JP2009033798A - Starting system for induction generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure that an excessive current does not flow when interconnecting an induction generator with a power system, and that a time required for the interconnection does not become long. <P>SOLUTION: An inverter 3 and a rectifier 16 are provided between the power system 1 and the induction generator 2. When interconnecting the induction generator 2 with the power system 1, the loss of the inverter 3 and the induction generator 2 is supplied from the rectifier 16, in a state that the induction generator 2 is rotated, and a current, which makes the voltage of the induction generator equal to the voltage of the power system, is calculated, and the calculated current is let flow from the inverter 3 to the induction generator 2, and then the induction generator is interconnected with the power system 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a distributed power source that supplies power to an electric power system by driving the induction generator by wind power, thermal power, an engine, or the like, and in particular, an inrush current that occurs when the induction generator is connected to the electric power system. The present invention relates to an induction generator starting method that can be suppressed.

FIG. 8 shows a conventional example disclosed in Patent Document 1, for example.
That is, the induction generator 2 in FIG. 8 generates power by controlling the rotational speed of the induction generator 2 after being connected to the power system 1. When the rotational speed of the induction generator 2 is set higher than the rated speed (corresponding to the frequency of the power system voltage), the active power can be supplied to the power system 1. On the other hand, if the rotational speed is lower than the rated rotational speed, the active power is supplied from the power system 1 to the induction generator 2.

  In the system as shown in FIG. 8, a circuit breaker 4 and a variable reactive power generator 3 are provided between the power system 1 and the induction generator 2 in order to start the induction generator 2. Note that the variable reactive power generator 3 generally uses a capacitor and a reactor, or an inverter.

Then, when starting the induction generator 2, with the circuit breaker 4 open, using an external means such as an engine (not shown), the induction generator 2 is rotated to the synchronous speed, and the voltage of the induction generator 2 is increased. When the reactive power generated by the variable reactive power generator 3 is adjusted so as to be equal to the voltage of the power system 1, and when the phase angle of the induction generator 2 and the phase angle of the voltage of the power system 1 substantially coincide, 4 is turned on to suppress the inrush current.
JP 2005-117879 A

  In the example of FIG. 8, in order to suppress the inrush current of the induction generator, it is necessary to generate a voltage having the same frequency and magnitude as the voltage of the power system before connecting to the power system. Is adjusted by external means such as an engine, and the magnitude is adjusted by reactive power from a variable reactive power generator. Since the variable reactive power generator 3 uses an inverter or a capacitor and a reactor, it is easy to control the reactive power. However, the external reactive means such as the engine controls the frequency to be the same as the power system voltage. The actual speed value may change as shown in FIG. 9 with respect to the rated speed. Moreover, since only reactive power is supplied, it is difficult to make the phase difference from the voltage of the power system zero.

  For this reason, conventionally, the circuit breaker 4 is turned on when the phase angle of the voltage of the induction generator and the voltage of the power system substantially coincide. As a result, the phase angle shifts due to the delay time from when the closing command is given to the breaker until the breaker is actually turned on, and an excessive current flows due to the difference between the induction generator voltage and the power system voltage. May cause equipment damage. In addition, since the circuit breaker cannot be turned on until the phase angles are almost the same, it may take a long time for the induction generator to connect to the power system after the operation command is input. obtain.

  Accordingly, an object of the present invention is to prevent an excessive inrush current from flowing when the induction generator is connected to the power system, and to shorten the time required to reach the connection.

  In order to solve such a problem, in the invention of claim 1, a circuit breaker between the power system and the induction generator is provided for an induction generator that supplies power to a load connected to the power system. In parallel, when a rectifier that converts AC power on the power system side to DC power and an inverter that converts the DC power to AC power on the induction generator side are connected to the induction generator, In a state where the generator is rotated, the loss of the inverter and the induction generator is supplied from the rectifier, the current for making the induction generator voltage the same as the power system voltage is calculated, and this current is derived from the inverter. It is characterized in that it is connected to the power system after flowing through.

