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Isolated Photovoltaic Grid - connected Inverter Structure

Author: Source: Datetime: 2016-10-05 00:53:35
In the isolated photovoltaic grid-connected inverter, but also according to the operating frequency of the isolation transformer, the frequency can be divided into two types of high-frequency isolation and isolation.

Grid - connected Isolated Photovoltaic Grid - connected Inverter

Frequency isolation is the most commonly used structure of PV grid-connected inverter, and it is also the most used PV inverter type on the market at present: the DC power from PV array is converted into 50 AC power through the inverter, Frequency transformer input power grid, the frequency transformer to complete the voltage matching and isolation. As the power frequency isolation PV grid-connected inverter structure using a power transformer to isolate the input and output, the main circuit and control circuit is relatively simple, and the PV array DC input voltage matching range. As the isolation of the transformer: on the one hand, can effectively prevent the person to come into contact with the positive side of the PV side or negative, the grid current through the arm to form a loop to the possibility of harm to people, improve system security; The solar powered portable generator system will not inject the DC component to the power grid, effectively preventing the distribution transformer saturation.

However, the frequency transformer has a large volume, the weight of the shortcomings, which account for about 50% of the total weight of the inverter, making the inverter size is difficult to reduce; In addition, the presence of frequency transformer also increases the system loss , Cost, and increased the difficulty of transport and installation. Grid-connected isolated PV grid-connected inverter is the earliest development and application of a photovoltaic grid-connected inverter in the form of the main circuit, with the development of inverter technology solar powered portable generator, to retain the advantages of isolated photovoltaic grid-connected inverter on the basis of , In order to reduce the volume and quality of the inverter, high-frequency isolated photovoltaic grid-connected inverter structure will emerge.

High - frequency Isolated Photovoltaic Grid - connected Inverter

High-frequency isolation PV grid-connected inverter and industrial frequency isolation PV inverter is different from the use of high-frequency transformer, which has a smaller size and quality, to overcome the power-frequency isolation PV grid-connected inverter The main drawback of the device. It is worth mentioning that, with the improvement of device and control technology, high-frequency isolation PV grid-connected inverter efficiency can also be done very high. In an isolated grid-connected system, the transformer converts electrical energy into magnetic energy, which in turn converts the magnetic energy into electrical energy. Obviously, this process leads to energy loss. Generally several kilowatts of small-capacity transformer energy loss caused by up to 5%, or even higher. Therefore, an effective means to improve the efficiency of PV grid-connected system is to adopt non-isolated photovoltaic grid-connected inverter structure without transformer. In a non-isolated system, the system structure becomes simpler, the quality becomes lighter, the cost is reduced, and the efficiency is relatively high, since a heavy-duty frequency transformer or a complicated high-frequency transformer is used.
Single-stage non-isolated Cui photovoltaic grid-connected inverter system, the PV array through the inverter direct coupling and network, so the inverter work in the labor-frequency mode. In addition, in order to make the DC side voltage can be directly grid-connected inverter voltage level, generally require PV array with high output voltage, which makes the PV modules and even the whole system must have a high degree of insulation, or will be prone to leakage phenomenon. It should be noted that, in non-isolated PV solar powered portable generator systems, the PV array is not isolated from the public grid, which will result in a direct connection of PV modules to the grid voltage. While a large area of solar cells inevitably with a large distributed capacitance between the ground and, therefore, will produce solar cells on the ground of the common mode leakage current. The system is easy to inject the DC component into the power grid due to the isolation of the transformer without power frequency.

In fact, for non-isolated grid-connected solar power generator system, as long as the appropriate measures, the same can guarantee the safety of the main circuit and control circuit operation; In addition, non-isolated photovoltaic grid-connected inverter with small size, light weight, high efficiency, Which makes this structure the main structure of PV grid-connected inverter in the future. TAG: Deployment Fixed SMA Tesvolt Unlimited Volt Army Sonnen Multi-Storage Reliability Shell Manganese 200MW Ørsted Micro