JP2797937B2 - Inverter control device - 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 device for an AC / DC converter in a power system, and more particularly to a control device for an inverter which can transmit the maximum AC power even when the AC voltage is reduced due to an AC system accident. The present invention relates to a control device.

[0002]

2. Description of the Related Art Generally, when a converter is operated as an inverse converter, the control angle α is operated in a range of 90 ° <180 °. On the other hand, in the inverter which converts the DC system power and feeds it to the AC system, it is desired to operate the control angle α near 180 ° because high power factor operation is desired.
When approaching °, a commutation margin angle cannot be secured, and commutation failure is induced. Conversely, power cannot be transmitted to the AC system approaching 90 °. Therefore, in this type of inverter, the commutation allowance angle is always kept to the minimum necessary,
° Driving near.

FIG. 2 is a main circuit diagram and a control device block diagram of this type of inverting device. In FIG. 2, reference numeral 1 denotes an on / off control by a firing pulse synchronized with an AC voltage to sequentially perform commutation. A separately-excited switching element constituting an inverter circuit for converting a DC voltage to an AC voltage, a transformer for transforming the AC output of the switching element 1, a DC reactor 3, an AC transformer for detecting the voltage of the AC system,
5 is an AC converter for detecting the current of the AC system, 6 is a DC converter for detecting the current of the DC system, 7 is a DC transformer for detecting the voltage of the DC system, 8 is a DC transformer 6, and an AC transformer. 5 is a commutation failure detection means for detecting a commutation failure of the switching element by comparing the outputs of the switching elements 5 and 5.

[0004] Reference numeral 10 introduces the outputs of the DC transformer 6 and the AC transformer 4 and executes a predetermined operation from these outputs.
Commutation failure prevention control means for calculating a firing phase angle that maintains a predetermined margin angle for preventing commutation failure of the switching element;
1 is a constant voltage control means for introducing a DC voltage detected by the DC transformer 7 and comparing it with a set voltage to derive a phase control signal corresponding to a firing phase angle with the DC system voltage as a set voltage; Is a control selection means for selecting and outputting the leading phase control signal from the input phase control signals, and 13 is a pulse for firing the switching element 1 based on the phase control means signal output from the control selection means. Is an AC voltage detected by the AC transformer 4, an AC voltage drop detecting means for detecting a voltage drop in the AC system, and 15 is a phase advance / return means. When a commutation failure is detected by the commutation failure detection means 8 described in JP-B-51-67918, the phase control signal output to the control selection means 12 is changed to a phase control signal corresponding to a predetermined phase angle on the leading side. And the signal, when an AC voltage by the AC voltage detection means 14 detects that the recovered above a predetermined level, a means for returning the direction delayed by a predetermined time constant.

[0005] The commutation failure prevention control means 10 comprises:
For example, as described in “DC Power Transmission Technology”, published by the Institute of Electrical Engineers of Japan in 1978, pp. 83-85, the following equation is obtained from the DC current and the AC voltage detected by the DC transformer 6 and the AC transformer 4. Is calculated, and a corresponding phase control signal is output to the control selecting means 12. cosγ-cos (180 ° −α) = (√2 · Xi · Id) / Ei (1) where γ is a margin angle α is a firing phase angle Xi is a commutation reactance Id is a DC current Ei is an AC voltage. That is, γ and Xi are constants, and the AC voltage Ei and the DC current I
The phase control signal at the time when the relationship with d satisfies the above equation (1) is output to the control selecting means 12.

Next, the operation will be described. The control selection means 12 selects the phase control signal of the most advanced ignition phase angle from the phase control signals output from the phase advance / return means 15, the commutation failure prevention control means 10, or the constant voltage control means 11. , To the ignition pulse generating means 13. The firing pulse generating means 13 generates a firing pulse at a timing based on the phase control signal input from the control selecting means 12, and controls the switching element 1 to fire.

The phase advance / return means 15, the commutation failure prevention control means 10, and the constant voltage control means 11 output a phase control signal by the above-described control operation. As in the state before the voltage drop, the phase control signal 3 output from the constant voltage control means 11 is a phase control signal of the ignition phase angle on the most advanced side, and the control selection means includes:
The phase control signal of the constant voltage controller 11 is selected and output to the firing pulse generator 13. Here, in the conventional example of FIG. 3, in a steady state, the phase control signal output from the constant voltage control means 11 is 135 °.

