JP2005341740A - Power generation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power generation system which reduces switching loss of a power converter, which enhances an efficiency, and enables miniaturization/weight reduction of the whole system. <P>SOLUTION: The power generation system includes the power converter 200 having a semiconductor switching element and a diode, and an ac generator 10 with a magnetic field connected to this power converter. The power generation system delivers and receives a power between its dc voltage part 50 and the generator 10 by the converting operation of the power converter 200. In the power generation system, as the operation mode of the power converter 200, the power generation system has a first mode for controlling on/off of the semiconductor switching element to regulate the generated power of the generator 10 and a second mode for turning off all the semiconductor switching elements and power generating by the rectifying operation of the diode. These first mode and second mode is switchable by a mode switching unit 70 and a switch 80. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power generation system including an AC generator having a field element made of a permanent magnet or a field winding, and a power converter for controlling the power generated by the field-equipped AC generator.

FIG. 8 shows the prior art of this type of power generation system. In the figure, 10 is an AC generator with a field, 20 is a power converter connected to the three-phase AC output side of the generator 10, 30 is a capacitor connected to the DC output side of the power converter 20, and 40 is a load. , 50 are DC voltage portions at both ends of the capacitor 30.
In the above configuration, the generator 10 is given a rotational force by a power source (not shown), and its field is constituted by a permanent magnet or a field winding.
The power converter 20 performs power conversion while appropriately controlling the terminal voltage of the generator 10, generates a predetermined DC voltage in the DC voltage unit 50, and supplies DC power to the load 40.

  Here, when the generated power of the generator 10 and the power consumption of the load 40 are equal, the voltage across the capacitor 30, that is, the voltage of the DC voltage unit 50 is maintained constant. Therefore, the power converter 20 is basically controlled by adjusting the power generated by the generator 10 so that the voltage across the capacitor 30 is constant.

Next, FIG. 9 is a circuit diagram showing a typical configuration of the power converter 20 in the above prior art.
This power converter 20 is a so-called three-phase voltage source inverter, which is a semiconductor switching element (IGBT in the figure) 21 connected in a three-phase full bridge, and a diode (freewheeling diode) 22 connected in reverse parallel to each switching element 21. It consists of and.
In this type of power converter 20, when it is desired to finely control the power generated by the generator 10, particularly when it is desired to reduce the harmonics of the current waveform and the torque pulsation of the generator 10, PWM control is generally performed. is there. Since the configuration and operation of a control circuit for performing this PWM control are well known, description thereof is omitted here.
As the power converter, various types of power converters other than the three-phase voltage source inverter of FIG. 9 can be used, and the number of phases is not limited to three.

  In addition, the power generation system as shown in FIG. 8 is disclosed by the following patent document 1, for example.

Japanese Patent Laid-Open No. 11-46456 (Claim 1, FIG. 1, FIG. 2, etc.)

In the case of PWM control of the power converter, it is well known that the switching loss becomes remarkable because each switching element is repeatedly turned on and off at a high frequency around several [kHz] to 10 [kHz].
On the other hand, since efficiency is important in the power generation system, reduction of switching loss is strongly desired. If the generated loss is reduced, the amount of heat generated from the switching element is reduced accordingly, so that the cooling structure can be simplified and the entire system can be reduced in size and weight.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a power generation system in which switching loss of a power converter is reduced to improve efficiency, and the entire system can be reduced in size and weight.

In order to solve the above-mentioned problem, the invention described in claim 1 is provided with a power converter having a semiconductor switching element and a diode, and an AC generator with a field connected to the power converter, and the power converter In the power generation system for transferring power between the DC voltage unit and the generator by the conversion operation of
As the operation mode of the power converter, a first mode in which the power generated by the generator is adjusted by controlling on / off of the semiconductor switching element, and the semiconductor switching element is turned off to generate power by the rectifying action of the diode. The second mode is switchable between the first mode and the second mode.

