CN110707975A - Control method of multiphase belt suspension capacitor motor drive topology - Google Patents
Control method of multiphase belt suspension capacitor motor drive topology Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P25/00—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details
- H02P25/02—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details characterised by the kind of motor
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
- H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
- H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
- H02P29/50—Reduction of harmonics
Abstract
The invention discloses a control method of a multiphase motor drive topology with a suspension capacitor, which comprises the following steps: carrying out vector control of rotor flux linkage orientation on a main inverter at the power supply side, and driving a multi-phase open winding motor to operate; based on a preset modulation ratio range and a voltage real-time value of the suspension capacitor, independently controlling the auxiliary inverter at the side of the suspension capacitor to obtain partial active power output by the main inverter through a multi-phase motor winding, and simultaneously independently controlling the auxiliary inverter to compensate and output reactive power; the main inverter only outputs active power and the voltage change of the suspension capacitor is controllable according to the actual operation condition. The invention combines the characteristics of the power supply side and two control cores (controllable capacitor voltage and reactive power compensation) of the capacitor side, adopts a mixed mode of torque flux linkage decoupling of the main inverter and active and reactive decoupling of the auxiliary inverter, ensures the stable working state of the auxiliary inverter of the capacitor side, exerts the advantage of reactive power compensation to the maximum extent, effectively reduces the switching loss of the inverter of the suspension capacitor side and improves the system efficiency.
Description
Technical Field
The invention belongs to the field of motor control, and particularly relates to a control method of a multi-phase motor drive topology with a suspension capacitor.
Background
Due to the global energy crisis caused by fossil energy and the non-negligible environmental pollution, the development and utilization of clean energy becomes the core problem of the energy industry. However, various forms of energy cannot be directly used, and electric energy is a form of energy which is most suitable for conversion of all clean energy such as wind energy, tidal energy and the like, so that the rapid development of the renewable energy power generation industry promotes the research of electric traction and transmission technologies mainly based on electric energy consumption.
However, through the development of many years, the traditional motor theory and the electric traction control technology can no longer meet the increasingly high industrial requirements, and a novel motor, a driving topology and a corresponding control strategy thereof are continuously found and proposed in research. The development of modern power electronic technology is benefited, the variable frequency speed regulation technology is mature in the field of power transmission, and the popularization and the use of a series of power electronic converters including an inverter lead a transmission system to break the inherent limitation of a three-phase power supply system and provide powerful support for the multi-phase development of a motor; the newly proposed Open-End winding motor (OEWM) is formed by opening a neutral point of a stator winding and then connecting an inverter on the basis of not changing the electromagnetic mechanical structure design of a traditional motor body.
Based on the advantages of high reliability and high redundancy of the multi-phase motor and high flexibility and high voltage utilization rate of the open-winding double converter after the winding neutral point is opened, the multi-phase open-winding motor becomes a novel motor which is widely researched in recent years. According to different power supply modes, the driving topological structures can be divided into three types: one is powered by two isolated direct current power supplies, the other is powered by a single direct current power supply and a direct current bus, and the other is powered by a direct current power supply and a capacitor in a mixed mode.
In the three structures, compared with a single power supply-common direct current bus topology (which has low cost and small volume but has the defect that zero-sequence current influences the performance of the motor), the dual-power supply discrete direct current bus topology adopts an isolated power supply, and zero-sequence loops do not exist between inverters on two sides of a motor winding, so that no zero-sequence current circulates in the winding; but this topology is costly and the system is bulky. Compared with the first two topological structures, the third topological structure has no zero sequence loop, only needs one direct-current power supply, and has lower hardware cost and system volume. However, the topology has the disadvantage that the direct-current voltage on the side of the floating capacitor needs to be specially controlled in real time, and the constraint condition in the control strategy is increased.
Disclosure of Invention
The invention provides a control method of a multiphase motor drive topology with a suspension capacitor, which is used for solving the technical problem that the existing control method of the three-phase motor drive topology with the suspension capacitor cannot be applied in a multiphase scene because the control dimensionality is small and the suspension capacitor needs to be controlled in real time under a specific constraint condition.
