JP2003259655A - Method for exciting transformer in power supply system and controller for power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve profitability by suppressing an exciting rush current of a transformer for a converter or a linkage transformer and eliminating an excess overload capacity. <P>SOLUTION: A method for exciting the transformer in a power supply system having a plurality of power converters connected to a common bus via the transformer for the power converters to supply power to the power system from the bus via the transformer for the converters comprises a step of exciting the transformer for the converter and the linkage transformer connected via one power converter from a low voltage gradually up to a rated voltage. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plurality of power converters, each of which is connected to a common busbar through a transformer for conversion, and which supplies electric power to a power system through a transformer for interconnection. The present invention relates to a transformer excitation method and a power converter control device in a power supply system.

[0002]

2. Description of the Related Art A power supply system is known in which a plurality of power converters are respectively connected to a common busbar via transformers for transformers, and electric power is supplied from the busbars to a power system via a transformer for interconnection. Is. FIG. 6 shows such a power supply system.

In the power supply system of FIG. 6, a first power converter 2a is connected to a common bus bar 1 via a first converter transformer 3a and a first converter switch 4a, The second power converter 2b is connected via the second converter transformer 3b and the second converter switch 4b. In the power supply system of FIG. 6, a first power converter including a first power converter 2a and a first converter transformer 3a, a second power converter 2b, and a second converter transformer. The second power conversion device composed of 3b is connected in parallel via the first converter switch 4a and the second converter switch 4b. These power conversion devices supply power to the power system 7 via the interconnection transformer 5 and the interconnection switch 6. The first power converter 2a receives power from the power supply 8a, and the second power converter 2b receives power from the power supply 8b. Although both power supplies 8a and 8b are shown as independent from each other in the drawing, they may be configured by a common power supply. For simplification, FIG. 6 shows a power supply system including two sets of power conversion devices, but it goes without saying that three or more sets may be provided.

As a configuration example of the power converters 2a and 2b, FIG. 7 shows a configuration example using a voltage type self-exciting converter. Here, the power converters 2a and 2b are respectively the input transformer 2
2, a forward converter 21, a DC capacitor 23, and an inverse converter 24. The AC power received from the power source 8 is converted into DC power by the forward converter 21, and the obtained DC power is converted by the inverse converter 24. Is reconverted into AC power, and the AC power thus obtained is supplied to the busbar 1 via the transformer 3 for converter and the switch 4 for converter. Here, an AC voltage source is assumed as the power source 8, but when a DC power source can be easily obtained, the forward converter 21 becomes unnecessary and the inverse converter 24 is provided.
The DC power may be directly supplied from the DC power supply.

The forward converter 21 is controlled so that the DC voltage Ed has a constant value. The DC voltage Ed is the voltage detector 21a
DC voltage reference Edref detected by
The output current reference Idref is calculated by the DC voltage control circuit 21b so that the deviation between and becomes zero. On the other hand, the input current Is of the forward converter 21 is detected by the current detector 21c, and the d-axis current components id and q are detected by the dq conversion circuit 21d.
It is converted to the axial current component iq. At this time, the phase signal θs used for dq axis conversion is obtained by the phase detection circuit 21f from the power supply voltage Vs detected by the instrument transformer 21e. The current control circuit 21g controls the d-axis control voltage Vd * and the q-axis so that the d-axis current component id follows the output current reference Idref and its deviation becomes zero, and the q-axis current component iq becomes zero. The control voltage Vq * is calculated. The pulse control circuit 21h uses the control voltages Vd * and Vq * to convert the forward converter 2
It outputs a gate pulse for 1 and the forward converter 2
The modulation angle of 1 and the conduction angle for the power supply voltage Vs are calculated to determine the on-timing and off-timing of the switching element. At this time, using the phase signal θs, the power supply voltage V
Synchronize with s.

The inverse converter 24 is controlled so that the voltage of the busbar 1, that is, the busbar voltage Vb becomes a predetermined value. Bus voltage V
b is detected by the voltage transformer 24a, and its effective value Vbe is calculated by the voltage detection circuit 24b. The d-axis control voltage V is controlled by the output voltage control circuit 24c so that the deviation between the bus voltage effective value Vbe and the voltage reference Vbref becomes zero.
Calculate d *. The pulse control circuit 24d outputs a gate pulse for the inverse converter 24 from the control voltage Vd *. At this time, the phase signal θc is calculated by the phase detection circuit 24e based on the bus voltage Vb, and the output voltage of the inverse converter 24 is controlled so as to be synchronized with the bus voltage Vb.

