Three Level Flying Capacitor Inverter Leg

Description of the Three Level Flying Capacitor Inverter Leg component in Schematic Editor.

A block diagram and input parameters for the Three Level Flying Capacitor Inverter Leg are given in Table 1.

Table 1. Three Level Flying Capacitor Inverter Leg in the Schematic Editor core library
component component dialog window component properties
  • General
    • Control (Digital inputs, Internal modulator, Model)
    • S1 (digital input selection for switch S1)
    • S2 (digital input selection for switch S2)
    • S3 (digital input selection for switch S3)
    • S4 (digital input selection for switch S4)
    • Gate control enabling (enables usage of an external digital signal to activate switching)
    • Sen (digital input selection for PWM enable)
Weight = 1
Figure 1. A schematic block diagram of a Three Level Flying Capacitor Inverter Leg with corresponding switch naming

Digital inputs, when selected as the Control parameter, enables you to assign gate drive inputs to any of the digital input pins (from 1 to 32(64)). For example, if S1 is assigned to 1, the digital input pin 1 will be routed to the S1 switch gate drive. In addition, the S1_logic parameter is set to either active high (i.e. high-level input voltage VIH which turns on the switch), or active low (i.e. low-level input voltage VIL which turns on the switch). The gate drive logic depends on your external controller design.

Internal modulator, when selected as the Control parameter, enables you to use the internal PWM modulator for controlling the switches instead of the digital input pins. In this configuration, two additional component inputs appear. The En input is used as enable/disable and In is used as the reference signal input for the internal PWM modulator.

Model, when selected as the Control parameter enables you to set the IGBT's gate drive signal directly from the signal processing model. The input pin gates appears on the component and requires a vector input of four gate drive signals in the following order: [S1, S2, S3, S4]. When controlled from the model, the logic is always set to active high.

Gate control enabling, when checked, enables using an external PWM enabling digital signal.

Figure 2 shows the schematic diagram of the PWM modulation strategy. The PWM Modulator1 uses a triangular carrier with signal range from 0 to 1, while the PWM Modulator2 uses a triangular carrier with signal range from -1 to 0. The red signal is the top output of a modulator, while the green signal is the bottom one.

Figure 2. A schematic diagram of an internal modulator for a Three Level Flying Capacitor Inverter Leg

Timing

Enable delays, when enabled, includes the turn on and turn off delay of the IGBTs in the simulation. More information about this feature can be found in the dedicated section switching delay.

Advanced

Model type enables you to choose between the two types of models: Reduced and Rectifier Optimization. When the Reduced model type is selected, the converter runs for a reduced number of states and therefore uses fewer resources. This model type is used for optimizing inverter operation. When the Rectifier Optimization model type is selected, the converter model is optimized for rectifier operation.

PESB Optimization

The PESB Optimization option is available in certain converter models. When PESB Optimization is enabled, all converter's short circuit state space modes will be merged and treated as the same state space mode. For example, if one converter leg within the three phase converter is short circuited and PESB Optimization is enabled, all of the legs within the three phase converter will also be short circuited. This simplification for short circuit modeling can save a significant amount of matrix memory.

Digital Alias

If a converter is controlled by digital inputs, an alias for every digital input used by the converter will be created. Digital input aliases will be available under the Digital inputs list alongside existing Digital input signals. The alias will be shown as Converter_name.Switch_name, where Converter_name is name of the converter component and Switch_name is name of the controllable switch in the converter.