JP2022143053A - Power conversion device and washing machine including the same - Google Patents

Abstract

To provide a washing machine that controls an output voltage at a constant level while maintaining a power factor of a power supply circuit at the maximum value even when a large power supply voltage fluctuation occurs.SOLUTION: A power conversion device is configured to obtain a DC output from an AC power source through a rectifier circuit capable of being switched to a full-wave rectifier circuit and a double voltage rectifier circuit and to short-circuit the AC power source by a pulse signal with a delay time and pulse width based on a zero crossing point of an AC voltage. The power conversion device is configured to perform a power factor improvement control corresponding to power supply fluctuations by setting a delay time in advance as a value corresponding to an input current or input power and determining a pulse width to control a DC voltage at a constant level when the rectifier circuit is switched to the full-wave rectifier circuit and the double-voltage rectifier circuit for operation when the power supply voltage is within a predetermined range and set the delay time in advance as a value corresponding to the input current or input power to perform a control with a pulse width preset corresponding to the DC voltage when the power supply voltage is out of the predetermined range.SELECTED DRAWING: Figure 1

Description

The present invention relates to a power converter that converts AC power into DC power and a washing machine equipped with the same.

As an example of a power converter, Patent Literature 1 discloses a power converter that improves the power factor by performing a short-circuit operation once or a plurality of times in a half cycle of an AC power supply. In Patent Document 1, a short-circuit start time (delay time) and a short-circuit period (pulse width) of a short-circuit means are determined based on an internal state such as an output voltage and a power supply voltage of a power supply circuit connected to a power supply device, and a load is controlled. A method is disclosed for controlling the power factor to an optimum point depending on the conditions. In Patent Document 1, the power factor is improved by estimating the power supply voltage from the output voltage of the power supply circuit and controlling the short-circuit period according to the fluctuation of the power supply voltage.

Japanese Patent Application Laid-Open No. 2006-180700

In Patent Document 1, control is performed so that the optimum short-circuit period is obtained according to fluctuations within ±5% of the power supply voltage. is doing. In addition, no power supply voltage detection circuit is provided, and the power supply voltage is estimated from the detected output voltage of the power supply circuit based on the relational expression between the output voltage of the power supply circuit and the power supply voltage derived in advance by simulation.

However, no consideration is given to improving the power factor in response to a large power supply voltage fluctuation exceeding ±5% of the power supply voltage.

In view of the above, an object of the present invention is to provide a power conversion device and a washing machine equipped with the same, which control the output voltage to be constant while maintaining the power factor of the power supply circuit at the maximum value even when the power supply voltage fluctuates significantly. to provide.

From the above, in the present invention, "a DC output is obtained through a rectifier circuit that can be switched from an AC power supply to a full-wave rectifier circuit and a voltage doubler rectifier circuit, and the AC power supply is delayed with respect to the zero crossing point of the AC voltage. A power conversion device that is configured to short-circuit by a pulse signal of time and pulse width, and when the power supply voltage is within a predetermined range when the rectifier circuit is switched between a full-wave rectifier circuit and a voltage doubler rectifier circuit. , the delay time is set in advance as a value corresponding to the input current or input power, the pulse width is determined so as to control the DC voltage constant, and the power factor improvement control corresponding to the power supply fluctuation is performed. When it is outside the predetermined range, the delay time is set in advance as a value corresponding to the input current or input power, and control is performed to set the pulse width in advance according to the DC voltage." It is what I did.

According to the present invention, even when the power supply voltage fluctuates by ±5% or more, the output voltage can be controlled to be constant while maintaining the power factor of the power supply circuit at the maximum value.

1 is a diagram showing a basic configuration example of a motor control device using a power conversion device according to an embodiment of the present invention; FIG. FIG. 4 is a diagram for explaining the efficiency, power factor, and input current dependency of a DC voltage of a power conversion device; FIG. 4 is a diagram for explaining the relationship between changes in efficiency, power factor, DC voltage, and pulse width in the power converter of Patent Literature 1; FIG. 4 is a diagram for explaining the relationship between efficiency, power factor, change in DC voltage, and pulse width in the power converter according to the present invention; FIG. 4 is a diagram for explaining the relationship between changes in efficiency, power factor, DC voltage, and pulse width in the power conversion device after switching to the voltage doubler control circuit;

