JPH04185285A - Power converter - Google Patents

Abstract

PURPOSE:To suppress an input voltage distortion by a method wherein an equation which is conformed to by a power supply voltage, a voltage between both the terminals of a reactor and a converter voltage is subjected to a software processing to make the waveform of an input current sinusoidal and have the same phase as the power supply voltage. CONSTITUTION:A power supply voltage Vin, a converter voltage (v) and a voltage vi between both the terminals of a reactor conform to an equation; Vin=vi+(v)=(r+Ip)(i)+(v), wherein p=d/dt. In order to make an input current (i) have a sinusoidal waveform an the same phase as the power supply voltage, the converter voltage (v) is controlled by switching. At every sampling period, a phase angle signal, the input current (i) and a DC voltage Vdc and a command DC voltage Vdc* are inputted to a control circuit 12 from a zero-cross detecting circuit 9, a current detecting circuit 8 and a voltage detecting circuit 10 respectively and v* is so calculated as to make the input current (i) has a sinusoidal waveform and the same phase as the power supply voltage Vin and, further, make the DC voltage Vdc equal to the command DC voltage Vdc*.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power converter that converts an AC power source into a DC power source and variably controls the DC voltage.

[Prior Art] Conventionally, a power converter that converts an AC power source into a DC power source has been used to extract a predetermined DC current (voltage) from an AC power source. FIG. 2 shows an example of a conventional power converter.

In FIG. 2, l is a single-phase AC power supply, 4 is a full-wave rectifier circuit, 5 is a smoothing capacitor connected in parallel to the output side of the full-wave rectifier circuit 4, and 17 is the a-blade terminal 1 of the smoothing capacitor 5.
A load is connected between 5 and 15', 6 is a switching element connected in parallel between the full-wave rectifier circuit 4 and the smoothing capacitor 5 at terminals 16-16', and 3 is a load connected between the full-wave rectifier circuit 4 and the terminal 1.
Reactor connected between 6 and 7, terminals 15-16
A first recovery diode is connected between the two.

8' is an input current detection circuit installed between the full-wave rectifier circuit 4 and the AC power supply 1 to detect the input current i, and 20 is connected between both terminals 2-2' of the AC power supply 1 and is in phase with the power supply voltage. 21 is a sine wave generation circuit that generates a sine wave of DC voltage command value V dc'' and both terminals 15-15' of the smoothing capacitor 5.
A voltage comparator circuit 22 performs proportional-integral control of the deviation from the DC voltage Vdc between 20 and 22, and a voltage comparison circuit 22 determines the input current command value I11 by multiplying the sine wave signal generated by the sine wave generation circuit 20 and the voltage deviation signal generated by the voltage comparison circuit 21. A multiplier 23 creates a hysteresis comparator for this input command value 18.
A current comparator circuit compares the input current i with a hysteresis width of Δi, and 13' is a drive circuit that drives the switching element 6.

In this power converter, as shown in Fig. 3, when the input current 1 goes outside the range of ±Δi hysteresis width with respect to the input current command value 11, the switching element is turned on and off to increase or decrease the input current. , the voltage is controlled by making it close to a sine wave and using the boosting action of the reactor to set the deviation between the DC voltage and the DC voltage command value as the input current command value.

[Problems to be Solved by the Invention] However, this type of power converter has the following problems. In other words, when the input current at the rising edge of the sine wave is small, the energy stored in the reactor is small, and when the energy is released, the input current i falls within the hysteresis width and cannot be tracked, causing distortion in the input current waveform. . In this case, control can be achieved by reducing the width of the hysteresis, but there is a problem in that the switching speed becomes too high where the current is large and exceeds the minimum pulse width limit for switching.

The present invention has been made in view of the above circumstances, and its purpose is to provide a power converter that can make the input current into a sinusoidal waveform in phase with the power supply voltage and further reduce input current distortion. It is in.

[Means for Solving the Problems] In order to achieve the above object, the present invention employs the following configuration.

That is, the present invention provides a full-wave rectifier circuit connected between terminals of an AC power source, a smoothing capacitor connected to the output side of this full-wave rectifier circuit, and a smoothing capacitor connected in parallel between the full-wave rectifier circuit and the smoothing capacitor. a switching element connected in series between the switching element and the smoothing capacitor, a reactor connected in series between the full-wave rectifier circuit and the switching element, and the switching element and the gold-wave rectifier circuit. , a voltage detection circuit connected to both ends of the smoothing capacitor, a voltage phase detection circuit connected to the terminals of the AC power supply, and a switching signal that turns on and off the switching element. A power converter comprising a control circuit that outputs an output signal, and a drive circuit that inputs an output signal of the control circuit to drive a switching element, the input current value being detected by the current detection circuit.

