h5-d non-isolated photovoltaic grid-connected inverter and its modulation method

Abstract

The invention discloses a H5-D type non-isolated photovoltaic grid-connected inverter and a modulation method thereof. The inverter includes a photovoltaic cell, and input filter capacitors are connected in parallel at both ends of the photovoltaic cell. The inverter link is connected to the input filter capacitor and the H5 type inverter link is also connected with a neutral point clamp switch, and the H5 type inverter link is connected to the power grid through the filter. The invention has the following advantages: it is composed of five switch tubes and a diode, which can ensure constant common-mode voltage and has better common-mode current suppression effect. Under unipolar SPWM modulation, two of the switch tubes work in the power frequency state, The cost and loss are greatly reduced, and the switch tube working at high frequency does not need to set a dead zone, which is beneficial to reduce the harmonic content of the grid-connected current.

Description

technical field [0001] The invention relates to the field of photovoltaic power generation inverters, in particular to an H5-D non-isolated photovoltaic grid-connected inverter and a modulation method thereof. Background technique [0002] Human beings' awareness of environmental issues is increasing and the energy crisis is approaching step by step, which has accelerated the pace of exploration of new energy and the development of utilization technology. Under this background, solar power generation technology has developed rapidly. As the core device of the solar power generation system, the photovoltaic grid-connected inverter has naturally become a key technology. However, the commonly used isolated photovoltaic inverter with transformer is not suitable for small and medium power applications due to its shortcomings such as large size, high cost, and low efficiency. high. Transformerless non-isolated photovoltaic grid-connected inverters are widely used in single-phase ...

AI Technical Summary

Problems solved by technology

However, since the system does not have electrical isolation, the photovoltaic array will form a current path through the parasitic capacitance to the ground, thereby generating a common mode current, which will increase system loss, reduce the quality of grid-connected current, and cause serious electromagnetic interference and personal safety issues.

[0003] In order to solve the problem of common-mode current generated by the capacitance of the photovoltaic array to the ground, some special inverter topologies have been proposed in recent years, including H5, HERIC, and H6, among which, when the H5 topology suppresses the common-mode current, there is a potential imbalance during the freewheeling period. Problem, the common-mode voltage produces high-frequency fluctuations, which reduces the suppression effect of the common-mode current

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