KR100734467B1 - Sensorless control system of a switched reluctance motor using impressing of voltage pulse and method thereof - Google Patents

Abstract

 The sensorless control method of the SRM using the voltage pulse injection method according to the present invention, in the method for controlling the SRM without the use of a sensor using the voltage pulse injection method, each of the three phases A, B, C of the SRM Applying a high frequency voltage pulse to detect a current flowing in each phase, and calculating inductance of each phase based on the current; And estimating the position of the rotor of the SRM using the obtained inductance, and controlling the operation of the SRM by adjusting a voltage applied to each phase based on the estimated position of the rotor. In detecting the current flowing in each phase, the current of each phase passes through the filter, and the phase shift circuit compensates for the phase difference according to the phase delay of the current passing through the filter.

According to the present invention, by injecting a high-frequency voltage pulse having a low duty enough to not induce torque in the unexcited section of each phase of the SRM to measure the current of each phase, based on it to estimate the inductance of each phase, As in the prior art, the sensorless operation of the SRM is possible by flowing a current in the inductance rising section, which is the constant torque region of the SRM, without using a separate optical sensor.

Voltage pulse, SRM, sensorless, control

Description

Sensorless control system of a switched reluctance motor using a voltage pulse injection method and its method {Sensorless control system of a switched reluctance motor using impressing of voltage pulse and method

1 shows an equivalent circuit of the voltage equation for the power supply of the SRM when a small current flows.

2 is a diagram showing phase voltage and phase current waveforms when a pulse voltage is applied to an SRM for inductance calculation.

3 is a diagram showing an inductance profile and an inductance detection current waveform according to an electrical position angle of a rotor of an SRM.

4 is a view showing a principle of estimating inductance using a voltage pulse injection method.

5 is a view showing an actual optical sensor output waveform according to inductance.

6 is a view showing an experimental sensor output signal waveform according to the inductance.

7 is a view showing the basic principle of the sensorless control method of the SRM using the voltage pulse injection method according to the present invention.

8 is a view showing a comparison of the signal of the ssa signal and the optical sensor sa with respect to the sensorless control method of the SRM using the voltage pulse injection method according to the present invention.

9 is a view showing the overall system configuration of the sensorless control device of the SRM using the voltage pulse injection method according to the present invention.

10 is a view showing the internal circuit configuration of a phase shift circuit in the sensorless control device of the SRM using the voltage pulse injection method according to the present invention.

11 is a view showing the internal circuit configuration of the sensorless circuit in the sensorless control device of the SRM using the voltage pulse injection method according to the present invention.

<Explanation of symbols for the main parts of the drawings>

100.DC power supply 110.Converter

120 ... Filter 130 ... Phase shift circuit

131 ... Sawtooth generator circuit section 132,133 ... First and second subtractor circuit section

134 Comparators 135 Inverters

140 Sensor-less circuit 141 Clock signal generator

142 ... D-FF (D-Flip flop) 143 ...

The present invention relates to a sensorless control device and a method of a switched reluctance motor (hereinafter referred to as SRM) using a voltage pulse injection method, and in particular, does not cause torque in an unexcited section of each phase of the SRM. Injecting high-frequency voltage pulses with an unduly low duty to estimate the inductance profile of each phase, thereby allowing a sensorless operation by flowing a current through the inductance rising section, the constant torque region of SRM. The present invention relates to a sensorless control device of SRM and a method thereof.

Since the excitation time of the upper winding is determined according to the position of the rotor, the SRM requires accurate position information of the rotor. Expensive encoders and resolvers are commonly used to detect rotor position, but these position sensors have poor performance in harsh environments such as vibration, EMI, high temperature, and dust, resulting in poor reliability, increased motor volume, and expensive positioning. There is a problem of increasing the unit cost due to the sensor.

The present invention was created in view of the above-mentioned matters, and injecting high frequency voltage pulses having a low duty enough to not induce torque in an unexcited section of each phase of the SRM can estimate the inductance profile of each phase. Accordingly, an object of the present invention is to provide a method of a sensorless control device of the SRM using a voltage pulse injection method that enables sensorless operation by flowing a current in an inductance rising section, which is a constant torque region of the SRM.

