Multiport DC-DC Converters for Hybrid Energy Systems

Renewable energy sources (RESs) like solar and wind have gained attention for their potential to reduce reliance on fossil fuels and mitigate climate change. However, integrating multiple RESs into a power grid is challenging due to their unpredictable nature. Power electronic converters can manage hybrid energy systems by controlling power flow between RESs, storages, and the grid. Conventional single input dc-dc converters have limitations such as low efficiency, bulky designs, and complex control systems. Multiport dc-dc converters (MPCs) have emerged as a solution for hybridizing multiple sources, storages, and load systems by providing a common interface. Existing MPCs have limitations such as high component count, limited operational range, complex control strategies and restrictions on the number of inputs to list a few. Thus, there is a need to develop new MPCs that combine the advantages of existing designs while overcoming their limitations. Isolated MPCs with unipolar or bipolar outputs are needed that can accommodate any number of inputs, offer high voltage gain, use fixed magnetic components for galvanic isolation (regardless of the number of ports), and have a simplified control strategy. Additionally, new non-isolated MPCs with unipolar or bipolar outputs are required, featuring reduced component count, simultaneous power transfer and power flow between input ports, high voltage gain, low control complexity, and modular design allowing for arbitrary increase in the number of input ports. There is also an opportunity to apply MPCs in the integration of RESs and storages to ac grids through multilevel inverters for low component count, high efficiency, low harmonics, and higher power density. Further, advances in bipolar MPCs provide the chance to balance the dc bus without requiring a complex control system.acceptedVersio

A High-Voltage Gain Non-Isolated DC–DC Converter Designed for Bipolar DC Microgrids

Publisher Copyright: © 2023 Taylor & Francis Group, LLC.DC microgrids are now starting to attract huge attention from researches and engineers. Among the several DC microgrid architectures, bipolar DC microgrids are advantageous to accommodate a wider range of DC loads. However, due to mismatched loads connected to the two poles, bipolar DC microgrids may show voltage balancing issues. In this context, this article presents a new high input-to-output voltage gain, non-isolated DC–DC converter specifically designed for bipolar DC Microgrids. The proposed converter supports the balance of voltages at both bipolar DC microgrid poles, as the converter can transfer energy between the two poles in an unbalanced way. The description, theoretical support, and operation of the proposed converter will be presented. The theoretical assumptions will be complemented with several results obtained from computer simulation tests. The simulation tests will be compared to laboratory results from an experimental prototype. The obtained results confirm the theoretical properties of the proposed converter.publishersversionpublishe

Novel Isolated Multiport DC Converter with Natural Bipolar Symmetry for Renewable Energy Source Integration to DC Grids

Due to their greater reliability, efficiency, and resilience as compared to unipolar dc grid systems, bipolar dc grid systems are swiftly gaining popularity for the integration of renewable energy sources. However, development of multiport converters for bipolar microgrid systems is still progressing slowly in terms of reducing costs or improving power density and compact designs. This paper proposes a multiport isolated dc-dc converter with naturally symmetric bipolar outputs (MIBDC). With respect to the number of input ports, voltage gain, and output symmetry that the proposed converter naturally possesses, it outperforms its few competitors. Additionally, the proposed MIBDC significantly reduces component count and control complexity by employing a fixed transformer with only one primary and secondary winding for any number of inputs. The suggested converter’s performance in both open and closed loops is evaluated quantitatively in simulation and experimentally using OPAL-OP5700 RT’s hardware-in-the-loop (HIL) platform under various situations.publishedVersio

A New Structure of High Voltage Gain SEPIC Converter for Renewable Energy Applications

The paper proposes a new structure of SEPIC with high voltage gain for renewable energy applications. The proposed circuit is designed by amalgamating the conventional SEPIC with a boosting module. Therefore, the converter benefits from various advantages that the SEPIC converter has, such as continuous input current. Also, high voltage gain and input current continuity make the presented converter suitable for renewable energy sources. The modified SEPIC converter (MSC) provides higher voltage gain compared to the conventional SEPIC and recently addressed converters with a single-controlled switch. The analysis of voltage gain in continuous current mode (CCM) and discontinuous current mode (DCM) is analyzed by considering the non-idealities of the semiconductor devices and passive components. The selection of the semiconductor devices depending on the voltage-current rating is presented along with the designing of reactive components. The numerical simulation and experimental work are carried out, and the obtained results prove the feasibility of the MSC concept and the theoretical analysis.This work was supported by the National Priorities Research Program (NPRP) through the Qatar National Research Fund (a member of the Qatar Foundation) under Grant X-033-2-007.Scopu

