Choose Blocks to Model Power Electronic Converters

The Simscape™ Electrical™ libraries include many blocks that you can use to model power electronic converters. You must choose a block that has sufficient modeling detail for the engineering design questions that you need to answer. It is also important not to use more detail than you need, because higher-fidelity models slow down simulation and are more complex to parameterize. The right block to use therefore depends on the level of complexity that you need to meet your design goals.

First, you need to determine whether to use a prebuilt converter block or to build your converter model from the fundamental components. The best approach depends on whether one of the prebuilt converter blocks supports your converter topology at the level of fidelity you need. If you use a prebuilt converter, you then need to:

1. Choose a mathematical model with the right level of complexity.

2. Select the right block to model your converter topology using the mathematical model you have chosen.

Choose Discretes or Prebuilt Converter Blocks

In Simscape Electrical, there are two approaches that you can use to build a model of a power electronic converter:

• Use a prebuilt converter — Use a block in the Simscape > Electrical > Semiconductors & Converters > Converters library.

• Build your converter model from fundamental components, also known as discretes.

  • Use blocks in the Simscape > Electrical > Semiconductors & Converters library to model the semiconductor devices, such as transistors and diodes.

  • Use blocks in the Simscape > Electrical > Passive library to model the passive reactive components such as inductors and capacitors.

Using prebuilt converters is the simplest approach. Use this approach when possible. The Converters sublibrary includes blocks that can model a wide range of converter topologies. Prebuilt converters and discrete semiconductors both support multiple levels of fidelity. However, only discretes support the highest level of fidelity. Use discretes only if you are modeling an uncommon topology that prebuilt converters do not support or if you need a very high level of fidelity.

The simplest models that prebuilt converter blocks use are behavioral and average-value models. These models exclude switching events and function based on power balance. Algebraic equations relate the converter output to the duty cycle, voltage reference, or current reference. The main advantage of these models is that they simulate very rapidly. Use these models for system-level applications such as designing outer-loop controllers or optimizing the systems in which you deploy power electronics. Behavioral and average-value models are very versatile. Because these models function based on a simple power balance, the exact circuit configuration is often unimportant. For example, the DC-DC Converter block uses a behavioral model. You can use this block to model a:

• Synchronous or nonsynchronous buck converter

• Synchronous or nonsynchronous boost converter

• Four-switch buck-boost converter

• Dual active bridge converter

• Isolated or nonisolated bidirectional DC-DC converter

Because these models are so versatile, you can find a prebuilt converter block to represent almost any converter topology at this level of fidelity. Use prebuilt converters, not discretes, for system-level applications.

Prebuilt converters also support more complex models that you can use for converter-level applications, such as selecting manufactured components or calculating switching and conduction losses. These models are, in increasing order of complexity:

• Equivalent models

• Averaged switching models

• Piecewise linear (PWL) switching models

You learn more about these models and when to use each one in the next section, Choose Prebuilt Converter Model. The important thing to appreciate now is that the blocks that support these models use equations that, unlike those used by behavioral models, are valid only for a specific equivalent circuit. Prebuilt converter blocks supports many common topologies at these fidelity levels. The best approach, if you can, is to use a prebuilt converter block. If you have an uncommon topology, that prebuilt converters do not support, you need to use discretes. You learn which topologies prebuilt converter blocks support at these levels of fidelity in the final section, Choose Prebuilt Converter Block.

Only discretes support the highest level of fidelity. For switch-level applications, like designing gate drives, you need to use discretes.

This table summarises the best approach to modeling converters for common simulation goals.