The invention described in claim 2 is the invention according to claim 1,
The power converter includes a number of phases composed of a series connection circuit of a plurality of semiconductor switching elements for the number of phases, and these arms are connected in parallel to the DC voltage unit, and between the semiconductor switching elements in each arm. Each phase terminal of the generator is connected to one connection point, and the diode is connected in the opposite direction between both ends of the DC voltage unit and the connection point.

The invention described in claim 3 is the invention according to claim 1 or 2,
When the amplitude of the no-load induced voltage between the generators is equal to or greater than the voltage amplitude of the DC voltage unit, the power converter is operated in the second mode.

The invention described in claim 4 is the invention according to claim 1 or 2,
The amplitude of the line no-load induced voltage of the generator is less than the voltage amplitude of the DC voltage unit, or the amplitude of the line no-load induced voltage of the generator is greater than or equal to the voltage amplitude of the DC voltage unit. When the generated power needs to be adjusted, the power converter is operated in the first mode.

The invention described in claim 5 is the invention according to claim 1 or 2,
When a direct-current power source is connected to the direct-current voltage unit, and the amplitude of the no-load induced voltage between the generators is greater than or equal to the voltage amplitude of the direct-current power source, the power converter is switched between the first mode and the second mode. It is used in combination or only in the second mode.

The invention described in claim 6 is the invention according to claim 1 or 2,
A direct current power source is connected to the direct current voltage unit via a diode having a polarity in which a current flows into the direct current voltage unit, and the amplitude of the line no-load induced voltage of the generator is greater than or equal to the voltage amplitude of the direct current power source. In some cases, the power converter is operated in combination of the first mode and the second mode or only in the second mode.

  The invention described in claim 7 is characterized in that, in claim 5 or 6, the voltage of the DC power supply can be controlled.

The invention described in claim 8 is any one of claims 1 to 7,
While the power converter is operating in the second mode, the generated power of the generator is controlled by switching to the first mode.

The invention described in claim 9 is any one of claims 1 to 8,
Before switching from the first mode to the second mode, the voltage of the DC voltage section is changed so as to approach the steady state value after switching to the second mode.

The invention described in claim 10 is any one of claims 1 to 9,
In the first mode, the power converter is controlled without using the rotor position detection value of the generator, and when switching from the second mode to the first mode, based on the current flowing through the generator, The rotor position of the generator is estimated, and control of the power converter is started based on the estimated value.

  According to an eleventh aspect of the present invention, in the tenth aspect, when the second mode is switched to the first mode, the rotor position of the generator is estimated based on the phase of the current flowing through the generator. is there.

According to the first to eighth aspects of the invention, the switching loss of the power converter can be reduced to improve the efficiency, and at the same time, the cooling system can be simplified to reduce the size and weight of the entire system. Moreover, it is possible to realize a power generation system capable of finely controlling the power generated by the generator as required.
According to the invention described in claims 9 to 11, an inrush current at the time of switching from the first mode to the second mode can be avoided to reduce the burden on the element overheating, the generator, the mechanical system, etc. Instability of control can be prevented by suppressing the voltage fluctuation. In addition, when switching from the second mode to the first mode, the rotor position can be appropriately estimated and the power converter is smoothly activated by position sensorless control, so that highly reliable power generation that does not generate excessive torque or current is possible. A system can be provided.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, FIG. 1 is a block diagram showing a first embodiment of the present invention. The same components as those in FIG. 8 are denoted by the same reference numerals and the description thereof will be omitted. Hereinafter, different parts will be mainly described. .

