High-frequency high-voltage frequency converter for high-speed magnetic suspension fan

Abstract

The invention discloses a high-frequency high-voltage frequency converter for a high-speed magnetic suspension fan, which relates to the field of frequency converters and comprises a power grid three-phase input end, three single-phase alternating current power supplies and a PWM (Pulse Width Modulation) regulation and control module, the single-phase AC power supply is composed of a plurality of pairs of phase-shifting transformers and power units. A primary winding input end of the phase-shifting transformer is connected with a three-phase input end of a power grid, a secondary winding output end of the phase-shifting transformer is connected with an input end of the power unit, and high-voltage three-phase power of the power grid is input into the power unit after voltage reduction and phase shifting; the output ends of the power units are sequentially connected in series to obtain and output high-voltage single-phase alternating current; the PWM regulation and control module receives a control signal of a main controller of the high-voltage permanent magnet synchronous motor, and controls on-off of an IGBT (Insulated Gate Bipolar Translator) in each power unit according to the frequency, amplitude and phase of each phase in the control signal; the output phase difference of the three single-phase alternating current power supplies is 120 degrees. According to the invention, the requirements of the high-voltage permanent magnet synchronous motor on voltage, power and accurate control of the driving power supply are met.

Description

Technical Field

[0001] The present invention relates to the technical field of frequency converters, and more particularly to a high-frequency and high-voltage frequency converter for a high-speed magnetic suspension fan. Background Art

[0002] High-speed magnetic levitation fans usually include centrifugal fans, centrifugal compressors, centrifugal blowers, etc. They use magnetic levitation technology to reduce or eliminate bearing friction, thereby improving the operating efficiency of the fan. Among them, the drive motor is classified according to the input voltage, mainly low-voltage motors below 1KV and high-voltage motors above 3.3KV.

[0003] Existing high-speed magnetic levitation fans usually use three-phase asynchronous induction motors with a fixed frequency of 50-60HZ, which have the disadvantages of narrow economic operation range, low torque density, low power factor and efficiency; high-voltage permanent magnet synchronous motors have the advantages of simple structure, high speed, high power density, good control performance, etc., and are increasingly valued. However, compared with asynchronous induction motors, high-voltage permanent magnet synchronous motors have higher requirements for the drive power supply. Not only does it need to meet the voltage requirements of the power supply, but it also needs to accurately output three-phase AC power of a specific frequency and phase according to the control parameters of the motor controller.

[0004] Therefore, how to provide a high-frequency and high-voltage inverter as a driving power source for the high-voltage permanent magnet synchronous motor of a high-speed magnetic levitation fan is a problem that technical personnel in this field urgently need to solve. Summary of the invention

[0005] In view of this, the present invention provides a high-frequency and high-voltage inverter for a high-speed magnetic levitation fan, which regulates the voltage and converts the frequency of the input three-phase alternating current to meet the voltage and frequency requirements of the driving power supply of the high-voltage permanent magnet synchronous motor.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention discloses a high-frequency and high-voltage inverter for a high-speed magnetic suspension fan, which specifically comprises: a three-phase input terminal of a power grid, three single-phase AC power supplies, and a PWM control module;

[0008] The single-phase AC power supply is composed of multiple pairs of phase-shifting transformers and power units; the primary winding input end of the phase-shifting transformer is connected to the three-phase input end of the power grid, and the secondary winding output end of the phase-shifting transformer is connected to the input end of the power unit, and the high-voltage three-phase electricity of the power grid is stepped down and phase-shifted before being input into the power unit; the output ends of the power units are connected in series in sequence to obtain high-voltage single-phase AC power and output it;

[0009] The PWM control module receives the control signal from the main controller of the high-voltage permanent magnet synchronous motor, and controls the switching of the IGBTs in each of the power units according to the frequency, amplitude, and phase of each phase of electricity in the control signal;

[0010] The output phase differences of the three single-phase AC power supplies are 120°. The output terminals of the three single-phase AC power supplies are connected to form a triangular loop, and the three vertices of the triangular loop are used as the three-phase output terminals; each terminal of the three-phase output terminals is respectively connected to the corresponding input terminal of the high-voltage permanent magnet synchronous motor.

[0011] Further, in one of the single-phase AC power supplies, the number of phase-shifting transformers is 8, and the output current phase differences of the secondary windings of the phase-shifting transformers are 7.5°.

