The following tutorials are planned for Friday 8 September 2023 in the afternoon:
TUTORIAL N° 13
(14:00 – 17:30)
Multi-sampling control of power electronic converters
- Frede BLAABJERG, Aalborg University, Denmark
- Shan HE, Aalborg University, Denmark
- Paolo MATTAVELLI, University of Padova, Italy
- Ivan PETRIC, University of Padova, Italy
Increasing the integration of renewables has been regarded as a critical pathway to de-carbonize the power system. As a bridge between the renewables and the power grid, power electronic converters are of importance to achieve efficient and reliable power conversion. Digital control is the most commonly used technology in power electronic converters due to its flexibility and adaptability. Nevertheless, for the regular single/double-sampling PWM-based control, significant control delay is introduced in the control loop. This control delay affects the achievable control bandwidth, stability margins, and overall dynamic performance.
With the gradually decreasing cost of high-performance microprocessors, multi-sampling control is a potential candidate to overcome the above-mentioned limitations. It relies on sampling the state variable and updating the duty cycle command multiple times within one switching period. As the control delays are inversely proportional to the sampling rate, multi-sampled control can enable dynamic performance close to the one obtained with analog control, for high-enough sampling rate. As a result, multi-sampling has been widely used to improve the control bandwidth of power electronic converters, including dc–ac converters, dc–dc converters, and motor drives. A particularly attractive and emerging application for multi-sampling PWM is within grid-connected converters. Due to delay reduction, multi-sampling PWM can inherently bring the required damping and help passivize the converter impedance in a wide frequency range, thus enabling robust stability.
Besides the average value, the switching ripple is always introduced in the control loop when using multi-sampling, which is the main difference compared to the regular sampling. This brings a set of nonlinearities caused by the vertical crossings between the carrier and the modulating signal. Some effects that may consequentially arise and that must be handled are multiple-switching, pulse-skipping, gain-reduction, and limit-cycle oscillations (jittering). Moreover, aliasing issues may appear. This all motivates the design of suitable digital filters needed to suppress or completely remove the arising nonlinear effects.
To fully utilize the benefits of multi-sampling in a practical application, the objectives of this tutorial will include multi-sampled PWM modeling, non-linearity analysis, ripple filter design, noise attenuation capabilities, and passivity-based multi-sampled control of grid-connected VSCs.
TUTORIAL N° 18
(14:00 – 17:30)
Reflective Wave Mitigation for SiC Motor Drive
- Hui “Helen” LI, Florida State University, United States
- Jiangbiao HE, University of Kentucky, United States
- Yu ZHANG, Xidian University, P.R. of China
SiC motor drives can achieve higher efficiency and higher power density which has been already applied to electric vehicles in the market. However, for electric ship and electric aircraft applications with longer cables, the overvoltage at motor terminals due to reflected wave phenomenon (RWP), which is recognized as a main source of premature winding insulation failures in drive systems, becomes more challenging due to the higher dv/dt of SiC devices leading to the RWP occurring in a motor drive system at shorter cable length. For instance, the overvoltage ratio at the motor terminal increased from 20% to 100% when PWM voltage rise time decreased from 200 to 25 ns with only 20 feet of the cable length. The traditional methods to solve this issue are no longer attractive solutions for SiC motor drives due to their higher losses caused by higher switching frequency of SiC motor drives. In this tutorial, both passive and active methods from industry and academia to mitigate the overvoltage caused by SiC devices are introduced covering a wide range of motor drives from 2-level to multilevel topologies. Moreover, these new techniques can also be applied to conventional IGBT motor drives with longer cables.