The Control Strategy And Realization Of Grid-connected Statie VA Generator(SVAG)

Distributed Generation (DG) is developing dramatically recently and its penetration in power system is also growing. However, with the increment of the proportion of DG in power system, the induced negative effects on distribution network cannot be ignored. The main problems normally include the voltage deviation, Voltage fluctuation, harmonics, DC bias, fault current and islanding operation. The most significant characteristic of these problems is that the traditional distribution network change into active network, which causes the power flow in both directions. The control strategy of distribution network with DG is not only need to control the reactive power, but also need to control the active power. Although the traditional static var generator (SVG, also called STATCOM) can dynamically control the reactive power to control the voltage fluctuations, it cannot achieve the regulation of active power. Distribution network with DG need to regulate the active power to meet the need of inverse power flow, power tracking, anti-islanded operation. In this case, the energy storage technology based Static VA Generator (SVAG) with both reactive power and active power regulating capabilities will play an important role in the distribution network control with DG.In order to realize reliable integration of DG and dynamic regulation of active power, it is important to research the grid-connection monitoring technology and control strategy. Based on the working principles and operation characteristics of three-phase grid-connected inverter, this dissertation proposes and analyzes the control strategy of three-phase grid-connected inverter. Based on instantaneous power theory, the decoupling control of active and reactive power is achieved in this dissertation. The dynamic tracking control of active power is realized by introducing a power control link. A systemic introduction on the main circuit and software design of SVAG is presented in this dissertation.Finally, a laboratory prototype of SVAG is developed and the control strategy has been succefully integrated within TMS320F28335Digital Signal Processor. The operation of the prototype after its integration to power grid is realized, achieving initially the active and reactive power decoupling control and the power tracking control under normal grid circumstances.