JPS5822586A - Regenerative control of power converter - Google Patents

Abstract

PURPOSE:To improve the power-factor and the fault when a current is regenerated on the titled power converter by a method wherein, when a current is commuted on a thyristor inverting bridge, a DC power source and the bridge are disconnected and after the commutation has been completed, they are connected again and a current is applied. CONSTITUTION:A thyristor power inverter 16 is provided to generate regenerative power from load, the DC terminals of both positive and negative electricity on the power inverter 16 are connected to bus of a DC power source through the intermediate of reactors 31 and 32, and DC switches 33 and 34, and besides, diodes 35 and 36 are connected in crossed form. Then the above DC switches 33 and 34 are open-circuited before commutation when the above power inverter 16 is commutated for power regeneration, and after the regenerated current running to the power inverter has been sufficiently attenuated, commutation is performed on it. After the commutation has been completed, the above DC switches 33 and 34 are close-circuited and the regenerated current is flown.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a regeneration control method for a power converter when power is regenerated from the load side.

In recent years, in the field of power conversion devices, applications such as variable speed drives have expanded, but especially when regenerating power from a load, it is important to avoid wasting it in resistors and regenerating it into AC power. Technology is desired.

Especially GD with voltage type inverters! When driving an electric motor connected to a large load ('!), the method of processing regenerated power is an important technology not only from the perspective of energy saving of regenerated power but also from the perspective of variable speed control performance of the AC motor. .

Conventionally, in order to meet these demands, the Y-type circuit shown in FIG. 1 has been adopted.

The alternating current voltage of the alternating current power supply 10 is converted to direct current by a diode forward converter 11, and smoothed by a large capacity smoothing capacitor]2 to become a direct current voltage 13.

On the other hand, the AC voltage of the AC power source 10 is stepped up by a step-up transformer 14 to become an AC power source 15 for regeneration, which is connected to a thyristor inverter 16 for regeneration. Thyristor inverter 16
The positive side bus bar of is connected to the positive side of the smoothing capacitor 12 via the DC reactor 17. Also, thyristor inverse converter 1
The negative side bus bar 6 is connected to the negative side of the smoothing capacitor 12.

The DC voltage 13 is detected by the voltage detector 18 and becomes a voltage feedback signal 19, which is input to the level detector distribution, and the phase control signal 21 of the thyristor inverter 16 is output, and the phase control device n is connected to the thyristor inverter 16. and controls the DC voltage 13 during regeneration.

FIG. 2 shows the operation of the thyristor inverter 16 during regeneration in the conventional circuit shown in FIG. 1, at time 1. In this case, the regenerative current flows from the positive side of the smoothing capacitor 12 to the DC reactor 1.
7→V thyristor→power fMW phase→power supply V phase→V-thyristor→power is regenerated from the smoothing capacitor 12 to the power supply through the negative side path of the smoothing capacitor 12. Time t2
When this occurs, an ignition signal is sent to the U+ thyristor, commutation is performed from the W+ thyristor to the U+ thyristor, and the path of the regenerative current is as follows: positive side of the smoothing capacitor 12 → DC reactor 17 → U thyristor → power supply U phase → power supply V The phase changes from the V-thyristor to the negative side of the smoothing capacitor 12.

The firing timing of this thyristor inverter 16 is generally expressed by a control angle β, and if β is made smaller, that is, the firing timing is advanced, the DC voltage of the thyristor inverter becomes smaller. If you delay,
The voltage of the thyristor inverter 16 increases, and by adding a current detector and a current control loop to the voltage of the smoothing capacitor 12 during regeneration, the regenerative current can also be controlled.

Here, if the DC voltage during regeneration is Ed', and the effective value of the AC voltage of the thyristor inverter 16 is Er, then if the commutation overlap angle is ignored, as is well known, Edl≠-1, 35E, 100β...
...... The relationship (1) is established.

Next, referring to FIG. 3, the state of commutation of the W+thyristor U+thyristor will be explained. At time t, W+
Since the thyristor and the V-thyristor are conducting and a regenerative current n is flowing, the W+ thyristor current is equal to the regenerative current, and the U+ thyristor is not conducting, so the U+ thyristor current 6 is O. In addition, the voltage part between the terminals of A- of W+ thyristor is only a forward voltage drop, and A- of U+ thyristor.
The terminal voltage is applied to 271, and the W-U voltage is applied to 271. At time t2, an ignition signal is sent to the U+ thyristor to start commutation. Since a forward voltage is applied to the U+ thyristor, it conducts along with the firing signal, creating a closed circuit of power supply W phase - W++ irisister U + thyristor → power supply U phase → power supply W phase, and this closed circuit current is caused by the impedance of the power supply and the power supply W
The voltage difference I between phase and U phase increases according to the rate of increase determined by this, thereby reducing W+thyristor current waste. At time t, the W+ thyristor current 24 is O6, the 1 H U+ thyristor magnetic current 5 is equal to the regeneration, and the 1 H Ascaris current is commutated, and the W+ thyristor becomes non-conducting and reverse biased to the W phase of the power supply. , the voltage difference of the power supply U phase is applied,
After a suitable turn-off time, the forward blocking ability is completely restored and the series of commutation operations is completed. Here, the time from time t2 to time t is called the commutation weight angle, and the current immediately before the start of commutation flowing through the commutating thyristor (here, the regenerative current 23), and the voltage difference (here: It depends on the voltage difference between the power supply W phase and the power supply U phase) and the impedance of the power supply, and in the range of 90<β<1800, as β increases, the weight angle also increases and the time that the power supply is shorted between phases increases. Become.

