Hybrid-clamped three-electric-level three-phase four-wired photovoltaic system based on 3D-SPWM (three-dimensional sinusoidal pulse width modulation)

A 3D-SPWM, three-phase four-wire system technology, applied in the direction of photovoltaic power generation, electrical components, single-net parallel feeding arrangement, etc., can solve the problems of three-phase grid-connected current imbalance, poor flexibility, difficulties, etc., to reduce System neutral current, ensure height balance, ensure balance effect

CN103023070AActive Publication Date: 2013-04-03SHANDONG UNIV
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Publication Date
2013-04-03

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Abstract

The invention relates to a hybrid-clamped three-electric-level three-phase four-wired photovoltaic system based on 3D-SPWM (three-dimensional sinusoidal pulse width modulation). By the use of a 3D-SPWM control method, system leak current is reduced effectively, neutral-point potential balance is guaranteed, balance of outputting three-phase voltage by the photovoltaic system in independent operation is guaranteed, and balance of three-phase grid-connecting current in grid-connecting operation is guaranteed. In addition, neutral current can be lowered effectively by controlling zero-sequence component. The photovoltaic system comprises three-phase bridge arms connected in parallel. Each bridge arm comprise four IGBTs (insulated gate bipolar transistors) connected in series, a neutral point of each phase bridge arm is connected with a corresponding resistor through a filter, and the resistors are grounded. A pair of a capacitor C1 and a capacitor C2 in series connection are connected at an input end of each bridge arm in parallel, the capacitors C1 and the capacitors C2 are connected with an acquisition photovoltaic array. A pair of diodes are connected between the first IGBT and the fourth IGBT of each bridge arm in series,and neutral points of the capacitors C1 and the capacitors C2 are grounded. In addition, clamped capacitors Cxi are connected on each pair of diodes in parallel, wherein i is equal to a, b and c. The IGBTs are controlled by a control circuit in a 3D-SPWM manner to balance potential at the neutral points.
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Description

technical field

[0001] The invention relates to a hybrid clamping three-level three-phase four-wire photovoltaic system based on 3D-SPWM. Background technique

[0002] Three-level inverters have the characteristics of high withstand voltage, small switching stress, and high-quality output waveforms, and are widely used in high-voltage and high-power occasions. With the rapid development of the photovoltaic industry, three-level and even more level inverters are gradually applied to photovoltaic power generation systems. However, for the non-isolated traditional diode-clamped three-level inverter system, it is difficult to solve problems such as the balance of the midpoint potential, the system leakage current, and the anti-three-phase load imbalance. For the cascaded non-isolated three-level photovoltaic inverter system, since it requires multiple independent power sources (usually independent photovoltaic panels), there is a parasitic capacitance between each independent p...

Examples

Embodiment Construction

[0030] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0031] figure 1 It is a system structure diagram, the main circuit is a hybrid clamp type three-level inverter, the midpoint of the DC side is directly connected to the photovoltaic cell array, and the filter is an LC filter circuit. The output terminal of the system is connected to the load and the three-phase grid, and the common terminal n of the three-phase grid is connected to the common terminal of the load, the common terminal of the filter capacitor and the midpoint of the DC side.

[0032] For the three-phase four-wire structure, if the 2D-SVPWM control method is adopted, since the final modulation waveform contains a large number of third harmonics, it will cause the output current i of the common terminal of the filter capacitor C If it is too large (more than 10A), if the load is unbalanced during independent operation, then i_n will be lar...