This study presents a control scheme for a grid-connected cascaded H-bridge multilevel inverter (CHBMLI) based solar energy conversion system (SECS) addressing the problem of distinct temperature and irradiations which raise to partial shading and panel mismatch conditions in large-scale photovoltaic (PV) generation. Along with feasibility in high-voltage system, the major advantage of isolated dc links in CHBMLI suffers the distinct dc-link voltage conditions when employed as a pulse-width modulated (PWM) converter governing either unequal dc loads or dc sources due to variable power consumption or generation, respectively. The proposed control scheme has the ability of balancing the dc-link capacitors in each H-bridge cell of CHBMLI adopted for this system and during the above-said power generation mismatch conditions in SECS. The proposed system along with maximum and efficient energy conversion, the power quality in the grid-side voltage and injected currents is also monitored and maintained as per standards. In addition, the modelling analysis of the converter has also been derived to define the mathematical model of CHBMLI as PWM converter adopted for this application. The performance of system has been analysed using MATLAB simulation and validated experimentally on prototype model by using dSPACE-1104.

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windmills may operate at variable speeds. 5 Because of variable speed operation and better performance, the doubly fed induction generator (DFIG) has been conventionally used in WECSs. However, permanent magnet synchronous generator (PMSG) has gained broad attention in wind energy applications due to its high efficiency operation, extended speed operating range, self-excitation capability, and leading to a high power factor. For obtaining high efficiency in WECS, it is essential to manage WT such that they can produce maximum power. MPPT algorithm is required for maximal power extraction from the wind energy sources (WES). 1,[6][7][8][9] The output of wind turbine generator (WTG) coupling are inherently unstable dc voltage. The unstable output of WTG contribute to the power quality and stability issues like voltage variations, harmonic generation, and flickers in the grid network. Unwanted harmonics are produced due to the presence of power converters. In addition, due to the varying wind speed, flicker or voltage variation occurs in output power supply. Thus, for the grid integration of WECS, the need of advanced power electronic converters (rectifier, boost converters, and inverters) under transient and steady-state operating condition configuration and their proficient control are necessary to standardize the converter output voltage, even under changing environmental conditions. 3,10 Nowadays, in this type of applications, the multilevel inverters are mostly used in comparison to elementary two-level inverters due to several advantages. [11][12][13][14] Among all standard MLI topologies, "cascaded H-bridge inverter (CHBI)" is primarily used for grid-integrated WECS applications owing to its simpler layout, modular design, reduced number of components as compared with other classical MLI topologies and the use of low voltage rated switches for achieving high or medium power level. [14][15][16][17][18][19] In proposed WECS, WTG coupled systems are connected to two individual H-bridges per phase of CHBMLI through isolated dc link along with respective independent boost converter-based maximum power point tracking (MPPT) system. In addition, by cascading these two H-bridges, the desired five-level output phase voltage is obtained.The major advantage of adopted CHBMLI topology possessing the isolated dc links plays the prominent role to legitimate in connecting two WECS with unequivocal power generation because of deviation of the wind speeds among the windmills at any point of time. In addition, this MLI support to adjoin two medium voltage WECS to feed the total power generated into the high voltage grid without any transformers, but at the same time, the system achieves the better synchronization along with calibrated and controlled power flow. It is an important note to consider that either the CHB topology used as an inverter or a rectifier the mandate of possessing equal dc link voltages is essential to justify identical permissible voltage stress among all switching devices in multilevel topologies at high ...

The contribution of renewable energy, especially small-scale solar photovoltaics (PV), is increasing exponentially in the energy sector. In general, high gain DC-DC converters are used as frontend converters to increase the low voltage of PV panels; further, the DC-AC converter (multilevel inverters) is used for standalone AC loads or grid integration. To avoid the front-end converter and achieve both objectives, this paper proposes a nine-level quadruple boost inverter topology for small-scale solar PV applications. The proposed topology operates on a switched capacitor technique to boost the voltage, and has self-voltage balancing of capacitors. This paper presents the detailed operation of the proposed nine-level inverter, voltage stress calculations, loss analysis, and designing of circuit parameters. In addition, a high-gain generalized multilevel inverter (MLI) topology is also reported. Furthermore, the proposed MLI is compared with competitive inverters available in the recent literature. The proposed MLI topology has advantages such as a minimum total standing voltage and a reduced component count; it can also produce bipolar voltage inherently. The performance of the proposed MLI topology is validated through the MATLAB-based simulations and an experimental prototype. Further, the experimental results are presented by considering load variations, modulation index variations, and output frequency variations. The experimental efficiency obtained is in the range of 96.2% to 92.8% for proposed 9-level inverter.INDEX TERMS High-gain multilevel inverter, small-scale solar PV, switched capacitor, self-voltage balancing.