JP3070606B1 - Power converter - Google Patents

Abstract

An object of the present invention is to provide a high-efficiency power conversion device in which power loss of a buck-boost power converter is small. An electric power converter obtains an effective level of a voltage waveform of a commercial AC power supply, multiplies the effective level by a coefficient of a normal commercial AC, and obtains a peak value Vinp of the commercial AC. A limiter 93 that outputs the peak value Vinp when the peak value Vinp is within a predetermined range, the upper limit value when the peak value Vinp is larger than the upper limit value of the predetermined range, and the lower limit value when the peak value Vinp is smaller than the lower limit value of the predetermined range. And a multiplier 94 for generating a command output voltage value from a product of the output signal of the limiter and the output signal of the oscillator 103 synchronized with the voltage waveform of the commercial AC power supply, and setting the command output voltage value in the control unit 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter used, for example, as an uninterruptible power supply for a computer system.

[0002]

2. Description of the Related Art Generally, an uninterruptible power controller uses a power converter. The configuration of this conventional power converter will be described below.

FIG. 8 is a schematic configuration diagram of a conventional power converter. This power converter inputs an AC voltage signal Vin of a commercial AC power supply 100 to a buck-boost power converter 101, and outputs an AC voltage signal V based on an output voltage command value Vd described later.
This is a configuration in which constant output power is supplied to the load 110 by raising and lowering in.

The AC voltage signal Vi of the AC power supply 100
Synchronization circuit 10 for generating a synchronization signal with n phase synchronization
4, a sine wave oscillator 103 that generates a sine wave signal of a predetermined level in phase synchronized with the synchronization signal, and an output voltage command value Vd obtained by multiplying the sine wave signal by the reference power supply 105. And a multiplier 106 for sending.

When the AC voltage signal Vin is larger than the predetermined command output voltage value Vd from the multiplier 106, the buck-boost power converter 101 outputs the AC voltage signal Vi.
n is reduced and a constant output voltage is sent to the load 110. When the output voltages are equal, the AC voltage signal Vin is not converted and output.

When the voltage is small, the AC voltage signal Vin
And a constant output voltage is sent to the load 110.

[0007]

However, the conventional power conversion device has an AC voltage signal of the commercial AC power supply 100 and an output voltage command value of the AC voltage signal generated by the device in synchronization with the AC voltage signal. And control based on the difference. For this reason, the switching operation becomes more frequent as the difference increases, so that there is a problem that the power loss in the power converter increases.

[0008] The present invention has been made in view of the above,
It is an object of the present invention to provide a high-efficiency power conversion device in which the power loss of a buck-boost power converter is small.

[0009]

According to the present invention, a commercial AC power supply is input, and the AC power supply voltage is switched by a switching operation based on a difference between the input AC power supply and a predetermined command output voltage value synchronized with the voltage waveform of the commercial AC power supply. In a power converter that obtains a constant output voltage at a load by stepping up and down, the DC amount of the voltage waveform of the commercial AC power supply is obtained, and the original DC voltage is calculated from the voltage of this DC amount and the coefficient of the voltage waveform of the commercial AC power supply without distortion. Means for obtaining a peak value of a voltage waveform of a commercial AC power supply; and, when the peak value is within a predetermined range, the peak value; when the peak value is larger than an upper limit value of the predetermined range, the upper limit value is set to a lower limit of the predetermined range. A command output voltage generator for generating a command output voltage value from a limiter means for outputting the lower limit value when the value is smaller than the value, and an output signal of the limiter and an output signal of an oscillator synchronized with a voltage waveform of the commercial AC power supply. And gist that a stage.

Further, the command output voltage generating means sets the product of the output signal of the limiter means and the output signal of the sine wave oscillator synchronized with the voltage waveform of the commercial AC power supply as the command output voltage value. .

