Aggregation of synchronous generators and induction motors in multimachine power systems

Author(s):  
Said Ahmed-Zaid ◽  
Seog Sue Jang ◽  
Omer Awed-Badeeb ◽  
Maamar Taleb
Electronics ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 115
Author(s):  
Nasser Hosseinzadeh ◽  
Asma Aziz ◽  
Apel Mahmud ◽  
Ameen Gargoom ◽  
Mahbub Rabbani

The main purpose of developing microgrids (MGs) is to facilitate the integration of renewable energy sources (RESs) into the power grid. RESs are normally connected to the grid via power electronic inverters. As various types of RESs are increasingly being connected to the electrical power grid, power systems of the near future will have more inverter-based generators (IBGs) instead of synchronous machines. Since IBGs have significant differences in their characteristics compared to synchronous generators (SGs), particularly concerning their inertia and capability to provide reactive power, their impacts on the system dynamics are different compared to SGs. In particular, system stability analysis will require new approaches. As such, research is currently being conducted on the stability of power systems with the inclusion of IBGs. This review article is intended to be a preface to the Special Issue on Voltage Stability of Microgrids in Power Systems. It presents a comprehensive review of the literature on voltage stability of power systems with a relatively high percentage of IBGs in the generation mix of the system. As the research is developing rapidly in this field, it is understood that by the time that this article is published, and further in the future, there will be many more new developments in this area. Certainly, other articles in this special issue will highlight some other important aspects of the voltage stability of microgrids.


Author(s):  
Shenghu Li

The induction generators (IGs) are basic to wind energy conversion. They produce the active power and consume the reactive power, with the voltage characteristics fragile compared with that of the synchronous generators and doubly-fed IGs. In the stressed system states, they may intensify var imbalance, yielding undesirable operation of zone 3 impedance relays.In this paper, the operation characteristics of the zone 3 relays in the wind power systems is studied. With the theoretical and load flow analysis, it is proved that the equivalent impedance of the IGs lies in the 2nd quadrature, possibly seen as the backward faults by the mho relays, i.e. the apparent impedance enters into the protection region from the left side. The undesirable operation may be caused by more wind power, larger load, less var compensation, and larger torque angle.


2020 ◽  
Vol 20 (4) ◽  
pp. 103-113

A synchronous generator is one of the key elements of any power system, having a significant impact on the stability and reliability of consumers’ power supply. Nowadays, the power systems emergency and operational control issues are being solved using computational models, the parameters whereof are determined using the reference data, or the data obtained during testing. High dependence of the models’ parameters on various external factors leads to a significant decrease in the accuracy of solving the issues of emergency and operational control. Identification based on the traditional telemetry systems or synchrophasor measurements is used to improve the accuracy of parameters of the power systems’ computational models. The purpose of this research lies in a meta-analysis of the available studies aimed at developing a methodology for determining parameters of a synchronous generator on the basis of measurement data. Russian and foreign studies were analyzed and grouped to achieve this goal. After that, for each group, advantages, disadvantages, and the area of application were identified. As a result, it is shown that the existing methods for determining parameters of synchronous generators based on measurement data cannot adapt to the source dataset and also require significant computing power. As a way to overcome these shortcomings, an adaptive model of a synchronous machine is proposed.


Author(s):  
H. H. Alhelou

It is critical for today's power system to remain in a state of equilibrium under normal conditions and severe disturbances. Power imbalance between the load and the generation can severely affect system stability. Therefore, it is necessary that these imbalance conditions be addressed in the minimum time possible. It is well known that power system frequency is directly proportional to the speed of rotation of synchronous machines and is also a function of the active power demand. As a consequence, when active power demand is greater than the generation, synchronous generators tends to slow down and the frequency decreases to even below threshold if not quickly addressed. One of the most common methods of restoring frequency is the use of under frequency load shedding (UFLS) techniques. In this chapter, load shedding techniques are presented in general but with special focus on UFLS.


Author(s):  
Sirisha Tanneeru ◽  
Joydeep Mitra ◽  
Yashwant J. Patil ◽  
Satish J. Ranade

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