PROJECT TITLE :

Operating Region of Modular Multilevel Converter for HVDC With Controlled Second-Order Harmonic Circulating Current: Elaborating P-Q Capability

ABSTRACT:

The operating region of the modular multilevel converter (MMC) is limited by the maximum-allowable voltage ripple of cells, which is related to the arm energy variation. Injecting the controlled second-order harmonic part into the circulating current can scale back energy variation of the arm and, so, extend the operating region of MMC. Care must be taken, but, that the second-order circulating current affects the arm current, and inappropriately injected harmonic current might cause an undesirable arm current polarity modification. So, this paper 1st investigates and proposes the most-allowable second-order circulating current for extending the operating region reliably and efficiently. The active and reactive power capability of MMC is more elaborated and illustrated in keeping with the maximum excess energy capability for two cases, running with: one) the first operating region and a couple of) the extended operating region. Finally, the P- Q diagrams for contingent operating conditions with faulty or disabled submodules are presented. Understanding the distinctive form and amendment of P- Q capability with credible submodule failure contingency ought to be crucial for designing MMC-HVDC lines, and determining the energy needs and the extent of redundancy in submodules properly in order to realize the envisioned edges of the new HVDC. The efficacy and accuracy of the research findings are validated for the MMC-HVDC system using PSCAD/EMTDC.