[0011]

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

FIG. 1 is a diagram showing an embodiment of the present invention. The power conversion device according to the present embodiment includes first and second AC power supply terminals 4 and 5 connected to commercial AC power supply 100.
In a configuration in which the voltage between the first and second AC output terminals 6 and 7 is stepped up and down by the conversion circuit 1 controlled by the control circuit 2 and the voltage is output between the first and second AC output terminals 6 and 7, The voltage signal Vin is obtained, its DC amount is obtained, and this DC amount Fi is multiplied by a predetermined value to obtain the AC voltage signal V
An ideal peak value Vinp without distortion of “in” (the peak value Vinp of the original waveform without distortion) is obtained.

Then, the peak value VinP is converted into a value within a predetermined range, and the converted value is output voltage command value Vd.
This is set in the control unit so as to prevent useless switching operation.

The above-described acquisition of the AC voltage signal Vin is a voltage proportional to the AC voltage signal Vin. However, in this embodiment, the same signal or the same voltage will be used for the sake of convenience.

There are various methods for obtaining the DC amount of the AC voltage signal Vin of the commercial AC power supply 100 described above.

For example, (1) An operational amplifier for calculating an effective value is used.

(2) The microcomputer takes in the AC voltage signal Vin, and finds the square root of a value obtained by averaging the square of the instantaneous value in one cycle. (1 / √2 of the maximum value for a sine wave) (3) The AC voltage signal Vin is rectified and then filtered with a large time constant to obtain an average value of the AC voltage signal Vin.

The peak value Vi of the original waveform without distortion
To find np, multiply by 1.5707.

In this embodiment, the method (2) will be described.

Next, the details of each component will be described.

The conversion circuit 1 includes first, second, third, fourth,
Fifth and sixth switches Q1, Q2, Q3, Q4, Q
5, Q6, a conversion capacitor C, a first reactor L1 in the input stage, a second reactor L2 in the output stage, an input stage filter capacitor C1, and an output stage filter capacitor C2.

The first to sixth switches Q1 to Q6 are insulated gate (MOS) field effect transistors each having a source connected to a bulk (substrate), and include first, second, third and third switches. Fourth, fifth and sixth FET switches S1, S2, S3, S4, S5, S6 and first, second, third, fourth, fifth and sixth diodes D1 connected in anti-parallel thereto. , D2, D3, D4, D5, D6. Note that diodes D1 to D6 are connected to switches Q1 to Q6.
It can be made into individual parts without being built in. Also,
FET switches S1 to S6 are bipolar transistors,
A semiconductor switch such as an IGBT can be used.

A first series circuit consisting of a series connection of first and second switches Q1, Q2, a second series circuit consisting of a series connection of third and fourth switches Q3, Q4, The third series circuit composed of the sixth switches Q5 and Q6 connected in series and the conversion capacitor C are connected in parallel with each other.

The middle point of the first series circuit, that is, the interconnection point 8 of the first and second switches Q1 and Q2 is an AC terminal of the first conversion circuit, and is connected via the first reactor L1 of the input stage. Connected to the first AC power supply terminal 4. The middle point of the second series circuit, that is, the interconnection point 9 of the third and fourth switches Q3 and Q4 is connected to the second AC power supply terminal 5 as a common terminal.
It is connected to the. In addition, the reactor L3 can be connected between the connection point 9 and the second AC power supply terminal 5 as shown by a dotted line. The middle point of the third series circuit, that is, the interconnection point 10 of the fifth and sixth switches Q5 and Q6 is the second AC terminal of the conversion circuit, and the second reactor L of the output stage.
2 to a first AC output terminal 6. The load 110 is connected between the first and second AC output terminals 6 and 7 as output means. Note that the second AC power supply terminal 5 and the second AC output terminal 7 are ground terminals and are commonly connected to each other.

The first filter capacitor C1 is connected between the first and second AC power supply terminals 4 and 5 for removing high frequency components of the input current. The second filter capacitor C2 is connected between the first and second AC output terminals 6 and 7 for removing high frequency components of the output voltage.

