Summary of design schemes for wind-solar hybrid power generation systems (details of two wind-solar hybrid power generation systems)

The typical communication base station power supply system is shown in Figure 1. It is mainly composed of AC power distribution, rectifier, battery, DC power distribution and other equipment. Under normal conditions of utility power, the mains supply directly supplies power to the AC load, and supplies power to the DC load and the battery through the rectifier. In the abnormal case of the mains supply, the DC load is supplied through the battery, or it is powered by the fuel generator by manual or automatic switching. The application characteristics of the integrated communication base station power supply system mainly include three aspects: (1) continuous operation of load 24h, stable load; (2) configuration of battery pack with a certain capacity; (3) output characteristics of the rectifier meet battery charging requirements, output current Related to the state of charge of the battery.

Figure 1 Block diagram of the communication base station power supply system

The wind and solar hybrid power supply system is mainly composed of wind turbines, solar photovoltaic cells, controllers, battery packs, DC loads, etc. The system is a renewable energy power generation system integrating wind energy, solar energy and system intelligent control technology. as shown in picture 2.

Figure 2 Block diagram of the communication base station wind-solar complementary energy-saving power supply system

The system uses a DC access mode that has been confirmed by practice. The wind turbine and solar photovoltaic battery pack directly charge the base station battery pack and load through the controller. There are fewer devices required for DC access. Except for wind turbines and controllers, there is no need to add additional equipment. The downside is that DC access cannot directly supply AC loads. The DC access fully utilizes the existing equipment of the base station power supply system, and is more in line with the characteristics of the base station power supply. The system is simple and reliable, and the energy conversion efficiency is high, and the efficiency is improved by about 20% compared with the conventional power supply method through the inverter.

2.1. Communication base station situation

The communication base station is located on a hill in a township in central Hunan. The altitude of the sea is about 1092m, and the north-south trend is wide. The solar and wind energy resources are abundant. The annual average sunshine hours are about 2000h, and the annual average effective wind hours are 2500-3000h. The average annual wind power is 3-8. The mobile communication base station is a 1-story building containing a diesel generator room. The base station has a carrier frequency of six and two sets of 500 Ah batteries. The total power consumption of the equipment is about 1 kW, and there is no air conditioner.

2.2, system design optimization program

2.2.1, battery capacity calculation

Since the battery is the backup power supply of the whole system, the performance of the battery directly affects the stability of the whole system. Therefore, the valve-regulated sealed lead-acid battery should meet the requirements of YD/T799-2002, and the valve-regulated sealant battery should be Meet the requirements of YD/TI360-2005. The base station equipment is powered by DC-48V, so a 48V battery or battery pack is required. According to the importance of the base station, in general, the backup working time of the entire system can reach 3 days. However, according to the analysis of local meteorological conditions, the wind power is large in the morning and evening, the sun is strong at noon, there is no wind and no light day, and there is mains access. The battery capacity is configured to meet the demand of all the power equipment in the base station for one day.

The battery capacity required for the total system load is:

Cb=(I&TImes;T&TImes;K)/(η&TImes;[1+α(t-25)])

=100048×1×24×1.25/(1×[1+0.006×(0-25)])

=625/0.85=735.29Ah

Where Cb is the capacity of the battery; I is the load current (A); T is the number of discharge hours (h); K is the safety factor, K = 1.25; η is the discharge coefficient, η = 1; α is the battery temperature coefficient ( 1 / ° C), α = 0.006; t is the lowest temperature of the actual location of the battery, according to 0 ° C.

After rounding, the capacity of the battery should be 800Ah/48V, and the existing two sets of 500Ah/48V battery packs can meet the system requirements.

According to the local meteorological department, the annual wind power is 3-8, that is, the wind speed is 3-20 m/s, and the annual average sunshine hours is about 2000 h. As an energy-saving power supply system, the capacity configuration of photovoltaic panels and fans is shown in Table 1.

Table 1 Photovoltaic panel and wind turbine configuration table

Wind power generator rated power and rated wind speed selection principle: Although wind energy itself does not require the use of cost, but as a power generation equipment to achieve energy conversion process, it requires cost, in the energy-saving and emission reduction wind-solar complementary power supply system, the efficiency of the wind turbine directly The effect of relationship reduction is also directly related to the return on investment. For wind turbines of the same rated power, the difference in power generation is very large when the rated wind speed is different. It is only meaningful that the rated power of the wind turbine must be linked to the rated wind speed. Compared with two 1kW rated power wind turbines with a rated wind speed of 9m/s and a rated wind speed of 11m/s, the annual power generation of a 9m/s rated wind speed unit is about 5m/s annual average wind speed and Rayleigh distribution wind speed. At 2628 kWh, the rated wind speed of 11 m/s is only 1825 kWh, and the low rated wind speed unit generates 44% more electric energy than the high rated wind speed unit. Figure 3 shows the power curve of a 2kW wind turbine. Figure 4 shows the annual power generation difference between the low-rated wind speed model and the high wind speed model when the annual average wind speed is 4m/s, 5m/s, 6m/s, and 7m/s.

Figure 3 Wind turbine power curve

Figure 4 Comparison of annual power generation of wind turbines with different rated wind speeds

When the new energy supply system is promoted for the purpose of energy saving and emission reduction, the wind speed resources at the installation site are uneven, but usually there are many low wind speed resources and few wind speed resources are abundant. Therefore, it is particularly important to select low wind speed models.

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