Power conversion devices and electrical equipment

Abstract

An embodiment of the present application provides a power conversion device and an electrical device, wherein the power conversion device supplies power to each phase of a three-phase motor, wherein the power conversion device includes: a boost circuit unit, which is connected to a DC power supply and boosts an input voltage input from the DC power supply according to a pulse width modulation boost signal; an inverter unit, which is connected to the boost circuit unit and has a three-phase switching circuit composed of a plurality of switching elements, and the inverter unit also has an output unit, which is connected to the three-phase switching circuit and supplies power to each phase of the three-phase motor; a control unit, which outputs the pulse width modulation boost signal to the boost circuit unit and, when detecting that the boost circuit unit is in a boost state, outputs a pulse width modulation switching signal to the inverter unit to control the switching elements of two phases in the three-phase switching circuit not to be turned on and switched in one pulse width modulation cycle.

Description

Technical Field

[0001] The present application relates to the field of electromechanical engineering. Background Art

[0002] In some DC / AC inverter application scenarios, the output voltage of the inverter needs to be higher than the input power voltage. Therefore, a boost converter needs to be added to the front end of the inverter to increase the inverter DC link (DC BUS) voltage, thereby increasing the inverter output voltage. However, due to the addition of the boost converter, the circuit loss is inevitably increased, resulting in a decrease in the efficiency of the boost converter.

[0003] The prior art proposes some solutions.

[0004] The first solution is to use a traditional boost converter between the three-phase full-bridge rectifier and the smoothing capacitor to increase the voltage on the DC link of the smoothing capacitor, and then the three-phase full-bridge inverter modulates the output three-phase AC voltage to drive the motor. The output voltage of the boost converter is determined according to the working conditions of the motor, thereby achieving the purpose of improving the motor efficiency.

[0005] The second solution uses a segmented boost converter circuit architecture. When the AC motor needs to exceed the rated speed, the driver needs to output a higher voltage. Therefore, the boost converter is used to increase the inverter DC link voltage to achieve the purpose of increasing the output voltage. In addition, according to the AC motor speed and load requirements, the boost converter is controlled to operate in three working modes and output appropriate voltage to achieve the purpose of improving the operating efficiency of the AC motor.

[0006] The third solution is to use the phase amplitude modulation (PAM) method in the inverter to generate a variable frequency three-phase AC power supply in the form of a six-step square wave voltage, and the output voltage amplitude is determined by the boost converter control. Since the six-step square wave modulation changes six switching states in one power cycle, the switching loss of the switch can be greatly reduced, thereby improving the drive efficiency.

[0007] The fourth solution is to use space vector pulse width modulation (SVPWM) to reduce the number of power switch switching times to achieve the purpose of reducing switching losses. For example, the traditional SVPWM divides the waveform of a three-phase pulse width modulation (PWM) signal of one cycle into seven segments (that is, the seven-segment SVPWM switching method), and there are six switching switches in each cycle of PWM. Or use the five-segment SVPWM switching method to divide the three-phase PWM waveform of one cycle into five segments, and there are four switching switches in each cycle of PWM, which can reduce 1 / 3 of the switching loss compared with the seven-segment SVPWM switching method. Or use the four-segment asymmetric SVPWM switching method to change the PWM waveform from symmetrical to asymmetric, making current sampling easier, but each cycle of PWM also has four switching switches, which does not further reduce the switching loss compared with the five-segment method.

[0008] The fifth solution is to use a combined SVPWM modulation method, and adopt different SVPWM switching methods according to the speed (stator frequency) and voltage requirements of the AC motor. For example, when the stator frequency of the AC motor is in the low frequency band, the half-frequency SVPWM method is used, which can reduce 1 / 2 switching loss compared with the seven-segment SVPWM switching method; when the stator frequency of the AC motor is in the medium and low frequency band, the flat-top SVPWM method is used, which can reduce 1 / 3 switching loss; when the stator frequency of the AC motor is in the medium and high frequency band, the seven-segment SVPWM method is used; when the stator frequency of the AC motor is in the high frequency band, the FFC SVPWM method is used, and the switching loss is minimized. In the above four methods, in terms of inverter power loss, generally, the seven-segment SVPWM> flat-top SVPWM> half-frequency SVPWM> FFC SVPWM, therefore, changing different SVPWM switching methods according to different operating conditions can reduce the driver switching loss to improve efficiency.

[0009] The SVPWM switching method is described below by taking the seven-segment SVPWM switching method as an example. Figure 8 This is a circuit diagram of a general three-phase inverter connected to a three-phase motor. Fig. 9 This is a waveform diagram of the traditional seven-segment SVPWM switching method. Fig.10 It is a schematic diagram of the space voltage vector. Fig. 9 The a, b, and c signals are shown for Figure 8 The three upper arm switching elements T of the inverter 801 in a ~T c Control the three lower arm switching elements T a '~T cThe control signals a', b', c' are inversely proportional to the a, b, c signals. Fig. 9 The signals a', b', c' are not shown.

