MMC Leg - Switching Function

This section describes the MMC Leg based on a switching function model.

Control for MMC Leg - NLC is a compatible component in our library for internal control the MMC Leg - Switching Function.

A block diagram and input parameters for the MMC Leg - Switching Function are given in Table 1.

Table 1. MMC Leg - Switching Function
component	component dialog window	component properties
MMC Leg - Switching Function		General Execution rate Resistance Inductance Capacitance Initial voltage Measurements Enable upper and lower arm voltages

MMC Leg - Switching Function is composed of two arms - upper and lower. Each arm consists of a series connection of voltage source (Vc_upper and Vc_lower), resistor, inductor and current measurement (I_upper and I_lower) shown in schematic block diagram below. Voltage source is controlled by Switching Function block (it replaces all capacitors and switches in arm) and represents a sum of all voltages across capacitors that are currenlty inserted in the arm. Inputs in this block are current measurements of both arms and an array Su which represents switching states for each sub-module. For example, in case when the value of element in the array Su is equal to 1, current will flow through the capacitor and if the value of element is equal to 0, current will bypass the capacitor. Number of voltage levels is determined by the length of array Su.

Figure 1. A schematic block diagram of upper and lower arm of the MMC Leg - Switching Function

Inputs and outputs

The MMC Leg - Switching Function component needs one input to operate. This input must be sent as an array and the following table describes it.

MMC Leg -Switching Function input


Input	Description
Su	A digital input that determinates which sub-modules will be inserted in the circuit.

The MMC Leg - Switching Function has 2 outputs. They are organized as an arrays and they are described in the following table.

MMC Leg - Switching Function outputs


Output	Description
Ia	The measured currents in both arms are provided as an array through analog output.
Vc	The measured voltages across the capacitors in both arms are provided as an array through analog output.

Component dialogue box and parameters

The MMC Leg - Switching Function component dialogue box consists of two tabs for specifying general parameters and for enabling measurements.

Tab: "1 - General"

In this tab, the user can specify general parameters of the MMC Leg - Switching Function model.

MMC Leg - Switching Function model "1 - General" parameters


Parameter	Code name	Description
Execution rate	ex_rate	Execution rate of all signal processing components in a model.[s]
Resistance	rd	Arm resistance. [Ω]
Inductance	ld	Arm inductance. [H]
Capacitance	cm	Capacitance of each capacitor in a leg. [F]
Initial voltage	init_vol	Initial voltage across each capacitor in a leg. [V]

Tab: "2 - Measurements"

In this tab, enabling checkbox user can observe voltage signals of upper and lower arm.

MMC Leg - Switching Function model "2 - Measurements" parameters


Parameter	Code name	Description
Enable upper and lower arm voltages	vol_arm	Enables observation of instantaneous voltage signals, separately in upper and lower arm.