In addition, the reverse bias time applied to the W+ thyristor is from time t to time t4 when the voltage difference between the power supply W phase and the power supply U phase becomes O. If this reverse bias time is shorter than the thyristor turn-off time, the The direction blocking ability is not recovered, and the W+ thyristor becomes conductive again at time t4.
Commutation fails and the thyristor inverter goes into an uncontrolled state. In order to prevent such a situation, it is necessary to ensure sufficient reverse bias time, and taking into account the increase in commutation weight angle mentioned above, for example, in a general thyristor inverter, the β limit is set at 1.50". Ta.

Therefore, the DC voltage that can be regenerated by the thyristor inverter is (
1) From the formula, J, i, /≦-1.35-E, -100150° valve 1.
1'1Er-・-・-(2), and for the one with the diode forward converter 11 as shown in Fig. 1, if the effective value of the AC voltage is E and the DC voltage is J]d, then "d=1.351i1 !...
・・・・・・ Expressed as (3) and performs regeneration control -E
Then, from equations (2) and (3), at least Er> 1.15 B -----
------- (4) is required to hold, the step-up transformer 14 cannot be omitted, and even if the step-up transformer 14 is provided, the DC voltage that can be regenerated depends on the transformation ratio of the step-up transformer, and the regenerative When the upper limit of possible voltage was raised, the power factor during normal regeneration deteriorated.

Further, since voltage control during regeneration is performed by β control, even when attempting to control the regenerative voltage to a low level in order to increase the regenerative current, the power factor decreases significantly.

On the other hand, we have expanded the range of DC voltage that can be regenerated without a step-up transformer, and also improved the phase control of cyrisk.
A power converter that improves the power factor by using a β limit of =1500 has been considered. FIG. 4 shows the circuit configuration of such a power converter.

Both positive and negative DC terminals of the thyristor inverter 16 are connected to DC reactors 31 and 32, respectively, and a self-extinguishable DC switch 33, such as a gate turn-off thyristor.
34 to the positive and negative busbars of the DC power supply. Further, the cathode of the diode is connected to the DC power supply side of the DC switch 33, the anode is connected between the DC switch 34 and the DC reactor 32, the cathode of the diode 36 is connected between the DC switch and the DC reactor 31, and the anode is connected to the DC switch 33. The DC switch is connected to that DC power supply side.

Further, the AC side of the thyristor inverter 16 is directly connected to the AC power supply 10.

In this case, the output of the level detector is used to control the DC switch 34 and the thyristor inverter 16 with the regeneration control command 37, and the DC switch controller A and the phase controller n
are input to control the DC switches 33 and 34 and the thyristor inverter, respectively. An example of a conventional control method applied to a power converter having the configuration described above will be explained with reference to FIG.

At time tIo, regeneration from the load begins, and the DC voltage 13 begins to rise. Time 14. When the set level 4o is reached, the regeneration control command 37 becomes 1 and the DC switch 33°3
4 is closed, and the phase control device sends an ignition signal 398 to the combination of thyristors that commutates earliest at β = 150° (in this case, the W+ thyristor and the V-thyristor) to conduct the regenerative current path and set the DC voltage. 13 is lowered. When the set level 41 is reached at time ttt, the output 37 of the level detector becomes 0, and the power supply V phase → thyristor inverter V
-1 Cut off the freewheeling circuit of diode forward converter U-→power supply U phase→power supply V phase. The DC switch 34 is opened, the DC power source and the thyristor inverter are disconnected, and the DC reactor 31 is disconnected.
, 32 is regenerated, and the DC voltage 13 (J) begins to rise again due to regeneration from the load. Time t1s
When the set level 40 is reached again, the same operation as described above is repeated, and the DC voltage is controlled. At time t14, the control angle β of the thyristor reaches the β limit of 1500, and commutation operation begins.

