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Research on Non - Isolated Photovoltaic Grid - connected Inverter

Author: Source: Datetime: 2016-10-05 01:07:16
With the development of PV grid-connected high-efficiency technology, transformer-less non-isolated grid-connected inverter is attracting more and more attention.Solar power generator is also the development direction of grid-connected inverter in the future, but there are corresponding difficult problems: First, because the inverter output does not use the frequency transformer isolation and boost, the inverter is easy to note to the grid, the DC component, will have adverse effects on the power grid equipment, such as transformer or transformer saturation caused transformer substation Grounding grid corrosion and other issues; Second, because the grid-connected inverter 屮 no frequency and high-frequency transformers, and photovoltaic cells due to the presence of parasitic capacitance, making the solar power generator system under certain conditions can produce large common-mode leakage current, Increase the system's conduction losses, reduce the electromagnetic compatibility, but also to the power grid into the harmonic and
Will have a security problem.

In theory, the grid-connected inverter only injects AC current into the grid. However, in practical applications, DC offset is often included in the grid-connected current due to the offset of detection and control. In the non-isolated photovoltaic grid-connected system, the direct current component of the inverter output is directly injected into the power grid, which will adversely affect the power grid equipment, such as the saturation of the transformer or transformer, and the corrosion of the substation grounding grid. Therefore, we must pay attention to the DC component of the grid-connected inverter and strictly control the DC component of the grid-connected current.

DC component of the most fundamental reason is the inverter output high-frequency wave contains a certain DC component. Inverter output pulse width modulation wave contains DC component of the reason can be attributed to the following points: This situation occurs in the analog control inverter, sine wave given signal generated by the analog device, because the components used in the characteristics Of the difference, given a sine wave signal itself contains a small DC component. Using closed-loop waveform feedback control, the output current waveform and the given waveform is basically the same, resulting in the output AC current also contains a certain degree of DC component.
portable solar power generator
The feedback path of the control system consists of the sensing element and the converter. The zero drift of the control system and the converter is attributed to the zero drift of the feedback channel and is the main cause of the DC component of the output current. Detection component zero drift: the introduction of the inverter output feedback control, inevitably to use a variety of detection components, the most commonly used is the voltage and current Hall sensors. These components are generally zero drift, because the zero-shift detection device components, making the output current contains DC component. Although the absolute value of zero drift is very small, but because the feedback coefficient is generally small, so the DC component can not be ignored, which is caused by output current DC component is one of the important factors.

Solar power generatorsystem to generate the signal to go through the pulse distribution and dead-zone circuit phase, set the dead zone, and then isolated by the drive circuit, amplified to drive the switch. In which the dispersion of the component parameters can cause the dead time to vary, that is, the loss of each turn-on time of each tube is inconsistent, and thus the inverter output contains the DC component. Even if the pulse width modulated wave generated by the control circuit is completely symmetrical solar powered portable generator, the difference between the characteristics of the power switch tube in the main circuit, such as the saturation voltage drop during turn-on and the inconsistency in the storage time at turn-off, Asymmetry, resulting in the output current contains DC component. TAG: Multi-Storage Reliability Shell Manganese 200MW Ørsted Micro ABB Programs Volvo 65MW Porsche Largest Volkswagen Lease