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In the last decades, electric power produced through photovoltaic conversion has been increasing because of the need to reduce fossil fuel burning. Recently, photovoltaic systems have become more competitive and their role in the renewable energies market share is steadily gaining in importance. Improvements in the power electronics employed in the DC/AC conversion are topics of interest in the quest for more efficient and eventually reduced-cost inverters. The goal of this paper is to perform an investigation of control strategies and propose a topology for a single-phase DC/AC converter for photovoltaic arrays using the simulation software Power System Computer Aided Design/ Electromagnetic Transient Design and Control (PSCAD/EMTDC). The circuit proposed in this paper employs an isolating transformer to a grid-connected photovoltaic inverter. The control strategy proposed uses the instantaneous reactive power theory (p–q theory) and phase-locked loop (PLL). The p-q theory uses two virtual axes in the Park Transformation, which provide to the control system a good dynamic response, accuracy, and decoupling between the control and power system. Computer simulations using the electromagnetic transient software PSCAD show the efficiency of the proposed strategy for a single-phase inverter. The control strategy and topology are quite simple and easy to implement in the future using a Digital Signal Processor (DSP). The results provide insights into new power electronics solutions, which can improve the efficiency and efficacy of the current available in DC/AC converters for photovoltaic systems.

For multi-applications, a novel universal switched-capacitor (SC) converter is proposed in this paper. The proposed converter consists of a rotation-type SC converter and a full-bridge circuit. Unlike the existing universal converter consisting of a series–parallel type converter and a full-bridge circuit, the rotation-type SC converter can offer an output voltage in all clock cycles by rotating the connection position of capacitors. Therefore, the proposed universal SC converter can achieve four types of conversion with high power efficiency, namely, step-up/step-down dc/dc conversion, step-down ac/dc conversion, step-up multilevel dc/ac conversion, and direct step-up/step-down ac/ac conversion. Through theoretical analysis, computer simulations, and bread board experiments, the characteristics of the proposed universal SC converter are evaluated. The result of these analyses demonstrates the feasibility of the proposed universal SC converter. Keywords: Universal converters, DC/DC converters, AC/DC converters, DC/AC converters, AC/AC converters, Inductor-less converters

With the ever-growing aviation industry, energy researches on aviation have turned to renewable energy sources providing electric propulsion. Fuel cells are one of the most popular sources of power for electric vehicles terms of being greener, more reliability, and higher efficiency. Among fuel cells, the most attractive option for flight is polymer electrolyte membrane fuel cells (PEMFC). This paper aims to compose of a hybrid propulsion system to a lightweight aircraft Cri-Cri for more electric aircraft concept. For this purpose, first, conceptual a hybrid propulsion system is designed for the prototype aircraft. The fuel-cell hybrid system proposed for this paper consists of electric motor, fuel cell system, battery, DC/AC converter, and DC/DC converter. Second, some analyses are done. These analyses contain required power, hydrogen consumption, energy consumption, etc.. As a result, Cri-cri needs 26 Kw during take-off, 30 Kw during climb, 10 kW during cruise, and 7 kW during descent. It also consumed 0.75 kg of hydrogen in total, including 0.21 kg in the take-off and climb, 0.42 kg in the cruise, and 0.12 in the descent. The remaining 0.25 kg of hydrogen is reserved for use in emergencies. The total amount of energy consumed is 33 kWh.

In many applications of power converters, an AC voltage with a controllable/variable frequency and voltage amplitude is desired (e.g., in motor-drive applications). By contrast, in the case of grid-connected applications (e.g., photovoltaic systems), the output AC voltage should be “constant” in terms of frequency and amplitude. In all, a power electronic interface is required to link the DC source with the load and to make the output AC voltage compatible in terms of phase, frequency, and amplitude. This power processing is called DC/AC conversion, and the power converters are referred to as DC/AC converters, also known as DC/AC inverters. Depending on the system power ratings, there are typically single- and three-phase DC/AC converters. In order to achieve the above goal (e.g., a constant-voltage and constant-frequency AC voltage), a proper control should be employed. In this chapter, the modeling and control of DC/AC converters are briefly presented in different reference frames (i.e., αβ- and dq-reference frames). The design of commonly employed DC-link and current controllers is in focus with different case studies.

International audience; This paper presents energy management improvement for a Hybrid Electric Boat (HEB) using frequency approach. Diesel generator is assisted by supercapacitors and lithium-battery to satisfy energetic demand of hybrid electric boat. Supercapacitors and lithium-battery are linked to DC-bus through two bidirectional converters, and diesel generator is connected to DC-bus using three phase controlled rectifier. DC/AC converters connected to two electric motors are used as thrusters system which enables to emulate energetic demand of Hybrid Electric Boat (HEB) in propulsion operations. The power requirement of thrusters is added to embedded appliances demand to obtain load's profile. The contribution of this paper is focused on load's profile sharing between Diesel generator, supercapacitors and lithium-battery according to the dynamic responses of these sources. Proposed method performances are evaluated through some simulations using MATALB/Simulink software.

A back-to-back HVDC converter system is typically used to connect two separate electrical grids or a remote large-scale renewable energy system with the electrical grid through a DC bus. The DC bus typically contains a large electrolytic capacitor giving a robust performance to the converter system. However, it is well known that the electrolytic DC bus capacitor is bulky and has a low reliability. Therefore, a possible solution to these drawbacks is to use a reduced DC bus capacitance, which will allow film capacitors to be used instead of electrolytic capacitors. This paper presents the performance evaluation of a five-level flying capacitor (FC) back-to-back converter system with reduced DC bus capacitance under different modulation schemes. Two carrier-based modulation strategies are studied, namely the phase shifted pulse-width modulation (PS-PWM) and the phase disposition pulse-width modulation (PD-PWM), along with their appropriate flying capacitor voltage balancing techniques. The classical synchronous reference frame control strategy has been implemented in order to provide DC bus voltage regulation and active/reactive power control. The performance of the two different modulation schemes is tested against the DC bus and FCs voltage ripples using the MATLAB/Simulink-PLECS software platform. The analyzed case studies demonstrate that the PS-PWM strategy is more suitable to operate the proposed FC converter system using reduced values for the DC bus and flying capacitors.

The advances in computing and communication technologies allow to connect inverters of energy generation systems in smart grids, to well control the power flows. Modeling tools would be helpful in the design of required new inverter topology. This paper presents a modeling technique, so called Power Oriented Graph, easy to use and to be implemented in Matlab-Simulink environment. This technique has been used for modeling a recently proposed soft-switching grid-connected DC/AC power converter for photovoltaic systems. Modifications in the structure of the DC/DC converter and in the control of the DC/AC converter for smart grid applications are proposed. Simulation results confirm the effectiveness of the presented models and the introduced improvements.