Real-Time Voltage Stability Limits Assessment Using Thevenin Equivalent in Power Systems

Abstract

In this study, voltage stability evaluation of an N-bus power system is made by using the Thevenin impedance observed from an any load bus and the impedance of the load in the bus. The Thevenin equivalent impedance seen from the bus is computed using an optimization-based approach. Only the current, voltage and power factor measurements of the related bus are used for the proposed approach. The impedance stability index of the bus is computed using the Thevenin equivalent impedance obtained with the proposed approach and the impedance of the load. The computed index provides an opportunity to evaluate the voltage stability status of the bus in real time. It is observed that the critical power values corresponding to the impedance stability index computed using Thevenin impedance obtained with the proposed approach and critical power values derived from power flow are very close to each other.

Keywords

• Voltage stability
• Optimization
• Thevenin equivalent

Güç Sistemlerinde Thevenin Eşdeğer Devresi Kullanılarak Gerilim Kararlılığı Sınırlarının Gerçek Zamanlı Değerlendirmesi

Abstract

Bu çalışmada, çok baralı bir güç sisteminin herhangi bir yük barasından görülen Thevenin empedansı ve yük empedansı kullanılarak yük barasına gerilim kararlılığı değerlendirmesi yapılmıştır. Gerilim kararlılığı analilizi yapılacak baradan görülen Thevenin eşdeğer devre empedansı optimizasyon esaslı bir yaklaşımla hesaplanmıştır. Optimizasyon yaklaşımı için yerel baradan sadece akım, gerilim ve güç faktörü ölçümleri yapılmıştır. Hesaplanan Thevenin eşdeğer devre empedansı ve baradaki yükün empedansı ile baraya ait empedans kararlılık indeksi hesaplanmıştır. Hesaplanan empedans kararlılık indeksi, baranın gerilim kararlılığı durumunu gerçek zamanlı olarak takip etme imkanı sunmuştur. Önerilen yaklaşımla elde edilen Thevenin empedansı ile hesaplanan empedans kararlılık indeksine karşılık gelen kritik güç değeri ve güç akışından elde edilen kritik güç değerinin birbirine çok yakın olduğu görülmüştür.

Keywords

• Gerilim Kararlılığı
• Optimizasyon
• Thevenin eşdeğer devresi

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