DSIM User’s Manual
1) GENERAL INFORMATION
1.1 Introduction
DSIM is a simulation engine specifically designed for power electronics. With a groundbreaking simulation engine and innovative modeling approach which fully exploits the characteristics of power electronic systems, it achieves an unprecedented and unparalleled performance. It increases the simulation speed by several orders of magnitude compared with any existing simulation software. Moreover, its ability to simulate large converter systems and at the same time switch transients is unique, and it makes it ideally suited for large scale power converter systems, high power converter systems, microgrid, and any systems that are computation intensive.
The DSIM engine is embedded in the PSIM simulation environment and shares the same graphic user interface. The simulation environment consists of the PSIM schematic capture, the DSIM simulation engine, and the waveform processing program SIMVIEW.
This manual covers necessary details about DSIM. The organization of this manual is as follows:
Chapter 1 – DSIM circuit structure, software/hardware requirements, and parameter format
Chapter 2 – Elements supported by DSIM simulation
Chapter 3 – Examples showing the performance of DSIM
First of all, in chapter 1, the working principles of DSIM will be briefly introduced, in terms of modeling and simulating, so that users can have a basic understanding of the DSIM engine.
1.2 Modeling Power Electronic Systems in DSIM
Power electronic systems are intrinsically hybrid dynamic systems composed of contiguous states and discrete events. Usually, continuous states include physical variables such as capacitor voltage and inductor current, while discrete events, such as switching events of semiconductor switches, lead to the transition of the system from one operating mode to another. In power electronic systems, these continuous states and discrete events not only coexist but also deeply interact with each other and co-determine the operating mode of the system, as shown below.
The power electronic system is represented in DSIM in four blocks: power circuit, control circuit, sensors, and switch controllers. The figure below shows the relationship between these blocks.
The power circuit usually consists of switching devices, RLC branches, and transformers. For the switching devices, DSIM does not offer discrete switch elements such as a single diode, IGBT, or MOSFET, to build the converter. Instead, switch modules such as two-level bridge leg, three-level T-type bridge leg, and three-level NPC bridge leg should be used to construct the circuit. See Elements >> Power >> Switches >> Switch Modules for all the switch modules supported in DSIM. DSIM does support bi-directional switches, but the bidirectional switch should be used for one-time events only (such as load change, open-circuit, or short-circuit). It should not be used for PWM operation as the DSIM engine is not optimized to handle it.
For the versions after DSIM 2021a, the single switches are supported for simulation. This feature enables the simulation of newly-designed topologies and largely increases users’ flexibility of constructing circuits. It needs to be mentioned that single switches are not suggested for large-scale circuits. If hundreds of switches are used, the advantages of DSIM will be greatly weakened.
For the switching modules, two types of models are supported in DSIM, namely the ideal model and transient model.
Ideal Model
If an ideal model is selected, DSIM will model the switch as a small resistance in on-state and as an open circuit in off-state. The on-state resistance is defined as a parameter called Switch Resistance. It is considered the same for all the active switches and the diodes in the module. The off-state resistance is ignored. The transitions between on-state and off-state are also ignored, so the system can be viewed as a piecewise-linear time-invariant (PLTI) system, which can be characterized by a set of n first-order ordinary differential equations (ODEs). Taking a two-level bridge leg as an example, the figure below shows how DSIM model the switch module. Please refer to the online help of each module to see its legal control input.
Transient Model
Switching transients between the two steady states are sometimes significant in terms of device protection, switching loss, voltage/current balancing, and EMI analysis. However, simulating switching transients in a large system is often challenging due to the high stiffness of the circuit. DSIM adopts an innovative modeling approach called the Piecewise Analytical Transient (PAT) model, which is capable of simulating the switching transients in a very fast and stable way. All the model parameters are available from the device datasheet.
Taking a two-level bridge leg as an example, the equivalent circuit for IGBT/diode bridge and for SiC MOSFET/diode bridge is shown below. Note that the stray inductors are already incorporated in the model whose values should be entered as parameters. One should not put extra stray components in the main circuit which will cause highly stiff equations and therefore low simulation speed.
DSIM now offers a transient model for all the switching modules except three-level NPC bridges. One can choose between the IGBT/diode model and the SiC MOSFET/diode model. Please turn to online help for more information about the definitions of the model parameters. In Chapter 3 Examples, comparisons of the model results and experimental results will be presented.
With the help of the transient model, the power loss of switch modules can be evaluated in DSIM since the version DSIM 2021a. The switch loss calculation is possible by interfacing the temperature and power loss with outside thermal circuits. Please refer to the corresponding tutorial for detailed information.
