Capacitors are one type of reliability-critical components in power electronic systems. In the last two decades, many efforts in academic research have been devoted to the condition monitoring of capacitors to estimate their health status. Industry applications are demanding more reliable power electronics products with preventive maintenance. Nevertheless, most of the developed capacitor condition monitoring technologies are rarely adopted by industry due to the complexity, increased cost, and other relevant issues. An overview of the prior-art research in this area is therefore needed to justify the required resources and the corresponding performance of each key method. It serves to provide a guideline for industry to evaluate the available solutions by technology benchmarking, as well as to advance the academic research by discussing the history development and the future opportunities. Therefore, this paper first classifies the capacitor condition monitoring methods into three categories, then the respective technology evolution in the last two decades is summarized. Finally, the state-of-the-art research and the future opportunities targeting for industry applications are given.

A Review of the Condition Monitoring of Capacitors in Power Electronic Converters

Capacitors are widely used in dc links of power electronic converters to balance power, suppress voltage ripple, and store short-term energy. Condition monitoring (CM) of dc-link capacitors has great significance in enhancing the reliability of power converter systems. Over the past few years, many efforts have been made to realize CM of dc-link capacitors. This article gives an overview and a comprehensive comparative evaluation of them with emphasis on the application objectives, implementation methods, and monitoring accuracy when being used. First, the design procedure for the CM of capacitors is introduced. Second, the main capacitor parameters estimation principles are summarized. According to these principles, various possible CM methods are derived in a step-by-step manner. On this basis, a comprehensive review and comparison of CM schemes for different types of dc-link applications are provided. Finally, application recommendations and future research trends are presented.

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An Overview of Condition Monitoring Techniques for Capacitors in DC-Link Applications

As electrolytic capacitor is apt to fail in power circuits, it is very important to identify its electrical parameters, mainly the equivalent series resistance (ESR) and capacitance ( C ). A noninvasive online identification method of capacitor's ESR and C for continuous-conduction-mode (CCM) buck converter is proposed in this paper. Based on the ac component of capacitor voltage, the calculation model is founded. By sampling the pulse width modulation signal and output voltage, the method needs no current sensor and is effective for the CCM buck converter operating at different conditions. Implementation of the identification system is presented. The tests are carried out for different aged capacitors and ambient temperatures. The experimental results validate the effectiveness of the method.

A Current-Sensorless Online ESR and C Identification Method for Output Capacitor of Buck Converter

To interconnect low-voltage solar photovoltaics (PV) with dc system, a dc–dc boost converter is required. To minimize the switching frequency oscillations in solar PV voltage, aluminum electrolytic capacitors (AECs) are connected between solar PV and the converter. Operational life of AECs depends on electrical and environmental parameters and is less than that of solar PV panels. Equivalent series resistance (ESR) of AEC increases with life, thereby increasing the voltage ripple across PV terminals. This results in less power extraction from solar PV. This paper proposes a method for health monitoring of AEC using the parameters measured for maximum power point tracking (MPPT) (PV voltage and current). The proposed technique is applicable for both continuous conduction mode and discontinuous conduction mode of operation of the converter. Effect of temperature on ESR is incorporated for accurate determination of the health of capacitor. Key advantage is that no additional current or voltage sensor is required to implement this technique, thereby offering a low-cost solution. Further, the proposed technique does not require significant processing capabilities and is implemented in the same digital controller used for MPPT. Detailed simulation studies are carried out and results are included in this paper. A laboratory prototype of dc–dc boost converter is developed for experimentation. Results are in agreement with that obtained from simulation studies.

Online Monitoring Technique for Aluminum Electrolytic Capacitor in Solar PV-Based DC System

As electrolytic capacitor is apt to fail in power converters, it is very important to monitor its electrical parameters, mainly the equivalent series resistance (ESR) and capacitance (C). A novel non-invasive online monitoring method of DC-link capacitor's ESR and C for boost power factor correction (PFC) converter is proposed in this paper. By analyzing the capacitor voltage ripple which is composed of that of ESR and C, the calculation model is founded, which shows that instead of additional current sensor, only two values of capacitor voltage in particular moments within a line cycle need to be sampled for the calculation of ESR and C. The schematic of the monitoring system together with the design considerations of the trigger circuit, the isolated voltage amplifier, the isolated current amplifier are described in detail. The experimental results show the effectiveness of the method.

