JPS607466B2 - Current type cycloconverter device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a current type cycloconverter device.

Recently, cycloconverters have been widely used as variable frequency power supplies for variable distance driving of AC motors, particularly squirrel cage induction motors or linear motors.

There are roughly two types of cycloconverters applied to these uses: '1' Sine wave modulation continuous cycloconverter ■ Comparing both current type cycloconverters, the former can obtain an almost sine wave output current, but
The control is complicated, a large number of electric valves are used, and it is therefore economically expensive, whereas the latter output current is a rectangular wave.
The control is simple and the number of electric valves used is only 1'2 compared to the former, so it is characterized by being economically advantageous.

Another drawback of the latter is that although the output frequency maintains a constant set frequency as an average value, as an instantaneous value it periodically fluctuates above and below the average frequency. Therefore, when an induction motor is used as a load, it is difficult to avoid large torque pulsations. This effect becomes particularly noticeable as the output frequency increases, and this is one of the major conditions that restricts the upper limit of the output frequency. This will be explained in more detail with reference to the drawings. FIG. 1 shows the basic circuit configuration of a conventional current type cycloconverter with three phases on the input side and three phases on the output side.

The device shown in Figure 1 is the three-phase output terminal R of the three-phase power transformer TRI.
, S, T and three-phase input terminals U, V, and W of the three-phase load LD are connected via a three-phase DC reactor DL and a thyristor type cycloconverter CCV. Both ends of the reactor DL are connected to the positive input terminal and negative input terminal of the cycloconverter CCV for each phase,
The midpoint tap is connected to the output terminal of the corresponding phase of transformer TRI. The cycloconverter CCV has three thyristors connected between each output terminal and the input terminals of different phases on both the positive and negative sides, and therefore has a total of 3 x 3 x 2 = 18 thyristors. Evening is set. Each thyristor is designated by three alphabetical symbols according to its insertion position. The first code is R, S, or T indicating the phase difference seen from the power supply side, the second code is U, V, or W indicating the phase difference seen from the load side, and the third suffix is The sign is P or N indicating whether the positive side (P side) is the negative side (N side). Therefore, for example, a thyristor called RUP is connected to the R phase when viewed from the power supply side, and the U phase when viewed from the load side.
Indicates that the thyristor is connected to the phase and further connected to the positive side. FIGS. 2a to 2e are time charts for explaining the operation of the apparatus shown in FIG. 1.

Figure 2 a shows the commutation command on the power supply side, b shows the commutation command on the load side, c shows the gate pulse given to each U-phase thyristor on the load side, and d
is the energization period of each thyristor, and e is the energization period of each phase current on the load side. In this example, the load side command frequency f with respect to the power supply frequency fi. The ratio f. The case of /f;=2/7 is shown. In conventional current-type cycloconverters, commutation between each thyristor is performed by power supply voltage commutation, so commutation between thyristors occurs at an electrical angle of 1200 degrees of the power frequency.
It is only done once in a while.

Therefore, as shown in FIG. 2, for example, while the commutation command for the thyristor UP→VP is issued at time L', the actual commutation is performed at a time ratio of 2, and 8d=(t2
This results in a commutation delay of 1 t,). This delay angle 8a usually takes a different value for each commutation, and the maximum value is about 120.
o Electrical angle is reached. Therefore, as described above, the average value of the output frequency maintains the set frequency, but the instantaneous value of the output frequency repeatedly fluctuates above and below the average frequency. This fluctuation has a certain periodicity, and therefore generates beats in the commutation cycle on the load side, and when driving a conduction motor as a load, large torque pulsations occur.Moreover, these effects are particularly important for output. As already mentioned, this becomes more noticeable as the frequency increases, and is one of the major conditions that restricts the upper limit of the output frequency. Therefore, an object of the present invention is to provide a current-type cycloconverter that can determine load side commutation timing without being affected by power supply side commutation timing, in order to effectively reduce torque pulsation when driving an induction motor as a load. Our goal is to provide the following.

To achieve this objective, the present invention connects the positive input terminal and negative input terminal of the cycloconverter to separate power transformer windings having a predetermined phase difference from each other, and The windings of each phase of the line are selectively connected in series via a DC reactor in accordance with each energization mode of the cycloconverter.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 3 shows an embodiment of the main circuit of a current type cycloconverter device according to the present invention.

