# Design of a Power Converter for Solar Energy Storage System
###### Abstract
When renewable energy ports are not supplying power and the energy storage ports are insufficiently charged, other sources of electrical energy cannot be used to charge the energy storage ports. In [10], a bidirectional three-energy-port DC-to-DC converter was proposed to combine interleaved buck and half-bridge converter structures and achieve power conversion between any two energy ports through phase-shift pulse width modulation (PWM) control. However, the half-bridge structure resulted in an unstable output voltage and low power capacity. An analysis and comparison of the full-bridge and half-bridge circuit structures with rated power in kilowatts revealed that the full-bridge structure exhibited a higher converter efficiency, even though it required more power switches and had higher costs. Therefore, in high-power applications, full-bridge converter structures can support a larger power capacity and have more voltage stability compared to half-bridge converter structures [11; 12]. In [13], the topology of interleaved Buck/Boost integrated with dual active bridge (DAB) is proposed, utilizing a centralized control method using Pulse Width Modulation (PWM) control on the primary side and Phase Shift Modulation (PSM) control on the secondary side. This method enables the control of system energy, bidirectional power flow, and single-stage power conversion between different ports. In [14], a novel three-port converter is proposed based on dual active bridge topology, interfacing two DC sources and an AC output. Power flow is achieved through dual phase shift modulation and standard sine pulse width modulation is used for AC synthesis. However, neither of the aforementioned articles conducted a comprehensive efficiency analysis on various power transfer modes. Additionally, their circuit topologies all have two DC input ports and output to DC and AC loads, respectively. The power transfer modes in the previous studies only involved PV charging the battery or transferring power between two DC ports to the third port, lacking the mode of transferring power from the third port to the battery port. If this converter is to be used in the case where the third port is a DC Grid, it must have the ability to convert DC Grid power to the battery port so that the battery port can be charged from the DC Grid port even without input from renewable energy sources. This can turn the battery port into a small energy storage system for regulating electrical energy. The power converter developed in this study has the power conversion mode to transfer power from the third port (DC Grid) to the battery port, making it suitable for use on a DC Grid. Given the advantages and disadvantages of the technologies discussed in the aforementioned literature, achieving an isolated renewable energy storage and supply system with three energy ports and a single-stage converter is both feasible and necessary. In this study, a single-stage converter with three energy ports utilizing a full-bridge circuit structure as an isolated circuit was designed and manufactured to achieve a high power conversion capacity and voltage gain. Various types of renewable energy conversion and energy storage systems discussed in [15; 16; 17; 18] were integrated and referenced. A single-stage structure was used to increase the efficiency of multistage converters and reduce the overall converter size and material costs. The proposed converter exhibited bidirectional energy transfer functionality, allowing the energy of the battery energy storage system to be combined with the energy produced by the renewable energy generation system to achieve energy regulation, thus providing stable electricity to the DC grid [19; 20; 21; 22].