Control device for ac excitation generator motor

Abstract

A control device for an AC excitation generator motor comprises a phase difference calculator (202) that outputs a slip excitation phase obtained by comparison of an armature winding phase and a rotor phase of an AC excitation generator motor, a variable frequency oscillator (209) that outputs a synchronous excitation phase as a frequency command value of a synchronous excitation frequency, output switches (201a, 201b) that select and output the slip excitation phase or the synchronous excitation phase in accordance with an excitation selection signal, a command value holder (323) that, when the synchronous excitation phase is selected, holds a horizontal axis current command at a horizontal axis current command value (Iqrf_0) at the time of switching from the slip excitation phase to the synchronous excitation phase, and a slip excitation frequency calculator (203) that calculates a slip excitation frequency of the slip excitation phase, wherein: a stabilization gain (213) is provided, and by means of said stabilization gain (213), a horizontal axis current command stabilization correction value (Iq_stb) is calculated using the result of comparing the synchronous excitation and slip excitation frequencies as input; and the horizontal axis current command stabilization correction value (Iq_stb) is biased to the horizontal axis current command value (Iqrf_0).

Description

AC excitation generator motor control device

[0001] The present invention relates to a control device for an AC-excited generator-motor that uses a power converter to control excitation currents on two axes.

[0002] In particular, the present invention relates to a control device for an AC-excited generator-motor that is suitable for achieving both stability and responsiveness in the input / output and rotational speed adjustment functions of a generator-motor whose speed is made variable for the purpose of stable operation of power systems such as hydroelectric power generation facilities, pumped-storage power generation facilities, and wind power generation facilities.

[0003] The present invention also relates to a control device for an AC-excited generator-motor that is suitable for achieving both acceleration / deceleration performance and re-adhesion performance in electrically driven two-wheeled and four-wheeled vehicles or electrically driven / braked railway vehicles, by taking advantage of the characteristic of being able to constrain the generator-motor with a synchronizing force in response to a rotational speed command determined by the output frequency of a power converter.

[0004] An AC-excited generator-motor using an excitation current-controlled power converter can reduce the capacity of the power converter compared to the stator capacity of the generator-motor, and can achieve high-speed torque control or active power control within a rotational speed range around the synchronous speed. This has the advantage that turbomachinery such as pump-turbine systems and wind power generation systems can be operated at maximum efficiency over a wider range of operating output and rotational speed compared to conventional fixed-speed generator-motors.

[0005] When compared with a full-converter type variable-speed generator-motor, which connects a power converter between the armature winding and the AC system, an advantage of an AC-excited generator-motor is that the capacity of the power converter can be reduced.

[0006] In the case of AC-excited generator-motors, the rotational speed range is limited by the capacity of the power converter. On the other hand, in the case of full-converter type variable-speed generator-motors, the rotational speed range is limited by the characteristics of the turbomachinery. For this reason, the rotational speed range determined by cost-effectiveness is narrower for AC-excited generator-motors.

[0007] On the other hand, fluctuations in rotation speed due to disturbances are determined by the characteristics of the directly connected turbomachinery and AC system, and the influence of the selection of an AC-excited generator-motor or a full-converter type variable-speed generator-motor is minor.

[0008] Whichever method is selected, the operational rotation speed range must be narrowed by the amount of rotation speed fluctuation due to disturbances.

[0009] As a result, when comparing the reduction rate obtained by dividing the rotational speed range taking into account rotational speed fluctuations due to disturbances by the rotational speed range not taking them into account, the reduction rate for the AC-excited generator-motor is smaller than that for the full-converter type variable speed generator-motor, which has the disadvantage of compromising the advantage of the AC-excited generator-motor of being able to reduce the capacity of the power converter.

[0010] To address this drawback, Patent Document 1 discloses a method in which slip excitation, which is controlled based on a slip frequency reference synchronized with the phase of the stator voltage or effective magnetic flux as seen from the rotor, is used as a first means for normal operation, and synchronous excitation, which fixes the slip frequency at the time of switching from slip excitation to the excitation frequency, is used as a second means, and during synchronous excitation, the rotational speed is restricted to the speed at the time of switching by a synchronizing force.

[0011] Patent Document 2 discloses a method for maintaining the rotational speed at the start of pumping by applying the technology of Patent Document 1, adjusting the quadrature axis current according to the operating conditions after switching to synchronous excitation, and continuing synchronous excitation even when there is a large output fluctuation after switching to synchronous excitation.

[0012] Patent Document 3 discloses a method for correcting an active power command during slip excitation when the rotational speed deviates from a rotational speed setting range centered on the synchronous speed.

[0013] Patent Document 4 discloses a basic configuration of a control device suitable for applying an AC excitation generator-motor using slip excitation to a power generation facility.

[0014] Patent Document 5 discloses a basic configuration of a control device suitable for applying an AC excitation generator-motor using slip excitation to a pumping facility.

[0015] Patent Document 6 discloses a prime mover control device for a fixed speed synchronous generator that is suitable for switching to variable speed operation.

[0016] Patent No. 2947831 JP 2010-93985 JP 1-231698 Patent 2555407 JP 6-103023 International Publication No. 2023 / 139734

[0017] When an AC-excited generator-motor is operated under synchronous excitation, it has been found that if the rotational speed fluctuates due to disturbances from directly connected turbomachinery or an AC power system, the rotational speed begins to oscillate, and the amplitude of this oscillation increases over time. This poses the first problem of limiting the duration of synchronous excitation.

[0018] Furthermore, when an AC-excited generator-motor is operated with synchronous excitation, there is no method for adjusting the quadrature-axis current command that can be applied even when the torque fluctuation of the directly connected turbomachinery is unpredictable, and there is a second problem in that it is not possible to deal with general fluctuations in operating conditions, except for operating patterns in which the torque fluctuation of the turbomachinery is predictable, such as phase-modifying operation, self-excited operation, and pumped-storage start-up.

[0019] Furthermore, when generating electricity with synchronous excitation using an AC-excited generator-motor directly connected to turbomachinery such as a hydroelectric or wind turbine, the rotational speed cannot be adjusted to a target value according to the operating conditions during synchronous excitation operation, so it is necessary to switch from synchronous excitation back to slip excitation. This poses a third problem in that the drawbacks of slip excitation cannot be eliminated even when switching to synchronous excitation.

[0020] Furthermore, when an AC-excited generator-motor directly connected to turbomachinery such as a pump or fan is used for electric operation with synchronous excitation, the rotation speed cannot be adjusted to a target value according to the operating conditions during synchronous excitation operation, so it is necessary to return from synchronous excitation to slip excitation, and there is a fourth problem in that the drawbacks of slip excitation cannot be eliminated even when switching to synchronous excitation.

[0021] In order to solve the first problem, a quadrature axis current stabilization correction value is calculated by inputting the result of matching between the synchronous excitation frequency and the slip excitation frequency, and by applying this quadrature axis current stabilization correction value to the quadrature axis current command, damping is given to the rotational speed vibration during synchronous excitation, and the amplitude can be attenuated and stabilized.

[0022] In order to solve the second problem, the result of matching the synchronous excitation phase with the slip excitation phase is input, a quadrature axis current command correction value is calculated according to the absolute value and sign of the result, and this quadrature axis current command correction value is applied to a quadrature axis current command value that is maintained at the quadrature axis current command value at the time of switching from slip excitation to synchronous excitation, thereby making it possible to continue synchronous excitation stably even if the output or rotation speed is changed.

[0023] By solving the first problem, it is possible to reduce the power fluctuations required to keep the rotation speed within a set range during slip excitation, which in turn has the effect of suppressing fluctuations in the AC power system.

[0024] Furthermore, since the rotational speed fluctuation during synchronous excitation is reduced, the cumulative fluctuation of the guide vane opening or pitch angle of the turbomachinery is reduced, which results in reduced wear on the drive device for the guide vane opening or pitch angle, thereby extending the life of the drive device.

[0025] By solving the second problem, it is possible to suppress speed fluctuations caused by disturbances from turbomachinery by regularly using synchronous excitation near the upper and lower limits of the rotational speed range. This has the effect of expanding the operational speed range that previously excluded rotational speed fluctuations, and improving partial load efficiency during power generation operation. Widening the input range during pumping operation has the effect of improving the frequency regulation capability of the AC system.

[0026] The above-described device configuration and control method can achieve the desired objectives.

[0027] FIG. 1 is a configuration diagram of a conventional AC excitation generator / motor. FIG. 2 is a configuration diagram of a conventional plant control device during power generation. FIG. 3 is a configuration diagram of a conventional excitation phase calculator. FIG. 4 is a configuration diagram of a conventional quadrature axis current command calculator. FIG. 5 is a diagram showing coordinate systems for slip excitation and synchronous excitation. FIG. 6 is a configuration diagram of a conventional synchronous excitation frequency calculator. FIG. 7 is a conventional state transition diagram. FIG. 8 is a configuration diagram of a conventional plant control device during adjustable speed pumped storage operation. FIG. 9 is a configuration diagram of a plant control device for a conventional fixed speed generator. FIG. 10 is a waveform diagram of an active power ramp response during conventional slip excitation for power generation. FIG. 11 is a waveform diagram of an active power ramp response during conventional synchronous excitation for adjustable speed power generation. FIG. 12 is a configuration diagram of a plant control device during power generation according to the first embodiment. FIG. 13 is a configuration diagram of a plant control device during motoring according to the first embodiment. FIG. 14 is a configuration diagram of a quadrature axis current command calculator according to the first embodiment. FIG. 15 is a waveform diagram of an active power ramp response during power generation according to the first embodiment. FIG. 16 is a waveform diagram of an active power ramp response during power generation according to the first embodiment. Fig. 17 is a configuration diagram of a plant control device during power generation according to the second embodiment. Fig. 18 is a configuration diagram of a plant control device during motorization according to the second embodiment. Fig. 19 is a configuration diagram of a quadrature axis current command calculator according to the second embodiment. Fig. 20 is a configuration diagram of a limiter with a dead band of the quadrature axis current command calculator according to the second embodiment. Fig. 21 is a state transition diagram according to the second embodiment. Fig. 22 is an active power ramp response waveform diagram during power generation according to the second embodiment.

