JPH09117056A - Self-excited dc transmission controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To operate a DC system stably even at the time of a system fault by providing a control means for sustaining the voltage of the DC system and the effective and reactive powers of a self-excited converter at constant levels and increasing the power level being designated by an effective power control means by an amount corresponding to the power margin. SOLUTION: Based on a command from an operation command unit 60, the effective power command value 302 of a self-excited converter during the inverter operation is added 306 with a power margin 304 and inputted to an effective power control circuit 308. On the other hand, a DC voltage command value 312 is added 316 with a voltage margin 314 and inputted to a DC voltage control circuit 318. Subsequently, an effective power 322 during conversion is added with a power margin 324 and inputted to an effective power control circuit 328. An optimal value is selected 340, as an effective power command value, from each control circuit 308-328 and inputted to a non-interference current circuit 370 along with a reactive power command value 360. It is then converted 370 into a three-phase voltage reference value and a PWM pulse 380 is delivered to the self-excited converter. Consequently, DC power transmission can be sustained even at the time of a system fault.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-excited DC power transmission control device including a self-excited DC power transmission control device including a self-excited converter, and more particularly to a self-excited DC power transmission control device capable of stably operating a self-excited DC power transmission facility even when a system fault occurs.

[0002]

2. Description of the Related Art A self-excited converter composed of a switching element having a self-extinguishing function is capable of converting power from AC to DC or from DC to AC without being affected by waveform distortion of an AC system. , Is expected to be applied to the electric power system as an ideal converter in the future, and is under development. The most promising application point is DC power transmission equipment, and by applying a self-exciting converter, not only can stable power transmission be performed regardless of the status of the AC system, but it is also possible to send power to an AC system without a power supply. Comes out. Currently, the self-excited converter is put to practical use as an uninterruptible power supply (CVCF) for industrial small-capacity facilities and an active filter, but a large-capacity converter that can be used for electric power is under development.

As an operation control method for self-excited DC power transmission, as shown in Japanese Patent Application No. 4-15012, a control method has been developed in which the voltage of the DC system is designated at one end and the active power is controlled at the other end. There is. However, if the converter station that controls the DC system voltage stops due to a system accident, the DC system voltage control converter will run out and stable operation will not be possible. Further, regarding the operation control method of DC multi-terminal power transmission configured by connecting a large number of self-excited converters to the DC system, the control method conventionally considered is not sufficient for stable operation.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art and to provide a self-excited DC power transmission control device capable of stably operating self-excited DC power transmission in the event of a system fault. .

[0005]

In a controller of a self-excited converter of a DC transmission facility having a self-excited converter composed of a switching element having a self-extinguishing function as a converter, the voltage of a DC system is changed. DC voltage control means for maintaining a specified constant value, active power control means for controlling the active power of the self-excited converter to a specified constant value, and reactive power on the AC side of the self-excited converter to a specified constant value The power margin setting that increases the power command value of the active power control means of the control device of the self-excited converter that performs the control to keep the voltage of the DC system at the specified constant value by the power margin. It is equipped with means.

In order to stably operate the self-excited DC power transmission equipment, one self-excited converter connected to the DC system controls the voltage of the DC system, and the remaining converters are controlled by active power. This rule is the same in the case of self-excited multi-terminal DC transmission.

The control device for the self-excited converter is provided with a DC control means, an active power control means, and a reactive power control means. The DC voltage control means operates the DC voltage controlled self-exciting converter so that the voltage of the DC system becomes a prescribed constant value. In addition, the active power control means controls the active power of the remaining self-excited converters in the DC system to be maintained at a specified constant value. The reactive power control means arbitrarily controls the reactive power with each self-exciting converter according to the characteristics of the AC system, regardless of whether the control is DC voltage control or active power control. Here, the self-excited converter that performs active power control controls active power by the active power control means according to the active power command value of each self-excited converter. The DC voltage command values of these self-exciting converters are given different voltage command values higher or lower than the voltage command value of the DC system by a voltage margin. In this case, it is convenient to set the converter that performs the forward converter operation high and the converter that performs the inverter operation low. On the other hand, the self-exciting converter for controlling the DC voltage controls the voltage of the DC system by the DC voltage control means according to the DC voltage command value. As the active power command value of the self-exciting converter, an active power command value at which the sum of active power command values of the DC system becomes zero is given, and an active power command value large by the power margin is given to this. However, the active power command value is a positive value in the forward converter and a negative value in the reverse converter. Therefore, in the converter performing the forward conversion operation, the power margin is added to the active power command value, and in the converter performing the inverter operation, the power margin is subtracted from the active power command value. As a result, the self-excited converter stops due to a system accident, and stable operation can be performed even when the converter is disconnected from the DC system.

