The Design Of High Precision Anti Isolating-island Protector With Reliable Isolation

With the rapid development of China's photovoltaic industry,distributed photovoltaic power stations have been widely developed in China.The installed capacity of the distributed photovoltaic power generation facility is small,and the construction is flexible and simple.It has attracted much attention in the household photovoltaic and industrial and commercial photovoltaic systems.Distributed PV systems may also give security and personal safety and security,especially in the power loss of pressure distributed photovoltaic power plants may be caused by the island effect and position near the outlets personnel shock or electrical damage,sometimes may damage the islanding of photovoltaic power generation facilities.Islanding effect means that when the power grid suddenly loses pressure,the grid connected photovoltaic power system still maintains an effect on the power supply state of the adjacent parts of the power grid.When the island effect occurs,there will be an unusual charge near the dot,which poses a threat to the personnel and facilities.To prevent the island effect mechanism is the most effective introduction of anti islanding protection measures in photovoltaic power generation system,China's current commercial general inverter with island protection function,but there are still potential danger in the island under the condition of the corresponding function inverter fault.The use of the anti isolated island protector is an effective means to further improve the protection capability of the photovoltaic grid connected facilities.This paper describes a design scheme of the anti islanding protector.The plan uses the isolation coupling device and integrated waveform chip to complete the power grid information collection,and further determines the data and finally drives off the grid connected by the microcontroller.The design scheme described in this paper includes hardware circuit,microcontroller program,shell,auxiliary PC software program and so on,covering all the main contents of the design of anti islanding protector.This design uses ARM-Cortex M3 microcontroller in the specific implementation,the internal integration of high-speed CPU,ADC module,general IO timer and other resources,with conditioning rms converter and Schmidt trigger circuit,formed a set of simple and effective network measurement system,the circuit has simple structure and low cost.Has a strong practical significance.A high integration,high precision true value converter chip and a Schmidt trigger chip are used in the design of voltage acquisition and frequency acquisition circuits.The anti islanding protection device designed in this paper has reliable high voltage isolation.It can realize grid voltage loss detection and PV facility off grid control while taking account of the detection accuracy and equipment safety of the anti islanding facility.The isolation at the same time satisfies three aspects,which are system power supply,incoming signal of power grid and control signal,which makes the low voltage measurement and control circuit of the anti islanding device completely isolated from high-voltage power grid.The mature transformer,voltage transformer and relay are used in isolation,which has good reliability.At the time of design,all technical problems have been added to the feasibility of production and practical use.The design of the circuit board uses double PCB,which is SMT process components except the edge connector,so it has very low cost and good machinability.The equipment shell is designed with a simple sheet metal scheme,which is low in cost and simple in processing.In the software and hardware planning of the main body,a variety of conditions of 220 V single or 380 V three-phase power grid are also considered.The overall solution of this design and the technology in it can be applied directly to the practice of photovoltaic grid connected.