Grid-Forming-Mode Operation of Boost-Power-Stage Converter in PV-Generator-Interfacing Applications

Abstract

Abstract:The application of constant power control and inclusion of energy storage in grid-connected photovoltaic (PV) energy systems may increase the use of two-stage system structures composed of DC-DC-converter-interfaced PV generator and grid-connected inverter connected in cascade. A typical PV-generator-interfacing DC-DC converter is a boost-power-stage converter. The renewable energy system may operate in three different operation modes-grid-forming, grid-feeding, and grid-supporting modes. In the last two operation modes, the outmost feedback loops are taken from the input terminal of the associated power electronic converters, which usually does not pose stability problems in terms of their input sources. In the grid-forming operation mode, the outmost feedback loops have to be connected to the output terminal of the associated power electronic converters, and hence the input terminal will behave as a negative incremental resistor at low frequencies. This property will limit the operation of the PV interfacing converter in either the constant voltage or constant current region of the PV generator for ensuring stable operation. The boost-power-stage converter can be applied as a voltage or current-fed converter limiting the stable operation region accordingly. The investigations of this paper show explicitly that only the voltage-fed mode would provide feasible dynamic and stability properties as a viable interfacing converter.

A Novel Two-Stage Photovoltaic Grid-Connected Inverter Voltage-Type Control Method with Failure Zone Characteristics

“…According to the function and control scheme of the inverter, renewable energy based inverter can be divided in grid-feeding inverter, grid-forming inverter and grid-supporting inverter [26]. The grid-forming inverters can set the voltage amplitude and frequency of the local grid.…”

“…The inverter in this paper is voltage source based grid-supporting inverter, belonging to the grid-supporting inverter. It should be noted that some of control details are omitted or simplified in consideration of the aesthetic appearance of figure, such as coordinate transformation parts and the According to the function and control scheme of the inverter, renewable energy based inverter can be divided in grid-feeding inverter, grid-forming inverter and grid-supporting inverter [26]. The grid-forming inverters can set the voltage amplitude and frequency of the local grid.…”

A Multifunctional Isolated and Non-Isolated Dual Mode Converter for Renewable Energy Conversion Applications

“…The flyback converter has been widely used in a large number of power conversions due to its relatively simple structure, good performance, and galvanic isolation [26][27][28]. A bidirectional buck/boost converter is a mature topology in power electronics systems due to its simplicity and high efficiency [29]; however, the conventional buck/boost converter cannot Compared to traditional converters, with the addition of the realization of conventional bi-directional function, the multifunctional converter can also be applied for both the isolated and non-isolated operation modes. Switching between the isolated and non-isolated operation modes is presented according to different applications by adjusting the control switch signals, which are flexible to change in the operation mode for renewable energy conversion applications.…”

“…The flyback converter has been widely used in a large number of power conversions due to its relatively simple structure, good performance, and galvanic isolation [26][27][28]. A bidirectional buck/boost converter is a mature topology in power electronics systems due to its simplicity and high efficiency [29]; however, the conventional buck/boost converter cannot achieve input and output galvanic isolation. To simultaneously implement the functions of isolated and non-isolated converters and benefit from the advantages of the two converter circuits, this paper proposes a novel multifunctional isolated and non-isolated dual mode converter by increasing the control transfer units.…”

“…As conventional bidirectional isolated or non-isolated converter control methods and strategies have been widely presented in the literature, details on the related control analyses and design are provided in [26][27][28][29][30][31][32][33][34][35][36][37][38]. Given that the proposed new converter has many different transition control strategies across different states and modes, the switching control is mainly used during the transition process between the switching devices depending on the application requirements.…”