On the other hand, in the steady state, when the voltage on the AC system side fluctuates slowly, the AC voltage Ei detected by the AC converter 4 by the commutation failure prevention control means 10 is controlled.
The phase control signal output from the commutation failure prevention control means 10 is output from the constant voltage control means 11 because the relation between the DC current Id detected by the DC transformer 6 and the DC current Id satisfies the above equation (1). The phase control signal becomes the leading phase control signal, and the control selecting means 12 controls the commutation failure prevention control means 1
The phase control signal output as 0 is selected and output to the firing pulse generating means 13.

Now, as shown in FIG. 3, it is assumed that an accident has occurred in the AC system and the AC voltage has dropped sharply. Here, the accident in the AC system is, for example, a ground fault accident, and it is assumed that the AC system protection device recovers in about four AC cycles after the occurrence of the accident. When the AC voltage drops sharply, the commutation failure prevention control means 10 operates and attempts to advance the firing phase angle based on the equation (1), but the control response is slow as shown by the characteristic curve 2 in FIG. This will cause commutation failure.

That is, the commutation failure prevention control means 10 needs to derive the peak value or the effective value Ei of the AC voltage from the detection output of the AC transformer 4 in order to execute the calculation by the equation (1). Usually, to derive the peak value or the effective value of the AC voltage, it is obtained by sampling the detection output of the AC transformer 4 at a predetermined sampling cycle and performing digital operation based on some sampling data. , It takes at least about half an AC cycle to derive the peak value or the effective value at the time of the decrease.
Therefore, the control response of the commutation failure prevention control means 10 is delayed, and a commutation failure is induced.

When a commutation failure occurs, the current on the DC side is converted to the AC side and stops flowing, so that the commutation failure detecting means 8 which inputs the outputs of the DC transformer 6 and the AC transformer 5 performs commutation failure. Is detected, and the phase advance / return means 15 is operated. When the commutation failure detecting means 8 detects the commutation failure, the phase advance / return means 15 sets the phase control signal to a signal corresponding to the firing phase angle of 120 ° as shown by the characteristic curve 1 in FIG. The firing phase angle of 120 ° is set empirically in consideration of system conditions and the like so that a predetermined transmission power can be secured.

As a result, since the control selecting means 12 selects the phase control signal of the phase advance / return means 15, the timing of the ignition pulse of the switching element 1 is advanced, and a margin angle is secured to prevent commutation failure. can do.

While the decrease in the AC voltage continues, the phase advance / return means 15 continuously outputs a phase control signal having a firing phase angle of 120 °.
When the AC voltage drop detecting means detects that the AC voltage has become equal to or higher than the predetermined level, as shown in FIG. 3, the phase advance / return means 15 returns the advanced ignition phase angle to the original by a predetermined time constant. Go to restore the DC voltage. Even if the DC voltage recovers, the response of the constant voltage control means 11 is set to be very slow, so that the phase control signal of the constant voltage control means 11 is not immediately selected by the control selection means 12, and the control signal shown in FIG. As shown in (1), until the phase control signal of the constant voltage control means 11 is selected, the phase control signal of the commutation failure prevention control means 10 is selected, and the ignition control is performed. FIG.
The characteristic curve 2 shows the DC power transmitted by the operation of this conventional device.

[0014]

In the conventional inverter control device, when the commutation failure is detected by the commutation failure detection means as described above, the phase advance / return means 15 takes into account system conditions and the like. However, if the commutation fails even if the ignition is performed at the set ignition phase angle, the commutation still fails. However, there is a problem that power transmission cannot be performed.

Further, even if the voltage drop on the AC system side is small and the commutation is sufficiently possible even if the ignition phase angle is delayed from the ignition phase angle set by the phase advance / return means, the predetermined level AC Since the firing control is continued at the set arc phase angle until the voltage recovers, there is a problem that even if commutation failure can be prevented, sufficient power transmission cannot be performed.