Phase signal detected by voltage phase detection circuit.

The DC voltage value detected by the voltage detection circuit and the command signal corresponding to the DC voltage command value across the smoothing capacitor are input to the control circuit every sampling period, and the AC power supply voltage, the voltage across the reactor, and the voltage across the switching element are input to the control circuit. It is characterized by calculating the converter voltage command value by calculation using a voltage equation established with a sample value system between the converter voltages between both ends, and outputting a switching signal by the drive circuit according to a predetermined algorithm.

Here, the predetermined algorithm is a switching element that combines a pulse train that is turned on or off once or multiple times in one sample period and has an on time, duty ratio, number of pulses, or pulse density that correlates with the converter input voltage command value. It is characterized by creating a switching signal.

[Function] Between the power supply voltage Vin, the converter voltage v1, and the voltage vj across the reactor, Vin=vi+v −(r+Ip)i+v (1) (However,
p""d/dt) holds true. The converter voltage V is controlled by switching to make the input current i a sine wave in phase with the power supply voltage.

At each sampling period, a phase angle signal is input from the voltage phase detection circuit, and a DC voltage Vdc and a DC voltage command value Vdc'' are input from the current detection circuit to the input current 11 to the control circuit, and the input current i is set to the power supply voltage. It becomes a sine wave in the same phase as Vin, and the DC voltage Vdc is the DC command voltage V dc
"Vl is calculated so that it is equal to ".

At a control period equal to the sampling period, the converter voltage V closest to the converter input voltage command value 6 is selected from two types, and switching is performed using a switching pattern that achieves this. However, instead of continuing to maintain the same switching state during one control cycle, the switching state and its pulse width are determined by the magnitude of the converter voltage command value v''.

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

FIG. 1 is a schematic diagram of a power converter according to an embodiment of the present invention. Note that the same parts as those shown in FIG. 2 according to the conventional example are given the same reference numerals, and the explanation thereof will be omitted.

In FIG. 1, 8 is an input current detection circuit installed between the full-wave rectifier circuit 4 and the terminal 16' to detect the input current i, and 9 is connected to both terminals 2-2' of the AC power supply 1. Power supply zero cross detection circuit (voltage phase detection circuit), 1
0 is a DC voltage detection circuit connected to both ends of the smoothing capacitor 5. Reference numeral 12 inputs the output signals and DC voltage command value 11 from the current detection circuit 8, power supply zero cross detection circuit 9, and voltage detection circuit 10, so that the input current i is a sine wave current in phase with the power supply voltage Vtn every sampling period. This is a control circuit that calculates the switching pattern. 13
is a drive circuit that turns on and off the switching element based on the output signal of the control circuit 12. Here, terminal 16-
16' is the converter voltage V.

Next, the operation of this embodiment will be explained.

Between the power supply voltage Vin, - converter voltage ■, and the voltage v1 across the reactor, V1n cod vi +v - (r + Ip) i + v ... (1) (However, p
= d / d t ) holds true. The converter voltage V is controlled by switching to make the input current i a sine wave in phase with the power supply voltage.

For each sampling period, the zero cross detection circuit 9 outputs a phase angle signal, the current detection circuit 8 outputs an input current i, and the voltage detection circuit 10 outputs a DC voltage Vdc and a DC voltage command value Vdc.
” are respectively input to the control circuit 12 so that the input current i becomes a sine wave in phase with the power supply voltage Vin and the DC voltage Vd
vl+ so that c is equal to the DC command voltage V dc''
is being calculated.

Since this calculation is performed in real time by a microcomputer, it is controlled by a sample value system, where the input current at sample point n is i (n), and the power supply voltage is V 1n (n
), and the DC output voltage is Vdc(rt). According to the voltage equation (1), the input current i (n+1) is changed to the input terminal command value I '' (n+
Converter input voltage command value v''(n) to be equal to 1)
is shown in the following equation.

v ” (n)-2V 1n(n)-v (n-1)
-2r 1(n-1) In order to make the DC voltage Vdc the DC voltage command value V dc'', the deviation between Vdc and V dc'' is controlled proportionally and integrally, and as a result, the input current command peak value J218 is obtained. ing.

J 21 ” (n+1)=K pΔVdc+1 Σ
ΔVdc (However, ΔVdc-Vdc-Vdc")
-(3) However, the converter voltage ■ is determined by the conduction state of the switching element 6, and is 0. Only two types of Vdc can be taken. Therefore, as a control, the converter voltage V closest to the converter input voltage command value ■8 is selected from two types with a control period equal to the sampling period, and switching is performed using a switching pattern that realizes this, and the sine of the input current is It performs variable control of waves and DC voltage.

