This paper presents an autotuning technique for the online selection of the cost function weight factors in model predictive control (MPC) The weight factors in the cost function with multiple control objectives directly affect the performance and robustness of the MPC The proposed method in this paper determines the optimum weight factors of the cost function for each sampling time; the optimization of the weight factors is done based on the prediction of the absolute tracking error of the control objectives and the corresponding constraints The proposed method eliminates the need of the trial-and-error approach to determine a fixed weight factor in the cost function The application considered is a capacitor-less static synchronous compensator based on the MPC of a direct matrix converter This technique compensates lagging power factor loads using inductive energy storage elements instead of electrolytic capacitors The result demonstrates that the proposed autotuning approach of cost function weights makes the control algorithm robust to parameter variation and other uncertainties in the system The proposed capacitor-less reactive power compensator based on the autotuned MPC cost function weight factor is verified experimentally

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Autotuning Technique for the Cost Function Weight Factors in Model Predictive Control for Power Electronic Interfaces

The urgency for an increased capacity boost bounded by enhanced reliability and sustainability through operating cost reduction has become the major objective of electric utilities worldwide. Power electronics have contributed to this goal for decades by providing additional flexibility and controllability to the power systems. Among power electronic based assets, high-voltage dc (HVdc) transmission systems and flexible ac transmission systems (FACTS) controllers have played a substantial role on sustainable grid infrastructure. Recent advancements in power semiconductor devices, in particular in voltage source converter based technology, have facilitated the widespread application of HVdc systems and FACTS devices in transmission networks. Converters with larger power ratings and higher number of switches have been increasingly deployed for bulk power transfer and large scale renewable integration—increasing the need of managing power converter assets optimally and in an efficient way. To this end, this paper reviews the state-of-the-art of asset management strategies in the power industry and indicates the research challenges associated with the management of high power converter assets. Emphasis is made on the following aspects: condition monitoring, maintenance policies, and ageing and failure mechanisms. Within this context, the use of a physics-of-failure based assessment for the life-cycle management of power converter assets is introduced and discussed.

Asset Management Strategies for Power Electronic Converters in Transmission Networks: Application to Hvdc and FACTS Devices

Utilities are faced with aged infrastructures with an upcoming unavoidable replacement wave to maintain a high reliability In this thesis a methodology is presented for the application of statistical lifetime management for network component populations in energy networks The methodology describes the process to use network component lifetime data to provide lifetime predictions which can be further used in the asset management decision process In the several presented case-studies the methodology is applied to collect the data, perform the statistical analysis and eventually obtain the future predictions to be evaluated in the decision process Decisions have to be made, based on eg economical or reliability reasons, on the strategy for managing the network as a whole, for a population of a certain asset or for individual components An indispensable part of the asset management decision processes is related to the problematic of asset remaining life estimation This information is of strategic importance to trigger maintenance and replacement activities on the right moment in time To provide the relevant tools suitable for application within asset management, this thesis elaborates on the use of statistical analysis for the evaluation of particular asset populations Despite the fact that the failure data for network components are often limited, incomplete and sometimes imperfect, the collected life time data in the presented case studies is appropriate to be used for statistical analysis as long as the input conditions are observed

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Statistical lifetime management for energy network components

Induction motors are widely used in industrial power plants due to their robustness, reliability and high performance under variable operating conditions in the electrical power system. Modern industrial progress is dependent on these ruggedly constructed induction motors. Almost every sophisticated process of the industry is based on induction motors. Most of these motors are controlled by means of inverters that change the line frequency. The change in parameters of inverter makes it possible to control the motor according to the design requirements. The reliability of inverter based motor control is an important issue for industrial applications and therefore, it becomes very vital for design engineers to have comprehensive analysis of the inverter fed induction machine. This paper investigates one of the faults that may occur on the DC link of an inverter fed induction motor. The effect of the capacitor short circuit is presented in this paper. It also deals with the effects of short circuited capacitor on freewheeling diode. DC link capacitors are well designed and even the probability of capacitor failure is high, it is always a rare case if they puncture, however this analysis will add to the reliability of the induction machine under variable operating condition.

Effect of short circuited DC link capacitor of an AC–DC–AC inverter on the performance of induction motor

This paper presents a D-STATCOM for reactive power compensation in a distribution system that uses inductive energy storage element connected to the grid via a matrix converter (MC). The MC is controlled using model predictive controller (MPC) technique. The D-STATCOM will provide load compensation without using electrolytic capacitors. Electrolytic capacitors have well-known failure modes. Therefore, reactive power compensators that use a voltage-source inverter (VSI) with electrolytic capacitors as energy storage involve periodic replacement and monitoring constantly. Consequently, this will incur an increase in the cost of the traditional approaches of load compensation significantly. MC system controlled using MPC provides reactive power compensation by controlling the output inductors and the input reactive power. Therefore, the proposed compensator which is based on MC and inductive energy storage has a longer expected service life and more reliability compared with VSI based compensators.

Capacitor-less D-STATCOM for reactive power compensation

This paper describes the study of the reliability of capacitor units installed and operated in distribution system during the period 1980 through 1990. Failures of capacitor units in distribution substations can be very costly to the supply of reliable power to consumers. To enhance utility reliability, failure analysis, and rates, failure origin and physical damage causes were performed for these capacitor units. Two approaches, statistical and physical, were utilized in this study. In the statistical area, failure modes, reliability levels and failure causes are analyzed. The physical study mainly deals with the mechanism of deterioration of the composite dielectric. This paper models capacitor's failure mathematical mode and calculates their failure rate. The results of the study of 2912 capacitor banks including 8736 capacitors installed at 153 distribution substations showed that the failure mode of capacitor units may be represented by Weibull distribution and each capacitor manufacturer has a diffe...

B. Palk

Papers

Failure Analysis of Composite Dielectric of Power Capacitors Used in Distribution Systems