The technical scheme for solving the technical problems is as follows: a control method of a multi-phase belt suspended capacitor motor drive topology comprises the following steps:
s1, carrying out vector control of rotor flux linkage orientation on the main inverter at the power supply side, and driving the multi-phase open winding motor to operate;
s2, controlling the auxiliary inverter on the suspension capacitor side to obtain partial active power output by the main inverter through the multi-phase motor winding based on the preset modulation ratio range and the voltage real-time value of the suspension capacitor, and controlling the auxiliary inverter to compensate and output reactive power; through the independent control between the active power and the reactive power, the main inverter only outputs the active power, the voltage change of the suspension capacitor is controllable according to the actual operation condition, and the control of the multi-phase motor drive topology with the suspension capacitor is realized.
The invention has the beneficial effects that: the invention is based on the vector control strategy of open-winding multiphase motor rotor flux linkage orientation, the operation of the multiphase motor is controlled, after the motor is operated, the auxiliary inverter at the side of the suspension capacitor is controlled, specifically, based on the voltage set value of the suspension capacitor and the preset voltage modulation ratio, the most appropriate suspension capacitor voltage can be selected according to the real-time working condition of the motor, the loss of the whole topological structure is greatly reduced, the service life is prolonged, meanwhile, the auxiliary inverter can fully compensate the reactive power required by the motor, and the main inverter only provides active power for the motor. Therefore, the method combines the characteristics of the power supply side and two control cores (the voltage of the suspension capacitor is controllable and the reactive power is compensated) of the capacitor side, adopts a hybrid control mode of torque flux decoupling (namely vector control based on rotor flux orientation) of the main inverter at the power supply side and active and reactive decoupling of the auxiliary inverter at the capacitor side, can control the flux and the torque of the motor, can ensure that the working state of the auxiliary inverter at the capacitor side is stable and the reactive power compensation advantage is exerted to the maximum extent, and reduces the switching loss of the inverter at the suspension capacitor side and improves the system efficiency while ensuring that a system (comprising the motor and the inverter) can keep stable and normal work when the motor operates.
On the basis of the technical scheme, the invention can be further improved as follows.
Further, in S2, the controlling the auxiliary inverter on the side of the floating capacitor to obtain a part of active power output by the main inverter through the multi-phase motor winding specifically includes:
when the current at the motor end is stable, the PI controller is used for controlling the decomposition amount of an output voltage vector output by the auxiliary inverter along the parallel direction of the current at the motor end, and controlling the auxiliary inverter to obtain the active power output by the main inverter through a multi-phase motor winding.
The invention has the further beneficial effects that: when the current at the motor end Is stable, the change of the capacitor voltage Is only related to the decomposition quantity of the output voltage vector output by the auxiliary inverter along the parallel direction of the current at the motor end, the capacitor voltage can be controlled by controlling the decomposition quantity, and because the reactive power output Is stable when the current Is at the motor end Is stable, the control of the magnitude of the absorbed active power can be realized.
Further, in S2, the controlling the auxiliary inverter to compensate for the output reactive power specifically includes:
and detecting a power angle of the main inverter, and based on the power angle, if the main inverter is judged not to be in a unit power factor state, controlling the resolution of an output voltage vector output by the auxiliary inverter along the direction vertical to the current of the motor end through a PI controller, and controlling the auxiliary inverter to compensate and output reactive power until the main inverter only outputs active power and is in the unit power factor state.
The invention has the further beneficial effects that: the capacitance voltage control and the reactive power compensation are respectively directly related to the active power absorbed by the auxiliary inverter and the reactive power output by the auxiliary inverter, in order to realize the independent control of the capacitance voltage control and the reactive power compensation, the output voltage of the auxiliary inverter is orthogonally decomposed along the direction parallel to and perpendicular to the current at the motor end, the decomposition quantity of the output voltage vector output by the auxiliary inverter along the direction parallel to the current at the motor end is used for realizing the independent control of the active power of the auxiliary inverter, the reactive power required by the motor is the sum of the reactive power output by the two inverters, in order to ensure that the main inverter does not output reactive power, the auxiliary inverter outputs all the reactive power, according to the principle of the magnitude of the reactive power output by the main inverter, the control of the reactive power compensated and output by the auxiliary inverter is realized by controlling the decomposition quantity of the output voltage vector output by the auxiliary, and the reliability is high.
