A non-intrusive online monitoring system for switching events of power electronic devices

Abstract

The present invention relates to a non-intrusive online monitoring system for power electronic device switching events, the system comprising: a high-frequency switch oscillation current capture module: non-contactly sleeved on the output end cable of the power converter, used to extract the high-frequency switch oscillation signal V RCS ;Threshold voltage dynamic adjustment circuit: used to dynamically output threshold reference voltage V ref (V in ,I c ,T j ); High-speed voltage comparison circuit: used to compare the high-frequency switching oscillation signal V RCS With the dynamic output threshold reference voltage V ref The size of the high-frequency switching oscillation signal is output according to the comparison result. TC ; Pulse trigger circuit: used to convert narrowband peak signal V TC Regulated to a stable fixed width pulse output signal V PL ; Pulse processor: connected to the pulse trigger circuit to output the pulse signal V PL Compared with the prior art, the present invention has the advantages of low monitoring delay, applicability to wide operating conditions and high-frequency operating conditions, simple structure and small interference.

Description

Technical Field

[0001] The invention relates to the field of online monitoring of power electronic devices, and in particular to a non-intrusive online monitoring system for switching events of power electronic devices. Background Art

[0002] With the development of power electronics technology, most of the world's electric energy is converted and controlled through high-frequency switching of power electronic devices. The operational reliability of power electronic systems is very important. Among them, power semiconductor devices are one of the most vulnerable components. Existing statistical data show that the degradation and failure of power devices are the main causes of power electronic converter failures, and the proportion is higher than 70%. Therefore, it is necessary to conduct online status monitoring of power electronic devices. Power electronic power devices are also called power electronic switching devices. Their basic attribute is switching action. By online monitoring of power electronic device switching events, the operation / status information of power electronic devices can be effectively obtained. For example, by monitoring switching events, it can not only reflect the switching frequency, duty cycle and other operating information of power devices, but also reflect whether the power device has open circuit or short circuit failure, gate-level trigger pulse loss, unreliable trigger and other status information, which has important engineering significance and value.

[0003] In the paper “Open and short-circuit switch fault diagnosis for noisolated DC-DC converters using field programmable gate array”, M.Shahbazi et al. monitored the switching events of power electronic devices through the inductance slope, but it required obtaining gate signals, which was intrusive to the driving circuit of the power electronic devices. Moreover, due to the nonlinear switching behavior of power electronic devices, dead time needs to be inserted to compensate for the detection delay, which has certain limitations in practical engineering applications.

[0004] SYKim et al. in the paper “Fault diagnosis of a ZVS DC–DC converter based on DC-link current pulse shapes” monitored the switching anomaly of the power device through the DC link current PWM pulse shape, but the monitoring time of this method is slow and the calculation process is complicated.

[0005] Chinese patent CN201811097550.4 discloses a method for detecting load switching events. The load switching events are actions of turning on or off the power switch of a load or electrical device. In principle, mechanical switching events are monitored. The switching event frequency of power electronic devices is in the kHz to MHz range. Therefore, the real-time performance of this method cannot meet the monitoring of high-frequency and high-speed switching events of power electronic devices.

[0006] Chinese patent CN202010127546.9 discloses a non-contact power device open circuit fault high-speed detection system and method. However, on the one hand, this method can only detect the open circuit fault of the power device, and cannot detect the switching frequency, duty cycle, trigger pulse loss and other information. On the other hand, the principle of this method is to compare the switch oscillation current signal with the reference voltage of the fixed threshold, and directly detect the rising edge or falling edge of the output signal to determine whether the power device has an open circuit fault. Since the peak value of the high-frequency switch oscillation current signal is affected by factors such as input voltage, operating current, and temperature, the fixed voltage threshold is difficult to apply to complex and changeable operating conditions, and the dominant frequency of the current oscillation signal is very high (above MHz), and the duration of the oscillation peak is only tens of nanoseconds. Direct edge detection will lead to false detection or missed detection. Summary of the invention

