CN105811848B - A kind of switched reluctance machines gain scheduling PI control method - Google Patents

Abstract

A kind of switched reluctance machines gain scheduling PI control method is to gather DC bus-bar voltage by Hall voltage sensor, and combines main circuit form calculus winding terminal voltage；By position sensor detection switch magnetic resistance motor rotor position signal, motor actual speed is calculated according to motor rotor position angle change in the set time；The proportionality coefficient and integration time constant of PI controllers are calculated according to winding terminal voltage and motor actual speed；The input of PI controllers is speed discrepancy, is exported as reference current or PWM duty cycle, and then controls power inverter, provides electric energy from power inverter to switched reluctance machines, controls motor speed.This method makes switched reluctance machines have good dynamic property and steady-state characteristic under different given rotating speeds, the dynamic Immunity Performance of system is improved while realizing quick, smooth step response, control method is simple and reliable, versatile, is easy to commercial introduction.

Description

A variable gain PI control method for switched reluctance motor

technical field

The invention relates to a control method of a switched reluctance motor, in particular to a variable gain PI control method of a switched reluctance motor based on online parameter identification.

Background technique

The switched reluctance motor has the characteristics of simple structure, low price, large starting torque, and high efficiency, which makes the switched reluctance motor speed control system very suitable for transmission control fields such as textiles, electric vehicles, and mining. An appropriate control strategy is the basis for achieving good performance of switched reluctance motors. The speed control system of switched reluctance motors is a highly nonlinear system. Traditional linear control strategies are not suitable for switched reluctance motors. There are many studies on the strategy, and some nonlinear control strategies such as intelligent control are applied to the switched reluctance motor, and certain control effects have been achieved.

Although the nonlinear control strategy can improve the control effect, the control method is complicated and the implementation cost is high, which is not conducive to the promotion and application of the switched reluctance motor in the field of high-performance electric transmission. At present, more mature systems at home and abroad still use traditional PI controllers, and use the speed and current double closed-loop PI for parameter setting to realize the control of switched reluctance motors. However, there are some problems in the traditional linear PI controller, such as large step response overshoot, difficulty in tuning control parameters, fixed parameters do not change during the entire control process, or are adjustable in sections. The structure and parameters of the switched reluctance motor model change under different control modes. The traditional PI controller cannot correct the control parameters in real time and continuously, and it is difficult to ensure that the switched reluctance motor speed control system has good performance in the entire speed range. control effect, especially in the process of dynamic change.

Contents of the invention

Aiming at the defects of the above-mentioned prior art, the present invention provides a variable gain PI control method for switched reluctance motors to realize adaptive adjustment of PI parameters at different speeds, solve the problem of step response overshoot and improve the dynamic immunity of the system at the same time performance.

In order to achieve the above technical purpose, the technical solution of the present invention is as follows.

(1) The DC bus voltage is collected by the Hall voltage sensor, and the winding terminal voltage is calculated in combination with the main circuit form;

(2) The rotor position signal of the switched reluctance motor is detected by the position sensor, and the

The actual speed of the motor is calculated by the change of the sub-position angle;

(3) Calculate the proportional coefficient and integral time constant of the PI controller according to the winding terminal voltage and the actual speed of the motor;

(4) The input of the PI controller is the speed difference, and the output is the reference current or PWM duty cycle, and then controls the power converter, which provides electric energy to the switched reluctance motor to control the motor speed.

In the above technical solution, further additional technical features are as follows.

The proportional coefficient of the PI controller is calculated according to the following formula:

in:

Kc is _the proportional coefficient of the PI controller;

is the winding terminal voltage, which is calculated according to the form of the main circuit and the collected DC bus voltage;

It is the actual speed of the motor, which is sent to the capture of the microprocessor according to the rotor position signal detected by the position sensor.

obtained by calculating the unit;

K1 is _the proportional correction coefficient, which is adjusted according to the experimental results.

The integral time constant is calculated according to the following formula:

in:

T _i is the integral time constant;

is the winding terminal voltage, which is calculated according to the form of the main circuit and the collected DC bus voltage;

It is the actual speed of the motor, which is sent to the microprocessor according to the rotor position signal detected by the position sensor.

The capture unit calculates;

K2 is _the integral correction coefficient, which is adjusted according to the experimental results.

The input of the PI controller is the speed difference, and the speed difference is the error between the given speed and the actual speed of the motor.

