Inverter output relay pull-in impact current suppression method and device

Abstract

The invention provides an inverter output relay pull-in impact current suppression method and device. The method comprises the following steps: S1, collecting the input quantity of an inverter circuit before the pull-in operation of a relay of an inverter, and modulating the input quantity; and S2, controlling the relay to perform actuation outside the overshoot time interval. According to the invention, the inverter applying the method can effectively reduce and eliminate the impact current generated when the relay of the inverter is actuated, can overcome the technical defects of the existing suppression method under extreme conditions, and improves the applicability of the impact current suppression method.

Description

technical field [0001] The invention relates to the technical field of inverter electric control in the electric power industry, in particular to a method and device for suppressing the inrush current of an inverter output relay. Background technique [0002] In new energy grid-connected power generation systems such as photovoltaic power generation, wind power generation, and energy storage, the inverter performs energy conversion and transmission tasks. The AC filter inside the inverter is connected to the grid through an AC switch such as a relay. The pull-in of the relay can make the inverter connect to the grid, so as to realize the energy transmission with the grid. [0003] In circuit science, when the load is energized, a large current is usually generated, which is the inrush current. Similarly, when the switching power supply in the inverter is started, it is also easy to generate inrush current due to the voltage difference between the two ends of the switch. Th...

AI Technical Summary

Problems solved by technology

However, the suppression method described in this prior art still cannot completely solve the problem of inrush current generated by the inverter output relay, and it still has the following technical defects:

[0006] 1) It is necessary to collect the AC port-to-ground voltage and the inverter-to-ground common-mode voltage at the same time, and to calculate the collected limited voltage. The suppression method itself is complicated and difficult to implement;

[0007] 2) While requiring the inverter to output complete AC, it also needs to superimpose DC. Since the input of most inverter applications does not have a boost function, then when 1 / 2 of the bus voltage is very close to the peak value of the mains voltage When it is close, there is almost no space to continue to superimpose the DC component on half of the bus voltage, that is, the suppression method fails;

[0009] 4) Based on defect 3, if the DC component to be compensated is large, the bus voltage needs to be boosted, and the boost of the bus voltage will directly lead to higher requirements for the withstand voltage level of devices such as IGBTs and capacitors on the bus

Taking the aforementioned invention patent application as an example, in order to meet its requirements, the input DC bus voltage is required to reach 933V (220*√2*2+(220*√2*2 / 2)), and the IGBT used under normal conditions The withstand voltage level is only 700V, that is, IGBT and capacitor devices with higher withstand voltage levels will directly increase the cost of equipment;

[0010] 5) Based on defect 3 and defect 4, another problem caused by boosting the bus voltage is the rise of the DC voltage that needs to be compensated, and it is difficult to achieve high-voltage inverter balance on the normal inverter.

[0011] In view of this, the existing technology should be improved to solve the technical problems that the inrush current generated by the pull-in of the inverter output relay is difficult to suppress, the scope of application is limited, and the suppression is not thorough.

Images