Energy-saving technology for communication power supply

1 Introduction

"Energy conservation and emission reduction" has become one of the hottest topics in the communications field in recent years. Seminars for discussion and exchange on this topic are constantly held in the industry, and operators such as China Mobile have even set up special management offices for this purpose. Many operators use energy conservation as an important technical evaluation indicator in the centralized procurement of various products. In the centralized procurement of China Mobile and China Unicom, the functional requirements of "energy conservation and emission reduction" are clearly stated for the entire series of communications power products.

ZTE's power product line has been focusing on the energy-saving functions of communication power supplies and UPS products for two years. In terms of communication power supplies, customized versions have been developed for domestic and international operators. In the early stages of the development of modular UPS products, the corresponding energy-saving functions were also written into the development task book. With the realization of the energy-saving function of communication power products and the advent of the modular UPS product T080, the "breathing" power management of ZTE's power products has also come into being.

2 The significance of breathing power management

The efficiency of communication power supply and UPS can reach 90% under load conditions above 50%, and their own energy consumption is less than 10%. In absolute terms, the power consumption of this type of power conversion equipment is much less than that of main equipment and dynamic environment equipment such as air conditioners. However, when it comes to their own operation, it can be seen that since the maximum load, battery charging capacity and backup capacity are taken into consideration when designing the initial capacity of communication power supply and UPS, the actual operating load is often in a light load and ultra-light load state. In this state, the efficiency of the power conversion equipment is often low, thus increasing its own losses.

The "breathing" power management tracks the changes in load and controls the power module's opening and sleeping, so that the system can work as close to the optimal efficiency point as possible, and changes the power module's backup mode from hot backup to cold backup and semi-cold backup, reducing the number of modules running under light load and ultra-light load. For the entire power system, it reduces power usage, saves electricity bills, and improves the operator's TCO.

3 Benefit Calculation of Breathing Power Management

From the perspective of the communications room as a whole, the "breathing" power management only makes a difference in efficiency of less than 10%. However, for the power supply itself, the efficiency is increased from 85% under light load to a high efficiency of about 92%, and the power supply equipment itself saves nearly 50% of energy.

Taking the 200A configuration of the base station power supply as an example, if it is composed of four 50A rectifiers and the long-term workload does not exceed 40A, ZTE's "breathing" power management can save 3 to 4 degrees of electricity per day. The total power saving in a year is more than 1,000 degrees. Assuming the electricity price is 1 yuan/degree, such a site may save more than 1,000 yuan per year. The service life of the communication power supply is mostly about 10 years, that is, in the entire equipment life cycle, the energy saving cost is equivalent to more than 80% of the total price of the equipment. For medium-sized provinces with operators with 15,000 base stations in a single province, more than 15 million yuan in electricity bills can be saved each year.

4. Implementation Method of Breathing Power Management

There are three main methods to implement breathing power management:

(1) By following the load power to control the start and sleep of the power module, the system can operate in the optimal efficiency area, optimize efficiency and maximize energy saving. Taking the communication power supply as an example, its optimal efficiency range is between 50% and 80% load (see Figure 1). By tracking the optimal efficiency, long-term light load operation caused by turning on multiple modules can be avoided.

(2) To achieve deeper energy saving, the dormant power consumption of the power module needs to be further reduced. In the traditional soft shutdown mode, the dormant power consumption is about 15W to 20W, and the dormant power consumption of 3 to 4 modules also reaches 50W to 80W, accounting for a large proportion of the energy saving of the communication power supply. Therefore, ZTE's new generation of communication power supply reduces the dormant power consumption of the rectifier module to less than 5W, which is icing on the cake on the basis of the power module switch and further enhances the energy saving effect.

(3) Energy-saving breathing power management that meets the needs of different customers is achieved through changes in energy-saving modes. A control method that combines four modes: safety, energy-saving, peak-shifting, and freedom is adopted. Customers with different energy-saving function requirements can adopt different control modes for the renovation and construction of existing stations and new stations according to the existing network conditions, and combine power environment monitoring to achieve optimal control.

5. Software and hardware fault-tolerant design of breathing power management

As a basic network product, the reliability of power equipment is the first priority. Breathing power management is essentially the management of energy consumption through software control of hardware. To some extent, there is a certain reliability risk. Reliability must be ensured through fault-tolerant design of software and hardware. The main measures are as follows.

(1) The working and dormant power modules are switched regularly (see Figure 2) to ensure that the working time of different modules remains basically consistent, avoiding reliability risks caused by a few modules working for a long time while other modules are dormant for a long time.

(2) Control of the number of redundant backups of the power modules, through a combination of software calculation and manual menu definition, ensures both energy saving and the redundant backup modules meet on-site operation requirements.

(3) The control mechanism of “on first, then off” and “on first, then off” ensures the reliable operation of the load during rectifier switching.

(4) Targeted calculation and control mechanism for the number of power modules turned on and off under ultra-light load conditions to ensure operational reliability with few or no backup modules.

(5) Targeted control mechanism under conditions of AC mains failure, battery failure, power module and monitoring unit failure, ensuring stable and reliable operation of the system by giving priority to ensuring reliability and then considering energy saving.

6 Conclusion

A journey of a thousand miles begins with a single step. The implementation of energy conservation and emission reduction is only the first step to make China greener and China more beautiful. "Breathing power management" is only a small step forward in the energy conservation of communication power systems, and there is still a lot of work to be done. It requires the unremitting efforts of operators, equipment manufacturers, industry experts and all power practitioners to move towards the goal of a green communication future.