Robust Output Feedback Control of the Voltage Source Inverter in an AC Microgrid

Abstract

This paper presents the mathematical model and control of the voltage source inverter (VSI) connected to an alternating current (AC) microgrid. The VSI used in this work was a six-switch three-phase PWM inverter, whose output voltages were controlled in a synchronous (dq) reference frame via a sliding mode control strategy. The control strategy required only output voltages; other states of the system were estimated by using a high-gain observer. The power-sharing among multiple inverters was achieved by solving power flow equations of the electrical network. The stability analysis showed that the error was ultimately bound in the case of the real PWM inverter and/or with a nonlinear load in the electrical network. The microgrid was simulated using the SimPowerSystems Toolbox from MATLAB/Simulink. The simulation results show the effectiveness of the proposed control scheme. The output voltage regulation of the inverter and power-sharing was achieved with the ultimately bounded error for the linear load. Later, the nonlinear load was also included in the electrical network and the error was shown to remain ultimately bounded. The output voltage regulation and power-sharing were achieved with the nonlinear load in the system.

Active and Reactive Power Control of the Voltage Source Inverter in an AC Microgrid

“…In Figure 2, the control system of master VSI controls the voltage at PCC and tracks the following reference voltages shown in Equation (28). The control scheme of master VSI is discussed in [18].…”

“…A microgrid can be operated in either grid-connected mode or in islanded mode [13][14][15], and VSI can be controlled in either voltage control mode (VCM) or in power control mode (PCM) [16]. In the islanded mode of operation, either all VSIs operate in VCM with power sharing achieved by solving optimal power flow equations [17,18] or by using the droop control method [19][20][21] or by operating in a master-slave configuration. In the master-slave configuration, a master VSI operates in VCM, and other VSIs operate in PCM [22,23].…”

Study and Implementation of a High-Quality True Sine Wave DC-to-AC Inverter for Solar Power Generation Systems

“…However, they are mathematically complex and computationally time consuming [ 27 , 28 , 29 ]. Recently, the improved sliding mode reaching law (ISMRL) has provided a terminable system state convergence time to reject the steady-state error (i.e., the terminable time for the system trajectory to reach the sliding mode region in the presence of uncertainty) [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 ]. However, it should be noted that even if ISMRL makes the solar power generation system achieve the expected control effect, it is easy for the solar array to become partially shielded by buildings, trees, dust, etc.…”