Further, when the main inverter is in the unit power factor state, the resolution of the output voltage vector output by the auxiliary inverter along the direction perpendicular to the motor-end current is as follows:
Further, in S2, the implementation that the change of the voltage of the floating capacitor is controllable according to the actual operating condition specifically is:
controlling the auxiliary inverter to output voltage based on the active power and the reactive power after independent control, and when the ratio of the output voltage to the capacitor voltage set value is smaller than the minimum value of the preset modulation ratio range, controlling the auxiliary inverter to reduce the acquisition of the active power output from the main inverter through the multi-phase motor winding so as to reduce the real-time value of the capacitor voltage; and when the ratio is larger than the maximum value of the preset modulation ratio range, controlling the auxiliary inverter to increase the acquisition of the active power output from the main inverter through the multi-phase motor winding so as to increase the real-time value of the capacitor voltage and complete the change control of the suspended capacitor voltage of the auxiliary inverter.
The invention has the further beneficial effects that: according to actual operation conditions, the active power consumed by the suspension capacitor and the output reactive power are independently controlled, and when the suspension capacitor outputs different output voltages based on different conditions, the real-time value of the capacitor voltage is adjusted to reach a set value under the limitation of a preset modulation ratio, so that the capacitance voltage is adjustable.
Further, the preset modulation ratio range is 0.85-0.95.
Further, the change step of the capacitance voltage set value depends on a preset capacitance voltage regulation rate.
Further, the S1 further includes:
based on PI control, a synchronous coordinate system with the rotation speed being multiple times of the fundamental wave is adopted to carry out harmonic suppression on the current at the motor end.
The invention has the further beneficial effects that: according to a series of problems caused by motor multi-phase, a harmonic suppression scheme is provided, and a PI controller is added to a harmonic plane under a rotating coordinate system to suppress harmonic components in phase current, so that the waveform quality is improved.
The invention also provides a multiphase belt suspension capacitor motor driving topological system, which comprises: the system comprises a controller, a power supply side main inverter, a suspension capacitor side auxiliary inverter and a multi-phase motor, wherein the power supply side main inverter, the suspension capacitor side auxiliary inverter and the multi-phase motor are respectively connected with the controller;
the controller is used for executing any one of the control methods of the multi-phase motor driving topology with the suspended capacitor.
The invention also provides a storage medium, wherein the storage medium stores instructions, and when a computer reads the instructions, the computer is enabled to execute the control method of any one of the above multiphase suspended capacitor motor drive topologies.
Drawings
Fig. 1 is a flowchart of a control method of a multi-phase motor drive topology with a floating capacitor according to an embodiment of the present invention;
fig. 2 is a graph showing a relationship between output voltages of the main and auxiliary inverters and current vectors at the motor terminal when the current at the motor terminal is stable according to the embodiment of the present invention;
fig. 3 is a vector control block diagram of an open-winding motor with a suspension capacitor bridge arm according to an embodiment of the present invention;
FIG. 4 is a flowchart of a process for providing a variable capacitance voltage control strategy according to an embodiment of the present invention;
fig. 5 is a waveform diagram of various electrical parameters of the motor under different working conditions when the drive topology provided by the embodiment of the invention supplies power to the motor;
FIG. 6 is a graph comparing harmonic suppression effects provided by embodiments of the present invention;
FIG. 7 is a waveform diagram of a variable capacitance voltage speed regulation experiment provided by an embodiment of the present invention;
FIG. 8 is a graph comparing losses of a variable-voltage and constant-voltage controlled capacitor-side auxiliary inverter according to an embodiment of the present invention;
fig. 9 is a diagram of a multi-phase belt floating capacitor motor driving topology system according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Example one
A method 100 for controlling a multi-phase belt suspended capacitor motor drive topology, as shown in fig. 1, comprising:
110, carrying out vector control of rotor flux linkage orientation on a main inverter at the power supply side, and driving a multi-phase open winding motor to operate;
step 120, controlling the auxiliary inverter at the side of the suspension capacitor to obtain partial active power output by the main inverter through the multi-phase motor winding based on a preset modulation ratio range and a voltage real-time value of the suspension capacitor, and controlling the auxiliary inverter to compensate and output reactive power; through the independent control between active power and reactive power, the main inverter only outputs active power, the voltage change of the suspension capacitor is controllable according to the actual operation condition, and the control of the multi-phase belt suspension capacitor motor driving topology is realized.
