Basic Theory Of Multi-terminal Circuit Instantaneous Power Research

With the continuous expansion of the grid size, a large number of non-linear asymmetric loads access to power system, moreover, the wide application of electronic converter device,and the rapid development of distributed energy, which leads to the deterioration of the grid environment. Therefore, the widely accepted traditional instantaneous power theory, which is based on symmetrical sinusoidal voltage and stable current has lost its effectiveness in analysis and calculation of the non-linear circuits such as hybrid compensation system. This thesis introduces the conception of multi-terminal circuits, studies the definition and the calculation of instantaneous power under the form of multi-terminal circuits, and establishes the theory of multi-terminal circuit instantaneous power, which is more compatible and more useful than the traditional theory of instantaneous power.This thesis analyzes the multi-terminal circuits structure, classifies the multi-terminal circuits, and analyzes the relationships of different types of multi-terminal circuit. In the general structure of multi-terminal circuits, the terminal voltage and terminal current are defined. On this basis, the theory of multi-terminal circuits instantaneous power is proposed.The theory of multi-terminal circuit instantaneous power is applied to the three-phase three-wire circuit system. Because of the particularity of the three-phase three-wire circuits,firstly this thesis studies how to correctly apply the calculation method of multi-terminal circuits instantaneous power to the three-phase three-wire circuits. Then, this thesis also verifies the effectiveness of the theory of multi-terminal circuits instantaneous power on three conditions of the fact that the voltage and current are sine and symmetrical, the voltage is sine and symmetrical and the current is in distortion, and both voltage and current are in distortion.What’s more, it is verified the theory of instantaneous power proposed by Hirofumi Akagi can be used in the condition of multi-terminal circuits.The theory of multi-terminal circuits instantaneous power is applied to the three-phase four-wire circuit system, directly applying the calculation method of multi-terminal circuits instantaneous power to the three-phase three-wire circuits, taking advantage of the instantaneous terminal voltage vector and instantaneous terminal current vector to calculate the instantaneous active and reactive power by dot product and cross product. This thesis also verifies the effectiveness of the theory of multi-terminal circuits instantaneous power on the conditions of the fundamental frequency component and general situations. What’s more, it is verified the theory of instantaneous power proposed by Hirofumi Akagi can be used in the condition of multi-terminal circuits.Analysis the theory of multi-terminal circuits instantaneous power proposed in this thesis,and study the exceptional case that does not meet the calculation method of multi-terminalcircuits instantaneous power. By comparing the theory of multi-terminal instantaneous power circuits with the theory of instantaneous power proposed by Mr Dai. and Hirofumi Akagi, the thesis analyzes the advantages and disadvantages of the three theories of instantaneous power.