In FIG. 1, reference numeral 200 denotes a power converter, which converts the power generated by the field AC generator 10 into DC power and supplies it to a load 40. The power converter 200 may have the same configuration as that of FIG. 9 described above, the configuration of FIG. 2 described later, or a configuration other than these.
Reference numeral 60 denotes a switching pattern generation unit, 70 denotes a mode switching unit, and 80 denotes a switch. The switching pattern generator 60 generates and outputs a switching pattern for the semiconductor switching element of the power converter 200. The mode switching unit 70 is a control signal for switching between a first mode in which the switching elements are turned on / off according to the switching pattern to adjust the generated power of the generator 10 and a second mode in which all the switching elements are turned off. Is output. The switch 80 is for switching the output signal (switching pattern) of the switching pattern generator 60 and the all-off signal according to the control signal and supplying it to the power converter 200.

  In the power converter 20 shown in FIG. 9, when all the switching elements 21 are turned off, the current substantially does not flow through the switching elements 21, so that the switching elements 21 are connected in antiparallel. It can be seen that only the diode 22 can conduct current. This means that the generator 10 and the DC voltage unit 50 are substantially coupled via a diode rectifier.

Since the AC generator 10 with a field generates a no-load induced voltage, if the line voltage amplitude becomes larger than the voltage amplitude of the DC voltage unit 50, the diode in the power converter is turned on to perform power generation operation. be able to. At this time, since no switching loss occurs in the power converter, the efficiency of the power converter can be greatly increased.
On the other hand, when the no-load induced voltage is low or the no-load induced voltage is high and it is desired to control the generated power finely, the switching element of the power converter is controlled on / off according to a predetermined switching pattern. It is possible to adjust the generated power.
Focusing on the above points, in the present invention, as an operation mode of the power converter 200, a first mode in which generated power is adjusted by controlling on / off of the switching elements, and a second mode in which all the switching elements are turned off. By using both of these, it is possible to control the generated power and improve the efficiency of the entire power generation system.

Specific operations based on the above-described principle are as follows.
First, when the load 40 of the power converter 200 is a passive element such as a resistor, the power supplied to the load 40 is proportional to the square of the voltage of the DC voltage unit 50. Further, the generated power of the generator 10 monotonously increases with respect to the difference between the amplitude of the no-load induced voltage and the voltage amplitude of the DC voltage unit 50 (that is, the generated power increases as the voltage difference increases). Since the no-load induced voltage is proportional to the speed of the rotor of the generator 10, the higher the rotational speed, the larger the generated power.
Therefore, in order to control the power supplied to the load 40 in the second mode described above, the rotational speed of the generator 10 may be controlled.

On the other hand, when the load 40 is active such as an inverter, the power of the load 40 is controlled by the inverter itself, and at this time, the power required by the inverter is absorbed from the DC voltage unit 50.
The inverter is often controlled so that the output power becomes a desired value even when the voltage of the DC voltage unit 50 changes. On the other hand, the generated power of the generator 10 monotonously increases with respect to the difference between the amplitude of the no-load induced voltage and the voltage amplitude of the DC voltage unit 50 as described above.
Therefore, in the second mode, the voltage of the DC voltage unit 50 automatically converges to a value at which the power absorbed by the inverter matches the power generated by the generator 10.

The above operation is the same not only when the power converter 200 is a three-phase voltage source inverter as shown in FIG. 9 but also when it is a neutral point clamp type multi-level inverter as shown in FIG. It holds. The power converter shown in FIG. 2 is a three-level inverter, and includes semiconductor switching elements 201 to 212 and diodes 221 to 232 and 241 to 246. The capacitors 31 and 32 correspond to the capacitor 30 in FIG.
The operation of this type of neutral-point clamped three-level inverter is known from, for example, Japanese Patent No. 3287137 “PWM control method for three-level inverter”, Japanese Patent No. 3248321 “control circuit for three-level inverter”, etc. , Omit the explanation.
That is, the present invention is applicable to all power generation systems in which a field generator is coupled to a DC voltage unit through a power converter that operates substantially as a diode rectifier when all switching elements are turned off. Yes, it is not limited by the form of power converter or the number of phases.

