TWI578677B - Power conversion device and control method thereof - Google Patents

Description

Power conversion device and control method thereof

The present invention relates to a power conversion device and a control method thereof, and more particularly to a power conversion device having an adaptive harmonic injection mechanism and a control method thereof.

According to the technical field of converting AC power into DC power (AC/DC), in order to correct the power factor, the single-switch three-phase power factor correction circuit is a commonly used power conversion circuit, but the single-switch three-phase power factor The correction circuit operates in Discontinuous Conduction Mode (DCM). Therefore, as shown in FIG. 1A and FIG. 1B, the input current of the AC power input single-switch three-phase power factor correction circuit has a higher fifth harmonic. The wave (frequency 300Hz) component causes severe distortion of the input current.

In order to improve the input current distortion phenomenon, a technique for reducing the fifth harmonic of the input current by using a harmonic injection mechanism is proposed, which generates a harmonic signal according to the input voltage of the input single-switch three-phase power factor correction circuit. The switching conduction ratio of the power factor correction circuit is modulated, thereby reducing the fifth harmonic component of the input current, and the distortion of the input current is reduced, and the relationship is as shown in the following formula (1). In addition, the duty cycle of the switch can be modulated as shown in equation (2).

D _mod ( t ) = D . [1+ V _inj ( t )]---------(2)

Where V _inj (t) is the sixth harmonic signal of the modulation switch conduction rate, D is the duty cycle before modulation, D _mod (t) is the duty cycle after modulation, and m is the modulation coefficient, which is equal to The ratio of peak-to-peak to a feedback signal for V _inj (t). The fifth harmonic of the input current can be reduced by the harmonic injection mechanism, thereby improving the input current distortion.

However, the above harmonic injection mechanism is to inject a fixed sixth harmonic signal, that is, the modulation coefficient m is a fixed value, which cannot effectively improve the operation of the single-switch three-phase power factor correction circuit at different voltage conversion ratios (voltage conversion ratio). The fifth harmonic distortion is equal to the ratio of the output voltage to the input line voltage. In other words, as shown in FIG. 1C, it is a theoretical waveform diagram of the average value of the input inductor current under the different voltage conversion ratio M of the single-switch three-phase boost type power factor correction circuit.

As can be seen from FIG. 1C, when the ratio of the voltage conversion ratio M is higher (for example, M=3), the closer the input average current waveform is to the sine wave, the smaller the distortion is, and the lower the fifth harmonic component is; however, When the ratio of the voltage conversion ratio to M is lower (for example, M=1.2), it is found that the larger the difference between the input average current waveform and the sine wave, that is, the larger the distortion, the higher the composition of the fifth harmonic.

Therefore, how to provide a power conversion device and a control method thereof can effectively reduce the distortion phenomenon of the input current under different voltage conversion ratios, thereby improving the power factor, and has become one of important topics.

The object of the present invention is to provide a power conversion device capable of effectively reducing the distortion of an input current at different voltage conversion ratios to improve the power factor and a control method thereof.

To achieve the above objective, a power conversion device according to the present invention is coupled to an AC power source, and the AC power source outputs an AC signal. The power conversion device includes an AC/DC conversion circuit, a feedforward circuit, and a harmonic control circuit. The AC/DC conversion circuit receives the AC signal and outputs an output voltage signal, and the AC/DC conversion circuit has a switching element. The feedforward circuit is coupled to the AC power source and the AC/DC converter circuit, and the feedforward circuit receives the AC signal and outputs a feedforward signal. The harmonic control circuit is coupled to the feedforward circuit and the AC/DC conversion circuit, respectively, and the harmonic control circuit comprises a feedback circuit, a detection circuit, an operation circuit and a pulse width modulation circuit. The feedback circuit receives the output voltage signal and outputs a feedback signal. The detecting circuit receives the output voltage signal and outputs a modulation control signal according to the voltage value of the output voltage signal. The arithmetic circuit receives the feedforward signal and Modulate the control signal and output a harmonic modulation signal. The pulse width modulation circuit outputs a switch control signal to control the switching element according to the harmonic modulation signal and the feedback signal to adjust the conduction ratio of the switching element according to the voltage value of the output voltage signal.

In one embodiment, the AC to DC conversion circuit is a three phase single switching boost converter.

In one embodiment, the feedforward circuit includes a voltage sensing unit, a high pass filtering unit, and a non-inverting amplifying unit. The voltage sensing unit senses the alternating current signal and outputs a gain signal, and the high pass filtering unit receives and filters the gain. The noise of the signal outputs a first filtered signal, and the non-inverting amplifying unit receives the first filtered signal and outputs a feedforward signal.

In one embodiment, the feedforward signal has a frequency that is six times the frequency of the alternating signal.

In one embodiment, the feedback circuit has a first voltage dividing unit and an error amplifying unit. The first voltage dividing unit divides the output voltage signal and outputs a first voltage dividing signal, and the first voltage dividing signal input error is amplified. At the negative end of one of the error amplifiers, a first reference voltage is input to the positive terminal of the error amplifier, and the output of the error amplifier outputs a feedback signal.

In one embodiment, the detecting circuit has a second voltage dividing unit, a low pass filtering unit and a subtracting unit, and the second voltage dividing unit divides the output voltage signal and outputs a second voltage dividing signal, low pass The filtering unit filters out the noise of the second voltage dividing signal and outputs a second filtering signal, the second filtering signal is input to the negative terminal of one of the subtracting units, the second reference voltage is input to the positive terminal of the subtractor, and the subtractor The output of the output outputs a modulation control signal.

In one embodiment, the arithmetic circuit multiplies the feedforward signal by the modulation control signal to obtain a harmonic modulation signal.

In an embodiment, the harmonic modulation signal changes according to the magnitude of the voltage value of the output voltage signal.

