A harmonic-eliminating anti-hunting motor uninterruptible power supply device

Abstract

The application relates to the technical field of uninterrupted power supply, in particular to a motor uninterrupted power supply device capable of eliminating harmonic waves and resisting flicker, which comprises an external connection unit, a detection unit, an energy storage unit and a control unit. The external connection unit comprises a rectifier, an inverter and an output filter. The detection unit is used for detecting the voltage drop amplitude of direct current output by the rectifier. The energy storage unit is used for storing electric energy. The control unit is used for determining whether the energy storage unit carries out a constant-power discharge mode or a variable-power discharge mode matched with the load power demand according to the voltage drop amplitude. The modulation ratio of the rectifier is adjusted according to the voltage fluctuation rate of the direct current under the condition of carrying out the constant-power mode discharge. The output mode of the inverter is determined according to the rated power ratio of the energy storage unit under the condition of carrying out the variable-power mode discharge matched with the load power demand. The output mode of the inverter comprises a full-capacity output mode and a double-modulation wave output mode. The application realizes the improvement of the precision of voltage drop compensation.

Description

A harmonic-suppressing and anti-vibration uninterruptible power supply device for electric motors Technical Field

[0001] This invention relates to the field of uninterruptible power supply technology, and in particular to an uninterruptible power supply device for motors that eliminates harmonics and resists vibration. Background Technology

[0002] In existing technologies, uninterruptible power supply (UPS) devices for motors include harmonic suppression, voltage fluctuation compensation, and uninterrupted power supply. They employ methods such as Fast Fourier Transform (FFT), Wavelet Transform (WFT), or instantaneous reactive power theory to quickly identify harmonic components generated by the motor load. A converter composed of power electronic devices such as IGBTs generates a reverse compensation current based on the detected harmonic signals, achieving dynamic and high-precision harmonic suppression. A phase-locked loop (PLL) is used to quickly track the phase, amplitude, and frequency of the grid voltage, identifying anomalies such as voltage dips, swells, or interruptions. A transformer is connected in series between the grid and the motor; when the grid voltage dips, a compensation voltage is quickly output to maintain stable voltage at the motor terminals. The energy storage devices in UPS technology use a hybrid energy storage scheme of batteries and supercapacitors to handle the high current demands during startup or dips, such as motor startup currents reaching 5-7 times the rated current, improving response speed. However, UPS technology still suffers from high costs and low efficiency due to converter switching losses.

[0003] Chinese Patent Publication No. CN115296388A discloses a method, control device, and system for detecting bypass power failure in an uninterruptible power supply (UPS). The load connected to the UPS includes a motor. The method includes: when the UPS is in an economic operating mode, acquiring the bypass voltage of each phase of the UPS in the previous cycle; wherein the phase of the bypass voltage at the beginning of each cycle of each phase is the same; wherein the economic operating mode is to supply power to the load via bypass; determining the DC component of the bypass voltage of each phase based on the bypass voltage of each phase; and determining that the bypass power failure occurs when the DC component of the bypass voltage of any phase exceeds a first preset threshold. Therefore, the UPS bypass power failure detection method, control device, and system suffer from the problem that voltage dips caused by short-circuit faults in the power grid, the start-up of large-capacity equipment, etc., can lead to production interruptions or a decrease in motor speed. Summary of the Invention

[0004] Therefore, the present invention provides a harmonic-suppressing and anti-sloshing uninterruptible power supply device for motors to overcome the problem in the prior art where voltage dips caused by short-circuit faults in the power grid, startup of large-capacity equipment, etc., lead to production interruptions or a decrease in motor speed.

