CN106324472A - Non-contact converter IGBT module state monitoring method - Google Patents

Abstract

The invention relates to a method for monitoring the state of a non-contact converter IGBT module, comprising the following steps: S1: measuring the output phase current of the converter, and measuring the case temperature of the converter IGBT module; S2: measuring the output phase current from the converter The IGBT equivalent turn-off time and IGBT turn-off current are extracted from , and the IGBT equivalent turn-off time is the time corresponding to the first wave head or trough caused by the turn-off of the IGBT module in the high-frequency oscillation signal of the output phase current, The IGBT turn-off current is the current corresponding to the moment when the output phase current starts to appear a high-frequency oscillation signal; S3: Obtain the turn-off characteristic curve reflecting the operating state of the IGBT module of the converter. Compared with the prior art, the present invention can conveniently measure the turn-off characteristics of all IGBT devices under different current conditions, is applicable to converter systems of various structures, and helps to improve the operation reliability of the converter system. The utility model has the advantages of simplicity, safety, good applicability and the like.

Description

A method for monitoring the state of a non-contact converter IGBT module

technical field

The invention relates to a method for monitoring the status of a converter, in particular to a method for monitoring the status of a non-contact converter IGBT module.

Background technique

A converter is a power conversion device that is widely used in new energy power generation, electric vehicles, rail transit, aerospace, and metallurgy. As the core component of the converter, the failure of the IGBT module can lead to the interruption of the operation of the entire converter system, and even cause safety accidents and major economic losses. Therefore, the operational safety and reliability issues of IGBT modules have become increasingly prominent.

Most IGBT failures in actual systems undergo a gradual development process. IGBT status monitoring technology uses various detection and analysis methods to monitor various variables that reflect the operating status of the device, and evaluates the current operating status of the device based on the system operating history. IGBT status monitoring technology can effectively improve the safety and reliability of converter system operation. On the one hand, the fault pre-diagnosis technology based on condition monitoring can detect faults before the IGBT module fails and take corresponding measures in time, thereby avoiding accidents and major economic losses and improving system operation safety; on the other hand, according to device status information Establishing a condition-based converter system maintenance plan can effectively reduce downtime, maintenance costs, improve operation and maintenance efficiency, and significantly improve the reliability and economy of system operation.

According to the different types of monitored state variables, current IGBT state monitoring methods can be divided into static monitoring methods and dynamic monitoring methods. The static monitoring method measures when the IGBT is in the on or off state. Such methods usually measure static state variables such as the IGBT saturation voltage drop V _ce(sat) , short-circuit current I _sc , and leakage current I _lk ; the dynamic monitoring method is used when the IGBT is in the The measurement is performed during turn-on or turn-off. Such methods usually measure dynamic state variables such as IGBT turn-on/turn-off time T _on /T _off , Miller plateau voltage V _gp , turn-on/turn-off delay time T _don /T _doff .

[1] Chinese patent CN104849644A discloses an IGBT state detection circuit and IGBT state detection method, using a special circuit to measure the collector-emitter voltage V _ce of the IGBT, and effectively judging that the IGBT is in the state according to the output signal of the circuit and the IGBT gate control signal. Turn-on, turn-off, abnormal turn-off or short-circuit status. However, this state monitoring method belongs to post-fault detection and cannot evaluate the health status of IGBT in real time, so it cannot identify early faults and take corresponding measures in time to avoid accidents and losses.

Literature [2] "UM Choi, F. Blaabjerg, S. Munk-Nielsen, et al. Condition monitoring of IGBT module for reliability improvement of power converters [C]. IEEE Transportation Electrification Conference and Expo, 2016: 602-607" using special design The advanced collector voltage detection circuit and state monitoring algorithm evaluate the operating state of the IGBT module according to the changes in the saturation voltage drop V _ce(sat) of the IGBT and the operating characteristics of the current and junction temperature to improve the reliability of the converter. However, the magnitude of the saturation voltage drop is very different from the DC bus voltage and changes sharply before and after the switch. Therefore, the precise measurement of the saturation voltage drop requires high resolution and dynamic characteristics of the measurement device. In addition, the state detection method proposed in the literature needs to modify the converter system and install additional measurement devices, which is not convenient for on-site implementation.