In order for the control circuit 2 to control the first to sixth switches Q1 to Q6, the control circuit 2 and the first to sixth switches
And the gates (control terminals) of the switches Q1 to Q6 are connected by lines 12, 13, 14, 15, 16, and 17. Also, in order for the control circuit 2 to form control signals for the switches Q1 to Q6, the first and second AC power supply terminals 4 and 5 are connected by lines 18 and 19, and the first AC output terminal 6 is connected by line 20. , And both ends of the capacitor C by lines 21 and 22 and the reactor L1
A current detector 23 for detecting a current flowing through the control circuit 2 is connected to the control circuit 2 by a line 24.

The control circuit 2 includes an input voltage detection circuit 41,
DC voltage detection circuit 42, output voltage detection circuit 43, first command value generation means 44, second command value generation means 45, square wave generator 46, first, second and third arithmetic circuits 47, 4
8, 49, first and second limiters 50, 51, a triangular wave generator 52, first, second and third comparators 53,
54, 55, first, second and third anti-phase signal forming circuits 5
6, 57, 58.

The control circuit 2 is connected to the output voltage command value generation circuit 90 according to the present embodiment.

The output voltage command value generating circuit 90 comprises an effective value calculating section 91, a peak calculating section 92, a limiter 93, a synchronizing circuit 104, a sine wave oscillator 103, and a multiplier 94.

The effective value calculating section 91 receives an AC voltage signal Vin as the commercial power supply 100 and receives the AC voltage signal Vi.
n is sampled at fixed time intervals to obtain an AC voltage signal Vin
The instantaneous value Si (S1, S2,...) Of the waveform is extracted.

Then, the effective value Gi of the commercial AC voltage signal Vin is determined using the maximum instantaneous value of the instantaneous value Si.

That is, the effective value calculating section 91 removes a noise component superimposed on the AC voltage signal Vin of the commercial power supply 100. That is, even if a very large noise is applied to the AC voltage signal Vin due to a lightning strike or the like, this will not be detected.

The peak calculator 92 multiplies the effective value Gi of the AC voltage signal Vin obtained by the effective value calculator 91 by √2 (1.41) to obtain the peak value Vin of the original waveform without distortion.
Find p.

This Δ2 is the crest factor δ of the ideal AC voltage signal Vin without distortion.

When the “peak value Vinp (DC level) of the original waveform without distortion” obtained by the peak calculator 92 is within a predetermined range, the limiter 93 uses the peak value Vinp as the limiter output Rvp as it is. The signal is sent to the multiplier 94.

When the peak value Vinp is larger (higher) than the upper limit value of the predetermined range, Vinp limited by the upper limit value is used as a limiter output Rvp as a multiplier 94.
To send to.

Further, when the peak value Vinp is smaller than the lower limit of the predetermined range, the V limited by the lower limit is used.
Inp is output to the multiplier 94 as a limiter output Rvp.

For example, the upper and lower limits of the limiter 93 are set to (10
0 ± 10) · √2V, if limiter input is greater than 110 · √2V, 100 · √2V is Rv
Output as p.

If the limiter input is smaller than 90√2V, 90√2V is output as Rvp.

Further, from 90√2V to 110√2V
If the value is up to, the input value is output as it is.

The multiplier 94 multiplies the output signal Rvp from the limiter 93 by the output of the sine wave oscillator 103 synchronized with the power supply voltage Vin by the synchronizing circuit 104, and uses this as an output voltage command value Vd. Output to 2.

Next, the configuration of the control unit 2 will be described.

The input voltage detection circuit 41 of the control section 2 detects a voltage proportional to the waveform of the AC voltage signal Vin of the commercial power supply 100 (hereinafter, simply referred to as a detected voltage of the commercial power supply). Although this detection circuit outputs a voltage lower than the actual value of the AC voltage signal Vin of the commercial power supply 100, it is assumed here that the same value as the actual voltage is output here for easy understanding.

The DC voltage detection circuit 42 of the control unit 2 is connected to both ends of the capacitor C by lines 21 and 22.
A detection signal indicating the voltage Vc of the capacitor C is output. The output voltage detection circuit 43 is connected to the first and second AC output terminals 6 and 7 by lines 20 and 19, and outputs the output voltage Vo.
Is output.

