Two-phase motor system with double operation modes and electrical product

Abstract

The invention discloses a two-phase motor system with double operation modes and an electrical product. The two-phase motor system comprises a two-phase motor, a frequency conversion module, a phase compensation module, a switch module and a signal processor. The frequency conversion module is used for converting a single-phase alternating current of a power grid into a two-phase alternating current for controlling the two-phase motor to operate, and controlling the two-phase motor to perform frequency conversion and speed regulation to a preset operation speed; the phase compensation module is used for shifting the single-phase alternating current of the power grid by a preset phase difference; the signal processor responds to an upper-layer control signal to generate a switch on-off signal and sends the switch on-off signal to the switch module and the inverter circuit; and the switch module is used for selecting the two-phase motor to perform frequency conversion operation through the frequency conversion module or perform grid-connected operation through the phase compensation module according to the switch on-off signal. The two-phase motor system has two modes of variable-frequency operation and grid-connected operation, and torque pulsating and vibration noise of the two-phase motor in the grid-connected or variable-frequency mode are reduced.

Description

Technical Field

[0001] This invention relates to the field of motor and control technology, and in particular to a two-phase motor system and electrical product with dual operating modes. Background Technology

[0002] In recent years, in pursuit of high efficiency and lightweight compressors, compressor systems driven by three-phase variable frequency permanent magnet synchronous motors have gradually demonstrated their advantages. A compressor system driven by a three-phase variable frequency permanent magnet synchronous motor mainly includes a drive controller, a three-phase permanent magnet drive motor, and a compressor cooling structure. The losses in the controller and motor, as well as the compressor's cooling performance, all affect the efficiency of the compressor system. Furthermore, the compressor motor operates at speeds ranging from approximately 1000-4500 rpm, with light-load, low-speed operation being a common condition, generally requiring the highest possible compressor system efficiency. Considering the losses in the controller's switching devices, directly connecting the compressor to the power grid at low speeds can further improve its efficiency under these conditions. Since everyday household appliances typically use 220V AC, 50Hz single-phase mains power, three-phase permanent magnet motors cannot be connected to the grid for parallel operation. However, using a single-phase permanent magnet motor for grid connection often results in excessive torque pulsation and a failure to self-start. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of existing three-phase variable frequency permanent magnet synchronous motors and single-phase permanent magnet motors that cannot simultaneously meet the requirements of variable frequency operation and grid-connected operation, and to provide a two-phase motor system and electrical product with dual operating modes.

[0004] The present invention solves the above-mentioned technical problems through the following technical solution:

[0005] This invention provides a two-phase motor system with dual operating modes. The two-phase motor system includes a two-phase motor, a frequency converter module, a phase compensation module, a switching module, and a signal processor. The switching module is connected to the frequency converter module, the phase compensation module, and the signal processor, respectively.

[0006] The frequency conversion module includes a rectifier circuit and an inverter circuit. The rectifier circuit is used to convert single-phase AC power from the power grid into DC power, and the inverter circuit is used to convert the DC power into two-phase AC power to control the operation of the two-phase motor and control the two-phase motor to adjust its speed to a preset operating speed.

[0007] The phase compensation module is used to offset the single-phase AC power of the power grid by a preset phase difference;

[0008] The signal processor generates a switch on / off signal in response to the upper-level control signal and sends it to the switch module and the inverter circuit.

[0009] The switching module is used to select, based on the switch on / off signal, whether the two-phase motor is connected to the power grid via the frequency converter module for frequency conversion operation or connected to the power grid via the phase compensation module for grid-connected operation.

[0010] Preferably, the inverter circuit is connected to the power grid through the rectifier circuit.

[0011] Preferably, the rectifier circuit includes a full-wave rectifier circuit; and / or,

[0012] The rectifier circuit includes a full-wave rectifier circuit employing a voltage doubler structure.

[0013] Preferably, the inverter circuit includes two H-bridge inverter topologies; the switching module includes a switch control circuit, two frequency converter switches, and two grid-connected switches.