In an embodiment, the harmonic modulation signal is added to the feedback signal and then input to the pulse width modulation circuit.

In order to achieve the above object, in accordance with a control method of a power conversion device of the present invention, the power conversion device is coupled to an AC power source, and the AC power source outputs an AC signal. The power conversion device includes an AC/DC conversion circuit, a feedforward circuit, and a The harmonic control circuit, the harmonic control circuit comprises a feedback circuit, a detection circuit, an operation circuit and a pulse width modulation circuit, and the control The method includes: receiving an alternating current signal by an AC/DC converting circuit and outputting an output voltage signal, wherein the AC/DC converting circuit has a switching component; receiving an AC signal by the feedforward circuit and outputting a feedforward signal; and receiving the output voltage signal by the feedback circuit And outputting a feedback signal; the detection circuit receives the output voltage signal, and outputs a modulation control signal according to the voltage value of the output voltage signal; the operation circuit receives the feedforward signal and the modulation control signal, and outputs a harmonic modulation The signal is controlled by the pulse width modulation circuit according to the harmonic modulation signal and the feedback signal outputting a switch control signal to adjust the conduction ratio of the switching element according to the voltage value of the output voltage signal.

In an embodiment, in the step of outputting the feedforward signal by the feedforward circuit, the feedforward circuit includes a voltage sensing unit, a high pass filtering unit, and a non-inverting amplifying unit, and the control method further includes: sensing by voltage The unit receives the AC signal and outputs a gain signal; the high-pass filter unit receives and filters out the noise of the gain signal and outputs a first filtered signal; and the non-inverting amplifying unit receives the first filtered signal and outputs a feedforward signal.

In an embodiment, in the step of outputting the feedforward signal by the feedforward circuit, the frequency of the feedforward signal is six times that of the alternating current signal.

In an embodiment, in the step of outputting the feedback signal by the feedback circuit, the feedback circuit has a first voltage dividing unit and an error amplifying unit, and the control method further comprises: dividing the output voltage signal by the first voltage dividing unit. And outputting a first voltage dividing signal; and receiving, by the error amplifying unit, the first voltage dividing signal and a first reference voltage, and outputting a feedback signal, wherein the first voltage dividing signal is input to the negative end of the error amplifier of one of the error amplifying units, The first reference voltage is input to the positive terminal of the error amplifier, and the output of the error amplifier outputs a feedback signal.

In an embodiment, in the step of the detecting circuit outputting the modulation control signal, the detecting circuit has a second voltage dividing unit, a low-pass filtering unit and a subtracting unit, and the control method further comprises: The voltage unit divides the output voltage signal and outputs a second voltage dividing signal; the low pass filtering unit filters out the noise of the second voltage dividing signal and outputs a second filtering signal; and the subtracting unit receives the second filtering signal And a second reference voltage, and outputting the modulation control signal, wherein the second filter signal is input to the negative terminal of one of the subtraction units, the second reference voltage is input to the positive terminal of the subtractor, and the output of the subtractor is modulated. Control signal.

In an embodiment, in the step of outputting the harmonic modulation signal by the operation circuit, the operation circuit multiplies the feedforward signal by the modulation control signal to obtain a harmonic modulation signal.

According to the power conversion device and the control method thereof, the feedback circuit receives the output voltage signal and outputs a feedback signal, and the detection circuit receives the output voltage signal, and outputs the modulation control signal according to the voltage value of the output voltage signal. The arithmetic circuit receives the feedforward signal and the modulation control signal, and outputs a harmonic modulation signal, and the pulse width modulation circuit controls the switching element according to the harmonic modulation signal and the feedback signal output switch control signal, according to the output voltage signal The voltage value modulates the conduction ratio of the switching element. Thereby, the power conversion device and the control method thereof of the present invention can effectively improve the input current distortion phenomenon under different voltage conversion ratios compared with the conventional techniques of the harmonic injection mechanism and the fixed harmonic injection mechanism. And improve the power factor.

1‧‧‧Power conversion device

11‧‧‧ AC and DC conversion circuit

2‧‧‧AC power supply

3‧‧‧Feedback circuit

31‧‧‧Voltage sensing unit

311‧‧‧ Full Bridge Rectifier

312‧‧‧Inverting amplifier

32‧‧‧High-pass filter unit

33‧‧‧Non-inverting amplification unit

331‧‧‧Non-inverting amplifier

4‧‧‧Harmonic control circuit

41‧‧‧Feedback circuit

411‧‧‧First partial pressure unit

412‧‧‧Error Amplification Unit

4121‧‧‧Error amplifier

42‧‧‧Detection circuit

421‧‧‧Second pressure division unit

422‧‧‧Low Pass Filter Unit

4221‧‧‧Voltage follower

423‧‧‧subtraction unit

4231‧‧‧Subtractor

43‧‧‧Operating circuit

44‧‧‧ Pulse width modulation circuit

5‧‧‧EMI filter

A‧‧‧Amp

C _h , C _h1 , C _h2 , C _k1 , C _o ‧‧‧ capacitor

CS‧‧‧Switch control signal

D, D ₁ ~ D ₆ , D _ap , D _an , D _bp , D _bn , D _cp , D _cn ‧ ‧ diode

L‧‧‧load

L _a , L _b , L _c ‧‧‧ inductance

M‧‧‧ voltage conversion ratio

R _a ~ R _d , R _D1 ~ R _D4 , R _f1 ~ R _f4 , R _h , R _h1 , R _h2 , R _k1 , R _s , Z _h1 , Z _h2 ‧ ‧ resistance

S‧‧‧Switching elements

S01~S06‧‧‧Steps

t‧‧‧Time

V‧‧ volts

V _A , V _B , V _C ‧‧‧ exchange signals

V _ab , V _bc , V _ca ‧ ‧ line voltage signal

V _aut ‧‧‧ harmonic modulation signal

V _c ‧‧‧ modulation control signal

V _d1 ‧‧‧ first partial pressure signal

V _d2 ‧‧‧second partial pressure signal

V _e ‧‧‧ feedback signal

V _f ‧‧‧ Gain signal

V _h ‧‧‧first filter signal

V _inj ‧‧‧Feedback signal

V _l ‧‧‧Second filter signal

V _o ‧‧‧ output voltage signal

V _r ‧‧‧6 times frequency signal

V _ref1 ‧‧‧first reference voltage

V _ref2 ‧‧‧second reference voltage

1A and 1B are respectively schematic diagrams of input voltage, input current and input current spectrum of a conventional single-switch three-phase power factor correction circuit.

