Fault-tolerant modulation method and system for three-level hybrid ANPC inverter

Abstract

The invention provides a fault-tolerant modulation method and system for a three-level hybrid ANPC inverter, and belongs to the field of three-level hybrid ANPC inverters, and the method comprises the steps: constructing a residual life prediction model of a power switch device and a DC side capacitor; constructing a life factor based on the residual life of the power switch device and the DC side capacitor; sVPWM-FT or DPWM-FT is selected for modulation according to the life factor; a fault-tolerant mode is selected by considering the residual life of a power switch device and a direct current side capacitor, a DPWM-FT with smaller switch loss is selected for modulation when the fatigue damage of the Si-IGBT is serious, an SVPWM-FT with smaller ripple current is selected for modulation when the fatigue damage of the direct current side capacitor is serious, the advantages of the two modulation modes are brought into full play, and the reliability of the system is improved. The switching loss is reduced to a certain extent, the system maintenance burden is reduced, and the reliability of the three-level hybrid ANPC inverter system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of three-level hybrid ANPC inverters, and in particular to a fault-tolerant modulation method and system for a three-level hybrid ANPC inverter. Background Art

[0002] As my country's energy structure shifts from fossil energy to new energy, three-level inverters are being widely used in photovoltaic power generation, wind power generation and electric vehicle charging systems. Traditional three-level inverters are composed of Si-IGBT and diodes. This structure easily causes unbalanced loss problems in power semiconductor switching devices, which in turn leads to increased temperature of the switching devices and reduced system reliability. In order to solve this problem, a three-level hybrid active terminal clamped (ANPC) inverter is proposed. The three-level hybrid active ANPC inverter consists of two power switching devices, Si-IGBT and SiC-MOSFET. Because the electron mobility of SiC devices is higher than that of Si devices and has better high-frequency characteristics, in many proposed ANPC modulation strategies, Si-IGBT is modulated at the base frequency and SiC-MOSFET is modulated at the switching frequency.

[0003] Although the three-level hybrid ANPC inverter has advantages in efficiency and power density, the possibility of failure is higher with the increase of power switching devices, and the reliability of the system is reduced. Power switch failures are divided into two types: short circuit failure and open circuit failure. Short circuit failure is caused by the failure of the switching device in the circuit to shut down normally, which will cause a sharp increase in current and may cause damage to the electrical system. Therefore, when a short circuit failure occurs, the machine must be shut down immediately. Open circuit failure is caused by the failure of the switching device in the circuit to close normally. Fault-tolerant control is a countermeasure designed for open circuit failure. Power switching devices are the main factor in improving system reliability. When an open circuit failure occurs in a switching device, the distorted current will increase the power loss of the device and reduce the life of the remaining switching devices. In addition, electrolytic capacitors, as the DC part of the inverter, are also the main factor in improving system reliability. According to the survey, 60%-72% of power failures are caused by the breakdown of electrolytic capacitors. The current ripple on the DC side will increase the power loss and thermal stress of the capacitor, resulting in a shortened life of the capacitor. Summary of the invention

[0004] The technical problem to be solved by the present invention is how to improve the reliability of a three-level hybrid ANPC inverter system.

[0005] The present invention solves the above technical problems through the following technical solutions: a fault-tolerant modulation method of a three-level hybrid ANPC inverter, comprising:

[0006] Step 1: Construct a remaining life prediction model for power switching devices and DC side capacitors;

[0007] Step 2: constructing a life factor based on the remaining life of the power switch device and the DC side capacitor;

[0008] Step 3: Select SVPWM-FT or DPWM-FT for modulation according to the life factor.

[0009] Preferably, in the step one, a remaining life prediction model of the power switching device is constructed with the help of Miner rules, and a remaining life prediction model of the DC side capacitor is constructed with the help of power loss.

