Frequency converter motor system and control method thereof

Abstract

The invention discloses a frequency converter motor system and a control method of the frequency converter motor system, relates to the technical field of air conditioners, and aims to solve the problem that harmonic waves generated by power grid side current in an electrolytic capacitor-free frequency converter driving system reduce the power grid side electric energy quality in the electrolytic capacitor-free frequency converter driving system. The method comprises the following steps: acquiring three-phase current of the permanent magnet synchronous motor and three-phase duty ratio of the inverter; and obtaining a reconstructed inductive current of the inductor according to the three-phase current and the three-phase duty ratio. And obtaining the inductive current of at least one frequency in the reconstructed inductive current. And obtaining a first compensation voltage of the permanent magnet synchronous motor according to the inductive current of the at least one frequency, the first compensation voltage being used for adjusting an input voltage of the permanent magnet synchronous motor.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioners, and in particular to a frequency converter motor system and a control method for the frequency converter motor system. Background Art

[0002] The electrolytic capacitor-free inverter motor system usually includes a permanent magnet synchronous motor, which is widely used in aerospace, industrial transmission, household appliances and other occasions as an electromechanical transducer.

[0003] At present, in order to extend the operating life of the electrolytic capacitor-free inverter motor system and reduce the volume of the electrolytic capacitor-free inverter motor system, the electrolytic capacitor-free inverter motor system usually uses small-capacity film capacitors to replace large electrolytic capacitors.

[0004] However, the use of small-capacity film capacitors to replace large electrolytic capacitors leads to LC resonance in the electrolytic capacitor-free inverter motor system, which generates harmonics in the grid-side current of the electrolytic capacitor-free inverter motor system, reducing the quality of the grid-side power in the electrolytic capacitor-free inverter motor system. Moreover, the 300Hz harmonics and 600Hz harmonics in the inductor current of the electrolytic capacitor-free inverter motor system show a positive correlation with the total harmonic distortion (THD) of the grid-side current. Summary of the invention

[0005] The embodiments of the present invention provide a frequency converter motor system and a control method for the frequency converter motor system, which solve the harmonics generated by the grid-side current in the electrolytic capacitor-free frequency converter drive system and reduce the problem of grid-side power quality in the electrolytic capacitor-free frequency converter drive system.

[0006] To achieve the above object, the embodiments of the present invention adopt the following technical solutions:

[0007] In a first aspect, the present application provides a frequency converter motor system, including a permanent magnet synchronous motor. A rectifier bridge, used to convert the alternating current output by a three-phase power supply into direct current. An inverter, coupled to the rectifier bridge and coupled to the permanent magnet synchronous motor, is used to convert the direct current output by the rectifier bridge into alternating current and transmit it to the permanent magnet synchronous motor. An inductor, coupled to the rectifier bridge and the inverter, respectively. A controller, coupled to the inverter. The controller is configured to obtain the three-phase current transmitted by the inverter to the permanent magnet synchronous motor and the three-phase duty cycle of the inverter. The controller is also configured to obtain a reconstructed inductor current of the inductor based on the three-phase current and the three-phase duty cycle. An inductor current of at least one frequency in the reconstructed inductor current is obtained. Based on the inductor current of at least one frequency, a first compensation voltage of the permanent magnet synchronous motor is obtained, and the first compensation voltage is used to adjust the input voltage of the permanent magnet synchronous motor.

[0008] Therefore, the present application obtains the reconstructed inductor current of the inductor according to the three-phase current, three-phase duty cycle and bus capacitor voltage of the acquired permanent magnet synchronous motor. Then, the compensation voltage of the permanent magnet synchronous motor is obtained according to the inductor current of at least one frequency in the reconstructed inductor current and the first given value. Then, the input voltage of the permanent magnet synchronous motor is adjusted by the compensation voltage. Compared with the prior art, the use of small-capacity film capacitors instead of large electrolytic capacitors leads to the existence of LC resonance in the electrolytic capacitor-free inverter drive system, which causes harmonics in the grid-side current of the electrolytic capacitor-free inverter drive system. The present application effectively suppresses the current harmonics of the inductor by adding a compensation voltage to the q-axis voltage of the permanent magnet synchronous motor, thereby suppressing the harmonics generated by the grid-side current and improving the quality of the grid-side electric energy.

[0009] In some embodiments, the controller is configured to obtain a reconstructed inductor current of the controller according to a current component of a bus capacitor of the inverter, a three-phase current and a three-phase duty cycle.