[0028] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a control device for an AC-excited generator-motor according to the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention is not limited to the embodiment.

[0029] FIG. 1 is a diagram showing the configuration of an AC excitation generator-motor disclosed in Patent Documents 1 to 5.

[0030] An armature winding terminal 1 a of an AC excitation generator motor (ASG) 1 is connected to an AC power system (PS) 2 via a main transformer (MTR) 3 and a synchronous circuit breaker (CB) 4 .

[0031] The rotor winding of the AC excitation generator motor (ASG) 1 is connected to the low frequency output side of the semiconductor power converter (ACEx) 5 via a slip ring 1b.

[0032] The AC frequency input side of the semiconductor power converter (ACEx) 5 is branch-connected between the synchronous circuit breaker (CB) 4 and the main transformer (MTR) 3 via an excitation circuit breaker (ExCB) 6 and an excitation transformer (ExTR) 7.

[0033] The turbomachine (WT) 8 is mechanically connected to the rotating shaft of the AC-excited generator motor (ASG) 1 .

[0034] The turbomachine (WT) 8 has fixed vanes 9 arranged around the rotor vanes. A governor (GOV) 10 adjusts the governor opening (GVO) of the fixed vanes 9 (hereinafter referred to as guide vanes in the present invention) in accordance with an opening command GVOrf from a plant control device 11, and feeds back the opening signal GVO to the plant control device 11.

[0035] When the plant is started up, the voltage signal Vs from the potential transformer 12 and the voltage signal Vg from the potential transformer 13 are input to a synchronism detector (Syn) 14 to check the voltage amplitude and phase difference before parallel connection, and then the synchronism circuit breaker (CB) 4 is closed in response to a parallel connection command (Synrf) from the plant control device 11 to start parallel operation.

[0036] During parallel operation, the system voltage signal (Vs) from the potential transformer 12 and the system current signal (Is) from the current transformer 15 are input to the output / voltage phase calculator 107, which measures and calculates the positive-sequence voltage phase (th_v) of the AC power system, and the active power output (Pfb) and reactive power output (Qfb) of the plant, and outputs them to the plant control device 11. The generator motor voltage signal (Vg) from the potential transformer 13 is input to the voltage amplitude calculator 19, which measures and calculates the generator positive-sequence voltage (Vfb), and outputs it to the plant control device 11.

[0037] The excitation current transformer 16 is composed of a Hall element or the like capable of measuring DC current, and outputs rotor currents (Iru, Irv, Irw) of the AC excitation generator motor (ASG) 1 to the plant control device 11.

[0038] The rotational speed measuring device (SS) 17 measures the rotational speed signal (Nfb) with a pulse counter that detects the speed with an air gap detector provided on the gear and stator side, and outputs the signal to the plant control device 11 .

[0039] Hereinafter, in this application, the synchronous speed at which the rotor currents (Iru, Irv, Irw) become DC is defined as the "rotation speed signal (Nfb=100[%])."

[0040] A resolver rotating machine (Res) 18 is used as the rotating machine for phase measurement. In Fig. 1, the resolver rotating machine (Res) 18 has two-phase windings on the stator side and rotor side, with the same number of poles as the AC excited generator motor (ASG) 1. The stator winding is excited using a two-phase oscillator output from a rotational phase calculator 108 as a modulation input, and a two-phase voltage signal of the rotor winding is output as a demodulated output to the rotational phase calculator 108 via slip ring 1b. The rotational phase calculator 108 outputs the rotational phase (th_rt) to the plant control device 11.

[0041] Figure 1 shows an example of a Francis pump turbine used as the turbomachine. When a Kaplan turbine or a wind turbine that adjusts the pitch angle of the rotor blades is used as the output adjustment means for the turbomachine, the explanation in Figure 1 is valid by replacing the governor opening (GVO) with the rotor blade pitch angle.

[0042] To avoid repetition, the present invention will be described below using a Francis pump turbine as an example of the turbomachinery (WT) 8, but the scope of application of the present invention is not limited to a Francis pump turbine.

[0043] FIG. 2 is a diagram showing the configuration of the plant control device 11 during variable speed power generation operation disclosed in Patent Documents 1, 3, and 4.

[0044] An optimum GVO function generator 101 outputs a governor opening signal (Yopt) corresponding to a plant active power command (Prf) from the turbine characteristics, and outputs a governor opening correction command (GVO_add) via a delay circuit 102 .

[0045] Hereinafter, for simplicity, the input of the effective head or static head signal to the optimum GVO function generator 101 will be omitted in the present invention.

[0046] An optimal speed function generator 103 outputs an optimal speed signal (Nopt) corresponding to a plant active power command (Prf), and outputs a rotational speed command (Nrf) via a delay circuit 104. The rotational speed command (Nrf) and the rotational speed signal (Nfb) are matched and input to a speed regulator (ASR) 105, and the output of the speed regulator (ASR) 105 is urged to a governor opening correction command (GVO_add), which outputs a governor opening command (GVOrf).

[0047] Hereinafter, for the sake of simplicity, the input of the effective head or static head signal to the optimum speed function generator 103 will be omitted in the present invention.

[0048] An automatic voltage regulator (AVR) 106 receives the result of matching the voltage command (Vrf) with the generator positive-phase voltage (Vfb) from the voltage amplitude calculator 19, and outputs a direct-axis current command (Idrf).

[0049] The output / voltage phase calculator 107 outputs two-phase signals cos(th_v) and sin(th_v) of the positive-sequence voltage phase (th_v) of the AC power system, and also outputs the plant active power output (Pfb).

[0050] The rotational phase calculator 108 outputs two-phase signals cos(th_rt) and sin(th_rt) of the rotational phase (th_rt) expressed in electrical angle of the AC excitation generator motor (ASG) 1 .

[0051] The excitation phase calculator 109 receives two-phase positive-sequence voltage phase signals cos(th_v) and sin(th_v), two-phase rotation phase signals cos(th_rt) and sin(th_rt), and a synchronous excitation frequency (Fs_soln), and outputs excitation phase signals cos(beta) and sin(beta) of the excitation phase (beta). It also outputs a sine function sin(dlt) of the phase difference (dlt) obtained by matching the synchronous excitation phase and the slip excitation phase. It also outputs the measurement and calculation result of the slip excitation frequency (Fs_sein).

[0052] The synchronous excitation frequency calculator 110 receives the slip excitation frequency (Fs_sein) and the excitation selection signal (A or S), and outputs an excitation selection command (A or S_rf) and the synchronous excitation frequency (Fs_soln).

[0053] The state transition controller 111 receives an excitation selection command (AorS_rf) from the synchronous excitation frequency calculator 110, receives a transition completion response (StoA_ack) from the quadrature axis current command calculator 113 to indicate the completion of transition from synchronous excitation to slip excitation, and toggles between outputting the excitation selection command (AorS_rf) and the excitation selection signal (AorS). Hereinafter, in the present invention, the excitation selection command (AorS_rf) and the excitation selection signal (AorS) are both set to level H during slip excitation and level L during synchronous excitation.

[0054] Hereinafter, the excitation selection signal (A or S) lines from the state transition controller 111 to the excitation phase calculator 109, the synchronous excitation frequency calculator 110 and the quadrature axis current command calculator 113 will be omitted to avoid complexity.

[0055] The three-phase to two-phase converter 112 converts the three-phase rotor currents (Iru, Irv, Irw) from the excitation current transformer 16 into two-phase rotor currents (Ird, Irq) according to the excitation phase (beta), and outputs the converted currents. The three-phase to two-phase converter 112 converts the two-phase rotor currents (Ird, Irq) into DC currents during steady operation. The calculation formula for the three-phase to two-phase converter 112 is shown in Equation (1).

[0056]

[0057] The quadrature axis current command calculator 113 receives an excitation selection command (AorS_rf), an active power command (Prf), an active power output (Pfb), and a matching phase (dlt) between the synchronous excitation phase and the slip excitation phase, and outputs a response indicating the completion of transition from synchronous excitation to slip excitation (StoA_ack) and a quadrature axis current command (Iqrf).

[0058] A quadrature axis current regulator (q_ACR) 114 receives the result of matching between the quadrature axis current command (Iqrf) and the quadrature axis current (Irq), and outputs a quadrature axis voltage command (αq) to a two-phase to three-phase converter 116 .

[0059] A direct-axis current regulator (d_ACR) 115 receives the result of matching between the direct-axis current command (Idrf) and the direct-axis current (Ird), and outputs a direct-axis voltage command (αd) to a two-phase to three-phase converter 116 .

