Power phase detection method and system for a sensorless variable frequency drive

Abstract

The application discloses a power phase detection method and system of electrolysis-free frequency conversion driving, which is based on a phase-locked loop and comprises an estimated phase module, a feedback signal generation module, a modulation module, an error effective signal module and an angular velocity adjustment module; the estimated phase module obtains an estimated phase angle from input angular velocity; the feedback signal generation module receives the estimated phase angle and outputs a feedback signal according to the estimated phase angle; the modulation module receives the feedback signal and modulates input power grid alternating current power voltage according to the feedback signal, and outputs an error signal; the error effective signal module receives the error signal, subtracts a component of double frequency of the estimated phase angle from the error signal, and outputs an error effective signal; the angular velocity adjustment module receives the error effective signal, adjusts actual angular velocity of the power grid alternating current power voltage signal through an automatic control method according to the error effective signal, and outputs an adjusted angular velocity to the estimated phase module; and the estimated phase module obtains the estimated phase angle according to the input adjusted angular velocity. The application improves the accuracy of the estimated phase angle.

Description

Technical Field

[0001] This invention belongs to the field of motor control technology, specifically, it relates to a power phase detection method and system for electrolytic converter drive. Background Technology

[0002] Electrolytic capacitor-free inverter drive technology, also known as electrolytic capacitor-free inverter drive technology, is a new type of permanent magnet synchronous motor inverter control technology that replaces traditional large-capacity electrolytic capacitors with small-capacity thin-film / CBB capacitors. Through special algorithms (such as input voltage following algorithm, virtual damping resonance suppression strategy, and sensorless FOC control), it solves problems such as bus voltage fluctuations, harmonic suppression, and LC resonance, achieving stable motor drive. It simplifies the system architecture by eliminating the need for the active power factor correction (PFC) circuit required in traditional solutions; and by using thin-film / CBB capacitors instead of electrolytic capacitors, it solves the problem of the liquid electrolyte in traditional high-capacity electrolytic capacitors aging and failing due to temperature variations. Currently, it is mainly used in refrigerators and air conditioners in the home appliance industry.

[0003] In electrolytic-free frequency conversion drive technology, phase detection of alternating current is an important aspect and has a crucial impact on electrode drive. Existing technologies include using incremental step values ​​to obtain the phase of the current alternating current, or using phase-locked loop (PLL) technology to obtain the phase of the current alternating current. However, using incremental step values ​​to obtain the phase of the current alternating current can occasionally result in abrupt changes in angle, while the phase obtained by PLL technology suffers from the problem of 2-harmonic interference.

[0004] The information disclosed in this background section is only intended to enhance the understanding of the background technology of this application, and therefore may include prior art that is not known to those skilled in the art. Summary of the Invention

[0005] This invention addresses the problem of difficult-to-eliminate second harmonic interference in the estimated phase angle obtained by phase-locked loop (PLL) technology in existing technologies. It proposes a power supply phase detection method and system for electrolytic inverter drive, which improves existing PLL technology by using error feedforward compensation, thereby reducing the second harmonic interference problem in the estimated phase angle, lowering the difficulty of adjusting PLL parameters, improving the smoothness and stability of angle tracking, and thus improving the stability and accuracy of motor control.

[0006] To achieve the above-mentioned invention / design objectives, the present invention adopts the following technical solution:

[0007] A power supply phase detection method for electrolytic-free frequency converter drive, based on phase-locked loop control, includes the following steps;

[0008] The estimated phase angle is obtained based on the input angular velocity;

[0009] A feedback signal related to the estimated phase angle is set; an error signal is obtained by modulating the AC power supply voltage signal of the power grid according to the feedback signal;

[0010] Subtract the component with twice the frequency of the estimated phase angle from the error signal to obtain the effective error signal;

[0011] The actual angular velocity of the AC power supply voltage signal of the power grid is adjusted by an automatic control method based on the effective error signal to obtain the adjusted angular velocity, which is used as the input angular velocity to obtain the estimated phase angle.

[0012] In some specific embodiments, the feedback signal is the cosine value of the estimated phase angle; the feedback signal modulates the grid AC power supply voltage signal by multiplying the grid AC power supply voltage signal by the feedback signal.

[0013] The component of the estimated phase angle at twice the frequency is the sine component of the estimated phase angle at twice the frequency.

[0014] In some specific embodiments, the automatic control method employs PI control, which includes a first proportional coefficient and an integral coefficient.

