Inverter power unit and control method thereof

Abstract

The invention discloses an inverter power unit and a control method thereof. The power unit comprises an upper bridge, the upper bridge comprises a first IGBT module and a first S C module which are connected in parallel, and a collector electrode of the first IGBT module and a drain electrode of the first S C module are connected and then connected to a positive electrode of a direct current bus; the emitting electrode of the first IGBT module is connected with the source electrode of the first Si C module and then is connected with a phase output end; the lower bridge comprises a second I-GBT module and a second S-C module which are connected in parallel, and a collector electrode of the second I-GBT module is connected with a drain electrode of the second S-C module and then connected with a phase output end; and the emitter of the second I-GBT module is connected with the source of the second S-C module and then is connected with the cathode of the direct-current bus. The above technical scheme has the characteristics of high power density and high efficiency, can effectively reduce the working loss of the power unit in a small current time region, effectively balances the loss of the IGBT and the S C in a large current time region, and achieves the maximum output current capability.

Description

Technical Field

[0001] The present invention relates to the technical field of inverters, and in particular to an inverter power unit and a control method thereof. Background Art

[0002] New energy motor control drive units need to use power semiconductors to convert high-voltage DC in the power battery into three-phase AC or convert three-phase AC into high-voltage DC to achieve motor control and power generation. Power semiconductors such as inverters are energy conversion modules, and their losses will directly affect the conversion efficiency of the control unit. To improve the efficiency of the control unit, the current mainstream approach is to upgrade IGBT (insulated gate bipolar transistor) to SiC (silicon carbide) modules. However, the cost of SiC is higher than that of IGBT, which directly affects the cost of the control unit.

[0003] In order to reduce the cost of using SiC and ensure that the conversion efficiency of the control unit will not drop too much, the industry has proposed the concept of hybrid (Si (silicon) and SiC hybrid) modules, such as Figure 7 As shown, the IGBT / SiC / FRD (fast recovery diode) ratio is designed according to the demand. Through the appropriate PWM (pulse width modulation) control timing, the amount of SiC can be reduced and the cost can be reduced.

[0004] At present, the hybrid solutions in mass production on the market mainly use SiC-FRD (FRD, fast recovery diode) to replace Si-FRD to reduce the turn-on loss of IGBT modules. Compared with pure SiC modules, the loss reduction is limited; hybrid drive generally adopts a single drive, that is, SiC and IGBT use the same opening and closing timing. There is a gap between the loss of hybrid modules and pure SiC modules, especially the high-voltage 800V module. The loss caused by Si-FRD reverse recovery accounts for a large proportion, and the efficiency of the control drive unit CLTC (China Passenger Car Operating Condition Test, domestic endurance standard) is quite different from that of pure SiC. Summary of the invention

[0005] The embodiment of the present invention provides an inverter power unit and a control method thereof to solve the problems of large power unit loss, single driving mode and low comprehensive endurance efficiency in the existing power unit.

[0006] An inverter power unit provided according to an embodiment of one aspect of the present invention includes:

[0007] An upper bridge, the upper bridge comprising a first IGBT module and a first SiC module connected in parallel, the collector of the first IGBT module is connected to the drain of the first SiC module and then connected to the positive pole of the DC bus; the emitter of the first IGBT module is connected to the source of the first SiC module and then connected to the phase output end;

[0008] The lower bridge comprises a second IGBT module and a second SiC module connected in parallel, the collector of the second IGBT module is connected to the drain of the second SiC module and then connected to the phase output end; the emitter of the second IGBT module is connected to the source of the second SiC module and then connected to the negative pole of the DC bus.

[0009] In some embodiments, the inverter power unit further includes a PWM control unit, and the gate of the first IGBT module and the gate of the first SiC module are respectively connected to an upper bridge control signal output port of the PWM control unit;

[0010] The gate of the second IGBT module and the gate of the second SiC module are respectively connected to the lower bridge control signal output port of the PWM control unit.

[0011] In some embodiments, the emitter of the first IGBT module and the source of the first SIC module are also connected to the upper bridge control signal output port of the PWM control unit;

[0012] The emitter of the second IGBT module and the source of the second SiC module are also connected to the lower bridge control signal output port of the PWM control unit.

