Predictive Voltage Hierarchical Controller Design for Islanded Microgrids Under Limited Communication

Second harmonic voltage injection‐based self impedance estimation for effective decoupled droop control in a microgrid

“…The real and reactive power‐sharing ratios are listed in Tables 2 and 3, respectively, during four time intervals. It can be seen that the power‐sharing ratio is very close to 0.5 with the proposed method as compared to [4], [12], [21] and [22]. The improvement is especially significant for the reactive power.…”

“…Similarly, the average reactive power deviation with the proposed method, conventional droop method, transformation matrix method, advanced angle method, and predictive voltage methods are 1.13%, 30.93%, 21.45%, 10.53% and 13.11%, respectively. With the proposed method, the average percentage deviation of active power is lower, less than 0.2% as compared to [4], [12], [21] and [22] which clearly indicates that efficient decoupling has been introduced between active and reactive power loops. Reactive power‐sharing is very poor in the droop control, transformation matrix method, advanced angle droop method and predictive voltage method.…”

“…In this case, real and reactive power‐sharing ratio of DG 3 to DG 2 is considered. The power‐sharing ratio with the proposed method is compared with conventional droop method [4], Transformation matrix method [12], advanced angle method [21] and Predictive voltage method [22]. In the present case, the ideal real and reactive power sharing ratio is 0.6, which is the ratio of DG 3 rating (150 kVA) and DG 2 rating (250 kVA).…”

“…The droop control method with a power‐sharing ratio close to ideal is considered to be performing better. The droop methods given in [4], [12], [21] and [22] are implemented on the four DG test case with four operating conditions: 400 kVA, 0.95 PF, 300 kVA, 0.9 PF, 200 kVA, 0.85 PF and 100 kVA, UPF. The real and reactive power generated by DG 1 , DG 2 , DG 3 and DG 4 with the proposed method and droop methods [4], [12], [21] and [22], under four operating conditions, are given in Figures 13 and 14.…”

“…Improper selection of gains may affect power sharing under changing network conditions such as line outages, DG cut‐in/cut‐out, and load changes. The controller proposed in [22] improves the voltage profile and real power‐sharing ratio under different loading conditions. However, changes in network topology were not considered.…”