JP5791567B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device for charging a battery.

  2. Description of the Related Art Conventionally, a power conversion device for charging a battery has been known that includes an ACDC converter, a smoothing capacitor, and a DCDC converter (see Patent Documents 1 and 2 below). This power conversion device converts an AC voltage input from an AC power source into a DC voltage using an ACDC converter, and smoothes the converted DC voltage using a smoothing capacitor. Then, the DC voltage after smoothing is transformed using the DCDC converter, and the DC voltage after transformation is applied to the battery. As a result, the battery is charged.

  In addition, the power converter is configured to make a voltage sensor that measures the voltage (output voltage) of the battery, a current sensor that measures a current (output current) flowing through the battery, and power (output power) supplied to the battery constant. The feedback control unit is provided. The feedback control unit controls the amount of output current so that the product (output power) of the output voltage and output current measured by the sensor becomes constant.

  When the battery is charged, the battery voltage (output voltage) gradually increases. Therefore, the output current is increased when the amount of charge of the battery is small and the output voltage is low, and the output current is decreased as the battery is charged and the output voltage increases. Thus, by performing feedback control to make the output power constant, the input power supplied from the AC power supply and the output power supplied to the battery are balanced.

JP 2010-63243 A JP 2010-200530 A

  However, the conventional power conversion device has a problem that the output current cannot be controlled when the effective value of the input voltage is momentarily decreased. That is, when the effective value of the input voltage decreases, the voltage applied from the ACDC converter to the smoothing capacitor decreases. In this state, if the same amount of output current as that before the input voltage is decreased continues to flow, the charge stored in the smoothing capacitor is reduced, and the voltage of the smoothing capacitor is likely to decrease. Then, it becomes difficult to supply a sufficient current from the smoothing capacitor to the DCDC converter, and the output current of the DCDC converter tends to oscillate. As a result, there arises a problem that the charging efficiency of the battery is lowered or the charging function is lost.

  For example, when a household commercial power source is used as the AC power source, the effective value of the input voltage may decrease at the moment when an electric device that consumes a large amount of power such as an air conditioner is operated. Even in such a case, a power converter capable of preventing the oscillation of the output current is desired.

  The present invention has been made in view of such a background, and an object of the present invention is to provide a power conversion device in which an output current hardly oscillates even when an effective value of an input voltage varies.

A first aspect of the present invention is a power conversion device for charging a battery,
An ACDC converter that converts an AC voltage input from an AC power source into a DC voltage;
A smoothing capacitor for smoothing the DC voltage converted by the ACDC converter;
A DCDC converter that transforms the smoothed DC voltage, applies the DC voltage after the transformation to the battery as an output voltage, and charges the battery;
Input voltage measuring means for measuring the input voltage of the AC power supply;
Output current measuring means for measuring the output current of the DCDC converter;
Output voltage measuring means for measuring the output voltage;
A feedback control unit that performs feedback control so that output power that is a product of the output current and the output voltage approaches a target value;
The feedback control unit is configured to change the target value of the output power so that the voltage of the smoothing capacitor becomes constant when the effective value of the input voltage measured by the input voltage measuring unit varies. Has been
The feedback control unit includes a storage unit that stores a correlation between a power efficiency obtained by dividing the output power by an input power of the AC power supply, and the output power and the output voltage, and the feedback control unit includes: Using the correlation, the power efficiency corresponding to the output power and the output voltage measured before the effective value fluctuates is obtained, and the effective value fluctuates using the obtained power efficiency. A target value for the output power afterwards is calculated. (Claim 1)
A second aspect of the present invention is a power converter for charging a battery,
An ACDC converter that converts an AC voltage input from an AC power source into a DC voltage;
A smoothing capacitor for smoothing the DC voltage converted by the ACDC converter;
A DCDC converter that transforms the smoothed DC voltage, applies the DC voltage after the transformation to the battery as an output voltage, and charges the battery;
Input voltage measuring means for measuring the input voltage of the AC power supply;
Output current measuring means for measuring the output current of the DCDC converter;
Output voltage measuring means for measuring the output voltage;
A feedback control unit that performs feedback control so that output power that is a product of the output current and the output voltage approaches a target value;
The feedback control unit is configured to change the target value of the output power so that the voltage of the smoothing capacitor becomes constant when the effective value of the input voltage measured by the input voltage measuring unit varies. Has been
Capacitor voltage measuring means for measuring the voltage of the smoothing capacitor, and input current measuring means for measuring an input current sent from the AC power source to the ACDC converter, the feedback control unit includes the measured input current and the measured current It is configured to perform feedback control so that the voltage of the smoothing capacitor approaches the target value,
The feedback control unit is a power conversion device configured to reduce a target value of the input current when an effective value of the input voltage is lower than a predetermined value ( Claim 2).

