KR101019342B1 - Online Failure Detection System of DC Output Filtering Capacitors in Power Converters - Google Patents

Abstract

  The electrolytic capacitor 33 is widely used in various power converters because of its large capacity, low cost, and fast charge and discharge characteristics. Such electrolytic capacitors are mainly used for temporary storage of DC energy and voltage smoothing, and are recently used in renewable energy fields for linking AC / DC voltage and buffering charge and discharge energy. However, the electrolytic capacitor uses an electrolyte for the rectifying conductive electrode plate, and it is pointed out that the reliability of the use is very weak due to structural disadvantages due to the very thin oxide film and the material characteristics of the dielectric. . As the usage time of power converters increases, the temperature and deterioration characteristics of the electrolytic capacitors become relatively worse, which may eventually lead to an explosion of electrolyte. The accident of electrolytic capacitors can lead to very dangerous situation such as short circuit through PCB, system breakdown of power converter and shutdown of production line. Accordingly, the present invention proposes an on-line diagnosis system by detecting a failure signal based on parameter calculation of a full capacitor used in various power converters.

) 또는 등가직렬저항(equivalet series resistor; 이하 'ESR'이라 칭함)의 추정에 의한 진단기법이 전통적으로 사용되고 있다. 커패시턴스의 용량 추정기법은 운전 중 실험이 난해하고 제작과정에서 이미 ±10∼20[%]의 허용오차가 존재하고 있기 때문에 대부분은 등가직렬저항의 추정에 의한 고장 신호 기법에 의존한다. The failure diagnosis system of the electrolytic capacitor has a change in the internal parameters of the capacitor, that is, the dielectric loss due to the temperature characteristic, rather than the capacitance measuring technique according to the increase in the use time.

Diagnostic method by estimation of equivalent series resistance (hereinafter referred to as 'ESR') is traditionally used. Capacitance estimation technique of capacitance depends on fault signal technique by estimating equivalent series resistance because the experiment is difficult during operation and the tolerance of ± 10 ~ 20 [%] already exists in the manufacturing process.

  Until now, fault diagnosis techniques related to electrolytic capacitors have been studied and invented mainly for specific power converters. Afroz M. Imam performs parametric calculations using adaptive signal processing (LMS) techniques from the voltage and current of the capacitor in the model of the boost converter, and ML Gasperi uses the ESR calculation and the amount of electrolyte flow in the AC inverter drive A life prediction model is presented. JwKolar proposes an ESR estimation method based on the current calculation of a capacitor according to the switching state mode of the inverter's space vector PWM method. In addition, Lee has a disadvantage in that most of it depends on arithmetic process and signal processing algorithm such as estimating ESR by calculating duty ratio according to switching state in PWM inverter. If the type is changed, there is a disadvantage that the scope of application thereof is limited.

  Therefore, the present invention devised a fault diagnosis technique by estimating the ESR of the on-line electrolytic capacitor applicable to the power converter of various switching converters (SMPS, DC / DC converter, variable speed inverter, etc.). Its fault detector method has the advantage that only the voltage sensor of the capacitor can detect the ESR magnitude change of the capacitor and warn of its deterioration. In addition, if the current sensor of the capacitor is additionally attached to the components of the present algorithm, it is possible to operate the failure and life prediction program by directly calculating the ESR value using the same algorithm as the voltage detector method.

  Simulation results are shown very well for the validity of the proposed technique. Good ESR estimation characteristics have been obtained by applying both the power converters of buck and boost DC / DC converters as well as the DC output filter capacitors of rectifiers using variable speed inverters as loads. In addition, the estimation result of the ESR according to the ESR variable during operation is expected to be sufficiently applicable to the detection of fault signals in the future. According to this result, it is expected that the fault diagnosis system can be more reliable if the capacitance value and the fine adjustment process according to the temperature characteristic change are confirmed in the future.

  In conclusion, the present invention proposes a new technique for estimating the capacitor ESR of the on-line technique for fault diagnosis of the electrolytic capacitor. It has the advantage that it can be used universally in various power converters such as converters and inverters, and its fault detector method can detect the deterioration and fault condition of the change of the ESR of the capacitor and alert the status by only the voltage sensor of the capacitor. There is an advantage. In addition, if the current sensor of the capacitor is additionally attached to the components of the algorithm, the signal of the same algorithm as the voltage detection can be applied directly to calculate the ESR value to run the failure and life prediction program. The present invention is expected to be applied to the current on-demand power equipment widely used, it is not possible to predict the failure of the electrolytic capacitor in particular, it is possible to apply the electrolytic capacitor to electric vehicles, wind power, solar systems using expensive film capacitors It is expected to be able to raise electricity.