FIG. 1C is a schematic diagram showing the theoretical waveform of the average value of the input inductor current under a different voltage conversion ratio of a single-switch three-phase boost type power factor correction circuit.

2A is a schematic diagram of a power conversion device according to a preferred embodiment of the present invention.

2B is a circuit diagram of a feedforward circuit of the power conversion device of FIG. 2A.

2C is a schematic diagram of related signal waveforms of the feed circuit of FIG. 2B.

2D is a circuit diagram of a feedback circuit of the harmonic control circuit of FIG. 2A.

2E is a circuit diagram of the detection circuit of the harmonic control circuit of FIG. 2A.

FIG. 3 is a schematic diagram showing the relationship between the input current total harmonic distortion rate and the different voltage conversion ratios of the prior art and the adaptive harmonic injection mechanism of the present invention.

4A to 4H are respectively schematic diagrams of input voltage, input current and input current spectrum at different voltage conversion ratios of the present invention.

FIG. 5 is a schematic diagram showing the flow of a control method of a power conversion device according to a preferred embodiment of the present invention.

Hereinafter, a power conversion device and a control method thereof according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings, wherein the same elements will be described with the same reference numerals.

Please refer to FIG. 2A, which is a schematic diagram of a power conversion device 1 according to a preferred embodiment of the present invention.

The power conversion device 1 of the present embodiment is coupled to an AC power source 2. The AC power source 2 can output an AC signal. Here, the AC signal output by the AC power source 2 is a three-phase AC voltage signal (indicated by V _A , V _B , V _C ). The AC power source 2 of the present embodiment generates three-phase AC signals V _A , V _B , and V _C for EMI filtering (by an EMI filter 5 ) and then input to the power conversion device 1 . Therefore, the three-phase power factor correction of the AC signals V _A , V _B , and V _C can be realized, and the distortion of the input current can be reduced. In one embodiment, the alternating current signals V _A , V _B , V _{C are,} for example but not limited to, three-phase 110 volts (V).

The power conversion device 1 includes an AC/DC conversion circuit 11, a feedforward circuit 3, and a harmonic control circuit 4, which are coupled to the feedforward circuit 3 and the AC/DC conversion circuit 11, respectively.

The AC/DC conversion circuit 11 converts the AC signals V _A , V _B , and V _C and outputs an output voltage signal V _o to a load L. The AC/DC conversion circuit 11 is an AC/DC converter, so that the output voltage signal V _o is a DC voltage. In the present embodiment, the AC/DC conversion circuit 11 is a three-phase single-switch boost converter and operates in discontinuous conduction mode (CCM). Since the AC signals V _A , V _B , and V _C output from the AC power source 2 are three-phase, the AC-DC conversion circuit 11 is also a three-phase circuit. However, the AC-DC conversion circuit 11 has only one switching element S, so it is a three-phase. The single-switch boost converter has the advantages of low component count, low cost, and simple control. By controlling the conduction ratio of the switching element S, the output voltage signal V _o supplied to the load L can be controlled.

The AC/DC conversion circuit 11 of the present embodiment has three inductors L _a , L _b , L _c , seven diodes D _ap , D _an , D _bp , D _bn , D _cp , D _cn , D and a capacitor C _o . Wherein, the diodes D _ap , D _an , D _bp , D _bn , D _cp , D _cn constitute a full-wave rectifier, and the full-wave rectifier is respectively connected by the inductances L _a , L _b , L _c and three phases AC power supply 2 is electrically connected. In addition, two ends of the capacitor C _o are electrically connected to one end of the diode D and one ground end, and are connected across the two ends of the load L, and the two ends of the switching element S are respectively connected to the other end of the diode D. And ground. In one embodiment, the capacitance values of the inductors L _a , L _b , and L _c are 50 μH, and the component types of the diodes D _ap , D _an , D _bp , D _bn , D _cp , D _cn , and D are FCF06A60, switches The component type of component S is IRFP27N60K, and the capacitance of capacitor C _o is 220μF. Since the operating principle of the three-phase single-switch boost converter is a conventional technique, it will not be described here.

2B and FIG. 2C, FIG. 2B is a circuit diagram of the feedforward circuit 3 of the power conversion device 1 of FIG. 2A, and FIG. 2C is a schematic diagram of related signal waveforms of the feedforward circuit 3 of FIG.

The feedforward circuit 3 is coupled to the AC power source 2 and the AC/DC converter circuit 11, respectively, and the feedforward circuit 3 can receive the AC signals V _A , V _B , V _C and output a feedforward signal V _inj . As shown in FIG. 2B, the feedforward circuit 3 includes a voltage sensing unit 31, a high pass filtering unit 32, and a non-inverting amplifying unit 33.