  In the invention of claim 2, for the induction generator for supplying power to the load connected to the power system, the AC power on the power system side in parallel with the circuit breaker between the power system and the induction generator. When the induction generator is connected to the power system, the rectifier that converts the DC power into the DC power and the inverter that converts the DC power into the AC power on the induction generator side are connected. The loss of the inverter and the induction generator is supplied from the rectifier, the current for making the induction generator voltage equal to the power system voltage is calculated, and the current frequency is calculated according to the DC voltage of the inverter. After the current having the above frequency is passed from the inverter to the induction generator, it is linked to the power system.

  In the invention of claim 3, an induction generator for supplying electric power to a load connected to the electric power system is connected to the electric power system via a circuit breaker, and a DC side is provided between the circuit breaker and the induction generator. When installing an inverter connected to the power storage facility and connecting the induction generator to the grid, the induction generator voltage is changed from the inverter to the induction generator with the induction generator rotated near the rated speed. Is connected to the power system after flowing a current equal to the power system voltage.

  In the invention of claim 4, an induction generator for supplying electric power to a load connected to the electric power system is connected to the electric power system via a circuit breaker, and a DC side is provided between the circuit breaker and the induction generator. If an inverter with a power storage facility is connected to the inverter and a separate circuit breaker connected to the power generator and the induction generator on the output side of the inverter, and the induction generator is connected to the grid, the number of revolutions of the induction generator After rotating the inverter at the rated speed or below, connect the inverter to the power system to charge or discharge the power storage equipment, connect the inverter to the induction generator, and induce the induction generator It is characterized in that it is connected to the power system after flowing a current whose machine voltage is the same as the power system voltage.

  In the invention of claim 5, an induction generator for supplying power to a load connected to the power system is connected to the power system via a circuit breaker, and a DC side is provided between the circuit breaker and the induction generator. If the inverter is connected to the power storage facility and the induction generator is connected to the grid, the output frequency of the inverter is the same frequency as the induction generator above the charge / discharge capacity of the power storage facility. Below the charge / discharge capacity of the facility, control the frequency to be the same as that of the power system, and after flowing a current that causes the induction generator voltage to be the same as the power system voltage from the inverter to the induction generator, It is characterized by doing.

  According to the first to fifth aspects of the present invention, it is possible to stably link the induction generator to the power system without flowing an excessive inrush current.

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, 5, 6 and 18 are voltage detectors, 7, 8 and 11 are coordinate converters, 9, 10 and 19 are voltage regulators, 12 is a current regulator, 13 is a ramp function generator, and 14 is an oscillator. , 15 is a multiplier, 16 is a rectifier, 17 is a capacitor, 20 is a setter, 21 is a lower limiter, 22 is a subtractor, and the others are the same as in FIG. Hereinafter, differences will be mainly described.
That is, the inverter 3 and the rectifier 16 are connected in parallel with the circuit breaker 4 inserted between the electric power system 1 and the induction generator 2. By configuring the rectifier 16 with a diode or a thyristor, the rectifier 16 can be made cheaper than providing an inverter using an IGBT or the like.

  When the induction generator 2 is connected to the power system 1, the rectifier 16 supplies DC power to the inverter 3, and the inverter 3 converts the DC power into AC power. The voltage detector 6 detects the power system voltages Vsa, Vsb, Vsc, while the voltage detector 5 detects the induction generator voltages Vga, Vgb, Vgc. The system voltages Vsa, Vsb, and Vsc are multiplied by the ramp function from the function generator 13 in the multiplier 15, and output Vsa ', Vsb', and Vsc 'as shown in FIG. This is because the power system voltage detection value is slowly changed from zero voltage to the rated voltage so as not to change the output voltage of the inverter 3 abruptly.

The coordinate converter 7 performs three-phase to two-phase conversion on the outputs Vsa ′, Vsb ′, and Vsc ′ of the multiplier 15 according to the following equation (1) expressed by Equation 1.

