CN113419155B - IGBT module on-line monitoring system and method - Google Patents

Abstract

The invention discloses an IGBT module online monitoring system and method, and belongs to the field of reliability of power electronic devices. The on-line monitoring system comprises a power supply conversion module, a relay selection module, a monitoring current injection module, a communication module, a voltage sampling module and the like, wherein the modules are all designed into independent hardware circuit boards. The on-line monitoring method comprises the steps that a monitoring system samples a plurality of groups of voltage parameters during the current injection monitoring period, and then the health state of an IGBT module is judged according to the voltage parameter values and an off-line fitting curve. The on-line monitoring system provided by the invention has strong coordination and coordination capability with a system to be tested, high integration level, convenient use and carrying and easy popularization to practical application.

Description

IGBT module on-line monitoring system and method

Technical Field

The invention relates to the field of reliability of power electronic devices, in particular to an IGBT module online monitoring system and an IGBT module online monitoring method.

Background

An Insulated Gate Bipolar Transistor (IGBT for short), which is an integrated device that combines the advantages of a power field effect Transistor, such as fast switching speed, low driving power, simple driving circuit, and high input impedance, and also combines the advantages of a Bipolar power Transistor, such as reduced saturation voltage, and large current. The IGBT is widely realized and applied to various occasions such as a power electronic system, a renewable energy power generation system, a power transmission system, wind power generation and the like. The operating environment of the application becomes worse as the working voltage, current and power level of the device rises, and related researches show that more than 30% of power electronic system faults are caused by IGBT module faults, so that the reliability of the device is also more strictly required.

According to the feedback of engineers, even if the IGBT power module is subjected to an offline test and an accelerated aging test under a simulated working condition after being produced, the modules passing the test standard are applied to the field, mass damage of unknown reasons can occur, and the damaged modules cannot confirm the reason of the fault, which brings new challenges to the improvement of the reliability of the system operation. Under the circumstances, an effective method for realizing on-line state monitoring, fault diagnosis and evaluation of the IGBT is required to be found, so that the self-checking level of the operation management of the power converter is improved, and the reliability of the power converter is improved. The IGBT power module is monitored on line in a field environment, and is an important link for health management and reliability evaluation of a converter.

The Chinese invention patent document (CN105337523B) entitled "NPC type three-level inverter reliability on-line monitoring system and method" introduces a relatively complete 3LNPC inverter on-line monitoring system and method, but the on-line monitoring system comprises a voltage acquisition card with heavy volume and a LABVIEW unit, and a power supply unit of the monitoring system is provided by a direct current power supply, so that the volume of the system is greatly increased, and the system is not easy to realize in-situ monitoring during the field operation of the inverter. The method only relates to the monitoring of two IGBT modules at the inner side of each phase, but does not relate to the monitoring of two IGBT modules at the outer side;

the invention discloses a Chinese patent document (CN207832955U) entitled IGBT on-line detection device, which has the advantages of simple structure, small volume and convenient carrying, but does not specifically describe the coordination and coordination of the device where the IGBT is located when on-line monitoring is realized.

In summary, the existing IGBT module online monitoring system has the following problems:

1) coordination and coordination between the monitoring system and the system to be tested are not considered;

2) the integration of an online monitoring system is not considered, and the conventional monitoring system is overlarge in size and difficult to carry;

3) only the monitoring of the two IGBT modules at the inner side of each phase bridge arm of the three-level NPC inverter is concerned, but the monitoring of the two IGBT modules at the outer side is not concerned.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provides an integrated online monitoring system and a monitoring method capable of monitoring an inner IGBT module and an outer IGBT module.

In order to achieve the aim, the invention provides an IGBT module online monitoring system, wherein the related IGBT module to be tested is positioned in a three-level NPC inverter, and the three-level NPC inverter comprises a direct current side power supply E, two identical direct current side capacitors, a three-phase inverter main circuit and a three-phase load resistorAnd a three-phase load inductance; the voltage of the DC side power supply E is recorded as a DC side voltage U_dcThe two DC-side capacitors are respectively denoted as DC-side capacitor C_HAnd a DC side capacitor CL, the DC side capacitor C_HAnd a DC side capacitor C_LConnected in parallel between a DC positive bus P and a DC negative bus Q of a DC power supply E after series connection, and a DC side capacitor C_HAnd a DC side capacitor C_LThe connecting point of (a) is marked as a neutral point O;

the three-phase inversion main circuit is divided into three-phase bridge arms, the three-phase bridge arms are connected with a direct-current side power supply E in parallel, the three-phase bridge arms are completely identical in topology, the three-phase bridge arms are respectively marked as k-phase bridge arms, k represents a phase sequence, and k is equal to A, B and C; in the three-phase bridge arm, each phase of bridge arm comprises 4 IGBT modules, and the 4 IGBT modules are recorded as a switch device S_kiI represents the serial number of the switching device, and i is 1, 2, 3, 4; in a three-phase bridge arm, each phase of the bridge arm comprises 2 clamping diodes, and 2 clamping diodes are recorded as clamping diodes D_kjJ denotes the number of the clamp diode, and j is 1, 2;

the switching device S_k1Switching device S_k2Switching device S_k3Switching device S_k4Serially connected in sequence, clamping diode D_k1Anode of the switching element is connected to the neutral point O, and cathode of the switching element S is connected to the cathode_k2Collector of, clamping diode D_k2Anode of (2) connecting the switching device S_k3The emitter and the cathode of the anode are connected with a neutral point O; the connection point of the k-phase bridge arm and the direct-current positive bus P is recorded as a connection point delta_k1Switching device S_k1And a switching device S_k2Is denoted as connection point delta_k2Switching device S_k2And a switching device S_k3Is denoted as connection point delta_k3Switching device S_k3And a switching device S_k4Is denoted as connection point delta_k4And the connection point of the k-phase bridge arm and the direct-current negative bus Q is recorded as a connection point delta_k5K represents phase sequence, k ═ a, B, C;

the three-phase load resistance is recorded as resistance R_kAnd the three-phase load inductance is recorded as inductance L_kResistance R_kOne end of and a connection point delta_k3Are connected with each otherThe other end and an inductor L_kConnected to each other by an inductance L_kThe other end of the first and second electrodes is grounded; the three-level NPC inverter is controlled by a controller DSP I;

the IGBT module online monitoring system comprises a controller DSP I, a controller DSP II, a power supply conversion module, a relay selection module, a monitoring current injection module, a communication module, a voltage sampling module and an upper computer, and the whole monitoring system is uniformly coordinated and controlled by the controller DSP II;

the monitoring system controller DSP I comprises a general output port T_o4And a universal input port T_r2；

The monitoring system controller DSP II comprises a peripheral function pin SCIRXDA, a peripheral function pin SCITXDA and a general output port T_ok1Universal output port T_ok2Universal output port T_ok3Universal output port T_o1Universal output port T_o2Universal output port T_o3Universal input port T_r1Sampling input port T_ck1Sampling input port T_ck2Sampling input port T_ck3Sampling input port T_ck4K represents phase sequence, k ═ a, B, C;

the power supply conversion module comprises two direct current voltage conversion circuits, namely a first direct current voltage conversion circuit and a second direct current voltage conversion circuit, and the input ends of the two direct current voltage conversion circuits are respectively connected with the voltage U at the two ends of the direct current side power supply E of the three-level NPC inverter_dcConnecting;

the relay selection module comprises a successive electrical appliance selection submodule A, a successive electrical appliance selection submodule B and a successive electrical appliance selection submodule C, and the successive electrical appliance selection submodules are identical in structure; setting any phase in three-phase relay selection submodules as a k successive electric appliance selection submodule, wherein four groups of relays are arranged in the k successive electric appliance selection submodule and comprise 4 double-contact relays and 4 single-contact relays, and the 4 double-contact relays are respectively recorded as a double-contact relay SPDT1_kSPDT2 double-contact relay_kSPDT3 double-contact relay_kSPDT4 double-contact relay_kThe 4 single-contact relays are respectively marked as single-contact relays SPST1_kSingle contact relaySPST2_kSingle contact relay SPST3_kSingle contact relay SPST4_kK represents phase sequence, k ═ a, B, C;