[0013] In some implementations, a current sensor is further provided on the phase output end, and the current sensor is connected to a current signal acquisition port of the PWM control unit.

[0014] According to another aspect of the present invention, a method for controlling an inverter power unit is provided, comprising:

[0015] Acquire a phase current signal of a phase output terminal, and divide a power frequency cycle T into a plurality of time periods according to the amplitude of the phase current signal within the cycle T;

[0016] For different time periods, according to the size and direction of the phase current signal, the timing of the drive signal output by the PWM control unit is formulated, and different timing control strategies are adopted for the first IGBT module and the first SiC module connected in parallel in the upper bridge and the second IGBT module and the second SiC module connected in parallel in the lower bridge: in the current time region where the phase current amplitude is less than the preset threshold, the timing of the two SiC modules being turned on first and then off is adopted compared with the two IGBT modules respectively; in the current time region where the phase current amplitude is greater than the preset threshold, the short-time working timing of the SiC module is adopted.

[0017] In some implementations, dividing a power frequency cycle T into a plurality of time periods according to the amplitude of the phase current signal within the cycle T includes:

[0018] During the time 0-T / 2, the phase current is positive and is divided into at least three time periods according to the phase current amplitude, wherein the period when the phase current amplitude is less than the preset threshold is the first current time region, and the period when the phase current amplitude is greater than the preset threshold is the second current time region;

[0019] During the T / 2-T time, the phase current is negative and is also divided into at least three time periods according to the current amplitude. The period when the phase current amplitude is less than the preset threshold is the first current time area, and the period when the phase current amplitude is greater than the preset threshold is the second current time area.

[0020] In some embodiments, for different time periods, according to the magnitude and direction of the phase current signal, the timing of the drive signal output by the PWM control unit is formulated, and different timing control strategies are adopted for the first IGBT module and the first SiC module connected in parallel in the upper bridge and the second IGBT module and the second SiC module connected in parallel in the lower bridge, including:

[0021] In a first current time region, controlling the first SiC module to be turned on before the first IGBT module, and then controlling the first SiC module to be turned off later than the first IGBT module; and / or,

[0022] In the first current time region, the second SiC module is controlled to be turned on before the second IGBT module; and then the second SiC module is controlled to be turned off later than the second IGBT module.

[0023] In some embodiments, the control method comprises:

[0024] The first SiC module in the upper bridge and the second SiC module in the lower bridge are turned on in sequence, and there is a time zone during the on-off conversion where neither the first SiC module nor the second SiC module is turned on;

[0025] The first IGBT module in the upper bridge and the second IGBT module in the lower bridge are turned on in sequence, and during the on-conversion, there is a time period in which neither the first IGBT module nor the second IGBT module is turned on.

[0026] In some embodiments, for different time periods, according to the magnitude and direction of the phase current signal, the timing of the drive signal output by the PWM control unit is formulated, and different timing control strategies are adopted for the first IGBT module and the first SiC module connected in parallel in the upper bridge and the second IGBT module and the second SiC module connected in parallel in the lower bridge, including:

[0027] In the second current-time region of 0-T / 2, the first SiC module is turned on for a short time only when the first IGBT module is turned on or off; and / or,

[0028] In the second current-time region of T / 2-T, the second SiC module is turned on for a short time only when the second IGBT module is turned on or off.

[0029] In some embodiments, the control method specifically includes:

[0030] In the second current time region of 0-T / 2, the timing sequence of the driving signal of the upper bridge is: in the upper bridge turn-on process, the first SiC module is turned on ahead of the first IGBT module, and is turned off after the first IGBT module is turned on; in the upper bridge turn-off process, the first SiC module is turned on before the first IGBT module is turned off, and is also turned off after the first IGBT module is turned off; the timing sequence of the driving signal of the lower bridge is: the second SiC module is turned on before the second IGBT module; the second SiC module is turned off later than the second IGBT module;

[0031] In the second current time region of T / 2-T, the timing sequence of the driving signal of the lower bridge is: in the lower bridge turn-on process, the second SiC module is turned on before the second IGBT module, and is turned off after the second IGBT module is turned on; in the lower bridge turn-off process, the second SiC module is turned on before the second IGBT module is turned off, and is also turned off after the second IGBT module is turned off; the timing sequence of the driving signal of the upper bridge is: the first SiC module is turned on before the first IGBT module, and the first SiC module is turned off later than the first IGBT module.