[0012] Further, the power unit is composed of a three-phase rectification link, a filtering link, and an inversion link;

[0013] The three-phase rectification link includes: after the three-phase AC input passes through a fuse protector, it is respectively connected to a three-phase bridge rectifier circuit composed of 6 diodes;

[0014] The filtering link includes: three capacitors connected in series in sequence between the output positive and negative poles of the three-phase bridge rectifier circuit, and resistors respectively connected in parallel with the three capacitors;

[0015] The inversion link includes: a first IGBT, a second IGBT, a third IGBT, and a fourth IGBT; the collectors of the first IGBT and the third IGBT are both connected to the positive pole, the emitters of the second IGBT and the fourth IGBT are both connected to the negative pole, the emitter of the first IGBT and the collector of the second IGBT are both connected to the first port of the output terminal of the power unit, and the emitter of the third IGBT and the collector of the fourth IGBT are both connected to the second port of the output terminal of the power unit; the gates of each IGBT are respectively connected to the corresponding control signal lines of the PWM control module.

[0016] Further, in the three-phase rectification link, the diodes are 1800V rectifier diodes; in the filtering link, the capacitors are 400V, 90μf / A electrolytic capacitors; in the inversion link, the withstand voltage value of the IGBT is 1700V.

[0017] Further, a diode is reversely connected in parallel with each of the first IGBT, the second IGBT, the third IGBT, and the fourth IGBT.

[0018] Further, the connection of the output terminals of the three single-phase AC power supplies into a triangular loop is specifically as follows:

[0019] Connect the first output terminal of the first single-phase power supply to the second output terminal of the second single-phase power supply, connect the first output terminal of the second single-phase power supply to the second output terminal of the third single-phase power supply, and connect the first output terminal of the third single-phase power supply to the second output terminal of the first single-phase power supply to form a triangular loop.

[0020] Further, controlling the IGBT switches in each of the power units specifically includes:

[0021] Step 1: Extract the frequency, amplitude, and phase of each phase of electricity from the control signal of the main controller, and generate three-phase reference sine wave signals based on the frequency, amplitude, and phase.

[0022] Step 2: Determine the frequency of the triangular carrier wave signal according to the frequency of the reference sine wave signal and a set multiple, and determine the amplitude of the triangular carrier wave signal of each power unit in each phase of electricity according to the amplitude of the reference sine wave signal.

[0023] Step 3: Compare the triangular carrier wave signal of each power unit with the reference sine wave signal of the corresponding phase. When the amplitude of the reference sine wave signal is greater than the amplitude of the triangular carrier wave signal, the PWM pulse signal outputs a high level; otherwise, it outputs a low level. Generate the PWM pulse signals of each power unit one by one.

[0024] Step 4: Control the IGBT switches according to the PWM pulse signals of each power unit.

[0025] Further, the three-phase reference sine wave signals are expressed as:

[0026]

[0027]

[0028] where V a (t), V b (t), V c (t) represent the reference sine wave signals of phases a, b, and c respectively; A, B, and C are the corresponding amplitudes; are the corresponding phase shift angles respectively, t is the time, and f is the frequency.

[0029] As can be seen from the above technical solutions, compared with the prior art, the present invention discloses a high-frequency high-voltage inverter for a high-speed magnetic levitation fan. Through the series connection of multiple power units, high-voltage and high-power output is successfully achieved, meeting the driving requirements of high-power high-voltage permanent magnet synchronous motors; the application of the phase-shifting transformer makes the input current waveform close to a sine wave, effectively eliminating a large number of harmonics, improving the input power factor, and reducing the harmonic pollution to the power grid; it can accurately control each power unit in real time according to the control signal of the motor main controller, thereby realizing the precise control of the inverter and meeting the precise control requirements of high-voltage permanent magnet synchronous motors. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to the provided drawings.

[0031] Figure 1 It is a schematic diagram of the main circuit topology of the high-frequency high-voltage inverter according to the embodiment of the present invention.