the monitoring current injection module comprises a large current branch, a small current branch and a large current interface, wherein the large current branch is connected with a large voltage power supply interface U_HAnd monitoring the inductance L_mSwitching device S₁Diode D₁Sequentially connected in series to form a freewheeling diode D_mIs connected in parallel to the monitoring inductor L_mTwo ends; the small current branch is routed by a 100mA small current source I_LSwitching device S₂Diode D₂Are sequentially connected in series to form a 100mA small current source I_LGenerated by the linear regulator chip LT 3080; the high-current branch circuit and the low-current branch circuit are connected in parallel, the circuit after the parallel connection is called a main circuit, the main circuit at the right end after the parallel connection is connected with a negative pole GND of a high-current interface, a current sensor N is connected in series on the main circuit at the left end, and the other end of the current sensor N is connected with a positive pole I of the high-current interface; recording a negative pole GND of the high-current interface as a negative pole GND and recording a positive pole I of the high-current interface as a positive pole I;

the communication module comprises an SCI communication circuit, a first serial port communication circuit and a second serial port communication circuit;

the voltage sampling module comprises an A phase voltage sampling submodule, a B phase voltage sampling submodule and a C phase voltage sampling submodule, each phase submodule consists of four identical differential sampling circuits which are respectively marked as a differential sampling circuit 1, a differential sampling circuit 2, a differential sampling circuit 3 and a differential sampling circuit 4;

a small voltage power supply interface U is arranged on the controller DSP II, the relay selection module, the monitoring current injection module, the communication module and the voltage sampling module_L；

The output end of the first direct current voltage conversion circuit is connected with a large voltage power supply interface U of the monitoring current injection module_H(ii) a The output end of the second direct-current voltage conversion circuit is respectively connected with a small-voltage power supply interface U in a controller DSPII, a relay selection module, a monitoring current injection module, a communication module and a voltage sampling module_LConnecting;

among the k successive appliance selection submodules, a double contact relay SPDT1_kTwo contacts at the left end are respectively connected with a contact point delta_k1And connection point delta_k2And a right end single contact relay SPST1_kLeft end, single contact relay SPST1_kThe right end of the anode is connected with a positive electrode I; double-contact relay SPDT2_kTwo contacts at the left end are respectively connected with a contact point delta_k2And connection point delta_k3And a right end single contact relay SPST2_kLeft end, single contact relay SPST2_kThe right end of the anode is connected with a negative pole GND; double-contact relay SPDT3_kTwo contacts at the left end are respectively connected with a contact point delta_k3And connection point delta_k4And a right end single contact relay SPST3_kLeft end, single contact relay SPST3_kThe right end of the anode is connected with a positive electrode I; double-contact relay SPDT4_kTwo contacts at the left end are respectively connected with a contact point delta_k4And connection point delta_k5And a right end single contact relay SPST4_kLeft end, single contact relay SPST4_kThe right end of the switch is connected with a negative pole GND;

in the k-phase voltage sampling submodule, the positive input end of the differential sampling circuit 1 is connected with a contact point delta_k1The negative input terminal is connected to the connection point delta_k2The output end is connected with a sampling input port T of the controller DSP II_ck1(ii) a The positive input terminal of the differential sampling circuit 2 is connected to the contact point delta_k2The negative input terminal is connected to the connection point delta_k3The output end is connected with the sampling input port T of the controller DSP II_ck2(ii) a The positive input end of the differential sampling circuit 3 is connected with the connection point delta_k3The negative input terminal is connected to the connection point delta_k4The output end is connected with the sampling input port T of the controller DSP II_ck3(ii) a The positive input end of the differential sampling circuit 4 is connected with the connection point delta_k4The negative input terminal is connected to the connection point delta_k5The output end is connected with the sampling input port T of the controller DSP II_ck4。

Preferably, the dual contact relay SPDT1_kSPDT2 double-contact relay_kSPDT3 double-contact relay_kSPDT4 double-contact relay_kBy the general output port T of controller DSP II_ok1Control, the single contact relay SPST1_kSingle contact relay SPST2_kBy the general output port T of the controller DSP II_ok2Control, single contact relay SPST3_kSingle contact relay SPST4_kBy the general output port T of controller DSP II_ok3And (5) controlling.

Preferably, the switching device S₁By the general output port T of controller DSP II_o1Control, switching device S₂By the general output port T of controller DSP II_o2And (5) controlling.

Preferably, one end of the SCI communication circuit is connected to a USB port of the upper computer, and the other end of the SCI communication circuit is connected to a peripheral function pin SCIRXDA and a peripheral function pin SCITXDA of the controller DSP II, respectively; the input end of the first serial port communication circuit is connected with the general output port T of the DSP I of the controller_o4The output end is connected with a general input port T of the controller DSP II_r1(ii) a The input end of the second serial port communication circuit is connected with the general output port T of the controller DSP II_o3The output end is connected with the general input port T of the DSP I of the controller_r2。

Preferably, the controller DSP II, the relay selection module, the monitoring current injection module, the communication module and the voltage sampling module are integrated on a power supply board, and the power supply board is a circuit board where the power supply conversion module is located.

The invention also provides an IGBT module online monitoring method, which adopts the IGBT module online monitoring system and comprises the following steps:

step 1, fitting of saturated pressure drop-temperature curve

Putting the healthy IGBT module into a thermostat in an off-line state, and controlling the temperature T of the IGBT module_jChange in 20-120 deg.C, and saturation voltage drop V at 10 times of large current every 20 deg.C_CEHOThe saturated voltage drop V under 10 times of large current is calculated_CEHOIs recorded as the average value of the saturated voltage drop V under large current_CEH，V_CEH＝V _CEHO10, obtaining the average value V of saturated voltage drop under 6 large currents in total through experiments_CEHAt a temperature T_jIs the average value V of the saturated voltage drop under X-axis and large current_CEHDrawing a curve in a plane coordinate system for Y axisLine and marked as V_CEH-T_jA health curve;

in an off-line state, putting the healthy IGBT module into a thermostat, and controlling the temperature T of the IGBT module_jChanging the temperature of the mixture to 20-120 ℃, and carrying out saturation voltage drop V under small current for 10 times at intervals of 20 DEG C_CEL0The saturated voltage drop V under 10 times of small current is calculated_CEL0Is taken as the average value of the saturated voltage drop V under the small current_CEL，V_CEL＝V _CEL010, obtaining the average value V of the saturated voltage drop under 6 small currents through experiments_CELAt a temperature T_jIs the average value V of the saturated voltage drop under X-axis and small current_CELDrawing a curve in a plane coordinate system for Y axis and marking as V_CEL-T_jA health profile;

experiments show that when the IGBT module fails, V is_CEH-T_jAverage value V of large current saturation voltage drop at 6 points in health curve_CEHWill increase by 5%, i.e. V when the IGBT module fails_CEH-T_jThe curve position will drift upwards by 5% overall, and V_CEL-T_jThe position of the health curve is unchanged; shift the whole body up by 5% of V_CEH-T_jThe curve is marked as V_CEH-T_jA failure curve;

step 2, presetting monitoring conditions

In a modulation wave period, a monitoring start time t is preset_mMonitoring the start time t_mStarting one round of online monitoring, namely sequentially monitoring the states of the switching devices of all bridge arms in the three-phase inversion main circuit by the online monitoring system, wherein the process of monitoring any switching device of any bridge arm is shown in steps 3-9;

step 3, the upper computer is controlled manually to send a monitoring instruction 1, a monitoring instruction 2, a monitoring instruction 3 and a monitoring instruction 4 to the monitoring system controller DSP II through the SCI communication circuit, wherein the monitoring instruction 1 determines the phase sequence of the switching device to be monitored and the serial number of the switching device, and the monitoring instruction 2 determines the monitoring starting time t in one modulation wave period_mThe monitoring instruction 3 determines a monitoring duration deltat,delta t is more than 0 and less than W, W is the duration of a modulation wave period, and the monitoring instruction 4 determines the monitoring times m; setting the phase sequence of the switching devices to be monitored as k and the serial number of the switching devices as i, namely, the bridge arm to be monitored is a k-phase bridge arm, and the switching device to be monitored is a switching device S_ki；

