Motor-to-casing short-circuit detection system and detection method based on capacitor charging and discharging model

Abstract

The invention relates to the technical field of motor drive and fault detection, and in particular to a motor-to-casing short-circuit detection system based on a capacitor charge-discharge model and a detection method thereof. The system comprises a system SOC control chip, and also comprises: a Y capacitor charge-discharge model operation module, a PWM wave generation module, a three-phase bridge drive module, a current sampling module, and a fault detection and protection module; the specific detection steps are as follows: S51, Y capacitor charge-discharge model construction; S52, short-circuit model key parameter operation; S53, PWM initialization component; S54, PWM state machine control; S55, PWM key parameter operation; S56, PWM wave generation module; S57, three-phase bridge drive module; S58, current sampling circuit; S59, Σ-Δ sampler and demodulator; S510, judging whether there is a fault at present; S511, fault post-processing; the key parameters calculated by the Y capacitor charge-discharge model operation module are used to provide theoretical guidance for the upper and lower bridge conduction time controlled by the PWM wave generation module and the fault detection and protection module.

Description

Technical Field

[0001] The present invention relates to the technical field of motor drive and fault detection, and in particular to a motor-to-casing short circuit detection system and a detection method thereof based on a capacitor charge and discharge model. Background Art

[0002] Motors and their drivers are widely used in many automation fields such as electric vehicles, precision CNC machine tools, industrial robots, textile equipment, and 3C manufacturing. Due to their huge market share, the fault detection function of motor drivers is becoming increasingly important for improving system reliability and work efficiency. As a common fault in motor drive systems, the short-circuit fault of the motor relative to the casing frequently affects the normal operation of the system and can cause equipment damage in severe cases. Existing methods for detecting motor-to-casing faults are mainly based on abnormal current or voltage detection of Y capacitors during motor operation. In the former, since the motor is already operating normally during detection, the short-circuit problem of the motor may cause irreversible permanent damage to the equipment. In the latter, it is often necessary to add circuits to the motor driver hardware to implement the fault detection function, which increases the hardware cost of the driver.

[0003] For example, in a circuit suitable for valve section power hedging and short-circuit testing with Chinese Patent No. 201910366488.2, the circuit consists of a valve section to be tested, a test valve section, a power module power supply circuit, a connecting inductor, a switching switch, a short-circuit current limiting inductor, a DC current excitation capacitor, an AC current excitation transformer and its power supply. The valve section power supply circuit is used to provide external energy support for the test valve section power module; the connecting inductor is used to realize the connection of two equivalent voltage sources to realize the output of the expected current; the switching switch is composed of a first switch and a second switch, which is used to exit the operating circuit and enter the short-circuit circuit; the short-circuit current limiting inductor is used to control the current rise rate under short-circuit conditions; the DC current excitation capacitor is used to excite the DC current component during short circuit; the AC current excitation transformer and the AC power supply are used to generate the AC current component in the short-circuit current. The present invention can test the overcurrent protection capability and fault current tolerance capability of the valve section. This method is mainly based on hardware implementation, which increases the accessory cost of the protection function; and the calculation of key protection parameters does not build a model, and the versatility and adaptability are low; and this method is mainly used in power systems, which is inconsistent with the application scenario of this patent. Summary of the invention

[0004] In order to solve the above problems, the present invention proposes a motor-to-casing short circuit detection system and a detection method based on a capacitor charging and discharging model.

