A current conversion control device, motor and current conversion control method thereof

Abstract

The present invention discloses a current conversion control device, a motor and a current conversion control method thereof, wherein the device comprises: a current conversion unit and a control unit; wherein the current conversion unit is used to output three-phase AC power to the motor after current conversion processing of single-phase AC power; wherein the current conversion processing comprises: rectification processing, filtering processing and inversion processing; the control unit is used to obtain the current conversion parameters of the current conversion unit and the operating parameters of the motor, and according to the current conversion parameters and the operating parameters, the current conversion unit is phase-shifted modulated and the circulating current is hierarchically controlled to realize hierarchical closed-loop control between the current conversion unit and the motor. The scheme of the present invention can solve the problem that the output waveform has a high harmonic content when the topology of the two-level inversion is adopted, and achieve the effect of reducing the harmonic content of the output waveform.

Description

Technical Field

[0001] The present invention belongs to the field of current conversion technology, and specifically relates to a current conversion control device, a motor and a current conversion control method thereof, and more particularly to a modular new type of current conversion control motor system, a motor and a current conversion control method thereof. Background Art

[0002] With the development of digital technology and energy conversion efficiency, new power electronics technology has been widely used in the field of contemporary power technology. Some household appliances and civil inverters mostly use two-level inverter topology, which consumes a lot of power and has a high harmonic content in the output waveform. In some products, it seriously affects energy consumption and product performance, and more filtering components are needed.

[0003] The above contents are only used to assist in understanding the technical solution of the present invention and do not constitute an admission that the above contents are prior art. Summary of the invention

[0004] The object of the present invention is to provide a current conversion control device, a motor and a current conversion control method thereof to address the above-mentioned defects, so as to solve the problem that the output waveform has high harmonic content when adopting a two-level inverter topology, thereby achieving the effect of reducing the harmonic content of the output waveform.

[0005] The present invention provides a current conversion control device, comprising: a current conversion unit and a control unit; wherein the current conversion unit is used to output three-phase alternating current to a motor after current conversion processing on single-phase alternating current; wherein the current conversion processing includes: rectification processing, filtering processing and inversion processing; the control unit is used to obtain the current conversion parameters of the current conversion unit and the operating parameters of the motor, and according to the current conversion parameters and the operating parameters, perform phase shift modulation and circulating current hierarchical control on the current conversion unit to realize hierarchical closed-loop control between the current conversion unit and the motor.

[0006] Optionally, the conversion unit includes: a modular single-phase rectifier module, a filter module and a modular three-phase inverter module; wherein the modular single-phase rectifier module is used to rectify the single-phase alternating current and output a DC bus voltage; the filter module is used to filter the DC bus voltage after the single-phase alternating current is rectified to obtain the filtered DC bus voltage; the modular three-phase inverter module is used to invert the filtered DC bus voltage and output three-phase alternating current, specifically, it can output a three-phase alternating current voltage.

[0007] Optionally, a modular single-phase rectifier module comprises: a boost module, a single-phase rectifier upper bridge arm and a single-phase rectifier lower bridge arm; wherein the boost module is arranged between the single-phase rectifier upper bridge arm and the single-phase rectifier lower bridge arm, and is used to boost the single-phase alternating current and then transmit it to the single-phase rectifier upper bridge arm and the single-phase rectifier lower bridge arm for rectification; each bridge arm in the single-phase rectifier upper bridge arm and / or the single-phase rectifier lower bridge arm comprises: a single-phase rectifier module; the number of single-phase rectifier modules is a first set value, and the first set value of single-phase rectifier modules are cascaded; each single-phase rectifier module comprises: a single-phase full-bridge rectifier module and / or a single-phase half-bridge rectifier module.

[0008] Optionally, a modular three-phase inverter module includes: a step-down module, a three-phase inverter upper bridge arm and a three-phase inverter lower bridge arm; wherein the step-down module is arranged between the three-phase inverter upper bridge arm and the three-phase inverter lower bridge arm, and is used to step down the three-phase alternating current after inverter processing by the three-phase inverter upper bridge arm and the three-phase inverter lower bridge arm before outputting it to the motor; each bridge arm in the three-phase inverter upper bridge arm and the three-phase inverter lower bridge arm includes: a three-phase inverter sub-module; the number of the three-phase inverter sub-modules is a second set value, and the second set value of three-phase inverter sub-modules are cascaded; each three-phase inverter sub-module includes: a three-phase full-bridge inverter sub-module and / or a three-phase half-bridge inverter sub-module.

[0009] Optionally, it also includes: a protection unit; the protection unit is used to filter the neutral, live and ground wires of the mains power to form single-phase alternating current.

[0010] Optionally, the control unit includes: a phase-shift modulation module; the phase-shift modulation module is used to use two independent sawtooth waves, adopt phase-shift modulation technology and circulating current layered control method, and output pulse signals to the rectification processing side and the inverter processing side in the conversion unit respectively, so as to drive the rectification processing side and the inverter processing side in the conversion unit through the pulse signal.

[0011] Optionally, the control unit also includes: a rectifier side sampling module; a rectifier side sampling module, which is used to collect the DC bus signal on the rectifier processing side in the conversion unit, the bridge arm voltage of each bridge arm, and / or the capacitor voltage of each single-phase rectifier module; a phase shift modulation module, which is also used to adjust the pulse signal on the rectifier processing side in the conversion unit based on the sawtooth carrier phase shift modulation technology according to the DC bus signal on the rectifier processing side, the bridge arm voltage of each bridge arm, and / or the capacitor voltage of each single-phase rectifier module, so as to achieve balanced control of the DC bus signal on the rectifier processing side, the bridge arm voltage of each bridge arm, and / or the capacitor voltage of each single-phase rectifier module.

[0012] Optionally, the control unit also includes: an inverter side sampling module; an inverter side sampling module, which is used to collect the three-phase electrical signal of the inverter processing side in the conversion unit, the inner loop current of each bridge arm, and / or the capacitor voltage of each three-phase inverter sub-module; a phase shift modulation module, which is also used to adjust the pulse signal of the inverter processing side in the conversion unit according to the three-phase electrical signal of the inverter processing side, the inner loop current of each bridge arm, and / or the capacitor voltage of each three-phase inverter sub-module, so as to realize the outer loop control and phase balance of the three-phase electrical signal of the inverter processing side, the inner loop current suppression of each bridge arm, and / or the capacitor voltage balance of each three-phase inverter sub-module.

[0013] Optionally, the control unit also includes: a load side sampling module; a load side sampling module, used to collect the three-phase current, rotor position, and / or rotor speed of the output side motor of the converter unit; a phase shift modulation module, also used to adjust the pulse signals of the rectification processing side and / or the inverter processing side in the converter unit according to the three-phase current, rotor position, and / or rotor speed of the motor, so as to realize closed-loop frequency conversion control of the output side motor of the converter unit.

[0014] Matching the above device, the present invention further provides a motor on the other hand, including: the above-mentioned current conversion control device.

[0015] To match the above-mentioned motor, the present invention provides a motor current conversion control method on the other hand, including: performing current conversion processing on single-phase AC power through a current conversion unit, and outputting three-phase AC power to the motor; wherein the current conversion processing includes: rectification processing, filtering processing and inversion processing; obtaining the current conversion parameters of the current conversion unit and the operating parameters of the motor through a control unit, and performing phase shift modulation and circulating current layered control on the current conversion unit according to the current conversion parameters and the operating parameters, so as to realize layered closed-loop control between the current conversion unit and the motor.

[0016] Optionally, the single-phase AC power is converted by a conversion unit, including: rectifying the single-phase AC power through a modular single-phase rectifier module and outputting a DC bus voltage; filtering the DC bus voltage after rectification of the single-phase AC power through a filter module to obtain a filtered DC bus voltage; inverting the filtered DC bus voltage through a modular three-phase inverter module to output three-phase AC power, which can specifically be outputting a three-phase AC voltage.

[0017] Optionally, it also includes: a protection unit for filtering the neutral, live and ground wires of the mains to form single-phase alternating current.

[0018] Optionally, the control unit performs phase-shift modulation and circulating current stratification control on the converter unit, including: using a phase-shift modulation module, utilizing two independent sawtooth waves, adopting phase-shift modulation technology and circulating current stratification control, and outputting pulse signals to the rectification processing side and the inverter processing side in the converter unit respectively, so as to drive the rectification processing side and the inverter processing side in the converter unit through the pulse signals.

[0019] Optionally, the control unit performs phase-shift modulation and circulating current layering control on the conversion unit, and also includes: collecting the DC bus signal on the rectification processing side of the conversion unit, the bridge arm voltage of each bridge arm, and / or the capacitor voltage of each single-phase rectifier module through the rectification side sampling module; through the phase-shift modulation module, also according to the DC bus signal on the rectification processing side, the bridge arm voltage of each bridge arm, and / or the capacitor voltage of each single-phase rectifier module, based on the sawtooth carrier phase-shift modulation technology, the pulse signal on the rectification processing side of the conversion unit is adjusted to achieve balanced control of the DC bus signal on the rectification processing side, the bridge arm voltage of each bridge arm, and / or the capacitor voltage of each single-phase rectifier module.

[0020] Optionally, the control unit performs phase-shift modulation and circulating current hierarchical control on the converter unit, and also includes: collecting the three-phase electrical signal of the inverter processing side in the converter unit, the inner loop current of each bridge arm, and / or the capacitor voltage of each three-phase inverter sub-module through the inverter side sampling module; through the phase-shift modulation module, the pulse signal of the inverter processing side in the converter unit is adjusted according to the three-phase electrical signal of the inverter processing side, the inner loop current of each bridge arm, and / or the capacitor voltage of each three-phase inverter sub-module, so as to realize the outer loop control and phase balance of the three-phase electrical signal on the inverter processing side, the inner loop current suppression of each bridge arm, and / or the capacitor voltage balance of each three-phase inverter sub-module.

[0021] Optionally, the control unit performs phase-shift modulation and circulating current stratification control on the converter unit, and also includes: collecting the three-phase current, rotor position, and / or rotor speed of the output side motor of the converter unit through the load side sampling module; and adjusting the pulse signals of the rectification processing side and / or the inverter processing side in the converter unit according to the three-phase current, rotor position, and / or rotor speed of the motor through the phase-shift modulation module, so as to realize closed-loop frequency conversion control of the output side motor of the converter unit.

[0022] The solution of the present invention, by adopting the topological structure of the sub-module single-phase full-bridge rectifier circuit and the three-phase half-bridge inverter cascade circuit, ensures the balanced energy conversion of each phase and each sub-module of the converter circuit through sawtooth wave phase shift modulation and voltage-sharing circulating current control theory, solves the problem of high power consumption of power device elements using the two-level inverter topology, and achieves the effect of reducing the power consumption of power device elements; further solves the problem of uneven distribution of power loss in the sub-modules, which is beneficial to reducing the power consumption of power components.

[0023] Furthermore, the solution of the present invention, by adopting the topological structure of the sub-module single-phase full-bridge rectifier circuit and the three-phase half-bridge inverter cascade circuit, through the sawtooth wave phase shift modulation and the voltage-sharing circulating current control theory, the three-phase AC voltage finally outputted has less harmonic content relative to the two-level IGBT trigger drive, and can realize the smooth control operation of the motor; thereby optimizing the problem of high-order harmonic content of the voltage waveform output by the inverter, so that the control effect of the motor is significant.

[0024] Furthermore, the solution of the present invention, by adopting two independent sawtooth carrier phase shifting technologies, is based on the modular circulating current suppression layered balance control and RFOC closed-loop control principles to establish inner and outer multi-layer control loops to respectively control the bus voltage on the rectifier side and the three-phase variable frequency voltage output on the inverter side, thereby realizing variable frequency drive control of the synchronous compression motor, reducing the energy loss of the power device IGBT, and significantly reducing the harmonic content of the output three-phase voltage.

[0025] Therefore, the solution of the present invention, by adopting a modular cascade conversion topology structure formed by a single-phase full-bridge rectifier module side and a three-phase half-bridge inverter module side, inputs single-phase AC power and outputs three-phase AC voltage, thereby solving the problem of high harmonic content in the output waveform caused by the use of a two-level inverter topology and achieving the effect of reducing the harmonic content of the output waveform.

[0026] Among them, the modular cascade conversion topology structure formed by the single-phase full-bridge rectifier module side and the three-phase half-bridge inverter module side is a flexible conversion cascade topology structure, which can flexibly realize the variable frequency modulation output of the motor power.

[0027] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention.

