Variable frequency speed regulation orthogonal space vector modulation algorithm for single-phase motor

Abstract

An orthogonal space vector modulation algorithm for variable-frequency speed regulation of a single-phase motor is used for controlling an inverter bridge to regulate the speed and torque of the single-phase motor, and variable-frequency speed regulation of the single-phase motor is achieved. According to the algorithm, the 360-degree electrical angle is divided into four sectors, each sector is 90 degrees, four vectors are constructed, and the included angle between every two adjacent vectors is 90 degrees. In each sector, two orthogonal vectors and a zero vector are respectively subjected to PWM (Pulse Width Modulation) according to sine requirements in a carrier period, sub-vectors are circularly changed anticlockwise or clockwise, and the synthesized vector rotates in the four sectors. The angle change rate is adjusted so that the rotation speed of the resultant vector is changed and the output frequency of the inverter bridge is changed. When the modulation ratio of PWM is adjusted, the amplitude of the resultant vector is changed, and the output voltage of the inverter bridge is changed. Through orthogonal space vector control of the invention, two phases of sine waves with the difference of 90 degrees and adjustable frequency voltage can be output, and the purpose of performing frequency conversion and speed regulation on a single-phase motor is achieved.

Description

Technical Field

[0001] This invention is used to control the speed of a single-phase motor. The algorithm is used to achieve variable frequency speed regulation of the single-phase motor, which enables the single-phase motor to achieve speed regulation and then achieve continuous regulation of physical quantities such as flow and pressure. Background Art

[0002] Motors have become indispensable equipment in human production and daily life. With the need for automation and rising demands for a higher quality of life, variable frequency speed regulation (VVVSR) technology, which allows for real-time adjustment of motor speed, has become widely used in production and daily life. However, this technology has been limited to three-phase motors or specialized multi-phase motors. Since the emergence of three-phase space vector modulation (SVM) or three-phase sinusoidal modulation algorithms in the 1980s, VVVSR technology and equipment for three-phase motors have rapidly developed. In particular, SVM has become the mainstream technology for three-phase motor VVVSR, making significant contributions to the development of industrial automation, energy conservation, and improved quality of life. However, SVM technology for single-phase motors has been largely unsatisfactory. Numerous methods have been employed to address the speed regulation needs of single-phase motors, but none have fundamentally solved the problem. Current methods for regulating the speed of single-phase motors include using electromagnetic couplers to adjust the output torque and, consequently, the terminal speed, by adjusting the magnetic field strength. However, these methods have drawbacks such as high energy consumption, constant fixed-frequency operation of single-phase motors, a terminal speed below the rated speed, and the ability to adjust the speed downwards, low output torque, and weak mechanical characteristics. Currently, single-phase motor speed regulation methods use winding tapping to switch winding size. This method has disadvantages: low winding efficiency, high copper consumption, and multi-step speed regulation, preventing continuous speed adjustment. Another current method for single-phase motor speed regulation involves using a frequency converter to output a single-phase sinusoidal voltage with variable frequency and voltage, while simultaneously using capacitors to separate the phases. The voltage is then fed to the main and auxiliary windings of the single-phase motor. Changing the voltage frequency results in a change in the motor's speed. This method has disadvantages: a narrow speed regulation range, with the phase-splitting capacitors only having impedance characteristics around 50 Hz that meet phase-splitting requirements. Operating under PWM voltage, the capacitors generate increased heat and have poor reliability. Another current method for single-phase motor speed regulation involves tapping both phases of the motor and using a special frequency converter to output a two-phase, orthogonal, sinusoidal modulated waveform, which is then fed to the main and auxiliary windings for speed regulation. This method is incompatible with current single-phase motor structures, requires four terminals, and requires two inverters, resulting in high costs. Summary of the Invention

[0003] The present invention realizes the variable frequency speed regulation of the single-phase motor.

[0004] The inverter bridge structure used in the present invention is a general structure, as shown in the attached Figure 1 .

[0005] The single-phase motor is a general-purpose single-phase motor with a main and auxiliary windings orthogonally distributed structure. It has three output terminals, namely the common point, the main winding, and the auxiliary winding. Figure 2 .

