JP2013247784A - Power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power converter which can ensure stability of a control system with a simple configuration, while suppressing LC resonance and decrease in efficiency.SOLUTION: A control unit 100 controls an inverter 12 so that the transmission characteristics of input voltage of the inverter 12 for the DC voltage Vfrom a diode bridge 11 become the attenuation characteristics by a phase lead element and a secondary lag element connected in series. The control unit 100 has a feedback loop from the voltage Vacross a reactor L detected by a voltage detection unit 101 to a current flowing through the reactor L, in the transmission characteristics of input voltage of the inverter 12 for the DC voltage Vfrom the diode bridge 11. The gain of the feedback loop and the resistance value of a resistor R connected in parallel with the reactor L are set so that the transmission characteristics of input voltage of the inverter 12 for the DC voltage Vfrom the diode bridge 11 become predetermined characteristics.

Description

  The present invention relates to a power conversion device.

  As a conventional first power conversion device, as a method of suppressing LC resonance of a three-phase electrolytic capacitorless inverter, the feedback characteristic of the voltage across the reactor is used to control the attenuation characteristics of the phase advance element and the secondary delay element connected in series. In some cases, the inverter is controlled (see, for example, Japanese Patent No. 4067021 (Patent Document 1)).

  In addition, as a conventional second power conversion device, there is a resonance suppression method using a resistor connected in parallel to a reactor (see, for example, JP-A-2003-244960 (Patent Document 2)).

  By the way, in the first conventional power conversion device, in applications where the carrier frequency is low, such as an inverter that drives a compressor motor such as an air conditioner, the resonance frequency of the LC filter that allows the ripple component of the power supply 6-fold frequency to pass through. However, since the 6-fold frequency of the power supply is set as the lower limit, the resonance frequency of the LC filter and the sampling frequency are close to each other, and it is difficult to ensure the stability of the control system.

  Moreover, in the said 2nd conventional power converter device, although control is unnecessary, since the harmonic component of an input electric current is consumed as a loss, it will cause an efficiency fall.

Patent No. 4067021 JP 2003-244960 A

  Therefore, an object of the present invention is to provide a power conversion device that can ensure stability of a control system with a simple configuration while suppressing LC resonance and efficiency reduction.

In order to solve the above problems, a power conversion device of the present invention is
A rectifier that rectifies a single-phase or multi-phase AC voltage into a DC voltage;
A PWM-controlled inverter unit that converts the DC voltage output from the rectifier unit into an AC voltage and outputs the AC voltage;
A capacitance element connected between the input terminals of the inverter unit;
An inductance element connected between one output terminal of the rectifying unit and one input terminal of the inverter unit, and constituting an LC filter with the capacitance element;
A resistor connected in parallel to both ends of the inductance element;
A voltage detector for detecting a voltage across the inductance element;
A control unit for controlling the inverter unit based on the voltage across the inductance element detected by the voltage detection unit;
The LC filter has a resonance frequency set so as to pass a ripple current component included in the DC current output from the rectifying unit and attenuate a current component having the same frequency as the carrier frequency of the inverter unit. And
The control unit
The inverter unit is controlled so that the transfer characteristic of the input voltage of the inverter unit with respect to the DC voltage from the rectifying unit becomes an attenuation characteristic by a phase advance element and a secondary delay element connected in series,
In the transfer characteristic of the input voltage of the inverter unit with respect to the DC voltage from the rectifier unit, a feedback loop from a voltage across the inductance element detected by the voltage detection unit to a current flowing through the inductance element is provided.
The gain k of the feedback loop and the resistance value of the resistor are set so that the transfer characteristic of the input voltage of the inverter unit with respect to the DC voltage from the rectifier unit becomes a predetermined characteristic. Features.

  According to the above configuration, the gain k of the feedback loop from the voltage across the inductance element detected by the voltage detector to the current flowing through the inductance element and the resistance value of the resistor connected in parallel across the inductance element are set. Then, by adjusting the open-loop gain characteristic and the phase characteristic, the transfer characteristic of the input voltage of the inverter unit with respect to the DC voltage from the rectifying unit is set to a predetermined characteristic. Therefore, stability of the control system can be secured with a simple configuration while suppressing LC resonance and efficiency reduction.

