Two stations allow develop simulation exercises. Pspice tool is ... It consists of power converters stages, simulation exercises and some ... PLL pulse generator.
Power electronics laboratory: simulation tools, power converters and tests bench based on industrial applications Herman Fernández Centro de Electrónica de Potencia y Accionamientos CEPAC Unexpo Puerto Ordaz U-22b Dialogue Keywords Education methodology, education tool, power electronics curriculum, industrial applications, power electronics laboratory. Abstract The Unexpo Puerto Ordaz is a Polytechnic University in Venezuela, located near of industrial conglomerate, where the power electronics playing a key role. Classroom instructions and experimental tests have been adapted to satisfy these requirements. This paper introduces a laboratory considering the power converters principles, simulation tools and industrial applications tests bench. The academic results are satisfactory. Introduction The power electronics and motion control represent fundamental elements in modern industrial process control, where is very important a high productivity [1]-[3]. The Unexpo is localized near of a great industrial environment. At these sites, the most common applications of power electronics are: conveyors, elevators, crane control, exciters field for synchronous generator, cells reduction, induction heating, balls mills, and others. These subset topics of industrial applications have been considered with emphasis in power electronics curriculum, which consists of two courses on power converters principles and its applications, followed by other course strictly realized in the laboratory. After some donations, the University has a laboratory with equipments related to industrials systems. Besides are available power converters tests bench and simulation exercises with PSpice, PSIM and PSCAD, which are activities recommendable to learn the power electronics [4]-[6]. Six stations are organized in the laboratory, where are combined the simulation tools, power converters analysis, and some cases of industrial applications. Power electronics laboratory: All schedule activities are summarized in table I. Each one stations can be used to demonstrate numerous tests. Below, some cases are described. First example: Pulse generator for AC/DC converter installed in aluminum reduction cell (S1) Fig.1 shows test bench. The gating module receives the sinusoidal input signal and reference command, which determines the firing angle. The gating system utilizes a phase locked loop, a ring counter and logic circuits, where are generates equidistant firing pulses spaced at 60° successively. Various test points are available in the gating module. Second example: Crane control unit (S3) Fig.2 is a three-phase pulse generator used for a crane control system. The synchronizing circuit provides synchronization with AC supply for counter and pulse generators. A voltage controlled oscillator with an output frequency proportional to the magnitude of its input voltage produce a train of pulses as input clock to counter stages. Each counter, determine when in the half cycle a firing pulse occurs. The pulse generator is a dual-timer integrated circuits connected as a one-shot multivibrator. Test probes are placed in different stages. Third example: Simulation (S5 and S6) Two stations allow develop simulation exercises. Pspice tool is oriented to power converters and circuit simulations. Moreover, aided with the sophisticated models in the PSIM and PSCAD, are resolved complex cases of power electronics systems: ac and dc drives, battery chargers, wound-rotor induction machines, brake units, soft starter induction machines, uninterrupted power supply and other applications. Using PSCAD tool, was simulated a DC/DC converter with a closed loop PI controller and PWM generator. The load profile and PI parameters can be changed during run time to evaluate the dynamic response of converter. Results Waveforms are collected to demonstrate laboratory setup. Fig.3 shows the results obtained for the pulse generator used in reduction cell test bench, and Fig.4, the pulses pattern of the crane control unit. In each case, the pulses sequence is synchronized to sinusoidal signal, adequate to trigger the power semiconductors integrated in line commutated three-phase converters (AC/DC and AC/AC). The firing angle can be adjusted via reference signal. As can be observed, a complete set of signals can be registered, therefore it procedure allow knowledge rigorous of each one industrial cases. Simulation results obtained with PSCAD tool is given in Fig.5, where DC/DC converter with voltage close loop controller is analyzed. The dynamic response of the system confirms an excellent regulation versus load changes.
Two workstations are showed in the Fig.6 equipped with the measuring instruments, loads configurable, and power converter module-control unit related. Actually, all stations are available and work correctly.