Model Scope	Goals	Models
System level	Design outer-loop controllers Design inner-loop controllers when harmonics or switching events are not relevant Validate system behavior including other parts of the system like the motor and mechanical load or an electrical load Optimize systems in which you deploy power electronics	If a prebuilt converter block supports your topology, use a prebuilt converter block that uses a behavioral or average-value model. For multilevel inverters only, use a prebuilt converter block that uses an equivalent model with waveform control. You can find a prebuilt converter block that supports almost any topology at this level of fidelity. However, if a prebuilt converter block does not support your topology, you can: Use a prebuilt converter block that supports a more complex model for converter-level applications. Build your converter model from discrete components. Use low-fidelity semiconductor models such as the MOSFET (Ideal, Switching) block.
Converter level	Design controllers Select manufactured components Perform thermal analysis to calculate switching and conduction losses	If a prebuilt converter block supports your topology, use a prebuilt converter block that uses one of these models: Equivalent model with PWM control Averaged switching PWL switching If Simscape does not support one of these models for your topology, you can use a model with a higher level of fidelity. For example, if you want to use an equivalent model but Simscape does not support it, you can use a averaged switching model instead. If a prebuilt converter block does not support your topology, at any of these fidelity levels, build your converter model from discrete components. Use low-fidelity semiconductor models such as the MOSFET (Ideal, Switching) block.
Switch level	Design gate drives Analyze circuit transients down to device time constraints; for example, to confirm a suitable blanking time to prevent shoot through Design circuits that use a semiconductor device over a range of on-state operating points; for example, in RF power amplifiers or resonant converters	Build your converter model from discrete components. Use high-fidelity semiconductor models such as the N-Channel MOSFET block.

Choose Discrete Semiconductors

The remainder of this guide focuses only on prebuilt converter blocks. If you need to model your converter using discretes, see Choose Blocks to Model Semiconductor Devices for more information about choosing blocks with the right level of complexity. Alternatively, you can learn more from the examples in this table.

Converter Examples Using Discretes
Low-Fidelity Models for System-Level and Converter-Level Applications	High-Fidelity Models for Switch-Level Applications
SEPIC Voltage Control Vienna Rectifier Control Three-Phase Matrix Converter	Buck Converter Class E DC-DC Converter Flyback Converter
DC-DC LLC Converter

Choose Prebuilt Converter Model

This table compares the characteristics of the different models that prebuilt converter blocks support. The models become more complex as you move towards the right from behavioral and average-value models towards PWL switching models. More complex models incorporate more physics but take longer to simulate. Use this table to help you decide which model you need. If you are still not sure which model to use, a good approach is to start with a simple model and gradually add complexity if you need more detailed results. If a block supports both the equivalent and PWL switching models, you can easily switch between the two models, simply by changing the Fidelity level parameter value because both models use PWM signals as the driving signals.

	Model
	Behavioral and Average-Value	Equivalent Model - PWM Controlled	Averaged Switching	PWL Switching
Model description	These very simple models exclude switching and function based on power balance, allowing them to simulate rapidly. Algebraic equations typically relate the converter output to the duty cycle or voltage reference. Some behavioral and average-value models optionally include dynamics, such as LC.	These simple models calculate the voltage and current waveforms at the converter level using PWM signals, allowing them to simulate quickly. The models do not include protection diodes or power dissipation.	These models average the effect of switching over one or more switching periods without modeling switching events. The models apply at the converter level, utilizing gate signals to calculate voltage and current waveforms. You can average the input signal, enabling model undersampling. An averaged switch can often function with modulation waveforms or duty cycles but this approach is not the most efficient. These models include protection diodes with no dynamics but do not include power dissipation.	These models incorporate models of the individual switching devices that use a piecewise-linear on-state I-V curve.
Goals	Design outer-loop controllers Design inner-loop controllers if harmonics or switching events are not relevant Validate system behavior including other parts of the system like the motor and mechanical load or an electrical load Optimize systems in which you deploy power electronics	Design controllers when switch dynamics are not relevant, but the switching events are	Design controllers	Select manufactured components Perform thermal analysis to calculate switching and conduction losses
Driving signals	Duty cycle Voltage reference Current reference	PWM signals	PWM signals — This model then behaves similarly to PWL switching models with ideal semiconductor switches. Averaged pulses — This is usually the best option. Modulation waveforms or duty cycle — This model then behaves similarly to averaged-value models.	PWM signals
Models individual switches	No	No	No	Yes
Models protection diodes	No	No	Yes, with no charge dynamics.	Yes, with optional charge dynamics.
Models switching events	No	Yes	Yes, for PWM signals only.	Yes
Models harmonics	No	Yes	Yes, for PWM signals and averaged pulses only.	Yes
Suitable for linearization	Yes	No	Yes, for averaged pulses, modulation waveforms, and duty cycle only.	No
Implementation	Use a prebuilt converter block that exclusively uses a behavioral or average value model.	Use a prebuilt converter block that supports the Fidelity level parameter and set this parameter to Equivalent model - PWM Controlled.	Use a prebuilt converter block that supports the Switching device parameter and set this parameter to Averaged Switch.	Use a prebuilt converter block that supports the Switching device parameter and set this parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor

