JP2007043774A - Power generation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power generation system which can be started stably at start of an engine. <P>SOLUTION: This power generation system includes the engine 4, an alternator 6 which is driven by the engine 4, a converter 8 which converts the power generated from the alternator 6 into specified DC power, and an inverter 10 which converts the DC power from the converter 8 into AC power. This power generation system 2 includes a temperature detecting means 24 for detecting the temperature of the alternator 6 and a control means 28 for controlling the revolution of the engine 4. At start of the engine 4, the control means 28 sets the revolution of the engine 4, based on the detected temperature of the temperature detecting means 24, whereby it becomes possible to stabilize the generation output of the power generation system 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power generation system that supplies generated power from an AC generator drive-coupled to an engine and AC power from a commercial power source to an electric power load.

  In recent years, there has been known a power generation system that supplies power generated from an AC generator connected to an engine and AC power from a commercial power source to an electric power load. This power generation system realizes efficient energy use. It is used in cogeneration systems that are gaining interest toward the future.

  This type of power generation system includes a self-excited synchronous generator, an engine for driving the synchronous generator, and a switching board for switching electric power. In the power generation system using this self-excited synchronous generator, it is necessary to make the frequency of the power generation output of the synchronous generator and the power frequency of the commercial power source coincide with each other. The engine speed is limited to a specific combination, for example, the number of poles of the electromagnet is set to 4 and the engine speed is set to 1800 rpm. Moreover, the generated voltage of a synchronous generator is performed by controlling an exciting current with an automatic voltage regulator.

In the system using the switching panel described above, there is a problem that the load factor of the applied cogeneration system cannot always be 100%.
Therefore, in order to solve the above-mentioned problems, those using inverters are becoming mainstream, and in systems using inverters, the generator output frequency of the generator is not limited. Therefore, a permanent magnet type high frequency generator (output voltage) To achieve higher efficiency. In an example of such a power generation system, an AC generator, a rectifier circuit for converting the generated power from the AC generator into predetermined DC power, and the DC power from the rectifier circuit are converted into predetermined AC power And a voltage detecting means for detecting a DC voltage on the DC side of the rectifier circuit, and a control means for controlling conduction of the thyristor constituting the rectifier circuit. When the detected voltage of the voltage detecting means exceeds a predetermined value, the control means turns off the thyristor of the rectifier circuit to cut off the current from the AC generator, and when the detected voltage falls below the predetermined value, the rectifier circuit The thyristor is turned on to release the interruption of the current from the AC generator, whereby the DC voltage on the DC side of the rectifier circuit is controlled to be constant.

  FIG. 7 shows another example of a power generation system using an inverter. In FIG. 7, a second type power generation system 100 includes an engine 102 and a permanent magnet type AC generator 104 driven by the engine 102. A converter 106 that converts the generated power from the AC generator 104 into predetermined DC power, an inverter 108 that converts the DC power from the converter 106 into predetermined AC power, and a DC voltage on the DC side of the converter 106 is detected. Voltage detecting means 110 for controlling the engine 102 and control means 112 for controlling the rotational speed of the engine 102 (see, for example, Patent Document 1). Power loads 116 a to 116 d are connected to the AC side of the inverter 108 via circuit breakers 118 a to 118 d, respectively, and AC power from the inverter 108 is connected to the commercial power source 114. AC power is supplied to the power loads 116a to 116d. When the detection voltage of the voltage detection unit 110 exceeds a predetermined value, the control unit 112 adjusts the throttle opening degree of the engine 102 to the opening degree side to decrease the rotation speed of the engine 102, and the detection voltage is a predetermined value. If the pressure is lower than that, the throttle opening of the engine 102 is adjusted to the large opening side to increase the rotational speed of the engine 102, whereby the DC voltage on the DC side of the converter 106 is controlled to be constant.

JP 2001-45799 A

  However, the conventional power generation system as described above has the following problems. In the first type power generation system, since the thyristor conduction is repeatedly turned on and off, a harmonic component is generated in the current flowing through the AC generator, and the power generation efficiency of the AC generator is reduced. .