Next, FIG. 3 is a block diagram showing a second embodiment of the present invention.
In FIG. 3, reference numeral 90 denotes a DC power source connected to the DC voltage unit 50 in FIG. 1, and the voltage of the DC voltage unit 50 is regulated by the voltage of the DC power source 90.
In this embodiment, the generated power of the generator 10 in the second mode monotonically increases with respect to the difference between the amplitude of the no-load induced voltage and the voltage amplitude of the DC voltage portion as described above. When the voltage is constant, the generated power increases as the no-load induced voltage increases, that is, as the rotational speed of the generator 10 increases.

  When the generated power is larger than the power of the load 40, surplus power is supplied to the DC power supply 90. For example, when the DC power supply 90 is a battery, this battery is charged with surplus power. On the contrary, if the generated power is smaller than the power of the load 40, the insufficient power is supplied from the DC power supply 90.

When it is desired to control the power that enters and exits the DC power supply 90 (the power that is exchanged with the power converter 200), the second mode is stopped and the mode is shifted to the first mode. It can be implemented indirectly by controlling 10 generated power. That is, when the power exchanged between the DC power supply 90 and the power converter 200 is P _S , the generated power of the generator 10 is P _G , and the load power is P _L , the relationship of Formula 1 is established, so the load by controlling the generated power P _G in accordance with the power P _L, it can control power P _S to a predetermined value.
[Formula 1]
P _S = P _G -P _L

  As described above, the present system can be applied even when the DC power supply 90 is connected. Normally, by selecting the second mode by the mode switching unit 70, the power converter 200 of the power converter 200 is similar to the embodiment of FIG. Switching loss can be reduced. When the power of the generator 10 needs to be adjusted, the mode switching unit 70 may switch to the first mode, and the switching pattern of the switching pattern generation unit 60 may be turned on / off.

When the voltage of the DC power supply 90 can be controlled, the generated power of the generator 10 depends on the voltage of the DC voltage unit (DC power supply 90) as described above. The generated power of the generator 10 can be controlled in a state where the switching is not performed.
However, when the rotational speed of the generator 10 is increased and the no-load induced voltage is increased, and the control upper limit of the voltage of the DC power supply 90 is determined, the generated power cannot be suppressed. In that case, if the power converter 200 is shifted to the first mode, the generated power of the generator 10 can be controlled.

Next, FIG. 4 is a block diagram showing a third embodiment of the present invention.
In this embodiment, the diode 100 is connected between the DC power supply 90 and the DC voltage unit 50 in FIG. 3 described above with the polarity shown (the polarity in which current flows from the DC power supply 90 to the DC voltage unit 50). .
In the present embodiment, when the voltage of the DC voltage unit 50 is higher than the voltage of the DC power supply 90, the current is blocked by the action of the diode 100, so the DC power supply 90 and the DC voltage unit 50 or the power converter 200 The power transfer between is theoretically zero. In such a configuration, by controlling the voltage of the DC voltage unit 50 to be higher than the voltage of the DC power supply 90 by the power converter 200, all the load power is transferred from the generator 10 via the power converter 200. Can be supplied. If the power converter 200 is controlled so as to reduce the voltage of the DC voltage unit 50 when the load power is large or when it is desired to reduce the generated power of the generator 10, only the insufficient power is supplied from the DC power supply 90. It is supplied via the diode 100.

  Here, as a normal operating condition, if the rotational speed of the generator 10 is determined so that the amplitude of the line-no-load induced voltage of the generator 10 is higher than the voltage amplitude of the DC power supply 90, the power converter 200 is Electric power can be supplied to the load 40 without switching in the two modes. In this case, when the load power is a predetermined value, the power and the rotational speed of the generator 10 are designed so that the predetermined power is obtained from the generator 10 and the voltage of the DC voltage unit 50 becomes an appropriate value. There is a need to.