[0007]

When the system shown in FIG. 6 is started, the converter transformers 3a and 3b and the interconnection transformer 5 are first loaded with no load, that is, the interconnection switch 6 is opened. Is excited by the power converters 2a and 2b. However, when the transformer is excited at a rated voltage all at once, a large inrush current flows, and its value reaches 5 to 6 times the rated current. The power converters 2a and 2b need to have short-time overload capability so that they can withstand it. When the power conversion device is composed of two power converters as shown in the figure, the rated capacity of the interconnection transformer 5 is twice the rated capacity of the power converter, and therefore the power converters 2a and 2b. Overload capacity is 10 to 1 of the rated capacity
Doubles are required, making the device very large and uneconomical. As one of the countermeasures against this inrush current, Japanese Patent Laid-Open No. 8-298783 describes that the transformer is excited without load by gradually changing from a switching frequency higher than the rated frequency to the rated frequency at the time of starting. . SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for starting a power converter that can suppress the inrush current of the transformer for the converter and the transformer for the interconnection and can improve the economical efficiency without requiring an excessive overload withstand amount. ..

[0008]

In order to achieve the above object, the invention according to claim 1 is such that a plurality of power converters are connected to a common busbar through converter transformers, respectively. In a method for exciting a transformer in a power supply system that supplies power to a power system via an interconnection transformer, the transformer for interconnection and the interconnection transformer connected to it by one power converter are low. The feature is that the voltage is gradually excited to the rated voltage.

According to a second aspect of the present invention, a plurality of power converters are connected to a common busbar through a transformer for a converter, respectively, and electric power is supplied from this busbar to a power system through a transformer for interconnection. In the excitation method of the transformer in the power supply system, the transformer for another converter is excited from the secondary side with the transformer for connection connected to it being excited by one power converter, The invention is characterized in that the power converter connected to the converter transformer is activated and then connected to the power system.

According to a third aspect of the present invention, a plurality of power converters are connected to a common busbar via transformers for transformers, respectively, and electric power is supplied from the busbars to a power system via a transformer for interconnection. In a method of exciting a transformer in a power supply system, a power transformer is excited by a power converter, and a transformer for a converter connected to the power transformer is excited by another power converter to generate power. It is characterized by being connected to the grid.

According to a fourth aspect of the present invention, there is provided a transformer excitation method in the power supply system according to the first aspect,
One power converter excites all the transformers for transformers and the transformers for interconnection, and then activates another power converter to establish interconnection with the power system.

According to a fifth aspect of the present invention, a plurality of power converters are connected to a common busbar via transformers for transformers, respectively, and electric power is supplied from the busbars to a power system via an interconnection transformer. In the control device for the power converter in the power supply system, the power converter includes an inverse converter for controlling the output voltage, and an inverse voltage control circuit for feedback controlling the output voltage of the inverse converter. The converter control device is provided, and the inverse converter control device can switch the output side of the output voltage control circuit to the closed loop side for performing feedback control or to the open loop side for invalidating the output voltage control circuit and guiding the detection voltage. The loop changeover switch and the first side provided on the output side of the loop changeover switch
The input terminal of is connected to the output terminal of the loop changeover switch, the soft start circuit that outputs a coefficient that starts by a start command and gradually increases from zero to 1, and the second input terminal of the multiplication circuit. And a selector switch for selectively inputting the output of the soft start circuit or the coefficient "1".

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<First Embodiment> (Corresponding to Claim 1) FIG. 1 is a block diagram showing a configuration of an apparatus for carrying out a starting method according to a first embodiment of the present invention. The same elements as those in FIG. 7 are designated by the same reference numerals, and detailed description thereof will be omitted. The main circuit configuration in FIG. 1 is the same as that in FIG. The control device is basically the same as that of FIG. 7, but a circuit for controlling the output of the output voltage control circuit 24c for controlling the output voltage of the inverse converter 24 in order to implement the soft start of the present invention. The difference is that parts are added.

In the device of FIG. 1, a loop changeover switch 24f and a multiplication circuit 24k are inserted between the output voltage control circuit 24c and the pulse control circuit 24d. The output of the loop changeover switch 24f becomes the first input of the multiplication circuit 24k. The loop changeover switch 24f is controlled by the changeover control circuit 24m to the output voltage control circuit 24c side in the closed loop and to the voltage detection circuit 24b side in the open loop. The output of the soft start circuit 24h can be input to the second input terminal of the multiplication circuit 24k via the changeover switch 24g. The changeover switch 24g has a soft start position and a normal position, and the changeover position is changeover controlled by the changeover control circuit 24n. The soft start circuit 24h is, so to speak, a constant circuit, and 0 to 1 so as to gradually rise from 0 (zero) to the rated value for soft start with respect to the output of the output voltage control circuit 24c.
This is a circuit that outputs a coefficient that gradually increases to (= 100%). After soft start, output voltage control circuit 2
Since the output of 4c may be directly applied to the 100% pulse control circuit 24d, the changeover switch 24g is changed over to the coefficient 1 side by the changeover control circuit 24n.

