JPS6056389B2 - Operation method of thyristor bridge circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a plurality of sets of thyristor bridge circuits connected in series on the DC side.

Conventionally, for example, in electric cars, thyristor converters are used to control DC voltage over a wide range of positive and negative ranges to control power running and regeneration of the vehicle. For this purpose, a method is adopted in which the secondary winding of the transformer is divided into a plurality of sets, a rectifier circuit is connected to each of the windings, and the DC sides are connected in series.

In other words, as shown in the conventional circuit example of FIG.
The next winding is divided into multiple sets, and a single-phase bridge circuit 2 consisting of thyristor arms 2PA, 2NA, 2PB, and 2NB and another single-phase bridge circuit 3 are connected to each set, and their DC terminals are connected in series. Configure the converter circuit. In such a conventional circuit configuration, in a region where the DC output voltage is low, for example, only the bridge circuit 3 performs forward conversion operation or inverse conversion operation (hereinafter, this operating state is referred to as rectification mode).
The other bridge circuit 2 blocks the gates of the thyristor arms 2PA, 2NA to make the thyristors non-conductive, while
Bypassing the load current by operating NB as a diode (hereinafter this operating state is referred to as bypass mode)
was. For this reason, the thyristor arms 2PB and 2NB required twice as much current capacity as the thyristor arms 2PA and 2NA. Therefore, the bridge circuit 2 is 1.5 times the number of thyristor elements required for only rectification mode.
This required twice the number of thyristor elements. The present invention solves the drawbacks of the conventional system, and provides a bridge circuit operation method that allows bypass mode operation with zero DC average voltage and few power harmonics without increasing the number of bridge circuit elements when only in rectification mode. This is what we provide.

FIG. 2 shows an embodiment of the present invention including a transformer 1, a bridge circuit 2,
3 and thyristor arms 2PA, 2NA, 2PB, 2
NB is connected in the same way as in FIG.

However, the current capacity of thyristor arms 2PB and 2NB is not increased compared to that of thyristor arms 2PA and 2NA. 4 is a circuit for detecting commutation margin angle γ, and its output signal is sent to bypass mode phase angle command circuit 5, where the phase control delay angle α is controlled to be equal to γ.

On the other hand, the phase angle command circuit 5 determines the control advance angle β based on a signal from the control advance angle β setting signal circuit 6. Reference numeral 7 denotes an arm selection circuit which selects the arm to be fired based on the control advance angle β or the control delay angle α.

8 is a timer circuit that performs bypass operation using thyristor arms 2PA and 2NA (hereinafter referred to as bypass mode A) and bypass operation using thyristor arms 2PB and 2NB. This is to determine the switching cycle of operation (hereinafter referred to as bypass mode B).

The output signal of the arm selection circuit 7 is sent to the thyristor gate circuit 9.
and sends a gate signal to the selected thyristor arm of the bridge circuit 2. 10 is an operation mode instruction circuit which sends an operation signal to the bypass mode phase angle command circuit 5 when performing bi-bus operation, and the rectification mode phase when performing rectification operation (including forward conversion operation and reverse conversion operation). Angle command circuit 1
Send driving signals to 1, respectively. The phase angle command circuit 11 receives a signal from the rectification mode phase angle setting signal circuit 12 and determines the control advance angle β or the control delay angle α. FIG. 3 shows the operating waveforms of the bridge circuit 2 according to the present invention.
s is the AC side voltage of the bridge circuit 2, Ed is the DC side voltage, Ia is the AC side current, and the polarities of each are as shown by the arrows in FIG. I2PA,i
2PB, i2NA, iN are each thyristor arm 2
Currents of PA, 2PB, 2NA, and 2NB are flowing. Next, the invention of the present invention will be explained in detail using FIGS. 2 and 3.