[0010] In some embodiments, the reconstructed inductor current is expressed as: Among them, i L_r = represents the reconstructed inductor current, represents the current component of the bus capacitance, T a , T b and T c represents the three-phase duty cycle, i a 、i b and i c Represents the three-phase current.

[0011] In some embodiments, the controller is configured to obtain a compensation voltage of the permanent magnet synchronous motor according to a difference between an inductor current of at least one frequency and a first given value.

[0012] In some embodiments, the controller is further configured to collect the harmonic components of the bus capacitor voltage of at least one inverter at a first sampling time and a second sampling time, and the second sampling time is after the first sampling time. According to the harmonic components of the bus capacitor voltage of at least one inverter sampled at the first time and the second time, a reconstructed value of the bus capacitor voltage of the inverter is obtained. The capacitor voltage of at least one frequency of the bus capacitor voltage is obtained. According to the capacitor voltage of at least one frequency and a second given value, a second compensation voltage of the permanent magnet synchronous motor is obtained, and the second compensation voltage is used to adjust the input voltage of the permanent magnet synchronous motor.

[0013] In a second aspect, the present application provides a control method for a frequency converter motor system, the frequency converter motor system including a controller, a rectifier bridge, an inverter and a permanent magnet synchronous motor, the method including: obtaining the three-phase current delivered by the inverter to the permanent magnet synchronous motor and the three-phase duty cycle of the inverter. According to the three-phase current and the three-phase duty cycle, a reconstructed inductor current of the inductor is obtained. An inductor current of at least one frequency in the reconstructed inductor current is obtained. According to the inductor current of at least one frequency, a first compensation voltage of the permanent magnet synchronous motor is obtained, and the first compensation voltage is used to adjust the input voltage of the permanent magnet synchronous motor.

[0014] Regarding the beneficial effects of the second aspect, please refer to the first aspect and will not be repeated here.

[0015] In some embodiments, a reconstructed inductor current of a controller is obtained according to the three-phase current and the three-phase duty cycle, including: obtaining the reconstructed inductor current of the controller according to the current component of the bus capacitor of the inverter, the three-phase current and the three-phase duty cycle.

[0016] In some embodiments, the reconstructed inductor current is expressed as: Among them, i L_r = represents the reconstructed inductor current, Represents the current component of the bus capacitance, T a , T b and T c Represents the three-phase duty cycle, i a 、i b and i c Indicates three-phase current.

[0017] In some embodiments, a first compensation voltage of the permanent magnet synchronous motor is obtained according to a difference between the inductor current of at least one frequency and a first given value.

[0018] In some embodiments, at a first sampling time and a second sampling time, the harmonic components of the bus capacitor voltage of at least one inverter are collected, and the second sampling time is after the first sampling time. According to the harmonic components of the bus capacitor voltage of at least one inverter sampled at the first time and the second time, a reconstructed value of the bus capacitor voltage of the inverter is obtained. The capacitor voltage of at least one frequency of the bus capacitor voltage is obtained. According to the capacitor voltage of at least one frequency and a second given value, a second compensation voltage of the permanent magnet synchronous motor is obtained, and the second compensation voltage is used to adjust the input voltage of the permanent magnet synchronous motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of an inverter motor system 100;

[0020] Figure 2 A topological diagram of a three-phase electrolytic capacitor-free drive system provided in this application;

[0021] Figure 3 A schematic diagram of the relationship between the 6-fold and 12-fold frequency components of a DC side current, i.e., the inductor current, and the grid-side current THD provided in this application;

[0022] Figure 4 A flow chart of a control method for a frequency converter motor system provided in the present application;

[0023] Figure 5 A schematic diagram of an inductor current feedback control provided in this application;

[0024] Figure 6 A flow chart of another control method of a frequency converter motor system provided in the present application;

[0025] Figure 7 A schematic diagram of bus voltage component prediction provided for this application;

[0026] Figure 8 A schematic diagram of inductor current feedback harmonic suppression for bus voltage reconstruction provided in this application;

[0027] Fig. 9 A schematic diagram of the effect of a bus voltage reconstruction inductive circuit harmonic suppression feedback control method provided in the present application;

[0028] Fig.10 A comparative schematic diagram of the control effect of each harmonic provided by the present application;

[0029] Fig.11 A schematic diagram of the effect of another bus voltage reconstruction inductive circuit harmonic suppression feedback control method provided in the present application. DETAILED DESCRIPTION

[0030] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0031] In the description of the present invention, it is to be understood that the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0032] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be internal communication between two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, when describing pipelines or channels, the "connected" and "connected" used in this application have the meaning of conduction. The specific meaning needs to be understood in conjunction with the context.

