JPH0284070A - Power conversion device - Google Patents

Abstract

PURPOSE:To obtain a power conversion device capable of supplying stable DC power to the load by subtracting midpoint voltage from sinusoidal wave voltage extracted by a filter circuit and by controlling switching elements with a control circuit based on the current reference signal of a lead phase from single phase AC voltage. CONSTITUTION:A control rectification circuit 7a works as a boosting type chopper circuit together with a reactor 2. The output of a resistance type potential divider 24 will be cosine wave voltage if the voltage at the connecting point 7b of capacitors 5 and 6 as a reference. In this case, the phase angle advances 90 deg. more than single phase AC voltage. Consequently, the output signal of a multiplier 13 will also be in lead phase. Transistors 8 and 9 are thereby turned ON and OFF complementarily without causing the period in which a diode 3 or a diode 4 will conduct. As a result, the current of single phase AC power source 1 is shifted in phase against the single phase AC voltage to get to a lead phase and not to be of a distorted waveform.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention is applicable to power sources for compressor motor drive inverters of household air conditioners and uninterruptible power supplies (U).

The present invention relates to a power conversion device that supplies stable power to a DC load such as a storage battery charging power source (P, S).

(b) Conventional technology Conventionally, this type of power conversion device was disclosed in Japanese Patent Application Laid-Open No. 62-22101.
As disclosed in Publication No. 4, DC voltage is controlled by current control based on a sine wave signal whose phase matches the voltage of a single-phase AC power supply, so-called operation with a power factor of 1.0 or -1.0. is under constant control. In other words, in the device disclosed in the same publication, when the power generated by the solar cells is less than the power consumption of the load, AC power from the commercial power source is rectified and supplied to the inverter, and the power generated by the solar cells exceeds the power consumption of the load. If the amount exceeds that amount, the excess amount is recycled to the commercial power source. Fig. 4 is a basic circuit diagram of a conventional power conversion device, where PS is a single-phase commercial power supply, L-beam accelerator, RC is a controlled rectifier circuit that serves as both rectification means and regeneration means, and diodes DI, D2 and capacitors are connected. C.I.

Diode DI of the voltage doubler rectifier circuit consisting of C2.

It is constructed by connecting transistors TR1 and TR2 in parallel to D2. B is a large FII battery, D3 is a backflow prevention diode, [V is an inverter, and M is an AC load of the inverter. When the output power of the Kiba battery B is less than the power consumption of the load, that is, in the case of continuous operation, the control rectifier circuit RC operates as a step-up chopper circuit, and the output voltage of the single-phase commercial power supply PS is increased. When e = Es + nωt, if 2ng<ωt<(2n+l)z, vl>e>
O... (1) If (2n+1)π<ωt<2(n+1)π, then 0>
e>v2...(2) (however, n=o, 1, 2...). Here, vl and v2 are terminal voltages of capacitors CI and C2, respectively. In other words, the control rectifier circuit RC is expressed by the formula (1),
When the step-up chopper circuit sufficiently operates to satisfy (2), the output current waveform i of the single-phase commercial power supply PS becomes a sine wave as shown in FIG. 5(a), and the corresponding voltage e.

The waveforms of vl and v2 are as shown in FIG. 5(b).

Note that a waveform of Δv=vl−v2 is shown.

(c) Problems to be Solved by the Invention However, when the capacitances of capacitors CI and C2 are small or when the load condition changes, the problem occurs when the load is turned off, as shown in FIGS. 6(a) and 6(b). Sometimes formulas (1) and (2)
There is a period T in which the control rectifier circuit RC does not operate as a boost type zipper circuit and the diode DI or the diode D4 is conductive, and the waveform of the current i becomes a distorted wave instead of a sine wave.

When the current waveform of the commercial power source is distorted due to such a phenomenon, there is a problem in that it causes harmonic interference such as abnormal noise, vibration, or burnout to other devices connected to the commercial power source.

In order to control the waveform of the current i as described above from becoming a distorted wave, the control rectifier circuit is controlled by a circuit including a PLL phase control circuit, and the current input from the commercial power supply to the rectifier is controlled. A method to maintain a distortion-free waveform by leading the phase of the commercial power supply voltage was also considered. However, the above circuit is complicated, and since the PLL-based phase control circuit operates in the low frequency range of commercial wave numbers, the response speed is slow, and the PLL becomes unstable due to transient fluctuations such as sudden changes in load. There was such a problem.