[0007] The purpose of the present invention is to overcome the defects of the prior art and provide a non-intrusive online monitoring system for switching events of power electronic devices.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] A non-intrusive online monitoring system for switching events of power electronic devices, the system comprising:

[0010] High-frequency switch oscillation current capture module: non-contact sleeved on the output cable of the power converter, used to extract the high-frequency switch oscillation signal V RCS ;

[0011] Threshold voltage dynamic adjustment circuit: used to adjust the current peak value I of the switching oscillation signal peak With input voltage V in , working current I c and temperature T j Calibration relationship of parameters, dynamic output threshold reference voltage V ref (Vin,Ic,T j );

[0012] High-speed voltage comparison circuit: used to compare the high-frequency switching oscillation signal V RCS With the dynamic output threshold reference voltage V refThe size of the high-frequency switching oscillation signal is output according to the comparison result. TC ;

[0013] Pulse trigger circuit: used to convert narrowband peak signal V TC Regulated to a stable fixed width pulse output signal V PL ;

[0014] Pulse processor: connected to the pulse trigger circuit to output the pulse signal V PL Detect and process.

[0015] The lower limit cut-off frequency of the high-frequency switch oscillation current capture module is greater than the switching frequency of the power electronic device to ensure that the high-frequency switch oscillation signal is accurately extracted.

[0016] The high-frequency switch oscillation current capture module specifically adopts a Rogowski coil, the threshold voltage dynamic adjustment circuit adopts a DA module in an MCU, DSP or FPGA to output a threshold reference voltage, the pulse trigger circuit selects appropriate resistance and capacitance to adjust the time constant through an RC circuit, and the pulse processor adopts a pulse counting circuit or an edge detection circuit.

[0017] The fixed width pulse output signal V PL The pulse width τ depends on the actual switching oscillation current frequency F C Make adjustments to avoid repeated false triggering.

[0018] The pulse width τ is greater than the duration of the switching oscillation event, that is, τ>3~5 / F C .

[0019] In the high-speed voltage comparison circuit, when the high-frequency switching oscillation signal V RCS Greater than the threshold reference voltage V ref When the high-frequency switching oscillation signal V RCS Less than the threshold reference voltage V ref Output low level when

[0020] Or when the high-frequency switching oscillation signal V RCS Greater than the threshold reference voltage V ref When the high-frequency switching oscillation signal V RCS Less than the threshold reference voltage V ref When the high level is output, a narrow-band peak signal V corresponding to the high-frequency switching oscillation signal is generated. TC .

[0021] In the pulse processor, the pulse output signal V PLEach pulse in represents a turn-on or turn-off event. If the pulse output signal can be monitored each time, it indicates that the switching state of the power electronic device to be monitored is normal. Otherwise, it indicates that the switching state is abnormal. It is further determined whether a trigger pulse is lost, an open circuit fault, or a short circuit fault occurs. The switching frequency of the power electronic device is monitored according to the time interval between two consecutive turn-on or turn-off events, and the duty cycle of the power electronic device is monitored according to the time interval between the turn-on event and the turn-off event.

[0022] In the threshold voltage dynamic adjustment circuit, the threshold reference voltage V ref Specifically according to the current peak value I of the switching oscillation signal peak Select according to the input voltage characteristic calibration, or according to the current peak value I of the switching oscillation signal peak Select according to the characteristic calibration of the operating current.

[0023] When the current peak value I peak When selecting the characteristic calibration of the input voltage, if only the turn-on event is captured, the threshold reference voltage V ref The selection range is V peak_off ~V peak_on ;

[0024] If both turn-on and turn-off events are captured, select the threshold reference voltage V ref <V peak_off , V peak_on V is the first positive peak value of the voltage oscillation output by the switch oscillation current capture module at the turn-on time. peak_off It is the first positive peak value of the voltage oscillation output by the switch oscillation current capture module at the turn-off moment.

