Abstract
With the increase of photovoltaic penetration rate, the fluctuation of photovoltaic power generation affects the reliability of ship power grids. Marine PV grid-connected systems with high penetration rates should generally have a low voltage ride-through capability. In the present paper, a strategy in which super capacitors are applied for energy storage in a marine photovoltaic grid-connected system is proposed, and an inverter adopts independent decoupling control of active and reactive currents to improve the LVRT capability of photovoltaic grid-connected systems. In addition, a comprehensive control strategy is also designed to control the supercapacitor, to regulate the active power through the control method of the voltage outer loop and the current inner loop, in order to maintain the DC bus voltage stability. At the same time, the inverter can increase the reactive power output to support the grid voltage. The advantage of this system is in smoothing the power imbalance in a short time, enhancing the low voltage ride-through capability of the photovoltaic grid-connected system, improving the power quality, and ensuring the safety and stability of the ship’s power grid. MATLAB/Simulink were employed to establish a ro-ro ship super capacitor–marine photovoltaic grid-connected power system model and to carry out simulation experiments by setting the grid voltage drop. The results show that when the grid voltage drops, the inverter adjusts the distribution of active and reactive power. The power factor drops from 1 to 0.77, and the effective value of the voltage drop increases from 150 V to 156 V, which proves that this strategy effectively reduces the depth of the grid voltage drop and improves the low voltage ride-through capability of the photovoltaic grid-connected system.
Highlights
Marine photovoltaic technology has developed rapidly in recent years, and this trend is expected to continue, driven by continuous cost reductions and policy support [1,2,3]
Based on the above research, this paper proposes a low voltage ride through control strategy of a super capacitor, to avoid the danger caused by severe power quality problems of a ship power grid
A sudden change in compensation or absorption makes the output power of the grid-connected inverter change slowly at a set rate; when the grid voltage drops, a low-voltage ride-through strategy based on supercapacitors is proposed, and the supercapacitor is used to absorb the unbalanced power during the grid voltage sag fault
Summary
Marine photovoltaic technology has developed rapidly in recent years, and this trend is expected to continue, driven by continuous cost reductions and policy support [1,2,3]. A operation low voltage ride through capability was proposed ingrid-connected wind power grid connectio stable of marine power systems, a marine photovoltaic system and been applied to thehave photovoltaic power generation field [9]. The above studies mainly focused on large and medium-sized rately He et al proposed a coordinated control scheme of low voltage ride throu land-based photovoltaic power stations, and rarely involved micro-grids, such as a ship for an intelligent solar inverter, which can absorb more solar energy power grid. Based on the above research, this paper proposes a low voltage ride through control strategy of a super capacitor, to avoid the danger caused by severe power quality problems of a ship power grid.
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