(d) Means for Solving the Problems This invention consists of two rectifying elements and two capacitors, and is connected to a single-phase AC power supply via a reactor, and supplies DC power to a load. a circuit, a semiconductor switching element connected in parallel to each of the two rectifying elements, a filter circuit that extracts a sine wave voltage that is in phase with the fundamental wave component of the voltage of a single-phase AC power supply, and a voltage at the connection point of the two capacitors. The current of the single-phase AC power source is suppressed from becoming a distorted waveform based on the addition circuit that adds the sine wave voltage to the extracted sine wave voltage, and the current reference signal whose phase is ahead of the single-phase AC voltage output from the addition circuit. This is a power conversion device characterized by comprising: a control circuit that controls each semiconductor switching element according to the present invention.

(e) When the voltage at the connection point of the two capacitors (hereinafter referred to as the midpoint voltage) is added to the sine wave voltage in phase with the fundamental wave component of the voltage of the single-phase AC power supply extracted by the action filter circuit in the addition circuit. , a current reference signal with a phase leading from the single-phase AC voltage can be obtained. Here, the midpoint voltage will be explained with reference to FIG. 2.

In the figure, the voltage of a single-phase AC power supply is 81 current, of which the portion flowing through capacitor C2 is il, the portion flowing via capacitor C1 is llq, the DC load current is i, and 172 of the DC load voltage is Common potential = 0 (
When the terminal voltage vl r vt of each capacitor CI and C2 is treated as V), each current has the following relationship from the voltage with the capacitor capacitance c, , c of each capacitor CI and C2.

Here, if the current of the single-phase AC power supply is maintained as a sine wave by the control operation of the power converter, the current ic is I c = ++ - L = Ic sin ωt - - - - - C
2-3) (r c ; wave height value).

Normally, capacitors CI and C2 are selected to have the same capacity, so if C, = C, = C, then from equation (2-1) - (2-2), the midpoint voltage is transformed as follows. , v, +V! = −−1a cosωt・・・・・・
・(2-6), which depends only on the current of the single-phase AC power supply, and the magnitude of the current from the DC power supply, in other words, the DC voltage -
It is unrelated to the magnitude of DC power when constant control is performed.

Therefore, the sine wave voltage extracted by the above filter circuit is (2
-6) By subtracting the midpoint voltage shown by the equation, a current reference signal having a phase leading from the single-phase AC voltage can be obtained. Moreover, since the midpoint voltage changes in proportion to the current amplitude of the single-phase AC power supply under constant DC load voltage control, the leading phase angle changes in proportion to the increase in DC load power.

Since the control circuit controls each switching element based on the current reference signal, the waveform of the current of the single-phase AC power source is maintained as a sine wave.

(f) Examples The present invention will now be described in detail based on examples shown in the drawings. This invention is not limited by this.

FIG. 1 is an electric circuit diagram showing an embodiment of the present invention.
! is a single-phase AC power supply, 2 is a reactor, 3゜4 is a rectifier diode, 5 and 6 are capacitors, 7 is a full-wave voltage doubler rectifier circuit composed of a diode 3.4 and a capacitor 5゜6, Transistors 8, which are semiconductor switching elements, are connected in parallel to the diodes 3 and 4, respectively.
9 are connected, thereby configuring the control rectifier circuit 7U. A load IO with relatively large power consumption, such as an inverter for driving a compressor motor of a domestic air conditioner, is connected to the output end of the control gIJ rectifier circuit 7a.

Reference numeral 11 denotes a control circuit for controlling 0N10FF of transistors 8 and 9, and is composed of an error amplifier 12, a multiplier 13, a hysteresis comparator I4, a pulse shaping circuit 15, and isolation amplifiers 16 and 17. The error amplifier 12 has a capacitor 5 applied to one input terminal thereof.
The positive voltage of the voltage, that is, the deviation between the load voltage detection signal obtained by dividing the load voltage by the voltage divider 18 and the DC reference voltage V rer applied to the other input terminal, is amplified and to be applied. Multiplier! At the other input end of 3,
A current reference signal 5rer whose phase is ahead of the voltage of a single-phase AC power source 1, which will be described later, is input. The hysteresis comparator 14 uses the output signal of the multiplier I3 and the single-phase AC power supply! It compares the current with the output signal of the current transformer 19 which converts the current into an appropriate level and outputs it, and outputs a PWM (/< pulse width modulation) pulse to the pulse shaping circuit 15. The pulses output from the pulse shaping circuit 15 are passed through the respective isolation amplifiers 16 and 17 to the respective transistors 8゜9.
applied to the base of

