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Power Converters Modeling Techniques

This example shows the operation of several types of power electronics converters that can be simulated using one of four selectable modeling techniques

Modeling Techniques Description

You can run this simulation using one of the following modeling techniques:

1. Switching Devices: Converters are modeled using standard SPS power switches and diodes controlled by firing pulses which are produced by the PWM generators.

2. Switching Function: Converters are modeled using a switching-function model controlled by firing pulses which are produced by the PWM generators.

3. Switching Function (PWM averaging): Converters are modeled using a switching-function model controlled by averaging the firing pulses produced by the PWM generators over a specified period.

4. Reference-Voltage (Uref or D-Controlled): Converters are modeled using a switching-function model directly controlled by the reference voltage (Uref) or the duty-cycle (D). PWM generators are not required.

Technique 1 is the most accurate modeling technique, while technique 4 yields to the fastest simulation. Techniques 2 and 3 are well-suited for real-time simulation.

Power Converters Description

The simulation allows you to observe operation of several types of power electronics converters:

1-MVA Active Rectifier: This active rectifier will produce the main DC supply (+/-500V) used by several other converters. The rectifier consists of a three-phase, 3-level NPC converter and a closed-loop control system. It can take or give back power to the grid in order to maintain the specified DC level.

60-Hz Load: The load is modeled using a half-bridge converter controlled by a PWM generator having a carrier frequency of 33*60.

DC Variable Load: The load variation is achieved using a buck converter and a variable DC source at the converter output.

DC Supply: A boost converter transfers power (125 kW) from a 500V DC source to the main DC supply.

DC Motor Drive: The drive consists of a speed-regulated 200-HP motor, a Two-Quadrant DC-DC Converter and a control system.

50-Hz Load: The load is modeled using a full-bridge converter controlled by a PWM generator having a carrier frequency of 1650 Hz and a modulation index of 0.9.

2-MVA STATCOM: This distribution STATCOM consists of two three-phase, 2-level converters (twin topology) and a closed-loop control system. It can generate or absorb 2 Mvars from the grid.

Simulation

During the simulation, the DC variable load will vary from 125 kW to 350 kW at 5 Hz. At 0.5 s, the DC motor speed setpoint is changed from 1200 to 800 RPM. At 0.6 s, the STATCOM reference (Qref) is changed from -1 Mvar to +1.5 Mvar. Run the simulation and observe the resulting signals on the various scopes. Select a different modeling technique and rerun the simulation, comparing results with previous runs.

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