Vector control based on rotor flux linkage orientation has been successfully applied in a large range, and has strong robustness, fast transient response and simple implementation scheme. In the method, the mature control strategy is still adopted on the power supply side in the mixed open winding topology with the floating capacitor. For the capacitor side, since the passive device cannot continuously output active power, and needs to absorb active power to compensate loss, a control strategy on the same power supply side cannot be adopted. However, the floating capacitor side can share the reactive output burden of the power supply side, and the most ideal situation is as follows: the main inverter only outputs active power required by the motor to operate and loss generated by parasitic parameters on the compensation capacitor side, and the auxiliary inverter outputs all reactive power required by the motor to operate. However, this condition must ensure that the voltage of the floating capacitor is stable and high enough, so that two control cores of the auxiliary inverter can be obtained: the method comprises the steps of capacitor voltage control and reactive power compensation, wherein the capacitor voltage (load is unchanged) is controlled by controlling the active power, and all reactive power compensation is controlled by controlling the reactive power.
The method comprises the steps of controlling the operation of a multiphase motor based on a vector control strategy of open winding multiphase motor rotor flux linkage orientation, controlling a suspension capacitor side auxiliary inverter after the motor operates, specifically, selecting the most appropriate suspension capacitor voltage according to the real-time working condition of the motor based on a suspension capacitor voltage set value and a preset voltage modulation ratio, greatly reducing the loss of the whole topological structure, prolonging the service life, simultaneously enabling the auxiliary inverter to fully compensate the reactive power required by the motor, and enabling a main inverter to only provide active power for the motor at the moment. Therefore, the method combines the characteristics of the power supply side and two control cores (controllable voltage of the suspension capacitor and reactive power compensation) of the capacitor side, adopts a hybrid control mode of torque flux decoupling (namely vector control based on rotor flux orientation) of the main inverter at the power supply side and active and reactive decoupling of the auxiliary inverter at the capacitor side, can control the flux and the torque of the motor, can ensure that the working state of the auxiliary inverter at the capacitor side is stable, can exert the advantage of reactive power compensation to the maximum extent, can ensure that the suspension capacitor voltage is stably adjustable for a long time when the hybrid power supply topology drives the motor, and the auxiliary inverter at the capacitor side outputs all reactive power required by the motor. When the system (comprising the motor and the inverter) can keep stable and normal operation when the motor operates, the switching loss of the inverter on the suspension capacitor side is reduced, and the system efficiency is improved.
Preferably, the above-mentioned auxiliary inverter on the side of controlling the floating capacitor obtains a part of active power output by the main inverter through a winding of the multi-phase motor, and specifically includes:
when the current at the motor end is stable, the PI controller is used for controlling the decomposition amount of an output voltage vector output by the auxiliary inverter along the parallel direction of the current at the motor end, and controlling the auxiliary inverter to obtain the active power output by the main inverter through a multi-phase motor winding.
When the current at the motor end Is stable, the change of the capacitor voltage Is only related to the decomposition quantity of the output voltage vector output by the auxiliary inverter along the parallel direction of the current at the motor end, the capacitor voltage can be controlled by controlling the decomposition quantity, and because the reactive power output Is stable when the current Is at the motor end Is stable, the control of the magnitude of the absorbed active power can be realized.
Preferably, the controlling the auxiliary inverter to compensate for the output reactive power specifically includes:
and detecting a power angle of the main inverter, and based on the power angle, if the main inverter is judged not to be in a unit power factor state, controlling the resolution of an output voltage vector output by the auxiliary inverter along the direction vertical to the current of the motor end through a PI controller, and controlling the auxiliary inverter to compensate and output reactive power until the main inverter only outputs active power and is in the unit power factor state.
Specifically, the capacitor voltage control and the reactive power compensation are respectively and directly related to the active power absorbed by the auxiliary inverter and the reactive power output by the auxiliary inverter, and in order to realize the independent control of the capacitor voltage control and the reactive power compensation, the output voltage of the auxiliary inverter is subjected to orthogonal decomposition along the direction parallel to and perpendicular to the current direction at the end of the motor. A motor stator current and voltage vector diagram based on the main inverter and the auxiliary inverter is shown in fig. 2. Wherein, IsFor motor end current, UMIs the main inverter voltage vector, UFFor auxiliary inverter voltage vectors, UFp、UFqIs along IsThe decomposition amount in the parallel and vertical directions, at this time, the active power and the reactive power of the auxiliary inverter can be respectively controlled by UFp、UFqAnd (4) independently controlling. ThetasIncluded angle of d-axis with motor terminal current, thetaMIs the included angle between the voltage vector of the main inverter and the d axis thetaFIs the tangent angle of the output voltage of the auxiliary inverter.
Starting from active power control, the change of the capacitor voltage can be represented by the following formula:
therefore, when the current at the motor end is stable, the change of the capacitor voltage is only equal to UFpRelated to, control UFpThe capacitor voltage can be controlled.