The control circuit is represented in the block diagram. DSIM supports only digital control temporarily. Components in z-domain, logic gates, and computational blocks can be used in the control circuit. Sensors are used to measure power circuit quantities and pass them to the control circuit. Gating signals are then generated from the control circuit and sent back to the power circuit through switch controllers to control switches.
The whole DSIM engine works in an event-driven manner, and one should use the switch controllers under Elements >> Other >> Switch Controllers to generate switching signals. The offered components cover most of the PWM generators including carrier-based PWM, SVPWM, square wave controller, etc. Otherwise, one should be careful in the current DSIM version since switching events may not be located accurately.
1.3 Simulating Power Electronic Systems in DSIM
DSIM engine uses a discrete state (DS) algorithm in an event-driven (ED) manner. It fully exploits the characteristics of power electronic systems and exhibits ultra-fast performance especially in large-scale or high-frequency systems, where typically hundred-fold acceleration can be achieved under the same accuracy, compared with existing simulation tools. Chapter 3 Examples shows some examples where such comparisons are presented.
The DS algorithm is intrinsically a variable step-size algorithm that achieves adaptive numerical integration of system states with less computational costs, and the ED manner avoids unnecessary iterative calculations for the frequently-occurred switching events in power electronics. Since a variable step-size algorithm is employed, it’s not necessary for users to select a proper step-size. Instead, the DSIM engine will choose the step-size adaptively in each calculation step. The following figure illustrates the DSIM simulation framework compared with the conventional one.
1.4 Installing the Program
Some of the files in the DSIM directory are:
- PSIM.exe – PSIM circuit schematic editor
- SIMVIEW.exe – Waveform processing program
File extensions used in DSIM are:
- *.psimsch – schematic file
- *.psimpjt – project file
- *.schpack – package file
- *.lib – library file
- *.txt – Simulation output file in text format
- *.smv – Simulation output file in binary format
1.5 Simulating a Circuit
To simulate the buck converter circuit “buck.dsimsch” in “examples\DSIM\dc-dc”:
- Start PSIM. From the File menu, choose Open Examples…, then, go to “DSIM\dc-dc” folder to load the file “buck.psimsch”.
- From the Simulate menu, choose Run DSIM Simulation to start the simulation. Simulation results will be saved to File “buck.smv”.
- By default, Auto-run SIMVIEW is selected in the Options menu. SIMVIEW will be launched automatically. In SIMVIEW, select curves for display. If this option is not selected, from the Simulate menu, choose Run SIMVIEW to start SIMVIEW
1.6 Simulation Control
DSIM adopts a variable-step algorithm, and users do not have to specify the simulation step. The Simulation Control element defines parameters and settings related to simulation.
To place the Simulation Control in the schematic, go to the Simulate menu, and select Simulation Control.
Image:
End time: The total simulation time, in sec.
Maximum step size: The maximum time step, in sec. If the adaptively chosen time step is larger than the “Maximum step size”, the step size is forced to be “Maximum step size”.
Relative error: “Relative error” is used to control the numerical error in state integration. The engine chooses the step size based on “Relative error”. Decreasing it leads to smaller time steps, hence more accurate results but longer consuming time. In most cases, at least 1e-3 “Relative error” is recommended. One can also decrease it until no changes are observed in the simulated waveforms.
Maximum display step size: The “Maximum display step size” (in sec.) is used to limit the display step between two points in the output waveforms. This is typically used for high-frequency waveforms when the engine gives accurate results at each point, but with low “sampling frequency” due to relatively large step size, as shown below (red waveform). Decreasing “Maximum display step size” forces the engine to show details between two points (i.e. during each time step), as shown below (blue waveform). This will cause extra calculations but is more efficient than decreasing the “Maximum step size”. It is recommended to use a larger “Maximum display step size” to save time when simulated waveforms are displayed with enough resolution.
Print time: Time from which simulation results are saved to the output file (default = 0). No output is saved before this time.
Absolute error: If the error of calculation is larger than the absolute error, the step size will be reduced for accuracy. If there is an error saying “fail to find stable states”, try a smaller absolute error for high accuracy.
Absolute Error for zero-crossing detection: If the absolute value of a variable is larger than this parameter, it is considered zero. Generally, the default value works well.
The figure below shows the effect when the Maximum Display Step Size is reduced.
Some tips on how to change simulation settings:
- Try to decrease the “Relative error” if you think the simulation is not accurate enough;
- Try to decrease the “Maximum display step size” if you think the results have a low resolution;
- Try to decrease the “Maximum step size” when you find that the simulation results do not converge.
Parameters for the BDSED solver
End Time: The total simulation time, in sec.
Maximum step size: The maximum time step, in sec. If the adaptively chosen time step is larger than the “Maximum step size”, the step size is forced to be “Maximum step size”.
