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Simulation of Power Electronic Systems Using PSpice

Simulation of Power Electronic Systems Using PSpice. Presented by Nik Din Muhamad. Presentation Outlines. In order to use Pspice for power electronic systems, we have to:. Know background of SPICE Understand Power Electronics Circuits/Systems

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Simulation of Power Electronic Systems Using PSpice

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  1. Simulation of Power ElectronicSystems Using PSpice Presented by Nik Din Muhamad

  2. Presentation Outlines In order to use Pspice for power electronic systems, we have to: • Know background of SPICE • Understand Power Electronics Circuits/Systems • Know how to use VPULSE to generate useful waveforms • Know how to make simple models using ABM

  3. Scope This presentation covers: • PSpice • System/Circuit Level Simulation • Power Electronic Circuits/Systems • Simulation

  4. Why simulation? Simulations are essential ingredients of the analysis and design process in power electronics: • Saving of development time • Saving of costs (‘burnt power circuits tend to be expensive’) • Better understanding of the function

  5. … continued • Testing and finding of critical states and regions of operation (Worst Case Analysis) • Stress test (Smoke Analysis) • Optimization of system

  6. Overview • Simulation of analog circuits normally uses three basic tools: • SPICE simulator, • Mathematical analysis package, • and Microsoft Excel.

  7. SPICE • Simulation Program for Integrated Circuit Emphasis • Uses iterative Newton-Raphson Algorithm • to solve a set of nonlinear equations. • The AC analyses are linear and do not use • iterative algorithm • Digital devices are evaluated using Boolean • algebra.

  8. SPICE LIMITATIONS • The Newton-Raphson algorithm is guaranteed • to converge if the equations is continuous and • the initial approximation is close enough to • the solution. • The transient analysis has the additional • possibility of unable to converge because the • time step required too small due to something • in the circuit moving too fast.

  9. SPICE LIMITATIONS Computer Hardware Limitation: • Voltage and currents are limited to +/-1e10. • Derivatives in PSpice are limited to 1e14. • The arithmetic used in PSpice is double • precision and has 15 digits of accuracy.

  10. Power Electronic Circuit • Power electronic circuits are characterized by switching on and off of power semiconductor switches; the generated waveform is passed through inductors and capacitors for filtering.

  11. Power Electronic Circuit • Due to switching action of the switch, discontinuity (in circuit variables and in time) can easily occurs during simulation, which leads to convergence problem. “Avoid discontinuity”

  12. Discontinuity Analogy: A Bump on the Road “Whole car shakes when I hit a bump on the road” PSpice doesn’t like discontinuity as we don’t like a bump on the road.

  13. VPULSEWaveform generator • PULSE • SAWTOOTH • TRIANGULAR

  14. VPULSEWaveform generator • In order to use PSpice for power electronic circuits, the first thing you have to know is to program VPULSE to produce these waveforms: • PULSE • Sawtooth • Triangular

  15. has 7 parameters to set • TD can be zero, others (TR and TF) can not be! VPULSEWaveform Generator Part V1= V2= TD= TR= TF= PW= PER= PW V2 TR TF TD V1 PER • know what parameters to adjust and to fix.

  16. Very small values for TR and TF relative to PER • Duty cycle = PW/PER VPULSETo Generate Pulse Waveform PW V1=0 V2=12 TD=0 TR=10n TF=10n PW=10u PER=20u V2 V1 TR ≈ 0 TF ≈ 0 PER

  17. A Typical applicationBuck Converter (Open Loop) A Pulse waveform is used to drive a MOSFET ON and OFF.

  18. Its Pulse (I) V1=0 V2=12 TD=0 TR=10n TF=10n PW=10u PER=20u Duty Cycle,

  19. Its Pulse (II) V1=0 V2=12 TD=0 TR=10n TF=10n PW=5u PER=20u Duty cycle of the waveform is adjusted by adjusting PW

  20. PW TR TF PER • Very small values for TF and PW • TR≈PER VPULSETo Generate Sawtooth V1=0 V2=12 TD=0 TR={20u-20n} TF=10n PW=10n PER=20u

  21. A Typical applicationBuck Converter (Closed Loop) Gate Driver Comparator - Sawtooth Gen. For Closed-loop, the control signal is compared with a sawtooth waveform to produce the pulse waveform. + Control Signal

  22. Gate Driver Comparator Control Signal PSpice Implementation Gate Driver  E Comparator  ETABLE Sawtooth VPULSE Control  VDC (open loop simulation) Vpulse

  23. Control Sawtooth Pulse Its Waveform (I)

  24. Control Sawtooth Pulse Its Waveform (II) Duty Cycle of the Pulse is adjusted by adjusting Control Signal.

  25. Very small value for PW • TR≈TF ≈PER/2 VPULSETo Generate Triangular wave PW V1= -1 V2= +1 TD=0 TR= {10u-10n} TF= {10u-10n} PW=20n PER=20u TF TR PER

