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Design and Implementation of a Programmable AC Load Based on 4-Leg Multilevel Converter

Saghali, Mohammad Kazem | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56852 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Zolghadri, Mohammad Reza
  7. Abstract:
  8. One of the challenges that always exists in the field of Testing the performance of converters, uninterruptible power supplies (UPSs) , etc. is to provide various types of loads to be applied to these equipments and test the quality of their performance in various load conditions. Leading or Lagging Power Factor loads, harmonic loads and non-linear loads are mainly required in this investigation. The use of inductors, resistors, capacitors and other devices for these tests is an old solution. Their disadvantages include high price, large volume and very high power loss, which was the initial idea of making programmable loads. A current source converter with the ability to Sink and source the current as a programmable load can simulate a wide range of loads, and on the other hand, by using bidirectional converters , power regeneration can be achieved and the energy absorbed from the equipment under test (EUT) return to the grid. In this Thesis, designing and implementation of a three-phase AC programmable load based on a 3KVA three-level 4-leg NPC converter and a power regeneration converter has been carried out. Due to the fourth leg, it is possible to simulate zero component currents such as DC current and harmonics multiple of 3. This device can be operated in constant current (up to 13th harmonic), constant voltage, constant impedance and constant power modes. In all mentioned modes, the setpoint value of the controlled variable is chosen by the user and the desired output is obtained by the current or voltage control loop. The voltage and current control loop is implemented by proportional resonant (PR) controller. The multi-level topology of the converter also leads to reduction in the size of the inductor filter used in the constant voltage mode. Two topology for the power recovery converter have been proposed. In addition to simulation in different conditions in the Simulink environment of MATLAB software, a prototype has also been manufactured and its performance has been investigated. The results of simulation and experimental tests confirm the performance of the designed system
  9. Keywords:
  10. Cascaded Converter ; Power Recycle ; Uninterruptible Power Supplies ; Harmonic Analysis ; Programmable Load

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