Next, from the obtained two-phase amount, coordinate axis conversion is performed by the following equation (2) expressed by Equation 2 to obtain Vsd and Vsq.

Similarly, the coordinate converter 8 performs three-phase to two-phase conversion on the output voltage detection values Vga, Vgb, and Vgc of the detector 5, and performs coordinate axis conversion from the obtained two-phase amount by the above equation (2). To obtain Vgd and Vgq.
Thereafter, the difference between Vsd and Vgd and the difference between Vsq and Vgq are respectively obtained and input to voltage regulators 9 and 10 each composed of a gain, an integral element, etc., so that current commands Id and Iq of inverter 3 are obtained. Get.

The coordinate converter 11 performs coordinate conversion of the following formula (3) shown in Equation 3.

Next, the coordinate converter 11 performs two-phase to three-phase conversion according to the following equation (4) expressed by Equation 4 to obtain three-phase current command values Ia, Ib, and Ic.

  Then, the current regulator 12 adjusts and calculates the three-phase current detection value separately detected via the current transformer so as to coincide with the three-phase current command value output from the coordinate converter 11, thereby the inverter. 3 is obtained, and a current according to the three-phase current command value is caused to flow through the induction generator 2. In the above equations (2) and (3), cos θ and sin θ are phase angles calculated by the oscillator 14 with reference to the power system voltage, cos θ is a component in phase with the power system voltage, and sin θ is calculated from the power system voltage. The components with 90 ° phase delay are shown.

A function generator 13 provided between the power system voltage detector 6 and the coordinate converter 7 is a power system voltage that is an output of the detector 6 in the multiplier 15 so that the inverter 3 does not output a sudden voltage. By multiplying the detection value by the ramp function, for example, as shown in FIG. 2, it is provided to obtain a voltage that rises from 0 to 100% at a constant rate.
When the induction generator 2 is connected to the power system 1 with the above-described configuration, the rotation speed of the induction generator 2 is set to the electric power by an external means such as an engine (not shown) with the circuit breaker 4 in the “open” state. Control is performed so that the frequency of system 1 is obtained.

  For example, as shown in FIG. 9, the rotational speed of the induction generator 2 is controlled with the rated speed as a target. However, since external means such as an engine cannot be controlled at high speed, speed fluctuation occurs. Here, when the rated power exceeds the rated speed and the active power flows from the induction generator 2 to the inverter 3, the rectifier 16 cannot regenerate the active power to the power system 1, and thus the DC voltage of the inverter 3 increases. . For this reason, the voltage of the DC capacitor 17 of the inverter 3 is detected by the voltage detector 18, and the voltage set by the setting device 20 is subtracted from the detected DC voltage by the subtractor 22, and zero is set as the lower limit. Input to the lower limiter 21.

  When the output of the lower limiter 21 is greater than or equal to zero, that is, when the detection voltage becomes higher than the set voltage, the voltage regulator 19 is operated and the output is added to the frequency setting unit of the oscillator 14 to change the frequency cos θ. Calculate ', sin θ'. By calculating the output frequency of the inverter 3 on the basis of the cos θ ′ and sin θ ′, the rotational speed of the induction generator 2 is made substantially the same, and the inflow of active power from the induction generator 2 can be suppressed.

  Next, when the inverter 3 is operated, the inverter 3 outputs a current to the induction generator 2 so that the difference between the power system voltage and the induction generator voltage becomes zero as described above. When 100% of the power system voltage is output from the multiplier 15, the induction generator voltage becomes the same as the power system voltage. After that, the circuit breaker 4 is “closed” so that the power system 1 can be connected.

Here, when the rotational speed of the induction generator is lower than the power system voltage frequency, the active power is supplied from the inverter 3 to the induction generator 2 via the rectifier 16. In addition, when the rotational speed of the induction generator is higher than the power system voltage frequency, the direct current voltage increases due to the flow of active power from the induction generator 2 to the inverter 3. In this case, the operation of the voltage regulator 19 is performed. Thus, by adjusting the frequency of the output current of the inverter 3 to the rotational frequency of the induction generator 2, it is possible to suppress an increase in DC voltage.
By doing so, the magnitude and frequency of the voltage of the induction generator can be controlled to be the same as the power system voltage without increasing the DC voltage of the inverter. It is possible to suppress the inrush current by supplying.