[0032] Figure 2 It is a schematic diagram of the power unit structure according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0034] The embodiment of the present invention discloses a high-frequency high-voltage inverter for a high-speed magnetic levitation fan, as Figure 1 shown, specifically including: a three-phase power grid input end, three single-phase AC power supplies, and a PWM regulation module;

[0035] The single-phase AC power supply consists of multiple pairs of phase-shifting transformers and power units; the input end of the primary winding of the phase-shifting transformer is connected to the three-phase power grid input end, and the output end of the secondary winding of the phase-shifting transformer is connected to the input end of the power unit, stepping down and phase-shifting the high-voltage three-phase power of the power grid and inputting it into the power unit; the output ends of the power units are connected in series in turn to obtain and output high-voltage single-phase alternating current;

[0036] The PWM control module receives the control signals from the main controller of the high-voltage permanent magnet synchronous motor, and controls the switching of the IGBTs in each power unit according to the frequency, amplitude, and phase of each phase of electricity in the control signals.

[0037] The output phase differences of the three single-phase AC power supplies are 120°. Connect the output terminals of the three single-phase AC power supplies into a triangular loop, and use the three vertices of the triangular loop as the three-phase output terminals; each terminal of the three-phase output terminals is respectively connected to the corresponding input terminal of the high-voltage permanent magnet synchronous motor.

[0038] In a specific embodiment, in a single-phase AC power supply, the number of phase-shifting transformers is 8, and the output current phase differences of the secondary windings of each phase-shifting transformer are 7.5°.

[0039] Specifically, the grid input voltage is three-phase 10 KV, which is transformed into 8 low-voltage, independent, phase-shifted secondary winding power supplies through phase-shifting transformers (isolation transformers, rectifier transformers); each secondary winding power supply is connected to a power unit, and after rectification, filtering, and inversion, a single-phase AC power supply is output. Thus, each phase is composed of 8 power units connected in series with an equivalent rated output voltage of 690 V, so that the rated value of the output phase voltage is 5520 V, and the equivalent line voltage of the three phases is 9561 V, close to 10 KV. Among them, the 8 secondary windings are connected in different connection methods to make the current phase differences between them 7.5°. The current waveforms reflected in the primary winding of the transformer are the superposition of the current waveforms of different phases of each secondary winding, forming a multi-step wave current waveform, eliminating a large number of harmonics, making the current waveform close to a sine wave, reducing the harmonic pollution to the grid, and the input power factor can be as high as 0.95.

[0040] In a specific embodiment, as Figure 2 shown, the power unit is composed of a three-phase rectification link, a filtering link, and an inversion link;

[0041] The three-phase rectification link includes: after the three-phase AC input passes through the fuse protector, it is respectively connected to a three-phase bridge rectifier circuit composed of 6 diodes;

[0042] The filtering link includes: three capacitors connected in series in turn between the positive and negative outputs of the three-phase bridge rectifier circuit, and resistors respectively connected in parallel with the three capacitors. Due to the capacitance value deviation of the capacitors, the voltages across each capacitor may not be consistent during charging and operation. The parallel resistors can make the voltages of each capacitor tend to be balanced, avoiding damage to a certain capacitor due to excessive voltage; and after the circuit is powered off, the charges stored in the capacitors can be released through the parallel resistors, preventing residual charges from causing electric shock hazards, and at the same time preparing for the next start and reducing start-up noise.

[0043] The inverter link includes: the first IGBT, the second IGBT, the third IGBT, and the fourth IGBT, corresponding to Figure 2 S1, S2, S3, and S4 in; the collectors of the first IGBT and the third IGBT are both connected to the positive pole, the emitters of the second IGBT and the fourth IGBT are both connected to the negative pole, the emitter of the first IGBT and the collector of the second IGBT are both connected to the first port of the output terminal of the power unit, and the emitter of the third IGBT and the collector of the fourth IGBT are both connected to the second port of the output terminal of the power unit; the gates of each IGBT are respectively connected to the corresponding control signal lines of the PWM regulation module.

[0044] In a specific embodiment, in the three-phase rectification link, the diode is a 1800V rectifier diode; in the filtering link, the capacitor is an electrolytic capacitor of 400V and 90μf / A; in the inverter link, the withstand voltage value of the IGBT is 1700V.

[0045] In a specific embodiment, a diode is reversely connected in parallel with each of the first IGBT, the second IGBT, the third IGBT, and the fourth IGBT. In the inverter circuit, when the IGBT is turned off, the inductive load (the subsequent load may be inductive) generates an induced current that requires a path. At this time, the reversely connected diode provides a freewheeling path for the induced current to avoid generating too high a back electromotive force and protecting the IGBT from being broken down. When the load is in the power generation state (such as when the motor decelerates, etc.), the energy generated by the load can be fed back to the DC-side capacitor through the reversely connected diode, thereby improving the synchronization of the synchronous motor control and the efficiency of the drive system.