[0033] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0034] like Figure 1 As shown, it is a schematic diagram of a frequency converter motor system 100. The frequency converter motor system 100 includes a three-phase power supply 101, a controller 102, a rectifier bridge 103, an inverter 104, a permanent-magnet synchronous motor (PMSM) 105, an inductor L and a bus capacitor C. Among them, the rectifier bridge 103 is used to convert the alternating current output by the three-phase power supply into direct current. The inverter 104 is coupled to the rectifier bridge 103 and coupled to the permanent-magnet synchronous motor 105, and is used to convert the direct current output by the rectifier bridge 103 into alternating current and transmit it to the permanent-magnet synchronous motor 105. The inductor L is coupled to the rectifier bridge and the inverter respectively. The controller 102 is coupled to the inverter 104.

[0035] The controller 102 is configured to obtain the three-phase current of the permanent magnet synchronous motor 105 and the three-phase duty cycle of the inverter 104. According to the three-phase current and the three-phase duty cycle, a reconstructed inductor current of the inductor L is obtained. An inductor current of at least one frequency in the reconstructed inductor current is obtained. According to the inductor current of at least one frequency, a first compensation voltage of the permanent magnet synchronous motor 105 is obtained, and the first compensation voltage is used to adjust the input voltage of the permanent magnet synchronous motor 105. According to the current component, the three-phase current and the three-phase duty cycle of the bus capacitor of the inverter 104, the reconstructed inductor current is obtained. According to the difference between the inductor current of at least one frequency and the first given value, the first compensation voltage of the permanent magnet synchronous motor 105 is obtained. At the first sampling time and the second sampling time, the harmonic component of the bus capacitor voltage of at least one inverter 104 is collected, and the second sampling time is after the first sampling time. According to the harmonic component of the bus capacitor voltage of at least one inverter 104 sampled at the first time and the second time, the reconstructed value of the bus capacitor voltage of the inverter 104 is obtained. The capacitor voltage of at least one frequency of the bus capacitor voltage is obtained. According to the capacitor voltage of at least one frequency and a second given value, a second compensation voltage of the permanent magnet synchronous motor 105 is obtained, and the second compensation voltage is used to adjust the input voltage of the permanent magnet synchronous motor 105. Among them, the bus capacitor voltage of the inverter 104 can be understood as the voltage of the bus capacitor C.

[0036] The rectifier bridge 103 can be understood as sealing the rectifier tube in a shell, which is divided into a full bridge and a half bridge. A full bridge is to seal the four diodes of the connected bridge rectifier circuit together. A half bridge is to seal half of the four diode bridge rectifier together. Two half bridges can form a bridge rectifier circuit, and a half bridge can also form a full-wave rectifier circuit with a center tap of the transformer. The selection of the rectifier bridge should consider the rectifier circuit and the working voltage. In each working cycle of the rectifier bridge, only two diodes work at the same time, and the unidirectional conduction function of the diode converts the alternating current into a unidirectional DC pulsating voltage.

[0037] The inverter 104 is configured to convert direct current (battery, storage bottle) into alternating current (generally 220v 50HZ sine or square wave), and generally consists of an inverter bridge, control logic and filter circuit.

[0038] The permanent magnet synchronous motor 105 is composed of components such as a stator, a rotor and an end cover. It uses permanent magnets to provide excitation, making the motor structure simpler, reducing processing and assembly costs, and eliminating collector rings and brushes that are prone to problems, thereby improving the reliability of motor operation. In addition, since no excitation current is required and there is no excitation loss, the efficiency and power density of the motor are improved. In addition, it has the advantages of small size, simple structure and high power density, and is widely used in position tracking control systems.

[0039] The bus capacitor C is a thin film capacitor, which is not limited in the present application. The inverter motor system 100 can also be understood as a three-phase electrolytic capacitor-free drive system.

[0040] The alternating current generated by the three-phase power supply 101 is rectified by the rectifier bridge 103 to obtain direct current, and the obtained direct current supplies power to the inverter 104 through the inductor L. The inverter 104 drives the permanent magnet synchronous motor 105 through the duty cycle signal generated by the controller 102 .

