# Modern MultiPort Converter Technologies: A Systematic Review
## 2 General Classification and Operation Principles
### Non-Isolated Multiport Converters  
Each category of converters is explained in general terms, and the corresponding comparisons are made in the current section. The converters that do not provide electrical isolation between the input and output stages fall under the category of non-isolated multiport converters (Figure 3). The input power ports share the same ground in a non-isolated multiport converter design. High power density, fewer switches, a relatively simple control scheme, and a compact design are a few benefits of non-isolated multiport converters. In addition, these types of MPCs not only help lower the overall cost but also achieve low electromagnetic interference (EMI). In [33], a family of non-isolated three-port converters for stand-alone renewable power systems is analyzed. After analyzing the power flow among the ports, the authors found out that a non-isolated three-port converter (NI-TPC) can be handled as a dual-output converter from the primary supply and as a dual-input converter from the load, respectively. A number of combined NI-TPC topologies and integrated NI-TPC topologies are provided as examples along with topology creation methods based on dual-input and dual-output converters. The proposed topologies of non-isolated three port converters have one power conversion stage. In a three-port MPC topology, it is possible to achieve a high system efficiency between any two of the three-ports and it is appropriate for stand-alone renewable power system applications. In order to feed a household load ranging from 50 watts to 3500 watts, the research presented by authors in [34] proposes a novel multi-stage non-isolated three-port converter with a 5H inverter where an additional semiconductor switch is connected to a conventional H bridge circuit. Both grid-connected and island power modes are supported by the proposed three-port converter. A description of a demand-side management algorithm with eight operational modes is also provided. A complete control system is also discussed. The suggested control system governs the 400 V DC bus voltage, the load voltage in island mode, and the grid-connected injected current in addition to controlling the photovoltaic maximum power point and battery charging and discharging. A converter that has one output port with a DC load and two unidirectional input ports that can accommodate both a fuel cell and a photovoltaic cell is proposed in [35]. The authors suggest a non-isolated three-port DC-DC converter based on Cuk topology to handle renewable energy sources. It is shown that the benefit of continuous input and output currents is due to the inductors at all of the ports. Additionally, compared to standard \"n - 1\" separate Cuk converters, it needs less switches, diodes, and inductors (Table 2). Another NI-TPC is proposed in [36]. The use of a novel single-inductor non-isolated three-port converter in a photovoltaic fed DC microgrid with a battery storage system is suggested. Since two of the three ports can handle reversible currents, as opposed to one bi-directional port in existing NITPCs, a more flexible power flow can be obtained. The authors state that the developed NITPC can operate and switch between islanded mode and DC grid-connected mode without any issues. Explanations of detailed operating principles, mode selection criteria, and control schemes are provided. Depending on the  
Figure 3: Structure of non-isolated n-port MPC system. mode chosen, the converter can be reconfigured as a single-input-single-output (SISO), single-input-double-output (SIDO), or double-input-single-output (DISO) converter. In [37], a novel multiport zero voltage switching DC-DC converter is proposed. The suggested topology can function in the boost, buck, and buck-boost operational modes. Additionally, it can reduce input current ripple and operate all switches at zero voltage. In addition, the input sources can be expanded on the low-voltage side.