Optimized reactive power support strategy for photovoltaic inverter to intensify the dynamic voltage stability of islanded microgrid

Abstract

Summary This study presents an innovative and optimized reactive power support (ORPS) strategy for photovoltaic (PV) inverters to improve the dynamic voltage stability (DVS) of islanded microgrid (MG) with induction motor (IM) load. On the occurrence of the fault, voltage instability (VI) happens due to the low‐inertia IM load and poor ride through capability of PV inverters of MG. Supplement of optimal RPS promptly, without exceeding the rated current value of the inverter, is aimed at the proposed control, to maintain DVS during severe voltage downfall as a result of a fault. Once the profiled voltage value is restored and the necessity of RPS is fulfilled, the PV inverter returns to its prefault power production combination. The detailed model of an inverter‐based islanded MG with IM load is built to examine the DVS, and the theoretical analysis and technical discussion are conducted. A comparison between the conventional and proposed strategies is carried out. From the demonstrated results, employing the proposed ORPS control can provide RPS effectively and helps to improve the DVS. This proposed strategy can also provide an equivalent service as an expensive 610‐kVA dynamic volt‐ampere reactive support device (ie, D‐STATCOM) in the studied MG.

Voltage Stability of Power Systems with Renewable-Energy Inverter-Based Generators: A Review

“…Many voltage support strategies for grid-connected IBGs have been reported in the literature, such as [19][20][21][22]. Enhancing voltage stability of islanded MGs with voltage support is reported in [23,24]. To mitigate the voltage instability of islanded MGs, prioritized reactive current injection from the inverter has been presented as a means for voltage support.…”

“…The network-load admittance ratio is in terms of the power network admittance matrix and the equivalent admittances of net loads, and the effects of constant-power and constant-current DGs are taken into consideration. Equation (24) gives a voltage stability index, M n/d under the condition that the power flow Jacobian is singular if, and only if, the network-load admittance ratio is unity, i.e., R n/d = 1.…”

Sensitivity Based Voltage Support Strategy to Enhance Dynamic Stability of Islanded Microgrid

“…In conventional power systems, this happens with reactive power injection predominantly because of negligible resistive line parameters [15]. Therefore, conventionally the VS strategy with constant peak current control has been designed to focus on the precedence of reactive current [16], [17], [18]. In the conventional strategy, the active current is considered as a subordinate component and decreased to increase the reactive current injection.…”

Dynamic voltage stability of unbalanced DNs with high penetration of roof‐top PV units

“…7,[15][16][17][18][19][20][21] In contrast, very few studies have focused on the short-term voltage stability, which is also known as dynamic voltage stability. [22][23][24][25][26][27][28] In Reference 22, the authors have investigated the impacts of LVRT by PV inverters on the DVS, and concluded that DVI is likely to occur in highly PV penetrated power systems after a severe fault if the PV inverters are incapable of providing the LVRT. In Reference 25, a new control strategy has been proposed with PV units to improve the DVS.…”

“…It is worth to reveal that numerous research have been conducted to contribute in better understanding of the long‐term voltage instability caused by large PV integration 7,15‐21 . In contrast, very few studies have focused on the short‐term voltage stability, which is also known as dynamic voltage stability 22‐28 . In Reference 22, the authors have investigated the impacts of LVRT by PV inverters on the DVS, and concluded that DVI is likely to occur in highly PV penetrated power systems after a severe fault if the PV inverters are incapable of providing the LVRT.…”