JP3241146B2 - Power converter controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a power converter control device used for DC interconnection equipment for transmitting DC power between two power systems.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram showing a schematic configuration of a DC interconnection facility for transmitting DC power between AC systems 1A and 1B. In this figure, a circuit breaker 2 is connected to an AC system 1A.
A, an input side of an AC / DC power converter (hereinafter abbreviated as AC / DC converter) 4A is connected via a transformer 3A, and an output side of the AC / DC converter 4A is connected to a DC transmission line 6 via a DC reactor 5A. Is connected.

The output side DC voltage of the AC / DC converter 4A is detected by a voltage detector 7A, and a detection signal converted to an easy-to-use value for a control circuit by a voltage conversion circuit 8A is sent to an adder 9A. A setting signal is also sent from the DC voltage setting unit 10A to the adder 9A, and the adder 9A outputs a deviation between both signals to the constant voltage control circuit 11A.

The output side DC current of the AC / DC converter 4A is detected by a current detector 12A, and a detection signal converted to an easy-to-use value for a control circuit by a current-voltage conversion circuit 13A is sent to an adder 14A. The setting signal from the current margin setting device 15A is sent to the adder 14A via the switch 16A, and the power control signal from the constant power control circuit 17 is also sent to the adder 14A. The constant power control circuit 17 outputs a power control signal based on an input from the adder 24, that is, a deviation between a setting signal from the power setting device 18 and a detection signal from the power detector 19. The adder 14A outputs the deviation of these signals to the constant current control circuit 20A.

The constant voltage control circuit 11A and the constant current control circuit 20A output control signals to the control lead angle priority circuit 21A based on the inputs from the adders 9A and 14A, respectively. The control lead angle priority circuit 21A selects a control signal of which the control lead angle of the AC / DC converter 4A is more advanced from both control signals.

The phase control circuit 22A converts the selected control signal into a pulse signal that determines the firing timing for the thyristor of the AC / DC converter 4A. The pulse amplifying circuit 23A amplifies the converted pulse signal and supplies it to the thyristano gate of the AC / DC converter 4A as a gate pulse signal.

The same components as described above are also provided on the AC system 1B side, but redundant description is omitted. In this conventional example, power is supplied from the AC system 1A to the AC system 1B, and the AC / DC converter 4A functions as a forward converter (converter), and the AC / DC converter 4B
Function as an inverter (inverter). In addition, as for the switches 16A and 16B, only the switch that functions as an inverse converter is turned on. Therefore,
In this case, it is assumed that the switch 16A is off and the switch 16B is on.

FIG. 7 shows the input / output characteristics of the AC / DC converters 4A and 4B. In the figure, CV is the output characteristic of AC / DC converter 4A functioning as a converter, and IV is the input characteristic of AC / DC converter 4B functioning as an inverter. In FIG.
Switch 16A is off, switch 16B is on,
The control lead angle priority circuit 21A selects a signal from the constant current control circuit 20A, and the control lead angle priority circuit 21B selects a signal from the constant voltage control circuit 11B.

Therefore, the operating points of both converters are normally at the point P where the constant current region of the CV characteristic, the constant voltage region of the IV characteristic, and the constant power curve intersect.

Note that the constant current region of the IV characteristic is lower than the constant current region of the CV characteristic by a current margin ΔIdp because the switch 16B is turned on.
If the constant current regions of both characteristics almost coincide with each other, the operating margin becomes an unspecified number of operating points, resulting in unstable control. This is provided for the purpose.

By the way, while the power is supplied from the AC / DC converter 1A to the AC / DC converter 1B, the AC voltage on the AC system 1A may be reduced due to a load change or a disconnection accident. .

In such a case, the level of the constant voltage control of the CV characteristic decreases to the position indicated by the dotted line in FIG. 6, and the control lead angle priority circuit 21A selects the signal from the constant voltage control circuit 11A. Therefore, the operating point in FIG. 6 moves to P '.

When the operating point moves from P to P ', the constant power control circuit 17 operates and the operating point returns from P' to P again.

[0014]

However, since the constant current control circuit 17 is a control system having a low response speed, it takes some time for the operating point to return from P 'to P. In this case, if the current value Idp at the operating point P is a level sufficiently higher than the minimum current reference, no particular problem occurs. However, if it is equal to the minimum current reference, the power converters 4A and 4B will be operated at a current value lower by a current margin ΔIdp than that shown in FIG.