  When the load 40 is an active load such as an inverter, if the load power is reduced in the second mode, the power absorbed by the load 40 from the DC voltage unit 50 is reduced, and the current flowing to the load 40 is reduced. The electric power supplied from the generator 10 via the power converter 200 exceeds the load power. For this reason, the voltage of the DC voltage unit 50 automatically increases, and as a result, the generated power of the generator 10 decreases and converges to an appropriate value. And if load electric power becomes zero, the voltage of the DC voltage part 50 will rise to the amplitude of the line | wire no load induction voltage of the generator 10, and will be stabilized by the peak charge from what is called the generator 10. FIG.

Note that it may be necessary to reduce the generated power of the generator 10 while the power converter 200 is operating in the second mode.
That is, when the drive source of the generator 10 is, for example, a turbine, and it is desired to increase the shaft output applied to another load (eg, pump) of the turbine, Can be given to the load. However, when the rotational speed and the load power are constant, the generated power of the generator 10 is not controllable in the second mode.
Therefore, in such a case, it is only necessary to switch to the first mode and control the power converter 200 to reduce the power generated by the generator 10. After the transition to the first mode, when the load power exceeds the generated power of the generator 10, the voltage of the DC voltage unit 50 decreases to reach the voltage of the DC power supply 90, and the insufficient power is supplied from the DC power supply 90. Will come to be.
In summary, the power converter 200 is normally operated in the second mode, and switching to the first mode is performed only when the shaft torque or the generated power of the generator 10 needs to be controlled. It is possible to configure a power generation system capable of controlling generated power as necessary while reducing loss and increasing power generation efficiency.

  The above operation is similarly applied to a configuration in which an AC power supply 110 and a diode rectifier 120 are combined as shown in FIG. 5 instead of the DC power supply 90 and the diode 100 in FIG. In this case, the line voltage amplitude or effective value of the AC power supply 110 corresponds to the voltage of the DC power supply 90 in FIG. 4, and the operation is the same as in FIG.

Next, a fourth embodiment of the present invention will be described.
As described above, in the second mode, the generated power of the generator 10 is uniquely determined by the voltage of the DC voltage unit 50 and the rotational speed of the generator 10. For example, in the configuration of FIG. 4, when the power converter 200 is operated in the second mode and all load power is supplied from the generator 10, the voltage of the DC voltage unit 50 is the power generated by the generator 10. It converges to a value that matches the load power.

  On the other hand, in the first mode, when the load 40 is an active load such as an inverter, various values can be selected as the voltage of the DC voltage unit 50. That is, even if the voltage of the DC voltage unit 50 changes, if the load 40 is an active circuit configuration including a power converter such as an inverter, the load power can be arbitrarily adjusted, and power generation The generated power of the machine 10 can also be controlled by controlling an inverter or the like that constitutes the load 40.

In this case, with respect to the voltage of the DC voltage unit 50 at the time of switching from the first mode to the second mode, a situation occurs in which the voltage E _dc1 in the first mode and the voltage E _dc2 that converges in the second mode are different. there is a possibility.
Here, when there is a relationship of E _dc1 <E _dc2 , if the switching element of the power converter 200 is suddenly turned off and switched to the second mode suddenly during operation with the DC voltage E _dc1 in the first mode, Since the induced voltage is excessive with respect to E _dc1 , a large current enters the DC voltage unit 50 from the generator 10 via the power converter 200. At this time, since the switching elements are all turned off by switching to the second mode, it is impossible to control even if an excessive current flows.
This not only causes overheating of the circuit elements, but also has an adverse effect that the control of the active load becomes unstable due to a large voltage fluctuation of the DC voltage unit 50. Moreover, when the field of the generator 10 is comprised with the permanent magnet, there exists a possibility that a permanent magnet may be demagnetized by overcurrent.

