Smart Multiport Bidirectional Non-Isolated DC-DC Converter for Solar PV-Battery Systems

A credit-card sized three-port dc-dc converter (TPC) has been designed and constructed. The TPC has three DC ports in one circuit, and DC power can be transferred without interference mutually. A dual active bridge converter (DAB) and a non-isolated bi-directional dc-dc converter (NBC) are integrated in the TPC by using a technique known as magnetic coupling inductor. Both thermal and soft-switching analysis are conducted to realize a high energy density of prototype, where a 750 W, 375 kHz, 18 W/cc is achieved. The efficiency and total losses have been measured in order to verify the validity of the proposed converter, and efficiency over 90% in wide range of output power is achieved by using Si MOSFETs.

A novel solution for nonisolated bidirectional dc-dc converters (NI-BDCs) with advantages of simple topology, high efficiency, and high reliability is proposed. A small negative-coupled inductor (NCI) is employed to split the switch branch in the NI-BDC into two power flows clearly and prevent the freewheeling current from flowing through the body diode of MOSFET. As a result, the reverse-recovery problem of the MOSFET's body diode is alleviated. The topology method is presented and a family of NI-BDCs with NCI is proposed. The idea is further extended to a positive-coupled-inductor (PCI) solution by merging the NCI and the filter inductor into a PCI. And a family of NI-BDCs with PCI is proposed. The key operational principle and design consideration are presented with experimental results given.

DC microgrids are starting to become quite important in the actual context of electrical energy distribution grids. There are two main structures for these grids, the unipolar and the bipolar DC microgrids. In this paper, a DC-DC converter that allows to interlink these two DC microgrids is proposed. This converter is a non-isolated bidirectional DC-DC converter with bipolar and unipolar interfaces. The converter was designed to transfer energy between these microgrids and, at the same time, to support the balance of the bipolar DC microgrid. Moreover, the proposed converter is also able to operate as a standalone voltage balancer to support the bipolar DC microgrid. The converter also presents bidirectional buck-boost characteristics. Simulations and experimental results of the DC-DC converter operating in both directions will be provided. From the presented results, it will be possible to verify the capability of the converter to operate as interlink interface for both microgrids.

Converting solar energy into power and hydrogen provides a promising pathway to fulfilling instantaneous electricity demand (power generation) as well as continuous demand via storing energy in chemical bonds (hydrogen generation). Co-generation of power and hydrogen is of great interest due to its potential to overcome expensive electricity storage in conventional PV plus battery systems. Both solar thermochemistry processes and photo-electrochemical cells (PECs) are extensively explored technologies to produce solar hydrogen. The key challenges for solar thermochemistry processes are extremely high operating temperature (~ 1500 oC) and low demonstrated efficiency (< 1% for hydrogen generation). For PECs, the limited solar absorption together with sluggish electrochemical reactions, especially for OER, leads to limited theoretical solar fuel generation. Operating PECs at high temperature will lead to decreased photovoltage and interface stability. Inspired by the thermally regenerative batteries, we propose a photo-thermo-electrochemical (PTEC) device that uses the solid oxide-based moderate high temperature cell (~1000 ℃) as the photo-absorber for simultaneously converting concentrated solar radiation into heat and generating fuel or power electrochemically driven by the discharging power from the low temperature cell (~700 ℃). PTEC device enables full solar spectrum utilization, highly favorable thermodynamics and kinetics, and cost-effectiveness. A continuous PTEC device has two working modes, which are voltage differential (VD) mode and current differential (CD) mode. The current-voltage characteristics of a PTEC device are shown in Figure 1. It mainly consists of five parts. A high temperature cell (HTC) serves as a solar absorber and a low temperature cell (LTC) serves as heat recovery. Besides, the opposite electrochemical reactions take place in two cells meaning that HTC and LTC can also function as a hydrogen production as well as an electricity generator component, respectively. Heat exchanger(s) is placed between the HTC and LTC and hot fluids pass through a heat exchanger before entering LTC to reduce heat losses to environment as well as reducing input solar energy. The VD mode and CD mode can be realized in PTECs via controlling of DC-DC converter. In order to identify the main parameters, we develop a multi-physics model based on finite element method, including mass, heat and charge transfer, and electrochemical reactions. In addition, heat exchange is modeled by solving energy balance equation, DC-DC convertor is assumed by constant efficiency, and a lumped parameter model is used to describe solar receiver including energy losses of conduction and reradiation. This framework also allows us to provide design guidelines for PTEC devices with high solar-to-electricity (STE) efficiency and solar-to-hydrogen (STH) efficiency. The maximum STE and STH efficiency under reference conditions of PTEC device was found to be 4 % and 2 %. A further improved performance in terms of STE and STH efficiency are about 19 % and 16 %, respectively, via optimizing temperature configuration between HTC and LTC and material properties. It is also interesting to note that STH can reach higher than 80 % of STE at a large temperature difference, which shows a promising energy storage device by storing excessive electrical power in form of hydrogen. The main results show that the temperature of HTC and efficiency of heat exchange are key parameters to optimize PTEC efficiency. The performance of DC-DC convertor dominates STH efficiency. Besides, ionic conductivity of electrolyte can contribute to significantly expanding the operating current density range. The PTEC is a promising technology for solar energy conversion and storage as it is able to produce electricity and hydrogen in a single device. The solar conversion efficiency predicted with our numerical model supports that by optimizing the design and operational conditions, this technology can compete with existing solar fuel pathways. Figure 1