Now, if the DC voltage controlled self-excited converters are disconnected from the DC system due to a system fault and the DC voltage controlled converters are lost, each self-excited converter is equipped with voltage control means. Then, the self-exciting converter having a set value of the voltage command value moves to the voltage control converter of the DC system for stable operation. On the other hand, if the active power control self-exciting converter is disconnected from the grid,
Since the voltage of the system remains voltage controlled by a sound self-exciting converter, there is no problem in stable operation. The voltage margin value takes into account the detection error of the voltage detector, the ripple of the voltage, and the like, and the value in consideration of the error due to these is taken as the margin value. Also, the value of the power margin should be larger than the value that accounts for the loss of the conversion equipment.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a control device for a self-excited DC power transmission facility according to the present invention will be described with reference to FIGS. FIG.
Shows the outline of the configuration of the self-excited DC transmission equipment. In FIG. 3, 1 and 2 are electric power systems, 11 and 12 are conversion transformers, and 2
Reference numerals 1 and 22 are self-exciting converters, 31 and 32 are current limiting reactors, 41 and 42 are flywheel diodes connected in parallel to the current limiting reactors, 50 is a power capacitor, and 60 is a self-exciting DC transmission facility. Operation command device,
Reference numerals 61 and 62 are control devices for the self-excited converters 21 and 22, respectively.

FIG. 2 shows an example of a detailed configuration of the self-excited converter 21. The configuration of the self-excited converter 22 is similar. Explaining the figure, GT1 to GT6 (201 to 206) are switching elements such as gate turn-off thyristors having a self-extinguishing function, and D1 to D6 (211 to 216) are connected in antiparallel to the switching elements GT1 to GT6. It is a diode. The self-excited converter is configured by bridge-connecting diodes that are connected in antiparallel with switching elements.
The reactor 31 suppresses the rise of the discharge current of the electric charge from the power capacitor 50 when the switching element causes commutation failure. The diode 41 bypasses the reactor in order to accelerate the charging of the capacitor from the system. It serves to pass the circulating current of the reactor.
The power capacitor 50 serves as a voltage source of the self-excited converter and suppresses voltage ripple. Further, the conversion transformer 11 serves to insulate the self-excited converter from the system and to step up / down the system voltage to a voltage suitable for the self-excited converter. The above-described devices / apparatuses and elements are added to the self-excited converter to perform the conversion operation of power from AC to DC or from DC to AC by the control pulse from the controller 61.

FIG. 1 shows an embodiment of the control device 61. A
D1 is an adder for adding the value of the active power command value 302 and the power margin 304 during the inverter operation of the self-exciting converter 21 which is a command from the operation command device 60, and API 308 is the power from the adder AD1 (306). The active power control circuit for controlling the active power of the self-excited converter 21 to a constant command value when the inverter receives the command value, AD2 (316) is the operation command device 6
The AVR318 is an adder AD2 that adds the DC voltage command value 312, which is a command from 0, and the value of the voltage margin 314.
A DC voltage control circuit that receives a DC voltage command value from the DC voltage control circuit and controls the DC output voltage of the self-exciting converter 21 to a constant command value.
AD3 (326) is an adder for adding the active power command value 322 in the forward conversion operation of the self-exciting converter 21 which is a command from the operation command device 60 and the value of the power margin 324, and the APR328 is an adder from the adder AD3. The active power control circuit that receives the power command value and controls the active power of the self-exciting converter 21 to a constant command value during the forward conversion operation. The SEL340 is the optimum value of the output signals of the control circuits of API308, AVR318, and APR328. A signal selection circuit for selecting, and this output becomes the active current command value of the current control circuit ACR350. AQR360 is a reactive power control circuit that receives the reactive power command value from the operation command device 60 and controls the reactive power of the self-exciting converter 21 to a constant command value, and this output is the reactive current command value of the control circuit ACR350. Become. ACR350 is a non-interference current control circuit that receives the active current command value
Of the active current control circuit for controlling the active current of the self-exciting converter 21 to the constant value of the command value and the reactive current control circuit for controlling the reactive current of the self-excited converter 21 to the constant value of the command value. The two current control circuits operate in a non-interfering manner at high speed so as to match the respective command values. TRF370 is a conversion circuit that converts the output of two current control circuits into a three-phase voltage reference value, and PWM380 is for generating an output voltage proportional to the voltage reference value from the three-phase voltage reference value by the self-exciting converter 21. It is a pulse creation circuit that creates a control pulse.

