JP6016712B2 - AC brushless exciter and power generation system - Google Patents

Description

  The present invention relates to a brushless exciter, and more particularly, to an AC excited brushless exciter that uses a multiphase winding as a primary winding and applies an AC voltage, and a power generation system including the AC excited brushless exciter.

  The brushless exciter generates a magnetic flux by passing current through the primary winding of the stator, and the secondary winding of the rotor that is directly connected to the field axis of the generator is linked to this magnetic flux. This generates exciting power necessary for power generation. Although the voltage applied to the primary winding is generally a direct current, an AC brushless excitation device has been developed in which the primary winding is a multiphase winding and an AC voltage is applied. If an AC brushless exciter is used, SFC (Static Frequency Converter) activation that cannot be realized with a normal DC excitation type brushless exciter becomes possible.

  A power generation system equipped with an AC brushless exciter is compatible with SFC activation by a thyristor. On the other hand, when the rotating direction of the rotor (armature) and the rotating magnetic field are the same direction, the voltage induced on the secondary side of the AC exciter decreases as the rotor speed of the armature increases. Even when the primary side voltage is constant, the field current of the main generator necessary for power generation cannot be maintained.

  In order to keep the field current necessary for power generation constant while supporting SFC start-up, which is a feature of the AC brushless exciter, AC excitation is performed by applying an AC voltage to the primary winding of the AC exciter at the start. A method of switching from AC excitation to DC excitation when the rotational speed of the generator reaches a certain value is used (for example, Patent Document 1). According to the switching procedure from AC to DC in this method, first, the AC power source side that is performing AC excitation is disconnected, and the first phase of the primary winding of the AC exciter is short-circuited with the second phase. By switching to DC excitation, DC voltage is applied. In this case, six circuit breakers are required for switching the excitation method.

JP-A-4-96698

  When switching from AC excitation to DC excitation by the method as described above, the proportion of DC current flowing through the primary winding of the exciter is different for each phase, which causes imbalance in the thermal stress on the primary winding of the exciter. Arise. The present invention has been made in order to solve such a problem, and aims to keep the thermal stress on the primary winding of the AC exciter uniform in each phase.

  The AC brushless exciter according to the present application has a d-axis two-phase winding and a q-axis two-phase winding on the secondary side, and inputs a three-phase AC power on the primary side, the d-axis two-phase winding and the q-axis 2 Scott transformer that outputs AC power to phase winding, first pole terminal and second pole terminal on secondary side, DC power is output from three-phase AC power to first pole terminal and second pole terminal An AC / DC converter, an AC exciter having a first two-phase winding and a second two-phase winding on the primary side and a secondary winding on the secondary side, and a first terminal and a second terminal. The first terminal is connected to one side of the d-axis two-phase winding, the second terminal is connected to one side of the first two-phase winding, the third terminal, It has a fourth terminal, the third terminal is connected to the other side of the d-axis two-phase winding and one side of the q-axis two-phase winding, and the fourth terminal is the other side of the first two-phase winding And a second side where one side of the second two-phase winding is connected The circuit breaker has a fifth terminal and a sixth terminal. The fifth terminal is connected to the first pole terminal of the AC / DC converter, and one side of the first two-phase winding is connected to the sixth terminal. A third circuit breaker, a speed detector for detecting the rotor speed, an AC / DC converter, a first circuit breaker, a second circuit breaker, and a third circuit breaker based on the output of the speed detector. A control unit for controlling, and the other side of the q-axis two-phase winding is connected to the other side of the second two-phase winding.

  When switching from AC excitation to DC excitation by the control unit, DC excitation is performed by a d-axis two-phase winding and a q-axis two-phase winding connected in parallel or in series to the output terminal of the AC / DC converter having a variable voltage function. . With such an excitation method, currents of the same value flow in the d-axis two-phase winding and the q-axis two-phase winding, respectively, so that imbalance due to thermal stress on each winding can be suppressed.