Solar energy conversion is the one modern power supply technology in which small units appear feasible. Economics may dictate large plants when the heat source is conventional boilers or nuclear reactors, but, along with sunlight collectors half the size of Arizona, solar units small enough to power not more than a single house are a serious feature of most solar-energy proposals. This wide variation of scale makes a variety of local and individual initiative possible in solar conversion. It's not necessary to draw up plans for a multimegawatt interconnection to start. An example of such a local initiative is San Jose State University in California, which is engaged in a 15-year program to apply solar energy to various uses on its campus. By the end of that time the university expects to get between 30 and 50 percent of its total energy requirements from sunlight collected on the campus, Donald W Aitken, director of the University's Center for Solar Energy Applications, told the American Physical Society Meeting in San Francisco. The San Jose team started the project in 1975 by taking a campus map and coloring in yellow the places where solar energy might be applicable. They were surprised at how yellow the map became. They ordered the ensuing projects in a logical sequence. One of the first to be done was what Aitken calls the largest solar hot water system yet built in the United States. It provides 70 percent of the hot water needs of 600 students in three dormitories. Like most successful solar energy systems it can rely on other sources of energy for backup when the sun is overcast. The 70 percent is a weather hazard figure, Aitken says. On a sunny day, we don't use any gas. When he spoke, northern California had just been through an extended rainy period, during which solar energy did very little. But, if you notice that the sun came out in earnest yesterday and a little bit the day before, ... yesterday afternoon we were delivering 1400 water. The 9,000-square-foot-system is laid out on top of the three buildings it serves. It was built with $180,000 of state funds. We have yet to write a research proposal, Aitken says. If we're really going to argue that solar energy is an available, practical resource, we've got to put our own dollars where our mouths are. The system was built by students, illustrating both the pedagogical value of the program and the talent available in the student body for pursuing solar-energy conversion. The program envisions starting at least one major project a year. The next one in line is a new library. The library is designed to use the heat of human bodies and artificial lighting for space heat. When the days are too hot, the coolness of the night will be used to cool the building in the day. For times when bodies and lights do not suffice, the south wall of the building will incorporate a solar energy system for backup heating. This system adds $600,000 or $700,000 to a $10-million building, and is expected to pay itself back in five or six years. Aitken maintains that nowhere in the San Francisco Bay area should new construction have to rely on burning fossil fuels for space heating or climate control generally. After the library will come the conversion of the dining commons, which feeds 2,500 students a day. First, the wasted heat from over the stoves and from the dishwashers will be harnessed for space heating. So much heat is lost from stoves and dishwashers, says Aitken, that if it can be used, no restaurant need rely on any other source for heat. Then a solar unit to heat water for the dishwashers will be added. After the dining commons, the student union will get the treatment. Each project is different. Each takes into account the activities that go on in a given building and the advantages that can be drawn therefrom. None of the existing or immediately planned installations generates electricity, but the later stages of the program will include generation of 400,000 watts in electric power along with 2 million watts thermal plugged into the university's central boiler. Aitken insists that conversion projects of this kind are feasible not only in San Jose, which has a mild climate and lots of sunny weather, but in any part of the country including Seattle, Washington, and Maine. O Students installed collecting panels and tanks for solar-powered hot water system on roofs of dormitories at San Jose State.