  Electrolytic Capacitor, Equivalent Series Resistance (ESR), Fault Diagnosis, Boost Converter, Frequency Analysis

Description

 Online Failure Detection System of DC Output Filtering Capacitors in Power Converters}

) 또는 등가직렬저항(equivalent series resistor; 이하 'ESR'이라 칭함)의 추정에 의한 진단기법이 전통적으로 사용되고 있다. 커패시턴스의 용량 추정기법은 운전 중 실험이 난해하고 제작과정에서 이미 ±10∼20[%]의 허용오차가 존재하고 있기 때문에 대부분은 등가직렬저항의 추정에 의한 고장 신호 기법에 의존한다. The diagnostic system of electrolytic capacitors has a dielectric loss due to changes in the internal parameters of the capacitors, rather than the capacitance measurement method.

Or diagnostic techniques based on the estimation of equivalent series resistors (hereinafter referred to as 'ESR') have traditionally been used. Capacitance estimation technique of capacitance depends on fault signal technique by estimating equivalent series resistance because the experiment is difficult during operation and the tolerance of ± 10 ~ 20 [%] already exists in the manufacturing process.

  Until now, fault diagnosis techniques related to electrolytic capacitors have been studied and invented mainly for specific power converters. Afroz M. Imam performs parametric calculations using adaptive signal processing (LMS) techniques from the voltage and current of the capacitor in the model of the boost converter, and ML Gasperi uses the ESR calculation and the amount of electrolyte flow in the AC inverter drive A life prediction model is presented. JwKolar presented the ESR estimation method by calculating the current of the capacitor according to the switching state mode of the space vector PWM method of the inverter. In addition, Lee has a disadvantage in that most of them depend on arithmetic process and signal processing algorithms, such as estimating ESR by calculating duty ratio according to switching state in PWM inverter. Is changed, the scope of application thereof is limited.

  Therefore, the present invention devised a fault diagnosis technique by estimating the ESR of the on-line electrolytic capacitor applicable to the power converter of various switching converters (SMPS, DC / DC converter, variable speed inverter, etc.). Its fault detector method has the advantage that only the voltage sensor of the capacitor can detect the ESR magnitude change of the capacitor and warn of its deterioration. In addition, if the current sensor of the capacitor is additionally attached to the components of the present algorithm, it is possible to operate the failure and life prediction program by directly calculating the ESR value using the same algorithm as the voltage detector method.

  Background of the Invention Background of the Invention The present invention is based on algorithms and measurement techniques for calculating ESR for online failure and life diagnosis without stopping the operation of the power converter in operation, and with poor power quality such as voltage and current harmonics. ESR calculation algorithm and technology that is strong against disturbance through proper filter and signal processing in the signal sensed by the converter.

  The core of the technical problem to be achieved by the present invention is a technique for diagnosing a failure of an electrolytic capacitor online. In order to realize this, an algorithm and a circuit for estimating a failure of an electrolytic capacitor by estimating ESR by sensing only voltage are realized. In addition to this, an algorithm and a circuit are generated to calculate ESR directly online through current sensing.

In order to realize this technical problem, as shown in FIG. 6, a bandpass filter 11, an RMS detector 12 through a rectifier, a lowpass filter 13, a hysteresis comparator 14 and an ESR are shown. The online possible fault diagnosis system which consists of an alarm 15 etc. was comprised. In the configuration of FIG. 6, the bandpass filter 11 obtains a pulsating voltage of the AC output from which high frequency noise is eliminated by ON-OFF switching of the DC converter 32 and a DC voltage component is removed.