Moreover, in the power converter of one embodiment,
The control unit
The one-round transfer characteristic is set such that the one-round transfer characteristic of the inductance element voltage control system obtained by equivalently converting the transfer characteristic of the input voltage of the inverter unit with respect to the DC voltage from the rectifier unit is a predetermined characteristic. The proportional gain of
The resistance value of the resistor is set so that the phase of the round transfer characteristic of the inductance element voltage control system becomes a predetermined characteristic.

  According to the above embodiment, the inductance element is set by setting a proportional gain of the round transfer characteristic of the inductance element voltage control system obtained by equivalently converting the transfer characteristic of the input voltage of the inverter unit with respect to the DC voltage from the rectifier unit. By adjusting the gain of the voltage control system and setting the resistance value of the resistor, the phase can be adjusted and the stability of the control system can be improved.

Moreover, in the power converter of one embodiment,
The reciprocal of the delay time when the control unit detects the voltage across the inductance element and performs PWM control of the inverter unit is greater than the resonance frequency of the LC filter and less than 10 times the resonance frequency. is there.

  According to the above embodiment, the reciprocal of the delay time when the control unit detects the voltage across the inductance element and performs PWM control of the inverter unit, that is, the carrier frequency when PWM control of the inverter unit is performed, and the resonance of the LC filter By making it larger than the frequency and not more than 10 times the resonance frequency of the LC filter, the phase improvement effect can be obtained with certainty. On the other hand, if the reciprocal of the delay time (that is, the carrier frequency) exceeds 10 times the resonance frequency of the LC filter, the loss due to resistance increases, and a sufficient phase improvement effect cannot be obtained.

Moreover, in the power converter of one embodiment,
The control unit
Only by the resistance value of the resistor, the attenuation coefficient of the transfer characteristic of the input voltage of the inverter unit with respect to the DC voltage from the rectifying unit is set to 1 or less.

  According to the above embodiment, the phase characteristic is set by setting the resistance value of the resistor connected in parallel to the inductance element for the target amplitude characteristic centered on one resonance point when the attenuation coefficient is 1 or less. It becomes possible to adjust. On the other hand, when the attenuation coefficient is larger than 1, the transfer characteristic can be regarded as a series configuration of first-order lag elements, and the characteristic has two resonance points. It is not easy to adjust the characteristics.

Moreover, in the power converter of one embodiment,
The control unit
In a circuit transfer characteristic of the inductance element voltage control system obtained by equivalently converting the input voltage transfer characteristic of the inverter unit with respect to the DC voltage from the rectifier unit, the inverter unit detects the voltage across the inductance element and detects the voltage across the inductance element. The reciprocal of the delay time when PWM is controlled is fs, and the gain in the frequency region of frequency fs / 4 or higher is set to 0 dB or lower.

  According to the above embodiment, in the loop transfer characteristic of the inductance element voltage control system, the phase is inverted at a frequency that is ¼ of the reciprocal fs (sampling frequency) of the delay time when the inverter unit is PWM-controlled. The control system can be stabilized by reducing the gain in the frequency region of / 4 or more to 0 dB or less.

  As is clear from the above, according to the present invention, it is possible to realize a power conversion device that can secure the stability of the control system with a simple configuration while suppressing LC resonance and efficiency reduction.

FIG. 1 is a configuration diagram of a power conversion device according to an embodiment of the present invention. FIG. 2 is a diagram showing an equivalent circuit of the power converter. FIG. 3 is a block diagram of the power converter. FIG. 4 is a Bode diagram showing transfer characteristics of the power converter. FIG. 5 is a block diagram of a power converter of a comparative example. FIG. 6 is a block diagram of the power conversion device of the comparative example. FIG. 7 is a block diagram showing transfer characteristics of the power converter of the comparative example. FIG. 8 is a Bode diagram showing transfer characteristics of the power converter of the comparative example. FIG. 9 is a Bode diagram showing the transfer characteristics of the discrete value system of the power converter of the comparative example. FIG. 10 is a Bode diagram showing the transfer characteristics of the disturbance suppression system of the power converter of the comparative example. FIG. 11 is a diagram illustrating a step response of the disturbance suppression system of the power conversion device of the comparative example. FIG. 12 is a block diagram of the power conversion device according to the embodiment of the present invention. FIG. 13 is a Bode diagram showing the open-loop transfer characteristics of the power converter. FIG. 14 is a Bode diagram showing the transfer characteristics of the disturbance suppression system of the power converter of the above embodiment. FIG. 15 is a diagram illustrating a step response of the disturbance suppression system of the power conversion device according to the above embodiment. FIG. 16 is a Bode diagram showing the phase improvement effect of the power conversion device of the above embodiment. FIG. 17 is a diagram showing the phase improvement effect by the attenuation coefficient of the power conversion device of the above embodiment. FIG. 18 is a diagram showing the relationship between the loss resistivity and the phase advance angle with respect to the attenuation coefficient of the power converter of the above embodiment.

