Dynamic Voltage Restorer-DVR

Overview

Voltage sag is the most important power quality problem in industry! the factory can not predict the occurrence of voltage sag accident in advance!

Voltage sag Introduction

Voltage sag is also called voltage drop, voltage sag, voltage sag and dangle, etc. refers to the sudden drop in the effective value of the voltage, and then suddenly return to normal phenomenon.

According to authoritative data EPRI( the American Academy of Electrical Sciences), more than 92% of power quality events are voltage sags and sags, and less than 8% of other power quality events. The International Association of Electrical and Electronic Engineers (IEEE) defines it as falling to 90 to 10 per cent of the rating with a typical duration of 0.1~1 s.

The Reasons for Voltage sag

There are many causes of voltage sag, when short-circuit fault, lightning strike, large-scale motor start-up events in transmission and distribution system, may cause voltage sag. Therefore, voltage sag can not be avoided.

-Weather reasons

-Accidental events

-Other faults

CoEpo DVR Dynamic Voltage Restorer Introduction

CoEpo DVR adopts power electronics technology, when the system voltage drops suddenly, the DVR can realize the fast regulation of the voltage, at the same time eliminate the voltage three-phase imbalance, and have the adjustment voltage deviation, ensure the seamless connection of the output voltage to the rated value, and protect the normal operation of the load.

DVR Working Principle

DVR in series between the supply supply and the protected load, it will continuously monitor the input side supply voltage. once it is found that the supply voltage deviates from the rated voltage level, DVR will produce a suitable compensation voltage injection system by IGBT the inverter system, which ensures that the output side (i.e., the load side) voltage is stable and that the protected load is not affected by voltage changes.

Grid voltage within limits: When the grid is supplying the load (in online mode), the inverter sleeps but remains in sync with the grid voltage for immediate action in case of grid disturbance.

Occurrence of voltage sag: when the power occurs in the power grid, the double reverse switch quickly shut off, thus isolated from the power grid, from the inverter to the load power supply.

Voltage re-stabilized: DVR the double reverse switch on, the inverter circuit is closed, the load will be supplied by the power grid again, and the rectifier circuit re-charges the energy storage capacitor.

Fault safety bypass operation:In the case of DVR failure or maintenance, the load current will be automatically transferred to the fault safety bypass. That is, the current will be directly supplied to the load through the contactor or bypass switch connected in parallel to the thyristor.

CoEpo DVR Working principle of high voltage products of dynamic voltage restorer