A Harmonic Elimination PWM Current Tracking Control Method Based on Instantaneous Current Direct Control

Abstract

The invention discloses an instantaneous current direct control-based PWM current tracking control method. The method comprises the following steps: carrying out PWM (pulse width modulation) through building a constraint condition, generating two PWM pulses which are different in duty ratio within a current regulation cycle and driving an output current to transfer under the constraint condition; stipulating the polarity of the area enclosed by an actual current, and determining the graph area of each switching time period of an inverter circuit within the regulation cycle; and with the condition that the sum of graph area vectors of various switching time periods of the inverter circuit within the regulation cycle is zero as the constraint condition, starting a PWM peripheral function on a DSP chip and setting period parameters of the PWM according to the predetermined current regulation cycle. Transfer control on an output instantaneous current vector is automatically achieved through control on the switching state of the inverter circuit; the output current tracks the change of an instruction current; and an additional harmonic current below the modulation frequency can be eliminated.

Description

technical field [0001] The invention relates to a harmonic elimination type PWM current tracking control method based on instantaneous current direct control. Background technique [0002] For inverter devices such as APF (active power filter), SVG (static var generator), photovoltaic and wind power generation inverter grid-connected equipment and other types of inverter devices, the output end is directly connected to the inverter through a series reactor. Connected to the grid, the output terminal voltage is supported by the grid voltage. The function of this type of device is mainly realized by accurately and quickly controlling the output current to track the command current. Different types of grid-connected inverters have different command current generation methods, but after the command current is generated, there is a problem of how to effectively control the actual output current to track the command current. This link directly affects the entire set of grid-connec...

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Problems solved by technology

[0004] Method 1, this method goes through a complete regulation cycle T through the selection of the current displacement factor and the action time control s To transfer i(k) to i(k+1), the current transfer path is as follows Figure 4 As shown, in a regulation cycle T s The internal current is transferred from i(k) to i(k+1) along the path of A→D→F. This method has greatly improved the difficulty of engineering realization and control accuracy compared with the traditional timing current comparison control method. , but still this method has slightly higher even harmonic content

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