Therefore, as shown in FIG. 6, when the voltage of the DC voltage unit 50 is operating at E _dc1 in the first mode, the DC voltage is applied between the times t _{1 and} t ₂ before switching to the second mode. By gradually increasing the voltage to _Edc2 and then shifting to the second mode, the inrush current can be prevented and the sudden change in the voltage of the DC voltage unit 50 can be prevented.
Even when the voltage of the DC voltage unit 50 does not coincide with E _dc2 when shifting to the second mode, if the value is larger than E _dc1 and close to E _dc2 , the effect of suppressing the inrush current is expected to some extent. can do.
Further, when E _dc1 > E _dc2 , overcurrent does not occur at the time of switching from the first mode to the second mode, but the voltage fluctuation of the DC voltage unit 50 becomes a disturbance to the control system. In order to avoid this, it is beneficial to reduce E _dc1 to a value equal to or close to E _dc2 over a period of time before switching.

Next, a fifth embodiment of the present invention will be described.
When a synchronous generator with a field is used as the generator 10, it is necessary to appropriately control the winding current in accordance with the position of the field magnetic pole in the rotor at the time of driving, so a rotor position detector is usually used. It has been. However, this position detector is generally expensive, and because the temperature conditions and mechanical constraints are larger than the generator body, its installation reduces the environment resistance of the entire device, and the rotor position detection signal There is a problem that wiring for sending the signal to the control circuit becomes complicated.

On the other hand, various so-called position sensorless driving methods have been proposed in which a field motor or generator is driven without using a rotor position detector. For example, Watanabe et al., “DC-Brushless Servo System without Rotor Position and Speed Sensor”, Proceedings of IEEE International Conference on Industrial Electronics, Control, and Instrumentation (IECON) '87, pp.228-234 ( 1987) and so on, but the explanation is omitted, but basically, the current detection value of the generator and the terminal voltage detection value of the generator (or the command of the voltage that the power converter applies to the generator) The rotor position is determined from the impedance characteristic of the generator based on the value.
In particular, the method using the voltage command value eliminates the need for a voltage detector, and only a current detector can be used as a detector, so that a low-cost system can be constructed.
According to the present invention, such a position sensorless driving method is a technique that can be used when the power converter 200 is operated in the first mode.

However, as in the present invention, the first mode in which the switching element of the power converter 200 is turned on and off to finely control the generated power of the generator 10 and the second mode in which the switching element is completely turned off and power is generated via the diode rectifier. When both modes are used, a current is flowing at the time of transition from the second mode to the first mode, but it is not a sine wave, and the voltage converter cannot use the power converter 200 because the power converter 200 is not operating. Further, when the rotational speed is reduced during operation in the second mode and the amplitude of the line no-load induced voltage of the generator 10 is lower than the voltage amplitude of the DC voltage unit 50, rectification by a diode included in the power converter 200 is performed. Since no operation is performed and the current becomes zero, no current information can be obtained.
Therefore, in order to switch from the second mode to the first mode in the present invention, it is necessary to estimate the rotor position using a technique other than the above-described general position sensorless driving method used in the first mode. .

In a position sensorless drive of a field generator (motor), a method for starting a power converter while the rotor is idling is described in, for example, “AC converter for AC rotating machine” described in JP-A-11-75394, etc. Exists.
In this known invention, the switching element is turned on while the rotor is idling, and the position, speed, and direction of rotation of the rotor are determined from the electric current flowing through the switching element. Generally, the position, speed, and direction of rotation of the rotor are determined. If it is known, it is possible to start the position sensorless operation by starting the power converter from the idling state of the rotor.

  However, the above-mentioned known invention assumes a case where the amplitude of the line no-load induced voltage while the rotor is idling is less than the voltage amplitude of the DC voltage section, and as in the second mode in the present invention, It cannot be applied to the position sensorless driving of the generator when the power converter is operating in the diode rectification mode.