[0025] When the current peak value I peak When selecting the characteristic calibration of the running current, if only the turn-on event is captured, the threshold reference voltage V ref The range is V peak_off ~V peak_on ;

[0026] If both turn-on and turn-off events are captured, select the threshold reference voltage V ref <V peak_off , V peak_on V is the first positive peak value of the voltage oscillation output by the switch oscillation current capture module at the turn-on time. peak_off It is the first positive peak value of the voltage oscillation output by the switch oscillation current capture module at the time of shutdown. Compared with the prior art, the present invention has the following advantages:

[0027] 1. Good real-time performance: The monitoring delay of the switching events of the power electronic devices of the present invention is less than 500ns.

[0028] 2. Safe and stable: The non-contact switch oscillation current capture module has no direct electrical connection with the main circuit of the power converter under test, ensuring safe operation of the system. Moreover, through dynamic threshold adjustment and fixed pulse width output, it can be applied to wide operating conditions and high-frequency operating conditions to avoid missed detection and false detection.

[0029] 3. Simple structure: The high-frequency switching oscillation current sensor is mounted on the wire at the output end of the power converter and is less restricted by the converter space and electromagnetic interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The block diagram of the non-intrusive online monitoring system for switching events of power electronic devices of the present invention is shown.

[0031] Figure 2 It is a system principle diagram of the present invention.

[0032] Figure 3 For I peak With input voltage V in relationship diagram.

[0033] Figure 4 For I peak With the working current I C relationship diagram.

[0034] Figure 5 This is the experimental waveform for online monitoring of switching events during normal system operation.

[0035] Figure 6 This is the experimental waveform for online monitoring of MOSFET pulse loss.

[0036] Figure 7 This is the online monitoring experimental waveform when an open circuit failure occurs in the MOSFET. DETAILED DESCRIPTION

[0037] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] like Figure 1As shown, the present invention proposes a non-intrusive online monitoring system for high-speed switching events of power electronic devices. The principle is that the high dv / dt and di / dt brought by the high-speed switching process of the power electronic devices will inevitably generate high-frequency switching oscillation signals on the high-frequency parasitic parameters of the system, which means that each time a switching oscillation signal is monitored, it means that a switching event has occurred. The present invention extracts the switching oscillation signal through a switching oscillation current capture module, generates a reference voltage through a threshold voltage dynamic adjustment circuit according to the operating conditions, compares the switching oscillation signal with the reference voltage, and generates a pulse signal corresponding to the switching event of the power electronic device through a pulse trigger circuit. Finally, real-time monitoring of the power electronic switching event is achieved by processing the pulse signal, providing reference information for further detecting the operating status and fault status of the power electronic device.

[0039] The non-intrusive online monitoring system for power electronic device switching events of the present invention is mainly divided into five modules: a switch oscillation current capture module, a threshold voltage dynamic adjustment circuit, a high-speed voltage comparison circuit, a pulse trigger circuit and a pulse processor. The specific introduction of each module is as follows:

[0040] 1. High-frequency switch oscillation current capture module: This module is mounted on the output cable of the power converter to extract the high-frequency switch oscillation signal V RCS ,To ensure accurate extraction of high-frequency oscillation signals, the lower cutoff frequency of the module should be greater than the switching frequency of the power electronic device, and it has the characteristics of compact structure, small size, strong anti-interference ability, high bandwidth, and fast response speed. The present invention adopts a Rogowski coil, and uses enameled wire wound on a non-magnetic material;

[0041] 2. Threshold voltage dynamic adjustment circuit: It should be based on the peak value of the switching oscillation signal and the input voltage V in , working current I c , Temperature T j Calibration relationship of parameters, dynamic output threshold reference voltage V ref (Vin,Ic,T j ), threshold reference voltage V ref The polarity and amplitude can be set according to the detection target of the switch event, such as the detection of the switch-on event, the switch-off event, and the simultaneous monitoring of the switch-on and switch-off events. In this example, the threshold voltage dynamic adjustment circuit adopts, including but not limited to, selecting the DA module output reference voltage in the MCU / DSP / FPGA;

