Three-phase synchronization AC generating circuit and its control method

Abstract

The invention provides a three-phase network jointing AC generation circuit and an attached controlling method thereof, which comprises a three level voltage increasing circuit and a three level inverting circuit, wherein, the three level voltage increasing circuit is connected with an input power and comprises a positive voltage increasing part and a negative voltage increasing part, the three level inverting circuit is connected with the three level voltage increasing circuit and comprises a positive inverting part and a negative inverting part; wherein, when the input power is on low voltage state, the low voltage can increase the voltage through the three level voltage increasing circuit and output through the inverting process by the three level inverting circuit; when the input power in on high voltage state, the high voltage can directly output through the inverting process by the three level inverting circuit; and the positive voltage increasing part and the positive inverting part can form a first voltage increasing-decreasing circuit used for outputting a positive semi-circle current wave shape, and the negative voltage increasing part and the negative inverting part can form a second voltage increasing-decreasing circuit used for outputting a negative semi-circle current wave shape. The invention can increase the efficiency of the inverting circuit.

Description

technical field [0001] The invention relates to a three-phase grid-connected AC generating circuit and a control method thereof, in particular to a three-phase grid-connected AC generating circuit applied to solar energy, fuel cell and wind power generation systems with wide input voltage variation ranges. Background technique [0002] Since the energy crisis, realizing the coordinated development among energy, environment and economy has become the goal of energy construction in all countries in the world. In addition, with the rapid growth of the load, the traditional centralized (centralized) power generation technology has gradually exposed many disadvantages, while the distributed power generation technology has the advantages of flexible power generation methods and good environmental protection performance. Applying distributed generation technology to the traditional power system can not only meet the specific requirements of the power system and users, but also impr...

AI Technical Summary

Problems solved by technology

[0006] Using this kind of circuit in Figure 1(b) can greatly expand the range of input voltage variation, but the disadvantages are also obvious: the two-stage circuit structure has low efficiency, and it is impossible to avoid the large energy storage capacitor in the middle. many negative effects

In addition, the rear-stage inverter 112 adopts a traditional half-bridge structure, which itself has low efficiency in high-voltage applications, and because the antiparallel diodes of the traditional half-bridge switching elements must act as a freewheeling circuit, therefore When the switching element is turned on, the diode must undergo reverse recovery

In order to reduce the loss caused by the reverse recovery, metal-oxide-semiconductor field-effect transistors (MOSFETs) are generally not used as switching elements because of the parasitic diode characteristics of metal-oxide-semiconductor field-effect transistors when they act as switching elements. not good enough

Since the MOSFET cannot be used as a switching element, it is impossible to use the on-state characteristics of the resistance it presents to reduce its on-state loss through parallel connection, and it is also impossible to use its good switching characteristics to reduce the switching loss of the system.

[0007] Three-level inverter circuits are generally considered suitable for high DC input voltage applications, but have no advantage in low voltage applications

Because the MOSFET itself has parasitic diodes, and the reverse recovery characteristics of the parasitic diodes are very poor, when a three-level inverter circuit is used in the field of uninterruptible power supply systems and motor drives, MOSFETs are generally not used as switching elements.

Since MOSFETs cannot be used as switching elements, the on-state characteristics of the resistors presented cannot be used to reduce the on-state losses through parallel connection, nor can the good switching characteristics be used to reduce the switching losses of the system

[0015] In addition, since solar cells, fuel cells, and other DC power supplies that supply power to the grid generally have a large voltage variation range, and the difference between the highest input voltage and the lowest input voltage can be several times (for example, more than 3 times), it is usually impossible to directly select three Level inverter circuit to supply power to the grid

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