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Multi - branch Photovoltaic Grid - connected Inverter

Author: Source: Datetime: 2016-10-05 01:10:49
With the photovoltaic solar power generator technology and the continuous development of the market, photovoltaic grid-connected systems in the city also benefit a wide range of applications. However, there is limited space available in the city, so to increase the total installed capacity of PV systems in limited space, on the one hand, to increase the capacity of individual power plants, on the other hand, PV power should be broadly integrated with urban buildings. However, the situation in urban buildings is more complex, the light, temperature, PV module specifications will vary depending on the installation place, so that the traditional centralized PV grid structure can not meet the requirements of high-performance PV systems, this can Using multi-branch-type photovoltaic grid-connected inverter structure. This kind of multi-branch type PV grid-connected inverter can independently carry out the maximum power tracking when the characteristics of each branch PV array are different or the lighting and temperature conditions are different, thus solving the problem of the inter- Power mismatch problem. In addition, the multi-branch photovoltaic grid-connected inverter installation flexibility, easy maintenance, to maximize the use of solar radiation energy, effectively overcome the slip between the power mismatch caused by the overall system inefficiency and other shortcomings, and maximum Reduce the influence of single branch fault, and have good application prospect.

For isolated multi-branch PV grid-connected inverters, the high frequency chain technology can be used for such isolated structures since more branches can be provided and the power of each branch converter can be relatively small. Figure 4-46 is a multi-branch high-frequency chain photovoltaic grid-connected inverter circuit structure, solar power generator the inverter circuit structure by the high-frequency inverter, high frequency transformer, rectifier, DC bus, inverter and input and output filter And the like. One of the input stage of the high-frequency chain structure based on full-bridge high-frequency isolation of the multi-branch design, and grid-connected inverter is a centralized design.

As the full-bridge high-frequency isolation and inverter front and rear circuit control through the middle of the DC capacitor decoupling, so when there are multiple branches, each front-end full-bridge circuit can be individually controlled, multiple branch output current Collected on the DC bus, and then through a centralized grid-connected inverter and network operation. System overall control diagram. For each PV input branch, the system controls the maximum power point tracking control of each branch on the basis of the detected voltage and current information of the PV module and the duty ratio control of the input high-frequency full-bridge. On the other hand, The rectifier output DC current is connected in parallel to the DC bus; and the latter stage of the grid-connected inverter DC voltage can be used outside the ring and AC current loop of the double-loop control strategy, by DC bus voltage control to achieve the photovoltaic energy Of the smooth transmission.
However, in the PV grid-connected system, a series of photovoltaic panels are usually connected in series as the DC-side input, so it is convenient to use a series of panels to obtain a separate DC source. In addition, cascaded multi-level inverter can independently control the power output of each unit, making the photovoltaic grid-connected systems work in the mismatch of the state can also be independent of the ^. For example, in a building integrated system, different walls have different maximum power points because of different irradiance. If a single centralized grid-connected PV inverter is used, it will cause loss of energy consumption. If cascaded photovoltaic grid-connected inverters are used in this case, the panels of different walls can be treated as independent DC units, and the system can be maximized by the independent control of the grid. In addition, cascaded PV grid-connected inverter can achieve satisfactory output at low switching frequency, which not only reduces the switching loss, reduces the filter size, saves the filter cost, and effectively improves The power conversion system efficiency. It can be seen that it is very suitable to adopt the cascaded multi-level PV grid-connected inverter structure in the PV solar powered portable generator system (especially the high power system).

Main Circuit Topology of Five - level Single - phase Photovoltaic Grid - connected Inverter Based on Two - unit. This is a basic cascade combination, the actual should be able to use multiple units cascade, and can be combined to form a three-phase cascade multi-level photovoltaic grid-connected inverter.

Wavelet stacking method is to triangular wave carrier space in the stack, and then through the modulated wave and carrier to control the intersection of the power tube switch, although this modulation method is relatively simple, but in the photovoltaic grid-connected systems need additional control strategies to meet The output power of each unit is balanced, and it is difficult to realize the individual carrier phase shift method of each unit is to obtain the same carrier signal as the  solar powered portable generator cascade number by carrier phase shift, and then control the corresponding power switch tube through the intersection point of modulation wave and each carrier, Carrier phase shift method can be used to solve the control problem of the unit alone, so here mainly introduce carrier phase shift method. TAG: Multi-Storage Reliability Shell Manganese 200MW Ørsted Micro ABB Programs Volvo 65MW Porsche Largest Volkswagen Lease