  26. VPULSETo Generate Triangular wave

  27. Bipolar SPWM Triangular WaveTypical applications Comparator

  28. Bipolar SPWM Triangular WaveTypical applications 1.0V 0V -1.0V V(TRI) V(SINE) 0 100 0 -100 40ms 42ms 44ms 46ms 48ms 50ms 52ms 54ms 56ms 58ms 60ms V(SPWM) 0 Time [ms]

  29. Unipolar SPWM Triangular WaveTypical applications Comparator 1 Comparator 2

  30. 1.0V 0V -1.0V V(SINE1) V(SINE2) V(TRI) 100V 0V -100V 40ms 42ms 44ms 46ms 48ms 50ms 52ms 54ms 56ms 58ms 60ms V(A)-V(B) V(A)-V(B) Time [ms] Unipolar SPWM Triangular WaveTypical applications

  31. Analog Behavior ModelMakes the Circuit SimplerUse equations to model circuits • Comparator • Single Phase Rectifier • Three Phase Rectifier • Buck Converter in CCM • Single Phase Inverter

  32. V(-) - V(out) V(+) + (1) Using IF-Then-Else function IF(V(+)>V(-),HI, LO) (2) Using signum function (V(+)-V(-))/ABS(V(+)-V(-)) IF the voltage at the terminal + is greater than the voltage at terminal - the output is HIgh, otherwise the output is LOw. ABMBehavior Model of Comparator

  33. V(-) - V(out) V(+) + V(+) V(out) V(out) + - 0 V(+)-V(-) A*(V(+)-V(-)) V(-) ABMBehavior Model of Comparator (3) Using I/Ograph (4) Using Op-amp alike

  34. 1 2 3 4 ABMComparator in PSpice • NO 2 is implemented using ETABLE • Others are implemented using ABM part • NO 2 & NO 4 are suitable for Op-amp (Error Amplifier)

  35. 1.0V 0V -1.0V V(TRI) V(SINE) 10V 0V -10V 40ms 42ms 44ms 46ms 48ms 50ms 52ms 54ms 56ms 58ms 60ms V(OUT3) V(OUT2) V(OUT1) V(OUT4) Time [ms] ABMBehavior Model of Comparator These waveforms come from the outputs of four comparators

  36. ABMBehavior Model of Rectifier (I) V(out)=ABS(V(IN))

  37. + ABMBehavior Model of Rectifier (II) Van V(out) = 0.5*(ABS(V(an)-V(bn) +ABS(V(bn)-V(cn)) +ABS(V(cn)-V(an))) Vbn Vcn -

  38. + Vd - + ABMBehavior Model of Buck in CCM Vd Vd = d*Vin - • d is a PWM signal with 1V amplitude.

  39. + E1 SINE Vab IN+ OUT+ IN- OUT- TRI - EVALUE VDC*(V(%IN+)-V( %IN-))/ABS(V(%IN+)-V( %IN-)) ABMBehavior Model of Inverter a + VDC Vab - b Bipolar SPWM 0

  40. There are many different ways to model the same thing. • So, Be Creative! #TIPS

  41. My quote about Model ! “Models are like shoes; there is no one-size- fits-all model.”

  42. Our Case Study A Buck Converter with VMC • A Simple PWM Controller IC Model • A PWM IC Controller IC Model including Soft-start • A PWM IC Controller IC Model Including Soft-start, Duty Cycle Max and Current Limiter

  43. Our Case Study A Buck Converter with VMC - + + - 0 SG3525 PWM Controller IC 0

  44. Key Functions: • Oscillator (Sawtooth Generator) • PWM Comparator and SR Flip-flop • Error Amplifier • 5.1 V Reference • Pulse Steering Logic • Shutdown and Soft-start Circuitry SG3525PWM Controller IC

  45. We do not need to have SG3525 model in PSpice’s library to simulate buck converter with VMC. • To verify our controller design, all we need are functional models of these: SG3525 • Error Amplifier • Comparator • Sawtooth generator

  46. Sawtooth - To MOSFET Driver + + - Comparator Error Amp. SG3525A Simple Model

  47. Buck Converter A Buck Converter with VMC • The controller is used to regulate the output voltage at 5 V. • Consider we know all circuit parameters. • Our interest is to simulate the system. Error Amp. Comparator Sawtooth

  48. The controller is a linear controller and the design is based on a small-signal model. • It means that the controller can not cope with large signal scenario such as start-up. • Therefore, we have to set initial values, which are equal to their steady state values, for the inductor current and the capacitor voltage. A Buck Converter with VMC

  49. 3A R = 5 W How to set a load disturbance ? Let’s say the load disturbance is: Load Disturbance 1 A 0 A 8 ms 8.5 ms R = 1.666 W R = 5 W • R changes from 5 W to 1.666 W

  50. ILOAD How to set load disturbance ? Using IPULSE Our Case Study • Allocate enough times for TR and TF, small enough relative to PER.

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