A Method of Using Redundant Voltage Vectors to Realize Fault-Tolerant Control of Medium Voltage Cascaded Statcom

Abstract

The invention relates to a fault-tolerant control method of a medium-voltage cascading STATCOM, wherein the fault-tolerant control is achieved through redundancy voltage vectors of a cascading inverter. When some cascading units in the cascading STATCOM break down, a voltage vector selected through an original control algorithm may not be normally used due to faults and is taken as a fault vector. At the moment, by means of the characteristics that the number of the redundancy voltage vectors of the cascading STATCOM is large and the positions of the redundancy voltage vectors are frequently coincident, another non-fault vector with the effect closest to the effect of the fault vector is selected to replace the fault vector. Therefore, the influences of the faults on a system are reduced to the maximum degree, and work reliability is improved. Compared with an existing frequently-used N+1 redundancy method, the method has the advantages that no additional hardware redundancy resources need to be added, cost is saved, and the method can be popularized to any cascading STATCOM. In the N+1 redundancy method, the method can also be used when the number of fault units is larger than the number of redundancy units.

Description

technical field [0001] The invention relates to the technical field of reactive power compensation, in particular to a method for realizing medium-voltage cascaded STATCOM fault-tolerant control by utilizing redundant voltage vectors. Background technique [0002] The H-bridge cascaded inverter has the advantages of large capacity, low equivalent switching frequency, flexible structure, and easy replacement, and is very suitable for medium-voltage and high-power applications. In 1996, F.Z.Peng et al. from the University of Tennessee proposed to apply H-bridge cascaded inverters to STATCOM. [0003] However, due to the large number of switching devices in the cascaded inverter, the failure probability of the cascaded inverter is much higher than that of the traditional two-level inverter. Since the H-bridge units of all levels are connected in series, when any cascaded unit fails, if no measures are taken, the phase where the faulty unit is located will not be able to contin...

AI Technical Summary

Problems solved by technology

However, this method belongs to reduced capacity operation, and the capacity of some non-faulty cascaded units cannot be fully utilized, resulting in a waste of resources

[0006] (2) The method based on the neutral point offset only shorts the faulty unit and can obtain a symmetrical line voltage; however, this method is mostly used in control systems with modulated waves, and is not suitable for the voltage vector method

[0008] ① System redundancy is to add a parallel redundant structure that is completely consistent with the original system. This method is not suitable for cascaded structures, otherwise it will cause serious waste of resources

[0009] ② Unit redundancy means that on the basis of the original N units connected in series, one or two spare units are added for each phase. N+1 redundancy is commonly used; once some cascaded units fail, the faulty unit will be bypassed immediately. At the same time, the redundant unit is put into work to replace the faulty unit; however, since the device works in a non-failure state in most cases, this method will cause a waste of redundant unit capacity

After reviewing domestic and foreign literature, no research has been found on "Using redundant voltage vectors to realize cascaded STATCOM fault-tolerant control"

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