The present application provides a method of controlling an electrical power system and an apparatus using the same. The electrical power system includes a DC bus and a DC bus capacitor connected to the DC bus. The method includes: receiving a virtual DC bus capacitance value of the DC bus capacitor; detecting a DC bus voltage; calculating an expected value of a DC bus current based on the virtual DC bus capacitance value and the DC bus voltage; and adjusting the DC bus current, so that the DC bus current reaches the expected value and thus the DC bus capacitor is equivalent to the virtual DC bus capacitance value.