The present invention has been made to solve such a problem, and it is an apparatus capable of reliably preventing commutation failure from continuing and maximizing power supply to an AC system. It is intended to provide.

[0017]

According to a first aspect of the present invention, there is provided a control device for an inverter, comprising: a commutation failure detecting means for detecting a commutation failure; Means for deriving a phase control signal for advancing the firing phase angle to about 90 ° and delaying it by a predetermined time constant immediately after that, and a point for maintaining a predetermined margin angle for preventing commutation failure of the switching element. A commutation failure control means for deriving a phase control signal corresponding to the arc phase angle, and a phase control signal on the leading side selected from the phase control signals derived by the phase advance / return means or the commutation failure prevention control means. And a control selecting means for outputting to the firing pulse generating means.

According to a second aspect of the present invention, there is provided a control device for an inverter, comprising: a voltage drop detecting means for detecting a voltage drop of an AC voltage; °, and a phase advance / return means for deriving a phase control signal that delays by a predetermined time constant immediately after that, and a phase corresponding to a firing phase angle that maintains a predetermined margin angle that prevents commutation failure of the switching element. A commutation failure prevention control means for deriving a control signal, and a phase control signal derived from the phase advance / return means or the commutation failure prevention control means, and selecting a leading phase control signal to generate an ignition pulse generating means And a control selecting means for outputting the data to the control unit.

According to a third aspect of the present invention, there is provided a control device for an inverter, comprising: a commutation failure detecting means for detecting a commutation failure; A phase advancing / returning means for deriving a phase control signal for advancing to near 90 ° and delaying by a time constant determined according to the degree of voltage drop of the AC immediately thereafter, a predetermined margin angle for preventing commutation failure of the switching element The commutation failure prevention control means for deriving a phase control signal according to the firing phase angle, and the phase advance signal of the phase advance / return means or the phase control signal derived by the commutation failure prevention control means. Control selection means for selecting a control signal and outputting it to the firing pulse generation means.

According to a fourth aspect of the present invention, there is provided a control device for an inverter, comprising: a voltage drop detecting means for detecting a voltage drop of an AC; ° to the vicinity, and immediately thereafter, a phase advancing and returning means for deriving a phase control signal that delays by a time constant determined according to the voltage drop of the AC, and a predetermined margin angle that does not cause the commutation failure of the switching element. A commutation failure prevention control means for deriving a phase control signal corresponding to the firing phase angle to be held, and a phase control on the leading side of the phase control signal derived by the phase advance / return means or the commutation failure prevention control means Control selection means for selecting a signal and outputting the signal to the ignition pulse generation means.

According to a fifth aspect of the present invention, there is provided a control device for an inverter according to the first to fourth aspects, wherein a DC voltage is introduced and the DC voltage is set according to a firing phase angle at which a set voltage is obtained. A constant voltage control means for deriving a phase control signal, wherein the control selection means outputs a phase control signal derived by the constant voltage control means together with a phase control signal of the phase advance / return means and the commutation failure prevention control means. It is.

[0022]

The control device for the inverter according to the first aspect of the present invention advances the ignition phase angle of the switching element to near 90 ° when the commutation failure is detected, so that the continuation of the commutation failure can be reliably prevented. Immediately after that, the ignition phase angle is delayed by a predetermined time constant, so that the power supply to the AC system can be maximized by the leading phase control signal selected by the control selecting means.

In the inverter control device according to the second aspect of the present invention, when the voltage drop is detected, the ignition phase angle of the switching element is advanced to near 90 °, so that the commutation failure induced by the voltage drop can be reliably prevented. In addition, since the ignition phase angle is delayed by a predetermined time constant immediately after that, the power supply to the AC system can be maximized by the leading phase control signal selected by the control selecting means.

According to the third aspect of the present invention, the control device for the inverter can advance the firing phase angle of the switching element to near 90 ° when the commutation failure is detected, so that the continuation of the commutation failure can be reliably prevented. Immediately after that, the ignition phase angle is quickly delayed without giving any fluctuation to the system by the time constant determined according to the degree of the voltage drop of the alternating current. Power supply to the AC system can be maximized.