Single-switch bipolar output DC-DC converter for photovoltaic application

Bipolar DC grids have become an adequate solution for high-power microgrids. This is mainly due to the fact that this configuration has a greater power transmission capacity. In bipolar DC grids, any distributed generation system can be connected through DC-DC converters, which must have a monopolar input and a bipolar output. In this paper, a DC-DC converter based on the combination of single-ended primary-inductor converter (SEPIC) and C´ uk converters is proposed, to connect a photovoltaic (PV) system to a bipolar DC grid. This topology has, as main advantages, a reduced number of components and a high e ciency. Furthermore, it can contribute to regulate/balance voltage in bipolar DC grids. To control the proposed converter, any of the techniques described in the literature and applied to converters of a single input and single output can be used. An experimental prototype of a DC-DC converter with bipolar output based on the combination of SEPIC and C´ uk converters was developed. On the other hand, a perturb and observe method (P and O) has been applied to control the converter and has allowed maximum power point tracking (MPPT). The combined converter was connected in island mode and in parallel with a bipolar DC microgrid. The obtained results have allowed to verify the behavior of the combined converter with the applied strategy.info:eu-repo/semantics/publishedVersio

Dual Output and High Voltage Gain DC-DC Converter for PV and Fuel Cell Generators Connected to DC Bipolar Microgrids

This paper introduces a new topology for a DC-DC converter with bipolar output and high voltage gain. The topology was designed with the aim to use only one active power switch. Besides the bipolar multiport output and high voltage gain this converter has another important feature, namely, it has a continuous input current. Due to the self-balancing bipolar outputs, the proposed topology is suitable for bipolar DC microgrids. Indeed, the topology balancing capability can achieve the two symmetrical voltage poles of bipolar DC microgrids. Furthermore, it is possible to create a midpoint in the output of the converter that can be directly connected to the ground of the DC power supply, avoiding common-mode leakage currents in critical applications such as transformerless grid-connect PV systems. The operating principle of the proposed topology will be supported by mathematical analysis. To validate and verify the characteristics of the presented topology, several experimental results are shown.info:eu-repo/semantics/publishedVersio

Two new families of high-gain DC-DC power electronic converters for DC-microgrids

Distributing the electric power in dc form is an appealing solution in many applications such as telecommunications, data centers, commercial buildings, and microgrids. A high gain dc-dc power electronic converter can be used to individually link low-voltage elements such as solar panels, fuel cells, and batteries to the dc voltage bus which is usually 400 volts. This way, it is not required to put such elements in a series string to build up their voltages. Consequently, each element can function at it optimal operating point regardless of the other elements in the system. In this dissertation, first a comparative study of dc microgrid architectures and their advantages over their ac counterparts is presented. Voltage level selection of dc distribution systems is discussed from the cost, reliability, efficiency, and safety standpoints. Next, a new family of non-isolated high-voltage-gain dc-dc power electronic converters with unidirectional power flow is introduced. This family of converters benefits from a low voltage stress across its switches. The proposed topologies are versatile as they can be utilized as single-input or double-input power converters. In either case, they draw continuous currents from their sources. Lastly, a bidirectional high-voltage-gain dc-dc power electronic converter is proposed. This converter is comprised of a bidirectional boost converter which feeds a switched-capacitor architecture. The switched-capacitor stage suggested here has several advantages over the existing approaches. For example, it benefits from a higher voltage gain while it uses less number of capacitors. The proposed converters are highly efficient and modular. The operating modes, dc voltage gain, and design procedure for each converter are discussed in details. Hardware prototypes have been developed in the lab. The results obtained from the hardware agree with those of the simulation models. --Abstract, page iv

A bidirectional power charging control strategy for Plug-in Hybrid Electric Vehicles

© 2019 by the authors. Plug-in Hybrid Electric Vehicles (PHEVs) have the potential of providing frequency regulation due to the adjustment of power charging. Based on the stochastic nature of the daily mileage and the arrival and departure time of Electric Vehicles (EVs), a precise bidirectional charging control strategy of plug-in hybrid electric vehicles by considering the State of Charge (SoC) of the batteries and simultaneous voltage and frequency regulation is presented in this paper. The proposed strategy can control the batteries charge which are connected to the grid, and simultaneously regulate the voltage and frequency of the power grid during the charging time based on the available power when different events occur over a 24-h period. The simulation results prove the validity of the proposed control strategy in coordinating plug-in hybrid electric vehicles aggregations and its significant contribution to the peak reduction, as well as power quality improvement. The case study in this paper consists of detailed models of Distributed Energy Resources (DERs), diesel generator and wind farm, a generic aggregation of EVs with various charging profiles, and different loads. The test system is simulated and analyzed in MATLAB/SIMULINK software