[0010] The PWM signals a, b, c, a', b', c' are used to control the six switching elements T a ~T c 、T a '~T c 'Control to make the upper arm or lower arm of each arm conductive, so as to output the voltage of the corresponding phase to the A, B, and C phases of the three-phase motor 802. Assume that the high level of the PWM signal represents "1" and the low level represents "0". The voltage vector in the voltage space is represented by (abc) corresponding to the signals a, b, and c. Fig.10 The six different space voltage vectors V 1 ~V 6 , and two zero voltage vectors V 0 and V 7 .

[0011] The six spatial voltage vectors differ by 60°, dividing the voltage plane into six intervals. In order for the three-phase AC motor to produce a smooth rotating magnetic field, the three-phase inverter must output a smooth circular voltage vector. At this time, a voltage vector in each different interval must be generated. The required circular voltage vector can be synthesized by using the two voltage vectors at the edge of the interval based on the concept of average voltage. 1 and V 2 Take the synthetic voltage as an example, let V 1 Voltage output time T 1 , and then let V 2 Voltage output time T 2 , and let V 0 or V 7 Voltage output time T 0 , then the equivalent average voltage output is:

[0012]

[0013] Where, PWM period T = T 1 +T 2 +T 0 .

[0014] According to the above formula, the adjustment time T 1 and time T 2 The ratio of the composite voltage can change the phase of the composite voltage, and the time T 0 The length of the output voltage can be changed. Therefore, the traditional SVPWM technology is to control the switching state of the six power switches in the inverter so that the space voltage vector combines the voltage of the required phase and amplitude.

[0015] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present application and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because they are described in the background technology section of the present application. Summary of the invention

[0016] The inventors of the present application have discovered that the first solution only improves the motor efficiency, but does not solve the problem of reduced overall driver efficiency caused by the additional boost converter. Although the second solution can also improve the efficiency of the AC motor, this solution increases the number and complexity of circuit elements, and does not solve the problem of increased driver losses after adding a boost converter. The third solution contains large odd harmonics, which will generate large harmonic currents, causing noise and vibration in the AC motor, and is not suitable for applications with high requirements for noise and vibration. Although the fourth and fifth solutions can reduce switching losses, they can only reduce a small part of the switching losses, and will increase current harmonics, and cannot effectively solve the problem of reduced overall driver efficiency caused by the additional boost converter.

[0017] In order to solve at least one of the above problems or other similar problems, an embodiment of the present application provides a power conversion device and an electrical equipment to reduce the overall switching loss of a boost converter and an inverter.

[0018] According to one aspect of an embodiment of the present application, there is provided a power conversion device, which supplies power to each phase of a three-phase motor, wherein the power conversion device comprises: a boost circuit unit, which is connected to a DC power supply and boosts an input voltage input from the DC power supply according to a pulse width modulation boost signal; an inverter unit, which is connected to the boost circuit unit and has a three-phase switching circuit composed of a plurality of switching elements, the inverter unit also having an output unit, the output unit being connected to the three-phase switching circuit and supplying power to each phase of the three-phase motor; and a control unit, which outputs the pulse width modulation boost signal to the boost circuit unit and, when detecting that the boost circuit unit is in a boost state, outputs a pulse width modulation switching signal to the inverter unit, the pulse width modulation switching signal controlling the switching elements of two phases in the three-phase switching circuit not to be switched on in one pulse width modulation cycle.

[0019] In at least one embodiment, when the control unit detects that the boost circuit unit is in a boost state, the control unit controls the switch element of another phase in the switch circuit to be turned on and switched in one pulse width modulation cycle.

[0020] In at least one embodiment, the three-phase switching circuit includes 6 switching elements, and the 6 switching elements are paired in pairs to form 3 arms of a bridge circuit, and the 3 arms respectively correspond to the three phases of the three-phase motor, and the 2 switching elements of each arm respectively constitute the upper arm and the lower arm of each arm, and when the control unit detects that the boost circuit unit is in the boost state, the control unit controls the upper arm and the lower arm of one of the 3 arms to be turned on and switched in one pulse width modulation cycle, and controls the upper arms and the lower arms of the other two arms of the 3 arms not to be turned on and switched in one pulse width modulation cycle, wherein the upper arm of one of the other two arms is controlled to be turned on and the lower arm is turned off, and the upper arm of the other arm of the other two arms is controlled to be turned off and the lower arm is turned on.

[0021] In at least one embodiment, in one pulse width modulation cycle, the control unit controls the upper arm and the lower arm of the one arm to perform one conduction switching.