The cycloconverter CCV of this device and the load LO connected thereto via three-phase terminals U, V, and W are both similar to those in FIG. The power transformer TR has a primary winding Wo.
In addition to the above, two sets of secondary windings W, , W2 which are separated from each other are provided. Output end R,,S,,T of secondary winding W,
, and the output terminals R2, S2, L of the secondary winding W2
There is a phase difference of 30o between the voltage generated at
The secondary winding W, so that both constitute a rectification phase number of 12,
is configured in a star-shaped connection, and the secondary winding W2 is configured in a triangular connection. The positive input end of the cycloconverter CCV is connected to the secondary winding W through terminals R, , S, , T, and the negative input end is connected to the secondary winding W through terminals R2, S2, and L. It is connected to the next winding W2. Furthermore, one terminal R,,
S, , T, have auxiliary thyristors R, N, S. N, T, and N are connected, and their free ends (anode sides) are commonly connected. Similarly, auxiliary thyristors R2P, S2P, and T2P are connected to the other terminals R2, S2, and T2 in the opposite direction to the main thyristors R UN to WN, and their free ends (cathode sides) are connected in common. has been done. Auxiliary thyristor R
, N~T, N common connection point and auxiliary thyristor R2P~T
It is connected to the common connection point of SHA via a direct reactor DL. Note that this DC reactor may have a common iron core type multi-winding structure inserted on the power supply side or the load side. Figure 4 shows the control device attached to the main circuit in Figure 3 only for the control circuit portion for the positive main thyristors R, PUP~T, PWP and the auxiliary thyristors R, N~T, N of the main circuit. It is.

For the negative side thyristor, a control circuit portion having substantially the same configuration as that shown in the drawing is provided. FIG. 5 shows a time chart for explaining the operation of the apparatus shown in FIGS. 3 and 4. The control device shown in FIG. 4 will be explained below with reference to the time chart shown in FIG. In Figure 4, PD
, P are the positive main thyristors R, PUP to T. This is a gate pulse distributor for PWP, and PD,N is a gate pulse distributor for positive side auxiliary thyristors R,N to T,N.

First, the power supply periodic signals R, Ps, S, P8, T, Ps (Fig. 5a) are input to the IP power supply side distributor PD, Ps, where the output signal of the OR circuit OR, ie, the QI pulse Power supply side commutation commands R, P, S, P, T, and P are output in synchronization with examples P and PQ1 (FIG. 5C) triggered by the commands.
This power supply side commutation command is input to gate pulse distributors PD and P. The OR circuit OR has a Q pulse train P, PQ (Fig. 5b) given as the output of the phase shifters PH, P, that is, a pulse train output at the phase point of the control angle Q with reference to the zero point of the power synchronization signal. , and the output pulses of the comparator CP are input, and the above QI pulse trains P, PQ are input by these inputs.
I is formed. The phase shifters PH and P receive the power synchronization signal (fifth
Based on the phase shift signal voltage VQ corresponding to the control angle Q, a Q pulse train (FIG. 5c) is output at a phase point shifted by the control angle Q from the zero point of the power synchronization signal. SB is a subtracter, which subtracts the result of subtracting the phase-shifted signal voltage VQ from the signal voltage V side corresponding to the reference signal voltage set by the reference signal voltage setter RV, that is, 120o in this embodiment, to the subtracted output signal V, N,=V side is outputted as -VQ, and this is inputted to one input terminal of the comparator CP. On the other hand, the IC is an integrating capacitor, and a switching transistor Tr is connected in parallel to both ends of the IC. It is assumed that the integrating capacitor IC can be charged with a constant current i via a constant current source CCS. As long as the transistor Tr is in a non-conducting state, the integral capacitor IC is charged by the constant current i to a charging voltage V, N2 proportional to the charging time. This voltage V,
N2 is input to the second input terminal of comparator CP. Comparator CP compares both inputs and outputs an output when V, N, - V, N2.

This world power is input to the reset terminal of flip-flop circuit FF and resets it. PD is a load-side distributor and has a load synchronization pulse 8.

Based on (Fig. 5 e), load side commutation commands UP, VP,
WP (Fig. 5 f) is output. This load side commutation command UP
, VP, WP are, on the one hand, respectively rising differential circuits T
The signal is input to the second OR circuit OR2 via DC. The output signal of the OR circuit OR2 is input to the set input terminal of the flip-flop circuit FF. Load side commutation command UP, VP
, WP are respectively input to one input terminal of the AND circuit AND. The output Q corresponding to the reset state of the flip-flop circuit FF is commonly input to the other input terminal of the AND circuit AND. The load-side commutation commands UP, VP, and WP (Fig. 5 f) are not actually the final commutation commands, but the load-side commutation commands with a rest period obtained on the output side by passing the AND circuit AND according to the present invention. Commutation commands UP', VP', WP' (FIG. 5g) are led to gate pulse distributors PD, P as final commutation commands. The idle period 8o corresponds to the period in which Q of the output of the flip-flop circuit FF exists. When the output 9 of the flip-flop circuit FF is present, that is, when the flip-flop circuit FF is in the reset state, the transistor Tr becomes conductive to short-circuit and discharge the integrating capacitor IC.
When the flip-flop circuit FF is in the set state, that is, when there is no Q output, it becomes non-conductive to enable charging of the integrating capacitor IC.

