A Review of Multilevel Inverter Topology and Control Techniques <s> II. MULTILEVEL INVERTER TOPOLOGY <s> Multilevel inverter structures have been developed to overcome shortcomings in solid-state switching device ratings so that they can be applied to high-voltage electrical systems. The general function of the multilevel inverter is to synthesize a desired AC voltage from several levels of DC voltages. For this reason, multilevel inverters are ideal for connecting either in series or in parallel an AC grid with renewable energy sources such as photovoltaics or fuel cells or with energy storage devices such as capacitors or batteries. In this paper the cascaded H-bridges multilevel inverter is described. <s> BIB001 </s> A Review of Multilevel Inverter Topology and Control Techniques <s> II. MULTILEVEL INVERTER TOPOLOGY <s> In this study, the most common multilevel inverter topologies and control schemes have been reviewed. Multilevel inverter topologies (MLIs) are increasingly being used in medium and high power applications due to their many advantages such as low power dissipation on power switches, low harmonic contents and low electromagnetic interference (EMI) outputs. The selected switching technique to control the inverter will also have an effective role on harmonic elimination while generating the ideal output voltage. Intensive studies have been performed on carrier-based, sinusoidal, space vector and sigma delta PWM methods in open loop control of inverters. The selection of topology and control techniques may vary according to power demands of inverter. This paper and review results constitute a useful basis for matching of inverter topology and the best control scheme according to various application areas. <s> BIB002 </s> A Review of Multilevel Inverter Topology and Control Techniques <s> II. MULTILEVEL INVERTER TOPOLOGY <s> PV connected to the single phase grid is discussed in this review. Also the types of multilevel inverter is discussed. Normally the line commutated inverter has square shaped waveform of line current. So it has large amount of harmonic and produces excess of heat which causes damage to the winding of transformer. Multilevel inverter gives the output current waveform which is nearly sinusoidal in nature. This line current has fewer harmonics as compared to line commutated inverter. Basically multilevel inverter produces the output by synthesis of DC voltages i.e. by increasing of DC voltages, the levels of the output increases. Multilevel inverter also used for electric drives applications for same reason i.e. harmonic reduction. The simulation can be done by MATLAB/SIMULINK. In simulation model we can use DC source instead of PV module. <s> BIB003
Generally, these inverters can be classified as voltage source or current source inverters as shown in Fig. 1 . Three major multilevel inverter configurations applied in industrial applications and mentioned in several literatures; cascaded H-bridges inverter with separate DC sources, neutral-point clamped, and flying capacitors used virtually in low, medium and high power applications are briefly discussed. However, there are "hybrid" circuits that are achieved through the combinations of two or more major multilevel topologies or slight reconfigurations to the original one. Some this MLIs has modular structures. The CHBMI conventionally requires separate DC sources, but recently a single source is analyzed both are well suited for various renewable energy sources such as photovoltaic  , BIB003 , fuel cell  and biomass. This configuration has recently become very ubiquitous in AC power supply and adjustable speed drive applications BIB001 . A single-phase n-level configuration of such inverter is shown in Fig. 2 . Each module consists of a separate DC source associated with a single-phase full-bridge inverter. The terminal voltage of each module is connected in series to form an output voltage V out . The output voltage is synthesized by the sum of each DC source from each module BIB002 . The number of module (m), which is the same as the number of DC sources required, depends on the number of levels (n) of the CHBMI. n is taken as odd, so as to give an integer-valued number of output phase voltage levels, m given by (n-1)/2  :