Power module group of three-phase power electronic transformer

Abstract

The invention provides a power module group of a three-phase power electronic transformer. The three-phase power electronic transformer comprises a high-voltage filter, the power module group, a fifth power module and a low-voltage filter. The power module group comprises power module units which are connected in series on the high-voltage side and connected in parallel on the low-voltage side. Each power module unit comprises a first power module, a high-voltage side capacitor, a second power module, a medium / high frequency transformer and a third power module, wherein the first power module, the high-voltage side capacitor, the second power module, the medium / high frequency transformer and the third power module are sequentially connected, and the third power module is connected with a low-voltage side capacitor in parallel. The power electronic transformer has the three-phase power automatic balance function, asymmetric loads on the low-voltage side can be well treated, and asymmetry on the low-voltage side can be naturally converted into symmetry on the high-voltage side through topological connection.

Description

technical field [0001] The invention relates to a device in the technical field of power electronic transformers, in particular to a power module group of a three-phase power electronic transformer. Background technique [0002] The concept of "active distribution network" and continuous practice can solve a series of technical problems brought about by the rapid development and accelerated application of distributed generation technology. The active distribution network aims to improve the active energy distribution ability and economic operation level of the distribution network, actively absorb renewable energy, improve the power supply reliability and power quality level of the distribution network, and make the distribution network more efficient and environmentally friendly. At the same time, the controllability of the distribution network is required to be higher. [0003] As the basic component equipment of the distribution network, the distribution transformer's op...

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Problems solved by technology

[0004] 1. The volume and weight are large, and the insulating oil of the transformer pollutes the environment;

[0005] 2. The no-load loss is high, and the output voltage fluctuates with the load when it is loaded;

[0006] 3. When a fault occurs on the load side, the fault cannot be isolated and will affect the power supply side;

[0007] 4. When carrying a nonlinear load, the distorted current is coupled into the power grid through the transformer, which will cause pollution to the power grid;

[0008] 5. When the voltage on the power supply side is disturbed, it will be transmitted to the load side, resulting in an impact on sensitive loads;

[0010] 7. The ferromagnetic element is non-linear, which will cause a large excitation inrush current when it is put into the grid, and harmonic pollution will be generated when the iron core is magnetically saturated, resulting in distortion of the grid voltage and current, and increased vibration and noise

The disadvantage is that the controllability is not strong, sometimes it is difficult to contribute to the improvement of power quality, and the power factor of the primary side is not adjustable

However, since photovoltaic, wind power and other renewable energy sources and energy storage devices are usually connected to the DC system, the voltage is usually low, and the DC voltage values ​​are not necessarily equal, that is, multiple low-voltage DCs are required instead of one high-voltage DC

Therefore, the advantage of a high-voltage direct current generated by multiple MMC bridge arms cannot be fully utilized, and the disadvantages of the relatively large number of power electronic devices and capacitors used in this scheme have not been effectively offset

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