[0028] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of an embodiment of a variable current control device of the present invention;

[0030] Figure 2A schematic diagram of a control system principle of an embodiment of a variable flow air conditioning compressor;

[0031] Figure 3 A schematic diagram of the structure of a single module on the rectifier and inverter side of a converter according to an embodiment;

[0032] Figure 4 A schematic diagram of the structure of another embodiment of a single module on the rectifier and inverter side of a converter;

[0033] Figure 5 Schematic diagram of the topological structure of an embodiment of a multi-level cascade converter when the number of inter-phase bridge arm modules is 6; wherein (a) is a schematic diagram of the structure of the first part of the multi-level cascade converter, (b) is a schematic diagram of the structure of the second part of the multi-level cascade converter, (c) is a schematic diagram of the structure of the third part of the multi-level cascade converter, and (d) is a schematic diagram of the structure of the fourth part of the multi-level cascade converter;

[0034] Figure 6 The present invention is a schematic diagram of the structure of an embodiment of a cascade converter topology overall drive control system, wherein (a) is a schematic diagram of the overall structure, and (b) is a schematic diagram of the structure of a sawtooth carrier phase shift modulation module;

[0035] Figure 7 Schematic diagram of the structure of an embodiment of hierarchical control of drive system modules; wherein (a) is a schematic diagram of the structure of capacitor voltage hierarchical balance control, (b) is a schematic diagram of the structure of the phase balance control loop, (c) is a schematic diagram of the structure of the upper and lower bridge arm balance control loop, (d) is a schematic diagram of the structure of the circulating current suppression control loop, and (e) is a schematic diagram of the structure of the MMC submodule energy balance control loop;

[0036] Figure 8 Schematic diagram of the structure of an embodiment of the control strategy loop of the modular inverter side and the rectifier side, wherein (a) is a schematic diagram of the structure of the RFOC modular inverter control of the synchronous motor, (b) is a schematic diagram of the structure of the rectifier side PI control, and (c) is a schematic diagram of the structure of the rectifier side closed-loop balancing control;

[0037] Fig. 9 A schematic flow chart of an embodiment of a variable current control method of the present invention;

[0038] Fig.10 It is a flow chart of an embodiment of the method of the present invention for converting single-phase alternating current;

[0039] Fig.11 It is a flow chart of an embodiment of a pulse signal for controlling a current conversion unit according to a rectifier side in a method of the present invention;

[0040] Fig.12It is a flow chart of an embodiment of a method of the present invention for controlling a pulse signal of a current conversion unit according to an inverter side;

[0041] Fig.13 The present invention is a flow chart of an embodiment of a method for controlling a pulse signal of a current conversion unit according to a load side. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only 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 making creative work are within the scope of protection of the present invention.

[0043] According to an embodiment of the present invention, a variable current control device is provided. Figure 1 The structure diagram of an embodiment of the device of the present invention is shown. The current conversion control device may include: a current conversion unit such as a cascade current conversion module and a control unit. The current conversion unit and the control unit may be arranged in sequence between an AC power supply and an electrical device such as a motor.

[0044] Specifically, the conversion unit is a modular single-phase-three-phase cascade conversion topology, which can be used to convert single-phase AC power and output three-phase AC voltage to electrical equipment. The modular single-phase-three-phase cascade conversion topology is a flexible conversion cascade topology structure, which can flexibly realize the variable frequency modulation output of motor power. Electrical equipment may include: motors such as air-conditioning compressors. The conversion process may include: rectification process, filtering process and inversion process.

[0045] In an optional example, the conversion unit may include: a modular single-phase rectifier module, a filter module and a modular three-phase inverter module. The modular single-phase rectifier module is such as a single-phase modular full-bridge rectifier circuit. The filter module is such as an LC filter circuit. The modular three-phase inverter module is such as a three-phase modular half-bridge inverter circuit. The output end of the modular single-phase rectifier module is connected to the input end of the modular three-phase inverter module, and the filter module is arranged between the modular single-phase rectifier module and the modular three-phase inverter module.

[0046] Specifically, the modular single-phase rectifier module can be used to output a DC bus voltage after rectifying single-phase alternating current such as single-phase AC.

[0047] Specifically, the filtering module can be used to filter the DC bus voltage after the single-phase AC power is rectified to obtain the filtered DC bus voltage.

[0048] Specifically, the modular three-phase inverter module can be used to invert the DC bus voltage after filtering and output three-phase AC power. Specifically, it can output three-phase AC voltage, which can be used as a driving voltage for a motor such as a compressor.

[0049] For example, the inverter topology structure of modular converter is adopted for compressor drive circuit, which reduces the breaking time of single power device and the energy loss of power device IGBT. Among them, the steady-state output ripple of DC bus on the rectifier side is smooth, and the output on the inverter side can act on synchronous motor control, which can meet the needs under different bus voltage, output power and speed conditions, and its speed regulation range is more flexible.

[0050] For example, the cascade conversion module of the system adopts single-phase full-bridge rectification and three-phase half-bridge inverter, and some of them adopt IGBT modular cascade. The LC filter circuit is used in the middle to ensure that the output DC bus DC fluctuation is smaller. This part can achieve three-phase conversion output with small harmonics and high power factor. Among them, the single-phase AC output enters the new conversion control system. The system is a modular single-phase full-bridge rectification and three-phase full-bridge inverter topology. The AC end first passes through the modular rectification circuit.

[0051] Therefore, the single-phase AC power is converted by the modular single-phase rectifier module, the filter module and the modular three-phase inverter module. The modular single-phase rectifier module and the modular three-phase inverter module are used to reduce the energy loss of the power device by reducing the disconnection time of the single power device. The DC bus steady-state output ripple on the rectifier side is smooth, so that the three-phase AC voltage output on the inverter side has less harmonic content, and the voltage waveform of the inverter output is optimized, which is conducive to the stable control and operation of electrical equipment such as motors.

[0052] Optionally, the modular single-phase rectifier module may include: a boost module (such as a rectifier-side inductor), a single-phase rectifier upper bridge arm and a single-phase rectifier lower bridge arm.

[0053] Specifically, the boost module is arranged between the single-phase rectifier upper bridge arm and the single-phase rectifier lower bridge arm, and can be used to boost the single-phase alternating current and then transmit it to the single-phase rectifier upper bridge arm and the single-phase rectifier lower bridge arm for rectification.

[0054] Specifically, each bridge arm in the single-phase rectifier upper bridge arm and / or the single-phase rectifier lower bridge arm may include: a single-phase rectifier module. The number of single-phase rectifier modules is a first set value, and the first set value of single-phase rectifier modules are cascaded. Each single-phase rectifier module may include: a single-phase full-bridge rectifier module and / or a single-phase half-bridge rectifier module, and of course, it may be preferably a single-phase full-bridge rectifier module.

[0055] For example, for the rectifier side circuit, a single-phase full-bridge modular multilevel converter technology (MMC) topology is used. The clean and reliable single-phase AC power formed by the mains neutral, live and ground wires after strong electric filtering is modularly rectified after the upper and lower bridge arms to form an adjustable DC bus voltage, which is more in line with the actual product design. The cascaded IGBT component topology makes the rectifier side output and control more flexible. At the same time, this part replaces the PFC circuit to achieve power factor correction. Among them, the output three-phase voltage harmonic content is significantly reduced, the filter component capacity is reduced, and the controller has a significant cost reduction effect.

[0056] For example: a modular full-bridge topology sub-circuit is used in which N IGBTs are connected in series and then in parallel. Each phase of the AC signal is divided into two upper and lower bridge arms. Each bridge arm can use N full-bridge topology sub-modules. The number of IGBTs in the bridge arm sub-module is 4, and the number of bridge arm sub-modules (SM) is 3. On the rectifier side, the AC power supply is filtered and then transferred through the inductor boost. Then the full-bridge sub-module on the rectifier side is turned on and rectified. The output voltage is filtered by the sub-capacitor energy storage, and finally the DC bus voltage U with a small output ripple is superimposed. dc The bridge arm submodule of the full-bridge module on the rectifier side is a cascade topology of four IGBTs. This solution has low output ripple and plays a role in power factor correction, replacing the PFC structure in some controllers.

[0057] Therefore, a modular single-phase rectifier module is formed by a boost module, a single-phase rectifier upper bridge arm and a single-phase rectifier lower bridge arm to achieve boost and rectification of single-phase AC power, which can make the steady-state output ripple of the DC bus on the rectifier side smooth, and is beneficial to reducing the harmonic content of the three-phase AC voltage finally output by the inverter.

[0058] Optionally, the modular three-phase inverter module may include: a step-down module (such as an inverter-side inductor), a three-phase inverter upper bridge arm, and a three-phase inverter lower bridge arm.

[0059] Specifically, the step-down module is arranged between the three-phase inverter upper bridge arm and the three-phase inverter lower bridge arm, and can be used to step down the three-phase alternating current after being inverted by the three-phase inverter upper bridge arm and the three-phase inverter lower bridge arm before outputting it to the motor.

[0060] For example: an inductor (L s ), can be used for voltage reduction, and the voltage signal can act on the three-phase synchronous compression motor through the inductor output.

[0061] Specifically, each bridge arm in the three-phase inverter upper bridge arm and the three-phase inverter lower bridge arm may include: a three-phase inverter submodule. The number of the three-phase inverter submodules is a second set value, and the second set value of three-phase inverter submodules are cascaded. Each three-phase inverter submodule may include: a three-phase full-bridge inverter submodule and / or a three-phase half-bridge inverter submodule, and of course, it can be preferably a three-phase half-bridge inverter submodule.

[0062] For example: the cascaded half-bridge IGBT module inverter topology adopts internal and external dual-loop control to make the control output more flexible and can meet the operation of synchronous motors under different output power or speed conditions.

[0063] For example: On the inverter side, the DC bus voltage U dc As the inverter input side, since it comes from modular multi-level rectification, the output range is relatively flexible. dc The three-phase AC power U is converted into the control motor through the modular inverter topology. A , U B , U C The submodule of the modular half-bridge inverter topology adopts a topology structure in which N IGBTs are connected in series and then cascaded in pairs, where N is a natural number.

[0064] If the number of IGBTs in the submodule is 2, the submodule capacitor voltage is U c_j , IGBT switch voltage is V x At the same time, the three-phase output comes from three inverter bridge arms. Like the rectifier side, the bridge arm of each phase of this part can adopt N half-bridge sub-module topologies. In the solution of the present invention, the number of bridge arm sub-modules (SM) can be 3.

[0065] Therefore, a modular three-phase inverter module is formed by a step-down module, a three-phase inverter upper bridge arm and a three-phase inverter lower bridge arm, so as to realize three-phase inverter of the DC bus voltage obtained by boosting and rectifying the single-phase AC power, and output a three-phase AC voltage with less harmonic content, which is beneficial to the smooth operation of the drive motor.

[0066] It can be seen that the preferred topology is the single-phase full-bridge rectifier-three-phase half-bridge inverter, and the flux vector and power control loops of the motor system are introduced at the same time. It is non-fixed frequency and more in line with the actual speed control of the synchronous compression motor. More specifically, the rectifier side is an AC voltage source, and the motor system uses RFOC and power speed control loops to adjust the speed.

[0067] In this way, a new modular cascade conversion topology is adopted, which is divided into a single-phase full-bridge rectifier module side and a three-phase half-bridge inverter module side, inputting single-phase AC power and outputting three-phase AC voltage, and both parts are modular signal hierarchical control. Through the modular single-phase rectifier module and the modular three-phase inverter module, a modular single-phase full-bridge rectifier + modular half-bridge inverter cascade topology can be formed. The number of bridge arm submodules can be flexibly set according to the use requirements, such as 3, and the output load is a three-phase synchronous motor. The input side voltage is: after strong electric filtering, the rectifier side single-phase AC input. The carrier control method is: sawtooth wave carrier phase shift + rotor flux directional control (i.e. RFOC control).

[0068] Among them, the first set value and the second set value can be the same or different. That is to say, the number of submodules in each bridge arm can be flexibly set according to the use requirements. For example, the number of upper and lower bridge arm submodules of the rectifier and inverter modules is 3. Both the rectifier and inverter are modular multi-level topologies, the rectifier is a single-phase full-bridge topology, and the inverter is a three-phase half-bridge topology. The upper and lower bridge arms of each phase use 3 submodules in series (N=3).

[0069] For example: it can be used in three-phase power output systems of different levels, but in high-power systems such as megawatt systems, a larger number of sub-modules are required. More sub-modules can effectively suppress high-order harmonics and protect the system, making it more suitable for application in power systems.

[0070] Another example: it can also be used in synchronous motor drive circuits of different powers, such as through rotor flux oriented control (RFOC) and carrier phase shift PWM pulse modulation, variable frequency speed regulation closed loop control of synchronous compressors can be achieved. It can strengthen the advantages of air-conditioning series products in variable frequency drive, enhance product performance quality and power utilization, and greatly extend the service life of our products due to the balanced power of submodules.

[0071] Specifically, the control unit can be used to obtain the conversion parameters of the conversion unit and the operating parameters of the motor, and perform phase shift modulation and circulating current layered control on the conversion unit according to the conversion parameters and operating parameters, so as to realize layered closed-loop control between the conversion unit and the motor.