[0006] The wiring method of the inverter bridge and the single-phase motor is shown in the attached Figure 3 .

[0007] Attachment Figure 3 The inverter bridge shown operates according to the orthogonal control algorithm of the present invention.

[0008] The three bridge arms of the inverter bridge operate in a switching state, and the corresponding output states are high and low. The high state corresponds to a DC+ level, and the low state corresponds to a DC- level. The high and low states are represented by 1 and 0 respectively.

[0009] The output states of the three bridge arms of the inverter bridge are determined by the orthogonal control algorithm of the present invention. Figure 3 The output terminals U, V, and W of the three bridge arms are connected to the common terminal, auxiliary winding, and main winding of the single-phase motor, respectively. Following the order of U, V, and W, the inverter bridge outputs 010, 110, 101, and 001 at different times. These four states are the four space vectors of the orthogonal modulation algorithm. 000 and 111 are zero vectors. The following description is based on this wiring arrangement. However, changing the connection points of U, V, and W to the single-phase motor will change the space vector description accordingly, but the essence remains the same and falls within the scope of protection of this invention.

[0010] The arrangement order of the orthogonal space vectors is as shown in the attached Figure 4 Circle 1 represents a sine wave cycle, or 360° electrical angle. The four space vectors are discretely distributed on the 360° electrical angle plane in a fixed order with intervals of 90° electrical angle. Every 90 degrees is a sector, with a total of 4 sectors. The vector sequence is counterclockwise 010-110-101-001 or clockwise 010-001-101-110, rotating cyclically. The starting vector can be any one of them or a vector synthesized from adjacent vectors. Figure 4 The @ in the formula is the angle between vector Q and the starting vector at any time, and @ can be any angle between 0 and 360 degrees.

[0011] The starting vector can be any one of four space vectors. The vector Q rotates in a 360° electrical angle plane. The direction can be clockwise or counterclockwise. The direction of rotation of the vector Q determines the direction of rotation of the motor.

[0012] The vector Q is composed of two adjacent vectors in the sector. Figure 4, the starting vector of vector Q is 010, which is composed of two vectors 010 and 110. In one carrier cycle, the inverter bridge is controlled to output these two vectors in time-sharing mode, with the action times being T1 and T2 respectively: T1=M*T*COS@ T2=M*T*SIN@ M is the modulation ratio and T is the carrier period.

[0013] By controlling the size of M, the output voltage is controlled.

[0014] The speed of the change of @ determines the frequency F output by the inverter bridge: @=k*t k is the angle change rate, and t is the vector rotation time.

[0015] If @=360°, then vector Q rotates once, and t is the period of the inverter bridge output frequency.

[0016] Then k*t=360 k=360 / t=360*F F=k / 360 Therefore, by controlling the size of K, the output frequency can be controlled.

[0017] Advantages of the present invention: The speed regulation range is wide. By changing the k value, the output frequency can be adjusted arbitrarily. The frequency range mainly depends on the characteristics of the mechanical system.

[0018] The output voltage can be changed arbitrarily to meet different torque requirements. Increasing the voltage can increase the torque, while reducing the voltage can save energy.

[0019] Description of the drawings: The drawings and description are a specific embodiment of the design concept of the present invention. The drawings clearly express the design concept of the present invention. Of course, there are other implementation methods of the design concept. Other technical solutions implemented in the field based on the inspiration of the design concept of the present invention are all within the scope of protection of the present invention.

[0020] Attached photos: Figure 1 、 Figure 2 、 Figure 3 For the application environment and application objects of the present invention, Figure 4 : It is the orthogonal vector diagram of the present invention.

[0021] Attachment Figure 5 Attached is a block diagram of an embodiment of the present invention. Figure 6 It is the orthogonal vector modulation waveform diagram of CPU2 in the specific implementation scheme. DETAILED DESCRIPTION

[0022] In conjunction with the specification and drawings, a specific implementation method is provided below to more clearly and completely describe the technical features of the present invention. The implementation method based on the present invention is not exclusive, and any other implementation methods obtained by scientific and technological personnel in this field based on the present invention without creative work are within the scope of protection of the present invention.