은 정류기(12)를 거쳐서 DC 맥동 전압의 RMS 값

로 변환된다. 이후 저역통과 필터(13)에서는 DC 전압

를 출력하게 되고 이 값이 커패시터 ESR의 등가치(Estimated ESR)(16)로 변환하게 된다. 그리고 이 값은 고장 알람을 트리거링 할 수 있는 미리 결정된 히스테리시스 비교기(14)의 기준치(Reference ESR)(17)와 비교하게 되며, 일정 지속시간의 유무를 판단하여 ESR 알람(15)에 신호를 보내게 된다.AC pulsation voltage through this filter (11)

Is the RMS value of the DC pulsating voltage through the rectifier (12)

Is converted to. The low pass filter (13) then the DC voltage

This value is converted into the equivalent ESR value 16 of the capacitor ESR. This value is compared with a reference value (Reference ESR) 17 of a predetermined hysteresis comparator 14 capable of triggering a failure alarm, and determines whether there is a constant duration and sends a signal to the ESR alarm 15. do.

의 전류 검출에 대하여

전압 검출과 동일한 알고리즘을 적용하여 ESR 값을 직접 계산하여 고장예측 프로그램을 가동할 수 있는 장점이 있다.Therefore, the fault detector method according to the configuration of the present circuit has an advantage that only the voltage sensor 18 of the capacitor can perform the deterioration state and the fault detection for the variation of the ESR of the capacitor. Therefore, the proposed method of detecting the variation of magnitude of ESR value has the advantage that the system can be processed online even when the system is in operation, and that the configuration of the circuit can be minimized so that it can be packaged with the electrolytic capacitor. And with the configuration of this circuit, if the current sensor 19 is additionally attached to the capacitor

Current detection

By applying the same algorithm as the voltage detection, the ESR value can be calculated directly to run the fault prediction program.

의 전류 검출에 대하여

전압 검출과 동일한 알고리즘을 적용하여 ESR 값을 시뮬레이션의 결과에서처럼 이를 직접 계산하여 고장 및 수명 예측 프로그램을 가동할 수 있는 장점이 있다. 본 발명은 현재 광범위하게 사용되는 주문형 전력기기에 적용될 것으로 기대되며, 특별히 전해커패시터의 고장 예측이 불가능하여 고가의 필름커패시터를 사용하고 있는 전기자동차, 풍력, 태양광 시스템에 전해커패시터를 적용 할 수 있는 전기를 마련 할 수 있을 것으로 기대 된다. The failure detection method of the electrolytic capacitor by the ESR proposed in the present invention has an advantage that only the voltage sensor of the capacitor can perform the deterioration state and the failure detection for the variation of the ESR of the capacitor. And its method has the advantage that it can be processed online, and the greatest advantage is that it can be used universally regardless of the type of DC / AC inverter and DC / DC power converter. Also, if you attach a capacitor's current sensor in addition to the components of this algorithm,

Current detection

By applying the same algorithm as the voltage detection, the ESR value can be calculated directly as in the simulation result to run the failure and life prediction program. The present invention is expected to be applied to the current on-demand power equipment widely used, in particular, it is impossible to predict the failure of the electrolytic capacitor can be applied to the electrolytic capacitor in the electric vehicle, wind power, solar system using expensive film capacitors It is expected to be able to raise electricity.

  Figure 1: Equivalent Model of Electrolytic Capacitors

1 shows an equivalent structure and an equivalent circuit of an aluminum electrolytic capacitor. Here, the capacitance C is generated at the anode and cathode, and the internal resistance R is represented by the resistance of the electrolyte and the insulating paper, and R _LC configured in parallel with C is the resistance due to the electrolyte leakage current and L _ESL stands for equivalent series inductance.

<Electrolytic Capacitor Equivalent Model>

  In the present invention, the equivalent model of the electrolytic capacitor is applied as a simplified equivalent model. Where ESR is the equivalent series resistance.

                         Equivalent Model Considering L-value Simplified Equivalent Model (Invention)

는 식 1과 같이 나타낼 수 있으며, 여기서

는 각 주파수(f)를 나타낸다.Complex impedance of capacitance from equivalent model circuit of electrolytic capacitor

Can be expressed as Equation 1, where

Denotes each frequency f.

(식 1)

(Equation 1)

  Figure 2: Failure Mode FTA (Fault Tree Analysis) of Electrolytic Capacitors

  Figure 2 shows the failure mode of electrolytic capacitors and their causes by fault tree analysis (FTA). The failure mode of an electrolytic capacitor can be divided into short circuits and open circuits, and electrical performance deterioration such as a decrease in capacitance, an increase in ESR, and an increase in leakage current. Short circuits and open circuits are mainly caused by mechanical stress, and there may be dielectric breakdown of the oxide film during the short circuit. However, due to the rapid return performance of the oxide film, almost no concentration of current occurs, so the formation of the short circuit is very rare.

