JP3788925B2 - Wind power generator using permanent magnet type synchronous generator and its starting method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wind power generator using a permanent magnet type synchronous generator and an improvement of a starting method thereof.
[0002]
[Prior art]
In a wind power generation system, for example, as disclosed in Japanese Patent Application Laid-Open No. 2000-345595, a wind turbine that rotates by wind energy is connected to a synchronous generator, and the wind turbine drives the synchronous generator so that the synchronous generator is Generate electricity. The AC power output from the synchronous generator is converted to DC power by a forward converter (first converter), and further converted to AC power at a commercial frequency by an inverse converter (second converter). Supplied.
[0003]
On the other hand, in order to drive a permanent magnet type synchronous machine at a variable speed, a generator speed sensor is required. Conventionally, a rotor position detector such as a pulse encoder or a resolver that can detect the absolute position of the rotor is used. It is common. As an example, Japanese Patent Laid-Open No. 2000-205002 describes a motor control system using a resolver. In sensorless vector control of a synchronous motor, for example, as shown in Japanese Patent Application Laid-Open Nos. 9-191698 and 2001-178174, magnetic pole position information is calculated from electric quantities such as terminal voltage and current. It is known.
[0004]
[Problems to be solved by the invention]
In wind power generation as well, it is desirable to adopt a variable speed drive control system that does not use a generator speed sensor because of cost reduction and space saving requirements, but the above prior art cannot meet such demands. Further, in the windmill, since the generator is installed in the nacelle located on the tower of the windmill, the distance from the generator speed sensor to the control device becomes long, so the generator speed sensor and the control device are connected. Noise is likely to enter the signal line, and such noise countermeasures are also required.
[0005]
It is an object of the present invention to drive a generator at a variable speed without using a generator speed sensor in a wind power generator using a permanent magnet type synchronous generator.
[0006]
[Means for Solving the Problems]
In one aspect of the present invention, in a wind power generation system in which a rotor of a permanent magnet type synchronous generator is connected to a shaft of a windmill and a first converter is connected to a stator winding of the generator, the synchronous generator A terminal voltage detector for detecting a terminal voltage of the current detector, a current detector for detecting a current flowing in a stator winding of the generator, and the terminal voltage detection value and the current detection value during operation of the first converter A first speed estimator for estimating the speed of the generator and a second speed estimator for estimating the speed of the generator based on the detected terminal voltage while the first converter is stopped. It is characterized by.
[0007]
By configuring in this way, the synchronous generator connected to the windmill can be driven at a variable speed without using a generator speed sensor, and the cost reduction of the wind power generator using the permanent magnet type synchronous generator can be achieved. Space can be saved.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the overall configuration of an embodiment of a wind turbine generator using a permanent magnet type synchronous generator according to the present invention. In FIG. 1, the rotor of the permanent magnet type synchronous generator 2 is connected to the shaft of the windmill 1, and when the windmill 1 is rotated by wind energy, the synchronous generator 2 has a variable frequency corresponding to the rotational speed of the windmill 1. Generates AC power. A forward converter (first converter) 3 is connected to the stator winding of the synchronous generator 2, and variable frequency AC power generated by the synchronous generator 2 is converted into DC power by the forward converter 3. Is done. The forward converter 3 is connected to a reverse converter (second converter) 5 via a direct current capacitor 4 in a direct current, and the reverse converter 5 converts the direct current power sent from the forward converter 3 into alternating current power having a fixed frequency. Convert to The reverse converter 5 is connected to the power system via the grid interconnection transformer 6 and supplies AC power of a fixed frequency to the power system.
[0009]
A generator terminal voltage detector 7 and a generator current detector 8 are installed between the synchronous generator 2 and the forward converter 3, and the generator terminal voltage detector 7 is a stator winding of the synchronous generator 2. The generator current detector 8 detects the current flowing through the stator winding of the synchronous generator 2. The detected voltage and current values are converted by the three-phase / two-phase converter 9 into two-axis components for an effective component and an invalid component.