[0032] Compared with the prior art, the embodiments of the present invention have the following advantages:

[0033] The power unit provided by the embodiment of the present invention has the characteristics of high power density and high efficiency, and has not only the excellent switching characteristics of SiC, but also the excellent large current conduction characteristics of IGBT. Since the Si FRD is eliminated, the turn-on loss caused by the reverse recovery of the Si FRD is effectively eliminated, and the cost is also effectively reduced.

[0034] Furthermore, the control method adopted by the above power unit can effectively reduce the working loss of the hybrid switch in the small current time area, and at the same time, effectively balance the IGBT and SiC losses in the large current time area to achieve maximum output current capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic diagram of the structure of an inverter power unit provided in some embodiments of the present invention;

[0036] Figure 2 is a flow chart of an inverter power unit control method provided by some embodiments of the present invention;

[0037] Figure 3 is a schematic diagram of phase current segmentation provided by some embodiments of the present invention;

[0038] Figure 4 is a power unit control PWM timing diagram within a switching cycle of a first current time region provided by some embodiments of the present invention;

[0039] Figure 5 It is a PWM timing diagram of power unit control within one switching cycle of the second current time region at 0-T / 2 provided by some embodiments of the present invention;

[0040] Figure 6 It is a PWM timing diagram of power unit control within one switching cycle of the second current time region at T / 2-T provided by some embodiments of the present invention;

[0041] Figure 7 It is a structural schematic diagram of an inverter power unit in the prior art. DETAILED DESCRIPTION

[0042] Many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention, so the present invention is not limited to the specific implementation disclosed below.

[0043] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0044] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0045] In the description of the present invention, the description with reference to terms such as "one embodiment", "some embodiments", "illustrative embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention.

[0046] See also Figure 1 As shown, an embodiment of the present invention discloses an inverter power unit, comprising:

[0047] The upper bridge comprises a first IGBT module and a first SiC module connected in parallel, wherein the collector (C pole) of the first IGBT module and the drain (D pole) of the first SiC module are connected and then connected to the DC bus positive pole DC+; the emitter (E pole) of the first IGBT module and the source (S pole) of the first SiC module are connected and then connected to the phase output end;

[0048] The lower bridge comprises a second IGBT module and a second SiC module connected in parallel, the collector of the second IGBT module is connected to the drain of the second SiC module and then connected to the phase output end; the emitter of the second IGBT module is connected to the source of the second SiC module and then connected to the negative pole DC- of the DC bus.

[0049] Among them, SiC modules can be selected as SiC-MOSFET chips. Figure 1 In the figure, SiC is used to represent it; the IGBT module can be selected as the traditional Si power device SiI GBT. Figure 1 In the figure, IGBT is used to represent it. Optionally, the upper bridge or the lower bridge only includes one SiC module and one IGBT module in parallel. Furthermore, the SiC module may include one or more SiC-MOSFET chips, and the IGBT module may include one or more Si power devices Si-IGBT, and the above-mentioned multiple chips or devices form a series and / or parallel relationship.

[0050] The above embodiments of the present invention delete the prior art Figure 7 The fast recovery diode FRD in the circuit effectively eliminates the turn-on loss caused by the reverse recovery of FRD and also effectively reduces the cost. Moreover, it has the characteristics of high power density and high efficiency. It not only has the excellent switching characteristics of SiC, but also has the excellent large current conduction characteristics of IGBT.

[0051] In some embodiments, in combination Figure 1 As shown, the power unit of the embodiment of the present invention further includes a PWM control unit, which generates a driving signal according to a preset control strategy to drive the SiC module and the IGBT module of the upper and lower bridges in the inverter power unit. In this embodiment, the driving signal output by the PWM control unit makes the SiC module and the IGBT module of each bridge in a delayed driving relationship, that is, by controlling the SiC module and the IGBT module not to be turned on or off at the same time, the efficiency is basically the same as that of the pure SiC module, and at the same time, the large current output demand can be met, and because the FRD module is cancelled, the cost of the pure SiC module is greatly reduced.