[0042] 3. High-speed voltage comparison circuit: connected to the switch oscillation current capture module and the threshold voltage dynamic adjustment circuit respectively, converting the high-frequency switch oscillation signal V RCS With the threshold reference voltage V ref As the input signal of the high-speed voltage comparison circuit, when V RCSGreater than V ref Output high level when V RCS Less than V ref Output low level, or when V RCS Greater than V ref Output low level, when V RCS Less than V ref When the output is high level, the high-speed voltage comparison circuit is used to compare V RCS With V ref Compare and generate a narrowband peak signal V corresponding to the high-frequency switching oscillation signal TC ;

[0043] 4. Pulse trigger circuit: It is set at the latter stage of the high-speed voltage comparison circuit to convert the narrow-band peak signal V output by the high-speed voltage comparison circuit into TC Regulated to a stable fixed width pulse output signal V PL , V PL The pulse width τ depends on the actual switching oscillation current frequency F C Adjust the pulse width τ to be greater than the duration of the switching oscillation event (τ>3~5 / F C ), avoid repeated false triggering and improve anti-interference ability. In this example, pulse width adjustment includes but is not limited to adjusting the time constant by selecting appropriate resistors and capacitors through an RC circuit.

[0044] 5. Pulse processor: connected to the pulse trigger circuit, the pulse output signal V PL For detection and processing, in this example, the pulse processor includes but is not limited to a pulse counting circuit, an edge detection circuit, etc. The pulse output signal V PL Each pulse in represents a turn-on or turn-off event. If the pulse signal can be monitored every time, it means that the power electronic device is switching normally. Otherwise, it means that the switching state is abnormal. It can be further determined whether a trigger pulse is lost, an open circuit fault, a short circuit fault, etc. occurs. The switching frequency of the power electronic device can be monitored according to the time interval between two consecutive turn-on or turn-off events, and the duty cycle of the power electronic device can be monitored according to the time interval between the turn-on event and the turn-off event.

[0045] Example

[0046] This embodiment takes the Buck circuit with SiC MOSFET as the power device as an example. The system mainly consists of a DC side input voltage source, a filter inductor L0, a filter capacitor C0, a power resistor R0 at the load end, a DSP controller, a high-frequency switch oscillation current capture module (a Rogowski coil is used in this example, and enameled wire is wound on a non-magnetic material), a threshold voltage dynamic adjustment circuit, a high-speed voltage comparison circuit and a pulse trigger circuit. The schematic diagram and parameters of the system are shown in FIG. Figure 2As shown in Table 1, the high-frequency switching oscillation current capture module is installed on the output wire of the Buck converter to extract the high-frequency switching oscillation signal, which is then sent to the high-speed voltage comparison circuit and the pulse trigger circuit to be modulated into a pulse signal. The pulse signal is then sent to the DSP controller to monitor the switching event.

[0047] Table 1 SiC MOSFET Buck converter system parameters

[0048] parameter value Input voltage 100V Duty Cycle 50％ SiC MOSFET Models C3M0075120K Load inductance 4mH Filter capacitor 800V / 5μF Load resistance 20Ω Switching frequency 100kHz DSP controller model TI TMS320F28335

[0049] 1. Threshold voltage V ref choose

[0050] 1) Characteristic calibration of switch oscillation current peak and input voltage

[0051] To investigate the switching oscillation current peak value I peak The relationship between the input voltage and the input voltage V in The voltage changes from 25V to 300V, and the first positive peak value I of the current oscillation at the turn-on time is observed. peak_on The first positive peak value I of the positive current oscillation at the turn-off moment peak_off , the ratio of the voltage signal output by the high-frequency switching oscillation current capture module to the measured inflow current K i =u0 / i L ≈0.82, such as Figure 3 shown.

