Research On Operation Control Strategy Of Super-UPS Based On Distributed Coordination

Uninterruptible power supply(UPS)is widely used in data centers,hospitals,financial institutions and other applications that have higher requirements for power quality and power continuity.As the demand for high-quality UPS continues to increase,the rated power of UPS also continues to increase.Traditional UPS usually uses lead-acid batteries as shortterm devices and diesel engines as long-term backup devices.Due to the short mean time between failures of lead-acid batteries and diesel engines,the reliability of traditional UPS is relatively low,the operation and maintenance costs are high,and the environmental pollution is severe.Therefore,this paper mainly takes super-UPS including photovoltaic cells,multiple energy storage units and loads as the research object,and proposes a distributed cooperative operation control strategy based on multi-agent.First of all,this article introduces the current status of domestic and international development of traditional UPS systems,as well as problems and challenges encountered,outlines the control methods used in this subject,and analyzes the existing problems in the research of this subject.Secondly,it analyzes in detail the typical topological structure of super-UPS system and the constituent principles of each part,including photovoltaic power generation system,energy storage system and grid-connected system.The two micro-power sources are mathematically modeled respectively,and corresponding simulation models are established.The topology structure,working principle and parameter design method of each interface circuit are described.Then,according to the different DC bus voltage sources in the super-UPS system,this paper divides the super-UPS system into two types of operation modes: grid-connected and isolated islands,and designs the switching between different working states of the large power grid,photovoltaic cells,energy storage and loads.The mechanism enables each node to realize the conversion between the various operating modes of the system through local control,ensuring the power balance between micro power,energy storage and load.Finally,in order to enable multiple energy storage systems to maintain the bus voltage stability while realizing current distribution among energy storage units,that is,each energy storage unit adjusts its output current in real time according to the bus voltage,its own SoC,and its installed capacity.While making the bus voltage stable,each energy storage unit SoC tends to always.In addition,in order to improve the control effect of the primary current controller,this paper improves the model-free intelligent PI controller,adds a differential tracker to reduce the output differential term jitter,and improves the current quality of the primary current control.The distributed cooperative control strategy proposed in this paper not only achieves the coordinated control of the bus voltage by the micro power sources in the super-UPS system,maintains the power balance of the system,but also solves the differences in the initial SoC and installed capacity among the units in the energy storage system.The resulting imbalance of energy storage,and a corresponding solution to the problem of attenuation of the installed capacity of the energy storage unit is also designed,which is conducive to plug-and-play of the micro power supply.Finally,a simulation model is built based on Matlab / Simulink platform,and the distributed collaborative control strategy of this paper is simulated and verified.The effect is good and meets expectations.