[0005] A motor-to-housing short circuit detection system based on a capacitor charge and discharge model includes a system SOC control chip and also includes:

[0006] The Y capacitor charge and discharge model calculation module constructs three different short-circuit models relative to the chassis ground, and calculates the corresponding key parameters such as capacitor charge and discharge current peak value, peak time, discharge time, and resonant frequency for each model;

[0007] The PWM wave generation module uses the Y capacitor charge and discharge model calculation module to obtain the charge and discharge current peak value, charge and discharge current peak time, and upper bridge test conduction time to obtain the fault detection current threshold, the upper bridge test conduction time of the test phase during the fault detection process, and the lower bridge discharge conduction time during the fault detection process;

[0008] The three-phase bridge driving module completes the conduction of the power switch device corresponding to the three-phase bridge according to the control signal output by the PWM wave generating module, and completes the charging and discharging process of the Y capacitor;

[0009] The current sampling module collects the motor U-phase current and V-phase current in the three-phase bridge drive module in real time during the fault detection process;

[0010] The fault detection and protection module is implemented using the logic resources of the FPGA. In the fault detection process, the two-phase current obtained by the current sampling module is obtained in real time, and the fault judgment is performed in combination with the key parameters obtained by the Y capacitor charge and discharge model calculation module.

[0011] The Y capacitor charge and discharge model calculation module includes a short circuit model component for constructing three Y capacitor charge and discharge models and a key parameter calculation component for realizing the calculation of short circuit protection parameters.

[0012] The Y capacitor charge and discharge model calculation module is divided into the test phase short-circuited to the chassis ground, the other two phases except the test phase are short-circuited to the chassis ground, and one of the other two phases except the test phase is short-circuited to the chassis ground.

[0013] The Y capacitor charge and discharge model calculation module can calculate the key parameters such as the Y capacitor charge and discharge current peak value, peak time, discharge time, and resonant frequency corresponding to the model according to each short-circuit model combined with the motor impedance parameters, the power switching device impedance parameters, and the Y capacitor parameters.

[0014] The PWM wave generating module includes a PWM initialization component for initializing the PWM switching frequency, duty cycle, and fault detection switch attributes, a PWM state machine controller for controlling the switching timing of the PWM function, and a PWM key parameter operator for calculating the conduction time of the three-phase bridge arm and the fault protection threshold.

[0015] The three-phase bridge driving module includes a PWM driving unit that converts the control signal sent by the PWM wave generating module into a driving signal that can control the power device of the three-phase bridge component to turn on and off, and a three-phase bridge component that completes the short-circuit test step relative to the casing required by the system through the three-phase bridge power device turn-on and turn-off driving signals obtained by the PWM driving unit.

[0016] The current sampling module includes a high-precision sampling resistor for converting a current signal into a voltage signal, a sampling voltage conditioner for adjusting the voltage signal to a desired range, a Σ-Δ sampler for converting the voltage signal into a digital signal, and a Σ-Δ demodulator for converting the digital signal into a digital voltage signal recognizable by ARM.

[0017] The fault detection and protection module includes a fault detection state machine for controlling the detection timing of a short-circuit fault relative to the housing, and a functional fault post-processing component for realizing rapid protection and reporting the fault when a fault is detected.

[0018] The detection method of the motor relative housing short circuit detection system based on the capacitor charging and discharging model has the following specific steps:

[0019] S51, Y capacitor charge and discharge model construction: construct a Y capacitor charge and discharge model based on three relative chassis ground short circuit conditions;

[0020] S52, short-circuit model key parameter calculation: According to the model constructed in step S51, the motor impedance parameters, the power switch device impedance parameters and the Y capacitor parameters are combined to calculate the Y capacitor charge and discharge current peak value, peak time, discharge time, resonant frequency and other key parameters corresponding to the model;

[0021] S53, PWM initialization component: initialize the PWM switching frequency, duty cycle, and fault detection switch attributes to facilitate subsequent fault detection;

[0022] S54, PWM state machine control: used to control the PWM state machine to determine whether to enable the relative housing ground fault detection function. If the fault detection is enabled, proceed to the next step. If the fault detection is not enabled, directly enter the end state.