[0015] In some specific embodiments, the automatic control method further includes a second proportional coefficient, which is a unit conversion coefficient for the effective error signal, to perform unit conversion on the effective error signal so that it is suitable for the PI control.

[0016] In some specific embodiments, the automatic control method further includes a third proportional coefficient, which is the unit conversion coefficient of the output signal of the PI control, and the output signal is converted to obtain an adjustment signal for adjusting the actual angular velocity.

[0017] A power phase detection system for electrolytic inverter drive, based on phase-locked loop control, includes a phase estimation module, a feedback signal generation module, a modulation module, an error effective signal module, and an angular velocity adjustment module.

[0018] The phase estimation module obtains the estimated phase angle from the input angular velocity;

[0019] The feedback signal generation module is connected to the estimated phase module, receives the estimated phase angle, and outputs a feedback signal accordingly.

[0020] The modulation module is connected to the feedback signal generation module, receives the feedback signal and modulates the input AC power supply voltage of the mains by the feedback signal, and outputs an error signal.

[0021] The effective error signal module is connected to the modulation module, receives the error signal, subtracts the component of twice the estimated phase angle from the error signal, and outputs the effective error signal.

[0022] The angular velocity adjustment module is connected to the error effective signal module and the estimated phase module. It receives the error effective signal and adjusts the actual angular velocity of the AC power supply voltage signal of the power grid through an automatic control method using the error effective signal, and outputs the adjusted angular velocity to the estimated phase module. The estimated phase module obtains the estimated phase angle based on the input adjusted angular velocity.

[0023] In some specific embodiments, the feedback signal generation module is configured to obtain the feedback signal from the cosine of the estimated phase angle; the modulation module obtains the error signal by multiplying the AC power supply voltage signal from the grid with the feedback signal.

[0024] The component of the estimated phase angle at twice the frequency is the sine component of the estimated phase angle at twice the frequency.

[0025] In some specific embodiments, the angular velocity adjustment module includes a PI control module, which includes a first proportional coefficient and an integral coefficient, for PI control of the actual angular velocity.

[0026] In some specific embodiments, the angular velocity adjustment module further includes a second proportional control module, which is located in front of and connected to the PI control module, and is provided with a second proportional coefficient, which is the unit conversion coefficient of the effective error signal, used to perform unit conversion on the effective error signal.

[0027] In some specific embodiments, the angular velocity adjustment module further includes a third proportional control module, which is located behind and connected to the PI control module, and is provided with a third proportional coefficient, which is the unit conversion coefficient of the output signal of the PI control module, used to perform unit conversion on the output signal.

[0028] Compared with the prior art, the advantages and positive effects of the present invention are:

[0029] The power phase detection method and system for electrolytic capacitor-free frequency converter drives of the present invention are based on the characteristics that the estimated phase angle is approximately equal to the actual phase angle when the phase-locked loop (PLL) is locked in electrolytic capacitor-free frequency converter drive control, and the actual waveform of the estimated phase angle controlled by the PLL. The method obtains a signal component in the error signal that contains a frequency twice the estimated phase angle or a frequency twice the actual phase angle. Since the estimated phase angle is known through PLL detection, the signal component with a frequency twice the estimated phase angle is used as a feedforward signal and subtracted from the feedback signal, greatly reducing the frequency twice interference of the estimated phase angle. This results in a more accurate and stable sinusoidal phase characteristic for the output estimated phase angle, smoother and more stable angle tracking, and significantly improved control performance.

[0030] Other features and advantages of the present invention will become clearer after reading the detailed embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of a phase detection control system based on existing technology;

[0033] Figure 2 This is a schematic diagram of the estimated phase angle, angular velocity, and live / neutral line voltage difference waveform under the existing phase detection and control system.

[0034] Figure 3 This is a schematic flowchart of the power phase detection method according to an embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram of the power phase detection system module composition and connection structure according to an embodiment of the present invention;

[0036] Figure 5 This is a schematic diagram of the composition and connection structure of the power phase detection system according to an embodiment of the present invention;

[0037] Figure 6 This is a schematic diagram of the estimated phase angle, angular velocity, and voltage difference waveform of the live and neutral lines according to an embodiment of the present invention;

[0038] Figure 7 This is a schematic diagram of the live and neutral line voltage signal acquisition circuit according to an embodiment of the present invention.