  Hereinafter, the power converter of this invention is demonstrated in detail by embodiment of illustration.

  FIG. 1 shows a configuration diagram of a power converter according to an embodiment of the present invention. As shown in FIG. 1, the power conversion apparatus includes a diode bridge 11 as an example of a rectifying unit including six diodes D1 to D6 that constitute a three-phase diode bridge circuit, and six switching that constitute a three-phase bridge circuit. And an inverter unit 12 including elements S1 to S6. In addition, the power converter includes a reactor L as an example of an inductance element connected between the positive output side of the diode bridge 11 and the positive input side of the inverter unit 12, and the input end of the inverter unit 12. The capacitor C as an example of the capacitance element connected to the terminal and a resistor R connected in parallel to the reactor L are provided. The reactor L and the capacitor C constitute an LC filter.

Furthermore, the power converter includes a voltage detector 101 for detecting a voltage across V _L of the reactor L, based on the VL signal representing the voltage across V _L of the reactor L from the voltage detector 10, the inverter unit 12 The control part 100 which outputs a PWM signal to each switching element S1-S6 is provided.

  The diode bridge 11 rectifies the three-phase AC voltage from the three-phase AC power source 10 into a direct current, and the rectified DC voltage is converted into a predetermined three-phase AC voltage by the inverter unit 12 and output. In this embodiment, a motor 13 is connected as a load of the inverter unit 12.

  The capacitance of the capacitor C of the LC filter in the DC link portion of the power converter shown in FIG. 1 is as small as 1 or less, which is several tenths of the conventional value, and the resonance frequency of the LC filter is several times to attenuate the carrier current component of the inverter device. It is set to about one kilohertz higher than the conventional one, and the inductance of the reactor L is also set to a small value.

  For this reason, the reactor L and the capacitor C in the DC link section do not have an effect of smoothing the commercial frequency component, and the DC link section generates a maximum phase potential based on the minimum phase of the phase voltage. Pulsates at double frequency. Similarly, with respect to the input current, since a direct current flows between the lines of the maximum phase and the minimum phase, a 120 ° energization waveform is obtained when the input current of the inverter unit 12 is constant.

FIG. 2 shows an equivalent circuit of the power converter. In FIG. 2, 14 is a current source that simply represents the inverter unit 12 (shown in FIG. 1) to which a load is connected, V _s is a DC voltage output from the diode bridge 11, and V _c is both ends of the capacitor C. Voltage, I _R is a current flowing through the resistor R, I _L is a current flowing through the reactor L, I _c is a current flowing through the capacitor C, and I _o is a current flowing through the DC link section.

FIGS. 3A to 3C are block diagrams in which the characteristics of the resonance suppression system are obtained when the voltage V _L across the reactor L is used for resonance suppression, and the DC voltage V _s output from the diode bridge 11. It shows the transfer characteristics across voltage V _c of the capacitor C (i.e. the input voltage of the inverter unit 12) for.

  When equivalent conversion is performed in the order of FIG. 3A to FIG. 3C, it can be seen that a series system composed of a phase advance element and a secondary delay element shown in FIG.

Next, the cutoff frequency of the resonance suppression system for suppressing resonance by the LC filter in the control system having the transfer characteristic of the input voltage of the inverter unit 12 with respect to the DC voltage V _s from the diode bridge 11 will be described below.

