Introduction

This block is put inside the OPAL Modular Multilevel Converter (MMC) model to configure the converter and calculate the capacitor and valve voltages. It processes the calculation based on users' selection in MMC CPU Parameters Block, which could configure the model into different mode: CPU mode and AVM mode. With CPU mode, the detailed switching phenomenon and individual cell voltages are modeled. This makes the model feasible in representing the deadtime between gate pulses and allows user to apply a temporary fault on particular cell. With AVM mode, the cell capacitors are been replaced by a valve equivalent capacitor therefore the computation efficiency of the test system is further improved. This block is highly correlated to the VSC Node Block, therefore the number of Valves in setting must matches the number of VSC Node Block presented in the model.

Mask and Parameters

Name	Description	Unit	Variable (Possible Values)
Initial capacitor voltage Vcap (V)	Initial capacitor voltage in cell	Volt	>=0
base value for total Vcap (V)	Summation of base capacitor voltage in a valve	Volt	should equals to MMC dc-side voltage
number of Valves	Specify the number of valves for signal routing	None	integers {1,2,3,4,5,6}
Sample time (s)	Sample timestep that used in discrete calculation	Seconds	[1e-6, 50e-6]
number of capacitors	Specify the number of capacitors for model operating in CPU mode. This value is used for signal routing.	None	[0, 50]
switch Ron (Ohm)	Switch on-state resistance for model operating in CPU mode. This value will be considered in valve voltage calculation.	Ohms	>=0
Forward voltage Vf (V)	Switch forward voltage for model operating in CPU mode. This value will be considered in valve voltage calculation	Volt	>=0

Inputs, Outputs and Signals Available for Monitoring

Inputs

Lower-level control (including PWM, VBC and Deadtime) is enable only when model is operating in CPU mode.

Name

Description

Unit

input

Input bus signal for valve voltage calculation:

mdlsel and para from MMC CPU Parameters Block
reference voltage
gate pulse.

None

Outputs

Name

Description

Unit

meas

Output bus signals that includes:

valve voltage for VSC Node Block
average capacitor voltage
measured valve current
measured valve voltage
individual capacitor voltage

None

Limitations

It is not recommend to run MMC with mixed cells in AVM mode.

MMC User Documentation

MMC CPU Model Configuration Block