Research Of Key Autonomous And Coordinate Control Technologies For Micro-grid Cluster

Along with growth of the world’s population, increased consumption of energy, seriousenvironmental problems and exhaustibility of fossil fuels, the development and utilization of renewableenergy attracts much more attention. Micro-grid is an effective way to support distributed generationintegrated into, it has become a hot topic that how to make full use of renewable energy, improve powerquality and guarantee reliability of power supplement through flexible control technology. Moreover,due to distributed characteristics and permeability of micro-grid increasing gradually, how to effectivelycontrol multi-microgrids operation becomes a serious problem that needs to be solved urgently.This paper mainly studies in coordinated control of a micro-grid cluster, which involves control ofa power generation unit, control of a micro-grid and control of a micro-grid cluster. The main results ofthis research are as follows:1) Aim at the frequency deviation problem existing in droop control of distributed generation, animproved droop control method based on virtual frequency is proposed. In this method, adjustment ofphase angle is achieved by changing setting value of virtual frequency, and then can get the controlcoefficient of voltage phase-angle droop. Consequently, reactive power output is achieved in thecondition of not changing frequency of distributed generation. Simulations results show that, comparedwith previous droop control method, when the same effect of power allocation is done, the proposeddroop control method based on virtual frequency need not change setting value of frequency.2) Concentrate on problem existing in multiple operation states of micro-grid and multiple controlmodes of distributed generation, a coordinating control method based on finite-state-machine matrix ispresented. The control method can provide global control and management for overall micro-grid. Also,in the condition of off-grid operation, secondary adjustment of voltage and frequency as well as powerover-limit control can be achieved through partition coordination and control.3) Not only a method to define the external control characteristic indexes that a micro-grid showsin the micro-grid cluster but also a method to realize the control of external characteristic of amicro-grid are proposed. Furthermore, a three-layer coordinated control architecture of micro-gridcluster is given, which is based on the control method mentioned above. Simulations are carried out todemonstrate the applicability and rationality of the indicator and this method.4) Based on functional decomposition and integration of the micro-grid, a control informationmodel on the grounds of IEC61850communication protocol is established, then providing a controlmethod used this information model to achieved3-layer control of the micro-grid cluster. Theinformation model provides basis for interoperations between different intelligent devices and makesthe process of the micro-grid control standardized. Also, typical control functions are tested and provenin the paper.