[0010]
The first generator speed estimator 10 estimates the speed of the synchronous generator 2 based on the voltage and current signals of the two-axis components output from the three-phase / two-phase converter 9. Several methods for estimating the generator speed have been proposed. For example, in Japanese Patent Laid-Open No. 2001-178174 described above, a γ-δ coordinate system arbitrarily set on the rotor and the magnetic pole of the rotor are set. Estimating the deviation angle from the dq coordinate system and correcting the position of the γ-δ coordinate system while estimating the generator induced voltages εγ and εδ generated on the γ-δ coordinate system, A method of estimating the generator speed from the machine induced voltage is shown. The first generator speed estimator 10 can be configured by applying such a method, for example.
[0011]
The input of the speed controller 11 is a generator speed command and an estimated speed of the generator given via the switch 15, and its output is a current command for the forward converter 3. When the estimated speed of the synchronous generator 2 is larger than the speed command, the speed controller 11 increases the effective amount of the current command to be output. As a result, the effective power output from the synchronous generator 2 is increased, the effective power output from the synchronous generator 2 is larger than the mechanical input given from the wind to the wind turbine 1, and the shortage of the input is the blade of the wind turbine 1. Therefore, the rotational speed of the windmill 1 decreases following the generator speed command. Conversely, when the estimated speed of the synchronous generator 2 is smaller than the speed command, the speed controller 11 decreases the effective amount of the current command to be output. As a result, the effective power output from the synchronous generator 2 becomes smaller, the effective power output from the synchronous generator 2 becomes smaller than the mechanical input given to the wind turbine 1 from the wind, and the surplus of the input is the blade of the wind turbine 1 Therefore, the rotational speed of the windmill 1 increases following the generator speed command.
[0012]
The input to the current controller 12 is the current detection value of the biaxial component output from the three-phase / two-phase converter 9 and the current command to the forward converter 3 output from the speed controller 11, and the output is forward converted. This is a voltage command to the device 3. The current controller 12 determines the voltage command to the forward converter 3 so that the deviation between the detected current value and the current command becomes zero. The switch 16 is a switch that is switched depending on the operation state. During normal operation, {circle over (1)} is selected and a voltage command output from the current controller 12 is output. Since the voltage command to the forward converter 3 output from the switch 16 is a voltage command of a two-axis component, it is converted into a three-phase voltage command by the two-phase / three-phase converter 13.
[0013]
The pulse generator 14 outputs a gate pulse signal to the forward converter 3 by PWM (Pulse Width Modulation) based on the three-phase voltage command to the forward converter 3 output from the 2-phase / 3-phase converter 13. . The forward converter 3 receives the gate pulse signal, and the forward converter 3 outputs an AC terminal voltage according to the command by high-speed switching of a switching element such as an IGBT. As a result, the generator 2 follows the generator speed command by increasing the output power to the grid if there is surplus wind power, and decreasing the output power if the wind power is insufficient.
[0014]
The voltage speed converter 17 calculates | requires a generator speed from the generator terminal voltage detected with the generator terminal voltage detector 7, so that it may mention later. The magnetic pole position estimator 18 estimates the rotor magnetic pole position of the synchronous generator from the voltage and current detection values output from the three-phase two-phase converter 9. Regarding the estimation of the magnetic pole position of the synchronous machine, for example, in Japanese Patent Application Laid-Open No. 9-191698, the deviation between the γ-δ coordinate system arbitrarily set on the rotor and the dq coordinate system set on the magnetic pole of the rotor. It is disclosed that the magnetic pole position is detected by estimating the angle θe and correcting the deviation angle.
[0015]
Next, a starting method in this apparatus will be described. First, either a normal start command or a self-start command is given from the outside as an operation command. The normal start command is a command that is selected when a certain amount of wind is blowing, and the self-start command is a command that is selected when there is no wind or a light wind. Since the generator induced voltage of the synchronous generator 2 is proportional to the generator speed, the generator terminal voltage detection value detected by the generator terminal voltage detector 7 is zero or a minute value when there is no wind or a slight wind. In such a case, it may be difficult to estimate the generator speed. If the generator speed cannot be estimated, the synchronous generator 2 cannot be driven at a variable speed. In view of this, a method is adopted in which the synchronous generator 2 is driven as an electric motor when there is no wind or light wind, the speed is increased to a point where the generator speed of the synchronous generator 2 can be estimated, and then the generator speed is estimated. In this case, a self-start command is given, and the generator speed is estimated after the synchronous generator 2 is accelerated and driven as an electric motor. When the estimation is completed, the normal operation is started.
