Methods for protecting network from islanding danger

The process of energizing loads from other sources like a distributed generator with a total disconnection of utility grid at the point of common coupling is called islanding. The islanding phenomenon affects the network by safety issues and bad impact on the utility and connected loads, especially the workers on the utility. Hence, it must be detected by a suitable anti-islanding (AI) technique which is needed to be faster in terms of time detection and smaller or negligible nondetection zone. To detect this phenomenon, there are local and remote AI techniques. In this paper, local AI techniques are illustrated, which are used for improving the performance regarding the size of the nondetection zone and detection speed.

An improved islanding detection algorithm based on AFDPF

Unplanned islanding is a harmful phenomenon that will cause a series of adverse effects on the power grid. Therefore, islanding detection is a necessary feature of a microgrid with distributed power generation. Based on the Active Frequency Drift with Positive Feedback (AFDPF) algorithm, this paper proposes an improved frequency offset method.The method uses the frequency difference between two cycles to determine the direction of the disturbance signal. The value of the third power is superimposed on the point of common coupling (PCC)to improve detection speed.And check the Nondetection zone of this method based on the Qf0×Cnom coordinate system. Finally, through MATLAB/simulink simulation, the effectiveness and superiority of the improved frequency shift islanding detection algorithm are verified.

An Enhanced Control Strategy for the Stable Operation of Distributed Generation during Grid-Connected and Islanded Mode

The incident of islanding occurs while the distributed generator fed constant power into the grid after power flow on the source of essential utility has been intermittent. If islanding is not rapidly detected, it can reason serious security and harmful condition. This paper presents coordinated manage of solar photovoltaic unit through maximum power point tracking technique to make available voltage and frequency support for an islanding condition. In normal condition, structure works as constant current control mode subsequent to islanding the structure switched to voltage control mode. The projected technique is capable to discriminate involving an islanding and a non-islanding occurrence. In this paper phase locked loop detection technique designed for detecting islanding situation is conceded out. The authentication of proposed system is established efficiently using MATLAB/ Simulink environment. The simulated results exhibit that the islanding detection technique has zero nondetection zone property and be able to detect islanding within few seconds

Method for Detecting the Inside of Coke Drum Using Acoustic Signals

A distance and acoustic intensity reverberation (DAIR) physical model is developed that can be successfully applied to the signal processing of the hydraulic decoking process online monitoring. In this model, the transmission characteristics of acoustic signals generated by a moving sound source in a dynamic confined space are first analyzed using data recursion and correction according to the coordinate continuity in adjacent area and adjacent time. The results show that the nondetection zone of acoustic signals generated directly by the impact of water is eliminated, and the surface distribution of coke in the drum can be mapped in real time.

Research on a New Control Scheme of Photovoltaic Grid Power Generation System

A new type of photovoltaic grid power generation system control scheme to solve the problems of the conventional photovoltaic grid power generation systems is presented. To aim at the oscillation and misjudgment of traditional perturbation observation method, an improved perturbation observation method comparing to the next moment power is proposed, combining with BOOST step-up circuit to realize the maximum power tracking. To counter the harmonic pollution problem in photovoltaic grid power generation system, the deadbeat control scheme in fundamental wave synchronous frequency rotating coordinate system of power grid is presented. A parameter optimization scheme based on positive feedback of active frequency shift island detection to solve the problems like the nondetection zone due to the import of disturbance in traditional island detection method is proposed. Finally, the results in simulation environment by MATLAB/Simulink simulation and experiment environment verify the validity and superiority of the proposed scheme.