JPH08289564A - Method of correcting overlapped period of commutation of high frequency link dc/ac converter - Google Patents

Abstract

PURPOSE: To improve the output voltage waveform from a cyclone converter part and reduce the distortion of waveform in the vicinity of zero cross by hastening the ON-OFF control of the bidirectional switching element of a cyclone converter part by the commutation overlapped period. CONSTITUTION: Since a switching element Su of U phase performs switching in the period while the output voltage is generated, the output voltage of the cyclone converter is delayed by the commutation overlapped period of the commutaion of power source. As a result, for the waveform of the output voltage of the cyclone converter part, the waveform in the vicinity of zero cross is distorted, and it becomes one which includes low-order higher harmonic components. Accordingly, the switching operation of the switching element Su is advanced by the commutation overlapped period. As a result, for the waveform of the output voltage of the cyclone converter part, the distortion of waveform decreases in the vicinity of zero cross, and the low-order harmonic components are suppressed.

Description

Detailed Description of the Invention

[0001]

This invention relates to a motor drive, U
The present invention relates to a control method of a high frequency link DC / AC converter by a cycloconverter used in a power supply circuit such as PS.

[0002]

2. Description of the Related Art The circuit configuration of a high frequency link DC / AC converter using a cycloconverter is shown in the block diagram of FIG. In FIG. 8, the DC power from the DC power supply 1 is input via the parallel capacitor 2 to the inverter unit 3 configured by connecting the four switching elements 11 and 12 and 13 and 14 in a single-phase bridge to generate high frequency power. To be converted. The high frequency power from the inverter unit 3 is transformed by the high frequency transformer 4 and input to the cycloconverter unit 5. Bidirectional switching elements 21 and 22, 23 and 2
The cycloconverter unit 5, which is composed of 4, 25, and 26 connected in a three-phase bridge, converts the high-frequency power input via the high-frequency transformer 4 into commercial-frequency power, and commercializes it via the AC filter 6 including a reactor and a capacitor. Output AC power of frequency.

The switching control of the high frequency link DC / AC converter described above is based on the method described below. That is, the operation sequence of each switching element forming the inverter unit 3 and the cycloconverter unit 5 is determined by the gate signal generated by using the instantaneous space vector, and 18 operation modes are selected from the phase relationship between the output voltage and the output current. As shown in FIG. In the operation mode described above, the operation sequence in the case of the operation modes 1 and 2 is as shown in FIG. 3, the output phase voltage of the cycloconverter unit 5 in this mode of operation _{e w> e u> 0,} e v < It is 0. Due to the magnitude relationship of the phase voltages to be output, the switching sequence of the inverter unit 3 is given based on the gate signal determined by comparing the maximum phase voltage _ew and the minimum phase voltage _ev with the sawtooth carrier. That is, the switching elements 11 and 12 and the switching elements 13 and 14 are alternately on / off controlled by different switching sequences. Further, the arms V phase and W phase of the cycloconverter unit 5 corresponding to the respective phases perform switching in synchronization with the sawtooth carrier, and the remaining arms U phase perform switching as the result compared with the sawtooth carrier. I do. The switching sequence of the upper switching elements S _u , S _v , S _w in the bidirectional switching elements 21, 23, 25 of the cycloconverter unit 5 is as shown in FIG. The operation states of the converter unit 3 and the cycloconverter unit 5 at this time are divided into eight ways, and the equivalent circuit diagrams in each state are as shown in FIGS. 5 and 6.

[0004]

Although the bidirectional switching elements of each phase arm constituting the cycloconverter section 5 perform switching by the power commutation method, in the operation modes 1 and 2, a voltage is generated in the high frequency transformer. U is switching during the period
Phase, and V phase and W phase are zero voltage switching (Z
VS), as shown in FIG. Therefore,
Doing switching of the U-phase by a switching sequence shown in Figure 3, it becomes a U-phase voltage e _u is cut switched waveform with a delay time T _sc overlap commutation by the power supply commutation, as shown in FIG. As a result, the output voltage is shown in FIG.
As shown in, there is a drawback that the waveform near the zero cross is distorted.

[0005]

The present invention has been made in order to solve the above-mentioned drawbacks of the switching control method according to the prior art, and among the bidirectional switching elements constituting the cycloconverter section 5, the power source is used. The bidirectional switching element S _u (21), which performs switching switching after a commutation overlap period T _sc due to commutation, is controlled to switch T _sc earlier.

[0006]

When the switching of the on / off control of the bidirectional switching element _Su (21) of the cycloconverter unit which performs the switching operation by the power supply commutation is advanced by the commutation overlap period T _sc due to the power supply commutation, FIG. As shown in. As a result, the output voltage waveform becomes a waveform in which low-order harmonics are reduced as shown in FIG. 7 (b).

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS High frequency link DC / A according to the present invention
An embodiment of a method of correcting the commutation overlap period of the C converter will be described with reference to the drawings. FIG. 8 is a block diagram showing a circuit configuration of a high frequency link DC / AC converter using a cycloconverter, which is composed of an inverter unit 3, a high frequency transformer 4, a cycloconverter unit 5, and an AC filter 6, and is the same as that of the conventional technique. Therefore, the description is omitted.