[0041] like Figure 2 As shown, it is a topological schematic diagram of a three-phase electrolytic capacitor-free drive system provided by the present application.

[0042] After the three-phase power supply 101 is rectified by the rectifier bridge 103, the source voltage Us obtained can be expressed as formula (1):

[0043]

[0044] Where n is a positive integer greater than or equal to 1, ω g is the grid phase voltage angular frequency, and U is the phase voltage effective value.

[0045] Performing Fourier decomposition on formula 1, we obtain formula 2.

[0046]

[0047] From formula 2, we can see that the source voltage Us contains a DC component and AC component Two parts, including Represents the amplitude of the AC component, cos(6nω g t) represents the phase of the AC component. It can be seen that as n increases, the amplitude of the AC component decreases.

[0048] Among them, the 6-fold and 12-fold grid frequency components account for a large proportion. Ignoring other high-order harmonic components, the bus inductance current can be regarded as containing DC components, 6-fold frequency components, and 12-fold frequency components. The u-phase current in the grid-side current can be expressed as Formula 3:

[0049]

[0050] In the formula, k is a positive integer, I dc0 ,I dc6 ,I dc12 are the amplitudes of the bus DC component, 6-fold frequency component and 12-fold frequency component respectively. The above formula is expanded into Fourier series form, as shown in Formula 4:

[0051]

[0052] in,

[0053] Therefore, the relationship between the 6-fold and 12-fold frequency components of the DC side current, i.e. the inductor current, and the grid side current THD can be expressed as: Figure 3 As shown in the figure, the 6-fold frequency represents the 300HZ harmonics in the inductor current, and the 12-fold frequency represents the 600HZ harmonics in the inductor current.

[0054] Among them, the horizontal axis K x6 Indicates the 6-fold component of the inductor current, the horizontal axis K x12 It represents the 12 times frequency component in the inductor current, and the vertical axis represents the THD of the grid-side current.

[0055] Depend on Figure 3 It can be seen that the 300Hz harmonics and 600Hz harmonics in the inductor current show a positive correlation with the grid-side THD.

[0056] In view of this, the present application adopts the inductor current feedback control method to extract and reconstruct the 300Hz and 600Hz harmonics in the inductor current through a bandpass filter as the input of the resonant controller. The output of the resonant controller is superimposed on the dq axis voltage command of the motor to suppress the 300HZ and 600Hz harmonics in the inductor current, thereby improving the power quality on the grid side.

[0057] like Figure 4 As shown, it is a flow chart of a control method of a frequency converter motor system provided by the present application, and the method includes the following process.

[0058] 401 . The controller 102 obtains the three-phase current transmitted by the inverter 104 to the permanent magnet synchronous motor 105 and the three-phase duty cycle of the inverter 104 .

[0059] Here the three-phase current can be understood as Figure 2 The three-phase current output by the three-phase power supply 101, the three-phase duty cycle here can be understood as a pulse width modulation (PWM) wave.

[0060] Exemplarily, the controller 102 samples and obtains the three-phase current of the permanent magnet synchronous motor 105 and the three-phase duty cycle of the inverter 104 .

[0061] 402. The controller 102 obtains a reconstructed inductor current of the controller 102 according to the three-phase currents and the three-phase duty cycles.

[0062] In some embodiments, the controller 102 obtains the reconstructed inductor current of the controller 102 according to the current component of the bus capacitor of the inverter 104 , the three-phase currents, and the three-phase duty cycle.

[0063] For example, the reconstructed current is expressed as iL_r represents the reconstructed inductor current, Represents the current component of the bus capacitance, T a , T b and T c Represents the three-phase duty cycle, i a 、i b and i c Indicates three-phase current.

[0064] 403. The controller 102 obtains an inductor current of at least one frequency in the reconstructed inductor current.

[0065] The at least one frequency of the inductor current here can be understood as reconstructing the harmonics of 300 Hz and 600 Hz in the inductor current.

[0066] Exemplarily, the controller 102 extracts the harmonics of 300 Hz and 600 Hz in the reconstructed inductor current through a bandpass filter.

[0067] 404 . The controller 102 obtains a first compensation voltage of the permanent magnet synchronous motor according to the inductor current of at least one frequency. The first compensation voltage is used to adjust the input voltage of the permanent magnet synchronous motor 105 .