[0052] Specifically, the gate (G pole) of the first IGBT module and the gate (G pole) of the first SiC module are electrically connected to the upper bridge control signal output ports G_I GBT_H_P and G_SiC_H_P of the PWM control unit respectively, and the emitter (E pole) of the first IGBT module and the source (S pole) of the first MOSFET module are electrically connected to the upper bridge control signal output port E(S)_H_P of the PWM control unit; the gate of the second I GBT module and the gate of the second SiC module are electrically connected to the lower bridge control signal output ports G_IGBT_L_P, G_SiC_L_P and E(S)_L_P of the PWM control unit respectively.

[0053] In this embodiment, Figure 1 The control signals (the voltage difference between the two) outputted by the upper bridge control signal output ports G_SiC_H_P and E(S)_H_P of the PWM control unit constitute the drive signal D_SiC_H of the first SiC module, the control signals outputted by the upper bridge control signal output ports G_I GBT_H_P and E(S)_H_P of the PWM control unit constitute the drive signal D IGBT_H of the first I GBT module, the control signals outputted by the lower bridge control signal output ports G_SiC_L_P and E(S)_L_P of the PWM control unit constitute the drive signal D_SiC_L of the second SiC module, and the control signals outputted by the upper bridge control signal output ports G_IGBT_L_P and E(S)_L_P of the PWM control unit constitute the drive signal D_IGBT_L of the second I GBT module.

[0054] Continue to see Figure 1 In some embodiments, a current sensor is also provided on the phase output end, and the current sensor is connected to the current signal acquisition port of the PWM control unit.

[0055] Specific, combined Figure 1 As shown, the upper bridge adopts a SiC module and an IGBT module in parallel, and optionally, only includes one SiC module and one IGBT module, and the D pole of the SiC module is short-circuited with the C pole of the IGBT and then connected to DC+, the S pole of the MOSFET module is short-circuited with the E pole of the IGBT module and then connected to the phase output (U), the G pole of the MOSFET module is separately led out and connected to the PWM control unit, the G pole of the IGBT module is separately led out and connected to the PWM control unit, and the E pole of the IGBT module and the S pole of the SiC are respectively connected to the PWM control unit.

[0056] The lower bridge also adopts the structure of connecting SiC module and IGBT module in parallel, that is, the D pole of SiC module is short-circuited with the C pole of IGBT module and then connected to the output phase (U), the S pole of SiC module is short-circuited with the E pole of IGBT module and then connected to DC-, the G pole of SiC module is led out separately and connected to PWM control unit, the G pole of IGBT module is led out separately and connected to PWM control unit, the E pole of IGBT module is short-circuited with the S pole of SiC module and then led out and connected to PWM control unit.

[0057] According to the above embodiments, the present invention discloses for the first time a power unit without FRD, which matches the PWM timing of the flexible driving signal, and can achieve the CLTC efficiency of the above hybrid module to be basically the same as that of the pure SiC module, while meeting the demand for high current output. In addition, the cost of the hybrid module without FRD is significantly reduced compared with the pure SiC unit.

[0058] According to another aspect of the present invention, a method for controlling an inverter power unit is provided. Figure 2 As shown, including:

[0059] Step S210, obtaining a phase current signal of a phase output terminal, and dividing a power frequency cycle T into a plurality of time periods according to the amplitude of the phase current signal within the cycle T;

[0060] Step S220, for different time periods, according to the magnitude and direction of the phase current signal, formulate the timing of the drive signal output by the PWM control unit, and adopt different timing control strategies for the first IGBT module and the first SiC module connected in parallel in the upper bridge and the second IGBT module and the second SiC module connected in parallel in the lower bridge: in the current time region where the phase current amplitude is less than the preset threshold, adopt the timing of the two SiC modules being turned on first and then off compared with the two IGBT modules respectively; in the current time region where the current amplitude is greater than the preset threshold, adopt the short-time working timing of the SiC module.

[0061] It can be understood that the above-mentioned power unit corresponds to a bridge arm circuit of one phase, such as a U-phase unit. The three-phase alternating current also includes a V-phase and a W-phase. Their bridge arm circuits can adopt the same structure as the U-phase unit, and the timing logic of the upper and lower bridge switches in the bridge arm circuits of each phase can also refer to the above-mentioned embodiment. However, it should be noted that the execution phase sequence between the three phases will determine different control schemes according to actual application requirements.