[0052] As you can see, I peak_on / I peak_off ∝V in , and I peak_on >I peak_off Therefore, the voltage signal output by the switch oscillation current capture module corresponds to the positive peak value V peak_on >V peak_off , if only the turn-on event is captured, the threshold voltage V ref The size of V peak_off ~V peak_on Then, V ref The choice of can be expressed by formula (1):

[0053] 0.00807×V in -0.0124<V ref <0.00995×V in +0.156 (1)

[0054] If both turn-on and turn-off events are captured, select the threshold voltage V ref <V peak_off .

[0055] 2) Characteristic calibration of switch oscillation current peak and operating current

[0056] Maintain input voltage V in When the voltage is 100V, the switching frequency is 100kHz. By changing the duty cycle of the control signal (the duty cycle of the control signal varies from 20% to 70%), the operating current of the system changes. Figure 4 As shown, the relationship between the peak value of the switch oscillation current and the operating current is calibrated.

[0057] It can be observed that the peak value of the turn-on current oscillation I peak_on The operating current has little influence on the peak value of the off current oscillation. peak_off With the working current I C The size of is positively correlated, and I peak_on >I peak_off , the corresponding switch oscillation current capture module outputs a voltage signal V peak_on >V peak_off , if only the turn-on event is captured, the threshold voltage V ref The size of V peak_off ~V peak_on If both the turn-on event and the turn-off event are captured, then the threshold voltage V ref <V peak_off .

[0058] 2. Experimental results of online monitoring of switching events of power electronic devices

[0059] The system operates at an input voltage of 300V, a switching frequency of 50kHz, and a duty cycle of 50%. Figure 5 As shown, it can be observed that U DS Normal ascent and descent, i L It rises when turned on and generates high-frequency turn-on oscillation, and falls when turned off and generates high-frequency turn-off oscillation. The switch oscillation current capture module normally outputs the turn-on and turn-off oscillation signals V RCS , the threshold voltage V of the high-speed voltage comparison circuit ref Less than the peak value of the turn-off oscillation V peak_off The pulse trigger circuit outputs a pulse signal V at the turn-on and turn-off times. PL , in order to monitor high-speed switching events of power electronic devices.

[0060] The system operates at an input voltage of 100V, a switching frequency of 100kHz, a duty cycle of 50%, and a threshold voltage V ref The size satisfies V peak_off <V ref <V peak_on , only capture opening events, such as Figure 6As shown, when a pulse loss occurs, the occurrence of the pulse loss is monitored within one cycle.

[0061] The system operates at an input voltage of 100V, a switching frequency of 100kHz, and a duty cycle of 50%. The gate signal is blocked to simulate an open circuit fault. The threshold voltage V ref The size satisfies V peak_off <V ref <V peak_on Only capture activation events, such as Figure 7 As shown, it can be observed that the open circuit fault is detected within one cycle after the open circuit fault occurs.

[0062] In summary, the present invention utilizes high-frequency switching oscillation current signals to monitor switching events of power electronic devices, and adopts a non-contact switching oscillation current capture module, which will not interfere with the normal operation of the power electronic system, and regulates the high-frequency switching oscillation signal into a stable pulse output signal through dynamic threshold adjustment and pulse triggering circuit, which can operate stably and reliably without false detection.

Claims

1. A non-intrusive online monitoring system for switching events of power electronic devices, characterized in that: The system includes: High-frequency switch oscillation current capture module: non-contact sleeved on the output cable of the power converter, used to extract the high-frequency switch oscillation signal V RCS ; Threshold voltage dynamic adjustment circuit: used to adjust the current peak value I of the switching oscillation signal peak With input voltage V in , working current I c and temperature T j Calibration relationship of parameters, dynamic output threshold reference voltage V ref (V in, I c, T j ); High-speed voltage comparison circuit: used to compare the high-frequency switching oscillation signal V RCS With the dynamic output threshold reference voltage V ref The size of the high-frequency switching oscillation signal is output according to the comparison result. TC ; Pulse trigger circuit: used to convert narrowband peak signal V TC Regulated to a stable fixed width pulse output signal V PL ; Pulse processor: connected to the pulse trigger circuit to output the pulse signal V PL Detect and process.

