First, an overview of the development of large-scale photovoltaic desert power station
Figure 1. Schematic diagram of domestic PV installed capacity
According to the planned installation volume data published by the state in 2014, the trend of such explosive growth has not diminished in any way. Currently, the final installed installation volume is 14 GW (6 GW for PV plants and 8 GW for DGs). This is almost equivalent to the sum of installed capacity of domestic PV power stations in all the past years.
Figure 2. System topology of a desert power plant
The trend of development of desert power plants toward a single power plant capacity is getting bigger and bigger, access to the voltage level is higher and higher direction.
Second, large-scale photovoltaic power plant power quality problems
1, how is harmonic produced?
The generation of photovoltaic power station harmonic mainly by the inverter, DC bus fluctuations, transformer core saturation nonlinearity and power grid distortion caused.
The harmonic generated by the inverter is mainly composed of two parts: one is caused by the dead time, including 3, 5, 7, 9 and other low harmonics; the other part is generated by the modulation process, and the groups are distributed at integer times of the switching frequency nearby. DC bus disturbance is also a source of harmonics. The DC bus voltage has a transient adjustment process. The influence on the current waveform can only be weakened by improving the MPPT method, but it can not be eliminated. Isolation transformer core saturation nonlinear characteristics can also lead to the generation of harmonics, while severe grid distortion, if the inverter sends an ideal sinusoidal voltage, reactance will produce harmonic voltage difference, resulting in the grid current contains the corresponding Harmonic component.
U tube heat exchanger is suitable for the large temperature difference between tube side and shell side. The shell side media is easy to scale and needs cleaning, while the tube side media is clean and not easy to scale. It is also suitable for high temperature, high pressure, fluid corrosive working conditions.
Each heat exchange tube is bent into U-shape, the two ends are fixed in the upper and lower areas of the same Tube Sheet, and divided into two chambers of inlet and outlet with the partition in the tube box. This kind of heat exchanger completely eliminates the thermal stress, the structure is simpler than the floating type, but the tube side is not easy to clean.
The number of tubes is small, the utilization of the tube sheet is not frequent, and the shell side fluid is easy to short circuiting, which is unfavorable to heat transfer. If there is a leak or damage in the tube, the external U-tube can be replaced, while the broken inner tube can not be replaced, only plugged, and one broken U-tube means two broken, so the U-tube easily scrapped.
U Tube Heat Exchanger,Beu Heat Exchanger,U Type Heat Exchanger,U Tube Type Heat Exchanger
Guangdong Jiema Energy Saving Technology Co.,Ltd , https://www.jiemaheatexchanger.com