[0039] In the picture,

[0040] 1. Phase estimation module; 2. Feedback signal generation module; 3. Modulation module; 4. Error effective signal module; 5. Angular velocity adjustment module; First proportional coefficient; Second proportionality coefficient; 61. Third proportional coefficient; 62. First voltage divider circuit; 71. Second voltage divider circuit; 72. First clamping circuit; R77. First current limiting resistor; R76. Second current limiting resistor; C37. First filter capacitor; C36. Second filter capacitor. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. In the description of embodiments, specific features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0043] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0044] In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0045] Reference Figure 1 In the existing block diagram of a power phase detection system without electrolytic inverter drive, , This is the unit conversion factor used in the system for programmable digital control; It is a proportional-integral controller; ε is the estimated phase angle of the phase-locked loop output, i.e., the estimated phase; ε is the error signal.

[0046] AC power supply voltage signal The input signal is represented by the following formula:

[0047] ;

[0048] In the formula,

[0049] This refers to the voltage amplitude of the power grid.

[0050] This is the actual angular frequency of the power grid;

[0051] This represents the initial phase of the power grid.

[0052] The modulation method is that the error signal is transmitted through the AC power supply voltage signal of the mains. Obtained by multiplying the feedback signal, it is expressed by the following formula:

[0053] ;

[0054] in, For feedback signals;

[0055] After transformation using trigonometric identities, we obtain:

[0056] ;

[0057] Then, the phase difference between the actual phase and the estimated phase Expressed as follows:

[0058] ;

[0059] When the phase-locked loop approaches locking... ,Right now, .

[0060] but, ;

[0061] and, Its frequency is This is a high-frequency component belonging to the second harmonic, which is considered interference and needs to be eliminated by software or filtered out by a low-pass filter.

[0062] Other, ;

[0063] because When, small angle approximation ,so, Error signal The effective control part is a DC component, which is used for PI regulation to generate the regulating angular velocity. The angle is obtained by integrating the regulating angular velocity, i.e., the phase is estimated.

[0064] The high-frequency components of the second harmonic require an ideal low-pass filter for removal, but creating an ideal digital low-pass filter is quite difficult. Therefore, the interference from the second harmonic high-frequency components, which cannot be eliminated in the loop, makes it difficult to set the PI parameters; and if the PI parameters are not set appropriately, the estimated phase will have even more significant second harmonic interference, as shown in the reference... Figure 2 .

[0065] exist Figure 2 In the diagram, the blue line represents the difference between the simulated voltage values ​​of lines L and N; this difference contains the phase and amplitude of the AC power supply voltage. The green line represents the estimated phase angle of the AC power supply voltage, and the red line represents the estimated angular velocity. It can be seen that both the estimated angular velocity and the estimated phase angle contain fluctuations at twice the frequency, affecting the accuracy of the estimated phase.

[0066] Reference Figure 3 The electrolytic-free frequency converter drive power phase detection method of the present invention, based on phase-locked loop control, eliminates the 2-fold frequency component as a feedforward quantity for closed-loop control, thereby improving the accuracy of the estimated phase angle.

[0067] The power supply phase detection method for electrolytic-free frequency converter drives includes the following steps:

[0068] S1. Obtain the estimated phase angle based on the input angular velocity;

[0069] S2. Set a feedback signal related to the estimated phase angle to modulate the AC power supply voltage signal of the power grid to obtain an error signal;

[0070] S3. Subtract the component with twice the frequency of the estimated phase angle from the error signal to obtain the effective error signal;

[0071] S4. The actual angular velocity of the AC power supply voltage signal of the power grid is adjusted by the effective error signal through an automatic control method to obtain the adjustment angular velocity, and the obtained adjustment angular velocity is used as input to obtain the estimated phase angle.

[0072] The power phase detection method of the electrolytic capacitor-free inverter drive of the present invention is based on the characteristics of the estimated phase angle being approximately equal to the actual phase angle when the electrolytic capacitor-free inverter drive is controlled by a phase-locked loop (PLL) and the actual waveform of the estimated phase angle controlled by the PLL. It obtains a signal component in the error signal that contains a frequency twice that of the estimated phase angle or the actual phase angle. Since the estimated phase angle is known through PLL detection, the frequency twice that of the estimated phase angle is subtracted from the feedback signal, greatly reducing the frequency twice interference of the estimated phase angle. This results in a more accurate and stable sinusoidal phase characteristic for the output estimated phase angle, smoother and more stable angle tracking, and significantly improved control performance.

[0073] In some specific embodiments, refer to Figure 3 , Figure 5 The feedback signal is the cosine value of the estimated phase angle; the feedback signal modulates the AC power supply voltage signal of the power grid to obtain the error signal, specifically by multiplying the AC power supply voltage signal of the power grid by the cosine value of the estimated phase angle; that is,

[0074] ;

[0075] In the formula,

[0076] This refers to the voltage amplitude of the power grid.

