روش تنظیم ولتاژ برای جبران ولتاژ و کاهش عدم تعادل در سیستم توزیع DC دوقطبی کم ولتاژ Voltage Regulation Method for Voltage Drop Compensation and Unbalance Reduction in Bipolar Low-Voltage DC Distribution System

I. INTRODUCTION TO reduce the energy losses, various studies on improving the power efficiency have been performed worldwide. In this paper, the low-voltage DC (LVDC) distribution system is investigated as a solution to the power efficiency problem, because of its many advantages. With a dc distribution system, power conversion within the appliance can be avoided and losses reduced. Moreover, the LVDC system is well suited for connection of various renewable energy systems such as photovoltaic and fuel cells producing DC power by reducing the number of conversions: DC/DC/AC to DC/DC conversion. In addition, the efficiency of the microturbine and variable speed wind turbine that produce the AC power can be improved in an LVDC system by reducing the number of conversions: AC/DC/AC to AC/DC conversion [1]–[6]. An LVDC distribution system can be constructed as a unipolar or a bipolar system. A unipolar LVDC distribution system has only one voltage level with two wires, making it impossible to meet the voltage requirements of all electronic devices. On the other hand, a bipolar LVDC distribution system transfers DC power through three wires. In a bipolar system, various voltage levels can be implemented, which can decrease the potential to ground in the conductors. However, if the capacity of the loads connected to each pole is different, voltage unbalance can occur, which can adversely affect the receiving voltage [7], [8]. In order to solve the voltage unbalance problem in a bipolar LVDC distribution system, a dual-buck and half-bridge balancer that keeps the positive pole voltage equal to the negative pole voltage has been proposed and studied [7]–[10]. In addition, a buck-boost type balancer and a dual-buck halfbridge type balancer have been proposed to be employed as the requirements for power quality increase [11], [12]. However, they operate in the perspectives of electric power converters rather than the balancer output voltage by voltage drop on the distribution line. The voltage drop on the distribution line may reduce the receiving voltage, which makes the voltage regulation method for the LVDC distribution system necessary to supply an appropriate voltage level.