How to estimate the power configuration of 5G base stations?

5G base station construction, supporting facilities first. With the implementation of 5G centralized procurement by the three major operators in 2020, the construction of 500,000 5G base stations is on the way. However, due to the increase of power consumption of the original 4G base station sites after the addition of 5G equipment, the corresponding base station power supply facilities need to be upgraded first to ensure the stable operation of 5G base stations.

How to transform the power supply of 5G base stations? How to calculate it?

The 5G base station consists of a BBU and an AAU. This article configures a base station with three cells (1 BBU + 3 AAUs), assuming that the power consumption of the 5G BBU is 350W and the power consumption of the AAU is 1100W, to calculate the relevant power supply.

1 Battery Pack Capacity Estimation

The battery capacity calculation formula is simplified as follows:

Q=K*(P1*T1/η+P2*T2/η)/43.2

In the formula: Q—battery capacity (Ah); K—safety factor, take 1.25; P1—actual working power of communication equipment on the primary power-off side (W); P2—actual working power of communication equipment on the secondary power-off side (W); T1—total backup time of equipment on the primary power-off side (h), usually 3 hours; T2—total backup time of equipment on the secondary power-off side (h), usually 10 hours; η—discharge capacity coefficient, 0.75 for battery discharge for 3 hours and 1.00 for 10 hours; 43.2—minimum discharge voltage allowed by the battery pack

Parameter explanation:

The DC power distribution circuit of the base station is divided into primary power-off and secondary power-off. The communication equipment on the primary power-off side refers to the base station equipment, and the communication equipment on the secondary power-off side refers to the transmission equipment and monitoring equipment.

When the city power goes out, the battery pack starts to discharge and continues to supply power to the base station equipment and transmission equipment. However, due to the limited capacity of the battery, at a threshold value, the power supply to the base station equipment with greater power consumption will be cut off, and only the transmission equipment and monitoring equipment with less power consumption will be powered, so that the battery pack can continue to work for a longer period of time, so that maintenance personnel can arrive in time to perform emergency power generation. This is called a primary power-off. When the primary power-off is completed and the transmission equipment and monitoring equipment have been working for a period of time, the power supply to the transmission equipment will be terminated in order to protect the battery. This is called a secondary power-off.

This article assumes that in the configuration of 1 BBU + 3 AAUs, the power consumption of the base station transmission and monitoring equipment is 500W, that is, P2 is 500W.

Let’s calculate P1 again: 1*BBU power consumption + 3*AAU power consumption = 1*300W + 3*1100W, that is, P1 is 3650W.

Therefore, according to the battery capacity calculation formula,

Q=1.25*(3650*3/0.75+500*10/1)/43.2=567(Ah).

That is to say, after adding a set of 5G base station equipment (1 BBU + 3 AAU) to the base station site, a corresponding set of batteries with a capacity of 500Ah needs to be added.

2 Switching Power Supply Configuration Estimation

The total capacity of the rectifier equipment should be determined by the sum of the load current and the balanced charging current of the battery. The calculation method is as follows:

I total = I negative + I storage

Itotal: switching power supply capacity, Inegative: communication load current, Istorage: battery charging current.

Among them, I storage = Q/T

Q: battery capacity, T: battery float charge time, generally 10 hours.

The minimum allowable discharge voltage of the battery pack is 43.2V, and I negative = total site power consumption/43.2, where the total site power consumption is the sum of the base station equipment power consumption and the transmission and monitoring equipment power consumption.

That is: I negative =

(1*300W+3*1100W+500W)/43.2V=96A

I storage = Q/T = 567/10 = 56.7 (A)

I total = I negative + I storage = 96 + 56.7 = 153 (A)

If the rectifier module is 50A, 4 rectifier modules are required.

3 Air conditioning configuration estimation

Total cooling capacity requirement = indoor equipment power consumption + 150W/m2 * room area

Among them, 150W/square meter is the heat load benchmark per unit area, and indoor equipment does not include outdoor AAU.

A simple calculation shows that the power consumption of indoor equipment = BBU power consumption + transmission and monitoring equipment power consumption = 350 + 500 = 850 (W).

Taking a computer room with an area of ​​15 square meters as an example, the total cooling capacity requirement of the computer room is 850+2250 (W), that is, 3100W.

Based on the calculation that 1P can generate 2.5KW of cooling capacity, an additional 1.5P air conditioner is required.

Normally, a 1P air conditioner consumes 735W of electrical power, so the power consumption of a newly added 1.5P air conditioner is 1.1KW.

4. Estimation of mains capacity

Mains power import capacity = (P communication equipment + P battery charging) / η + P air conditioning + P lighting + P other

Mains power supply capacity = (total equipment power consumption + battery charging power consumption) / η + air conditioning power consumption + other power consumption

Among them, η is the efficiency, and η is generally taken as 0.9. Other power consumption refers to the power consumption of lighting, etc., and in this example, the value is 500W.

Battery charging power consumption = battery capacity * 54 * 0.1 (equalizing current coefficient) = 500 * 54 * 0.1 = 2700W

Therefore, the mains power import capacity =

(4150+2700)/0.9+1100+500=9.2(KW)

From the above calculations, it can be seen that after adding a set of 5G equipment to the original site, capacity expansion needs to be considered from batteries, switching power supplies to external AC power supply.

Considering that the base station facilities are built uniformly by the tower company and shared by China Mobile, China Telecom and China Unicom, each site needs to add 2-3 sets of 5G equipment, and the corresponding capacity expansion demand doubles.