A Comparison of Simulation and Hardware-in-the- Loop Alternatives for Digital Control of Power Converters

Abstract

El acceso a la versión del editor puede requerir la suscripción del recurso Access to the published version may require subscription A comparison of simulation and hardware-in-the-loop alternatives for digital control of power converters Alberto Sanchez, Angel de Castro, Member, IEEE, and Javier Garrido, Member, IEEE Abstract-Debugging digital controllers for power converters can be a problem because there are both digital and analog components. This paper focuses on debugging digital controllers to be implemented in FPGAs or ASICs, which are designed in hardware description languages. Four methods are proposed and described. All of them allow simulation, and two methods also allow emulation -synthesizing the model of the converter to run the complete closed loop system in actual hardware. The first method consists in using a mixed analog and digital simulator. This is the easiest alternative for the designer, but simulation time can be a problem, specially for long simulations like those necessary in power factor correction or when the controller is very complex, for example with embedded processors. The alternative is to use pure digital models, generating a digital model of the power converter. Three methods are proposed: real type, float type and fixed point models (in the latter case including hand-coded and automatic-coded descriptions). Float and fixed point models are synthesizable, so emulation is possible, achieving speedups over 20,000. The results obtained with each method are presented, highlighting the advantages and disadvantages of each one. Apart from that, an analysis of the necessary resolution in the variables is presented, being the main conclusion that 32-bit floating point is not enough for medium and high switching frequencies.

Resolution Analysis of Switching Converter Models for Hardware-in-the-Loop

“…Finally, a comparison of several simulation techniques, such as mixed-signal simulators, VHDL synthesizable and nonsynthesizable models, fixed and floating-point models, and automatically translated VHDL models, is shown in [5]. This comparison proves that fixed point arithmetic obtains the best synthesis results (area and speed), but increases design time.…”

“…This is known as HIL (Hardware in the Loop),and it can use any hardware devices, including computers and FPGAs, for emulating the power converter. As shown in [5], the emulation of HIL systems can increase the speed of the second testing stage up to 29,000 times approximately in comparison with mixed-simulation tools, so the usefulness of the HIL approach is beyond doubt.…”

Finite control set model predictive control for grid-tied quasi-Z-source based multilevel inverter

“…The development and application of Model-based Predictive Control was initially slowed down due to its high computational cost. However, in the last two decades, powerful digital control platforms have been developed, e.g., FieldProgrammable Gate Arrays (FPGAs) and Digital-SignalProcessors (DSPs) have become the conventional solution for control of electrical and electronics engineering systems [24][25]. MPC is characterized by its capability to be used in a variety of processes and application and by its simplicity for advanced engineering systems with high number of dynamics, where hardconstraints, soft-constraints and non-linearities can be included easily into the control law.…”

Modeling of power converters for debugging digital controllers through FPGA emulation

“…This modification increases the working frequency, thus reducing the time required for the emulation. This optimization is explained in more detail in [13].…”

“…If we were to increase the value of ∆t to ∆t = 100 ns, the resolution of the duty cycle would be reduced to 1 %, which is far from optimal for simulating power converters. The discussion about the problems due to the resolution of the different data types is extended in [13]. This evaluation has been also applied to the models including losses.…”