で表され、

とすると、上記式(１)を変形して、次の式(３)で表すことができる。

ここで、カットオフ周波数ｆ_cは、式(３)の２項目に依存し、

となる。また、減衰係数ζは、

となる。 In the resonance suppression system shown in FIG. 3, the transfer function G (s) for the voltage V _c across the capacitor C with respect to the DC voltage V _s output from the diode bridge 11 is

Represented by

Then, the above equation (1) can be modified and expressed by the following equation (3).

Here, the cut-off frequency f _c, depending on the two items of the formula (3),

It becomes. The attenuation coefficient ζ is

It becomes.

  FIG. 4 shows the transfer characteristics when the attenuation coefficient ζ is 0.25, 0.5, 0.75, and 1 in the above power converter. As shown in FIG. 4, by setting k + 1 / r so that the attenuation coefficient ζ becomes 1, the first-order lag characteristic is obtained.

[Comparative example]
Next, a power conversion device of a comparative example (Japanese Patent No. 4067021 (Patent Document 1)) will be described with reference to block diagrams shown in FIGS. When the equivalent conversion is performed in the order of FIGS. 5B and 5C, the control system of the power conversion device of the comparative example shown in FIG. 5A controls the voltage V _L across the reactor L based on the target voltage V _L ^*. The disturbance suppression system (the DC voltage V _s output from the diode bridge 11 is a disturbance factor) is expressed. Furthermore, although equivalent conversion can be performed as shown in FIGS. 6A and 6B, the stability of the disturbance suppression system is evaluated by the one-cycle transmission characteristic with the closed loop of FIG. 6A opened.

7 and 8 show the transfer characteristics of the power conversion device of the comparative example, where the circuit constants are L = 0.5 mH and C = 40 μF (resonance frequency fn = 1125 Hz). This one-round transfer characteristic (open loop) has a serial configuration of a proportional gain ke ^−sT , a phase advance element Ls, and a second order delay element 1 / (LCs ² +1), and the proportional gain is assumed to be digitally controlled. ^Is considered the ^dead time e ^−sT of the discrete value system. Here, the proportional gain k = 1 and the sampling frequency f = 6 kHz.

Since the second-order lag element 1 / (LCs ² +1) does not have an attenuation term (term having s in the denominator), the phase is inverted at the resonance frequency of the LC filter as in the transfer characteristic indicated by the two-dot chain line.

  Next, since the phase advance element Ls indicated by the alternate long and short dash line is connected in series, a gain of 20 dB / dec and a 90 deg advance phase are added, and the one-round transfer characteristic (open loop) indicated by the solid line is ± The characteristics are 20 dB / dec and ± 90 deg.

Further, when the proportional gain ke- ^sT indicated by the dotted line of the discrete value system is added, the phase is inverted at 1.5 kHz that is 1/4 of the sampling frequency fs due to the influence of the ^dead time e- ^sT .

The characteristic indicated by the dotted line of the ^dead time e ^−sT is that the phase is inverted at fs / 2, the phase is delayed by 90 ^deg at fs / 4, and the phase advance element Ls and the second order delay element 1 / (LCs ² connected in series are connected. Since the characteristic indicated by the fine dotted line of +1) is 90 deg phase lag in the region above the resonance point, the phase is inverted at fs / 4. Since the amplitude at f / 4 is 15.66 dB, the closed loop system becomes unstable and oscillates.

  In the power conversion device of the comparative example, in order to stabilize the closed loop system, the gain at the fs / 4 point needs to be 0 dB or less, and generally a gain margin of 10 dB to 20 dB is secured.

を用いて求めた外乱抑制系の減衰係数ζは０.１で、ダンピングが不十分であり、図１０に示す外乱抑制系の伝達特性に示すように、伝達特性の共振点のピーク値が２５ｄＢ以上と大きくなると共に、図１１に示すステップ応答も行き過ぎ量が大きく、整定時間も長いものとなる。 FIG. 9 shows the transfer characteristics when the control gain of the power conversion device of the comparative example is set to k = 0.057 (−25 dB) and the gain margin is 10 dB. here,

The damping coefficient ζ of the disturbance suppression system obtained using the above is 0.1 and damping is insufficient. As shown in the transmission characteristic of the disturbance suppression system shown in FIG. 10, the peak value of the resonance point of the transmission characteristic is 25 dB. In addition to the above increase, the step response shown in FIG. 11 also has a large overshoot amount and a long settling time.