For more information about the differences between averaged switching and PWL switching, see these examples:

• DC-DC Converter Model Fidelity Comparison

• Chopper Model Fidelity Comparison

• Power Converter Model Fidelity Comparison — This example also includes the equivalent model option.

To design controllers using classical control theory concepts, such as gain and phase margin, you need a linearized model. You cannot linearize equivalent models or PWL models exactly because of the discontinuities in the voltage waveform, at each switching event. For more information about linearizing converter models and designing controllers for linearized converter models, see the Linearize DC-DC Converter Model and Design PI Controller for DC-DC Converter examples, respectively.

You can also use PWL switching models to simulate the sudden stop of a converter by using zeros for the driving signals.

Choose Prebuilt Converter Block

The tables in this section show the converter blocks that model different topologies at each level of fidelity. Use these tables to select the right block to model your converter. For more information about a specific converter topology and an equivalent circuit diagram, see the block reference page for blocks that support equivalent models with PWM Control, averaged switching, or PWL switching.

DC-DC Converters

You can categorize DC-DC converter topologies based on quadrant operation. This figure shows how each quadrant describes whether the output currents and voltage are positive or negative.

Converters operate in one or more of these quadrants depending on the application requirements. For example, a nonsynchronous buck converter operates only in the first quadrant, while a fully-controlled converter like a four-quadrant chopper can operate in all four quadrants, providing full control over the direction and magnitude of power flow.

If you want to use a behavioral or average-value model of a DC-DC converter, you often have a choice between the Average-Value DC-DC Converter block and the DC-DC Converter block. The Average-Value DC-DC Converter block is simpler and easier to parameterize but has fewer customization options. Use the DC-DC Converter block if you want to model voltage droop or open-circuit faults. You can also use this block if you need more a more detailed efficiency model that includes a dependency on voltage or temperature. If you do not need these options, use the Average-Value DC-DC Converter block.

First Quadrant

Converter Topology	Block
	Behavioral and Average-Value	Equivalent Model - PWM Controlled	Averaged Switching	PWL Switching
Class A chopper	Average-Value Chopper Set the Chopper type parameter to Class A - first quadrant.	Not supported	One-Quadrant Chopper Set the Chopper type parameter to Class A - first quadrant. Set the Switching device parameter to Averaged Switch.	One-Quadrant Chopper Set the Chopper type parameter to Class A - first quadrant. Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor.
Nonsynchronous buck converter	Average-Value DC-DC Converter DC-DC Converter Set the Power direction parameter to Unidirectional power flow from supply to regulated side .	Not supported	Buck Converter Set the Modeling option parameter to Nonsynchronous. Set the Switching device parameter to Averaged Switch.	Buck Converter Set the Modeling option parameter to Nonsynchronous. Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor.
Nonsynchronous boost converter		Not supported	Boost Converter Set the Modeling option parameter to Nonsynchronous. Set the Switching device parameter to Averaged Switch.	Boost Converter Set the Modeling option parameter to Nonsynchronous. Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor.

