Dual Bus Modular (N+X) Solution Description:
The internet data center (IDC) and media data center (MDC) are the regulation and control centers of high-speed internet. They can make the remote processing, storage and transfer of "timeliness"for the information resources (data, voice and image information) which the requirements are ultra-high. Even if it is just a few seconds of the "stop" will bring the immeasurable losses for the safe operation of entire Internet and production operation of users. When it is serious that can cause the serious damage for the social and economic activities. Therefore, the IDC must provide the 365×24h continuous high-speed, safe and reliable information resource value added services. For this purpose, the whole supply system of IDC has to adopt the high "fault-tolerance" function of redundant power supplying solution from the design principle to ensure that whatever the main power electrical network or inverter of "double conversion online UPS" is on the failure and it is on the daily maintenance operation or the fuse is blown/the breaker is off the inverter of online type UPS will supply the power to the internet devices, it shouldn't supply the power though the AC bypass of UPS that connected with the main power emergency standby generator unit, because that is only the inverter of online UPS can supply the same voltage regulation, non- frequency "saltation", non-interference, minimum waveform distortion, high quality and sine power for the loads of users. For the off-line UPS and online interactive UPS, they mainly adjust the voltage of input supply and do not "substantively" improve the frequency jitter of input voltage, all kinds of supply interference and voltage distortion, that means there is no "bottleneck" fault risk in the whole power supplying system, so it must configure with the high "fault-tolerance"function of UPS redundant power supplying system, in other words when some "components" occasionally occur the fault in the operation of UPS power supplying system the whole UPS power supplying system must still be able to run.
It is compared with the traditional UPS the UPS configurations of dual bus modular (N+X) have the more advantages. In the construction of information network power supplying system of industrial users, they always wrongly estimate the capacity of high-end UPS to lead the too high purchasing costs for the result that cannot be satisfied with the loads' requirements or cause the resources, spaces and energy waste situations etc. The dual bus modular (N+X) can effectively resolve this problem through the extensible module structure, it can help the users to make the next-step UPS construction and investment in the future. When the requirement of using power loads of users is increasing we just need to add the power module piece by the using power planning stage, meanwhile, through the modular integration the expansibility requirement of system is able to be satisfied fully and also has the flexible mobility and better reliability which will be the milestone in the power supply protection fields. In addition, in the traditional high-ends UPS productions, there always exist the single point fault problem that UPS is easily occurred, in the past times the users choose the traditional "1+1"or "N+1" redundant system to make the security that not only increase the purchase, installation and maintenance costs but also can make the fault-tolerance once. In the dual bus modular (N+X) system, the each single parallel module is the Intelligent individual of internal redundancy that doesn't need the system controller to make the centralized control for the parallel operation system. After any module (including the system control module) occurred the fault, the redundant design will maximally achieve the fault redundancy. That means the users just need to purchase the relative power modules to achieve the "N+X"fault redundancy upgrading capacity expansion in the dual bus modular (N+X) system which can effectively resolve the UPS existed conditionality problem to let the users got the excellent expansibility. And also it can make the self distribution and assembly for the system in the necessary time and decrease the initial purchasing costs for the users.
According to the technological development level of present UPS industry, it is advisable to choose the "dual bus input" and "dual bus output" power supplying function of modular (N+X) UPS redundant power supplying system. It is composed of the following several parts of power supply system: 
1)Dual bus input power supplying system
The basic configurations of dual bus input power supplying are main power input supply + "auto-switching"control cabinet + input distribution cabinet. The auto-switching control system always monitors the real time operation status of all kinds of input supply that can ensure to send the one route of most reliable supply to the input of UPS. For some important IDC computer rooms, theirs "emergency generator" supply is actually a set of "multi-diesel generator + generator combining control cabinet"consisted of the redundant type of generator power supplying system. The users must highly pay attention to the"technology compatibility" and "switching parameter"correct settings between the all kinds of devices which we mention above those in the redundant power supplying system which can ensure the "N+1" type UPS redundant power supplying system is able to operate absolutely safe and reliable.
2)Dual bus output power distribution system
For eliminating the "single point bottleneck" fault risk between the input of UPS parallel operation system and the user sides, it is necessary to configure with the dual bus output distribution system, its basic configurations consist of the "N+1" type UPS redundant power supplying system (preferred, "1 +1" or "2 +1"-type parallel operation power supplying solution) + output distribution cabinet + load auto-switch (LTS) consisted of the UPS output distribution system. For some high requirement of places, it should configure with the load isochronous controller (LBS) + two sets of"N+1"type UPS redundant power supplying system consisted of the extreme high"fault-tolerance"function of power supplying system. According to the 30~50% of used servers and disk array machines and other productions in the IDC computer rooms which adopt the "dual-supply power supplying" system of productions, for these devices, we can directly connect the separate supply from the two sets of "N+1" parallel operation system with the two input ends of "dual-supply input device". For the key loads which have the "single supply input power supplying" mode, we will separately connect the supply heads of two sets of "N+1" type parallel operation system with the input ends of "load auto-switch" (commonly they are STS type of static switch and SS type of quick switch) and then to connect the key loads of users with the output ends of "load auto-switch".