[0010] Preferably, the calculation method of constructing the remaining life prediction model of the power switch device by using the Miner rule is:

[0011] 1.1.1. Calculate the life loss LC of the power switching device Si-IGBT by formula (1):

[0012]

[0013] In formula (1), n i N is the number of load cycles actually completed by the power switching device Si-IGBT under a certain thermal stress level, fi N is the maximum number of cycles that the power switching device Si-IGBT can withstand under test conditions at the same stress level. fi Calculated by formula (2):

[0014]

[0015] In formula (2), ΔT j is the junction temperature variation, V C I is the voltage that the capacitor withstands, B is the rated current of the capacitor, T j,min is the lower limit of capacitance temperature, β1, β2, β3, β4, β5, and β6 are all correlation coefficients;

[0016] 1.1.2. Calculate the remaining life L of the power switching device Si-IGBT by formula (3): IGBT :

[0017] L IGBT =L IGBT(Rated) -LC (3)

[0018] In formula (3), L IGBT(Rated) is the rated life of the power switching device Si-IGBT.

[0019] Preferably, the calculation method of constructing the remaining life prediction model of the DC side capacitor by means of power loss is:

[0020] 1.2.1. Calculate the power loss P of the DC side capacitor using formula (4): loss :

[0021]

[0022] In formula (4), ESR is the equivalent resistance of the DC side capacitor, I cap is the DC side capacitor current, f i is the frequency band of the fast Fourier transform analysis result;

[0023] 1.2.2. Calculate the hot spot temperature T of the DC side capacitor using formula (5): h :

[0024] T h =T a +R ha ·P loss (5)

[0025] In formula (5), T a is the ambient temperature, R ha Indicates heat resistance;

[0026] 1.2.3. Calculate the remaining life L of the DC side capacitor using formula (6): cap :

[0027]

[0028] In formula (6), L0 is the rated life of the DC side capacitor, T0 is the rated temperature of the DC side capacitor, K v is the voltage factor, which is calculated by formula (7):

[0029]

[0030] In formula (7), U A is the working voltage of the DC side capacitor, U R is the rated voltage of the DC side capacitor.

[0031] Preferably, in step 2, the life factor f of the power switch device is constructed IGBT The calculation method is:

[0032]

[0033] Preferably, in step 2, the life factor f of the DC side capacitor is constructed Cap The calculation method is:

[0034] Among them, L Cap(Rated) is the rated life of the DC side capacitor, L Cap(Rated) =L0.

[0035] Preferably, in step 3, when the switch tube S is monitored x2 Or switch tube S x3 When an open circuit failure occurs, compare the life factor f of the power switch device IGBT and the life factor f of the DC side capacitor Cap , if the life factor of the power switch device is IGBT >Life factor f of DC side capacitor Cap , select SVPWM-FT for modulation, if the life factor of the power switching device is f IGBT <Life factor f of DC side capacitor Cap , select DPWM-FT for modulation.

[0036] Preferably, the SVPWM-FT is established as follows: Assuming that the switch tube S x2 When an open circuit fault occurs, in the positive half cycle of the reference pole voltage, the power switch device SiC-MOSFET and the power switch device Si-IGBT still work at the switching frequency and base frequency respectively as in the normal state, and the modulation voltage v′ of the power switch device Si-IGBT xn(IGBT) and the modulation voltage v′ of the power switching device SiC-MOSFET xn(MOSFET) It is expressed as follows:

[0037]

[0038] v′ xn(MOSFET) =v′ xn -v′ xn(IGBT) (9)

[0039] Among them, v′ xn is the reference pole voltage, V dc is the DC side capacitor voltage;

[0040] In the negative half cycle of the reference pole voltage, due to O - The state cannot be generated, so use O + The state is replaced. At this time, the power switching device SiC-MOSFET works at the base frequency, the power switching device Si-IGBT works at the switching frequency, and the modulation voltage v′ of the power switching device SiC-MOSFET xn(MOSFET) and the modulation voltage v′ of the power switching device Si-IGBT xn(IGBT) It is expressed as follows:

[0041]

[0042] v′ xn(IGBT) =v′ xn -v′ xn(MOSFET) (11)

[0043] The modulation voltage and the carrier are compared to obtain the PWM wave of the power switching devices SiC-MOSFET and Si-IGBT.