The reactive power of the induction motor is the sum of the reactive powers provided by the inverters on two sides, and the reactive power output by the main inverter can be deduced according to the mathematical equation of the induction motor:
wherein the content of the first and second substances,the first term on the right of the equation is the reactive power required by the motor, the second term is the reactive power output by the auxiliary inverter, and Q isMAvailable as 0:
i.e. the decomposition quantity of the output voltage vector output by the auxiliary inverter along the direction vertical to the motor end current when the main inverter is in a unit power factor state, wherein omega is the electrical angular velocity of the motor,is stator flux linkage isIs the motor terminal current.
As shown in fig. 3, the main inverter is mainly divided into a rotation speed control loop and a current control loop: the photoelectric encoder measures the difference between the actual rotating speed and the set rotating speed, the PI controller of the rotating speed loop calculates a torque instruction through errors, a q-axis current instruction is obtained after linear conversion, the q-axis current instruction and the set d-axis current are sent to the PI controller of the current loop together to obtain the required output voltage, the d-axis current controls the flux linkage of the motor, and the q-axis current controls the output torque of the motor. For the induction motor, because the slip exists, the slip is calculated by a rotor flux observer to obtain a synchronous angular velocity, and then a flux angle is provided for coordinate transformation.
For the auxiliary inverter, according to the analysis, the main tasks are capacitor voltage control and reactive power compensation. The capacitor voltage control loop ensures that the capacitor voltage is controllable when the system works. The reactive power control loop firstly needs to detect the angle between the current at the motor end and the voltage vector at the power supply side to obtain a power angle, judges the power factor of the main inverter at the moment, and controls the auxiliary inverter to output more reactive power if the power factor of the main inverter is not 1 until the power factor at the power supply side is constantly 1. After obtaining the required UFp、UFqAnd then, projecting the voltage to a dq plane under a rotating coordinate system to obtain d and q axis components of the voltage, and then performing classical inverse Park conversion to obtain each phase output voltage of the inverter. The formula for calculating the angle is: thetas＝sin-1(iq/is)；θM＝sin-1(UMq/UM)。
The capacitance voltage control and the reactive power compensation are respectively directly related to the active power absorbed by the auxiliary inverter and the reactive power output by the auxiliary inverter, in order to realize the independent control of the capacitance voltage control and the reactive power compensation, the output voltage of the auxiliary inverter is orthogonally decomposed along the direction parallel to and perpendicular to the current at the motor end, the decomposition quantity of the output voltage vector output by the auxiliary inverter along the direction parallel to the current at the motor end is used for realizing the independent control of the active power of the auxiliary inverter, the reactive power required by the motor is the sum of the reactive power output by the two inverters, in order to ensure that the main inverter does not output reactive power, the auxiliary inverter outputs all the reactive power, according to the principle of the magnitude of the reactive power output by the main inverter, the control of the reactive power compensated and output by the auxiliary inverter is realized by controlling the decomposition quantity of the output voltage vector output by the auxiliary, and the reliability is high.
The above-mentioned realization is according to actual operation operating mode and the suspension capacitor voltage variation is controllable, specifically is: based on the active power and the reactive power after independent control, the output voltage of the auxiliary inverter is controlled, and when the output voltage and the capacitor voltage set value V are adoptedrefWhen the ratio of (a) is less than the minimum value of the preset modulation ratio range, controlling the auxiliary inverter to reduce the acquisition of the active power output from the main inverter through the multi-phase motor winding so as to reduce the capacitance voltage real-time value (when the ratio is found to be less than the first preset voltage modulation ratio, the set value has changed, the acquisition of the active power adjusted by the auxiliary inverter is in the process of changing the real-time value, the set value is the target, and the real-time value is the actual condition); and when the ratio is larger than the maximum value of the preset modulation ratio range, controlling the auxiliary inverter to increase the acquisition of the active power output from the main inverter through the multi-phase motor winding so as to increase the real-time value of the capacitor voltage and complete the change control of the suspension capacitor voltage of the auxiliary inverter.
According to actual operation conditions, the active power consumed by the suspension capacitor and the output reactive power are independently controlled, and when the suspension capacitor outputs different output voltages based on different conditions, the real-time value of the capacitor voltage is adjusted to reach a set value under the limitation of a preset modulation ratio, so that the capacitance voltage is adjustable.
