A New Voltage Stability Prediction and Control Strategy for Power Systems Driven by Artificial Intelligence

Voltage instability and voltage collapse have been considered as a major threat to present power system networks due to their stressed operation. It is very important to do the power system analysis with respect to voltage stability. Flexible AC Transmission System (FACTS) is an alternating current transmission system incorporating power electronic-based and other static controllers to enhance controllability and increase power transfer capability. A FACTS device in a power system improves the voltage stability, reduces the power loss and also improves the load ability of the system. FACTS have made the power systems operation more flexible and secure. Amongst the several FACTS controllers, the Unified Power Flow Controller (UPFC) is most effective to improve the enhancement of voltage stability and reduces the power loss. This study investigates the application of Particle Swarm Optimization (PSO) to find sizing of Unified Power Flow Controller (UPFC) device to minimize the voltage stability index, total power loss, load voltage deviation, and cost of FACTS devices to improve voltage stability in the power system. A new model is proposed in this thesis to improve existing power-based model by using the Norton Equivalent Theorem. The proposed model can be integrated with the Equivalent Current Injection (ECI) power flow model easily. By ECI algorithm, it is much quickly and precisely to implement power flow calculations. Finally It is observed from the results that the voltage stability margin is improved, the voltage profile of the power system is increased and real power losses also reduced by optimally sizing UPFC device in the power system. Index Terms: Voltage stability, Unified Power Flow Controller (UPFC), Equivalent -Current Injection (ECI), Modified particle swarm optimization (MPSO)

In the microgrid with high penetration rate of renewable energy, multiple distributed generations operate in parallel. To ensure stable operation of the microgrid, research for multi-inverter coordination control is necessary. Master-slave control can realize various functions with the combination of different control strategies. Voltage and active power control strategy can provide voltage support for the grid and reduce the voltage fluctuation in the point of common coupling. Previous voltagesupporting methods are usually based on constant droop coefficient, where the control curve is linear. When the voltage fluctuation is too large, the change of the distributed generations power is too small to support the gird voltage. This paper presented an improved master-slave voltage and active power control strategy for multiple photovoltaic inverters. The master inverter operates under maximum power point tracking control strategy as the sample. The slave inverter adopts nonlinear voltage and active power control. When the voltage is too high, increase the droop coefficient to accelerate the power reduction. Conversely, when the voltage is much below the rated value, the distributed power supply will output its maximum power. Finally, the effectiveness of the proposed control strategy is verified by simulation.

Guest Editorial: Situational awareness of integrated energy systems

Voltage stability of power systems reflects challenges to the power system operators due to its effect on the power systems components performances. Therefore, many solutions were invented in order to keep the systems within the voltage stability accepted limits. Because of the huge expansion of the power grids and the different loads natures on the grids, many techniques and solutions are used. The On Load Tap Changing Transformer (OLTC) was one of those techniques. In this paper, a review of past works that deal with the voltage stability limits, voltage stability improvement ways, OLTC types, the OLTC reverse action, and OLTC effect on voltage stability, in addition to several ways that make the OLTC work better. are discussed. The paper also sheds the light on the possible ways that may be employed to prevent the OLTC reverse action.

The high penetration of photovoltaic (PV) generation can cause many technical issues such as power quality and impact on the power system voltage stability. To improve voltage stability and reducing power loss in a power system with PV generators, appropriate planning of PV generators is considered by optimal placement of PV. Thus, an effective heuristic optimization technique such as the Wind Driven Optimization (WDO) technique is applied for determining optimal location of PV generators in a power system. For determining the optimal location of PV, the objective function considers maximizing the Improved Voltage Stability Index. The proposed method for optimal location of PV generators is implemented on the IEEE 118 and 30 bus transmission systems and the 69-radial distribution system. The optimization results show that integrating PV into the test systems improves voltage stability in the system. Comparing the performance of the WDO with the particle swarm optimization technique, it is shown that the WDO technique gives faster convergence.