Step 4, after the controller DSP II receives the monitoring instruction 1, firstly controlling the contact of the double-contact relay and the contact of the single-contact relay in the relay selection module to release upwards or attract downwards, and specifically, connecting the point delta_kiConnecting the positive electrode I with the connection point delta_k(i+1)Is connected with the cathode GND; meanwhile, the controller DSP II transmits a monitoring instruction 2, a monitoring instruction 3 and a monitoring instruction 4 to the controller DSP I through a second serial port communication circuit;

step 5, after the DSP I of the controller receives the monitoring instruction 2, the monitoring instruction 3 and the monitoring instruction 4, the time is determined by counting through a timer, and when the DSP I runs to the monitoring starting time t in a modulation wave period_mAnd meanwhile, the modulation waves of other two-phase bridge arms are added with the modulation wave variable quantity of the k-phase bridge arm to keep three-phase balance in the period, and the output voltage of the k-phase bridge arm to be monitored is modified into a zero level, the duration of the zero level is the monitoring time delta t, and the three-phase balance in the period is kept:

if the switching device to be monitored is a switching device S_k2Switching device S_k3If the DSP I10 controls the k-phase bridge arm to output zero level, the switching device S_k1Switching device S_k2Switching device S_k3And a switching device S_k4The states of the switch are off, on and off respectively; when a load current of k-phase to be monitored flows from a neutral point O through a clamping diode D_k1Switching device S_k2Flow direction resistance R_kAnd an inductance L_kThen, the switching device S is performed_k3Monitoring; when the load current of k-phase to be monitored is from resistor R_kCurrent flowing through inductor L_kSwitching device S_k3A clamping diode D_k2When the current flows to the neutral point O, the switching device S is operated_k2Monitoring;

if the switching device to be monitored is a switching device S_k1Then DSP I10 controls k-phase bridge arm outputSwitching device S at zero level_k1Switching device S_k2Switching device S_k3Switching device S_k4The states of the switch are respectively on, off, on and off; the load current of the k-phase to be monitored at this time is driven by the resistor R_kCurrent flowing through inductor L_kSwitching device S_k3A clamping diode D_k2Flow to neutral O;

if the switching device to be monitored is a switching device S_k4If the DSP I10 controls the k-phase bridge arm to output zero level, the switching device S_k1Switching device S_k2Switching device S_k3Switching device S_k4The states of the switch are off, on, off and on respectively; the load current of the k phase to be monitored now flows from the neutral point O through the clamping diode D_k1Switching device S_k2Flow direction resistance R_kAnd an inductance L_k；

Step 6, when the phase modulation wave to be monitored begins to be modified to be zero level, the controller DSP I feeds back a synchronous signal to the controller DSP II through the first serial port communication circuit, and after the controller DSP II receives the synchronous signal, the synchronous signal passes through the general output port T_o1Switching device S in open heavy current branch₁Through a general output port T_o2Switching on switching devices S in small current branches₂Starting a current sensor N to monitor the main circuit current I;

step 7, setting the preset value of the main circuit current as I₀The following monitoring is performed by the current sensor N:

when 98% I₀≤I＜I₀Then, the controller DSP II controls the sampling input port T_ckiWorking, sampling the saturated voltage drop under 10 times of large current, storing the average value of the saturated voltage drop, and recording the average value as the large current saturated voltage drop monitoring average value V_CEH′；

When I ═ I₀Then, the controller DSP II passes through the general output port T_o1Switching-off of switching device S in a high-current branch₁In the switching device S₂Sampling 10 times of saturation voltage drop under small current in a continuous opening state, storing the average value of the saturation voltage drop, and recording the average value as a small current saturation voltage drop monitoring average value V_CEL', when the small current is injected for 0.1ms continuously, the current passes through the general output port T_o2Turn-off switching device S₂；

Step 8, according to the monitoring times m given by the monitoring instruction 4, repeating the steps 5-7 in m modulation wave periods to obtain m large-current saturated voltage drop monitoring average values V_CEH' and m small current saturation voltage drop monitoring average value V_CEL' monitoring average value V of m large current saturation voltage drops_CEH' averaging again to obtain the first monitored pressure drop value V_CEHZMonitoring the average value V of m small current saturated voltage drops_CEL' averaging again to obtain a second monitored pressure drop value V_CELZThe first monitor voltage drop value V is transmitted through the SCI communication circuit_CEHZAnd a second monitored pressure drop value V_CELZTransmitting to an upper computer;

after m-time online monitoring is completed, the controller DSP I restores the three-phase modulation wave of the k-phase bridge arm to be monitored to a sine wave state, and the controller DSP II disconnects a relevant relay in the relay selection module, specifically, a connection point delta is connected_kiDisconnecting from the positive electrode I and connecting the point delta_k(i+1)Disconnected from the negative electrode GND;

step 9, according to the second monitoring pressure drop value V_CELZThe upper computer is arranged at V_CEL-T_jFinding the corresponding temperature on the health curve, and recording the temperature as the monitoring temperature T_j', and then based on the first monitored pressure drop value V_CEHZAnd monitoring the temperature T_jAt V_CEH-T_jFinding out a corresponding point F in a plane coordinate system of the health curve, and if the point F falls on V_CEH-T_jOn the failure curve or falling at V_CEH-T_jThe upper part of the failure curve is identified as the switching device S to be monitored_kiAnd (4) failing.

Compared with the prior art, the invention has the following beneficial effects:

1. the communication module of the system greatly coordinates the mutual coordination between the monitoring system and the system to be tested, and avoids the influence of the on-line monitoring process on the normal operation of the system to be tested;

2. compared with the existing design, the monitoring system has the advantages that the simple circuit board replaces modules with overlarge voltage acquisition card, LABVIEW unit, direct-current power supply and the like, the system is reduced in size and convenient to carry, and plays an important role in field monitoring during the operation of the IGBT module;

3. by switching a plurality of groups of relays of the system and changing the state of each IGBT when the output voltage of the monitored phase is zero, all monitoring of 4 IGBT modules on each phase bridge arm can be realized.

Drawings

Fig. 1 is a three-level NPC inverter topology diagram of an IGBT module to be tested according to the present invention.

Fig. 2 is a schematic diagram of an IGBT module online monitoring system in an embodiment of the present invention.

Fig. 3 is a schematic diagram illustrating connection and control of a relay selection module according to an embodiment of the present invention.

Fig. 4 is a circuit diagram of a monitoring current injection module according to an embodiment of the present invention.

FIG. 5 is a drawing of V in an embodiment of the present invention_CEH-T_jA health curve and a failure curve.

FIG. 6 is a drawing of V in an embodiment of the present invention_CEL-T_jHealth curve.

FIG. 7 is a diagram of a switching device S to be monitored according to an embodiment of the present invention_A3The waveform diagram of the three-phase modulation wave of the inverter.

FIG. 8 is a flow chart of the on-line monitoring method of the present invention.

Detailed Description

The invention will be further explained with reference to the drawings.

