharing control by means of thermal reliability management. Carsten Nesgaard Department of Electric Power Engineering Technical University of Denmark Henrik Møller. Power system configuration. Parallel-connected units:

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Optimized load sharing control by means of thermal reliability management

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  1. Optimized load sharing control by means of thermal reliability management Carsten Nesgaard Department of Electric Power Engineering Technical University of Denmark Henrik Møller

  2. Power system configuration Parallel-connected units: Parallel-operation of multiple converters is employed when specifications require: • Fault tolerance • Reliability enhancement • Redundancy • Modular system structure.

  3. Converter Schematic overview of key converter elements:

  4. Reliability Annual ‘down-time’: A test system comprised of two parallel-connected converters utilizing current sharing has an annual ‘down-time’ of 10 minutes and 14 seconds. Tav = 95,7C 10 min. 14 sec. / year Tav = 77,3C Different Tav due to: • Parameter/component variations • Working environment conditions

  5. Current sharing technique (“Prior art”) Converter and current sharing structure:

  6. Current sharing technique (“Prior art”) Measurements: The following two graphs show actual measurements of a two-converter power system. Current division in a two-converter system: Efficiency in a two-converter system: Converter 1 Converter 2 NO sharing efficiency Current sharing efficiency

  7. Thermal reliability management (Invention) Principle of the invention: Thermal reliability management implementation is simple and cost-effective. The temperature sensing device is simply mounted at the most critical location within the converter. Temperature sensing signal replaces current sensing signal:

  8. Thermal reliability management (Invention) Measurements: The following two graphs show actual measurements of a two-converter power system utilizing thermal reliability management. Efficiency in a two-converter system: Current division in a two-converter system: Converter 1 Converter 2 NO sharing efficiency Current sharing efficiency Thermal rel. man. efficiency

  9. Thermal reliability management (Invention) Dynamic change in power throughput:

  10. Reliability Annual ‘down-time’: Applying thermal reliability management to the previously shown two-converter power system results in an annual ‘down-time’ of 6 minutes and 11 seconds. Total annual ‘down-time’ is reduced by almost 40%. 6 min. 11 sec. / year Tav = 78,5C

  11. Summary Advantages: • Optimized reliability  fundamentally different load sharing control • Minimized losses  increased overall efficiency • Simple implementation • Ready for immediate implementation in both new and existing designs Disadvantages: • Individual converter failure rate might increase slightly. However, it is aaby far compensated through a much lower average temperature.

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