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a basic configuration example of a motor control device using a power conversion device according to an embodiment of the present invention. As shown in FIG. 1, the power converter 1 of the present embodiment includes a reactor 3 having one end connected to one output end of a single-phase AC power supply 2, and short-circuit means for short-circuiting the AC power supply 2 via the reactor 3. 4 and a rectifier circuit connected via an input current detection circuit 12 between the other end of the reactor 3 that is not connected to the AC power supply 2 and the other end of the AC power supply 2 that is not connected to the reactor 3. 5, a smoothing capacitor 6 connected in series to both ends of the DC output of the rectifier circuit 5, one of the AC inputs of the rectifier circuit 5, and a connection point between the smoothing capacitor 7 and the smoothing capacitor 8 constituting the smoothing capacitor 6. The connected rectifier circuit switching means 9, the zero cross detection circuit 10 for detecting the zero cross of the AC power supply 2, and the DC voltage Vd across the smoothing capacitor 6 are inputted to operate the short circuit means 4 with the zero cross signal 50 as a reference timing. A control circuit 11 that outputs a pulse signal 51 and outputs a rectifier circuit switching signal 52 to the rectifier circuit switching means 9, and an input current Is that is input from the AC power supply 2 is detected and an input current detection signal 53 is sent to the control circuit 11. and a power supply voltage detection circuit 16 for outputting a power supply voltage signal 55 of the AC power supply 2 to the control circuit 11 .

FIG. 1 also shows a motor drive system 15 including an inverter circuit 13 connected to the DC output Vd of the power converter 1 and a compressor 14 containing an electric motor. Here, the control circuit 11 is composed of, for example, a semiconductor integrated circuit (IC) such as a one-chip microcomputer, and executes all operations by software processing.

The zero-cross detection circuit 10 receives the voltage across the AC power supply 2, and changes from a High signal to a Low signal at the timing when the AC voltage of the AC power supply 2 (hereinafter abbreviated as power supply voltage Vs) passes through the zero-cross point and the polarity changes. , or a zero-cross signal 50 that switches from a Low signal to a High signal. This zero cross signal 50 is input to the control circuit 11 .

The control circuit 11 uses the rise or fall of the input zero-cross signal 50 as a reference timing, and the period until the short-circuiting means 4 starts the short-circuiting operation (hereinafter referred to as delay time Td) and the short-circuiting period (hereinafter referred to as pulse width Tw), and outputs a short-circuit pulse signal 51 (High and Low signals) to the short-circuit means 4 . The delay time Td and the pulse width Tw are stored in advance in the control circuit 11 or calculated by the control circuit 11 .

The short-circuit means 4 performs short-circuit opening/closing operation according to the short-circuit pulse signal 51 . In this embodiment, when the short-circuit pulse signal 51 output from the control circuit 11 is High, the short-circuit means 4 performs a short-circuit operation. The short-circuiting means 4 is composed of a power semiconductor switching element such as a diode bridge and an IGBT, a bipolar transistor, or a MOSFET, and short-circuits the AC power supply 2 via the reactor 3 according to the short-circuit pulse signal 51 . The power factor of the AC power supply 2 is improved by this short-circuit switching operation.

The rectifier circuit switching means 9 is composed of a bidirectional switch such as a combination of a power relay, a triac, a diode bridge and a power semiconductor switching element (IGBT, bipolar transistor, MOSFET). The rectifier circuit 5 is switched according to the high and low signals). In this embodiment, the rectifier circuit 5 is switched to a full-wave rectifier circuit when the rectifier circuit switching signal 52 is a Low signal, and switched to a voltage doubler rectifier circuit when it is a High signal.

The control circuit 11 inputs a zero-cross signal 50, a DC voltage value 54 that is the DC voltage Vd across the smoothing capacitor 6, an input current detection signal 53, and a power supply voltage value 55 of the AC power supply 2, and generates a short-circuit pulse signal 51 , the rectifier circuit switching signal 52 is output.

The power converter 1 of the present embodiment short-circuits the AC power supply 2 via the reactor 3 once or multiple times in a half cycle of the power supply to widen the conduction angle of the power supply current and improve the power factor of the power supply. while converting AC power into DC power. The power conversion device 1 of this embodiment includes a rectifier circuit switching means 9, which switches the rectifier circuit 5 to a full-wave rectifier circuit or a voltage doubler rectifier circuit to operate. Therefore, in addition to controlling the DC voltage Vd with the pulse width Tw, a wide range of DC voltages Vd can be output.

