Coordinated Control Of Active And Reactive Power Of Microgrid

According to the research status all over the world, the features of microgrid differed from main grid are discussed in this thesis. The first feature of microgrid is the uncertainties of renewable energy power(such as wind power and photovoltaic power) prediction and load prediction, the second is the coupling characteristic of active-reactive power. In a word, Hierarchical control strategy is adopted to control microgrid with the considering of the two main features.Towards the problem on the economic dispatch of microgrid, firstly, considering the uncertainties of renewable energy power(such as wind power and photovoltaic power) prediction and load prediction, the interval numbers are utilized to describe uncertainty. After that, the active-reactive power combined optimal dispatch model of the microgrid is established since the fact that the active power and the reactive power are strongly coupled in microgrid system. Subsequently, for the sake of finding the solution easily, the interval-based uncertain dispatch model is transformed into a general certain one by a mathematical transformation method based on the interval order relation. Finally, the numerical simulation tests are performed on a typical microgrid system with the professional optimization software(GAMS) to verify the proposed optimal dispatch method of microgrid system. Based on the testing results, the impact of the interval uncertainty level on the operating cost of microgrid and the power output of the microsources are analyzed.In order to realize the transient stability of microgrid, the primary control and secondary control are designed in this thesis. Firstly, a coordinate rotational transformation based virtual power droop control method is applied on microgrid to realize the primary control with the consideration of a mainly resistive line impedance. However, it might not return the microgrid to the normal operating conditions, and the secondary control is designed to restore the voltage and frequency, which compensates for the voltage and frequency deviations caused by the primary control.