It is a circuit diagram which shows the electric power generation system provided with the alternating current brushless exciting device by Embodiment 1 of this invention. It is a circuit diagram which shows the relationship between the excitation system switching apparatus by Embodiment 1 of this invention, and a control part. It is a flowchart which shows the excitation system switching procedure by embodiment of this invention. It is a circuit diagram which shows operation | movement of a Scott transformer. It is a vector diagram which shows the relationship between the primary side voltage in a Scott transformer, and a secondary side voltage. It is a figure which shows the relational expression formed among the synchronous speed Ns, the power supply frequency f, the pole pair number p, and the slip S. It is a circuit diagram which shows the relationship between the excitation system switching apparatus by Embodiment 2 of this invention, and a control part. It is a circuit diagram which shows the electric power generation system provided with the alternating current brushless exciting device by Embodiment 3 of this invention. It is a circuit diagram which shows the relationship between the excitation system switching apparatus by Embodiment 3 of this invention, and a control part. It is a circuit diagram which shows the relationship between the excitation system switching apparatus by Embodiment 4 of this invention, and a control part.

  Hereinafter, an AC brushless exciter according to the present invention and a power generation system including the AC brushless exciter will be described in detail with reference to the drawings. In addition, this invention is not limited to the following description, In the range which does not deviate from the summary of this invention, it can change suitably.

Embodiment 1 FIG.
FIG. 1 is a circuit configuration diagram showing a power generation system including an AC brushless excitation device according to Embodiment 1 of the present invention. As shown in the figure, a power generation system 200 having an AC brushless exciter is composed of an AC brushless exciter 100, a rotary rectifier 7, and a field winding type synchronous generator 14. The AC brushless excitation device 100 includes a Scott transformer 1, an AC / DC converter 2, an excitation method switching device 3, an AC exciter 13, and the like. The AC brushless exciter 100 rectifies the three-phase AC output of the AC exciter 13 directly connected to the main shaft of the field winding type synchronous generator 14 by the rotary rectifier 7 attached to the armature of the AC exciter 13, The magnetic winding synchronous generator 14 is excited. The secondary winding 4, the rotary rectifier 7 and the synchronous generator field winding 8 are integrated and directly connected to the turbine for power generation.

  The rotary rectifier 7 and the field winding type synchronous generator 14 constitute a main generator (rotating armature type synchronous generator). Scott transformer 1 which is a phase conversion transformer obtains a two-phase AC output with a three-phase AC input. The Scott transformer 1 is supplied with three-phase AC power (u, v, w) from the grid. The AC / DC converter (AC-DC converter) 2 is connected in parallel to the primary side of the Scott transformer 1 and has a variable voltage function. The excitation method switching device 3 has terminals a to j. The excitation method switching device 3 switches the excitation circuit from DC excitation to AC excitation in accordance with a command from the control unit 16. The AC exciter 13 includes a secondary winding 4, a two-phase winding 5, a two-phase winding 6, and the like.

  The speed detector 17 detects the rotor speed of the rotor (secondary winding 4, rotary rectifier 7, synchronous generator field winding 8) optically, for example. The secondary winding 4 of the AC exciter 13 is a multiphase winding. The two-phase winding 5 of the AC exciter 13 is connected to the secondary side of the Scott transformer 1. The two-phase winding 6 of the AC exciter 13 is connected to the secondary side of the Scott transformer 1. The two-phase winding 5 and the two-phase winding 6 correspond to the d-axis side and the q-axis side, respectively. The rotary rectifier 7 is disposed on the secondary rotating shaft of the AC exciter 13 and converts AC to DC. The synchronous generator field winding 8 of the field winding type synchronous generator 14 is connected to the DC side of the rotary rectifier 7. The synchronous generator armature winding 9 of the field winding type synchronous generator 14 is located on the secondary side of the synchronous generator field winding 8 and is stationary. The secondary winding 4, the rotary rectifier 7, and the synchronous generator field winding 8 rotate during excitation. The two-phase winding 5 and the two-phase winding 6 are stationary. The AC / DC converter 2 outputs DC power.

  FIG. 2 shows the relationship among the AC / DC converter 2, the excitation method switching device 3, the speed detector 17, and the control unit 16. The figure shows the internal configuration of the excitation method switching device 3. The excitation method switching device 3 includes terminals a to j and circuit breakers A to C. The circuit breaker A10 has an input side terminal 10a and an output side terminal 10b. The circuit breaker B10 has an input side terminal 11a and an output side terminal 11b. The circuit breaker C10 has an input side terminal 12a and an output side terminal 12b. Here, the terminals a to d of the excitation method switching device 3 correspond to the terminals a to d of the Scott transformer 1 (see FIG. 4). The circuit breakers A to C open and close the circuit based on a command from the control unit 16.

