Control Strategies For Voltage And Frequency Regulation And Power Balance Of Microgrid In Transient Conditions

With the growing consumption of energy in the whole world, utilization of new energy becomes the inevitable trend in the future. Microgrid, as the best form of new energy power generation, has been increasingly recognized. At the same time, the development of microgrid supports voltage and frequency of large power grid, so that becomes a effective complement to power.Because of the interfaces of distributed power supply in microgrid are mostly power electronics interface, its transient characteristics are more complex than its in the traditional grid. Under disturbance, how to ensure the stable electrical parameters such as voltage,frequency and the smooth transition of system operation mode is becoming one of the biggest problems when scholars research microgrid. The article regards the microgrid under transient conditions as the main research subject and analyzes mathematical model and control mechanism in depth. Besides, the optimal design methods of microgrid topology and control strategy are discussed. Finally, two high-performance strategies of the voltage frequency regulation and power balance control in microgrid are verified.First, the mathematical models of the inverter system, controller, network, load in the microgrid are established,and they are linearized to be small-signal model, the parameters of the micro-grid system and its controllers are selected by small signal model analysis,and parameter changes how to effect on dynamic performance and stability of microgrid are proposed, understand the transient stability of microgrid By the establishment of microgrid mathematical model in transient conditions.A new topology of hybrid-bus micro-grid and its corresponding power balance control strategy is proposed. The bus of the DC side and the AC side is regarded respectively as two level power balance points so that the distributed power group combines with energy storage devices to supply the power via the DC bus. In transient conditions, by stabilizing the DC voltage, the power of supply-side and demand-side is matched quickly. Accordingly, it adjusts the control strategy of inverter to stabilize voltage, frequency of the system and to adjust power quality. Finally,according to the situation that the traditional control strategies need a switch process and don’t consider the restoration of the voltage and frequency.author proposed an improved droop control strategy. Eliminate the power deviation and Oscillation produced by the traditional droop control through improve the power loop.Add the feedforward of the voltage and frequency deviation at the same time,therefor the secondary control is provided to voltage and frequency. the simulation experiments shows the performance of the two control strategies.