Electric motor-driven generator

Abstract

To provide an electric motor-driven generator capable of improving the stability of a power system while operating a rotating machine under torque control.SOLUTION: An electric motor-driven generator includes a power storage device, a power conversion device that converts a DC voltage of the power storage device into an AC voltage, a rotating machine driven by the AC voltage of the power conversion device, a rotation detector that detects the rotational speed of the rotating machine, a synchronous generator whose shaft is directly connected to the rotating machine, a power system connected to the synchronous generator, and an external control device that outputs an external torque command value and the state of the power system to the power conversion device, and automatically switches between torque control and speed control in the power conversion device according to the rotational speed of the rotating machine and a state signal of the power system.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electric motor-driven power generation device.

Background Art

[0002] In a system stabilization system using a power storage device, an electric motor-driven power generation device using a rotary machine and a generator is used.

[0003] Fig. 4 shows an example of an electric motor-driven power generation device using a power storage device according to the prior art shown in Patent Document 1. In Fig. 4, 1 is a synchronous generator, 2 is a rotary machine, 3 is a power storage device, 4 is a power conversion device, 5 is a rotation detector, and 6 is a power system.

[0004] In the electric motor-driven power generation device shown in Fig. 4, when the rotational speed of the rotary machine 2 detected by the rotation detector 5 is higher than the specified frequency of the power system 6, the power conversion device 4 performs speed control (deceleration operation) so that the rotational speed of the rotary machine 2 matches the specified frequency of the power system 6. At this time, the power storage device 3 performs a charging operation. When the rotational speed of the rotary machine 2 detected by the rotation detector 5 is lower than the specified frequency of the power system 6, the power conversion device 4 performs speed control (acceleration operation) so that the rotational speed of the rotary machine 2 becomes the specified frequency of the power system 6. At this time, the power storage device 3 performs a discharging operation. By the above charging and discharging operations, frequency fluctuations in the power system 6 are suppressed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, since the conventional method adjusts the active power by controlling the speed of the rotary machine 2 using the power conversion device 4, in the case of a system where the active power command value is directly given to the power conversion device 4, it is necessary to convert the active power command value into a speed command value and indirectly control the active power, resulting in a problem that the response to the active power command value is slower compared to torque control.

[0007] On the other hand, torque control has a faster response to the active power command value than speed control, but since it does not directly contribute to suppressing frequency fluctuations, when an accident such as a short circuit or ground fault occurs in the power system 6, the power system 6 may become unstable.

[0008] Therefore, there is a need for a motor-driven power generation device that can perform torque control with a fast response to the active power command value while improving the stability of the power system.

[0009] The problem to be solved by the present invention is to provide a motor-driven power generation device capable of improving the stability of the power system while operating the rotary machine under torque control.

Means for Solving the Problem

[0010] The motor-driven power generation device according to an embodiment of the present invention includes a power storage device, a power conversion device that converts the DC voltage of the power storage device into an AC voltage, a rotary machine driven by the AC voltage of the power conversion device, a rotation detector that detects the rotation speed of the rotary machine, a synchronous generator directly coupled to the rotary machine by a shaft, a power system connected to the synchronous generator, and an external control device that outputs an external torque command value and a state signal of the power system to the power conversion device, and automatically switches between torque control and speed control in the power conversion device according to the rotation speed of the rotary machine and the state signal of the power system.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0012] FIG. 1 is a diagram showing a configuration example of a motor-driven power generation device according to an embodiment of the present invention.

[0013] In the motor-driven power generation device shown in FIG. 1, 1 is a synchronous generator, 2 is a rotary machine, 3 is a power storage device, 4 is a power conversion device, 5 is a rotation detector, 6 is a power grid, 7 is a capacitor, and 8 is an external control device.

[0014] First, the DC voltage of the power storage device 3 is smoothed by the capacitor 7, and the smoothed DC voltage is supplied to the power conversion device 4. Note that the capacitor 7 for smoothing may not be provided in the configuration.

[0015] The power conversion device 4 converts the DC voltage smoothed by the capacitor 7 into an AC voltage and supplies it to the rotary machine 2. The power conversion device 4 receives an external torque command value T EXT * from the external control device 8, the state signal of the power grid 6, and the rotational speed ω m of the rotary machine 2 detected by the rotation detector 5. Based on the state signal of the power grid 6 and the rotational speed ω m , the torque control and speed control of the power conversion device 4 are switched.

[0016] The rotary machine 2 is driven by the AC voltage supplied by the power conversion device 4 and rotates the directly coupled synchronous generator 1.

[0017] The synchronous generator 1 is driven by a directly shaft-connected rotary machine 1 and supplies power to the power grid 6. The power grid 6 is generally composed of an AC power source such as a diesel generator or a commercial AC power supply and load equipment.

[0018] Here, as a detailed description of the power conversion device 4, the case where the rotary machine 2 is an induction motor will be described as an example.

[0019] FIG. 2 is a block diagram showing a configuration example of a power conversion device in a motor-driven power generation device according to an embodiment of the present invention.

