When AC is converted to DC using rectifier and boost converter or capacitor filter is used, current drawn at AC sides contains harmonics (is non-sinusoidal). This simulation model modifies the boost converter so that boost converter along with load works as pure resistor so that there is no harmonics in current in AC side.
It first measures output voltage and subtracts with reference voltage. Their difference is passed to PI controller which calculates power to be drawn. Voltage at the output of rectifier is measured. Then current proportional to the voltage is calculated where constant of proportionality determined by the power to be drawn. In this way, reference current is calculated. This reference current is compared with actual current. Then gate signal is generated by hysteresis band controller which is fed to switching MOSFET S. Since the voltage and current are proportional, it behaves as pure resistor. When pure resistor is used as load in rectifier, current at ac side is also sinusoidal. So, in this case too, current at AC side will be sinusoidal.