Keywords: voltage stabilisation, voltage sag compensation, optimisation, switching strategy, three-level neutral point clamped VSI, NPC voltage source inverter, two-quadrant three-level chopper, reactive power compensation, superconducting magnetic energy storage, simulation, space vector PWM, pulse width modulation, SVPWM, power networks
Voltage stabilisation of SMES VSI DC-link and compensation of reactive power by SMES using optimised switching strategies
This paper presents a novel and optimised switching strategy and control approach for a three-level two-quadrant chopper in a three-level neutral point clamped (NPC) voltage source inverter (VSI) superconducting magnetic energy storage (SMES). Using the proposed switching strategy, the voltage of the inverter capacitors in SMES can be independently controlled. Also, the minimum power and switching losses as well as the proper convection can be achieved using this switching strategy. The simulation results indicate that the proposed switching strategy along with a proportional-integral (PI) control approach can be easily implemented in the power networks, and it can balance and stabilise the capacitors' voltage level of the multi-level inverters while satisfying the IEEE standard specifications. Considering the fact that the space vector pulse width modulation (SVPWM) is highly effective in decreasing the low order harmonics, in this article, this type of modulation combined with the most optimised switching strategy is utilised. In addition, in this study, a new algorithm is presented for SMES to compensate the voltage sag in the power networks.