Preferably, the minimum value of the preset modulation ratio range is 0.85, and the maximum value of the preset modulation ratio range is 0.95.
Preferably, the step size of the change of the capacitor voltage set value depends on a preset capacitor voltage adjustment rate.
Specifically, in the current research of the three-phase topology, the capacitor voltage is kept unchanged in the whole process, but the constant capacitor voltage control has two non-negligible disadvantages: 1. if the working condition of the motor operation enables the capacitor side not to output more reactive power (such as during low speed and heavy load), the modulation ratio of the capacitor side is lower at the moment, but the switching loss directly related to the capacitor voltage and the heating caused by the parasitic resistance of the capacitor are not reduced due to the low modulation ratio, so that the waste of electric energy is caused, and the service life of the capacitor is also reduced due to the continuous high voltage. 2. The adjustable range of the capacitor voltage at the capacitor side is very wide, and the motor winding can be directly star-connected when the reactive power requirement is very low; when the reactive power demand is high (such as the motor runs at ultra high speed), the capacitor voltage can be increased to be two times or more than that of the direct current power supply on the power supply side.
If the voltage of the fixed capacitor can limit the reactive power output range of the bridge arm, the power supply side can not keep the unit power factor state, and the maximum voltage utilization rate is achieved.
Therefore, the method provides an optimization method of the variable capacitor voltage on the basis of the control strategy, the adjustment purpose of the capacitor voltage is to enable the auxiliary inverter to always keep a higher modulation ratio (the ratio of the current output voltage determined by the motor requirement to the maximum output voltage determined by the capacitor voltage), the complete compensation of the reactive power can be ensured (the capacitor voltage is low, the output capability is reduced, and further the complete compensation cannot be carried out), and the loss of a bridge arm at the side of the capacitor can be reduced to the maximum extent.
A program flow chart of the Capacitor Voltage Determination Block (CVDB) is shown in fig. 4, wherein m is shown in fig. 42That is, the output modulation ratio, V, of the auxiliary invertermaxFor the maximum setting value of the floating capacitor voltage, when the modulation ratio of the auxiliary inverter is lower than 0.85, the setting value of the capacitor voltage is lowered (setThe value, i.e., the control target, is adjustable, so the capacitor voltage is adjustable); when the modulation ratio of the inverter is higher than 0.95, the voltage set value of the capacitor is increased; the modulation ratio is not constantly controlled to be 1 but controlled in a higher interval, so that the capacitance voltage fluctuation caused by measurement errors can be effectively reduced, and the capacitance voltage is more stable.
The large adjustment of the capacitor voltage mainly occurs during the operating condition transition (e.g. low speed to high speed, light load to full load, etc.), and the Δ V value in fig. 4 is related to the limited capacitor voltage adjustment rate, for example, if the capacitor voltage adjustment rate is set to 50V/s and the control frequency of the controller is set to 10kHz, then:
preferably, step 110 further comprises:
based on PI control, a synchronous coordinate system with the rotation speed being multiple times of the fundamental wave is adopted to carry out harmonic suppression on the current at the motor end.
Because of the nonideal of PWM modulation, the necessity of setting a dead zone for a controller to prevent bridge arm direct connection and the like, the output voltage of the inverter inevitably has harmonic waves instead of ideal sinusoidal voltage, and for a common motor, the impedance parameter of a harmonic plane is far smaller than that of a fundamental plane, so that the stator current has larger harmonic current, and the part of the current generates loss and can hardly generate torque, and the suppression is needed.
The closed loop control for the fundamental plane in fig. 3 cannot control harmonics because harmonic currents cannot be mapped to the fundamental plane. In order to perform harmonic suppression by the PI controller, it is necessary to convert harmonic components into dc components using a new synchronous coordinate system. For five-phase machines, the harmonics that occur are mainly third harmonics, so that a synchronous coordinate system with a rotational speed three times the fundamental wave is used, i.e. the formula
It should be noted that, since the harmonic plane parameter is much smaller than the fundamental plane, a smaller harmonic voltage will result in a larger current, and therefore the harmonic suppression PI controller parameter should also be much smaller than the fundamental plane PI controller, for example, the harmonic suppression PI controller parameter of the experimental five-phase motor is about 0.2 times of the fundamental plane.
According to a series of problems caused by motor multi-phase, a harmonic suppression scheme is provided, and a PI controller is added to a harmonic plane under a rotating coordinate system to suppress harmonic components in phase current, so that the waveform quality is improved.