Each of the detection circuits 42 and 43 outputs a voltage lower than the actual values of the capacitor voltage Vc and the output voltage Vo. However, in order to facilitate understanding, the same value as the actual voltage is output here. Shall be.

The first command value generating means 44 can be called an input stage or converter voltage command value generating means, and includes a DC reference voltage source 59 and two subtractors 60 and 6.
3, two proportional integral (PI) circuits 61 and 64, and a multiplier 62.

The subtractor 60 outputs to the reference voltage source 59 an error signal indicating the difference between the reference voltage and the detection output of the DC voltage detection circuit 42. This error signal is input to a multiplier 62 via a proportional integration circuit 61, and is multiplied by a reference sine wave (for example, a sine wave having an effective value of 100 V) obtained from the input voltage detection circuit 41.

The output of the multiplier 62 is the voltage V of the capacitor C.
This is an input current command value for keeping c constant. Subtractor 6
3 outputs a signal indicating the difference between the output of the multiplier 62 (input current command value) and the detection value of the line 24 connected to the current detector 23 (detection current value).

The output of the subtractor 63 is output via a proportional integration circuit 64. The output of the proportional integration circuit 64 is the first command value Vrc. The first command value Vrc is equal to the interconnection point 8 of the first and second switches Q1 and Q2 and the third and fourth
Is a command value for setting the voltage Vconv of the fundamental wave between the switches Q3 and Q4 to the interconnection point 9 to a desired value.

The first command value Vrc is a sine wave synchronized with the AC voltage signal Vin, and contains information for controlling the voltage of the capacitor C to a predetermined value and information for improving the input power factor. including.

The second command value generating means 45 can be called an output stage or an inverter voltage command value generating means, and comprises a subtracter 67 and a proportional-integral-derivative (PID) circuit 68. The subtracter 67 outputs a signal indicating the difference between the output of the reference voltage command value generator 90 and the output of the output voltage detection circuit 43.

The output of this subtracter 67 is proportional integral integral derivative (P
ID) output via the circuit 68 and the second command value Vri
Becomes The second command value Vri is determined by the interconnection point 9 between the third and fourth switches Q3 and Q4 and the fifth and sixth switches Q
5, the voltage Vin of the fundamental wave between the interconnection point 10 of Q6 and Vin
This is a command value for setting v to a desired value. Vri is a sine wave synchronized with the AC voltage signal Vin.

The square wave generator 46 includes an amplifier 69 and a limiter 70. The amplifier 69 includes the input voltage detection circuit 41
The reference sine wave Vf of the frequency (hereinafter, 50 Hz) of the AC voltage signal Vin as the commercial power source obtained from
Is amplified to a voltage whose peak is sufficiently higher than 200V. The limiter 70 limits the amplifier output between + Vs (+200 V) equal to the maximum value Vt of the output triangular wave generator 52 and -Vs (-200 V) equal to the minimum value, and sets the high level of + Vs and the -Vs A square wave voltage Vs having alternating low levels is generated.

The first arithmetic circuit 47 includes a converter voltage command value generating means 44 and an inverter stage voltage command value generating means 4
5, and a square wave generator 46, and Vrc +
The operation of Vs-Vri is executed. That is, the first arithmetic circuit 47 includes an adder and a subtractor, and subtracts the inverter voltage command value Vri from the value obtained by adding the square wave voltage Vs to the converter voltage command value Vrc. It should be noted that the order of addition and subtraction can be reversed to Vrc−Vri + Vs. The first arithmetic circuit 47 calculates the inverter voltage command value Vri
Has a function of automatically selecting the high frequency on / off operation or the low frequency on / off operation of the first and second switches Q1 and Q2 in response to the change of

The second arithmetic circuit 48 is connected to the converter voltage command value generating means 44, the inverter voltage command value generating means 45 and the square wave generator 46, and Vri + Vs-
Execute the calculation of Vrc. That is, the second arithmetic circuit 48 includes an adder and a subtractor, and the inverter voltage command value Vri
The converter voltage command value Vrc is subtracted from the value obtained by adding the square wave voltage Vs to the converter voltage Vs. It should be noted that the order of addition and subtraction can be reversed to Vri−Vrc + Vs. This second
Has a function of automatically selecting the high-frequency on / off operation or the low-frequency on / off operation of the fifth and sixth switches Q5 and Q6 in response to a change in the inverter voltage command value Vri.