[0062] This embodiment aims to further improve the conduction performance of power semiconductor devices on the basis of generating sinusoidal alternating current through a specific control strategy, and reduce or avoid the loss of opening. The PWM control unit independently controls the SiC module and IGBT module in the power unit. During the control process, various PWM timings can be flexibly implemented according to the current demand size and direction. In each switching cycle in the low current time area, the timing of the SiC module is turned on first and then off to reduce switching losses and improve the efficiency of the hybrid switching device. In the high current time area, the SiC short-time working timing is adopted, that is, in one switching cycle, the total opening working time of the SiC module is less than the total opening time of the SiC module in the low current area.

[0063] This balances the losses of the SIC module and the IGBT module and improves the output current capability of the hybrid switch device.

[0064] In some embodiments, in step S210, one power frequency cycle T is divided into a plurality of time periods according to the amplitude of the phase current signal within the cycle T:

[0065] During the 0-T / 2 time, the phase current is positive and is divided into at least three time periods according to the current amplitude;

[0066] During the T / 2-T time, the phase current is negative, and it is also divided into at least three time periods according to the current amplitude;

[0067] The time period when the amplitude is less than the preset threshold is the first current time region, and the time period when the amplitude is greater than the preset threshold is the second current time region.

[0068] The preset threshold value is based on the actual EDS CLTC working condition requirements, and the hybrid module can match different ratios according to the actual EDS power requirements (current).

[0069] Optionally, the size of the preset threshold can be set to any value between 0.3-0.7 times the phase current amplitude A, preferably a value between 0.4-0.6 times the phase current amplitude A.

[0070] In an optional embodiment, in combination Figure 3 As shown, the PWM control unit performs periodic segmentation of the current signal according to the signal input by the current sensor (CurrentSensor), including:

[0071] During the 0-T / 2 time, the phase current is positive and is divided into three time periods according to the current amplitude: t1, t2, and t3;

[0072] During the T / 2-T time, the phase current is negative, and is divided into three time periods according to the current amplitude: t4, t5, and t6;

[0073] Among them, combined Figure 3 As shown, the time periods when the current amplitude is less than I u1 are t1, t3, t4 and t6, and the time periods when the current amplitude is between I u1 and I umax are t2 and t5. If I u1 is taken as the preset threshold, t1, t3, t4 and t6 are the first current time zone, and t2 and t5 are the second current time zone.

[0074] In some embodiments, in step S220, for different time periods, according to the magnitude and direction of the phase current signal, the timing of the drive signal output by the PWM control unit is formulated, and different timing control strategies are adopted for the first IGBT module and the first SiC module connected in parallel in the upper bridge and the second IGBT module and the second SiC module connected in parallel in the lower bridge, including:

[0075] In the first current time region, the gate of the first SiC module is controlled to be turned on before the gate of the first IGBT module, and the gate of the first SiC module is controlled to be turned off after the gate of the first IGBT module; and

[0076] In the first current time region, the gate of the second SiC module is opened before the gate of the second IGBT module; and the gate of the second SiC module is turned off later than the gate of the second IGBT module.

[0077] In some embodiments, in combination Figure 4 As shown, the method specifically includes:

[0078] In the upper bridge opening process, the first IGBT module is controlled to be turned on after the first S i C module by Td2 time period; in the upper bridge closing process, the first IGBT module is controlled to be turned off before the first S i C module by Td1 time period;

[0079] In the lower bridge turn-on process, the second IGBT module is controlled to be turned on after the second Si C module by a time period of Td2. In the lower bridge turn-off process, the second IGBT module is controlled to be turned off before the second Si C module by a time period of Td1.

[0080] Specifically, the timing of D_SiC_H, D_IGBT_H, D_SiC_L, and D_IGBT_L is as follows: Figure 4The timing control shown in FIG. Among them, D_Si C_H and D_I GBT_H correspond to the driving signals of the first S i C module and the first I GBT module of the upper bridge respectively, and D_IGBT_L and D_Si C_L correspond to the driving signals of the second I GBT module and the second S i C module of the lower bridge respectively. In the upper bridge turn-on process, D_I GBT_H lags behind D_Si C_H by Td2 time to pull high, and in the upper bridge turn-off process, D_I GBT_H leads D_Si C_H by Td1 time to pull low. Similarly, in the lower bridge turn-on process, D_I GBT_L lags behind D_Si C_L by Td2 time to pull high, and in the lower bridge turn-off process, D_I GBT_H leads D_Si C_H by Td1 time to pull low. There is a dead zone Tdt between D_Si C_H and G_Si C_L.