[0068] In some embodiments, the controller 102 obtains the compensation voltage of the permanent magnet synchronous motor 105 according to the difference between the inductor current of at least one frequency and the first given value.

[0069] Exemplarily, the controller 102 makes a difference between the 300 Hz and 600 Hz harmonics in the inductor current and the first given value, and inputs the obtained difference into the resonant controller. The resonant controller obtains a first compensation voltage of the permanent magnet synchronous motor 105 according to the difference, and obtains the obtained compensation voltage u comq and the voltage reference value u to the permanent magnet synchronous motor 105 q * Add to obtain a new voltage reference value u of the permanent magnet synchronous motor 105 q *, thereby suppressing the 300HZ and 600HZ harmonics in the inductor current.

[0070] Therefore, the present application obtains the reconstructed inductor current of the inductor according to the three-phase current, three-phase duty cycle and bus capacitor voltage of the acquired permanent magnet synchronous motor 105. Then, the compensation voltage of the permanent magnet synchronous motor 105 is obtained according to the inductor current of at least one frequency in the reconstructed inductor current and the first given value. Then, the input voltage of the permanent magnet synchronous motor 105 is adjusted by the compensation voltage. Compared with the prior art, the use of small-capacity film capacitors instead of large electrolytic capacitors leads to the LC resonance phenomenon in the electrolytic capacitor-free inverter drive system, which causes harmonics to be generated in the grid-side current in the electrolytic capacitor-free inverter drive system. The present application effectively suppresses the current harmonics of the inductor by adding a compensation voltage to the q-axis voltage of the permanent magnet synchronous motor 105, thereby suppressing the harmonics generated by the grid-side current and improving the quality of the grid-side electric energy.

[0071] based on Figure 4 Introduction to steps 401-404, Figure 5 A schematic diagram of an inductor current feedback control provided in this application.

[0072] Among them, G BFS (s) represents a bandpass filter, G PR_C (s) represents a resonant controller. For example, it can be a PR controller. According to the internal model control theory, when the resonant controller includes a mathematical model of a reference input signal, zero-error control can be achieved without considering the disturbance signal. The PR controller can be used to achieve zero-error control of a sinusoidal signal. Therefore, for the 6-fold and 12-fold frequency components in the inductor current, the PR controller can have a larger gain at the desired frequency, so that the power closed-loop controller of the inverter 104 achieves better results.

[0073] i a 、i b 、i c Indicates three-phase current. S uvw Indicates the three-phase duty cycle T a , T b and T c .u comq Indicates the compensation voltage. L_ref Indicates the first given value. L Indicates the 300HZ and 600HZ harmonics in the inductor current. For current reconstruction, please refer to Figure 4 Step 402 in .

[0074] Clark said that the three-phase current i a 、i b and i c Transform from a stationary abc coordinate system to a stationary αβ coordinate system

[0075] Tie. Indicates that the three-phase current ia 、i b and i c The current regulator can be a linear proportional integral controller (PI) controller. Svpwm represents space vector pulse width modulation, which takes the ideal flux circle of the stator of a three-phase symmetrical motor when powered by a three-phase symmetrical sine wave voltage as the reference standard, and appropriately switches the different switching modes of the three-phase inverter to form a PWM wave, and uses the actual flux vector formed to track its accurate flux circle.

[0076] I d * represents the current reference value of the d-axis of the permanent magnet synchronous motor 105, I q * represents the current reference value of the q-axis of the permanent magnet synchronous motor 105, u d * represents the voltage reference value of the d-axis of the permanent magnet synchronous motor 105, u q * represents a voltage reference value of the q-axis of the permanent magnet synchronous motor 105 .

[0077] The current reference value Id* is used to obtain the voltage reference value u of the d-axis of the permanent magnet synchronous motor 105 through the PI controller. d *, the current reference value I of the q-axis of the permanent magnet synchronous motor 105 q * The voltage reference value u of the q axis of the permanent magnet synchronous motor 105 is obtained by the PI controller q *. Then the voltage reference value u of the d-axis of the permanent magnet synchronous motor 105 d *Through coordinate transformation, we can transform u from the rotating dq coordinate system to the stationary αβ coordinate system. α *. The voltage reference value u of the q-axis of the permanent magnet synchronous motor 105 q *Through coordinate transformation, we can transform u from the rotating dq coordinate system to the stationary αβ coordinate system. β *.u α * and u β * Generate three-phase duty ratios for controlling the inverter 104 through vector pulse width modulation Svpwm.

