A Review of Multilevel Inverter Topology and Control Techniques <s> IV. SIMULATION RESULTS AND DISCUSSION <s> Analytical solutions of pulsewidth-modulation (PWM) strategies for multilevel inverters are used to identify that alternative phase opposition disposition PWM for diode-clamped inverters produces the same harmonic performance as phase-shifted carrier PWM for cascaded inverters, and hybrid PWM for hybrid inverters, when the carrier frequencies are set to achieve the same number of inverter switch transitions over each fundamental cycle. Using this understanding, a PWM method is then developed for cascaded and hybrid inverters to achieve the same harmonic gains as phase disposition PWM achieves for diode-clamped inverters. Theoretical and experimental results are presented in the paper. <s> BIB001 </s> A Review of Multilevel Inverter Topology and Control Techniques <s> IV. SIMULATION RESULTS AND DISCUSSION <s> This paper presents an active harmonic elimination method to eliminate any number of specific higher order harmonics of multilevel converters with equal or unequal dc voltages. First, resultant theory is applied to transcendental equations characterizing the harmonic content to eliminate low order harmonics and to determine switching angles for the fundamental frequency switching scheme and a unipolar switching scheme. Next, the residual higher order harmonics are computed and subtracted from the original voltage waveform to eliminate them. The simulation results show that the method can effectively eliminate the specific harmonics, and a low total harmonic distortion (THD) near sine wave is produced. An experimental 11-level H-bridge multilevel converter with a field programmable gate array controller is employed to implement the method. The experimental results show that the method does effectively eliminate any number of specific harmonics, and the output voltage waveform has low THD. <s> BIB002 </s> A Review of Multilevel Inverter Topology and Control Techniques <s> IV. SIMULATION RESULTS AND DISCUSSION <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> BIB003
A case study simulation of single phase single source multilevel inverter is considered in this paper. The proposed cascaded H-Bridge inverter model used, consists of three parallel connected H-bridge modules, fed through a single DC voltage source supply. Each of the H-bridge modules has four semiconductor switches and is configured in such a way, that it generate a quasiJournal of Automation and Control Engineering Vol. 4, No. 3, June 2016 ©2016 Journal of Automation and Control Engineering square voltage waveform (+E, 0, -E) at its output terminal. E is the main DC source from the supply unit. S 1 , S 2 , S 3 …S 12 , are the semiconductor switches V P1 , V P2 , and V P3 are the output terminals of the respective bridges. The total output voltage of the inverter in the Fig. 12 is The modulation technique employed on any kind of the inverter topology plays a major role in determining the properties of its output waveform. The selective harmonic elimination method is the modulation technique used in generating the 11-level of the output voltage. Therefore, the switching angles need to be carefully chosen such that the selected odd harmonics are eliminated  , BIB001 . This technique apart from producing a power quality output with a lower total harmonic distortion THD, it also reduces the amount of electro-Magnetic interference EMI and switching losses caused by high switching frequency modulation BIB003 , BIB002 . Specifically in this paper the switching angle used is proposed in  . In an effort to verify the proposed multilevel inverter design procedure were set up in PSIM software platform package, both circuit was supply with 100V DC as an input voltage supply, and switching frequency of 5 kHz, details are presented in  . The circuit configuration in Fig. 12 is simulated using a load of 100 Ω to avoid floating of the system output terminal during the simulation, and the following results are obtained. From the Fig. 16 and Fig. 17 it can be seen that an 11-level staircase output signal was obtained with total harmonic distortion (THD) of 5.5%. The voltage waveform and FFT analysis spectrum shows the magnitude of fundamental component and that of harmonic at the above frequencies. The fundamental component amplitude is much higher than that of harmonic order component. It can also be observed that the triple harmonics are concealed out automatically, only the non-triple harmonics are present at lower amplitude. A combination of resistor-inductor, resistor-capacitor, inductor-capacitor, and combination of both was simulated in each case at nominal values as in Fig. 18 . The value was selected arbitrarily to represent approximate value for the purpose of design and simulation. The actual impedance may vary considerably depending application, in this study nominal impedance is implicitly referring to the frequency response of the circuit under consideration, in which the change in voltage or current waveform, and harmonic level of the inverter is observed. Form Fig. 18 it clearly shows that combination of resistor-capacitor has the lowest THD compare to the rest, meaning for filter design capacitor filter will be of significant choice for this inverter type. For RL, LC, and RLC loads are having almost similar harmonic contain level. 