PUBLICATIONS

This paper compares and analyzes various methods for accurate detection of grid voltage magnitude in the grid-connected power

conversion system (PCS) such as wind power generation system, solar energy generation system, and energy storage system (ESS). In

addition, it compares and analyzes low voltage ride through (LVRT) control method, which is required to keep the continuous operation

of the system when the grid voltage drops. The LVRT control methods are used for stable operation of the system including the grid-

connected PCS such as wind power generation system, solar energy generation system, and ESS when the grid voltage drops. Recently,

the LVRT control methods based on the grid code for the systems are widely researched. Regardless of the energy sources, the main

purpose of the LVRT control method is similar to each other. It is to inject the reactive current into the grid through the grid-connected

PCS depending on the grid code when the grid voltage drops. In the systems including the grid-connected PCS, the injection quantity

of the active and reactive currents is determined to the voltage drop ratio by the LVRT control method. However, unlike the wind

power generation system and solar energy generation system having the characteristic of unidirectional power transmission, the ESS

has the characteristic of bidirectional power transmission. Therefore, in the LVRT control method of the ESS, it should consider the

charging and discharging states of the ESS, in addition, this paper analyzes the variations of the point of common coupling (PCC)

voltage depending on the phase of the reactive current during the charging and discharging states of the ESS. The validity of the LVRT

control method of the grid-connected PCS is verified and the variations of the PCC voltage are analyzed by simulation results.