Gate pulse distributors PD, P are power supply side commutation commands R, P,
Based on S, P, T, P (Fig. 5 d) and load side commutation commands UP', VP', WP with rest period (Fig. 5 g), the positive side main thyristors R, PUP~T, A gate pulse (Fig. 5h) given to PWP is output. In this case, for example, the gate pulses for the main thyristors R and PUP are given as outputs that satisfy the AND condition of the power supply side commutation commands R and P and the load side commutation command UP' with a rest period. The gate pulse distributor PD, N for the positive side auxiliary thyristor receives the power synchronization signals R, Ns, S, Ns, T, Ns (Fig. 5a)
commutation commands for the auxiliary thyristors R, N, S, N, ST, and N are formed based on the Q pulse train P melon Q (FIG. 5b).

In this case, for example, the R-phase commutation commands R and N are output at the time when the logical product of the power synchronization signal R (FIG. 5a) and the Q pulse trains P and NQ (FIG. 5b) is satisfied. Q pulse train P,
NQ is the same power source signal R, Ns, S, Ns, T, Ns,
Based on the phase shift signal voltage VQ just mentioned, the phase shifter PH,
N is given as a pulse train generated at a phase point shifted by a control angle Q from the zero point of the power synchronization signal. Hereinafter, before explaining the commutation operation performed by the apparatuses shown in FIGS. 3 and 4, some supplementary explanations will be given regarding the operation of the apparatus shown in FIG. 4.

The load-side commutation command with a rest period (Fig. 5g) corresponds to the load-side commutation command shown in Fig. 2b, but unlike that, immediately before the load-side commutation command, the previous load-side energization is It is controlled by the output of the flip-flop circuit FF so as not to apply an ignition pulse to the phase for a predetermined period.

As a result, the gate pulse given to each main thyristor (Fig. 5h) is changed from the power supply side commutation command pulse (Fig. 5d)
is the said suspension period 8. When the power supply side commutation command pulse is within the period of time, the power supply side commutation command pulse is delayed until the time of the load side commutation command (Fig. 5g), and the power supply side commutation command pulse is suspended for a period of 8. If not, the power supply side commutation command pulse of the phase to start energization next is controlled to advance to the time of the load side commutation command. In FIG. 5g, the pulse indicated by a broken line has a rest period of 8. The dew source commutation command pulse is shown entering and being erased. In addition, Fig. 5i shows the positive main thyristor R, PUP~
The energization periods of T, PWP and the positive side auxiliary thyristors R·N to TIN are shown, and FIG. 5i shows the energization period of each phase load current. Next, the commutation operation by the apparatus shown in FIGS. 3 and 4 will be explained.

m 1st commutation mode: Load commutation is performed from the main thyristors R, PUP to T, N to S, PVP to T, N at the time ratio of Fig. 5, but immediately before the commutation command Since there is no open source commutation command pulse that was erased during the rest period 8o, in this case, the main thyristors S and P to be energized next
The firing pulse of VP is advanced to the time of the load-side commutation command, and commutation is performed from the main thyristor RIPUP to S, PVP in synchronization with the load-side commutation command.

The necessary condition for commutation is that at time t=t, the relationship between the S-phase voltage Vs,P and the R-phase voltage VR,P of the transformer winding W is Vs,P>VR,P. However, from FIG. 6, it is clear that this condition is satisfied. {
2} Second commutation mode: Even at the time ratio 2 in Fig. 5, the main thyristors S, PWP~R, N to T, PUP~R, N
However, in this case, the above-mentioned rest period a
Since the dew source commutation commands T and P that have entered within o are erased, the main thyristors S and PWP continue to be energized and the ignition pulses of the main thyristors T and PUP are delayed until the time of the load side commutation command. from the main thyristor S・PWP to T,PUP
Commutation is performed in synchronization with the load side commutation command. The necessary condition for commutation is that at time t=t2, the relationship between the T-phase voltage VT,P of the transformer winding W, and the S-phase voltage Vs,P is VT,
P>Vs,P, and it is clear from FIG. 7 that this condition is satisfied. In the above case,
Pause period 8. As shown in FIG. =120
If the control circuit is configured to maintain the 0-Q relationship, the above conditions necessary for commutation will always be satisfied, regardless of the value of Q. If the main commutation pulse enters within the period of rest period 8o, delayed commutation is performed in the second commutation mode, and if the main commutation pulse does not enter within the period of rest period ao. In the above-mentioned first commutation mode, advance commutation can be performed in synchronization with the load commutation command. Therefore, it is possible to avoid phenomena such as fluctuations in the output frequency, generation of beats in the commutation period on the load side, and increased pulsation in the motor torque associated therewith, which are observed in the conventional current type cycloconverter.

