Penetration of wind power plants (WPPs) in the electric power system will complicate the system load flow analysis. Consequently, the traditional load flow algorithm can no longer be used to find the solution to the load flow problem of such a system. This paper proposes a doubly fed induction generator (DFIG)-based WPP model for a load flow analysis of the electric power system. The proposed model is derived based on the power formulations of the WPP—namely, DFIG power, DFIG power loss, and WPP power output formulas. The model can be applied to various DFIG power factor operating modes. In the present paper, applications of the proposed methods in two representative electric power systems (i.e., IEEE 14-bus and 30-bus systems) have been investigated. The investigation results verify the proposed method’s capability to solve the load flow problem of the system embedded with DFIG-based variable-speed WPPs.

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IntroductionThe year 2020 saw the emergence of novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which became a great threat to public health worldwide. The exponential spread of the disease with millions of lives lost worldwide saw the emergence of an accelerated vaccine development with emergency approval from well-known regulatory bodies such as the US Food and Drug Administration, followed by widespread vaccine deployment despite a paucity in safety profile data. This issue becomes even more pronounced when it involves expectant mothers considering the possible undesirable effect toward the unborn child.MethodThis was a retrospective cohort study which was conducted at six general hospitals in the state of Penang, Malaysia. All the pregnant employees who have consented to take the mRNA COVID-19 vaccine and participate in this study were monitored from the time of their first vaccination and up to 28 days after they delivered their babies.ResultsAll the participants had adequate maximum vertical pocket (MVP) and no obvious anomalies or detection of intrauterine growth restriction (IUGR) were detected during the second trimester. However, one subject was reported to have miscarried during the second trimester. The reported mean neonate birth weight was 3.0 kg with the mean Apgar score of 8.8 and 9.8 at 1 and 5 min, respectively. Approximately seven (5.8%) neonates were reported to be small for their gestational age. Another three (2.5%) neonates were reported to have anomalies.ConclusionAs a whole, the inference that can be made from this study is that mRNA COVID-19 vaccine appears to be safe in pregnant women regardless of the trimester as the findings did not show obvious safety warning signs.

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