[0081] According to the above-mentioned Figure 4 It can be seen that the first SiC module in the upper bridge and the second SiC module in the lower bridge are turned on in sequence, that is, the two cannot be turned on at the same time but are turned on in sequence, and there is a time zone when the first SiC module and the second SiC module are not turned on during the turn-on conversion, that is, the dead zone Tdt; the first IGBT module in the upper bridge and the second IGBT module in the lower bridge are turned on in sequence, and there is a time zone when the first IGBT module and the second IGBT module are not turned on during the turn-on conversion, that is, the dead zone Td1+Tdt+Td2, and according to the attached Figure 4 It can be seen that due to the existence of the above-mentioned dead zone, a short circuit caused by direct connection between the upper and lower bridges can be avoided.

[0082] Through the above control strategy, the SiC module is turned on earlier than the IGBT module and turned off later than the IGBT module. Therefore, the SiC module bears the switching loss, and the IGBT module realizes zero-voltage switching, which ultimately reduces the low-current time area loss of the power unit (hybrid switch) and improves the efficiency of the power unit.

[0083] In some embodiments, in step S220, for different time periods, according to the magnitude and direction of the current signal, the timing of the drive signal output by the PWM control unit is formulated, and different timing control strategies are adopted for the first IGBT module and the first SiC module connected in parallel in the upper bridge and the second IGBT module and the second SiC module connected in parallel in the lower bridge, including:

[0084] In the second current time region (t2) of 0-T / 2, the first SiC module is turned on for a short time only when the first IGBT module is turned on or off; and / or,

[0085] In the second current time region (t5) of T / 2-T, the second SiC module is turned on for a short time only when the second IGBT module is turned on or off.

[0086] The SiC module of this embodiment only sets a pulse drive signal before and after the IGBT module is turned on or off, and the total turn-on time of the SiC module in a switching cycle in the second current time region is less than the total turn-on time of the SiC module in a switching cycle in the first current time region, thereby balancing the losses of the SiC module and the IGBT module in high current scenarios and improving the output current capacity of the hybrid switch.

[0087] In some embodiments, see Figure 5 and Figure 6 As shown, the control method specifically includes:

[0088] In the second current time region of 0-T / 2, the timing sequence of the driving signal of the upper bridge is: in the upper bridge turn-on process, the first SiC module is turned on before the first IGBT module, and is turned off after the first IGBT module is turned on; in the upper bridge turn-off process, the first SiC module is turned on before the first IGBT module is turned off, and is also turned off after the first IGBT module is turned off; the timing sequence of the driving signal of the lower bridge is: control the second SiC module to turn on before the second IGBT module; then control the second SiC module to turn off later than the second IGBT module; in addition, by setting the dead zone, the short circuit of the upper and lower bridges is avoided.

[0089] Specifically, in the second current time region of 0-T / 2 (positive sequence current scenario), the timing of the gate drive signals of the drive signal D_SiC_H of the first SiC module and the drive signal D_I GBT_H of the first IGBT module, and the drive signal D_Si C_L of the second SiC module and the drive signal D_I GBT_L of the second IGBT module are as follows: Figure 5 The timing is controlled: In the upper bridge turn-on process: D_SiC_H is pulled high before D_IGBT_H Td2 time, D_SiC_H is pulled low after Td2+Td3 time period, and D_IGBT_H is continuously at high level. In the upper bridge turn-off process: D_SiC_H is pulled high before D_IGBT_H is pulled low for Td4 time, and is pulled low after Td4+Td5 time period. The timing of D_SiC_L and D_IGBT_L of the lower bridge is the same as the control of the first current time area. In the turn-on process, D_SiC_L is pulled high before D_IGBT_L Td6 time, and in the turn-off process, D_SiC_L is pulled low after D_IGBT_L Td1 time. There is a dead zone Tdt between D_SiC_H and D_SiC_L.

