阅读说明：本技术 一种带负荷观测器的变频调速控制系统和变频器 (Variable-frequency speed regulation control system with load observer and frequency converter ) 是由 祖军 赵岚 于胜涛 于 2020-06-03 设计创作，主要内容包括：本发明实施例公开了一种带负荷观测器的变频调速控制系统和变频器,变频调速控制系统由转速和电流双闭环系统组成,变频调速控制系统还包括负荷观测器,负荷观测器包括调节器和积分器；调节器的输入端输入转速实际值与转速观测值的差值,调节器的第一输出端与转速调节模块的输出端电连接并输出第一负载转矩观测值；积分器用于根据第二负载转矩观测值与系统的输出转矩计算转速观测值并从其输出端输出至调节器的输入端。本发明实施例提供的技术方案通过负荷观测器来实时检测负载的变化情况,当负载发生变化时,能够快速对负载状态进行响应,并精确调节电机的转速,且结合矢量控制,能够最大程度地减小电机转速的动态下降,有利于保持系统的稳定性。(The embodiment of the invention discloses a variable-frequency speed regulation control system with a load observer and a frequency converter, wherein the variable-frequency speed regulation control system consists of a rotating speed and current double closed-loop system, the variable-frequency speed regulation control system also comprises the load observer, and the load observer comprises a regulator and an integrator; the input end of the regulator inputs a difference value between the actual rotating speed value and the observed rotating speed value, and the first output end of the regulator is electrically connected with the output end of the rotating speed regulating module and outputs a first observed load torque value; the integrator is used for calculating a rotating speed observed value according to the second load torque observed value and the output torque of the system and outputting the rotating speed observed value to the input end of the regulator from the output end of the integrator. According to the technical scheme provided by the embodiment of the invention, the change condition of the load is detected in real time through the load observer, when the load changes, the load state can be quickly responded, the rotating speed of the motor can be accurately adjusted, and the dynamic reduction of the rotating speed of the motor can be reduced to the greatest extent by combining vector control, so that the stability of a system is favorably maintained.)

1. A variable frequency speed control system with a load observer is composed of a rotating speed and current double closed-loop system, wherein the rotating speed and current double closed-loop system comprises a rotating speed adjusting module, an exciting current adjusting module, a first vector transformation module and a second vector transformation module, and the rotating speed adjusting module, the exciting current adjusting module and the first vector transformation module are electrically connected with the second vector transformation module;

the regulator comprises an input end, a first output end and a second output end, the rotating speed regulating module comprises an input end and an output end, the input end of the regulator inputs a difference value between an actual rotating speed value and an observed rotating speed value, and the first output end of the regulator is electrically connected with the output end of the rotating speed regulating module and outputs a first observed load torque value;

the integrator comprises an input end and an output end, the input end of the integrator is electrically connected with the second output end of the regulator, and the integrator is used for calculating the rotating speed observed value according to the second load torque observed value and the output torque of the system and outputting the rotating speed observed value to the input end of the regulator from the output end of the integrator.

2. The variable frequency speed-regulating control system with a load observer according to claim 1, wherein the regulator comprises a proportional unit and a first integral unit;

the proportional unit comprises an input end and an output end, the input end of the proportional unit is electrically connected with the input end of the regulator, and the proportional unit is used for outputting a torque calculated value according to a difference value between a rotating speed actual value and a rotating speed observed value;

the first integration unit comprises an input end and an output end, the input end of the first integration unit is electrically connected with the output end of the proportional unit, and the first integration unit is used for generating a first load torque observed value according to the torque calculated value and outputting the first load torque observed value from the output end of the first integration unit.

3. The variable frequency speed control system with a load observer according to claim 2, wherein the integrator comprises a second integration unit;

the second integration unit comprises an input end and an output end, the input end of the second integration unit is electrically connected with the output end of the first integration unit, and the output end of the second integration unit is electrically connected with the input end of the proportional unit.

4. A frequency converter comprising a variable-frequency governor control system with a load observer according to any one of claims 1 to 3, the frequency converter further comprising: the system comprises an incoming line unit, a transformer unit and a current transformer;

the input end of the wire inlet unit is electrically connected with the bus, the output end of the wire inlet unit is electrically connected with the primary side of the transformer unit, the secondary side of the transformer unit is electrically connected with the input end of the converter, and the output end of the converter is electrically connected with the motor;

and the variable-frequency speed regulation control system of the load observer acquires the voltage and the current output by the converter and regulates the rotating speed of the motor through vector control.