[0014] The switch control circuit is used to control the on / off state of the two frequency converters and the two grid-connected switches according to the switch on / off signal;

[0015] One phase winding of the two-phase motor is connected to an H-bridge inverter topology via a frequency converter switch; the other phase winding of the two-phase motor is connected to another H-bridge inverter topology via another frequency converter switch.

[0016] One phase winding of the two-phase motor is connected to the power grid via a grid-connected switch; the other phase winding of the two-phase motor is connected to the power grid via another grid-connected switch.

[0017] Preferably, the signal processor is specifically used to control the two frequency converter switches to close and the two grid-connected switches to open through the switch control circuit, so that the two-phase motor operates in frequency conversion mode;

[0018] The signal processor is specifically used to control the two frequency converter switches to open and the two grid-connected switches to close through the switch control circuit, so that the two-phase motor operates in a grid-connected state.

[0019] The signal processor is specifically used to control the two frequency converter switches and the two grid-connected switches to be disconnected through the switch control circuit, so that the two-phase motor is running in a stopped state.

[0020] Preferably, the signal processor is specifically used to generate a rotational speed signal based on the upper-level signal;

[0021] Specifically, the signal processor is used to control the two frequency converter switches and the two grid-connected switches to disconnect when the speed signal is 0 through the switch control circuit.

[0022] Specifically, when the speed signal is a preset grid-connected speed, the signal processor first controls the two frequency converter switches to close and the two grid-connected switches to open via the switch control circuit, then controls the two-phase motor to adjust its speed to the preset grid-connected speed via the frequency converter module, and finally controls the two frequency converter switches to open and the two grid-connected switches to close via the switch control circuit.

[0023] The signal processor is specifically used to control the two frequency converter switches to close and the two grid-connected switches to open through the switch control circuit when the speed signal is not 0 and is not a preset grid-connected speed, and to control the two-phase motor to adjust its speed to the running speed corresponding to the speed signal through the frequency converter module.

[0024] Preferably, the signal processor is further configured to determine whether the parameters of the current speed of the two-phase motor and / or the output voltage of the frequency converter module meet the grid connection conditions;

[0025] The signal processor is also specifically used to adjust the current speed of the two-phase motor and / or the output voltage parameters of the frequency converter module until the grid connection conditions are met when the grid connection conditions are not met.

[0026] Preferably, the no-load back EMF of one phase winding of the two-phase motor leads the given electrical angle of the other phase winding, and is connected to the power grid through a compensation capacitor and / or a compensation resistor.

[0027] The present invention also provides an electrical product comprising a two-phase motor system with dual operating modes as described above.

[0028] The positive and progressive effects of this invention are as follows:

[0029] This invention provides a two-phase motor system with dual operating modes. Based on the upper-level signal, the two-phase motor is selected by a switching module to operate via frequency conversion or grid-connected without the frequency conversion module. Under a single-phase AC power grid, it has both frequency conversion and grid-connected operation modes, enabling the two-phase motor to have self-starting capability and reducing torque pulsation and vibration noise of the two-phase motor in grid-connected or frequency conversion modes. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments in this specification, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of this specification. For those skilled in the art, these drawings can be applied to other similar scenarios without creative effort. Unless obvious from the context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0031] Figure 1 This is a schematic diagram of the first structure of a two-phase motor system with dual operating modes in Embodiment 1 of the present invention.

[0032] Figure 2 This is a schematic diagram of the second structure of a two-phase motor system with dual operating modes in Embodiment 1 of the present invention.

[0033] Figure 3 This is a schematic diagram of the third structure of a two-phase motor system with dual operating modes in Embodiment 1 of the present invention.

[0034] Figure 4 This is a schematic diagram of the first structure of the rectifier circuit of the two-phase motor system with dual operating modes in Embodiment 1 of the present invention.

[0035] Figure 5 This is a schematic diagram of the second structure of the rectifier circuit of the two-phase motor system with dual operating modes in Embodiment 1 of the present invention.

[0036] Figure 6 This is a schematic diagram of the working process of a two-phase motor system with dual operating modes in Embodiment 1 of the present invention.

