Design of Three Port Isolated Converters and its Analysis with Various Modulation Techniques for DC Microgrid Applications

Abstract

Multiple energy generation units are essential for the reliable operation of newlinepower supply systems in microgrids. Factors such as integration of renewable power newlinegeneration units, environmental effects, increasing energy demand and other economic newlineaspects lead to wide range of voltage variations in DC microgrids. In this scenario, newlineproductive power conversion and utilization can be achieved by employing an effective newlinepower electronic converter interface. A DC microgrid comprises multiple levels of DC newlinebus voltages, namely high-voltage (HV), medium-voltage (MV) and low-voltage (LV) newlineDC bus. In conventional system, two-port isolated DC DC converter is employed for newlinecoupling the DC bus voltages. But, more number of DC DC conversion units are newlinerequired and this will increase the size and cost of the system. The number of DC DC newlineconversion stages can be minimized by utilizing a three-port isolated converter (3PIC). newlineHere, port 1 is connected to high voltage DC (HVDC) bus system, port 2 and port 3 are newlinecoupled to medium voltage (MV) and low voltage (LV) DC bus system respectively. newlineThe application of 3PIC can be extended for data centers, electric vehicles (EVs) and newlineresidential purposes. newlineThree-port isolated converter (3PIC) consists of three H-bridges and a newlinethree-winding high-frequency transformer. Leakage inductance of high-frequency newlinetransformer is a key element for energy transfer between the ports. Similar to two-port isolated converter the amount of power flow between the ports in a 3PIC is also newlinedetermined by the phase-shift angles. DC microgrid is prone to voltage and current newlinevariations. The performance of 3PIC degrades when there is a voltage mismatch from newlinethe nominal value between the ports. This may induce high current stress and newlineassociated losses in the converter. The reliable and economical solution to this issue is by applying different switch modulation strategies. The simple and preferred one is the phase-shift modulation schemes.