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Running Parallel UPS Configurations

Running two or more UPS in parallel adds redundancy or greater capacity. Consequently, there are two types of parallel configurations: parallel-redundancy and parallel capacity UPS. In any parallel UPS system, the key challenges are:

  • Controlling how each UPS ‘co-operates’ seamlessly as one unified system.

  • Synchronising the outputs of each UPS so it can flow into a shared output.

  • Balancing the load equally amongst all UPS in the configuration.

  • When a problem occurs, identifying the UPS with the problem and decommissioning it.

A parallel-redundant UPS system is where multiple modules are installed on the same system in what is termed an N+X arrangement with N representing the power capacity required by the connected loads and X representing number of modules of additional capacity. Parallel-redundancy allows for the failure of a single UPS module in the configuration to occur without the need for the protected load to be transferred to mains power. If this happens the other UPS modules, which will have spare capacity, can take over the total load.

The key advantages of a parallel-redundant UPS system are that it offers a much higher level of availability than parallel-capacity systems due to the extra ‘reserve’ capacity within each UPS module. This capacity can be utilised if a UPS malfunctions or needs to be removed from service for maintenance. The system is also less likely to fail than other parallel configurations because there are fewer breakers and no step loads with modules constantly. It is also scalable when the power requirement grows. Such a hardware arrangement is simple and cost-effective.

A parallel-capacity UPS system is created by connecting multiple UPS modules in parallel but without allowing extra capacity for redundancy. This means each UPS is operating at full capacity. This configuration will not increase the overall system’s resilience; however, it does optimise system efficiency because each UPS is operating at full capacity. The system does, however, provide power availability over and above what it would be through mains power alone. Parallel-capacity UPS systems normally have a by-pass to mains. If one module in the system breaks down, the others will be unable to accommodate the additional load therefore it will be switched to by-pass and thus to mains, which is an unprotected power source.

Control of parallel UPS is normally managed using a master slave arrangement whereby a master controller acts as the brains of the system and determines operating parameters: how UPS modules synchronise their outputs, how they share loads and where their control information comes from. It does, however, require a mess of control wiring between UPS modules.

Huawei’s next generation 2000G series modular UPS utilises an advanced peer-to-peer control system architecture. This works in a similar way to peer-to-peer computing, with each UPS assessing its own operating parameters and determining how to interface with the others. There is no need for an external master controller or inter-module control wiring. The installation and commissioning of the Huawei UPS 2000G for parallel-redundant operation is simple, flexible and fast. Up to 4 UPS modules may connected in parallel with automatic synchronization of parallel parameters and no need to set parallel addresses. One communication card can monitor the whole parallel system, significantly reducing TCO.

With the optional SNMP card fitted combined with the Huawei NetEco intelligent power system the UPS 2000G series enables online real-time monitoring with dynamic visual layouts of run states and UPS operation, delayed shut down and graceful safe shutdown of applications plus operating system multi-mode alarm notifications, such as apps, email and SMS.

Huawei’s 2000G UPS series delivers these advanced features which can significantly reduce TCO and are not commonly available at the 1-20 kVA UPS market level. Huawei’s and CertaOne’s pricing policy to support local market development could contribute to significantly lower data centre project costs. For more details please contact CertaOne on 1300 856 757.