[0077] This is the actual angular frequency of the power grid;

[0078] This represents the initial phase of the power grid.

[0079] The actual phase angle of the AC power supply voltage signal from the power grid;

[0080] For feedback signals;

[0081] ε is the error signal.

[0082] After transformation using trigonometric identities, we obtain:

[0083] ;

[0084] Due to the phase-locked loop control locking... and , For small angles;

[0085] but, ;

[0086] Then the effective error signal ;

[0087] and All of these are known quantities.

[0088] That is, the component of the estimated phase angle at twice the frequency is the sinusoidal component of the estimated phase angle at twice the frequency; that is, .

[0089] In some specific embodiments, refer to Figure 3 , Figure 5 The actual angular velocity of the AC power supply voltage signal is adjusted by PI control based on the effective error signal; PI control includes... Integral coefficient; that is, automatic control methods include PI control, whose parameters include the first proportional coefficient. Integral coefficient.

[0090] Using the estimated phase angle as a feedforward quantity, and subtracting the sine component of the estimated phase angle at twice the frequency from the error signal eliminates the second harmonic interference, resulting in a pure DC quantity used for PI control, thus improving the stability and accuracy of the control. Simultaneously, the PI control parameters are easier to set, and the PI control adjustment range is significantly improved, resulting in a substantial increase in system reliability. (See reference for results). Figure 6 .

[0091] exist Figure 6 In the process, after applying the feedforward of the estimated phase angle and subtracting the effective error signal of the second harmonic component, that is, at the position to the right of the horizontal axis at 8.5s, the estimated angular velocity and the second harmonic interference of the estimated phase angle are significantly reduced, and the estimated phase angle becomes a straight line, which is more accurate.

[0092] In addition, the estimated angular velocity is the actual angular velocity after being adjusted by PI control of the effective error signal; the estimated phase angle is obtained by integrating the estimated angular velocity.

[0093] In some specific embodiments, refer to Figure 3 , Figure 5 The automatic control method also includes a second proportional coefficient. It is the unit conversion coefficient of the effective error signal, used to convert the effective error signal to a unit to make it suitable for PI control adjustment.

[0094] In some specific embodiments, refer to Figure 3 , Figure 5 The automatic control method also includes a third proportional coefficient. Its unit conversion coefficient for the output signal of PI control is used to perform unit conversion on the output signal, and is suitable for adjusting the actual angular velocity of the AC power supply voltage signal of the power grid.

[0095] In some specific embodiments, the second scaling factor Third proportion The first proportional coefficient integrated into PI control In this case, the control system is simplified.

[0096] Reference Figure 4 , Figure 5 The present invention also discloses a power phase detection system without electrolysis frequency conversion drive, which is based on phase-locked loop control and includes an estimation phase module 1, a feedback signal generation module 2, a modulation module 3, an error effective signal module 4, and an angular velocity adjustment module 5.

[0097] The phase estimation module 1 obtains the estimated phase angle from the input angular velocity; the feedback signal generation module 2 is connected to the phase estimation module 1, receives the estimated phase angle and outputs a feedback signal based on the received estimated phase angle; that is, the feedback signal is related to the estimated phase angle; the modulation module 3 is connected to the feedback signal generation module 2, receives the feedback signal and modulates the input AC power supply voltage signal from the mains by the feedback signal, and outputs an error signal.

[0098] The error valid signal module 4 is connected to the modulation module 3, receives the error signal and subtracts the component of twice the estimated phase angle from the error signal, and outputs the error valid signal; the angular velocity adjustment module 5 is connected to the error valid signal module 4 and the estimated phase module 1 respectively, receives the error valid signal, and adjusts the actual angular velocity of the AC power supply voltage signal of the power grid through an automatic control method based on the error valid signal, and outputs the adjusted angular velocity to the estimated phase module 1; the estimated phase module 1 obtains the estimated phase angle based on the input adjusted angular velocity and outputs it.

[0099] The electrolytic capacitor-free frequency converter drive power phase detection system of the present invention, based on the characteristic that the estimated phase angle of the phase-locked loop (PLL) control phase-locked loop during electrolytic capacitor-free frequency converter drive is approximately equal to the waveform of the actual phase and the estimated phase angle of the PLL, obtains the component of the second harmonic signal of the estimated phase angle or the actual phase angle contained in the error signal. This component generates second harmonic interference to the estimated phase angle, estimated angular velocity, etc. Since the estimated phase angle is known through the PLL detection output, the second harmonic signal component of the estimated phase angle is subtracted from the feedback signal, which greatly reduces the second harmonic interference of the estimated phase angle. This makes the output estimated phase angle have a more accurate and stable sinusoidal phase characteristic, the angle tracking is smoother and more stable, and the control effect is significantly improved.