In the second type power generation system 100, the DC voltage on the DC side of the converter 106 changes at a time interval of about several ms (10 ⁻³ seconds), whereas the control means 112 determines the rotational speed of the engine 102. Since the control is performed at a time interval of about several s (seconds), a control delay occurs between the time when the DC voltage on the DC side of the converter 106 changes and the time when the control means 112 controls the rotational speed of the engine 102, and the accuracy is high. There is a problem that the DC voltage on the DC side of the converter 106 cannot be controlled to be constant. Further, the generated voltage of the AC generator 104 is affected by the temperature of the AC generator 104 (in general, as the temperature rises, the magnetic force of the permanent magnet decreases and the resistance of the coil increases, resulting in this) Therefore, there is a problem in that the DC voltage on the DC side of the converter 106 when the engine 102 is started depends on the temperature of the AC generator 104 and the power generation system 100 cannot be started stably. is there. Furthermore, since the power generation voltage of AC generator 104 greatly fluctuates between the time when engine 102 is started and the temperature of AC generator 104 reaches the saturation temperature, the DC voltage on the DC side of converter 106 is not stable. There is a problem.

An object of the present invention is to provide a power generation system capable of stably starting a power generation system when the engine is started.
Another object of the present invention is to prevent a reduction in power generation efficiency of the AC generator after the engine is started, and to control the DC voltage on the DC side of the converter with a high degree of accuracy. It is to provide a power generation system that can.

In the power generation system according to claim 1 of the present invention, an engine, an AC generator driven by the engine, a converter for converting generated power from the AC generator into predetermined DC power, and the converter And an inverter for converting the DC power from the inverter into a predetermined AC power. The AC power from the inverter is interconnected with a commercial power source, and the AC power from the inverter and the commercial power source is supplied to a power load. A power generation system,
Temperature detecting means for detecting the temperature of the AC generator, and control means for controlling the rotational speed of the engine are provided,
When the engine is started, the control means sets the engine speed based on the temperature detected by the temperature detection means.

Further, in the power generation system according to claim 2 of the present invention, the control means includes a rotation speed setting means for setting the rotation speed of the engine, a temperature of the AC generator, and a rotation speed of the engine. A storage means for storing set rotational speed data indicating the relationship; and a reading means for reading the set rotational speed data stored in the storage means,
At the time of starting the engine, the reading means reads rotation speed data corresponding to the detected temperature of the temperature detection means from the set rotation speed data, and the rotation speed setting means reads the read rotation speed data to the engine. It is characterized in that it is set as the initial rotation speed.

Furthermore, in the power generation system according to claim 3 of the present invention, an engine, an AC generator driven by the engine, a converter for converting the generated power from the AC generator into predetermined DC power, An inverter for converting the DC power from the converter into predetermined AC power, the AC power from the inverter is grid-connected to a commercial power source, and the AC power from the inverter and the commercial power source is a power load A power generation system supplied to
Temperature detecting means for detecting the temperature of the AC generator, and control means for controlling the rotational speed of the engine are provided,
After starting the engine, the control means predicts the temperature of the AC generator after a predetermined time based on the temperature detected by the temperature detection means, and sets the engine speed based on the predicted temperature. Features.

Further, in the power generation system according to claim 4 of the present invention, load power detection means for detecting load power in the power load is provided in association with the power load,
The control means includes a rotation speed setting means for setting the rotation speed of the engine, a predicted temperature calculation means for calculating a predicted temperature of the AC generator, a magnitude of the power load, and a rotation speed of the engine. And storage means for storing the set rotational speed data indicating the relationship between and a reading means for reading the set rotational speed data stored in the storage means,
The predicted temperature calculating means calculates a predicted temperature of the AC generator after a predetermined time based on the temperature detected by the temperature detecting means, and the reading means is detected by the load power detecting means from set rotational speed data. The rotational speed data corresponding to the detected load power is read, and the rotational speed setting means sets the read rotational speed data as a reference rotational speed of the engine.

  Furthermore, in the power generation system according to claim 5 of the present invention, the control means includes a rotation speed correction means for correcting a reference rotation speed, and the rotation speed correction means corrects the reference rotation speed based on the predicted temperature. The engine speed setting means sets the corrected reference engine speed as the engine speed.