Fig. 1 is a three-level NPC inverter topology diagram of an IGBT module to be tested according to the present invention. As can be seen from fig. 1, the IGBT module to be tested according to the present invention is located in a three-level NPC inverter, and the three-level NPC inverter includes a dc-side power supply E, two identical dc-side capacitors, a three-phase inverter main circuit, a three-phase load resistor, and a three-phase load inductor. The voltage of the DC side power supply E is recorded as a DC side voltage U_dcTwo, twoThe capacitors on the DC side are respectively marked as capacitors C on the DC side_HAnd a DC side capacitor C_LThe direct current side capacitor C_HAnd a DC side capacitor C_LConnected in parallel between a DC positive bus P and a DC negative bus Q of a DC power supply E after series connection, and a DC side capacitor C_HAnd a DC side capacitor C_LThe connection point of (b) is denoted as neutral point O.

The three-phase inversion main circuit is divided into three-phase bridge arms, the three-phase bridge arms are connected with a direct-current side power supply E in parallel, the three-phase bridge arms are completely identical in topology, the three-phase bridge arms are respectively marked as k-phase bridge arms, k represents a phase sequence, and k is equal to A, B and C; in the three-phase bridge arm, each phase of bridge arm comprises 4 IGBT modules, and the 4 IGBT modules are recorded as a switch device S_kiI represents the serial number of the switching device, and i is 1, 2, 3, 4; in a three-phase bridge arm, each phase of the bridge arm comprises 2 clamping diodes, and 2 clamping diodes are recorded as clamping diodes D_kjJ denotes the number of the clamp diode, and j is 1 or 2.

Said switching device S_k1And a switching device S_k2Switching device S_k3Switching device S_k4Serially connected in sequence, clamping diode D_k1Anode of the switching element is connected to the neutral point O, and cathode of the switching element S is connected to the cathode_k2Collector of, clamping diode D_k2Anode of (2) connecting the switching device S_k3The emitter and the cathode of the anode are connected with a neutral point O; the connection point of the k-phase bridge arm and the direct-current positive bus P is recorded as a connection point delta_k1Switching device S_k1And a switching device S_k2Is denoted as connection point delta_k2Switching device S_k2And a switching device S_k3Is denoted as connection point delta_k3Switching device S_k2And a switching device S_k4Is denoted as connection point delta_k4And the connection point of the k-phase bridge arm and the direct-current negative bus Q is recorded as a connection point delta_k5K represents phase sequence, k ═ a, B, and C.

The three-phase load resistance is recorded as resistance R_kAnd the three-phase load inductance is recorded as inductance L_kResistance R_kOne end of (d) and a connection point delta_k3Connected to another end of the inductor L_kConnected to each other by an inductance L_kThe other end of the first and second electrodes is grounded; three-level NPThe C inverter is controlled by a controller DSP I10.

Fig. 2 is a schematic diagram of an IGBT module online monitoring system according to an embodiment of the present invention, fig. 3 is a schematic diagram of connection and control of a relay selection module according to an embodiment of the present invention, and fig. 4 is a circuit structure diagram of a monitoring current injection module according to an embodiment of the present invention. As can be seen from fig. 2 to 4, the IGBT module online monitoring system according to the present invention includes a controller DSP I10, a controller DSP II20, a power conversion module 30, a relay selection module 40, a monitoring current injection module 50, a communication module 60, a voltage sampling module 70, and an upper computer 80, and the entire monitoring system is coordinately controlled by the controller DSP II20 in a unified manner.

In this embodiment, the controller DSP II20, the relay selection module 40, the monitoring current injection module 50, the communication module 60, and the voltage sampling module 70 are integrated into a power supply board, where the power supply board is a circuit board on which the power conversion module 30 is located.

The monitoring system controller DSP I10 comprises a general output port T_o4And a universal input port T_r2。

The monitoring system controller DSP II20 comprises a peripheral function pin SCIRXDA, a peripheral function pin SCITXDA and a general output port T_ok1Universal output port T_ok2Universal output port T_ok3Universal output port T_o1Universal output port T_o2Universal output port T_o3Universal input port T_r1Sampling input port T_ck1Sampling input port T_ck2Sampling input port T_ck3And a sampling input port T_ck4K represents phase sequence, k ═ a, B, and C.

The power conversion module 30 includes two dc voltage conversion circuits, which are a first dc voltage conversion circuit 31 and a second dc voltage conversion circuit 32, and the input terminals of the two dc voltage conversion circuits are both connected to the voltage U at the two ends of the dc side power E of the three-level NPC inverter_dcAre connected with each other.

The relay selection module 40 comprises a successive electrical appliance selection submodule A, a successive electrical appliance selection submodule B and a successive electrical appliance selection submodule C, and the successive electrical appliance selection submodules are identical in structure; three-phase relayAny phase in the selection submodules is a k successive electric appliance selection submodule, four groups of relays are arranged in the k successive electric appliance selection submodule and comprise 4 double-contact relays and 4 single-contact relays, and the 4 double-contact relays are respectively marked as double-contact relays SPDT1_kSPDT2 double-contact relay_kSPDT3 double-contact relay_kSPDT4 double-contact relay_kThe 4 single-contact relays are respectively marked as single-contact relays SPST1_kSingle contact relay SPST2_kSingle contact relay SPST3_kSingle contact relay SPST4_kK represents phase sequence, k ═ a, B, and C.

The monitoring current injection module 50 comprises a large current branch 51, a small current branch 52 and a large current interface 53, wherein the large current branch 51 is provided with a large voltage power supply interface U_HAnd monitoring the inductance L_mSwitching device S₁Diode D₁Sequentially connected in series to form a freewheeling diode D_mIs connected in parallel to the monitoring inductor L_mTwo ends; the small current branch 52 is composed of a 100mA small current source I_LSwitching device S₂Diode D₂Are sequentially connected in series to form a 100mA small current source I_LGenerated by the linear regulator chip LT 3080; the high-current branch 51 and the low-current branch 52 are connected in parallel, the parallel circuit is called a trunk, the trunk at the right end is connected with the cathode GND of the high-current interface 53 after parallel connection, the trunk at the left end is connected with a current sensor N in series, and the other end of the current sensor N is connected with the anode I of the high-current interface 53; the negative electrode GND of the large-current interface 53 is referred to as the negative electrode GND, and the positive electrode I of the large-current interface 53 is referred to as the positive electrode I.

The communication module 60 includes an SCI communication circuit 61, a first serial communication circuit 62, and a second serial communication circuit 63.

The voltage sampling module 70 includes an a-phase voltage sampling submodule, a B-phase voltage sampling submodule, and a C-phase voltage sampling submodule, each phase of the submodule is composed of four identical differential sampling circuits, which are respectively marked as a differential sampling circuit 1, a differential sampling circuit 2, a differential sampling circuit 3, and a differential sampling circuit 4.

The controller DSP II20 and the relay selection module40. The monitoring current injection module 50, the communication module 60 and the voltage sampling module 70 are all provided with a small-voltage power supply interface U_L。

The output end of the first dc-to-dc voltage conversion circuit 31 is connected to the large-voltage power supply interface U of the monitoring current injection module 50_H(ii) a The output end of the second dc voltage conversion circuit 32 is respectively connected with the small voltage power supply interface U in the controller DSPII20, the relay selection module 40, the monitoring current injection module 50, the communication module 60 and the voltage sampling module 70_LAre connected with each other.

Among the k successive appliance selection submodules, a double contact relay SPDT1_kTwo contacts at the left end are respectively connected with a contact point delta_k1And connection point delta_k2And a single-contact relay SPST1 connected with the right end_kLeft end, single contact relay SPST1_kThe right end of the anode is connected with a positive electrode I; double-contact relay SPDT2_kTwo contacts at the left end are respectively connected with a contact point delta_k2And connection point delta_k3And a single-contact relay SPST2 connected with the right end_kLeft end, single contact relay SPST2_kThe right end of the anode is connected with a negative pole GND; double-contact relay SPDT3_kTwo contacts at the left end are respectively connected with a contact point delta_k3And connection point delta_k4And a right end single contact relay SPST3_kLeft end, single contact relay SPST3_kThe right end of the anode is connected with a positive electrode I; double-contact relay SPDT4_kTwo contacts at the left end are respectively connected with a contact point delta_k4And connection point delta_k5And a right end single contact relay SPST4_kLeft end, single contact relay SPST4_kThe right end of the switch is connected with a cathode GND.