[0078] For example, the three-phase current i a 、i b and i c The reconstructed inductor current i is obtained by current reconstruction and summing with the bus capacitor voltage L_r . Bandpass filter G BFS (s) Extract and reconstruct the inductor current i L_r The harmonics △i of 300HZ and 600HZ L . Reconstruct the inductor current i L_r The harmonics △i of 300HZ and 600HZ Land the first given value i L_ref The difference is input to the resonant controller G PR_C (s). Resonance controller G PR_C (s) Output compensation voltage u comq The controller 102 obtains the compensation voltage u comq and the voltage reference value u to the permanent magnet synchronous motor 105 q * Add to obtain a new voltage reference value u of the permanent magnet synchronous motor 105 q *.

[0079] On the basis of inductor current control, the influence of bus voltage sampling delay and bus voltage small signal fluctuation on the inductor current closed-loop control loop is considered. The bus voltage sampling delay is compensated, and closed-loop control is implemented on the 300Hz harmonics and 600Hz harmonics in the bus voltage, and the harmonic suppression method of the inductor circuit based on bus voltage reconstruction is obtained.

[0080] like Figure 6 As shown, in Figure 4 Based on step 404, a flow chart of another method for controlling a frequency converter motor system provided by the present application is provided, and the method includes the following process.

[0081] 601. At a first sampling time and a second sampling time, the controller 102 collects harmonic components of a bus capacitor voltage of at least one inverter 104, and the second sampling time is after the first sampling time.

[0082] The harmonic components of the bus capacitor voltage here can be understood as the harmonics of 6ωg and 12ωg in the bus voltage.

[0083] For example, taking the harmonic of bus voltage of 6ωg as an example, Figure 7 This is a schematic diagram for predicting bus voltage components.

[0084] The horizontal axis represents time in seconds (s), and the vertical axis represents bus voltage in volts (V).

[0085] Depend on Figure 7 It can be seen that the bus voltage is sampled at time nTs, and the sampling value is u dc_s_6ωg(z) , the sampling value participates in the nth duty cycle signal update, at this time the bus voltage sampling value is PO, the actual value is MN. If the bus voltage average at (n+1)Ts and (n+2)Ts can be obtained at nTs, the bus voltage sampling update error can be effectively reduced, and the same is true for the 12ωg harmonic.

[0086] Using the periodic characteristics of the bus voltage 6ωg frequency component, the bus voltage sampling values ​​one and two sampling cycles ahead can be expressed as and Therefore, the average bus voltage at (n6+2)Ts and (n6+2)Ts can be approximately expressed as shown in Formula 5:

[0087]

[0088] in,

[0089] In the formula, u dc_s_6ωgr(z) is the predicted value of the 6ωg frequency voltage, f s is the switching frequency, f g is the grid frequency, k is the rounding coefficient, the purpose is to make n6 the smallest positive integer.

[0090] Similarly, for the bus voltage frequency component of 12ωg, the sampling value is u dc_s_12ωg(z) , the bus voltage sampling value one and two sampling cycles ahead can be expressed as and Therefore (n 12 +2)Ts and (n 12 +2) The average bus voltage at time Ts can be approximately expressed as shown in Formula 6:

[0091]

[0092] in,

[0093] In formula 6, u dc_s_12ωgr(z) is the predicted value of the 12ωg frequency voltage, k is the rounding coefficient, the purpose is to make n 12 Get the smallest positive integer. Since the switching frequency is 5kHz in both simulation and experiment, n6 and n 12 Take 50 and 25 respectively.

[0094] The bus voltage frequency components of 6ωg and 12ωg can be obtained through a bandpass filter and can be expressed as shown in Formula 7:

[0095]

[0096] Among them, B in formula 7 6ωg(z) and B 12ωg(z) The center frequency is 6ω g and 12ω g The bandpass filter, u dc_s(z) is the bus voltage sampling value.

[0097] 602. The controller 102 obtains a reconstructed value of the bus capacitor voltage of the inverter 104 according to the harmonic components of the bus capacitor voltage of at least one inverter 104 sampled at the first moment and the second moment.

[0098] For example, the controller 102 sets 6ω g and 12ω g The frequency voltage prediction value replaces the 6ωg and 12ωg frequency voltages in the bus voltage, and finally the bus voltage reconstruction value can be obtained, as shown in Formula 8:

[0099]

[0100] Among them, u dc_sr is the reconstructed value of the bus voltage (V).