As a result, the DC current between the AC / DC converters 1A and 1B is interrupted until the operating point returns from P 'to P, so that normal operation cannot be maintained, and the AC system is controlled by the AC / DC converter. Cannot achieve the initial purpose of stabilization. Further, if gate pulses of a capacity or more frequently occur in the pulse amplifier circuits 23A and 23B due to intermittent DC current, these pulse amplifier circuits 23A and 23B
The continuation of operation becomes impossible due to the tolerance of B.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a power converter control device capable of stably transmitting and receiving power between power systems.

[0017]

According to the present invention, as a means for solving the above problems, the input and output are controlled according to control characteristics having a constant voltage control region and a constant current control region. The first and second power converters whose levels are separated from each other by a predetermined current margin are connected to the first and second power systems, and the first and second power converters are connected to a constant power. By controlling, in a power system control system for transmitting and receiving power between the two systems, a power for making the power constant based on a deviation between a detected value and a set value of the power transferred between the two systems. Output control signal
The constant power control circuit and the power transferred between the two systems
The power based on the deviation between the detected value and the set value
And a constant power control circuit for outputting a power control signal for
A high-speed constant power control circuit having a faster response speed, and selecting a power control signal from the constant power control circuit during normal operation among the two power control signals from the constant power control circuit and the high-speed constant power control circuit. Switching means for immediately switching to a power control signal from a high-speed constant power control circuit when the first and second power converters are operated with a current equal to or less than a minimum current reference value; The present invention is characterized in that current control of the first and second power converters is performed using a power control signal output from the switching circuit.

[0018]

In the above configuration, during normal operation, that is, when the first and second power converters are operated at a current sufficiently larger than the minimum current reference value, even if the operating current is reduced by the current margin, There is no danger of interrupted current.
Therefore, in this case, the switching means selects the power control signal from the constant power control circuit, and the same control as in the related art is performed.

However, when the voltage of the power system on the side of the power converter functioning as a forward converter decreases while the first and second power converters are operated at a current substantially equal to the minimum current reference value. Since these power converters are operated with a current lower than the minimum current reference value by a current margin, the current between the converters may be interrupted.

Therefore, in this case, switching is performed so that the switching means immediately selects the power control signal from the high-speed constant power control circuit. According to the high-speed constant power control circuit, the control for raising the current value to the constant power level is performed at a high speed, so that the above-described current interruption can be prevented.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. However, the same components as those in FIGS. 6 to 8 are denoted by the same reference numerals, and redundant description will be omitted.

FIG. 1 is a block diagram showing the configuration of the first embodiment of the present invention. FIG. 1 differs from FIG. 6 in that a power margin setter 51, an adder 52, a high-speed constant power control circuit 53,
The point is that a maximum current reference value selection circuit 54 is newly added.

Next, the operation of FIG. 1 will be described with reference to the characteristic diagrams of FIG. 2 and FIG. In the case of normal operation, the maximum current reference value selection circuit 54 selects a power control signal from the constant power control circuit 17 and sends it to the adders 14A and 14B. Therefore, as shown in FIG. 2, the operating point in this case is P
Becomes When the voltage of the AC system 1A decreases, C
The constant voltage control region of the V characteristic drops to the dotted line, and the operating point moves to P '. Thereafter, the operation point P 'returns to the point P by the operation of the constant power control circuit 17. That is, in the case of the normal operation, the same control as in the related art is performed.

However, the current value at the operating point P is
When the voltage of the AC system 1A drops, the current value of the operation P 'becomes smaller than the minimum current reference value by the current margin △ Idp when the voltage is substantially equal to the minimum current reference value as shown in FIG. There is.

At this time, since the maximum current reference value selection circuit 54 selects the power control signal from the high-speed constant power control circuit 53, the operating point P 'in FIG. 3 moves to the operating point Po at high speed. This can prevent the current converters 4A and 4B from interrupting the current. After the operating point rapidly moves to Po, the operating point further moves to P ″ at a normal speed.
After the possibility of current interruption is eliminated, the maximum current reference value selection circuit 54 selects the power control signal from the constant power control circuit 17 again.

