Back-to-back HVDC Reactive Power Calculation Research

With the development of global economy, the ways of using electricity are turned out tobe diversified. Therefore, the total electricity demand is increasing. Separate grid can’t meetthe demand for electricity. Power grid interconnection problems are becoming increasinglyprominent. Obviously there exist shortcomings in the traditional way of AC interconnected.For example the frequency and phase of the two power grids which are linked to each othershould be the same, or the pollution of power grid will be caused. Another shortcoming is thatthe spread of grid disaster can not be stopped timely from one network to another network.Because of the existing of the DC link, these two problems is no problem to the back-to-backHVDC. There is no need to consider the same frequency and phase of the two linked powergrids. Also cutting down the DC link can immediately stop the spread of the grid disaster.Back-to-back HVDC technology plays an important role in today’s interconnection areas. Inthe condition of grid voltage balance, this paper establishes the simulated model of theconverter, and discusses the control method of the converter.An important indicator of the inverter power transmission quality is power factor. Thecalculation of the reactive power provides reliable quantitative basis for the reactive poweroptimization of the system. This paper reviews the three kinds of reactive power calculationtheory which are commonly used in the previous literature. Some of the methods are defectsin theory and some of them are insufficient in practical application. It is difficult to applyBudeanu calculation method in practice. And when is defined as zero, its components can notbe zero. While theoretically Fryze calculation method is lack of clear purpose in physicalsignificance and it could not provide information for the improvement in system power factor.What’s more, it can not reflect the information about the load effectively. In theory, Czarneckicalculation method can not make equal the generated current with the non-linear generatedcurrent. On the base of analyzing the advantages and disadvantages of the three traditionalmethods, an improved calculation method of reactive power which is based on Hilbertorthogonal space is developed in this paper. Compared with the three traditional methods, thismethod has obvious advantages both in theory and practical application.In this paper, the simulation result of the converter model is processed by the fourmethods. Through the comparison of results, it also verifies the superiority of the improvedmethod. It has positive significance to promote the power conveying efficiency of the powergrid interconnection.