  Of the secondary output of the Scott transformer 1, the d-axis is connected to the terminals a and b. Of the secondary output of the Scott transformer 1, the q-axis is connected to the terminals c and d. A positive (positive) terminal 2a and a negative (negative) terminal 2b of the AC / DC converter 2 are connected to the terminals e and f, respectively. Of the primary side input of the AC exciter 13, the two-phase winding 5 serving as the d axis is connected to the terminals g and h. Of the primary side input of the AC exciter 13, the two-phase winding 6 serving as the q axis is connected to the terminals i and j. A circuit breaker A10 is disposed between the terminals a and g. A circuit breaker B11 is disposed between the terminal b and the terminal h. A circuit breaker C12 is disposed between the terminal e and the terminal g. The control unit 16 controls the AC / DC converter 2 and the excitation method switching device 3 based on the output of the speed detector 17.

  The procedure for switching the excitation circuit from AC excitation to DC excitation will be described below along the excitation method switching flowchart of FIG. In the initial state of the excitation method switching device 3 (before the generator is started), all of the circuit breakers A to C are in a disconnected state, and the AC / DC converter 2 is in a gate block state. First, in order to start SFC (Static Frequency Converter) activation by AC excitation, the control unit 16 turns on the circuit breaker A10 and the circuit breaker B11 (step S001). A voltage having a phase difference of 90 ° is applied to the two-phase winding 5 and the two-phase winding 6 connected to the secondary side of the Scott transformer 1, and a rotating magnetic field is generated. The rotating magnetic field is linked to the secondary winding 4 of the AC exciter 13 to supply power to the secondary side of the AC exciter 13 and corresponds to SFC activation. Next, the control unit 16 measures the rotor speed Wr of the rotor with the speed detector 17 and compares it with the set rotor speed N set to an arbitrary value (step S002). If the rotor speed Wr of the rotor is lower than the set rotor speed N, step S002 is repeated.

  The controller 16 disconnects the circuit breaker A10 and the circuit breaker B11 when the rotor speed Wr of the rotor reaches the set rotor speed N due to the SFC activation (step S003). Thereafter, the gate block of the AC / DC converter 2 is released, and the DC voltage control is started (step S004). Finally, the circuit breaker C12 is turned on (step S005). By the above procedure, the two-phase winding 5 of the AC exciter 13 and the two-phase winding 6 of the AC exciter 13 are connected in series to the output terminal of the AC / DC converter 2 to generate a fixed magnetic field. When a fixed magnetic field is linked to the secondary winding 4 of the AC exciter 13 in the rotating state, power is supplied to the secondary side of the AC exciter 13 and the field current necessary for power generation is synchronized with the synchronous generator. It flows in the field winding 8.

  The AC brushless excitation device 100 has the circuit configuration as described above, and switches the excitation method from AC excitation to DC excitation as shown in the excitation method switching flowchart. At the time of direct current excitation, it becomes possible to allow the same current to flow through the two-phase winding 5 of the alternating current exciter 13 and the two-phase winding 6 of the alternating current exciter 13, and to the primary winding of the alternating current exciter 13 which has been a problem. Eliminates heat stress imbalance. Simultaneously with the above-described effect, by generating constant fixed magnetic fields orthogonal to each other from the two-phase winding 5 and the two-phase winding 6 during direct current excitation, the two-phase windings 5 and 2 required for obtaining a predetermined magnetic flux are generated. The magnitude of the excitation current flowing through the phase winding 6 can be suppressed to an effective value when the current flowing through one phase of the primary winding of the AC exciter in the DC excitation method of Patent Document 1 is a peak value. .

  However, the above effect is based on the premise that the excitation winding is designed so that the rated voltage is generated on the secondary side of the AC exciter. Here, since the number of phases is reduced from three phases to two phases using the Scott transformer 1, it is considered that the number of excitation windings is increased, but the two-phase windings have three-phase windings. A reduction in volume can be expected compared to the device. In the present invention, the primary side winding of the AC exciter 13 is the two-phase winding 5 and the two-phase winding 6, and the excitation method is switched by devising the connection method between the AC excitation circuit and the DC excitation circuit. The device 3 is realized with three circuit breakers.