Minimum step size: The minimum simulation time step size(for reference only), in seconds. This parameter is referred to so as to know the level of time scale that users care about. The real step sizes may not all be larger than the minimum step size. If this parameter is increased, the solver is prone to choose a larger step, which improves the efficiency but sacrifices the accuracy, and vice versa. This parameter can be adjusted to meet the demand for both accuracy and efficiency. Generally, the default value works well.
Relative error: “Relative error” is used to control the numerical error in state integration. The engine chooses the step size based on “Relative error”. Decreasing it leads to a smaller time step, hence more accurate results but a longer consuming time. In most cases, at least 1e-3 “Relative error” is recommended. One can also decrease it until no changes are observed in the simulated waveforms.
Print time: Time from which simulation results are saved to the output file (default = 0). No output is saved before this time.
Absolute Error: If the error of calculation is larger than the absolute error, the step size will be reduced for accuracy. If there is an error saying “fail to find stable states”, try a smaller absolute error for high accuracy.
Absolute Error for zero-crossing detection: If the absolute value of a variable is larger than this parameter, it is considered zero. Generally, the default value works well.
Some tips on how to change simulation settings:
1) When the system is highly stiff and the simulation parameters are not well chosen, there is a possibility of divergence. Try to increase the minimum step size for better numerical stability. Try to decrease the “Relative error” if you think the simulation is not accurate enough;
2) When the efficiency of the BDSED solver is not good, try a larger minimum step size, for example, 1e-5.
2) ELEMENTS SUPPORTED IN A DSIM SIMULATION
This chapter lists all the elements that are supported in DSIM simulation. Users can choose to display only DSIM supported elements in Options >> Settings >> Advanced.
The following elements are supported in DSIM.
Under Elements >> Power:
- RLC branches
Resistor
Inductor
Capacitor
Capacitor (Electrolytic)
R3
L3
C3
RL3
RC3
RLC3 - Switches
– Switch Modules
1-ph Inverter
2-level Bridge Leg
3-level T-Type Bridge Leg
3-level NPC Bridge Leg
3-ph Inverter
3-ph 3-level T-Type Bridge Leg
3-ph 3-level NPC Bridge
Dual Active Bridge (DAB)
1-ph Diode Bridge
3-ph Diode Bridge
– Bi-directional Switch
– 3-ph Bi-directional Switch - Transformers
Ideal Transformer
1-ph Transformer
1-ph Transformer (no Lm) - Renewable Energy Module
Solar Module (physical model) - Motor Drive
Squirrel-cage Ind. Machine (with load)
PMSM (with load)
*The above motor drive modules contain the following types of mechanical loads: constant torque, constant speed, constant power, general.
Under Elements >> Control:
- Computational Blocks
Multiplier
Divider
Square-root
Sine
Sine (rad.)
Sine (p.u.)
Arcsine
Cosine
Cosine (rad.)
Cosine (p.u.)
Arccosine
Sine/Cosine (rad.)
Sine/Cosine (p.u.)
Tangent
Arctangent
Arctangent (p.u.)
Arctangent 2 (rad.)
Arctangent 2 (p.u.)
Exponential (a^x)
Power (x^a)
LOG (base e)
LOG10 (base 10)
Absolute Value
Sign Block
Maximum / Minimum Block - Other Function Blocks
Multiplexer (2-input)
Space Vector PWM
Space Vector PWM (alpha / beta) - Logic Elements
AND Gate
AND Gate (3-input)
OR Gate
OR Gate (3-input)
XOR Gate
NOT Gate
NAND Gate
NOR Gate - Digital Control Module
Zero-Order Hold
Unit Delay
Integrator
Differentiator
PI
z-domain Transfer Function - Under the Control menu
Proportional
Comparator
Limiter
Upper Limiter
Lower Limiter
Range Limiter
Summer (+/-)
Summer (+/+)
Summer (3-input)
Under Elements >> Other:
- Switch Controllers
On-Off Controller
Square Wave Controller (Variable freq.)