[0005] To achieve the above objectives, the present invention provides a harmonic-suppressing and anti-vibration uninterruptible power supply device for electric motors, comprising:

[0006] External connection unit, used to connect external devices, including rectifiers and inverters connected to the power grid, and output filters connected to the load;

[0007] A detection unit, which is connected to the external connection unit, is used to detect the voltage drop amplitude of the DC output of the rectifier;

[0008] An energy storage unit, which is connected to the detection unit, is used to store electrical energy;

[0009] The control unit, which is connected to the external connection unit, the detection unit, and the energy storage unit respectively, is used to determine whether the energy storage unit should perform constant power discharge mode or variable power discharge mode matching the load power demand based on the voltage drop amplitude. Under the condition of constant power discharge mode, the modulation ratio of the rectifier is adjusted according to the DC voltage fluctuation rate. Under the condition of variable power discharge mode matching the load power demand, the output mode of the inverter is determined according to the rated power ratio of the energy storage unit. The output modes of the inverter include full capacity output mode and dual modulation wave output mode.

[0010] Furthermore, the detection unit includes:

[0011] A DC bus, which is connected to the output terminal of the rectifier;

[0012] A voltage sensor, which is connected to the DC bus, is used to detect the voltage of the DC power supply.

[0013] Furthermore, the energy storage unit includes:

[0014] An energy storage battery, which is connected to the DC bus, is used to provide electrical energy to the DC bus;

[0015] A bidirectional DC / DC converter, which is connected to the energy storage battery, is used to control the charging or discharging of the energy storage battery.

[0016] Furthermore, the voltage drop amplitude is the absolute value of the difference between the minimum actual DC voltage and the rated reference voltage.

[0017] Furthermore, the control unit is connected to both the voltage sensor and the energy storage battery to calculate the voltage drop amplitude based on the DC voltage.

[0018] If the voltage drop amplitude is greater than or equal to a preset second amplitude, then the energy storage battery is controlled to perform the constant power discharge mode.

[0019] If the voltage drop amplitude is less than the preset second amplitude but greater than the preset first amplitude, the energy storage battery is controlled to perform a variable power discharge mode that matches the load power demand.

[0020] Furthermore, the voltage fluctuation rate is the ratio of the difference between the maximum and minimum voltage sample values ​​within a unit detection time to the rated reference voltage.

[0021] Furthermore, the control unit is connected to the rectifier to obtain the voltage fluctuation rate under the condition that the energy storage battery is in the constant power discharge mode.

[0022] If the voltage fluctuation rate is greater than or equal to the preset fluctuation rate, then the modulation ratio is reduced.

[0023] Furthermore, the rated power ratio is the ratio of the actual output power of the energy storage battery to its rated power.

[0024] Furthermore, the control unit is connected to the inverter to obtain the rated power ratio under the condition that the energy storage battery is in a variable power discharge mode that matches the load power demand.

[0025] If the rated power ratio is greater than or equal to the preset power ratio, the inverter will operate in full-capacity output mode.

[0026] If the rated power ratio is less than the preset power ratio, the inverter will operate in dual-modulation output mode.

[0027] Furthermore, the full-capacity output mode is that the inverter supplies power to the load terminal with rated output voltage and rated output current;

[0028] The dual-modulation output mode is a mode in which the inverter's modulation wave is superimposed with a sinusoidal fundamental wave and an anti-phase compensation harmonic obtained based on the load harmonic current to supply power to the load.

[0029] Compared with the prior art, the beneficial effects of the present invention are that the device of the present invention, by setting up an external connection unit, a detection unit, an energy storage unit, and a control unit, can quickly respond and maintain a stable power supply to the motor side when the voltage drops due to external disturbances such as short-circuit faults or the start-up of large-capacity equipment, thus avoiding problems such as production interruption, motor speed reduction, or even shutdown, and improving the continuity of generator operation. Traditional UPS systems often use fixed discharge strategies or only support a single output mode when dealing with voltage drops, making it difficult to balance energy efficiency, dynamic response, and load adaptability, resulting in energy waste or... To address insufficient voltage dip duration, the system intelligently switches the discharge mode of the energy storage unit based on the voltage drop amplitude. During mild dips, a variable power mode matching the load power demand is used; during moderate dips, a constant power mode is activated. The rectifier modulation ratio is dynamically adjusted based on voltage fluctuation rate to suppress DC bus voltage fluctuations and improve system stability. The inverter output mode is switched according to the rated power ratio to ensure sufficient load power supply at full capacity. In dual-modulation mode, a balance between harmonic compensation and efficient power supply is achieved, enhancing the device's harmonic suppression and anti-sloshing capabilities and improving the accuracy of compensation for grid voltage dips.