In addition, another object of the present invention is to provide a sensorless control device and a method of the SRM using the voltage pulse injection method that can solve the phase delay problem in the conventional voltage pulse injection method and the initial driving problem in the conventional sensorless method. .

In order to achieve the above object, the SRM sensorless control apparatus using the voltage pulse injection method according to the present invention,

An apparatus for controlling SRM without using a sensor by using a voltage pulse injection method,

A converter for receiving a voltage from a DC power supply and outputting a three-phase AC voltage;

A filter for filtering a three-phase current output from the converter to the SRM;

A phase shift circuit for compensating the phase difference according to the phase delay of the three-phase current passed through the filter;

It is characterized in that it comprises a sensorless circuit that outputs a gate drive signal for controlling the SRM based on the three-phase current input through the phase transition circuit, and generates a clock signal for the initial driving of the SRM. have.

Here, as the filter, a low pass filter for passing a low pass portion of the input current frequency is used.

In addition, the sensorless control method of the SRM using the voltage pulse injection method according to the present invention to achieve the above object,

 In the method for controlling the SRM without using a sensor by using a voltage pulse injection method,

a) applying high frequency voltage pulses to each of A, B, and C three phases of the SRM, detecting current flowing through each phase, and obtaining inductance of each phase based thereon; And

b) controlling the operation of the SRM by estimating the position of the rotor of the SRM using the obtained inductance and adjusting the voltage applied to each phase based on the estimated position of the rotor. Has its features.

Here, preferably, in detecting the current flowing in each phase in step a), passing the current of each phase through a filter and compensating the phase difference according to the phase delay of the current through the filter by the phase transition circuit. It includes more.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Here, prior to the description of the embodiment of the present invention, the relationship between the inductance profile and the peak current in the SRM will be discussed first.

In the SRM, since an intermittent excitation power supply is sequentially applied to each phase winding due to the electromagnetic structure, there is always a phase in which phase current for torque generation does not conduct. Therefore, the inductance can be measured from the phase in which no phase current flows.

The phase inductance can be measured by applying a voltage to the phase in which the phase current does not flow and detecting the current. However, the back EMF cannot be ignored while the SRM is in operation, and the voltage drop due to the resistance cannot be ignored.

In particular, the phase current for inductance detection should not cause torque pulsation. To meet this limitation, the current for inductance measurement must be very small.

For this purpose, if a very narrow pulse voltage is applied and the phase current is detected at this time, the voltage drop and the counter electromotive force component may be ignored by the very small current, and may be simply viewed as an inductance. Therefore, if the phase current is very small in the SRM, the voltage equation of Equation 1 is simply expressed as Equation 2.

The electrical equivalent circuit of Equation 2 may be represented as shown in FIG. 1. To detect the inductance in the circuit of FIG. 1, the phase switch may be turned on and a current may be detected after a predetermined time and calculated.

2 is a diagram illustrating a phase current waveform when voltage is applied to the SRM for inductance calculation.

In FIG. 2, when the phase switch is turned off, a solution of the current may be expressed as Equation 3 below.

When the switch-on time is given from Equation 3 as shown in FIG. 2, the peak current at which the switch is turned off can be obtained from Equation 4 below, and the inductance can be obtained from Equation 5 from the peak current. .

In Equation 5, since the applied voltage and the switch-on time are fixed constant values, an inductance function as shown in Equation 6 can be finally obtained.

If the current value is correctly known to detect the inductance profile of the phase in which the phase current does not flow, the phase inductance of the SRM is simply calculated from Equation 6, and the position of the rotor can be estimated using this.

3 is a diagram showing an inductance profile (FIG. 3A) and an inductance detection current waveform (FIG. 3B) according to the electrical position angle of the rotor. As can be seen from Figure 3, it can be seen that the inductance profile and the current are inversely related to each other.

On the other hand, Figure 4 is a diagram showing the principle of estimating inductance using the voltage pulse injection method.

The phase current waveform can be obtained by applying a voltage pulse having a narrow duty not to induce torque in the non-excited section to the gate stage. The waveform after filtering can also be obtained by using a high pass filter and a low pass filter from the phase current.

As shown in FIG. 4, since the current waveform after filtering is inversely related to the inductance, the inductance can be estimated using the voltage pulse injection method, and as a result, the sensorless operation can be performed.

