JP2800584B2 - Control method of pulse width modulation inverter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method of a pulse width modulation inverter, and more particularly to a method of switching a pulse width modulation mode.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram of an inverter 1 described in, for example, the 23rd National Symposium on Use of Cybernetics in Railways, 417 "New 3-1 Pulse Switching Method for Inverter Controlled Trains". In the figure,
101 (a) (b), 102 (a) (b), 103
(A) and (b) are main circuit switching elements of U, V, and W phases, 104 is an induction motor as a load of the inverter 1, 105 is a DC power supply, P is a positive terminal, and N is a negative terminal.

Next, the operation will be described. FIG. 5 shows operation waveforms of pulse width modulation, and shows two types of modulation schemes, mode 1 and mode 2. That is, as described in the above-mentioned literature, when the output voltage of the inverter is further increased from the level of the inter-pulse voltage having the three-pulse waveform shown in FIG. 5, the inter-pulse voltage becomes a one-pulse waveform. When switching from three pulses to one pulse in mode 1, there is a phenomenon in which the output voltage of the inverter jumps discontinuously due to the minimum arc extinguishing time required for the switching element of the inverter. A method has been developed in which three pulses of 1 are first switched to three pulses of mode 2 and then switched to one pulse.

FIG. 5 will be described below. First, in mode 1, U _{R in} (A) is a U-phase modulated wave having a sinusoidal waveform, and T _R is a carrier wave that is a triangular-wave modulated wave that is synchronized with the U-phase modulated wave U _{R and} has a frequency three times as high. . Mode 1 (B)
Shows a U-phase output voltage waveforms obtained by pulse-width-modulated at a carrier T _R shown in (A). This switching element UP is ON when U _R> T _R, obtained by the switching elements UN when U _R <T _R is turned ON. Mode 1
(C) shows a V-phase output voltage waveform obtained for a V-phase modulated wave V _R (not shown) having a phase difference of 120 ° with the U-phase modulated wave U _R. (D) of mode 1 is the same as (B)
3C shows a UV-phase output voltage waveform obtained from (C). As can be seen from the (D), each voltage waveform has a three pulse waveform having a voltage drop portion F of the two locations, the modulated wave U _R, the voltage drop unit F according to the change in the amplitude of V _R Is changed and the output voltage is controlled.

Next, operation waveforms in mode 2 in FIG. 5 will be described. In the mode 2 (A), U _S is a U-phase modulated wave having a rectangular (square) waveform, and T _SU is a U-phase carrier which is a modulated wave having an inverted trapezoidal waveform. (B) is a U-phase output voltage waveform obtained by pulse width modulation, and (C) is a V-phase modulated wave V _S and V-phase carrier T _SV (both not shown) obtained in the same manner.
(D) is a UV phase output voltage waveform.

FIG. 6 shows the relationship between the inverter output voltage and the voltage drop angle θ for both mode 1 and mode 2. From this figure, it can be seen that the output voltage is higher in mode 2 than in mode 2. As described above, the modulation method using the mode 2 has a feature that a higher voltage can be output, a power supply utilization factor is high, and a voltage fluctuation at the time of switching to the one-pulse operation (180 ° conduction operation) is small.

[0007]

By the way, the mode is switched from mode 1 to mode 2 at the position of P (FIG. 5) which usually corresponds to the phase angle of 180 ° in the U phase in order to maintain the continuity of the waveform. FIG. 7 shows the mode 1 taking the U phase as an example.
The output voltage waveform is shown mainly at the time when the mode is switched from the mode to the mode 2. As can be seen from the figure, immediately after the switching, the time width θ corresponding to the side pulse of three pulses in mode 2
It takes the form of a pulse width extending from ₁ just before switching, there is a problem that excessive current flows at the moment of switching.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a pulse width modulation inverter capable of suppressing fluctuations in output current that may occur when the modulation method is switched between mode 1 and mode 2. The purpose is to obtain a control method of

[0009]

According to a first aspect of the present invention, there is provided a control method of a pulse width modulation inverter for forcibly driving a switching element of an inverter during a predetermined time width from a mode switching time irrespective of a mode after switching. By doing so, a sudden change in the inverter output current due to the mode switching is suppressed.

According to a second aspect of the present invention, there is provided a control method of a pulse width modulation inverter, wherein a mode switching time is set to 0 for a modulated wave.
By delaying a predetermined time width from the phase of {or 180}, a sudden change in the inverter output current due to the mode switching is suppressed.

[0011]

According to the present invention, after the mode is switched, the operation is not immediately performed in the modulation mode after the switching, but is performed for a predetermined time width.
The switching element is forcibly driven in a direction to suppress the fluctuation of the output voltage, or the mode switching point itself is delayed from the normal phase of 0 ° or 180 ° by a predetermined time width. Then, after the above-described transient operation in the predetermined time width, the operation enters the modulation mode after switching.