In the control device for an inverter according to the fourth aspect of the present invention, when the voltage drop is detected, the ignition phase angle of the switching element is advanced to near 90 °, so that the commutation failure induced by the voltage drop can be reliably prevented. Further, immediately after that, the ignition phase angle is quickly delayed without giving any fluctuation to the system by a time constant determined according to the degree of AC voltage drop, so that the phase control on the leading side selected by the control selection means is performed. The signal can maximize the power supply to the AC system.

According to a fifth aspect of the present invention, there is provided a control device for an inverter, which is provided with the voltage control means according to the first to fourth aspects of the present invention. A phase control signal derived from the prevention control means or the constant voltage control means is output to the ignition pulse generation means.

[0027]

[Embodiment 1] Hereinafter, an embodiment of the present invention will be described with reference to FIG. In FIG. 1, reference numeral 9 denotes a phase advancing / returning unit. When a commutation failure is detected by the commutation failure detection unit 8, the firing phase angle of the switching element is set to 9;
A phase control signal which advances to near 0 ° and is delayed by a predetermined time constant immediately thereafter is derived and output to the control selecting means.

Next, the operation of the control device of the separately-excited inverse converter according to the first embodiment will be described with reference to FIG. When the AC voltage suddenly drops due to an accident in the AC system, the control response of the commutation failure prevention control means 10 cannot follow the voltage drop. In the control, a margin angle cannot be secured, and commutation failure occurs. When the commutation failure detecting means 8 detects this commutation failure, the firing phase angle command by the phase advance / return means 9 advances to the phase angle set near 90 ° as shown by the characteristic curve 1 in FIG. , And the selection is made by the control selection means 12. As a result, the timing of the firing pulse is advanced, and a sufficient margin angle can be secured to prevent a commutation failure. Immediately thereafter, the phase advance / return means 9 delays the advanced ignition phase angle by a predetermined time constant, and starts phase return. In parallel with this operation, the ignition phase angle at which the response of the commutation failure prevention control means 10 follows the AC voltage drop and secures a predetermined margin angle can be set. Then, as shown in FIG. 4, when the curve 2 of the commutation failure prevention control means 10 and the curve 1 of the phase advance / return means 9 intersect and have the same phase angle, the arc of the commutation failure prevention control means 10 is controlled by the control selection means 12. The phase angle is selected. As a result, it is possible to perform the maximum power transmission as compared with the conventional curve 2 while preventing commutation failure as shown by the curve 1 in FIG. Therefore, the recovery of the AC system after the restoration of the accident can be accelerated.

Embodiment 2 FIG. FIG. 6 is a block diagram of a control device of an inverter according to Embodiment 2 of the present invention. In the first embodiment, the commutation failure is detected, and the phase advance / return means 16 advances the ignition phase angle to around 90 °. In the second embodiment, the AC voltage drop detection means 14 reduces the AC voltage to a predetermined value or less. , The phase advance / return means 16 advances the firing phase angle to around 90 °.

As described above, in the apparatus of the second embodiment, the phase advance / return means 16 detects the drop of the AC voltage itself which causes the commutation failure. It is possible to perform quick control, and in some cases, it is possible to continue operation without causing a commutation failure, and it is possible to perform larger power transmission.

Embodiment 3 FIG. FIG. 7 is a block diagram of a control device of an inverter according to Embodiment 3 of the present invention. In the first embodiment, the phase advance / return means 17 returns the ignition phase angle advanced to around 90 ° by a predetermined time constant.
In the third embodiment, the return time constant of the ignition phase angle according to the degree of decrease in the AC voltage detected by the AC voltage decrease detection means 14 is determined. That is, when the voltage drop is large, the AC system needs to be restored slowly, and in this case, the time constant is set long. Conversely, when the voltage drop is small, the time constant is shortened. As a result, there is no upset in the AC system,
And quick recovery can be expected.

As described above, in the apparatus according to the third embodiment, the phase advance / return means 17 returns the firing phase angle with the time constant determined according to the degree of decrease of the AC voltage. The ignition phase angle set by 10 can be selected earlier, and larger power can be obtained.