Literature [3] "P.Sun, C.Gong, X.Du, et al.Condition Monitoring IGBT Module BondWires Fatigue Using Short-Circuit Current Identification[J]. IEEE Transactions on Power Electronics, 2016" on the premise of not damaging the IGBT module In order to improve the reliability of the IGBT module, the relationship between the short-circuit current I _sc of the IGBT, the junction temperature and the gate voltage is measured through the short-circuit experiment, and the degree of fracture of the bonding wire is monitored. However, this method needs to reduce the gate voltage of the IGBT in fault detection, which cannot be monitored in real time on-line, and it is difficult to be practical in engineering.

Literature [4] "H.Luo, Y.Chen, P.Sun, et al. Junction Temperature Extraction Approach With Turn-Off Delay Time for High-Voltage High-Power IGBT Modules[J]. IEEE Transactions on Power Electronics, 2016, 31(7):5122-5132 "Use the turn-off delay time _Tdoff as a temperature-sensitive variable to measure the junction temperature of the IGBT module and predict the health status of the power device. This method needs to measure the voltage V _eE between the emitter of the module and the auxiliary emitter. In actual systems, IGBTs are packaged as discrete components or modules are installed inside the converter, and it is difficult to measure gate variables on site.

Literature [5] "Bryant A T, Mawby P A, Palmer P R, et al. Exploration of powerdevice reliability using compact device models and fast electro-thermalsimulation [C]. IEEE Industry Applications Conference, 2006: 1465-1472" and literature [6] "Musallam M, Johnson C M, Yin C, et al. Real-time life consumption power modules prognosis using on-line rainfall algorithm in metro applications [C]. IEEE Energy Conversion Congress and Exposition (ECCE), 2010:970-977" using IGBT The compact electrothermal model and the fast electrothermal simulation technology of the converter can perform "online" life prediction of the IGBT module under the condition that the operating conditions of the converter system are constantly changing. However, the accuracy of life prediction results in this method depends on the accuracy of the model (device reliability model, electrothermal model). Considering the dispersion of device parameters in the actual system, the complexity and variety of failure modes, and the influence of device states on junction temperature estimation, it is difficult for this technology to accurately predict the lifetime of converter IGBT modules.

Contents of the invention

The purpose of the present invention is to provide a non-contact converter IGBT module state monitoring method in order to overcome the above-mentioned defects in the prior art, using the IGBT equivalent turn-off time as the characteristic state variable, which can conveniently measure the The turn-off characteristics of all IGBT devices under different current conditions are applicable to converter systems of various structures, which helps to improve the operation reliability of the converter system, and has the advantages of simplicity, safety, and good applicability.

The purpose of the present invention can be achieved through the following technical solutions:

A method for monitoring the state of a non-contact converter IGBT module comprises the following steps:

S1: Use a non-contact current measuring element to measure the output phase current i of the converter, and measure the case temperature T _c of the IGBT module of the converter;

S2: Extract the IGBT equivalent turn-off time t _sw.off and the IGBT turn-off current I _off from the output phase current i, the IGBT equivalent turn-off time is corresponding to the high-frequency oscillation signal of the output phase current i The time t _sw.off of the first wave head or trough caused by the shutdown of the IGBT module, the IGBT shutdown current I _off is the current corresponding to the moment when the output phase current i begins to appear a high-frequency oscillation signal;

S3: Obtain the IGBT turn-off characteristic curve reflecting the operating state of the converter IGBT module, the IGBT turn-off characteristic curve is the IGBT equivalent turn-off time t _sw.off and the IGBT turn-off current I at the case temperature T _c The functional relationship of _off .

The high-frequency oscillating signal refers to an oscillating signal with a frequency ranging from 150 kHz to 30 MHz.

The IGBT turn-off characteristic curve measured on site is compared with the IGBT turn-off characteristic curve under normal working conditions. If the IGBT turn-off characteristic curve measured on site changes beyond the set allowable range, the converter IGBT module is deemed to be in operation. Status changes.

The setting allowable range is that the absolute value of the deviation is less than or equal to 0.5%.

The bandwidth of the non-contact current measuring element is greater than 500 kHz.

The case temperature _Tc is measured by the temperature measuring element that comes with the IGBT module or is additionally installed.

Compared with the prior art, the present invention has the following advantages:

1) The project is easy to implement: compared with the prior art [1]-[4], the method of the present invention is based on the first wave head (or trough) of the high-frequency oscillation of the output phase current of the converter caused by the IGBT turn-off process The basic principle is that the time coincides with the IGBT turn-off process, and the switching characteristics of the IGBT are obtained by measuring the output phase current of the converter. This method does not need to implant a detection circuit inside the converter, and it is easy to implement on site.