Therefore, in the fifth embodiment of the present invention, when switching from the second mode to the first mode, the rotor position is estimated by the following method.
1) When the amplitude of the line no-load induced voltage while the rotor is idling is less than the voltage amplitude of the DC voltage section, the switching element is turned on as in the known invention described in JP-A-11-75394. Then, a current is passed through the generator, and the rotor position is determined based on the current.
2) If the amplitude of the line no-load induced voltage while the rotor is idling is greater than or equal to the voltage amplitude of the DC voltage section, the current is intermittently or continuously flowing through the generator, and therefore based on the current To determine the rotor position.

FIG. 7 shows an example of the no-load induced voltage waveform and each phase (U, V, W phase) current waveform of the generator in the case of 2).
As shown in the figure, the generator current is not a sine wave, but is an alternating current dependent on the phase of the no-load induced voltage, that is, depending on the rotor position. Therefore, it is possible to estimate the rotor position based on this current.

More specifically, the method 2) is as follows.
In a field generator (electric motor), the relationship between the phase of the no-load induced voltage and the rotor position is always fixed. Therefore, the rotor position can be determined if the phase of the no-load induced voltage is known. Also, since the frequency of the no-load induced voltage is proportional to the rotation speed of the rotor (proportional constant is the number of pole pairs of the rotor), the rotation speed can be detected if the frequency of the no-load induced voltage is known. The direction of rotation of the child can be determined from the phase order of the multiphase no-load induced voltage.

  As described above, the generated power being generated in the second mode is uniquely determined by the voltage of the DC voltage unit 50 and the rotation speed. Further, as shown in FIG. 7, the current waveform of the generator 10 and the phase of the current with respect to the no-load induced voltage are also uniquely determined by the voltage of the DC voltage unit 50 and the rotation speed. The reason is that when the voltage and the rotation speed of the DC voltage unit 50 are constant, the circuit including the generator 10, the power converter 200 (substantially a diode rectifier in the second mode) and the DC voltage unit 50 has a frequency and an amplitude. Is constituted by a constant no-load induced voltage, an impedance of the generator 10, a diode rectifier, and a DC power source having a constant voltage, and thus the steady state is uniquely determined. In this case, the ambient temperature is constant.

Since the frequency of the no-load induced voltage coincides with the frequency of the generator current, the frequency of the no-load induced voltage can be found from the detected frequency of the generator current, and the proportional rotation speed can be detected.
Further, if the voltage of the DC voltage unit 50 is detected, the generator current waveform is known from the voltage and the rotation speed, and the phase relationship between the generator current and the no-load induced voltage is also known. The rotor position is determined.
Furthermore, since the phase sequence of the generator current matches the phase sequence of the no-load induced voltage, it is possible to determine the rotation direction.
From the above, it is necessary to start the power converter 200 and start the position sensorless drive even when the amplitude of the line no-load induced voltage while the rotor is idling is equal to or greater than the voltage of the DC voltage unit. Information such as rotor position, speed and direction of rotation can be obtained.

The phase of the generator current may be detected by passing the generator current detection value through a low-pass filter or detecting the phase of the fundamental wave extracted by frequency analysis, or when the current becomes zero more easily. You may detect from.
Although the phase relationship between the no-load induced voltage and the generator current varies depending on the voltage of the DC voltage unit 50 and the rotation speed of the rotor, the change is relatively small, so refer to the voltage and rotation speed of the DC voltage unit 50. It is also possible to estimate the rotor position only from the phase of the generator current. In that case, even if there is an error between the estimated value and the actual value of the rotor position, the control system operates so that the error is reduced by starting the position sensorless drive, and then the operation is shifted to the normal operation. be able to.
Also, for two-phase generator currents of the three phases, the time when the same phase value (for example, zero phase) is measured, respectively, and the time difference and the electrical angle between the two phases (120 ° or 240 ° in the case of three phases) ) To obtain the rotation speed.

  In each of the embodiments described above, the power generation system in which the power converter 200 and the generator 10 are combined has been described. However, it is also possible to consider these as a combination of an inverter and an electric motor. It is also possible to obtain a shaft output by driving the electric motor with AC output power.