[0037] Figure 7 This is a schematic diagram of the grid-connected control process of a two-phase motor system with dual operating modes in Embodiment 1 of the present invention. Detailed Implementation

[0038] The present invention will be further illustrated by way of embodiments below, but the present invention is not limited to the scope of the embodiments described herein.

[0039] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the document does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0040] It should be understood that the terms “device,” “system,” “unit,” and / or “module” used herein are one way to distinguish different components, elements, parts, sections, or assemblies at different levels. However, if other terms can achieve the same purpose, they may be replaced by other expressions.

[0041] As illustrated herein, unless the context clearly indicates otherwise, the words “a,” “an,” “an,” and / or “the” do not specifically refer to the singular and may also include the plural. Generally speaking, the terms “comprising” and “including” only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0042] The definitions used herein, such as the terms “having,” “may have,” “comprising,” or “may include,” indicate the presence of the corresponding function, operation, element, etc., and do not limit the presence of one or more other functions, operations, elements, etc. Furthermore, it should be understood that the terms “comprising” or “having” as used herein indicate the presence of the features, figures, steps, operations, elements, components, or combinations thereof described in the specification, without excluding the presence or addition of one or more other features, figures, steps, operations, elements, components, or combinations thereof.

[0043] Example 1

[0044] Please refer to Figure 1 This is a schematic diagram of the first structure of the two-phase motor system with dual operating modes in this embodiment. Specifically, as shown... Figure 1 As shown, the two-phase motor system includes a signal processor 1, a switching module 2, a phase compensation module 3, a frequency converter 4, and a two-phase motor 5; the switching module 2 is connected to the frequency converter 4, the phase compensation module 3, and the signal processor 1 respectively.

[0045] The frequency converter module 4 is used to convert the single-phase AC power of the power grid into two-phase AC power to control the operation of the two-phase motor 5, and to control the two-phase motor 5 to adjust its speed to the preset operating speed.

[0046] Please refer to Figure 2 and 3 These are the second and third structural schematic diagrams of the two-phase motor system with dual operating modes in this embodiment. Specifically, as shown... Figure 2 and 3 As shown, in this embodiment, the frequency converter module 4 includes a rectifier circuit 41 and an inverter circuit 42; the inverter circuit 42 is connected to the power grid through the rectifier circuit 41.

[0047] The rectifier circuit 41 is used to convert the single-phase AC power of the power grid into DC power. The power grid in this embodiment is a common single-phase AC power grid. The rectifier circuit is connected to the single-phase AC power grid through lines L3 and L4.

[0048] Inverter circuit 42 is used to convert direct current into two-phase alternating current.

[0049] Phase compensation module 3 is used to offset the single-phase AC power of the power grid by a preset phase difference;

[0050] Signal processor 1 generates a switch on / off signal in response to the upper-level control signal and sends it to switch module 2 and inverter circuit 42;

[0051] The switch module 2 is used to select, based on the switch on / off signal, whether the two-phase motor is connected to the power grid via the frequency converter module 4 for frequency conversion operation or via the phase compensation module 3 for grid-connected operation.

[0052] Please refer to Figure 4 This is a schematic diagram of the first structure of the rectifier circuit of the two-phase motor system with dual operating modes in this embodiment. Specifically, as shown... Figure 4 As shown, in one alternative implementation, the rectifier circuit 41 may include a full-wave rectifier circuit.

[0053] Please refer to Figure 5 This is a second structural diagram of the rectifier circuit of the two-phase motor system with dual operating modes in this embodiment. Specifically, as shown... Figure 5 As shown, in another alternative embodiment, the rectifier circuit 41 may include a full-wave rectifier circuit employing a voltage doubler structure. The full-wave rectifier circuit employing a voltage doubler structure can achieve an output bus voltage that is any multiple of the input voltage amplitude.