The first limiter 50 is a first operation circuit 47
Of the square wave voltage Vs to the high level + Vs and the low level −
Vs1 and the first switch control command value Vr1
Is output. Vr1 is the input stage switches Q1, Q2
Of the generated voltage command value.

The second limiter 51 is connected to the second arithmetic circuit 48
Of the square wave voltage Vs to the high level + Vs and the low level −
Vs and the second switch control command value Vr3
Is output. Note that Vr3 is set to the output stage switches Q5 and Q6.
Of the generated voltage command value.

The third arithmetic circuit 49 is connected to the inverter voltage command value generating means 45 and the second limiter 51,
Execute the calculation of r3-Vri.

The triangular wave generator 52 generates a triangular wave voltage Vt, that is, a sawtooth voltage having a frequency (for example, 20 kHz) sufficiently higher than the frequency (50 Hz) of the AC voltage signal Vin of the power supply 3. In FIG. 1, one triangular wave generator 52 is connected to the first, second and third comparators 53, 54 and 55, but the first, second and third comparators 53, 5
A dedicated triangular wave generator for 4,55 can also be provided. Also, one triangular wave generator 52 can generate three types of triangular waves.

The first comparator 53 is connected to the first limiter 50 and the triangular wave generator 52. The first comparator 53 compares the command value Vr1 with the triangular wave voltage Vt and outputs an on / off control signal for the first switch Q1 to the line 12. Is output in binary format.

The second comparator 54 is connected to the third arithmetic circuit 49 and the triangular wave generator 52, compares the command value Vr2 with the triangular wave voltage Vt, and controls the line 14 to turn on / off the third switch Q3. Output the signal in binary format.

The third comparator 55 is connected to the second limiter 51 and the triangular wave generator 52. The third comparator 55 compares the command value Vr3 with the triangular wave voltage Vt and outputs an on / off control signal for the fifth switch Q5 to the line 16. Is output in binary format.

The first negative-phase signal forming circuit 56 is composed of a NOT circuit, is connected to the first comparator 53, and is connected to the second switch Q2 composed of the negative-phase signal of the ON / OFF control signal of the first switch Q1. Line 13 on / off control signal
Output to

The second negative-phase signal forming circuit 57 is composed of a NOT circuit, is connected to the second comparator 54, and is connected to the fourth switch Q4, which is a negative-phase signal of the ON / OFF control signal of the third switch Q3. Line 15 on / off control signal
Output to

The third negative-phase signal forming circuit 58 is formed of a NOT circuit, is connected to the third comparator 55, and is connected to the sixth switch Q6 which is a negative-phase signal of the ON / OFF control signal of the fifth switch Q5. Outputs on / off control signal.

The first, second, and third comparators 53, 54, and 55 can include first, second, and third negative-phase signal forming circuits 56, 57, and 58, respectively. In addition, the first, second and third anti-phase signal forming circuits 5
6, 57 and 58 are not formed by NOT circuits but are constituted by three comparators for negative phase signals, and the three comparators for negative phase signals are connected in the same manner as the comparators 53, 54 and 55 for positive phase signals, It is also possible to reverse only the polarity of the sine wave signal comparators 53, 54, 55.

Next, the operation of the embodiment of the present invention will be described. As described in detail in Japanese Patent Application No. 11-063994, the step-up / step-down power conversion circuit 1 operates in three modes. The first mode is the AC voltage signal Vin of the power supply 100.
(For example, 100 V), a non-conversion mode in which the same output voltage Vo is obtained between the first and second AC output terminals 6 and 7, and a second mode in which the output voltage Vo is lower than the AC voltage signal Vin.
The third mode is a step-down mode for obtaining an AC voltage signal Vi.
This is a boost mode in which an output voltage Vo higher than n is obtained. The control circuit 2 compares the AC voltage signal Vin from 47, 48, 50, 51 with the output voltage command value Vd,
The above modes are automatically switched. Strictly speaking, Vr
When the magnitude of c is larger than Vr1, the mode is switched to the step-down mode, when the magnitude is equal to the non-conversion mode, and when it is smaller, the mode is switched to the boost mode.