[0022] In at least one embodiment, the control unit sets a duty cycle of the pulse width modulation switching signal according to the output voltage of the boost circuit unit, and controls the conduction switching of the upper arm and the lower arm of the one arm according to the duty cycle.

[0023] In at least one embodiment, the control unit includes a voltage controller and a PWM signal generator, the voltage controller determines the duty cycle of the pulse width modulated boost signal according to the output voltage and target voltage of the boost circuit unit, the target voltage is obtained by multiplying a preset target duty cycle by an input voltage input from the DC power supply, and the PWM signal generator generates the pulse width modulated boost signal according to the duty cycle and provides it to the boost circuit unit to perform boost control on the boost circuit unit.

[0024] In at least one embodiment, the power conversion device further includes: a DC power supply, which provides a DC voltage to the boost circuit unit.

[0025] According to another aspect of an embodiment of the present application, an electrical device is provided, which includes the aforementioned power conversion device and a three-phase motor, wherein the power conversion device supplies power to each phase of the three-phase motor.

[0026] One of the beneficial effects of the embodiment of the present application is that: in the power conversion device, the switch elements of two phases in the three-phase switch circuit of the inverter unit are not turned on and switched in one pulse width modulation cycle, and only the switch elements of the other phase are turned on and switched in one pulse width modulation cycle, thereby forming a two-stage space vector pulse modulation method. Therefore, compared with the seven-stage SVPWM switching method, the inverter switch switching loss can be reduced by 2 / 3 times, and the driver efficiency can be improved.

[0027] In addition, the embodiment of the present application generates a variable DC link voltage by the boost circuit unit, so that the inverter unit does not need to control the amplitude of the output voltage by outputting a zero voltage vector, but only needs to change the output time ratio of two different voltage vectors to achieve the purpose of outputting a smooth circular voltage vector and controlling the voltage phase.

[0028] With reference to the following description and accompanying drawings, the specific embodiments of the present application are disclosed in detail, indicating the way in which the principles of the present application can be adopted. It should be understood that the embodiments of the present application are not limited in scope. Within the scope of the terms of the appended claims, the embodiments of the present application include many changes, modifications and equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The elements and features described in one figure or one implementation of the present application embodiment may be combined with the elements and features shown in one or more other figures or implementations. In addition, in the accompanying drawings, similar reference numerals represent corresponding parts in several figures and can be used to indicate corresponding parts used in more than one implementation.

[0030] The included drawings are used to provide a further understanding of the embodiments of the present application, which constitute a part of the specification, are used to illustrate the implementation methods of the present application, and together with the text description, explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0031] Figure 1 It is a modular schematic diagram of the power conversion device of an embodiment of the present application.

[0032] Figure 2 yes Figure 1 A circuit diagram of a portion of a power conversion device is shown.

[0033] Figure 3 It is a timing diagram of the switching signal in one PWM cycle.

[0034] Figure 4 So Figure 3 Schematic diagram of the switching state of each switching element when the switching signal shown controls the switching element.

[0035] Figure 5 Schematic diagram of the relationship between the conduction time and phase of each phase of the three-phase switching circuit according to an embodiment of the present application.

[0036] Figure 6 It is a timing diagram of the switching signal over a period of time.

[0037] Figure 7 It is a circuit diagram of the control unit generating a boost signal.

[0038] Figure 8 It is a schematic diagram of a general three-phase inverter circuit.

[0039] Fig. 9 It is a waveform diagram of the traditional seven-segment SVPWM switching method.

[0040] Fig.10 It is a schematic diagram of the space voltage vector of the three-phase inverter.

[0041] Fig.11 It is a schematic diagram comparing the efficiency of applying the power conversion device of the embodiment of the present application to a motor driver and applying the power conversion device controlled by the traditional seven-segment SVPWM switching method to the same motor driver. DETAILED DESCRIPTION

[0042] With reference to the accompanying drawings, the above and other features of the present application will become apparent through the following description. In the description and the accompanying drawings, specific embodiments of the present application are specifically disclosed, which show some embodiments in which the principles of the present application can be adopted. It should be understood that the present application is not limited to the described embodiments. On the contrary, the present application includes all modifications, variations and equivalents falling within the scope of the attached claims.

[0043] In the embodiments of the present application, the terms "first", "second", "upper", "lower", etc. are used to distinguish different elements in terms of title, but do not indicate the spatial arrangement or time order of these elements, etc., and these elements should not be limited by these terms. The term "and / or" includes any one and all combinations of one or more of the associated listed terms. The terms "comprising", "including", "having", etc. refer to the presence of the stated features, elements, components or components, but do not exclude the presence or addition of one or more other features, elements, components or components.