[0044] Preferably, the DPWM-FT is established by compensating the reference pole voltage, the compensation voltage v sn Calculated by formula (12):

[0045]

[0046] In formula (12), V max 、V min are the maximum phase reference pole voltage and the minimum phase reference pole voltage respectively, and the compensation voltage v sn The three-phase pole voltage is injected to obtain a new reference pole voltage, and then the modulation voltage of the power switching device Si-IGBT and the modulation voltage of the power switching device SiC-MOSFET are calculated according to the establishment method of SVPWM-FT. The modulation voltage and the carrier are compared to obtain the PWM wave of the power switching device SiC-MOSFET and Si-IGBT.

[0047] The present invention also provides a fault-tolerant modulation system for a three-level hybrid ANPC inverter, comprising:

[0048] A remaining life prediction model building module is used to build a remaining life prediction model for power switching devices and DC side capacitors;

[0049] A life factor building module, used to build a life factor based on the remaining life of the power switch device and the DC side capacitor;

[0050] The fault-tolerant modulation module is used to select SVPWM-FT or DPWM-FT for modulation according to the life factor.

[0051] The advantages provided by the present invention are:

[0052] The present invention makes full use of the advantages of SVPWM-FT and DPWM-FT, selects a fault-tolerant mode by considering the remaining life of a power switch device and a DC side capacitor, establishes a life prediction model of the Si-IGBT and the DC side capacitor when an open-circuit fault occurs in a certain Si-IGBT of the three-level hybrid ANPC inverter, establishes a life factor by using the ratio of the remaining life to the rated life to characterize the fatigue damage degree of the device, selects SVPWM-FT or DPWM-FT according to the life factor, selects DPWM-FT with smaller switching loss for modulation when the Si-IGBT is severely fatigued, and selects SVPWM-FT with smaller ripple current for modulation when the DC side capacitor is severely fatigued, and gives full play to the advantages of the two modulation modes, reduces the switching loss to a certain extent, reduces the system maintenance burden, and improves the reliability of the three-level hybrid ANPC inverter system. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 A circuit diagram of a three-level hybrid ANPC inverter in a fault-tolerant modulation method of a three-level hybrid ANPC inverter provided by an embodiment of the present invention;

[0054] Figure 2 A schematic diagram of four switching states of a three-level hybrid ANPC inverter in a fault-tolerant modulation method of a three-level hybrid ANPC inverter provided by an embodiment of the present invention;

[0055] Figure 3 A flow chart of a fault-tolerant modulation method for a three-level hybrid ANPC inverter provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the technical solution of the present invention is clearly and completely described below in combination with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] This embodiment provides a fault-tolerant modulation method for a three-level hybrid ANPC inverter, including:

[0058] Step 1: Construct a remaining life prediction model for power switching devices and DC side capacitors;

[0059] In the step 1, a remaining life prediction model of the power switch device is constructed with the help of Miner rules, and a remaining life prediction model of the DC side capacitor is constructed with the help of power loss.

[0060] Among them, the calculation method of constructing the remaining life prediction model of power switching devices with the help of Miner rules is:

[0061] 1.1.1. Calculate the life loss LC of the power switching device Si-IGBT by formula (1):

[0062]

[0063] In formula (1), n i N is the number of load cycles actually completed by the power switching device Si-IGBT under a certain thermal stress level, fi N is the maximum number of cycles that the power switching device Si-IGBT can withstand under test conditions at the same stress level. fi Calculated by formula (2):

[0064]

[0065] In formula (2), ΔT j V is the junction temperature variation amplitude, that is, the periodic variation amplitude of the junction temperature of the IGBT as the device is turned on and off, and is positively correlated with the power loss of the device. C I is the voltage that the capacitor withstands, B is the rated current of the capacitor, T j,min is the lower limit of the capacitance temperature; β1, β2, β3, β4, β5, and β6 are all correlation coefficients. The remaining parameters and device models are determined according to the manual data. Please refer to the data manual. LC and the remaining life of the device are negatively correlated. When LC = 1, that is, the actual number of cycles is equal to the maximum number of cycles, it means that the power switching device Si-IGBT has accumulated fatigue failure and the remaining life is 0.