In the future, renewable energy sources will be a more sustainable solution. Solar energy can be used by the factory to charge a substation’s battery charger. The plan is to use solar energy to charge a battery charger in a factory. Solar energy is more efficient than coal, petroleum, and natural gas. This paper demonstrates the design or reconstruction of an existing circuit drawing to achieve the goal of this project. The design incorporates a changeover switch to perform the power supply changeover for solar energy in order to compare the efficiency of the battery charger using solar power energy to the existing loads. The solar simulation will be built and performed by the MATLAB Simulink model for the simulation part. The PV array represents solar energy by stimulating the I-V and P-V for various irradiance (W/m2) and temperatures (oC). This project aims to improve the circuit design in the substation’s battery charger, develop a solar energy harvesting system, and create an efficient prototype of an energy storage automatic transfer switching system. As a result, this project helps to reduce the rate of global electricity consumption, which has an impact on the environment. Commercials’ pollution is significantly reduced by solar energy. We can demonstrate the global benefits and relevance of implementing this concept, particularly in our industry, by preparing this study. Solar energy is a dependable and cost-effective energy source. The sun is a renewable energy source. While fossil fuels will eventually run out, sunlight will not.

Changing in structure systems although in power plants, it must be concerned, because if one of the components out of the system, will be followed by changes in power flow and voltage profile. Study of power flow becomes very necessary to analyze power flow that occurs in electric power systems, both now and for the planning system in the future. ETAP 4.0 (Electric Transient and Analysis Program) is a software that supports the power system. Iteration method (numerical) is one of the techniques to solve power flow studies, one of the method is Newton Raphson Method. The advantage of this method is more appropriate to calculate the power flow in systems with large numbers. From the results obtained with two study cases or two conditions that is used to power flow analyze, that is : normal conditions and with the installation of shunt capacitors on the bus who suffered critical voltage, where for Buses are experiencing critical voltage at Bosowa distribution bus of 10.438 kV or 94,9% and Tanjung Bunga distribution bus at 18.818 kV or 94.1%, whereas after the addition of shunt capacitors on Bosowa distribution Bus at 10.490 kV or 95.4 % and Tanjung Bunga distribution bus at 19.209 kV or 96.0 %. Total losses amounted to 7.483 MW, where the biggest losses are on the transmission line Barru to Pangkep, that is 950.6 kW. The greatest of Active Power (P) is 62.46 MW, which flows from bus 7 Barru to bus 8 Pangkep. The greatest of Reactive Power ( Q ) is 12.55 MVAR, which flows from Bus 26 Pangkep 70 kV to Bus 27 Tonasa 70 kV. The largest voltage Buses is Bus 22 Bone about 152,315 kV or 101,54 % for normal conditions and 152,893 kV or 101.93 % after the addition of the capacitor. Thus, analysis of the results it can be concluded that after the addition of a shunt capacitor, voltage improvement made to meet the standard operating voltage, because the minimum limit of PT.PLN standard is +5% and -5%

