The equivalent impedance characteristic analysis of the AC microgrid and its decoupled power flow calculation

Int Trans Electr Energ Syst

et al. 2021

Summary The fault calculation of microgrid is an important method for fault characteristic analysis. The traditional fault analysis methods ignore the connection of inverter interfaced distributed generation (IIDG) and are not suitable for microgrids. A new fault analysis method suitable for the master‐slave controlled microgrid is proposed in this article, which considers the control strategy of IIDGs, low voltage ride through (LVRT) and the fault current limiting. The fault models of PQ‐controlled IIDG (PQ‐IIDG) and U/f‐controlled IIDG (U/f‐IIDG) are analyzed, then an equivalent Norton model of microgrid is established, and a new fault calculation method is presented. By analyzing the fault models, the working state of U/f‐IIDG is divided into a constant voltage state and a constant current state. In the constant voltage state, a grid‐connected microgrid fault calculation method is adopted. In the constant current state, the improved nodal voltage equation based on the current limiting is adopted. Without complicated calculation, high precision results can be obtained after simple iterative calculation. The results of the microgrid simulation model established in PSCAD/EMTDC and the fault calculation method programmed on MATLAB are compared to verify the effectiveness and accuracy of the proposed fault analysis method.

Section: Introductionmentioning

confidence: 99%

The fault analysis method of islanded microgrid based on the U/f and PQ control strategy

Int Trans Electr Energ Syst

et al. 2021

“…There into, the sensitivity analysis was proposed to obtain the most optimal location for placement and their optimal control variable setting [7]. The power flow calculation of the power system with numerous DGs is, however, an important issue [9].…”

Section: Introductionmentioning

confidence: 99%

Power flow calculation based on local controller impedance features for the AC microgrid with distributed generations

IET Energy Systems Integration

Sun

Liu

et al. 2019

Self Cite

In AC microgrid, since the impedance features of the power electronic converter are not considered, the accuracy of power flow calculation is degraded. Thus, this study, firstly presents a power flow calculation approach based on local controller impedance features for the AC microgrid consisting of numerous distributed generations. Firstly, the source‐side equivalent output impedance matrix of the converter is estimated by small‐signal perturbation approach and the equivalent transformation among the dq axis, αβ axis and abc axis. Then, the bus–bus line impedance model is proposed by converting the bus line equivalent impedance model. Moreover, the equivalent impedance model is embedded into Jacobian matrix iterative process to improve the accuracy of the power flow calculation approach. Eventually, the power flow calculation based on local controller impedance features is simulated by IEEE 4‐bus MATLAB/Simulink test system, PG&E 69‐bus test system and IEEE 118‐bus test system, indicating that the proposed power flow calculation approach is more accurate.

“…Meanwhile, smart home system, campus microgrid system, and plateau, island system always adopted wind/solar/battery hybrid power supply. 16 Therefore, the isomorphic topological disturbance observer control strategy considering both wind/solar/battery fluctuations and energy supply uncertainties should be proposed urgently.…”

mentioning

confidence: 99%

Disturbance observer based generalized wind/solar/battery consistent control strategy for AC microgrids

Int Trans Electr Energ Syst

Sun

et al. 2020

Self Cite

Although the distributed renewable energy source is an advisable solution for ac microgrids to reduce fuel consumption and CO 2 emission, the fluctuation and uncertainty of renewable energy source also brings significant problem to the safe and stable operation. Based on this, a disturbance observer method based on generalized wind/solar/battery consistent model is proposed in the primary control level. Firstly, it is through establishing the analogy model between the interface wind rectifier circuit and the interface solar/battery boost circuit that the equivalent model of the isomorphic solar/wind/battery with single input and single output (SISO) is first proposed in this article. With this effort, the wind, solar, and battery can achieve the consistency of the generalized model, which reduces the design complexity of the following control strategy. Furthermore, in order to solve the fluctuation and uncertainty problems, a continuous-time disturbance observer is introduced to control the equivalent generalized SISO model, which can achieve quick response, stable operation, and no-difference adjustment under disturbance. Finally, the effectiveness of the proposed method is verified by simulation results.