It is a block diagram which shows 1st Embodiment of this invention. It is a block diagram which shows an example of the power converter in FIG. It is a block diagram which shows 2nd Embodiment of this invention. It is a block diagram which shows 3rd Embodiment of this invention. It is a figure which shows the modification of 3rd Embodiment. It is operation | movement explanatory drawing in 4th Embodiment of this invention. It is a wave form diagram of the no-load induction voltage and current of a generator in a 5th embodiment of the present invention. It is a block diagram which shows a prior art. It is a typical block diagram of the power converter in FIG.

Explanation of symbols

10: AC generator with field 30: Capacitor 40: Load 50: DC voltage unit 60: Switching pattern generation unit 70: Mode switching unit 80: Switch 90: DC power supply 100: Diode 110: AC power supply 120: Diode rectifier 200: Power converter

Claims (11)

A power converter having a semiconductor switching element and a diode, and a field-connected AC generator connected to the power converter, between the DC voltage unit and the generator by the conversion operation of the power converter In power generation systems that send and receive electricity,
As the operation mode of the power converter, a first mode in which the power generated by the generator is adjusted by controlling on / off of the semiconductor switching element, and the semiconductor switching element is turned off to generate power by the rectifying action of the diode. A power generation system having a second mode, wherein the first mode and the second mode can be switched. The power generation system according to claim 1,
The power converter includes a number of phases composed of a series connection circuit of a plurality of semiconductor switching elements for the number of phases, and these arms are connected in parallel to the DC voltage unit, and between the semiconductor switching elements in each arm. Each phase terminal of the generator is connected to one connection point, and the diode is connected in the opposite direction between both ends of the DC voltage unit and the connection point. The power generation system according to claim 1 or 2,
The power generation system, wherein the power converter is operated in a second mode when the amplitude of the no-load induced voltage between the generators is equal to or greater than the voltage amplitude of the DC voltage unit. The power generation system according to claim 1 or 2,
The amplitude of the line no-load induced voltage of the generator is less than the voltage amplitude of the DC voltage unit, or the amplitude of the line no-load induced voltage of the generator is greater than or equal to the voltage amplitude of the DC voltage unit. When the generated power needs to be adjusted, the power converter is operated in the first mode. The power generation system according to claim 1 or 2,
A DC power source is connected to the DC voltage unit,
When the amplitude of the no-load induced voltage between the generators is greater than or equal to the voltage amplitude of the DC power supply, the power converter is operated in combination with the first mode and the second mode or only in the second mode. Power generation system characterized by The power generation system according to claim 1 or 2,
A direct current power source is connected to the direct current voltage part via a diode having a polarity in which current flows into the direct current voltage part,
When the amplitude of the no-load induced voltage between the generators is greater than or equal to the voltage amplitude of the DC power supply, the power converter is operated in combination with the first mode and the second mode or only in the second mode. Power generation system characterized by The power generation system according to claim 5 or 6,
A power generation system capable of controlling a voltage of the DC power supply. In the electric power generation system given in any 1 paragraph of Claims 1-7,
A power generation system that controls the power generated by the generator by switching to the first mode during operation of the power converter in the second mode. In the electric power generation system given in any 1 paragraph of Claims 1-8,
Before switching from the first mode to the second mode, the voltage of the DC voltage unit is changed so as to approach the steady state value after switching to the second mode. In the electric power generation system given in any 1 paragraph of Claims 1-9,
In the first mode, the power converter is controlled without using the rotor position detection value of the generator, and when switching from the second mode to the first mode, based on the current flowing through the generator, A power generation system that estimates a rotor position of a generator and starts control of the power converter based on the estimated value. The power generation system according to claim 10,
When switching from the second mode to the first mode, the rotor position of the generator is estimated based on the phase of the current flowing through the generator.

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