In the k-phase voltage sampling submodule, the positive input end of the differential sampling circuit 1 is connected with a contact point delta_k1The negative input terminal is connected to the connection point delta_k2The output end is connected with the sampling input port T of the controller DSP II20_ck1(ii) a The positive input terminal of the differential sampling circuit 2 is connected to the contact point delta_k2The negative input terminal is connected to the connection point delta_k3The output end is connected with the sampling input port T of the controller DSP II20_ck2(ii) a The positive input end of the differential sampling circuit 3 is connected with the connection point delta_k3The negative input terminal is connected to the connection point delta_k4Output terminal controlSampling input port T of DSP II20_ck3(ii) a The positive input end of the differential sampling circuit 4 is connected with the connection point delta_k4Negative input terminal is connected to the connection point delta_k5The output end is connected with the sampling input port T of the controller DSP II20_ck4。

The dual contact relay SPDT1_kSPDT2 double-contact relay_kSPDT3 double-contact relay_kSPDT4 double-contact relay_kBy the general output port T of the controller DSP II20_ok1Control, the single contact relay SPST1_kSingle contact relay SPST2_kBy the general output port T of the controller DSP II20_ok2Control, single contact relay SPST3_kSingle contact relay SPST4_kBy the general output port T of the controller DSP II20_ok3And (5) controlling.

The switching device S₁By the general output port T of the controller DSP II20_o1Control, switching device S₂By the general output port T of the controller DSP II20_o2And (5) controlling.

One end of the SCI communication circuit 61 is connected with a USB port of the upper computer 80, and the other end is respectively connected with a peripheral function pin SCIRXDA and a peripheral function pin SCIRXDA of the controller DSP II 20; the input end of the first serial port communication circuit 62 is connected with the general output port T of the controller DSP I10_o4The output end is connected with the general input port T of the controller DSP II20_r1(ii) a The input end of the second serial port communication circuit 63 is connected with the general output port T of the controller DSP II20_o3The output end is connected with a general input port T of the controller DSP I10_r2。

The invention also provides an IGBT module online monitoring method, which adopts the IGBT module online monitoring system, and the flow chart is shown in figure 8. As can be seen from fig. 8, the following steps are included:

step 1, fitting of saturated pressure drop-temperature curve

Putting the healthy IGBT module into a thermostat in an off-line state, and controlling the temperature T of the IGBT module_jChange in 20-120 deg.C, and saturation voltage drop V at 10 times of large current every 20 deg.C_CEHOThe saturated voltage drop V under 10 times of large current is calculated_CEHOIs recorded as the average value of the saturated voltage drop V under large current_CEH，V_CEH＝V _CEHO10, obtaining the average value V of saturated voltage drop under 6 large currents in total through experiments_CEHAt a temperature T_jIs the average value V of the saturated voltage drop under X-axis and large current_CEHDrawing a curve in a plane coordinate system for Y axis and marking as V_CEH-T_jHealth curve.

Putting the healthy IGBT module into a thermostat in an off-line state, and controlling the temperature T of the IGBT module_jChange in 20-120 deg.C, and saturation voltage drop V at small current for 10 times every 20 deg.C_CEL0The saturated voltage drop V under 10 times of small current is calculated_CELOAnd is recorded as the average value V of the saturated voltage drop under small current_CEL，V_CEL＝V _CEL010, obtaining the average value V of the saturation voltage drop under 6 small currents in total through experiments_CELAt a temperature T_jIs the average value V of the saturated voltage drop under X-axis and small current_CELDrawing a curve in a plane coordinate system for Y axis and marking as V_CEL-T_jHealth curve.

Experiments show that when the IGBT module fails, V is_CEH-T_jAverage value V of large-current saturation voltage drop at 6 points in health curve_CEHWill increase by 5%, i.e. V when the IGBT module fails_CEH-T_jThe curve position will drift upwards by 5% overall, and V_CEL-T_jThe position of the health curve is unchanged; shift the whole body up by 5% of V_CEH-T_jThe curve is denoted as V_CEH-T_jFailure curve.

FIG. 5 is a drawing of V in an embodiment of the present invention_CEH-T_jHealth curves and failure curves, FIG. 6 is a graph of V plotted in an example of the invention_CEL-T_jHealth curves. In FIGS. 5 and 6, V is_CEH-T_jThe health curves are marked as curves 1 and V_CEL-T_jThe health curve is recorded as curve 2 and V_CEH-T_jThe failure curve is recorded as curve 3.

Step 2, presetting monitoring conditions

In one modulated wave periodA monitoring start time t is preset_mMonitoring the start time t_mAnd starting one round of online monitoring, namely, the online monitoring system sequentially monitors the states of the switching devices of all bridge arms in the three-phase inverter main circuit, wherein the process of monitoring any switching device of any bridge arm is shown in steps 3-9.

Step 3, the artificial control upper computer 80 sends a monitoring instruction 1, a monitoring instruction 2, a monitoring instruction 3 and a monitoring instruction 4 to the monitoring system controller DSP II20 through the SCI communication circuit 61, wherein the monitoring instruction 1 determines the phase sequence of the switching device to be monitored and the serial number of the switching device, and the monitoring instruction 2 determines the monitoring starting time t in one modulation wave period_mThe monitoring instruction 3 determines a monitoring time length delta t, delta t is more than 0 and less than W, W is the time length of a modulation wave period, and the monitoring instruction 4 determines a monitoring frequency m; setting the phase sequence of the switching devices to be monitored as k and the serial number of the switching devices as i, namely, the bridge arm to be monitored is a k-phase bridge arm, and the switching device to be monitored is a switching device S_ki。

Step 4, after the controller DSP II20 receives the monitoring instruction 1, first, the contacts of the dual-contact relay and the single-contact relay in the relay selection module 40 are controlled to release upward or pull downward, specifically, the connection point δ is connected_kiConnecting the positive electrode I with the connection point delta_k(i+1)Is connected with the cathode GND; meanwhile, the controller DSP II20 transmits the monitoring instruction 2, the monitoring instruction 3, and the monitoring instruction 4 to the controller DSP I10 through the second serial communication circuit 63.

Step 5, after receiving the monitoring instruction 2, the monitoring instruction 3 and the monitoring instruction 4, the DSP I10 of the controller determines the time through counting of a timer, and when the DSP I runs to the monitoring starting time t in a modulation wave period_mAnd meanwhile, the modulation waves of other two-phase bridge arms are added with the modulation wave variable quantity of the k-phase bridge arm to keep three-phase balance in the period, and the output voltage of the k-phase bridge arm to be monitored is modified into a zero level, the duration of the zero level is the monitoring time delta t, and the three-phase balance in the period is kept:

if the switching device to be monitored is a switching device S_k2Switching device S_k3If the DSP I10 controls the k-phase bridge arm to output zero level, the switching device S_k1Switching device S_k2Switching device S_k3Switching device S_k4The states of the switch are off, on and off respectively; when a load current of k-phase to be monitored flows from a neutral point O through a clamping diode D_k1Switching device S_k2Flow direction resistance R_kAnd an inductance L_kThen, the switching device S is performed_k3Monitoring; when the load current of k-phase to be monitored is from resistor R_kCurrent flowing through inductor L_kSwitching device S_k3A clamping diode D_k2When the current flows to the neutral point O, the switching device S is operated_k2Monitoring;

if the switching device to be monitored is a switching device S_k1If the DSP I10 controls the k-phase bridge arm to output zero level, the switching device S_k1Switching device S_k2Switching device S_k3Switching device S_k4The states of the switch are respectively on, off, on and off; the load current of the k-phase to be monitored at this time is driven by the resistor R_kCurrent flowing through inductor L_kSwitching device S_k3A clamping diode D_k2Flow to neutral O;

if the switching device to be monitored is a switching device S_k4If so, the DSP I10 controls the switching device S when the k-phase bridge arm outputs zero level_k1Switching device S_k2Switching device S_k3Switching device S_k4The states of the switch are off, on, off and on respectively; at this time, the load current of the k-phase to be monitored flows from the neutral point O through the clamping diode D_k1And a switching device S_k2Flow direction resistance R_kAnd an inductance L_k。