Second Quadrant

Converter Topology	Block
	Behavioral and Average-Value	Equivalent Model - PWM Controlled	Averaged Switching	PWL Switching
Class B chopper	Average-Value Chopper Set the Chopper type parameter to Class B - second quadrant.	Not supported	One-Quadrant Chopper Set the Chopper type parameter to Class B - second quadrant. Set the Switching device parameter to Averaged Switch.	One-Quadrant Chopper Set the Chopper type parameter to Class B - second quadrant. Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor.

First and Second Quadrants

Converter Topology	Block
	Behavioral and Average-Value	Equivalent Model - PWM Controlled	Averaged Switching	PWL Switching
Class C chopper	Average-Value Chopper Set the Chopper type parameter to Class C - first and second quadrant.	Not supported	Two-Quadrant Chopper Set the Modeling option parameter to First and second quadrant. Set the Switching device parameter to Averaged Switch.	Two-Quadrant Chopper Set the Modeling option parameter to First and second quadrant. Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor. Half-Bridge (Ideal, Switching)
Synchronous buck converter	Average-Value DC-DC Converter DC-DC Converter Set the Power direction parameter to Bidirectional power flow.	Not supported	Buck Converter Set the Modeling option parameter to Synchronous converter Set the Switching device parameter to Averaged Switch.	Buck Converter Set the Modeling option parameter to Synchronous converter. Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor.
Synchronous boost converter		Not supported	Boost Converter Set the Modeling option parameter to Synchronous converter. Set the Switching device parameter to Averaged Switch.	Boost Converter Set the Modeling option parameter to Synchronous converter . Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor.
Four-switch buck-boost converter		Not supported	Buck-Boost Converter Set the Modeling option parameter to Four-switch converter. Set the Switching device parameter to Averaged Switch.	Buck-Boost Converter Set the Modeling option parameter to Four-switch converter. Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor.
Nonisolated bidirectional DC-DC converter		Bidirectional DC-DC Converter Set the Modeling option parameter to Nonisolated converter. Set the Fidelity level parameter to Equivalent model - PWM-controlled.	Bidirectional DC-DC Converter Set the Modeling option parameter to Nonisolated converter. Set the Fidelity level parameter to Detailed model - switching devices. Set the Switching device parameter to Averaged Switch.	Bidirectional DC-DC Converter Set the Modeling option parameter to Nonisolated converter Set the Fidelity level parameter to Detailed model - switching devices. Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor.
Dual active bridge converter		Bidirectional DC-DC Converter Set the Modeling option parameter to Dual Active Bridge converter. Set the Fidelity level parameter to Equivalent model - PWM-controlled.	Bidirectional DC-DC Converter Set the Modeling option parameter to Dual Active Bridge converter. Set the Fidelity level parameter to Detailed model - switching devices. Set the Switching device parameter to Averaged Switch.	Bidirectional DC-DC Converter Set the Modeling option parameter to Dual Active Bridge converter. Set the Fidelity level parameter to Detailed model - switching devices Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor.
Isolated bidirectional DC-DC converter		Not supported	Bidirectional DC-DC Converter Set the Modeling option parameter to Nonisolated converter. Set the Fidelity level parameter to Detailed model - switching devices. Set the Switching device parameter to Averaged Switch	Bidirectional DC-DC Converter Set the Modeling option parameter to Nonisolated converter. Set the Fidelity level parameter to Detailed model - switching devices. Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor.

Third Quadrant

Converter Topology	Block
	Behavioral and Average-Value	Equivalent Model - PWM Controlled	Averaged Switching	PWL Switching
Buck-boost converter inverting topology	Not supported	Not supported	Buck-Boost Converter Set the Modeling option parameter to Inverting converter. Set the Switching device parameter to Averaged Switch.	Buck-Boost Converter Set the Modeling option parameter to Inverting converter. Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor.