Embodiment 4 FIG. FIG. 8 is a block diagram of a control device of the inverter according to the fourth embodiment. In the second embodiment, the phase advance / return means 18 returns the ignition phase angle advanced to around 90 ° by a predetermined time constant.
Then, the return time constant of the ignition phase angle corresponding to the degree of the low AC voltage detected by the AC drop detecting means 14 is determined.

As described above, in the apparatus of the fourth embodiment, the phase advance / return means 18 returns the firing phase angle with the time constant determined according to the degree of decrease in the AC voltage. The ignition phase angle set by 10 can be selected earlier, and larger power transmission can be performed.

[0035]

As described above, the first aspect of the present invention is as follows.
According to the invention according to the above, by the operation of the commutation failure detection means,
Advance the firing phase angle of the switching element to around 90 °,
Immediately thereafter, a phase advance / return means for deriving a phase control signal to be delayed by a predetermined time constant, and a phase control signal corresponding to a firing phase angle for maintaining a predetermined margin angle for preventing commutation failure of the switching element. The commutation failure prevention control means, the phase advance / return means, or the phase control signal derived from the commutation failure prevention control means, the leading phase control signal is selected and output to the firing pulse generation means. Therefore, the continuation of the commutation failure can be reliably prevented, and the power supply to the AC system can be maximized.

According to the second aspect of the present invention, the ignition phase angle of the switching element is advanced to about 90 ° by the operation of the voltage drop detecting means, and immediately thereafter, the ignition phase angle is delayed by a predetermined time constant. Phase advance / return means for deriving a phase control signal, commutation failure prevention control means for deriving a phase control signal corresponding to a firing phase angle that maintains a predetermined margin angle for preventing commutation failure of the switching element, and The phase control signal on the leading side is selected from the phase control signals derived by the advance / return means or the commutation failure prevention control means and is output to the ignition pulse generating means. Failure can be reliably prevented, and power supply to the AC system can be maximized.

As described above, according to the third aspect of the present invention, by the operation of the commutation failure detecting means, the firing phase angle of the switching element is advanced to about 90 °, and immediately thereafter, the AC Phase advance / return means for deriving a phase control signal that delays by a time constant determined according to the degree of voltage drop, and phase control according to a firing phase angle that maintains a predetermined margin angle that prevents commutation failure of the switching element The commutation failure prevention control means for deriving a signal, and the phase advance / return means, or the phase control signal derived from the commutation failure prevention control means, select the leading phase control signal and select the ignition pulse generation means. Since the output is performed, the continuation of the commutation failure can be reliably prevented, and the power supply to the AC system can be maximized without causing the AC system to fluctuate.

According to the invention of claim 4 of the present invention, the ignition phase angle of the switching element is advanced to about 90 ° by the operation of the voltage drop detecting means, and immediately thereafter, the ignition phase angle is changed according to the AC voltage drop degree. Phase advancing means for deriving a phase control signal to be delayed by a time constant determined in accordance with the present invention, and a phase advancing means for deriving a phase control signal corresponding to a firing phase angle which maintains a predetermined margin angle for preventing commutation failure of the switching element. Among the phase control signals derived from the flow failure prevention control means, the phase advance / return means, or the commutation failure prevention control means, the phase control signal on the leading side is selected and output to the firing pulse generation means. Therefore, the commutation failure induced by the voltage drop can be reliably prevented, and the power supply to the AC system can be maximized without causing any fluctuation in the AC system.

[Brief description of the drawings]

FIG. 1 is a control block diagram illustrating a control device of an inverter according to a first embodiment of the present invention.

FIG. 2 is a control block diagram illustrating a control device of a conventional inverter.

FIG. 3 is a characteristic diagram showing a relationship between a firing phase angle and time set by each control means constituting a conventional control device.

FIG. 4 is a characteristic diagram showing a relationship between a firing phase angle and time set by each control means constituting the control device according to the embodiment of the present invention.

FIG. 5 is a characteristic diagram showing a relationship between DC transmission power by a conventional control device and DC transmission power by a control device according to an embodiment of the present invention and time.

FIG. 6 is a control block diagram illustrating a control device of an inverter according to a second embodiment of the present invention.

