This paper articulates the novel topology for modified SEPIC converter and much suitable for renewable energy and high-voltage applications. Power circuit incorporated with one additional inductor and capacitor to the classical SEPIC converter as a voltage lift component. Hence, it overcomes the effect of parasitic effects of the circuit components (MOSFET/passive elements). Conventional DC-DC boost/SEPIC converters are utilized for renewable energy and industrial applications. But they suffer from parasitic effects with reduced output voltage, and limited with low efficiency. Henceforth, these difficulties overcomes with the modified SEPIC converter topology for maximizing the output voltage generation. Numerical simulation outcomes are presented and validate the developed theoretical analysis and the accuracy of modified circuit.

This paper proposes a new approach on the novel current control strategy for grid-tied voltage-source inverters (VSIs) with circumstances of asymmetrical voltage conditions. A standard grid-connected inverter (GCI) allows the degree of freedom to integrate the renewable energy system to enhance the penetration of total utility power. However, restrictive grid codes require that renewable sources connected to the grid must support stability of the grid under grid faults. Conventional synchronously rotating frame dq current controllers are insufficient under grid faults due to the low bandwidth of proportional-integral (PI) controllers. Hence, this work proposes a proportional current controller with a first-order low-pass filter disturbance observer (DOb). The proposed controller establishes independent control on positive, as well as negative, sequence current components under asymmetrical grid voltage conditions. The approach is independent of parametric component values, as it estimates nonlinear feed-forward terms with the low-pass filter DOb. A numerical simulation model of the overall power system was implemented in a MATLAB/Simulink (2014B, MathWorks, Natick, MA, USA). Further, particular results show that double-frequency active power oscillations are suppressed by injecting appropriate negative-sequence currents. Moreover, a set of simulation results provided in the article matches the developed theoretical background for its feasibility.

This study analyze more efficient modified Cuk converter circuit configuration for renewable energy applications. One additional inductor and capacitor to the classical Cuk converter is added as voltage booster. Therefore, it minimizes the parasitic effects of the circuit components. Diverse classical DC-DC boost converter types are used in renewable energy applications. However, the output voltage is limited due to parasitic effects which cause voltage drop, and lower efficiency. Modified Cuk converter circuit overcomes these difficulties and maximizes the output voltage generation with higher efficiency. Numerical simulations conducted on Matlab/Simulink and validate the analytical analysis and accuracy of the modified topology.

In the modern world of technology, the cascaded DC-DC converters with multiple output configurations are contributing a dominant part in the DC distribution systems and DC micro-grids. An individual DC-DC converter of any configuration exhibits complex non-linear dynamic behavior resulting in instability. This paper presents a cascaded system with one source boost converter and three load converters including buck, Cuk, and Single-Ended Primary Inductance Converter (SEPIC) that are analyzed for the complex non-linear bifurcation phenomena. An outer voltage feedback loop along with an inner current feedback loop control strategy is used for all the sub-converters in the cascaded system. To explain the complex non-linear dynamic behavior, a discrete mapping model is developed for the proposed cascaded system and the Jacobian matrix’s eigenvalues are evaluated. For the simplification of the analysis, every load converter is regarded as a fixed power load (FPL) under reasonable assumptions such as fixed frequency and input voltage. The eigenvalues of period-1 and period-2 reveal that the source boost converter undergoes period-2 orbit and chaos whereas all the load converters operate in a stable period-1 orbit. The proposed configuration eliminates the period-2 and chaotic behavior from all the load converters and is also validated using simulation in MATLAB/Simulink and experimental results.

The popularity of renewable energy conversion systems, and especially of wind energy, has been growing in recent years. Doubly fed induction generator (DFIG)-based wind energy systems are extensively used due to their wide range of active and reactive power controllability. Conventional DFIG control structures consist of decoupled PI rotor current controllers with stator flux orientation and machine parameter-dependent compensating terms. The accuracy of stator flux calculations is dependent on how accurately the stator resistance is known. Integration problems also exist and additional low-pass filters are implemented to accurately calculate the stator flux. In the current study, machine-dependent compensating terms are estimated with a rst-order low-pass filter disturbance observer. Therefore, a single proportional (P) controller is sufficient to control decoupled rotor currents. The proposed controller structure is implemented on a MATLAB/Simulink platform with the parameters of 500 kW DFIG used in the M_ILRES (Turkish National Wind Energy) project. The proposed controller is also experimentally validated in an experimental setup