5. The frequency converter according to claim 4, wherein the incoming line unit comprises a first switch, a second switch and a current limiting unit;

the first end of the first switch is electrically connected with the bus, the second end of the first switch is electrically connected with the primary side of the transformer unit through the current limiting unit, and the second switch is connected with the current limiting unit in parallel.

6. The frequency converter according to claim 4, further comprising a first switching unit;

the first end of the first switching unit is electrically connected with the output end of the converter, the second end of the first switching unit is electrically connected with the motor, and the first switching unit is used for switching the working mode of the converter into a motor driving mode; the first switching unit includes a third switch.

7. The frequency converter according to claim 4, further comprising a second switching unit;

the first end of the second switching unit is electrically connected with the primary side of the transformer unit, the second end of the second switching unit is electrically connected with the output end of the converter, and the second switching unit is used for switching the working mode of the converter to an active filtering mode.

8. The frequency converter according to claim 7, wherein the second switching unit comprises a fourth switch and a commutation unit, and the commutation unit comprises a first inductor, a second inductor and a capacitor;

the first end of the fourth switch is electrically connected with the primary side of the transformer unit, the second end of the fourth switch is electrically connected with the first end of the first inductor, the second end of the first inductor is electrically connected with the output end of the converter through the second inductor, the first end of the capacitor is electrically connected with the second end of the first inductor, and the second end of the capacitor is grounded.

9. The frequency converter according to claim 4, further comprising a current sensor electrically connected to the current transformer, the current sensor being configured to collect a current signal of the upper transformer to the current transformer.

10. The frequency converter according to claim 4, wherein the converter is an AC-DC-AC type inverter.

Technical Field

The embodiment of the invention relates to the technical field of variable frequency speed regulation, in particular to a variable frequency speed regulation control system with a load observer and a frequency converter.

Background

The frequency converter is an electric control device which applies a frequency conversion technology and a microelectronic technology and controls an alternating current motor by changing the frequency mode of a working power supply of the motor. With the continuous improvement of the industrial automation degree, the frequency converter is also widely applied.

The existing frequency converter usually has a speed regulation function, but when the load changes, the existing frequency converter cannot respond quickly, so that the rotating speed of a motor fluctuates greatly, and the running performance of equipment is influenced.

Disclosure of Invention

The embodiment of the invention provides a variable-frequency speed regulation control system with a load observer and a frequency converter, so as to quickly respond to the change of a load, further improve the speed regulation precision and the dynamic response speed of the frequency converter and be beneficial to improving the stability of the system.

In a first aspect, an embodiment of the present invention provides a variable frequency speed control system with a load observer, where the variable frequency speed control system is composed of a rotating speed and current double closed-loop system, where the rotating speed and current double closed-loop system includes a rotating speed adjusting module, an excitation current adjusting module, a first vector transformation module and a second vector transformation module, and the rotating speed adjusting module, the excitation current adjusting module and the first vector transformation module are all electrically connected to the second vector transformation module, and the variable frequency speed control system is characterized by further including a load observer, where the load observer includes a regulator and an integrator;

the regulator comprises an input end, a first output end and a second output end, the rotating speed regulating module comprises an input end and an output end, the input end of the regulator inputs a difference value between an actual rotating speed value and an observed rotating speed value, and the first output end of the regulator is electrically connected with the output end of the rotating speed regulating module and outputs a first observed load torque value;

the integrator comprises an input end and an output end, the input end of the integrator is electrically connected with the second output end of the regulator, and the integrator is used for calculating the rotating speed observed value according to the second load torque observed value and the output torque of the system and outputting the rotating speed observed value to the input end of the regulator from the output end of the integrator.

Optionally, the regulator comprises a proportional unit and a first integration unit;

the proportional unit comprises an input end and an output end, the input end of the proportional unit is electrically connected with the input end of the regulator, and the proportional unit is used for outputting a torque calculated value according to a difference value between a rotating speed actual value and a rotating speed observed value;

the first integration unit comprises an input end and an output end, the input end of the first integration unit is electrically connected with the output end of the proportional unit, and the first integration unit is used for generating a first load torque observed value according to the torque calculated value and outputting the first load torque observed value from the output end of the first integration unit.

Optionally, the integrator comprises a second integration unit; the second integration unit comprises an input end and an output end, the input end of the second integration unit is electrically connected with the output end of the first integration unit, and the output end of the second integration unit is electrically connected with the input end of the proportional unit.