In order to further verify the feasibility of the method provided by the embodiment, experiments are performed on the symmetrical five-phase open winding asynchronous motor by applying the control method provided by the embodiment.
Table 1 experimental parameter settings
The complete loading experimental waveform is shown in fig. 5. As can be seen from the waveforms, after a start instruction is given, the main inverter and the auxiliary inverter provide direct current to complete a pre-excitation process for 2s, and at the same time, the main inverter injects active power into the auxiliary inverter to pre-charge the suspension capacitor to 200V. It should be noted that, since the current is a direct current when the motor is pre-excited, and the capacitor side cannot supplement the reactive power to the power supply side, it is determined in the experiment that the reactive power required by the motor is compensated only when the motor rotates at a speed higher than 100rpm (if the determination is not made, the capacitor voltage fluctuates sharply at the time of starting, and the electrolytic capacitor may be damaged at risk).
After pre-excitation is finished, the q-axis current is immediately increased to the maximum value, the maximum torque is provided, so that the motor is accurately increased to 1000 revolutions within 0.6s, the adjustment speed is high, and meanwhile, overshoot is basically avoided, which indicates that the parameter setting of the controller is reasonable.
During sudden load increase and sudden load decrease, the motor has obvious rotation speed change, but the system can provide proper torque to maintain the rotation speed at 1000 revolutions in a relatively quick response mode, and the regulation time is basically within 1 s. Meanwhile, the voltage of the capacitor is automatically regulated according to the amount of the required output reactive power, and the voltage regulation is stable without large fluctuation. The PF removal transient state adjusting process of the power supply side inverter can be stabilized at 1, and the adjusting capability of the reactive power of the capacitor side is better. After a braking instruction is given, the motor can stop under the negative torque within 0.4s, and the capacitor voltage can be stably controlled after the motor stops.
The feasibility that the strategy provided by the invention can control the motor to stably operate under various working conditions is proved by complete experimental waveforms.
The waveform diagram of the harmonic suppression experiment is shown in fig. 6. Compared with the current component (mainly q-axis current) of the no-load operation fundamental wave plane, the current component with the load phase is much larger, the proportion of harmonic components is smaller, and the obvious effect of harmonic suppression is not easy to highlight, so that the harmonic suppression selects the current waveform of the no-load operation of the motor at the rated rotating speed for comparative analysis.
When no harmonic suppression is added, the existence of third harmonic superimposed in the fundamental component can be visually seen on the current waveform, and the third harmonic component accounts for 9.4% after FFT analysis. After harmonic suppression is carried out, the peak on the current waveform is obviously reduced, the third harmonic only contains 0.3% in the FFT analysis result, and the result shows that the effect of suppressing the third harmonic under the synchronous coordinate system of triple fundamental wave speed is good, the current distortion degree THD reaches 14.41% before harmonic suppression, the current distortion degree THD is only 5.5% after suppression, and the waveform quality is obviously improved.
In the speed regulation experiment in fig. 7, the modulation ratio at the side of the auxiliary inverter is not lower than 0.9 all the time, the motor continuously increases and decreases the speed, the variation range of the capacitor voltage is 60-160V, and the variation range is basically in direct proportion to the rotating speed of the motor, thereby proving the feasibility of the variable capacitor voltage control method in the invention. The invention is measured for the loss of the smaller auxiliary inverter for constant voltage control. The comparative results are shown in FIG. 8.
Setting experimental conditions: the load torque is 4 N.m; the rotating speed is 200, 400, 600, 800 and 1000rpm five operating points; the capacitor voltage was controlled to 200V at the time of constant voltage regulation (the sub-inverter modulation ratio was close to 1 at 1000 rpm).
From the results of fig. 8, it can be seen that when the motor speed is low, the required reactive power is small, the higher capacitor voltage will generate significant extra loss, and the lower the speed, the more significant this phenomenon is, the variable capacitor control can reduce the capacitor side loss by nearly 68.5% at 200 rpm.
Example two
A multi-phase band floating capacitor motor drive topology system, as shown in fig. 9, comprising: a controller, and a power supply side main inverter (power supply voltage V) connected to the controller respectivelydc) Suspension capacitor side auxiliary inverter (capacitor voltage is V)cap) And a multi-phase motor (number of phases n); the controller is configured to execute any one of the control methods of the multi-phase suspended capacitor motor drive topology described in the first embodiment above. In the figure, g1And g2Representing the reference ground potential of the main and auxiliary inverters.
