Multi-parallel capacity optimal distributing method for active harmonic suppression device

Abstract

The invention discloses a multi-parallel capacity optimal distributing method for an active harmonic suppression device. The method is characterized in that a multi-unit redundancy and main and secondary control structure is adopted, and the complete set system is switched under two running modes according to the load harmonic content. The method comprises the following steps: 1) distributing the compensating capacity according to the principle of minimizing the number of running power units when the harmonic capacity is less than the complete set compensating capacity, and coordinating the switching of each power unit to realize the fullest utilization of the complete set compensating capacity; (2) considering three capacity limiting factors, namely, the rated compensating capacity, the effective utilization range of the voltage at the DC side, and the running temperature of a main circuit device when the harmonic capacity is more than the complete set compensating capacity; outputting the capacity limiting coefficient according to the variable step size strategy; preferentially compensating the low-frequency harmonic wave with relatively high compensating content, so as to realize the maximum utilization of the complete set compensating capacity. According to the method, the upper and lower main and secondary controllers are coordinated and matched to realize the optimal utilization of the multi-parallel APF (Active Power Filter) compensating capacity; the feasibility and practical value are raised.

Description

technical field [0001] The invention relates to a capacity optimal utilization method and a capacity limiting strategy of a multi-machine parallel large-capacity APF (Active Power Filter), and belongs to the technical field of power electronic technology applied in power systems. Background technique [0002] As a large number of power electronic devices are put into use, the harmonic content of the power grid is increasing day by day. Restricted by the technology of thyristor devices, it is difficult for a single APF to achieve large-capacity output. Currently, a multi-machine parallel structure is often used. When using a multi-machine parallel structure, two problems are involved: 1) When the harmonic content is small and lower than the compensation capacity of the whole machine, how to coordinate the operation of each unit, and realize the compensation of the whole machine on the basis of ensuring the compensation performance 2) How to ensure the safe and reliable opera...

AI Technical Summary

Problems solved by technology

Due to the limitation of thyristor device technology, it is difficult for a single APF to achieve large-capacity output. Currently, a multi-machine parallel structure is often used.

When using a multi-machine parallel structure, two problems are involved: 1) When the harmonic content is small and lower than the compensation capacity of the whole machine, how to coordinate the operation of each unit, and realize the compensation of the whole machine on the basis of ensuring the compensation performance 2) When the harmonic content is large and higher than the compensation capacity of the whole machine, how to ensure the safe and reliable operation of the device and realize the maximum utilization of the compensation capacity of the whole machine

Disadvantage: All power units operate at the same time. When the harmonic content is low, the utilization rate of the compensation capacity of the whole machine is low; when a single point of failure occurs, the compensation performance of the whole machine will be affected

Disadvantages: multiple CTs are required, the cost is high, and the synchronization of sampling current is poor; the APF closest to the load side runs continuously at full load for a long time, which is prone to hardware aging; lack of coordination between various power units

Disadvantages: Poor scalability; if the power unit of the latter stage fails, and the compensation capacity of the former stage is insufficient, it will easily lead to overload operation of the power unit of the former stage

Disadvantages: When the harmonic capacity is low, resources are wasted; when the capacity is expanded, the parameters of the main controller need to be modified, and there is a contradiction between unitized operation and centralized control; when a single point of failure occurs, each power unit may be overloaded

[0013] 3. For the operating temperature of the main circuit components, generally only IGBT is considered

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