Improving the Stability of Islanded DC Microgrid with Constant Power Loads

Abstract

The AC power system is leading due to its established standards. The depleting thread of fossil fuels, the significant increase in cost and the alarming environmental situation raises concerns. An Islanded DC microgrid, due to its novel characteristics of being able to withstand faulty conditions, has increased the reliability, accuracy, ease of integration, and efficiency of the power system. Renewable energy sources, characteristically DC, have wide usability in a distributive network and, accordingly, less circuitry and conversion stages are required, eliminating the need of reactive power compensation and frequency sync. Constant power loads (CPLs) are the reason for instability in the DC microgrid. Various centralized stability techniques have been proposed in the literature; however, the grid system collapses if there is a fault. To compensate, an efficient distributive control architecture, i.e., droop control method is proposed in this research. The significant advantage of using the droop control technique includes easy implementation, high reliability and flexibility, a reduced circulating current, a decentralized control with local measurements, the absence of a communication link and, thus, it is economic. Moreover, it offers local control for each individual power source in the microgrid. To investigate the stability of the islanded DC microgrid with constant power loads using the droop control technique, a small signal model of the islanded DC microgrid was developed in MATLAB/Simulink. Simulations were carried out to show the efficiency of the proposed controller and analyze the stability of the power system with constant power loads.

Hierarchical Control Strategy of Constant Power Load-based DC Micrograds using a New Distributed Averaging Proportional Integral Secondary Controller

“…Lee et al (25) employed a consensus distributed-based load sharing for DC MG by considering the identical per-unit current of each converter, which is based solely on a proportional controller. In addition to the voltage and current regulations, the presence of CPLs poses certain challenges, particularly stability issues (26,27). The presence of CPLs is studied in numerous literature sources (28,29), and the compensation methods are also surveyed and reviewed (30,31).…”

An intelligent sliding mode control for stabilization of parallel converters feeding CPLs in DC‐microgrid

“…On the other hand, power electronic converters when tightly regulated, act as a constant power load (CPL). CPLs in the DCMG have negative impedance characteristics, which may destabilize the DC bus in the DCMG and cause voltage oscillation and consequently blackout in the whole islanded DCMG [7,8]. Furthermore, adding a capacitor or resistor known as the passive damping method can improve the stability of the DCMG, whereas they are costly and increase the size of the converters [9].…”