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Fault injection has already been used to access the dependability of web services. However, most of the existing work focuses on how to inject faults. Problems such as where to inject faults and what faults should be injected still have not been systematically studied in literature, especially for the testing of performance related issues in composite web services. This paper presents an approach that defines coverage criteria to guide fault injection testing of performance related issues in composite web services. We generate fault injection configurations that follows the defined test criteria for systematic fault injection. The configurations specify where to inject faults and what faults should be injected, and the injected faults (e.g. message delays) are generated according to the characteristics of each individual sub-service in order to make the faults more realistic. With the fault injection configurations, the fault injection process can be automatically conducted and the performance of a composite service can be effectively evaluated.

This study proposes a model predictive control (MPC) method with a fixed weighting factor for three‐phase four‐switch inverter‐fed permanent magnet synchronous motor drives to suppress the capacitor voltage offset. The prediction model of the capacitor voltage difference is obtained based on the relationship between capacitor voltage and phase current. Then by analysing the relationship between basic voltage vector, electromagnetic torque and flux amplitude, the control of electromagnetic torque and flux in the model predictive torque control is transformed into the control of the voltage vector. The dimension of the capacitor voltage difference is the same as that of the voltage vector, hence the cost function with the fixed weighting factor is defined with the consideration of the capacitor voltage offset suppression. The effectiveness of the proposed MPC method is validated by the simulation and experiment.