First and Fourth Quadrants

Converter Topology	Block
	Behavioral and Average-Value	Equivalent Model - PWM Controlled	Averaged Switching	PWL Switching
Class D chopper	Average-Value Chopper Set the Chopper type parameter to Class D - first and fourth quadrant.	Not supported	Two-Quadrant Chopper Set the Modeling option parameter to First and fourth quadrant. Set the Switching device parameter to Averaged Switch.	Two-Quadrant Chopper Set the Modeling option parameter to First and fourth quadrant. Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor.

Four Quadrants

Converter Topology	Block
	Behavioral and Average-Value	Equivalent Model - PWM Controlled	Averaged Switching	PWL Switching
Class E chopper	Average-Value Chopper Set the Chopper type parameter to Class E - four quadrant.	Four-Quadrant Chopper Set the Fidelity level parameter to Equivalent model - PWM-controlled.	Four-Quadrant Chopper Set the Fidelity level parameter to Detailed model - switching devices. Set the Switching device parameter to Averaged Switch.	Four-Quadrant Chopper Set the Fidelity level parameter to Detailed model - switching devices. Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor.

DC-AC Converters

Converter Topology	Block
	Behavioral and Average-Value	Equivalent Model - PWM Controlled	Averaged Switching	PWL Switching
Single-phase inverter	Average-Value Voltage Source Converter — Supports frequency and time simulation.	Four-Quadrant Chopper Set the Fidelity level parameter to Equivalent model - PWM-controlled.	Four-Quadrant Chopper Set the Fidelity level parameter to Detailed model - switching devices. Set the Switching device parameter to Averaged Switch.	Four-Quadrant Chopper Set the Fidelity level parameter to Detailed model - switching devices. Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor.
Three-phase inverter	Average-Value Voltage Source Converter (Three-Phase) — Supports frequency and time simulation. Average-Value Inverter (Three-Phase) The Average-Value Inverter (Three-Phase) block is uncontrolled. You can control the Average-Value Voltage Source Converter (Three-Phase) block using a modulation waveform or the magnitude and phase for frequency and time simulation.	Converter (Three-Phase) Set the Fidelity level parameter to Equivalent model - PWM-controlled.	Converter (Three-Phase) Set the Fidelity level parameter to Detailed model - switching devices. Set the Switching device parameter to Averaged Switch.	Converter (Three-Phase) Set the Fidelity level parameter to Detailed model - switching devices. Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor.
Multilevel inverter	Modular Multilevel Converter (Three-Phase) Set the Fidelity level parameter to Equivalent model - waveform-controlled. Modular Multilevel Converter Arm Set the Fidelity level parameter to Equivalent model - waveform-controlled. Modular Multilevel Converter Leg Set the Fidelity level parameter to Equivalent model - waveform-controlled.	Modular Multilevel Converter (Three-Phase) Set the Fidelity level parameter to Equivalent model - PWM-controlled. Modular Multilevel Converter Arm Set the Fidelity level parameter to Equivalent model - PWM-controlled. Modular Multilevel Converter Leg Set the Fidelity level parameter to Equivalent model - PWM-controlled.	Modular Multilevel Converter (Three-Phase) Set the Fidelity level parameter to Detailed model - switching devices. Set the Switching device parameter to Averaged Switch. Modular Multilevel Converter Arm Set the Fidelity level parameter to Detailed model - switching devices Set the Switching device parameter to Averaged Switch. Modular Multilevel Converter Leg Set the Fidelity level parameter to Detailed model - switching devices. Set the Switching device parameter to Averaged Switch. Three-Level Converter (Three-Phase) Set the Switching device parameter to Averaged Switch.	Modular Multilevel Converter (Three-Phase) Set the Fidelity level parameter to Detailed model - switching devices. Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor. Modular Multilevel Converter Arm Set the Fidelity level parameter to Detailed model - switching devices. Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch. IGBT MOSFET Thyristor. Modular Multilevel Converter Leg Set the Fidelity level parameter to Detailed model - switching devices. Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor. Three-Level Converter (Three-Phase) Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET.