[0060] The two-phase to three-phase converter 116 receives the direct-axis voltage command (αd) and the quadrature-axis voltage command (αq) and outputs three-phase voltage commands (αu, αv, αw) to the semiconductor power converter (ACEx) 5. The calculation formula of the two-phase to three-phase converter 116 is shown in Equation (2).

[0061]

[0062] FIG. 3 is a diagram showing an excitation phase calculator 109 disclosed in Patent Documents 1 and 3, etc.

[0063] The output switches 201a, 201b, and 201c select and output the input on the terminal a side during slip excitation, and the input on the terminal s side during synchronous excitation.

[0064] The phase difference calculators (PDF) 202, 204, and 210 input two sets of two-phase signals and output two-phase phase difference signals, which are obtained by subtracting the phase of the second set of terminals (c, d) from the phase of the first set of terminals (a, b), and output the resulting two-phase signal from the third set of terminals (e, f).

[0065] The phase difference calculator (PDF) 202 outputs a two-phase signal of the slip excitation phase (th_sein). The relationship between the slip excitation phase (th_sein), the positive sequence voltage phase (th_v), and the rotation phase (thrt) is (th_sein=th_v-th_rt).

[0066] The two-phase signal of the slip excitation phase (th_sein) is branched and input to a first set of terminals (a, b) of the phase difference calculator (PDF) 204, and then input to a second set of terminals (c, d) of the phase difference calculator (PDF) 204 via a delay circuit 205.

[0067] The delay circuit 205 comprises two sets of Nf delay elements 206a connected in series. The delay elements 206a delay the output by a calculation period ΔT.

[0068] The delay circuit 205 outputs a two-phase signal of the slip excitation phase (th_sein_old) Nf×ΔT [seconds] before.

[0069] The phase difference calculator (PDF) 204 outputs a two-phase signal of the phase change (th_df) of the slip excitation phase (th_sein) for Nf×ΔT seconds from a third set of terminals (e, f).

[0070] The relationship between the phase change (th_df), the slip excitation phase (th_sein), the slip excitation phase (th_sein_old) Nf×ΔT [seconds] before, and the phase change (th_df) is "th_df=th_sein-th_sein_old".

[0071] A two-phase signal of the phase change (th_df) is input to an arcsine function calculator 207, which outputs a slip excitation frequency (Fs_sein) via a gain [1 / (2πNfΔT)] 208.

[0072] A two-phase variable frequency oscillator (VCO) 209 receives a synchronous excitation frequency (Fs_soln) from a terminal a, receives a reference phase signal from a terminal b, and outputs a two-phase signal of a synchronous excitation phase (th_soln) from terminals (c, d).

[0073] A two-phase variable frequency oscillator (VCO) 209 receives an excitation selection signal (A or S) and operates selectively.

[0074] A two-phase variable frequency oscillator (VCO) 209 outputs a two-phase signal of the synchronous excitation frequency (Fs_soln) from the synchronous excitation frequency calculator 110 .

[0075] During slip excitation, the switch 201c selects and outputs the slip excitation phase signal sin(th_sein) from the input to the terminal a, and updates the reference phase signal to the terminal b of the two-phase variable frequency oscillator (VCO) 209 as the slip excitation phase signal sin(th_sein) every calculation period. Also, the synchronous excitation frequency command (Fs_soln) input from the terminal a of the two-phase variable frequency oscillator (VCO) 209 tracks the slip excitation frequency (Fs_sein). In this way, the two-phase signal of the synchronous excitation phase (th_soln) from the terminals (c, d) of the two-phase variable frequency oscillator (VCO) 209 tracks and outputs the slip excitation phase (th_sein).

[0076] During synchronous excitation, the switch 201c fixes and holds the slip excitation phase signal sin (th_sein) at the time of switching from slip excitation to synchronous excitation via the delay element 206b from the terminal s. As a result, the two-phase signal of the synchronous excitation phase (th_soln) from the terminals (c, d) of the two-phase variable frequency oscillator (VCO) 209 is updated and output with the phase advanced by (2π×Fs_soln×ΔT) every calculation period, thereby outputting a two-phase signal following the synchronous excitation frequency (Fs_soln) from the synchronous excitation frequency calculator 110.

[0077] The slip excitation phase signals cos(th_sein) and sin(th_sein) or the synchronous excitation phase signals cos(th_soln) and sin(th_soln) are selectively output as excitation reference phase signals cos(th_beta) and sin(th_beta) by output switches 201a and 201b.

[0078] FIG. 4 is a diagram showing a quadrature axis current command calculator 113 disclosed in Patent Documents 1 and 3, etc.

[0079] The one-shot switch 302 of the active power regulator 301 always selects and outputs the R terminal side, and selects and outputs the OneShot side only for one calculation period when transitioning from synchronous excitation to slip excitation.

[0080] The operation of active power regulator 301 when one-shot switch 302 selects and outputs the R terminal side will be described below.

[0081] During slip excitation, the plant active power command (Prf) and the plant active power output (Pfb) are compared and input to a proportional gain (Cp) 303. The output of the proportional gain (Cp) 303 is branched and input to an integrator consisting of an integral gain 304, an adder 305a, and a delay element 206c, and a proportional-integral controller is configured with an adder 305b. In the example of FIG. 4, limiters 306a and 306b of the proportional-integral controller are provided. A command value holder 323 is composed of a delay element 206d and an output switch 307a, and outputs the output of limiter 306b as a quadrature-axis current command (Iqrf) via the inputs of terminals a of switches 307a and 307b.

[0082] During synchronous excitation, the s terminals of the output switches 307a and 307b are selected, and the output (Iqrf_0) of the output switch 307a immediately before the synchronous excitation was selected by the delay element 206d is held. This prevents a sudden change in the output of the output switch 307a when switching from slip excitation to synchronous excitation.

[0083] The output of the output switch 307a activates the quadrature axis current correction (Iq_ad) that is output via the s terminal of the output switch 307c, and outputs the quadrature axis current command (Iqrf) via the s terminal of the output switch 307b.

[0084] When the AND 316 of the quadrature axis current correction calculator 317 selects slip excitation at level H for the excitation selection command (AorS_rf) while the excitation selection signal (AorS) is at level L for synchronous excitation, the output of the flip-flop 309 is set via the OR 315, and the signal (StoA_ack) during transition from synchronous excitation to slip excitation becomes level H.

[0085] A limiter 310 with a dead band inputs a phase difference (dlt) obtained by matching the synchronous excitation phase and the slip excitation phase from the x terminal, and when the absolute value of the phase difference exceeds a threshold value (ep), the output of the flip-flop 309 is set via a logical sum 315 and a logical product 316, and the signal (StoA_ack) indicating a transition from synchronous excitation to slip excitation becomes level H.

[0086] When the absolute value of the phase difference (dlt) between the synchronous excitation phase and the slip excitation phase falls below the threshold value (ep), the limiter with dead band 310 outputs 0, and activates the reset input of the flip-flop 309 via the absolute value output 312, the comparator 313 that outputs level L when the input is positive, the delay element 206g, and the logical product 314, and the signal (StoA_ack) during the transition from synchronous excitation to slip excitation becomes level L.

[0087] The limiter 310 with dead band selectively outputs a negative fixed output (-ΔI) when the phase difference (dlt) between the synchronous excitation phase and the slip excitation phase exceeds a threshold value (+ep) in the positive direction, a positive fixed output (+ΔI) when the phase difference (dlt) exceeds the threshold value (-ep) in the negative direction, or 0 when the absolute value is equal to or less than the threshold value (ep).

[0088] When the output of the limiter with dead band 310 is a negative fixed output (-ΔI), the quadrature axis current correction (Iq_ad) is subtracted by (-ΔI) for each calculation cycle by the adder 311 and the delay element 206f, and when the output is a positive fixed output (+ΔI), it is added and output.

[0089] In the example of FIG. 4, a limiter 306c is provided, and the quadrature axis current correction (Iq_ad1) whose output absolute value is limited is passed through the s terminal of the output switch 307 and applied to the quadrature axis current command (Iqrf) as the quadrature axis current correction (Iq_ad).

[0090] FIG. 4 shows a case where the sign of the quadrature axis current command (Iqrf) is defined so that the absolute value increases in the positive direction as the active power or torque output increases in both the power generation and motoring directions.

[0091] The sign of the phase difference (dlt) indicates the case where the leading phase of the synchronous excitation phase (th_soln) relative to the slip excitation phase (th_sein) is defined as positive.

[0092] FIG. 5 shows a vector diagram illustrating the relationship between the slip excitation phase (th_sein) and the synchronous excitation phase (th_soln) of the AC excitation generator motor (ASG) 1.

[0093] The horizontal axis is the direct axis (d-axis) of the slip excitation phase (th_sein), and the vertical axis (q-axis) which leads the direct axis (d-axis) by 90 degrees is synchronized with the stator positive sequence voltage phase as seen from the rotor of the AC excitation generator motor (ASG) 1, and the case where it rotates counterclockwise at a positive slip excitation frequency (Fs_sein) will be described.