In the above power converter, the feedback control unit is configured to change the target value of the output power so that the smoothing capacitor voltage becomes constant when the effective value of the input voltage varies.
For example, when the effective value of the input voltage decreases, the feedback control unit reduces the target value of the output power. In this way, since the output current is reduced, it is possible to prevent the charge stored in the smoothing capacitor from being reduced. As a result, the output current can be stably supplied from the smoothing capacitor to the DCDC converter, and oscillation of the output current can be prevented.

  Note that “so that the voltage of the smoothing capacitor becomes constant” means that the average value of the voltage is prevented from fluctuating, and does not mean that the pulsation of the voltage is suppressed.

  As described above, according to this example, it is possible to provide a power conversion device in which the output current is less likely to oscillate even if the effective value of the input voltage varies.

The circuit diagram of the power converter device in the reference example 1. FIG. FIG. 5 is a detailed diagram of a feedback control unit in Reference Example 1. The graph showing the relationship between the target value of output power and the input voltage in Reference Example 1. The graph showing the time change of the input voltage in the reference example 1. FIG. The graph showing the time change of the input current in Reference Example 1. The graph showing the time change of the output current in Reference Example 1. The graph showing the time change of the capacitor voltage in Reference Example 1. The graph showing the relationship between output power and power efficiency in Example 1. FIG. The graph showing the relationship between the target value of output power and the input voltage in Reference Example 2 . 9 is a flowchart of a feedback control unit in Embodiment 2 . 9 is a graph showing a relationship between a gain adjustment degree and an input voltage in the second embodiment. The graph showing the time change of input voltage, input current, capacitor voltage, and output current when the effective value of input voltage in Example 2 falls. The circuit diagram of the power converter device in a comparative example. The graph showing the time change of the input voltage in a comparative example. The graph showing the time change of input current in a comparative example. The graph showing the time change of output current in a comparative example. The graph showing the time change of the capacitor voltage in a comparative example.

  The power converter can be an in-vehicle power converter for charging a battery mounted on a vehicle such as an electric vehicle or a hybrid vehicle. Further, the AC power source can be a commercial power source for home use, for example.

Further, in the first aspect of the present invention, the feedback control unit obtains a correlation between the power efficiency obtained by dividing the output power by the input power of the AC power supply, and the output power and the output voltage. The feedback control unit obtains the power efficiency corresponding to the output power and the output voltage measured before the effective value fluctuates using the correlation, and the obtained power efficiency. using the power efficiency, that is configured to calculate a target value of the output power after providing the effective value varies.
Therefore , the target value of output power can be calculated more accurately. That is, the power efficiency varies depending on output power and output voltage. Therefore, accurate power efficiency can be calculated by obtaining the power efficiency corresponding to the measured output power and output voltage using the correlation. Then, by calculating the target value of output power using the obtained accurate power efficiency, it becomes possible to calculate the target value with high accuracy.

The feedback control unit measures the instantaneous value of the input voltage for ¼ period or more of the input voltage, calculates the effective value, and performs the feedback control using the obtained effective value. It is preferable to be configured (Claim 3).
In this case, the effective value of the input voltage can be accurately obtained. That is, the effective value can be estimated from the rate of change by measuring the instantaneous value of the input voltage for a certain period of time. However, if the measurement time of the instantaneous value is short, the effective value may not be accurately estimated. Therefore, the effective value can be accurately estimated if the measurement time of the instantaneous value of the input voltage is made sufficiently long to be ¼ period or more. This makes it possible to accurately perform feedback control.