When the power converter shown in FIG. 1 is soft-started, first, the converter switch 4a is closed, the converter switch 4b and the interconnection switch 6 are opened, and the power converter 2 is opened.
The transformer 3a for converter and the transformer 5 for interconnection are excited by a. Therefore, the power converter 2a is processed by the following procedure.
The output voltage is controlled so that it gradually rises from 0 (zero) to the rated voltage.

(1) The changeover control circuit 24m turns the changeover switch 24f to the closed loop side (the output voltage control circuit 24c).
To the control voltage Vd * as the output of the output voltage control circuit 24c.

(2) At the same time, the changeover switch 24
g to the soft start side, and the output of the soft start circuit 24h is output to the multiplier 2 via the changeover switch 24g.
Give to 4k.

(3) The start command 24j starts the functions of the output voltage control circuit 24c and the soft start circuit 24h.

The output of the soft start circuit 24h gently changes from 0 to 1, and in response to this, the multiplication circuit 24k multiplies the output of the output voltage control circuit 24c by a coefficient that gently changes from 0 to 1, and the pulse control circuit In 24d, the control voltage V gradually increases from 0 and changes to 100%.
d * is entered. Therefore, the output voltage of the power converter 2a is controlled so as to gradually rise from 0 to the rated voltage. This state is shown in FIG. In FIG. 2, the start command 2
4j, the output of the output voltage control circuit 24c, the output of the soft start circuit 24h, the control voltage Vd * input to the pulse control circuit 24d, and the output voltage of the power converter 2a are shown.

As described above, according to the first embodiment,
The exciting inrush current can be suppressed by gradually raising the exciting voltages of the converter transformer 3a and the interconnection transformer 5.

Although the power converter 2a is used to excite the interconnection transformer 5 here, the same control can be performed by the power converter 2b.

<Second Embodiment> (Corresponding to Claim 2) FIG. 3 is a diagram showing a second embodiment of the present invention, which differs from that of FIG. 1 according to the first embodiment. The same elements will be denoted by the same reference symbols and detailed description thereof will be omitted.

In the starting method of the power converter according to this embodiment, in the state where the interconnection transformer 5 is excited by the power converter 2a as described in the first embodiment,
While the power converter 2b is stopped, the other converter switch 4b is turned on to excite the converter transformer 3b from the secondary side. The power converter 2b activates the power converter 2b after the exciting inrush current due to the turning-on of the converter transformer 3b has subsided. The activation is performed by the following procedure.

(1) The loop changeover switch 24f is switched to the closed loop side, and the output of the output voltage control circuit 24c is input to the multiplier 24k.

(2) The selector switch 24g is switched to the "1" side.

(3) The function of the output voltage control circuit 24c is started by the start command 24j.

After activating the power converter 2b in the above procedure, the interconnection switch 6 is turned on to establish interconnection with the power system 7.

By turning on the transformer 3b for the converter in this way, the exciting inrush current supplied by the power converter 2a is equivalent to one transformer for the converter, and the exciting inrush current for the interconnection transformer 5 is Since it does not flow, the exciting inrush current can be reduced as compared with the conventional one.

<Third Embodiment> (Corresponding to Claim 3) FIG. 4 is a diagram showing a third embodiment. The same elements as those of FIG. 1 showing the first embodiment are the same. The same reference numerals are given and detailed description thereof is omitted.

In the starting method of the power converter according to this embodiment, the power converter 2b is excited while the interconnection transformer 5 is excited by the power converter 2a as described in the first embodiment. Then, the transformer for transformer 3b is excited. In this case, the output voltage of the power converter 2b is controlled to gradually rise from 0 to the rated voltage by the following procedure.

(1) The loop switch 24f is switched to the open loop side as shown in the figure, and the output of the voltage detection circuit 24b is input to the first input terminal of the multiplier 24k.

(2) The selector switch 24g is switched to the "soft start" side.

(3) The function of the soft start circuit 24h is started by the start command 24j.

By the above procedure, the output voltage of the power converter 2b is controlled so that it gradually rises from 0 to the rated voltage, and after the output voltage reaches the rated value, the converter switch 4b is turned on, and The switch 6 for interconnection is turned on to connect with the power system 7.

As described above, by gradually raising the voltage applied to the transformer 3b for the converter, it is possible to suppress the exciting inrush current.

<Fourth Embodiment> (corresponding to claim 4) FIG. 5 is a diagram showing a fourth embodiment. The same elements as those of FIG. 1 showing the first embodiment are the same. The same reference numerals are given and detailed description thereof is omitted.

When starting up the power converter according to this embodiment, first the converter switches 4a and 4b are closed,
The switch 6 for interconnection is opened, and the transformers 3a and 3b for converters and the transformer 5 for interconnection are excited by the power converter 2a. At this time, the output voltage of the power converter 2a is controlled so as to gradually rise from 0 to the rated voltage by the following procedure.

