IOT Based Multiport Bidirectional DC-DC Converter for PV-Battery Systems

Now a days, solar energy become one of the most important renewable energy resources, because of reduction in fossil fuels. This project presents a “IOT Based Monitoring and Control of Multiport Bidirectional DC-DC Converter for PV-Battery Systems. One port for unidirectional purpose and another port for bidirectional purpose. Previously, we use SISO (single input single output) power flow system which leads to power quality issue which is out of range of the PV converters setting. Now it’s modified in to multiport system along with usage of LES (Local energy storage), in order to overcome the power quality issue and provide continuous supply. This modified technique provides high efficiency, high power density and reduction of conversion stages. This technique uses IOT.So, the entire system can be monitored and controlled in order to maintain the constant power flow.

Earth is running out of fuel, so almost all the countries are racing towards the usage of renewable energy sources. One of the reliable renewable energy sources in the solar energy, which is abundant in nature. The first solar cell was constructed by Charles Fritts in 1883 and it was installed in 1884 on a New York City rooftop. The commercial concentrated solar power plants were first developed in the 1980s. Since then the generation of power through solar energy had been escalated. But for as much as three decapods renewable energy resources became most important sources for electricity generation, in order to reduce the pollution and also because of limited fuels. This paper expounds about the type of converter used to provide an effective power flow between the systems.

In previous system there was power flow between PV system and the load (Grid/Domestic load). This case encountered two types of power quality issues which ruined the connectivity between PV system and load. It also affected the converter system. One is voltage sag which leads to the interruption of power flow in system, thus consumers experienced shutdown of power. Voltage sag is incurred in the system due to the fault like single line to ground or due to lighting strokes on transmission lines ( DC line bus ) or also due to the incorporation of large loads. During this types of situations the system could not be able to supply the load. Another issue is over voltages which lead to the overflow of power to the consumer side which could damage the load equipments. Rather than there are other issues such as harmonics, flicker, fluctuations etc,.

The important role of this paper is to overcome the power quality issues and provide the constant power flow with increased efficiency. It can be accomplished by introducing LES (Local Energy System) or EES (Energy Storage System). This system is connected with the DC-DC converter which is feeded by PV system. Now, the part of energy is bifurcated and sends to both load as well as ESS. It due to any misoperation if overvoltage occurs with the help of converter help of converter only the allowable part is fed to load and excess part of energy is fed to ESS, where it get stored. In the same way if there is voltage sag or if the production is lower in PV system then the power from ESS and provider constant power to load. Thus both the power quality issues are vindicated from the system.

As the system consists of LES, if is not effective to use two port converter. Because this increases the no.of conversion stages as no.of converters are increased. So, we go with multiport converter(MPC). Since 10 years this has gained the interact of many engineers. There are many advantages in TPC over SISO(single I/P single output), such as increased efficiency, power density etc,. Here were are Three Port Converter(TPC). There are three topologies of TPC. They are non-isolated three port converter, partially isolated three port converter and isolated three port converter. In this topologies isolated TPC and partially isolated TPC are obtained from half bridge, boost half bridge and full bridge. In case of isolated topology it does not requires dc common, but it was magnetic coupling via high frequency transformer. Whereas in case of partially isolated topology it requires both magnetic coupling and dc common bus.

These partially isolated and isolated topologies has advantages such as protection through ZCS(Zero Current Switching) and ZVS(Zero Voltage Switching) and it also increases the no.of ports and can be used for vast voltage ranges. But the weight of the system gets increased, size increases, obviously the cost does the same. In this paper we use a Non-Isolated topology of TPC. It is desired from buck and boost converters. This non-isolated topology has advantages over isolated and partially isolated topologies. Those includes enhanced efficiency, high power density etc.,

In existing system the number of converters is more, so the conversion stage will also gets increased. It doesn’t have IOT, so it cannot be monitored and controlled as well. As the converters are more the reliability, stability, and efficiency gets reduced. This matter the system unsuitable for feed constant power supply to the load.

The proposed system consists of PV panels which absorb the rays from the sun and convert them into electric energy and feeds to the DC-DC converter. The converter used here is multiport non isolated converter. It requires electric energy from PV panel and converts the fined DC into variable DC. One port of the converter is connected to DC link and another one is connected with ESS. The connection between ESS and DC-DC converter is in bidirectional way. The flows from DC-DC converter to grid or domestic load through DC link and DC-DC converter. When the energy from PV panels gets reduced then it is supplied by the ESS. ESS is a battery which stores the electric energy from solar panel as well as from grid. The advantage of our proposed system is IOT with which the whole system can be monitored and controlled effectively, thereby increasing the efficiency, reliability and stability of the system as well. The IOT module gets inputs from the system then it transmits the data to operate through Wi-Fi which is explained in circuit diagram with IOT.

Proposed topology has greater advantage over tradition topology in different aspects such as multiport, bidirectional operation which paved the way to decrease the conversion stages thereby decrease the no. of converters and increasing the reliability as well as efficiency. So, this system uses one dual input single output (DISO) instead of one (SISO) single input single output

The circuit is obtained from the non-isolated three port converter topology. Since the no. of power devices and other components (filters) are required in less number, this topology is pertained for increased performance as well as efficiency where high gain of voltage is not required. In case of conventional buck and boost converter the number of passive components and power devices are more which leads to the reduced performance for high power application. So, the proposed topology is very much efficient and effective one with many benefits. The proposed converter of four switches T1, T2, T3, T4 which are very much controllable in order to regulate the power flow at different ports. It also for freewheeling purposes. There are two inductor L1 and L2 where inductor L1 is present in boost side of circuit and L2 inductor is in buck side of the circuit. Similarly there are two capacitors Cpv present in panel side and Cbt present in ESS (Battery) side.

The first panel of own project introduces the requirements of renewable energy, then provides a brief explanation of previous system and then states the proposed system and mention the advantage of proposed system over the existing system. The second part shows the block diagram approach of both the existing and proposed system rather than that is also explains the power flow between the system. The third part evinces the proposed topology. It first explains the topology without IOT and then reveals the topology with IOT. The fourth part of the project conveys the operating principle of the whole system including the operation of each mode. The fifth part discloses the simulation work using PSIM software for each mode with circuit diagram, components rating, output waveform and description of waveform. Thus with help of our proposed topology the constant power flow can be achieved and efficiency of the output power can be increased, thereby providing effective generation and transmission as well.