Next, the output voltage command value generating circuit 90 according to the present embodiment will be described.

(1) The passing range of the limiter 93 is set to (100
± 10) · √2 V will be described.

FIG. 2 shows the output characteristics of the output voltage command value generation circuit 90, FIG. 3 is an explanatory diagram for explaining the operation of the limiter, and FIG. 4 shows an operation example of the buck-boost power conversion circuit 1. The operation will be described below with reference to FIG.

(A) For example, when the peak value Vinp (DC level) of the original waveform obtained by the effective value calculation section 91 and the peak calculation section 92 is 100 V√2 V, the limiter 93 has an input value of 90 ・√2V ~ 110V ・ √
Since the predetermined range for passing 2V is set, the input value 100V · √2V is output as it is.

The multiplier 94 outputs the output signal Rvp (100 V√2 V) from the limiter 93 and the output of the sine wave signal of the sine wave oscillator 103 whose phase is synchronized with the input commercial AC power supply signal vin (this signal is The product with the peak value is sent to the subtractor 67 of the second command value generating means 45 of the control circuit 2.

The control circuit 2 sets the conversion circuit 1 in the non-conversion mode because the AC voltage signal Vin (effective value is 100 V) and the output voltage command value Vd (corresponding to = 100 V) are equal.
The step-up / step-down power conversion circuit 1 receives the input AC voltage signal Vi.
n = 100 V is output as it is (non-conversion mode).

That is, in the non-conversion mode in which the same output voltage Vo as the AC voltage signal Vin is obtained, the first comparator 53, the second comparator 54, the third comparator 55, and the first reverse comparator 53 of the control circuit 2 are used. Phase signal forming circuit 56,
From the second negative-phase signal forming circuit 57 and the third negative-phase signal forming circuit 58, the first to sixth switches Q1 to Q6
Control signals (B) to (G) are supplied.

That is, the first and fifth switches Q1, Q
5 is turned on intermittently at 180 ° intervals by a 50 Hz square wave pulse having the same frequency as the fundamental wave of the voltage of the power supply 3, and the second and sixth switches Q2 and Q6 operate in the opposite manner to Q1 and Q5.

Further, the third and fourth switches Q3 and Q4
Is turned on / off at a frequency (for example, 20 kHz) sufficiently higher than the frequency of the AC voltage signal Vin in FIG. In the non-conversion mode, the third and fourth switches Q3 and Q4 can be kept off. However, in the present embodiment, they are turned on and off like other modes to improve the power factor. When the switches Q1 to Q6 are controlled as shown in FIG. 4, the input AC voltage signal Vin is in a positive half-wave period (t0
In t1), a forward current flows in the closed circuit of the AC power supply 3, the first reactor L1, the first switch Q1, the fifth switch Q5, the second reactor L2, and the load 110.

During the period (t1 to t2) when the input AC voltage signal Vin is a negative half wave, the AC power supply 3 and the load 11
0, the second reactor L2, the sixth switch Q6, the second
Negative current flows through the switch Q2 and the closed circuit of the first reactor L1.

In the non-conversion mode, the input AC voltage signal Vin becomes an output voltage Vo with a slight voltage drop. In this case, the first, second, fifth and sixth switches Q
Since 1, Q2, Q5, and Q6 are not turned on / off at a high frequency (for example, 20 kHz), the number of times of switching per unit time is reduced, and the decrease in efficiency due to switching loss is reduced. In this embodiment, the non-conversion mode is set when the AC voltage signal Vin is in the range of about 100 V -10% to + 10%, and the efficiency is improved in this range compared to the case of 11-063994.