[0016]
On the other hand, when the normal start command is given, the generator speed of the synchronous generator 2 is estimated, and when the estimation is completed, the normal operation is started.
[0017]
In addition, for the acceleration driving in the case of performing self-starting, one of two types of acceleration driving methods is selected according to the generator speed at the time of starting. One is when the generator speed at the start is extremely low. In this case, the stator winding of the synchronous generator 2 is first DC-excited for a certain period. By this direct current excitation, the magnetic pole position of the synchronous generator 2 is fixed at a designated position, and thereafter, excitation is performed with an alternating voltage and frequency at which the ratio of the voltage and the frequency applied to the stator winding of the synchronous generator 2 becomes constant. The excitation frequency is increased with the lapse of time, and the synchronous generator 2 is accelerated from that position.
[0018]
The other is when the generator speed at the start is somewhat high. In this case, acceleration driving like the former cannot be performed. When the stator winding of the synchronous generator 2 is DC-excited in this speed range, the synchronous generator 2 is suddenly braked, which may cause damage to the blades of the windmill 1 and the like. Accordingly, in this case, the generator speed is estimated with a slightly reduced estimation accuracy and the estimation speed is slightly reduced. Then, the synchronous generator 2 is accelerated and driven in a state where the generator speed is temporarily estimated.
[0019]
Hereinafter, the self-starting method will be described in more detail. There are two types of acceleration drive methods for self-starting, and it is necessary to determine the generator speed at the start-up in order to determine which one should be selected. However, it is difficult to estimate the generator speed at the start, and the generator speed is obtained by the following method. For simplicity, a cylindrical synchronous generator will be described, but the same applies to a salient pole synchronous generator. When the d-axis synchronous reactance of the synchronous generator is Xd, the stator winding resistance is R, the generator induced voltage is E, the generator terminal voltage is V, and the generator current is I, equation (1) is established. However, here, the generator induced voltage E and the generator terminal voltage V are phase voltages.
[0020]
E = V + (R + jXd) · I ……………………………………………… (1)
Further, when the generator induced voltage constant is Ke and the generator speed is ω, the generator induced voltage E can be expressed by equation (2).
[0021]
E = Ke · ω ………………………………………………………………… (2)
Further, since the gate of the forward converter 3 is blocked at the time of starting, the generator current I is zero. At this time, the expression (3) is established from the expressions (1) and (2).
[0022]
V = Ke · ω ………………………………………………………………… (3)
That is, it can be seen that when the generator current is zero, the generator terminal voltage V and the generator speed ω are proportional. That is, if the generator terminal voltage V of the synchronous generator 2 is detected, the generator speed ω can be obtained. Therefore, at the time of starting, in order to obtain the generator speed ω from the detected generator terminal voltage V of the synchronous generator 2, the switch 15 is selected as (3), and the second generator speed estimator (voltage speed converter) is selected. 17 is used to determine the generator speed ω. The voltage speed converter 17 determines the generator speed ω by multiplying the detected generator terminal voltage value V detected by the generator terminal voltage detector 7 by a gain determined by the generator induced voltage constant Ke.