The given rotational speed is set through an operation panel, an external communication device or an external analog port.

The actual rotational speed is calculated by the capture unit sent to the microprocessor according to the rotor position signal detected by the position sensor.

The output is the reference current or the PWM duty cycle is determined by the actual rotation speed of the motor.

Using the above technical scheme to realize a variable gain PI control method for switched reluctance motors, while solving the step response overshoot problem, it also realizes the adaptive adjustment of PI parameters at different speeds. Compared with the prior art, this method has The switched reluctance motor has good dynamic performance and steady-state characteristics at different given speeds, and while realizing a fast and smooth step response, it further improves the dynamic anti-disturbance performance of the system, and the control method is simple, reliable and universal Strong and easy for industrial promotion.

Description of drawings

FIG. 1 is a flowchart of the PI control method.

Fig. 2 is a specific embodiment of the PI control method, the relative position relationship diagram of the three-phase 12/8-pole switched reluctance motor stator, rotor, photoelectric code disc and photoelectric generator.

Fig. 3 is a specific embodiment of the PI control method, a structural block diagram of the switched reluctance motor speed regulation system.

Fig. 4 is the measured rotational speed curve of the existing PI controller and this method when the step setting is 500r/min and no-load starting.

Fig. 5 is the measured speed curve of the existing PI controller and the method when the step setting is 1500r/min and no-load starting.

Fig. 6 is the measured rotational speed curve of the existing PI controller and this method when the load is suddenly added in a steady state of 1500r/min.

Detailed ways

The specific implementation manners of the present invention are further described below.

FIG. 1 is a flow chart of a variable gain PI control method according to an embodiment of the present invention. As shown in the figure, the variable gain PI control method of this embodiment includes the following steps:

Step 1, collect the DC bus voltage through the Hall voltage sensor, and calculate the winding terminal voltage in combination with the main circuit form;

Step 2, detect the rotor position signal of the switched reluctance motor through the position sensor, according to the fixed time

The actual speed of the motor is calculated by the change of the rotor position angle;

Step 3, calculating the proportional coefficient and integral time constant of the PI controller according to the winding terminal voltage and the actual rotational speed of the motor;

Step 4, the input of the PI controller is the speed difference, and the output is the reference current or PWM duty cycle, and then controls the power converter, and the power converter supplies electric energy to the switched reluctance motor to control the motor speed.

In step 1 of this embodiment, a three-phase 12/8-pole switched reluctance motor is taken as a specific embodiment, through

The DC bus voltage is collected by the Hall voltage sensor. The main circuit adopts a three-phase asymmetric half-bridge type. Effectively, the entire power supply voltage can be used to control the phase winding current, and the winding terminal voltage is the DC bus voltage.

In step 2 of this embodiment, a three-phase 12/8-pole switched reluctance motor is used as a specific example. The rotor teeth of the motor are 16°, the slots are 29°, and the number of photoelectric code discs and rotor slots is the same and evenly distributed. The angle between adjacent photoelectric pulse generators is 15°, so when the A-phase winding in the three-phase winding is aligned with the rotor teeth, the relative positional relationship of the motor stator, rotor, photoelectric code disc and photoelectric generator is shown in Figure 2 .

In Figure 2, when the motor rotates counterclockwise or clockwise, the photoelectric code disc coaxial with the rotor will block or transmit the infrared light emitted by the photoelectric generator O, P, Q, and the position signal of the motor will follow change. In the hardware circuit, a position signal is connected to the DSP capture pin, and the capture interrupt is set in the program to capture two edges, so every time 22.5° passes through, a capture interrupt will be entered, and this angle is divided by the time required for the rotor to turn 22.5° Time can get the actual speed of the motor.

In step three of this embodiment, the proportional coefficient and the integral time constant of the PI controller are calculated according to the winding terminal voltage and the actual rotational speed of the motor, specifically involving the design of the variable gain PI controller as follows:

The expressions of variable gain PI controller proportional coefficient K _c , integral time constant T _i , winding terminal voltage and motor actual speed are taken as:

(1)

(2)

In the formula: is the actual speed of the motor; Is the winding terminal voltage; K ₁ is the proportional correction coefficient; K ₂ is the integral correction coefficient. For specific switched reluctance motors and their applications, K ₁ and K ₂ need to be adjusted and obtained through experiments.

