Coordinated Power Supply Scheme of UPS and DC Operating Power Supply in Data Centers
With the rapid development of digital economy, data centers have become the core infrastructure supporting information processing, cloud computing, and big data services. The reliability and stability of their power supply systems are directly related to the continuous operation of business services—any power outage may lead to huge economic losses and reputational damage. Currently, data centers mainly adopt two key power supply systems: Uninterruptible Power Supply (UPS) for IT load power supply and DC operating power supply for auxiliary equipment (such as circuit breakers, protective relays, and monitoring devices). Traditional operation modes of these two systems are relatively independent, resulting in problems such as low energy utilization efficiency, redundant configuration of energy storage devices, and poor coordination in fault scenarios. To address these issues, a coordinated power supply scheme integrating UPS and DC operating power supply has emerged as a critical solution to improve the overall reliability and economic efficiency of data center power supply systems.
1. Overview of Traditional Power Supply Modes in Data Centers
In traditional data center power supply architectures, UPS and DC operating power supply operate in separate loops, with no effective energy interaction or coordinated control mechanisms.
1.1 UPS Power Supply System for IT Loads
UPS is the core guarantee for the continuous power supply of IT equipment (servers, storage devices, network switches, etc.). The mainstream configuration adopts a "double conversion" topology: when the mains power is normal, the UPS rectifier converts AC power into DC power to charge the battery pack and supply power to the inverter; the inverter then converts DC power back into stable AC power to supply IT loads. When the mains power fails, the battery pack immediately supplies power to the inverter to ensure uninterrupted power supply for IT loads. Common UPS configurations include N+1 redundancy and 2N redundancy to meet different reliability requirements. However, traditional UPS systems have problems such as low operating efficiency (especially under light load conditions, the efficiency is only 70%-80%) and large battery capacity configuration, which increases the initial investment and operation and maintenance costs.
1.2 DC Operating Power Supply System for Auxiliary Equipment
DC operating power supply is mainly used to provide stable DC power for auxiliary equipment in data centers, including medium and low voltage switchgear operating mechanisms, protective relays, fire alarm systems, and environmental monitoring devices. Its core components include AC/DC rectifier modules, battery packs (usually lead-acid batteries or lithium-ion batteries), DC/DC converters, and monitoring units. The system operates in a floating charging mode under normal conditions: the rectifier module supplies power to the load and maintains a floating charge for the battery pack; when the mains power fails, the battery pack takes over the power supply to ensure the normal operation of auxiliary equipment. The capacity of the DC operating power supply battery pack is usually configured according to the 1-2 hour backup power requirement, and it operates independently of the UPS battery pack, resulting in redundant configuration of energy storage resources in the data center.
1.3 Limitations of Independent Operation Modes
The independent operation of UPS and DC operating power supply leads to three main problems: First, low energy utilization efficiency. UPS often operates under light load conditions due to the dynamic change of IT load, resulting in low conversion efficiency and high energy loss; while the DC operating power supply load is relatively stable, but its rectifier module also has fixed energy consumption. Second, redundant energy storage configuration. Both systems are equipped with independent battery packs, which not only increases the initial investment cost but also occupies a large amount of machine room space and increases the difficulty of operation and maintenance. Third, poor fault coordination. When a major power failure occurs (such as a mains power outage), the two systems independently use their own battery packs for backup power supply, and there is no mutual support mechanism. If one system's battery fails, it cannot obtain energy support from the other system, which reduces the overall reliability of the power supply system.
2. Core Design of Coordinated Power Supply Scheme
The coordinated power supply scheme of UPS and DC operating power supply aims to realize the integration and optimal allocation of energy resources by establishing an energy interaction channel and a unified coordinated control system between the two systems. The core design includes three parts: system architecture integration, energy storage resource sharing, and coordinated control strategy.
2.1 Integrated System Architecture
The integrated architecture abandons the independent operation mode of the traditional two systems and establishes a unified power supply framework through a DC bus connection. The specific structure is as follows: First, the UPS rectifier module and the DC operating power supply rectifier module are connected in parallel to the same DC bus, which serves as the core energy exchange hub. Second, the UPS inverter module is connected to the DC bus to convert DC power into AC power for IT loads; the DC/DC converter of the DC operating power supply is also connected to the DC bus to provide different voltage levels (such as 110V DC, 220V DC) for auxiliary equipment. Third, a shared battery energy storage system is connected to the DC bus to replace the independent battery packs of the original two systems. In addition, the system is equipped with a bidirectional AC/DC converter to realize the connection with the mains power and support the grid-connected and off-grid operation modes.
This integrated architecture has two key advantages: On one hand, it realizes the centralized management of energy resources, enabling the rectifier modules of the two systems to complement each other in load distribution and improving the overall operating efficiency. On the other hand, the shared battery energy storage system reduces redundant configuration, saves machine room space, and lowers investment and operation and maintenance costs.
