Transient Response Analysis of Inverter-Based Microgrids Under Unbalanced Conditions Using a Dynamic Phasor Model

Abstract

Microgrids (MGs) are often unbalanced due to the integration of single-phase generators, unbalanced loads and asymmetrical faults. To better analyze such a MG, this paper presents an approach to analyze the transient response for an inverter-based MG under unbalanced condition. The dynamic phasor (DP) concept is used for the MG modeling under stationary abc reference frame. First, the DP model of the inverter-based DG is developed. The influence of unbalanced conditions on the inverter including oscillations on dc side are considered in this paper. Then, the model of the network and loads is developed. Finally, all the sub-modules are combined on a time-variable system frequency to obtain the complete DP model of unbalanced MG. To validate the proposed approach, the DP method is applied to a MG test system with three-phase and single-phase DGs. Small signal analysis is carried out to derive the dominant modes and their influence on the system response. Simulation results from the DP model are compared against the detailed model built in MATLAB/SimPowerSystem. The results from load disturbances and asymmetrical faults are used to verify the DP model.

Stabilization Method Considering Disturbance Mitigation for DC Microgrids with Constant Power Loads

“…In [40], the stability criteria for an electrical system with multistage LC filters (presented in Figure 5) were obtained based on the Brayton-Moser mixed potential theory. In Figure 5 According to the Equation (8) in Reference [40], the state equation of the DC microgrid with Nstage LC filters is given by: According to the Equation (8) in Reference [40], the state equation of the DC microgrid with N-stage LC filters is given by:…”

“…Usually, they can be worked in two modes: grid-connected mode, and islanded mode. Usually, the main control objectives of a DC microgrid include maintaining stability [4][5][6][7][8][9], minimizing cost [10][11][12], sharing power and regulating voltage [13]. For these objectives, there are mainly three control methods: decentralized control [10,12,[14][15][16][17], distributed control [18][19][20][21][22][23][24][25][26] and centralized control [11,27].…”

Improved Voltage Unbalance and Harmonics Compensation Control Strategy for an Isolated Microgrid

“…For performance comparisons, the magnitudes of the fundamental components, and the PVUR of all various loads, for the conventional control strategy and the suggested control scheme are presented in Table 3. According to the IEEE standards, the PVUR needs to be maintained at lower than 2% for sensitive loads [17]. According to IEEE, PVUR is defined as:…”

“…Moreover, the stationary reference frame equivalent of the PI voltage controllers in the rotating frame can ensure a tiny steady-state error for the proposed multi-loop control strategy. needs to be maintained at lower than 2% for sensitive loads [17]. According to IEEE, PVUR is defined as:…”

Non-Cartesian Frame Transformation-Based Control of a Three-Phase Power Converter During Unbalanced Voltage Dip – Part II: Simulation And Experiment

“…Positive-and negative-sequence components' decomposition of signals in different coordinate frames and their separate control paths (Kim et al 1993;Rioual et al, 1993) was done using proportional integral terms or, in some publications, proportional-integral-resonant controllers in a rotating frame (Hu and He, 2008). Sometimes, current control is realized by proportional-resonant terms in a stationary frame (Guo et al, 2018;Shabestary and Mohamed, 2019;Shuai et al, 2019) or in a natural abc frame (Guo et al, 2017). The first family of methods with separate control paths for positive and negative sequences causes problems in realization of current limitation methods, which are complicated when an asymmetrical current target is selected.…”