In the present invention, the inductance rising section detected using the sensorless method is compared with the inductance rising section known using the conventional optical sensor. In addition, by replacing the light sensor signal with a sensorless signal, it is possible to implement a sensorless control system. 5 and 6 are views showing the output waveform of the optical sensors sa, sb, sc according to the inductance.

In the present invention, in order to solve the phase delay problem, which is a problem of the voltage pulse method, a phase shift circuit is configured to accurately detect the inductance rising section, which is the constant torque generation region, from the initial driving to the high speed region.

By applying a voltage pulse to each phase, it is possible to obtain an ideal current waveform inversely related to the inductance as shown in FIG. However, if the ideal current waveform passes through the low pass filter, a phase delayed current waveform occurs.

In addition, the delayed current waveform can be compared with the reference voltage to obtain the ssa, ssb, and ssc signals, but since there are many differences from the inductance rising interval signal, an additional phase shift circuit is required to match them.

The delayed current waveform is almost identical to the ideal current waveform in the initial and low speed regions, but since the phase delay increases as the speed increases, it is necessary to advance the phase so that the SRM can be driven without generating negative torque.

In FIG. 8, the sa signal generated on the optical sensor A is compared with the current generated through the low pass filter and the reference voltage (Ref. Voltage). Therefore, a phase shift circuit was used to detect the inductance rise by matching the ssa signal with the optical sensor signal sa.

 9 is a view showing the overall system configuration of the sensorless control device of the SRM using the voltage pulse injection method according to the present invention.

9, the sensorless control device of the SRM using the voltage pulse injection method according to the present invention includes a converter 110, a filter 120, a phase shift circuit 130, and a sensorless circuit 140. It is configured to include.

The converter 110 receives a voltage from the DC power supply 100 and outputs a three-phase AC voltage. Such a converter 110 is composed of a series / parallel combination circuit of a plurality of semiconductor switching elements (eg, IGBTs).

The filter 120 filters three-phase currents Ia, Ib, and Ic output from the converter 110 and input to the SRM 200. As the filter 120, a low pass filter for passing a low pass portion of the input current frequency is used.

The phase shift circuit 130 compensates for the phase difference due to the phase delay of the three-phase currents Ia, Ib, and Ic passing through the filter 120. Here, as shown in FIG. 10, the phase shift circuit 130 receives a three-phase current (Ia, Ib, Ic) signal through the filter 120 and generates a sawtooth wave generator circuit unit ( 131, a first subtractor circuit section 132 that receives the output of the sawtooth generator circuit section 131 and outputs a sawtooth wave having a constant peak value, and a second subtractor circuit section 133 that outputs a reference voltage (Ref. Voltage); And a comparator 134 for comparing a sawtooth wave signal from the first subtracter circuit unit 132 with a reference voltage (Ref. Voltage) signal from the second subtractor circuit unit 133 and outputting a clock signal. Inverter 135 receives the output signal of the inverted polarity and outputs.

The sensorless circuit 140 outputs a gate driving signal for controlling the SRM 200 based on a three-phase current input through the phase transition circuit 130, and a clock for initial driving of the SRM 200. Generate a signal. As illustrated in FIG. 11, the sensorless circuit 140 includes a clock signal generator 141 including a combination of a plurality of AND gates and an OR gate, a clock signal from the clock signal generator 141, and the phase transition. Three D-FF (flop flops) 142 for receiving each phase current signal passed through the circuit 130 and outputting a result value (1 or 0) according to a logic operation, and any of three phases at the time of initial driving of the SRM. It consists of an initial drive switch 143 for generating a clock signal by forcibly exciting one phase (e.g., phase A).

Meanwhile, the ssa signal obtained by comparing the current generated through the low pass filter in FIG. 8 with the reference voltage (Ref. Voltage) may be utilized as an input of the f / V converter to obtain an output voltage proportional to the speed. In addition, this voltage is used as an input power source of the sawtooth generator circuit portion 131 of FIG. 10 to obtain a sawtooth wave voltage having a nearly constant peak value even when the speed changes, and is compared with the output voltage of the second subtractor circuit portion 133 to clock. You can make a signal.

