Abstract
In this paper, an effective power flow control strategy (PFCS) based on the centralized control method and a reliable DC-link voltage (DCV) restoration algorithm for a DC microgrid (DCMG) under grid fault conditions are proposed. Considering the relationship of supply-demand power and the statuses of system units, thirteen operating modes are presented to ensure the power balance in DCMG under various conditions. In the PFCS, the battery charging/discharging procedure is implemented considering the battery power limit to avoid overheating and damage. Moreover, load shedding and load reconnection algorithms are presented to maintain the system power balance, even in critical cases. To prevent the system power imbalance in DCMG caused by the delay of grid fault detection, a reliable DCV restoration algorithm is also proposed in this paper. In the proposed scheme, as soon as abnormal behavior of the DCV is detected, the battery or wind power generation system instantly enters a local emergency control mode to restore the DCV rapidly to the nominal value, regardless of the control mode assigned from the central controller. Comprehensive simulations and experiments based on the DCMG testbed are carried out to prove the effectiveness of the PFCS and the proposed DCV restoration algorithm.
Highlights
In recent years, renewable energy sources (RESs) such as wind and solar are attracting a great deal of attention due to the scarcity of fossil energy and environmental issues [1]
This paper presents an effective power flow control strategy (PFCS) and a reliable DC-link voltage (DCV) restoration algorithm for DC microgrid (DCMG) under grid fault conditions
This paper develops an effective load shedding (LS) algorithm considering the state of charge (SOC) and the maximum capability of the battery to maintain the system power balance, even in the critical cases
Summary
Renewable energy sources (RESs) such as wind and solar are attracting a great deal of attention due to the scarcity of fossil energy and environmental issues [1]. In Ref [16], an improved voltage control strategy for a DCMG composed of photovoltaic and hybrid ESSs, such as batteries and supercapacitors, is proposed to stabilize the DCV In this scheme, the entire system operation is divided into four states with individual control modes considering the photovoltaic generation power, load demand, and battery state of charge (SOC). In both cases, maintaining the power balance in DCMG by a battery is not possible due to the power limit To deal with this issue, the maximum charging and discharging currents of the battery are considered in the design of PFCS under the grid-connected mode in Ref [18]. This paper presents an effective PFCS and a reliable DCV restoration algorithm for DCMG under grid fault conditions.
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