[0072] For example: the cascade conversion topology control system of modular single-phase full-bridge rectification and multi-level half-bridge three-phase inverter adopts two independent sawtooth carrier phase shifting technologies, based on modular circulating current suppression hierarchical balance control and RFOC closed-loop control principles, to establish internal and external multi-layer control loops to control the rectifier side bus voltage and the inverter side three-phase variable frequency voltage output respectively, to realize the synchronous compression motor variable frequency drive control.

[0073] For example, for low- and medium-power compressors in the field of household air conditioners, a new inverter structure-controlled single-cylinder compressor inverter control system design scheme is proposed. Based on the air conditioner compressor control circuit, the topology of the sub-module single-phase full-bridge rectifier circuit and the three-phase half-bridge inverter cascade circuit is adopted. Through the sawtooth wave phase shift modulation and voltage-sharing circulation control theory, the energy conversion balance of each phase and each sub-module of the inverter circuit is guaranteed. Compared with the two-level IGBT trigger drive, the final output three-phase AC voltage has less harmonic content, which can realize the smooth control operation of the motor. Therefore, it not only solves the problem of uneven distribution of sub-module power loss, but also optimizes the problem of high-order harmonic content of the inverter output voltage waveform, and the control effect of the motor is significant.

[0074] Therefore, by using the conversion unit and the control unit, the conversion processing is performed based on the single-phase AC point, and the phase shift modulation and circulating current control are performed on the conversion unit. This can solve the problem of high power consumption of power device components using the two-level inverter topology, that is, solve the problem of uneven distribution of sub-module power losses, and reduce the power consumption of power device components; it can also optimize the problem of high high-order harmonic content in the inverter output voltage waveform, reduce the harmonic content, and facilitate the smooth control and operation of electrical equipment such as motors.

[0075] In an optional example, the control unit may include: a phase shift modulation module, such as a sawtooth wave phase shift modulation module, which may be connected to the single-phase modular full-bridge rectifier circuit and the three-phase modular half-bridge inverter circuit in the conversion unit respectively.

[0076] Specifically, the phase-shift modulation module can be used to utilize two independent sawtooth waves, adopt phase-shift modulation technology and circulating current layered control method, and output pulse signals to the rectification processing side and the inverter processing side in the conversion unit respectively, such as outputting pulse signals to the modular single-phase rectification module and the modular three-phase inverter module in the conversion unit respectively. Preferably, it can be a PWM pulse signal to drive the rectification processing side and the inverter processing side in the conversion unit through the pulse signal.

[0077] For example: two independently acting sawtooth waves are generated by means of a DSP processor or hardware analog circuit, and phase-shift modulation technology and circulating current layered control are used to output PWM pulse signals to each sub-module of the single-phase rectifier bridge arm and the three-phase modular inverter bridge arm respectively.

[0078] For example: the modulation system uses two independent control loops to output multiple channels on the rectifier side and the inverter side respectively. The PWM mode combining full-bridge and half-bridge makes the system control more flexible. The overall control mode of the system can be divided into DC modular control on the rectifier side and motor variable frequency drive control on the inverter side. Both use sawtooth carrier phase shift modulation technology and layered circulating current balancing control. The difference is that the rectifier side uses the DC bus voltage as the output reference signal, and the inverter side uses the actual variable frequency speed or PQ control as the reference point for closed-loop control.

[0079] Therefore, through the phase-shift modulation module, based on two independent sawtooth waves through phase-shift modulation technology and circulating current layered control, pulse signals are output to the rectification processing side and the inverter processing side respectively, so that the rectification processing side and the inverter processing side can be driven separately, and the reliability of the drive can be guaranteed.

[0080] Optionally, the control unit may further include: a rectifier side sampling module, such as a rectifier side AC / DC voltage and current sampling module, a submodule capacitor voltage sampling module, etc. The control unit performs phase shift modulation and circulating current layering control on the converter unit, and may further include: a process of controlling the pulse signal of the converter unit according to the rectifier side.

[0081] Specifically, the rectifier side sampling module can be used to collect the DC bus signal on the rectifier processing side in the converter unit, the bridge arm voltage of each bridge arm (i.e., the bridge arm voltage of each bridge arm in the single-phase rectifier upper bridge arm and / or the single-phase rectifier lower bridge arm), and / or the capacitor voltage of each single-phase rectifier module (i.e., the single-phase rectifier module in each bridge arm). The DC bus signal may include the DC bus voltage, the DC bus current, etc.

[0082] Specifically, the phase-shift modulation module can also be used in a single-phase closed-loop control circuit with the DC bus voltage output on the rectifier side as a reference. According to the DC bus signal on the rectifier processing side, the bridge arm voltage of each bridge arm, and / or the capacitor voltage of each single-phase rectifier module, based on the sawtooth carrier phase-shift modulation technology, the pulse signal on the rectifier processing side in the conversion unit is adjusted to achieve balanced control of the DC bus signal on the rectifier processing side, the bridge arm voltage of each bridge arm, and / or the capacitor voltage of each single-phase rectifier module.

[0083] For example: the rectifier side adopts a single-phase closed-loop control circuit with the output DC bus voltage as a reference. Based on the sawtooth carrier phase-shift modulation technology, the DC bus voltage, current, bridge arm voltage, and sub-module capacitor voltage are balanced and controlled to achieve different levels of DC bus voltage output under constant AC power.

[0084] For example: the rectifier switch device topology uses sawtooth carrier phase shift modulation technology as the PWM modulation signal. Under the action of 220VAC voltage, the phase-to-phase energy balance, the total voltage of each phase bridge arm and the capacitor voltage of each submodule are detected respectively. The output voltage amplitude of the rectifier side can be controlled with the duty cycle of the rectifier submodule switch (SMn). For example, the PI closed-loop control circuit on the rectifier side uses the DC output power or DC bus voltage as the reference point, and calculates the DC bus current after the actual sampling to obtain the DC bus reference voltage U ref , and then through the sawtooth carrier signal comparator, a PWM drive signal that can be used to adjust the full-bridge sub-module is obtained to control the DC bus output.

[0085] Among them, for the rectifier feedback loop, the control method adopts the voltage energy layered transmission method. It is mainly inner and outer loop control. The inner loop adopts phase voltage balance control, bridge arm voltage balance control, submodule capacitor voltage balance, and the feedback reference signal is power or DC bus DC voltage U dc The carrier phase shift on the rectifier side uses N sawtooth waves to shift the phase by π / N in sequence to obtain the best harmonic elimination characteristics, that is, the range of the carrier phase shift angle is 0-π / 2N.

[0086] Therefore, through a single-phase closed-loop control circuit with the output DC bus voltage as a reference on the rectifier side, based on the sawtooth carrier phase-shift modulation technology, the DC bus voltage, current, bridge arm voltage, and sub-module capacitor voltage are balanced and controlled respectively, so that different levels of DC bus voltage output under constant AC power can be achieved, and the output DC bus voltage can be flexibly adjusted.

[0087] Optionally, the control unit may further include: an inverter side sampling module, such as an inverter side three-phase current and voltage sampling module, a submodule capacitor voltage sampling module, etc. The control unit performs phase shift modulation and circulating current layering control on the converter unit, and may further include: a process of controlling the pulse signal of the converter unit according to the inverter side.

[0088] Specifically, the inverter side sampling module can be used to collect the three-phase electrical signals of the inverter processing side in the converter unit, the inner loop current of each bridge arm (i.e., the inner loop current of each bridge arm in the three-phase inverter upper bridge arm and / or the three-phase inverter lower bridge arm), and / or the capacitor voltage of each three-phase inverter submodule (i.e., the three-phase inverter submodule in each bridge arm). The three-phase electrical signals may include: three-phase voltage signals, three-phase current signals, etc.

[0089] Specifically, the phase-shift modulation module can also be used in a closed-loop control loop with the speed and output power of the motor driven by the three-phase AC power output from the inverter processing side as a reference. According to the three-phase electrical signal of the inverter processing side, the inner loop current of each bridge arm, and / or the capacitor voltage of each three-phase inverter sub-module, the pulse signal of the inverter processing side in the converter unit is adjusted to achieve outer loop control and phase balance of the three-phase electrical signal on the inverter processing side, suppression of the inner loop current of each bridge arm, and / or hierarchical control of capacitor voltage balance of each three-phase inverter sub-module.

[0090] For example: the inverter side submodule of the converter module is a 2-IGBT cascade half-bridge structure. With the speed and output power of the synchronous motor as reference, the three-phase variable frequency voltage and current output is achieved through the hierarchical control method of outer loop voltage control, phase balance, bridge arm inner loop current suppression and submodule capacitor voltage balance. For example, a sawtooth phase-shift carrier is used to control the full-bridge PWM output. The outer loop establishes a control loop through the output voltage and power of the rectifier side to meet the voltage requirements of different levels on the inverter side within the demand range. The dual-loop control can act independently on the rectifier inverter outer loop, but the inner layer adopts hierarchical control to meet the module capacitor voltage balance.

[0091] Among them, the DC bus voltage output from the modular rectifier side enters the modular multi-level inverter circuit after capacitor filtering. The inverter circuit adopts a half-bridge sub-module structure with dual IGBTs in parallel, and uses speed or power as the feedback adjustment of the rotor flux oriented control (RFOC) of the entire motor system, so that the module outputs a three-phase AC signal. The first stage is the overall control of the converter feedback system, the outer loop control is the motor speed control or output power control, and the inner loop is the current control of the dq0 rotating coordinate system. The second stage of modular inversion is phase balance control. The third stage is bridge arm balance control. The fourth stage is sub-module capacitor voltage balance. Each sub-module of each bridge arm corresponds to an independent control loop, and its reference voltage is one-Nth of the capacitor voltage of the bridge arm.

[0092] For example: In the link of outer loop parameter control, the current signal I of the three-phase output is sampled A ,I B ,I C , the AC component is converted into the DC component of the dq quadrant through Park and Clarke transformation. At the same time, the torque, position, angular velocity and other signals of the motor stator load are sampled. The i in the q quadrant is formed through PI operation with the external reference given value. q Component given value. In the system d quadrant i d The component given value is initially 0. When the relevant DC components (position, angular velocity, torque power, etc.) are injected into the system as output reference components, the components of the dq quadrants are inversely transformed and converted into AC components that can act on the motor system, and its output is mainly a three-phase reference voltage.

[0093] For example: sampling the upper and lower bridge arm capacitor voltage signal U on each submodule c_pj(n) , U c_nj(n) . At the same time, the voltage signal obtained in the previous step is injected into the modulation system. The modulation system uses sawtooth carrier phase shift modulation, and the submodule capacitor voltage and three-phase voltage signal are subjected to PI iterative operation to form the PWM fundamental wave on each submodule. Then the fundamental waves on the upper and lower bridge arms are compared with the phase-shifted sawtooth carrier to form multiple PWM output signals on the rectifier module and inverter module, and control the gate signal on each IGBT in the topology.

[0094] Therefore, through a single-phase closed-loop control loop with the output DC bus voltage as a reference on the rectifier side, based on the sawtooth carrier phase-shift modulation technology, the outer loop control and phase balance, bridge arm inner loop current suppression, and capacitor voltage balance of the three-phase electrical signal are respectively controlled in a hierarchical manner, so that flexible adjustment of the three-phase variable frequency voltage and current output can be achieved.

[0095] Optionally, the control unit may further include: a load side sampling module, such as a motor position and speed sensor, etc. The control unit performs phase shift modulation and circulating current layering control on the converter unit, and may further include: a process of controlling a pulse signal of the converter unit according to the load side.

[0096] Specifically, the load-side sampling module can be used to collect the three-phase current, rotor position, and / or rotor speed of the output-side motor of the converter unit.

[0097] Specifically, the phase-shift modulation module can also be used in a closed-loop control loop with the rotational speed and output power of a motor driven by the three-phase AC power output from the inverter processing side as a reference. According to the three-phase current, rotor position, and / or rotor speed of the motor, the pulse signals of the rectification processing side and / or the inverter processing side in the converter unit are adjusted to achieve closed-loop frequency conversion control of the motor on the output side of the converter unit.

[0098] For example: the output of the modular cascade converter acts as a synchronous compressor. The output end monitors the three-phase current, rotor position and speed, while the input end adds power regulation and speed reference point regulation. The overall new control system uses RFOC to achieve closed-loop variable frequency control of the compressor.

[0099] For example, the submodules inside the rectifier module and the inverter module all use carrier phase shift hierarchical control to rectify the single-phase AC power and then output the inverter output, which can make the three-phase motor frequency conversion AC signal. The overall external control loop of the two parts, the DC bus voltage closed-loop feedback control and the RFOC motor speed control, control their own modules separately, making the regulation capability of the entire converter system more flexible.

[0100] Among them, the specific hierarchical control strategy of carrier phase shift modulation is that the upper and lower bridge arms of the rectifier and inverter parts cannot be opened at the same time, so it is necessary to invert the fundamental signal, and then the carrier phase shift angle is 2π / N for each submodule of the full bridge and π / N for the half bridge. The outer loop control is the motor RFOC closed-loop control. Different from the direct output of three-phase voltage, the reference point of this system is mainly the stator speed or torque, and the control method can be diversified according to actual needs.