In this case, the thyristor firing signal 39 is input to the DC switch control device, and the power supply W phase → diode order converter W+ →
Thyristor inverse converter U+ → power supply U phase - power supply W phase freewheeling circuit 8 The DC switch 33 that interrupts the circuit is opened, and the thyristor U
+ is fired, commutation from thyristor W+ to thyristor U+ is performed, and at time '1B when the completion of commutation is expected, the DC switch regulator is closed and regeneration operation continues. If the command to close the DC switch is not issued even after a sufficient period of time '16 during which the regenerative current n is expected to reach O after the command to open the DC switch is issued, it is assumed that the regeneration operation has ended, and both DC switches 33° 34 is opened.

In the example shown in FIG. 4 described above, the DC power source and the thyristor inverter are disconnected during commutation, so commutation is possible even when the DC voltage becomes high, and regeneration control can be performed without a step-up transformer.

Also, since the phase control is fixed at β = 150° and the DC voltage and regenerative current are controlled by chopping the DC switch, a smaller DC reactor is sufficient compared to the example in Figure 1, and the regenerative current can be increased. When desired, the power factor did not decrease.

However, the β limit of 1500, which is generally determined for the above-mentioned reason in a thyristor inverse converter, corresponds to α-3001 of a thyristor forward converter, and is compared to the α limit of 10° of a general thyristor forward converter. The situation was even worse, and the effect it had on AC power sources was still a major problem. Furthermore, if the current flowing through the commutating thyristor increases, the effect of the commutating type on the AC side becomes a problem that cannot be ignored, and to prevent this, an AC reactor must be connected to the AC input side.

Furthermore, if commutation is performed at β=βi, which is more advanced than β-1500, βi will increase between β<180°, and as described in the example of FIG. A reflux circuit is formed. When commutation is carried out at β-1500, a reflux circuit will be formed for 300 mm, which corresponds to 50% of the customs clearance period, and the DC reactor will be smaller compared to the example shown in Figure 1. ,
This reflux circuit also had to be taken into consideration.

The present invention was made in view of this point, and by operating a DC switch, the β limit of the thyristor inverter is brought as close to 180° as possible, the power factor is improved, the weight angle during commutation is shortened as much as possible, and the AC Reduces the impact of interference on the power supply,
Another object of the present invention is to provide a highly reliable, compact and high-performance regeneration control method for a power converter by minimizing the time required to form a freewheeling circuit using a power supply, a thyristor inverter, and a diode forward converter.

The present invention will be described below with reference to an embodiment shown in FIG. 6, but since there is no difference in normal regeneration control from the previous example, the explanation will be omitted, and only the commutation operation of the thyristor inverter will be described. This will be explained with reference to FIG.

When the commutation from the W+ thyristor to the U+ thyristor approaches, commutation is carried out for a set time of '20 in anticipation that the current flowing through the thyristor will be sufficiently small so that almost no commutation-type turning angle will occur when performing the commutation of the thyristor. Timing t8. At an earlier time t21, the commutation preparation signal 42 is output from the phase control device n and inputted between the DC switch control devices. The DC switch control device determines the commutation preparation signal 42 and selects an appropriate DC switch (DC switch 33 in Figures 6 and 7) to prevent a reflux loop.
) is opened. As a result, the thyristor inverter 16 and the DC power supply are disconnected, so the regenerative current generator decreases, and by the commutation timing t□, the regenerative current flowing through the commutating thyristor becomes a sufficiently short commutating angle. It decreases to the point where it can be commutated.

Regarding the opening of the DC switch at the time of thyristor commutation, it is not necessary to open only one appropriate one, and both DC switches may be opened. In this case, the current flowing through the thyristor inverter 16 is as follows: thyristor inverter 16 → DC reactor 32 → diode 35 → smoothing capacitor 12 → diode A → thyristor inverter 16
Since the current flows through the path of the thyristor and is reduced by the voltages of both the AC power source and the DC voltage, the current flowing through the thyristor can be reduced in a shorter time than if the appropriate one is closed.

Now, at t,2, the ignition signal is transferred from U+thyristor to V-
When it is sent to the thyristor, commutation from the W+ thyristor to the U+ thyristor is performed, which removes the disturbance caused by the commutated turning angle, and the W+ thyristor becomes non-conductive. The time from this point until the time tts when the voltage difference between the power supply W phase and the power supply U phase disappears is the reverse bias time of the W+ thyristor, and the commutation timing and t2° are determined to ensure the turn-off time of the thyristor U+ After sending the ignition signal to the SIRISK, if the DC switch 33 is closed after a delay of an extremely short commutation type turning angle, the regenerative current starts flowing again and the system shifts to normal regenerative control.

