Power System Dynamic Stability Analysis and Stability Type Discrimination

Optimal allocation of Var source involves optimal location and determination of the size of the Var source. The purpose is to find the right tradeoff between the investment cost of the new Var source and the benefits in system operation derived from the presence of the additional reactive compensators. Traditionally, the locations for placing new Var sources were either simply estimated or directly assumed. This paper categorizes the literature relevant to optimal allocation of shunt dynamic Var source SVC and STATCOM, based on the voltage stability analysis tools used. Those tools include static voltage stability analysis ones such as P-V and V-Q curve analysis, continuation power flow (CPF), optimization methods (OPF), modal analysis, saddle-node bifurcation analysis, and dynamic voltage stability analysis ones such as Hopf bifurcation analysis and time-domain simulation. Static voltage stability analysis techniques are also used in dynamic Var planning. At the end of the paper, the advantages of static and dynamic voltage stability analysis tools are summarized. (7 pages)

This paper presents a methodology for selection of location of static VAR compensator based on static voltage stability analysis of a power system. The analysis presented here uses the L-index of load buses. This includes voltage stability information of a normal power flow in the range of 0 to 1(no load to voltage collapse). An approach has been developed to select a suitable size and location of static VAR compensator as required in an IEEE-14 bus system. The STATCOM and SVC are used in the continuation power flow process for static voltage stability analysis to enhance stability margin.

With the rapid development of the Chinese power grid, its dynamic behavior becomes increasingly complex. How to prevent voltage instability and voltage collapse at the receiving-end system has become an urgent problem at present. To prevent voltage collapse, the key is to determine the stability margin at the operating point of the power system, and the load margin is the most basic and widely accepted voltage stability margin indicator. Considering the role of medium and long-term slow-acting elements in the actual system that affect the system voltage stability, this paper combines the static voltage stability analysis with the transient, medium, and long-term dynamic voltage stability analysis based on whole process simulation, and uses time-domain simulation methods to evaluate the voltage stability of the actual system. By analyzing the various dynamic characteristics of generator overexcitation limits and transformer on-load regulation on the development process of voltage-collapsing accidents, this paper proposes an evaluation index for the whole process dynamic stability margin of the receiving-end system. On this basis, the whole process dynamic defense system of the power grid is also constructed. The proposed method is validated by using a provincial power grid in China as an example.

The rapid growing in electrical load, and increasing the dependency on renewable energy recourses; highly affect the Jordanian power system stability and operation. This paper presents a static voltage stability analysis for the northern part of the Jordanian grid. The main purpose of this study is finding out the domain of the system from facing voltage instability conditions. In order to analyze voltage stability of the study system, static analysis techniques such as P-V curve and Q-V curve methods are applied. The DIgSILENT PowerFactory® program is used in this study to obtain the results.

In order to analyze the power system dynamic stability of electro-mechanical transmission, a new method of variable time scale was proposed. The paper applied all the high power devices and battery as the excitation source, and support capacitor as a response to the power system. Based on these, a whole mathematical model of power system was constructed by using C language to design the simulation program. Then, the method of variable time scale, which has realized the power stability analysis in large time scale and the energy stability analysis in small time scale, was applied to analyze the dynamic stability of power system. The results optimize the selection of system equivalent capacitor, and provide the important theoretic reference to the harmonization of control technology and the drive control strategy in the vehicle.

The study of static voltage stability is actually based on asymptotic stability, which is affected by the operation state of the power grid. In this paper, the voltage stability margin index is deduced, and the stability margin of the existing power grid under different actual working conditions is analyzed based on the proposed index. the leading factors and the worst system conditions are determined by practical experience. The correctness of the proposed method is verified by the simulation analysis of the actual provincial power grid.

The power system is experiencing a higher penetration of renewable energy generations (REGs). The short circuit ratio (SCR) and the grid impedance ratio (GIR) are two indices to quantify the system strength of the power system with REGs. In this paper, the critical short circuit ratio (CSCR) is defined as the corresponding SCR when the system voltage is in the critical stable state. Through static voltage stability analysis, the mathematical expression of the CSCR considering the impact of GIR is derived. The maximum value of CSCR is adopted as the critical value to distinguish the weak power system. Based on the static equivalent circuit analysis, it is proved that the CSCR is still effective to evaluate critical system strength considering the interactive impact among REGs. Finally, we find that the GIR can be neglected and the SCR can be used individually to evaluate the system strength when SCR>2 or GIR>5. The correctness and rationality of the CSCR and its critical value are validated on ADPSS.