[0094] For simplicity, it is assumed below that the quadrature axis current command (Iqrf) and the quadrature axis current (Iq) and the direct axis current command (Idrf) and the direct axis current (Id) are the same. This assumption is reasonable because it considers a case where the change in the current command value in Fig. 5 occurs at a frequency sufficiently low relative to the response frequencies of the quadrature axis current regulator (q_ACR) 114 and the direct axis current regulator (d_ACR) 115, and the absolute value change is small.

[0095] In the case of slip excitation, the current (Id, Iq) corresponds to point A. When synchronous excitation is performed with a phase difference (dlt) between the synchronous excitation phase and the slip excitation phase, even if the excitation current command is the same (Id, Iq) as in slip excitation, the excitation current acting on the AC excitation generator motor (ASG) 1 rotates and moves from point A to point B, which is advanced by the phase difference (dlt), and the effective current becomes (d0, q0).

[0096] Here, when the quadrature axis current command (Iqrf) decreases by ΔIqrf, the point moves from point B to point C, and the quadrature axis current decreases from q0 to q1.

[0097] When the direct-axis current command (Idrf) increases by ΔIdrf, the point moves from point B to point D, and the direct-axis current increases from d0 to d1.

[0098] When the quadrature axis current command (Iqrf) and the direct axis current command (Idrf) are changed simultaneously, the point moves from point B to point E.

[0099] Now, when the quadrature axis current command is decreased in a stepwise manner by ΔIqrf, the actual quadrature axis current also decreases from q0 to q1 at the response speed of the quadrature axis current regulator (q_ACR).

[0100] The power generation mode will be described below: In the power generation mode, the turbomachine (WT) 8 generates an acceleration torque, and the generator generates a deceleration torque.

[0101] If the response of the turbomachine (WT) 8 to changes in the quadrature-axis current Iq is sufficiently slow and the output torque can be considered constant, the deceleration torque of the AC-excited generator motor (ASG) 1 decreases with a decrease in the quadrature-axis current, the rotation phase advances slightly, and the synchronizing force settles it at a balanced phase with the acceleration torque of the turbomachine (WT) 8. As a result, the phase difference (dlt) between the synchronous excitation phase and the slip excitation phase decreases.

[0102] Next, the case of the electric mode will be explained. In the case of a pump-turbine, the rotation direction is actually reversed, and the vector rotation direction in Figure 5 is also reversed. Here, we will simplify the explanation by assuming that "it rotates counterclockwise, the same as when generating electricity."

[0103] In the electric mode, the electric motor generates an accelerating torque, and the turbomachinery (WT) 8 generates a decelerating torque by pumping.

[0104] The response of the turbomachine (WT) 8 to changes in the quadrature-axis current Iq is sufficiently slow, and when the load torque can be considered constant, the acceleration torque of the AC-excited generator motor (ASG) 1 decreases with a decrease in the quadrature-axis current, the rotation phase lags slightly, and the synchronizing force settles it at a balanced phase with the deceleration torque of the turbomachine (WT) 8. As a result, the phase difference (dlt) between the synchronous excitation phase and the slip excitation phase decreases.

[0105] As described above, if the time rate of change of the quadrature axis current command is within the limit value, the phase difference (dlt) between the synchronous excitation phase and the slip excitation phase can be adjusted to match by gradually increasing or decreasing the quadrature axis current command. This makes it possible to switch from synchronous excitation to slip excitation without causing a sudden change in torque.

[0106] A method for switching from synchronous excitation to slip excitation using the above-mentioned action will be explained by returning to FIG.

[0107] When slip excitation is selected during synchronous excitation operation (A or S is level L) and the excitation selection command (A or S_rf) becomes level H, if the synchronous excitation phase (th_soln) leads the slip excitation phase (th_sein) and sin (dlt) exceeds the threshold value (+ep), the quadrature axis current correction (Iq_ad) gradually decreases from 0 in the negative direction, reducing the deceleration torque of the AC excitation generator motor (ASG) 1, the rotation phase (th_rt) leads, the phase difference (dlt) decreases toward 0, the slip excitation phase (th_sein) and the synchronous excitation phase (th_soln) change in the direction of matching and fall below the threshold value (ep), and the output of the limiter with dead band 310 becomes 0.

[0108] On the other hand, when the synchronous excitation phase (th_soln) is in the lagging direction and sin(dlt) exceeds the threshold value (-ep), the quadrature axis current correction (Iq_ad) gradually increases from 0 in the positive direction, the slip excitation phase (th_sein) and the synchronous excitation phase (th_soln) change in the direction of matching, and the output of the limiter with dead band 310 becomes 0.

[0109] The absolute value of the phase difference (dlt) gradually decreases due to the above adjustment of the quadrature axis current correction (Iq_ad). When the absolute value of the phase difference (dlt) falls below the threshold (ep), the output of the limiter with dead band 310 is branched to an absolute value output 312, a comparator 313 that outputs a level L when the input is positive, a delay element 206g, and a logical product circuit 314, and the reset input of the flip-flop 309 is activated.

[0110] The output of the flip-flop 309 is output to the outside as a signal (StoA_ack) indicating that the excitation is in transition from synchronous excitation to slip excitation.

[0111] When detecting the falling edge of the signal (StoA_ack) during transition from synchronous excitation to slip excitation, the output switches 307a, 307b, and 307c switch the output from the s-terminal input to the a-terminal input.

[0112] Only during one calculation period when switching from synchronous excitation to slip excitation, one-shot switch 302 selects and outputs correction signal (Iq_bump). The correction signal (Iq_bump) is the result of matching the quadrature axis current command (Iqrf) during synchronous excitation held by delay element 206e with the output of proportional gain (Cp) 303, and by energizing correction signal (Iq_bump) by adder 305a, it is possible to suppress sudden changes in the integral output of active power regulator 301, suppress sudden changes in the quadrature axis current command (Iqrf), and suppress sudden changes in the output of AC excitation generator motor (ASG) 1.

[0113] The smaller the threshold value (ep), the more the output fluctuation of the AC excitation generator motor (ASG) 1 can be suppressed when transitioning from synchronous excitation to slip excitation, but the longer the transition period during which the transition signal (StoA_ack) is at level H. One electrical angle is a guideline for setting the threshold value (ep).

[0114] The larger the fixed output set value (ΔI), the shorter the transition period, but the higher the risk of output fluctuation during the transition of the AC excitation generator-motor (ASG) 1. The fixed output set value (ΔI) needs to be smaller the smaller the short-circuit ratio of the AC excitation generator-motor (ASG) 1, the shorter the inertia time constant of the rotating part, and in the case of hydroelectric power generation equipment, the longer the time constant of the hydraulic system.

[0115] FIG. 6 is a diagram showing the synchronous excitation frequency calculator 110.

[0116] When the slip excitation is selected, the output switch 401 selects the input to the terminal a, and the synchronous excitation frequency (Fs_soln) outputs the slip excitation frequency (Fs_sein).

[0117] The limiter 402 with dead band and hysteresis outputs a negative fixed output (-ΔF) when the rotation speed of the AC excitation generator motor (ASG) 1 decreases and the slip excitation frequency (Fs_sein) exceeds a threshold value (Fs_1), and returns to 0 output when it falls below a threshold value (Fs_2).Furthermore, when the rotation speed of the AC excitation generator motor (ASG) 1 increases and the slip excitation frequency (Fs_sein) exceeds the threshold value (-Fs_1) in the negative direction, the limiter outputs a positive fixed output (+ΔF), and returns to 0 output when it exceeds the threshold value (-Fs_2).

[0118] When the limiter 402 with dead band and hysteresis selects and outputs a value other than 0, the output of the comparator 404 changes from level H to level L due to the absolute value output 403, the excitation selection command (A or S_rf) becomes level L, and a request to switch from slip excitation to synchronous excitation is output to the state transition controller 111.

[0119] When the excitation selection signal (AorS) from the state transition controller 111 becomes level L, the excitation is switched to synchronous excitation and the quadrature axis current command (Iqrf) is maintained.

[0120] Only during one calculation cycle in which the excitation selection signal (A or S) output switches from level H to level L, the one-shot switch 405 selects and outputs the slip excitation frequency (Fs_sein), the output switch 401 selects and outputs the One_Shot terminal, and thereafter selects the R terminal and holds the slip excitation frequency (Fs_sein) at the time of transition by the delay element 206h.

[0121] When synchronous excitation is selected, the limiter 402 with dead band and hysteresis outputs a fixed value on the positive side (+ΔF) or negative side (-ΔF). Therefore, the adder 407 and delay element 206i gradually increase or decrease the synchronous excitation frequency correction (Fs_ad) in each calculation cycle in the direction of decreasing the absolute value of the synchronous excitation frequency (Fs_soln). The synchronous excitation frequency correction (Fs_ad) is applied to the output of the one-shot switch 405 by the adder 409.

[0122] As the absolute value of the synchronous excitation frequency (Fs_soln) gradually decreases, the rotation speed approaches the synchronous speed due to the synchronizing force of the AC excitation generator motor (ASG) 1, and the absolute value of the slip excitation frequency (Fs_sein) falls below the threshold value (Fs_2). At this point, the excitation selection command (AorS_rf) output to the state transition controller 111 changes to level H, the state transition controller 111 outputs the excitation selection command (AorS_rf) at level H, the quadrature axis current command calculator 113 outputs a level H response (StoA_ack) indicating completion of transition from synchronous excitation to slip excitation, starts transition to slip excitation, and gradually increases or decreases the quadrature axis current command (Iqrf) so that the absolute value of the phase difference (dlt) between the synchronous excitation phase and the slip excitation phase approaches 0. When the absolute value of the phase difference (dlt) falls below the threshold value (ep), the transition completion response (StoA_ack) from synchronous excitation to slip excitation outputs level L, and slip excitation begins.