[0020] The power conversion device 4 includes a speed control unit 4a, a torque command value switching unit 4b, a current command value conversion unit 4c, a slip frequency calculation unit 4d, an angle calculation unit 4e, a uvw-dq conversion unit 4f, a current control unit 4g, a dq-uvw conversion unit 4h, and a gate signal conversion unit 4i.

[0021] The speed control unit 4a receives a rotational speed command value ω m * and a rotational speed ω m . Then, the speed control unit 4a calculates an internal torque command value T m * such that the rotational speed command value ω m matches the rotational speed ω ASR * by PID control or the like.

[0022] The torque command value switching unit 4b receives the internal torque command value T ASR * calculated by the speed control unit 4a, the rotational speed ω m , the external torque command value T EXT * output from the external control device 10, and the state signal of the power grid 6. Then, the torque command value switching unit 4b determines whether the torque command value T m is set to the internal torque command value T m * (speed control) or the external torque command value T ASR * based on the rotational speed ω EXT* Switch between (torque control) and output the torque command value T m * to output.

[0023] Based on the equivalent circuit constants and mechanical constants of the rotating machine 2, the current command value conversion unit 4c converts the torque command value T m * into the torque current command value I q * for conversion.

[0024] Based on the torque current command value I q * , the excitation current command value I d * , and the equivalent circuit constants of the rotating machine 2, the slip frequency calculation unit 4d calculates the slip angular frequency ω m * required to output the torque command value T slip for calculation.

[0025] The angle calculation unit 4e calculates the rotation angle θ m obtained by integrating the angular velocity obtained by adding the rotation speed ω slip and the slip angular frequency ω m+slip for calculation.

[0026] Based on the rotation angle θ m+slip , the uvw-dq conversion unit 4f performs a three-phase to two-phase conversion to convert the U-phase current I u , the V-phase current I v , and the W-phase current I w into the torque current I q and the excitation current I d for conversion.

[0027] The torque current command value I q * , the excitation current command value I d * , the torque current I q , and the excitation current I d are input to the current control unit 4g. Then, the current control unit 4g compares the torque current command value I q * with the torque current I qmatches, and the excitation current command value I d * and the excitation current I d such that the q-axis voltage command value V q * and the d-axis voltage command value V d * are calculated by PID control or the like.

[0028] The dq-uvw conversion unit 4h performs two-phase to three-phase conversion based on the rotation angle θ m+slip to convert the q-axis voltage command value V q * and the d-axis voltage command value V d * into the U-phase voltage command value V u * the V-phase voltage command value V v * and the W-phase voltage command value V w * respectively.

[0029] The gate signal conversion unit 4i converts the U-phase voltage command value V u * the V-phase voltage command value V v * and the W-phase voltage command value V w * into gate signals.

[0030] Here, as a detailed explanation of the torque command value switching unit, an example of the mechanism will be described using the flowchart of FIG. 3.

[0031] First, the torque command value switching unit 4b sets the upper frequency limit value ω upper in the power system 6 in process S101.

[0032] The operating entity of each subsequent process is the torque command value switching unit 4b. Therefore, in the following description, duplicate descriptions indicating that the operating entity is the torque command value switching unit 4b are avoided.

[0033] In process S102, the lower frequency limit value ω lower in the power system 6 is set.

[0034] In process S103, the rotational speed ω of the rotary machine 2 detected by the rotation detector 5 m is acquired.

[0035] In process S104, if the rotational speed ω m is greater than the frequency upper limit value ω upper or less than the frequency lower limit value ω lower , the process proceeds to process S105. If the rotational speed ω m is between the frequency upper limit value ω upper and the frequency lower limit value ω lower , the process proceeds to process S106.

[0036] In process S105, the power conversion device 4 is switched to speed control, and the process returns to process S103.

[0037] In process S106, if the power conversion device 4 is in speed control and the power system is in a normal state, the process proceeds to process S107. Otherwise, the process returns to process S103.

[0038] In process S107, the power conversion device 4 is switched to torque control, and the process returns to process S103.

[0039] With the above configuration, in the motor-driven power generation device according to the embodiment of the present invention, by automatically switching between the torque control and speed control of the power conversion device according to the rotational speed of the rotary machine and the state signal of the power system, it is possible to improve the stability of the power system while operating the rotary machine under torque control.

[0040] Although some embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, as well as in the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0041] 1 Synchronous generator 2 Rotating machine 3 Energy storage device 4 Power conversion device 4a Speed control unit 4b Torque command value switching unit 4c Current command value conversion unit 4d Slip frequency calculation unit 4e Angle calculation unit 4f uvw-dq conversion unit 4g Current control unit 4h dq-uvw conversion unit 4i Gate signal conversion unit 5 Rotation detector 6 Power system 7 Capacitor 8 External control device

Claims

【Claim 1】 A power storage device, a power conversion device that converts the DC voltage of the power storage device into an AC voltage, a rotating machine driven by the AC voltage of the power conversion device, a rotation detector that detects the rotation speed of the rotating machine, a synchronous generator directly coupled to the rotating machine by a shaft, a power grid connected to the synchronous generator, and an external control device that outputs an external torque command value and a state signal of the power grid to the power conversion device, An electric motor-driven power generation device characterized in that torque control and speed control in the power conversion device are automatically switched according to the rotation speed of the rotating machine and the state signal of the power grid.

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