JP2006304382A - Power converter - Google Patents

Abstract

Provided is a power converter that winds an auxiliary coil at the end of a choke coil and selectively cancels a high-frequency noise component of an output current with a magnetic flux generated from an antiphase current.
A high-frequency transformer, a first inverter that converts a DC voltage into high-frequency power, a rectifier on a secondary side of the high-frequency transformer, and a second inverter that controls an output current of the rectifier. , The auxiliary coil 16 is wound around the end of the choke coil 17, and the high frequency noise component of the output current of the second inverter 15 is selectively canceled by the magnetic flux generated from the antiphase current, The high frequency noise component of the output current can be removed and the output current distortion can be reduced.
[Selection] Figure 1

Description

  The present invention relates to a power conversion device that converts direct current power, such as a fuel cell or a solar cell, into commercial power and injects power into a system.

  As a conventional power converter, for example, a resonant capacitor and a switching element are arranged on the primary side of a high-frequency transformer, and a rectifier and a switching element are arranged on the secondary side to convert DC power into AC power. (For example, see Patent Document 1).

  FIG. 4 shows a configuration of a conventional power converter described in Patent Document 1, and the first inverter 1 converts the power of the DC power source 2 into high-frequency power. The first inverter 1 is connected to the primary side of the high-frequency transformer 3 and includes a resonance capacitor 4 and a switching element 5.

The voltage waveform of the switching element 5 is resonated to perform a zero voltage switching operation, and the first inverter 1 performs sinusoidal modulation with a commercial double cycle. Further, on the secondary side of the high-frequency transformer 3, the rectifier 6 comprising the diodes Q1 to Q4 and the capacitor 7 rectify the high-frequency component, and the polarity is switched by the second inverter 8, so that a sine wave current having a power factor of 1 is obtained. It was generated and supplied to the system 9.
JP 2000-32751 A

  However, in the conventional configuration, as a filter for removing the high frequency noise component of the output current of the second inverter, the constants of the inductance L and the capacitor C are increased, and as a result, the reactive power component is increased and the power factor is increased. It has a problem that the output current waveform is distorted.

  The present invention solves the above-described conventional problems, and reduces the constants of the inductance L and the capacitor C, which are filters for removing the high-frequency noise component of the output current, and the reactive power component as much as possible, thereby reducing the output current distortion. The purpose is to make it smaller.

  In order to solve the above-described conventional problems, the power conversion device of the present invention includes an inductance L and a capacitor C, which are filters for removing high-frequency noise components of the output current by winding an auxiliary coil at the end of the choke coil. The constant is reduced.

  With this configuration, the reactive power component can be minimized and the output current distortion can be kept small.

  According to the power conversion device of the present invention, it is possible to reduce inductance and capacitor constants that are filters for removing high-frequency noise components of output current, and as a result, it is possible to reduce reactive power components as much as possible and to suppress output current distortion to a minimum. It is something that can be done.

  A first invention includes a high-frequency transformer, a first inverter that converts a DC voltage into high-frequency power, a rectifier on the secondary side of the high-frequency transformer, a second inverter that controls the output current of the rectifier, and a choke coil The auxiliary coil is wound around the end of the choke coil, and the high frequency noise component of the output current of the second inverter is selectively canceled by the magnetic flux generated from the antiphase current, thereby removing the high frequency noise component of the output current. Therefore, the constants of the inductance L and the capacitor C that are filters for reducing the power consumption can be reduced. As a result, the reactive power component can be reduced as much as possible, and the output current distortion can be reduced.

  In the second invention, in particular, the choke coil according to the first invention can cancel the magnetic flux surely by wrapping the auxiliary coil around the same core as the choke coil, thereby saving space and reducing the size. It becomes.

  In the third aspect of the invention, in particular, the choke coil of the first aspect of the invention has a high coupling coefficient as a transformer by winding the auxiliary coil in the opposite direction from the terminal end of the choke coil while being overlapped on the choke coil. The magnetic flux can be canceled more reliably and efficiently, and the high frequency noise component is further reduced.

  In particular, the fourth invention is one in which the power converter of the first to third inventions is mounted on a solar cell.

  In the fifth aspect of the invention, in particular, the power conversion device of the first to third aspects of the invention is mounted on a fuel cell.

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

(Embodiment 1)
In FIG. 1, a switching element Q1 and a switching element Q2 connected in series, a switching element Q3 and a switching element Q4 constitute a first inverter 11, and between the collector-emitter (or drain-source) of each switching element Q1 to Q4. Are connected to resonance capacitors 12a to 12d for zero voltage switching.

  The output of the first inverter 11 is connected to the primary side of the high-frequency transformer 13, and the rectifier 14 and the second inverter 15 are connected to the secondary side. Here, the output from the second inverter 15 is connected to the choke coil 17 having the auxiliary coil 16 connected to the terminal, and is connected to the system 19 via the filter circuit 18 in the subsequent stage.

  In the power conversion device configured as described above, the switching element Q1 and the switching element Q4 in the first inverter 11 and the switching element Q2 and the switching element Q3 have high-frequency switching with a phase of 180 degrees, respectively. High frequency power is generated on the primary side of the transformer 13.

  Here, the resonance capacitor is charged when the switching element that has been turned on is turned off, and the resonance capacitor is discharged in parallel with the switching element that has been turned off, and the reverse conduction diode is turned on at the timing when it is turned on. Thus, zero voltage switching of each element is realized.

