Zeta Converter

Converter Configurations and Schematic Block Diagram

The Zeta Converter component supports multiple modifications to its topology. Modifications that can be done are based on the following three principles:

Inductor modification: The idea is to use a so-called switched inductor configuration instead of a single inductor. In steady state operation, when the controllable switch is in 'ON' state, diodes D_p1 and D_p2 are conducting, meaning that the inductors L₁ and L₂ are charged while connected in parallel. When the controllable switch is in 'OFF' state, only the D_s diode is conducting, thus connecting these inductors in series during discharge. For this reason, it is necessary to use the inductors of same value. This means that it is possible to obtain a larger voltage gain, since the inductance is 'easier to charge and harder to discharge'.
Figure 2. Switched inductor
Capacitor modification: Similarly to the switched inductor, it is possible to use two capacitors, here refered to as a 'hybrid-switched capacitor', which further increases the voltage step-up ability of the converter.
It is possible to use two inductances with corresponding switches. This way, two inductances are charged while in a parallel connection and discharged while in a series connection. The two switches are controlled simultaneously.

Available converter configurations are given in Table 1. Their schematic diagrams can be seen in Figure 3 to Figure 10. The input to output voltage ratio formula is derived under the assumptions of continuous current conduction mode and constant capacitor voltage, with D representing the duty cycle of controllable switch(es). The output LC filter should be connected externally for each of the configurations in order for the converter to be functional.

Table 1. Converter configurations
Property value			Vout/Vin	Configuration name
Inductance type	Double switch/inductor	Use hybrid switched capacitor	Input to output voltage ratio of the converter	Name of the configuration variant that is configured with each set of property values
Inductor	False	False	$\frac{D}{1 - D}$	Single inductor
Inductor	False	True	$\frac{2 D}{1 - D}$	Single inductor with hybrid-switched capacitor
Inductor	True	False	$\frac{2 D}{1 - D}$	Double inductor
Inductor	True	True	$\frac{3 D + 1}{1 - D}$	Double inductor with hybrid-switched capacitor
Switched inductor	False	False	$\frac{D (D + 1)}{1 - D}$	Switched inductor
Switched inductor	False	True	$\frac{D (D + 3)}{1 - D}$	Switched inductor with hybrid-switched capacitor
Switched inductor	True	False	$\frac{2 D (D + 1)}{1 - D}$	Double switched inductor
Switched inductor	True	True	$\frac{{2 D}^{2} + 5 D + 1}{1 - D}$	Double switched inductor with hybrid-switched capacitor

Configurations that utilize a double inductor contain two switches. Since these switches are controlled simultaneously, only one switching signal is used. Therefore, the switch designated as 'S1' in the component parameters can represent one or two controllable switches, depending on how many are included.

Weight of the Zeta Converter component for real-time/VHIL simulation is 2 if Double switch/inductor option is selected, otherwise, weight of the Zeta Converter component for real-time/VHIL simulation is 1.

Figure 4. Single inductor with hybrid-switched capacitor

Figure 6. Double inductor with hybrid-switched capacitor

Figure 8. Switched inductor with hybrid-switched capacitor

Figure 10. Double switched inductor with hybrid-switched capacitor

Control

Selecting Digital inputs as the Control parameter enables assigning 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 gate_logic parameter selects either active high (High-level input voltage VIH turns on the switch), or active low (Low-level input voltage VIL turns on the switch) gate drive logic, depending on the design of the external controller. In TyphoonSim, digital signals are read from the internal virtual IO bus. Hence, if some signal is sent to digital ouput 1, it will appear on digital input 1.

Selecting Internal modulator as the Control parameter, enables use of the internal PWM modulator for driving S1 switch instead of the digital input pins. In this configuration, two additional component inputs will be present. En input is used to enable/disable the internal PWM modulator, while In is used as a reference signal input.

Selecting Model as the Control parameter, enables setting of the IGBT gate drive signal directly from the signal processing model. The input pin gate appears on the component. It is a 1-element (scalar) input which controls the S1 switch gate. When controlled from the model, logic is always active high.

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.

Ports

In+ (electrical)
- DC input + port.

In- (electrical)
- DC input - port.