The above variable gain PI controller design is based on the following principles:

Taking the one-phase winding as the analysis object, the voltage equation of the k -th phase winding of the switched reluctance motor is:

(3)

Where: u _k is the voltage of the kth phase; i _k is the current of the kth phase; R _k is the resistance of the kth phase; Ψ _k is the flux linkage of the kth phase.

Assuming that the phases of the motor are symmetrical, the inductance between the phases is ignored, and the inductance of the phase winding has nothing to do with the current, the simplified linear model of the switched reluctance motor can be obtained:

(4)

(5)

Where: L _k is the winding inductance of the kth phase.

Under the simplified linear model, the relationship between phase inductance and rotor position change can be expressed as: .

Where: Ψ _s is the saturation flux linkage; N _r is the number of rotor poles.

The mechanical motion equation of the rotor under the action of the electromagnetic torque T of the motor and the load torque T _L :

(6)

Where: ω is the angular velocity of the rotor; J is the moment of inertia of the motor rotor and the load. According to formula (3) and formula (5), the expression can be obtained:

(7)

Substituting the simplified torque model and inductance model into the mechanical motion equation, the speed change rate can be obtained as:

(8)

Substituting the simplified inductance model into formula (7), the change rate of the phase winding current is obtained as:

(9)

The resistance voltage drop is much smaller than the control voltage, so the resistance voltage drop can be ignored; due to the large mechanical inertia of the switched reluctance motor, the dynamic response speed of the current is much faster than that of the mechanical state variable. After the excitation phase winding is energized, the current quickly reaches a steady state. The expression of the phase winding current after steady state is:

(10)

In the formula: The average value during the excitation phase of the phase winding.

Substitute formula (10) into formula (8) to get formula (11);

(11)

Let f represent the speed change rate, which is at the motor speed and winding terminal voltage The small-signal linearization equation near the two operating points is:

;in:

;

The small-signal linearization equation of the speed change rate after reaching the steady state can be expressed as: , according to which the steady-state speed can be obtained .

The obtained steady-state speed substitute , further derivation can be obtained

,

Then substitute the obtained two formulas into

The linearized equation can be expressed as:

(12)

The small signal of the rotor angular velocity can be obtained by performing Laplace transform on both sides of the equation (12) small signal with control voltage Ratio.

(13)

In the formula: .

Equation (13) is the first-order model transfer function of the small signal in the s-domain of the speed loop under the simplified model of the motor.

The PI controller is a necessary part of the SRM speed control system, and its transfer function is:

(14)

Where: K _c is the proportional coefficient; T _i is the integral time constant.

Equation (13) is the approximate small-signal dynamic model of SRD, which is a first-order inertia link, and the PI controller is a part of the SRD system, so the proportional coefficient K _c and the integral time constant T _i should be related to the system parameters K _p , T _p is a function relationship, combined with the SRD first-order approximate model and the transfer function of the PI controller, the relationship between the proportional coefficient K _c of the variable gain PI controller, the integral time constant T _i and the winding terminal voltage and the actual speed of the motor are shown in formula (1) And formula (2) shown.

In step 4 of this embodiment, the current chopper control mode is used to limit the current of each phase when the motor is running at low speed, and the output of the PI controller is the reference current; when the motor is running at a high speed, the voltage PWM control mode is used to adjust the average voltage at both ends of the phase winding. Voltage, the output of the PI controller is the PWM duty cycle; the high and low speed range is determined by the speed range of the specific motor, and adjusted according to the experimental results; at the intersection of the two control methods, the hysteresis mode is used to switch, and the size of the hysteresis It is determined by the speed range of the specific motor and adjusted according to the experimental results. Taking a three-phase 12/8-pole switched reluctance motor as a specific example, the rated speed of the motor is 1500r/min, and the speed range is 50~2000r/min. When the motor speed is less than 900r/min, the current chopping control method is adopted. When the motor When the speed is greater than 1000r/min, the voltage PWM control method is adopted. When the motor speed is 900r/min~1000r/min, the previous control method is adopted.

Example 1

A variable gain PI control method for switched reluctance motors provided by the present invention is applicable to all types of switched reluctance motors, and the application in a three-phase 12/8-pole switched reluctance motor speed control system is taken as an example.