However, rather than continuing to maintain the same switching state during one control cycle, the switching state and its pulse width are determined by the magnitude of converter voltage command value 1.

The selected switching state is maintained during the period TonO of the determined pulse width, and the switching state becomes y - m Q during the period Toff from the end of the Ton period until the next control, thereby controlling the converter input voltage. V can be equivalently changed within the range of 0≦■≦Vdc. Here, if the power supply voltage Vin is Vin≧0 or Vi
Since the switching conditions are the same even when n<0, V
Let us consider the range of in≧0.

In this embodiment, if the pulse width is set to 0 times, 173 times, 2/3 times, and 1 times the maximum width Tc, the converter input voltage V is O, 1/3 V dc, and 2/3 V dc.

Four types of Vdc can be equivalently taken. Therefore,
An example of selection of the pulse width Ton depending on the magnitude of the converter voltage command value is shown in the table on the next page.

By driving the switching element with the selected switching state and pulse width in each control period, the input current is controlled in a sinusoidal waveform in phase with the power supply voltage, and the DC voltage is controlled to be the command value.

Table In this way, in this embodiment, the types of converter input voltages V that can be selected can be equivalently increased by changing the pulse width, and thereby the actual output V and the command value ■8
The deviation from the input current can be reduced, and the input current distortion can be reduced.

Input current distortion can generally be further improved by increasing the control frequency, but this method alone places a burden on the microcontroller, so input current distortion can be further reduced by changing the pulse width as in this method. I can do it. Also,
The minimum pulse width can also be easily set.

In addition, in this embodiment, a method of outputting a switching signal that is a combination of a pulse train that turns on once per sample period and has an on time that correlates to the converter input voltage command value has been described. Even if a method is used in which a switching signal is output to a switching element by combining a pulse train with a duty ratio, a number of pulses with a constant pulse width, or a pulse density with a constant pulse width, the input terminal can be input at one sample period in time. It is clear that the waveform distortion of the input current can be similarly reduced by controlling with the following fineness.

[Effects of the Invention] As detailed above, according to the present invention, an appropriate switching state can be selected by software calculation of a voltage equation that is established between the power supply voltage, the voltage across the reactor, and the converter voltage. Control is possible even when the input current is small. Furthermore, since the control period and the minimum switching pulse width can be set in advance, the minimum switching pulse width limit will not be exceeded. Therefore, the DC voltage can be variably controlled, and the input current can be made into a sinusoidal waveform in phase with the power supply voltage, thereby making it possible to further reduce input current distortion.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of a power converter according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing a conventional follow-up analog current control method, and FIG. 3 is a block diagram showing a converter voltage command value and FIG. 3 is a diagram showing selection of pulse width. 1... AC power supply, 3... Reactor, 4... Full wave rectifier circuit, 5... Smoothing capacitor, 6... Switching element, 7... Rectifying element, 8... Input current detection Circuit, 9... Power supply zero cross detection circuit (voltage phase detection circuit), 10... Voltage detection circuit, 11... Voltage command value, 12... Control circuit, 13... Drive circuit, 17... Load, 20... Sine wave generation circuit, 21... Voltage comparison circuit, 22... Multiplier, 23... Current comparison circuit, 2.15.17... Terminal,

Claims (1)

[Claims] A full-wave rectifier circuit connected between terminals of an AC power source, a smoothing capacitor connected to the output side of the full-wave rectifier circuit, and a parallel circuit between the full-wave rectifier circuit and the smoothing capacitor. a rectifying element connected in series between the switching element and the smoothing capacitor;
A reactor connected in series between the full-wave rectifier circuit and the switching element, a current detection circuit arranged between the switching element and the full-wave rectifier circuit, and a current detection circuit connected to both ends of the smoothing capacitor. a voltage detection circuit, a voltage phase detection circuit connected to a terminal of the AC power source, a control circuit that outputs a switching signal for turning on and off the switching element, and an output signal of the control circuit that is input to the switching element. A power converter comprising a drive circuit that drives an input current value detected by the current detection circuit, a phase signal detected by the voltage phase detection circuit, and a DC voltage detected by the voltage detection circuit. value and a command signal corresponding to the DC voltage command value across the smoothing capacitor are input to the control circuit every sampling period, the voltage command value is calculated by a predetermined calculation, and the voltage command value is calculated by a predetermined algorithm. A power converter characterized by outputting a switching signal to a circuit.