[0030] Furthermore, the device described in this invention monitors the DC voltage status at the rectifier output terminal in real time by setting up a DC bus and a voltage sensor, and calculates the voltage drop amplitude and voltage fluctuation rate. By adopting a non-invasive voltage detection method, it avoids complex modifications to the main circuit structure, improves the system integration and the ability to capture transient voltage changes.

[0031] Furthermore, the device described in this invention controls the energy storage battery to enter a constant power mode for discharge, which is suitable for operating conditions where the voltage drop is large but still within an adjustable range. In this mode, the energy storage unit continuously outputs at a preset rated power to make up for the power grid supply gap, stabilize the DC bus voltage, and prevent the inverter input voltage from being too low, which would lead to output instability. In this mode, the control unit adjusts the modulation ratio of the rectifier according to the voltage fluctuation rate. When the fluctuation rate exceeds a preset threshold, the modulation ratio is actively reduced to suppress excessive current surges, reduce system harmonic content, improve power quality, and achieve active suppression of grid-side disturbances and flexible adjustment of internal voltage, thereby enhancing the stability of charging voltage regulation.

[0032] Furthermore, the device described in this invention controls the energy storage battery to enter a variable power mode discharge that matches the load power demand. This is suitable for scenarios with minor voltage drops. In this mode, the energy storage unit dynamically adjusts its output power according to the actual load power consumption, avoiding unnecessary energy release, extending backup power supply time, and improving energy efficiency. In this mode, the control system adjusts the inverter's output mode according to the rated power ratio of the energy storage battery. When the rated power ratio is high and the system load capacity is sufficient, the full-capacity output mode is activated to ensure the motor operates at full load. When the rated power ratio is low and energy storage resources are limited, the system switches to a dual-modulation wave output mode. A modulation wave is generated by superimposing a sinusoidal fundamental wave and an anti-phase compensation harmonic to cancel the characteristic harmonic current generated on the load side, thereby achieving harmonic suppression and reactive power compensation functions, improving the quality of output power, reducing motor heating and torque pulsation, and improving the stability and efficiency of the motor operation under non-ideal power conditions.

[0033] Furthermore, the device described in this invention reduces the total harmonic distortion rate of the inverter output current by introducing a dual-modulation wave output mode, thereby reducing problems such as motor insulation aging, bearing damage, and increased electromagnetic noise caused by harmonic accumulation.

[0034] Furthermore, the device described in this invention achieves charging and discharging control of the energy storage battery through a bidirectional DC / DC converter. When the power grid is normal, it efficiently absorbs excess energy to complete charging and quickly switches to the discharging state when the voltage drops. It has a fast response speed, high conversion efficiency, and suppresses voltage oscillation during the charging and discharging process. Attached Figure Description

[0035] Figure 1 is an overall structural block diagram of the anti-harmonic and anti-sloshing motor uninterruptible power supply device according to an embodiment of the present invention;

[0036] Figure 2 is a block diagram showing the connection structure between the detection unit and the control unit of the anti-harmonic and anti-sloshing motor uninterruptible power supply device according to an embodiment of the present invention.