[0066] 1.1.2. Calculate the remaining life L of the power switching device Si-IGBT by formula (3): IGBT :

[0067] L IGBT =L IGBT(Rated) -LC (3)

[0068] In formula (3), L IGBT(Rated) is the rated life of the power switching device Si-IGBT.

[0069] The calculation method for building the remaining life prediction model of the DC side capacitor with the help of power loss is:

[0070] 1.2.1. Calculate the power loss P of the DC side capacitor using formula (4): loss :

[0071]

[0072] In formula (4), ESR is the equivalent resistance of the DC side capacitor, and its value is affected by the harmonic components of the capacitor current. cap is the DC side capacitor current, f i is the frequency band of the fast Fourier transform analysis result;

[0073] 1.2.2. Calculate the hot spot temperature T of the DC side capacitor using formula (5): h :

[0074] T h =T a +R ha ·P loss (5)

[0075] In formula (5), T a is the ambient temperature, R ha Indicates heat resistance and can be obtained from the data sheet.

[0076] 1.2.3. Calculate the remaining life L of the DC side capacitor using formula (6): cap :

[0077]

[0078] In formula (6), L0 = L Cap(Rated) K is the rated life of the DC side capacitor, which is determined according to the manual. T0 is the rated temperature of the DC side capacitor. L0 and T0 can be obtained from the data sheet. v is the voltage factor, which is calculated by formula (7):

[0079]

[0080] In formula (7), U A is the working voltage of the DC side capacitor, U R is the rated voltage of the DC side capacitor, and k is determined by the ratio of the two.

[0081] Step 2: Construct a life factor based on the remaining life of the power switch device and the DC side capacitor; Construct a life factor f of the power switch device IGBT The calculation method is:

[0082]

[0083] Construct the life factor f of the DC link capacitor Cap The calculation method is:

[0084] Among them, L Cap(Rated) is the rated life of the DC side capacitor.

[0085] Step 3: Select SVPWM-FT or DPWM-FT for modulation according to the life factor.

[0086] First monitor the device status. If S x2 and S x3 All are working normally, and the system is operating normally; when the switch tube S is monitored x2 Or switch tube S x3 When an open circuit failure occurs, compare the life factor f of the power switch device IGBT and the life factor f of the DC side capacitor Cap , if the life factor of the power switch device is IGBT >Life factor f of DC side capacitor Cap , select SVPWM-FT for modulation, if the life factor of the power switching device is f IGBT <Life factor f of DC side capacitor Cap , select DPWM-FT for modulation.

[0087] Among them, the establishment method of SVPWM-FT is: Assume that the switch tube S x2 When an open circuit fault occurs, in the positive half cycle of the reference pole voltage, the power switch device SiC-MOSFET and the power switch device Si-IGBT still work at the switching frequency and base frequency respectively as in the normal state, and the modulation voltage v′ of the power switch device Si-IGBT xn(IGBT) and the modulation voltage v′ of the power switching device SiC-MOSFET xn(MOSFET) It is expressed as follows:

[0088]

[0089] v′ xn(MOSFET) =v′ xn -v′ xn(IGBT) (9)

[0090] Among them, v′ xn is the reference pole voltage, V dc is the DC side capacitor voltage;

[0091] In the negative half cycle of the reference pole voltage, due to O - The state cannot be generated, so use O + The state is replaced. At this time, the power switching device SiC-MOSFET works at the base frequency, the power switching device Si-IGBT works at the switching frequency, and the modulation voltage v′ of the power switching device SiC-MOSFET xn(MOSFET) and the modulation voltage v′ of the power switching device Si-IGBT xn(IGBT) It is expressed as follows:

[0092]

[0093] v′ xn(IGBT) =v′ xn -v′ xn(MOSFET) (11)

[0094] The modulation voltage and the carrier are compared to obtain the PWM wave of the power switching devices SiC-MOSFET and Si-IGBT.