The voltage sensing unit 31 receives the AC signals V _A , V _B , V _C and outputs a gain signal V _f . Here, the voltage sensing unit 31 includes a full bridge rectifier 311 (including six diodes D ₁ to D ₆ ), eight resistors (including two resistors R _a , one resistor R _b , two resistors R _{c )} 2 resistors R _d , 1 resistor R _s ) and an inverting amplifier 312. The full-bridge rectifier 311 is respectively connected to the two ends of the three-phase AC signals V _A , V _B , V _C and the resistor R _s and the two resistors R _a , and the two ends of the resistor R _b and the two resistors R _a respectively the other end is connected, and are respectively connected to one end of two resistors R _c, R _c the other end of the second resistor are respectively connected to the negative terminal and the positive terminal of the inverting amplifier 312, a resistor R _d and the two connected across the inverting amplifier The negative terminal and the output terminal of the 312, the other ends of the other resistor R _d are connected across the positive terminal and the ground terminal of the inverting amplifier 312. The full-bridge rectifier 311 can rectify the three-phase AC signals V _A , V _B , and V _C to output a six-fold frequency signal V _r (the six-fold frequency signal V _r is the voltage difference between the two ends of the resistor R _b ). Here, since the frequencies of the AC signals V _A , V _B , and V _{C are the same} as the frequencies of the line voltage signals V _ab , V _bc , and V _ca , as shown in FIG. 2C , the frequency of the sixth-frequency signal V _r is the AC signal V. _The frequency of _A , V _B and V _C is 6 times, so it is called the six-fold frequency signal V _r . In addition, the sixth frequency signal V _{r is} input to the positive terminal and the negative terminal of the inverting amplifier 312 through the resistor R _c , respectively, and the output terminal of the inverting amplifier 312 outputs the gain signal V _f . Here, the gain signal V _f = (-V _r × R _c / R _d ), and the gain signal V _{f is} input to the high pass filtering unit 32.

The high-pass filter unit 32 has a capacitor C _h and a resistor R _h , and the non-inverting amplifying unit 33 has two resistors Z _h1 , Z _h2 and a non-inverting amplifier 331 . Wherein the output end of the capacitor C _h one end is connected to the inverting amplifier 312, the other end of the capacitor C _h are connected to the positive terminal and end of the resistance R _h of non-inverting amplifier 331, and a ground terminal and the other end of the resistor R _h connection. Further, the negative terminal of the non-inverting amplifier 331 is connected to one end of the resistors Z _h1 and Z _h2 , the other end of the resistor Z _h1 is connected to the ground terminal, and the other end of the resistor Z _h2 is connected to the output terminal of the non-inverting amplifier 331. The high pass filtering unit 32 filters out the low frequency noise portion of the gain signal V _f and outputs a first filtered signal V _h .

The non-inverting amplifying unit 33 receives the first filtered signal V _h and outputs a feedforward signal V _inj . The feedforward signal V _inj and the first filtered signal V _h are in-phase signals, and the feedforward signal V _inj =V _h (1+Z _h2 /Z _h1 ). In addition, as shown in FIG. 2C, since the frequency of the six-fold frequency signal V _r is six times the frequency of the line voltage signals V _ab , V _bc , and V _ca , the gain signal V _f , the first filtered signal V _{h ,} and the feedforward The frequency of the signal V _inj is also six times the frequency of the line voltage signals V _ab , V _bc , and V _ca .

In one embodiment, the component type of the full bridge rectifier 311 is FCF06A60, the resistances R _a , R _s , and R _c are respectively 4 MΩ, the resistance R _b is 400 kΩ, the resistance R _d is 100 kΩ, the resistance _Rh is 150 kΩ, and the resistance Z _h1 It is 1 kΩ, the resistance Z _h2 is 4.3 kΩ, and the capacitance C _h is 220 nF. The inverting amplifier 312 and the non-inverting amplifier 331 are realized by an integrated circuit (IC) of the type LM324N.

Since the ratio of the voltage conversion ratio of the AC/DC conversion circuit 11 is higher, the inductor current waveform distortion of the input inductors L _a , L _b , and L _c is smaller, and the power factor is higher; conversely, if the ratio of the voltage conversion ratio is lower, the ratio is lower. The larger the distortion of the inductor current waveform, the lower the power factor. Therefore, the lower the voltage conversion ratio of the AC/DC converting circuit 11, the higher the current of the input AC/DC converting circuit 11 has a larger fifth harmonic component, resulting in distortion of the input current waveform. Therefore, in order to reduce the fifth harmonic component, a sixth harmonic component (the sixth harmonic is a six-fold input voltage frequency) can be added to the switching control signal of the AC/DC converting circuit 11 to improve the input current. Waveform. Therefore, the present invention overcomes the problem of severe distortion of the input three-phase alternating current signal at a low voltage conversion ratio of the three-phase single-switch boost converter, and the pulse width modulation of the switching element S of the input AC/DC converting circuit 11 A PWM signal (ie, the feedforward signal V _inj ) is injected into the (PWM) signal, thereby improving the distortion of the input current. The frequency of the modulation signal (feedforward signal V _inj ) is six times the frequency of the AC signals V _A , V _B , and V _C output by the AC power source 2, so it is called a six-frequency harmonic injection mechanism.

However, as in the prior art of the present invention, if the switching element is modulated only by the modulation signal (ie, the feedforward signal V _inj ), the ratio of the voltage conversion ratio M is lower (for example, M=1.2 in FIG. 1C). The difference between the input average current waveform and the sine wave is higher, and the fifth harmonic component is higher. In other words, if the switching element S of the AC/DC converting circuit 11 is controlled only by the harmonic of the sixth harmonic, not all of the voltage conversion ratios M have the same improvement effect. Therefore, the present embodiment is not limited to six times. The feed signal V _{inj is} injected into the pulse width modulation signal of the switching element S of the AC/DC conversion circuit 11, and a modulation control signal V _c is simultaneously injected into the pulse width modulation signal of the control switching element S to convert the AC and DC signals. Circuit 11 operates at different voltage conversion ratios M and may have fewer fifth harmonic components. Here, this function is achieved by the above-described harmonic control circuit 4, which will be described in detail below.