The relationship between the delay time Td, the pulse width Tw, the efficiency, the power factor, and the DC voltage Vd with respect to the input current Is of the power converter 1 of this embodiment will be described with reference to FIG. FIG. 2 shows experimental results obtained by changing the delay time Td and the pulse width Tw so that the power factor is maximized when the input current Is is changed. The horizontal axis of FIG. 2 is the input current Is, the efficiency and power factor in FIG. 2(a), the DC voltage in FIG. 2(b), and the delay time Td and pulse width in FIG. 2(c). Tw. Here, although the horizontal axis of FIG. 2 represents the input current, the same applies if the horizontal axis represents the input power. In this embodiment, the case where the horizontal axis represents the input current will be described below.

FIG. 2 shows experimental results of a full-wave rectifier circuit and a voltage doubler rectifier circuit. Section A in FIG. 2 indicates the input current range in which the full-wave rectifier circuit operates. Sections B and C indicate the input current range in which the voltage doubler rectifier circuit operates. When the power supply device is started (when the input current is near zero), the full-wave rectifier circuit operates in section A, and shifts to the voltage doubler rectifier circuit operation in section B as the input current Is increases. As the input current Is decreases, the operation of the voltage doubler rectifier circuit in Section B shifts to the operation of the full-wave rectifier circuit in Section A. You can move smoothly because you have

In the case of the input current Is in sections A and B, the delay time Td monotonously decreases with respect to the input current Is, and the pulse width Tw monotonously increases, as shown in FIG. The sum with the pulse width Tw is a constant value. That is, the delay time Td and the pulse width Tw are associated with each other, and if one of them is determined, the other can be determined. In other words, if the detected input current Is is in section A and section B, the delay time Td and the pulse width Tw can be determined. Further, as shown in FIG. 2(b), the DC voltage Vd is substantially constant with respect to the input current Is.

In view of the power conversion circuit illustrated in FIG. 1 to which the present invention can be applied and the various events shown in FIG. As methods for determining the width Tw, the following first, second, and third methods are known. Among these methods, the third method is the method described in Patent Document 1, and the fourth method according to the embodiment of the present invention is a further development of the third method.

First, as a first method for determining the delay time Td and the pulse width Tw, the pulse width Tw is controlled so as to keep the DC voltage Vd constant, and the sum of the delay time Td and the pulse width Tw is kept constant. there is something to do This method is the same as controlling the point at which the short-circuiting device starts short-circuiting so that the DC voltage becomes constant, and the point at which the short-circuiting operation ends. As a result, in the sections A and B shown in FIG. 2, it is possible to control the DC voltage Vd to be constant and at the same time to operate at the maximum power factor. It should be noted that the current detection signal is used to determine whether or not it is in section A or section B. FIG.

As a second method for determining the delay time Td and the pulse width Tw, the input current is detected according to the input current detection signal 53 from the input current detection circuit 12 without correlating the delay time Td and the pulse width Tw. There is one that independently determines the delay time Td and the pulse width Tw according to the signal. The delay time Td and the pulse width Tw that enable operation at a high power factor are obtained in advance by simulation, and a function that obtains the value of the delay time Td from the input current Is and a function that obtains the value of the pulse width Tw from the input current Is. It is input to the control circuit 11 in advance. This method is a good method for easily obtaining the delay time Td and the pulse width Tw.

Next, a third method for determining the delay time Td and the pulse width Tw corresponding to fluctuations in the power supply voltage Vs of the AC power supply 2 will be described. In this method, the relationship shown in FIG. 2 is used to determine the delay time Td according to the relationship between the input current Is and the delay time Td. On the other hand, the pulse width Tw is determined so as to keep the DC voltage Vd constant. Note that the function for obtaining the delay time Td from the input current Is was obtained in advance through experiments and simulations.

Regarding this third method, as shown in FIG. It is characterized in that it can cope with fluctuations in the power supply voltage Vs. According to FIG. 3, the efficiency, power factor, and DC voltage fluctuate as the power supply voltage Vs fluctuates (VS: 95%, 100%, 105%), but the outlines of these graphs do not change. In other words, the efficiency and the power factor change according to the power supply voltage in the form of a quadratic function in which the pulse width Tw shown in FIG. 3 has maximum peaks at TwA, TwB, and TwC. Also, the DC voltage Vd changes in a monotonically increasing function. Also, it can be seen that the DC voltage Vd is the same when the pulse width Tw in FIG. 3 is TwA, TwB, and TwC. That is, the power factor can be controlled to the maximum value by controlling the pulse width Tw (TwA, TwB, TwC) so that the DC voltage Vd remains constant even if the power supply voltage Vs changes.

