Search

Reactive power optimization falls into the category of multi-objective optimization. The simulation model of multi-objective reactive power optimization is built on the basis of the conventional reactive power optimization model in this paper, wherein the objective function is consisted of minimum active power losses and minimum reactive power compensation cost. The multi-objective reactive power optimization model is built via following MOEAD algorithm. The simulation results prove that the multi-objective reactive power optimization based on MOEAD could reduce the system active power loss and reactive power compensation cost in fast and effective fashion.

Fractional Frequency Transmission System (FFTS) provides a novel approach to integrating the remote wind farm into grid. This approach can overcome the great challenges caused by the randomicity and the intermittence of the wind power. In 2005, the FFTS has been realized for the first time under the conditions of active inversion of phased-controlled cycloconverter, the result of it proves its effectiveness and feasibility. But this system can not fit the wind power well because the Total Harmonic Distortion (THD) of 6-pulse cycloconverter is very large. In this paper, the experimental FFTS is illustrated firstly, then the power circuit and the control circuit of the 12-pulse cycloconverter are designed, which is the key equipment of FFTS. In this experimental system, a synchronizing generator is used to simulate the Permanent Magnet Synchronous Generators (PMSG) in wind farm. Furthermore, the operation mode of cycloconverter is discussed in this paper. Finally, the open-loop active power regulations method is also introduced. Experiment results show that this system is capable of transmitting 20kW electric power into grid, and the feasibility of the system, which can be used to integrate wind power into grid via FFTS, is verified.

Fractional Frequency Transmission System (FFTS) is a new approach to integrate large-scale, remote wind power into grid. It adopts lower frequency, such as 50/3Hz, to transmit remote wind power to the load center directly. Therefore, it could reduce the voltage influence caused by the intermittence of wind power. In order to analysis the Stable characteristics of FFTS, power flow analysis of this system should be conducted. However, traditional Newton-Raphson method cannot be utilized directly due to two reasons. First, the node admittance matrix should be modified according to the exact operation frequency in lower frequency side (LFS). Second, the cycloconverter is installed as the converter to transmit the power from LFS to grids. So the model of cycloconverter must be incorporated. Therefore, a new unified iterative method is proposed in this paper to calculate power flow of FFTS. With this method, the admittances of the transformers and transmission lines in LFS are modified according to their operation frequency before the admittance matrix is built. Moreover, base on the model of cycloconverter, the Jacobi matrix also needs to be extended. Case studies are implemented to prove the valid of this method.