Reference numeral 20 denotes a bandpass filter, which is a filter circuit, which extracts a sine wave voltage having the same phase as the fundamental wave component of the voltage of the single-phase AC power supply 1, and outputs it to an adder circuit 23 consisting of resistors 21 and 22. A voltage obtained by equally dividing the load voltage by a resistor voltage divider 24 is applied to the resistor 22 of the adder circuit 23 . The output end of the adder circuit 23 is connected to the other input end of the multiplier 13. In other words, the above current reference signal S rer is added to the sine wave voltage output from the bandpass filter 20 by the addition circuit 23 to 1/2 of the voltage across the capacitor 5.6.
It is obtained by adding the voltages at the voltage dividing points. Therefore, the output signal output from the multiplier 13 is amplitude-modulated by the current reference signal Sre'' output from the adder circuit 23 using the DC signal from the error amplifier!2.

In the above configuration, the controlled rectifier circuit 7a operates together with the reactor 2 as a step-up chopper circuit. The operation of this step-up chopper circuit is basically the same as that shown in Japanese Unexamined Patent Publication No. 82-221014, but in this embodiment, the output of the resistor voltage divider 24 is connected to the capacitor 5.6. When the voltage at the connection point 7b is used as a reference, it becomes a cosine wave voltage and has a phase angle that is 90 degrees ahead of that of the single-phase AC voltage.Therefore, the output signal of the multiplier 13 similarly becomes a signal that has a leading phase. As a result, the respective transistors 8, 9 are turned on in a complementary manner by the control circuit If without producing a period in which the diode 3 or the diode 4 is conductive. As a result, single-phase AC power supply 1
The current is shifted in phase with respect to the single-phase AC voltage and has a leading phase, and does not have a distorted waveform.

FIG. 3 shows the error amplifier 1 regarding the phase shift effect of this embodiment.
2 shows the phase difference that the output signal of the multiplier I3 makes with respect to the phase of the voltage of the single-phase AC power supply when the maximum output of the multiplier I3 is set to 1.0 and the output amplitude is varied.

Here, kl and k are the summation ratio summaries of the adder circuit 23, and the resistance voltage divider 21 is applied to the output signal of the bandpass filter 20.
When the ratio of adding the output signals of is increased, it is 1, and when it is low, it is 2.

(G) Effects of the Invention According to the present invention, a power conversion device can be obtained that can supply stable DC power to a load without distorting the current waveform of a single-phase AC power source. It also has the following effects.

(1) Control that automatically increases the current advance angle as the load power increases can be stably realized with a simple circuit configuration.

(2) Since a feedback control loop is configured in which the unbalanced voltage of the average DC voltage of the capacitor is corrected, stress on the capacitor due to bias is reduced, and even harmonic currents are not generated in the commercial power supply.

[Brief explanation of the drawing]

Fig. 1: An electric circuit diagram showing an embodiment of Yoji's invention; Fig. 2 is an electric circuit diagram for explaining the basic principle of the leading phase 1f'tL reference signal in this invention; Fig. 3;
Graph showing the operating characteristics at the actual sound ρj, Figure 4:!
FIGS. 5 and 6 are waveform diagrams showing the waveforms of various parts of FIG. 4. FIGS. 1st Flash■...Single-phase alternating tl'1M source, 2...
・Reactor, 3.4...Diode, 5.6
...Capacitor, 7...Full wave@voltage rectifier circuit, 8.9...Transistor, 11...$
Control circuit, 20...Band pass filter, 23
...Addition circuit. Scroll

Claims (1)

[Claims] 1. A full-wave voltage doubler rectifier circuit consisting of two rectifying elements and two capacitors, connected to a single-phase AC power source via a reactor, and supplying DC power to a load; and two rectifiers. A semiconductor switching element connected in parallel to each element, a filter circuit that extracts a sine wave voltage that is in phase with the fundamental wave component of the voltage of the single-phase AC power supply, and a sine wave that extracts the voltage at the connection point of the two capacitors. Based on an adder circuit that adds to the voltage and a current reference signal whose phase is ahead of the single-phase AC voltage output from the adder circuit, each semiconductor switching element is used to suppress the current of the single-phase AC power source from becoming a distorted waveform. A power conversion device characterized by comprising: a control circuit that controls;