  According to the power generation system of the first aspect of the present invention, the power generation system includes the temperature detection means for detecting the temperature of the AC generator and the control means for controlling the rotational speed of the engine. The control means sets the engine speed based on the temperature detected by the temperature detecting means, so that the engine can be rotated at an optimum speed for stabilizing the power generation voltage of the AC generator when the engine is started. This can suppress the fluctuation of the DC voltage on the DC side of the converter, and can stably start the power generation system. For example, if the detected temperature of the temperature detecting means is high (or low), the generated voltage tends to decrease (or increase), so the engine speed at startup is set to be somewhat higher (or lower). .

  According to the power generation system of the second aspect of the present invention, when the engine is started, the reading means reads the rotation speed data corresponding to the temperature detected by the temperature detection means from the set rotation speed data, and sets the rotation speed. The means sets the read rotational speed data as the initial rotational speed of the engine, so that an optimal rotational speed in consideration of the ambient temperature is set when the engine is started, so that the DC voltage on the DC side of the converter is set. Fluctuation can be suppressed, and the power generation system can be started stably.

  Furthermore, according to the power generation system according to claim 3 of the present invention, after the engine is started, the control means predicts the temperature of the AC generator after a predetermined time based on the temperature detected by the temperature detection means, and this prediction is performed. Since the engine speed is set based on the temperature, there is no control delay in controlling the engine speed by the control means, and it is possible to accurately control the DC voltage on the DC side of the converter. In particular, it is possible to control the DC voltage with higher accuracy by suppressing the fluctuation of the generated voltage of the AC generator from when the engine is started until the temperature of the AC generator reaches the saturation temperature. It is possible to operate the power generation system stably. In addition, unlike the conventional power generation system, it is not necessary to perform continuity control that repeatedly turns the thyristor on and off, so that no high tide component is superimposed on the current flowing through the AC generator, reducing the power generation efficiency of the AC generator. It is possible to prevent this.

  In the power generation system according to claim 4 of the present invention, the reading means reads the rotation speed data corresponding to the detected load power detected by the load power detection means from the set rotation speed data, and the rotation speed setting means. Sets the read rotation speed data as the engine reference rotation speed, so that the engine can be rotated with the optimum reference rotation speed according to the magnitude of the load power, and the AC generator can be efficiently operated. In addition to being able to operate, even when load fluctuations occur in the power load, it is possible to suppress fluctuations in the DC voltage on the DC side of the converter, and it is possible to stably operate the power generation system It becomes.

  Furthermore, according to the power generation system of claim 5 of the present invention, the rotation speed correction means corrects the reference rotation speed based on the predicted temperature, and the rotation speed setting means uses the corrected reference rotation speed as the engine rotation speed. Since it is set as a number, the DC voltage on the DC side of the converter can be controlled to be constant with high accuracy. For example, if the predicted temperature is high (or low), the power generation voltage after a predetermined time tends to decrease (or increase), so that the engine speed after this predetermined time is corrected to be somewhat higher (or lower). Is done.

  Hereinafter, an embodiment of a power generation system according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram schematically illustrating a power generation system according to an embodiment of the present invention, and FIG. 2 is a diagram illustrating a relationship between the temperature of an AC generator and an initial rotation speed of an engine. FIG. 4 is a diagram showing the relationship between the magnitude of load power and the reference engine speed, and FIG. 4 is a diagram showing the relationship between the temperature difference between the predicted temperature and the reference temperature and the corrected engine speed, and FIG. FIG. 6 is a waveform diagram showing a DC voltage waveform on the DC side of a converter in a comparative experiment using a conventional power generation system, and FIG. 6 shows a DC voltage waveform on the DC side of the converter in an experiment using the power generation system of the present invention. FIG.

  In FIG. 1, a power generation system 2 of this embodiment includes an engine 4, an AC generator 6 driven by the engine 4, and a converter 8 for converting the generated power from the AC generator 6 into predetermined DC power. And an inverter 10 for converting the DC power from the converter 8 into predetermined AC power. The AC power from the inverter 10 is connected to the commercial power source 12 and is connected to the AC power from the inverter 10 and the commercial power source 12. Is supplied to the power loads 14a to 14d. Hereinafter, each of these components will be described in detail.

  The engine 4 is composed of a natural gas engine, for example, and is driven to rotate using city gas or the like as fuel. The engine 4 is provided with a throttle valve 16 for controlling the amount of air supplied to the combustion chamber (not shown) of the engine 4 through the intake passage (not shown). The throttle valve 16 is rotationally driven by a motor 18 such as a stepping motor. The opening degree of the throttle valve 16 is controlled by a predetermined pulse signal supplied to the motor 18, and the shaft output of the engine 4 (that is, the rotation of the engine 4) is adjusted by adjusting the opening degree of the throttle valve 16 in this way. Number) is controlled.