[0090] Furthermore, according to the present embodiment, in the second current time region of T / 2-T, the timing sequence of the driving signal of the lower bridge is as follows: in the lower bridge turn-on process, the second SiC module is turned on before the second IGBT module, and is turned off after the second IGBT module is turned on; in the lower bridge turn-off process, the second SiC module is turned on before the second IGBT module is turned off, and is also turned off after the second IGBT module is turned off; the timing sequence of the driving signal of the upper bridge is as follows: the first SiC module is controlled to be turned on before the first IGBT module, and then the first SiC module is controlled to be turned off later than the first IGBT module.

[0091] That is, the timing of D_Si C_H and D_I GBT_H, D_Si C_L and D_I GBT_L is as follows: Figure 6 The timing control is shown in the figure. During the lower bridge turn-on process, D_Si C_L is pulled high before D_IGBT_L by Td6, and D_SiC_L is pulled low after Td6+Td8. During the lower bridge turn-off process, D_Si C_L is pulled high before D_I GBT_L is pulled low by Td7, and is pulled low after Td7+Td1. The timing of the upper bridge D_Si C_H and D_I GBT_H is the same as the first current time area control. During the turn-on process, D_SiC_H is pulled high before D_IGBT_H by Td2, and during the turn-off process, D_SiC_H is pulled low after D_I GBT_H by Td5. There is a dead time Tdt between D_SiC_H and D_Si C_L.

[0092] It should be pointed out that the above-mentioned driving signals such as D_SiC_H and D_SiC_L are PWM signals. The high or low pull of each driving signal refers to the rising edge and falling edge of the PWM signal, which also correspond to the opening and closing of the switch respectively.

[0093] In addition, it should be emphasized that the time Td1 / Td2 / Td3 / Td4 / Td5 / Td6 / Td7 / Td8 can be adjusted according to the actual current demand to balance the losses of the SiC module and the IGBT module in the second current time zone scenario and improve the current output capacity of the power unit.

[0094] In summary, the embodiments of the present invention can achieve the following beneficial effects:

[0095] The power unit in the embodiment of the present invention cancels the FRD, effectively preventing the turn-on loss of the power unit caused by the reverse recovery of the FRD. Meanwhile, the cost is further reduced after the FRD is canceled.

[0096] The PWM control method in the embodiment of the present invention independently controls the SiC module and the IGBT module. During the control process, various PWM timings can be flexibly realized according to the current demand size and direction. In each switching cycle of the first current time region, the timing of the SiC module being turned on first and then turned off is adopted, that is, the driving signal of the SiC module is pulled up before the PWM driving signal of the IGBT module, and later than the PWM driving signal of the IGBT module is pulled down, thereby reducing the switching loss and improving the efficiency of the power unit. In each switching cycle of the second current time region, the total on-time of the SiC module is less than the total on-time of the SiC module in each switching cycle of the first current time region, reducing the conduction time of the SiC module, thereby balancing the losses of the SiC module and the IGBT module, and improving the output current capacity of the power unit.

[0097] It should be noted that although the present invention is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any technical personnel in this field may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. An inverter power unit, It is characterized in that The inverter power unit comprises: An upper bridge, the upper bridge comprising a first IGBT module and a first SiC module connected in parallel, the collector of the first IGBT module is connected to the drain of the first SiC module and then connected to the positive pole of the DC bus; the emitter of the first IGBT module is connected to the source of the first SiC module and then connected to the phase output end; The lower bridge comprises a second IGBT module and a second SiC module connected in parallel, wherein the collector of the second IGBT module is connected to the drain of the second SiC module and then connected to the phase output end; the emitter of the second IGBT module is connected to the source of the second SiC module and then connected to the negative pole of the DC bus.

2. The inverter power unit according to claim 1, It is characterized in that The inverter power unit further includes a PWM control unit, and the gate of the first IGBT module and the gate of the first SiC module are respectively connected to the upper bridge control signal output port of the PWM control unit; The gate of the second IGBT module and the gate of the second SiC module are respectively connected to the lower bridge control signal output port of the PWM control unit.

3. The inverter power unit according to claim 2, It is characterized in that The emitter of the first IGBT module and the source of the first SiC module are also connected to the upper bridge control signal output port of the PWM control unit; The emitter of the second IGBT module and the source of the second SiC module are also connected to the lower bridge control signal output port of the PWM control unit.

4. The inverter power unit according to any one of claims 1 to 3, It is characterized in that A current sensor is also provided on the phase output end, and the current sensor is connected to the current signal acquisition port of the PWM control unit.