In a second aspect, an embodiment of the present invention further provides a frequency converter, including the variable-frequency speed-regulation control system with a load observer in the first aspect, where the frequency converter further includes: the system comprises an incoming line unit, a transformer unit and a current transformer;

the input end of the wire inlet unit is electrically connected with the bus, the output end of the wire inlet unit is electrically connected with the primary side of the transformer unit, the secondary side of the transformer unit is electrically connected with the input end of the converter, and the output end of the converter is electrically connected with the motor;

and the variable-frequency speed regulation control system of the load observer acquires the voltage and the current output by the converter and regulates the rotating speed of the motor through vector control.

Optionally, the incoming line unit includes a first switch, a second switch and a current limiting unit;

the first end of the first switch is electrically connected with the bus, the second end of the first switch is electrically connected with the primary side of the transformer unit through the current limiting unit, and the second switch is connected with the current limiting unit in parallel.

Optionally, a first switching unit is further included;

the first end of the first switching unit is electrically connected with the output end of the converter, the second end of the first switching unit is electrically connected with the motor, and the first switching unit is used for switching the working mode of the converter into a motor driving mode; the first switching unit includes a third switch.

Optionally, a second switching unit is further included;

the first end of the second switching unit is electrically connected with the primary side of the transformer unit, the second end of the second switching unit is electrically connected with the output end of the converter, and the second switching unit is used for switching the working mode of the converter to an active filtering mode.

Optionally, the second switching unit includes a fourth switch and a commutation unit, where the commutation unit includes a first inductor, a second inductor, and a capacitor;

the first end of the fourth switch is electrically connected with the primary side of the transformer unit, the second end of the fourth switch is electrically connected with the first end of the first inductor, the second end of the first inductor is electrically connected with the output end of the converter through the second inductor, the first end of the capacitor is electrically connected with the second end of the first inductor, and the second end of the capacitor is grounded.

Optionally, the transformer further comprises a current sensor, the current sensor is electrically connected with the current transformer, and the current sensor is used for collecting a current signal of the upper transformer to the current transformer.

Optionally, the converter is an ac-dc-ac type inverter.

The embodiment of the invention adds the load observer on the basis of the variable-frequency speed regulation control system consisting of the rotating speed and current double closed loops to realize the real-time detection of the load state, and introduces the detected load state into the rotating speed closed loop system to improve the rotating speed precision and the dynamic response speed of the variable-frequency speed regulation system. The load observer provided by the embodiment comprises a regulator and an integrator; the regulator comprises an input end, a first output end and a second output end, the rotating speed regulating module comprises an input end and an output end, the input end of the regulator inputs a difference value between an actual rotating speed value and an observed rotating speed value, and the first output end of the regulator is electrically connected with the output end of the rotating speed regulating module and outputs a first load torque observed value; the integrator comprises an input end and an output end, the input end of the integrator is electrically connected with the second output end of the regulator, and the integrator is used for calculating a rotating speed observed value according to the second load torque observed value and the output torque of the system and outputting the rotating speed observed value to the input end of the regulator from the output end of the integrator. According to the technical scheme provided by the embodiment of the invention, the change condition of the load is detected in real time through the load observer, when the load changes, the load state can be quickly responded, the detected load state is introduced into the double closed-loop system so as to accurately adjust the rotating speed of the motor, and the dynamic reduction of the rotating speed of the motor can be reduced to the greatest extent by combining vector control, so that the stability of the system is favorably maintained.

Drawings

FIG. 1 is a schematic structural diagram of a variable frequency speed control system in the prior art;

fig. 2 is a schematic structural diagram of a variable-frequency speed-regulating control system with a load observer according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of another variable-frequency speed-regulating control system with a load observer according to an embodiment of the present invention;

fig. 4 is a schematic structural diagram of a frequency converter according to an embodiment of the present invention;

fig. 5 is a schematic structural diagram of another frequency converter according to an embodiment of the present invention;

fig. 6 is a schematic structural diagram of another frequency converter according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

