The Control Study Of Microgrid Network Interface With Unified Power Quality Conditioner Function

Microgrid contains a lot of non-linear loads, which seriously affect the microgrid common connection point(PCC) power quality. Meanwhile, the voltage drop, phase unbalance, voltage distortion voltage and other problems, affect the normal operation of grid-connected inverter. The microgrid networking interface, as a bridge connected to the main power grid, can convey the energy and improve power quality by multi-objective control. In this paper, a network interface controller with UPQC function is selected as an object, expanding research aspects in the frequency-locked loop, voltage and current harmonics, power calculation, general inverter control system, adaptive PR controller, and network interfaces and operating mode, the control methods of different modes.In this paper, a detection of synchronization signal based on MSOGI, instead of traditional phase-locked loop, is adopted in the grid voltage unbalance, voltage distortion and other case. For the lack of low-frequency harmonic suppression of SOGI, this paper sets the low-frequency harmonic cancellation of the feedback network; optimizes the frequency detecting and implements adaptive frequency; extracts voltage synthesis fundamental positive sequence component form fundamental signal. It also describes the voltage and current harmonics, power grid complex detection methods based on MSOGI. Finally, the simulation results show the effectiveness of the method. For networking interfaces possible operating conditions, the network interface is divided into five operating modes. According to the general structure of the inverter system, the input and output of expression is deduced, which can not only explain why the output of the inverter system error resulting from the mathematics, but also the principles of PR controller errors. Respectively, PR controller principle of series and parallel inverters in different modes is derived. Considering of compensation for the higher harmonics of the distribution network in multi-objective control, the frequency adaptive PR controller is used.Finally, five modes by computer simulation are validated. The simulation results show the effecting of network interface access and distribution with or without adaptive MPR controller. By setting different output of microgrid, the network interface control method is availability to control grid voltage, current, and the flow of power.