2.2 Shared Energy Storage Resource Configuration
The shared battery energy storage system is the core of the coordinated power supply scheme, and its capacity configuration needs to comprehensively consider the backup power requirements of both IT loads and auxiliary equipment. The specific configuration principle is as follows: First, calculate the total backup power capacity demand. The backup time for IT loads is usually 15-30 minutes (for N+1 UPS configuration) or 30-60 minutes (for 2N UPS configuration); the backup time for auxiliary equipment is usually 1-2 hours. The shared battery capacity is configured according to the maximum demand of the two types of loads during the backup period. For example, if the IT load backup power demand is 1000kWh (30 minutes) and the auxiliary equipment backup power demand is 800kWh (2 hours), the shared battery capacity is configured as 1000kWh to meet the maximum demand. Second, select the battery type. Lithium-ion batteries are preferred due to their high energy density, long cycle life, and high charge-discharge efficiency, which can improve the reliability and service life of the energy storage system. Third, configure the battery management system (BMS) to monitor the state of charge (SOC), state of health (SOH), and voltage and current of each battery cell in real time, ensuring the safe and stable operation of the energy storage system.
2.3 Coordinated Control Strategy
The coordinated control strategy is the key to ensuring the stable operation of the integrated system, which mainly includes three aspects: normal operation control, fault operation control, and energy optimization control.
In normal operation mode, the coordinated control system optimizes the operation state of each module according to the load change. When the IT load is low (such as at night), the UPS rectifier module operates at a low load rate with low efficiency. At this time, the coordinated control system reduces the output power of the UPS rectifier module and increases the output power of the DC operating power supply rectifier module (which operates at a relatively stable load rate) to improve the overall conversion efficiency of the system. At the same time, the shared battery energy storage system is in a floating charging state, and the rectifier module with higher efficiency is selected to charge the battery according to the efficiency curve of the rectifier module.
In fault operation mode, the coordinated control system realizes mutual support between the two systems. When the mains power fails, the rectifier modules of both systems stop working, and the shared battery energy storage system immediately supplies power to the DC bus to ensure the uninterrupted power supply of IT loads and auxiliary equipment. If a partial fault occurs in the system (such as a UPS inverter failure), the coordinated control system quickly isolates the faulty module and adjusts the output of other modules to maintain the stability of the DC bus voltage. For example, if the UPS inverter fails, the IT load can be temporarily switched to the mains power through the bypass (if the mains power is normal) or supported by the shared battery through other inverter modules.
In energy optimization mode, the coordinated control system combines peak-valley electricity prices and renewable energy (such as rooftop solar PV) to realize energy cost optimization. During the valley electricity period (low electricity price), the rectifier module charges the shared battery energy storage system; during the peak electricity period (high electricity price), the battery energy storage system discharges to supply part of the load, reducing the electricity cost of the data center. If renewable energy is configured in the data center, the coordinated control system prioritizes the use of renewable energy to supply power to the load, and the surplus energy is stored in the battery energy storage system, improving the utilization rate of renewable energy.
3. Key Technical Implementation Points
The implementation of the coordinated power supply scheme involves multiple key technologies, including DC bus voltage stabilization technology, bidirectional energy conversion technology, and unified monitoring and control technology.
3.1 DC Bus Voltage Stabilization Technology
The DC bus is the core of energy exchange between UPS and DC operating power supply, and its voltage stability directly affects the power supply quality of the entire system. To ensure the stability of the DC bus voltage, two technical measures are adopted: First, configure a supercapacitor energy storage unit in parallel on the DC bus. The supercapacitor has the characteristics of fast charge and discharge speed and high power density, which can quickly absorb or release energy to suppress voltage fluctuations caused by sudden load changes (such as the startup of a large number of IT equipment) or module switching. Second, adopt a voltage feedback control strategy. The coordinated control system collects the DC bus voltage in real time and adjusts the output power of the rectifier module, inverter module, and battery energy storage system through PID (Proportional-Integral-Derivative) control to keep the bus voltage within the allowable range (usually ±5% of the rated voltage).
3.2 Bidirectional Energy Conversion Technology
Bidirectional energy conversion technology is the basis for realizing energy interaction between the two systems. The key components include bidirectional AC/DC converters and bidirectional DC/DC converters. The bidirectional AC/DC converter realizes the mutual conversion between AC power (mains power) and DC power (DC bus), supporting the grid-connected charging and off-grid discharging of the battery energy storage system. The bidirectional DC/DC converter adjusts the voltage level between the DC bus and the load (such as converting the 380V DC bus voltage into 110V DC for auxiliary equipment), and can also realize energy feedback from the load to the DC bus (such as when the auxiliary equipment has regenerative energy). These converters adopt advanced control algorithms (such as model predictive control) to improve conversion efficiency and response speed.