Referring to FIG. 2A again and FIG. 2D and FIG. 2E, FIG. 2D is a circuit diagram of the feedback circuit 41 of the harmonic control circuit 4 of FIG. 2A, and FIG. 2E is a Detector of the harmonic control circuit 4 of FIG. 2A. Circuit diagram of circuit 42.

As shown in FIG. 2A, the harmonic control circuit 4 of the present embodiment includes a feedback circuit 41, a detection circuit 42, an operation circuit 43, and a pulse width modulation circuit 44.

The feedback circuit 41 receives the output voltage signal V _o and outputs a feedback signal V _e . The feedback circuit 41 can output the feedback signal V _e according to the output voltage signal V _o outputted by the AC/DC conversion circuit 11 and a first reference voltage V _ref1 . Here, the feedback signal V _e can provide compensation for the switching control signal CS outputted by the pulse width modulation circuit 44 according to the change of the output voltage signal V _o outputted by the AC/DC conversion circuit 11 .

As shown in FIG. 2D, in the present embodiment, the feedback circuit 41 has a first voltage dividing unit 411 and an error amplifying unit 412. The first voltage dividing unit 411 can divide the output voltage signal V _o and output a first voltage dividing signal V _d1 . Here, the first voltage dividing unit 411 includes two resistors R _f3 , R _f4 , and the first voltage dividing unit 411 outputs a first voltage dividing signal V _d1 =R _f4 /(R _f3 +R _f4 )×V _o .

The first voltage dividing signal V _{d1 is} input to the negative terminal of the error amplifier 4121 of the error amplifying unit 412 , and the first reference voltage V _ref1 is input to the positive terminal of the error amplifier 4121, and the output terminal of the error amplifier 4121 outputs the feedback signal V _{e .} . Herein, the first divided voltage signal V _d1 is the negative input terminal of the error amplifier 4121 via a resistor R _h1, and the capacitor C _h2 series with a resistor R _h2, and then in parallel with the capacitance C _h1 connected across the negative terminal of the error amplifier 4121 Between the output and the output. The error amplifying unit 412 of this embodiment is a voltage error amplifier, and the first reference voltage V _ref1 is a DC voltage. In one embodiment, the first reference voltage V _ref1 voltage value of 7.5 volts, the resistance R _f3 is 430kΩ, resistor R _f4 is 8.2kΩ, resistor R _h1 is 82kΩ, resistor R _h2 is 51kΩ, the capacitance C _h1 is 160pF, The capacitor C _h2 is 390 nF, and the error amplifier 4121 is realized by an integrated circuit (IC) of the type LM324N.

In addition, as shown in FIG. 2E, the detecting circuit 42 receives the output voltage signal V _o and outputs a modulation control signal V _c . The detecting circuit 42 can output the modulation control signal V _c according to the output voltage signal V _o and the second reference voltage V _ref2 outputted by the AC/DC converting circuit 11 . Here, the modulation control signal V _c can change the switching control signal CS output by the pulse width modulation circuit 44 according to the change of the voltage value of the output voltage signal V _o outputted by the AC/DC conversion circuit 11 .

The detecting circuit 42 has a second voltage dividing unit 421, a low pass filtering unit 422 and a subtracting unit 423. The second voltage dividing unit 421 can divide the output voltage signal V _o and output a second voltage dividing signal V _d2 , and the low pass filtering unit 422 can filter the high frequency noise of the second voltage dividing signal V _d2 and output a second filtered signal V _l , the second filtered signal V _{l is} input to the negative terminal of one of the subtractors 4231 of the subtraction unit 423, and the second reference voltage V _{ref2 is} input to the positive terminal of the subtractor 4231, and the output of the subtractor 4231 is output. Modulation control signal V _c .

In this embodiment, the second voltage dividing unit 421 includes two resistors R _f1 and R _f2 , so the second voltage dividing signal output by the second voltage dividing unit 421 is V _d2 =R _f2 /(R _f1 +R _f2 )×V. _o . The second voltage dividing signal V _d2 is filtered by the low-pass filtering unit 422 including the voltage follower 4221, the resistor R _k1 and the capacitor C _k1 to filter out the high-frequency noise, and the output second filtered signal V _l is transmitted again. The resistor R _{D1 is} input to the negative terminal of the subtracter 4231, and the resistor R _{D2 is} connected between the negative terminal and the output terminal of the subtractor 4231, and the second reference voltage V _{ref2 is} input to the positive terminal of the subtractor 4231 through the resistor R _D3 , and the resistor The two ends of R _D4 are connected between the positive terminal of the subtractor 4231 and the ground. The second reference voltage V _{ref2 of} this embodiment is also a DC voltage. In one embodiment, the second reference voltage V _{ref2 has} a voltage value of 3.6 volts, the resistance R _f1 is 300 kΩ, the resistance R _f2 is 2 kΩ, the resistance R _k1 is 390 kΩ, and the resistors R _D1 , R _D2 , R _D3 , and R _D4 are respectively It is 100kΩ, the capacitance C _k1 is 400nF, and the voltage follower 4221 and the subtractor 4231 are realized by an integrated circuit (IC) of the type LM324N.

Therefore, the adaptive harmonic injection mechanism proposed by the present invention is under different voltage conversion ratios M (the voltage conversion ratio M is equal to the ratio of the output voltage signal V _o to the input line voltage), and is detected by the detection circuit 42. The measured voltage value of the output voltage signal V _o is obtained by the modulation control signal V _c . The relationship between the modulation control signal V _c and the output voltage signal V _o can be obtained from the detection circuit 42 of FIG. 2E , as shown in the following formula (3).