  The power conversion device of the comparative example has a problem that it is difficult to ensure the stability of the control system when the resonance frequency of the LC filter is close to the sampling frequency. Particularly, in the case of an inverter for an air conditioner, since a motor is incorporated as a hermetic motor in the compressor, there is little problem of carrier sound, and the carrier frequency is selected to be about 4 to 6 kHz from the viewpoint of efficiency. In addition, since the three-phase electrolytic capacitorless inverter does not have a smoothing function, the voltage and current of the DC link unit are controlled to pulsate at 300 Hz to 360 Hz, which is 6 times the power supply frequency. Therefore, the resonance frequency of the LC filter is 500 Hz to The resonance frequency of the LC filter and the sampling (carrier) frequency must be set close to each other.

On the other hand, the power conversion device according to the embodiment of the present invention converts the transfer function when the resistor R shown in FIG. 1 is connected in parallel to the reactor L to the equivalent conversion shown in FIGS. Thus, it is represented by a round transfer characteristic (open loop) of the inductance element voltage control system. When FIG. 12 is compared with FIGS. 5 and 6 of the comparative example, since only the proportional gain is a discrete value system, a ^dead time e- ^sT occurs, but the resistance R can be handled in a continuous system.

  Further, since the second-order lag element in the one-cycle transfer characteristic (open loop) of FIG. 12C has an attenuation term, the open loop can have an attenuation characteristic by the resistor R.

  FIG. 13 shows the open-loop transfer characteristics of the power converter shown in FIG. 1 of this embodiment. In FIG. 13, k = 0.141 (−17 dB) and the proportional gain is set to about 2.5 times larger than the transfer characteristic shown in FIG. 9 of the comparative example, and the gain margin is 2 dB and the margin is not large. It is in a sufficient state.

  Here, the case where the resistance R is set as small as 10Ω (ζ = 0.18) and 5Ω (ζ = 0.35) with respect to the initial value 50Ω (ζ = 0.04) of the resistance R is also shown. ing. In FIG. 13, the thick solid line is k = 1, R = 50Ω, the thin solid line is k = 0.141, R = 50Ω, the dotted line is k = 0.141, R = 10Ω, and the alternate long and short dash line is k = 0.141, R. = 5Ω. In the phase characteristic shown in the lower side of FIG. 13, the thin solid line overlaps the thick solid line.

  As shown in FIG. 13, by setting the attenuation coefficient ζ large, the amount of change in phase lag with respect to the frequency can be reduced, and the frequency at which the phase is inverted can be shifted to a high frequency range. Further, since the amplitude characteristic is −20 dB / dec, it is possible to secure a gain margin as a result. When the resistance R is 5Ω, the gain margin can be secured up to about −10 dB, which can be regarded as a stable state.

  Further, the effect of the resistance R is that, in addition to ensuring the stability of the inductance element voltage control system as described above, the proportional gain k = 0.141 (ζ = 0.25) and the resistance R for the disturbance suppression system. = 50Ω (ζ = 0.04), 10Ω (ζ = 0.18), and 5Ω (ζ = 0.35), the feedback gain is increased.

  FIG. 14 shows the transfer characteristic of the disturbance suppression system, and FIG. 15 shows the step response of the disturbance suppression system. Here, the case where the resistance R is set as small as 10Ω (ζ = 0.18) and 5Ω (ζ = 0.35) with respect to the initial value 50Ω (ζ = 0.04) of the resistance R is also shown. ing. In FIG. 14, the thick solid line is k = 1, R = 50Ω, the thin solid line is k = 0.141, R = 50Ω, the dotted line is k = 0.141, R = 10Ω, and the alternate long and short dash line is k = 0.141, R. = 5Ω. In FIG. 15, the solid line is k = 0.141, R = 50Ω, the dotted line is k = 0.141, R = 10Ω, and the alternate long and short dash line is k = 0.141, R = 5Ω.

  As shown in FIGS. 14 and 15, by reducing the peak gain at the resonance point of the transfer characteristic and improving the phase characteristic by the resistance R, the overshoot amount of the step response and the settling time can be reduced, and the resonance suppression effect can be obtained. Can be big.