[0123] FIG. 7 is a state transition diagram showing the operation of the state transition controller 111 described above.

[0124] The operating state transitions between three states. There are two state variables that distinguish these three states: excitation selection (AorS) and synchronous excitation selection (SWs).

[0125] The excitation selection (A or S) is a binary selection of slip excitation (level H) and synchronous excitation (level L).

[0126] The synchronous excitation selection (SWs) is a binary selection of either gradually decreasing the synchronous excitation frequency (Fs_soln) (level 1) or gradually decreasing the phase difference (dlt) up to a threshold value (ep) (level 0).

[0127] Iqrfd in FIG. 7 indicates the previous output value of the quadrature axis current command (Iqrf).

[0128] The state control signals for the state transition include an excitation selection command (AorS_rf) and a response indicating completion of transition from synchronous excitation to slip excitation (StoA_ack). The state transition controller 111 controls the state transition using the above state variables and state control signals.

[0129] FIG. 8 is a diagram showing the configuration of a plant control device 11 during variable speed pumping operation disclosed in Patent Documents 1 and 5, etc.

[0130] The same numbers and symbols as those in the previous Figures 1 to 8 indicate the same components and signals, respectively, and therefore their explanations will be omitted to avoid duplication.

[0131] The optimum GVO function generator 701 outputs an optimum governor opening signal (Yopt) according to the higher-order active power command (Prf_0) from the pump characteristics, and outputs it as a governor opening command (GVOrf).

[0132] Hereinafter, for simplicity, the input of the effective head or static head signal to the optimum GVO function generator 701 will be omitted in the present invention.

[0133] The optimum speed function generator 702 outputs an optimum speed signal (Nopt) according to the higher-order active power command (Prf_0) from the pump characteristics, and outputs a rotation speed command (Nrf) via a delay circuit 703 .

[0134] Hereinafter, for simplicity, the input of the effective head or static head signal to the optimum speed function generator 702 will be omitted in the present invention.

[0135] The rotation speed command (Nrf) and the rotation speed signal (Nfb) are matched and input to a speed regulator (ASR) 704, the output of the speed regulator (ASR) 704 is biased to a higher-order active power command (Prf_0) as an active power correction (Prf_ad), and the biased output is input to a quadrature axis current command calculator 113 as an active power command (Prf).

[0136] With the above configuration, the output of the speed regulator 704 is biased to a command to the input side of the active power regulator 301 inside the quadrature axis current command calculator 113, which has the effect of allowing the internal active power regulator 301 to control the active power (Pfb) at high speed while preventing deviations from the rotational speed.

[0137] FIG. 9 is a diagram showing the configuration of a plant control device 11 for a fixed-speed power generating system using a synchronous generator disclosed in Patent Document 6 and the like.

[0138] Synchronous excitation differs from DC-excited synchronous generators in that the excitation current is AC and has a variable frequency, but it is the same as DC-excited synchronous generators in that the rotational speed is adjusted by a synchronizing force.

[0139] Here, the configuration is shown in which the optimum GVO function generator 101 is common to the optimum GVO function generator 101 in FIG. 2 and only the function at the synchronous speed is used.

[0140] The same numbers and symbols as those in the previous Figures 1 to 8 indicate the same components and signals, and therefore their explanations will be omitted to avoid duplication.

[0141] The optimum governor opening signal (Yopt) from the optimum GVO function generator 101 is delayed by a first-order lag circuit consisting of an adder / subtractor 802, a limiter 803, and an integrator 801 with a time constant Ty, with a first-order lag characteristic of the time constant Ty, if the time rate of change of the opening command Yd is below a limit value. A limiter 808 operates to suppress the time rate of change below the response limit of the water turbine (WT). The opening command Yd and the governor opening (GVO) are matched and input to a droop rate gain 805, and the output is induced by an adder / subtractor 806 to a constant synchronous speed command (N_0) as a rotational speed command correction (N_ad), matched with the rotational speed signal (Nfb), and input to the speed regulator (ASR) 105.

[0142] In actual plant operation, rather than when the output command (Prf) from the upper control system is given as an absolute value in power units, unit increase / decrease commands are given in the form of intermittent pulses, and matching between the output command (Prf) and the power generation output (Pfb) is often performed by the upper control system. Here, the operation of the above upper control system is simulated by a limiter 807 and an integrator 808, and the cumulative value of the output increase / decrease commands is represented by the guide vane command correction Yrf_ad.

[0143] Figure 10 shows a transient phenomenon in an adjustable speed pumped storage power generation system designed with the device shown in Figures 1 to 7 and a plant variable speed range of 4%. From a steady operating state with a power generation output of 30%, at time t1 = 0 seconds, the output command (Prf) ramps up by 10% over 3 seconds (at a so-called 30-second rate), and after time t2 = 3 seconds, the output command (Prf) is maintained constant at 40%.

[0144] In the above case, since the range of change of the power generation output (Pfb) is low relative to the rated output, the rotational speed command (Nrf) of the optimal speed function 103 is set to approximately the minimum speed of 96% in order to increase the efficiency of the Francis pump turbine.

[0145] FIG. 10 shows a transient response when the plant control device 11 of FIG. 2 is used, the set value (Fs_1) is temporarily set to a value one digit larger than 4.67% and only slip excitation is used.

[0146] When the governor opening GVO of the Francis pump turbine (turbomachine (WT) 8) begins to open, the flow rate Flow increases, but this is offset by the decrease in the effective head Hef, and the output (Pt) hardly increases.

[0147] Since the output (Pfb) of the AC excitation generator motor (ASG) 1 increases before the output (Pt) of the Francis pump turbine (turbomachine (WT) 8) increases, the shortage of power supply from the turbine output (Pt) is compensated for by the flywheel energy of the rotating part and converted into the output (Pfb) of the AC excitation generator motor (ASG) 1. As a result, the rotation speed (Nfb) decreases and the slip excitation frequency (Fs_sein) begins to increase. At time t3 = 2.8 [seconds], the slip excitation frequency (Fs_sein) reaches the original set value (Fs_1 = 4.67 [%], Nfb = 95.33 [%]).

[0148] If it is the original set value (Fs_1), the excitation selection command (AorS_rf) becomes level L, and switching to synchronous excitation occurs.

[0149] In the case of FIG. 10, slip excitation is continued for temporary settings, and at time t4 = 3.4 [seconds] the slip excitation frequency reaches (Fs_1 = 4.92 [%]), which is 1.23 times the setting change range of 4 [%], but operation continues with slip excitation because the semiconductor power converter (ACEx) has a margin in its operating capacity.

[0150] In actual plant operation, a combination of variable factors occurs, such as the hydraulic head, the generator positive-sequence voltage amplitude (Vfb) of the AC excitation generator motor (ASG) 1, and the reactive power output (Qfb). To deal with these, it is not possible to ensure an excessive margin in the set value (Fs_1) of the slip excitation frequency. Therefore, measures to prevent a decrease in rotation speed are required.

[0151] Continuing slip excitation poses another problem: because priority is given to active power response, rotational speed fluctuations increase, which in turn increases governor opening (GVO) fluctuations.

[0152] 10 is a percentage display of the cumulative sliding angle of the governor opening GVO converted into a unit value based on the range of change in the governor opening before and after the start of the ramp response. The cumulative GVO sliding ratio is an index of mechanical wear of the governor (GOV) 10.

[0153] In the case of FIG. 10, the cumulative GVO sliding ratio is 250%, which indicates that the sliding is 2.5 times the minimum sliding opening.

[0154] Patent Document 3 discloses a method in which, when the slip excitation frequency (Fs_sein) exceeds a set range, an output correction command is applied to the output command (Prf) in accordance with the excess.

[0155] However, it was found that it is difficult to adjust the proportional gain of the output command correction appropriately in accordance with variable factors such as the hydraulic system head described above, the generator positive-phase voltage amplitude (Vfb) of the AC excitation generator motor (ASG) 1, and the reactive power output (Qfb), and that it is difficult to achieve both the deviation range of the slip excitation frequency (Fs_sein) and the suppression of output (Pfb) fluctuations.

[0156] A method of switching to synchronous excitation instead of applying an output correction command and adjusting the synchronous excitation frequency (Fs_soln) after the switching using the synchronous excitation frequency calculator 110 in Fig. 6 can be considered an alternative that can be easily imagined by experts in the field. Unlike the output correction command in Patent Document 3, this alternative has the advantage that "gain adjustment is not required." However, this alternative has the problem shown in Fig. 11.

[0157] FIG. 11 is a diagram showing a case where, under the same conditions as FIG. 10 , the set value (Fs_1) is returned to the original value (4.67 [%]), the active power correction command is changed to that of Patent Document 1, the slip excitation is switched to synchronous excitation, and the synchronous excitation frequency (Fs_soln) is gradually reduced to return to the set range.

[0158] The process up to time t3=2.8 [seconds] is the same as in FIG. 10, so the description will be omitted to avoid duplication.