The feedback control unit measures the instantaneous value of the input voltage for ½ period or more of the input voltage, calculates the effective value, and performs the feedback control using the obtained effective value. It is preferable to be configured (claim 4).
In this case, the effective value of the input voltage can be accurately measured. That is, the effective value can be calculated by dividing the maximum value of the input voltage by √2, but if the input voltage measurement time is too short, the maximum value cannot be measured, and it is difficult to accurately determine the effective value. Therefore, if the instantaneous value of the AC voltage is measured for ½ period or more, the maximum value of the voltage can be measured at least once, and the effective value can be accurately calculated. This makes it possible to accurately perform feedback control when the effective value fluctuates.

The second aspect of the present invention includes a capacitor voltage measuring unit that measures the voltage of the smoothing capacitor, and an input current measuring unit that measures an input current sent from the AC power source to the ACDC converter. feedback control unit, that the voltage of the measured said input current and said smoothing capacitor is configured to perform feedback control so as to approach the target value.
Therefore , when the effective value of the input voltage varies, the voltage of the smoothing capacitor can be further stabilized. Therefore, the output current can be stably supplied from the smoothing capacitor, and the oscillation of the output current can be easily suppressed.

In the second aspect of the present invention, the feedback control unit is configured to decrease the target value of the input current when the effective value of the input voltage is lower than a predetermined value. The
Therefore, it is possible to prevent a problem that the input current flows too much. That is, when the effective value of the input voltage decreases, feedback control for increasing the input current is facilitated in order to suppress the voltage decrease of the smoothing capacitor. As a result, the input current flows too much, and problems such as breakage of electronic components constituting the power conversion device are likely to occur. Therefore, if the feedback control is performed so that the target value of the input current is reduced when the effective value is reduced, it is possible to prevent the input current from flowing too much and to easily suppress the above-described problems.

( Reference Example 1)
A reference example related to the power conversion apparatus will be described with reference to FIGS.
As shown in FIGS. 1 and 2, the power conversion apparatus 1 of this example includes an ACDC converter 2, a smoothing capacitor 3, a DCDC converter 4, an input voltage measurement unit 12, an output current measurement unit 13, and an output voltage measurement. Means 14 and a feedback control unit 5 are provided.
The ACDC converter 2 converts an AC voltage input from the AC power supply 10 into a DC voltage.
The smoothing capacitor 3 smoothes the DC voltage converted by the ACDC converter 2.
The DCDC converter 4 transforms the smoothed DC voltage and applies the DC voltage after the transformation to the battery 11 as the output voltage V _O to charge the battery 11.

The input voltage measuring unit 12 measures the input voltage V _i of the AC power supply 10.
The output current measuring unit 13 measures the output current I _O of the DCDC converter 4.
The output voltage measuring means 14 measures the output voltage V _O (the voltage of the battery 11) of the DCDC converter 4.
Feedback control unit 5, the output power P _O is the product of the output current I _O and an output voltage V _O is a feedback control so as to approach the target value P _O ^*.
The feedback control unit 5 sets the target value P of the output power P _O so that the voltage V _c of the smoothing capacitor 3 becomes constant when the effective value of the input voltage V _i measured by the input voltage measuring unit 12 fluctuates. It is configured to change _O ^* .

  The power converter 1 of this example is a vehicle-mounted power converter for charging a battery 11 mounted on a vehicle such as an electric vehicle or a hybrid vehicle.

The ACDC converter 2 of this example is a so-called PFC circuit. As shown in FIGS. 1 and 2, the ACDC converter 2 includes a diode bridge 20, a choke coil 21, a switching element 22 (IGBT element), and a discharge prevention diode 23. The diode bridge 20 performs full-wave rectification on the AC current sent from the AC power supply 10. The rectified current (input current I _i ) flows through the choke coil 21.