  FIG. 16 shows the open loop transfer characteristics of the power converter of the above embodiment in a continuous system, and the control gain and the resistance value of the resistor R are set in the same manner as in FIG.

とすると、

となり、振幅は、

で表される。また、位相は、

で表される。 In addition, the general expression of the transfer function of the secondary system is

Then,

And the amplitude is

It is represented by The phase is

It is represented by

  In the power conversion device according to the embodiment of the present invention, when the resistance value of the resistor R is set to be small and the attenuation coefficient ζ is increased, the peak gain at the resonance point is lowered and the amount of change in the phase delay with respect to the frequency is reduced. Become. This is apparent from the fact that the attenuation coefficient ζ included in the denominator of Expression (9) representing the amplitude and Expression (11) representing the phase is included.

Therefore, when the attenuation coefficient ζ is increased, the amount of change in the phase delay with respect to the frequency is reduced, and the frequency at which the phase of the open loop characteristic is inverted is higher than the characteristic in which the frequency of the ^dead time e ^−sT shown in FIG. Will rise.

  FIG. 17 shows the phase improvement effect by the attenuation coefficient ζ at the frequency representative point based on the above equation (11), but the phase improvement effect is large in the vicinity of 2 to 3 times the resonance frequency. At a distance of 1 dec (ω / ωn = 10), the phase improvement effect remains at about 10 deg. This result means that the resonance suppression effect by the damping coefficient ζ is mainly due to the feedback gain due to the resistance, so that the loss due to the resistance R connected in parallel increases.

  FIG. 18 shows the phase improvement effect and the resistance loss characteristic with respect to the attenuation coefficient ζ at ω / ωn = 2 of the power conversion device of the above embodiment. Here, L = 0.5 mH and C = 40 μF.

  The phase improvement effect due to the resistance R indicates a phase advance angle from the delayed phase 90 ° when the damping coefficient ζ = 0, and the resistance loss is a reduction ratio ΔPdf = (P1−Pdf) / P1 from the loss P1 when ζ = 1. Is shown.

  As shown in FIG. 18, from the trade-off characteristic between the phase improvement effect and the resistance loss, the resistance R is preferably about 5Ω when the circuit constant is L = 0.5 mH and C = 40 μF. As shown in FIG. A gain margin of about 10 dB can be secured together with the control gain k.

  Further, if the resistance value of the resistor R is reduced, the phase can be advanced from the current state of 25.2 deg, and the frequency at which the phase is inverted can be shifted with fs / 2 = 3 kHz as the upper limit, but on the other hand, the resistance loss is increased.

According to the power conversion device configured as described above, connected to the gain k of the feedback loop until the current I _L flowing from the voltage across V _L of the reactor L, which is detected by the voltage detection unit 101 to the reactor L, in parallel across the reactor L By setting the resistance value of the resistor R and adjusting the open loop gain characteristic and the phase characteristic, the transfer characteristic of the input voltage of the inverter unit 12 with respect to the DC voltage V _s from the diode bridge 11 is determined in advance. Be characteristic. Therefore, stability of the control system can be ensured with a simple configuration while suppressing LC resonance and efficiency reduction.

Further, by setting the proportional gain of the round transfer characteristic of the inductance element voltage control system obtained by equivalently converting the transfer characteristic of the input voltage of the inverter unit 12 with respect to the DC voltage V _s from the diode bridge 11, the inductance element voltage is set. By adjusting the gain of the control system and setting the resistance value of the resistor R, the phase can be adjusted and the stability of the control system can be improved.

Further, the reciprocal of the delay time when the control unit 100 detects the voltage V _L across the reactor L and performs PWM control of the inverter unit 12, that is, the carrier frequency when PWM control of the inverter unit 12 is performed. By making the frequency higher than the resonance frequency and not more than 10 times the resonance frequency of the LC filter, the phase improvement effect can be surely obtained. On the other hand, when the reciprocal of the delay time (carrier frequency) exceeds 10 times the resonance frequency of the LC filter, the loss due to the resistance R increases, and a sufficient phase improvement effect cannot be obtained as shown in FIG. .