[0159] At time t3=2.8 [seconds], the slip excitation frequency (Fs_sein) exceeds the set value (Fs_1), the excitation selection command (AorS_rf) becomes level L, and switching to synchronous excitation occurs.

[0160] At time t3=2.8 [seconds], the limiter 402 with dead band and hysteresis outputs a negative fixed value (-ΔF), and the synchronous excitation frequency (Fs_soln) is gradually decreased by the synchronous excitation frequency correction (Fs_ad).

[0161] At time t4=3.2 [seconds], the rotation speed signal (Nfb) drops to the minimum value of 95.25 [%] (corresponding to Fs_sein=2.85 [Hz]).

[0162] At time t5=7.8 [s], the slip excitation frequency (Fs_sein) reaches the set value (Fs_2=3.83 [%]), and the excitation selection command (AorS_rf) from synchronous excitation to slip excitation becomes level H.

[0163] At time t5=7.8 [s], the phase difference (dlt) between the synchronous excitation phase and the slip excitation phase is a positive value exceeding the threshold value (ep), so the limiter 301 with dead band and hysteresis outputs a negative fixed value (-ΔI), and the quadrature axis current command (Iqrf) gradually decreases due to the quadrature axis current correction (Iq_ad).

[0164] The phase difference (dlt) between the synchronous excitation phase and the slip excitation phase gradually decreases due to the synchronizing force of the AC excitation generator motor (ASG) 1 described in FIG.

[0165] At time t6=8.1 [s], the phase difference (dlt) becomes equal to or less than the threshold value (eps), and the output of the response (StoA_ack) for completing the transition from synchronous excitation to slip excitation is switched to level H.

[0166] After time t6=8.1 [s], the excitation selection signal (A or S) from the state transition controller 111 becomes level H, and the system returns to slip excitation. In the example of Fig. 11, at t7=17.5 [sec], the rotation speed signal (Nfb) approaches the command value and stabilizes.

[0167] With the above-described conventional technology, when the rotation speed exceeds the variable speed range of the plant during slip excitation operation, the synchronous excitation frequency is switched to synchronous excitation, the synchronous excitation frequency is adjusted, the rotation speed is returned to within the variable speed range, and the operation is switched back to slip excitation.

[0168] However, the rotation speed during the synchronous excitation operation period fluctuates greatly, although the moving average value returns to the variable speed range as intended.

[0169] A more serious problem than the amplitude of vibration is that the amplitude of the phase difference (dlt) between the synchronous excitation phase and the slip excitation phase, and the frequency difference (ΔFs = Fs_soln - Fs_sein) between the synchronous excitation frequency (Fs_soln) and the slip excitation frequency (Fs_sein) increase over time, resulting in unstable vibration with a negative damping coefficient. Stabilization is necessary to ensure plant stability.

[0170] Furthermore, the cumulative GVO sliding ratio is 400% which is 60% higher than that in Figure 10. As a result, there is a higher possibility that the life of the guide vane drive system comprising the governor (GOV) 10 will be shortened due to wear. Also, there is a problem that the equipment capacity of the governor (GOV) 10 will increase, such as the pressure oil tank capacity when driven by a hydraulic servo motor. Claim 1 of the present invention is effective as a means for solving these problems.

[0171] Fig. 12 is a block diagram of a plant control device during power generation according to claim 1 of the present invention. Components with the same numbers as those in the block diagram of the plant control device during power generation in Fig. 2 are designated by the same numbers, and therefore descriptions thereof will be omitted to avoid duplication.

[0172] The synchronous excitation frequency (Fs_soln) from the synchronous excitation frequency calculator 110 is branched and output and input to the quadrature axis current command calculator 200 .

[0173] The slip excitation frequency (Fs_sein) is branched and output from the excitation phase calculator 109 and input to the quadrature axis current command calculator 200 .

[0174] Fig. 13 is a block diagram of a plant control device in an electrically operated state according to claim 1 of the present invention. Components with the same numbers as those in the block diagram of the plant control device in an electrically operated state in Fig. 8 are designated by the same numbers, and therefore explanations thereof will be omitted to avoid duplication.

[0175] The synchronous excitation frequency (Fs_soln) from the synchronous excitation frequency calculator 110 is branched and output and input to the quadrature axis current command calculator 200 .

[0176] The slip excitation frequency (Fs_sein) is branched and output from the excitation phase calculator 109 and input to the quadrature axis current command calculator 200 .

[0177] 14 is a diagram showing a quadrature axis current command calculator 200 according to claim 1 of the present invention. Components with the same numbers as those in the quadrature axis current command calculator 113 in FIG. 4 indicate the same components, and therefore will not be described to avoid duplication.

[0178] The synchronous excitation frequency (Fs_soln) and the slip excitation frequency (Fs_sein) are compared by a subtractor 212 , and a quadrature axis current command stabilization correction (Iq_stb) is output via a stabilization gain (Kd) 213 .

[0179] In the example of FIG. 14, a limiter 214 is provided, which has the effect of preventing loss of synchronism due to excessive quadrature axis current command stabilization correction (Iq_stb).

[0180] The quadrature axis current command stabilization correction (Iq_stb) is applied to the quadrature axis current correction (Iq_ad1) from the limiter 306c by an adder 215, and is input to the s terminal of the output switch 307c.

[0181] FIG. 15 shows the operation of the first embodiment (claim 1 of the present invention).

[0182] FIG. 15 shows an operation under the same conditions as in FIG. 11 except that the stabilization gain (Kd) 213 in FIG. 14 is activated.

[0183] This shows a transient phenomenon when the output command (Prf) is ramped up from a power generation output of 30% to 40% at a 30-second rate, and after the ramp up, the output command (Prf) is kept constant at 40%.

[0184] The following description will be made in comparison with FIG.

[0185] The process up to time t3=2.8 seconds is the same as in FIG. 11, so the description will be omitted to avoid duplication.

[0186] At time t3=2.8 [seconds], the excitation selection command (AorS_rf) from synchronous excitation to slip excitation becomes level L, and the excitation is switched to synchronous excitation.

[0187] At time t4 = 3.2 [seconds], the rotation speed signal (Nfb) drops to a minimum value of 95.3 [%] (corresponding to Fs_seil = 2.82 [Hz]). This minimum value is almost the same as in Figure 11, and the effect of the stabilization gain (Kd) 213 is not evident. However, the subsequent vibration is attenuated by 80% in one cycle.

[0188] Furthermore, the frequency difference (ΔFs) between the synchronous excitation frequency (Fs_soln) and the slip excitation frequency (Fs_sein) also decays by 80% over two periods.

[0189] As in FIG. 11, the excitation selection signal (AorS) becomes level H at time t5=7.8 [seconds].

[0190] At time t6=8.1 [s], the phase difference (dlt) becomes equal to or less than the threshold value (eps), and the output of the response (StoA_ack) for completing the transition from synchronous excitation to slip excitation is switched to level H.

[0191] In FIG. 15, at t=17.5 [s], the rotation speed signal (Nfb) approaches the command value and stabilizes.

[0192] As described above, according to the prior art of claim 1, when the rotation speed exceeds the variable speed range of the plant during slip excitation operation, the synchronous excitation frequency is adjusted by switching to synchronous excitation, and the fluctuation in the rotation speed is rapidly damped while returning it to within the variable speed range, and operation can be switched back to slip excitation.

[0193] The cumulative GVO sliding ratio is 200% which is 50% less than 400% in FIG. 11 where the stabilization gain (Kd) 213 is inactivated, and 20% less than FIG. 10 where only slip excitation is used.

[0194] As described above, the stabilization gain (Kd) 213 has the effect of extending the life of the equipment in addition to the stabilization effect. However, the stabilization gain (Kd) 213 is subject to the following constraints.

[0195] The larger the stabilization gain (Kd) 213, the faster the response and the greater the vibration damping effect.

[0196] On the other hand, as can be seen from the oscillation of the waveform of the frequency difference (ΔFs) between the synchronous excitation frequency (Fs_soln) and the slip excitation frequency (Fs_sein) from time t2 to time t6 in Fig. 15, the input signal (Fs_soln-Fs_sein) to the stabilization gain (Kd) 213 is susceptible to the influence of measurement noise. For this reason, the setting range of the stabilization gain (Kd) has an upper limit due to measurement noise.

[0197] In particular, since the slip excitation frequency (Fs_sein) is susceptible to the influence of measurement noise and disturbances, it is necessary to add a delay circuit with a time constant Tf to the measurement circuit.

[0198] The slip excitation frequency (Fs_sein) is affected by torque pulsation due to the number of fixed and rotating blades of the turbomachinery (WT) 8, pulsation due to the number of winding slots of the AC excitation generator motor (ASG) 1, as well as torque pulsation due to harmonic currents.

[0199] From the above, it has been empirically determined that the filter time constant Tfm added to the rotation phase measurement circuit must be set to 20 ms or more. The value of the filter time constant Tfm is longer than the time constant Tfv set value of the system-side positive-sequence voltage phase measurement circuit, which can generally be adjusted to approximately 60% (10 to 12 ms) of one cycle of the AC power system (PS) 2. As a result, the time constant Tf of the slip excitation frequency measurement circuit is determined by the time constant Tfm on the rotation phase side.

[0200] The technology of the first embodiment (claim 1) contributes to the stability of synchronous excitation, but does not take into consideration the long-term operation of synchronous excitation. As a result, if the operation time after switching to synchronous excitation becomes long, the range of change in the output command (Prf) may become larger than 10% in FIG. 11.