  Almost all failure modes of electrolytic capacitors are caused by electrochemical reactions, which are caused by a decrease in electrolyte vaporization and a decrease in capacitance at the anode and cathode. Is caused by In particular, the excess of temperature is directly related to the performance of the electrolyte, and it can be seen that the increase in temperature is caused by the increase of the other pulsating current.

(또는 ESR)의 증가를 초래한다고 할 수 있다. Therefore, the mechanism of failure and deterioration of the electrolytic capacitor is the biggest factor due to the drying up of the electrolyte as the temperature rises.

(Or ESR) can be said to increase.

  3: Circuit diagram for failure test of the electrolytic capacitor

  3 is a circuit configuration in which P. Venet performed an experiment to confirm a failure mechanism of the electrolytic capacitor. According to the American MIL-HDBK 217F, a modified SMPS circuit as shown in FIG. 2 was configured to perform failure tests for each component of the power converter. The switching frequency of the MOSFET was 66 [kHZ], and the experiment was conducted by constructing an electrolytic capacitor having rated capacity of 2,200 [μF], 10 [V], 105 [℃] at ambient temperature of 25 [℃]. It was concluded that the failure of power conversion systems is the most common (60%) in electrolytic capacitors (P. Venet, F.Perisse, MH El-Hussein1, and G. Rojat, "Realization of a smart electrolytic capacitor circuit"). , IEEE of Industry Applications Magazine, No.1, pp. 16-20. 2002.) Therefore, in power converters such as SMPS, the life of electrolytic capacitors is relatively shorter than that of other elements such as semiconductors. It can lead to a very deteriorating reliability of.

  4: Typical DC / DC Converter with LC Filter

  4 shows a circuit configuration of a typical DC / DC converter including a rectifier circuit used in an SMPS and the like, and its output includes an LC output filter.

은 그 값이 매우 크다면 정전류 소스로 취급할 수 있으나 이는 크기 및 비용의 문제 때문에 이의 값은 매우 제한적으로 사용 가능하며, 전류의 맥동 성분을 저감 시켜주는 전류 평활용 소자로 작용하게 된다. 이때에 인덕터에 흐르는 전류

은 DC전류의 성분

와 AC성분의 전류

로 구분하여 나타낼 수 있고 이는 식 2와 같이 표현할 수 있다.Inductance at the LC output of FIG. 4

If the value is very large, it can be treated as a constant current source, but because of its size and cost, its value is very limited and can be used as a current smoothing device to reduce the pulsation component of the current. Current flowing through the inductor

Is a component of DC current

And AC current

It can be expressed as and can be expressed as Equation 2.

(식 2)

(Equation 2)

  5: Simplified circuit of LC filter for AC output analysis

은 AC 전류소스

로 대체할 수 있으며, 이때의 전해 커패시터는 도 1에서 설명된 간략화 등가모델에 근거하여 도 5와 같이 나타낼 수 있다. 도 4와 같은 SMPS 전력변환회로의 경우 스위 칭 동작 주파수는 최소 20[kHz]가 넘고 일반적인 DC/DC 컨버터의 경우에도 거의 다 10[kHz]가 넘으며 또한 커패시터의 경우에도 그 값이 최소 수 백 [μF]을 초과하게 된다. 이러한 특성 때문에 전해 커패시터의 임피던스는 ESR 값의 크기가 그 특성을 좌우하게 된다. 따라서 도 5와 같은 회로 구조에서 커패시터

는 단락회로로 전환시킬 수 있으며, 이에 따라 부하저항

에서의 출력 AC 맥동 전압(

)은 식 3으로 표현할 수 있다.Therefore, the output inductor of the LC filter represented as shown in FIG.

Silver AC current source

In this case, the electrolytic capacitor may be represented as shown in FIG. 5 based on the simplified equivalent model described in FIG. 1. In the SMPS power conversion circuit as shown in FIG. 4, the switching operating frequency is at least 20 [kHz], and in the case of a general DC / DC converter, it is almost 10 [kHz], and in the case of a capacitor, the value is at least several hundreds. [μF] is exceeded. Because of this characteristic, the impedance of the electrolytic capacitor is determined by the magnitude of the ESR value. Therefore, in the circuit structure as shown in FIG.