The above control method is based on the conventional 3-phase input side, 3-phase output side current type cycloconverter (18 thyristor elements,
It can be applied as is to a rectification phase (6 phases), but in this case, due to the delay and advance control of the control angle performed at the time of commutation, the current fluctuation is large, resulting in torque pulsation, resulting in the above-mentioned problem. The effect of synchronous commutation is reduced.

On the other hand, in the case of this circuit system, the positive side transformer winding W
, and the negative side transformer winding W2 are used in series via the auxiliary thyristor, the influence of current fluctuations associated with the delay and advance control during commutation is small, and torque pulsation is significantly reduced. improved. Also, since the main circuit in Figure 3 has 12 rectification phases, compared to a case with 6 rectification phases, if the size of the DC reactor is the same, the current pulsation is smaller. There is also less harmful effect of harmonics on the power supply side. Above, we have explained an example in which the same Nada commutation is performed as a control method for the main circuit in Fig. There is no problem in adopting a simple control method that allows commutation of
Of course, torque pulsation is reduced compared to the phase case. Figure 8 shows a modification of the main circuit in Figure 3. Here, the main thyristors connected to the same output terminal are grouped together by positive side or negative side, and the positive side is shown in three groups. The main thyristors UP, VP, WP of
Moreover, the negative side is shown by three groups of main thyristors UN, VN, and WN. Similarly, the auxiliary thyristors on the positive side are indicated by A and N, and the auxiliary thyristor on the negative side is indicated by A. Both auxiliary thyristors A, N and A-tight are connected in series, and their common connection point ○ is connected to the neutral point OL of the load LD. Since the main circuit shown in FIG. 8 has the power supply side and the load side connected to the neutral point, it can be suitably applied depending on the structure of the protection device.

[Brief explanation of the drawing]

Figure 1 is a connection diagram of a conventional current-type cycloconverter device, Figure 2 is a time chart of the operation of the device in Figure 1, and Figure 3
The figure shows the current type SiC of the present invention. A connection diagram showing one embodiment of the converter device, FIG.
A connection diagram showing an embodiment of the control device for controlling the device shown in the figure, FIG. 5 is a time chart for explaining the operation of the device shown in FIGS. 3 and 4, and FIGS. 6 and 7 are FIG. 8 is a connection diagram showing a different embodiment of the main circuit of FIG. 3. TR...
・...Power transformer, W,, W2...Power transformer T
Secondary winding of R, CCV...Cyclo converter, R, PUP~T, PWP, R2NUN~T shoe WN...
Main thyristor, R, N~T, N, R2P~T2P...
...・Auxiliary thyristor, DL, DL,, DL...
DC IJ actor, LD...Load, PD, P...
...gate pulse distributor for main thyristor, PD, Ps
...Power supply side distributor, PD, N... Gate pulse distributor for auxiliary thyristor, PH, P, PH, N
... Phase shifter, PDL ... Load side distributor, FF ... Flip-flop circuit, CP ...
...Comparator, CB.... ．． ．． Subtractor, IC...
Integrating capacitor, Tr...Switching transistor, TDC...Rising differential circuit, OR,,O
R2...OR circuit, AND...AND circuit, UP~WP, UN~WN...main thyristor, A,
N, A2P... Auxiliary sirens evening. Rare 8th figure N Kozucho Toge Leopard 2nd figure Dooji figure 0 figure 6 Younger brother ku figure

Claims (1)

[Claims] 1. A first secondary winding connected to the first output terminal and a predetermined phase difference between the first secondary winding and the second output terminal. a power transformer having a second secondary winding connected to the DC reactor; a first thyristor group commonly connected to one end of the DC reactor; and a first thyristor group provided for each of the second output ends, an anode connected to the second output end, and each cathode connected to the other end of the DC reactor. and a second thyristor group connected in common, the auxiliary thyristor selectively connects the output phases of both secondary windings in series via the reactor according to the output end line phases of both the secondary windings. a positive input terminal is connected to a first output terminal of the power transformer, a negative input terminal is connected to a second output terminal of the power transformer, and an AC output terminal is connected to an induction motor. A current-type cycloconverter device comprising a cycloconverter and a cycloconverter.