# Design of a Power Converter for Solar Energy Storage System
###### Abstract  
This paper presents a single-stage three-port isolated power converter that enables energy conversion among a renewable energy port, a battery energy storage port, and a DC grid port. The proposed converter integrates an interleaved synchronous rectifier boost circuit and a bidirectional full-bridge circuit into a single-stage architecture, which features four power conversion modes, allowing energy adjustment for both the renewable energy and the battery storage energy ports when power is supplied by the renewable energy port. It also features bidirectional functionality that allows the battery storage energy port to provide energy storage through the DC grid port, thereby providing uninterrupted power supply functionality. The converter uses four power switches and two inductors to boost and convert energy from the renewable energy port to the battery storage energy port or to the DC grid port through the bidirectional full-bridge circuit. The converter is also capable of 1 kW power energy conversion by utilizing an adjustable duty cycle with a fixed frequency of 100 kHz and phase-shift control through a built-in pulse width modulation control module of a TMS320F28 series digital signal processor. According to the experimental results, the converter developed in this study can achieve a conversion efficiency of up to 94%. three-port converter; interleaved synchronous rectifier boost converter; bidirectional full-bridge converter +
Footnote †: journal: Applied  
small circuit volume and few power components, the voltage gain is solely determined by the duty cycle of the switch and is suitable only for low DC voltage loads, such as in solar LED applications. Hence, it is not suitable for energy systems interconnected with the power grid or battery equipment that requires a high voltage gain. In [7], an independent regenerative energy converter with a high voltage gain was proposed. This converter uses only three power switches to achieve power conversion. It also uses inductance energy storage for power conduction and transfer to achieve a high voltage conversion ratio. Although this converter can output voltages of up to 400 V, the power capacity of the circuit is rather limited. Similar circuit architectures proposed in other studies have a higher voltage gain, but they use additional inductors, which are expensive and bulky, and lack electrical isolation characteristics. Operating such circuits in high-voltage and high-power environments may compromise electrical safety. In [8], multiple isolated three-electricity-port converters relying on various transformer induction methods were proposed to conduct electrical power. For instance, in [8], a multi-winding transformer was used to design isolated input and output ports to improve electrical safety. However, multi-winding transformers have large volumes and are associated with high costs, and they are capable of only one-way power flow control. Although transformer leakage inductance has been used in other studies to achieve zero-voltage switching in a primary-side switch and improve the conversion efficiency of converters, these converters are capable of only one-way power conversion. In [9], multiple transformers were used to achieve bidirectional power transmission, which is applicable to energy storage systems. However, this architecture requires additional power switches, making the circuit complex and difficult to control. In [10], a similar multi-group full-bridge connection architecture and series resonance were used to achieve bidirectional power conversion and high-power transmission, which is applicable to fuel cells and other regenerative energy systems. However, this architecture increases the volume of the transformer and requires additional power switches, thereby resulting in additional costs. In the aforementioned multi-energy port renewable energy systems, the battery energy storage ports rely solely on surplus and unused energy for energy storage when supplied only by renewable energy ports.