Static Voltage Stability Analysis and Improvement Method for Distribution Network Considering DG

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)

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.

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.

In the static voltage stability analysis, the dynamics of the components in the power system are not considered and the creditability of the results obtained is more or less affected. Based on the continuation algorithm, this paper investigates the dynamic stability using the small signal analysis method. The stability type is distinguished by the modal participation factors of the state variables. Firstly, the equilibrium manifold is traced by a locally parameterized continuation method. Then, the dynamic stability of each equilibrium point is analyzed using the small disturbance analysis method considering the components dynamics. The system state matrix is calculated numerically by applying small perturbation to each state in turn. Simulation results show remarkable differences in the stability critical points obtained by the small signal perturbation dynamic analysis and the static analysis. Also a region of dynamic voltage stability is found in the lower portion of the PV curve.

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.

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 paper presents two different methods of static voltage stability analysis, one using indices based on the singular value decomposition of the system Jacobian matrix (SVD Method), while the other is based on finding a path of the system load flow equations solutions in presence of a load parameter (continuation method). Both methods were successfully implemented and applied on the Israel Electric Corporation (IEC) network consisting of about 200 nodes. The voltage collapse critical points were determined by both methods for different conditions, and the regions most exposed to voltage collapse in the network were identified.

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.

A development of longitudinal static stability analysis method of a Wing-In-Ground effect vehicle in cruise during the design process

With the development of power electronic devices, the research of Flexible AC Transmission System (FACTS) in regulating line power flow and improving static voltage stability is more in-depth. This paper discusses the static voltage stability of power grid with new energy taking into account the distributed static series compensator (DSSC), and evaluates the power flow control efficiency of DSSC from the aspect of system static voltage stability. First, the equivalent circuit and working principle of DSSC are analyzed, and the power flow equations are obtained based on the equivalent power injection model of DSSC; Secondly, based on the power flow calculation equation, the efficiency evaluation index that can reflect the static voltage stability of the system is proposed, and the impact of new energy with different capacities on the static voltage stability is calculated and analyzed; Finally, the proposed method is verified by the simulation analysis of IEEE-24 bus system and actual power grid: the proposed method is fast and simple, and has certain engineering application value.

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.

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.

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