[0101] Therefore, by monitoring the three-phase current, motor yoke rotor position and speed on the output side of the converter unit and adding power regulation and speed reference point adjustment at the input end, closed-loop frequency conversion control of the compressor can be achieved, which is beneficial to further ensure the operating stability of the motor.

[0102] In an optional implementation, the system may further include: a protection unit. The protection unit, such as a strong electric filter and protection circuit, may be arranged between an AC power source such as 220V AC and a conversion unit such as a cascaded conversion module.

[0103] Specifically, the protection unit can be used to filter the neutral, live and ground wires of the mains to form single-phase alternating current, that is, to form clean and reliable single-phase alternating current. In other words, the protection unit can be used to filter the alternating current power supply to form an alternating current that meets practical needs (stable and clean). Figure 4 In the example shown, the mains power is 220V AC, and the three wires are respectively the neutral, live and ground wire (i.e. N, L, PE), and then the strong current filtering and protection module outputs a stable and clean single-phase AC (i.e. two wires L and N). The so-called clean and stable means reducing the interference (harmonics, etc.) in the external power grid through secondary filtering.

[0104] For example: when the power supply of the compressor main controller is started, the zero, live and ground wire ports connected to the mains power are output through the strong electric secondary filter circuit to obtain a single-phase AC voltage. At the same time, a strong electric filter and protection circuit (such as a discharge control chip) is added to the zero and live wire output ports. When AC power is present, the circuit is broken, and when AC power is disconnected, a short circuit is formed, thereby forming a rapid discharge and releasing the residual pressure of large capacitor components in the system.

[0105] For example, 220V AC voltage passes through the neutral, live and ground wire strong electric filter protection circuit to output single-phase AC voltage. Then the single-phase voltage enters the cascade converter module.

[0106] Therefore, the protection unit outputs a single-phase AC voltage through a strong electric filter from the neutral and live ground of the mains, and then outputs it to the motor after current conversion based on the single-phase AC voltage with low power consumption. This can reduce the breaking time of a single power device and thus reduce the energy loss of power devices such as IGBTs.

[0107] After a large number of experimental verifications, the technical solution of the present invention is adopted, by adopting the topological structure of the sub-module single-phase full-bridge rectifier circuit and the three-phase half-bridge inverter cascade circuit, through the sawtooth wave phase shift modulation and the voltage-sharing circulating current control theory, to ensure the balanced energy conversion of each phase and each sub-module of the converter circuit, solve the problem of uneven distribution of power loss of the sub-module, which is beneficial to reduce the power consumption of power components.

[0108] According to an embodiment of the present invention, a motor corresponding to the current conversion control device is also provided. The motor may include: the current conversion control device described above.

[0109] In some synchronous compressor drive circuit designs, SPWM or SVPWM software drive algorithms are often used to stabilize the motor flux control. However, the control method of SVPWM is too complicated in three-level and above topologies, with high harmonic content, which greatly wastes design resources and is not conducive to rapid product development and design.

[0110] In an optional embodiment, the scheme of the present invention proposes a design scheme for a single-cylinder compressor current conversion control system controlled by a new type of converter structure for medium and low power compressors in the field of household air conditioners. Based on the air-conditioning compressor control circuit, the topological structure of the sub-module single-phase full-bridge rectifier circuit and the three-phase half-bridge inverter cascade circuit is adopted. Through the sawtooth wave phase shift modulation and the voltage-sharing circulating current control theory, the energy conversion balance of each phase and each sub-module of the converter circuit is guaranteed. The final output three-phase AC voltage has less harmonic content than the two-level IGBT trigger drive, and the smooth control operation of the motor can be achieved. Thereby, not only the problem of uneven distribution of power loss in the sub-module is solved, but also the problem of high content of high-order harmonics in the voltage waveform of the inverter output is optimized, and the control effect of the motor is significant.

[0111] That is to say, the solution of the present invention proposes a novel modular single-phase full-bridge rectifier and multi-level half-bridge three-phase inverter cascade conversion topology control system, adopts two independent sawtooth carrier phase shifting technologies, and based on the modular circulating current suppression layered balance control and RFOC closed-loop control principles, establishes internal and external multi-layer control loops to respectively control the rectifier side bus voltage and the inverter side three-phase variable frequency voltage output, thereby realizing the synchronous compression motor variable frequency drive control.

[0112] Among them, in the scheme of the present invention, the topology is: modular single-phase full-bridge rectifier + modular half-bridge inverter cascade topology, the number of bridge arm submodules is 3, and the output load is a three-phase synchronous motor. The input side voltage is: single-phase AC input on the rectifier side after strong electric filtering. The carrier and motor control mode is: sawtooth wave carrier phase shift + rotor flux oriented control (i.e. RFOC control).

[0113] Optionally, in the solution of the present invention, the inverter topology structure of the modular converter is adopted for the compressor drive circuit, which reduces the disconnection time of a single power device and reduces the energy loss of the power device IGBT. Among them, the steady-state output ripple of the DC bus on the rectifier side is smooth, and the output on the inverter side acts on the synchronous motor control, which can meet the requirements under different bus voltages, output power and speed conditions, and its speed regulation range is more flexible.

[0114] Optionally, in the solution of the present invention, for the rectifier side circuit, a single-phase full-bridge modular multilevel converter technology (i.e., MMC) topology is adopted. The clean and reliable single-phase AC power formed after the strong electric filtering of the city power is modularly rectified after the upper and lower bridge arms to form an adjustable DC bus voltage, which is more in line with the actual product design. The cascaded IGBT component topology makes the output and control of the rectifier side more flexible; at the same time, this part replaces the PFC circuit to achieve power factor correction. Among them, the output three-phase voltage harmonic content is significantly reduced, the filter device capacity is reduced, and the controller has a significant cost reduction effect.

[0115] Optionally, in the solution of the present invention, the cascaded half-bridge IGBT module inverter topology adopts internal and external dual-loop control to make the control output more flexible and can meet the operation of the synchronous motor under different output power or speed conditions.

[0116] Among them, the scheme of the present invention can be applied to three-phase power output systems of different levels, but in high-power systems such as megawatt-level systems, the number of sub-modules required is large. More sub-modules can effectively suppress high-order harmonics and protect the system, which is more suitable for application in power systems. However, in synchronous compressor systems, too many sub-modules will cause excessive hardware costs, and more sampling data, which requires higher computing power for system chips. At the same time, when starting at low frequency, it is technically necessary to add a boost circuit to achieve pre-start boost.

[0117] In addition, the solution of the present invention can also be applied to synchronous motor drive circuits of different powers. For example, variable frequency speed regulation closed-loop control of synchronous compressors can be achieved through rotor flux oriented control (RFOC) and carrier phase-shifted PWM pulse modulation; the advantages of air-conditioning series products in variable frequency drive can be strengthened, and the performance quality and power utilization of products can be enhanced. Due to the power balance of sub-modules, the service life of our products can be greatly extended. However, the number of modules required for high-power motor control is large, and the component cost is large; at the same time, the circuit topology network samples more data, and requires higher DSP data computing capabilities.

[0118] For example, the full-speed range motor drive solution based on MMC is suitable for low-speed operation, has good starting performance, and a wide speed regulation range, but this drive mode only considers DC side voltage inversion, and the main effect is on the induction motor. In other words, the full-speed range motor drive based on MMC is the full-speed speed regulation of the IM motor, and the system flexibility is high, but the rectifier side is DC voltage and the speed regulation is VF speed regulation; while in the solution of the present invention, the rectifier side is an AC voltage source, and the motor system uses RFOC and power speed regulation control loop to regulate the speed.

[0119] For example: the modular multi-level converter four-quadrant inverter solution is to solve the problems such as capacitor voltage fluctuations when MMC is running at low frequency, and the high-frequency injection method will bring about large current impacts. However, this method is more suitable for high-voltage and high-power electric energy conversion occasions. At the same time, the low-frequency operation is at 5Hz and 50Hz, and there is no control loop, which cannot reflect the transient changes in the frequency conversion regulation process. In other words, the MMC four-quadrant converter mainly focuses on the capacitor fluctuation and current impact problems when running at low frequency, and adopts a rectifier module to adopt three-phase rectification while the upper and lower bridge arms are full bridge and half bridge. However, the solution of the present invention adopts the current conversion topology of single-phase full-bridge rectification-three-phase half-bridge inversion, and introduces the control loops such as the flux vector and power of the motor system at the same time, which is non-fixed frequency and more in line with the actual speed control of the synchronous compression motor.

[0120] For example: full-bridge MMC type high-voltage three-phase to single-phase direct converter and its control scheme, the converter includes H-bridge links and filter inductors, and the topology uses star linking to achieve single-phase load output, but the system output is a single-phase load, which mainly plays a role in grid-side rectification and is not suitable for three-phase AC motor drive. In other words, the full-bridge MMC type high-voltage three-phase to single-phase direct converter and its control scheme are three-phase modular rectification, the sub-modules use full-bridge modules, the number of H-bridge chains is 6, and the star-linked output mainly meets the voltage of single-phase loads, which is suitable for grid rectification output, but not suitable for drive circuits.

[0121] In an optional example, the solution of the present invention adopts a novel modular cascade conversion topology structure, which is divided into a single-phase full-bridge rectifier module side and a three-phase half-bridge inverter module side, inputs single-phase AC power, and outputs three-phase AC voltage. Both parts are modular signal hierarchical control. In this solution, the number of upper and lower bridge arm submodules of the rectifier and inverter modules is 3.

[0122] Optionally, two independently acting sawtooth waves are generated by means of a DSP processor or a hardware analog circuit, and phase shift modulation technology and circulating current layered control are used to output PWM pulse signals to each submodule of the single-phase rectifier bridge arm and the three-phase modular inverter bridge arm respectively.

[0123] Among them, two independently acting sawtooth waves act on two module units respectively, and they are independent of each other and do not interfere with each other, which is convenient for subsequent phase shift processing of different modules. Using DSP processor programming output or hardware simulation circuit is a way to realize the carrier, both of which can be used. DSP saves peripheral circuit design resources, but using pure hardware simulation is cheaper.

[0124] Optionally, the bridge arm submodule of the full-bridge module on the rectifier side is a 4-IGBT cascade topology. This solution has low output ripple and plays a role in power factor correction, replacing the PFC structure in the original controller.

[0125] Optionally, the rectifier side adopts a single-phase closed-loop control circuit with the output DC bus voltage as a reference, and based on the sawtooth carrier phase-shift modulation technology, the DC bus voltage, current, bridge arm voltage, and submodule capacitor voltage are balanced and controlled to achieve different levels of DC bus voltage output under constant AC. In this way, flexible output can be achieved, and the output is more flexible, and the conduction of IGBTs of different modules can be changed to meet different DC voltage outputs within the adjustable range.

[0126] Optionally, the inverter submodule of the converter module is a 2-IGBT cascade half-bridge structure, which takes the speed and output power of the synchronous motor as reference, and realizes three-phase variable frequency voltage and current output through a hierarchical control method of outer loop voltage control, phase balance, bridge arm inner loop current suppression and submodule capacitor voltage balance. In this way, compared with the rectifier module, the inverter submodule adopts a cascade half-bridge, mainly considering that the number of three-phase output modules is large, and the use of a half-bridge can save costs.

[0127] Optionally, the output of the new modular cascade converter acts as a synchronous compressor. The output end monitors the three-phase current, rotor position and speed, while the input end adds power regulation and speed reference point regulation. The overall new control system uses RFOC to achieve closed-loop variable frequency control of the compressor.

[0128] Among them, the output motor terminal signal can be sampled through a sampling resistor or sensor to obtain the load terminal signal. RFOC is a vector control that can be directly controlled by the motor stator signal at the terminal, which is simplified and accurate.

[0129] In an alternative embodiment, see Figures 2 to 8 The example shown can be divided into two parts: converter topology structure and system internal and external modular hierarchical control strategy, which exemplifies the specific implementation of the solution of the present invention.

[0130] In an optional specific example, the relevant description of the converter topology structure can refer to the following exemplary description.

[0131] When the power supply of the compressor main controller is started, the connected AC power zero and live wire ports are output through the strong electric secondary filter circuit to obtain a single-phase AC voltage. At the same time, a strong electric filter and protection circuit (such as a discharge control chip) is added to the zero and live wire ports. When AC power is present, the circuit is broken, and when AC power is disconnected, a short circuit is formed, resulting in rapid discharge.

[0132] Figure 2 The invention is a schematic diagram of the control system principle of an embodiment of a variable flow air conditioning compressor.

[0133] like Figure 2 As shown, the single-phase AC power output enters the new inverter control system, which is a modular single-phase full-bridge rectifier and three-phase full-bridge inverter topology. The AC end first passes through the modular rectifier circuit.