2) High safety: Compared with the prior art [3] and [4], the method of the present invention measures the output phase current of the converter at the engineering site in a non-contact manner, and the current measuring element used is indistinguishable from the converter system Direct electrical connection and online status monitoring of IGBT without affecting the normal operation of the system ensure the safety of the system.

3) Good applicability: Compared with the prior art, the method of the present invention is applicable to converter systems of various topological structures. Regardless of the structure of the converter (such as three-level neutral point clamped converter, modular multi-level converter), the high-frequency oscillation of the output phase current is caused by each IGBT device inside the converter. A certain sequence of alternating switches is generated. The method of the invention can obtain the switching characteristics of each IGBT device in the same phase bridge arm of the converter by measuring the high-frequency oscillation characteristics of the output phase current of the converter, and monitor the health status of the IGBT module of the converter according to the change of the IGBT turn-off characteristic. monitor.

Description of drawings

Fig. 1 is the working flow chart of the inventive method;

Fig. 2 is the schematic diagram that the method of the present invention is applied on the converter;

Figure 3 is a schematic diagram of the definition of the equivalent turn-off time and turn-off current of the IGBT of the converter;

Fig. 4 is a schematic diagram of the state monitoring experiment results of the converter IGBT module.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is carried out on the premise of the technical solution of the present invention, and detailed implementation and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

The present invention proposes a non-contact converter based on the principle that the time of the first wave head (or trough) of the high-frequency oscillation of the output current of the converter caused by the IGBT shut-off process coincides with the IGBT shut-off process. The IGBT module state monitoring method, as shown in Figure 1 and Figure 2, includes the following steps:

S1: Install a non-contact current measuring element to measure the output phase current i of the converter, and install or use the temperature measuring element that comes with the IGBT module to measure the case temperature T _c of the IGBT module of the converter. Among them, the non-contact current measuring element requires sufficient bandwidth, the bandwidth is greater than 500kHz, so as to measure the high-frequency oscillation signal in the output phase current of the converter. On-site high-speed measurement of output phase current i and case temperature T _c and continuous data recording.

S2: extract the IGBT equivalent off time t _sw.off and the IGBT off current I _off from the output phase current i.

As shown in Figure 3, the method of the present invention defines the IGBT equivalent turn-off time as the time t _sw.off of the first wave head or trough caused by the turn-off of the IGBT module in the high-frequency oscillation signal of the output phase current i , and as a characteristic state variable; at the same time, the IGBT turn-off current I _off is defined as the current corresponding to the moment when the output phase current i begins to appear a high-frequency oscillation signal, and the moment when the output phase current i begins to appear a high-frequency oscillation signal is the IGBT The moment the shutdown process begins. Among them, the high-frequency oscillating signal refers to an oscillating signal with a frequency range of 150 kHz to 30 MHz, which corresponds to the frequency range of the conductive electromagnetic interference signal. This frequency band can well reflect the off state of the IGBT, and other interference factors are small.

S3: Obtain the IGBT turn-off characteristic curve reflecting the operating state of the IGBT module of the converter, and define the IGBT turn-off characteristic curve as the IGBT equivalent turn-off time t _sw.off and the IGBT turn-off current I at a certain case temperature T _c The functional relationship of _off . The turn-off characteristic curve of the converter IGBT under different temperature conditions can be obtained by processing the data measured on site. Using the IGBT turn-off characteristics measured on site, the operating status and fault conditions of the IGBT power module of the converter can be effectively evaluated. If a certain degree of change (such as offset, deformation, etc.) is found in the turn-off characteristics, it can be determined that the operating state of the IGBT module has changed.

During the long-term operation of the converter IGBT module, the aging of the solder layer is prone to occur under the action of temperature cycle and power cycle. The cracks and voids caused by the aging of the solder layer will hinder the heat dissipation of the IGBT chip, causing the temperature to rise and even eventually burn out and fail. The method of the invention can detect the change of the health state of the IGBT module, and timely diagnose the aging of the solder layer of the power module.

