An overview of the reliability prediction related aspects of high power IGBTs in wind power applications

Reliability is becoming more and more important as the size and number of installed Wind Turbines (WTs) increases. Very high reliability is especially important for offshore WTs because the maintenance and repair of such WTs in case of failures can be very expensive. WT manufacturers need to consider the reliability aspect when they design new power converters. By designing the power converter considering the reliability aspect the manufacturer can guarantee that the end product will ensure high availability. This paper represents an overview of the various aspects of reliability prediction of high power Insulated Gate Bipolar Transistors (IGBTs) in the context of wind power applications. At first the latest developments and future predictions about wind energy are briefly discussed. Next the dominant failure mechanisms of high power IGBTs are described and the most commonly used lifetime prediction models are reviewed. Also the concept of Accelerated Life Testing (ALT) is briefly reviewed.     

Power losses in PWM-VSI inverter using NPT or PT IGBT devices

This paper investigates the power losses for two different IGBT technologies (nonpunch through and punch through) for use in PWM-VSI inverters in order to choose the right device technology for a given application. A loss model of the inverter is developed based on experimental determination of the power losses. The loss model is used on two different modulation strategies which are a sine wave with a third harmonic added and a 60°-PWM modulation where only two inverter legs are active at the same time. The two IGBT technologies are characterized on an advanced measurement system which is described. The total power losses in the inverter are estimated by simulation at different conditions and it is concluded that the nonpunch through (NPT) technology is most useful for higher switching frequencies, while the punch through (PT) technology is especially useful at lower switching frequencies and high load currents. It is also concluded that the 60°-PWM modulation has the lowest power losses and the power losses are almost independent of phase angle cos(φ) for normal motor operation     

Evaluation of modulation schemes for three-phase to three-phase matrix converters

This paper presents a method for evaluating different modulation schemes employed with three-phase to three-phase matrix converters. The evaluation method addresses three important modulator characteristics: the output waveform quality, the input waveform quality and the switching losses associated with the modulation schemes. The method is used to evaluate four different modulation strategies, all based on the direct space-vector modulation approach. Further, regarding the switching losses, the paper proposes a new space-vector approach by which the switching losses can be reduced by 15%-35%, depending on the output load angle. This new modulation approach is applicable whenever the output voltage reference is below half the input voltage and the output voltage quality is then superior to that of the conventional space vector modulation scheme. The functionality of the new modulation scheme is validated by both simulations and experimental results and compared to waveforms obtained by using exiting space vector modulation schemes. The output voltage of the proposed scheme turns out to be comparable to the best of the conventional schemes while the input current is more distorted.     

Link voltage peak control of parallel resonant converter by controlof the converter switching instant

This paper describes a new control strategy of the parallel resonant DC link converter called voltage peak control (VPC). VPC limits the link voltage to twice the DC link voltage. The strategy eliminates the need of additional power electronic components that clamp the link voltage. The operation of the resonant link is described highlighting the factors that influence on the link voltage peak. The paper describes how control of the link voltage peak is possible by appropriate timing of the converter switching. The VPC strategy is implemented in a parallel resonant DC link converter, and simulations with the VPC strategy turned on and turned off are compared. Experimental verification of the VPC strategy is done in a three-phase parallel resonant DC link converter and measurements of switching losses are present. It is concluded that the switching losses are low and the link voltage peak can be controlled without any additional clamp circuits using VPC     

Simulation with Ideal Switch Models Combined with Measured Loss Data Provides a Good Estimate of Power Loss

Ideally,converter losses should be determined without using an excessive amount of simulation time.State-of-the-art power semiconductor models provide good accuracy,unfortunately they often require a very long simulation time.This paper describes how to estimate power losses from simulation using ideal switches combined with measured power loss data.The semiconductor behavior is put into a look-up table,which replaces the advanced semiconductor models and shortens the simulation time.To extract switching and conduction losses,a converter is simulated and the semiconductor power losses are estimated.Measurement results on a laboratory converter are compared with the estimated losses and a good agreement is shown.Using the ideal switch simulation and the post processing power estimation program,a ten to twenty fold increase in simulation speed is obtained,compared to simulations using advanced models of semiconductors.