2. A non-intrusive online monitoring system for switching events of power electronic devices according to claim 1, characterized in that: The lower limit cut-off frequency of the high-frequency switch oscillation current capture module is greater than the switching frequency of the power electronic device to ensure that the high-frequency switch oscillation signal is accurately extracted.

3. The non-intrusive online monitoring system for switching events of power electronic devices according to claim 1, characterized in that: The high-frequency switch oscillation current capture module specifically adopts a Rogowski coil, the threshold voltage dynamic adjustment circuit adopts a DA module in an MCU, DSP or FPGA to output a threshold reference voltage, the pulse trigger circuit selects appropriate resistance and capacitance to adjust the time constant through an RC circuit, and the pulse processor adopts a pulse counting circuit or an edge detection circuit.

4. The non-intrusive online monitoring system for switching events of power electronic devices according to claim 1, characterized in that: The fixed width pulse output signal V PL The pulse width τ depends on the actual switching oscillation current frequency F C Make adjustments to avoid repeated false triggering.

5. A non-intrusive online monitoring system for switching events of power electronic devices according to claim 4, characterized in that: The pulse width τ is greater than the duration of the switching oscillation event, that is, τ>3~5 / F C .

6. The non-intrusive online monitoring system for switching events of power electronic devices according to claim 1, characterized in that: In the high-speed voltage comparison circuit, when the high-frequency switching oscillation signal V RCS Greater than the threshold reference voltage V ref When the high-frequency switching oscillation signal V RCS Less than the threshold reference voltage V ref Output low level when Or when the high-frequency switching oscillation signal V RCS Greater than the threshold reference voltage V ref When the high-frequency switching oscillation signal V RCS Less than the threshold reference voltage V ref When the high level is output, a narrow-band peak signal V corresponding to the high-frequency switching oscillation signal is generated. TC .

7. The non-intrusive online monitoring system for switching events of power electronic devices according to claim 1, characterized in that: In the pulse processor, the pulse output signal V PL Each pulse in represents a turn-on or turn-off event. If the pulse output signal can be monitored each time, it indicates that the switching state of the power electronic device to be monitored is normal. Otherwise, it indicates that the switching state is abnormal. It is further determined whether a trigger pulse is lost, an open circuit fault, or a short circuit fault occurs. The switching frequency of the power electronic device is monitored according to the time interval between two consecutive turn-on or turn-off events, and the duty cycle of the power electronic device is monitored according to the time interval between the turn-on event and the turn-off event.

8. The non-intrusive online monitoring system for switching events of power electronic devices according to claim 1, characterized in that: In the threshold voltage dynamic adjustment circuit, the threshold reference voltage V ref Specifically according to the current peak value I of the switching oscillation signal peak Select according to the input voltage characteristic calibration, or according to the current peak value I of the switching oscillation signal peak Select according to the characteristic calibration of the operating current.

9. A non-intrusive online monitoring system for switching events of power electronic devices according to claim 8, characterized in that: When the current peak value I peak When selecting the characteristic calibration of the input voltage, if only the turn-on event is captured, the threshold reference voltage V ref The selection range is V peak_off ~V peak_on ; If both turn-on and turn-off events are captured, select the threshold reference voltage V ref <V peak_off , V peak_on V is the first positive peak value of the voltage oscillation output by the switch oscillation current capture module at the turn-on time. peak_off It is the first positive peak value of the voltage oscillation output by the switch oscillation current capture module at the turn-off moment.

10. The non-intrusive online monitoring system for switching events of power electronic devices according to claim 8, characterized in that: When the current peak value I peak When selecting the characteristic calibration of the running current, if only the turn-on event is captured, the threshold reference voltage V ref The range is V peak_off ~V peak_on ; If both turn-on and turn-off events are captured, select the threshold reference voltage V ref <V peak_off , V peak_on V is the first positive peak value of the voltage oscillation output by the switch oscillation current capture module at the turn-on time. peak_off It is the first positive peak value of the voltage oscillation output by the switch oscillation current capture module at the turn-off moment.

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