[0201] As the range of change in the output command (Prf) increases, the range of change in the phase difference (dlt) between the synchronous excitation phase and the slip excitation phase also increases. As can be inferred from the vector diagram in Figure 5, as the phase difference (dlt) increases, the phase difference (dlt) between the direct axis (d_soln) of synchronous excitation and the actual direct axis (d) also increases. This causes mutual interference between the current controls of the two axes to become apparent. When the phase difference (dlt) exceeds 45 degrees and approaches 90 degrees, the direct axis current command (Idrf) controlled by synchronous excitation actually acts similarly to the quadrature axis current (Iqrf). This can cause problems such as operation that is different from what was intended at the time of design, making plant control unpredictable.

[0202] This problem will be explained below with reference to the operation shown in FIG.

[0203] Figure 16 shows a transient phenomenon in which the technology of Example 1 (Claim 1) is applied to an adjustable speed pumped storage power generation system designed with a plant variable speed range of 4% as in the previous Figures 10, 11, and 15, and the system switches from a steady operating state of 10% power generation output to synchronous excitation at time t0 = -3 seconds, the output command (Prf) begins to ramp up at time t1 = 0 seconds, ramps up to 30% in 9 seconds (at a so-called 30-second rate), and is kept constant from time t2 = 9 seconds when the output command (Prf) reaches 40%.

[0204] 16, the excitation is switched from slip excitation to synchronous excitation at time t0=-3 seconds. The synchronous excitation frequency (Fs_soln) does not change suddenly during the transition due to the operation of the one-shot switch 405 of the synchronous excitation frequency calculator 110. Therefore, the transition from slip excitation to synchronous excitation does not occur suddenly in the active power output (Pfb).

[0205] After the transition to synchronous excitation, the plant control of the Francis pump turbine (turbomachine (WT) 8) is switched to the plant control device of the conventional fixed-speed power plant using a synchronous generator shown in FIG.

[0206] When the output command (Prf) begins to rise at time t1 = 0 seconds, the governor opening (GVO) opens, increasing the turbine output (Pt). This, in turn, increases the active power output (Pfb) of the AC-excited plant, which is dominated by the output of the AC-excited generator-motor (ASG) 1, due to the assimilation force. Because the rotational speed signal (Nfb) is constant, the quadrature-axis current (Iq) also increases in proportion to the active power output (Pfb). However, in the case of synchronous excitation, the phase difference (dlt) between the synchronous excitation phase and the slip excitation phase increases in order to maintain the quadrature-axis current command (Iqrf). As a result, the deviation between the quadrature-axis current (Iq) and the quadrature-axis current command (Iqrf) increases, and the phase difference (dlt) also increases.

[0207] At time t2 (9 seconds) when the output command (Prf) reaches 40%, the phase difference (dlt) widens to -30 degrees, and at time t3 (12 seconds) to -32 degrees. Furthermore, as the output change range exceeds 30%, the phase difference (dlt) also increases, increasing the effect of the direct-axis current command (Idrf) on the quadrature-axis current (Iqf), making it impossible to continue the intended two-axis current control. Claim 2 of the present invention is effective as a means for solving these problems.

[0208] 17 is a block diagram of a plant control device during power generation according to claim 2 of the present invention. Components with the same numbers as those in the block diagram of the plant control device during power generation in FIG. 12 are designated by the same numbers, and therefore descriptions thereof will be omitted to avoid duplication.

[0209] The second excitation selection command (AorS_rf2) is input from the quadrature axis current command calculator 300 to the state transition controller 127, and is input from the state transition controller 127 to the quadrature axis current command calculator 300.

[0210] 18 is a block diagram of a plant control device in an electrically operated state according to claim 2 of the present invention. Components with the same numbers as those in the block diagram of the plant control device in an electrically operated state in FIG. 12 are designated by the same numbers, and therefore explanations thereof will be omitted to avoid duplication.

[0211] The second excitation selection command (AorS_rf2) is input from the quadrature axis current command calculator 300 to the state transition controller 127, and is input from the state transition controller 127 to the quadrature axis current command calculator 300.

[0212] Fig. 19 is a diagram showing a quadrature axis current command calculator 300 according to claim 2 of the present invention. Components with the same numbers as those in the quadrature axis current command calculator 200 in Fig. 14 are the same components. To avoid duplication, descriptions of components with the same numbers as those in the quadrature axis current command calculator 200 in Fig. 14 will be omitted.

[0213] The limiter 320 with dead zone of the second quadrature axis current correction calculator 319 branches and inputs the phase difference (dlt) obtained by matching the synchronous excitation phase and the slip excitation phase from the x terminal, and outputs a negative fixed output (-ΔI_2) when the input value exceeds a threshold value (+ep_1) in the positive direction, and outputs a positive fixed output (+ΔI_2) when the input value exceeds the threshold value (-ep_1) in the negative direction.

[0214] When the output of the limiter with dead band 320 is a negative fixed output (-ΔI_2) and the input falls below the positive threshold (+ep_2), it outputs 0.

[0215] When the output of the limiter with dead band 320 is a fixed positive output (+ΔI_2), if the input exceeds a negative threshold (−ep_2), it outputs 0.

[0216] When the output of the limiter with dead band 320 is a negative fixed output (-ΔI_2), the second quadrature axis current correction (Iq_ad2) is subtracted by (-ΔI_2) for each calculation cycle by the adder 321 and the delay element with reset control 322, and when the output is a positive fixed output (+ΔI_2), it is added and output.

[0217] When the output of the limiter with dead band 310 is 0, the previous value of the second quadrature axis current correction (Iq_ad2) is maintained.

[0218] The delay element 322 with reset control resets the held value to 0 when slip excitation is selected and the excitation selection signal (A or S) becomes level H.

[0219] In the example of FIG. 19, a limiter 323 is provided to limit the output absolute value, and the output is output as a quadrature axis current correction (Iq_ad2) via a second terminal of an output switch 324.

[0220] The quadrature axis current correction (Iq_ad2) is applied to the quadrature axis current command stabilization correction (Iq_stb) by the adder 215, and is applied to the quadrature axis current command (Iqrf) as the quadrature axis current correction (Iq_ad) via the s terminal of the output switch 307c.

[0221] The output switch 324 selects and outputs the first terminal when the signal (StoA_ack) indicating transition from synchronous excitation to slip excitation is at level H, and selects and outputs the second terminal when the signal is at level L.

[0222] With the above configuration, no matter which terminal the output switch 324 selects to output, the quadrature axis current command stabilization correction (Iq_stb) is activated, which has the effect of continuing stable synchronous excitation.

[0223] In FIG. 19, the signs of the quadrature axis current command (Iqrf) and the phase difference (dlt) are defined in the same way as in FIG.

[0224] When synchronous excitation is selected and the synchronous excitation phase (th_soln) leads the slip excitation (th_sein) and sin (dlt) exceeds the threshold value (+ep_1), the quadrature axis current correction (Iq_ad2) gradually decreases from 0 in the negative direction, reducing the torque of the AC excitation generator motor (ASG) 1, the phase difference (dlt) decreases toward 0, the slip excitation phase (th_sein) and the synchronous excitation phase (th_soln) change in the direction of matching and fall below the threshold value (ep_1), and the output of the limiter with dead band 320 becomes 0.

[0225] On the other hand, when the synchronous excitation phase (th_soln) lags behind the slip excitation (th_sein) and sin (dlt) exceeds the threshold value (-ep_1), the quadrature axis current correction (Iq_ad2) gradually increases from 0 in the positive direction, the slip excitation phase (th_sein) and the synchronous excitation phase (th_soln) change in the direction of matching, and the threshold value is set so that the output of the limiter with dead band 320 becomes 0.

[0226] In normal operation, the threshold value (ep_2) is set to a value greater than the threshold value (ep). However, the smaller the threshold value (ep_2), the shorter the transition period from synchronous excitation to slip excitation.

[0227] By setting the fixed output set value (ΔI_2) to be smaller than the fixed output set value (ΔI), output fluctuations of the AC excitation generator motor (ASG) 1 due to increases or decreases in the second quadrature axis current correction (Iq_ad2) can be suppressed.

[0228] However, there is a lower limit to the fixed output set value (ΔI_2), which is determined by the upper limit of the rate of change of the output command (Prf).

[0229] If the fixed output setting value (ΔI_2) falls below the lower limit, the change in the quadrature axis current command (Iqrf) cannot follow the change in the quadrature axis current (Iq) corresponding to the output command (Prf), the absolute value of the phase difference (dlt) cannot be reduced, and the intended function cannot be achieved.

[0230] The larger the threshold value (ep_1-ep_2) that determines the hysteresis characteristic, the fewer the number of times the output of the limiter with dead band 320 is switched, which has the effect of reducing the number of times the output fluctuates.

[0231] On the other hand, the smaller the threshold value (ep_1-ep_2) that determines the hysteresis characteristic, the smaller the output width accompanying output switching of limiter 320 with dead band, which has the effect of realizing a smooth output close to slip excitation even in synchronous excitation.

[0232] In the case of power generation operation, other factors become constraints when setting thresholds.

[0233] The larger the ratio between the fixed output set value (ΔI_2) and the threshold value (ep_1-ep_2), the closer the response characteristic becomes to that of the limiter 325 with dead zone shown in FIG.