FIG. 3 shows another embodiment of the present invention.
This is characterized in that a power storage facility 26 is connected to the DC side of the inverter 3 provided between the induction generator 2 and the circuit breaker 4. The power storage facility 26 is a facility such as a lead storage battery, a flywheel or an electric double layer capacitor, and a converter such as a chopper for stepping up and down the DC voltage may be connected as necessary. The inverter 3 has a generally well-known configuration including, for example, semiconductor switch elements Ta to Tf, diodes Da to Df, a capacitor C, and the like as shown in FIG.

  When the induction generator 2 is linked to the power system 1 with the above configuration, the rotational speed of the induction generator 2 is set to the power system 1 by an external means such as an engine (not shown) with the circuit breaker 4 in the “open” state. It controls so that it may become the frequency vicinity of. As shown in FIG. 9, the rotational speed of the induction generator 2 is controlled with the rated speed as a target. However, since external means such as an engine cannot be controlled at high speed, speed fluctuation occurs. For this reason, when there is no power storage facility 26, the DC voltage rises or falls according to this speed fluctuation.

  That is, when the rotational speed of the induction generator 2 becomes equal to or higher than the rated frequency, effective power flows from the induction generator 2 to the inverter 3, so that the DC voltage of the inverter 3 may increase and cause device damage. Further, when the rotational speed of the induction generator 2 becomes lower than the rated frequency, the effective power flows from the inverter 3 to the speed induction generator 2, so that the voltage of the capacitor C connected to the inverter 3 is lowered, and the inverter operation is performed. The problem that it becomes impossible.

  For this reason, by connecting the power storage facility 26 to the DC side of the inverter 3, even if the rotational speed of the induction generator 2 fluctuates, the power storage facility 26 is charged and discharged to increase the DC voltage. As a result, the apparatus can be prevented from being damaged, and an inoperable state of the inverter due to a DC voltage drop can be avoided.

  In the control device 27 that controls the inverter 3, the voltage of the power system 1 is detected by the voltage detector 6, the voltage of the induction generator 2 is detected by the voltage detector 5, and the output current of the inverter 3 is detected by current detection. This is detected by the instrument 25. Then, the inverter 3 is controlled so as to output a current such that the voltage of the power system 1 and the voltage of the induction generator 2 are the same. After that, when the voltage of the induction generator 2 becomes the same as the voltage of the power system 1, the circuit breaker 4 is "closed" to connect to the power system 1. At this time, since the voltage of the induction generator 2 is the same as the voltage of the power system 1, there is no possibility that an excessive current flows.

FIG. 5 shows a modification of FIG.
As is clear from comparison with FIG. 3, the feature is that two circuit breakers 28a and 28b are connected to the output of the inverter 3. This is because, depending on the charge amount of the power storage facility 26 and fluctuations in the rotational speed of the induction generator 2, the power storage facility 26 can generate power from the induction generator 2 while the rotational speed of the induction generator 2 is higher than the rated rotational speed. When the power storage facility 26 cannot completely discharge power to the induction generator 2 when the induction generator 2 cannot be fully charged or when the rotation speed of the induction generator 2 is lower than the rated rotation speed .

As methods for dealing with the above cases, the following methods 1 and 2 are conceivable.
Method 1: A method in which the number of revolutions of the induction generator 2 is reduced to an average lower than the rated number of revolutions, and the electric discharge is averaged from the power storage facility 26. That is, the induction generator 2 is connected to the power system 1. In this case, after the circuit breaker 28a is in the “closed” state and the inverter 3 is connected to the power system 1 and the power storage facility 26 is charged, the circuit breaker 28b is “open” and the circuit breaker 28a is “closed”. As shown in FIG. 6A, the number of revolutions of the induction generator 2 is controlled to be lower than the rated speed on average, and the electric power storage facility 26 is discharged to the induction generator 2.

