Improving Load Power Sharing Accuracy in Standalone Microgrid DC Networks Using Intelligent Adaptive Droop Control Based on Fuzzy Logic Control

DC Microgrid refers to a network that connects distributed DC generators. The control of the DCMG converters is employed to achieve proportional load sharing and optimal DC bus voltage restoration. Conventional droop control is a common technique used in DC Microgrids with multiple converter units. However, the performance of this technique is limited when considering channel resistance differences. In this article, we propose an adaptive droop control that utilizes secondary control to minimize DC bus voltage deviation while improving load power-sharing accuracy. The droop resistance is adjusted using a proportional controller to compensate for load current sharing errors while reducing DC bus voltage deviation through a PI controller. To determine the actual load current conditions, the exchange of output currents between converter units through communication channels is taken into account. The proposed control strategy can maintain a balanced load power distribution among the three sources with a ratio close to 1:1:1. Comparative analysis results between the conventional droop control method and the proposed method are fully simulated in Matlab/Simulink with varying load power values.

I. Introduction

DC-DC converters are essential in DCMG networks, as they enable the parallel sharing of load power among multiple DCGs. This is accomplished by connecting the DCGs to a DC bus, as depicted in Fig. 1. The DCMG control system is responsible for keeping the power distribution among the converters precise and for maintaining a low voltage drop in the DC bus [1]. Different approaches have been devised to manage DCMGs, such as master-slave approaches and droop techniques. These techniques involve high-speed communication and a centralized controller to maintain the DC bus voltage of DCMGs and distribute information to all parts to make sure the load power is shared equally [2]. Centralized control with delay compensation techniques can also be employed for power distribution among DC power sources to expedite data transmission processes [3]. When proportional load power sharing is necessary for larger DC grid systems, centralized control enhances coordination across DC sources [4]. However, the main drawback of such systems is the presence of a single point of failure (the central control). Specifically, the entire DCMG system is shut down when the central control is disabled [5]. The essential parameters of each droop controller in the converters are droop resistance and reference voltage [6]. The maximum droop resistance value determines the maximum allowed voltage deviation ratio from the converter and the maximum load current. Despite the widespread use of droop control, it has the following limitations: load distribution errors due to transmission channel resistance differences [7]. Fig. 1.

DCMG configuration system with parallel converter