Micro Grid
K. Mazlumi; A. Shabani
Abstract
In recent years, most of the loads and distributed generations are connected to the AC grid through the power electronic converters. Using the DC grid beside the AC grid can reduce the conversion stages and power losses. Protection of the DC grids is a challenging issue because of the new structures ...
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In recent years, most of the loads and distributed generations are connected to the AC grid through the power electronic converters. Using the DC grid beside the AC grid can reduce the conversion stages and power losses. Protection of the DC grids is a challenging issue because of the new structures of DC grids and fast transients of the DC faults. This paper studies the protection of the low voltage DC (LVDC) system in the presence of the photovoltaic (PV) and energy storage systems (ESS). An LVDC system consisting of a DC microgrid is considered and Different operating modes are analyzed. DC faults behavior and protection challenges are discussed for each mode through simulations employing MATLAB software. Finally, some methods are presented to solve the protection challenges. The results show that changing the protection arrangement of the system and choosing suitable control logics for the ESS and the PV prevent the unwanted outage of the loads and provide the possibility of the microgrid operation in islanded mode.
Power Electronic
Mohammad Farhadi Kangarlu; Ebrahim Babaei; Frede Blaabjerg
Volume 4, Issue 1 , June 2016, , Pages 54-65
Abstract
Integration of the PV into the electrical grid needs power electronic interface. This power electronic interface should have some key features and should come up with grid codes. One of the important criteria is the quality and harmonic contents of the current being injected to the grid. High-order harmonics ...
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Integration of the PV into the electrical grid needs power electronic interface. This power electronic interface should have some key features and should come up with grid codes. One of the important criteria is the quality and harmonic contents of the current being injected to the grid. High-order harmonics of the grid current should be very limited (lower than 0.3% of the fundamental current). Beside the topology of the power electronic interface, the output filter also affects the quality of the grid current. In this paper, a 5-level inverter is presented for grid integration of PV systems along with its output LCL filter design. Analytical calculation of losses for the 5-level inverter and the output LCL filter is presented. It is also compared to the H-bridge inverter in terms of output voltage and current harmonics, and the overall losses. Second-order generalized integral phase locked loop is used to synchronize the system with the grid voltage and the proportional resonant (PR) with harmonic compensation control method is used to control the output current. The proposed system has been simulated in the PSCAD/EMTDC environment to verify its operation and control.