  Incidentally, here, in the configuration of the first inverter 11, the four stone switching elements Q1 to Q4 and the four resonance capacitors 12a to 12d are described, but one stone switching element and one resonance capacitor are also possible. Of course, a single switching element without a resonant capacitor may be used.

  On the secondary side of the high-frequency transformer 13, a sine wave current is generated by rectifying a high-frequency component with a rectifier 14 made of a diode and switching the polarity with a second inverter 15.

  Further, the auxiliary coil 16 is wound around the end of the choke coil 17 to operate as a transformer, and a signal having a phase opposite to that of the high frequency noise is extracted to cancel the noise. The remaining high-frequency signal is reduced by the filter circuit 18.

  In this way, the auxiliary coil 16 is wound around the end of the choke coil 17, and the high-frequency noise component of the output current of the second inverter 15 is selectively canceled by the magnetic flux generated from the antiphase current.

  Here, the choke coil 17 has a ratio of 114 turns and 4 turns for a total of 1.8 mH, and C1 is 1.5 μF. In the filter circuit 18, the coil inductance L1 is 250 μH, and the capacitor capacitance C2 is 0.33 μF.

  Further, the operation will be described with an equivalent simulation circuit in FIG. In order to confirm the effect of the filter circuit 18, a rectangular wave having a frequency of 17 kHz and ± 200 V, that is, 400 V is input as the input voltage V1.

  In FIG. 2, the end of the choke coil and the auxiliary coil are connected, and here it is regarded as equivalent to a transformer having a coupling coefficient of 0.94. Furthermore, LA = 1.8 mH, LB = 2.2 μH, C1 = 1.5 μF, L1 = 250 μF, C2 = 0.33 μF, and R2 = 33Ω. 1) to 4) indicate node number points.

  With the above configuration, the rectangular wave is the sine waveform of FIG. 3a at the node 2) of the circuit of FIG. 2, and the voltage waveform generated at both ends of the auxiliary winding is a voltage waveform having a phase opposite to that of the input waveform as shown in FIG. Become.

  By synthesizing the waveforms of FIGS. 3a and 3b, the synthesized waveform of FIG. 3c is output at node 3) of FIG. This synthesized waveform is a waveform including a high frequency twice the carrier frequency.

  Further, the combined output waveform of FIG. 3C is made into the smooth waveform of FIG. This smooth output waveform has been proved by frequency analysis that the high frequency component of 17 kHz is attenuated to about 1/10 (not shown).

  Thus, as a normal filter circuit 18, it is difficult to attenuate the high frequency noise component unless the inductance L1 = 1 mH and the capacitor capacitance C2 = 10 μF or more. However, when a capacitor having a large capacitance of C2 = 10 μF or more is used. The reactive power component increases in the output current, the power factor decreases, and the output current waveform is distorted. Here, by winding the auxiliary coil 16 at the end of the choke coil 17, the high frequency noise component can be attenuated without distorting the output current waveform.

  According to such a configuration, the high frequency current can be selectively canceled by the magnetic flux generated from the current in the opposite phase with respect to the output current, so that the inductance L and the capacitor C which are filters for removing the high frequency noise component of the output current The constant can be reduced, and as a result, the reactive power component can be reduced as much as possible, and the output current distortion can be reduced.

  The choke coil 17 winds the auxiliary coil 16 around the same core as the choke coil 17.

  According to such a configuration, the magnetic flux can be canceled with certainty, space saving can be achieved, and miniaturization can be achieved.

  In addition, the choke coil 17 winds the auxiliary coil 16 while being superposed on the choke coil 17 in the reverse direction from the end of the choke coil 17.

  According to this configuration, the coupling coefficient of the transformer is increased, the magnetic flux can be canceled more reliably and efficiently, and the high frequency noise component is further reduced.

  The power conversion device described above can be applied to a fuel cell, a solar cell, or the like so as to convert DC power into AC power having a commercial frequency.

  The power conversion device of the present invention can remove the high frequency noise component of the output current, and can reduce the constants of the inductance L and the capacitor C, which are the filters. As a result, the reactive power component can be minimized and the output current distortion can be kept small. A power converter is provided. This can be applied not only to fuel cell power generation but also to other power conversion devices such as solar power generation.

(A) Block configuration diagram of power converter in Embodiment 1 of the present invention (b) Circuit diagram of first inverter Simulation circuit diagram of choke coil of the same power converter Operation waveform diagram of simulation circuit diagram for choke coil of power converter Block diagram of a conventional power converter

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 1st inverter 12a-d Resonance capacitor 13 High frequency transformer 14 Rectification means 15 2nd inverter 16 Auxiliary coil 17 Choke coil 18 Filter circuit 19 System

Claims (5)

A high-frequency transformer, a first inverter that converts a DC voltage into high-frequency power, a rectifier on the secondary side of the high-frequency transformer, a second inverter that controls the output current of the rectifier, and a choke coil. An electric power converter characterized by winding an auxiliary coil at the end and selectively canceling a high frequency noise component of the output current of the second inverter with a magnetic flux generated from an antiphase current. 2. The power converter according to claim 1, wherein the choke coil has an auxiliary coil wound around the same core as the choke coil. 2. The power converter according to claim 1, wherein the choke coil is wound back while overlapping the auxiliary coil on the choke coil in the reverse direction from the end of the choke coil. A fuel cell that converts direct-current power into alternating-current power at a commercial frequency by the power conversion device according to any one of claims 1 to 3. The solar cell which converted direct-current power into the alternating current power of commercial frequency with the power converter device of any one of Claims 1-3.

Images