Fig. 1 is a schematic structural diagram of a variable frequency speed control system in the prior art. Referring to fig. 1, the variable-frequency speed-regulating control system is composed of a rotating speed and current double closed-loop system, wherein the rotating speed and current double closed-loop system includes a rotating speed regulating module 10, an exciting current regulating module 20, a first vector transformation module 30 and a second vector transformation module 40, and the rotating speed regulating module 10, the exciting current regulating module 20 and the first vector transformation module 30 are all electrically connected with the second vector transformation module 40. The inverter 60 is a three-phase inverter, and respectively collects the current and voltage of the a-phase, b-phase and c-phase of the inverter 60, the three-phase coordinates are transformed into the stationary d-q axis coordinates by the first vector transformation module 30 (3/2 transformation), and then the torque current i is obtained by the flux linkage equation_qAnd an excitation current i_dRealizing a torque current i_qAnd an excitation current i_dAnd (4) decoupling. The rotating speed regulating module 10 regulates the difference value between the set value and the actual value of the rotating speed or the angular speed of the motor and outputs a set value i of the torque current_q ^*The adaptive current regulation module 11 sets the torque current to a given value i_q ^*And the actual torque current i_qAnd obtaining a given voltage value v of the q axis according to a voltage equation_q ^*. The exciting current regulating module 20 regulates the difference between the given value and the actual value of the magnetic flux and outputs the given value i of the exciting current_d ^*The self-adaptive current regulation module 11 sets the given value i of the exciting current_d ^*And the actual excitation current i_dAnd obtaining a given voltage value v of the d axis according to a voltage equation_d ^*. Voltage set value v for d-axis by second vector transformation module 40_d ^*And given value v of voltage of q axis_q ^*2/3 transformation is carried out to obtain three-phase alternating current to control the rotation of the motor. When the load changes suddenly, the existing variable frequency speed regulation control system is easily influenced by disturbance, the speed regulation precision of the system is reduced, and the change of the load cannot be quickly responded, so that the rotating speed of a motor fluctuates greatly, and the running performance of equipment is influenced.

In view of this, the embodiment of the present invention provides a variable-frequency speed-regulating control system with a load observer, so as to improve the precision of the motor speed regulation and improve the stability of the system. Fig. 2 is a schematic structural diagram of a variable-frequency speed-regulating control system with a load observer according to an embodiment of the present invention. The variable-frequency speed regulation control system with the load observer, provided by the embodiment of the invention, is suitable for asynchronous motors and synchronous motors, and can meet the high-precision speed regulation requirements of the asynchronous motors and the synchronous motors. The variable-frequency speed regulation control system provided by the embodiment of the invention further comprises a load observer 70, wherein the load observer 70 comprises a regulator 701 and an integrator 702;

the regulator 701 comprises an input end, a first output end and a second output end, the rotating speed regulating module 10 comprises an input end and an output end, the input end of the regulator 701 inputs a difference value between an actual rotating speed value and an observed rotating speed value, and the first output end of the regulator 701 is electrically connected with the output end of the rotating speed regulating module 10 and outputs a first observed load torque value; the integrator 702 includes an input terminal and an output terminal, the input terminal of the integrator 702 is electrically connected to the second output terminal of the regulator 701, and the integrator 702 is configured to calculate a speed observed value from the second load torque observed value and the output torque of the system and output the speed observed value from the output terminal thereof to the input terminal of the regulator 701.

Specifically, the load observer 70 is composed of a regulator 701 and an integrator 702, and the regulator 701 is configured to output a first observed load torque value according to a difference value between an actual rotation speed value and an observed rotation speed value input by an input end of the regulator 701, wherein the observed rotation speed value can be calculated by the integrator 702 according to the observed first blocking torque value, and the first observed load torque value is introduced into the rotation speed adjustment module 10 to be used as feed-forward compensation of the torque current so as to improve the response speed of the system. As shown in fig. 2, after the given value of the angular velocity of the motor is different from the actual value of the angular velocity of the motor, the angular velocity difference is output to the rotation speed adjusting module 10, and the rotation speed adjusting module 10 adjusts the angular velocity difference. The torque current is then regulated to effect control of the output voltage of the inverter 60, wherein the given value i of the torque current_q ^*A given value i of the torque current, which is the sum of the output of the speed regulation module 10 and the output of the regulator 701_q ^*The actual value of the sum torque current is output to the adaptive current regulation module 11 for self-adaptationGiven value v of q-axis voltage output by current-applying regulating module 11_q ^*(ii) a The exciting current regulating module 20 regulates the difference between the given value and the actual value of the magnetic flux and outputs the given value i of the exciting current_d ^*The self-adaptive current regulation module 11 sets the given value i of the exciting current_d ^*And the actual excitation current i_dAnd obtaining a given voltage value v of the d axis according to a voltage equation_d ^*. Voltage set value v for d-axis by second vector transformation module 40_d ^*And given value v of voltage of q axis_q ^*2/3 transformation is carried out to obtain three-phase alternating current to control the rotation of the motor. When the load changes, the observed value of the rotation speed output by the integrator 702 changes correspondingly, and the regulator 701 adjusts the observed value of the first load torque adaptively according to the actual value of the rotation speed of the motor and the observed value of the rotation speed. That is, the load observer 70 responds to the load state quickly and adjusts the first load torque observed value according to the detected load state, the first load torque observed value is differentiated from the system torque output by the rotation speed adjusting module to adjust the torque current, and then three-phase alternating current is obtained according to a voltage equation and vector transformation to control the rotation speed of the motor so as to adapt to the change of the load.