[0234] In the configuration of FIG. 19, when the absolute value of the phase difference (dlt) is between the threshold value (ep_1) and the threshold value (ep_2), the quadrature axis current command (Iqrf) operates as a virtual second speed regulator having a proportional gain.

[0235] Therefore, cooperation with the speed regulator 105 that adjusts the opening command GVOrf to the turbomachinery (WT) 8 and avoidance of conflict are required.

[0236] Specifically, it is necessary to constantly adjust the gain range within which the second speed regulation can be performed, calculated from the turbine characteristics, which have significant nonlinear characteristics, depending on the operating conditions.

[0237] 5, the precondition for the "function of adjusting the phase difference (dlt) by the quadrature axis current command correction (Iq_ad)" is that the output torque of the turbo machine (WT) 8 is constant. Therefore, it is necessary to set the response characteristic sufficiently faster than the turbo machine side, ideally one order of magnitude faster.

[0238] On the other hand, a prerequisite for the "function of adjusting the phase difference (dlt) by the quadrature axis current command correction (Iq_ad)" is that "the current command (Iqrf, Idrf) matches the current value (Iq, Ir)." More precisely, the prerequisite is that "the voltage command (Vfr) matches the generator positive-sequence voltage amplitude (Vfb) on the premise that the "current command (Iqrf, Idrf)" matches the current value (Iq, Ir)."

[0239] Therefore, it is necessary to set the response characteristics sufficiently slower than the automatic voltage regulator (AVR) 106, the quadrature axis current regulator (q_ACR) 114, and the direct axis current regulator (d_ACR) 115, ideally one order of magnitude slower.

[0240] In the case of electric operation, especially when using a turbomachine as a pump, the torque of the turbomachine hardly changes even if the governor opening (GVO) is changed under normal operating conditions, so a speed regulator that adjusts the opening command (GVOrf) is not required. Therefore, arbitration like that required during power generation operation is not required.

[0241] From the above, the limiter 325 with dead zone shown in FIG. 20 is a practical option, especially during electric driving.

[0242] FIG. 22 is a diagram showing the operation of the second embodiment (claim 2 of the present invention).

[0243] 16 only differs from the previous one in that the quadrature axis current command calculator 200 is replaced with a quadrature axis current command calculator 300, and other configurations and operating conditions are the same. In the following, to avoid duplication, explanations of the same operational parts as in FIG. 16 will be omitted.

[0244] When the output command (Prf) starts to rise at time t1=0 [seconds], the phase difference (dlt) between the synchronous excitation phase and the slip excitation phase increases in the negative direction.

[0245] At time t3=2.9 [seconds], the phase difference (dlt) exceeds the threshold value (ep_1=6 degrees), and the quadrature axis current command calculator 300 starts to gradually increase the quadrature axis current command (Iqrf).

[0246] Even when the quadrature axis current command (Iqrf) starts to increase gradually, the phase difference (dlt) continues to decrease due to the effect of the moment of inertia of the rotor, and after reaching a minimum value (dlt = -8.7 degrees) at time t4 = 6.0 seconds, it begins to increase, and the absolute value begins to decrease.

[0247] At time t5=8.2 [seconds], the absolute value of the phase difference (dlt) falls below the threshold value (ep_2=4 degrees), the quadrature axis current command (Iqrf) is maintained, and the phase difference (dlt) turns negative again.

[0248] At time t6=8.8 [seconds], the phase difference (dlt) again exceeds the threshold value (ep_1=6 degrees), and the axial current command (Iqrf) starts increasing again.

[0249] After the output command (Prf) reaches 40% at time t2=9.0 [seconds], the output command (Prf) is maintained.

[0250] At time t7=11.2 [seconds], the phase difference (dlt) falls below the threshold value (ep_2=4 degrees), and the quadrature axis current command (Iqrf) is maintained.

[0251] The phase difference (dlt) when returning to the steady state at time t8=12.5 [seconds] has settled to a value of −3.7 degrees, which is a 90% reduction from the set value of −32 degrees in the case of FIG.

[0252] On the other hand, almost no change is observed in the waveforms of the rotation speed (Nfb) and the output (Pfb) from Figure 16. This shows that the operation is in line with the intention of "adjusting the phase difference (dlt) without affecting other characteristics."

[0253] As described above, according to Example 2 (technology of Claim 2), even when synchronous excitation operation continues for a long period of time and the output command (Prf) fluctuates greatly, the phase difference (dlt) can be adjusted to be below the threshold value (ep_1), thereby having the effect of continuing stable current control of two axes.

[0254] Furthermore, since the phase difference (dlt) is adjusted to be equal to or less than the threshold value (ep_2), the phase difference (dlt) adjustment period by the quadrature axis current correction calculator 317 can be shortened, which has the effect of enabling a quick transition from synchronous excitation to slip excitation.

[0255] REFERENCE SIGNS LIST 1 AC excitation generator motor (ASG) 1a Armature winding terminal 1b Slip ring 2 AC power system (PS) 3 Main transformer (MTR) 4 Synchronous breaker (CB) 5 Semiconductor power converter (ACEx) 6 Excitation breaker (ExCB) 7 Excitation transformer (ExTR) 8 Turbomachinery (WT) 9 Guide vane 10 Governor (GOV) 11 Plant control device 12, 13 Instrument transformer 14 Synchronous detector (Syn) 15 Instrument current transformer 16 Excitation current transformer 17 Rotational speed measuring device (SS) 18 Resolver rotating machine (Res) 19 Voltage amplitude calculator 101, 701 Optimum GVO function generator 102, 104, 124, 205 Delay circuit 103, 702 Optimum speed function generator 105, 704 Speed ​​regulator (ASR) 106 Automatic voltage regulator (AVR) 107 Output / voltage phase calculator 108 Rotation phase calculator 109 Excitation phase calculator 110 Synchronous excitation frequency calculator 112 Three-phase to two-phase converter 113, 200, 300 Quadrature axis current command calculator 114 Quadrature axis current regulator (q_ACR) 115 Direct axis current regulator (d_ACR) 116 Two-phase to three-phase converter 123, 212, 802 Subtractor 201a, 201b, 201c, 324, 307a, 307b, 307c Output switch 202, 204, 210 Phase difference calculator (PDF) 203 Slip excitation frequency calculator 206, 206c, 206d, 206g, 206f, 322 Delay element 207 Arc sine function calculator 208 Gain [1 / (2πNfΔT)] 209 Two-phase variable frequency oscillator (VCO) 211, 216, 317, 319 Quadrature axis current correction calculator 213 Stabilization gain 214, 306a, 306b, 306c, 803, 807, 323, 408 Limiter 301 Active power regulator 302 One-shot switch 303 Proportional gain (Cp) 304 Integral gain 305a, 305b, 311, 806, 321, 128, 215 Adder 309 Flip-flop 310, 325 Limiter with dead band 312 Absolute value output 313 Comparator 314, 316 Logical AND 315 Logical OR 320, 301, 320 Dead band / hysteresis limiter 322 Delay element with reset control323 Instruction value retainer 801, 808 Integrator 805 Vertical gain

Claims

1. A control device for an AC excitation generator-motor, in which an armature winding (1a) of an AC excitation generator-motor (1) is connected to an AC power system (2), a semiconductor power converter (5) is connected between a slip ring (1b) of a rotor winding of the AC excitation generator-motor and the AC power system, a direct-axis current regulator (115) for adjusting voltage or reactive power adjusts a direct-axis current on the rotor winding side of the semiconductor power converter to a direct-axis current command, and a quadrature-axis current regulator (114) for adjusting torque or active power adjusts a quadrature-axis current on the rotor winding side of the semiconductor power converter to a quadrature-axis current command, the control device comprising: a phase difference calculator (202) for outputting a slip excitation phase (th_sein) that matches the armature winding phase and rotor phase of the AC excitation generator-motor; a variable frequency oscillator (209) for outputting the synchronous excitation phase (th_soln) as a frequency command value of a synchronous excitation frequency (Fs_soln); an output switch (201a, 201b) for selecting the slip excitation phase (th_sein) or the synchronous excitation phase (th_soln) in accordance with an excitation selection signal and outputting the selected phase as an excitation reference phase; a command value holder (323) for holding the quadrature axis current command (Iqrf) at a quadrature axis current command value (Iqrf_0) at the time of switching from the slip excitation phase to the synchronous excitation phase when the synchronous excitation phase is selected; and a slip excitation frequency calculator (203) for calculating a slip excitation frequency (Fs_sein) of the slip excitation phase, wherein a stabilization gain (213) is provided for inputting a result of matching between the synchronous excitation frequency and the slip excitation frequency to calculate a quadrature axis current command stabilization correction value (Iq_stb), and the quadrature axis current command stabilization correction value is biased to the quadrature axis current command value (Iqrf_0) from the command value holder (323). A control device for an AC-excited generator-motor, characterized in that:

2. The control device for an AC excitation generator motor according to claim 1, characterized in that a result (dlt) of matching between a synchronous excitation phase (th_soln) and a slip excitation phase (th_sein) is input to calculate a quadrature axis current command correction value (Iq_ad0), and when the synchronous excitation phase is selected, this quadrature axis current command correction value (Iq_ad0) is biased to the quadrature axis current command stabilization correction value (Iq_stb).

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