Step 6, when the phase modulation wave to be monitored begins to be modified to zero level, the controller DSP I10 feeds back a synchronous signal to the controller DSP II20 through the first serial port communication circuit 62, and after the controller DSP II20 receives the synchronous signal, the synchronous signal passes through the general output port T_o1Switching on the switching device S in the high-current branch 51₁Through a general output port T_o2Switching on the switching device S in the small current branch 52₂And starting the current sensor N to carry out the operation of the main circuit current IAnd (5) monitoring.

Step 7, setting the preset value of the main circuit current as I₀The following monitoring is performed by the current sensor N:

when 98% I₀≤I＜I₀When the sampling input port T is controlled by the controller DSP II20_ckiWorking, sampling the saturated voltage drop under 10 times of large current, storing the average value of the saturated voltage drop, and recording the average value as the large current saturated voltage drop monitoring average value V_CEH′；

When I ═ I₀When the controller DSP II20 passes through the general output port T_o1Switching off the switching device S in the high-current branch 51₁In the switching device S₂Sampling 10 times of saturation voltage drop under small current in a continuous opening state, storing the average value of the saturation voltage drop, and recording the average value as a small current saturation voltage drop monitoring average value V_CEL', when the small current is injected continuously for 0.1ms, the small current passes through the universal output port T_o2Turn-off switching device S₂。

Step 8, according to the monitoring times m given by the monitoring instruction 4, repeating the steps 5-7 in m modulation wave periods to obtain m large-current saturated voltage drop monitoring average values V_CEH' and m small current saturated voltage drop monitoring average value V_CEL' monitoring average value V of m large current saturation voltage drops_CEH' averaging again to obtain the first monitored pressure drop value V_CEHZMonitoring average value V of m small current saturated voltage drops_CEL' averaging again to obtain a second monitored pressure drop value V_CELZThe first monitor voltage drop value V is transmitted via SCI communication circuit 61_CEHZAnd a second monitored pressure drop value V_CELZTransmitted to the upper computer 80.

After m-time online monitoring is completed, the controller DSP I10 restores the three-phase modulation wave of the k-phase bridge arm to be monitored to a sine wave state, and the controller DSP II20 disconnects the relevant relay in the relay selection module 40, specifically, disconnects the connection point delta_kiDisconnecting from the positive electrode I and connecting the point delta_k(i+1)Disconnected from the negative GND.

Step 9, according to the second monitoring pressure drop value V_CELZUpper computer 80 is at V_CEL-T_jFind the corresponding temperature on the health curveTemperature, which is recorded as the monitored temperature T_j', and then based on the first monitored pressure drop value V_CEHZAnd monitoring the temperature T_jAt V_CEH-T_jFinding out a corresponding point F in a plane coordinate system of the health curve, and if the point F falls on V_CEH-T_jOn the failure curve or falling at V_CEH-T_jThe upper part of the failure curve is identified as the switching device S to be monitored_kiAnd (4) failure.

In order to prove the effect of the invention, the monitoring method of the invention is simulated. FIG. 7 shows an embodiment of the present invention, in which the switching device S to be monitored is selected as the switching device S_A3The waveform diagram of the three-phase modulation wave of the inverter. Wherein, f_a(ωt)、f_b(ωt)、f_c(ωt)Respectively an A-phase modulation wave, a B-phase modulation wave and a C-phase modulation wave. As can be seen from FIG. 7, the A-phase modulated wave f_a(ωt)Is modified to zero after 0.002S from the beginning of each modulation wave period so that the a-phase voltage outputs a zero level with a zero level duration of 0.8ms, and the process is repeated 5 times during which 5 times the zero level the switching device S_A1Switching device S_A2Switching device S_A3Switching device S_A4Is turned off, turned on, and turned off, if the load current of the A phase flows from the neutral point O through the clamping diode D_A1Switching device S_A2Flow direction resistance R_AAnd an inductance L_AThen the switching device S in the on state but not belonging to the load current loop can be monitored_A3。

Claims (2)

1. An IGBT module on-line monitoring method relates to an IGBT module to be tested which is positioned in a three-level NPC inverter, and also relates to an IGBT module on-line monitoring system;

the three-level NPC inverter comprises a direct-current side power supply E, two identical direct-current side capacitors, a three-phase inverter main circuit, a three-phase load resistor and a three-phase load inductor; the voltage of the DC side power supply E is recorded as a DC side voltage U_dcThe two DC-side capacitors are respectively denoted as DC-side capacitor C_HAnd a DC side capacitor C_LThe direct current side capacitor C_HAnd a DC side capacitor C_LConnected in parallel between a DC positive bus P and a DC negative bus Q of a DC power supply E in series, and a DC side capacitor C_HAnd a DC side capacitor C_LThe connecting point of (a) is marked as a neutral point O;

the three-phase inversion main circuit is divided into three-phase bridge arms, the three-phase bridge arms are connected with a direct-current side power supply E in parallel, the three-phase bridge arms are completely identical in topology, the three-phase bridge arms are respectively marked as k-phase bridge arms, k represents a phase sequence, and k is equal to A, B and C; in the three-phase bridge arm, each phase of bridge arm comprises 4 IGBT modules, and the 4 IGBT modules are recorded as a switch device S_kiI represents the serial number of the switching device, and i is 1, 2, 3, 4; in a three-phase bridge arm, each phase of the bridge arm comprises 2 clamping diodes, and 2 clamping diodes are recorded as clamping diodes D_kjJ denotes the number of the clamp diode, and j is 1, 2;

the switching device S_k1Switching device S_k2Switching device S_k3Switching device S_k4Serially connected in sequence, clamping diode D_k1Anode of the switching element is connected to the neutral point O, and cathode of the switching element S is connected to the cathode_k2Collector of, clamping diode D_k2Anode of (2) connecting the switching device S_k3The emitter and the cathode of the anode are connected with a neutral point O; the connection point of the k-phase bridge arm and the direct-current positive bus P is recorded as a connection point delta_k1Switching device S_k1And a switching device S_k2Is denoted as connection point delta_k2Switching device S_k2And a switching device S_k3Is denoted as connection point delta_k3Switching device S_k3And a switching device S_k4Is denoted as connection point delta_k4And the connection point of the k-phase bridge arm and the direct-current negative bus Q is recorded as a connection point delta_k5K represents phase sequence, k ═ a, B, C;

the three-phase load resistance is recorded as resistance R_kAnd the three-phase load inductance is recorded as inductance L_kResistance R_kOne end of and a connection point delta_k3Connected to another end of the inductor L_kConnected to each other by an inductance L_kThe other end of the first and second electrodes is grounded; the three-level NPC inverter is controlled by a controller DSP I (10);

the IGBT module online monitoring system comprises a controller DSP I (10), a controller DSP II (20), a power supply conversion module (30), a relay selection module (40), a monitoring current injection module (50), a communication module (60), a voltage sampling module (70) and an upper computer (80), and the whole monitoring system is uniformly coordinated and controlled by the controller DSP II (20);

the monitoring system controller DSP I (10) comprises a general output port T_o4And a universal input port T_r2；