The embodiment of the invention adds the load observer on the basis of the variable-frequency speed regulation control system consisting of the rotating speed and current double closed loops to realize the real-time detection of the load state, and introduces the detected load state into the rotating speed closed loop system to improve the rotating speed precision and the dynamic response speed of the variable-frequency speed regulation system. The load observer provided by the embodiment comprises a regulator and an integrator; the regulator comprises an input end, a first output end and a second output end, the rotating speed regulating module comprises an input end and an output end, the input end of the regulator inputs a difference value between an actual rotating speed value and an observed rotating speed value, and the first output end of the regulator is electrically connected with the output end of the rotating speed regulating module and outputs a first load torque observed value; the integrator comprises an input end and an output end, the input end of the integrator is electrically connected with the second output end of the regulator, and the integrator is used for calculating a rotating speed observed value according to the second load torque observed value and the output torque of the system and outputting the rotating speed observed value to the input end of the regulator from the output end of the integrator. According to the technical scheme provided by the embodiment of the invention, the change condition of the load is detected in real time through the load observer, when the load changes, the load state can be quickly responded, the detected load state is introduced into the double closed-loop system to accurately adjust the rotating speed of the motor, and the dynamic reduction of the rotating speed of the motor can be reduced to the greatest extent by combining vector control, so that the stability of the system is favorably maintained.

Fig. 3 is a schematic structural diagram of another variable-frequency speed-regulating control system with a load observer according to an embodiment of the present invention, and fig. 3 is an embodiment of the variable-frequency speed-regulating control system with the load observer in fig. 2. On the basis of the above technical solution, referring to fig. 3, the regulator 701 includes a proportional unit 7011 and a first integral unit 7012, and the integrator 702 includes a second integral unit 7021; the proportional unit 7011 includes an input end and an output end, the input end of the proportional unit 7011 is electrically connected to the input end of the regulator 701, and the proportional unit 7011 is configured to obtain the actual value n of the rotation speed and the observed value n of the rotation speed according to the actual value n of the rotation speed and the observed value n of the rotation speed_obThe difference output torque calculation; first integral unit 7012 includes an input end and an output end, the input end of first integral unit 7012 is electrically connected to the output end of proportional unit 7011, and first integral unit 7012 is configured to generate a first observed load torque value T according to a torque calculation value_Lob1And output from its output; second integral unit 7021 includes an input end and an output end, the input end of second integral unit 7021 is electrically connected to the output end of first integral unit 7012, and the output end of second integral unit 7021 is electrically connected to the input end of proportional unit 7011.

Specifically, the regulator 701 is a PI regulator with a ratio and an integral separated from each other, and the regulator 701 is specifically configured to obtain the actual value n of the rotation speed and the observed value n of the rotation speed_obTo generate a first load torque observation T_Lob1And the first load torque observed value T is measured_Lob1Introduced into the speed regulation module 10, the speed and current double closed-loop system according to the first load torque observed value T_Lob1The rotational speed of the motor is adjusted to reduce the influence of rotational speed fluctuations due to load variations. The input end of the proportional unit 7011 inputs the actual value n and the observed value n_obDifference of (2)Example unit 7011 generates an adjustment action based on the difference, outputs the calculated torque value to the input terminal of first integrating unit 7012, and first integrating unit 7012 generates an adjustment action based on the calculated torque value and outputs first observed load torque value T_Lob1. The speed regulation module 10 introduces a first load torque observation T_Lob1First observed load torque value T_Lob1And the given torque value T output by the rotating speed regulating module 10^*And inputting the difference to a torque control module ATL for torque current regulation so as to control the alternating current of the driving motor. Furthermore, a first load torque observed value T_Lob1Summing the torque calculated value to form a second load torque observed value T_Lob2Second load torque observed value T_Lob2Forming a torque difference value after making a difference with the torque output by the speed regulating system, adjusting and calculating the torque difference value by a second integral unit 7021, and outputting a rotating speed observed value n_obTo the input of a proportional unit 7011, wherein the integration time constant of a second integrating unit 7021 is T_mEqual to the electromechanical time constant of the motor.