The point to note here is that the advance of phase control is only the turn-off time of the thyristor, so the β limit is 17
It becomes possible to delay the power factor to around 5o, and the power factor is significantly improved compared to the general conventional β limit l-150' described above. Furthermore, since the commutation type bending angle is extremely short, the influence of power supply short circuits on the AC power supply side is hardly a problem. Nu, β-175
When commutation is carried out at °, the above-mentioned AC source 10
The time for forming the free wheel circuit of the thyristor inverse converter 16 and the diode forward converter 1 is 5°, which is a significant improvement. Next, another embodiment of the present invention will be described with reference to FIG. A current detector 43 is connected between the negative side of the thyristor inverter 16 and the DC reactor 32 to detect the regenerative current 23 and input it to the commutation preparation signal generator 44 .

The commutation preparation signal generator 44r uses the power supply phase information 45 outputted from the phase control device 22 and the detected value of the regenerative current generator to determine that the regenerative current generator is sufficiently decreased at β-175° and the commutation weight angle is i'Iq to be opened for very short commutation
Determine the current switch and opening timing and send the commutation preparation signal 4
2 is generated and input to the DC switch control device A. According to such a method, when the regenerative current is small, the timing of opening the DC switch is delayed, so that the regenerative control time can be maintained without wasting it.

As explained above, the regeneration control method for a power converter according to the present invention improves the power factor during regeneration by controlling the DC switch connected to the DC bus, and significantly reduces short circuits in the power supply due to commutation weight angle. This significantly reduces the hindrance effect that the power converter has on the AC power supply during regeneration.
This has an excellent effect in providing a highly reliable, compact, high-performance, and economical power converter.

[Brief explanation of the drawing]

Figure 1 shows a conventional power converter that can control regeneration.
A configuration diagram showing an example, Figures 2 and 3 are operation explanatory diagrams of Figure 1, Figure 4 is a configuration diagram of a power converter that has a switch on the DC bus and is capable of regenerative control, and Figure 5 is a diagram explaining the operation of Figure 4. FIG. 6 is a configuration diagram showing an embodiment of the power converter according to the present invention, FIG. 7 is an explanatory diagram of the operation of the embodiment of FIG. 6, and FIG. 8 is another embodiment of the present invention. It is a block diagram which shows an example. 10... AC power supply 11... Diode forward converter 12
... Smoothing capacitor 13 ... DC voltage 14 ...
Step-up transformer 15... AC power supply for regeneration 16...
Regenerative thyristor inverse converter 17... DC reactor 18... Voltage detector J9... Voltage feedback signal side... Level detector 21... Phase control signal n... Phase control device prisoner...・Regenerative current ・
...Thyristor current resistance part...U+thyristor current...W+thyristor' acid pressure capital...U+thyristor voltage 31.32...DC reactor loop, 34...DC switch 35.36... Diode 37...
Regeneration control finger cover...DC switch control device 39.
...Ignition signal 40.41...Setting level 42...
・Commutation preparation signal 43...Current detector 44...
Commutation preparation signal generator 45...Power supply phase information (7317) Agent: Patent attorney Kensuke Norichika (and one other person)
Procedural amendment (voluntary) Month, day, 56.12, Showa. -3 Commissioner of the Japan Patent Office 1, Indication of the case, Patent Application No. 1983-121412, 2, Title of the invention: Regeneration control method for power converter 3, Person making the amendment Relationship with the case Patent applicant (307) Tokyo Shibaura Electric Co., Ltd. Company 4, Agent Address: Tokyo Shibaura Electric Co., Ltd. Tokyo Office, 1-1-6 Uchisaiwai-cho, Chiyoda-ku, Tokyo 100 Japan Detailed Description of the Invention Column 6, Contents of Amendment (1) The bottom line of page 4 of the specification of the present application. Description [Ed”=,
-1,35Er100β'JEd'=5-1.35E
rcosβ'' (2 corrections. (2) [Ed'≦-1,35 described in page 7, line 5 of the same ')
-Er-100150°41.17 Ed [Ed'≦
-1,35-E, -008150° first 1.17 Erj
Correct. that's all

Claims (2)

[Claims] (1) Having a DC-DC converter such as a chopper or a DC-AC converter such as an inverter as a load of the DC power supply,
An inverter that regenerates the regenerated power from those loads to the AC power source is connected in series to the positive and negative bus bars of the DC power source, respectively, and a switch and a current limiting element, a diode connected crosswise to the switch, and the current limiting element. In a power converter configured with a thyristor inversion bridge connected to the other end of the element, when the thyristor inversion bridge commutates during regeneration, the switch is opened in advance before commutation, and the DC The thyristor inversion bridge is disconnected from the power source, commutation is performed after the regenerative current flowing through the thyristor inversion bridge is sufficiently attenuated, and after commutation is completed, the switch is closed again to control the regeneration current to flow. A regeneration control method for a power converter, characterized in that: (2) The regeneration control method for a power converter according to claim 1, characterized in that the opening timing of the switch is determined in accordance with the value of the regenerative current.