Comprehensive evaluation of voltage stability based on EW-AHP and Fuzzy-TOPSIS

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

In new distribution systems, the proportion of distributed renewable energy generation is gradually increasing. Existing methods for static voltage stability analysis struggle to accurately reflect the impact of distributed generation output. First, this paper introduces robustness indices to quantify the impact of active and reactive power output fluctuations from distributed generation on load buses, based on the L-index. Second, a static voltage stability indicator system is constructed. Based on the characteristics of the indicators, definitions for voltage stability weak bus, active power vulnerable bus and reactive power vulnerable bus are established. Third, an optimization model to enhance static voltage stability is developed specifically for these buses. The Pareto front of the solutions obtained by it based on the NSGA-III algorithm includes the optimal solutions under different index preferences, and then it is achieved by adjusting the power output of the power source. Last, the effectiveness of the indicator system and the enhancement methods are validated through the IEEE 118-bus system.

To address the issue of static voltage stability in distribution networks with high proportion distributed pv generation(DG) during fault, this paper establish a fault equivalent model which consider the characteristics of PV equipment during low-voltage ride-through(LVRT). The model derives the constraints on the PV current phase angle required to maintain static voltage stability. Subsequently, the impact of DG capacity at the point of common coupling and the electrical distance between the distribution network and the AC power source on the PV output current phase angle constraint is quantitatively analyzed. On this basis, a current control method is proposed: when there is a voltage stability risk in the system, the active and reactive current injection from the PV is adjusted, while under no voltage stability risk, the low-voltage ride-through control strategy remains unaffected. Finally, simulation examples based on the Matlab/Simulink testing platform verify the validity of the analysis and the proposed control strategy.

This research proposes the design of a mooring system that allows the floating platform to stably dive deep enough to prevent damage induced by typhoon waves. The design principle of the mechanism is that the submarined floating platform with negative buoyancy is connected to a pontoon with positive buoyancy. The diving depth of the floating platform is determined by the rope length. If the static equilibrium of the two forces is satisfied, the diving depth will be kept. If the diving depth of the floating platform is enough, the platform will not be directly damaged by the wave impact. In reality, the system will be greatly subjected to the typhoon wave and the ocean current. The stability of the system and the dynamic tension of the rope must be significantly concerned. In this study, the linear elastic model of the mooring system composed of a floater platform, towed parachute, pontoon, traction rope, and mooring foundation is derived. The theoretical solution of the static and dynamic stability analysis of the mooring system is proposed. The dynamic behaviors of the floating platform and pontoon, and the tension of the rope under the effects of waves and ocean currents, are investigated. It is discovered that the buffer spring helps reduce the tension of the rope. The proposed protection procedure can avoid the damage of the floating platform and the mooring line, due to Typhoon wave impact.

Fast electric vehicle(EV) charging stations have become one of the fastest-growing penetrated power electronics (PE) interfaced loads to the electric power system. The lack of accurate model of the fast EV charger in transient stability (TS) simulation tools limits the effectiveness of power system dynamic performance evaluation and stability analysis. In this paper, The electromechanical model of a fast EV charging unit is proposed, which is suitable for large-scale power system dynamic analysis in TS simulators. The EV charger model is simplified to guarantee a balance between model accuracy and simplicity. The validity of the proposed model has been demonstrated by a comparative study with the benchmark model created in PSCAD/EMTDC.

Electric propulsion systems are widely used in modern shipbuilding due to multiple advantages over systems with mechanical power transmission from the primary engine to the propeller. There is a necessity to use multi-motor drive in order to increase reliability and power in high power propulsion systems. One of the main multi-motor electric drive challenges is load distribution between different electrical machines, which leads to the problem of dynamic and static stability analysis. The aim of this paper is to obtain stability region boundaries of two induction machines coupled by mechanical gear. Approach of stability analysis is proposed. A distinctive feature of this approach is changes of whole system stability region boundaries as compared with single induction machine research.

Power systems are being operated close to their voltage security limit which makes their reliable operation more challenging. Voltage stability has been a major problem faced by utilities now a days. Many blackout have been reported around the world related to voltage instability problem. Many voltage stability analysis methods have been presented up till now. Here artificial neural network based approach for voltage stability analysis of power system is presented. Voltage stability analysis of power system has been done in terms of voltage stability margin. Voltage stability margin is calculated by estimating distance from current operating point to maximum voltage stability point according to loading parameter. Principal Component Analysis is an efficient feature selection method used here to find few input variables required to estimate voltage stability margin with sufficient accuracy and execution speed. Major drawback of previously published work is they need to train new neural network whenever change in system topology occur which is very time consuming process. Therefor in this paper single ANN has been prepared for estimating VSM for several system configuration. Feed forward neural network and radial basis function neural network have been used for voltage stability analysis of power system. The final result indicate that proposed method provide an efficient and compact ANN model for different system configuration as well as base case operating condition with lowest possible input required.