  In the control device 27 that controls the inverter 3, the voltage of the power system 1 is detected by the voltage detector 6, the voltage of the induction generator 2 is detected by the voltage detector 5, and the output current of the inverter 3 is detected by current. This is detected by the instrument 25. Then, the inverter 3 is controlled so as to output a current such that the voltage of the power system 1 and the voltage of the induction generator 2 are the same. After that, when the voltage of the induction generator 2 becomes the same as the voltage of the power system 1, the circuit breaker 4 is "closed" to connect to the power system 1. At this time, since the voltage of the induction generator 2 is the same as the voltage of the power system 1, there is no possibility that an excessive current flows. Moreover, since the charge / discharge capacity of the power storage facility 26 does not become insufficient, the induction generator 2 can be stably started.

Method 2: A method in which the number of revolutions of the induction generator 2 is set to be higher than the rated number of revolutions on an average and the average is charged from the power storage facility 26. That is, the induction generator 2 is connected to the power system 1. In this case, after the circuit breaker 28b is in the “closed” state, the inverter 3 is connected to the power system 1 and the power storage facility 26 is discharged, the circuit breaker 28b is “open”, and the circuit breaker 28a is “closed”. As shown in FIG. 6B, the induction generator 2 is controlled so that the number of revolutions is increased above the rated speed on average, and the induction generator 2 is charged from the power storage facility 26.

  In the control device 27 that controls the inverter 3, the voltage of the power system 1 is detected by the voltage detector 6, the voltage of the induction generator 2 is detected by the voltage detector 5, and the output current of the inverter 3 is detected by current. This is detected by the instrument 25. The inverter 3 is controlled so as to output a current such that the voltage of the power system 1 and the voltage of the induction generator 2 are the same. After that, when the voltage of the induction generator 2 becomes the same as the voltage of the power system 1, the circuit breaker 4 is "closed" to connect to the power system 1. At this time, since the voltage of the induction generator 2 is the same as the voltage of the power system 1, there is no possibility that an excessive current flows. Moreover, since the charge / discharge capacity of the power storage facility 26 does not become insufficient, the induction generator 2 can be stably started.

FIG. 7 shows another modification of FIG.
This is the third method for dealing with the charge amount of the power storage facility 26 and the rotational speed fluctuation of the induction generator 2, and a detector 29 for detecting the charge amount of the power storage facility 26 is added. This is a feature. That is, it is a method of detecting the amount of charge of the power storage facility 26 and changing the output frequency of the inverter 3 to prevent charging or discharging when it is determined that charging or discharging exceeding the capacity is necessary.

  That is, when the induction generator 2 is connected to the power system 1, the control device 27 that controls the inverter 3 detects the voltage of the power system 1 with the voltage detector 6 and detects the voltage of the induction generator 2 with voltage. And the output current of the inverter 3 is detected by the current detector 25. The inverter 3 is controlled so as to output a current such that the voltage of the power system 1 and the voltage of the induction generator 2 are the same. Further, when the charge amount of the power storage facility 26 is detected and it is determined that charging or discharging exceeding the capacity is necessary, the output frequency of the inverter 3 is matched with the frequency of the induction generator 2.

  As described above, the electric power of the induction generator 2 is caused by the frequency difference between the induction generator 2 and the inverter 3 in the same manner as the active power is input / output due to the frequency difference from the power system 1. Since input / output is performed, if the frequency of the inverter 3 and the frequency of the induction generator 2 match, there is no input / output of active power. In short, the output frequency of the inverter 3 outputs the same frequency as that of the power system 1 when the power storage facility 26 has the charge / discharge capacity, and when the power storage facility 26 does not have the charge / discharge capacity, the induction power generation. The same frequency as that of the machine 2 is output.