  The action of AC excitation and DC excitation shown in the first embodiment will be described below with reference to FIG. First, AC excitation will be described. The Scott transformer 1 includes a T seat transformer Tb and an M seat transformer Ta. The Scott transformer 1 has a d-axis two-phase winding 1d and a q-axis two-phase winding 1q on the secondary side. Here, the terminals a to d on the secondary side correspond to the terminals a to d shown on the secondary side of the Scott transformer 1 of FIG. The turn ratio of the T seat transformer Tb and the M seat transformer Ta is equal.

  The arrows shown in the figure indicate the directions of the voltages (Vy1 and Vx1) applied to the primary winding and the voltages (Vy2 and Vx2) induced in the secondary winding. The tap S is provided at about 86% (= √3 / 2) of the total number of turns in the primary winding of the T-slot transformer Tb. The tap N is provided at the midpoint of the M seat transformer Ta. One end of a T seat transformer Tb is connected to the tap N. Two phases of the three-phase AC power (u, v, w) are connected to both ends of the M seat transformer Ta. The remaining one phase of the three-phase AC power (u, v, w) is connected to the tap S.

  Under the above conditions, the primary and secondary voltage vectors in the Scott transformer 1 are expressed as shown in FIG. As can be seen from the figure, a two-phase alternating current (d-axis, q-axis) having a peak value of 90 ° and a phase difference equal to each other is obtained from the Scott transformer 1 by making the connection as shown in FIG. By applying this two-phase alternating current to the two-phase winding 5 of the alternating current exciter 13 and the two-phase winding 6 of the alternating current exciter 13, a rotating magnetic field is generated. The rotating magnetic field supplies power to the secondary side of the AC exciter 13 by interlinking with the secondary winding 4 of the AC exciter 13 that is stationary at the time of startup. When the current rectified by the rotary rectifier 7 provided in the rotor of the generator flows to the synchronous generator field winding 8, a fixed magnetic field linked to the synchronous generator armature winding 9 is generated, and the SFC is activated. Corresponding to

The AC voltage induced in the secondary winding 4 of the AC exciter 13 is proportional to the slip S of the AC exciter 13. The slip S is expressed by equation (1) in FIG. Here, the symbol Ns is the synchronization speed, and the symbol N is the rotor speed of the rotor. The synchronization speed Ns is expressed by equation (2). The symbol f represents the power supply frequency on the primary side of the AC exciter 13. The symbol p is the number of pole pairs that the AC exciter 13 has. When the power supply frequency f on the primary side of the AC exciter 13 is fixed, the slip S decreases as the rotor speed N of the rotor increases as shown in the equation (1). Accordingly, the voltage induced in the secondary winding 4 of the AC exciter 13 decreases as the rotational speed increases, and the current flowing through the synchronous generator field winding 8 cannot be kept constant. Therefore, the control unit 16 employs a method of switching from AC excitation to DC excitation by the excitation method switching device 3.

  Hereinafter, DC excitation will be described. At the time of DC excitation, the circuit breaker A10 and the circuit breaker B11 are disconnected, and the DC voltage control by the AC / DC converter 2 is started. A constant fixed magnetic field is generated by turning on the circuit breaker C12 and causing currents of the same value to flow in the two-phase winding 5 of the AC exciter 13 and the two-phase winding 6 of the AC exciter 13 which are orthogonal to each other. A constant fixed magnetic field generated from the two-phase winding 5 and the two-phase winding 6 is linked to the secondary winding 4 of the rotating AC exciter 13 to supply power to the secondary side. When the current rectified by the rotary rectifier 7 provided in the rotor of the generator flows through the synchronous generator field winding 8, a fixed magnetic field linked to the synchronous generator armature winding 9 is generated, and synchronous power generation is performed. The machine gets output.