[0095] The DPWM-FT is established by compensating the reference pole voltage, the compensation voltage v sn Calculated by formula (12):

[0096]

[0097] In formula (12), V max 、V min are the maximum phase reference pole voltage and the minimum phase reference pole voltage respectively, and the compensation voltage v sn The three-phase pole voltage is injected to obtain a new reference pole voltage, and then the modulation voltage of the power switching device Si-IGBT and the modulation voltage of the power switching device SiC-MOSFET are calculated according to the establishment method of SVPWM-FT. The modulation voltage and the carrier are compared to obtain the PWM wave of the power switching device SiC-MOSFET and Si-IGBT.

[0098] Working principle: Figure 1 As shown in the figure, the x-phase (x=a, b, c) of the three-level hybrid ANPC inverter consists of four power switching devices Si-IGBT (S x1 , S x2 , S x3 , S x4 ) and two power switching devices SiC-MOSFET (Q x1 , Q x2 ) is composed of four working states (P, O) according to the on or off operation of the power switching devices Si-IGBT and SiC-MOSFET. + , O - and N), such as Figure 2 As shown, under normal conditions, the power switching device Si-IGBT works at the base frequency, and the power switching device SiC-MOSFET works at the switching frequency. The specific working process is as follows:

[0099] First, the modulation voltage v′ of the power switching device Si-IGBT is obtained according to the following formulas: xn(IGBT) and the modulation voltage v′ of the power switching device SiC-MOSFET xn(MOSFET) :

[0100]

[0101] v′ xn(MOSFET) =v′ xn -v′ xn(IGBT)

[0102] Among them, v′ xn is the reference pole voltage, V dc is the DC side capacitor voltage, then the modulation voltage and the carrier are compared, and finally the PWM wave of the power switching devices SiC-MOSFET and Si-IGBT is obtained.

[0103] The three-level hybrid ANPC inverter has four switching states. Figure 2 , it is found that when the switch tube S x2 Or switch tube S x3 When an open circuit fault occurs in the inverter, the P state and the N state are still available, which means that within the full modulation range, the ANPC inverter has a certain fault tolerance capability. The specific modulation process is described in the following example. Assume that S x2 When an open circuit fault occurs, in the positive half cycle of the reference pole voltage, the power switching devices SiC-MOSFET and Si-IGBT still operate at the switching frequency and base frequency respectively as in the normal state; in the negative half cycle, such as Figure 2 As shown, due to O - The state cannot be generated, so O is needed + The state is replaced, at this time the power switching device SiC-MOSFET works at the base frequency, and the power switching device Si-IGBT works at the switching frequency.

[0104] In the switch tube S x2 Or switch tube S x3 When an open circuit fault occurs, the use of SVPWM-FT can improve system reliability. However, as the operating frequency of the power switching device Si-IGBT increases significantly, it will produce higher switching losses, thereby accelerating the aging of the device. In order to reduce the switching loss, a new DPWM-FT fault-tolerant modulation method suitable for open circuit faults is proposed. The specific working process is as follows: First, the reference pole voltage is compensated, and the compensation voltage v sn Calculated by the following formula:

[0105]

[0106] Among them, V max 、V min They are the maximum phase reference pole voltage and the minimum phase reference pole voltage respectively. After the compensation voltage is injected into the three-phase pole voltage, the new reference pole voltage v′ is obtained. xn, then calculate the modulation voltage of the two switching tubes, and then compare them with the carrier respectively to generate PWM wave.