[0100] In some specific embodiments, refer to Figure 4 , Figure 5 Feedback signal generation module 2 is configured to take the cosine of the estimated phase angle; that is, the feedback signal is the cosine value of the estimated phase angle; modulation module 3 multiplies the AC power supply voltage signal of the power grid with the feedback signal to obtain the error signal; error effective signal module 4 subtracts the sinusoidal component of twice the frequency of the estimated phase angle from the error signal and outputs the error effective signal; expressed by the following formula:

[0101] .

[0102] In the formula,

[0103] This refers to the voltage amplitude of the power grid.

[0104] This is the actual angular frequency of the power grid;

[0105] This represents the initial phase of the power grid.

[0106] The actual phase angle of the AC power supply voltage signal from the power grid;

[0107] For feedback signals;

[0108] ε is the error signal.

[0109] After transformation using trigonometric identities, we obtain:

[0110] ;

[0111] Due to the phase-locked loop control locking... and , For small angles;

[0112] but, ;

[0113] and All of these are known quantities.

[0114] That is, the component of the estimated phase angle at twice the frequency is the sinusoidal component of the estimated phase angle at twice the frequency; that is, .

[0115] In some specific embodiments, refer to Figure 4 , Figure 5 The angular velocity adjustment module 5 includes a PI control module, which includes a first proportional coefficient. The integral coefficient is used for PI control adjustment of the actual angular velocity of the AC power supply voltage signal of the power grid.

[0116] Using the estimated phase as a feedforward quantity, the component of the second harmonic sine value of the estimated phase is subtracted from the error signal to eliminate second harmonic interference, resulting in a pure DC quantity used for PI control, thus improving the stability and accuracy of the control. Simultaneously, the PI control parameters are easier to set, and the PI control adjustment range is significantly improved, resulting in a substantial increase in system reliability. (See reference for results). Figure 6 .

[0117] In some specific embodiments, refer to Figure 4 , Figure 5 The angular velocity adjustment module 5 also includes a second proportional control module, which is located in front of the PI control module and is connected to the error valid signal module 4 and the PI control module respectively. It is equipped with a second proportional coefficient. It is the unit conversion coefficient of the effective error signal, used to convert the effective error signal to a unit to make it suitable for PI control adjustment.

[0118] In some specific embodiments, refer to Figure 4 , Figure 5 The angular velocity adjustment module 5 also includes a third proportional control module, which is located after the PI control module, connected to the PI control module, and is equipped with a third proportional coefficient. , is the unit conversion coefficient of the output signal of the PI control module, used to perform unit conversion on the output signal so that it is suitable for adjusting the actual angular velocity of the AC power supply voltage signal.

[0119] In some specific embodiments, the second proportional control module and the third proportional control module are included in the angular velocity adjustment module 5; the second proportional coefficient Third proportion The first proportional coefficient integrated into PI control In this case, the control system is simplified.

[0120] In some specific embodiments, refer to Figure 7 The electrolysis-free frequency converter drive power supply detection system also includes a grid AC power supply voltage acquisition module, which includes a neutral line voltage acquisition circuit and a live line voltage acquisition circuit, used to acquire neutral line voltage signals and live line voltage signals, and process them to obtain grid AC power supply voltage signals.

[0121] The neutral voltage acquisition circuit includes a first voltage divider circuit 61, a first clamping circuit 71, a first current-limiting resistor R77, and a first filter capacitor C37. The first voltage divider circuit 61 includes multiple resistors, with its two ends connected to the neutral line and ground, respectively. The first clamping circuit 71 consists of two diodes connected in series, with the positive terminal connected to the low-voltage power supply and the negative terminal grounded. The two ends of the first current-limiting resistor R77 are connected to the middle of the first voltage divider circuit 61 and the middle of the first clamping circuit 71, respectively. The common point of the first clamping circuit 71 and the first current-limiting resistor R77 is connected to the first analog signal acquisition terminal. The two ends of the first filter capacitor C37 are connected to ground and the first analog signal acquisition terminal, respectively.

