What is the application scope of solar photovoltaic power generation?

Photovoltaic power generation system in China at present is mainly dc system, the energy from the solar cell battery, the battery directly to the load power supply, such as using in northwest China more solar household photovoltaic power generation systems and away from the grid micro

at present, photovoltaic power generation system mainly dc system in our country, it is using energy from the solar cell battery, battery directly to the load power supply. The northwest region in China, for example, the widely used solar household photovoltaic power generation systems and away from the grid power supply system of microwave station are dc system. This system has simple structure, low cost. However, due to the load of the DC voltage, For example, 12 v, 24 v, 48 v, etc. ) 。 ) , it is difficult to realize the standardization of system and the compatibility, especially for the civil power. Because most are ac load, by the DC power supply of photovoltaic (pv) power supply can hardly be a commodity to enter the market. In addition, photovoltaic power generation will eventually achieve parallel operation, this requires a mature market model. In the future, ac photovoltaic system will become the mainstream of photovoltaic power generation. Photovoltaic power generation system of inverter power supply requirements is to adopt ac output of the photovoltaic power generation system, the system consists of photovoltaic array, scenery complementary controller, storage battery and scenery complementary inverter ( Grid generation system generally can be omitted) battery Inverter is the key part. Photovoltaic power generation systems have higher request for inverter: 1. Need high efficiency. Due to the price of solar cells is very high, in order to make full use of solar cells, and improve the efficiency of the system, we must try to improve the efficiency of the inverter. 2. Require high reliability. At present, the photovoltaic power generation system is mainly used in remote areas, many power plants unattended and maintenance. This requires inverter has the reasonable structure of circuit, the strict components selection and various protective functions, such as input DC reverse polarity protection, ac output short circuit protection, overheat and overload protection. 3. Requires a DC input voltage has extensive adaptability. Due to the voltage of the solar cell changes with load and sunshine intensity, while the battery on the solar battery voltage plays an important role, but the battery voltage with battery remaining capacity and internal resistance change and volatility, especially when the battery aging, its terminal voltage change is very big, such as the 12 v battery, its voltage can change between 10 v and 16 v, which requires the inverter must ensure that the large DC input voltage within the scope of work, and ensure the stability of the ac output voltage. 4. In the large capacity of photovoltaic power generation system, the output of the inverter power supply should be sine wave, and less distortion. This is because the large capacity of the system, if you are using a square wave power supply, the output will contain more harmonic components, higher harmonic will generate additional loss. Many photovoltaic power generation systems are equipped with communication or instrument equipment, these devices have higher requirements on power quality. The large capacity of photovoltaic power generation system is connected to the electricity grid, inverter output sine wave current, to avoid the power of public power grid pollution. Inverter to convert direct current (dc) to alternating current. If the dc voltage is low, by ac voltage transformer booster for standard ac voltage and frequency. Inverter for large capacity, high due to the DC bus voltage, ac output generally can reach 220 v, without transformer booster. For medium and small capacity inverter, due to the low DC voltage, such as the 12 v and 24 v, must design the boost circuit. Medium and small capacity inverter generally has three types: push-pull inverter circuit, full bridge inverter circuit and high frequency inverter circuit of pressure. Push-pull circuit will step-up transformer neutral plug connected to the power supply, two power tube alternating work output ac power. Because of the power transistor grounding side by side, drive and control circuit is simple. In addition, the leakage inductance of transformer has certain, can limit short circuit current, so as to improve the reliability of circuit. Its defect is low utilization rate of transformer, drive the perceptual load ability is poor. Full bridge inverter circuit overcomes the drawback of push-pull circuit. Output power transistor to adjust the output pulse width, and the effective value of ac voltage change accordingly. Due to renew the circuit has a flow loop, even for inductive load, the output voltage waveform is not distorted. The disadvantage of this circuit is upper and lower bridge arm of power transistor is not altogether, so must use special driving circuit or isolated power supply. In addition, in order to prevent the bridge arm and the lower bridge arm conduction together, circuit must be designed to shut off before conducting, namely must set up the dead zone, and its circuit structure is relatively complex.