[0107] The present invention considers the life of power switch devices and DC side capacitors when performing fault-tolerant modulation on the three-level hybrid ANPC inverter. When a switch open circuit fault occurs, the SVPWM-FT method can be applied, which makes the power switch device Si-IGBT work at a high switching frequency. Therefore, the switching loss of these devices increases significantly. In order to reduce the switching loss, the DPWM-FT method is proposed. However, the DPWM-FT method increases the power loss of the DC side capacitor and reduces its life. The present invention makes full use of the advantages of SVPWM-FT and DPWM-FT, selects a fault-tolerant mode by considering the remaining life of a power switch device and a DC side capacitor, establishes a life prediction model of the Si-IGBT and the DC side capacitor when an open-circuit fault occurs in a certain Si-IGBT of the three-level hybrid ANPC inverter, establishes a life factor by using the ratio of the remaining life to the rated life to characterize the fatigue damage degree of the device, selects SVPWM-FT or DPWM-FT according to the life factor, selects DPWM-FT with smaller switching loss for modulation when the Si-IGBT is severely fatigued, and selects SVPWM-FT with smaller ripple current for modulation when the DC side capacitor is severely fatigued, and gives full play to the advantages of the two modulation modes, reduces the switching loss to a certain extent, reduces the system maintenance burden, and improves the reliability of the three-level hybrid ANPC inverter system.

[0108] The present invention also provides a fault-tolerant modulation system for a three-level hybrid ANPC inverter, comprising:

[0109] A remaining life prediction model building module is used to build a remaining life prediction model for power switching devices and DC side capacitors;

[0110] A life factor building module, used to build a life factor based on the remaining life of the power switch device and the DC side capacitor;

[0111] The fault-tolerant modulation module is used to select SVPWM-FT or DPWM-FT for modulation according to the life factor.

[0112] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fault-tolerant modulation method for a three-level hybrid ANPC inverter, characterized in that: include: Step 1: Construct a remaining life prediction model for power switching devices and DC side capacitors; Step 2: constructing a life factor based on the remaining life of the power switch device and the DC side capacitor; Step 3: Select SVPWM-FT or DPWM-FT for modulation according to the life factor.

2. The fault-tolerant modulation method of the three-level hybrid ANPC inverter according to claim 1, characterized in that: In the step 1, a remaining life prediction model of the power switch device is constructed with the help of Miner rules, and a remaining life prediction model of the DC side capacitor is constructed with the help of power loss.

3. The fault-tolerant modulation method of the three-level hybrid ANPC inverter according to claim 1, characterized in that: The calculation method of constructing the remaining life prediction model of the power switch device by using the Miner rule is: 1.1.

1. Calculate the life loss LC of the power switching device Si-IGBT by formula (1): In formula (1), n i N is the number of load cycles actually completed by the power switching device Si-IGBT under a certain thermal stress level, fi N is the maximum number of cycles that the power switching device Si-IGBT can withstand under test conditions at the same stress level. fi Calculated by formula (2): In formula (2), ΔT j is the junction temperature variation, V C I is the voltage that the capacitor withstands, B is the rated current of the capacitor, T j,min is the lower limit of capacitance temperature, β1, β2, β3, β4, β5, and β6 are all correlation coefficients; 1.1.

2. Calculate the remaining life L of the power switching device Si-IGBT by formula (3): IGBT : L IGBT =L IGBT(Rated) -LC (3) In formula (3), L IGBT(Rated) is the rated life of the power switching device Si-IGBT.

4. The fault-tolerant modulation method of the three-level hybrid ANPC inverter according to claim 1, characterized in that: the calculation method of constructing the remaining life prediction model of the DC side capacitor by means of power loss is: 1.2.

1. Calculate the power loss P of the DC side capacitor using formula (4): loss : In formula (4), ESR is the equivalent resistance of the DC side capacitor, I cap is the DC side capacitor current, f i is the frequency band of the fast Fourier transform analysis result; 1.2.

2. Calculate the hot spot temperature T of the DC side capacitor using formula (5): h : T h =T a +R ha ·P loss (5) In formula (5), T a is the ambient temperature, R ha Indicates heat resistance; 1.2.