[0101] 603. The controller 102 obtains a capacitor voltage of at least one frequency of the bus capacitor voltage.

[0102] The capacitor voltage of at least one frequency here can be understood as the harmonics of 300 Hz and 600 Hz in the bus capacitor voltage.

[0103] Exemplarily, the controller 102 extracts 300 Hz and 600 Hz harmonics from the bus capacitor voltage through a bandpass filter.

[0104] 604. The controller 102 obtains a second compensation voltage of the permanent magnet synchronous motor according to the capacitor voltage of at least one frequency and a second given value, where the second compensation voltage is used to adjust an input voltage of the permanent magnet synchronous motor.

[0105] Exemplarily, the controller 102 makes a difference between the 300 Hz and 600 Hz harmonics in the bus voltage and the second given value, and inputs the obtained difference into the resonant controller. The resonant controller obtains a second compensation voltage of the permanent magnet synchronous motor 105 according to the difference. The second compensation voltage is summed with the first compensation voltage, and the obtained sum is added to the voltage reference value u of the permanent magnet synchronous motor 105. q * Add to obtain a new voltage reference value u of the permanent magnet synchronous motor 105 q *. This can suppress the 300HZ and 600HZ harmonics in the bus voltage.

[0106] based on Figure 6 Steps 601-604 in Figure 8 A schematic diagram of an inductive current feedback harmonic suppression method based on bus voltage reconstruction provided in the present application.

[0107] Among them, ZOH represents zero-order holder, BPF represents bandpass filter, G PR_V(s) represents the PR controller, Δu dc Indicates 300HZ and 600HZ harmonics in bus voltage, Δu dcref represents the second given value, u dc_r Indicates the predicted value of bus voltage. s Represents the three-phase current i a 、ib and i c .

[0108] The harmonic suppression effect of the present application will be introduced below.

[0109] Assuming that the speed of the permanent magnet synchronous motor 105 is 65 rps and the effective value of the grid-side input current lrms=16.7 A, the experimental test results of the present application are introduced below.

[0110] like Fig. 9 As shown, it is a schematic diagram of the effect of a harmonic suppression feedback control method of an inductive circuit with bus voltage reconstruction provided by the present application.

[0111] Among them, the harmonic suppression of the inductive circuit of bus voltage reconstruction can also be understood as RCR-DVR feedback control.

[0112] Depend on Fig. 9 It can be seen that the peak-to-peak values ​​of the grid-side current waveform and the bus voltage waveform are significantly reduced after RCR-DVR feedback control.

[0113] based on Fig. 9 , Fig.10 A comparative schematic diagram of the control effects on various harmonics provided in this application.

[0114] Among them, the horizontal axis represents the harmonic order, and the vertical axis represents the ratio of each harmonic to the fundamental wave.

[0115] Depend on Fig.10 It can be seen that after adopting RCR-DVR control, the 5th harmonic, 7th harmonic, 11th harmonic and 13th harmonic are all lower than the national standard.

[0116] Assuming that the speed of the permanent magnet synchronous motor 105 is 85 rps and the effective value of the grid-side input current lrms=24 A, the experimental test results of the present application are introduced below.

[0117] like Fig.11 , which is a schematic diagram of the effect of another bus voltage reconstruction inductive circuit harmonic suppression feedback control method provided by the present application.

[0118] Depend on Fig.11 It can be seen that at this speed, the RCR-DVR control method can still perform switching control, the waveform of the grid-side current and the peak-to-peak value of the bus voltage are significantly reduced, and the harmonics meet the IEC61000-3-12 standard.

[0119] Although the present application is described herein in conjunction with various embodiments, in the process of implementing the claimed application, those skilled in the art may understand and implement other changes to the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit may implement several functions listed in the claims. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0120] Although the present application has been described in conjunction with specific features and embodiments thereof, it is obvious that various modifications and combinations may be made thereto without departing from the spirit and scope of the present application. Accordingly, this specification and the drawings are merely exemplary illustrations of the present application as defined by the appended claims, and are deemed to have covered any and all modifications, variations, combinations or equivalents within the scope of the present application. Obviously, those skilled in the art may make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

