Effektelektronisk modulation

Modulation of power converters plays a decisive role in modern power electronics where low losses as well as dynamical requirements, harmonics and electromagnetic interference (EMI) are of great importance. The course covers synthesis and analysis of modulation methods for Voltage Source Converters (VSC).

Aim

After the examination the student should be able to

• Apply Fourier series expansions to analyze arbitrary periodic signals in the frequency domain.
• Compute all electrical quantities in symmetric LTI three-phase networks when these are energized by periodical three-phase sources (asymmetric sinusoidal and symmetric non-sinusoidal).
• Apply waveform symmetries to identify spectral components in periodic signals.
• Compute common figures of merit to quantify the harmonic distortion of periodic signals, notably THD.
• Design carrier based pulse width modulators for single and polyphase voltage source converters (with natural or regular sampling).
• Explain the effect of phase shifting the carrier and reference on the harmonic components resulting from PWM in phase and line-line quantities.
• Describe different kinds of zero-vector placement in three-phase carrier-based PWM.
• Explain the operation of simple space vector modulator and explain the analogies with carrier-based modulators
• Determine suitable sets of eliminated harmonics to be used in selective harmonic elimination for different applications and compute the corresponding switching angles.
• Explain the qualitative differences between carrier-based and programmed PWM with regard to harmonic and dynamic properties.
• Conceptually design and simulate simple direct torque control systems, including derivation of the switch table.
• Draw schematics of the most common multi-level power converter topologies and explain their operation. Describe the impact on the harmonic spectra of increasing the number of levels in the waveform. Describe the synthesis of different types of carrier-based multilevel waveforms.