V _c = V _{ref 2} - V _o ×( R _{f 2} /( R _{f 1} + R _{f 2} )---------(3)

In addition, referring to FIG. 2A again, the arithmetic circuit 43 receives the feedforward signal V _inj and the modulation control signal V _c and outputs a harmonic modulation signal V _aut . In this embodiment, the arithmetic circuit 43 is a multiplier/divider, and multiplies the feedforward signal V _inj by the modulation control signal V _c to output a harmonic modulation signal V _aut . Since the modulation control signal V _c is changed according to the magnitude of the voltage value of the output voltage signal V _o , the harmonic modulation signal V _aut also changes according to the magnitude of the voltage value of the output voltage signal V _o . In an embodiment, the arithmetic circuit 43 is, for example but not limited to, an integrated circuit (IC) including the model number AD633.

The operation of the operation circuit 43 can multiply the modulation control signal V _c changed according to the output voltage signal V _o and the six-fold forward feed signal V _inj generated by the feedforward circuit 3 to obtain a harmonic modulation injection signal. V _aut , the relationship is as shown in the following formula (4). The value of the new modulation coefficient m _aut with adaptive harmonic injection mechanism can also change with the modulation control signal V _c , as shown in equation (5). Where m is the ratio of the peak-to-peak value of the feedforward signal V _{inj to} the feedback signal V _e .

V _aut (t)=V _inj (t). V _c ---------(4)

m _aut =m. V _c ---------(5)

Further, the following formula (6) can be obtained from the above formulas (1), (4), and (5):

In addition, as shown in FIG. 2A, the pulse width modulation circuit 44 can receive the harmonic modulation signal V _aut and the feedback signal V _e , and output a switch control according to the harmonic modulation signal V _aut and the feedback signal V _{e .} switching element control signal CS S, according to the conduction rate of the output voltage signal V _o of the voltage modulation switching element S. Here, the harmonic modulation signal V _aut and the feedback signal V _e are added to the input pulse width modulation circuit 44, and the pulse width modulation circuit 44 generates the switching control signal CS. In other words, the switch control signal CS of the present embodiment modulates the conduction ratio of the switching element S according to the feedforward signal V _inj , the modulation control signal V _{c ,} and the feedback signal V _e .

It can be seen from the above formula and description that the modulation control signal V _c changes according to the voltage value of the output voltage signal V _o (Equation 3), and the harmonic modulation signal V _aut changes according to the modulation control signal V _c (formula) 4), and the modulation coefficient m _aut will also change according to the modulation control signal V _c (Equation 5). Therefore, in this embodiment, under the different output voltage signals V _o , the obtained new modulation coefficient m _aut with the adaptive harmonic injection mechanism changes the amplitude of the harmonic modulation signal V _aut (Equation 6) The conduction ratio of the switching element S is changed, thereby reducing the fifth harmonic distortion of the input current to achieve the function of the adaptive harmonic injection mechanism.

Please refer to FIG. 3 , which is a schematic diagram of the relationship between the input current total harmonic distortion rate (THD%) and the different voltage conversion ratio M of the prior art and the adaptive harmonic injection mechanism of the present invention.

In this embodiment, the voltages of the AC signals V _A , V _B , and V _C are three-phase 110V rms (rms, ie, an effective value), and the peak voltage (peak voltage) is 155.5V. The peak value of the three-phase line voltage is 269.4V, and the output voltage signal V _o is between 320V and 400V, so the corresponding voltage conversion ratio M is about 1.18 to 1.48 (320/269.4≒1.18; 400/269.4≒1.48). ).

As can be seen from FIG. 3, in the present invention with an adaptive harmonic injection mechanism, the total harmonic distortion rate (THD%) is better than the conventional technique of no harmonic injection mechanism and fixed harmonic injection mechanism. Come low. Especially at a lower voltage conversion ratio M (for example, M=1.18 or 1.22), the present invention can effectively reduce the total harmonic distortion rate of the input current with respect to the prior art.

Please refer to FIG. 4A to FIG. 4H , which are schematic diagrams of the input voltage, the input current and the input current spectrum of the present invention at different voltage conversion ratios M. 4A and FIG. 4B, the voltage conversion ratio M is 1.48, the voltage conversion ratio M of FIG. 4C and FIG. 4D is 1.33, and the voltage conversion ratio M of FIG. 4E and FIG. 4F is 1.22, and the voltage conversion of FIG. 4G and FIG. The ratio M is 1.18.

As can be seen from FIG. 4A to FIG. 4H, compared to the input current waveform of FIG. 1A and the input current spectrum of FIG. 1B, the current at a frequency of 300 Hz is relatively low under different voltage conversion ratios M. Therefore, the fifth harmonic component of the input current can be reduced, and the waveform of the input current is less deformed. Therefore, the adaptive harmonic injection mechanism of the present invention can improve the input current distortion under different voltage conversion ratios M. And improve the power factor.

2A to FIG. 2E and FIG. 5, FIG. 5 is a schematic flow chart of a control method of a power conversion device according to a preferred embodiment of the present invention.

The control method of the power conversion device 1 is coordinated with the AC power source 2. The AC power supply 2 outputs AC signals V _A , V _B , V _C , and the power conversion device 1 includes an AC/DC conversion circuit 11 , a feedforward circuit 3 , and a harmonic control circuit 4 , and the harmonic control circuit 4 includes a feedback. The circuit 41, a detecting circuit 42, an arithmetic circuit 43, and a pulse width modulation circuit 44. The technical features of the power conversion device 1 have been described in detail above and will not be described again.

As shown in FIG. 5, the control method of the power conversion device includes at least the following steps: the AC/DC conversion circuit 11 receives the AC signals V _A , V _B , and V _C and outputs an output voltage signal V _o , wherein the AC/DC conversion circuit 11 has a switch. Element S (step S01); receiving the AC signals V _A , V _B , V _C by the feedforward circuit 3 and outputting the feedforward signal V _inj (step S02); receiving the output voltage signal V _o by the feedback circuit 41 and outputting the feedback signal V _e (step S03); receiving the output voltage signal V _o by the detecting circuit 42 and outputting the modulation control signal V _c according to the voltage value of the output voltage signal V _o (step S04); receiving the feedforward signal V _inj by the operation circuit 43 And modulating the control signal V _c and outputting the harmonic modulation signal V _aut (step S05); and outputting the switch control signal CS by the pulse width modulation circuit 44 according to the harmonic modulation signal V _aut and the feedback signal V _e The switching element S modulates the conduction ratio of the switching element S in accordance with the voltage value of the output voltage signal V _o (step S06).