  When the voltage of the induction generator 2 becomes the same as the voltage of the power system 1, the circuit breaker 4 is "closed" to connect to the power system 1. At this time, since the voltage of the induction generator 2 is the same as the voltage of the power system 1, there is no possibility that an excessive current flows. Moreover, since the charge / discharge capacity of the power storage facility 26 does not become insufficient, the induction generator 2 can be stably started.

Block diagram showing an embodiment of the present invention Waveform diagram showing an example of the multiplier output shown in FIG. The block diagram which shows another embodiment of this invention Circuit diagram showing a general example of an inverter used in FIG. The block diagram which shows the 1st modification of FIG. Waveform diagram explaining the operation of the invention of FIG. The block diagram which shows the 2nd modification of FIG. Block diagram showing a conventional example Waveform diagram explaining the operation of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electric power system, 2 ... Induction generator, 3 ... Inverter, 4,28a, 28b ... Circuit breaker, 5, 6, 18, 29 ... Voltage detector, 7, 8, 11 ... Coordinate converter, 9, 10, DESCRIPTION OF SYMBOLS 19 ... Voltage regulator, 12 ... Current regulator, 13 ... Ramp function generator, 14 ... Oscillator, 15 ... Multiplier, 16 ... Rectifier, 17 ... Capacitor, 20 ... Setting device, 21 ... Lower limiter, 22 ... Subtractor , 25 ... current detector, 26 ... power storage facility, 27 ... control device.

Claims (5)

  A rectifier that converts AC power on the power system side to DC power in parallel with a circuit breaker between the power system and the induction generator for an induction generator that supplies power to a load connected to the power system. And an inverter that converts the DC power into AC power on the induction generator side, and when the induction generator is connected to the power system, the inverter and the induction generator are switched from the rectifier while the induction generator is rotated. The current for supplying the loss of the current, the current for making the induction generator voltage equal to the power system voltage is calculated, and this current is passed from the inverter to the induction generator, and then linked to the power system. Induction generator start-up method.   A rectifier that converts AC power on the power system side to DC power in parallel with a circuit breaker between the power system and the induction generator for an induction generator that supplies power to a load connected to the power system. And an inverter that converts the DC power into AC power on the induction generator side, and when the induction generator is connected to the power system, the inverter and the induction generator are switched from the rectifier while the induction generator is rotated. And calculating the current for making the induction generator voltage equal to the power system voltage, calculating the frequency of the current according to the DC voltage of the inverter, and calculating the current of the calculated frequency to the inverter Induction generator start-up method, characterized in that after flowing into the induction generator, it is linked to the power system.   An induction generator that supplies power to a load connected to the power system is connected to the power system via a circuit breaker, and a power storage facility is connected to the DC side between the circuit breaker and the induction generator. When the induction generator is connected to the grid, the induction generator voltage is the same as the power grid voltage from the inverter to the induction generator with the induction generator rotated near the rated speed. Induction generator start-up system characterized by connecting to the power system after flowing current.   An induction generator that supplies power to a load connected to the power system is connected to the power system via a circuit breaker, and a power storage facility is connected to the DC side between the circuit breaker and the induction generator. Inverter and another inverter that connects to the inverter and the power system on the output side of this inverter, and when the induction generator is connected to the system, the number of revolutions of the induction generator is less than or equal to the rated number of revolutions. In this state, after connecting the inverter to the power system and charging or discharging the power storage facility, the inverter is connected to the induction generator, and the induction generator voltage is connected to the power system voltage. An induction generator start-up system characterized in that after the same current flows, it is linked to the power system.   An induction generator that supplies power to a load connected to the power system is connected to the power system via a circuit breaker, and a power storage facility is connected to the DC side between the circuit breaker and the induction generator. If the induction generator is connected to the grid, the output frequency of the inverter must be the same frequency as the induction generator above the charge / discharge capacity of the power storage facility, or below the charge / discharge capacity of the power storage facility. Induction characterized in that, while controlling to the same frequency as the power system, an electric current that causes the induction generator voltage to be the same as the power system voltage flows from the inverter to the induction generator, and then is linked to the power system. Generator start-up method.

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