Reliability Analysis of Dual bus Modular (N+X):
How to evaluate the executing duty reliability of UPS system, it not only has to consider the MTBF of UPS but also the MTTR of UPS and MTBF of main power. When the UPS is on the failure at the same time the main power also is broken down, the loads will lost the power that means the UPS key duty is loss. The loads are not on the protection of main power their time depends on the time of maintenance. If maintaining one UPS needs one week and the MTBF is also one week when the UPS is on the failure the loads will possibly lost the power. If the MTTR of UPS is one hour the MTBF of main power would not greatly affect the failure probability of key loads. It is apparently to reduce the MTTR of UPS that will decrease the failure probability of key loads, so the best way of reducing the MTTR of UPS that decreases the factors which can affect the maintenance of UPS as much as possible. Because the dual bus modular (N+X) has the hot plug-in function it is the best choice for the users.
From the view of design principle, the whole system which takes the power supplying mission must adopt the high "fault-tolerance"function of redundant power supplying program to ensure that when the electrical power network or any modules (including the system control modules) are on the failure and daily maintenance testing operations or the switch of breaker is off which is caused by the blown fuse the power supply of inverter of online UPS will supply the power for the devices of internet. It should not be on the AC bypass of UPS which the power is supplied by the standby electric generating set.         
As stated above, the dual bus modular (N+X) UPS which has the longest mean time to failure (λmission), minimum mean time to restoration (MTTR), most powerful anti-interference ability and high "fault-tolerance" function should use this set of program system to get the stable, high efficient, safe 24 hours UPS power support, it is the apotheosis of the most professional computer room power system and the most reliable power protection.
Chosen good “compatibility” UPS redundant power supplying
It is satisfied with the requirements of nobody or less people attended management and remote centralized monitoring for the IDC and MDC computer rooms to improve the "manageability"of UPS power supplying system. For the internet data center, except that it configures with the real-time monitoring network management system for its IT devices it should build up a set of "non-IT devices"centralized monitoring system to monitor and analyze the cooling equipments, power distribution cabinet, battery units, electric generating set, leakage alarm, security system and fire-fighting system and so on operation situations, for this point the chosen UPS redundant power supplying system should configure with the following communication interface.
1) Configured with the RS232/RS485 interfaces on the UPS, Modem or SNMP adapter;  
2) It is used to display the UPS's operation status and alarm information of "relay dry contact" type of output communication interface; 
3) "User-defined" input signal (door access, smoking, temperature, humidity etc. alarm signals) of "relay dry contact" type of input communication interface;   
4) Configured with the essential data collector for all kinds of "non-IT devices";
5) Configured with the relative centralized monitoring and management software package or communication protocols;     
Using the above input/output communication interfaces and relative power supply management software package or users'network centralized monitoring system to assemble the intelligentized IDC and MDC centralized monitoring system. In this network management system, we can achieve the main regulation and control functions have:     
1) Please read the UPS real-time operation parameters (such as: input/output voltage, current, frequency, active power/ apparent output, power factor, charge/discharge voltage, current of battery units etc. parameters) on the LED/LCD of UPS;
2) All kinds of :"operation events" of computer room environmental regulation and control devices in the "internet data center" (the occurred faults/alarm/executed operation information of users in time orders since the all kinds of devices start up); 
3) In case that the fault occurred, the system will execute the network broadcast alarm (pop-up the alarm windows), telephone/mobile phone auto-dialing/auto-papering or sending E-mail operations etc. it is handy to inform the staffs on duty to arrive the locations on time to exclude the problem and maintain;    
4) Making the "self testing" operation for the battery capacity of standby battery units of UPS. If the system finds the "fact capacity" is lower the system will automatically send the early-warning signal of "need to change the batteries";     
5) The"user-defined"alarm signals (door access, fire-fighting, temperature, humidity etc. alarm signals) will be integrated into the uniform centralized monitoring system of IDC computer rooms or intelligent buildings through the input communication interfaces.    
The operator will be designated by the IDC and MDC, according to the different authority levels, they are classified by the "readjustment" settings which are the operation parameters of relative devices or remote fault analysis and diagnosis.
Dual Bus Modular (2+2)simulated diagram: