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VOLTAGE ORIENTED CONTROL – SIMULATION

3.4 Current controller

This section is mainly based on the reference [4] and [14] . We are giving a summary for controller design based on Internal Model Control (IMC) with synchronous PI control (decoupled controller). To make the following more understandable, a first schematic for decoupled controller is given Figure 3.6 with the current controller and the dc link voltage controller (describe in section “3.5 DClink voltage controller”).

Figure 3.6 : Decoupled controller (current and dclink voltage controller)

3.4.1 Internal Model Control

Internal Model Control (IMC) is a method for controller design, for which the resulting controller becomes directly parameterized in terms of the plant model parameters and the desired closed loop bandwidth. For example, the controller transfer function will be

(3.3)

that is, a low pass filter with bandwidth , or G.

is an estimation of the plant (process), and n the order

A brief tutorial is available in [14] , Chapter 6, page 83. This method is used for the following controller design.

3.4.2 Synchronous PI control

PI controllers are inherently incapable of giving zero steady state control error for a sinusoidal reference. The integral action removes the error only if the reference value is constant in steady state.

Using Clarke and Park transformations, the current measurements are transformed to DC quantities, then, a simple PI controller can give good results (but not always optimal performances).

Main qualities for dq frame current controller are then :

  • fast dynamic response,

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