AC-DC Converters

The Average-Value Voltage Source Converter and Average-Value Voltage Source Converter (Three-Phase) blocks support frequency and time simulation.

Converter Topology	Block
	Behavioral and Average-Value	Equivalent Model - PWM Controlled	Averaged Switching	PWL Switching
Single-phase uncontrolled rectifier	Not supported	Four-Quadrant Chopper Set the Fidelity level parameter to Equivalent model - PWM-controlled. Set all the driving signals to zero.	Not supported	Four-Quadrant Chopper Set the Fidelity level parameter to Detailed model - switching devices. Set all the driving signals to zero. Set the Model dynamics parameter to Diode with no dynamics or Diode with charge dynamics.
Three-phase uncontrolled rectifier	Average-Value Rectifier (Three-Phase)	Converter (Three-Phase) Set the Fidelity level parameter to Equivalent model - PWM-controlled. Set all the driving signals to zero.	Not supported	Converter (Three-Phase) Set the Fidelity level parameter to Detailed model - switching devices. Set all the driving signals to zero. Set the Integral Protection Diode parameter to Diode with no dynamics or Diode with charge dynamics. Rectifier (Three-Phase) The Rectifier (Three-phase) block is a more complex block than the Converter (Three-Phase) block. The Converter (Three-Phase) block can model a passive rectifier or a switch rectifier with bidirectional power flow. The Rectifier (Three-Phase) block models a passive rectifier with 6 diodes and unidirectional power flow.
Single-phase controlled rectifier	Average-Value Voltage Source Converter — Supports frequency and time simulation.	Four-Quadrant Chopper Set the Fidelity level parameter to Equivalent model - PWM-controlled.	Four-Quadrant Chopper Set the Fidelity level parameter to Detailed model - switching devices. Set the Switching device parameter to Averaged Switch.	Four-Quadrant Chopper Set the Fidelity level parameter to Detailed model - switching devices. Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor.
Three-phase controlled rectifiers	AC-DC Converter (Three-Phase) Average-Value Voltage Source Converter (Three-Phase) — Supports frequency and time simulation. The AC-DC Converter (Three-Phase) block is simpler to parameterize and typically simulates faster than the Average-Value Voltage Source Converter (Three-Phase) block. You control the AC-DC Converter (Three-Phase) using the reference voltage. You control the Average-Value Voltage Source Converter (Three-Phase) block using modulation waves or the magnitude and phase for frequency and time simulation. Use the Average-Value Voltage Source Converter (Three-Phase) to model power losses or bidirectional power flow. Otherwise, the AC-DC Converter (Three-Phase) block is usually the better option.	Converter (Three-Phase) Set the Fidelity level parameter to Equivalent model - PWM-controlled.	Converter (Three-Phase) Set the Fidelity level parameter to Detailed model - switching devices. Set the Switching device parameter to Averaged Switch. Three-Level Converter (Three-Phase) Set the Switching device parameter to Averaged Switch.	Converter (Three-Phase) Set the Fidelity level parameter to Detailed model - switching devices. Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET Thyristor. Three-Level Converter (Three-Phase) Set the Switching device parameter to one of these options: GTO Ideal Semiconductor Switch IGBT MOSFET.

AC-AC Converters

To convert from AC to AC, you can connect two converter blocks: one to convert from AC to DC and another to convert from DC to AC. You can also can use the Bidirectional DC-DC Converter block to model a dual active bridge converter or use the Four-Quadrant Chopper block.

The Three-Phase Bridge Cycloconverter example shows how to lower the frequency of an AC input voltage by using six Converter (Three-Phase) blocks.