5. A control method for an inverter power unit, It is characterized in that The control method comprises: Acquire a phase current signal of a phase output terminal, and divide a power frequency cycle T into a plurality of time periods according to the amplitude of the phase current signal within the cycle T; For different time periods, according to the size and direction of the phase current signal, the timing of the drive signal output by the PWM control unit is formulated, and different timing control strategies are adopted for the first IGBT module and the first SiC module connected in parallel in the upper bridge and the second IGBT module and the second SiC module connected in parallel in the lower bridge: in the current time region where the phase current amplitude is less than the preset threshold, the timing of the two SiC modules being turned on first and then off is adopted compared with the two IGBT modules respectively; in the current time region where the phase current amplitude is greater than the preset threshold, the short-time working timing of the SiC module is adopted.

6. The control method according to claim 5, It is characterized in that Dividing a power frequency cycle T into multiple time periods according to the amplitude of the phase current signal within the cycle T includes: During the time 0-T / 2, the phase current is positive and is divided into at least three time periods according to the phase current amplitude, wherein the period when the phase current amplitude is less than the preset threshold is the first current time region, and the period when the phase current amplitude is greater than the preset threshold is the second current time region; During the T / 2-T time, the phase current is negative and is also divided into at least three time periods according to the current amplitude. The period when the phase current amplitude is less than the preset threshold is the first current time area, and the period when the phase current amplitude is greater than the preset threshold is the second current time area.

7. The control method according to claim 6, It is characterized in that For different time periods, according to the magnitude and direction of the phase current signal, the timing of the drive signal output by the PWM control unit is formulated, and different timing control strategies are adopted for the first IGBT module and the first SiC module connected in parallel in the upper bridge and the second IGBT module and the second SiC module connected in parallel in the lower bridge, including: In a first current time region, controlling the first SiC module to be turned on before the first IGBT module, and then controlling the first SiC module to be turned off later than the first IGBT module; and / or, In the first current time region, the second SiC module is controlled to be turned on before the second IGBT module; and then the second SiC module is controlled to be turned off later than the second IGBT module.

8. The control method according to claim 7, It is characterized in that The control method comprises: The first SiC module in the upper bridge and the second SiC module in the lower bridge are turned on in sequence, and there is a time zone during the on-off conversion where neither the first SiC module nor the second SiC module is turned on; The first IGBT module in the upper bridge and the second IGBT module in the lower bridge are turned on in sequence, and during the on-off conversion, there is a time zone in which neither the first IGBT module nor the second IGBT module is turned on.

9. The control method according to claim 6, It is characterized in that For different time periods, according to the magnitude and direction of the phase current signal, the timing of the drive signal output by the PWM control unit is formulated, and different timing control strategies are adopted for the first IGBT module and the first SiC module connected in parallel in the upper bridge and the second IGBT module and the second SiC module connected in parallel in the lower bridge, including: In the second current-time region of 0-T / 2, the first SiC module is turned on for a short time only when the first IGBT module is turned on or off; and / or, In the second current-time region of T / 2-T, the second SiC module is turned on for a short time only when the second IGBT module is turned on or off.

10. The control method according to claim 9, It is characterized in that The control method specifically includes: In the second current time region of 0-T / 2, the timing sequence of the driving signal of the upper bridge is: in the upper bridge turn-on process, the first SiC module is turned on ahead of the first IGBT module, and is turned off after the first IGBT module is turned on; in the upper bridge turn-off process, the first SiC module is turned on before the first IGBT module is turned off, and is also turned off after the first IGBT module is turned off; the timing sequence of the driving signal of the lower bridge is: the second SiC module is turned on before the second IGBT module; the second SiC module is turned off later than the second IGBT module; In the second current time region of T / 2-T, the timing sequence of the driving signal of the lower bridge is: in the lower bridge turn-on process, the second SiC module is turned on before the second IGBT module, and is turned off after the second IGBT module is turned on; in the lower bridge turn-off process, the second SiC module is turned on before the second IGBT module is turned off, and is also turned off after the second IGBT module is turned off; the timing sequence of the driving signal of the upper bridge is: the first SiC module is turned on before the first IGBT module, and the first SiC module is turned off later than the first IGBT module.

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