[0121] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A frequency converter motor system, characterized in that: include: Permanent magnet synchronous motor; Rectifier bridge, used to convert the AC power output by the three-phase power supply into DC power; an inverter, coupled to the rectifier bridge and to the permanent magnet synchronous motor, for converting the direct current output by the rectifier bridge into alternating current and transmitting the alternating current to the permanent magnet synchronous motor; An inductor, coupled to the rectifier bridge and the inverter respectively; a controller coupled to the inverter; The controller is configured to obtain the three-phase current delivered by the inverter to the permanent magnet synchronous motor and the three-phase duty cycle of the inverter; The controller is further configured to obtain a reconstructed inductor current of the inductor according to the three-phase current and the three-phase duty cycle; Acquire an inductor current of at least one frequency in the reconstructed inductor current; A first compensation voltage of the permanent magnet synchronous motor is obtained according to the inductance current of the at least one frequency, and the first compensation voltage is used to adjust the input voltage of the permanent magnet synchronous motor.

2. The inverter motor system according to claim 1, characterized in that: The controller is configured to obtain the reconstructed inductor current according to the current component of the bus capacitor of the inverter, the three-phase current and the three-phase duty cycle.

3. The inverter motor system according to claim 1 or 2, characterized in that: The reconstructed inductor current is expressed as: Among them, i L_r = represents the reconstructed inductor current, represents the current component of the bus capacitance, T a 、T b and T c represents the three-phase duty cycle, i a 、i b and i c Represents the three-phase current.

4. The inverter motor system according to claim 1, characterized in that: The controller is configured to obtain a first compensation voltage of the permanent magnet synchronous motor according to a difference between the inductor current of the at least one frequency and a first given value.

5. The inverter motor system according to claim 4, characterized in that: The controller is further configured to collect harmonic components of a bus capacitor voltage of at least one of the inverters at a first sampling time and a second sampling time, wherein the second sampling time is after the first sampling time; Obtaining a reconstructed value of the bus capacitor voltage of the inverter according to the harmonic components of the bus capacitor voltage of the at least one inverter sampled at the first moment and the second moment; Acquire a capacitor voltage of at least one frequency of the bus capacitor voltage; A second compensation voltage of the permanent magnet synchronous motor is obtained according to the capacitor voltage of the at least one frequency and a second given value, and the second compensation voltage is used to adjust the input voltage of the permanent magnet synchronous motor.

6. A control method for a frequency converter motor system, characterized in that: The inverter motor system includes a controller, a rectifier bridge, an inverter, an inductor and a permanent magnet synchronous motor, and the method includes: Acquire the three-phase current delivered by the inverter to the permanent magnet synchronous motor and the three-phase duty cycle of the inverter; Obtaining a reconstructed inductor current of the inductor according to the three-phase current and the three-phase duty cycle; Acquire an inductor current of at least one frequency in the reconstructed inductor current; A first compensation voltage of the permanent magnet synchronous motor is obtained according to the inductance current of the at least one frequency, and the first compensation voltage is used to adjust the input voltage of the permanent magnet synchronous motor.

7. The method according to claim 6, characterized in that The step of obtaining the reconstructed inductor current of the controller according to the three-phase current and the three-phase duty cycle includes: The reconstructed inductor current is obtained according to the current component of the bus capacitor of the inverter, the three-phase current and the three-phase duty cycle.

8. The method according to claim 6 or 7, characterized in that: The reconstructed inductor current is expressed as: Among them, i L_r = represents the reconstructed inductor current, represents the current component of the bus capacitance, T a 、T b and T c represents the three-phase duty cycle, i a 、i b and i c Represents the three-phase current.

9. The method according to claim 6, characterized in that The step of obtaining a first compensation voltage of the permanent magnet synchronous motor according to the inductor current of the at least one frequency comprises: A first compensation voltage of the permanent magnet synchronous motor is obtained according to a difference between the inductor current of the at least one frequency and a first given value.

10. The method according to claim 9, characterized in that The method further comprises: At a first sampling time and a second sampling time, collecting harmonic components of a bus capacitor voltage of at least one of the inverters, the second sampling time being after the first sampling time; Obtaining a reconstructed value of the bus capacitor voltage of the inverter according to the harmonic components of the bus capacitor voltage of the at least one inverter sampled at the first moment and the second moment; Acquire a capacitor voltage of at least one frequency of the bus capacitor voltage; A second compensation voltage of the permanent magnet synchronous motor is obtained according to the capacitor voltage of the at least one frequency and a second given value, and the second compensation voltage is used to adjust the input voltage of the permanent magnet synchronous motor.

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