[0044] In the embodiments of the present application, the singular forms "a", "the", etc. include plural forms and should be broadly understood as "a kind" or "a type" rather than being limited to the meaning of "one"; in addition, the term "said" should be understood to include both singular and plural forms, unless the context clearly indicates otherwise. In addition, the term "according to" should be understood as "at least in part according to...", and the term "based on" should be understood as "at least in part based on...", unless the context clearly indicates otherwise.

[0045] Embodiments of the first aspect

[0046] The first aspect of the present application provides a power conversion device. Figure 1is a modular schematic diagram of a power conversion device according to an embodiment of the present application, Figure 2 yes Figure 1 A circuit diagram of a portion of a power conversion device is shown.

[0047] In the embodiments of the present application, Figure 1 As shown, the power conversion device 100 may include a boost circuit unit 101, an inverter unit 102, a control unit 103 and a DC power supply 104, and the power conversion device 100 provides three-phase AC power to the three-phase motor 200. Among them, the control unit 103 can output a pulse width modulated boost signal PB (hereinafter referred to as "boost signal PB") to the boost circuit unit 101; the boost circuit unit 101 is connected to the DC power supply 104, and the output voltage U of the DC power supply 104 can be modulated according to the boost signal PB from the control unit 103. dc The voltage is stepped up and the stepped-up voltage is output to the inverter unit 102 .

[0048] like Figure 2 As shown, the inverter unit 102 may include an output part 1021 and a three-phase switching circuit 1022. The three-phase switching circuit 1022 may be composed of multiple switching elements. The output part 1021 is connected to the three-phase switching circuit 1022 to supply power to each phase of the three-phase motor 200. The output part 1021 includes electrical components such as diodes. For details, please refer to the relevant technology, and this application does not limit this.

[0049] In the embodiment of the present application, the control unit 103 detects the output voltage of the boost circuit unit 101. When the boost circuit unit 101 is in the boost state, the control unit 103 outputs a pulse width modulation switching signal PI (hereinafter referred to as "switching signal PI") to the inverter unit 102, controls the switching elements of two phases in the three-phase switch circuit 1022 not to conduct in a pulse width modulation cycle (hereinafter referred to as "PWM cycle"), and controls the switching element of the other phase to conduct in the PWM cycle. Thus, due to the reduction in the number of switching times, the switching loss is reduced as a whole.

[0050] In at least one embodiment, Figure 2 As shown, the three-phase switch circuit 1022 can be composed of 6 switch elements to form a bridge circuit, with T 1 ~T 3 、T 1 '~T 3 ' represents these 6 switching elements, T 1 and T 1 '、T 2 and T 2 '、T 3 and T 3' are paired to form the first arm, the second arm and the third arm of the bridge circuit, where T 1 , T 2 , T 3 T is the upper arm. 1 '、T 2 '、T 3 ' is recorded as the lower arm, and the three arms of the bridge circuit correspond to the three phases of the three-phase motor 200, and are controlled by the switching signal PI to supply power to each phase of the three-phase motor 200. Figure 2 The figure shows a situation where the three-phase switch circuit 1022 is composed of 6 switch elements, but the present application is not limited thereto. Other numbers of switch elements may also be used to form a switch circuit to power a three-phase motor. For details, reference may be made to the relevant art. Figure 2 In the figure, the switching element is represented by the circuit symbol of a transistor, but the switching element of the present application is not limited to a transistor, and the switching element can also be composed of other electrical elements.

[0051] Figure 3 The control unit 103 sends a signal to the upper arm T of the inverter unit 102 in one PWM cycle T. 1 , T 2 , T 3 Output switching signal PI 1 ~PI 3 Schematic diagram, the control unit 103 to the lower arm T of the inverter unit 102 1 '、T 2 '、T 3 'Output switching signal PI 1 '~PI 3 'With the switching signal PI 1 ~PI 3 Inverting, no Figure 3 Shown in. Figure 4 So Figure 3 The switching signal shown in FIG. 1 ~T 3 , T 1 '~T 3 'When controlling, the switching state of each switching element.

[0052] Below, Figures 2 to 4 The conduction control performed by the control unit 103 will be described by taking as an example.

[0053] In at least one embodiment, when the control unit 103 detects that the boost circuit unit 101 is in the boost state, the control unit 103 outputs a switching signal PI (eg, a switching signal PI ) to the three-phase switch circuit 1022. 1 ~PI 3 and the switching signal PI 1 '~PI 3'). The switching signal PI controls the upper arm and the lower arm of two arms in the three-phase switch circuit 1022 not to perform switching in one PWM cycle, and controls the upper arm and the lower arm of another arm to perform switching in the PWM cycle.