The embodiment of the invention adds the load observer on the basis of the variable-frequency speed regulation control system consisting of the rotating speed and current double closed loops to realize the real-time detection of the load state, and introduces the detected load state into the rotating speed closed loop system to improve the rotating speed precision and the dynamic response speed of the variable-frequency speed regulation system. The load observer provided by the embodiment comprises a regulator and an integrator; the regulator comprises an input end, a first output end and a second output end, the rotating speed regulating module comprises an input end and an output end, the input end of the regulator inputs a difference value between an actual rotating speed value and an observed rotating speed value, and the first output end of the regulator is electrically connected with the output end of the rotating speed regulating module and outputs a first load torque observed value; the integrator comprises an input end and an output end, the input end of the integrator is electrically connected with the second output end of the regulator, and the integrator is used for calculating a rotating speed observed value according to the second load torque observed value and the output torque of the system and outputting the rotating speed observed value to the input end of the regulator from the output end of the integrator. According to the technical scheme provided by the embodiment of the invention, the change condition of the load is detected in real time through the load observer, when the load changes, the load state can be quickly responded, the detected load state is introduced into the double closed-loop system to accurately adjust the rotating speed of the motor, and the dynamic reduction of the rotating speed of the motor can be reduced to the greatest extent by combining vector control, so that the stability of the system is favorably maintained.

Fig. 4 is a schematic structural diagram of a frequency converter according to an embodiment of the present invention, where the frequency converter according to the embodiment of the present invention includes the variable-frequency speed control system with a load observer according to any technical scheme described above, so that the frequency converter according to the embodiment of the present invention has the above beneficial effects. On the basis of the above embodiment, referring to fig. 4, the frequency converter provided in the embodiment of the present invention further includes an incoming line unit 61, a transformer unit 62, and a current transformer 63; the input end of the wire inlet unit 61 is electrically connected with the bus 100, the output end of the wire inlet unit 61 is electrically connected with the primary side of the transformer unit 62, the secondary side of the transformer unit 62 is electrically connected with the input end of the converter 63, and the output end of the converter 63 is electrically connected with the motor 64; the variable-frequency speed regulation control system 200 with the load observer collects the voltage and current output by the converter 63 and regulates the rotating speed of the motor 64 through vector control.

Specifically, the incoming line unit 61 controls the voltage on the bus 100 to enter the transformer unit 62, the transformer unit 62 converts the voltage on the bus 100 and sends the converted voltage to the converter 63, and the converter 63 converts the voltage of the ac voltage output by the transformer unit 62 and outputs the ac voltage required by the motor 64 to drive the motor 64 to rotate. The converter 63 is an ac-dc-ac inverter for rectifying the ac voltage output from the transformer unit 62 into a dc voltage and then inverting the dc voltage into an ac voltage of the motor 64. The variable-frequency speed control system 200 with the load observer collects the voltage and current output by the converter 63 and controls the rotation speed of the motor 64 according to the collected voltage and current. When the load suddenly changes, the rotating speed of the motor 64 fluctuates, in order to improve the precision of the rotating speed of the motor 64, the variable-frequency speed regulation control system 200 with the load observer quickly responds to the load state, and the vector control is combined to accurately regulate the rotating speed of the motor, so that the dynamic reduction of the rotating speed of the motor can be reduced to the greatest extent, and the stability of the system is favorably maintained.

Optionally, fig. 5 is a schematic structural diagram of another frequency converter provided in an embodiment of the present invention, and based on the above technical solution, referring to fig. 5, the incoming line unit 61 includes a first switch 611, a second switch 612, and a current limiting unit 613; a first terminal of the first switch 611 is electrically connected to the bus 100, a second terminal of the first switch 611 is electrically connected to the primary side of the transformer unit 62 via the current limiting unit 613, and the second switch 612 is connected in parallel to the current limiting unit 613.

