Research On Harmonic Detection And Suppression Method Of Micro-grid System Based On Wireless Sensor Networks

As an important supplement of large power grid, the micro-grid system can take advantage of wind, solar and other clean renewable energy to generate electrical energy, and it can effectively solve the energy shortage and environmental problems. However, the large number of power electronic devices of the micro-grid lead to a significant increase in harmonic levels. The existence of harmonics could cause serious problems such as increased losses, lower power factor, equipment damaged, malfunction of protective equipment and some other serious power quality problems. Real-time harmonic detection and suppression strategy has important significance to develop effective solution of micro-grid harmonics. This paper has the following main contents:1. This paper analyzes the relevant structure and harmonic sources characteristics of micro-grid system, and makes a description of wind turbines system, solar power system, non-linear loads and the characteristics of their produced harmonics. As a result a theoretical premise is provided to the study about harmonic detection and suppression of micro-grid system.2. This paper explores a micro-grid communication system based on wireless sensor network. Considering the poor environment and the complex structure of the micro-grid system, this paper applies wireless sensor network to build the micro-grid communication system so that it can meet the real-time and reliability requirements of micro-grid harmonic detection and suppression. The structure of the wireless sensor networks, sensor nodes locations and a find reliable link routing policy (FRL routing policy) are presented to ensure the real-time requirements of the micro-grid communication.3. A distributed related Kalman filter method for time-varying micro-grid system harmonic detection is presented. According to the randomness and non-stationary of the micro-grid system harmonic state, and for the fact that micro-grid system harmonic injection at neighbor buses are correlated to some extent, the concept of neighbor correlation coefficient is introduced to represent the degree of correlation between neighbor nodes. And then, a method to calculate the neighbor node fusion variables (the fused inverse-covariance matrices and the fused sensor data) which is suitable for micro-grid system harmonic measurements is proposed. Distributed fusion processing among the neighbor nodes of estimated values are utilized to ensure the unanimous correlation of the estimation results between neighbors. Make the IEEE-14 bus system as the simulation object, and we reconstruct the iterative process of the algorithm to simplify the calculations. The results demonstrate the effectiveness of this method, and it can improve the accuracy of the micro-grid harmonic detection.4. This paper proposes to use a hybrid active power filter to suppress the micro-grid harmonic. Considering the harmonic sources and harmonic characteristics of the micro-grid system, this paper explores a kind of HAPF to suppress the micro-grid harmonic. A detailed introduction on structure and work characteristics of the HAPF is presented. The simulation results indicate the validation of the method.