Can be switched to short-circuit and therefore the load resistance

Output AC pulsation voltage at

) Can be expressed by Equation 3.

(식 3)

(Equation 3)

 Equation 3 shows that the output pulsation voltage of the DC / DC converter is related to the ESR value of the capacitor, and also to the AC pulsation current of the inductor and the magnitude of the load resistance. However, in order to obtain the smoothing characteristics of the output voltage, the ESR value must be much smaller than the load resistance, and considering this characteristic, the output AC pulsation voltage can be rewritten as shown in Equation 4.

(식 4)

(Equation 4)

값에도 지배적임을 알 수 있다. 그리고 실제의 동작에서는 인덕터에 대한 맥동 전류의 크기는 인덕턴스 값, 입출력 전압의 차 이 및 스위칭 듀티(duty) 비에 의하여 결정된다. 그러나 DC/DC 컨버터가 정상상태에서 운전되는 경우에는 인덕터의 맥동 전류는 위의 세 가지 요소에 의해서는 거의 작용하지 않기 때문에 이의 전류 값은 거의 일정하게 유지하게 된다. 따라서 AC 출력 전압의 맥동성분은 커패시터의 ESR 값의 크기에 직접 비례하게 됨을 알 수 있다. 지배된다고 할 수 있다.In this relation, the pulsation of the output voltage is very affected by the ESR value of the capacitor and also the pulsating current of the inductor.

It can be seen that it is also dominant in the value. In actual operation, the magnitude of the pulsating current for the inductor is determined by the inductance value, the difference between the input and output voltages, and the switching duty ratio. However, when the DC / DC converter is operated in a steady state, the pulsating current of the inductor is hardly acted upon by the above three factors, so the current value thereof is almost constant. Therefore, it can be seen that the pulsation component of the AC output voltage is directly proportional to the magnitude of the ESR value of the capacitor. It can be said to be controlled.

  Therefore, the high pulsation component voltage will appear in the deteriorated electrolytic capacitor with high ESR value connected in parallel with the load resistance, and the increase in the pulsation voltage of the electrolytic capacitor will be indicated by the increase of the ESR value. It can be diagnosed.

을 부착하지 않더라도 위의 알고리즘은 성립한다. 왜냐하면 DC/DC 컨버터에서 전해 커패시터가 LC 필터의 형태인 인덕터

과 함께 사용되지 않는 경우라 하더라도 커패시터의 맥동전압은 부하 전류의 크기에 의하여 영향을 받게 된다. 이러한 경우 AC 출력 맥동 성분의 전압 변동은 전해 커패시터의 ESR 값의 크기와 직접 관계되어 나타나므로 이를 통하여 열화 상태를 진단할 수 있기 때문이다. 그러나 대부분의 전력변환 장치에는 내부라인의 인덕터가 미세하게라도 존재하기 때문에 이의 염려는 없어도 된다.In most DC / DC converters, such as SMPS, the attachment of inductor L is almost essential, but as in the case of rectifiers

The algorithm above holds true even if no Inductors in which the electrolytic capacitor is in the form of an LC filter in a DC / DC converter

Even if not used together, the pulsation voltage of the capacitor is affected by the magnitude of the load current. In this case, the voltage fluctuation of the AC output pulsation component is directly related to the magnitude of the ESR value of the electrolytic capacitor, and thus the degradation state can be diagnosed. However, most power converters do not have to worry about the small amount of inductor in the internal line.

  6 is a block diagram of an electrolytic capacitor failure detection company proposed in the present invention.

  Figure 6 shows a block diagram of the on-line troubleshooting method of the electrolytic capacitor proposed in the present invention. It is an online possible fault diagnosis system consisting of a bandpass filter (11), an RMS detector (12) through a rectifier, a lowpass filter (13), a hysteresis comparator (14) and an ESR alarm (15). It is the composition. In the configuration of FIG. 6, the bandpass filter 11 obtains a pulsating voltage of the AC output from which high frequency noise is eliminated by ON-OFF switching of the DC converter 32 and a DC voltage component is removed.