  The AC generator 6 is constituted by, for example, a permanent magnet generator, and is drivingly connected to the output shaft 20 of the engine 4. When the engine 4 is started, its output shaft 20 is rotationally driven in a predetermined direction, whereby the AC generator 6 is driven through the output shaft 20 of the engine 4 to generate AC power (that is, generated power). . In the alternator 6 composed of such a permanent magnet generator, the generated voltage is affected by the temperature of the alternator 6 and the rotational speed of the engine 4, and the temperature of the alternator 6 (in particular, the alternating current). When the temperature of the permanent magnet built in the generator 6 is increased (decreased), the generated voltage is decreased (increased), and when the rotational speed of the engine 4 is increased (decreased), the generated voltage is increased (decreased). Have.

  The converter 8 is a power conversion device for converting alternating current power into direct current power, and includes, for example, a diode bridge. The AC side of the converter 8 is connected to the AC generator 6 and converts the generated power from the AC generator 6 into predetermined DC power (for example, DC power of about 400V).

  The inverter 10 is a power conversion device for converting DC power into AC power, and includes, for example, an IGBT bridge. The DC side of the inverter 10 is connected to the DC side of the converter 8, and the DC power from the converter 8 is a predetermined AC power (AC power similar to AC power from the commercial power supply 12, for example, a single phase of 100 V, 60 Hz. AC power). A plurality of power loads 14a to 14d are connected to the AC side of the inverter 10 via circuit breakers 22a to 22d, respectively, and the AC power from the inverter 10 is system-connected to the commercial power source 12, whereby the commercial power source 12 and the AC power from the inverter 10 are supplied to each of the power loads 14a to 14d, and these AC power is consumed in each of the power loads 14a to 14d. The electric power loads 14a to 14d are configured by, for example, an air conditioner, various mechanical devices, or a lighting device installed in a general home or factory. Each of the circuit breakers 22a to 22d is configured to be openable and closable. For example, when the circuit breaker 22a (or 22b, 22c, or 22d) is in a closed state, the power load 14a (or 14b, 14c, or 14d) is turned on and the circuit breaker is disconnected. When the device 22a (or 22b, 22c, 22d) is opened, the power load 14a (or 14b, 14c, 14d) is cut off. In addition, although this embodiment demonstrates the case where four electric power loads are provided, the number can be set suitably.

  Next, the operation of the power generation system 2 will be described as follows. When the engine 4 is started, the output shaft 20 of the engine 4 is rotationally driven, whereby the alternator 6 is driven via the output shaft 20, and the generated power generated in the alternator 6 is supplied to the converter 8. After being converted into predetermined DC power by the converter 8, it is supplied to the inverter 10. The DC voltage on the DC side of converter 8 is controlled to a predetermined value (for example, 400 V) as described later. The DC power supplied to the inverter 10 in this way is converted into, for example, single-phase AC 100V, 60 Hz AC power and then supplied to each of the power loads 14a to 14d. Single-phase AC 100V, 60 Hz AC power is supplied to each of the power loads 14a to 14d, and these AC power is consumed by each of the power loads 14a to 14d.

  Furthermore, in the power generation system 2 of this embodiment, the temperature detection means 24 for detecting the temperature of the AC generator 6, the load power detection means 26 for detecting the load power in the power loads 14 a to 14 d, and the engine 4 And a control means 28 for controlling the number of revolutions. These components prevent the DC voltage on the DC side of the converter 8 from fluctuating due to the temperature of the AC generator 6. Hereinafter, each of these components will be described. In the following description, the description of the unit of rotation (rpm), the unit of temperature (° C.), and the unit of power (kW) is omitted.

  The temperature detection means 24 is composed of, for example, a temperature sensor and is provided in a coil (not shown) of the AC generator 6 (or in the vicinity thereof), and the temperature of the coil of the AC generator 6 (that is, AC power generation). Temperature of the machine 6). Although it is desirable to detect the temperature of a permanent magnet (not shown) of the AC generator 6, the temperature of the coil is detected because the temperature of the permanent magnet cannot be directly detected. When the temperature detection means 24 detects the temperature of the AC generator 6 in this way, a detection signal of the detection temperature of the AC generator 6 is sent to the control means 28 (described later). The detection of the temperature of the AC generator 6 by the temperature detection means 24 is started immediately before the engine 4 is started, and is continuously performed while the power generation system 2 is operating.