[0023] S55, PWM key parameter calculation: using the charge and discharge current peak value obtained in step S52, the fault detection current threshold can be calculated, and the upper bridge test conduction time of the test phase during the fault detection process can be calculated using the obtained charge and discharge current peak time, and the lower bridge discharge conduction time during the fault detection process can be calculated using the Y capacitor discharge time obtained in step S52;

[0024] S56, PWM wave generating module: converting the control logic signal obtained in step S55 into a driving signal that can drive the power switch device to turn on and off;

[0025] S57, three-phase bridge driving module: receiving the driving signal of step S56, and completing the short-circuit fault detection step relative to the chassis ground required by the system by controlling the opening and closing actions of the three-phase bridge power device;

[0026] S58, current sampling circuit: used to convert the characteristic current signal generated in the fault detection process of step S57 into a voltage signal that can be recognized by the system;

[0027] S59, Σ-Δ sampler and demodulator: convert the voltage signal output in step S58 into a digital signal for subsequent program processing;

[0028] S510, determine whether there is a fault currently: if there is no fault, enter the fault detection end state; if there is a fault, enter step S511;

[0029] S511, post-fault processing: complete the functions of realizing rapid protection and reporting faults when a fault is detected.

[0030] The specific control process of the step S56 PWM wave generating module is as follows:

[0031] S31, whether to enable relative housing ground fault detection;

[0032] S32, if the system enables the relative housing ground fault detection function, then the fault detection state machine is entered to start the fault detection related tasks;

[0033] S33, firstly, perform fault detection on the test phase U, and output the corresponding PWM to the three-phase bridge drive module to turn on the upper tube of the U phase and turn off the lower bridge to charge the Y capacitor. The minimum conduction time is T Hmin , the maximum is t Hmax ;

[0034] S34, obtaining fault information in real time through the fault detection and protection module;

[0035] S35: If a fault exists, immediately proceed to step S38;

[0036] S36, if it is determined that there is no fault currently, proceed to step S37;

[0037] S37, output PWM to turn off the upper bridge of the U phase and turn on the lower bridge to discharge the Y capacitor. To ensure reliable discharge, the discharge time is five times the time constant of the Y capacitor short-circuit model. After the discharge is completed, the same test task can be performed on the V phase;

[0038] S38, post-fault processing related tasks;

[0039] S39. If it is determined that there is no fault in the entire test process, the PWM wave generating module turns off the PWM output and exits the fault detection state machine.

[0040] The specific control process of the three-phase bridge drive module in step S57 is as follows:

[0041] S41, when the fault detection and protection module detects that the system has entered the fault detection state machine, it immediately starts the U and V phase current sampling and fault identification functions, and repeats this step if no detection is made;

[0042] S42, if the collected phase current exceeds the fault detection threshold I min , then the next step;

[0043] S43, executing PWM sealing protection action;

[0044] S44, setting a fault flag of the motor relative to the housing to inform the PWM generating module of the fault.

[0045] The beneficial effects of the present invention are as follows: three different short-circuit models relative to the casing are constructed by using a Y capacitor charge and discharge model calculation module, and corresponding key parameters such as capacitor charge and discharge current peak value, peak time, discharge time, and resonant frequency are calculated for each model. The beneficial effect is that the model covers all working conditions of short circuit relative to the casing, and the key parameters calculated by the calculation provide theoretical guidance for the setting of the upper and lower bridge conduction time controlled by the PWM wave generation module and the fault threshold of the fault detection and protection module, solve the problem that the detection parameters need to be frequently tried and matched, greatly improve the fault detection efficiency, and reduce the risk of missed reporting and false reporting of faults relative to the casing; the PWM wave generation module is used to control the three-phase bridge drive module to test the upper bridge conduction of the phase The Y capacitor is charged and discharged by turning on the lower bridge arm. The current sampling module based on the second-order Σ-Δ modulator cooperates with the PWM wave generation module to collect the U-phase and V-phase currents in the fault detection process in real time. The beneficial effect is that the Y capacitor voltage detection hardware circuit is omitted and only two test phase currents need to be sampled, which reduces the implementation cost of the method and system and improves its adaptability to most motor drivers. The fault detection and protection function module is realized by using the FPGA logic resources in the SOC control chip. The beneficial effect is that the fault can be judged in real time during the fault detection process. If a fault is detected, the PWM wave generation module is turned off as quickly as possible, thereby reducing the risk of equipment damage due to the fault. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0047] Figure 1 It is a structural block diagram of the operating principle of the present invention;