[0046] In a specific embodiment, the output terminals of three single-phase AC power supplies are connected into a triangular loop, specifically:

[0047] Connect the first output terminal of the first single-phase power supply to the second output terminal of the second single-phase power supply, connect the first output terminal of the second single-phase power supply to the second output terminal of the third single-phase power supply, and connect the first output terminal of the third single-phase power supply to the second output terminal of the first single-phase power supply to form a triangular loop.

[0048] In a specific embodiment, controlling the switches of the IGBTs in each power unit is specifically as follows:

[0049] Step 1: Extract the frequency, amplitude, and phase of each phase of electricity from the control signal of the main controller, and generate three-phase reference sine wave signals according to the frequency, amplitude, and phase;

[0050] Step 2: Determine the frequency of the triangular carrier signal according to the frequency of the reference sine wave signal and the set multiple, and determine the amplitude of the triangular carrier signal of each power unit in each phase according to the amplitude of the reference sine wave signal. Specifically, the ratio of the amplitude of the reference sine wave signal to the amplitude of the triangular carrier signal is set as the modulation ratio. The modulation ratio determines the duty cycle and waveform quality characteristics of the output signal. According to the voltage amplitude in the control signal of the main controller and the actual output voltage amplitude of each phase, adjust the modulation ratio so that the actual output voltage is closer to the target voltage. Further, the voltage value after filtering in the filtering link of the power unit usually still has a sine wave fluctuation. The amplitude of the sine wave fluctuation is different under different load conditions. The modulation ratio can be dynamically adjusted according to the amplitude of the fluctuation to make the output waveforms of each power unit more stable.

[0051] Step 3: Compare the triangular carrier signal of each power unit with the reference sine wave signal of the corresponding phase. When the amplitude of the reference sine wave signal is greater than the amplitude of the triangular carrier signal, the PWM pulse signal outputs a high level; otherwise, it outputs a low level. Generate the PWM pulse signals of each power unit one by one.

[0052] Step 4: Control the IGBT switch according to the PWM pulse signals of each power unit.

[0053] Specifically, the frequency of the triangular carrier signal should be much higher than the frequency of the reference sine wave signal. The higher the set multiple, the better the accuracy and effectiveness of the PWM modulation. In a PWM cycle, S1 and S2 are complementary-conducted, that is, when S1 is conducted, S2 is turned off; conversely, when S1 is turned off, S2 is conducted. Similarly, S3 and S4 are also complementary-conducted. The purpose of doing this is to avoid short-circuiting between the positive and negative poles. When the PWM signal is at a high level, the corresponding IGBT is conducted; when the PWM signal is at a low level, the corresponding IGBT is turned off. When outputting the positive half-cycle voltage, it is necessary to make S1 and S4 conducted, and S2 and S3 turned off. The current flows from the positive pole of the DC bus through S1, the load, and S4 back to the negative pole of the DC bus; when the amplitude of the reference sine wave signal is greater than the amplitude of the triangular carrier signal, a high level is output to S1 and S4. When outputting the negative half-cycle voltage, make S2 and S3 conducted, and S1 and S4 turned off. The current flows from the negative pole of the DC bus through S3, the load, and S2 back to the positive pole of the DC bus; when the amplitude of the reference sine wave signal is greater than the amplitude of the triangular carrier signal, a high level is output to S2 and S3.

[0054] In a specific embodiment, the three-phase reference sine wave signals are expressed as:

[0055]

[0056] where V a (t), V b (t), V c(t) respectively represent the reference sine wave signals of phases a, b, and c; A, B, and C are the corresponding amplitudes; are the corresponding phase shift angles respectively, t is the time, and f is the frequency.

[0057] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple. For the relevant parts, reference can be made to the description in the method section.