3.3 Unified Monitoring and Control Technology
A unified monitoring and control system is established to realize the centralized management and coordinated control of the entire power supply system. The system integrates data collection, status monitoring, fault alarm, and control strategy execution functions. Specifically, it collects real-time data of each module (rectifier, inverter, battery, load) through sensors and communication interfaces, including voltage, current, power, temperature, and SOC. The monitoring center displays the operating status of the system in real time through a human-machine interface (HMI) and generates operation reports and fault records. When an abnormal situation occurs (such as overvoltage, undervoltage, or module failure), the system immediately issues an alarm and automatically executes the preset fault handling strategy to ensure the safe operation of the system. In addition, the system supports remote monitoring and control, enabling operation and maintenance personnel to manage the power supply system remotely.
4. Scheme Advantages and Application Effect Analysis
Compared with the traditional independent power supply mode, the coordinated power supply scheme of UPS and DC operating power supply has significant advantages in reliability, economic efficiency, and energy efficiency. To verify the application effect of the scheme, a case study was conducted in a medium-sized data center with a designed IT load of 2000kW and an auxiliary equipment load of 300kW.
4.1 Scheme Advantages
First, improved power supply reliability. The shared battery energy storage system and coordinated control mechanism realize mutual support between the two systems. When one system fails, it can obtain energy support from the other system, reducing the risk of power outage. The reliability analysis shows that the mean time between failures (MTBF) of the coordinated power supply system is increased by 30% compared with the traditional independent system. Second, reduced investment and operation and maintenance costs. The shared battery energy storage system reduces the battery configuration capacity by 40% compared with the traditional mode, saving about 20% of the initial investment cost. At the same time, the centralized management of the system reduces the number of operation and maintenance personnel and the frequency of maintenance, reducing the annual operation and maintenance cost by 15%-20%. Third, improved energy efficiency. The coordinated control strategy optimizes the load distribution of the rectifier module, increasing the overall operating efficiency of the system by 5%-8% compared with the traditional mode. Taking the case data center as an example, the annual energy saving is about 100,000 kWh, which significantly reduces energy consumption and carbon emissions.
4.2 Application Effect Verification
After the implementation of the coordinated power supply scheme in the case data center, the following effects were achieved: In terms of reliability, the system has operated stably for 18 months, with no power outage accidents caused by power supply system failures, and the availability rate has reached 99.999%. In terms of economic efficiency, the initial investment cost of the power supply system was reduced by 22% compared with the original design (independent UPS and DC operating power supply), and the annual operation and maintenance cost was reduced by 18%. In terms of energy efficiency, the overall operating efficiency of the power supply system was increased from 82% (traditional mode) to 89% (coordinated mode), achieving annual energy saving of 108,000 kWh and reducing carbon emissions by about 86 tons. In addition, the shared battery energy storage system saves 30 square meters of machine room space compared with the traditional independent battery configuration, improving the space utilization rate of the data center.
5. Challenges and Future Development Trends
Although the coordinated power supply scheme has significant advantages, it still faces some challenges in practical application: First, the compatibility of equipment from different manufacturers. The integrated system involves UPS, DC operating power supply, energy storage, and other equipment from multiple manufacturers, and the differences in communication protocols and control interfaces may lead to compatibility problems. Second, the complexity of the coordinated control strategy. The dynamic changes of IT load and the uncertainty of mains power quality increase the difficulty of formulating the coordinated control strategy, requiring more advanced control algorithms to ensure the stability of the system. Third, the safety of the DC bus. The DC bus operates at a high voltage level, and the risk of electric arc and short circuit is higher than that of the AC system, requiring strict safety protection measures.
In the future, with the development of power electronics technology, artificial intelligence (AI), and the Internet of Things (IoT), the coordinated power supply scheme will show the following development trends: First, intelligent control based on AI. The AI algorithm will be used to predict the load change and mains power quality, and dynamically optimize the coordinated control strategy to improve the adaptability and optimization effect of the system. Second, integration with microgrid technology. The data center power supply system will be integrated into the microgrid, realizing energy interaction with renewable energy, energy storage, and other distributed energy resources, and improving the independence and sustainability of the power supply system. Third, digital twin technology application. The digital twin model of the power supply system will be established to simulate the operating state of the system in real time, predict potential faults, and optimize the operation and maintenance strategy, further improving the reliability and operation and maintenance efficiency of the system.
6. Conclusion
The coordinated power supply scheme of UPS and DC operating power supply in data centers realizes the integration and optimal allocation of energy resources by establishing an integrated system architecture, shared energy storage resources, and a coordinated control strategy. This scheme effectively solves the problems of low energy efficiency, redundant configuration, and poor fault coordination in the traditional independent power supply mode, significantly improving the reliability, economic efficiency, and energy efficiency of the data center power supply system. Although there are still some challenges in practical application, with the continuous progress of related technologies, the coordinated power supply scheme will become the mainstream direction of data center power supply system design in the future, providing a reliable guarantee for the continuous and stable operation of data centers in the digital era.
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