Converting solar energy into electrochemical energy is a sustainable strategy, but the design of photo-assisted zinc-air battery (ZAB) with efficient utilization of sunlight faces huge challenges. Herein, a photo-assisted ZAB of a three-electrode system using MoS2/oxygen vacancies-rich TiO2 heterojunction as charge cathode and Fe, N-doped carbon matrix (FeNC) as discharge cathode is constructed, where MoS2 is chosen as solar light-responsive catalytic material and TiO2 acts as electron transport layer and hole blocking layer, arising from a train of thought for efficient charging under sunlight irradiation and light-independent discharging. The introduction of oxygen vacancies in TiO2 facilitates the temporary trapping of carriers and triggers rapid carrier transfer at the interface of the heterojunction, which hinders the recombination of photogenerated holes, thereby facilitating their further participation in the oxygen evolution reaction. Moreover, FeNC exhibits superior oxygen reduction reaction performance due to strong d-π interactions. As a result, the well-built ZABs deliver a low charge voltage (0.71 V) under illumination at 0.1 mA cm-2, and a high power density (167.6mW cm-2) in dark. This work paves a special way for the development of ZABs by directly harvesting solar energy in charging and efficiently discharging regardless of lighting conditions.

The natural gas system and electricity system are coupled tightly by gas turbines in an integrated energy system. The uncertainties of one system will not only threaten its own safe operation but also be likely to have a significant impact on the other. Therefore, it is necessary to study the variation of state variables when random fluctuations emerge in the coupled system. In this paper, a multi-slack-bus model is proposed to calculate the power and gas flow in the coupled system. A unified probabilistic power and gas flow calculation, in which the cumulant method and Gram–Charlier expansion are applied, is first presented to obtain the distribution of state variables after considering the effects of uncertain factors. When the variation range of random factors is too large, a new method of piecewise linearization is put forward to achieve a better fitting precision of probability distribution. Compared to the Monte Carlo method, the proposed method can reduce computation time greatly while reaching a satisfactory accuracy. The validity of the proposed methods is verified in a coupled system that consists of a 15-node natural gas system and the IEEE case24 power system.

PurposeTo analyze the operating performance of a fuzzy logic control (FLC) based solar energy conversion modular system controlled by a digital signal processor (DSP) microcontroller.Design/methodology/approachA range of published works relevant to the solar energy conversion modular systems are evaluated and their limitations are indicated in the first section of the paper. The circuit diagram of the panel‐boost converter system is described in the second section. In the third section, a neural network model is suggested for the photovoltaic panel and the model is created in the MATLAB/SIMULINK and then combined with other blocks existing in the system. The design of the FLC method is described in section 4. The simulation and experimental results corresponding to the control of the duty‐cycle of the converter to set the operating point of the solar panel at the maximum power point (MPP) are given in sections 5 and 6, respectively. Section 7, summarizes the results and conclusions of the study.FindingsThe paper suggests a simple dc‐dc boost converter controlled by FLC method. The proposed converter model can be used to obtain maximum power from a photovoltaic panel.Research limitations/implicationsIn preparing this paper, the resources books existing in the library of our university and the resources relative to the solar energy conversion and FLC published in English language and reachable through the internet were researched.Practical implicationsThe paper suggests a neural network model for a solar panel, which can be used in the simulation of the solar energy panel‐boost converter system. The solar energy panel‐boost converter system proposed in this study can be used by the researchers who are working in the solar energy conversion area.Originality/valueThe suggestion of a neural network model for a solar panel and creation of this model in the MATLAB/SIMULINK environment provides researchers to simulate and to analyze the performance of the solar energy panel‐boost converter system using the MATLAB/SIMULINK simulation program. In addition, since the control approach proposed in this paper does not require the information on temperature and solar irradiance that affect the maximum output power, can effectively find the MPP of the solar panel.