[0134] Figure 3 The figure is a schematic diagram of the structure of a single module on the rectifier and inverter side of a converter according to an embodiment of the present invention.

[0135] like Figure 3 As shown, a modular full-bridge topology sub-circuit is used in which N IGBTs are connected in series and then in parallel. Each phase of the AC signal is divided into two upper and lower bridge arms, and each bridge arm can use N full-bridge topology sub-modules. In this solution, the number of IGBTs in the bridge arm sub-module is 4, and the number of bridge arm sub-modules (SM) is 3.

[0136] Among them, on the rectifier side, the AC power supply is filtered and then transferred through the inductor boost. Then the full-bridge sub-module on the rectifier side is disconnected and rectified. The output voltage is filtered by the sub-capacitor energy storage, and finally the DC bus voltage U with a smaller output ripple is superimposed. dc The on-off rectification specifically refers to the on-off driving of the IGBT of the submodule by the pulse signal, and the rectification output after the inductor energy transfer is realized by turning the IGBT on and off.

[0137] On the inverter side, the DC bus voltage U dc As the inverter input side, since it comes from modular multi-level rectification, the output range is relatively flexible. dc The three-phase AC power U is converted into the control motor through the modular inverter topology. A , U B , U C The submodule of the modular half-bridge inverter topology adopts a topology structure in which N IGBTs are connected in series and then cascaded in pairs, where N is a natural number.

[0138] Among them, multi-level specifically refers to the output line voltage waveform on the inverter side as a waveform of multiple level signals superimposed. It is similar to the output sine signal, but it is not a standard sine signal, so there are harmonics. The more levels there are, the closer it is to a sine wave, the smaller the output waveform distortion is, and the fewer harmonic signals there are.

[0139] Similarly, the same is true for the rectifier part. The module output voltage level U after the AC passes through multiple power devices is c_j The DC bus voltage energy is a DC constant value after multi-level rectification and can be adjusted flexibly.

[0140] For specific adjustment methods, please refer to Figure 8 The closed-loop control method shown in (b) and (c) is similar to the inverter principle, which also combines carrier phase shift and balancing control, but the control object is the single-phase full-bridge module. By adjusting the on-off state of the IGBT, the multiple superposition output states of the sub-module capacitance level are adjusted. This part is PI control, combined with Figure 8 , for example, given a reference It is greater than the actual U dc , then you need to increase U dc , through PWM carrier phase shift adjustment and circulating current balancing control, the IGBT conduction energy in the module is increased, thereby improving the superimposed rectification output of multiple capacitor levels.

[0141] Figure 4 The figure is a schematic diagram of the structure of another embodiment of a single module on the rectifier and inverter side of a converter.

[0142] like Figure 4 As shown, the number of IGBTs in the submodule in this solution is 2, where the submodule capacitor voltage is U c_j , IGBT switch voltage is V x At the same time, the three-phase output comes from three inverter bridge arms. Like the rectifier side, the bridge arm of each phase of this part can adopt N half-bridge sub-module topologies. In the solution of the present invention, the number of bridge arm sub-modules (SM) can be 3.

[0143] Figure 5 The topological structure diagram of the multi-level cascade converter when the number of interphase bridge arm modules is 6; wherein, (a) is a schematic diagram of the structure of the first part of the multi-level cascade converter, (b) is a schematic diagram of the structure of the second part of the multi-level cascade converter, (c) is a schematic diagram of the structure of the third part of the multi-level cascade converter, and (d) is a schematic diagram of the structure of the fourth part of the multi-level cascade converter.

[0144] Among them, an inductor (L s ), can be used for voltage reduction, the voltage signal is output through the inductor to act on the three-phase synchronous compression motor, the complete modular multi-level hardware conversion topology is as follows Figure 5 shown.

[0145] In an optional specific example, the relevant description of the system modular hierarchical control strategy can be found in the following exemplary description.

[0146] Figure 6 It is a structural schematic diagram of the overall drive control system of the cascade converter topology.

[0147] like Figure 6 The overall drive control system of the cascade converter topology shown can be mainly divided into three parts: a cascade converter module, a sawtooth carrier phase shift modulation module, and an outer loop parameter control.

[0148] The 220V AC voltage passes through the neutral and live wire strong electric filter protection circuit and outputs a single-phase AC voltage. Then the single-phase voltage enters the cascade converter module. The specific control process can be seen in the following exemplary description.

[0149] First, the cascade conversion module of the system adopts single-phase full-bridge rectification and three-phase half-bridge inverter. At least the inverter part adopts IGBT modular cascade. The specific topology can be seen in Figure 3 and Figure 4 The example shown in the figure. The LC filter circuit is used in the middle to ensure that the output DC bus DC fluctuation is smaller. This part can achieve a three-phase current conversion output with less harmonics and higher power factor.

[0150] For example, the rectifier part can use a single-phase IGBT module, or a cascade of two or more phases of IGBT modules. The inverter part needs to use a cascade of two or more phases of IGBT modules, such as a three-phase IGBT module cascade.

[0151] Secondly, in the link of outer loop parameter control, the current signal I of the three-phase output is sampled A ,I B ,I C , the AC component is converted into the DC component of the dq quadrant through Park and Clarke transformation. At the same time, the torque, position, angular velocity and other signals of the motor stator load are sampled. The i in the q quadrant is formed through PI operation with the external reference given value. q Component given value. In the system d quadrant i d The component given value is initially 0. When the relevant DC components (position, angular velocity, torque power, etc.) are injected into the system as output reference components, the components of the dq quadrants are inversely transformed and converted into AC components that can act on the motor system, and its output is mainly a three-phase reference voltage.

[0152] Finally, the upper and lower bridge arm capacitor voltage signals U on each submodule are sampled. c_pj(n) , U c_nj(n); At the same time, the voltage signal obtained in the previous step is injected into the modulation system. The modulation system uses sawtooth carrier phase shift modulation, and the submodule capacitor voltage and three-phase voltage signal are subjected to PI iterative operation to form the PWM fundamental wave on each submodule. Then the fundamental waves on the upper and lower bridge arms are compared with the phase-shifted sawtooth carrier to form multiple PWM output signals on the rectifier module and inverter module, and control the gate signal on each IGBT in the topology.

[0153] The specific hierarchical control strategy of carrier phase shift modulation can be found in Figure 6 It should be noted that the upper and lower bridge arms of the rectifier and inverter parts cannot be opened at the same time, so the fundamental signal needs to be inverted, and then the carrier phase shift angle of each submodule of the full bridge is shifted by 2π / N, and the half bridge is π / N.

[0154] In other words, the structural improvements of the overall drive control system of the cascade converter topology can mainly include the following points:

[0155] First, both the rectifier and inverter are modular multi-level topologies, the rectifier is a single-phase full-bridge topology, and the inverter is a three-phase half-bridge topology. The upper and lower bridge arms of each phase use 3 sub-modules connected in series (N=3).

[0156] Second, the outer loop control is the motor RFOC closed-loop control. Different from the direct output of three-phase voltage, the reference point of this system is mainly the stator speed or torque, and the control method can be more diversified according to actual needs.

[0157] Third, the modulation system uses two independent control loops to output multiple channels on the rectifier side and the inverter side respectively. The PWM mode combining full-bridge and half-bridge makes the system control more flexible. At the same time, unlike most triangular carrier converters, this scheme uses sawtooth carrier. After data comparison, it is found that the output waveforms of the two schemes are slightly different, which can be used as a new backup scheme.

[0158] Among them, in Figure 6 In the example shown, the overall control mode of the system can be divided into DC modular control on the rectifier side and variable frequency drive control on the inverter side. Both use sawtooth carrier phase shift modulation technology and layered circulating current balance control. The difference is that the rectifier side uses the DC bus voltage as the output reference signal, and the inverter side uses the actual variable frequency speed or PQ control as the reference point for closed-loop control.

[0159] Figure 7 It is a structural schematic diagram of an embodiment of hierarchical control of drive system modules; wherein, (a) is a structural schematic diagram of capacitor voltage hierarchical balance control, (b) is a structural schematic diagram of phase balance control loop, (c) is a structural schematic diagram of upper and lower bridge arm balance control loop, (d) is a structural schematic diagram of circulating current suppression control loop, and (e) is a structural schematic diagram of MMC submodule energy balance control loop. Figure 8 It is a structural schematic diagram of an embodiment of the control strategy loop of the modular power conversion inverter side and the rectifier side, wherein (a) is a structural schematic diagram of the RFOC modular power conversion inverter control of the synchronous motor, (b) is a structural schematic diagram of the rectifier side PI control, and (c) is a structural schematic diagram of the rectifier side closed-loop balancing control.

[0160] Combination Figure 6 ,right Figure 7 and Figure 8 In the example shown, the rectifier switch device topology adopts sawtooth carrier phase-shift modulation technology as the PWM modulation signal. Under the action of 220V AC voltage, the phase-to-phase energy balance, the total voltage of each phase bridge arm and the capacitor voltage of each sub-module are detected respectively. The output voltage amplitude of the rectifier side can be controlled according to the duty cycle of the rectifier sub-module switch (SMn).

[0161] Figure 8 For the control strategy loop.

[0162] Figure 8 (a) is the outer loop of RFOC inverter control. Figure 5 The detailed expansion of each coefficient is carried out in detail, and the outer loop based on speed, torque or power control is established in combination with the following formula. The specific analysis of the mathematical model is described in detail in step (13). The outer loop is mainly used to realize the first layer of control in the subsequent hierarchical control, and obtain the three-phase voltage output component under the given reference component condition, so as to facilitate the subsequent carrier phase shift to calculate the PWM signal.

[0163] Figure 8 (b) and Figure 8 (c) is the PI closed-loop control circuit on the rectifier side. The DC bus reference voltage U is obtained by taking the DC output power or DC bus voltage as the reference point and calculating the actual sampled DC bus current. ref , and then through the sawtooth carrier signal comparator, the PWM drive signal that can be used to adjust the full-bridge submodule is obtained to control the DC bus output. Figure 8 (b) is the PI control on the rectifier side. Figure 8 (c) is Figure 8 (b) The specific expansion loop after combining module voltage balancing control.

[0164] Among them, in the scheme of the present invention, a sawtooth phase-shifted carrier is used to control the full-bridge PWM output; the outer loop establishes a control loop through the output voltage and power of the rectifier side to meet the voltage requirements of different levels on the inverter side within the demand range; the dual-loop control acts independently on the rectifier inverter outer loop, but the inner layer adopts hierarchical control to meet the module capacitor voltage balance.

[0165] like Figure 8In the example shown in (c), the DC bus output rated voltage of 311V is used as the reference voltage. The actual output voltage of the DC bus is U dc In the control loop, the current of the upper bridge arm and the lower bridge arm of the single-phase input is detected, and half of the value is taken after summing to obtain the interphase circulating current i cj , and the DC bus current i dc After calculation and PI control, the DC bus feedback reference voltage is obtained and compared with U dc After calculation, the reference value of each sub-module voltage between phases is obtained. After inversion, the sub-module capacitor voltage component is added to form the fundamental waveform of PWM modulation. The number is 2N. dc As a pre-adjustment.

[0166] like Figure 8 (b) and Figure 6 In the example shown, the entire DC output side forms an outer loop main feedback loop, detecting and sampling the AC voltage U at both ends of the rectifier side. ac , DC voltage U dc And system power. Use bus DC control or power PQ control to perform PI operation on the difference between the actual rectified voltage and the reference voltage to obtain the reference current of the dq quadrant after rectification. After iterative calculation, the reference current vector of the upper and lower bridge arms of each phase is obtained. The current vector is subtracted from the actual value of the DC bus current to form the DC bus reference current The obtained current is processed by PI operation to obtain the variable voltage, and then the actual output voltage component U is added. dc , and get the fundamental output reference voltage. Figure 8 (c) is Figure 8 (b) Extension of the drive signal conditioning logic. Figure 8 In (c), the average pressure value of each SM is U c_ji With actual value After voltage balancing control, the fundamental reference voltage of each phase submodule is obtained After the sawtooth wave phase-shift carrier PWM operation, the PWM pulse signal corresponding to the full-bridge submodule switch is obtained, and the DC voltage is output. dc and power, realizing closed-loop control of adjustable DC voltage or adjustable power.

[0167] In the solution of the present invention, for the rectifier feedback loop, the control method adopts the voltage energy layered transmission method. It is mainly inner and outer loop control. The inner loop adopts phase voltage balance control, bridge arm voltage balance control, and submodule capacitor voltage balance. The feedback reference signal is the power or DC bus DC voltage U dc .

