Methods to Improve Dynamic System Response of Power Compensators Using Supercapacitors in Low-Voltage Ride-Through (LVRT) Conditions

Abstract

In this paper, a power compensator using supercapacitors in parallel to protect grid-connected devices connected to the distributed power supply in the case of a low-voltage ride-through (LVRT) situation in designed, and a grid-connected device control method with improved responsiveness is proposed. In the LVRT situation, the distributed generation power may boost the DC_link voltage, increasing the risk of destroying grid-connected devices. To prevent this, the power compensator designed in this study absorbs active power in a fault situation and stores it in the supercapacitor to suppress the DC_link voltage rise and efficiently use the power. In addition, we propose methods to improve the response of the grid reactive power through the reactive power compensation of the power compensator in LVRT situation. To this end, the power angle (θPW) was extracted through the formula, and the reactive power command, to be compensated by the power compensator, and the reactive power command, compensated by the grid-connected devices, were calculated according to the active power value. In this way, the grid power controlled by the power compensation device and the grid-connected devices was controlled by the active/reactive power of the same power angle and analyzed mathematically. Active power control and static grid support were performed in the normal state where the reduction rate of the normal value of the grid voltage was around 10%. However, when the grid voltage dropped by 10% to 100%, the reactive power control was appropriately performed with dynamic grid support by increasing the voltage from 10% to 20% or more. We conducted a simulation of the new and renewable energy grid-connected devices using the OPAL-RT-based Hardware-in-the Loop Simulation (HILS) system to control the proposed active/reactive power.