[0054] like Figure 3 As shown, the switching signal PI is a PWM signal, and a PWM cycle T = t 1 +t 2 In one PWM cycle T, PI can be set 1 Always high level, PI 3 Always low level, PI 2 The low level duration is t 1 , the high level duration is t 2 ; Correspondingly, in this PWM cycle, PI 1 'Always low level, PI 3 'Always high level, PI 2 The high level duration of ' is t 1 , the low level duration is t 2 .like Figure 4 As shown, in Figure 3 In one PWM cycle shown, the upper arm T 1 Always in the on state (ON), the lower arm T 1 'Always in the cut-off state (OFF); upper arm T 3 Always in the cut-off state (OFF), lower arm T 3 'Always in the on state (ON); upper arm T 2 In t 1 During the period, it is in the cut-off state. 2 During this period, the lower arm T 2 'In t 1 During the period, it is in the on state. 2 Therefore, in one PWM cycle, only the second arm (upper arm T 2 Switching from cut-off to conduction and lower arm T 2 'Switched from on to off) and the first arm (upper arm T 1 Always on and lower arm T 1 'Always cut off) and the third arm (upper arm T 3 Always cut off and lower arm T 3 'Always on) without switching. If (PI 1 PI 2 PI 3 ) is recorded as the space voltage vector, then Figure 3 In one PWM cycle shown in the figure, the space voltage vector V 1(100) Duration is t 1 , space voltage vector V 2 (110) Duration is t 2 , the output voltage of the inverter unit 102 varies within the range of 0° to 60° in the vector space.

[0055] Similarly, in another PWM cycle, PI can be set 1 Always high level, PI 2 Always low level, PI 3 The low level duration is t 1 , the high level duration is t 2 ; Correspondingly, in this PWM cycle, PI 1 'Always low level, PI 2 'Always high level, PI 3 The high level duration of ' is t 1 , the low level duration is t 2 Then, in this PWM cycle, the upper arm T 1 Always in the on state (ON), the lower arm T 1 'Always in the cut-off state (OFF); upper arm T 2 Always in the cut-off state (OFF), lower arm T 2 'Always in the on state (ON); upper arm T 3 In t 1 During the period, it is in the cut-off state. 2 During this period, the lower arm T 3 'In t 1 During the period, it is in the on state. 2 Therefore, in one PWM cycle, only the third arm (upper arm T 3 Switching from cut-off to conduction and lower arm T 3 'Switched from on to off) and the first arm (upper arm T 1 Always on and lower arm T 1 'Always cut off) and the second arm (upper arm T 2 Always cut off and lower arm T 2 'Always on) without switching. In this PWM cycle, the space voltage vector V 1 (100) Duration is t 1 , space voltage vector V 6 (101) Duration is t 2 , the output voltage of the inverter unit 102 varies within 300° to 360° in the vector space.

[0056] Similarly, in another PWM cycle, PI can be set 2 Always high level, PI 3 Always low level, PI 1 The low level duration is t 1 , the high level duration is t 2 ; Correspondingly, in this PWM cycle, PI 2 'Always low level, PI 3 'Always high level, PI 1 The high level duration of ' is t 1 , the low level duration is t 2 Then, in this PWM cycle, the upper arm T 2 Always in the on state (ON), the lower arm T 2 'Always in the cut-off state (OFF); upper arm T 3 Always in the cut-off state (OFF), lower arm T 3 'Always in the on state (ON); upper arm T 1 In t 1 During the period, it is in the cut-off state. 2 During this period, the lower arm T 1 'In t 1 During the period, it is in the on state. 2 Therefore, in one PWM cycle, only the first arm (upper arm T 1 Switching from cut-off to conduction and lower arm T 1 ' from on to off) is switched, the second arm (upper arm T 2 Always on and lower arm T 2 'Always cut off) and the third arm (upper arm T 3 Always cut off and lower arm T 3 'Always on) without switching. In this PWM cycle, the space voltage vector V 3 (010) duration is t 1 , space voltage vector V 2 (110) Duration is t 2 , the output voltage of the inverter unit 102 varies within 60° to 120° in the vector space.

[0057] Similarly, in another PWM cycle, you can set PI 1 Always low level, PI 3 Always high level, PI 2 The low level duration is t 1 , the high level duration is t 2 ; Correspondingly, in this PWM cycle, PI1 'Always high level, PI 3 'Always low level, PI 2 The high level duration of ' is t 1 , the low level duration is t 2 Then, in this PWM cycle, the upper arm T 1 Always in the cut-off state (OFF), lower arm T 1 'Always in the on state (ON); upper arm T 3 Always in the on state (ON), the lower arm T 3 'Always in the cut-off state (OFF); upper arm T 2 In t 1 During the period, it is in the cut-off state. 2 During this period, the lower arm T 2 'In t 1 During the period, it is in the on state. 2 Therefore, in one PWM cycle, only the second arm (upper arm T 2 Switching from cut-off to conduction and lower arm T 2 'Switched from on to off) and the first arm (upper arm T 1 Always on and lower arm T 1 'Always cut off) and the third arm (upper arm T 3 Always cut off and lower arm T 3 'Always on) without switching. In this PWM cycle, the space voltage vector V 5 (001) duration is t 1 , space voltage vector V 4 (011) Duration is t 2 , the output voltage of the inverter unit 102 varies within 180° to 240° in the vector space.