[0054] In this embodiment, the inverter circuit 42 includes two H-bridge inverter topologies; the switching module 2 includes a switch control circuit 23, two frequency converter switches 21 and two grid-connected switches 22;

[0055] The switch control circuit 23 is used to control the on / off state of the two frequency converter switches 21 and the two grid-connected switches 22 according to the switch on / off signal;

[0056] One phase winding of the two-phase motor is connected to an H-bridge inverter topology via a frequency converter switch 21; the other phase winding of the two-phase motor is connected to another H-bridge inverter topology via another frequency converter switch 21.

[0057] One phase winding of the two-phase motor is connected to the power grid through a grid-connected switch 22; the other phase winding of the two-phase motor is connected to the power grid through another grid-connected switch 22.

[0058] Specifically, the motor is connected to the inverter circuit 42 via lines L7, L8, L9, and L10, and to the single-phase AC power grid via lines L11 and L12. Frequency converter switches are located on lines L7, L8, L9, and L10, and grid-connected switches are located on lines L11, L12, L13, and L14. The frequency converter switches and grid-connected switches can be, but are not limited to, solid-state relays and electromagnetic relays. The frequency converter switches and grid-connected switches do not close simultaneously; when the frequency converter switch is closed and the grid-connected switch is open, the corresponding motor system operates in frequency conversion mode; when the frequency converter switch is open and the grid-connected switch is closed, the corresponding motor system operates in synchronous speed grid-connected mode. When both the frequency converter switch and the grid-connected switch are open, the corresponding motor system operates in a stopped state.

[0059] In addition, the two-phase motor drive system also includes a voltage acquisition unit 6, which is connected to lines L3 and L4 via lines L5 and L6. The voltage acquisition unit 6 is used to acquire single-phase grid voltage signals and input them to the signal processor 1. The signal processor 1 processes the acquired voltage signals, upper-level signals, and motor signals, controls the inverter circuit 42 through a control algorithm, and simultaneously outputs signals to the switch control circuit 23.

[0060] The working principle of the two-phase motor system with dual operating modes is described in detail below. Specifically, signal processor 1 is used to control the closing of two frequency converter switches 21 and the opening of two grid-connected switches 22 via switch control circuit 23, so that the two-phase motor operates in frequency conversion mode;

[0061] The signal processor 1 is specifically used to control the two frequency converter switches 21 to open and the two grid-connected switches 22 to close through the switch control circuit 23, so that the two-phase motor can operate in the grid-connected state.

[0062] The signal processor 1 is specifically used to control the two frequency converter switches 21 and the two grid-connected switches 22 to be disconnected through the switch control circuit 23, so that the two-phase motor is running in a stopped state.

[0063] Please refer to Figure 6 This is a schematic diagram illustrating the workflow of the two-phase motor system with dual operating modes in this embodiment. Specifically, as shown... Figure 6 As shown, signal processor 1 is specifically used to generate a rotational speed signal based on the upper-level signal;

[0064] The signal processor 1 is specifically used to control the two frequency converter switches 21 and the two grid-connected switches 22 to disconnect through the switch control circuit 23 when the speed signal is 0.

[0065] The signal processor 1 is specifically used to control the two frequency converter switches 21 to close and the two grid-connected switches 22 to open through the switch control circuit 23 when the speed signal is the preset grid-connected speed. Then, it controls the two-phase motor 5 to adjust its speed to the preset grid-connected speed through the frequency converter module 4. Finally, it controls the two frequency converter switches 21 to open and the two grid-connected switches 22 to close through the switch control circuit 23.

[0066] The signal processor 1 is specifically used to control the two frequency converter switches 21 to close and the two grid-connected switches 22 to open through the switch control circuit 23 when the speed signal is not 0 and is not the preset grid-connected speed, and to control the two-phase motor to adjust the speed to the running speed corresponding to the speed signal through the frequency converter module 4.

[0067] Specifically, the signal processor processes the upper-level signal and outputs a speed signal n*. The current compressor status needs to be determined, and then the motor speed n is adjusted accordingly to equal n*.

[0068] 1. When n*=0, it indicates shutdown mode, and the shutdown operation command is executed. The current operating mode of the compressor is determined as follows:

[0069] 1) Determine that the compressor is currently in a stopped state and maintain the stopped state;

[0070] 2) Determine that the compressor is currently in grid-connected mode, then directly disconnect the grid-connection switch (the same applies below) to shut down the power.