[0048] Figure 2 This is a short circuit indication for the motor relative to the chassis ground. Figure 1 ;

[0049] Figure 3 This is a short circuit indication for the motor relative to the chassis ground. Figure 2 ;

[0050] Figure 4 This is a short circuit indication for the motor relative to the chassis ground. Figure 3 ;

[0051] Figure 5 It is a control flow chart of the PWM wave generating module of the present invention;

[0052] Figure 6 is a control flow chart of the fault detection and protection module of the present invention;

[0053] Figure 7 It is the overall flow chart of the system of the present invention. DETAILED DESCRIPTION

[0054] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below.

[0055] like Figures 1 to 7 As shown, the motor-to-housing short circuit detection system based on the capacitor charge and discharge model includes a system SOC control chip and also includes:

[0056] Y capacitor charge and discharge model calculation module 1, constructs three different short-circuit models relative to the chassis, and calculates the corresponding key parameters such as capacitor charge and discharge current peak value, peak time, discharge time, and resonant frequency for each model;

[0057] PWM wave generating module 2, using the Y capacitor charge and discharge model calculation module to obtain the charge and discharge current peak value, charge and discharge current peak time, and upper bridge test conduction time, respectively obtain the fault detection current threshold, the upper bridge test conduction time of the test phase during the fault detection process, and the lower bridge discharge conduction time during the fault detection process;

[0058] The three-phase bridge driving module 3 completes the conduction of the power switch device corresponding to the three-phase bridge according to the control signal output by the PWM wave generating module 2, and completes the charging and discharging process of the Y capacitor;

[0059] The current sampling module 4 collects the motor U-phase current and V-phase current in the three-phase bridge drive module 3 in real time during the fault detection process;

[0060] The fault detection and protection module 5 is implemented using the logic resources of the FPGA. In the fault detection process, the two-phase current obtained by the current sampling module is obtained in real time, and the fault judgment is performed in combination with the key parameters obtained by the Y capacitor charge and discharge model operation module 1.

[0061] Three different short-circuit models relative to the casing are constructed using the Y capacitor charge and discharge model calculation module 1. For each model, the corresponding key parameters such as capacitor charge and discharge current peak, peak time, discharge time, and resonant frequency are calculated. The beneficial effect is that the model covers all working conditions of short circuit relative to the casing. The key parameters calculated provide theoretical guidance for the setting of the upper and lower bridge conduction time controlled by the PWM wave generation module 2 and the fault threshold of the fault detection and protection module 5, which solves the problem of frequent trial and error of detection parameters, greatly improves the fault detection efficiency, and reduces the risk of missed and false alarms of faults relative to the casing.

[0062] The Y capacitor charge and discharge model calculation module includes a short circuit model component for constructing three Y capacitor charge and discharge models and a key parameter calculation component for realizing the calculation of short circuit protection parameters.

[0063] The schematic diagrams of the three short-circuit conditions are as follows: Figure 2 , Figure 3 , Figure 4 As shown, Figure 2 To test the short-circuit condition relative to the chassis ground, that is, only one phase of the two-phase winding of the motor to which the test voltage is applied is short-circuited relative to the chassis ground; Figure 3 This is a non-test short-circuit condition relative to the chassis ground, that is, the winding of one phase of the motor to which the test voltage is not applied is short-circuited relative to the chassis ground; Figure 4 The two non-test phases are short-circuited to the chassis ground, that is, the two-phase windings of the motor without the test voltage applied are short-circuited to the chassis ground; by modeling and analyzing these three conditions, the corresponding charging circuit model transfer function and step response can be obtained as shown in Table 1. The results are as follows:

[0064] Table 1

[0065]

[0066] According to the modeling analysis results shown in Table 1, the short-circuit current peak values ​​and short-circuit current peak times corresponding to the three short-circuit conditions can be obtained, and only in the third condition, that is, Figure 4 In this state, when only one of the other two phases except the test phase is short-circuited to the chassis ground, the short-circuit current peak value is the smallest.

