Design and Implementation of a Modular Multilevel Inverter with FACTS Capability for Wind and PV systems

In this paper, a new three-phase inverter with flexible AC transmission system (FACTS) capability is
presented. The proposed inverter is placed between the PV cell and the grid, same as a regular inverter,
and is able to regulate active and reactive power transferred to the grid. This inverter is equipped with
distribution static synchronous compensators option in order to control the power factor (PF) of the local
feeder lines. Using the proposed inverter for small-to-medium-size wind applications will eliminate the use
of capacitor banks as well as FACTS devices to control the PF of the distribution lines. The goal of this
paper is to introduce new ways to increase the penetration of renewable energy systems into the distribution
systems. This will encourage the utilities and customers to act not only as a consumer, but also as a supplier
of energy. Moreover, using the new types of converters with FACTS capabilities will significantly reduce the
total cost of the renewable energy application. In this paper, modular multilevel converter is used as the
desired topology to meet all the requirements of a three-phase system such as compatibility with IEEE
standards, total harmonic distortion (THD), efficiency, and total cost of the system. The proposed control
strategy regulates the active and reactive power using power angle and modulation index, respectively. The
function of the proposed inverter is to transfer active power to the grid as well as keeping the PF of the
local power lines constant at a target PF regardless of the incoming active power from the wind turbine.
The simulations for an 11-level inverter have been done in MATLAB/Simulink. To validate the simulation
results, a scaled prototype model of the proposed inverter has been built and tested