[0168] In the scheme of the present invention, the rectifier side carrier phase shift uses N sawtooth waves to sequentially shift by π / N to obtain the best harmonic elimination characteristics, that is, the range of the carrier phase shift angle is 0-π / 2N. In this modulation system, since there are 4 IGBTs in the module and each phase bridge arm has two voltage reference signals, it is necessary to invert the fundamental waveform obtained above to correspond to the left and right half bridge arms of the same submodule, and obtain the reference voltage formula for the left and right half sides of the upper and lower bridge arms. As follows. Where p represents the upper bridge arm; n represents the lower bridge arm; U SMc =U dc / N is the given submodule capacitor voltage; M is the modulation ratio).

[0169]

[0170]

[0171] Where ω represents the three-phase AC voltage output angular frequency (ω=2πf); θ j is the initial quadrant angle of phase j (j=A, B, C).

[0172] In the solution of the present invention, the DC bus voltage outputted by the modular rectifier side enters the modular multi-level inverter circuit after capacitor filtering. The inverter circuit adopts a half-bridge sub-module structure with dual IGBTs in parallel. The overall control method can be as follows: Figure 6 and Figure 8 The example shown in (a) in Figure 1 uses speed or power as the feedback regulation of the rotor flux oriented control (RFOC) of the entire motor system, so that the module outputs a three-phase AC signal.

[0173] In the solution of the present invention, the inverter topology control of the entire system also adopts a hierarchical control structure. Figure 7 The structure is the same as described above, and the control loops at each level are analyzed in detail here.

[0174] First, the first stage is the overall control of the variable current feedback system, the outer loop control is the motor speed control or output power control, and the inner loop is the current control of the dq0 rotating coordinate system. Figure 6 and Figure 8 In the example shown in (a), the basic idea of ​​the inner loop control is to sample the voltage, current, position and angular velocity signals on the three-phase output side. The abc current signal is transformed by Clarke and Park to obtain the DC component signal (i q ,i d ). At the same time, the motor outputs the angular velocity signal ω e And the position angle signal θ, after PI transformation, the speed signal is obtained, which is compared with the reference speed ω * Comparison is made to form the speed difference and obtain the torque signal T * , and then the current reference signal of the q quadrant is obtained through PI transformation The given current reference signal in quadrant d is initially

[0175] At the same time, combined with the transformed DC component signal (i q ,i d )Do Operation, get the voltage variable signal in dq coordinate system After Clarke inverse transformation and Park inverse transformation, the final three-phase AC output reference voltage of the first stage is obtained. In the first stage of control, the transformation formula of part of the signal is as follows:

[0176]

[0177]

[0178]

[0179]

[0180]

[0181]

[0182]

[0183]

[0184] Where, P is the converter output power, P dev and T dev is the power and speed output from the converter to the motor, λ f is the stator flux (which can be obtained through the stator inductance and induced current), λ d ,λ q is the stator flux component in the dq quadrant, L d , L q is the inductance component of the motor in the dq coordinate system, U sd , U sq is the voltage component of the three-phase AC output voltage in the dq quadrant, P * is the reference power variable signal, T * is the torque reference variable signal of the camless synchronous motor, p is the number of stator pole pairs, ω e is the motor rotation angular velocity.

[0185] Furthermore, the second stage of modular inversion is phase balance control. Figure 7 In the example shown, the basic idea is that the voltage given by the phase-to-phase outer loop is the DC bus voltage U dcThe feedback signal is half of the sum of the capacitor voltages of all submodules. After comparing the two and performing PI calculation, the given phase circulating current DC component I is obtained. cj (j represents any one of the three phases A, B, and C).

[0186] Furthermore, the third stage is the bridge arm balance control. Figure 7 As shown, the given reference value is the DC component of the sum of the upper and lower bridge arm capacitor voltages of each phase. The difference between the two is calculated through PI operation, and then the reference phase signal of the AC voltage of the phase is added to obtain the AC component of the reference phase circulating current i cj_ac The two are added together to obtain the given reference signal of the circulating current, which is then compared with the actual circulating current signal. The output is adjusted by the PI-resonant to obtain the DC reference signal of the inner loop voltage. Then add and subtract the AC component in the reference voltage respectively Get the reference voltage signal of the upper and lower bridge arms and

[0187] Furthermore, the fourth stage is the submodule capacitor voltage balance. Each submodule of each bridge arm corresponds to an independent control loop. Its reference voltage is one-Nth of the capacitor voltage of the bridge arm. The capacitor voltage of each module is used as feedback, and after proportional adjustment, the current direction of the bridge arm of the phase is added, and the sum is made with one-Nth of the voltage of the bridge arm, to obtain the voltage reference signal of each submodule of the upper and lower bridge arms ( and ). Finally, it is sent to the carrier phase shift modulation to generate the respective PWM pulse signals.

[0188] Among them, the half-bridge submodule of the inverter module also adopts carrier phase shift modulation. In this invention, the inverter topology carrier phase shift adopts N sawtooth waves to be phase shifted by 2π / N in sequence to obtain the best harmonic elimination characteristics, that is, the range of the carrier phase shift angle is 0-π / N. In this modulation system, the voltage reference signal of each submodule of the upper and lower bridge arms is:

[0189]

[0190] The rectifier module and the internal submodules of the inverter module all adopt carrier phase shift hierarchical control, and the single-phase AC power is rectified and then the inverter output is an AC signal that can make the three-phase motor variable frequency. The overall external control loop of the two parts, the DC bus voltage closed-loop feedback control and the RFOC motor speed control, control their respective modules separately, making the regulation capability of the entire converter system more flexible.

[0191] In an optional specific example, the solution of the present invention is applicable to compressor drive circuits of different power levels. Due to the modular structure control, the improvement and transformation of the circuit topology are more flexible, the output voltage and current harmonic content is small, and the power quality is high. The solution of the present invention adopts a more complex topological structure in the conversion structure, which can replace the PFC module in the relevant air-conditioning compressor control system, and can be widely used in high-power air-conditioning conversion systems, which is conducive to improving the competitiveness of products. The variable frequency conversion method improved by the solution of the present invention can be analogically derived and applied to the fields of motor control and new energy inverter.

[0192] Since the processing and functions implemented by the motor of this embodiment are basically corresponding to the aforementioned Figure 1 The embodiments, principles and examples of the device shown are as follows. Therefore, for matters not fully described in the description of this embodiment, reference can be made to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be given here.

[0193] After a large number of experimental verifications, the technical solution of the present invention is adopted, by adopting the topological structure of the sub-module single-phase full-bridge rectifier circuit and the three-phase half-bridge inverter cascade circuit, through the sawtooth wave phase shift modulation and the voltage-sharing circulating current control theory, the three-phase AC voltage finally outputted has less harmonic content than the two-level IGBT trigger drive, and the stable control operation of the motor can be achieved. Thus, the problem of high-order harmonic content of the voltage waveform output by the inverter is optimized, and the control effect of the motor is remarkable.

[0194] According to an embodiment of the present invention, a current conversion control method for a motor corresponding to the motor is also provided, such as Fig. 9 The flow chart of an embodiment of the method of the present invention is shown in FIG. The motor current conversion control method may include: step S110 and step S120.

[0195] At step S110, the single-phase AC power is converted by the conversion unit and then output to the power-consuming device a three-phase AC voltage. The power-consuming device may include a motor such as an air-conditioning compressor. The conversion process may include rectification, filtering and inversion.

[0196] In an optional example, the conversion unit may include: a modular single-phase rectifier module, a filter module and a modular three-phase inverter module. The modular single-phase rectifier module is such as a single-phase modular full-bridge rectifier circuit. The filter module is such as an LC filter circuit. The modular three-phase inverter module is such as a three-phase modular half-bridge inverter circuit. The output end of the modular single-phase rectifier module is connected to the input end of the modular three-phase inverter module, and the filter module is arranged between the modular single-phase rectifier module and the modular three-phase inverter module. Among them, the single-phase alternating current is converted by the conversion unit, and the following exemplary description can be referred to.

[0197] Combine the following Fig.10The flowchart of an embodiment of the method of the present invention for converting single-phase alternating current is shown, which further illustrates the specific process of converting single-phase alternating current in step S110, and may include: steps S210 to S230.

[0198] Step S210: After rectifying single-phase alternating current such as single-phase AC through a modular single-phase rectifier module, a DC bus voltage is output.

[0199] Step S220: filtering the DC bus voltage after the rectification of the single-phase AC power through a filtering module to obtain a filtered DC bus voltage.

[0200] Step S230, inverting the filtered DC bus voltage through a modular three-phase inverter module to output three-phase AC power, specifically outputting a three-phase AC voltage that can be used as a driving voltage for a motor such as a compressor.

[0201] For example, the inverter topology structure of modular converter is adopted for compressor drive circuit, which reduces the breaking time of single power device and the energy loss of power device IGBT. Among them, the steady-state output ripple of DC bus on the rectifier side is smooth, and the output on the inverter side can act on synchronous motor control, which can meet the needs under different bus voltage, output power and speed conditions, and its speed regulation range is more flexible.

[0202] For example, the cascade conversion module of the system adopts single-phase full-bridge rectification and three-phase half-bridge inverter, and some of them adopt IGBT modular cascade. The LC filter circuit is used in the middle to ensure that the output DC bus DC fluctuation is smaller. This part can achieve three-phase conversion output with small harmonics and high power factor. Among them, the single-phase AC output enters the new conversion control system. The system is a modular single-phase full-bridge rectification and three-phase full-bridge inverter topology. The AC end first passes through the modular rectification circuit.

[0203] Therefore, the single-phase AC power is converted by the modular single-phase rectifier module, the filter module and the modular three-phase inverter module. The modular single-phase rectifier module and the modular three-phase inverter module are used to reduce the energy loss of the power device by reducing the disconnection time of the single power device. The DC bus steady-state output ripple on the rectifier side is smooth, so that the three-phase AC voltage output on the inverter side has less harmonic content, and the voltage waveform of the inverter output is optimized, which is conducive to the stable control and operation of electrical equipment such as motors.

[0204] In step S120, the control unit obtains the conversion parameters of the conversion unit and the operating parameters of the motor, and performs phase shift modulation and circulating current hierarchical control on the conversion unit according to the conversion parameters and the operating parameters, so as to realize hierarchical closed-loop control between the conversion unit and the motor.

[0205] For example: the cascade conversion topology control system of modular single-phase full-bridge rectification and multi-level half-bridge three-phase inverter adopts two independent sawtooth carrier phase shifting technologies, based on modular circulating current suppression hierarchical balance control and RFOC closed-loop control principles, to establish internal and external multi-layer control loops to control the rectifier side bus voltage and the inverter side three-phase variable frequency voltage output respectively, to realize the synchronous compression motor variable frequency drive control.

[0206] For example, for low- and medium-power compressors in the field of household air conditioners, a new inverter structure-controlled single-cylinder compressor inverter control system design scheme is proposed. Based on the air conditioner compressor control circuit, the topology of the sub-module single-phase full-bridge rectifier circuit and the three-phase half-bridge inverter cascade circuit is adopted. Through the sawtooth wave phase shift modulation and voltage-sharing circulation control theory, the energy conversion balance of each phase and each sub-module of the inverter circuit is guaranteed. Compared with the two-level IGBT trigger drive, the final output three-phase AC voltage has less harmonic content, which can realize the smooth control operation of the motor. Therefore, it not only solves the problem of uneven distribution of sub-module power loss, but also optimizes the problem of high-order harmonic content of the inverter output voltage waveform, and the control effect of the motor is significant.

[0207] Therefore, by using the conversion unit and the control unit, the conversion processing is performed based on the single-phase AC point, and the phase shift modulation and circulating current control are performed on the conversion unit. This can solve the problem of high power consumption of power device components using the two-level inverter topology, that is, solve the problem of uneven distribution of sub-module power losses, and reduce the power consumption of power device components; it can also optimize the problem of high high-order harmonic content in the inverter output voltage waveform, reduce the harmonic content, and facilitate the smooth control and operation of electrical equipment such as motors.

[0208] In an optional example, the control unit may include: a phase-shift modulation module, such as a sawtooth wave phase-shift modulation module, which may be connected to the single-phase modular full-bridge rectifier circuit and the three-phase modular half-bridge inverter circuit in the converter unit, respectively. In step S120, the phase-shift modulation and circulating current layering control of the converter unit by the control unit may include: using the phase-shift modulation module, using two independent sawtooth waves, adopting the phase-shift modulation technology and the circulating current layering control method, respectively outputting pulse signals to the rectifier processing side and the inverter processing side in the converter unit, such as respectively outputting pulse signals to the modular single-phase rectifier module and the modular three-phase inverter module in the converter unit, preferably a PWM pulse signal, so as to drive the rectifier processing side and the inverter processing side in the converter unit by the pulse signal.

[0209] For example: two independently acting sawtooth waves are generated by means of a DSP processor or hardware analog circuit, and phase-shift modulation technology and circulating current layered control are used to output PWM pulse signals to each sub-module of the single-phase rectifier bridge arm and the three-phase modular inverter bridge arm respectively.