[0058] Similarly, in another PWM cycle, PI can be set 1 Always low level, PI 2 Always high level, PI 3 The low level duration is t 1 , the high level duration is t 2 ; Correspondingly, in this PWM cycle, PI 1 'Always high level, PI 2 'Always low level, PI 3 The high level duration of ' is t 1 , the low level duration is t 2 Then, in this PWM cycle, the upper arm T 1Always in the cut-off state (OFF), lower arm T 1 'Always in the on state (ON); upper arm T 2 Always in the on state (ON), the lower arm T 2 'Always in the cut-off state (OFF); upper arm T 3 In t 1 During the period, it is in the cut-off state. 2 During this period, the lower arm T 3 'In t 1 During the period, it is in the on state. 2 Therefore, in one PWM cycle, only the third arm (upper arm T 3 Switching from cut-off to conduction and lower arm T 3 'Switched from on to off) and the first arm (upper arm T 1 Always cut off and lower arm T 1 'Always on) and the second arm (upper arm T 2 Always on and lower arm T 2 'Always off) no switching is performed. In this PWM cycle, the space voltage vector V 3 (010) duration is t 1 , space voltage vector V 4 (011) Duration is t 2 , the output voltage of the inverter unit 102 varies within 120° to 180° in the vector space.

[0059] Similarly, in another PWM cycle, PI can be set 2 Always low level, PI 3 Always high level, PI 1 The low level duration is t 1 , the high level duration is t 2 ; Correspondingly, in this PWM cycle, PI 2 'Always high level, PI 3 'Always low level, PI 1 The high level duration of ' is t 1 , the low level duration is t 2 Then, in this PWM cycle, the upper arm T 2 Always in the cut-off state (OFF), lower arm T 2 'Always in the on state (ON); upper arm T 3 Always in the on state (ON), the lower arm T 3 'Always in the cut-off state (OFF); upper arm T 1 In t 1 During the period, it is in the cut-off state.2 During this period, the lower arm T 1 'In t 1 During the period, it is in the on state. 2 Therefore, in one PWM cycle, only the first arm (upper arm T 1 Switching from cut-off to conduction and lower arm T 1 ' from on to off) is switched, the second arm (upper arm T 2 Always cut off and lower arm T 2 'Always on) and the third arm (upper arm T 3 Always on and lower arm T 3 'Always off) no switching is performed. In this PWM cycle, the space voltage vector V 5 (001) duration is t 1 , space voltage vector V 6 (101) Duration is t 2 , the output voltage of the inverter unit 102 varies within 240° to 300° in the vector space.

[0060] Therefore, compared with the traditional seven-segment SVPWM control method, in the traditional seven-segment SVPWM control method, six switching times are required in one PWM cycle, among which, due to the existence of zero voltage vectors (such as Fig. 9 As shown, the zero voltage vector V 0 and V 7 ), four zero voltage vector switching operations are required, while in the present application, only one switching operation is performed in one PWM cycle, which belongs to a two-stage SVPWM control method. Since the present application has no zero voltage vector in one PWM cycle, the inverter switching loss can be reduced by 2 / 3 times.

[0061] Figure 5 Schematic diagram of the relationship between the conduction time and phase of each phase of the three-phase switch circuit output by the power converter controlled by the two-stage SVPWM control method of the present application. Figure 5 As shown, phase A corresponds to the first arm (upper arm T 1 and lower arm T 1 '), the B phase corresponds to the second arm (upper arm T 2 Lower arm T 2 '), C phase corresponds to the third arm (upper arm T 3 and lower arm T 3 '), the following is an example of the interval 0°~60° in the vector space. Figure 5 In the vector space, in the interval of 0° to 60°, the duty cycle of phase A is always greater than 1, indicating that the upper arm T of phase A 1The lower arm T is always on during the entire PWM cycle. 1 'It is always off during the entire PWM cycle; the duty cycle of phase C is always less than -1, indicating that the upper arm T of phase C 3 The lower arm T is always off during the entire PWM cycle. 3 'Always on during the entire PWM cycle; the duty cycle of phase B is between -1 and 1. When the phase is 0°, the duty cycle is 1, indicating that the upper arm T 2 When the duty cycle is less than 1, it means that the upper arm T 2 With lower arm T 2 'When switching between on and off (i.e., switching), the actual PWM duty cycle (DUTY_PWM) has the following functional relationship, for example: DUTY_PWM = 0.5 × DUTY + 0.5. When the phase is, for example, 30°, the duty cycle (DUTY) is 0, and the actual PWM duty cycle (DUTY_PWM) is 0.5, indicating that the upper and lower arms are each on for 50% of the PWM cycle. In addition, since the upper arm of phase A and the lower arm of phase C are continuously turned on and the output voltage of the inverter unit cannot be increased, the boost circuit unit can be used to increase the DC link voltage of the inverter unit, and the voltage value is proportional to the absolute value of the conduction time ratio of phase A or phase C, then the inverter unit will output a sine wave voltage that matches the required voltage. Since the amplitude of the output voltage of the inverter unit can be controlled and determined by the boost circuit unit, in one PWM cycle, it is only necessary to control the on-time ratio of the upper and lower arms of a certain phase switch in the inverter unit to determine the phase of the spatial voltage vector, thereby reducing the inverter switch switching loss by 2 / 3 times.