The monitoring system controller DSP II (20) comprises a peripheral function pin SCIRXDA, a peripheral function pin SCITXDA and a general output port T_ok1Universal output port T_ok2Universal output port T_ok3Universal output port T_o1Universal output port T_o2Universal output port T_o3Universal input port T_r1Sampling input port T_ck1Sampling input port T_ck2Sampling input port T_ck3Sampling input port T_ck4K represents phase sequence, k ═ a, B, C;

the power supply conversion module (30) comprises two direct-current voltage conversion circuits, namely a first direct-current voltage conversion circuit (31) and a second direct-current voltage conversion circuit (32), and the input ends of the two direct-current voltage conversion circuits are respectively connected with the voltage U at the two ends of the direct-current side power supply E of the three-level NPC inverter_dcConnecting;

the relay selection module (40) comprises a sequential electrical appliance selection submodule A, a sequential electrical appliance selection submodule B and a sequential electrical appliance selection submodule C, and the sequential electrical appliance selection submodules are identical in structure; setting any phase in three-phase relay selection submodules as a k successive electric appliance selection submodule, wherein four groups of relays are arranged in the k successive electric appliance selection submodule and comprise 4 double-contact relays and 4 single-contact relays, and the 4 double-contact relays are respectively recorded as a double-contact relay SPDT1_kSPDT2 double-contact relay_kSPDT3 double-contact relay_kSPDT4 double-contact relay_kThe 4 single-contact relays are respectively marked as single-contact relays SPST1_kSingle contact relay SPST2_kSingle contact relay SPST3_kSingle contact relay SPST4_kK represents phase sequence, k ═ a, B, C;

the monitoring current injection module (50) comprises a large current branch (51), a small current branch (52) and a large current interface (53), wherein the large current branch (51) is provided with a large voltage power supply interface U_HAnd a monitoring inductor L_mSwitching device S₁Diode D₁Sequentially connected in series to form a freewheeling diode D_mIs connected in parallel to the monitoring inductor L_mTwo ends; the small current branch (52) is composed of a 100mA small current source I_LSwitching device S₂Diode D₂Are sequentially connected in series to form a 100mA small current source I_LGenerated by the linear regulator chip LT 3080; the high-current branch (51) and the low-current branch (52) are connected in parallel, the parallel circuit is called a trunk circuit, the trunk circuit at the right end is connected with the negative pole GND of the high-current interface (53) after parallel connection, a current sensor N is connected in series on the trunk circuit at the left end, and the other end of the current sensor N is connected with the positive pole I of the high-current interface (53); marking the negative pole GND of the large-current interface (53) as the negative pole GND, and marking the positive pole I of the large-current interface (53) as the positive pole I;

the communication module (60) comprises an SCI communication circuit (61), a first serial port communication circuit (62) and a second serial port communication circuit (63);

the voltage sampling module (70) comprises an A-phase voltage sampling submodule, a B-phase voltage sampling submodule and a C-phase voltage sampling submodule, wherein each phase of submodule consists of four identical differential sampling circuits which are respectively marked as a differential sampling circuit 1, a differential sampling circuit 2, a differential sampling circuit 3 and a differential sampling circuit 4;

a small voltage power supply interface U is arranged on each of the controller DSP II (20), the relay selection module (40), the monitoring current injection module (50), the communication module (60) and the voltage sampling module (70)_L；

The output end of the first direct current voltage conversion circuit (31) is connected with a large voltage power supply interface U of the monitoring current injection module (50)_H(ii) a The output end of the second direct current voltage conversion circuit (32) is respectively connected with a small voltage power supply interface U in the controller DSP II (20), the relay selection module (40), the monitoring current injection module (50), the communication module (60) and the voltage sampling module (70)_LConnecting;

the above-mentionedk successive appliance selection submodules, double contact relay SPDT1_kTwo contacts at the left end are respectively connected with a contact point delta_k1And connection point delta_k2And a right end single contact relay SPST1_kLeft end, single contact relay SPST1_kThe right end of the anode is connected with a positive electrode I; double-contact relay SPDT2_kTwo contacts at the left end are respectively connected with a contact point delta_k2And connection point delta_k3And a single-contact relay SPST2 connected with the right end_kLeft end, single contact relay SPST2_kThe right end of the anode is connected with a negative pole GND; double-contact relay SPDT3_kTwo contacts at the left end are respectively connected with a contact point delta_k3And connection point delta_k4And a single-contact relay SPST3 connected with the right end_kLeft end, single contact relay SPST3_kThe right end of the anode is connected with a positive electrode I; double-contact relay SPDT4_kTwo contacts at the left end are respectively connected with a contact point delta_k4And connection point delta_k5And a right end single contact relay SPST4_kLeft end, single contact relay SPST4_kThe right end of the anode is connected with a negative pole GND;

in the k-phase voltage sampling submodule, the positive input end of the differential sampling circuit 1 is connected with a contact point delta_k1The negative input terminal is connected to the connection point delta_k2The output end is connected with the sampling input port T of the controller DSP II (20)_ck1(ii) a The positive input terminal of the differential sampling circuit 2 is connected to the contact point delta_k2The negative input terminal is connected to the connection point delta_k3The output end is connected with the sampling input port T of the controller DSP II (20)_ck2(ii) a The positive input end of the differential sampling circuit 3 is connected with the connection point delta_k3Negative input terminal is connected to the connection point delta_k4The output end is connected with the sampling input port T of the controller DSP II (20)_ck3(ii) a The positive input end of the differential sampling circuit 4 is connected with the connection point delta_k4The negative input terminal is connected to the connection point delta_k5The output end is connected with the sampling input port T of the controller DSP II (20)_ck4；

The dual contact relay SPDT1_kSPDT2 double-contact relay_kSPDT3 double-contact relay_kSPDT4 double-contact relay_kBy a general output port T of the controller DSP II (20)_ok1Control, the single contact relay SPST1_kSingle contact relaySPST2_kBy a general output port T of the controller DSP II (20)_ok2Control, single contact relay SPST3_kSingle contact relay SPST4_kBy a general output port T of the controller DSP II (20)_ok3Controlling;

the switching device S₁By a general output port T of the controller DSP II (20)_o1Controlling, switching devices S₂By a general output port T of the controller DSP II (20)_o2Controlling;

one end of the SCI communication circuit (61) is connected with a USB port of the upper computer (80), and the other end of the SCI communication circuit is respectively connected with a peripheral function pin SCIRXDA and a peripheral function pin SCITXDA of the controller DSP II (20); the input end of the first serial port communication circuit (62) is connected with a general output port T of the controller DSP I (10)_o4The output end is connected with the general input port T of the controller DSP II (20)_r1(ii) a The input end of the second serial port communication circuit (63) is connected with the general output port T of the controller DSP II (20)_o3The output end is connected with the general input port T of the DSP I (10) of the controller_r2；