[0023]
FIG. 2 is an explanatory diagram of self-starting operation when the generator speed is low according to an embodiment of the present invention. The operation when the generator speed at the start is low in the self-start will be described with reference to this figure. In this case, (2) is selected for the switch 15 and (2) is selected for the switch 16, the generator speed of the synchronous generator 2 is given from the self-starting speed command, and the voltage command to the forward converter 3 is the self-starting voltage. Given from the directive. Next, when the gate of the forward converter 3 is unblocked and the stator winding of the synchronous generator 2 enters a DC excitation mode, the self-start voltage command gives a command corresponding to the DC excitation voltage, and the self-start The speed command outputs zero for a certain period. When the DC excitation for fixing the rotor at a predetermined angular position is completed, the self-starting voltage command and the self-starting speed command are increased while maintaining a constant ratio and applied to the stator winding of the synchronous generator 2 The synchronous generator 2 can be accelerated and driven as a synchronous motor by exciting with a voltage and a frequency so that the ratio of the voltage and the frequency becomes constant and increasing the excitation frequency with the passage of time. However, the angular position of the rotor is not necessary. Since the synchronous generator 2 follows the self-starting speed command, the self-starting speed command is used as the generator speed. Eventually, when the speed of the synchronous generator 2 increases and reaches a speed higher than a preset value, the gate of the forward converter 3 is blocked in order to accurately estimate the magnetic pole position and speed of the generator. Further, (3) is selected for the switch 15 and (1) is selected for the switch 16. Then, in the free-running state of the synchronous generator 2, the magnetic pole position estimator 18 estimates the magnetic pole position of the synchronous generator. At the same time, the generator speed is estimated by the second speed estimator 17. When the estimation is completed in 1 to 2 seconds, the forward converter 3 unblocks the gate. Further, the switch 15 is selected as (1) and the switch 16 is selected as (1), and the acceleration operation in the normal operation is started. During this normal operation, the operation is performed while always estimating the speed by the first speed estimator 10 and estimating the magnetic pole position by the magnetic pole position estimator 18.
[0024]
FIG. 3 is a diagram for explaining the self-starting operation when the generator speed is high to some extent according to one embodiment of the present invention. With reference to this figure, the operation when the generator speed at the time of starting is somewhat high in self-starting will be described. In this case, (3) is selected for the switch 15 and (1) is selected for the switch 16. Then, the judgment condition for estimating the generator magnetic pole position is relaxed, and the magnetic pole position is estimated with the estimation accuracy slightly reduced. For example, a relatively coarse magnetic pole position is estimated by selecting the allowable value of the deviation angle θe to be relatively large θ1 by the magnetic pole position estimation method described in Japanese Patent Laid-Open No. 9-191698. At the same time, the speed is estimated by the second generator speed estimator. These continue until the judgment condition is cleared. When the estimation of the generator speed and the magnetic pole position is temporarily completed, the gate of the forward converter 3 is unblocked. Further, the switch 15 is selected as (1) and the switch 16 is selected as (1), and the normal operation is temporarily entered while the relatively rough magnetic pole position is estimated. Then, the synchronous generator 2 is accelerated and driven by gradually increasing the generator speed command. Eventually, when the speed of the synchronous generator 2 increases and reaches a speed higher than a preset value, the gate of the forward converter 3 is blocked in order to accurately estimate the magnetic pole position and speed of the generator. Further, (3) is selected for the switch 15 and (1) is selected for the switch 16. Then, the magnetic pole position of the synchronous generator 2 is estimated by the magnetic pole position estimator 18 in the free running state of the synchronous generator 2. The judgment conditions for estimating the magnetic pole position at this time are strict, and the magnetic pole position is estimated with the estimation accuracy improved. For example, in the magnetic pole position estimation described in Japanese Patent Laid-Open No. 9-191698, a relatively fine magnetic pole position is estimated by selecting a relatively small allowable angle θe (θ2 <θ1). At the same time, the generator speed is estimated by the second speed estimator 17. When the estimation is completed, the forward converter 3 unblocks the gate. Further, the switch 15 is selected as (1) and the switch 16 is selected as (1), and the acceleration operation in the normal operation is started. During this normal operation, the operation is performed while always estimating the speed by the first speed estimator 10 and estimating the magnetic pole position by the magnetic pole position estimator 18.
