CO SIMULATION OF GENERIC POWER CONVERTER USING MATLAB/SIMULINK AND MODELSIM

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1 CO SIMULATION OF GENERIC POWER CONVERTER USING MATLAB/SIMULINK AND MODELSIM Ajay Singh MIT, Modinagar U.P (India) ABSTRACT In this paper we discuss about the co-simulation of generic converter using MATLAB and ModelSim. Generic converter is used to provide fixed DC to variable DC conversion as well as DC/AC conversion according to their switching pattern algorithm. This simulation is performed by using two programs: MATLAB/Simulink and ModelSim. In recent years MATLAB bridged the gap between system developer and researcher. As system developer and researcher are working on same platform so it reduced required time to translating a research paper or technical specification into functional specifications. ModelSim used HDL (Hardware Description Language) simulator. The interface provides direct bidirectional link between hardware Description Language (HDL) Simulator, ModelSim, and software, MATLAB/Simulink, for direct hardware design verification and cosimulation. The most common method of creating hardware design is by using HDL such as VHDL or Verilog. Keyword: Co-Simulation, HDL, Generic Converter, MATLAB, Modelsim, VHDL. I INTRODUCTION Due to rapid invention in field of power electronics many different kinds of power electronics of devices have appeared in recent years and in near future the advancement in power electronics field will be much more. Generic power converter is shown in figure 1. In this converter we can get either variable DC or AC according to switching pattern. Previously from researcher to system developer technical specification to functional specification conversion was manual. It involved generic MATLAB code to flat m-code. Now in MATLAB based design flow MATLAB can be effectively utilized as a test bench to evaluate the system performance. HDL codes can be easily integrated in MATLAB environment. Thus it reduces the time taken in code conversion. II PRINCIPLE AND OPERATION OF GENERIC CONVERTER As shown in figure 1, generic converter works on switching pattern. The operation of the output voltage can be controlled by on period of the various switches. When switch S 0 is switched on the output is short circuited and hence the zero output is achieved. In the second case when switches S 1 and S 2 are in on state then the input voltage appears across the output terminal. In third case when the switches S 3 and S 4 are switched on the input with a reverse polarity is appeared across the output terminal. The different waveform according to switching algorithms with input are shown in figure 2 (DC input), figure 3 (DC output) and figure 4 (AC output) respectively. 99 P a g e

2 Fig. 1. Generic Converter 2.1 Algorithm I. The switching algorithm is given below: Case 1: when switch S 1 and S 2 are on and S 3, S 4 and S 0 are off V 0 = V i (state u = +1) Case 2: when switch S 3 and S 4 are on and S1, S 2 and S 0 are off V 0 = - V i (state u = -1) Case 3: when switch S 3 is on V 0 = 0 (state u = 0) Fig. 2. DC input Fig. 3. DC output 100 P a g e

3 Fig. 4(a) 2 level AC output (b) 3 level AC output III MODEL SIM BASED DESIGN ModelSim is a verification and simulation tool for VHDL, Verilog, System Verilog and mixed language designs. From the point of view of design methodology, one of the key points is the simulation of the overall system. Digital controlling of the generic power converter, usually designed by means of a hardware description language (HDL) such as VHDL or Verilog, power stage (analog circuitry) and the interface (analog to digital A/D converter). There are specific simulator for analog power stage (MATLAB, PSPICE, PSIM, etc) and specific simulator for HDL (ModelSim, etc). IV MATLAB BASED DESIGN MATLAB provides easy and interactive tools for simulation. There are a lot of tools defined in MATLAB which make it fastest. The accuracy provided in MATLAB is much more in comparison with any other analog simulator tools. MATLAB is an interpreted language for numerical computation. It allows one to perform numerical calculations, and visualize the results without the need for complicated and time consuming programming. MATLAB allows its users to accurately solve problems, produce graphics easily and produce code efficiently. V CO-SIMULATION SIMULINK/MODELSIM The link that is used for ModelSim is a co-simulation interface that integrates Electronic Design Automation (EDA) workflow for field programmable gate array (FPGA) and application specific integrated circuit(asic).this interface provides bidirectional link between ModelSim like hardware description language simulator with MATLAB/SIMULINK software for direct hardware design verification and co-simulation.the MATLAB/Simulink function block and ModelSim commands are used to provide the link for ModelSim interface.when ModelSim receives a simulation requests from co-simulation blocks used in Simulink it responds. Thus a connection is established between ModelSim and Simulink. Once a session is started, we can use Simulink and ModelSim to monitor Simulation progress and results.similar to other types of project in Simulink a base project is written to MATLAB/Simulink environment. 101 P a g e

4 This project consists of Simulink toolboxes and a block that provides a connection with Simulink and ModelSim.In this block the input and output are any HDL code such as VHDL code which we are using in our simulation.the output of this block is given as the control input for Simulink toolboxes block. The co-simulation is shown in figure 5. Simulink Design Co-simulation and Verification VHDL Simulation Fig. 5. Modelsim Co-Simulation VI DESCRIPTION OF SIMULATION AND RESULTS The simulation diagram of generic converter in Simulink is shown in figure 6 and outputs are shown in figure 7 whereas cosimulation diagram is shown in figure 8.In this diagram ModelSim block is Simulink block which provides a communication link between HDL simulator, ModelSim, and software MATLAB/Simulink. The simulation code for ModelSim block is written in hardware description language VHDL. The switching pattern is generated by VHDL code is in digital form which is being provided into the on/off switches such as MOSFET/IGBT used in Simulink simulator.the outputs obtained by this simulation are shown in figure 9. Continuous powergui Generator g m Terminator Ideal Switch Generator 1 g m Terminator 1 Generator 4 Ideal Switch v + - v Voltage Measurement Scope 1 g m 1 2 Scope Generator 2 g m Terminator 2 Ideal Switch 1 Terminator 4 Generator 3 g m Terminator 3 Ideal Switch 3 Fig. 6. Simulink Simulation Diagram Fig. 7 (a) DC Output 102 P a g e

5 Fig. 7 (b) 2 Levels AC Output Fig. 7 (c) 3 level AC Output Fig. 8. Co-Simulation Diagram Fig. 9. Co-Simulation Output VII CONCLUSION Simulation is a mandatory step in the design process of a Power converter. When controller is digitally implemented by Means of FPGA or ASICs, hardware description languages are Normally used, such as VHDL or Verilog. 103 P a g e

6 This work presents the simulation of a system which is used as DC/DC converter as well as DC/AC converter and called as generic converter. The MATLAB allows performing the dynamics of system while the ModelSim runs a program written in HDL language VHDL. The kind of simulation done in this paper allows reducing the risk of significant changes of code for one future implementation in hardware and elimination of errors. VIII ACKNOWLEDGEMENT I wish to express my profound thanks to my faculty Dr. Asheesh Singh, Associate Professor, MNNIT, for his great lecture on generic converter by which I could be able to understand the algorithm of generic converter s operation. REFERENCES [1]. Ned Mohan, tore M. Undeland, and William P. Robbins, Power Electronics Converter, Applications and Design, Wiley India, 3 rd edition [2]. MATLAB User s Guide [3]. EDA Simulator Link MQ 2.5 for Mentor Graphcs ModelSim, The Mathworks, available at [4]. Douglas L.Perry, VHDL programming by example Tata McGraw-Hill, 4th edition [5]. ModelSim SE User s Manual Version 6.0 (2004) [6]. ModelSim SE Foreign Language Interface (FLI) Reference Version P a g e