[0210] For example: the modulation system uses two independent control loops to output multiple channels on the rectifier side and the inverter side respectively. The PWM mode combining full-bridge and half-bridge makes the system control more flexible. The overall control mode of the system can be divided into DC modular control on the rectifier side and motor variable frequency drive control on the inverter side. Both use sawtooth carrier phase shift modulation technology and layered circulating current balancing control. The difference is that the rectifier side uses the DC bus voltage as the output reference signal, and the inverter side uses the actual variable frequency speed or PQ control as the reference point for closed-loop control.

[0211] Therefore, through the phase-shift modulation module, based on two independent sawtooth waves through phase-shift modulation technology and circulating current layered control, pulse signals are output to the rectification processing side and the inverter processing side respectively, so that the rectification processing side and the inverter processing side can be driven separately, and the reliability of the drive can be guaranteed.

[0212] Optionally, the control unit may further include: a rectifier side sampling module, such as a rectifier side AC / DC voltage and current sampling module, a submodule capacitor voltage sampling module, etc. Wherein, the control unit performs phase shift modulation and circulating current layering control on the converter unit in step S120, and may further include: a process of controlling the pulse signal of the converter unit according to the rectifier side.

[0213] Combine the following Fig.11 The flowchart of an embodiment of the method of the present invention according to the pulse signal of the rectifier side controlling the converter unit further illustrates the specific process of the pulse signal of the rectifier side controlling the converter unit, which may include: step S310 and step S320.

[0214] Step S310, through the rectifier side sampling module, collect the DC bus signal of the rectifier processing side in the converter unit, the bridge arm voltage of each bridge arm (i.e., the bridge arm voltage of each bridge arm in the single-phase rectifier upper bridge arm and / or the single-phase rectifier lower bridge arm), and / or the capacitor voltage of each single-phase rectifier module (i.e., the single-phase rectifier module in each bridge arm). The DC bus signal may include the DC bus voltage, the DC bus current, etc.

[0215] Step S320, through the phase-shift modulation module, a single-phase closed-loop control loop with the DC bus voltage output on the rectifier side as a reference is used to adjust the pulse signal on the rectifier processing side in the conversion unit based on the sawtooth carrier phase-shift modulation technology according to the DC bus signal on the rectifier processing side, the bridge arm voltage of each bridge arm, and / or the capacitor voltage of each single-phase rectifier module, so as to achieve balanced control of the DC bus signal on the rectifier processing side, the bridge arm voltage of each bridge arm, and / or the capacitor voltage of each single-phase rectifier module.

[0216] For example: the rectifier side adopts a single-phase closed-loop control circuit with the output DC bus voltage as a reference. Based on the sawtooth carrier phase-shift modulation technology, the DC bus voltage, current, bridge arm voltage, and sub-module capacitor voltage are balanced and controlled to achieve different levels of DC bus voltage output under constant AC power.

[0217] For example: the rectifier switch device topology uses sawtooth carrier phase shift modulation technology as the PWM modulation signal. Under the action of 220VAC voltage, the phase-to-phase energy balance, the total voltage of each phase bridge arm and the capacitor voltage of each submodule are detected respectively. The output voltage amplitude of the rectifier side can be controlled with the duty cycle of the rectifier submodule switch (SMn). For example, the PI closed-loop control circuit on the rectifier side uses the DC output power or DC bus voltage as the reference point, and calculates the DC bus current after the actual sampling to obtain the DC bus reference voltage U ref , and then through the sawtooth carrier signal comparator, a PWM drive signal that can be used to adjust the full-bridge sub-module is obtained to control the DC bus output.

[0218] Among them, for the rectifier feedback loop, the control method adopts the voltage energy layered transmission method. It is mainly inner and outer loop control. The inner loop adopts phase voltage balance control, bridge arm voltage balance control, submodule capacitor voltage balance, and the feedback reference signal is power or DC bus DC voltage U dc The carrier phase shift on the rectifier side uses N sawtooth waves to shift the phase by π / N in sequence to obtain the best harmonic elimination characteristics, that is, the range of the carrier phase shift angle is 0-π / 2N.

[0219] Therefore, through a single-phase closed-loop control circuit with the output DC bus voltage as a reference on the rectifier side, based on the sawtooth carrier phase-shift modulation technology, the DC bus voltage, current, bridge arm voltage, and sub-module capacitor voltage are balanced and controlled respectively, so that different levels of DC bus voltage output under constant AC power can be achieved, and the output DC bus voltage can be flexibly adjusted.

[0220] Optionally, the control unit may further include: an inverter side sampling module, such as an inverter side three-phase current and voltage sampling module, a submodule capacitor voltage sampling module, etc. Wherein, the control unit performs phase shift modulation and circulating current layering control on the converter unit in step S120, and may further include: a process of controlling the pulse signal of the converter unit according to the inverter side.

[0221] Combine the following Fig.12 The flowchart of an embodiment of the method of the present invention according to the pulse signal of the inverter side controlling the converter unit is shown, which further illustrates the specific process of the pulse signal of the inverter side controlling the converter unit, and may include: step S410 and step S420.

[0222] Step S410, through the inverter side sampling module, collect the three-phase electrical signals of the inverter processing side in the conversion unit, the inner loop current of each bridge arm (i.e., the inner loop current of each bridge arm in the three-phase inverter upper bridge arm and / or the three-phase inverter lower bridge arm), and / or the capacitor voltage of each three-phase inverter submodule (i.e., the three-phase inverter submodule in each bridge arm). Among them, the three-phase electrical signals may include: three-phase voltage signals, three-phase current signals, etc.

[0223] Step S420, through the phase-shift modulation module, a closed-loop control loop is also used as a reference to the speed and output power of the motor driven by the three-phase AC power output from the inverter processing side. According to the three-phase electrical signal of the inverter processing side, the inner loop current of each bridge arm, and / or the capacitor voltage of each three-phase inverter sub-module, the pulse signal of the inverter processing side in the converter unit is adjusted to achieve outer loop control and phase balance of the three-phase electrical signal on the inverter processing side, suppression of the inner loop current of each bridge arm, and / or hierarchical control of capacitor voltage balance of each three-phase inverter sub-module.

[0224] For example: the inverter side submodule of the converter module is a 2-IGBT cascade half-bridge structure. With the speed and output power of the synchronous motor as reference, the three-phase variable frequency voltage and current output is achieved through the hierarchical control method of outer loop voltage control, phase balance, bridge arm inner loop current suppression and submodule capacitor voltage balance. For example, a sawtooth phase-shift carrier is used to control the full-bridge PWM output. The outer loop establishes a control loop through the output voltage and power of the rectifier side to meet the voltage requirements of different levels on the inverter side within the demand range. The dual-loop control can act independently on the rectifier inverter outer loop, but the inner layer adopts hierarchical control to meet the module capacitor voltage balance.

[0225] Among them, the DC bus voltage output from the modular rectifier side enters the modular multi-level inverter circuit after capacitor filtering. The inverter circuit adopts a half-bridge sub-module structure with dual IGBTs in parallel, and uses speed or power as the feedback adjustment of the rotor flux oriented control (RFOC) of the entire motor system, so that the module outputs a three-phase AC signal. The first stage is the overall control of the converter feedback system, the outer loop control is the motor speed control or output power control, and the inner loop is the current control of the dq0 rotating coordinate system. The second stage of modular inversion is phase balance control. The third stage is bridge arm balance control. The fourth stage is sub-module capacitor voltage balance. Each sub-module of each bridge arm corresponds to an independent control loop, and its reference voltage is one-Nth of the capacitor voltage of the bridge arm.

[0226] For example: In the link of outer loop parameter control, the current signal I of the three-phase output is sampled A ,I B ,I C, the AC component is converted into the DC component of the dq quadrant through Park and Clarke transformation. At the same time, the torque, position, angular velocity and other signals of the motor stator load are sampled. The i in the q quadrant is formed through PI operation with the external reference given value. q Component given value. In the system d quadrant i d The component given value is initially 0. When the relevant DC components (position, angular velocity, torque power, etc.) are injected into the system as output reference components, the components of the dq quadrants are inversely transformed and converted into AC components that can act on the motor system, and its output is mainly a three-phase reference voltage.

[0227] For example: sampling the upper and lower bridge arm capacitor voltage signal U on each submodule c_pj(n) , U c_nj(n) . At the same time, the voltage signal obtained in the previous step is injected into the modulation system. The modulation system uses sawtooth carrier phase shift modulation, and the submodule capacitor voltage and three-phase voltage signal are subjected to PI iterative operation to form the PWM fundamental wave on each submodule. Then the fundamental waves on the upper and lower bridge arms are compared with the phase-shifted sawtooth carrier to form multiple PWM output signals on the rectifier module and inverter module, and control the gate signal on each IGBT in the topology.

[0228] Therefore, through a single-phase closed-loop control loop with the output DC bus voltage as a reference on the rectifier side, based on the sawtooth carrier phase-shift modulation technology, the outer loop control and phase balance, bridge arm inner loop current suppression, and capacitor voltage balance of the three-phase electrical signal are respectively controlled in a hierarchical manner, so that flexible adjustment of the three-phase variable frequency voltage and current output can be achieved.

[0229] Optionally, the control unit may further include: a load side sampling module, such as a motor position and speed sensor, etc. Wherein, the control unit performs phase shift modulation and circulating current layering control on the converter unit in step S120, and may further include: a process of controlling the pulse signal of the converter unit according to the load side.

[0230] Combine the following Fig.13 The flowchart of an embodiment of the method of the present invention for controlling the pulse signal of the converter unit according to the load side further illustrates the specific process of controlling the pulse signal of the converter unit according to the load side, which may include: step S510 and step S520.

[0231] Step S510: collecting the three-phase current, rotor position, and / or rotor speed of the output side motor of the converter unit through the load side sampling module.

[0232] Step S520, through the phase-shift modulation module, a closed-loop control loop is formed, which takes the rotation speed and output power of the motor driven by the three-phase AC power outputted from the inverter processing side as a reference. According to the three-phase current, rotor position, and / or rotor speed of the motor, the pulse signals of the rectifier processing side and / or the inverter processing side in the converter unit are adjusted to realize closed-loop frequency conversion control of the motor on the output side of the converter unit.

[0233] For example: the output of the modular cascade converter acts as a synchronous compressor. The output end monitors the three-phase current, rotor position and speed, while the input end adds power regulation and speed reference point regulation. The overall new control system uses RFOC to achieve closed-loop variable frequency control of the compressor.

[0234] For example, the submodules inside the rectifier module and the inverter module all use carrier phase shift hierarchical control, and the single-phase AC power is rectified and then the inverter output is an AC signal that can make the three-phase motor variable frequency. The overall external control loop of the two parts, the DC bus voltage closed-loop feedback control and the RFOC motor speed control, control their respective modules separately, making the regulation ability of the entire conversion system more flexible. Among them, the specific hierarchical control strategy of carrier phase shift modulation, the upper and lower bridge arms of the rectifier and inverter parts cannot be opened at the same time, so it is necessary to invert the fundamental signal, and then the carrier phase shift angle is shifted by 2π / N for each submodule of the full bridge, and π / N for the half bridge. The outer loop control is the motor RFOC closed-loop control. Different from the direct output of the three-phase voltage, the reference point of this system is mainly the stator speed or torque, and the control method can be more diversified in combination with actual needs.

[0235] Therefore, by monitoring the three-phase current, motor yoke rotor position and speed on the output side of the converter unit and adding power regulation and speed reference point adjustment at the input end, closed-loop frequency conversion control of the compressor can be achieved, which is beneficial to further ensure the operating stability of the motor.

[0236] In an optional embodiment, it may further include: a protection unit. The protection unit, such as a strong current filter and protection circuit, may be arranged between an AC power source such as a 220V AC mains neutral, live, and ground wire and a conversion unit such as a cascaded conversion module.

[0237] Specifically, the protection unit can be used to filter the neutral, live and ground wires of the mains to form single-phase alternating current, that is, to form clean and reliable single-phase alternating current. In other words, the protection unit can be used to filter the alternating current power supply to form an alternating current that meets practical needs (stable and clean). Figure 4 In the example shown, the mains power is 220V AC, and the three wires are respectively the neutral, live and ground wire (i.e. N, L, PE), and then the strong current filtering and protection module outputs a stable and clean single-phase AC (i.e. two wires L and N). The so-called clean and stable means reducing the interference (harmonics, etc.) in the external power grid through secondary filtering.

[0238] For example: when the compressor main controller is powered on, the zero-live-ground port connected to the mains is output through the strong electric secondary filter circuit to obtain a single-phase AC voltage. At the same time, a strong electric filter and protection circuit (such as a discharge control chip) is added to the zero-live output port. When AC power is present, the circuit is disconnected, and when AC power is disconnected, a short circuit is formed, forming a rapid discharge to release the residual pressure of large capacitor components in the system. For example: 220V AC voltage passes through the zero-live strong electric filter protection circuit and outputs a single-phase AC voltage. Then the single-phase voltage enters the cascade converter module.