(B) Effective value calculating section 91, peak calculating section 9
2. When the peak value Vinp obtained in Step 2 is 120 V√2 V, the limiter 93 sets the output to 110√√2 V when the input value is 110√2 V or more.
± 10 · １２０2V is reduced from the input value of 120 · √2V. That is, as shown in FIG.
・ Output 2V.

The multiplier 94 outputs the output signal Rvp (110 V√2 V) subjected to the limiter from the limiter 93.
The product of the sine wave of the sine wave oscillator 103 synchronized with the commercial AC voltage signal Vin (the maximum value of this wave) is sent to the subtractor 67 of the second command value generating means 45 of the control circuit 2. I do.

The control circuit 2 outputs the AC voltage signal Vin (for example, the effective value of this signal is 120 V) to the output voltage command value V
Since it is larger than d, the step-up / step-down power conversion circuit 1 switches to the step-down mode, and the step-up / step-down power conversion circuit 1 steps down the AC voltage signal Vin = 120V to Vd = 110V and outputs it (step-down mode).

In other words, in the case of the step-down mode in which the output voltage Vo lower than the input AC voltage signal Vin is obtained, the first to sixth main switches Q1 to Q6 are connected to each other as shown in FIGS.
Are supplied.

In other words, in this step-down mode,
The efficiency is the same as 63994.

(C) When the peak value Vinp obtained by the effective value calculating section 91 and the peak calculating section 92 is 80V√2, the limiter 93 outputs 90V when the input value is 90√2V or less.・ Because it is set to $ 2V
± 10 · √2V is increased from the input value 90 · √2V. That is, as shown in FIG.
Output V.

The multiplier 94 calculates the product of the limiter applied waveform (90 V · √2 V) from the limiter 93 and the output of the sine wave oscillator 103 by the subtractor of the second command value generating means 45 of the control circuit 2. 67.

The control circuit 2 supplies the AC voltage signal Vin = 80
Since V is smaller than the output voltage command value Vd, the buck-boost power conversion circuit 1 is switched to the boost mode. The buck-boost power conversion circuit 1 boosts Vin = 80V to Vd = 90V and outputs the same.

That is, in the case of the boost mode in which an output voltage Vo higher than the input AC voltage signal Vin is obtained, FIG.
The first to sixth switches Q1 to Q6 are on / off controlled by the control signals shown in (B) to (G).

That is, in this step-up mode, the flat 11-0
The efficiency is the same as 63994.

FIG. 7 shows the power conversion efficiency of the buck-boost power conversion circuit 1. As described above, the AC voltage signal Vin is 9
When the voltage is input between 0 V and 110 V, the buck-boost power conversion circuit 1 operates in the non-conversion mode, and therefore shows the maximum power conversion efficiency of the buck-boost power conversion circuit 1 within the range. When the AC voltage signal Vin is input at 90 V or lower or 110 V or higher, the step-up / step-down power conversion circuit 1 operates in the step-up or step-down mode, so that the upper limit 110 V or the lower limit 90 V of the command output voltage Vd and the AC voltage signal Vin As the difference between the two increases, the power conversion efficiency decreases.

The range of the AC voltage signal Vin that operates in the non-conversion mode in which the power exchange efficiency is high as compared with the conventional case where the non-conversion mode is set only when the AC voltage signal Vin is equal to the fixed output voltage command value Vd is equal to that of the prior art. Because of the expansion, the overall power conversion efficiency is improved.

As described above, according to the above-described embodiment, when the peak value Vinp of the AC voltage signal Vin is within the range limited by the limiter 93, the peak value is transmitted as it is and the output signal Rvp And the sine wave signal (amplitude 1) synchronized with the commercial AC voltage signal Vin is set as the command output voltage value Vd.

That is, the AC voltage signal V within the set range
When in is input, the AC voltage signal Vin becomes equal to the command output voltage value Vd, and the AC voltage signal Vi is input.
Since n is output without conversion, the frequency of the switching operation is reduced, the power loss is reduced, and the power exchange efficiency is improved.