은 정류기(12)를 거쳐서 DC 맥동 전압의 RMS 값

로 변환된다. 이후 저역통과 필터(13)에서는 DC 전압

를 출력하게 되고 이 값이 커패시터 ESR의 등가치(Estimated ESR)(16)로 변환하게 된다. 그리고 이 값은 고장 알람을 트리거링 할 수 있는 미리 결정된 히스테리시스 비교기(14)의 기준치(Reference ESR)(17)와 비교하게 되며, 일정 지속시간의 유무를 판단하여 ESR 알람(15)에 신호를 보내게 된다.AC pulsation voltage through this filter (11)

Is the RMS value of the DC pulsating voltage through the rectifier (12)

Is converted to. The low pass filter (13) then the DC voltage

This value is converted into the equivalent ESR value 16 of the capacitor ESR. This value is compared with a reference value (Reference ESR) 17 of a predetermined hysteresis comparator 14 capable of triggering a failure alarm, and determines whether there is a constant duration and sends a signal to the ESR alarm 15. do.

의 전류 검출에 대하여

전압 검출과 동일한 알고리즘을 적용하여 ESR 값을 직접 계산하여 고장예측 프로그램을 가동할 수 있는 장점이 있다.Therefore, the fault detector method according to the configuration of the present circuit has an advantage that only the voltage sensor 18 of the capacitor can perform the deterioration state and the fault detection for the variation of the ESR of the capacitor. Therefore, the proposed method of detecting the variation of magnitude of ESR value has the advantage that the system can be processed online even when the system is in operation, and that the configuration of the circuit can be minimized so that it can be packaged with the electrolytic capacitor. And with the configuration of this circuit, if the current sensor 19 is additionally attached to the capacitor

Current detection

By applying the same algorithm as the voltage detection, the ESR value can be calculated directly to run the fault prediction program.

  7: Simulation circuit of boost converter for ESR estimation

  7 is a simulation result using a PSIM 6.0 tool by configuring a DC / DC buck converter. (However, circuit configurations such as LPF are omitted below).

와 전류

를 계측하여 신호처리를 수행하였다. 이때 추정하고자하는 ESR 값은 PSIM 상에서 커패시터의 내부파라 설정모드가 없는 관계로 인하여 이를 직렬로 주입(Injected ESR)하여 연결하였으며(0.5, 1.0[Ω] 및 1.5[Ω]으로 각각 주입), 전압의 계측에 대한 신호처리 과정은 도 6과 마찬가지로

,

및

의 순으로 하였다. 이때의 모의실험 조건은 벅 컨버터 및 부스트 컨버터 모두 동일하며 다음과 같다.In addition, in this simulation, a boost converter was constructed to identify its characteristics. ESR to be estimated by this algorithm selects a capacitor at DC load

And current

Was measured to perform signal processing. At this time, the ESR value to be estimated was connected by injecting ESR in series (injected with 0.5, 1.0 [Ω] and 1.5 [Ω] respectively) because there is no internal parameter setting mode of the capacitor on the PSIM. Signal processing for measurement is the same as in FIG.

,

And

It was in order. The simulation conditions at this time are the same for both the buck converter and the boost converter.

=50[V_peak), 60[Hz], 부하저항 : 100[Ω]*power

= 50 [V _peak ), 60 [Hz], load resistance: 100 [Ω]

Duty ratio: 0.5, MOSFET switching frequency: 5 kHz

(정류기) 및

커패시터 : 6,800[μF] 및 4,700[μF]*

(Rectifier) and

Capacitors: 6,800 [μF] and 4,700 [μF]

* Inductor L: 0.1 [mH]

  8: Voltage signal waveform (buck converter) when ESR = 0.5 [kV]

  In FIG. 8, the waveforms after the filter pass according to the procedure of FIG. 6 are shown for the voltage waveforms of the output capacitors of the buck converter (V (BPF), V (recti), and V (LPF)). At this time, the steady state after 20 [ms] was measured, and the injected ESR value was set to 0.5 [Ω].

  9: Voltage signal waveform (buck converter) when ESR = 1.5 [kV]

  FIG. 9 shows that the voltage measurement changes according to the change of the ESR value as a result of selecting the ESR value as 1.5 [kV] under the condition of the buck converter shown in FIG. 8. Therefore, measuring its value alone can be used as a preventive diagnosis system for failure alarms of capacitors according to ESR status.