[0058] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-frequency and high-voltage inverter for a high-speed magnetic suspension fan, characterized in that: Specifically include: Three-phase grid input, three single-phase AC power supplies, and PWM control module; The single-phase AC power supply is composed of multiple pairs of phase-shifting transformers and power units; the primary winding input end of the phase-shifting transformer is connected to the three-phase input end of the power grid, and the secondary winding output end of the phase-shifting transformer is connected to the input end of the power unit, and the high-voltage three-phase electricity of the power grid is stepped down and phase-shifted before being input into the power unit; the output ends of the power units are connected in series in sequence to obtain high-voltage single-phase AC power and output it; The PWM control module receives the control signal of the main controller of the high-voltage permanent magnet synchronous motor, and controls the switch of the IGBT in each power unit according to the frequency, amplitude and phase of each phase electricity in the control signal; The output phase difference of the three single-phase AC power supplies is 120°. The output ends of the three single-phase AC power supplies are connected into a triangular loop, and the three vertices of the triangular loop are used as three-phase output ends; each terminal of the three-phase output end is respectively connected to the corresponding input terminal of the high-voltage permanent magnet synchronous motor.

2. A high-frequency and high-voltage inverter for a high-speed magnetic suspension fan according to claim 1, characterized in that: In one of the single-phase AC power supplies, the number of the phase-shifting transformers is 8, and the phase difference of the output current of the secondary winding of each phase-shifting transformer is 7.5°.

3. A high-frequency and high-voltage inverter for a high-speed magnetic suspension fan according to claim 1, characterized in that: The power unit is composed of a three-phase rectification link, a filtering link and an inverter link; The three-phase rectification link includes: after the three-phase AC input passes through the fuse protector, it is respectively connected to a three-phase bridge rectification circuit composed of 6 diodes; The filtering link includes: three capacitors connected in series between the output positive electrode and the negative electrode of the three-phase bridge rectifier circuit, and resistors connected in parallel with the three capacitors respectively; The inverter link includes: a first IGBT, a second IGBT, a third IGBT, and a fourth IGBT; the collectors of the first IGBT and the third IGBT are both connected to the positive electrode, the emitters of the second IGBT and the fourth IGBT are both connected to the negative electrode, the emitter of the first IGBT and the collector of the second IGBT are both connected to the first port of the output end of the power unit, and the emitter of the third IGBT and the collector of the fourth IGBT are both connected to the second port of the output end of the power unit; the gates of each IGBT are respectively connected to the control signal lines corresponding to the PWM control module.

4. A high-frequency and high-voltage inverter for a high-speed magnetic suspension fan according to claim 3, characterized in that: In the three-phase rectification link, the diode is a 1800V rectification diode; in the filtering link, the capacitor is a 400V, 90μf / A electrolytic capacitor; in the inverter link, the withstand voltage value of the IGBT is 1700V.

5. A high-frequency and high-voltage inverter for a high-speed magnetic suspension fan according to claim 3, characterized in that: The first IGBT, the second IGBT, the third IGBT, and the fourth IGBT are all connected in reverse parallel with a diode.

6. A high-frequency and high-voltage inverter for a high-speed magnetic suspension fan according to claim 1, characterized in that: The output ends of the three single-phase AC power supplies are connected into a triangle loop, specifically: Connect the first output end of the first single-phase power supply to the second output end of the second single-phase power supply, connect the first output end of the second single-phase power supply to the second output end of the third single-phase power supply, and connect the first output end of the third single-phase power supply to the second output end of the first single-phase power supply to form a triangle loop.

7. A high-frequency and high-voltage inverter for a high-speed magnetic suspension fan according to claim 1, characterized in that: The controlling of the switch of the IGBT in each of the power units is specifically: Step 1: extracting the frequency, amplitude and phase of each phase of electricity from the control signal of the main controller, and generating a three-phase reference sine wave signal according to the frequency, amplitude and phase; Step 2: Determine the frequency of the triangular carrier signal according to the frequency of the reference sine wave signal and the set multiple, and determine the amplitude of the triangular carrier signal of each power unit in each phase according to the amplitude of the reference sine wave signal; Step 3: Compare the triangular carrier signal of each power unit with the reference sine wave signal of the corresponding phase. When the amplitude of the reference sine wave signal is greater than the amplitude of the triangular wave carrier signal, the PWM pulse signal outputs a high level, otherwise it outputs a low level; generate the PWM pulse signal of each power unit one by one; Step 4: Control the IGBT switch according to the PWM pulse signal of each power unit.

8. The high-frequency and high-voltage inverter for a high-speed magnetic suspension fan according to claim 1, characterized in that: The three-phase reference sine wave signal is expressed as: Where V a (t), V b (t), V c (t) represents the reference sine wave signals of phases a, b, and c respectively; A, B, and C are the corresponding amplitudes respectively; are the corresponding phase shift angles, t is the time and f is the frequency.

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