[0067] If the minimum reliable current detection threshold of the current sampling module 4 based on the second-order Σ-Δ modulator is I min , then the minimum on-time of the test phase upper bridge fault detection of PWM wave generator module 2 can be determined as Where ω n is the resonant frequency of the Y capacitor charging loop.

[0068] When the lower bridge arm of the test phase is turned on, the Y capacitor will be discharged. Due to the damping in the Y capacitor discharge circuit Small, its discharge time domain response and time constant are When the lower bridge arm conduction time is greater than 5 times the time constant τ, the capacitor voltage is only 0.67% of the voltage before discharge. Therefore, it is considered that the capacitor discharge has basically ended and the fault detection of the second test phase can be performed. Therefore, the lower bridge conduction time of the test phase of PWM wave module 2 can be set to t Lmin =5 times the discharge time constant = 5τ.

[0069] The PWM wave module 2 can increase the conduction time of the test phase bridge by 1μS / time during the fault detection process, and the maximum value does not exceed the capacitance peak time of the Y capacitor charging circuit. Minimum not less than t Hmin , let the lower bridge of the test phase discharge according to the minimum conduction time t Lmin Conducting discharge.

[0070] The Y capacitor charge and discharge model operation module 1 is implemented in the ARM core of the system SOC control chip, and the short circuit of the motor relative to the casing is divided into the test phase short circuit relative to the casing ground, the other two phases except the test phase are short circuited to the casing ground, and one of the other two phases except the test phase is short circuited to the casing ground.

[0071] The Y capacitor charge and discharge model calculation module 1 can calculate the key parameters such as the Y capacitor charge and discharge current peak value, peak time, discharge time, and resonant frequency corresponding to the model according to each short-circuit model combined with the motor impedance parameters, the power switching device impedance parameters, and the Y capacitor parameters.

[0072] The Y capacitor charge and discharge model calculation module 1 constructs three different short-circuit models relative to the housing.

[0073] The PWM wave generating module 2 includes a PWM initialization component for initializing the PWM switching frequency, duty cycle, and fault detection switch attributes, a PWM state machine controller for controlling the switching timing of the PWM function, and a PWM key parameter operator for calculating the conduction time of the three-phase bridge arm and the fault protection threshold.

[0074] The PWM wave generating module 2 uses the key parameters obtained by the Y capacitor charge and discharge model calculation module 1 to output PWM control signals to the upper and lower tubes of the U phase and the V phase respectively.

[0075] The three-phase bridge driving module 3 includes a PWM driving unit that converts the control signal sent by the PWM wave generating module 2 into a driving signal that can control the power device of the three-phase bridge component to turn on and off, and a three-phase bridge component that completes the short-circuit test step relative to the casing required by the system through the three-phase bridge power device turn-on and turn-off driving signals obtained by the PWM driving unit.

[0076] The current sampling module 4 includes a high-precision sampling resistor for converting a current signal into a voltage signal, a sampling voltage conditioner for adjusting the voltage signal to a desired range, a Σ-Δ sampler for converting the voltage signal into a digital signal, and a Σ-Δ demodulator for converting the digital signal into a digital voltage signal recognizable by ARM.

[0077] The PWM wave generation module 2 is used to control the upper bridge of the test phase of the three-phase bridge drive module 3 to charge the Y capacitor, and the lower bridge arm is turned on to discharge the Y capacitor. The current sampling module 4 based on the second-order Σ-Δ modulator cooperates with the PWM wave generation module 3 to collect the U-phase and V-phase currents in the fault detection process in real time. The beneficial effect is that the Y capacitor voltage detection hardware circuit is omitted and only the two test phase currents need to be sampled, which reduces the implementation cost of the method and system and improves its adaptability to most motor drivers. The FPGA logic resources in the SOC control chip are used to implement the fault detection and protection function module 5. The beneficial effect is that the fault can be judged in real time during the fault detection process. If a fault is detected, the PWM wave generation module 2 is turned off as quickly as possible, thereby reducing the risk of equipment damage due to the fault.

