A single current sampling type three-phase power conversion circuit

Abstract

The invention belongs to the technical field of three-phase power conversion circuits, in particular to a single current sampling type three-phase power conversion circuit, the power part is a three-phase active power conversion circuit, including a DC bus filter capacitor C, a power device S 1 ‑S 6 , freewheeling diode D 1 -D 6 , the DC bus and its voltage u DC , and the load, only one current sensor is needed, with simple structure and low cost. In all sectors, the A-phase current value at the zero moment of the PWM cycle can be accurately collected, which can ensure that there is no error in the A-phase current sampling; for B-phase or C-phase Phase current sampling, since ‑i can be collected during all active vector action times of sector II C , while ‑i can be collected during all effective vector action times of sector V B , so in most sectors, the current sampling time of phase B or phase C is close to the zero time of the PWM cycle, and the sampling result is more accurate than the single current sampling of the conventional bus.

Description

Technical field: [0001] The invention belongs to the technical field of three-phase power conversion circuits, and in particular relates to a single-current sampling type three-phase power conversion circuit, which can realize controllable conversion and adjustment of active and reactive power. Background technique: [0002] Three-phase power converters are generally used in motor drive, new energy power generation, static var compensation and other fields, and can realize controllable conversion and adjustment of active and reactive power. During use, in order to realize the closed-loop control of the power conversion system, it is usually necessary to collect three-phase current through two or three current sensors. The current sensor is installed in figure 1 shown on the three-phase output side or figure 2 The three-phase lower bridge arm shown, where, S 1 -S 6 It is a power switching device, which can be IGBT, MOSFET, etc.; D 1 -D 6 It is a freewheeling diode; the...

AI Technical Summary

Problems solved by technology

[0007] However, the three-current or two-current sensor sampling scheme has the disadvantages of complex system structure and high cost

The single current sensor sampling scheme on the high-voltage side of the conventional busbar cannot collect and reconstruct the phase current at the zero point of the PWM cycle, that is, the current sampling time is deviated from the sampling time required by the control system, which leads to errors in the sampling current; phase current reconstruction is unobservable The area is large, and there are two unobservable areas in each sector; the disadvantage of large voltage harmonics caused by voltage phase shift in the unobservable area

Other single current sensor sampling schemes have complex circuit structures and poor practicability; current sensors can only use expensive Hall devices, but cannot use sampling resistors, which not only increases the circuit volume, reduces power density, and increases costs; PWM The interval time between two current samplings in a cycle is relatively large, which leads to poor accuracy of reconstructed current and reduces the performance of the control system.

[0008] Therefore, the development and design of a single current sampling three-phase power conversion circuit solves the problems of high sampling cost, large unobservable area and poor current reconstruction accuracy, which has social and economic benefits

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