Abstract
Compared with the AC micro-grid, the DC micro-grid has low energy loss and no issues of frequency stability, which makes it more accessible for distributed energy. Thus, the DC micro-grid has good potential for development. A variety of renewable energy is included in the DC micro-grid, which is easily affected by the environment, causing fluctuation of the DC voltage. For grid-connected DC micro-grid with droop control strategy, the tie-line power is affected by fluctuations in the DC voltage, which sets higher requirements for coordinated control of the DC micro-grid. This paper presents a simplified control method to maintain a constant tie-line power that is suitable for the DC micro-grid with the droop control strategy. By coordinating the designs of the droop control characteristics of generators, energy storage units and grid-connected inverter, a dead band is introduced to the droop control to improve the system performance. The tie-line power in the steady state is constant. When a large disturbance occurs, the AC power grid can provide power support to the micro-grid in time. The simulation example verifies the effectiveness of the proposed control strategy.
Highlights
Increasing the proportion of renewable energy in energy production and consumption is an important measure to solve the problems of energy crisis and environmental pollution
In order to solve this problem, an improved droop control strategy is proposed in this paper, which can simplify tie-line power control of a DC micro-grid
The master device is responsible for stabilizing and complementing the power output of renewable energy, and the slave devices output constant power, which is similar to the traditional master-slave control
Summary
Increasing the proportion of renewable energy in energy production and consumption is an important measure to solve the problems of energy crisis and environmental pollution. Taking reduction in the tie-line power fluctuation as the optimization goal, a previous study [15] proposed a micro-grid energy management control strategy Most of these methods depend on the communication system to coordinate the operation of devices in a micro-grid, resulting in a high cost and complex control. In order to solve this problem, an improved droop control strategy is proposed in this paper, which can simplify tie-line power control of a DC micro-grid With this control strategy, the grid-connected inverter can keep the advantages of droop control, such as on the lack of reliance on the communication system and high reliability, and maintain the advantage of maintaining a constant tie-line power in the steady state that will not be affected by renewable energy fluctuation. The results show that the control strategy has a good transient and steady performance
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