An Online Monitoring Scheme of DC-Link Capacitor's ESR and C for a Boost PFC Converter

Aluminum electrolytic capacitors are usually used in DC-DC converters as smoothing capacitors. According to the statistics data, they are the weakest among various power components in the DC-DC converter. With the increase of the running time, the performance degradation of electrolytic capacitors reflects in electrical parameters, mainly the Equivalent Series Resistance (ESR) and capacitance. The best indicator of the output filter capacitor failure is the increase of ESR. And the output ripple voltage of the converter increases with respect to ESR. Monitoring the ESR variation of the electrolytic capacitor, achieving by voltage and current ripple, can estimate the health state of the converter.

ESR estimation method for DC-DC converters based on improved EMD algorithm

Aluminum electrolytic capacitor is one of the key components that restrict the life of DC-DC converter. Studying its deterioration analysis has advanced to realizing the prognostics and health management (PHM) technology of DC-DC converter. The main deterioration modes of aluminum electrolytic capacitor include the capacitance decrease and the equivalent series resistance (ESR) increases. These cause the ripple voltage to increase and eventually lead to the DC-DC converter failure. Some parameters of DC-DC converter (such as the ripple voltage, the ripple current, etc.) are selected as the feature signals of the aluminum electrolytic capacitor deterioration. By monitoring the changes of the feature signals, the aluminum electrolytic capacitor deterioration degree can be measured indirectly. Through theoretical analysis, this paper proposed a new idea to predict the remaining useful life (RUL) of DC-DC converter, that is, establishing the curve of the ripple voltage as the aluminum electrolytic capacitor deterioration and setting a warning point in the curve. When the change rate of the ripple voltage reached the warning point, the life of the DC-DC converter will come to an end. So, the RUL of the DC-DC converter can be predicted. In this paper, the buck converter is verified by simulation and physical experiments amid good agreements with the theory.

	 

	Key words: Aluminum electrolytic capacitor, DC-DC converter, deterioration, capacitance, equivalent series resistance (ESR), ripple voltage, remaining useful life (RUL), prognostics and health management (PHM).

Deterioration analysis of aluminum electrolytic capacitor for DC-DC converter

The Space Solar Telescope (SST) is the first Chinese space astronomy mission. This paper introduces the design of a high-performance 2K × 2K charge coupled device (CCD) camera that is an important payload in the Space Solar Telescope. The camera is composed of an analogue system and a digital embedded system. The analogue system is first discussed in detail, including the power and bias voltage supply circuit, power protection unit, CCD clock driver circuit, 16 bit A/D converter and low-noise amplifier circuit. The digital embedded system integrated with an NIOS II soft-core processor serves as the control and data acquisition system of the camera. In addition, research on evaluation methods for CCDs was carried out to evaluate the performance of the TH7899 CCD camera in relation to the requirements of the SST project. We present the evaluation results, including readout noise, linearity, quantum efficiency, dark current, full-well capacity, charge transfer efficiency and gain. The results show that this high-performance CCD camera can satisfy the specifications of the SST project.

Design and evaluation of a high-performance charge coupled device camera for astronomical imaging

The high reliable embedded system in rugged environment has huge potential application value. There are 34% faults in electronic system by the cause of the fault of power system. So the prognostics mechanism and the algorithm of power health has been a core support technology in applications. the fault and the deterioration and healing model of the power system in rugged environment is constructed by analysis of FFP, DFP and healing(alleviation)for improving the reliability, the usability and the maintainability. And many questions such as fixed-time maintenance and back-down maintenance depending on conventional statistical method are solved fundamentally. Finally, the prognostics and health management methods of power health in domestic and foreign presently are contrasted and analyzed.

Power Supply Prognostics and Health Management of High Reliability Electronic Systems in Rugged Environment

Disclosed is a fault monitoring and forecasting method of direct current (DC)-direct current (DC) power source system, which includes the following steps: combining with electrical characteristics of a DC-DC power source system, respectively providing criterions for power sources when faults occur and when faults are about to occur based on the monitoring and analysis for output voltage of the DC-DC power source system; and beginning to monitor the output voltage after the DC-DC power source system powers on and when the output voltage achieves a steady state and, and monitoring or forecasting the faults based on the criterions The method has the advantages of being capable of determining the faults which occur to the DC-DC power source system in real time, providing the DC-DC power source system barrier state in three determining clock cycle, and being rapid in alarming and capable of protecting the DC-DC power source system and the load of the system well when faults occur to the DC-DC power source system

Wei Pan

Papers

ESR estimation method for DC-DC converters based on improved EMD algorithm

Deterioration analysis of aluminum electrolytic capacitor for DC-DC converter

Design and evaluation of a high-performance charge coupled device camera for astronomical imaging

Power Supply Prognostics and Health Management of High Reliability Electronic Systems in Rugged Environment

Fault monitoring and forecasting method of direct current (DC)-direct current (DC) power source system