Out+ (electrical)
- DC output + port
Out- (electrical)
- DC output - port

s_ctrl (in)
- Available if model control is selected
- 1-element (scalar) input gate signal for switch

En (in)
- Available if Internal modulator control is selected
- Used to enable/disable internal modulator

In (in)
- Available if Internal modulator control is selected
- Used to specify modulation signal value for internal modulator

Freq (in)
- Available if Internal modulator control is selected and Variable carrier frequency is selected as the modulator's operation mode
- Used to specify modulator's carrier frequency

General (Tab)

Control
- Specifies how switches are controled. It is possible to choose between: Digital inputs, Internal modulator, and Model
- More details about each type of control can be found in the Control section

If Digital inputs is selected as Control, the following properties can be used:
- S1
  - Digital input that is used to control S1 switch
- S1_logic
  - Logic that will be applied to control signal for S1
  - Active high or active low
- Gate control enabling
  - If enabled, gives a possibility to control if changes in the gate control signal is applied or not
- Sen
  - Available if Gate control enabling is enabled
  - Digital input that enables/disables switching
- Sen_logic
  - Available if Gate control enabling is enabled
  - Logic that will be applied to Sen signal

If Model is selected as Control, the following properties can be used:
- Execution rate
  - Defines the period between two updates of gate signals for the component. Gate signals are provided as a signal processing input to component.

If Internal modulator is selected as Control, the following properties can be used:
- Operation mode
  - Specifies the source of the internal modulator carrier frequency
  - If Operation mode is Fixed carrier frequency, then frequency can be specified on the component properties
  - If Operation mode is Variable carrier frequency, then the frequency can be specified using a signal processing port
- Carrier frequency (Hz)
  - Available if the Operation mode is a Fixed carrier frequency
  - Specifies the internal modulator's carrier frequency
- Carrier phase offset
  - Specifies the internal modulator's carrier phase offset in degrees
- Dead time period
  - Specifies dead time for the internal modulator in seconds
- Reference signal [min, max]
  - Specifies carrier signal minimal and maximal value
  - Vector containing two values: the minimal carrier signal value, followed by the maximal carrier signal value
- Load mode
  - Specifies on which event the new value of the modulation signal will be applied in the internal modulator
    - If on min is selected, new value will be applied when carrier reaches minimal value
    - If on max is selected, new value will be applied when carrier reaches maximal value
    - If on either is selected, new value will be applied when carrier reaches minimal or maximal value

Electrical (Tab)

Inductance type
- Type of inductor in converter
- Available options are inductor and the switched inductor
Double switch/inductor
- Enables the use of two equal inductances, each with a corresponding controllable switch. More details in Converter Configurations and Schematic Block Diagram section.
Inductance
- Inductance of a single inductor [H]
Initial current
- Inductor initial current [A]
Hybrid-switched capacitor
- Enables the use of two equal capacitors, along with two diodes instead of one. More details in Converter Configurations and Schematic Block Diagram section.
Capacitance
- Capacitance of a single capacitor [F]
Capacitor's ESR
- Specifies equivalent series resistance of a single capacitor [Ω]
Initial voltage
- Capacitor initial votage [V]

Extras (Tab)

The Extras tab gives you the opportunity to set Signal Access Management for the component.

Signal visibility is calculated based on the 'signal_access' property and whether or not a parent component in its hierarchy is locked or not. Components that are not contained within locked components expose their signals regardless of the 'signal_access' property. The 'signal_access' property can have one of three values:

Public - Components marked as public expose their signals on all levels.
Protected - Components marked as protected will hide their signals to components outside of their first locked parent component.
Inherit - Components marked as inherit will take the nearest parent 'signal_access' property value that is set to a value other than inherit.

References

B. Axelrod, Y. Berkovich and A. Ioinovici, 'Hybrid Switched - Capacitor Ćuk/Zeta/SEPIC Converters in Step-up Mode', 2005 IEEE International Symposium on Circuits and Systems, May 2005.
M. S. Bhaskar et al., "A New Hybrid Zeta-Boost Converter With Active Quad Switched Inductor for High Voltage Gain," in IEEE Access, vol. 9, pp. 20022-20034, 2021, doi: 10.1109/ACCESS.2021.3054393.