[0071] 3) Determine that the compressor is currently in inverter mode. After adjusting the inverter speed to low speed, cut off the power to stop the machine or directly disconnect the grid connection switch to cut off the power to stop the machine.

[0072] 2. When n*=n s (n) s =60*f / p, where f is the power grid frequency, p is the number of pole pairs of the motor, and n s (Synchronous speed), indicating grid-connected mode, executing the grid-connected operation command. Determine the compressor's current operating mode:

[0073] 1) Determine that the compressor is currently in a stopped state, close the inverter switch, and after the inverter starts, adjust the speed to n. s The grid-connected control algorithm in the signal processor controls the inverter circuit to meet the grid-connected conditions, controls the first grid-connected switch state, and switches to grid-connected mode.

[0074] 2) Determine if the compressor is currently in grid-connected mode and maintain the current grid-connected mode;

[0075] 3) Determine that the compressor is currently in inverter mode, and adjust the inverter speed to n. s The grid-connected control algorithm in the signal processor controls the inverter circuit to meet the grid-connected conditions, controls the first grid-connected switch state, and switches to grid-connected mode.

[0076] 3. When n*≠n s And n*≠0, indicating variable frequency mode, executing variable frequency operation commands. The current operating mode of the compressor needs to be determined:

[0077] 1) Determine that the compressor is currently in a stopped state, close the inverter switch, start the inverter, and adjust the speed to n* for operation;

[0078] 2) Determine that the compressor is currently in grid-connected mode, disconnect the grid-connected switch, close the inverter switch, switch to inverter operation mode and adjust the speed to n* operation;

[0079] 3) Determine that the compressor is currently in variable frequency mode, and adjust the variable frequency speed to n* operation.

[0080] Please refer to Figure 7 This is a schematic diagram of the grid-connected control process of a two-phase motor system with dual operating modes in this embodiment. Specifically, as shown... Figure 7 As shown, the signal processor 1 is also specifically used to determine whether the current speed of the two-phase motor and / or the output voltage parameters of the frequency converter module 4 meet the grid connection conditions.

[0081] The signal processor 1 is also specifically used to adjust the current speed of the two-phase motor and / or the output voltage parameters of the frequency converter module 4 until the grid connection conditions are met when the grid connection conditions are not met.

[0082] First, the signal processor determines whether the rotational speed has reached the grid-connected speed n. s If n is not reached s The signal processor adjusts the inverter circuit frequency, thereby regulating the rotational speed to n. s After the rotational speed is consistent, it is determined whether the output voltage amplitude of the inverter module is consistent with the grid voltage amplitude. If they are inconsistent, the output voltage amplitude of the inverter module is adjusted by the signal processor to make it consistent with the grid voltage. Then, it is determined whether the output voltage phase of the inverter module is consistent with the grid voltage phase. If they are inconsistent, the output voltage phase of the inverter module is adjusted by the signal processor to make it consistent with the grid phase. It is then determined whether the phase at this time meets the initial phase requirement φ0 of the grid at the time of grid connection (φ0 is determined by the capacitors C1 and R1 connected in series with the motor A phase). If it does not meet the requirement, the grid connection is switched on after the grid phase is met.

[0083] In addition, the no-load back EMF of one phase winding of the two-phase motor leads the other phase winding by a given electrical angle, and is connected to the power grid through a compensation capacitor and / or a compensation resistor. Specifically, the motor includes two-phase windings, A and B, where the no-load back EMF of phase A leads phase B by a certain electrical angle (80°~100°). Phase A winding is connected in series with capacitor C1 and resistor R1 (or a single capacitor C1 in series) through line L15. Sensors are installed on the motor to input the collected motor-related signals into a signal processor.