[0078] The fault detection and protection module 5 includes a fault detection state machine for controlling the timing of short-circuit fault detection relative to the housing, and a functional fault post-processing component for implementing rapid protection and reporting the fault when a fault is detected.

[0079] When the fault detection and protection module 5 detects a fault, it turns off the PWM wave generating module as quickly as possible to reduce the risk of damage to the equipment due to the fault.

[0080] The detection method of the motor relative housing short circuit detection system based on the capacitor charging and discharging model has the following specific steps:

[0081] S51, Y capacitor charge and discharge model construction: construct a Y capacitor charge and discharge model based on three relative chassis ground short circuit conditions;

[0082] S52, short-circuit model key parameter calculation: According to the model constructed in step S51, the motor impedance parameters, the power switch device impedance parameters and the Y capacitor parameters are combined to calculate the Y capacitor charge and discharge current peak value, peak time, discharge time, resonant frequency and other key parameters corresponding to the model;

[0083] S53, PWM initialization component: initialize the PWM switching frequency, duty cycle, and fault detection switch attributes to facilitate subsequent fault detection;

[0084] S54, PWM state machine control: used to control the PWM state machine to determine whether to enable the relative housing ground fault detection function. If the fault detection is enabled, proceed to the next step. If the fault detection is not enabled, directly enter the end state.

[0085] S55, PWM key parameter calculation: using the charge and discharge current peak value obtained in step S52, the fault detection current threshold can be calculated, and the upper bridge test conduction time of the test phase during the fault detection process can be calculated using the obtained charge and discharge current peak time, and the lower bridge discharge conduction time during the fault detection process can be calculated using the Y capacitor discharge time obtained in step S52;

[0086] S56, PWM wave generating module: converting the control logic signal obtained in step S55 into a driving signal that can drive the power switch device to turn on and off;

[0087] S57, three-phase bridge driving module: receiving the driving signal of step S56, and completing the short-circuit fault detection step relative to the chassis ground required by the system by controlling the opening and closing actions of the three-phase bridge power device;

[0088] S58, current sampling circuit: used to convert the characteristic current signal generated in the fault detection process of step S57 into a voltage signal that can be recognized by the system;

[0089] S59, Σ-Δ sampler and demodulator: convert the voltage signal output in step S58 into a digital signal for subsequent program processing;

[0090] S510, determine whether there is a fault currently: if there is no fault, enter the fault detection end state; if there is a fault, enter step S511;

[0091] S511, post-fault processing: complete the functions of realizing rapid protection and reporting faults when a fault is detected.

[0092] The specific control process of the step S56 PWM wave generating module is as follows:

[0093] S31, whether to enable relative housing ground fault detection;

[0094] S32, if the system enables the relative housing ground fault detection function, then the fault detection state machine is entered to start the fault detection related tasks;

[0095] S33, firstly, perform fault detection on the test phase U, and output corresponding PWM to the three-phase bridge drive module 3 to turn on the upper tube of the U phase and turn off the lower bridge to charge the Y capacitor. The minimum conduction time is T Hmin , the maximum is t Hmax ;

[0096] S34, obtaining fault information in real time through the fault detection and protection module 5;

[0097] S35: If a fault exists, immediately proceed to step S38;

[0098] S36: If it is determined that there is no fault at present, proceed to step S37

[0099] S37, output PWM to turn off the upper bridge of U phase and turn on the lower bridge to discharge the Y capacitor, and then turn on the lower bridge arm

[0100] The time constant is greater than 5 times that of the short-circuit model. When the capacitor is discharged, it is considered that the discharge has basically been completed. After the discharge is completed, the same test task can be performed on the V phase;

[0101] S38, post-fault processing related tasks;

[0102] S39. If it is determined that there is no fault in the entire test process, the PWM wave generating module turns off the PWM output and exits the fault detection state machine.