Time T. Until then, the thyristor arms 2PA and 2NA are in conduction and the operation is in bypass mode A. Time T corresponding to control advance angle β. When this happens, a signal is sent from the phase angle command circuit 5, and the arm selection circuit 7 selects the thyristor arm 2PB.
A gate signal is sent to ignite thyristor 2PB. At a certain time, the commutation from thyristor arm 2PA to 2PB is completed, and bridge circuit 2 enters the rectification mode and generates the DC voltage shown by diagonal lines. The margin angle detection circuit 4 detects when the AC voltage Es becomes zero from the time point onward! A commutation margin angle γ corresponding to the time up to 1L2 is detected and a signal is sent to the phase angle command circuit 5. The phase angle command circuit 5 sends a control delay angle signal to the arm selection circuit 7 at time T3 when the magnitude of the control delay angle α becomes equal to γ. As a result, arm selection circuit 7 sends a gate signal to thyristor arm 2NB at time T3 to fire the thyristor arm, and commutation from thyristor arm 2NA to thyristor arm 2NB is started. The commutation is completed at time T4, and the operating state becomes bypass mode B using the thyristor arms 2PB and 2NB. Time T. Therefore, during T4, a negative current 18 flows on the AC side. This means that bypass mode A has been switched to bypass mode B, but the AC side current is 1. ．． Since there is only a negative half-wave and a DC component remains, a positive half-wave current 11 is caused to flow between time T and T9. That is, thyristor arm 2PA is fired at a time corresponding to control advance angle β, half a cycle after time t, to commutate the current from thyristor arm 2PB to thyristor arm 2PA, and at this time, the commutation margin angle γ has a magnitude equal to that of thyristor arm 2PA. At time T8 corresponding to control delay angle α, thyristor arm 2PB
is ignited to cause commutation from thyristor arm 2PA to thyristor arm 2PB. As a result, bypass mode B is restored again.
Switching of the bypass arm was not performed again.As for the AC current 1a, between time T5 and time T9, a current of the same magnitude and opposite direction flows from time T5 to time T4, and the DC component is canceled. be done. At the same time as the arm selection circuit outputs a signal indicating the control advance angle β, the timer circuit 8 starts operating and the bypass mode B continues for the time TB up to the time TlO. The arm selection circuit 7 is activated by the signal from the timer circuit 8 which reaches the time TlO, and the arm selection circuit 7 is activated for the first time at or after the time TlO.
Time T. The thyristor arm 2NA is fired at a time Tll corresponding to the control advance angle β at a voltage having the same polarity as the voltage Es in the thyristor arm 2NA, and the current is commutated from the thyristor arm 2NB to the thyristor arm 2NA. Similarly, at time Tl2 corresponding to α=γ, thyristor arm 2PB to 2PA is
The current is diverted to bypass mode A. Furthermore, at a time Tl3 corresponding to the control advance angle β after half a cycle, the thyristor arm 2NA is commutated to 2NB, and further, at a time Tl4 corresponding to the control delay angle α such that α=γ, the thyristor arm 2NB is transferred.
The AC current 1a is commutated again to 2NA so that no DC component remains in the AC current 1a. In this way, switching from bypass mode B to bypass mode A is completed. On the other hand, from time T4l, the timer circuit 8 starts operating again and sends a signal again after time TB, and starts the same bypass mode switching operation from time T4l to T9. By operating the bridge circuit in this way, since γ = α, the average value of the bridge circuit DC voltage (shaded area in Figure 3) in the bypass operation state becomes zero, and there is no effect on the average value of the DC output voltage. Not affected.

The alternating current 1a can be kept to a minimum by setting the control advance angle β to a value as small as possible within the allowable range for operation, or by controlling the commutation margin angle γ to always maintain the minimum allowable value. I can do things. In this way, when the present invention is used, alternating current 1. Since it can be controlled so that it only needs to flow for a short period of time as required for commutation, the influence on the power supply side can be minimized. Next, when the bypass mode switching period T8 (=TlO-TO) is selected as TB=n/f (n=2 or a positive integer greater than 2) with respect to the AC power frequency f, the AC side current is 1.

contains the power supply frequency wave and its harmonic components. However, as n increases, the value of the ★harmonic component and its harmonics decreases, so if n is selected to be larger than a certain degree, the value of the different frequency component on the power supply side can be practically ignored. In the present invention, the switching period of the bypass current-carrying arm is set to be longer than the period due to the power supply frequency.
is 2 or more, and the different frequency components of the power supply can be reduced. On the other hand, the cooling fin thermal time constant of the thyristor element is usually in the range of several tens of seconds to several minutes, so for example, bypass mode A is used every second.
, B, the element cooling fin temperature hardly changes. Therefore, if the bridge circuit DC output current is assumed, the temperature rise of the element cooling fin is equivalent to the average current of the thyristor arm/2, which is the same temperature rise as in the rectification mode, and it is possible to keep only one arm connected in the conventional way. The temperature rise is half that of operating in bypass mode. Therefore, unlike the conventional method, there is no need to increase the number of thyristor elements. On the other hand, for example, when the AC power frequency is 50Hz, if γ = 10 volts and the bypass mode is switched every second, the 1Hz component current is about a few percent, and the current is 1Hz.
Since the harmonics of the z component further decrease as the order increases, the harmonics on the alternating current side can be suppressed to a value that causes almost no problem. FIG. 4 shows another operating waveform according to the present invention.

