PV grid-connected cabinet manufacturer interprets UPS power supply and distribution system
The UPS power supply and distribution system can be powered by a single unit or in a redundant manner. Redundant power supply can still meet the power demand in the equipment room when a few equipments fail, which cannot be achieved by single-unit power supply. From the perspective of redundant configuration schemes, there are several ways: (1) host-slave model "hot backup" UPS power supply mode; (2) direct parallel redundant UPS power supply mode; (3) dual bus redundancy Power supply.
(1) Host-slave type "hot backup" UPS power supply mode host with load, standby machine no-load, standby machine access to the host's BYPASS (bypass) input. This way is more flexible, does not require two UPS brands, and does not add additional auxiliary circuits, does not increase the cost of acquisition. However, the two UPSs have different degrees of aging in this power supply mode, and the battery pack of the standby machine is in a floating state for a long time, which affects the battery life. This structure has many single points of failure. If the primary UPS fails, the other must take over the entire load. This means that within about 8ms, the other must increase the power supply from 0 to 100%. The drawback of this method is that the standby UPS is in a no-load state for a long time, its battery life will be shortened, the capacity will be reduced, and the backup UPS will be It has step load carrying capacity and no capacity expansion. Since it is difficult for people to know in real time whether there are any faults or hidden dangers in the spare parts of the standby UPS, when the standby machine is to be started, it may not work properly.
(2) Direct parallel redundant UPS power supply mode To overcome the weakness of the host-slave "hot backup" power supply system, with the advancement of UPS control technology, UPSs with the same rated output power can be directly connected in parallel to form redundant power supply. system. In order to ensure a high-quality parallel system, each power supply must be kept at the same frequency, in phase, and the machines are evenly distributed. This power supply mode has a strong instantaneous overload capability and can automatically divide the power. However, there is a circulation, which increases reactive power loss and reduces system reliability. Additional auxiliary circuits need to be added, which in turn increases costs and increases the point of failure.
(3) Dual bus redundant power supply mode The dual bus power supply mode uses two buses to supply power to the backend devices, and each bus has the same set of UPS power supply modes. Eliminate the “single point bottleneck” fault that may occur between the UPS output and the end user load to improve the “fault tolerance” function of the output power supply system. This power supply mode can be online maintenance, online expansion, online upgrade, improve the availability of important buses, meet the needs of dual power consumers, and truly achieve the goal of 7 × 24 × 365 operation. However, the dual-bus redundant power supply mode is equivalent to the construction of two sets of the above-mentioned power supply circuit, which requires more than two times the cost.
In addition, the UPS output power distribution uses a separate loop for each individual cabinet (one open loop controls one loop), and uses a socket or industrial connector to power the individual cabinets; for important equipment, it needs to provide two independent power supplies, which need to be from two A separate UPS for output distribution. The UPS power supply is sent to the cabinets of the machine room separately for safety, reliability, convenience and daily maintenance. If the room is subdivided into different rooms or spaces, each room or space is supported by their separate emergency power switches (EPOs), then these spaces should have their own independent horizontal distribution.