Direct grid connected type photovoltaic power station circuit topological structure

Abstract

The invention discloses a direct grid connected type photovoltaic power station circuit topological structure and belongs to the power and electronic technical field. The direct grid connected type photovoltaic power station circuit topological structure includes photovoltaic components, DC-AC unit modules and a control system; each DC-AC unit module comprises a first H-bridge converter, a second H-bridge converter, a third H-bridge converter and an isolation transformer, wherein the AC side of the first H-bridge converter is connected with one side of the isolation transformer, the other side of the isolation transformer is connected with the AC side of the second H-bridge converter, the DC side of the second H-bridge converter is connected with the DC side of the third H-bridge converter, and the first H-bridge converter and the second H-bridge converter are adopted as a whole and carry out simultaneous phase shifting control to realize soft switching actions of all switches. According to the direct grid connected type photovoltaic power station circuit topological structure of the invention, modular design is adopted. The direct grid connected type photovoltaic power station circuit topological structure has the advantages of easiness in expansion, cascade connection and high frequency.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and mainly relates to a circuit topology structure of a direct grid-connected photovoltaic power station. Background technique [0002] At present, distributed photovoltaic power plants will usher in an unprecedented development opportunity. There are mainly two solutions for large-scale photovoltaic power plants, namely centralized photovoltaic power plants and string photovoltaic power plants. The corresponding centralized photovoltaic grid-connected power station circuit structure adopts the connection scheme of "component-DC cable-combiner box-DC cable-DC confluence distribution cabinet-DC cable-inverter-isolation transformer-AC power distribution-grid" ; The circuit structure of the string photovoltaic grid-connected power station adopts the connection scheme of "component-DC cable-inverter-AC combiner box-boost transformer-AC power distribution-grid". [0003] figure 1 It is a ...

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Problems solved by technology

[0005] The main disadvantages of the centralized photovoltaic grid-connected power station circuit are: 1. The DC combiner box has a high failure rate, which affects the entire system; 2. The MPPT voltage range is narrow, generally 450-820V, and the component configuration is not flexible

[0008] The main disadvantages of the string photovoltaic grid-connected power station circuit are: 1. There are many electronic components, and the power device and the signal circuit are on the same board, which is difficult to design and manufacture, and the reliability is slightly poor; 2. The electrical clearance of the power device Small, not suitable for high altitudes

Outdoor installation, wind and sun can easily lead to aging of the shell and heat sink; 3. Without isolation transformer design, the electrical safety is slightly poor, not suitable for the negative grounding system of thin film modules, and the DC component is large, which has a great impact on the power grid; 4. When multiple inverters are connected in parallel, the total harmonics are high, and the THDI of a single inverter can be controlled to 2%, but when many inverters are connected in parallel, the total harmonic content will increase; 5. The number of inverters is large, and the total The failure rate will increase, and the system monitoring will be difficult; 6. There is no DC circuit breaker and AC circuit breaker, and there is no DC fuse. When the system fails, it is not easy to disconnect; 7. A single inverter can achieve zero voltage ride through function, but when multiple machines are connected in parallel, it is difficult to realize functions such as zero voltage ride through function, reactive power adjustment, and active power adjustment

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