The related technical solution is the same as the first embodiment, and is not described herein again.
EXAMPLE III
A storage medium having stored therein instructions which, when read by a computer, cause the computer to execute a method of controlling a polyphase band suspended capacitor motor drive topology as any one of the above.
The related technical solution is the same as the first embodiment, and is not described herein again.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A control method of a multi-phase belt suspension capacitor motor drive topology is characterized by comprising the following steps:
s1, carrying out vector control of rotor flux linkage orientation on the main inverter at the power supply side, and driving the multi-phase open winding motor to operate;
s2, controlling the auxiliary inverter on the suspension capacitor side to obtain partial active power output by the main inverter through the multi-phase motor winding based on the preset modulation ratio range and the voltage real-time value of the suspension capacitor, and controlling the auxiliary inverter to compensate and output reactive power; through the independent control between the active power and the reactive power, the main inverter only outputs the active power, the voltage change of the suspension capacitor is controllable according to the actual operation condition, and the control of the multi-phase motor drive topology with the suspension capacitor is realized.
2. The method according to claim 1, wherein in S2, the control floating capacitor side auxiliary inverter obtains a part of active power output by the main inverter through the windings of the multi-phase motor, specifically:
when the current at the motor end is stable, the PI controller is used for controlling the decomposition amount of an output voltage vector output by the auxiliary inverter along the parallel direction of the current at the motor end, and controlling the auxiliary inverter to obtain the active power output by the main inverter through a multi-phase motor winding.
3. The method according to claim 2, wherein in step S2, the controlling the auxiliary inverter compensates for the output reactive power, specifically:
and detecting a power angle of the main inverter, and based on the power angle, if the main inverter is judged not to be in a unit power factor state, controlling the resolution of an output voltage vector output by the auxiliary inverter along the direction vertical to the current of the motor end through a PI controller, and controlling the auxiliary inverter to compensate and output reactive power until the main inverter only outputs active power and is in the unit power factor state.
4. The method according to claim 3, wherein when the main inverter is in the unity power factor state, the resolution of the output voltage vector output by the auxiliary inverter along the direction perpendicular to the motor-side current is:
5. The method according to claim 1, wherein in S2, the implementation that the voltage change of the floating capacitor is controllable according to the actual operating condition is specifically:
controlling the auxiliary inverter to output voltage based on the active power and the reactive power after independent control, and when the ratio of the output voltage to the capacitor voltage set value is smaller than the minimum value of the preset modulation ratio range, controlling the auxiliary inverter to reduce the acquisition of the active power output from the main inverter through the multi-phase motor winding so as to reduce the real-time value of the capacitor voltage; and when the ratio is larger than the maximum value of the preset modulation ratio range, controlling the auxiliary inverter to increase the acquisition of the active power output from the main inverter through the multi-phase motor winding so as to increase the real-time value of the capacitor voltage and complete the change control of the suspended capacitor voltage of the auxiliary inverter.
6. The method as claimed in claim 5, wherein the preset modulation ratio is in a range of 0.85-0.95.
7. The method as claimed in claim 5, wherein the step of the real-time variation of the capacitor voltage is determined by a preset capacitor voltage regulation rate.
8. The method for controlling the multi-phase belt suspended capacitor motor drive topology according to any one of claims 1 to 7, wherein the step S1 further comprises:
based on PI control, a synchronous coordinate system with the rotation speed being multiple times of the fundamental wave is adopted to carry out harmonic suppression on the current at the motor end.
9. A multi-phase belt suspended capacitor motor drive topology system, comprising: the system comprises a controller, a power supply side main inverter, a suspension capacitor side auxiliary inverter and a multi-phase motor, wherein the power supply side main inverter, the suspension capacitor side auxiliary inverter and the multi-phase motor are respectively connected with the controller;
wherein the power supply side main inverter, the floating capacitor side auxiliary inverter and each phase of the multi-phase motor are connected in sequence, and the controller is used for executing the control method of the multi-phase motor driving topology with the floating capacitor as claimed in any one of claims 1 to 8.
10. A storage medium having stored therein instructions which, when read by a computer, cause the computer to execute a method of controlling a multi-phase band floating capacitor motor drive topology according to any of claims 1-8.
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| WO2022110277A1 (en) * | 2020-11-26 | 2022-06-02 | 江苏大学 | Model predictive decomposition control method and apparatus for open-winding five-phase permanent magnet synchronous motor |
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