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Static var compensator (SVC) and thyristor controlled series compensator (TCSC) are used to improve Transient Voltage Stability of the asynchronous wind farm in this paper. The related structure model of the wind farm power system is built in Matlab / Simulink. The contributions of SVC and TCSC to Transient Voltage Stability of the asynchronous wind farm and power grid are verified by the simulation...
Wind turbine power output is totally intermittent in the nature. For grid connected wind turbine generators, power system operators (transmission system operators) need reliable and robust wind power forecasting system. Rapid changes in the wind generation relative to the load require proper energy management system to maintain the power system stability and of course to balance the power generation,...
As is well known, Smart Grid is a complex nonlinear system whose dynamical behavior has many complicated forms such as low frequency oscillation, subsynchronous oscillation and even chaos. Thus this paper focuses on the chaotic phenomenon of the widely concerned Smart Grid and presents its stabilization condition via establishing generalized fuzzy hyperbolic model. Firstly, the concept of Smart Grid...
A method of quantitative contribution assessment of power source in critical branch is proposed in this paper. During the various operation modes, a branch must keep its power flow within the critical boundary. A simple branch model is given to represent the overhead line, cable or transformer. The index proximity of criticality (IPC) is formulated to evaluate the severity. An electrical decomposition...
With the introduction of new guidelines regarding the connection of large wind farms to the grid, wind farms and equipment providers are facing with new opportunities and challenges. One of which is low voltage ride-through (LVRT). Despite of the new installations, there are a considerable number of wind turbines to be reformed to meet the requirements. In this paper, a brief explanation of the principle...
This paper presents the possible improvements of voltage quality in connection of a wind farm to transmission network using VSC-HVDC (Voltage source converter high voltage direct current) link. For a 80 MW wind farm consisting of 40 individual 2 MW doubly fed induction generators, the main influence of voltage fluctuation caused by the wind farm integration is analyzed. The use of a reactive controller...
This paper uses concepts of eigenvalue structure analysis, and defines disturbance variables sensitivity and load sensitivity of PQ bus to determine voltage weak point and find the reason of voltage collapse. It provides numerical method of calculating disturbance variables sensitivity and load sensitivity of PQ bus, and verifies the numerical method with WSCC 9-bus system.
Wind generation rapid development has brought challenge to the grid. Reactive voltage is the most outstanding and one of the most concerned problems. This paper introduces the concept of wind farms reactive power compensation and wind power grid code with respect to reactive power regulation all over the world, gives the simplified approach to estimate reactive power compensation capacity, and validates...
This paper presents an on-line equivalent algorithm for power system based on phasor measurement unit. The method considers the changes of the system parameters and load level, which overcome parameters rift problem and the shortage of traditional two points power flow method that supposing the parameters are fixed after a small disturbance. On this basis, voltage stability and Alert margin are proposed,...
In this paper, an algorithm for diagnosis of voltage collapse point is proposed. The algorithm is based on load characteristics, voltage and current measurements. When all loads at a bus are voltage independent type, the voltage collapse point coincides with Maximum Loading Point. In maximum loading point, with voltage and current changes, apparent power delivered to the bus does not increase. In...
Load model has great uncertainty characteristic due to the time-variation of load. As a consequent, it is essential to analyze the influence of load model on power system stability. The effect of load model structure and parameter on Yunnan power grid transient stability is researched in this paper. Simulation results indicate that load model has great influence on Yunnan power great transient stability...
Power System Stabilizer (PSS) is widely applied in power systems as an effective measure to damping the low frequency oscillations. The control effectiveness of PSS is fundamentally determined by appropriate parameters. The conventional method for setting the parameters of PSS only takes a single oscillation mode into account, which may have sub optimal damping performance in other modes. As a further...
The mechanism of Emergency DC Power Support (EDCPS) is analyzed based on a model in which two AC systems are connected by a HVDC Link. This model can be considered as an equivalent two-machine power system, and it is demonstrated that stepping up (or stepping down) DC power during the angle-swing-up (or angle-swing-back) course of the equivalent system can help absorb (or compensate) active power...
Based on analysis of the case of the saddle-node bifurcation and the limit-induced bifurcation, a new method for identifying and calculation bifurcation points in steady-state voltage stability analysis is presented. By using continuation power flow based on piecewise linear load prediction curve, in which the load increasing directions are determined by load prediction curve, it go through the collapse...
A dynamic equivalent approach based on coherency is researched for dynamic simulation test in ±800 kV DC transmission project from Yunnan to Guangdong in China. To reduce the full system, the dynamic equivalent model of large-scale power system based on coherency is established, in which the identification of coherent generator groups, coherent buses reduction, aggregation coherent generator parameters...
Voltage stability has become rather important in modern power systems, the bifurcation of the adjoint system has been proposed for computing the saddle-node bifurcation point of the voltage stability. We derive the bifurcation analysis of the adjoint system, an example is given.
As power system interconnections become more prevalent, there has been an increase in use of thyristor controlled shunt connected compensation devices for dynamic power compensation and enhancement of real power transmission capacity. In this paper, an enhancement technique of real power transfer capacity of transmission lines is presented. A static var compensator (SVC) is designed and applied to...
The main factors are found out for planning DC links terminating at AC system locations from the point of interactions between AC and DC systems, such as Short-Circuit Ratio (SCR), Voltage Static Indicator (VSI), and the power losses of the whole system. Based on the linear weighted summation method for multi-objective decision-making problems, a new method is proposed in this paper to select the...
A new heuristic optimization algorithm is proposed in the paper, that is an improved ant colony algorithm for solving continuous space optimization problems. It is used in dynamic parameter aggregation based on frequency domain aggregation. The result from aggregation of generator electromagnetic circuit and excitation system show that an improved ant colony algorithm in aggregation of generator dynamic...
Because of the larger trigger lighting area, 220 kV double circuit transmission line is more vulnerable by lightning, and shielding failure and back flashover are more prominent. Therefore, the accurate assessment of the lightning protection performance of 220 kV double circuit transmission line is crucial to ensure the security and stability of the transmission network. This paper presents the main...
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