Mathematical representation, stability analysis and performance improvement of DC microgrid system comprising hybrid wind/battery sources and CPLs

Abstract

A microgrid is a well known solution to increase the technical and economical capability of distributed generations. Recently, DC microgrids, as small‐scale DC networks, have attracted more attention due to lower losses and simple control structure. Stability of DC microgrids can be an important issue under high penetration of constant power loads (CPLs). In this study, stability analysis of the DC microgrid system including hybrid wind/battery and CPLs is studied, and then three different types of stabilising compensators are presented in two groups to increase the stability margin and to stabilise the system under high penetration of CPLs. The proposed stabilising compensators modify the voltage reference, current reference and duty cycle by adding active damping signals in the external, middle and internal parts of the interfaced converter control loops. These active damping signals are obtained by the feedback of the output voltage and current and modify the DC microgrid control structure. To evaluate the system stability under different stabilising compensators, small signal and frequency response analyses are done with and without active damping signals. Simulation results based on a detailed DC microgrid model are given to verify the effectiveness of the proposed compensators.

Optimised damping control of islanded DC power systems using state feedback

“…R S <0. According to (5), the attenuation coefficient increases with a smaller filter inductance or larger resistive load and capacitor. In addition, more attention should be paid to CPL because the attenuation coefficient is reduced after the addition of CPL.…”

“…However, with the rapid growth of wind-power generators, photovoltaic (PV) arrays, and DC loads, increased amounts of fluctuating power disturb the balance between power generation and consumption. In addition, the constant power control of voltage source converters (VSCs) for load demand introduces negative impedances to the power grid [4,5]. These impedances might cause severe DC-voltage fluctuation and instability.…”

Review of hierarchical control strategies for DC microgrid

“…In the architecture of microgrid, mainly three topologies, i.e. single-bus topology, multibus topology and reconfigurable bus topology are used [8][9][10]. An effective robust and intelligent control strategy for stable and reliable operation is an indispensable need for a microgrid with any bus topology.…”

“…The control system of a DC microgrid needs to perform several control actions such as voltage regulation, proper current sharing, import and export of power, balancing in energy storage, minimising the cost of operation, power management for OPF etc. These different control actions govern the planning, designing and implementation of a particular control scheme in a microgrid to have an economical operation in a robust manner [8][9][10]. Moreover, a lot of solutions like load shedding, utilisation of storage system, back-up generator, an interconnection between microgrid and utility grid and coupling of neighbouring microgrids have been suggested by many researchers to meet the unexpected power production and demand in a microgrid.…”

Selection of capacitance for stable operation of low power DC system with constant power loads

“…© 2020 The Authors. IET Generation, Transmission & Distribution published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology thereby behaving as constant power loads (CPL) for the dc system [12][13][14]. The typical examples of CPLs used in low power dc system are telecom switches, wireless communications base stations, servers used in data centers, closed-loop electric drives used in electric vehicles, electronic loads (like laptops, mobile phones, compact florescent lamps, light emitting diode bulbs) etc.…”