[0103] The specific control process of the three-phase bridge drive module in step S57 is as follows:

[0104] S41, when the fault detection and protection module 5 detects that the system has entered the fault detection state machine, it immediately starts the U and V phase current sampling and fault identification functions, and repeats this step if no detection is made;

[0105] S42, if the collected phase current exceeds the fault detection threshold I min , then the next step;

[0106] S43, executing PWM sealing protection action;

[0107] S44, setting a fault flag of the motor relative to the housing to inform the PWM generating module of the fault.

[0108] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A motor-to-housing short circuit detection system based on a capacitor charge and discharge model, including a system SOC control chip, characterized in that: Also includes: A Y capacitor charge and discharge model calculation module (1) constructs three different short-circuit models relative to the chassis ground, and calculates the corresponding key parameters of the capacitor charge and discharge current peak value, peak time, discharge time, and resonant frequency for each model; The PWM wave generating module (2) uses the Y capacitor charge and discharge model calculation module to obtain the charge and discharge current peak value, the charge and discharge current peak time, and the upper bridge test conduction time to respectively obtain the fault detection current threshold, the upper bridge test conduction time of the test phase during the fault detection process, and the lower bridge discharge conduction time during the fault detection process; The three-phase bridge driving module (3) completes the conduction of the power switch device corresponding to the three-phase bridge according to the control signal output by the PWM wave generating module (2), and completes the charging and discharging process of the Y capacitor; A current sampling module (4) collects the U-phase current and V-phase current of the motor in the three-phase bridge drive module (3) in real time during the fault detection process; The fault detection and protection module (5) uses the FPGA logic resources in the system SOC control chip to realize fault detection.

2. The motor-to-casing short circuit detection system based on the capacitor charge-discharge model according to claim 1 is characterized in that: The Y capacitor charge and discharge model calculation module includes a short circuit model component for constructing three Y capacitor charge and discharge models and a key parameter calculation component for realizing the calculation of short circuit protection parameters.

3. The motor-to-casing short circuit detection system based on the capacitor charge-discharge model according to claim 1, characterized in that: The Y capacitor charge and discharge model operation module (1) is divided into the test phase short-circuited to the chassis ground, the other two phases except the test phase are short-circuited to the chassis ground, and one of the other two phases except the test phase is short-circuited to the chassis ground.

4. The motor-to-casing short circuit detection system based on a capacitor charge-discharge model according to claim 1, characterized in that: The PWM wave generating module (2) comprises a PWM initialization component for initializing the switching frequency, duty cycle and properties of the fault detection switch of the PWM, a PWM state machine controller for controlling the switching timing of the PWM function, and a PWM key parameter operator for calculating the conduction time of the three-phase bridge arm and the fault protection threshold.

5. The motor-to-casing short circuit detection system based on a capacitor charge-discharge model according to claim 1, characterized in that: The three-phase bridge drive module (3) comprises a PWM drive unit that converts the control signal sent by the PWM wave generating module (2) into a drive signal that can control the on and off of the power device of the three-phase bridge component, and a three-phase bridge component that completes the short-circuit test step relative to the casing required by the system through the on and off drive signals of the three-phase bridge power device obtained by the PWM drive unit.

6. The motor-to-casing short circuit detection system based on a capacitor charge-discharge model according to claim 1, characterized in that: The current sampling module (4) comprises a high-precision sampling resistor for converting a current signal into a voltage signal, a sampling voltage conditioner for adjusting the voltage signal to a desired range, a Σ-Δ sampler for converting the voltage signal into a digital signal, and a Σ-Δ demodulator for converting the digital signal into a digital voltage signal recognizable by an ARM.

7. The motor-to-casing short circuit detection system based on a capacitor charge-discharge model according to claim 1, characterized in that: The fault detection and protection module (5) comprises a fault detection state machine for controlling the detection timing of a short-circuit fault relative to the housing, and a functional fault post-processing component for implementing rapid protection and reporting the fault when a fault is detected.