In the step S02 of the feedforward signal V _inj , the feedforward circuit 3 includes a voltage sensing unit 31, a high-pass filtering unit 32, and a non-inverting amplifying unit 33, and the control method may further include: The AC signal V _A , V _B , V _{C is} received by the voltage sensing unit 31 and the gain signal V _{f is} output; the noise of the gain signal V _f is received and filtered by the high-pass filtering unit 32 and the first filtered signal V _{h is} output; The first filtered signal V _{h is} received by the non-inverting amplifying unit 33 and the feedforward signal V _{inj is} output. In step S02, the frequency of the feedforward signal V _inj is six times that of the alternating current signals V _A , V _B , and V _C .

In addition, in step S03 of outputting the feedback signal _Ve by the feedback circuit 41, the feedback circuit 41 has a first voltage dividing unit 411 and an error amplifying unit 412, and the control method may further include: outputting by the first voltage dividing unit 411 The voltage signal V _o is divided and outputs a first voltage dividing signal V _d1 ; and the first voltage dividing signal V _{d1 is} received by the error amplifying unit 412 and the first reference voltage V _ref1 , and the feedback signal V _{e is} outputted, wherein the first point is The voltage signal V _{d1 is} input to the negative terminal of the error amplifier 4121 of the error amplifying unit 412. The first reference voltage V _{ref1 is} input to the positive terminal of the error amplifier 4121, and the output terminal of the error amplifier 4121 outputs the feedback signal V _e .

Further, that detection circuit 42 outputs modulation control signal V _c in step S04, the detection circuit 42 having a second dividing unit 421, low-pass filtering unit 422 and the subtraction unit 423, and the control method may further comprise: a The second voltage dividing unit 421 divides the output voltage signal V _o and outputs the second voltage dividing signal V _d2 ; the low pass filtering unit 422 filters out the noise of the second voltage dividing signal V _d2 and outputs the second filtering signal V _L; and the subtraction unit 423 is received by the second filter signal and the second reference voltage V _l V _ref2, and outputs the modulated control signal V _c, wherein the second filter input signal V _l subtracting unit 423 of the negative terminal of the subtracter 4231, The second reference voltage V _{ref2 is} input to the positive terminal of the subtracter 4231, and the output of the subtracter 4231 outputs the modulation control signal V _c .

In addition, in step S05 of outputting the harmonic modulation signal V _aut by the arithmetic circuit 43 , the arithmetic circuit 43 multiplies the feedforward signal V _inj by the modulation control signal V _c to obtain a harmonic modulation signal V _aut . In addition, the harmonic modulation signal V _{aut is} added to the feedback signal V _e and then input to the pulse width modulation circuit 44 , and the pulse width modulation circuit 44 can output the switch control signal CS to control the switching element S according to the output voltage. The voltage value of the signal V _o modulates the conduction ratio of the switching element S, thereby achieving a distortion phenomenon that can effectively reduce the input current at different voltage conversion ratios, and improving the power factor.

In addition, other technical features of the control method of the power conversion device of the present invention have been described in detail above, and will not be described herein.

In summary, in the power conversion device and the control method thereof, the feedback circuit receives the output voltage signal and outputs a feedback signal, and the detection circuit receives the output voltage signal, and outputs the modulation control signal according to the voltage value of the output voltage signal. The arithmetic circuit receives the feedforward signal and the modulation control signal, and outputs a harmonic modulation signal, and the pulse width modulation circuit controls the switching element according to the harmonic modulation signal and the feedback signal output switch control signal, according to the output voltage signal The voltage value modulates the conduction ratio of the switching element. Thereby, the power conversion device and the control method thereof of the present invention can effectively improve the input current distortion phenomenon under different voltage conversion ratios compared with the conventional techniques of the harmonic injection mechanism and the fixed harmonic injection mechanism. And improve the power factor.

The above is intended to be illustrative only and not limiting. Any equivalent modifications or alterations to the spirit and scope of the invention are intended to be included in the scope of the appended claims.

1‧‧‧Power conversion device

11‧‧‧ AC and DC conversion circuit

2‧‧‧AC power supply

3‧‧‧Feedback circuit

31‧‧‧Voltage sensing unit

32‧‧‧High-pass filter unit

33‧‧‧Non-inverting amplification unit

4‧‧‧Harmonic control circuit

41‧‧‧Feedback circuit

42‧‧‧Detection circuit

43‧‧‧Operating circuit

44‧‧‧ Pulse width modulation circuit

5‧‧‧EMI filter

C _o ‧‧‧ capacitor

CS‧‧‧Switch control signal

D, D _ap , D _an , D _bp , D _bn , D _cp , D _cn ‧‧‧ diode

L‧‧‧load

L _a , L _b , L _c ‧‧‧ inductance

S‧‧‧Switching elements

V _A , V _B , V _C ‧‧‧ exchange signals

V _aut ‧‧‧ harmonic modulation signal

V _c ‧‧‧ modulation control signal

V _e ‧‧‧ feedback signal

V _f ‧‧‧ Gain signal

V _h ‧‧‧first filter signal

V _inj ‧‧‧Feedback signal

V _o ‧‧‧ output voltage signal

Claims (16)