Further, the front stage portion 50 of the feedback control unit 5 performs switching control of the switching element 22. As a result, the waveform of the input current I _i is brought close to the waveform of the rectified input voltage V _i , the power factor of the input power Pi is improved, and the input voltage V _i is boosted.

The boosted input voltage V _i is smoothed by the smoothing capacitor 3. Further, the discharge prevention diode 23 prevents the electric charge stored in the smoothing capacitor 3 from being discharged through the switching element 22 when the switching element 22 is turned on.

  The DCDC converter 4 includes a bridge circuit 40, a transformer 42, a rectifier circuit 43, a current smoothing coil 44, and a voltage smoothing capacitor 45. The bridge circuit 40 includes four IGBT elements 41. By switching control of the IGBT element 41, the DC voltage smoothed by the smoothing capacitor 3 is converted into an AC voltage and applied to the primary coil 421 of the transformer 42. A voltage proportional to the turn ratio N2 / N1 between the primary coil 421 and the secondary coil 422 is output from the secondary coil 422 of the transformer 42. This voltage is rectified by the rectifier circuit 43, smoothed by the coil 44 and the capacitor 45, and applied to the battery 11.

The duty of the H bridge circuit is determined by the rear stage portion 60 (see FIG. 2) of the feedback control unit 5. By adjusting this duty, the amount of output current _IO flowing in the battery 11 is controlled.

The feedback control unit 5 of this example is configured by a microcomputer. As shown in FIG. 2, the front stage portion 50 of the feedback control unit 5 includes a target value input unit 51 that inputs a target value V _C ^* of the capacitor voltage V _C, a first subtraction unit 52, a first PI control unit 53, A limiter 54, a second subtracting unit 55, a second PI control unit 56, a third subtracting unit 57, a first multiplying unit 58, and a first adding unit 59 are provided.

The first subtracting unit 52 includes a target value _V ^{C *} of the capacitor voltage _{V C,} the difference between the measured capacitor voltage _{V C,} and outputs a control deviation [Delta] V _1. The first PI control unit 53 multiplies the control deviation ΔV ₁ by a gain and outputs the result as a first current target value I ₁ ^* . The first target current value I ₁ ^* is input to the limiter 54. The limiter 54 defines the upper limit of the first current target value I ₁ ^* . The first current target value I ₁ ^* is input to the second subtracting unit 55 after passing through the limiter 54.

The second subtraction unit 55 outputs the difference between the first current target value I ₁ ^* and the measured input current I _i as a control deviation ΔI ₁ . Then, the second PI control unit 56 multiplies the control deviation ΔI ₁ by the gain and outputs the second current target value I ₂ ^* . Thereafter, the third subtractor 57 outputs a difference Δ ₁ between the second current target value I ₂ ^* and the measured input voltage V _i . Then, in the first multiplication section 58 multiplies the inverse of the capacitor voltage _{V C} to the difference delta _1. Thereafter, 1 is added by the first adding unit 59 and the result is output as the duty of the switching element 22.

By performing the above processing, the front stage portion 50 of the feedback control unit 5 brings the waveform of the input current I _i closer to the waveform of the input voltage V _i and improves the power factor of the input power P _i .

On the other hand, the rear stage portion 60 of the feedback control unit 5 includes a power target value generation unit 61 that generates a target value P _O ^* of output power, a second multiplication unit 62, a fourth subtraction unit 63, and a third PI control unit 64. And a third multiplying unit 65 and a second adding unit 66.

Power target value generating section 61 as shown in FIG. 3, the relationship between the effective value of the input power V _i, the output power can be output without changing the voltage of the smoothing capacitor 3 in its effective value (target value P _{O ^*)} Is remembered. The power target value generating unit 61 is measured, the effective value of the input voltage V _i is inputted (see Fig. 1, Fig. 2). The power target value generation unit 61 calculates a target value P _O ^* corresponding to the measured effective value based on the correlation shown in FIG. For example, when the effective value is 200 V, the target value _PO ^{* is set} to 3300 (W). When the effective value decreases to 140V, the target value P _O ^* is changed to 2310 (W).