FIG. 4 is a block diagram showing a configuration of a main part of a second embodiment of the present invention. In the second embodiment, a dead zone circuit 55 is provided on the input side of the high-speed constant power control circuit 53 so that the high-speed constant power control circuit 53 is not selected by the maximum current reference value selection circuit 54 during normal operation. Then, at the time of the minimum current operation, the current margin △ Idp
When the current value decreases only by the
Will be selected.

FIG. 5 is a block diagram showing a configuration of a main part of a third embodiment of the present invention. In the third embodiment, instead of the maximum current reference value selection circuit 54 in the first and second embodiments,
A contact circuit 58 including a normally closed contact 5b and a normally open contact 57 is provided. Then, the voltage drop detection circuit 5
9 switches the contact states of the normally closed contact 56 and the normally open contact 57 when detecting a voltage drop below a predetermined level in the AC system on the side of the forward converter.

[0028]

As described above, according to the present invention, a high-speed constant power control circuit is added, and when the power converter is about to be operated at a current less than the minimum current reference value, the high-speed A constant power control circuit is used to control the current level to increase at high speed.Therefore, even if the voltage of the power system on the power supply side drops, the current can be stably connected without interrupting the current. Power can be transmitted and received.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a characteristic diagram of the power converter in FIG. 1 during normal operation.

FIG. 3 is a characteristic diagram of the power converter of FIG. 1 at the time of minimum current operation.

FIG. 4 is a block diagram showing a configuration of a main part of a second embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a main part of a third embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a conventional example.

FIG. 7 is a characteristic diagram of the conventional power converter at the time of normal operation.

FIG. 8 is a characteristic diagram of the conventional power converter at the time of minimum current operation.

[Explanation of symbols]

 1A, 1B AC system 4A, 4B Power converter (AC / DC converter) 6 DC transmission line 11A, 11B Constant voltage control circuit 15A, 15B Current margin setting device 17 Constant power control circuit 20A, 20B Constant current control circuit 51 Power margin setting Sensor 53 High-speed constant power control circuit 54 Maximum current reference value selection circuit 55 Dead zone circuit 56 Normally closed contact 57 Normally open contact 58 Contact circuit 59 Voltage drop detection circuit

Claims (4)

(57) [Claims] An input / output is controlled according to a control characteristic having a constant voltage control region and a constant current control region, and the level of each constant current control region is separated from each other by a predetermined current margin. A power system that connects a second power converter to first and second power systems and controls the first and second power converters to perform constant power control, thereby transmitting and receiving power between the two systems. In the control system, a power control signal for keeping power constant based on a deviation between a detected value and a set value of power transmitted and received between the two systems.
A constant power control circuit that outputs a signal, and a detected value and setting of power transmitted and received between the two systems.
Power control signal to keep power constant based on deviation from value
And a faster response speed than the constant power control circuit.
A high-speed constant power control circuit having , among the two power control signals from the constant power control circuit and the high-speed constant power control circuit, during normal operation, select a power control signal from the constant power control circuit, Switching means for immediately switching to the power control signal from the high-speed constant power control circuit when the first and second power converters are operated at a current equal to or less than the minimum current reference value. A power converter control device, wherein current control of the first and second power converters is performed using a power control signal to be performed. 2. The power converter control device according to claim 1, wherein said switching means controls said high-speed constant power control circuit so that said constant power control characteristic is a predetermined level with said constant power control characteristic of said constant power control circuit. A power margin setting device for providing a power margin for separating the power control signal from the power control circuit and the power control signal from the high-speed constant power control circuit. And a maximum current reference value selection circuit. 3. The power converter control device according to claim 1, wherein said switching means includes a dead band circuit for restraining an input of said deviation to said high-speed constant power control circuit until said deviation reaches a predetermined level. A maximum current reference value selection circuit that selects and outputs a signal having a larger current reference value among the two power control signals from the constant power control circuit and the high-speed constant power control circuit. Power converter control device. 4. The power converter control device according to claim 1, wherein the switching unit is configured to switch a voltage of a power system that functions as a forward converter among the first and second power converters to a predetermined level. A voltage drop detection circuit that detects a drop, a normally closed contact connected to the output side of the constant power control circuit, and a normally closed contact connected to the output side of the high-speed constant power control circuit, A contact circuit for reversing the open / close state of these contacts when the voltage drop detection circuit detects a voltage drop.