[0093]

As described above, according to the present invention, the DC amount of a commercial AC voltage signal is determined, and this DC level is
The peak value of the original commercial AC voltage signal is obtained by multiplying the waveform coefficient of the ideal commercial AC voltage signal without distortion, and a limiter control is performed on this peak value within a predetermined range to keep the output constant. By using the command output voltage signal to the control unit to be maintained, the output voltage can be changed within a range in which there is no problem with the load.

In other words, since the output voltage is not made uselessly constant, the frequency of the switching operation is reduced, the power loss is reduced, and the power exchange efficiency is improved.

Further, by setting the product of the output signal of the limiter and the output signal of the sine wave oscillator synchronized with the voltage waveform of the commercial AC power supply as the command output voltage value, a command of a predetermined level that does not wastefully turn on / off the switching element is obtained. An output voltage value can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a power conversion device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a characteristic example of an output voltage command value generation circuit according to the embodiment.

FIG. 3 is a diagram showing an output example of a limiter in the embodiment.

FIG. 4 is a waveform diagram illustrating an operation of the power conversion circuit in a non-conversion mode when the output voltage command value generation circuit according to the present embodiment is used.

FIG. 5 is a waveform diagram illustrating an operation of the power conversion circuit in the step-down mode when the output voltage command value generation circuit according to the present embodiment is used.

FIG. 6 is a waveform diagram illustrating an operation of the power conversion circuit in the boost mode when the output voltage command value generation circuit according to the present embodiment is used.

FIG. 7 is a diagram showing a power conversion efficiency characteristic of the step-up / step-down power conversion circuit in the embodiment.

FIG. 8 is a block diagram showing a conventional power converter.

[Description of Signs] 1 step-up / step-down power conversion circuit 2 control circuit 44 converter voltage command value generating means 45 inverter voltage command value generating means 46 square wave generators 47, 48, 49, first, second and third arithmetic circuits 50, 51 First and second limiters 52 Triangular wave generator 53, 54, 55 First, second and third comparators 56, 57, 58 First, second and third inverse signal forming circuits 90 Output voltage Command value generation circuit 91 Effective value calculation unit 92 Peak value calculation unit 93 Limiters Q1 to Q6 First to sixth switches C Capacitors L1, L2 First and second reactors 100 Power supply 101 Step-up / step-down power converter 102 Output voltage command Value 103 Sine wave oscillator 104 Synchronous circuit 105 DC power supply

Continuing from the front page (72) Inventor Yuichiro Sugano 3-6-3 Kitano, Niiza-shi, Saitama Prefecture Within Sanken Electric Co., Ltd. (72) Inventor Satoru Ishikuma 3-6-1, Kitano, Niiza-shi, Saitama Prefecture Sanken Electric Co., Ltd. In-company (72) Inventor Shoichi Kawachi 3-6-3 Kitano, Niiza-shi, Saitama Sanken Electric Co., Ltd. (56) References JP-A-11-333382 (JP, A) (58) Fields surveyed (58) Int.Cl. ⁷ , DB name) H02M 7/48 H02M 5/45

Claims (2)

(57) [Claims] 1. A commercial AC power supply is inputted, and the AC power supply voltage is stepped up and down by a switching operation based on a difference from a predetermined command output voltage value synchronized with a voltage waveform of the commercial AC power supply to output a constant output to a load. In a power converter for obtaining a voltage, a DC amount of a voltage waveform of the commercial AC power supply is obtained, and the original commercial AC power supply is obtained from a voltage of the DC amount and a coefficient of the voltage waveform of the commercial AC power supply without distortion. Means for determining the peak value of the voltage waveform of the following: when the peak value is within a predetermined range, the peak value, when the peak value is larger than the upper limit of the predetermined range, the upper limit, the lower limit of the predetermined range When smaller than, a limiter means for outputting the lower limit value; and a command output voltage value is generated from an output signal of the limiter and an output signal of an oscillator synchronized with a voltage waveform of the commercial AC power supply. And a command output voltage generating means. 2. The command output voltage value means sets a product of an output signal of the limiter means and an output signal of a sine wave oscillator synchronized with a voltage waveform of the commercial AC power supply as the command output voltage value. A power converter characterized by the above-mentioned.