FIG. 7 is a control block diagram illustrating a control device of an inverter according to a third embodiment of the present invention.

FIG. 8 is a control block diagram illustrating a control device of an inverter according to a fourth embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 separately-excited switching element 2 transformer 3 reactor 4 AC transformer 5 AC transformer 6 DC transformer 7 DC transformer 8 Commutation failure detection means 9 Phase advance return means 10 Commutation failure prevention control means 11 Constant voltage control means 12 Control selecting means 13 Firing pulse generating means 14 AC voltage drop detecting means 15 Phase advance / return means 16 Phase advance / return means 17 Phase advance / return means 18 Phase advance / return means

Claims (5)

(57) [Claims] 1. A plurality of switching elements constituting an inverter circuit for converting direct current to alternating current, commutation failure detection means for detecting commutation failure of the switching elements, and a predetermined margin angle for preventing commutation failure of the switching elements. The commutation failure prevention control means for deriving a phase control signal corresponding to the firing phase angle to be held, by the commutation failure means, when detecting the commutation failure of the switching element, the ignition phase angle of the switching element Phase advance / return means for deriving a phase control signal that advances to near 90 ° and delays by a predetermined time constant immediately thereafter, among phase control signals derived from the phase advance / return means or the commutation failure prevention control means Control selecting means for selecting a leading phase control signal, and firing the switching element based on the phase control signal selected by the control selecting means. Controller of inverter, characterized in that it comprises a pulse generating means. 2. A plurality of switching elements constituting an inverter circuit for converting a direct current into an alternating current, voltage drop detecting means for detecting a voltage drop of the alternating current, and a point for maintaining a predetermined margin angle for preventing commutation failure of the switching elements. Commutation failure prevention control means for deriving a phase control signal according to the arc phase angle,
When the AC voltage drop is detected by the voltage drop detecting means, the ignition phase angle of the switching element is advanced to near 90 °, and immediately after that, a phase advance signal for deriving a phase control signal for delaying by a predetermined time constant is returned. Control selection means for selecting a leading phase control signal from the phase control signals derived by the means, the phase advance / return means, or the commutation failure prevention control means, based on the phase control signal selected by the control selection means. And an ignition pulse generating means for igniting the switching element. 3. A plurality of switching elements constituting an inverter circuit for converting DC to AC, commutation failure detection means for detecting commutation failure of the switching element, and a predetermined margin angle for preventing the switching element from failing in commutation. The commutation failure prevention control means for deriving a phase control signal corresponding to the firing phase angle to be held, by the commutation failure means, when detecting the commutation failure of the switching element, the ignition phase angle of the switching element Phase advance / return means for deriving a phase control signal that advances to near 90 ° and delays by a time constant determined according to the AC voltage drop immediately thereafter, the phase advance / return means, or the commutation failure prevention Among the phase control signals derived by the control means, control selection means for selecting a leading phase control signal, based on the phase control signal selected by the control selection means, Controller of inverter, characterized in that it comprises a firing pulse generating means that it firing a switching element. 4. A plurality of switching elements constituting an inverter circuit for converting direct current to alternating current, voltage drop detecting means for detecting a voltage drop of the alternating current, and a point for maintaining a predetermined margin angle for preventing commutation failure of the switching elements. Commutation failure prevention control means for deriving a phase control signal according to the arc phase angle,
When the AC voltage drop is detected by the voltage drop detecting means, the ignition phase angle of the switching element is advanced to near 90 °, and immediately thereafter, the switching element is delayed by a time constant determined according to the AC voltage drop degree. Control means for selecting a leading phase control signal from phase control signals derived by the phase advance / return means, the phase advance / return means, or the commutation failure prevention control means; A control device for an inverter, comprising a firing pulse generating means for firing the switching element based on a phase control signal selected by the selecting means. 5. A constant voltage control means for introducing a DC voltage and deriving a phase control signal corresponding to a firing phase angle at which the DC voltage becomes a set voltage, wherein the control selection means comprises a constant voltage control means. The phase control signal on the leading side is selected from the phase control signals derived by the phase advance / return means or the commutation failure prevention control means. Inverter control device.