The operation command device 60 is a self-exciting converter 21.
Outputs a power margin ΔP to the adders AD1 and AD3 when operates as a DC system voltage control converter. When operating as an active power control circuit, the power margin ΔP is not output, the voltage margin ΔV is output, and the margin ΔV is subtracted from the voltage command value.

FIG. 4 shows the characteristics of the DC voltage with respect to the active power of the self-excited converter 21 having the control device of FIG. The positive range of active power represents the forward converter operation of the self-excited converter, and the negative range represents the inverter operation. Therefore, P1 is the control circuit AP
The command value of R, Vp is the command value of AVR, and P2 is the characteristic by the operation of the control circuit according to the command value of API.

That is, when the active power is increased in the forward converter operation, a control operation is performed to keep the DC voltage constant at Vp up to P1, and the DC voltage is lowered to keep P1 constant at P1 or higher. Conversely, if the active power is increased by inverter operation, P
Up to 2, the control operation is performed to keep the DC voltage constant at Vp, and above that, P2 is kept constant and the DC voltage increases. The signal selection circuit SEL of FIG. 3 is operated so as to have such characteristics. FIG. 5 shows an operating point on the active power-DC voltage of the converter when the forward converter and the inverter of the self-excited DC power transmission are combined. The figure shows the case where direct voltage control is performed by the forward converter (REC) and active power control is performed by the inverter (INV). The forward converter performs DC voltage control with the DC voltage command value Vp1 from the operation command device 60. Therefore, the command value P11 (command value of APR) and P12 (command value of API) whose active power command value is larger than the value of the DC transmission power P22 by ΔP are given from the operation command device 60. On the other hand, the inverter uses active power control to determine the active power command value P22.
Is given to the control circuit API and P21 is given to the APR from the operation command device 60. Further, the command value of the voltage control circuit AVR is smaller than Vp1 by a voltage margin ΔV, which is a command value V.
p2 is given from the operation command device 60. As a result, the operating point is the intersection point O1 on the characteristics of each self-excited converter.
The operation is stable. The DC power can be transmitted by changing the value of the active power command value P22 from the operation command device 60.

Next, the operation in the case of self-excited multi-terminal power transmission is shown in FIG.
FIG. FIG. 6 shows a system configuration diagram of self-excited three-terminal power transmission. In the figure, those having the same numbers as those in FIG. 1 represent the same functions as those in FIG.
Is an AC system, 13 is a conversion transformer, 23 is a self-exciting converter of the third terminal, 33 is a reactor, 43 is a diode, 6
3 is a control device for the self-excited converter 23, which is the control device 6 described above.
The circuit configuration is the same as that of 1 or 62, and only the command value of each control circuit is given a different command value from the operation command device 60. The operation of these three terminals will be described with reference to FIG. Now, it is assumed that the self-exciting converter 21 controls the DC voltage of the DC multi-terminal system, and the self-exciting converters 22 and 23 perform active power control by the inverters. Therefore, the DC voltage command value VP is transferred from the operation command device 60 to the self-exciting converter 21.
1 is given and the active power command value is given a command value larger than the sum (P22 + P32) of the active power command values of the other self-exciting converters (inverters) by the power margin ΔP.
Further, the inverter 22 has a voltage command value Vp2 smaller than the voltage command value Vp1 by a voltage margin ΔV1.
3 is given Vp3 which is smaller by ΔV2. The active power command values are P22 and P32, respectively. The operating point at this time is O1, and stable operation can be performed.

Here, when the inverter 23 is disconnected from the DC system due to a system fault, the operating point shifts to O2 as shown in FIG. 7 (b), and stable operation can be achieved even when the inverter is disconnected.

Further, when the self-exciting converter 21 of the voltage control terminal is disconnected, the forward converter disappears, so that the inverter 2
If 2 and 23 remain, and the inverter 23 having a large power command value is allowed to reverse the power flow, the power flow is reversed to serve as a voltage control terminal for forward conversion operation, and voltage control operation is performed with the voltage command value Vp3. At this time, the converter 22 can operate stably as an inverter at the operating point O3.

As described above, each self-excited converter is provided with the voltage control circuit and the active power control circuit, and by giving a margin to the voltage command value and the active power command value to obtain an appropriate command value, a system fault occurs. It is also possible to separate the converter in case of system failure and perform stable operation with a healthy converter.

