Nonlinear control method for micro-grid inverter with anti-disturbance

A method for controlling power transmission between a micro-grid system and a power grid, comprising

• providing a micro-grid system and a nonlinear controller for the micro-grid system, wherein the micro-grid system comprises a distributed electric generation element that is connected to a power grid through a grid-connected point switch, a three-phase AC bus, a three-phase AC load, and a central controller;
• the distributed electric generation element comprises a DC voltage source, three-phase voltage source full-bridge inverter having six switch tubes corresponding to six channels, and an LCL-type filter circuit;
• and the LCL-type filter circuit comprises an inverter-side filter circuit, a grid-side filter circuit, and a filter capacitor,
• collecting voltage vc of the filter capacitor and current i0 of the grid-side inductance from the LCL-type filter circuit and establishing a mathematical model of a two-phase stationary coordinate system based on coordinate transformation of the voltage vc to vcαβ and the grid-side inductance current i0 to i0αβ by the nonlinear controller,
• collecting voltage vg of the three-phase AC bus and local load current iload, generating a grid-side inductance current reference signal ioαβ_ref in the two-phase stationary coordinate system based on the voltage vg and local load current iload according to instantaneous reactive power theory, and calculating grid-connected current igαβ based on the grid-side inductance current reference signal ioαβ_ref, active power command Pset, and reactive power command Qset from the central controller of the micro-grid,
• obtaining a first derivative {dot over (i)}oαβ_ref (t) and a second derivative ïoαβ_ref (t) of the grid-side inductance reference current signal ioαβ_ref (t) by an observer, and using the first derivative and the second derivative as input signal values of the nonlinear controller,
• setting an original tracking error eαβ and a filter tracking error Eαβ of a control variable i0, and building a grid-connected inverter nonlinear control model based on the original tracking error and the filter error by the nonlinear controller,
• obtaining a three-phase modulated wave signal according to the mathematical model of the LCL type grid-connected inverter and the grid-connected inverter nonlinear control model in a three-phase stationary coordinate system after coordinate transformation by the nonlinear controller,
• obtaining modulated pulse signals of six channels S1 to S6 from the three-phase modulated wave signal by the sine wave vector modulation module,
• inputting the modulated pulse signals of the six channels S1 to S6 and applying Lyapunov function to the three-phase voltage source full-bridge inverter, and
• transmitting power applied with the modulated pulse signals and the Lyapunov function between the three-phase voltage source full-bridge inverter of the micro-grid system and the power grid through the grid-connected point switch and maintaining stability of the power voltage therebetween.