The online monitoring method is characterized by comprising the following steps:

step 1, fitting of saturated pressure drop-temperature curve

Putting the healthy IGBT module into a thermostat in an off-line state, and controlling the temperature T of the IGBT module_jChange in 20-120 deg.C, and saturation voltage drop V at 10 times of large current every 20 deg.C_CEHOThe saturated voltage drop V under 10 times of large current is calculated_CEHOIs recorded as the average value of the saturated voltage drop V under large current_CEH，V_CEH＝V_CEH010, obtaining the average value V of saturated voltage drop under 6 large currents in total through experiments_CEHAt a temperature T_jIs the average value V of the saturated voltage drop under X-axis and large current_CEHDrawing a curve in the plane coordinate system for the Y axis and marking as V_CEH-T_jA health curve;

putting the healthy IGBT module into a thermostat in an off-line state, and controlling the temperature T of the IGBT module_jChange in 20-120 deg.C, and saturation voltage drop V at small current for 10 times every 20 deg.C_CEL0The saturated voltage drop under 10 times of small current is calculatedV_CEL0Is taken as the average value of the saturated voltage drop V under the small current_CEL，V_CEL＝V_CEL010, obtaining the average value V of the saturated voltage drop under 6 small currents through experiments_CELAt a temperature T_jIs the average value V of the saturation voltage drop under X-axis and small current_CELDrawing a curve in a plane coordinate system for Y axis and marking as V_CEL-T_jA health curve;

experiments show that when the IGBT module fails, V is_CEH-T_jAverage value V of large current saturation voltage drop at 6 points in health curve_CEHWill increase by 5%, i.e. V when the IGBT module fails_CEH-T_jThe curve position will drift upwards by 5% overall, and V_CEL-T_jThe position of the health curve is unchanged; shift the whole body up by 5% of V_CEH-T_jThe curve is denoted as V_CEH-T_jA failure curve;

step 2, monitoring the presetting of conditions

In a modulation wave period, a monitoring start time t is preset_mMonitoring the start time t_mStarting a round of online monitoring, namely, the online monitoring system sequentially monitors the states of the switching devices of each bridge arm in the three-phase inverter main circuit, wherein the process of monitoring any switching device of any bridge arm is shown in steps 3-9;

step 3, sending a monitoring instruction 1, a monitoring instruction 2, a monitoring instruction 3 and a monitoring instruction 4 to a monitoring system controller DSP II (20) by an artificial control upper computer (80) through an SCI communication circuit (61), wherein the monitoring instruction 1 determines the phase sequence of a switching device to be monitored and the serial number of the switching device, and the monitoring instruction 2 determines the monitoring starting time t in a modulation wave period_mThe monitoring instruction 3 determines a monitoring time length delta t, delta t is more than 0 and less than W, W is the time length of a modulation wave period, and the monitoring instruction 4 determines a monitoring frequency m; setting the phase sequence of the switching device to be monitored as k and the serial number of the switching device as i, namely, the bridge arm to be monitored is a k-phase bridge arm, and the switching device to be monitored is a switching device S_ki；

Step 4, when the controller DSP II (20)After receiving the monitoring instruction 1, firstly controlling the contact of the double-contact relay and the contact of the single-contact relay in the relay selection module (40) to release upwards or pull downwards, and specifically, connecting the point delta_kiIs connected with the positive electrode I and connects the connection point delta_k(i+1)Is connected with the cathode GND; meanwhile, the controller DSP II (20) transmits the monitoring instruction 2, the monitoring instruction 3 and the monitoring instruction 4 to the controller DSP I (10) through a second serial port communication circuit (63);

step 5, after the DSP I (10) of the controller receives the monitoring instruction 2, the monitoring instruction 3 and the monitoring instruction 4, the time is determined by counting through a timer, and when the DSP I runs to the monitoring starting time t in a modulation wave period_mAnd meanwhile, the modulation waves of other two-phase bridge arms are added with the modulation wave variable quantity of the k-phase bridge arm to keep three-phase balance in the period, and the output voltage of the k-phase bridge arm to be monitored is modified into a zero level, the duration of the zero level is the monitoring time delta t, and the three-phase balance in the period is kept:

if the switching device to be monitored is the switching device S_k2Switching device S_k3If the DSP I (10) controls the k-phase bridge arm to output zero level, the switching device S_k1Switching device S_k2Switching device S_k3Switching device S_k4The states of the switch are off, on and off respectively; when a load current of k-phase to be monitored flows from a neutral point O through a clamping diode D_k1Switching device S_k2Flow direction resistance R_kAnd an inductance L_kThen, the switching device S is performed_k3Monitoring; when the load current of k-phase to be monitored is from resistor R_kFlowing through the inductor L_kSwitching device S_k3A clamping diode D_k2When the current flows to the neutral point O, the switching device S is operated_k2Monitoring;

if the switching device to be monitored is a switching device S_k1If the DSP I (10) controls the k-phase bridge arm to output zero level, the switching device S_k1Switching device S_k2Switching device S_k3Switching device S_k4The states of the switch are respectively on, off, on and off; the k-phase load current to be monitored at this time is derived from the resistance R_kCurrent flowing through inductor L_kAnd a switching device S_k3Clamping deviceDiode D_k2Flow to neutral O;

if the switching device to be monitored is the switching device S_k4If the DSP I (10) controls the k-phase bridge arm to output zero level, the switching device S_k1Switching device S_k2Switching device S_k3Switching device S_k4The states of the switch are off, on, off and on respectively; the load current of the k phase to be monitored now flows from the neutral point O through the clamping diode D_k1Switching device S_k2Flow direction resistance R_kAnd an inductance L_k；

Step 6, when the phase modulation wave to be monitored begins to be modified to be zero level, the controller DSP I (10) feeds back a synchronous signal to the controller DSP II (20) through the first serial port communication circuit (62), and after the controller DSP II (20) receives the synchronous signal, the synchronous signal passes through the general output port T_o1Switching on a switching device S in a high-current branch (51)₁Through a general output port T_o2Switching on a switching device S in a low current branch (52)₂Starting a current sensor N to monitor the main circuit current I;

step 7, setting the preset value of the main circuit current as I₀The following monitoring is performed by the current sensor N:

when 98% I₀≤I＜I₀Then, the controller DSP II (20) controls the sampling input port T_ckiWorking, sampling the saturated voltage drop under 10 times of large current, storing the average value of the saturated voltage drop, and recording the average value as the large current saturated voltage drop monitoring average value V_CEH′；

When I ═ I₀The controller DSP II (20) is connected with the universal output port T_o1Switching-off of a switching element S in a high-current branch (51)₁In the switching device S₂Sampling 10 times of saturation voltage drop under small current in a continuous opening state, storing the average value of the saturation voltage drop, and recording the average value as a small current saturation voltage drop monitoring average value V_CEL', when the small current is injected for 0.1ms continuously, the current passes through the general output port T_o2Turn-off switching device S₂；

Step 8, according to the monitoring times m given by the monitoring command 4, repeating the steps 5-7 in m modulation wave periods to obtain m large modulation wave periodsCurrent saturation voltage drop monitoring average value V_CEH' and m small current saturation voltage drop monitoring average value V_CEL' monitoring average value V of m large current saturation voltage drops_CEH' averaging again to obtain the first monitored pressure drop value V_CEHZMonitoring the average value V of m small current saturated voltage drops_CEL' averaging again to obtain a second monitored pressure drop value V_CELZThe first monitor voltage drop value V is transmitted via SCI communication circuit (61)_CEHZAnd a second monitored pressure drop value V_CELZTransmitting to an upper computer (80);

after m-time online monitoring is completed, the controller DSP I (10) restores the three-phase modulation wave of the k-phase bridge arm to be monitored to a sine wave state, and the controller DSP II (20) disconnects a relevant relay in the relay selection module (40), specifically, disconnects a connection point delta_kiDisconnecting from the positive electrode I and connecting the point delta_k(i+1)Disconnected from the negative electrode GND;

step 9, according to the second monitoring pressure drop value V_CELZThe upper computer (80) is at V_CEL-T_jFinding the corresponding temperature on the health curve, and recording the temperature as the monitoring temperature T_j', again based on the first monitored pressure drop value V_CEHZAnd monitoring the temperature T_jAt V_CEH-T_jFinding out a corresponding point F in a plane coordinate system of the health curve, and if the point F falls on V_CEH-T_jOn the failure curve or falling at V_CEH-T_jThe upper part of the failure curve is identified as the switching device S to be monitored_kiAnd (4) failing.

2. The IGBT module online monitoring method according to claim 1, wherein the controller DSP II (20), the relay selection module (40), the monitoring current injection module (50), the communication module (60) and the voltage sampling module (70) are integrated on a power supply board, and the power supply board is a circuit board where the power conversion module (30) is located.

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