In current data center usage, direct parallel and 2N power supply schemes are the most common.

UPS, as the guardian of data center operations, plays a vital role in the design and selection of power supply systems for data centers. In current data center usage, direct parallel and 2N power supply schemes are the most common.

There are five common power supply methods in UPS applications: single-machine power supply scheme, hot backup series power supply scheme, direct parallel power supply scheme, modular parallel power supply scheme, and dual-bus (2N) power supply scheme.

1. Single-machine power supply scheme:

The single-machine power supply scheme is the simplest structure in UPS power supply schemes, where a single UPS output is directly connected to the load. This scheme is generally used in small networks, individual servers, office areas, etc. It consists of a UPS host and battery system, requiring no special distribution design or construction. It is quick to install, but its reliability is relatively low.

2. Hot backup series power supply scheme:

The series backup technology is an early, simple, and mature technology that has been widely used in various fields. In the series backup configuration, the backup UPS inverter output is directly connected to the bypass output of the main unit. In operation, if the main unit inverter fails, it quickly switches to the bypass, and the backup inverter supplies power to the load, ensuring uninterrupted power supply. The UPS in the series configuration must meet the following technical conditions: the inverter must maintain synchronization with the bypass when using online UPS power; the UPS must have dual inputs for rectifier and bypass; the UPS must withstand load jumps of 100%.

Advantages: Simple structure, convenient installation, and cost-effective for different companies and power ratings of UPS to be connected in series.

Disadvantages: Dangerous live operation required for non-interrupted load expansion, inconsistent aging status between the main and backup units leading to reduced backup unit battery life, and vulnerability of backup inverter to damage in case of load short circuit faults.

3. Direct parallel power supply scheme:

The direct parallel power supply scheme involves connecting multiple UPS units of the same model and power rating in parallel through a parallel cabinet, parallel module, or parallel board to share the load power. The basic principle is that under normal conditions, all UPS units have inverter output, load rating, and current. When one UPS unit fails, the remaining UPS units assume the entire load. The essence of parallel redundancy is load sharing among UPS units. The network configuration can be N+1 or M+N.

Advantages: Load power is shared among multiple UPS units, significantly improving reliability; convenient expansion compared to previous schemes; improved system lifespan and maintainability due to load sharing during normal operation.

Disadvantages: Load control is required; increased cost; single point of failure still exists on the output side of the parallel configuration.

4. Modular parallel power supply scheme:

The modular parallel scheme is essentially a solution to the direct parallel power supply scheme, but its specific implementation differs. The modular UPS includes racks, paralleled power modules, paralleled battery modules, and charging modules.

Features of the modular parallel power supply scheme:

- Consists of racks, UPS power modules, battery modules, and distribution systems.

- Power modules configured for N+1 redundancy, reducing maintenance time.

- Shared input, output, paralleled battery system, and control system.

Advantages: Dynamic scalability and zero maintenance time.

5. Dual-bus (2N) power supply scheme:

The 2N power supply scheme, also known as the dual-bus or dual-bus power supply system, has been widely used in medium to large-scale data centers to ensure reliable UPS power supply. It consists of two independent UPS systems, load bus synchronization tracking controller (LBS), one or multiple static transfer switch (STS) systems, input and output distribution panels.

Advantages: High reliability; allows online maintenance, expansion, and upgrade; resolves single-point failures in power supply circuits; improves system safety and fault tolerance.

Disadvantages: Higher construction cost.

When choosing a UPS power supply scheme, it is necessary to consider factors such as reliability, safety, scalability, maintainability, and cost-effectiveness, taking into account the specific requirements of the data center. Each scheme has its own advantages and disadvantages, and there is no absolute best solution. The selection and optimization should be based on the specific situation.