A large number of modern electrical equipment and devices are used in the data center industry, such as credit card terminal equipment, communication systems, computers, network control equipment, various digital office equipment, lighting control systems, fire protection systems, monitoring systems, etc. A large number of nonlinear power loads bring serious harmonic interference to the power supply system. The harsh harmonic environment poses a great threat to ensure the safe and normal operation of the system and equipment, such as: program operation errors, data errors, time errors, crashes, unexplained restarts, and even damage to electrical equipment, causing irreparable losses to large-scale work. Therefore, the harmonic governance of data centers has attracted more and more attention.

Data center load analysis

Harmonic currents in data center industry equipment are caused by rectifier input circuits for various types of power electronics. Because the impedance of the rectifier circuit at the input end of various power electronic equipment is not a fixed value, its impedance changes with the change of the applied voltage, which causes the current drawn by the rectifier from the grid to be not a sine wave current. Among them, the main rectifier equipment is as follows:

1. Frequency conversion equipment

The data center industry uses a large number of frequency conversion energy-saving equipment, such as: frequency conversion air conditioners, frequency conversion elevators, frequency conversion pumps, etc. The internal work of frequency conversion equipment is basically rectification and inverter process, so harmonics will be generated. The types of harmonics produced are related to the number of rectifier pulses, which are 5th, 7th, 11th and 13th.

2. UPS power supply

Data centers have high requirements for the power supply stability of important computer rooms, so UPS uninterruptible power supplies are often used. The working principle of UPS power supply is similar to that of frequency conversion equipment, so the way and type of harmonics are also similar. Generally speaking, a 6-pulse UPS mainly produces 5 and 7th harmonics, and a 12-pulse UPS mainly produces 11th and 13th harmonics.

3. Lighting

The energy-saving lamp electronic ballast converts the 50Hz power supply into a high frequency of about 38kHz, so it reduces the flicker of the electric lamp to a level that cannot be felt. When the high-frequency electronic ballast operates, harmonics are generated because the current waveform is not a sine wave due to nonlinear loading. In general, energy-saving lamps mainly produce 3rd harmonics.

Data center harmonic characteristics

Harmonics in the power supply system can be divided into grid-side harmonics and load-side harmonics.

1. Grid-side harmonics

Also known as low-frequency harmonics, usually refers to harmonics below 40 degrees, especially represented by harmonics such as 3, 5, 7, and 9, which mainly cause harm to the power supply system, causing the power supply efficiency of the power grid to decrease, and the capacitor heats up or even burns.

2. Load side harmonics

Also known as high-frequency harmonics, usually refers to harmonics of more than 40 degrees, the frequency is usually above 2kHz, mainly harmful to electrical equipment, resulting in reduced work quality, crash, damage, life decline, etc.

The harmonics of large data centers have their own characteristics:

• There are concentrated harmonic sources, and the distribution of harmonics is dense;
• There are many equipment at the lower end of UPS, there are many large data rooms, and the distribution of computer equipment is very wide, which requires harmonic control;
• The harmonic distortion rate is very high, generally as high as 40%~50%, which is much higher than the national standard.

Data center power quality problem hazards

1. Energy saving and loss problem

Inverterized HVDC, UPS, inverter, switching power supply, etc. produce a large number of capacitive reactive power and harmonics, and reactive current and harmonic current increase the loss of lines and transformers, about 5% of electricity consumption;

2. The impact on the life of electrical equipment

Reactive current and harmonic current accelerate insulation aging, shorten the life of equipment (transformers, cables, motors, etc.), and are expected to be reduced by 3~6 years;

3. Harm to the stability of equipment operation

Harmonic currents cause distortion of sampled data (voltage, current, output control signals, etc.), causing the protection or control system to malfunction or rejection, increasing the probability of data center equipment failure, thereby causing system operation interruption and causing greater economic losses;

4. Electricity safety issues

Harmonic currents cause power grid resonance, cause safety hazards such as neutral lines, and may cause accidents such as fire and even explosion;

5. Power supply voltage stability problem

According to the statistics of the 2021 Data Center Quality Development Conference Report, almost 90% of the voltage sagg/power supply interruption in the data center power supply system directly or indirectly comes from power distribution equipment failures, and most of the power distribution equipment failures are caused by power quality problems.

Power quality problems such as harmonics, reactive power, and voltage sag have become key factors restricting the reliability of data centers.

Solution

The existence of power quality problems has brought serious harm to data centers, for this reason, Bowo provides a complete set of solutions, as follows:

User value of harmonic governance

1. Reduce the influence of harmonics, avoid various faults such as voltage amplification caused by harmonics damaging electrical equipment, improve power supply security, and ensure data security;

2. Control harmonics, reduce the harmonic current of the injection system, and meet the requirements of national standards;

3. Dynamic compensation of reactive power, power factor up to standard, avoid fines from power supply companies;

4. Eliminate the safety hazards caused by transformer heating, power supply cable heating and ampacity drop and voltage waveform distortion caused by harmonics of UPS and other electronic products;

5. Improve the energy consumption of equipment such as air conditioning in the computer room, improve the power factor of the system, and achieve the purpose of energy saving and consumption reduction.

Application case

1. Application of BW-APF in Baidu data center

2. Application of BW-APF in Unitech data center