Example: The method of the present invention is used to test the IGBT turn-off characteristic t _sw.off = f(I _off ) of the IGBT module (FF50R12RT4) in the 380V/10kW three-phase two-level converter before and after the fault. As shown in Figure 4 of the experimental results, by comparing the deviation of the IGBT turn-off characteristic f(I _off ) before and after the fault, it can be found that the health status of the IGBT module has changed. The implementation process is as follows:

1. Install a current probe at the A-phase output of the converter system. The current probe model is CP8030A with a bandwidth of 50MHz, which is used to measure the high-frequency oscillation signal in the output phase current of phase A of the converter and record the off-current I _off . Use a thermocouple to measure the case temperature T _c of the IGBT module. This patented method can monitor the state of all IGBT tubes in a certain phase bridge arm. If you need to monitor the IGBTs of other phase bridge arms, you only need to extend this method to other bridge arms, or specific to the line where a certain IGBT output is located.

2. Use healthy and fault-free IGBT power modules for each bridge arm of the converter, run the converter system at the load state (such as rated load), use a high-speed digital oscilloscope to measure the output phase current signal of the converter on site and record the data continuously, and at the same time Measure and record the IGBT module case temperature.

3. According to the equivalent turn-off time, turn-off current and turn-off characteristics defined by the method of the present invention, the IGBT turn-off characteristic curve f(I _off ) is obtained by processing the data measured on site when the case temperature of the IGBT module is 25°C. Finally, all the measured equivalent off-time and off-current values are stored in a two-dimensional table to obtain the IGBT off-characteristic f(I _off )_1 of the healthy IGBT module.

4. Stop the operation of the converter system, replace the A-phase bridge arm power module with an IGBT power module with solder layer aging, repeat steps 1 to 3, and measure the IGBT turn-off characteristic f(I _off )_2 of the aging IGBT module .

5. Plot the IGBT turn-off characteristic f(I _off )_1 of the healthy IGBT module and the IGBT turn-off characteristic f(I _off )_2 of the aged IGBT module in FIG. 4 . At the same case temperature Tc, under the same current condition, the IGBT equivalent turn-off time of the solder layer aging IGBT module is tens of nanoseconds longer than the IGBT equivalent turn-off time of the healthy module, and the IGBT turn-off characteristics before and after aging occur. If there is a deviation, and the degree of deviation exceeds the set normal allowable range (caused by measurement error), the set normal allowable range is that the absolute value of the deviation is less than or equal to 0.5%. Therefore, the operating status and fault conditions of the IGBT power module of the converter can be effectively evaluated by using the IGBT turn-off characteristics measured on site.

Similarly, the method of the invention can be used to monitor the state of IGBT modules in various converter systems such as neutral point clamping three-level (NPC) and modular multi-level (MMC).

Claims (6)

1. a contactless current transformer IGBT module state monitoring method, it is characterised in that comprise the following steps:

S1: use non-contact electric current measurement element to measure the output current phase i of current transformer, and measure current transformer IGBT module Watchcase temperature T_c；

S2: extract IGBT equivalence turn-off time t from output current phase i_sw.offWith IGBT cut-off current I_off, described IGBT etc. The effect turn-off time be output current phase i high-frequency oscillation signal in corresponding to this IGBT module turn off first wave head causing or The time t of person's trough_sw.off, described IGBT cut-off current I_offFor with output current phase i start to occur high-frequency oscillation signal time Carve corresponding electric current；

S3: obtain the IGBT turn-off characteristic curve of reflection current transformer IGBT module running status, described IGBT turn-off characteristic curve For in watchcase temperature T_cUnder IGBT equivalence turn-off time t_sw.offWith IGBT cut-off current I_offFunctional relationship.

One the most according to claim 1 contactless current transformer IGBT module state monitoring method, it is characterised in that institute State high-frequency oscillation signal and refer to the frequency range oscillator signal at 150kHz～30MHz.

One the most according to claim 1 contactless current transformer IGBT module state monitoring method, it is characterised in that existing The IGBT turn-off characteristic curve that field records contrasts, if scene records with the IGBT turn-off characteristic curve under normal operating conditions IGBT turn-off characteristic curve occur more than set allowed band change, then assert current transformer IGBT module running status occur Change.

One the most according to claim 3 contactless current transformer IGBT module state monitoring method, it is characterised in that institute State and set allowed band as departure absolute value less than or equal to 0.5%.

One the most according to claim 1 contactless current transformer IGBT module state monitoring method, it is characterised in that institute The band stating non-contact electric current measurement element is wider than 500kHz.

One the most according to claim 1 contactless current transformer IGBT module state monitoring method, it is characterised in that institute State watchcase temperature T_cThat IGBT module carries or the extra temperature-measuring element installed is used to measure.