The target value P _O ^*, without lowering the voltage V _c of the smoothing capacitor may be an output can power, also a value smaller than the value calculated from the correlation of FIG. 3 as the target value P _O ^* Good.

As shown in FIG. 2, the target value P _O ^* output from the power target value generation unit 61 is input to the second multiplication unit 62. The second multiplication unit 62 multiplies the target value P _O ^* of the output power P _O by the reciprocal of the measured output voltage V _{O and} outputs the result as a third current target value I ₃ ^* . The fourth subtractor 63 outputs the difference between the third current target value I ₃ ^* and the measured output current I _O as a control deviation ΔI ₂ and inputs it to the third PI controller 64. The third PI control unit 64 multiplies the control deviation ΔI ₂ by a gain and outputs the result as a parameter V _o ^* . Third multiplying unit 65, the parameter _V ^{o *,} multiplied by the reciprocal of the measured capacitor voltage _{V C.} This result is input to the second adder 66. The second adder 66 adds the FF term to the input value and outputs it as the duty of the bridge circuit 40.
By performing the above processing, the subsequent portion 60 of the feedback unit 5 determines the duty of the bridge circuit 40 so that the output current I _O is reduced when the effective value of the input voltage V _i is reduced.

The experimental result using the power converter device 1 of this example is shown in FIGS. 4 is a waveform of the input voltage Vi, and FIGS. 5 to 7 are waveforms of the input current I _i , the output current I _O , and the voltage of the smoothing capacitor 3 (capacitor voltage V _C ), respectively. In this experiment, as shown in FIG. 4, the effective value V _e1 of the first wave W1 and the second wave of the input voltage V _i is set to 200 V, and the effective value V _e2 is decreased to 140 V from the third wave. In this way, the feedback control section 5 of the power conversion apparatus 1 lowers the target value P _O of the output power P _O ^*. Along with this, as shown in FIG. 6, the output current _IO decreases from 8A to about 6A. Thus, as shown in FIG. 7, the average value of the capacitor voltage Vc is not significantly lowered, even after the effective value of the input voltage V _i is reduced, so that the current from the smoothing capacitor 3 to the DCDC converter can be stably supplied become. Therefore, the output current _IO does not oscillate (see the comparative example shown in FIG. 16).

In this example, the effective value is calculated by measuring the instantaneous value of the input voltage V _i (see FIG. 4) for ¼ period or more of the input voltage. Then, feedback control of output power is performed using the obtained effective value. The feedback control unit 5 repeats this feedback control every ¼ period. Further, in this embodiment, the instantaneous value of the input voltage V _i, is repeatedly measured, for example, every 33 .mu.s.

The effect of this example will be described. In this example 1, as shown in FIG. 2, when the effective value of the input voltage V _i is changed, so that voltage V _c of the smoothing capacitor 3 is constant, the feedback control unit 5, the output power P _O The target value _PO ^* is configured to be changed.
That is, when the effective value of the input voltage V _i decreases, the feedback control unit 5 reduces the target value P _O ^* of the output power P _O. In this way, since the output current _IO is reduced, it is possible to prevent the charge Q stored in the smoothing capacitor 3 from being reduced. Therefore, the output current I _O can be stably supplied from the smoothing capacitor 3 to the DCDC converter 4, and oscillation of the output current I _O can be prevented.

In addition, the feedback control unit 5 of this example measures the instantaneous value of the input voltage for ¼ period or more of the input voltage and calculates the effective value. Then, feedback control is performed using the obtained effective value.
In this way, the effective value of the input voltage V _i can be accurately obtained. That is, the effective value can be estimated from the rate of change by measuring the instantaneous value of the input voltage V _i for a certain period of time. However, if the measurement time of the instantaneous value is short, the effective value may not be accurately estimated. Therefore, the effective value can be accurately estimated if the measurement time of the instantaneous value of the input voltage V _i is sufficiently long to be ¼ period or more. This makes it possible to accurately perform feedback control.