Embodiment 2. FIG.
FIG. 7 illustrates the relationship among the AC / DC converter 2, the excitation method switching device 3, the speed detector 17, and the control unit 16 according to the second embodiment. In the second embodiment, the internal wiring of the excitation system switching device 3 is slightly different from the internal wiring of the excitation system switching device 3 according to the first embodiment. In the second embodiment, the two-phase winding 5 of the AC exciter 13 and the two-phase winding 6 of the AC exciter 13 are connected in parallel to the output terminal of the AC / DC converter 2. However, the overall circuit configuration of AC brushless excitation device 100 is the same as that of the first embodiment. The switching procedure from AC excitation to DC excitation is the same as the excitation method switching flowchart shown in the first embodiment.

By switching the excitation method from AC excitation to DC excitation by such a circuit configuration and excitation method switching flowchart, the two-phase winding 5 of the AC exciter 13 and the two-phase winding of the AC exciter 13 are switched during DC excitation. 6 has the same current. It is possible to obtain the same effect as that shown in the first embodiment.

Embodiment 3 FIG.
FIG. 8 is a circuit configuration diagram showing a rotating field type synchronous generator in the third embodiment of the present invention. In the third embodiment, the Scott transformer 1 shown in the first and second embodiments is a general three-phase transformer, and AC excitation is performed between any two wires on the secondary side of the three-phase transformer 15. The two-phase winding 5 of the machine 13 and the two-phase winding 6 of the AC exciter 13 are connected. The three-phase transformer 15 has a secondary side first phase line 15a, a secondary side second phase line 15b, and a secondary side third phase line 15c. The procedure for switching from AC excitation to DC excitation is the same as the excitation method switching flowchart shown in the first and second embodiments.

  FIG. 9 shows an internal circuit configuration of the excitation method switching device 3 according to the third embodiment. In this case, unlike the case where the Scott transformer 1 shown in the first embodiment is used, the two-phase winding 5 of the AC exciter 13 and the two-phase winding 6 of the AC exciter 13 have a phase difference of 120 °. Current with it flows. This current generates a rotating magnetic field interlinked with the secondary winding 4 of the AC exciter 13. Thus, even when the connection of a general three-phase transformer is changed, AC excitation is possible, and it is possible to cope with SFC activation of the generator. In addition, it is possible to obtain the same effect as that shown in the first or second embodiment.

Embodiment 4 FIG.
In the fourth embodiment, the Scott transformer 1 shown in the second embodiment is a general three-phase transformer, and two phases of the AC exciter 13 are arranged between any two wires on the secondary side of the three-phase transformer 15. The winding 5 and the two-phase winding 6 of the AC exciter 13 are connected. The three-phase transformer 15 has a secondary side first phase line 15a, a secondary side second phase line 15b, and a secondary side third phase line 15c. The fourth embodiment is different from the third embodiment in the internal circuit configuration of the excitation method switching device 3. The switching procedure from AC excitation to DC excitation is the same as the excitation method switching flowchart shown in the first embodiment.

  FIG. 10 shows an internal circuit configuration of the excitation method switching device 3 according to the fourth embodiment of the present invention. The three-phase transformer 15 has a secondary side first phase line 15a, a secondary side second phase line 15b, and a secondary side third phase line 15c. In this case, unlike the case where the Scott transformer 1 shown in the first and second embodiments is used, the two-phase winding 5 and the two-phase winding 6 of the AC exciter 13 have a phase difference of 120 °. Current with it flows. This current generates a rotating magnetic field interlinked with the secondary winding 4 of the AC exciter 13. Thus, even when the connection of a general three-phase transformer is changed, AC excitation is possible, and it is possible to cope with SFC activation of the generator. Further, it is possible to obtain the same effects as those shown in the first to third embodiments.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

  1 Scott transformer, 1d d-axis two-phase winding, 1q q-axis two-phase winding, 2 AC / DC converter, 2a plus pole terminal, 2b minus pole terminal, 3 excitation system switching device, 4 secondary winding, 5 2 Phase winding, 6 Two-phase winding, 7 Rotary rectifier, 8 Synchronous generator field winding, 9 Synchronous generator armature winding, 10 Breaker A, 10a terminal, 10b terminal, 11 Breaker B, 11a terminal , 11b terminal, 12 circuit breaker C, 12a terminal, 12b terminal, 13 AC exciter, 14 field winding synchronous generator, 15 three-phase transformer, 15a secondary side first phase wire, 15b secondary side second Phase wire, 15c Secondary side third phase wire, 16 control unit, 17 speed detector, 100 AC brushless excitation device, 200 power generation system

