Which is better for PV grid connected and photovoltaic off g

Source : 未知      Time : 2018-05-21 14:53

The off net power generation system consists of solar panels, batteries, charge and discharge controllers and off grid inverters. The solar power controller (PV controller and wind PV controller) regulates and controls the power of the generator. On the one hand, the adjusted energy is sent to the DC load or the AC load, on the other hand, the energy is much more. The remaining energy is sent to the battery store, and when the power is not able to meet the load needs, the controller sends the battery's electrical energy to the load. When the battery is full of electricity, the controller must control the battery from being overcharged. When the electrical energy stored in the battery is discharged, the controller must control the battery not to be discharged and protect the battery.


Grid connected power generation system


Grid connected power generation system is a power generation system that generates renewable energy generated by photovoltaic arrays, wind turbines and fuel cells without storage of storage battery and directly invert into power grid through grid connected inverters. Because the electricity can be input directly into the power grid, the storage battery is eliminated, the storage and release process of the battery is eliminated, and the power produced by the renewable energy can be fully utilized to reduce the energy loss and reduce the system cost. Grid connected power generation system can use power supply and renewable energy in parallel as local AC load power supply, and reduce the load and power failure rate of the whole system. At the same time, the renewable energy grid connected system can play a peaking role on the public power grid. Grid connected power generation system is the development direction of solar energy and wind power generation, representing the most attractive energy utilization technology in twenty-first Century.


In the photovoltaic off grid system and photovoltaic grid connected system, we compare the following aspects:


First, the cost problem:


In the system, the battery and solar charge and discharge controller should be used to increase the cost. The price quoted in the PV system is more than 1.5 times that of the solar grid system.


The service life of the battery is generally about 5 years (with the different depth of charge and discharge, the life of the battery is different. Under the condition of daily charge and discharge, the battery life is generally not more than 3-5 years). This is a great investment in the replacement of the battery, and it also needs to be maintained regularly, and the workload is increased.


Two. The problem of efficiency:


(1) efficiency of PV isolation system


1, battery pack: Tianwei Yingli YL180 (35) 1580x808


Component parameters:


Component type: polysilicon photovoltaic module


Peak power: 180W;


Peak voltage: 35.5V; open circuit voltage: 44.0V;


Peak current: 5.07A; short circuit current: 5.45A;


Module size: 1580mm * 808mm * 50mm module efficiency: 14.1%


2, solar controller: ideal efficiency 90%;


3, the battery uses special photovoltaic gel batteries, 12 volts series of colloidal batteries; in ideal cases, the efficiency is 85%.


4. Independent system inverter, the maximum efficiency is 90%.


The highest efficiency of the whole system is =0.141 * 0.9 x 0.85 x 0.9 x 100%=9.7% (ideally).


5. After the battery of the independent system is filled with electricity, the power of the battery board will be wasted, which can not only save energy, but also reduce the actual operating efficiency of the system.


(two) efficiency of PV grid connected network system


1, battery pack: Tianwei Yingli YL180 (35) 1580x808


Component parameters:


Component type: polysilicon photovoltaic module


Peak power: 180W;


Peak voltage: 35.5V; open circuit voltage: 44.0V;


Peak current: 5.07A; short circuit current: 5.45A;


Module size: 1580mm * 808mm * 50mm module efficiency: 14.1%


2, the maximum efficiency of PV grid connected inverter can reach 97%.


In the grid connected system, solar controllers and batteries are omitted, and the efficiency of their losses is not considered.


The efficiency of the whole system is =0.141 * 0.97 * 100%=13.677% (ideally).


Three. The problem of reliability:


1, the equipment used in the grid system is designed according to the normal work for 25 years, and the design life of the equipment in the system is generally 8-10 years, even in the short running time, the reliability is also different.


2. There are more components in the off grid system, the corresponding increase in the fault point, and the reliability is reduced, and the performance of the battery will decrease with the use.


3. Although the system can improve the reliability of the system in the weather of rain or failure, the impact of the system on the load and the equipment itself is also an important cause of the system failure.


4. The grid connected PV system does not have any energy storage and switching units. The power is automatically allocated by the system, and the equipment is always automatically regulated and operated under the best working condition. The performance is stable and the reliability is high.


Three. Monitoring problems:


In order to monitor the state and efficiency of the system, a DC meter is connected to the DC output end of the solar cell array and an AC meter is connected to the output end of the inverter. The monitoring software is compiled to monitor the DC and AC tables, because the frequency of the ammeter is relatively high and is not well achieved in the software writing. So high frequency, meter box display system accuracy is also different, display data will be different from the data displayed by the meter, so the monitoring and display software is a gross estimation.


The grid connected inverter itself integrates the RS-485 and Ethernet communication interface, and transfers data to the computer by 485/232 converter. The monitoring system can monitor the following parameters and show the following parameters: the voltage and current of the solar cell array, the AC output voltage and current, the current power generation power, the day hair. Electric quantity, accumulation
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