autally my doubt is ,how to increase the battery discharge or decrease the discharge while design the UPS?

huh?

you are designing this? You are asking some basic questions.

500 kW is a very large UPS. Very! enough to run 100 homes. The largest UPS that APC makes is 9.6 kW and that costs $10000, and it has a backup time of 30 minutes. You would need 50 of these!

If you want the operating time on battery to go from 4 hr to 7hr, you need a bigger battery. No way around that.

500 kW is increased due to efficiency losses in the inverter, so figure 600 kW. For 7 hours that is 4200 kw-hrs.

A large lead acid battery has a capacity of 100 amp hours, which translates to 1000 watt-hrs or 1 kW-hr.

You will need *** 4200 *** large lead acid batteries to hold for 7 hours, and 2400 batteries for 4 hours.  Enough for a large submarine.



I think some of your numbers are wrong. First rule: get the numbers correct!

Double it(ok  multiply it by 7/4ths which is a little less than double).Twice the time at the same load.

Volts is missing from your problem so we'll assume 120volts.
p = i times e,  so i equals 500000/120=4166 amps per hour.
So your battery, which is rated in amp hours will be 4 X 4166 amp hours or 7 X 4166 amp hours. of course if your battery is some other voltage, say 12 VDC, then multiply the above  times a factor of 10.

4h x 500kW = 2000 kWh
7h x 500kW = 3500 kWh

kiloAmpere-hours = kWh divided by volts.

Assuming 120V,

2000 kWh / 120V = 16.6 kAh
3500 kWh / 120V = 29.2 kAh

I would suggest a diesel generator the size of a mini-van, complete with auto-transfer switch as your UPS.