Research On Active Power Flow Control Technology Of Medium-Voltage Distribution Network Based On Power Exchange Node

Distribution network is the essential part of power network, which is responsible for distributing electricity to consumers. The medium-voltage distribution network, which makes up to the largest part of distribution network, always operates with problems like high loss, low efficiency, unbalanced line resource and comparatively low reliability. With the penetration of distributive generation(DG) getting higher and higher, the distribution network has received support from DG but also got new problems such like power flow getting more complex, protection configuration becoming harder to decide and how to distribute and consume the extra power generated by DG. Inspired by the energy management idea of active distribution network, a new device called "power exchange node" is proposed in this paper, which is able to manage the power flow of the distribution network. Based on power electronics technology, oriented by the idea of active distribution network, power exchange node is designed to manage the power flow quantitatively and change the situation in which power flow is affected by the structure and configuration of network.According to the feature set, the inner structure of power exchange node consists of several AC/DC converters with a mutual DC bus. And the feasible application of the device has been discussed. With the knowledge of the model-built theory in synchronous rotating coordinates, the mathematical model of power exchange node has been established. The AC/DC converters have been labeled as(Q, Udc) converter or (P,Q)converter with the method of the direct current control mechanism. The zero-sequence current among the converters has been suppressed under a optimized SVPWM modulation algorithm and a front feedback control has been applied in (Q, Udc) converter to maintain the stability of DC voltage. All mentioned above contribute to the control scheme of power exchange node.Guidelines for the device has been proposed, this paper comes up with a two-layer control structure and two operational modes:distribution network level control and station level control; loss-reducing mode and emergency mode. The implement details of the two operation modes have been introduced.The simulation research has verified the flexibility and stability of the proposed control scheme. A example network has been used to assess the loss-reducing ability and adaptability of power exchange node.