Furthermore, in one embodiment of the present invention, the value of the power margin is such that the voltage control converter of the DC system compensates for the loss of the DC transmission equipment including the loss of the converter and sets the voltage to a prescribed constant value. Therefore, voltage control cannot be performed unless the capacity of the converter is large by the loss. Therefore, it is necessary to set the active power setting value of the self-exciting converter that performs voltage control to a value larger than this loss amount, and this increased amount is set as a power margin.

In one embodiment of the present invention, the voltage control terminal must be set to a value with a margin larger than the voltage command value of another self-excited converter and larger than the voltage detection error and the voltage ripple. There is a risk of voltage control of the system even though it is not a control converter. Therefore, it is preferable for stable operation to operate the active power control converter by lowering the voltage command value from the voltage control terminal with a voltage margin having a value larger than the voltage detection error and the ripple.

[0021]

According to the control device of the present invention described above, it becomes possible to stably operate the self-excited DC power transmission even in the event of a system fault, and particularly when the DC power transmission is performed by a plurality of self-excited converters. Even if a system accident occurs, it has the effect of maintaining stable power transmission.

[Brief description of the drawings]

FIG. 1 is a diagram showing one configuration example of a self-excited DC power transmission facility to which the present invention is applied.

FIG. 2 is a diagram showing the configuration of the self-excited converter of FIG.

FIG. 3 is a configuration example of a control device for a self-excited converter according to the present invention.

4 is an active power-DC voltage characteristic diagram illustrating the operation of the self-excited converter of FIG.

FIG. 5 is an active power-DC voltage characteristic diagram illustrating the operation of a self-excited DC power transmission facility.

FIG. 6 is a diagram showing one configuration example of a self-excited multi-terminal DC power transmission facility that is a target of the present invention.

FIG. 7 is an active power-DC voltage characteristic diagram illustrating the operation of a self-excited multi-terminal DC power transmission facility.

[Explanation of symbols]

1, 2, 3 ... Power system, 11, 12, 13 ... Conversion transformer, 21, 22, 23 ... Self-excited converter, 31, 32, 3
3 ... Reactor for limiting current, 41, 42, 43 ... Flywheel diode, 50 ... Capacitor for power, 60
... Operation command device, 61, 62, 63 ... Control device, 20
1, 202, 203, 204, 205, 206 ... Switching elements such as gate turn-off thyristors, 211,
212, 213, 214, 215, 216 ... Diode, 306, 316, 326 ... Adder, 308 ... Active power control circuit during inverter operation, 318 ... DC voltage control circuit, 328 ... Active power control circuit during forward conversion operation , 34
0 ... Signal selection circuit, 350 ... Non-interference current control circuit, 36
0 ... Reactive power control circuit, 370 ... Conversion circuit, 380 ... Pulse generation circuit.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location H02M 7/48 9181-5H H02M 7/48 E 7/757 9181-5H 7/757

Claims (6)

[Claims] 1. A self-excited DC power transmission control device configured by connecting a self-excited converter composed of a controllable semiconductor element having a self-extinguishing function through a DC power transmission system, wherein the self-excited converter is provided. Is provided with the DC transmission voltage control circuit, the active power control circuit, and the reactive power control circuit, and increases the power command value of the active power control circuit of the self-excited converter that controls the voltage of the DC transmission system by a power margin. Characteristic self-excited DC power transmission control device. 2. The self-excited DC power transmission control device according to claim 1, wherein the voltage command value of the voltage control circuit of the self-excited converter for controlling active power is set to a voltage margin when the converter is in the forward converter operation. In addition, the self-excited DC power transmission control device is characterized in that a voltage command value higher than the voltage of the DC system is set, and when the converter is operating in an inverter, a voltage margin is subtracted to set the voltage command value lower than the voltage of the DC system. 3. The self-excited DC power transmission control device according to claim 1, wherein when there are a plurality of inverter-operated self-excited converters, the active power command value of the forward converter is set to the active power command of the plurality of self-excited converters. A self-excited DC power transmission control device, wherein the value is equal to or more than the total value of the values and is larger by the power margin. 4. The self-excited DC power transmission control device according to claim 1, wherein when there are a plurality of inverter-operated self-excited converters, the voltage command values for the plurality of converters are lower than the voltage command values for the forward converter. A self-excited DC power transmission control device having different values. 5. The self-excited DC power transmission control according to claim 1, wherein the value of the power margin is larger than a value that accounts for the loss of the conversion equipment and the transmission line. apparatus. 6. The self-excited DC power transmission control device according to claim 1, wherein the value of the voltage margin is larger than the sum of the error of the voltage detector and the ripple of the DC voltage. Control device.