  In addition, when the attenuation coefficient is 1 or less, the phase characteristic is adjusted by setting the resistance value of the resistor R connected in parallel to the reactor L with respect to the target amplitude characteristic centered on one resonance point. Is possible. On the other hand, when the attenuation coefficient is greater than 1, the transfer characteristic is regarded as a series configuration of first-order lag elements and has two resonance points. Therefore, unlike the characteristic having an attenuation coefficient of 1 or less, the resistance R It is not easy to adjust the phase characteristics.

  Further, in the one-round transfer characteristic of the inductance element voltage control system, the phase is inverted at a frequency that is 1/4 of the reciprocal fs (sampling frequency) of the delay time when the inverter unit 12 is PWM-controlled, so that the frequency fs / 4 or more. The control system can be stabilized by reducing the gain in the frequency region of 0 dB or less.

  Although specific embodiments of the present invention have been described, the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 ... Three-phase alternating current power supply 11 ... Diode bridge 12 ... Inverter part 13 ... Motor 14 ... Current source R ... Resistance L ... Reactor C ... Capacitor 100 ... Control part 101 ... Voltage detection part

Claims (5)

A rectifying unit (11) for rectifying a single-phase or multi-phase AC voltage into a DC voltage;
A PWM-controlled inverter unit (12) that converts the DC voltage output from the rectifier unit (11) into an AC voltage and outputs the AC voltage;
A capacitance element (C) connected between the input terminals of the inverter unit (12);
An inductance element (L) connected between one output terminal of the rectifying unit (11) and one input terminal of the inverter unit (12), and constituting an LC filter with the capacitance element (C);
A resistor (R) connected in parallel to both ends of the inductance element (L);
A voltage detector (101) for detecting a voltage across the inductance element (L);
A control unit (100) for controlling the inverter unit (12) based on the voltage across the inductance element (L) detected by the voltage detection unit (101),
The LC filter passes a ripple current component included in the direct current output from the rectifier (11) and attenuates a current component having the same frequency as the carrier frequency of the inverter (12). The resonance frequency is set and
The control unit (100)
Inverter section (11) so that the transfer characteristic of the input voltage of the inverter section (12) with respect to the DC voltage from the rectifier section (11) is an attenuation characteristic by a phase advance element and a secondary delay element connected in series. 12) and controlling
In the transfer characteristic of the input voltage of the inverter unit (12) with respect to the DC voltage from the rectifier unit (11), the inductance is obtained from the voltage across the inductance element (L) detected by the voltage detection unit (101). A feedback loop up to the current flowing through the element (L),
The gain k of the feedback loop and the resistance of the resistor (R) so that the transfer characteristic of the input voltage of the inverter unit (12) with respect to the DC voltage from the rectifier unit (11) becomes a predetermined characteristic. A power conversion device characterized in that a value is set. The power conversion device according to claim 1,
The control unit (100)
The circular transfer characteristic of the inductance element voltage control system obtained by equivalently converting the transfer characteristic of the input voltage of the inverter unit (12) with respect to the DC voltage from the rectifier unit (11) is a predetermined characteristic. In addition, a proportional gain of the one-round transfer characteristic is set, and
The power converter according to claim 1, wherein a resistance value of the resistor (R) is set so that a phase of a round transfer characteristic of the inductance element voltage control system is a predetermined characteristic. In the power converter device according to claim 1 or 2,
The reciprocal of the delay time when the control unit (100) detects the voltage across the inductance element (L) and performs PWM control of the inverter unit (12) is greater than the resonance frequency of the LC filter, and A power conversion device having a resonance frequency of 10 times or less. In the power converter according to any one of claims 1 to 3,
The control unit (100)
The attenuation coefficient of the transfer characteristic of the input voltage of the inverter unit (12) with respect to the DC voltage from the rectifier unit (11) is set to 1 or less only by the resistance value of the resistor (R). A power converter. In the power converter according to any one of claims 1 to 4,
The control unit (100)
In a round transfer characteristic of the inductance element voltage control system obtained by equivalently converting the transfer characteristic of the input voltage of the inverter part (12) with respect to the DC voltage from the rectifier part (11), the inductance element (L) A power conversion device characterized in that the reciprocal of the delay time when PWM control is performed on the inverter unit (12) by detecting the voltage at both ends is fs, and the gain in the frequency region of frequency fs / 4 or higher is 0 dB or lower.

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