Carrier PWM Controller (z-domain)
Square Wave Controller (z-domain)
Phase Shift Controller (z-domain)
Phase Shift Controller (fixed D) (z-domain)
Space Vector PWM (2-level) (z-domain)
Space Vector PWM (3-level) (z-domain) - Sensors
Voltage Sensor
Current Sensor
Voltage Sensor (average)
Current Sensor (average) - Probes
Voltage Probe
Current Probe
Voltage Probe (node-to-node) - Function Blocks
abc-dqo Transformation
dqo-abc Transformation
Clarke Transformation (abc-alpha/beta)
Clarke Transformation (ab-alpha/beta)
Clarke Transformation (ac-alpha/beta)
Inverse Clarke Transformation (alpha/beta-abc)
Park Transformation (alpha/beta-dq)
Park Transformation (alpha/beta/sin/cos-dq)
Inverse Park Transformation (dq-alpha/beta)
Inverse Park Transformation (dq/sin/cos- al/be)
x/y-r/angle Transformation
r/angle-x/y Transformation
Math Function
Math Function (2-input)
Math Function (5-input)
Math Function (10-input)
C Block
Simplified C Block
Under Elements >> Sources:
- Voltage
DC
Sine
3-ph Sine
Grounded Source (multiple) (constant, sine, triangular, sawtooth, square, step, step(2-level)) - Under the Sources menu:
Constant
Time
Ground
Ground (1)
Ground (2)
3) EXAMPLES
The high performance of DSIM and its ability to simulate switching transients makes it an ideal solution for large-scale power converter systems, high power converter systems, microgrid, and any systems that are computation intensive. In this chapter, some examples are described to show how DSIM empowers the design and research of relatively complicated systems.
Example: 200kHz LLC Circuit
The LLC circuit usually operates in a high-frequency range. With the conventional simulation approach, a very small simulation time step is needed to get correct results, making the whole simulation time-consuming. DSIM offers an event-driven mechanism that greatly shortens the simulation time. This LLC circuit can be found under Examples >> DSIM >> LLC converter (200kHz).
The following figure shows the circuit structure. The studied case is an LLC isolated bidirectional DC-DC converter, with a variable-frequency control around 200kHz. A variable-frequency square wave controller is used to generate the switching signals. Note that for simplicity, the same switching signals are used for both primary and secondary side bridges. This is not the case in practice, but just an approximation to show the performance of DSIM in similar cases.
To use an existing simulation tool with a fixed step-size, a very small time step must be selected. A test result is shown in the following figure, where the simulated waveforms of the output DC voltage Vo under different time steps are shown. It can be observed that any time step larger than 1e-9s is not enough to get correct waveforms.
With a 1e-9s time step, the existing tool takes more than 20 minutes for a 0.1-second simulation. However, with the Discrete State Event-Driven algorithm, DSIM takes less than 1 second to get the same results, which is more than 1300 times faster. The following figure shows the comparisons of the simulated results, where Vo is the output DC voltage, and Vcr is the resonant capacitor voltage. The tests are conducted with an Intel Core i7-6600U CPU.
Example: 50kVA Solid-State Transformer
This example shows a 50kVA solid-state transformer (SST). The system consists of three stages, as shown in the following figure. It is tested under a 5-second grid-side low-voltage ride-through dynamic, where the waveform of the grid-side voltage is also shown below.
The DSIM circuit of this example is shown below.
For the 5-second dynamic, if the ideal switch model is used, DSIM takes less than 5 seconds to finish the simulation, which is about 50 times faster than current software; if the transient switch model is used, DSIM takes about 50 seconds, which is 700 times faster than another commercial software. The comparisons are shown below. The tests are conducted with an Intel Core i7-7700K CPU.
The simulated results are in good agreement with experimental results. Some comparisons of the grid-side waveforms and the DC-link voltage are shown below.
The PAT model in DSIM also gives good results compared with measured ones, as shown below.
Example: 10kV four-port Solid-State Transformer
This example shows how DSIM helps to simulate a very large system: a four-port solid-state transformer (SST), also known as an electric energy router (EER). It consists of 576 switches in total and the rated power for each port is 1MW. The system diagram and the circuit built in DSIM are shown below.
To simulate a 0.2s dynamic, DSIM takes only 17 seconds, which is more than 1000 times faster than a commercial software specialized in power electronics, while the simulated results are very close, with less than 0.01% relative error, as shown below. DSED represents the DSIM algorithm.
Example 4: Experimental Verifications of the Transient Model
This example shows the experimental verifications of the PAT model in DSIM. Double pulse tests are conducted on Infineon IGBT FZ600R65KF1 (6500V, 600A). Some experimental results are shown below.
Generally PAT model gives good results compared with experimental waveforms if the input parameters are accurate enough. Under some small-current conditions, the model error can be larger.
DSIM User’s Manual
Version 2020a
Release 2
May 2020
Copyright © 2020 DSIM Technology Co.
All rights reserved. No part of this manual may be photocopied or reproduced in any form or by any means without the written permission of DSIM Technology Co.
Disclaimer
DSIM Technology Co. (“DSIM Tech”) makes no representation or warranty with respect to the adequacy or accuracy of this documentation or the software which it describes. In no event will DSIM Tech or its direct or indirect suppliers be liable for any damages whatsoever including, but not limited to, direct, indirect, incidental, or consequential damages of any character including, without limitation, loss of business profits, data, business information, or any and all other commercial damages or losses, or for any damages in excess of the list price for the license to the software and documentation.