[0025]
In the above embodiment, the rotor of the permanent magnet type synchronous generator 2 is connected to the shaft of the wind turbine 1, and the first converter 3 is connected to the stator winding of the generator 2. The converter is connected to the second converter 5 connected to the power system with a DC 4, converts the generated power of the generator 2 into DC power, and the second converter 5 uses the fixed frequency AC power. In the wind power generation apparatus that converts the voltage into the wind turbine generator, the voltage detector 7 that detects the terminal voltage of the stator winding, the current detector 8 that detects the current flowing through the stator winding, and the first converter 3 A first speed estimator 10 for estimating the speed of the generator 2 based on the terminal voltage and current detected during operation, and the voltage detection value based on the detected voltage value while the first converter 3 is stopped. A second speed estimator 17 for estimating the speed of the generator 2 and the second speed estimator at the start Means for estimating the speed of the generator 2 by means of 7 and means for direct current excitation of the stator winding of the generator 2 for a certain period of time using the first converter 3 when this estimated speed is less than a predetermined value; Then, self-starting control for controlling the first converter 3 so as to accelerate the generator 2 by exciting the stator winding of the generator 2 with an alternating current having a constant voltage-frequency ratio and gradually increasing. And when the estimated speed of the second speed estimator 17 at the start is equal to or higher than a predetermined value, the first converter 3 is operated so that the estimated speed by the first speed estimator 10 follows the speed command. A speed controller 11 for accelerating the generator 2 and after each acceleration, the first converter 3 is stopped and the speed of the generator 2 is determined based on the output of the second speed estimator 17. Means for estimating and then restarting the first converter 3 And a means for controlling the first transducer so as to re-accelerate the generator to follow the output of the first speed estimator 10 to the speed command.
[0026]
By adopting such a starting method, a wind power generator using a permanent magnet type synchronous generator can be used not only when the wind is blowing to some extent but also when there is no wind or light wind without using a generator speed sensor. It is possible to drive at a variable speed, thereby reducing costs and saving space.
[0027]
【The invention's effect】
According to the present invention, in a wind turbine generator using a permanent magnet type synchronous generator, the synchronous generator can be driven at a variable speed without using a generator speed sensor.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an embodiment of a wind power generator using a permanent magnet type synchronous generator according to the present invention.
FIG. 2 is an explanatory diagram of self-starting operation when the generator speed is low according to an embodiment of the present invention.
FIG. 3 is an operation explanatory view of self-starting when the speed is high to some extent according to one embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Windmill, 2 ... Permanent magnet type synchronous generator, 3 ... 1st converter (forward converter), 4 ... DC capacitor, 5 ... 2nd converter (reverse converter), 6 ... For grid connection Transformer, 7 ... Generator terminal voltage detector, 8 ... Generator current detector, 9 ... 3-phase / 2-phase converter, 10 ... First generator speed estimator, 11 ... Speed controller, 12 ... Current Controller, 13 ... 2-phase / 3-phase converter, 14 ... Pulse generator, 15, 16 ... Switch, 17 ... Second generator speed estimator (voltage speed converter), 18 ... Magnetic pole position estimator.

Claims (8)

A rotor of a permanent magnet type synchronous generator is connected to the shaft of the windmill, a first converter is connected to the stator winding of the generator, and the first converter is connected to a power system. In the wind power generator connected to the converter of No. 2 by DC and converting the electric power generated by the generator into DC electric power and converting the electric power to the fixed frequency AC electric power by the second converter, the terminal of the stator winding A voltage detector for detecting a voltage; a current detector for detecting a current flowing through the stator winding; and a speed of the generator based on a terminal voltage and a current detected during operation of the first converter. And a second speed estimator for estimating the speed of the generator based on the detected voltage value while the first converter is stopped. Wind power generator using a permanent magnet type synchronous generator. 2. The wind power using a permanent magnet type synchronous generator according to claim 1, wherein the second speed estimator estimates a value obtained by multiplying the terminal voltage detection value by a preset constant as a generator speed. Power generation device. 2. The means for direct current excitation of the stator winding of the generator using the first converter when the generator speed is less than a preset value, and then the voltage and frequency are compared to each other. Means for controlling the first converter so as to accelerate the generator by exciting the stator winding with a gradually increasing alternating current while maintaining the constant, and the excitation frequency or the first generator speed. And a means for stopping the first converter when the estimated speed by the estimator reaches a predetermined value and estimating the speed of the generator based on the output of the second speed estimator. Wind power generator using a permanent magnet type synchronous generator. 