[0037] Figure 3 is a control flowchart of the anti-harmonic and anti-sloshing motor uninterruptible power supply device according to an embodiment of the present invention. Detailed Implementation

[0038] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0039] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0040] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0041] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] Please refer to Figures 1, 2, and 3, which are respectively an overall structural block diagram, a connection structure diagram of the detection unit and the control unit, and a control flowchart of the harmonic suppression and anti-sloshing uninterruptible power supply device for motors according to an embodiment of the present invention. The present invention provides a harmonic suppression and anti-sloshing uninterruptible power supply device for motors, comprising:

[0043] External connection unit, used to connect external devices, including rectifiers and inverters connected to the power grid, and output filters connected to the load;

[0044] A detection unit, which is connected to the external connection unit, is used to detect the voltage drop amplitude of the DC output of the rectifier;

[0045] An energy storage unit, which is connected to the detection unit, is used to store electrical energy;

[0046] The control unit, which is connected to the external connection unit, the detection unit, and the energy storage unit respectively, is used to determine whether the energy storage unit should perform constant power discharge mode or variable power discharge mode matching the load power demand based on the voltage drop amplitude. Under the condition of constant power discharge mode, the modulation ratio of the rectifier is adjusted according to the DC voltage fluctuation rate. Under the condition of variable power discharge mode matching the load power demand, the output mode of the inverter is determined according to the rated power ratio of the energy storage unit. The output modes of the inverter include full capacity output mode and dual modulation wave output mode.

[0047] Specifically, external equipment includes public power supply networks and electric motors that require power.

[0048] Specifically, the rectifier is a PWM rectifier, the inverter is a three-phase voltage-source PWM inverter, the output filter is an LC filter, and the control unit is implemented as a digital signal processor.

[0049] In practice, the device described in this invention, by setting up an external connection unit, a detection unit, an energy storage unit, and a control unit, can quickly respond and maintain a stable power supply to the motor side when the voltage drops due to external disturbances such as short-circuit faults or the start-up of large-capacity equipment, thus avoiding problems such as production interruption, motor speed reduction, or even shutdown, and improving the continuity of generator operation. Traditional UPS systems often use fixed discharge strategies or only support a single output mode when dealing with voltage drops, making it difficult to balance energy efficiency, dynamic response, and load adaptability, resulting in energy waste or insufficient support time. This invention intelligently switches the discharge mode of the energy storage unit according to the voltage drop amplitude. For minor drops, it uses a variable power mode matching the load power demand; for moderate drops, it activates a constant power mode. By dynamically adjusting the rectifier modulation ratio through voltage fluctuation rate, it suppresses DC bus voltage fluctuations and improves system operational stability. The inverter output mode is switched according to the rated power ratio, ensuring sufficient load power supply at full capacity output. In dual-modulation wave mode, it achieves a balance between harmonic compensation and efficient power supply, enhancing the device's harmonic suppression and anti-sloshing capabilities, and improving the accuracy of compensation for grid voltage drops.

[0050] Specifically, the detection unit includes:

[0051] A DC bus, which is connected to the output terminal of the rectifier;

[0052] A voltage sensor, which is connected to the DC bus, is used to detect the voltage of the DC power supply.

[0053] In practice, the device of the present invention monitors the DC voltage status at the output of the rectifier in real time by setting up a DC bus and a voltage sensor, and calculates the voltage drop amplitude and voltage fluctuation rate. By adopting a non-intrusive voltage detection method, it avoids complex modifications to the main circuit structure, improves the system integration and the ability to capture transient voltage changes.

[0054] Specifically, the energy storage unit includes:

[0055] An energy storage battery, which is connected to the DC bus, is used to provide electrical energy to the DC bus;

[0056] A bidirectional DC / DC converter, which is connected to the energy storage battery, is used to control the charging or discharging of the energy storage battery.

[0057] In practice, the device described in this invention uses a bidirectional DC / DC converter to control the charging and discharging of the energy storage battery. When the power grid is normal, it efficiently absorbs excess energy to complete the charging process and quickly switches to the discharging state when the voltage drops. It has a fast response speed, high conversion efficiency, and suppresses voltage oscillations during the charging and discharging process.

[0058] Specifically, the voltage drop amplitude is the absolute value of the difference between the minimum actual DC voltage and the rated reference voltage.