  10: Result of Estimated ESR According to ESR Variation (Buck Converter)

  FIG. 10 is a graph showing the ESR estimation value trend due to the measurement relationship between the voltage waveform and the current waveform of the output capacitor of the buck converter under the above conditions. ESR was estimated using the relationship of the algorithm described in FIG. 6, and after 50 [ms] time elapsed, the ESR of the capacitor was injected in series with the inside to change the value. The ESR was initially set to 1.0 [Ω] by a simulated internal switch connection and then changed to 0.5 [Ω] after 50 [ms]. The results can be confirmed that the estimated ESR value corresponding to the injected ESR value is very well estimated with little error.

  11: Result of Estimated ESR According to ESR Variation (Boost Converter)

  11 illustrates the estimation results of the ESR operated by the boost converter under the same conditions as in FIG. 10. As a result, ESR was experimented to 1.0 [Ω] at the initial stage and 0.5 [Ω] after 50 [ms], but it was confirmed that the estimated ESR value was well estimated with little error.

  12: Result of estimated ESR according to the variation of ESR (rectifier of inverter load)

이 부착하지 않았다. 60[Hz], 선간 RMS 560[V]의 전압을 인가하였으며, 커패시터의 조건은 도 10 및 도 11과 같게 설정하였다. 이때의 ESR의 가변에 의한 추정은 150[ms]의 시간 경과 후 커패시터의 ESR이 변하도록 하였다. 이의 결과는 기동전류(Ia)의 변화에 따라 약간의 노이즈는 나타나고 있으나, 이는 커패시터의 전압/전류에 대한 필터 통과 후의 파형이 같이 변화하기 때문에 ESR의 추정에는 아무런 영향이 없고 다만 ESR의 가변에 따른 과도상태에서만 이의 값이 변화할 따름이다. 12 shows the trend of the ESR estimation value by measuring the capacitor voltage and the current waveform of the rectifier DC output stage including the VVVF (variable speed) inverter. The speed controller of the three-phase four-pole induction motor by the VVVF inverter was attached to the rectifier load of the DC capacitor, and the simulation was performed.

This did not attach. A voltage of 60 [Hz] and line RMS 560 [V] was applied, and the capacitor conditions were set as shown in FIGS. 10 and 11. The estimation by the variable ESR at this time caused the ESR of the capacitor to change after 150 [ms]. As a result of this, a little noise appears due to the change of starting current (Ia). However, since the waveform after passing through the filter with respect to the voltage / current of the capacitor changes together, there is no influence on the estimation of ESR. Its value only changes in the transient state.

  Figure 1: Equivalent Model of Electrolytic Capacitors

  Figure 2: Failure Mode FTA (Fault Tree Analysis) of Electrolytic Capacitors

  3: Circuit diagram for failure test of the electrolytic capacitor

  4: Typical DC / DC Converter with LC Filter

  5: Simplified circuit of LC filter for AC output analysis

  6 is a block diagram of an electrolytic capacitor failure detection company proposed in the present invention.

  7: Simulation circuit of boost converter for ESR estimation

  8: Voltage signal waveform (buck converter) when ESR = 0.5 [kV]

  9: Voltage signal waveform (buck converter) when ESR = 1.5 [kV]

  10: Result of Estimated ESR According to ESR Variation (Buck Converter)

  11: Result of Estimated ESR According to ESR Variation (Boost Converter)

12: Result of estimated ESR according to the variation of ESR (rectifier of inverter load)
Table 1: ESR reference data of hysteresis comparator 14

<Explanation of Signs for Main Parts>

11: Bandpass Filter of Electrolytic Capacitor Voltage Value

  Circuit for obtaining high frequency noise elimination by ON-OFF switching of DC converter 32 and pulsating voltage of AC output from which DC voltage component is removed

12 RMS detector through rectifier of electrolytic capacitor voltage value

을 DC 맥동 전압의 RMS 값

로 변 환하기 위한 정류기 AC pulsation voltage through band pass filter (11)

RMS value of DC pulsating voltage

Rectifier for conversion

13: lowpass filter of electrolytic capacitor voltage value

를 DC 전압

를 출력하여 이 값을 커패시터 ESR의 등가치(Estimated ESR)(16)로 변환하기 위한 필터RMS value of the DC pulsating voltage through the RMS detector 12