[0062] Figure 6 Is the switching signal PI 1 ~PI 3 An example diagram of the switching signal PI 1 '~PI 3 'With the switching signal PI 1 ~PI 3 Inverting, no Figure 6 The switching signal PI 1 ~PI 3 and the switching signal PI 1 '~PI 3 ', the phase of the output voltage of the inverter unit 102 changes continuously in the vector space. In addition, the variable DC link voltage can be generated by the boost circuit unit 101, so that the inverter unit 102 can output a voltage that meets the amplitude requirement of the three-phase motor without outputting a zero voltage vector. Therefore, it is only necessary to change the output time ratio of two different non-zero voltage vectors to achieve the output of a smooth circular voltage vector and reduce current harmonics.

[0063] Figure 7 FIG. 1 is a circuit diagram of the control unit 103 generating the boost signal PB.

[0064] In at least one embodiment, Figure 7 As shown, the control unit 103 may include a voltage controller 1031 and a PWM signal generator 1032. The voltage controller 1031 may generate a PWM signal according to the output voltage U of the boost circuit unit 101. B and target voltage U M Determine the duty cycle D of the boost signal PB PB , target voltage U M For example, the voltage U required by the three-phase motor 300 M , by the preset target duty cycle D M Multiply the output voltage U of the DC power supply 104 dc Get; PWM signal generator 1032 according to the duty cycle D PB The generated boost signal PB is provided to the boost circuit unit 101 to perform boost control on the boost circuit unit 101 .

[0065] In at least one embodiment, Figure 7 As shown, the peak value D of the preset target duty cycle can be M Multiply the output voltage U of the DC power supply 104 dc The obtained signal is used as a voltage control command and is compared with the output voltage U fed back from the boost circuit unit 101. B Subtract the voltage error, and the voltage controller 1031 can calculate the duty cycle D of the boost signal PB according to the voltage error. PB , the PWM signal generator 1032 sets the duty cycle D PB After comparison with the triangle wave signal, a boost signal PB is generated.

[0066] In addition, the control unit 103 can also determine which two space voltage vectors are needed and their respective durations according to the phase of the voltage required by the three-phase motor, thereby determining the duty cycle of the switching signal PI, and compare the duty cycle with another triangular wave signal to generate the switching signal PI. The frequency of the triangular wave generating the switching signal PI may be unrelated to the frequency of the triangular wave generating the boost signal PB.

[0067] In at least one embodiment, the control unit 103 may further detect whether the boost circuit unit 101 is in a boost state, for example, Figure 1 As shown, the control unit 103 can detect the output voltage U of the boost circuit unit 101. B and the output voltage U of the DC power supply 104 dc , if the output voltage U B Higher than the output voltage U of the DC power supply 104dc and is less than the voltage U required by the three-phase motor 200 M , it is determined that the boost circuit unit 101 is in the boost state; otherwise, it is determined that the boost circuit unit 101 is not in the boost state. When the boost circuit unit 101 is not in the boost state, the control unit 103 controls the inverter unit 102, for example, using a conventional seven-segment SVPWM switching method or a five-segment SVPWM switching method.

[0068] Fig.11 The power conversion device of the embodiment of the present application is applied to the motor driver and the power conversion device controlled by the traditional seven-segment SVPWM switching method is applied to the same motor driver. The power conversion device of the embodiment of the present application is applied to the motor driver and controls an AC permanent magnet synchronous motor. In contrast, the power conversion device controlled by the traditional seven-segment SVPWM switching method is also applied to the motor driver and controls the AC permanent magnet synchronous motor. The efficiencies of the two are measured respectively, as shown in FIG. Fig.11 As shown, curve TS corresponds to the efficiency of the two-stage SVPWM switching method of the present application, and curve CS corresponds to the efficiency of the traditional seven-stage SVPWM switching method. It can be seen that the efficiency of the two-stage SVPWM switching method of the present application is significantly higher than the efficiency of the traditional seven-stage SVPWM switching method.