[0023] Attachment Figure 5 is a block diagram of one embodiment of the present invention.

[0024] In the described implementation scheme, AC power is input to the power input rectifier unit 5, converted into DC power, and then delivered to the switching power supply unit 4 and the IPM unit 6. The switching power supply 4 generates the power required for the operation of each functional unit. The IO interface unit 3 is the input unit for external control instructions and the output unit for CPU instructions. It is responsible for transmitting instruction signals and level changes and isolation to meet the interface requirements of the CPU unit 2. The parameter display and setting unit 1 communicates with the CPU unit 2 to display the operating parameters of the inverter. This unit 1 also displays and sets the control parameters required by the CPU for single-phase motor drive, such as output voltage and frequency. IPM 6 is short for intelligent regulation module and internally includes a CPU interface, drive, and inverter bridge. The CPU interface receives six orthogonal modulated PWM signals from the CPU 2, and the drive converts these six PWM signals into the bridge arm drive signals required by the inverter bridge. After the PWM signals are amplified by the inverter bridge, they are output as orthogonal modulated vectors to drive the single-phase motor.

[0025] In the embodiment, the CPU 2 is the control core. Currently, there are many CPU models to choose from. The CPU has a PWM signal generator that generates the 6-way orthogonal space vector modulation signal of the present invention under program control.

[0026] The orthogonal space vector modulation algorithm of the present invention can adopt unilateral modulation or bilateral modulation. This embodiment adopts unilateral modulation to implement the algorithm.

[0027] According to the orthogonal space vector modulation method of the present invention, the CPU 2 controls the IPM 6 to output waveforms in four sectors as shown in the attached figure. Figure 6 U, V, and W are the three-phase output waveforms of the inverter bridge, which are output to the common terminal, auxiliary winding, and main winding of the single-phase motor respectively. The output high level is represented by 1, and the output low level is represented by 0. Each sector has multiple carrier cycles. The three-phase waveforms of each carrier cycle are represented by 0 and 1, and the combination is an orthogonal space vector. Figure 6As can be seen, the vectors for sector I are 010 and 110, the vectors for sector II are 110 and 101, the vectors for sector III are 101 and 001, and the vectors for sector IV are 001 and 010. 111 and 000 are zero vectors. The generation of these vectors is a specific implementation of the algorithm described in the present invention.

[0028] Since the polarity of the PWM interface of IPM is different, the PWM waveform of CPU 2 controlling IPM will also be different. Taking high level as an example, the six PWM signals output by CPU2 are as shown in the attached figure. Figure 6 UH / UL, VH / VL, and WH / WL are the upper and lower bridge arm driving signals of the corresponding phases respectively.

[0029] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the essence and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An orthogonal space vector control algorithm that directly adjusts the speed and torque of a single-phase motor. It is characterized by Within the 360° electrical angle, 4 working vectors and 2 zero vectors are used.

2. An orthogonal space vector control algorithm that directly adjusts the speed and torque of a single-phase motor. It is characterized by The angle between adjacent vectors is 90°.

3. An orthogonal space vector control algorithm that directly adjusts the speed and torque of a single-phase motor. It is characterized by The 360° electrical angle is divided into four sectors, each sector is 90°.

4. An orthogonal space vector control algorithm that directly adjusts the speed and torque of a single-phase motor. It is characterized by The rotation vector is synthesized by the time-sharing action of two orthogonal vectors in the sector.

5. An orthogonal space vector control algorithm that directly adjusts the speed and torque of a single-phase motor. It is characterized by The inverter bridge it controls outputs three phases, and within the speed regulation range, the main winding and the auxiliary winding have a phase difference of 90°.

6. An orthogonal space vector control algorithm that directly adjusts the speed and torque of a single-phase motor. It is characterized by During vector synthesis, a sinusoidal modulation algorithm is used to divide the vector so that the output current is sinusoidal.

7. An orthogonal space vector control algorithm that directly adjusts the speed and torque of a single-phase motor. It is characterized by The three outputs of the inverter bridge have different functions and are connected to the common point, auxiliary winding, and main winding respectively. If the wiring is swapped, the inverter will still rotate, but the performance will be degraded and the noise and vibration will increase.

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