中文摘要：

为准确分析计算交直流输电系统的无功功率，采用基于任意周期电压电流的无功功率数学模型，推导了交直流输电系统的无功功率模型，阐述了交直流输电系统中无功功率的物理本质。利用实时仿真软件PSCAD／EMTDC对一个典型的交直流输电系统建模并分析计算其仿真输出波形及数据，求得电路中的有功功率、无功功率，证明了无功电压、电流偶对概念的普适性和基于任意周期电压电流的无功功率数学模型的通用性。指出电路中无功功率的物理本质就是不同频次电压电流的相互作用，并且满足能量守恒定律。

英文摘要：

Based on the mathematical model of reactive power for arbitrarily periodical voltage and current waveform, which obey the fundamental energy conservation law, reactive power of rectifier（inverter） dc-side in AC/DC system is analyzed and calculated, its mathematical model is derived and physical essence is described. The model of a typical AC/DC power system is established using the PSCAD/EMTDC software, output data and curves of simulation are analyzed, and the reactive power of the AC/DC system is calculated. The full system, including AC and DC systems, is modeled by connecting all individual transfers together with appropriate system equations and nodal analysis. The example is presented to verify the correctness and feasibility of the definition of the reactive power I/V pair and reactive power for arbitrarily periodical voltage and current. It is pointed out that the physical essence of reactive power is interactions of voltages and currents of different frequencies, which suffices fundamental energy conservation.