Specifically, the first switch 611 is used to control the voltage on the bus bar 100 to enter the incoming line unit 61, functioning as a main switch. The bus 100 is an ac bus on the secondary side of the upper grid-side transformer, when the first switch 611 is closed, the voltage on the bus 100 is transmitted to the primary side of the transformer unit 62 through the current limiting unit 613, and the current limiting unit 613 is used for limiting the bus current, so as to prevent the transformer unit 62 from being damaged by the excessive bus current. The second switch 612 is a bypass switch, and when the second switch 612 is closed, the current limiting unit 613 is short-circuited, so that the current output from the incoming line unit 61 can be increased. The primary side of the transformer unit 62 is an autotransformer which comprises a high-voltage wiring terminal and a low-voltage wiring terminal; the secondary side of the transformer unit 62 is a plurality of windings for connecting a load.

Optionally, on the basis of the foregoing technical solution, with reference to fig. 5, the frequency converter provided in the embodiment of the present invention further includes a first switching unit 65; a first end of the first switching unit 65 is electrically connected with an output end of the inverter 63, a second end of the first switching unit 65 is electrically connected with the motor 64, and the first switching unit 65 is used for switching the working mode of the inverter 63 to a motor driving mode; the first switching unit 65 includes a third switch 651.

When the third switch 651 in the first switching unit 65 is closed, the inverter 63 is electrically connected to the motor 64, and at this time, the inverter 63 operates in the motor driving mode and the driving motor 64 operates. The converter 63 is an ac-dc-ac inverter for converting the ac voltage output from the secondary side of the transformer unit 62 into the driving voltage required by the motor 64, and the converter 63 may be formed of thyristors.

Optionally, fig. 6 is a schematic structural diagram of another frequency converter provided in the embodiment of the present invention, and based on the above technical solution, referring to fig. 6, the frequency converter provided in the embodiment of the present invention further includes a second switching unit 66; a first end of the second switching unit 66 is electrically connected to the primary side of the transformer unit 62, a second end of the second switching unit 66 is electrically connected to the output end of the converter 63, and the second switching unit 66 is configured to switch the operation mode of the converter 63 to the active filtering mode.

Specifically, the primary side of the transformer unit 62 is an autotransformer, and a first end of the second switching unit 66 is electrically connected to a low-voltage terminal of the autotransformer. Since the converter 63 is an ac-dc-ac inverter, a large amount of odd harmonics are generally absorbed into the power grid in the link of rectifying ac voltage into dc voltage, which causes large harmonic current and voltage distortion. By means of the second switching unit 66, the converter 63 can be switched to operate in an active filtering mode to filter out harmonics. When the load changes, the variable-frequency speed regulation control system 200 with the load observer can quickly respond to the change of the load, the voltage and the current output by the converter 63 are adjusted by detecting the load state in real time and combining a vector control technology, and meanwhile, the converter 63 working in an active filtering mode can also adjust the system energy in a self-adaptive manner so as to keep the system energy balance.

Illustratively, with continued reference to fig. 6, the second switching unit 66 includes a fourth switch 661 and a commutation unit 662, the commutation unit 662 including a first inductance L1, a second inductance L2 and a capacitance C; a first end of the fourth switch 661 is electrically connected to the primary side of the transformer unit 22, a second end of the fourth switch 661 is electrically connected to a first end of the first inductor L1, a second end of the first inductor L1 is electrically connected to an output end of the converter 63 through the second inductor L2, a first end of the capacitor C is electrically connected to a second end of the first inductor L1, and a second end of the capacitor C is grounded. The fourth switch 661 is used to control the operation mode of the converter 63 to be switched to the active filtering mode. When the fourth switch 661 is closed and the third switch 651 is open, the voltage of the primary side of the transformer unit 62 (the voltage output by the secondary side of the upper-stage grid-side transformer) is actively filtered by the converter unit 662, and the converter unit 662 is formed by a reactor and/or a filter to filter out harmonics output to the grid.

Optionally, the frequency converter provided in the embodiment of the present invention further includes a current sensor 67, the current sensor 67 is electrically connected to the converter 63, and the current sensor 67 is configured to collect a current signal of the upper transformer to the converter 67. Specifically, the current sensor 67 is capable of collecting a total current signal of the upper grid-side transformer, and also collecting an input current signal of an external load branch (not shown), and transmitting the collected current signal to the converter 63. The converter 63 adaptively adjusts the voltage and current output by the converter 63 according to the received current signal, thereby adjusting the rotation speed of the motor 64.