DC voltage

Filter to convert this value to the equivalent ESR (16) of the capacitor ESR

14: ESR hysteresis comparator

And a comparison device for comparing the estimated ESR (16) estimated by the low pass filter (13) with the failure reference value (17) of the preset ESR.
And a comparison device for comparing the estimated ESR (16) estimated by the low pass filter (13) with the failure reference value (17) of the preset ESR. The failure reference value of the ESR is based on the data 17 stored in a table form according to the characteristics of the manufacturer, the operating voltage, the capacity, and the model. Estimation of ESR of electrolytic capacitor is applied to failure diagnosis algorithm that judges the beginning of Abnormal signs when the estimated value of ESR is about 2 times more than normal as deterioration progresses. Detailed setting is possible by referring to the data on the sensitivity of change of ESR value. The hysteresis comparator is a means for overcoming the shortcomings of the simple comparator, and is a means for preventing malfunction due to sudden changes in ESR estimation data due to disturbances around the designed device or transients that may occur during the ESR estimation process.

15: ESR alarm

  ESR alarm to warn of electrolytic capacitor failure

16: ESR (Estimated ESR)

17: Reference ESR
The failure threshold of ESR is based on data stored in table form according to manufacturer, operating voltage, capacity and model. The failure threshold of ESR is based on the technical data supplied by the manufacturer. Table 1 shows an example of ESR data for the product of Japan Chemicon (www.chemi-con.co.jp), the industry leader in aluminum electrolytic capacitors. It is shown. ESR values of domestic manufacturers are based on the data provided by manufacturers, and in the case of models without data, the data is based on the data of Japanese Chemicon, which is a benchmark model for various domestic and foreign companies.

18: voltage sensor or voltage value of the electrolytic capacitor

19: Current sensor or current value in the electrolytic capacitor

20: Bandpass filter of the electrolytic capacitor current value

21: RMS detector through rectifier of electrolytic capacitor current value

22: lowpass filter of electrolytic capacitor current value

23: calculator for ESR operation

  A calculator for calculating the ESR from the values calculated by the voltage value calculation (11, 12, 13) and the current value calculation (20, 21, 22) of the electrolytic capacitor.

31: Power Source

32: DC / DC Converter

33: electrolytic capacitor
Table 1 ESR reference data of hysteresis comparator 14 (an example of Japanese chemistry)

Claims (3)

Power source 31 that supplies power to the load side using power, DC / DC Converter 32 for controlling the input power to the desired DC output, voltage sensor 18 for detecting the voltage across the electrolytic capacitor and DC / Electrolytic capacitor voltage value for acquiring high frequency noise by ON-OFF switching of DC / DC converter 32 and smoothing voltage of DC converter output and acquiring pulsating voltage of AC output with DC voltage component removed AC pulsation voltage through the bandpass filter 11 and the bandpass filter of the

RMS value of DC pulsating voltage

RMS value of the DC pulsating voltage through the RMS detector 12 and the RMS detector through the rectifier of the electrolytic capacitor voltage value for conversion to

DC voltage

The low pass filter 13 and the low pass filter of the electrolytic capacitor voltage value for converting the value to the equivalent ESR 16 of the electrolytic capacitor ESR by outputting ESR hysteresis comparator 14 for comparing the set ESR fault reference value 17 of the set ESR and ESR alarm 15 for warning of the failure of the electrolytic capacitor so that the ESR has only the voltage value 18 of the electrolytic capacitor. "Online fault detection system of direct current output filter capacitor in power converter", characterized in that on-line fault diagnosis of electrolytic capacitor is possible by estimating (16). In addition to converting the pulsation values passed through the bandpass filter 28 and the bandpass filter of the current sensor 19 and the electrolytic capacitor current value for sensing the current of the electrolytic capacitor to the RMS value of the DC pulsation value in addition to claim 1 The RMS value of the DC pulsation passing through the RMS detector 21 and the RMS detector through the rectifier of the electrolytic capacitor current value is output as a DC value, and this value is compared with respect to the voltage value (11, 12, 13) of the electrolytic capacitor. On-line fault of DC output filter capacitor in power conversion device, characterized in that it consists of a calculator 23 for calculating ESR by dividing operation, so that ESR can be directly calculated to enable on-line failure prediction and life prediction program of electrolytic capacitor. Detection system ″ Power conversion, which is composed of claim 1 or 2, which can be used for diagnosing electrolytic capacitor failure and predicting life by general online ESR calculation regardless of the type of DC / AC inverter and DC / DC power converter. On-line Fault Detection System of DC Output Filter Capacitor in Device ″

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