Active damping strategy of LCL grid-connected inverter

Abstract

The invention discloses an active damping strategy of an LCL grid-connected inverter. The strategy mainly comprises the steps that according to a state equation of an LCL filter, a Kalman filter is designed, a state quantity of a system is evaluated by detecting network voltage and inverter side inductive current, and sending output voltage of the inverter obtained by a modulating wave gaining through an inverter bridge to the Kalman filter. The inverter side inductive current, grid-connected current and capacitor voltage are evaluated by the Kalmen filter. Capacitive current is obtained by subtraction between the inverter side inductive current and the grid-connected current, the obtained capacitive current and the grid-connected current are sent to a current controller, a direct controlstrategy of feedforward grid-connected current of the active damping and network voltage is finally achieved. According to the active damping strategy of the LCL grid-connected inverter, the advantages of the active damping strategy and Kalmen filter are combined, a Kalmen filtering algorithm is used to accurately evaluate the state quantity of the LCL filter so as to be used for active damping feedback, and so that the problem is solved that extra inverter expenses are brought by the active damping strategy.

Description

technical field [0001] The invention belongs to the field of power systems, and in particular relates to an active damping strategy for an LCL grid-connected inverter. Background technique [0002] At present, the simplest way to suppress the resonance peak of the LCL filter is to use passive damping. However, the resistance introduced by passive damping will increase the system loss, and at the same time weaken the ability of the LCL filter to suppress high-frequency harmonics, which is obviously a big disadvantage. The solution to this disadvantage is the active damping method, which increases the damping of the system by feedbacking the system state quantity. This method can well suppress the resonance peak of the LCL filter without causing additional loss. [0003] For the above problems, there are several solutions at this stage: [0004] 1. Using the inductor current on the inverter side as the feedback quantity suppresses the resonance peak and realizes stable contr...

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Problems solved by technology

[0007] The present invention proposes an active damping strategy for an LCL grid-connected inverter. The purpose of the present invention is to overcome the deficiencies of the existing methods. By using the Kalman filter as a state observer to estimate the feedback variable, the method can effectively solve the sensor cost The problem of being too high without affecting the stability of the system

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