  In this example, the effective value is calculated by measuring the instantaneous value of the input voltage for ¼ period or more, but the effective value may be calculated by measuring ½ period or more.

In this example, as shown in FIGS. 1 and 2, the front stage portion 50 of the feedback control unit 5 performs feedback control so that the input current I _i and the capacitor voltage V _c approach the target values.
In this way, when the effective value of the input voltage V _i varies, the voltage V _c of the smoothing capacitor 3 can be further stabilized. Therefore, the output current _IO can be stably supplied from the smoothing capacitor 3, and the oscillation of the output current _IO can be easily suppressed.

  As described above, according to this example, it is possible to provide a power conversion device in which the output current is less likely to oscillate even if the effective value of the input voltage varies.

(Example 1 )
This example is an example of changing the target value P _O ^* method for calculating the output power P _O. As shown in FIG. 8, the feedback control unit 5 of this example stores the correlation between the power efficiency η, which is a value obtained by dividing the output power P _O by the input power P _i , and the output power P _O and the output voltage V _O. doing. The feedback control unit 5 obtains the power efficiency η corresponding to the output power P _O and the output voltage V _O measured before the effective value V _e of the input voltage V _i fluctuates using this correlation.
For example, when the output voltage V _O is 335 V and the output power P _O is 3000 W before the effective value V _e fluctuates, the power efficiency η ₁ is 0.88 from the graph of FIG.

Then, the target value P _O ^* of the output power P _O after the effective value V _e fluctuates is calculated using the obtained power efficiency η ₁ .
A method for calculating the target value _PO ^* will be described. First, as shown in Equation 1 below, the output power P _O is divided by η ₁ to calculate the input power P _i before the effective value fluctuates.
P _O / η ₁ = P _i (1)

Thereafter, as shown in Equation 2 below, the input power P _i is divided by the effective value V _e of the input voltage V _i . Thereby, the input current I _i before the effective value V _e fluctuates is calculated.
P _i / V _e = I _i (2)

When the effective value V _e of the input power V _i decreases to V _e ′, feedback control for increasing the input current I _i works to suppress the voltage drop of the smoothing capacitor 3 by the front stage portion 50 of the feedback control unit 5. However, since this feedback control has a slow response, the same current I _i continues to flow for a while. Therefore, _'input after the decrease in power P _i' effective value V _e is as shown in Equation 3 below, the product of the effective value V _{e 'and} the input current I _i.
P _i ′ = V _e ′ · I _i (3)

Thereafter, the feedback control unit 5, by using the following Equation 4, at the time when the input power P _{i 'becomes} a value determined by the above equation 3 can be output without changing the voltage V _C of the smoothing capacitor 3 Output to calculate the value of the power _{P O} (target value _P ^{O *).}
P _O ^* = P _i '× η ₂ (4)
Note that η ₂ is the power efficiency when the input power is P _i ′. η ₂ is stored in advance in the feedback control unit 5.
In addition, the configuration is the same as in Reference Example 1.

The effect of this example will be described. With the above configuration, the target value P _O ^* of the output power P _O can be calculated more accurately. That is, the power efficiency η varies depending on the output power P _O and the output voltage V _O. Therefore, by obtaining the power efficiency η corresponding to the measured output power P _O and output voltage V _O using the graph of FIG. 8, it is possible to calculate the accurate power efficiency η. Then, using η accurate power efficiency obtained by calculating the target value P _O of the output power P _O ^*, it is possible to accurately calculate the target value P _O ^*.
In addition, the same effects as those of Reference Example 1 are obtained.

( Reference Example 2 )
In this example, the calculation method of the target value P _O ^* of the output power is changed. In this embodiment, as shown in FIG. 9, the target value P _O of the output power ^*, the relationship between the effective value of the input voltage V _i, are stored in the hysteresis. For example, when the effective value is between V _{1 and} V ₄ , the first constant value (2700 W) is output as the target value P _O ^* . Then, if the effective value is greater than V _4, and outputs a larger second predetermined value (3000W) than the first predetermined value. Moreover, until the effective value becomes V ₃ or less decreased keeps outputting a second predetermined value as a target value (3000W). When the effective value is smaller than _{V 3} is reduced to a first predetermined value (2700 W).
In this example, such a hysteresis is provided in a plurality of places on the graph.
In addition, the same configuration as the reference example 1 is provided.