Bridge circuit 2 is operated in bypass mode A until time T. to T4, bypass mode A is switched to bypass mode B in a process similar to that shown in FIG.
Bypass mode B continues for time T8 up to 1t10. It's time. When the time Tl. Hail first on or after O, time T. The current is commutated from the thyristor arm 2PB to the thyristor arm 2PA at a time corresponding to the control advance angle β at a voltage of opposite polarity to the voltage Es at the time. After the voltage is reversed at the handover time, the time corresponds to the control delay angle α where α = γ! Thyristor arm 2NB
The current is then commutated to the thyristor arm 2NA. Thus, the bridge circuit 2 switches from the bypass mode B to the bypass mode A during the time interval. On the other hand, the timer circuit 8 starts operating again after the time TB, and the arm selection circuit 7
A signal is sent to , and the state is returned to the same state as at the time corresponding to the control advance angle β at a voltage of opposite polarity to the voltage E3 at time T5, that is, at time T5, and the state is periodically repeated.
On the other hand, the AC side current 1a is at time T. A negative current flows from to T4, and a positive current flows from time ζ to T4, and no DC component remains. According to the operation method shown in FIG. 4, compared to the operation method shown in FIG. 3, the AC side current 1a is 1/! It only requires a flash, and the impact on the power supply side can be further reduced. As described above, in the present invention, in the bridge circuit in the bypass mode, by periodically switching the bypass current carrying arm at a frequency lower than the AC power frequency, compared to the case where the control is performed as in the conventional mixed bridge circuit operation. Therefore, the current carrying capacity of the thyristor arm is small, and the number of thyristor elements can be reduced.

In addition, the thyristor arm switching is performed at the control advance angle β, and the commutation margin angle γ at this time is controlled so that the control delay angle α for the next half cycle is equal, so the DC average voltage of the bridge circuit becomes zero and the DC side The effect on can be ignored. Furthermore, in the present invention, since the alternating current for bypass arm switching lasts only for an electrical angle of 2β, if the control advance angle β is made sufficiently small without commutation failure, the alternating current for commutation can be made sufficiently small compared to the load current. In addition, since the bypass arm switching cycle is periodically switched at a frequency lower than the bridge circuit AC power supply frequency, the AC side current flowing for switching can be suppressed to a small value, and an increase in harmonic current can be prevented. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional operating method, FIG. 2 is a circuit diagram showing an operating method according to an embodiment of the present invention, FIG. 3 is an operating waveform diagram according to an embodiment of the present invention, and FIG. 4 is a circuit diagram showing an operating method according to an embodiment of the present invention. FIG. 6 is an operational waveform diagram according to another embodiment of the present invention. In the figure, 1 is a transformer, 2 and 3 are thyristor bridge circuits, 2
PA, 2NA, 2PB, 2NB are thyristor arms, 4
5 is a commutation margin angle detection circuit, 5 is a phase angle command circuit, 6 is a control advance angle setting signal circuit, 7 is an arm selection circuit, 8 is a timer circuit, 9 is a thyristor gate circuit, 10 is an operation method instruction circuit, α is a The control delay angle, β is the control advance angle, and γ is the commutation margin angle.

Claims (1)

[Scope of Claims] 1. In bypass mode operation of a plurality of sets of thyristor bridge circuits connected in series on the DC side, controlling the DC voltage average value of the thyristor bridge circuits to be zero,
Then, the commutation margin angle γ is detected when the commutation operation is started at a certain control advance angle β, and the control delay angle α is equal to the commutation margin angle γ in the subsequent reverse half-wave of the voltage. 1. An operating method for a thyristor bridge circuit, characterized in that the bypass current carrying arm of the thyristor bridge circuit is controlled to be controlled so as to be controlled so as to periodically switch the bypass current energizing arm of the thyristor bridge circuit with a cycle longer than the cycle of the AC power supply frequency. 2 The control lead angle β and the control delay angle α are the first control lead angle β_1, the corresponding control delay angle α_1 immediately after, and the half cycle subsequent to the first control lead angle β_1 and the control delay angle α_1. Let the second control advance angle β_2 be the immediately following corresponding control delay angle α_2, and the first α_1, β_1
and the second β_2, α_2, the bypass current carrying arm is switched by controlling the two sets of α and β such that the DC component of the AC side current becomes zero. Operation method of the thyristor bridge circuit described in Section 2. 3 The above-mentioned switching of the energizing arm is performed using the first control advance angle β_1
Then, the first switching of the bypass current carrying arm is completed at the corresponding control delay angle α_1 immediately after, and after being energized for a time determined by the prescribed switching cycle of the bypass current carrying arm, the AC side current in the first switching is Then, the bypass current carrying arm is switched again at the second control advance angle β_2 and the corresponding control delay angle α_2 immediately after the polarity of the AC voltage such that the AC side current flows in the opposite direction, and β_1.
3. The operating method of the thyristor bridge circuit according to claim 2, wherein control is performed so that = β_2 and α_1 = α_2.