Janne Hannonen

Acoustic Emission in Power Semiconductor Modules—First Observations

Traditionally, condition monitoring of power semiconductor modules has been based on electrical measurements. Acoustic emission has been utilized for condition monitoring in many other applications, but is an unknown phenomenon in power semiconductor modules. In this paper, the authors present an experimental setup used to show that acoustic emission does occur because of the switching of power semiconductor components. An analysis based on propagation delays is used to determine the source of the acoustic emission.

Design of digitally controlled isolating 1-phase AC/DC converter by using centralized processing unit

This paper presents a fully digital control design for 1-phase 3 kW AC/DC converter. The centralized control system is designed and implemented on microcontroller-FPGA combination. This paper emphasizes the control design flexibility for switching mode power supplies when the programmable controller approach is used.

Capacitor aging detection in DC-DC converter output stage

One of the most significant reliability issues in switching-mode power supplies is electrolytic capacitor degradation caused by aging. This paper proposes an output voltage transient analysis method to detect capacitor wear-out at the output stage of a step-down dc-dc converter. Changes in the converter output voltage dynamics are evaluated by analyzing the output voltage step response with respect to a decrease in the capacitance. The sensitivity of the method is assessed with respect to parameter variations using an equivalent main circuit model. The feasibility of the presented method is verified by experimental tests using a converter prototype. The results show that the presented method is practical and adequate for detecting capacitor degradation in various operating conditions.

Single phase PFC control with Lyapunov method

In this paper a current control method based on Lyapunov function for single phase active power factor correction (PFC) is presented. Lyapunov functions can be used for defining control law for either linear or nonlinear systems. The control is designed with cascade structure, where a voltage controller feeds the current amplitude reference to the current controller. The operation and performance are demonstrated with measurements from 3 kW power supply which uses power factor correction. The designed controller is shown to track the mains voltage with close to unity power factor.

Step-up DC-DC converter passive component dimensioning in photovoltaic applications

Boost converter is a common solution for power conditioning of photovoltaic systems. Inductance and capacitance values of the boost converter are of high importance when the panel voltage ripple is examined. The ripple has a severe effect on the maximum power point tracking efficiency. Dimensioning guidelines for these components are presented in this paper. They are examined with simulations and experimental measurements.

Luenberger state observer based condition monitoring method in digitally controlled switching mode power supply

The use of digital control in switching mode power supplies has increased as the performance of programmable controller circuits have advanced. The use of digital control provides possibility to run monitoring, prognostics and maintenance functions alongside the system core control functions. This paper suggests a model based online condition monitoring method for DC-DC power supply, based on Luenberger state observer. It is shown that abnormal operating conditions, such as increased losses in main circuit, can be detected by monitoring the state observer adaptation value variations.

Flux and winding current balancing control for a medium-frequency six-winding transformer

Solid state transformers normally include a transformer whose operating frequency is well above the usual grid frequencies. These transformers are supplied by power electronic inverters such as an H-bridge. The average value of transformer supply voltage can drift to a non-zero value which may lead to saturation of the magnetic core. This paper presents an active control method to prevent saturation of a multi-winding medium-frequency transformer. The control method comprises two control loops: the first balances the flux of the transformer and the other balances the currents in different windings. Simulation results which show the feasibility of the proposed control method are shown.