In this third method, the delay time Td is set in advance as a value corresponding to the input current Is or the input power in the interval A and the interval B in FIG. 2, and the DC voltage Vd is controlled to be constant. The pulse width Tw is determined to perform power factor improvement control corresponding to power fluctuations. However, as shown in FIG. 3, the range in which the above conditions are satisfied is about ±5% of the rated voltage.

As a fourth method for determining the delay time Td and the pulse width Tw, in the present invention, by changing the pulse width Tw according to the power supply voltage value 55 output from the power supply voltage detection circuit 16, ± It can handle voltage fluctuations of more than 5%. In Patent Document 1, which adopts the third method in this regard, when a voltage fluctuation exceeding ±5% of the rated voltage occurs, the pulse width Tw is fixed to a limit value, for example, the minimum pulse width 101 or the maximum pulse width 102. Was. Therefore, in the voltage fluctuation range exceeding ±5% of the rated voltage as shown in FIG. 4, the efficiency and the power factor are not maximized.

In the fourth method of the present invention, the pulse width Tw is determined by the third method as in Patent Document 1 up to about ±5% of the rated voltage. 5, the optimal pulse width Tw corresponding to the power supply voltage value 55 determined in advance by simulation. As a result, even if the power supply voltage fluctuates by ±5% or more, which has not been optimized in the prior art, the power factor of the power supply circuit can be maintained at the maximum value and the output voltage can be controlled to be constant.

Next, a control method for section C in FIG. 2 will be described. In section C of FIG. 2, the condition that the sum of the delay time Td and the pulse width Tw is constant does not hold, but the delay time Td is set to a fixed value and the pulse width Tw is changed to change the DC voltage Vd. can be kept constant. In other words, by fixing the delay time Td and controlling the pulse width Tw so as to keep the DC voltage Vd constant, the power factor can be maximized. Also in this case, if the delay time Td (fixed value) corresponding to the magnitude of the power supply voltage Vs is stored in the control circuit 11 and the fixed value is changed based on the magnitude of the power supply voltage Vs, the power supply voltage Vs It can also handle changes.

As described in the above embodiments, the power supply apparatus of the present invention, which is equipped with a power factor correction circuit that short-circuits the power supply once or multiple times in a half cycle of the power supply voltage Vs, maintains the power factor at the maximum value while maintaining the DC current. Voltage Vd can be controlled to be constant.

Further, by using the power supply device of the present invention in a home appliance such as a washing machine, it is possible to realize a stable DC voltage Vd even when the voltage of the home power source fluctuates.

DESCRIPTION OF SYMBOLS 1... Power converter, 2... AC power supply, 3... Reactor, 4... Short circuit means, 5... Rectifier circuit, 6... Smoothing capacitor, 7... Smoothing capacitor, 8... Smoothing capacitor, 9... Rectifier circuit switching means, 10... Zero crossing Detection circuit 11 Control circuit 12 Input current detection circuit 13 Inverter circuit 14 Compressor 15 Motor drive system 16 Power supply voltage detection circuit 50 Zero cross signal 51 Short circuit pulse signal 52 Rectifier circuit switching signal 53 Input current detection signal 54 DC voltage value 55 Power supply voltage value 101 Minimum pulse width 102 Maximum pulse width

Claims (3)

A DC output is obtained from an AC power supply through a rectifier circuit that can be switched to a full-wave rectifier circuit and a voltage doubler rectifier circuit, and the AC power supply is short-circuited by a pulse signal having a delay time and a pulse width based on the zero cross point of the AC voltage. A power conversion device configured to
When the rectifier circuit is switched between a full-wave rectifier circuit and a voltage doubler rectifier circuit, and the power supply voltage is within a predetermined range, the delay time is set in advance as a value corresponding to the input current or the input power, and the DC The pulse width is determined so as to control the voltage to be constant, power factor improvement control corresponding to power supply fluctuations is performed, and when the power supply voltage is outside a predetermined range, the delay time is adjusted to the input current or input power. A power converter characterized in that a corresponding value is set in advance and control is performed to set the pulse width in advance according to the DC voltage. The power converter according to claim 1,
After switching the rectifier circuit from a full-wave rectifier circuit to a voltage doubler rectifier circuit, the power conversion device is characterized in that the delay time is set to a fixed value and the pulse width is changed to keep the DC voltage constant. A washing machine comprising the power converter according to claim 1 or 2.

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