The interesting feature article “Solar Energy Conversion” by George Crabtree and Nathan Lewis (Physics Today, March 2007, page 37) devoted only two sentences to the simplest and cheapest form of solar conversion, the use of un-concentrated sunlight to “heat space and water in residential and commercial applications.” Instead, the article focused on expensive high-tech applications not presently available, at least to the general public.The immediate answer to the energy crisis is low-tech. Before President Harry Truman left office in 1953, he started a program to develop solar energy, but Dwight Eisenhower scuttled it. I remember attending an energy symposium in the early 1970s where the claim was made that solar energy would never be feasible because it would exhaust our water supply. President Jimmy Carter made a serious attempt to revive solar energy during the 1970s energy crisis, but he was ridiculed. He installed solar collectors on the White House roof, but Ronald Reagan had them ripped out.Even some members of the technical community have tried to discredit solar energy by making claims that, among other things, solar installations are visually polluting. See, for example, the letters and comments in the October–November 2002 issue of The Industrial Physicist (page 12).Six years ago, for about $1200, I built and retrofitted from secondhand components a solar space-heating system for our residence, which was built in 1916. In those days, circulating hot-water heating systems were common. They are uniquely suited to conversion to solar heat because the interior heat-transfer arrangement is already in place. All that is needed is to connect solar collectors to the existing system.A neat feature of the conversion is that the solar heating supplements rather than supplants the gas heating system. On very cold days, we fire up the natural gas and have gas and solar systems working together, with the benefit that free solar heat tempers the cost of the metered gas heat. If the weather is really bad and the sun isn't shining, we leave the circulating pump from the collectors turned off and rely exclusively on gas heat. Our heating bill has been cut in half.Our system is sort of a hybrid, like the hybrid autos that when outfitted with plug-in capability will go a long way toward solving that aspect of the energy problem. But that's another story.© 2007 American Institute of Physics.

A high light-absorption coefficient and long-range hot-carrier transport of hybrid organic-inorganic perovskites give huge potential to their composites in solar energy conversion and environmental protection. Understanding interfacial interactions and their effects are paramount for designing perovskite-based heterostructures with desirable properties. Herein, we systematically investigated the interfacial interactions in monolayer and few-layer SnS/CH3 NH3 PbI3 heterostructures and their effects on the electronic and optical properties of these structures by density functional theory. It was found that the interfacial interactions in SnS/CH3 NH3 PbI3 heterostructures were van der Waals (vdW) interactions, and they were found to be insensitive to the layer number of 2D SnS sheets. Interestingly, although their band gap decreased upon increasing the layer number of SnS, the near-gap electronic states and optical absorption spectra of these heterostructures were found to be strikingly similar. This feature was determined to be critical for the design of 2D layered SnS-based heterostructures. Strong absorption in the ultraviolet and visible-light regions, type II staggered band alignment at the interface, and few-layer SnS as an active co-catalyst make 2D SnS/CH3 NH3 PbI3 heterostructures promising candidates for photocatalysis, photodetectors, and solar energy harvesting and conversion. These results provide first insight into the nature of interfacial interactions and are useful for designing hybrid organic-inorganic perovskite-based devices with novel properties.

In recent years, with the distributed generation (DG) technology widely applied, traditional distribution power flow algorithms can not satisfy needs of DG system. The model for distribution power flow calculation of typical DG, including wind power generation, solar electrical energy generation and micro-turbine, are presented and the problems are taked into account the capacities of DGs and the network parameters. Based on the above, a new algorithm for the distribution power flow are presented, which uses the power losses sensitivity and network parameters based on distributed slack bus model. The algorithm is available to calculate distribution power flow with multi-type DGs and different levels of DG penetration. The models are applied to calculate power flow of IEEE 14-bus test system including DGs and the results are simulated. The results are analyzed contratively with traditional algorithm, and proved the feasibility of the method proposed.

This paper presents modelling and control study of a bidirectional non-isolated interleaved DC- DC converter with high voltage gain. The nonisolated converter under study combines the advantages of switched capacitors and coupled inductors. Series connected switched capacitors with inductor cells helped to achieve high conversion ratio and reduced voltage stress on power components. An average current mode control is used to control output current and input current of non-isolated bidirectional dc-dc converter at both stages boost converter as well as buck converter. A state space modeling and an average current mode control analysis at the boost stage are given in details in this paper. Simulation results are based on some experimental data of non-isolated bidirectional dc-dc converter of high power application.

A Prognostic Energy Optimization Technique with unified power quality conditioner for energy stabilization in grid system