The switching sequence of the switching elements 11, 12, 13, and 14 which form the inverter section 3 and the upper switching element S _u (21) of the bidirectional switching elements which form the cycloconverter section 5,
The switching sequence of S _v (23) and S _w (25) is shown in Fig. 3.
Further, the equivalent circuit diagrams in the operating state of the converter unit 3 and the cycloconverter unit 5 are as shown in FIGS. 5 and 6, and are the same as those in the prior art.

In the operating state 2 shown in FIG. 5B, the inverter unit 3 has a DC power supply 1, a switching element 11,
Since a closed loop including 14 is formed, the output voltage e _T is generated in the secondary circuit of the high-frequency transformer 4, and the operating state 3
Will continue for a period of. In addition, the operation state 6 shown in FIG.
In the inverter section 3, a closed loop including the DC power supply 1 and the switching elements 12 and 13 is formed, and the direction of the current flowing through the primary side of the high frequency transformer 4 is opposite. Therefore, in the secondary circuit of the high frequency transformer 4, The output voltage becomes −e _T , which continues during the operating state 7. The switching sequence described above causes the output voltage of the high frequency transformer 4 to change as shown in FIG.

Of the bidirectional switching elements constituting the cycloconverter unit 5, the switching sequence of the upper switching elements S _u (21), S _v (23) and S _w (25) in each arm is shown in FIG. The street, V
The phase-and W-phase switching elements S _v (23) and S _w (25) perform switching when the output voltage e _T of the high frequency transformer 4 is zero. However, the U-phase switching element S
_{Since u} (21) performs switching during the period in which the output voltage e _T is generated, e _u of the output voltage of the cycloconverter unit 5 is converted by power commutation as shown in FIG. _{Switching is performed with a} delay of the flow overlap period T _sc . As a result, as shown in FIG. 7A, the output voltage waveform of the cycloconverter unit 5 is distorted in the waveform near the zero cross and contains a low-order harmonic component. In order to improve the distortion of the output voltage waveform of the cycloconverter unit 5 described above, the switching operation of the switching element _Su (21) may be advanced by the commutation overlap period T _sc . As a result, the voltage waveform of the output voltage e _u of cycloconverter unit 5 is shown in FIG. 1, the output period voltage 7
It is improved as shown in (b), and the waveform distortion near the zero crossing is reduced, so that the lower harmonic components are also reduced.

The above-described switching sequence of the switching elements forming the inverter section 3 and the cycloconverter section 5 is a well-known technique that can be easily realized, and a description thereof will be omitted.

[0012]

As described above, the method for correcting the commutation overlap period of the high-frequency link DC / AC converter according to the present invention is capable of switching due to power commutation during the period when voltage is generated in the output circuit of the high-frequency transformer. The bidirectional switching element that constitutes the cycloconverter unit that performs switching is controlled so as to switch earlier by the commutation overlap period due to the power commutation. By this switching correction, the output voltage waveform from the cycloconverter unit is improved, the waveform distortion near the zero cross is reduced, and the low-order harmonic components are also reduced.

[Brief description of drawings]

FIG. 1 is an output voltage waveform diagram of a cycloconverter unit according to the present invention.

FIG. 2 is a switching sequence diagram of a conventional inverter unit and a cycloconverter unit and an output voltage waveform diagram of the cycloconverter unit.

FIG. 3 is a switching sequence of a conventional inverter unit and cycloconverter unit.

FIG. 4 is an operation mode of the cycloconverter unit.

FIG. 5 is an equivalent circuit diagram.

FIG. 6 is an equivalent circuit diagram.

FIG. 7 is an output voltage waveform diagram of the cycloconverter unit.

FIG. 8 is a block diagram showing a circuit configuration of a high frequency link DC / AC converter.

[Explanation of symbols]

1 DC power supply 2 Capacitor 3 Inverter section 4 High frequency transformer 5 Cycloconverter section 6 AC filter 11, 12, 13, 14 Switching element 21, 22, 23, 24, 25, 26 Bidirectional switching element

Claims (1)

[Claims] 1. An inverter unit comprising switching elements connected in single-phase bridge for inputting DC power and converting it to high-frequency power, and a high-frequency transformer for transforming the high-frequency power input from this inverter unit and outputting it to a cycloconverter unit. A cycloconverter unit in which bidirectional switching elements for converting high-frequency power input via the high-frequency transformer into commercial-frequency power are connected in a three-phase bridge, and an AC filter including a reactor and a capacitor provided in an output circuit of the cycloconverter unit. In the high frequency link DC / AC converter configured according to the above, the bidirectional switching element in the cycloconverter unit, which switches the switching by the power supply commutation during the period when the voltage is generated in the output circuit of the high frequency transformer, is converted by the power commutation. Overflow period RF link DC, characterized in that only early in was to switch
/ AC converter commutation overlap period correction method.