3. Calculate the remaining life L of the DC side capacitor using formula (6): cap : In formula (6), L0 is the rated life of the DC side capacitor, T0 is the rated temperature of the DC side capacitor, K v is the voltage factor, which is calculated by formula (7): K V =(U A / IN R )-k, In formula (7), U A is the working voltage of the DC side capacitor, U R is the rated voltage of the DC side capacitor.

5. The fault-tolerant modulation method of the three-level hybrid ANPC inverter according to claim 3, characterized in that: The life factor f of the power switch device constructed in step 2 IGBT The calculation method is:

6. The fault-tolerant modulation method of the three-level hybrid ANPC inverter according to claim 4, characterized in that: The life factor f of the DC side capacitor constructed in step 2 Cap The calculation method is: Among them, L Cap(Rated) is the rated life of the DC side capacitor, L Cap(Rated) =L0.

7. The fault-tolerant modulation method of the three-level hybrid ANPC inverter according to claim 1, characterized in that: In step 3, when the switch tube S is detected x2 Or switch tube S x3 When an open circuit failure occurs, compare the life factor f of the power switch device IGBT and the life factor f of the DC side capacitor Cap , if the life factor of the power switch device is IGBT >Life factor f of DC side capacitor Cap , select SVPWM-FT for modulation, if the life factor of the power switching device is f IGBT <Life factor f of DC side capacitor Cap , select DPWM-FT for modulation.

8. The fault-tolerant modulation method of the three-level hybrid ANPC inverter according to claim 7, characterized in that: The SVPWM-FT is established as follows: Assuming that the switch tube S x2 When an open circuit fault occurs, in the positive half cycle of the reference pole voltage, the power switch device SiC-MOSFET and the power switch device Si-IGBT still work at the switching frequency and base frequency respectively as in the normal state, and the modulation voltage v′ of the power switch device Si-IGBT xn(IGBT) and the modulation voltage v′ of the power switching device SiC-MOSFET xn(MOSFET) It is expressed as follows: v′ xn(MOSFET) =v′ xn -v′ xn(IGBT) (9) Among them, v′ xn is the reference pole voltage, V dc is the DC side capacitor voltage; In the negative half cycle of the reference pole voltage, due to O - The state cannot be generated, so use O + The state is replaced. At this time, the power switching device SiC-MOSFET works at the base frequency, the power switching device Si-IGBT works at the switching frequency, and the modulation voltage v′ of the power switching device SiC-MOSFET xn(MOSFET) and the modulation voltage v′ of the power switching device Si-IGBT xn(IGBT) It is expressed as follows: v′ xn(IGBT) =v′ xn -v′ xn(MOSFET) (11) The modulation voltage and the carrier are compared to obtain the PWM wave of the power switching devices SiC-MOSFET and Si-IGBT.

9. The fault-tolerant modulation method of the three-level hybrid ANPC inverter according to claim 8, characterized in that: The DPWM-FT is established by compensating the reference pole voltage, the compensation voltage v sn Calculated by formula (12): In formula (12), V max 、V min are the maximum phase reference pole voltage and the minimum phase reference pole voltage respectively, and the compensation voltage v sn The three-phase pole voltage is injected to obtain a new reference pole voltage, and then the modulation voltage of the power switching device Si-IGBT and the modulation voltage of the power switching device SiC-MOSFET are calculated according to the establishment method of SVPWM-FT. The modulation voltage and the carrier are compared to obtain the PWM wave of the power switching device SiC-MOSFET and Si-IGBT.

10. A fault-tolerant modulation system for a three-level hybrid ANPC inverter, characterized in that: include: A remaining life prediction model building module is used to build a remaining life prediction model for power switching devices and DC side capacitors; A life factor building module, used to build a life factor based on the remaining life of the power switch device and the DC side capacitor; The fault-tolerant modulation module is used to select SVPWM-FT or DPWM-FT for modulation according to the life factor.

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