8. A detection method for a motor-to-casing short circuit detection system based on a capacitor charge-discharge model according to any one of claims 1 to 7, characterized in that: The specific steps are as follows: S51, Y capacitor charge and discharge model construction: construct a Y capacitor charge and discharge model based on three relative chassis ground short circuit conditions; S52, short-circuit model key parameter calculation: According to the model constructed in step S51, the motor impedance parameters, the power switch device impedance parameters and the Y capacitor parameters are combined to calculate the key parameters of the Y capacitor charge and discharge current peak value, peak time, discharge time and resonant frequency corresponding to the model; S53, PWM initialization component: initializing the switching frequency, duty cycle, and properties of the fault detection switch of the PWM to facilitate subsequent fault detection; S54, PWM state machine control: used to control the PWM state machine to determine whether to enable the relative housing ground fault detection function. If the fault detection is enabled, proceed to the next step. If the fault detection is not enabled, directly enter the end state. S55, PWM key parameter calculation: using the charge and discharge current peak value obtained in step S52, the fault detection current threshold can be calculated, and the upper bridge test conduction time of the test phase during the fault detection process can be calculated using the obtained charge and discharge current peak time, and the lower bridge discharge conduction time during the fault detection process can be calculated using the Y capacitor discharge time obtained in step S52; S56, PWM wave generating module (2): converting the control logic signal obtained in step S55 into a driving signal that can drive the power switch device to turn on and off; S57, three-phase bridge driving module (3): receiving the driving signal of step S56, and completing the short-circuit fault detection step relative to the casing ground required by the system by controlling the opening and closing actions of the three-phase bridge power device; S58, current sampling circuit: used to convert the characteristic current signal generated in the fault detection process of step S57 into a voltage signal that can be recognized by the system; S59, Σ-Δ sampler and demodulator: convert the voltage signal output in step S58 into a digital signal for subsequent program processing; S510, determine whether there is a fault currently: if there is no fault, enter the fault detection end state; if there is a fault, enter step S511; S511, post-fault processing: complete the functions of realizing rapid protection and reporting faults when a fault is detected.

9. The detection method of the motor-to-casing short circuit detection system based on the capacitor charge-discharge model according to claim 8, characterized in that: The specific control process of the PWM wave generating module in step S56 is as follows: S31, whether to enable relative housing ground fault detection; S32, if the system enables the relative housing ground fault detection function, then the fault detection state machine is entered to start the fault detection related tasks; S33, firstly, perform fault detection on the test phase U, and output corresponding PWM to the three-phase bridge drive module (3) to turn on the upper tube of the U phase and turn off the lower bridge to charge the Y capacitor. The minimum conduction time is T Hmin , the maximum is t Hmax ; S34, obtaining fault information in real time through the fault detection and protection module (5); S35: If a fault exists, immediately proceed to step S38; S36, if it is determined that there is no fault currently, proceed to step S37; S37, output PWM to turn off the upper bridge of the U phase and turn on the lower bridge to discharge the Y capacitor. To ensure reliable discharge, the discharge time is five times the time constant of the Y capacitor short-circuit model. After the discharge is completed, the same test task can be performed on the V phase; S38, post-fault processing related tasks; S39. If it is determined that there is no fault in the entire test process, the PWM wave generating module turns off the PWM output and exits the fault detection state machine.

10. The detection method of the motor-to-casing short circuit detection system based on the capacitor charge-discharge model according to claim 8, characterized in that: The specific control process of the three-phase bridge drive module in step S57 is as follows: S41, when the fault detection and protection module (5) detects that the system has entered the fault detection state machine, it immediately starts the U and V phase current sampling and fault identification functions, and repeats this step if no fault is detected; S42, if the collected phase current exceeds the fault detection threshold I min , then the next step; S43, executing PWM tube sealing protection action; S44, setting a fault flag of the motor relative to the housing to inform the PWM generating module of the fault.

Images