[0012]

[Embodiment 1] FIG. 1 is a circuit diagram showing a control method of a pulse width modulation inverter according to Embodiment 1 of the present invention. In the figure, reference numeral 11 denotes a frequency command generation circuit, and 12 denotes a voltage command generation circuit, which determines the output voltage and output frequency of the inverter. Reference numeral 13 denotes a modulated wave (carrier) generation circuit, and reference numeral 14 denotes a modulated wave generation circuit. These circuits generate output signals of the frequency command generation circuit 11 and the voltage command generation circuit 12, that is, voltages and frequency signals in FIG. A phase carrier wave and a modulated wave having the waveforms shown are generated. Reference numeral 15 denotes a modulation for instructing the modulation wave generation circuit 13 and the modulated wave generation circuit 14 to select the mode 1 or mode 2 modulation system by referring to the output signals of the frequency command generation circuit 11 and the voltage command generation circuit 12. Wave / modulated wave switching circuit, 1
Reference numeral 6 denotes output signals of the modulated wave generating circuit 13 and the modulated wave generating circuit 14, T _R (T _SU , T _SV ) and U _R , V _R (U _S , V _S ).
And generates a firing timing signal to the switching element of the inverter by comparing the magnitude relation with the inverter.

Reference numeral 17 denotes a δ generation circuit for forcibly correcting the ignition timing signal from the comparator 16. That is, as shown in FIG. 2, the switching element is forcibly driven so that the output voltage becomes zero for a time width of δ at the time of mode switching. The time width δ is set in a range smaller than the short pulse width θ ₁ of mode 2.

As described above, the provision of the δ generation circuit 17 suppresses an increase in the voltage pulse width which can occur at the time of switching from mode 1 to mode 2, and as a result, the output current at the time of switching is reduced. Bouncing is suppressed.

Embodiment 2 FIG. FIG. 3 is a circuit diagram showing a control method of a pulse width modulation inverter according to Embodiment 2 of the present invention.
The difference from the first embodiment is that Δt is replaced with δ generation circuit 17.
The only difference is that a delay circuit 18 is provided. That is, in the embodiment of FIG. 3, the switching signal from the modulated wave / modulated wave switching circuit 15 is delayed by the Δt delay circuit 18 by the time Δt corresponding to the time width δ in the first embodiment, and the modulated wave generation circuit 13 And the modulated wave generation circuit 14. As a result, the same output voltage waveform as that shown in FIG. 2 is obtained, and an equivalent result of suppressing the jump of the output current is obtained.

Embodiment 3 FIG. In each of the above embodiments, the case where the modulation method is switched from mode 1 to mode 2 has been described. However, even when switching in the opposite direction, a sudden change in the output current can be suppressed by performing processing in the same manner.

[0017]

According to the control method of the pulse width modulation inverter according to the present invention, as described above, the switching element of the inverter is forcibly driven during a predetermined time width from the time of mode switching regardless of the mode after switching. Alternatively, since the mode switching point is delayed from the normal phase by a predetermined time width, a sudden change phenomenon of the inverter output current due to the switching is suppressed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a control method of a pulse width modulation inverter according to Embodiment 1 of the present invention.

FIG. 2 is a diagram showing an output voltage waveform at the time of mode switching obtained by FIG.

FIG. 3 is a circuit diagram showing a control method of a pulse width modulation inverter according to a second embodiment of the present invention.

FIG. 4 is a main circuit configuration diagram of a pulse width modulation type inverter.

FIG. 5 is a waveform diagram for explaining a modulation method of mode 1 and mode 2.

FIG. 6 shows an inverter output voltage effective value and a voltage drop angle θ.
FIG.

FIG. 7 is a diagram showing an output voltage waveform at the time of mode switching obtained by a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inverter 11 Frequency command generation circuit 12 Voltage command generation circuit 13 Modulated wave generation circuit 14 Modulated wave generation circuit 15 Modulated wave / modulated wave switching circuit 16 Comparator 17 δ generation circuit 18 Δt delay circuit 101 to 103 Inverter switching element

Claims (2)

(57) [Claims] 1. A first pulse width modulation mode for outputting a three-pulse inter-phase voltage by using a sine-wave modulated wave and a triple-frequency triangular-wave modulated wave, and a rectangular-wave modulated wave and an inverted trapezoidal wave. In the control method of the pulse width modulation inverter in which the second pulse width modulation mode that outputs a three-pulse waveform interphase voltage with the modulation wave can be controlled to be switched at a predetermined phase, a predetermined time width from the time of mode switching is used. A pulse width modulation inverter control method, wherein a sudden change in the inverter output current due to the mode switching is suppressed by forcibly driving the switching element of the inverter regardless of the mode after the switching. 2. A first pulse width modulation mode for outputting a three-pulse inter-phase voltage using a sine-wave modulated wave and a triple-frequency triangular-wave modulated wave, and a rectangular-wave modulated wave and an inverted trapezoidal wave. In the control method of the pulse width modulation inverter in which the second pulse width modulation mode for outputting a three-pulse waveform interphase voltage with the modulation wave of the modulation wave can be controlled, the mode switching time is set to 0 ° or 180 ° of the modulated wave. A control method of a pulse width modulation inverter, characterized in that a sudden change in the inverter output current due to the mode switching is suppressed by delaying the phase of ゜ by a predetermined time width.