The effect of this example will be described. With the above configuration, it is difficult to be affected by noise. That is, even if noise enters the measured effective value of the input voltage V _i and fluctuates between V _{3 and} V ₄ , the target value P _O ^* does not change during that period. Therefore, noise by can be prevented target value P _O ^* is switched many times, it is possible to output the target value P _O ^* stable.
In addition, the same effects as those of Reference Example 1 are obtained.

(Example 2 )
This example is an example in which the control method in the front stage portion 50 of the feedback control unit 5 is changed. The feedback control unit 5 of this example reduces the target value (first current target value I ₁ ^* ) of the input current I _i when the effective value of the input voltage V _i is lower than a predetermined value. It is configured as follows.
That is, when the effective value is lower than a predetermined value, the gain in the first PI control unit 53 (see FIG. 2) is reduced. Thereby, the first current target value I ₁ ^* is reduced and the input current I _i is reduced.

FIG. 10 shows a flowchart of the feedback control unit 5. First, in step S1, the effective value of the input voltage V _i is determined whether the variation. If YES is determined here, the process proceeds to step S2 to determine whether or not the effective value of the input voltage V _i has decreased. If YES is determined here, the process proceeds to step S3, and the gain of the first PI control unit 53 (see FIG. 2) is decreased. If it is determined No in step S2, the process proceeds to step S4, and the gain of the first PI control unit 53 is increased. FIG. 11 shows the relationship between the effective value of the input voltage V _i and the gain adjustment degree. Such a relationship is stored in advance by the feedback control unit 5, and the gain is adjusted using this.
In addition, the same configuration as the reference example 1 is provided.

The effect of this example will be described. With the above configuration, it is possible to prevent a problem that the input current I _i flows excessively. That is, when the effective value of the input voltage V _i decreases, feedback control for increasing the input current I _i is facilitated to suppress the voltage decrease of the smoothing capacitor 3. As a result, the input current I _i flows too much, and problems such as breakage of electronic components constituting the power conversion device 1 are likely to occur. Therefore, if the feedback control is performed so that the target value of the input current I _i is lowered when the effective value is lowered, it is possible to prevent the input current I _i from flowing too much and to easily suppress the above problems.

The experimental result of this example is shown in FIG. In this experiment, up to the first wave to third wave of the input voltage V _i is Yes and the effective value to 200V, which reduces the effective value to 140V from the fourth wave. When the effective value decreases, the capacitor voltage V _C decreases, the input current I _i is likely to rise. However, in this example, when the effective value decreases, the feedback control works so as to decrease the target value of the input current I _i (first current target value I ₁ ^* ), so the input current I _i does not increase greatly. As shown in FIG. 12, the input current I _i is about 21 A at the maximum value, and can be sufficiently suppressed.
In addition, the same effects as those of Reference Example 1 are provided.

(Comparative example)
This example is an example in which the configuration of the feedback control unit 95 is changed as a comparative example, as shown in FIG. The feedback control unit 95 of this example always generates a constant target value P _o ^* in the rear stage portion 960, and performs feedback control of the output current I _O using this target value P _o ^* . That is, even when the effective value of the input voltage V _i decreases, the target value P _o ^* of the output power does not change.

Therefore, in this embodiment, the output current I _O is not reduced even if the effective value of the input voltage V _i drops. Therefore, when the effective value is decreased, the charge Q accumulated in the smoothing capacitor 93 tends to decrease, the voltage V _C of the smoothing capacitor 93 tends to decrease. As a result, the output current _IO tends to oscillate.