Many technological advancements in the modern era have made actual use of electrical power and the constrained operating of power systems within stability limits. Some expeditious load variations and rising power demands initiate complications in voltage stability and can put stress on performance, leading to voltage instability. Voltage Stability Indices can be used to perform voltage stability assessment. This review evaluates various VSIs based on mathematical derivations, assumptions, critical values, and methodology. VSIs determine the maximum loadability, voltage collapse proximity, stability margin, weak areas, and contingency ranking. Stability indices can also specify the optimal placing and sizing of Distributed Generators. Thus, VSIs play a vital role in power system voltage stability. This review is a comprehensive survey of various indices and analyses their accuracy in determining the instability of power systems. Voltage stability is a crucial concern in operating a reliable power system, and the systematic evaluation of voltage stability is essential in a power system. This review considered and analyzed 34 indices from 138 articles from the literature for their significant performance in various power system stability problems. Of 33 indices, were 22 derived from transmission line parameters, referred to as line indices, and 12 from bus and line parameters, referred to as bus indices.

As power systems grow in their size and interconnections, their complexity increases. Rising costs due to inflation and increased environmental concerns has made transmission, as well as generation systems be operated closer to design limits. Hence power system voltage stability and voltage control are emerging as major problems in the day-to-day operation of stressed power systems. For secure operation and control of power systems under normal and contingency conditions it is essential to provide solutions in real time to the operator in energy control center (ECC). Artificial neural networks (ANN) are emerging as an artificial intelligence tool, which give fast, though approximate, but acceptable solutions in real time as they mostly use the parallel processing technique for computation. The solutions thus obtained can be used as a guide by the operator in ECC for power system control. This paper deals with development of an ANN architecture, which provide solutions for monitoring, and control of voltage stability in the day-to-day operation of power systems.

Impact of renewable energy penetration rate on power system transient voltage stability

Voltage stability problems and renewable energy penetration in power systems are the main issues in the electric power system at this time. This paper aims to examine the condition of voltage stability at the time before and after the entry of wind power plants in the sulseltrabar interconnection system. There are two wind power-generating units that will be studied, namely the PLTB Sidrap with a capacity of 75 MW and the PLTB Jeneponto with a capacity of 72 MW. The simulation using Matlab program. From the simulation results, it can be seen that Sulseltrabar’s voltage stability interconnection system at the time of the entry of PLTB Sidrap and PLTB Jeneponto, has improved stability, this can be seen from the eigenvalue and bus participation factor values. From the minimum eigenvalues it can be seen that the penetration of PLTB Jeneponto is slightly better than PLTB Sidrap in improving voltage stability. The condition that has the greatest influence on improving stability is when the two wind power plant enter to the Sulseltrabar interconnection power system.

Voltage Stability Improvement In Multi-bus System Using Static Synchronous Series Compensator

Static voltage stability improvement with battery energy storage considering optimal control of active and reactive power injection

This paper addresses the determination of the maximum penetration rate of renewable energy sources (RES) in island power systems. This issue is analyzed through a probabilistic approach which gives an interesting set of results giving to system operators the possibility to faces challenges brought up by massive RES connections. RES, especially wind farms and photovoltaic solar plants may affect significantly power systems in terms of power flows (risk of congestions), voltage level, stability or reserves. For the purpose of this study, a probabilistic model of the power system has been developed. The mathematical model mixes the probabilistic characterization of the power system with a probabilistic RES production model to estimate defined reliability criteria. Practical application on a typical French island network is presented and contributions of the probabilistic methods are discussed, compared to the deterministic approach. The maximum penetration rate obtained with the last one is 13% instead of 30% with the probabilistic approach. The large quantity of results obtained with the probabilistic approach allows further analysis such as the influence of RES on the dispatching and the impact of the sudden RES generation loss.

An improved voltage stability index and its application

In the power system, voltage instability is one of the important issues and it may cause voltage sag, voltage swell, change in load and generation of harmonics. To tackle all these problems, the transmission power system makes use of an intelligent control model to improve the stability of power system. In this paper, a new adaptive neuro fuzzy inference system (ANFIS) based power system stabiliser (PSS) for the enhancement of voltage stability in power systems is proposed. A hybrid learning algorithm, which combines the least squares method and the back propagation algorithm, is used to train the ANFIS. The performance of the power system by using fuzzy based PSS is about 60.1% when compared to that of the conventional PSS. To evaluate the effectiveness of the proposed technique the performance of the proposed technique was compared with the results obtained by using fuzzy PSS model and its performance was analysed. Simulation results described in the paper demonstrate that the adaptive neuro-fuzzy based PSS can give 33.43% of improvement in voltage stability when compared to that of fuzzy based PSS over a wide range of operating conditions.

Enhancing voltage stability and LVRT capability of a wind-integrated power system using a fuzzy-based SVC