[0069] According to the embodiment of the present application, the switch elements of two phases in the three-phase switch circuit of the inverter unit are not turned on and switched in one pulse width modulation cycle, and only the switch element of the other phase is turned on and switched in one pulse width modulation cycle, thereby forming a two-stage space vector pulse modulation method. As a result, the switching loss of the inverter switch can be reduced by 2 / 3 times, and the driver efficiency can be improved.

[0070] Embodiments of the second aspect

[0071] The second aspect of the present application provides an electrical device having the power conversion device described in the first aspect and a three-phase motor, wherein the power conversion device supplies power to each phase of the three-phase motor. Since the features of the power conversion device have been described in detail in the first aspect of the embodiment, the content thereof is incorporated herein and the description is omitted here.

[0072] In the embodiments of the present application, there is no limitation on the application field and / or application scenario of the electrical equipment. For example, it can be applied to application scenarios such as AC motor drivers and DC / AC power converters, for example, drivers powered by batteries, such as electric vehicles or robotic arms; or used for high-speed air-conditioning / compressor equipment, or it can also be household appliances such as water dispensers, washing machines, sweepers, compressors, blowers, mixers, etc., or it can be electrical equipment in other fields.

[0073] According to the embodiment of the present application, in the power conversion device, the switch elements of two phases in the three-phase switch circuit of the inverter unit are not turned on and switched in one pulse width modulation cycle, and only the switch elements of the other phase are turned on and switched in one pulse width modulation cycle, thereby forming a two-stage space vector pulse modulation method. As a result, the switching loss of the inverter switch can be reduced by 2 / 3 times, the driver efficiency can be improved, and thus the efficiency of the electrical equipment can be improved.

[0074] The present application is described above in conjunction with specific implementation methods, but it should be clear to those skilled in the art that these descriptions are exemplary and are not intended to limit the scope of protection of the present application. Those skilled in the art can make various modifications and variations to the present application based on the spirit and principles of the present application, and these modifications and variations are also within the scope of the present application.

Claims

1. A power conversion device, which supplies power to each phase of a three-phase motor, characterized in that: The power conversion device comprises: A boost circuit unit, connected to a DC power supply, boosts an input voltage input from the DC power supply according to a pulse width modulation boost signal; an inverter unit connected to the boost circuit unit, having a three-phase switching circuit composed of a plurality of switching elements, the inverter unit further having an output unit, the output unit being connected to the three-phase switching circuit to supply power to each phase of the three-phase motor; and a control unit, which outputs the pulse width modulation boost signal to the boost circuit unit, and when detecting that the boost circuit unit is in a boost state, outputs a pulse width modulation switching signal to the inverter unit, wherein the pulse width modulation switching signal controls the switching elements of two phases in the three-phase switching circuit not to be turned on and switched in one pulse width modulation cycle, When the control unit detects that the boost circuit unit is in a boost state, the control unit controls the switch element of another phase in the switch circuit to be turned on and off in a pulse width modulation cycle. The three-phase switching circuit includes six switching elements, and the six switching elements form three arms of a bridge circuit in pairs, and the three arms correspond to the three phases of the three-phase motor respectively, and the two switching elements of each arm respectively constitute the upper arm and the lower arm of each arm, When the control unit detects that the boost circuit unit is in a boost state, the control unit controls the upper arm and the lower arm of one of the three arms to be switched on in one pulse width modulation cycle, and controls the upper arm and the lower arm of the other two arms of the three arms not to be switched on in one pulse width modulation cycle, wherein the upper arm of one of the other two arms is controlled to be turned on and the lower arm is turned off, and the upper arm of the other arm of the other two arms is controlled to be turned off and the lower arm is turned on.

2. The power conversion device according to claim 1, wherein: In one pulse width modulation cycle, the control unit controls the upper arm and the lower arm of the one arm to perform one conduction switching.

3. The power conversion device according to claim 1 or 2, wherein: The control unit sets a duty ratio of the pulse width modulation switching signal according to an output voltage of the boost circuit unit, and controls conduction switching of an upper arm and a lower arm of the one arm according to the duty ratio.

4. The power conversion device according to claim 1, wherein: The control unit includes a voltage controller and a PWM signal generator, The voltage controller determines the duty cycle of the pulse width modulation boost signal according to the output voltage of the boost circuit unit and a target voltage, wherein the target voltage is obtained by multiplying a preset voltage by an input voltage input from the DC power supply. The PWM signal generator generates the pulse width modulated boost signal according to the duty cycle and provides the signal to the boost circuit unit to perform boost control on the boost circuit unit.

5. The power conversion device according to claim 1, wherein: The power conversion device further comprises: A DC power supply provides a DC voltage to the boost circuit unit.

6. An electrical device, characterized in that: The electrical device comprises the power conversion device according to any one of claims 1 to 5 and a three-phase motor, wherein the power conversion device supplies power to each phase of the three-phase motor.

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