The structural block diagram of the switched reluctance motor speed control system of the present invention is shown in Fig. 3. The speed control system includes a DSP controller, a current detection module, a position detection module, a power conversion module and a switched reluctance motor. Wherein, the inside of the dotted box is the DSP controller part, and its internal functions are all realized by software programming, and the control algorithm adopts the variable gain PI control of the present invention. The current detection module collects the current signal of the three-phase winding and uses it for current chopper control mode and overcurrent protection after A/D conversion; the position detection module detects the rotor position signal to determine the commutation, and is also used to calculate the motor speed; the given speed and The actual speed value enters the variable gain PI controller of the present invention, and after PI adjustment is performed on the speed difference, the DSP outputs a reference current or a PWM duty ratio to control the power converter, and the power converter provides electric energy to the switched reluctance motor, and finally controls the motor Rotating speed.

The rated power of the motor is 7.5kW, the rated voltage is DC514V, the rated speed is 1500r/min, and the speed range is 50~2000r/min.

In the actual control of the switched reluctance motor, the motor is required to have good performance at different speeds, and the winding terminal voltage remains unchanged, so the PI parameters only need to be adaptively adjusted according to the actual speed of the motor.

The dynamic performance of the switched reluctance motor under the present invention and the traditional PI controller is tested, and the data is collected and fitted into a curve. The measured rotational speed curves of the traditional PI controller and the present invention are shown in Fig. 4 and Fig. 5 respectively when the step setting is 500r/min and 1500r/min and the no-load starts. In Fig. 4, using the traditional PI controller, the speed overshoot is 4.5%, and reaches a steady state after two oscillation cycles of 14s; using the variable gain PI control method of the present invention, the speed overshoot is 1%, and can quickly reach a steady state . In Fig. 5, the traditional PI controller is adopted, since the PI parameter is fixed, the speed overshoot is 3.5%, and the oscillation cycle becomes longer; the variable gain PI control method of the present invention is adopted, and the PI parameter can be adaptively adjusted according to the actual speed, and the overshoot Reduced to 0.5%, and quickly reached a steady state.

The actual speed curves of the traditional PI controller and the present invention when the load is suddenly added at 1500r/min steady state are shown in Figure 6. In Figure 6, the traditional PI controller is adopted, and after a sudden load of 10N, the speed drops to 200r/min. It returns to the steady state after 30s; adopts the variable gain PI control method of the present invention, the speed drops to 30r/min, and returns to the steady state after 8s.

Claims (5)

1. a kind of switched reluctance machines gain scheduling PI control method, the control method follows these steps to carry out：

（1）DC bus-bar voltage is gathered by Hall voltage sensor, and combines main circuit form calculus winding terminal voltage；

（2）By position sensor detection switch magnetic resistance motor rotor position signal, turn according in the set time

Sub- position angle change calculates motor actual speed；

（3）The proportionality coefficient and integration time constant of PI controllers are calculated according to winding terminal voltage and motor actual speed；

（4）The input of PI controllers is speed discrepancy, is exported as reference current or PWM duty cycle, and then controls power inverter, Electric energy is provided from power inverter to switched reluctance machines, controls motor speed；

The proportionality coefficient of the PI controllers is calculated by following equation：

Wherein：K _c It is the proportionality coefficient of PI controllers；It is winding terminal voltage, it is female according to main circuit form and the direct current of collection Line voltage is calculated；It is motor actual speed, the rotor-position signal detected according to position sensor is sent into microprocessor Capturing unit be calculated；K ₁ It is ratio correction coefficient, is adjusted according to experimental result；

The integration time constant is calculated according to following equation：

Wherein：T _i It is integration time constant；It is winding terminal voltage, according to main circuit form and the DC bus-bar voltage meter of collection Obtain；It is motor actual speed, the rotor-position signal detected according to position sensor is sent into the capture list of microprocessor Member is calculated； K ₂ It is integration correction factor, is adjusted according to experimental result.

2. control method as claimed in claim 1, inputting as the speed discrepancy of speed discrepancy for the PI controllers is that motor gives Rotating speed and actual speed error.

3. control method as claimed in claim 2, the given rotating speed is by operation panel, external communications equipment or outer Portion's analog port setting.

4. control method as claimed in claim 1, the actual speed is that the rotor-position detected according to position sensor is believed The capturing unit of number feeding microprocessor is calculated.

5. control method as claimed in claim 1, the output for reference current or PWM duty cycle is turned by motor is actual Quick decision is determined.