Claims (9)

When d-phase two-phase winding and q-axis two-phase winding are provided on the secondary side and three-phase AC power is input to the primary side, AC power is supplied to the d-axis two-phase winding and the q-axis two-phase winding. A Scott transformer to output,
An AC / DC converter having a first pole terminal and a second pole terminal on the secondary side, and outputting DC power from the three-phase AC power to the first pole terminal and the second pole terminal;
An AC exciter having a first two-phase winding and a second two-phase winding on the primary side and a secondary winding on the secondary side, a first terminal and a second terminal, and the first terminal Is connected to one side of the d-axis two-phase winding, and the first circuit breaker is connected to the second terminal on one side of the first two-phase winding;
A third terminal and a fourth terminal, wherein the third terminal is connected to the other side of the d-axis two-phase winding and one side of the q-axis two-phase winding; A second circuit breaker to which another side of the one two-phase winding and one side of the second two-phase winding are connected;
The fifth terminal is connected to the first pole terminal of the AC / DC converter, and one side of the first two-phase winding is connected to the sixth terminal. A third circuit breaker,
A speed detector for detecting the rotor speed;
A controller for controlling the AC / DC converter, the first circuit breaker, the second circuit breaker, and the third circuit breaker based on the output of the speed detector;
The AC brushless excitation device, wherein the other side of the q-axis two-phase winding is connected to the other side of the second two-phase winding.   2. The AC brushless exciter according to claim 1, wherein a second pole terminal of the AC / DC converter is connected to another side of the second two-phase winding.   The other side of the q-axis winding is connected to the fifth terminal, and the second pole terminal of the AC / DC converter is connected to one side of the second two-phase winding. Item 2. The AC brushless excitation device according to Item 1. The secondary side first phase line, the secondary side second phase line, and the secondary side third phase line, and when three-phase AC power is input to the primary side, the secondary side first phase line and the secondary side A three-phase transformer that outputs AC power to the second phase line and the secondary side third phase line;
An AC / DC converter having a first pole terminal and a second pole terminal on the secondary side, and outputting DC power from the three-phase AC power to the first pole terminal and the second pole terminal;
An AC exciter having a first two-phase winding and a second two-phase winding on the primary side and a secondary winding on the secondary side, a first terminal and a second terminal, and the first terminal Is connected to the secondary-side first phase wire, and the second terminal is connected to one side of the first two-phase winding, the first circuit breaker,
A third terminal and a fourth terminal, wherein the third terminal is connected to the secondary-side second phase wire, and the fourth terminal is connected to another side of the first two-phase winding and the second terminal A second circuit breaker to which one side of the two two-phase windings is connected;
The fifth terminal is connected to the first pole terminal of the AC / DC converter, and one side of the first two-phase winding is connected to the sixth terminal. A third circuit breaker,
A speed detector for detecting the rotor speed;
A controller for controlling the AC / DC converter, the first circuit breaker, the second circuit breaker, and the third circuit breaker based on the output of the speed detector;
The AC brushless excitation device, wherein the secondary third phase line is connected to another side of the second two-phase winding.   5. The AC brushless exciter according to claim 4, wherein the second pole terminal of the AC / DC converter is connected to another side of the second two-phase winding.   The secondary side third phase line is connected to the fifth terminal, and the second pole terminal of the AC / DC converter is connected to one side of the second two-phase winding. Item 5. The AC brushless excitation device according to Item 4.   When the SFC activation starts, the control unit turns on the first circuit breaker and the second circuit breaker, and when the rotor speed detected by the speed detector exceeds a set value, The AC brushless exciter according to any one of claims 1 to 6, wherein the circuit breaker and the second circuit breaker are disconnected and the third circuit breaker is inserted. An AC brushless excitation device according to any one of claims 1 to 7,
A rotary rectifier connected to the secondary winding of the AC exciter of the AC brushless exciter and outputting DC power to the secondary side;
And a field winding type synchronous generator to which DC power output from the rotary rectifier is input.   The field winding type synchronous generator has a synchronous generator field winding on the primary side and a synchronous generator armature winding on the secondary side, and the speed detector includes the secondary winding, the rotation The power generation system according to claim 8, wherein a rotor speed of a rectifier or the synchronous generator field winding is detected.

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