Since the output voltage of the second subtractor circuit unit 133 decreases as the speed increases, it is possible to gradually advance the ON point of the clock signal. Even if the speed increases from the output of the D-FF (flop flop) 142 in FIG. 11, the delayed current waveform can be advanced in proportion to the speed as shown in FIG. Signals on phases B, C can be obtained.

In the sensorless circuit of Fig. 11, since a clock signal entering the clock terminal of the D-FF 142 cannot be produced initially, a separate initial driving mechanism is required. Therefore, when ssa, ssb, and ssc signals obtained by comparing the current generated through the low pass filter and the reference voltage (Ref. Voltage) are slightly overlapped with each other during initial operation, the D-FF 142 of each phase in the overlapped portion is set. The clock signal entering the clock terminal can be obtained.

However, since the clock signal does not occur until a portion where the phases overlap each other initially, in the present invention, the clock signal is generated by forcibly exciting the A phase by the initial drive switch 143.

As described above, the SRM sensorless control apparatus and method using the voltage pulse injection method according to the present invention is a high frequency voltage pulse having a low duty that does not cause torque in the unexcited section of each phase of the SRM It measures the current of each phase by injecting and estimates the inductance of each phase based on it. Therefore, even if a separate optical sensor is not used as in the prior art, the sensorless operation of the SRM is performed by flowing a current in the inductance rising section, which is the constant torque area of the SRM. There are possible advantages.

In addition, in order to solve the initial driving problem in the sensorless control method, an initial driving switch is provided in the sensorless circuit, and a clock signal is generated by forcibly exciting an arbitrary phase during the initial driving. There is an advantage that can solve the initial driving problem.

Claims (6)

An apparatus for controlling SRM without using a sensor by using a voltage pulse injection method. A converter for receiving a voltage from a DC power supply and outputting a three-phase AC voltage; A filter for filtering a three-phase current output from the converter to the SRM; A phase shift circuit for compensating the phase difference according to the phase delay of the three-phase current passed through the filter; And a sensorless circuit configured to output a gate driving signal for controlling the SRM based on a three-phase current input through the phase transition circuit, and generate a clock signal for initial driving of the SRM. Sensorless control device of SRM using pulse injection method. The method of claim 1, And the filter is a low pass filter for passing a low pass portion of an input current frequency. The method of claim 1, The phase shift circuit receives a three-phase current (Ia, Ib, Ic) signal passing through the filter to generate a sawtooth wave to generate a sawtooth wave, and the output of the sawtooth generator circuit unit 131 has a constant peak value A first subtractor circuit portion 132 for outputting a sawtooth wave, a second subtractor circuit portion 133 for outputting a reference voltage (Ref. Voltage), a sawtooth signal from the first subtractor circuit portion 132 and the second subtractor circuit portion; A comparator 134 for comparing a reference voltage (Ref. Voltage) signal from 133 and outputting a clock signal, and an inverter 135 for receiving an output signal of the comparator 134 and inverting its polarity to output the clock signal. Sensorless control device of SRM using a voltage pulse injection method. The method of claim 1, The sensorless circuit inputs a clock signal generator 141 including a combination of a plurality of AND gates and an OR gate, a clock signal from the clock signal generator 141, and each phase current signal that has passed through the phase transition circuit 130. 3 D-FF (flop flops) 142 that receive the result (1 or 0) according to the logical operation and any one of three phases (e.g., A phase) during initial operation of the SRM. SRM sensorless control device using a voltage pulse injection method, characterized in that consisting of an initial drive switch (143) for generating a clock signal by excitation.  In the method for controlling the SRM without using a sensor by using a voltage pulse injection method, a) applying high frequency voltage pulses to each of A, B, and C three phases of the SRM, detecting current flowing through each phase, and obtaining inductance of each phase based thereon; And b) estimating the position of the rotor of the SRM using the obtained inductance, and controlling the operation of the SRM by adjusting the voltage applied to each phase based on the estimated rotor position. Sensorless control method of SRM using voltage pulse injection method. The method of claim 5, In detecting the current flowing in each phase in the step a), passing the current of each phase through the filter, and further comprises the step of compensating the phase difference according to the phase delay of the current through the filter by the phase transition circuit Sensorless control method of SRM using voltage pulse injection method.

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