14 to 17 show the experimental results of this example. As in this experiment shown in Figure 14, the input voltage _{V i,} the first wave W1 were refer to effective value of the second wave W2 to 200V, which reduces the effective value to 140V from the third wave W3. In this example, since the input voltage V _i is not reduced even if the output current is decreased, as shown in FIG. 17, the capacitor voltage Vc gradually decreases. Then, it becomes impossible to supply sufficient output current _{I O} from the smoothing capacitor 93 to the DCDC converter 94, as shown in FIG. 16, the output current _{I O} begins to oscillate. In this case, problems such as a decrease in charging efficiency of the battery 911 are likely to occur.

DESCRIPTION OF SYMBOLS 1 Power converter 10 AC power supply 11 Battery 12 Input voltage measuring means 13 Output current measuring means 14 Output voltage measuring means 2 ACDC converter 3 Smoothing capacitor 4 DCDC converter 5 Feedback control part

Claims (4)

A power converter (1) for charging a battery (11),
An ACDC converter (2) for converting an AC voltage input from the AC power supply (10) into a DC voltage;
A smoothing capacitor (3) for smoothing the DC voltage converted by the ACDC converter (2);
A DCDC converter (4) for transforming the smoothed DC voltage, applying the DC voltage after the transformation to the battery (11) as an output voltage, and charging the battery;
Input voltage measuring means (12) for measuring the input voltage of the AC power source (10);
Output current measuring means (13) for measuring the output current of the DCDC converter (4);
Output voltage measuring means (14) for measuring the output voltage;
A feedback control unit (5) that performs feedback control so that output power that is a product of the output current and the output voltage approaches a target value;
The feedback control unit (5) outputs the output so that the voltage of the smoothing capacitor (3) becomes constant when the effective value of the input voltage measured by the input voltage measuring means (12) varies. It is configured to change the power target value ,
The feedback control unit (5) includes a storage unit that stores a correlation between a power efficiency obtained by dividing the output power by an input power of the AC power supply, and the output power and the output voltage, and the feedback The control unit (5) obtains the power efficiency corresponding to the output power and the output voltage measured before the effective value fluctuates using the correlation, and uses the obtained power efficiency, A power converter (1), wherein a target value of the output power after the effective value fluctuates is calculated.   A power converter (1) for charging a battery (11),
  An ACDC converter (2) for converting an AC voltage input from the AC power supply (10) into a DC voltage;
  A smoothing capacitor (3) for smoothing the DC voltage converted by the ACDC converter (2);
  A DCDC converter (4) for transforming the smoothed DC voltage, applying the DC voltage after the transformation to the battery (11) as an output voltage, and charging the battery;
  Input voltage measuring means (12) for measuring the input voltage of the AC power source (10);
  Output current measuring means (13) for measuring the output current of the DCDC converter (4);
  Output voltage measuring means (14) for measuring the output voltage;
  A feedback control unit (5) that performs feedback control so that output power that is a product of the output current and the output voltage approaches a target value;
  The feedback control unit (5) outputs the output so that the voltage of the smoothing capacitor (3) becomes constant when the effective value of the input voltage measured by the input voltage measuring means (12) varies. It is configured to change the power target value,
  Capacitor voltage measuring means for measuring the voltage of the smoothing capacitor (3), and input current measuring means for measuring an input current sent from the AC power supply (10) to the ACDC converter (2), the feedback control unit (5) is configured to perform feedback control so that the measured input current and the voltage of the smoothing capacitor approach a target value,
  The feedback control unit (5) is configured to reduce the target value of the input current when the effective value of the input voltage is lower than a predetermined value. (1).   3. The power conversion device (1) according to claim 1, wherein the feedback control unit (5) measures the instantaneous value of the input voltage for ¼ period or more of the input voltage and calculates the effective value. The power conversion device (1) is configured to perform the feedback control using the obtained effective value.   The power conversion device (1) according to claim 1 or 2, wherein the feedback control unit (5) measures the instantaneous value of the input voltage for ½ period or more of the input voltage and calculates the effective value. The power conversion device (1) is configured to perform the feedback control using the obtained effective value.

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