[0084] The following example further illustrates the operation and grid connection switching strategy of the two-phase motor system with dual operating modes in this embodiment:

[0085] Assuming the single-phase AC power grid frequency f is 50Hz, the number of motor pole pairs p is 3, and the grid-connected speed n s The speed is 1000 rpm, and the motor speed n ranges from 0 to 4500 rpm, i.e., n ∈ [0, 4500]. When the signal processor provides the speed signal n... * When this is done, it is necessary to first determine the current state of the compressor, and then adjust the motor speed n to make it equal to n*. The compressor has 3 states: the stop state when the speed n is 0, the grid-connected state when the speed n is 1000 rpm, and the variable frequency state when the speed n∈(0,1000)U(1000,4500].

[0086] 1. When the speed signal n output by the signal processor * At 0 rpm:

[0087] 1) Determine that the compressor is currently in a stopped state and maintain the stopped state;

[0088] 2) Determine that the compressor is currently in grid-connected mode, then directly disconnect the grid-connection switch (the same applies below) to shut down the power.

[0089] 3) Determine that the compressor is currently in inverter mode. After adjusting the inverter speed to low speed, cut off the power to stop the machine or directly disconnect the grid connection switch to cut off the power to stop the machine.

[0090] 2. When the speed signal n output by the signal processor * When the grid connection speed is 1000 rpm:

[0091] 1) Determine that the compressor is currently in a stopped state, close the inverter switch, start the inverter and adjust the speed to 1000rpm. The grid-connected control algorithm in the signal processor controls the inverter circuit to meet the grid-connected conditions, controls the first grid-connected switch state, and switches to grid-connected mode.

[0092] 2) Determine if the compressor is currently in grid-connected mode and maintain the current grid-connected mode;

[0093] 3) Determine that the compressor is currently in variable frequency mode, adjust the variable frequency speed to 1000 rpm, and the grid-connected control algorithm in the signal processor controls the inverter circuit to meet the grid connection conditions, controls the first grid connection switch state, and switches to grid connection mode.

[0094] The specific steps for switching to a single-phase AC power grid are as follows:

[0095] First, determine if the rotational speed has reached 1000 rpm. If it has not, adjust the inverter circuit frequency through the signal processor to adjust the rotational speed to 1000 rpm. Once the rotational speed is consistent, determine if the output voltage amplitude of the inverter module is consistent with the grid voltage amplitude. If not, adjust the output voltage amplitude of the inverter module through the signal processor to make it consistent with the grid voltage. Then, determine if the output voltage phase of the inverter module is consistent with the grid voltage phase. If not, adjust the output voltage phase of the inverter module through the signal processor to make it consistent with the grid phase. Finally, determine if the phase at this time meets the initial phase requirement φ0 of the grid at the time of grid connection (φ0 is determined by the capacitors C1 and R1 connected in series with the motor's A phase). If not, wait for the grid phase to meet the requirement before switching to grid connection.

[0096] 3. When the speed signal n output by the signal processor * It is 2400 rpm, that is, n * When ∈(0,1000)U(1000,4500]:

[0097] 1) Determine that the compressor is currently in a stopped state, close the inverter switch, and after the inverter starts, adjust the speed to 2400rpm;

[0098] 2) Determine that the compressor is currently in grid-connected mode, disconnect the grid-connected switch, close the inverter switch, switch to inverter operation mode, and adjust the speed to 2400 rpm;

[0099] 3) Determine that the compressor is currently in inverter mode and adjust the inverter speed to 2400rpm.

[0100] Example 2

[0101] This embodiment provides an electrical appliance, which includes the two-phase motor system with dual operating modes of Embodiment 1. Optionally, the electrical appliance is a refrigerator.

[0102] This embodiment provides an electrical product that drives a compressor motor using a two-phase motor system with dual operating modes, which has both variable frequency operation and grid-connected operation modes. This enables the compressor motor to have self-starting capability and reduces torque pulsation and vibration noise of the motor in grid-connected or variable frequency modes.