Conclusions Unified power electronics laboratory is presented. It consists of power converters stages, simulation exercises and some cases of industrial applications platforms. Classic control and simple regulation strategies for power converters are verified: phase control, cycle control, PWM, HIPWM, voltage or current PI regulator, etc. Indeed, sophisticate techniques can be implemented using the DSP development system and simulation tools. Actually, the laboratory is destined to undergraduate courses, without additional lecture time. Table I. Activities scheduled with test benches Station Basic topics or industrial Focused: test bench: Drive systems
S1
Voltage conditioner and UPS both installed in rooms control. PLL pulse generator
Weg drives: soft starter, V/F and vector control of induction machine. Siemens: VC drive. Regulators and control stages.
Cell reduction of aluminum extraction.
Brake unit used on crane control.
Cosine control for single-phase AC/DC converter. Lineal function is demonstrated.
DC drive with a microcontroller. Resistive heating used in thermal process.
Programmable regulator: P, PI and PID. DC/DC converter. Phase control, cycle control and mixture control.
Crane control
VCO pulse generator.
AC drives Variable torque applications.
HIPWM generator DC/AC converter.
Crane control based on wound-rotor AC induction machine drive.
Regulators and control units.
Power converters
AC/DC AC/AC
S2
S3
S4
S5 Simulation tasks S6
Semiconductors, power converters, control units, and power electronics systems.
Measurements (test points) User interface Simulation tasks Voltage and current probes. Drive interface programs: Super Monitor and Super Drive. Voltage and current probes. THD analysis. Tap-changer and backup tests. Waveform analysis: phase synchronization, logic circuits, pulse patterns, etc. Waveform analysis: passive filter stage, phase synchronization, cosine control unit, pulse amplification. Different loads are supported: resistive, inductive and low power dc machine. Transient response using permanent magnet DC machine. Waveform analysis: phase and cycle control units, load voltage. Temperature measurement. Waveforms analysis: phase synchronization, VCO circuit, logic stages and pulses sequence for AC/AC converter. Show the harmonic injection sinusoidal signal and carrier wave. MGD bootstrap circuits and IGBT inverter. Loads connected: resistive, inductive and low voltage induction machine. Waveforms analysis: active filter stage, phase synchronization, phase control unit, relays sequence for resistance elimination and others functions. Waveforms analysis. PSpice Circuits and converters PSIM Motor drives PSCAD Power systems.
Fig.1: Test bench installed in S1
Fig.3: Waveforms obtained
Fig.2 Test bench installed in S3
Fig.4: Pulses pattern Convertidor CC/CC reductor Ecarga
Regulated voltage
Voltaje
80 70 60 50 40 30 20 10 0
Intensidad
10.0
Iin
Current transition 5.0
0.0 IL
Intensidad
10.0
5.0
0.0 10.0
SalidaPI
SalidaPI
Output PI controller 5.0
0.0 0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
... ... ...
Fig.5: Simulation results. Meas. instr.
Loads
Siemens AC Drive HIPWM generator
Power module
DSP Controller
Resistive heating controller
Meas. instr.
Loads DC motors
AC/DC with cosine controller
Fig.6: Physical structure of S3 (left side) and S2 (right side). Both workstations are equipped with measuring instruments, power module, control unit, configurable load and industrial application bench. References [1] Gedra T., An S., Arsalan Q., and Ray S.: Unified power engineering laboratory for electromechanical energy conversion, power electronics, and power systems, IEEE Trans. on power systems, Vol.19, No.1, pp. 112-119. [2] Hess H.: Power electronics instructions in the USA and Canada: Topics, Curricula and Trends, Int. J. Eng., [3] Probst U.: Economic and versatile laboratory setup for teaching power electronics in bachelor course, EPE 2011, pp. 8. [4] Roasto I., Vinnikov D., and Lehtla T.: Laboratory setup for studying ultracapacitors in industrial applications, EPE-PEMC, 2008, pp. 2034-2037. [5] Miniböck J. and Kolav J.: A highly versatile laboratory setup for teaching basics of power electronics in industrial related form, PCIM, 2002, pp.5. [6] Rashid M.: Power electronics laboratory using SPICE: A self-study course, IEEE Press, 2000. [7] Westinghouse Electric Corporation.: Booster-controller technical manual, Pittsburg, 1978 [8] Eaton Cutler-Hammer.: Trouble-shooting manual three-phase pulse generator, Milwaukee.