[0239] Therefore, the protection unit outputs a single-phase AC voltage through a strong electric filter from the neutral and live ground of the mains, and then outputs it to the motor after current conversion based on the single-phase AC voltage with low power consumption. This can reduce the breaking time of a single power device and thus reduce the energy loss of power devices such as IGBTs.

[0240] Since the processing and functions implemented by the method of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned motor, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be made here.

[0241] After a large number of experimental verifications, the technical solution of this embodiment is adopted, by adopting two independent sawtooth carrier phase shifting technologies, based on modular circulating current suppression layered balance control and RFOC closed-loop control principles, to establish internal and external multi-layer control loops to respectively control the bus voltage on the rectifier side and the three-phase variable frequency voltage output on the inverter side, thereby realizing variable frequency drive control of the synchronous compression motor, reducing the energy loss of the power device IGBT, and significantly reducing the harmonic content of the output three-phase voltage.

[0242] In summary, it is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0243] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims

1. A variable current control device, characterized in that: include: A current conversion unit and a control unit; wherein, The current conversion unit is used to convert the single-phase AC power and output the three-phase AC power to the motor; wherein the current conversion process includes: rectification process, filtering process and inversion process; A control unit is used to obtain the conversion parameters of the conversion unit and the operating parameters of the motor, and to perform phase shift modulation and circulating current hierarchical control on the conversion unit according to the conversion parameters and the operating parameters, so as to realize hierarchical closed-loop control between the conversion unit and the motor; by adopting a modular cascade conversion topology structure formed by a single-phase full-bridge rectifier module side and a three-phase half-bridge inverter module side, single-phase alternating current is input, and three-phase alternating current voltage is output, so as to reduce the harmonic content of the output waveform; wherein, the modular cascade conversion topology structure formed by a single-phase full-bridge rectifier module side and a three-phase half-bridge inverter module side is a flexible conversion cascade topology structure; The outer loop establishes a control loop through the output voltage and power of the rectifier side to meet the voltage requirements of different levels on the inverter side within the demand range; and / or, the inner loop adopts phase voltage balancing control, bridge arm voltage balancing control, submodule capacitor voltage balancing, and the feedback reference signal is power or bus DC voltage; and / or, Using bus DC control or power PQ control, the difference between the actual rectified voltage and the reference voltage is subjected to PI operation to obtain the reference current of the dq quadrant after rectification; after iterative operation, the reference current vector of the upper and lower bridge arms of each phase is obtained, and the reference current vector is subtracted from the actual value of the DC bus current to form the DC bus reference current. The obtained current is subjected to PI operation to obtain the variable voltage, and then the actual output bus DC voltage is added to obtain the fundamental output reference voltage; the voltage balancing value and the actual value of each sub-module SM are subjected to voltage balancing control to obtain the fundamental reference voltage of each phase sub-module, and then the sawtooth wave phase-shifted carrier PWM operation is performed to obtain the PWM pulse signal corresponding to the full-bridge sub-module switch, and the DC voltage is output; finally, by changing the bus DC voltage and power, closed-loop control of adjustable DC voltage or adjustable power is achieved.

2. The variable current control device according to claim 1, characterized in that: The conversion unit includes: a modular single-phase rectifier module, a filter module and a modular three-phase inverter module; wherein, Modular single-phase rectifier module, used to rectify single-phase AC power and output DC bus voltage; A filtering module is used to filter the DC bus voltage after the single-phase AC power is rectified to obtain the filtered DC bus voltage; The modular three-phase inverter module is used to invert the filtered DC bus voltage and output three-phase AC power.

3. The variable current control device according to claim 2, characterized in that: The modular single-phase rectifier module includes: a boost module, a single-phase rectifier upper bridge arm and a single-phase rectifier lower bridge arm; wherein, The boost module is arranged between the single-phase rectifier upper bridge arm and the single-phase rectifier lower bridge arm, and is used to boost the single-phase alternating current and then transmit it to the single-phase rectifier upper bridge arm and the single-phase rectifier lower bridge arm for rectification. Each bridge arm in the single-phase rectifier upper bridge arm and / or the single-phase rectifier lower bridge arm includes: a single-phase rectifier module; the number of single-phase rectifier modules is a first set value, and the first set value of single-phase rectifier modules are cascaded; each single-phase rectifier module includes: a single-phase full-bridge rectifier module and / or a single-phase half-bridge rectifier module.

4. The variable current control device according to claim 2, characterized in that: The modular three-phase inverter module includes: a step-down module, a three-phase inverter upper bridge arm and a three-phase inverter lower bridge arm; wherein, The step-down module is arranged between the three-phase inverter upper bridge arm and the three-phase inverter lower bridge arm, and is used to step down the three-phase alternating current after being inverted by the three-phase inverter upper bridge arm and the three-phase inverter lower bridge arm, and then output it to the motor; Each bridge arm in the three-phase inverter upper bridge arm and the three-phase inverter lower bridge arm includes: a three-phase inverter submodule; the number of the three-phase inverter submodules is a second set value, and the second set value three-phase inverter submodules are cascaded; each three-phase inverter submodule includes: a three-phase full-bridge inverter submodule and / or a three-phase half-bridge inverter submodule.

5. The variable current control device according to any one of claims 1 to 4, characterized in that: Also includes: Protection unit; The protection unit is used to filter the neutral, live and ground wires of the mains power to form single-phase alternating current.

6. The variable current control device according to any one of claims 1 to 4, characterized in that: A control unit, comprising: a phase shift modulation module; The phase-shift modulation module is used to use two independent sawtooth waves, adopt phase-shift modulation technology and circulating current layered control method, and output pulse signals to the rectification processing side and the inverter processing side in the conversion unit respectively, so as to drive the rectification processing side and the inverter processing side in the conversion unit through the pulse signals.

7. The variable current control device according to claim 6, characterized in that: The control unit also includes: a rectifier-side sampling module; A rectifier-side sampling module, used to collect the DC bus signal on the rectifier processing side in the converter unit, the bridge arm voltage of each bridge arm, and / or the capacitor voltage of each single-phase rectifier module; The phase-shift modulation module is also used to adjust the pulse signal on the rectification processing side in the conversion unit based on the sawtooth carrier phase-shift modulation technology according to the DC bus signal on the rectification processing side, the bridge arm voltage of each bridge arm, and / or the capacitor voltage of each single-phase rectifier module, so as to achieve balanced control of the DC bus signal on the rectification processing side, the bridge arm voltage of each bridge arm, and / or the capacitor voltage of each single-phase rectifier module.

8. The variable current control device according to claim 6, characterized in that: The control unit also includes: an inverter side sampling module; The inverter side sampling module is used to collect the three-phase electrical signals of the inverter processing side in the converter unit, the inner loop current of each bridge arm, and / or the capacitor voltage of each three-phase inverter submodule; The phase-shift modulation module is also used to adjust the pulse signal on the inverter processing side in the conversion unit according to the three-phase electrical signal on the inverter processing side, the inner loop current of each bridge arm, and / or the capacitor voltage of each three-phase inverter sub-module, so as to realize the outer loop control and phase balance of the three-phase electrical signal on the inverter processing side, the inner loop current suppression of each bridge arm, and / or the capacitor voltage balance of each three-phase inverter sub-module.

9. The variable current control device according to claim 6, characterized in that: The control unit also includes: a load-side sampling module; A load-side sampling module, used to collect the three-phase current, rotor position, and / or rotor speed of the output-side motor of the converter unit; The phase-shift modulation module is also used to adjust the pulse signals on the rectification processing side and / or the inverter processing side in the converter unit according to the three-phase current, rotor position, and / or rotor speed of the motor, so as to realize closed-loop frequency conversion control of the motor on the output side of the converter unit.

10. A motor, characterized in that: include: The variable current control device according to any one of claims 1 to 9.

11. A current conversion control method for the motor according to claim 10, characterized in that: include: After the single-phase AC power is converted by the conversion unit, the three-phase AC power is output to the motor; wherein the conversion process includes: rectification process, filtering process and inversion process; The control unit is used to obtain the conversion parameters of the conversion unit and the operating parameters of the motor, and the conversion unit is phase-shifted and modulated and the circulating current is hierarchically controlled according to the conversion parameters and the operating parameters, so as to realize the hierarchical closed-loop control between the conversion unit and the motor; by adopting the modular cascade conversion topology structure formed by the single-phase full-bridge rectifier module side and the three-phase half-bridge inverter module side, single-phase AC power is input and three-phase AC voltage is output, thereby reducing the harmonic content of the output waveform; wherein, the modular cascade conversion topology structure formed by the single-phase full-bridge rectifier module side and the three-phase half-bridge inverter module side is a flexible conversion cascade topology structure.

12. The variable current control method according to claim 11, characterized in that: The single-phase AC power is converted by the conversion unit, including: Through the modular single-phase rectifier module, the single-phase AC power is rectified and the DC bus voltage is output; The DC bus voltage after rectification of the single-phase AC power is filtered by the filtering module to obtain the filtered DC bus voltage; The filtered DC bus voltage is inverted through a modular three-phase inverter module to output three-phase AC power.

13. The variable current control method according to claim 11 or 12, characterized in that: Also includes: The protection unit filters the neutral, live and ground wires of the mains power to form single-phase alternating current.

14. The variable current control method according to claim 11 or 12, characterized in that: The control unit is used to perform phase shift modulation and circulating current layering control on the converter unit, including: Through the phase-shift modulation module, two independent sawtooth waves are used, and the phase-shift modulation technology and the circulating current layered control method are adopted to output pulse signals to the rectification processing side and the inverter processing side in the conversion unit respectively, so as to drive the rectification processing side and the inverter processing side in the conversion unit through the pulse signals.

15. The variable current control method according to claim 14, characterized in that: The control unit is used to perform phase shift modulation and circulating current stratification control on the converter unit, and also includes: The DC bus signal on the rectifier processing side in the converter unit, the bridge arm voltage of each bridge arm, and / or the capacitor voltage of each single-phase rectifier module are collected through the rectifier side sampling module; Through the phase-shift modulation module, the pulse signal on the rectification processing side in the conversion unit is adjusted based on the sawtooth carrier phase-shift modulation technology according to the DC bus signal on the rectification processing side, the bridge arm voltage of each bridge arm, and / or the capacitor voltage of each single-phase rectifier module, so as to achieve balanced control of the DC bus signal on the rectification processing side, the bridge arm voltage of each bridge arm, and / or the capacitor voltage of each single-phase rectifier module; The outer loop establishes a control loop through the output voltage and power of the rectifier side to meet the voltage requirements of different levels on the inverter side within the demand range; and / or, the inner loop adopts phase voltage balancing control, bridge arm voltage balancing control, submodule capacitor voltage balancing, and the feedback reference signal is power or bus DC voltage; and / or, Adopt bus DC control or power PQ control, perform PI operation on the difference between the actual rectified voltage and the reference voltage to obtain the reference current of the dq quadrant after rectification; after iterative operation, obtain the reference current vector of the upper and lower bridge arms of each phase, and make a difference between the reference current vector and the actual value of the DC bus current to form the DC bus reference current, and the obtained current is subjected to PI operation to obtain the variable voltage, and then the actual output bus DC voltage is added to obtain the fundamental output reference voltage; the voltage balancing value and the actual value of each SM are subjected to voltage balancing control to obtain the fundamental reference voltage of each phase sub-module, and then the sawtooth wave phase-shifted carrier PWM operation is performed to obtain the PWM pulse signal corresponding to the full-bridge sub-module switch, and the DC voltage is output; finally, by changing the bus DC voltage and power, the closed-loop control of adjustable DC voltage or adjustable power is realized.

16. The variable current control method according to claim 14, characterized in that: The control unit is used to perform phase shift modulation and circulating current stratification control on the converter unit, and also includes: The three-phase electrical signal of the inverter processing side in the converter unit, the inner loop current of each bridge arm, and / or the capacitor voltage of each three-phase inverter submodule are collected through the inverter side sampling module; Through the phase-shift modulation module, the pulse signal on the inverter processing side in the converter unit is adjusted according to the three-phase electrical signal on the inverter processing side, the inner loop current of each bridge arm, and / or the capacitor voltage of each three-phase inverter sub-module, so as to realize the outer loop control and phase balance of the three-phase electrical signal on the inverter processing side, the inner loop current suppression of each bridge arm, and / or the capacitor voltage balance of each three-phase inverter sub-module.

17. The variable current control method according to claim 14, characterized in that: The control unit is used to perform phase shift modulation and circulating current stratification control on the converter unit, and also includes: The three-phase current, rotor position, and / or rotor speed of the output side motor of the converter unit are collected through the load side sampling module; Through the phase-shift modulation module, the pulse signals on the rectification processing side and / or the inverter processing side in the converter unit are adjusted according to the three-phase current, rotor position, and / or rotor speed of the motor, thereby realizing closed-loop frequency conversion control of the motor on the output side of the converter unit.

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