[0103] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A two-phase motor system with dual operating modes, characterized in that, The two-phase motor system includes a two-phase motor, a frequency converter module, a phase compensation module, a switching module, and a signal processor; the switching module is connected to the frequency converter module, the phase compensation module, and the signal processor respectively. The frequency conversion module includes a rectifier circuit and an inverter circuit. The rectifier circuit is used to convert single-phase AC power from the power grid into DC power, and the inverter circuit is used to convert the DC power into two-phase AC power to control the operation of the two-phase motor and control the two-phase motor to adjust its speed to a preset operating speed. The phase compensation module is used to offset the single-phase AC power of the power grid by a preset phase difference; The signal processor generates a switch on / off signal in response to the upper-level control signal and sends it to the switch module and the inverter circuit. The switching module is used to select, based on the switch on / off signal, whether the two-phase motor is connected to the power grid via the frequency converter module for frequency conversion operation or connected to the power grid via the phase compensation module for grid-connected operation.

2. The two-phase motor system with dual operating modes as described in claim 1, characterized in that, The inverter circuit is connected to the power grid through the rectifier circuit.

3. The two-phase motor system with dual operating modes as described in claim 2, characterized in that, The rectifier circuit includes a full-wave rectifier circuit; And / or, The rectifier circuit includes a full-wave rectifier circuit employing a voltage doubler structure.

4. The two-phase motor system with dual operating modes as described in claim 2, characterized in that, The inverter circuit includes two H-bridge inverter topologies; the switching module includes a switch control circuit, two frequency converters, and two grid-connected switches. The switch control circuit is used to control the on / off state of the two frequency converters and the two grid-connected switches according to the switch on / off signal; One phase winding of the two-phase motor is connected to an H-bridge inverter topology via a frequency converter switch; the other phase winding of the two-phase motor is connected to another H-bridge inverter topology via another frequency converter switch. One phase winding of the two-phase motor is connected to the power grid via a grid-connected switch; the other phase winding of the two-phase motor is connected to the power grid via another grid-connected switch.

5. The two-phase motor system with dual operating modes as described in claim 4, characterized in that, The signal processor is specifically used to control the two frequency converter switches to close and the two grid-connected switches to open through the switch control circuit, so that the two-phase motor operates in frequency conversion mode. The signal processor is specifically used to control the two frequency converter switches to open and the two grid-connected switches to close through the switch control circuit, so that the two-phase motor operates in a grid-connected state. The signal processor is specifically used to control the two frequency converter switches and the two grid-connected switches to be disconnected through the switch control circuit, so that the two-phase motor is running in a stopped state.

6. The two-phase motor system with dual operating modes as described in claim 5, characterized in that, The signal processor is specifically used to generate a rotation speed signal based on the upper-level signal; Specifically, the signal processor is used to control the two frequency converter switches and the two grid-connected switches to disconnect when the speed signal is 0 through the switch control circuit. Specifically, when the speed signal is a preset grid-connected speed, the signal processor first controls the two frequency converter switches to close and the two grid-connected switches to open via the switch control circuit, then controls the two-phase motor to adjust its speed to the preset grid-connected speed via the frequency converter module, and finally controls the two frequency converter switches to open and the two grid-connected switches to close via the switch control circuit. The signal processor is specifically used to control the two frequency converter switches to close and the two grid-connected switches to open through the switch control circuit when the speed signal is not 0 and is not a preset grid-connected speed, and to control the two-phase motor to adjust its speed to the running speed corresponding to the speed signal through the frequency converter module.

7. The two-phase motor system with dual operating modes as described in claim 6, characterized in that, The signal processor is also specifically used to determine whether the current speed of the two-phase motor and / or the output voltage of the frequency converter module meet the grid connection conditions. The signal processor is also specifically used to adjust the current speed of the two-phase motor and / or the output voltage parameters of the frequency converter module until the grid connection conditions are met when the grid connection conditions are not met.

8. The two-phase motor system with dual operating modes as described in claim 1, characterized in that, The no-load back EMF of one phase winding of the two-phase motor leads the given electrical angle of the other phase winding, and is connected to the power grid through a compensation capacitor and / or a compensation resistor.

9. An electrical appliance, characterized in that, The electrical product includes a two-phase motor system with dual operating modes as described in any one of claims 1 to 8.

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