2. The means according to claim 1, wherein the second speed estimator estimates the speed of the generator at start-up, and when the estimated speed is greater than or equal to a predetermined value, the first converter is operated to operate the first speed. A speed controller for accelerating the generator by following an estimated speed of the estimator according to a speed command, and stopping the first converter when the estimated speed of the first speed estimator reaches a predetermined value; A wind power generator using a permanent magnet synchronous generator, characterized by comprising means for estimating the speed of the generator based on the output of a second speed estimator. 5. The first speed estimation according to claim 3, wherein after the acceleration, after estimating the speed of the generator based on the output of the second speed estimator, the first converter is restarted. A wind power generator using a permanent magnet type synchronous generator, comprising means for controlling the first converter so that the output of the generator follows a speed command and re-accelerates the generator. A rotor of a permanent magnet type synchronous generator is connected to the shaft of the windmill, a first converter is connected to the stator winding of the generator, and the first converter is connected to a power system. In the wind power generator connected to the converter of No. 2 by DC and converting the electric power generated by the generator into DC electric power and converting the electric power to the fixed frequency AC electric power by the second converter, the terminal of the stator winding A voltage detector for detecting a voltage; a current detector for detecting a current flowing through the stator winding; and a speed of the generator based on a terminal voltage and a current detected during operation of the first converter. A first speed estimator that estimates the generator speed, a second speed estimator that estimates the speed of the generator based on the detected voltage value while the first converter is stopped, and the second speed estimator at start-up. Means for estimating the speed of the generator by means of a speed estimator; Means for DC excitation of the generator stator winding for a period of time using the first converter when full, and then the generator winding of the generator gradually increases with a constant voltage to frequency ratio. Self-starting control means for controlling the first converter to accelerate the generator by exciting with alternating current; and when the estimated speed of the second speed estimator at the time of starting is equal to or higher than a predetermined value, the first A speed controller for operating the first converter to cause the speed estimated by the first speed estimator to follow the speed command and to accelerate the generator, and after each acceleration, stop the first converter. Means for estimating the speed of the generator based on the output of the second speed estimator, and then restarting the first converter and causing the output of the first speed estimator to follow the speed command; Control the first converter to re-accelerate the generator A wind power generator using a permanent magnet type synchronous generator characterized by comprising means. A rotor of a permanent magnet type synchronous generator is connected to the shaft of the windmill, a first converter is connected to the stator winding of the generator, and the first converter is connected to a power system. In the starting method of the wind power generator, which is connected to the converter of No. 2 by direct current, converts the generated power of the generator into direct current power, and converts it into alternating current power of a fixed frequency by the second converter. A step of direct current exciting the stator winding of the generator when the generator is less than a predetermined speed, and exciting the stator with an alternating current in which the ratio of voltage to frequency is substantially constant and increasing. A step of accelerating, a step of estimating a generator speed based on the excitation frequency during the acceleration, and when the estimated speed reaches a predetermined speed, the first converter is stopped to be in a free-run state. Estimating the speed from the voltage, and Restarting the first converter after completing the estimation, and estimating the speed based on the output voltage and output current of the generator so that the estimated speed follows the speed command. A method for starting a wind power generator using a permanent magnet type synchronous generator, comprising the step of further accelerating the generator by controlling a generator. A rotor of a permanent magnet type synchronous generator is connected to the shaft of the windmill, a first converter is connected to the stator winding of the generator, and the first converter is connected to a power system. In the starting method of the wind power generator, which is connected to the converter 2 by DC, converts the generated power of the generator into DC power, and converts it into AC power of a fixed frequency by the second converter, From the step of estimating the speed of the generator from the terminal voltage of the child winding, and starting the first converter when the estimated speed is equal to or higher than the predetermined speed, the terminal voltage and the current of the stator winding A step of accelerating the generator so that the estimated speed of the determined generator follows a speed command; and when the estimated speed reaches a predetermined speed, the first converter is stopped to be in a free-run state and the fixed Estimating the speed from the terminal voltage of the slave winding And after the estimation is completed, the first converter is restarted, and the estimated speed follows the speed command while estimating the speed based on the terminal voltage and the current of the stator winding. A method for starting a wind power generator using a permanent magnet synchronous generator, comprising the step of controlling the converter 1 to further accelerate the generator.

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