The frequency converter provided by the embodiment of the invention can drive the motor and perform active filtering on a power grid in a time-sharing manner through the first switching unit and the second switching unit, can be flexibly switched according to actual needs, and can meet the situation that the frequency converter is in an idle state and harmonic wave treatment is needed, such as application of a frequency converter redundancy configuration system or frequency conversion soft start of the motor. Meanwhile, the load state can be detected in real time, when the load changes, the change of the load can be quickly responded through the variable-frequency speed regulation control system with the load observer, the rotating speed of the motor is prevented from being greatly reduced, and the precision of motor speed regulation is improved.

With reference to fig. 2 and fig. 6, a specific working principle of the frequency converter provided in the embodiment of the present invention is as follows:

the upper network side transformer outputs an ac voltage to the bus 100, controls the first switch 611 of the incoming line unit 61 to be closed, and controls the ac voltage on the bus 100 to enter the primary side of the transformer unit 62 after being limited by the current limiting unit 613, during this process, the on/off of the second switch 612 can be controlled to control the switching state of the current limiting unit 613. The primary side of the transformer unit 62 is an autotransformer, which includes a high voltage terminal and a low voltage terminal, wherein the high voltage terminal is electrically connected to the current limiting unit 613, the low voltage terminal is electrically connected to the fourth switch 661, and the secondary side of the transformer unit 62 is a plurality of windings for connecting to a load. The third switch 651 is controlled to be closed, and the ac voltage output from the secondary side of the transformer unit 62 is input to the input terminal of the inverter 63. The converter 63 is an AC-DC-AC inverter, which first outputs AC power from the secondary side of the transformer unit 62The voltage is rectified to a dc voltage and then the dc voltage is inverted to an ac voltage to drive the motor 64 to rotate. The variable-frequency speed-regulating control system 200 with the load observer is electrically connected with the output end of the converter 63 to detect the load state in real time, and when the load changes, the input end of the proportion unit 7011 inputs the actual rotating speed value n and the observed rotating speed value n through the voltage, the current and the rotating speed (angular speed) of the load observer motor 64_obProportional unit 7011 will generate an adjustment according to the difference, output the calculated torque value to the input end of first integral unit 7012, and first integral unit 7012 will generate an adjustment according to the calculated torque value and output a first observed load torque value T_Lob1. The speed regulation module 10 introduces a first load torque observation T_Lob1First observed load torque value T_Lob1And the given torque value T output by the rotating speed regulating module 10^*And inputting the difference to a torque control module ATL for torque current regulation so as to control the alternating current of the driving motor. Furthermore, a first load torque observed value T_Lob1Summing the torque calculated value to form a second load torque observed value T_Lob2Second load torque observed value T_Lob2Forming a torque difference value after making a difference with the torque output by the speed regulating system, adjusting and calculating the torque difference value by a second integral unit 7021, and outputting a rotating speed observed value n_obTo the input of proportional unit 7011 to form a closed loop capable of improving first load torque observation T_Lob1The calculation precision of the motor is improved, and the precision of the rotating speed of the motor is improved.

In the rectifying process, a diode is generally adopted to rectify the alternating-current voltage, and a large amount of harmonic waves are absorbed to a power grid, so that the rectified direct-current voltage contains high-frequency pulsating voltage, the fourth switch 661 is controlled to be closed, the switching converter 63 works in an active filtering mode, and the harmonic waves are filtered by the converter unit 662, so that the stability of the system voltage is improved.

The frequency converter provided by the embodiment of the invention can drive the motor and perform active filtering on a power grid in a time-sharing manner through the first switching unit and the second switching unit, can be flexibly switched according to actual needs, and can meet the situation that the frequency converter is in an idle state and harmonic wave treatment is needed, such as application of a frequency converter redundancy configuration system or frequency conversion soft start of the motor. In addition, a load observer is added on the basis of a variable-frequency speed regulation control system consisting of a rotating speed and current double closed loop to realize real-time detection of a load state, and the detected load state is introduced into the rotating speed closed loop system to improve the rotating speed precision and the dynamic response speed of the variable-frequency speed regulation system. The load observer is used for detecting the change condition of the load in real time, when the load changes, the load state can be quickly responded, the detected load state is introduced into the double closed-loop system, the rotating speed of the motor is accurately adjusted, the dynamic reduction of the rotating speed of the motor can be reduced to the greatest extent by combining vector control, and the stability of the system is favorably maintained.

It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.