[0059] Specifically, the rated reference voltage is the stable voltage value of the DC bus when the power grid is operating normally. For example, the stable voltage value measured on the DC bus after rectification of a 380V AC power grid is 700V.

[0060] Specifically, the control unit is connected to both the voltage sensor and the energy storage battery to calculate the voltage drop amplitude based on the DC voltage.

[0061] If the voltage drop amplitude is greater than or equal to a preset second amplitude, then the energy storage battery is controlled to perform the constant power discharge mode.

[0062] If the voltage drop amplitude is less than the preset second amplitude but greater than the preset first amplitude, the energy storage battery is controlled to perform a variable power discharge mode that matches the load power demand.

[0063] Specifically, if the voltage drop is less than or equal to the preset first value, the power grid will continue to supply power to the motor.

[0064] Specifically, under the conditions of a rated reference voltage of 700V and a load motor being an industrial production motor, the general range of the preset first amplitude is [40V, 100V], the general range of the preset second amplitude is [180V, 260V], the preferred embodiment of the preset first amplitude is 70V, and the preferred embodiment of the preset second amplitude is 210V.

[0065] Those skilled in the art will understand that the selectable range of the preset first amplitude and the preset second amplitude provided in this embodiment, as well as the preferred embodiment, are the values ​​that best achieve the technical problem solved by the technical solution of the present invention under the condition that the rated reference voltage is 700V and the load motor is an industrial production motor. In actual applications or experiments, those skilled in the art can make adaptive adjustments to the preset first amplitude and the preset second amplitude according to the actual application environment and application scenario.

[0066] Specifically, in constant power discharge mode, the control unit controls the bidirectional DC / DC converter to discharge the energy storage battery to the DC bus at a set constant power value;

[0067] In the variable power discharge mode that matches the load power demand, the control unit monitors the instantaneous load power of the motor at the load end in real time and controls the bidirectional DC / DC converter to make the output power of the energy storage battery the difference between the instantaneous load power and the power provided by the current grid.

[0068] For example, by collecting the voltage and current on the output side of the inverter, the instantaneous load power is calculated. In constant power discharge mode, the power command of the bidirectional DC / DC converter is locked to a set constant power value. In this embodiment, the constant power value is set to 50% of the rated power of the energy storage battery. In variable power discharge mode that matches the load power demand, the difference between the instantaneous load power and the power provided by the current grid is calculated, and the output power of the energy storage battery is adjusted to the difference value.

[0069] In practice, the device described in this invention controls the energy storage battery to enter a constant power mode for discharge. This mode is suitable for situations where the voltage drop is large but still within an adjustable range. In this mode, the energy storage unit continuously outputs at a preset rated power to compensate for the power grid supply gap, stabilize the DC bus voltage, and prevent the inverter input voltage from being too low, which could lead to output instability. In this mode, the control unit adjusts the modulation ratio of the rectifier according to the voltage fluctuation rate. When the fluctuation rate exceeds a preset threshold, the control unit actively reduces the modulation ratio to suppress excessive current surges, reduce system harmonic content, improve power quality, and achieve active suppression of grid-side disturbances and flexible adjustment of internal voltage, thereby enhancing the stability of charging voltage regulation.

[0070] In practice, the device described in this invention controls the energy storage battery to enter a variable power mode discharge that matches the load power demand. This is suitable for scenarios with minor voltage drops. In this mode, the energy storage unit dynamically adjusts its output power according to the actual load power consumption, avoiding unnecessary energy release, extending backup power supply time, and improving energy efficiency. In this mode, the control system adjusts the inverter's output mode according to the rated power ratio of the energy storage battery. When the rated power ratio is high and the system load capacity is sufficient, the full-capacity output mode is activated to ensure the motor operates at full load. When the rated power ratio is low and energy storage resources are limited, the system switches to a dual-modulation wave output mode. A modulation wave is generated by superimposing a sinusoidal fundamental wave and an anti-phase compensation harmonic to cancel the characteristic harmonic current generated on the load side, thereby achieving harmonic suppression and reactive power compensation functions, improving the output power quality, reducing motor heating and torque pulsation, and improving the stability and efficiency of the motor operation under non-ideal power conditions.