A power conversion device is coupled to an AC power source, the AC power source outputs an AC signal, the power conversion device includes: an AC/DC conversion circuit, receives the AC signal, and outputs an output voltage signal, the AC/DC conversion circuit has a a switching element; a feedforward circuit coupled to the AC power source and the AC/DC conversion circuit, the feedforward circuit receiving the AC signal and outputting a feedforward signal; and a harmonic control circuit respectively coupled to the feedforward circuit And the AC/DC conversion circuit is coupled, the harmonic control circuit includes: a feedback circuit that receives the output voltage signal and outputs a feedback signal; a detection circuit that receives the output voltage signal and is based on the voltage of the output voltage signal The value outputs a modulation control signal; an operation circuit receives the feedforward signal and the modulation control signal, and outputs a harmonic modulation signal; and a pulse width modulation circuit, according to the harmonic modulation signal and The feedback signal outputs a switch control signal to control the switching element to modulate the conduction of the switching element according to the voltage value of the output voltage signal. . The power conversion device according to claim 1, wherein the AC/DC conversion circuit is a three-phase single-switch boost converter. The power conversion device of claim 1, wherein the feedforward circuit comprises a voltage sensing unit, a high pass filtering unit and a non-inverting amplifying unit, wherein the voltage sensing unit senses the alternating signal and outputs a gain signal, the high pass filtering unit receives and filters out the noise of the gain signal and outputs a first filtered signal, and the non-inverting amplifying unit receives the first filtered signal and outputs the feed forward signal. The power conversion device of claim 1, wherein the feedforward signal has a frequency that is six times the frequency of the alternating signal. The power conversion device of claim 1, wherein the feedback circuit has a first voltage dividing unit and an error amplifying unit, and the first voltage dividing unit divides the output voltage signal and outputs a first a voltage dividing signal, the first voltage dividing signal is input to one of the error amplifying units At the negative end of the error amplifier, a first reference voltage is input to the positive terminal of the error amplifier, and an output of the error amplifier outputs the feedback signal. The power conversion device of claim 1, wherein the detection circuit has a second voltage dividing unit, a low pass filtering unit and a subtracting unit, and the second voltage dividing unit divides the output voltage signal Pressing and outputting a second voltage dividing signal, the low pass filtering unit filters out the noise of the second voltage dividing signal and outputs a second filtering signal, and the second filtering signal is input to the negative end of one of the subtracting units A second reference voltage is input to the positive terminal of the subtractor, and an output of the subtractor outputs the modulation control signal. The power conversion device of claim 1, wherein the operation circuit multiplies the feedforward signal by the modulation control signal to obtain the harmonic modulation signal. The power conversion device of claim 1, wherein the harmonic modulation signal changes according to a magnitude of a voltage value of the output voltage signal. The power conversion device of claim 1, wherein the harmonic modulation signal is added to the feedback signal and then input to the pulse width modulation circuit. A control method for a power conversion device, the power conversion device being coupled to an AC power source, the AC power source outputting an AC signal, the power conversion device comprising an AC/DC conversion circuit, a feedforward circuit, and a harmonic control circuit, The harmonic control circuit includes a feedback circuit, a detection circuit, an operation circuit and a pulse width modulation circuit. The control method includes: receiving, by the AC/DC conversion circuit, the AC signal and outputting an output voltage signal, where The AC/DC conversion circuit has a switching component; the AC signal is received by the feedforward circuit and a feedforward signal is output; the feedback circuit receives the output voltage signal and outputs a feedback signal; and the detection circuit receives the output voltage signal And outputting a modulation control signal according to the voltage value of the output voltage signal; receiving, by the operation circuit, the feedforward signal and the modulation control signal, and outputting a harmonic modulation signal; and converting the pulse width modulation signal The circuit controls the switching element according to the harmonic modulation signal and the feedback signal outputting a switch control signal to be based on the output voltage No. modulation voltage conducting ratio of the switching element. The control method of claim 10, wherein the feedforward circuit outputs a feedforward signal, the feedforward circuit includes a voltage sensing unit, a high pass filter unit, and a non-inverting amplifier unit. And the control method further includes: receiving, by the voltage sensing unit, the alternating current signal and outputting a gain signal; receiving, filtering, and filtering the noise of the gain signal by the high-pass filtering unit and outputting a first filtered signal; The inverting amplifying unit receives the first filtered signal and outputs the feedforward signal. The control method of claim 10, wherein in the step of outputting the feedforward signal by the feedforward circuit, the frequency of the feedforward signal is six times that of the alternating signal. The control method of claim 10, wherein in the step of outputting the feedback signal by the feedback circuit, the feedback circuit has a first voltage dividing unit and an error amplifying unit, and the control method further comprises: The first voltage dividing unit divides the output voltage signal and outputs a first voltage dividing signal; and the error amplifying unit receives the first voltage dividing signal and a first reference voltage, and outputs the feedback signal, wherein The first voltage dividing signal is input to the negative terminal of the error amplifier of the error amplifying unit, the first reference voltage is input to the positive terminal of the error amplifier, and the output end of the error amplifier outputs the feedback signal. The control method of claim 10, wherein the detecting circuit outputs the modulation control signal, the detecting circuit has a second voltage dividing unit, a low pass filtering unit and a subtracting unit And the controlling method further comprises: dividing, by the second voltage dividing unit, the output voltage signal and outputting a second voltage dividing signal; and filtering, by the low pass filtering unit, the noise of the second voltage dividing signal And outputting a second filtered signal; and receiving, by the subtracting unit, the second filtered signal and a second reference voltage, and outputting the modulated control signal, wherein the second filtered signal is input to a negative end of the subtractor of the subtracting unit The second reference voltage is input to the positive terminal of the subtractor, and the output of the subtractor outputs the modulation control signal. The control method according to claim 10, wherein in the step of outputting the harmonic modulation signal by the operation circuit, the operation circuit multiplies the feedforward signal by the modulation control signal to obtain the harmonic adjustment Change signal. The control method of claim 10, wherein the harmonic modulation signal is added to the feedback signal and then input to the pulse width modulation circuit.