(1) The loop changeover switch 24f is switched to the closed loop side, and the output of the output voltage control circuit 24c is input to the multiplier 24k.

(2) The selector switch 24g is switched to the soft start side, and the output of the soft start circuit 24h is input to the second input terminal of the multiplier 24k.

(3) The start command 24j starts the functions of the output voltage control circuit 24c and the soft start circuit 24h. The circuit operation is the same as that of the first embodiment,
The description is omitted here.

As described above, the transformers 3a and 3 for the converter are used.
By gradually raising the voltage applied to b and the interconnection transformer 5, the magnetizing inrush current of the transformer can be suppressed.

[0043]

As described above, the excitation inrush current of the transformer is suppressed by controlling the power converter and gradually raising the voltage applied to the converter transformer and the interconnection transformer. This allows the power converter to improve the economics of the system without requiring large overload tolerances.

[Brief description of drawings]

FIG. 1 is a block diagram of a control device that implements a first embodiment of the present invention.

FIG. 2 is a time chart for explaining the first embodiment of the invention.

FIG. 3 is a block diagram of a control device that implements a second embodiment of the present invention.

FIG. 4 is a block diagram of a control device that implements a third embodiment of the present invention.

FIG. 5 is a block diagram of a control device that implements a fourth embodiment of the present invention.

FIG. 6 is a wiring diagram of a power supply system to which the present invention is applied.

7 is a block diagram showing a detailed configuration of a power converter shown in FIG. 6 and a control device.

[Explanation of symbols]

1 bus 2a, 2b power converter 3a, 3b Transformer transformer 4a, 4b Converter switch 5 Transformers for interconnection 6 Switch for interconnection 7 power system 8a, 8b power supply 21 Forward converter 21a Voltage detector 21b DC voltage control circuit 21c Current detector 21d dq conversion circuit 21e Instrument transformer 21f Phase detection circuit 21g current control circuit 21h Pulse control circuit 22 Input transformer 23 DC capacitor 24 Inverter 24a Instrument transformer 24b voltage detection circuit 24c output voltage control circuit 24d pulse control circuit 24e Phase detection circuit 24f loop switch 24g changeover switch 24h soft start circuit 24j Start command 24k multiplication circuit 24m switching control circuit 24n switching control circuit

Claims (5)

[Claims] 1. A plurality of power converters are respectively connected to a common busbar through a transformer for a converter, and a transformer in a power supply system that supplies electric power from this busbar to a power system through a transformer for interconnection. In a method for exciting a transformer, in a power supply system, a transformer for transformer and a transformer for interconnection which are connected to it by one power converter are excited from a low voltage to a rated voltage gradually. Excitation method of transformer. 2. A transformer in a power supply system, wherein a plurality of power converters are connected to a common busbar through a transformer for a converter, respectively, and electric power is supplied from this busbar to a power system through a transformer for interconnection. In the excitation method of a transformer, in the state that the interconnection transformer connected to it by one power converter is excited, another transformer for the transformer is excited from the secondary side and connected to this transformer for the transformer. A method for exciting a transformer in a power supply system, comprising: activating an existing power converter and then connecting the power converter to the power system. 3. A transformer in a power supply system, wherein a plurality of power converters are respectively connected to a common busbar via a transformer for a converter, and power is supplied from this busbar to a power system via an interconnection transformer. In the excitation method of a transformer, in the state where the transformer for interconnection is excited by one power converter, the transformer for transformer connected to it is excited by another power converter to be connected to the power system. A method for exciting a transformer in a power supply system characterized by the above. 4. The method for exciting a transformer in a power supply system according to claim 1, wherein all the transformers for the converter and the interconnection transformers are excited by one power converter, and then the other power conversion is performed. A method for activating a power converter, which comprises activating the power converter and connecting it to the power system. 5. A power supply system in which a plurality of power converters are respectively connected to a common busbar via a transformer for conversion, and power is supplied from this busbar to a power system via an interconnection transformer. In a converter control device, each of the power converters includes an inverse converter that controls an output voltage, and an inverse converter control device that includes an output voltage control circuit for feedback controlling the output voltage of the inverse converter. The inverse converter control device can switch the output side of the output voltage control circuit to a closed loop side for performing feedback control or an open loop side for invalidating the output voltage control circuit to guide a detection voltage. The changeover switch and the first switch provided on the output side of the loop changeover switch,
The input terminal of is connected to the output terminal of the loop changeover switch, and starts from 0 by the start command
A soft start circuit that outputs a coefficient that gradually increases to 1), and a changeover switch that switches and inputs the output of the soft start circuit or the coefficient “1” to the second input terminal of the multiplication circuit. A control device for a power converter in a characteristic power supply system.