[0071] Specifically, the voltage fluctuation rate is the ratio of the difference between the maximum and minimum voltage sample values ​​within a unit detection time to the rated reference voltage.

[0072] Specifically, the unit detection time is 100 microseconds.

[0073] Specifically, the control unit is connected to the rectifier to obtain the voltage fluctuation rate under the condition that the energy storage battery is in the constant power discharge mode.

[0074] If the voltage fluctuation rate is greater than or equal to the preset fluctuation rate, then the modulation ratio is reduced.

[0075] Specifically, the modulation ratio is the modulation coefficient of the rectifier's voltage utilization rate.

[0076] Specifically, if the voltage fluctuation rate is less than the preset fluctuation rate, the default modulation ratio is used, where the default modulation ratio is 0.95.

[0077] Specifically, under the conditions of a rated reference voltage of 700V and a load motor being an industrial production motor, the general range of the preset volatility is [0.9%, 2%], and the preferred embodiment of the preset volatility is 1%.

[0078] Those skilled in the art will understand that the range of preset volatility and the preferred embodiment provided in this embodiment are the values ​​that best address the technical problem solved by the present invention under the conditions of a rated reference voltage of 700V and a load motor being an industrial production motor. In actual applications or experiments, those skilled in the art can make adaptive adjustments to the preset volatility according to the actual application environment and application scenario.

[0079] In practice, for every 1% increase in the difference between the voltage fluctuation rate and the preset fluctuation rate, the modulation ratio decreases by 0.1. For example, if the difference between the voltage fluctuation rate and the preset fluctuation rate is 2% and the default modulation ratio is 0.95, then the modulation ratio decreases to 0.95-0.1-0.1=0.75.

[0080] Specifically, the rated power ratio is the ratio of the actual output power of the energy storage battery to its rated power.

[0081] Specifically, the control unit is connected to the inverter and is used to obtain the rated power ratio under the condition that the energy storage battery is in a variable power discharge mode that matches the load power demand.

[0082] If the rated power ratio is greater than or equal to the preset power ratio, the inverter will operate in full-capacity output mode.

[0083] If the rated power ratio is less than the preset power ratio, the inverter will operate in dual-modulation output mode.

[0084] Specifically, the full-capacity output mode is when the inverter supplies power to the load at the rated output voltage and rated output current;

[0085] The dual-modulation output mode is a mode in which the inverter's modulation wave is superimposed with a sinusoidal fundamental wave and an anti-phase compensation harmonic obtained based on the load harmonic current to supply power to the load.

[0086] Specifically, under the conditions of a rated reference voltage of 700V and a load motor being an industrial production motor, the general range of the preset power ratio is [0.7, 0.9], and the preferred embodiment of the preset power ratio is 0.8.

[0087] Those skilled in the art will understand that the range of preset power ratios and preferred embodiments provided in this embodiment are the values ​​that best address the technical problem solved by the present invention under the conditions of a rated reference voltage of 700V and a load motor being an industrial production motor. In actual applications or experiments, those skilled in the art can make adaptive adjustments to the preset power ratios according to the actual application environment and application scenario.

[0088] Specifically, in the dual-modulation output mode, the phase current flowing into the motor load is detected by a current sensor. The harmonic extraction algorithm based on Fast Fourier Transform (FFT) harmonic analysis separates the main harmonic components from the phase current. In this embodiment, the fifth harmonic current is separated. The detected harmonic current components are inverted and used as a given to generate a voltage compensation command to cancel the harmonic. The voltage compensation command is divided by the DC bus voltage and normalized to obtain the inverted compensation harmonic. The amplitude and frequency of the sinusoidal fundamental wave correspond to the fundamental voltage required by the motor. The sinusoidal fundamental wave is added to the inverted compensation harmonic to obtain the synthesized modulation wave.