[0122] The live wire voltage acquisition circuit includes a second voltage divider circuit 62, a second clamping circuit 72, a second current-limiting resistor R76, and a second filter capacitor C36. The second voltage divider circuit 62 includes multiple resistors, with its two ends connected to the neutral wire and ground, respectively. The second clamping circuit 72 consists of two diodes connected in series, with the positive terminal connected to the low-voltage power supply and the negative terminal grounded. The two ends of the second current-limiting resistor R76 are connected to the middle of the second voltage divider circuit 62 and the middle of the second clamping circuit 72, respectively. The common point of the second clamping circuit 72 and the second current-limiting resistor R76 is connected to the second analog signal acquisition terminal. The two ends of the second filter capacitor C36 are connected to ground and the second analog signal acquisition terminal, respectively.

[0123] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions claimed by the present invention.

Claims

1. A power source phase detection method of an electrolysis-free variable frequency drive, characterized by, Phase-locked loop (PLL) control includes the following steps: The estimated phase angle is obtained based on the input angular velocity; A feedback signal related to the estimated phase angle is set; an error signal is obtained by modulating the AC power supply voltage signal of the power grid according to the feedback signal; Subtract the component with twice the frequency of the estimated phase angle from the error signal to obtain the effective error signal; The actual angular velocity of the AC power supply voltage signal of the power grid is adjusted by an automatic control method based on the effective error signal to obtain the adjusted angular velocity, which is used as the input angular velocity to obtain the estimated phase angle.

2. The power supply phase detection method according to claim 1, characterized in that, The feedback signal is the cosine value of the estimated phase angle; the feedback signal modulates the AC power supply voltage signal of the power grid by multiplying the AC power supply voltage signal of the power grid by the feedback signal. The component of the estimated phase angle at twice the frequency is the sine component of the estimated phase angle at twice the frequency.

3. The power supply phase detection method according to claim 1 or 2, characterized in that, The automatic control method adopts PI control, which includes a first proportional coefficient and an integral coefficient.

4. The power supply phase detection method according to claim 3, characterized in that, The automatic control method also includes a second proportional coefficient, which is a unit conversion coefficient for the effective error signal, to perform unit conversion on the effective error signal so that it is suitable for the PI control.

5. The power supply phase detection method according to claim 4, characterized in that, The automatic control method also includes a third proportional coefficient, which is the unit conversion coefficient of the output signal of the PI control, and the output signal is converted to obtain the adjustment signal for adjusting the actual angular velocity.

6. A power phase detection system for electrolytic inverter drive, characterized in that, Phase-locked loop (PLL) based control includes: The phase estimation module obtains the estimated phase angle from the input angular velocity; A feedback signal generation module, which is connected to the estimated phase module, receives the estimated phase angle and outputs a feedback signal accordingly; A modulation module, which is connected to the feedback signal generation module, receives the feedback signal and modulates the input AC power supply voltage from the mains by the feedback signal, and outputs an error signal. An effective error signal module is connected to the modulation module, receives the error signal, subtracts the component of twice the estimated phase angle from the error signal, and outputs an effective error signal. An angular velocity adjustment module is connected to the error effective signal module and the estimated phase module. It receives the error effective signal and adjusts the actual angular velocity of the AC power supply voltage signal of the power grid through an automatic control method using the error effective signal. It then outputs the adjusted angular velocity to the estimated phase module. The estimated phase module obtains the estimated phase angle based on the input adjusted angular velocity.

7. The power phase detection system according to claim 6, characterized in that, The feedback signal generation module is configured to obtain the feedback signal from the cosine of the estimated phase angle; the modulation module is configured to multiply the AC power supply voltage signal from the grid with the feedback signal to obtain the error signal. The component of the estimated phase angle at twice the frequency is the sine component of the estimated phase angle at twice the frequency.

8. The power phase detection system according to claim 6 or 7, characterized in that, The angular velocity adjustment module includes a PI control module, which includes a first proportional coefficient and an integral coefficient, for PI control of the actual angular velocity.

9. The power phase detection system according to claim 8, characterized in that, The angular velocity adjustment module further includes a second proportional control module, which is located in front of and connected to the PI control module. It is equipped with a second proportional coefficient, which is the unit conversion coefficient of the effective error signal, and is used to perform unit conversion on the effective error signal.

10. The power phase detection system according to claim 9, characterized in that, The angular velocity adjustment module also includes a third proportional control module, which is located behind and connected to the PI control module. It is equipped with a third proportional coefficient, which is the unit conversion coefficient of the output signal of the PI control module, and is used to perform unit conversion on the output signal.

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