[0089] In practice, the device described in this invention reduces the total harmonic distortion rate of the inverter output current by introducing a dual-modulation wave output mode, thereby reducing problems such as motor insulation aging, bearing damage, and increased electromagnetic noise caused by harmonic accumulation.

[0090] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A harmonic-suppressing and anti-vibration uninterruptible power supply device for electric motors, characterized in that, include: External connection unit, used to connect external devices, including rectifiers and inverters connected to the power grid, and output filters connected to the load; A detection unit, connected to the external connection unit, is used to detect the voltage drop amplitude of the DC output of the rectifier; an energy storage unit, connected to the detection unit, is used to store electrical energy; a control unit, connected to the external connection unit, the detection unit, and the energy storage unit respectively, is used to determine whether the energy storage unit should perform constant power discharge mode or variable power discharge mode matching the load power demand based on the voltage drop amplitude; under constant power discharge mode, the modulation ratio of the rectifier is adjusted according to the DC voltage fluctuation rate; under variable power discharge mode matching the load power demand, the output mode of the inverter is determined according to the rated power ratio of the energy storage unit; the output modes of the inverter include full capacity output mode and dual modulation wave output mode. The control unit is connected to the rectifier and is used to obtain the voltage fluctuation rate under the condition that the energy storage unit is in the constant power discharge mode. If the voltage fluctuation rate is greater than or equal to the preset fluctuation rate, the modulation ratio is reduced. The control unit is connected to the inverter and is used to obtain the rated power ratio under the condition that the energy storage unit is in a variable power discharge mode that matches the load power demand. If the rated power ratio is greater than or equal to the preset power ratio, the inverter will perform a full capacity output mode. If the rated power ratio is less than the preset power ratio, the inverter will operate in dual-modulation wave output mode. The full-capacity output mode is that the inverter supplies power to the load at the rated output voltage and rated output current; The dual-modulation output mode is a mode in which the inverter's modulation wave is superimposed with a sinusoidal fundamental wave and an anti-phase compensation harmonic obtained based on the load harmonic current to supply power to the load.

2. The harmonic suppression and anti-shake uninterruptible power supply device for electric motors according to claim 1, characterized in that, The detection unit includes: a DC bus connected to the output terminal of the rectifier; and a voltage sensor connected to the DC bus for detecting the voltage of the DC power.

3. The harmonic suppression and anti-shake uninterruptible power supply device for electric motors according to claim 2, characterized in that, The energy storage unit includes: an energy storage battery connected to the DC bus for providing power to the DC bus; and a bidirectional DC / DC converter connected to the energy storage battery for controlling the charging or discharging of the energy storage battery.

4. The harmonic suppression and anti-shake uninterruptible power supply device for electric motors according to claim 3, characterized in that, The voltage drop amplitude is the absolute value of the difference between the minimum actual DC voltage and the rated reference voltage.

5. The harmonic suppression and anti-shake uninterruptible power supply device for electric motors according to claim 4, characterized in that, The control unit is connected to the voltage sensor and the energy storage battery respectively, and is used to calculate the voltage drop amplitude based on the DC voltage. If the voltage drop amplitude is greater than or equal to a preset second amplitude, the control unit controls the energy storage battery to perform the constant power discharge mode. If the voltage drop amplitude is less than the preset second amplitude but greater than the preset first amplitude, the energy storage battery is controlled to perform a variable power discharge mode that matches the load power demand.

6. The harmonic suppression and anti-shake uninterruptible power supply device for electric motors according to claim 5, characterized in that, The voltage fluctuation rate is the ratio of the difference between the maximum and minimum voltage sample values ​​within a unit detection time to the rated reference voltage.

7. The harmonic suppression and anti-shake uninterruptible power supply device for electric motors according to claim 6, characterized in that, The rated power ratio is the ratio of the actual output power of the energy storage battery to its rated power.

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