The load power detection means 26 is composed of, for example, a wattmeter and is connected to the AC side of the inverter 10 and detects the total power consumed by each of the power loads 14a to 14d (ie, load power). The load power detection by the load power detection means 26 is continuously performed while the power generation system 2 is operating. In the present embodiment, the power consumed in each of the power loads 14a to 14d is assumed to be equal, and one, two, three, and four power loads among the power loads 14a to 14d are input. In this case, the load power is assumed to be W ₁ , W ₂ , W ₃ and W ₄ , respectively.

  The control means 28 includes a storage means 30 in which set rotational speed data is stored, a reading means 32 for reading out the set rotational speed data stored in the storage means 30, and a rotational speed for setting the rotational speed of the engine 4. A setting unit 34, a predicted temperature calculation unit 36 for calculating the predicted temperature of the AC generator 6, and a rotation speed correction unit 38 for correcting the reference rotation speed of the engine 4 are provided.

The storage means 30 is composed of a memory, for example, and the storage means 30 stores set rotational speed data. The set rotational speed data includes first set rotational speed data and second set rotational speed data. The first set rotational speed data includes the temperature of the AC generator 6 and the rotational speed of the engine 4 (that is, the first rotational speed data). (Rotational speed data) and is used when setting the rotational speed when the engine 4 is started, and the second set rotational speed data is the amount of load power and the rotational speed of the engine 4 (that is, the rotational speed data). , The second rotation speed data), and is used when setting the rotation speed when a power load is applied after the engine 2 is activated. The first rotation speed data is data relating to the rotation speed of the engine 4 set when the engine 4 is started, and is the optimum rotation speed for stabilizing the generated voltage of the AC generator 6 when the engine 4 is started. It is data about. The second rotational speed data is obtained when the temperature of the AC generator 6 reaches the reference temperature (T _b ) (temperature near the saturation temperature) at each load power W ₁ , W ₂ , W ₃ and W ₄ . 8 is data relating to the rotational speed of the engine 4 when the DC voltage on the DC side becomes a predetermined value (for example, 400 V). Each of the first and second set rotational speed data is obtained, for example, by performing a measurement experiment or the like a plurality of times in advance, and the first set rotational speed data is stored in the storage means 30 in a map format as shown in FIG. The second set rotational speed data is stored in the storage means 30 in a table format as shown in FIG. 3, for example.

  The reading means 32 is for reading the first and second rotational speed data from the first and second set rotational speed data stored in the storage means 30. When the engine 4 is started, the reading unit 32 reads the first rotation speed data corresponding to the temperature (detected temperature) of the AC generator 6 from the first set rotation speed data, and the power load after the engine 4 is started. At the time of operation, the second rotational speed data corresponding to the load power (detected load power) of the power loads 14a to 14d is read from the second set rotational speed data.

  The rotation speed setting means 34 sets the rotation speed of the engine 4 as follows using the first and second set rotation speed data stored in the storage means 30. When a predetermined pulse signal is sent from the rotation speed setting means 34 to the motor 18 of the engine 4, the opening degree of the throttle valve 16 of the engine 4 is adjusted, and thereby the rotation speed of the engine 4 is controlled. The pulse signal sent from the rotation speed setting means 34 is composed of an output increase signal and an output decrease signal. When one pulse of the output increase signal is sent from the rotation speed setting means 34, the opening of the throttle valve 16 is opened. When the rotation speed of the engine 4 increases by a predetermined speed and the generated voltage of the alternator 6 increases somewhat, and when the output reduction signal is sent by one pulse, The opening degree of the throttle valve 16 is reduced by one step to the smaller opening degree, whereby the rotational speed of the engine 4 is reduced by a predetermined rotational speed, and the generated voltage of the AC generator 6 is somewhat lowered. The rotation speed setting means 34 sets the first rotation speed data read by the reading means 32 as the initial setting rotation speed of the engine 4 when the engine 4 is started, and the power load after the engine 4 is started. During the operation, the second rotation speed data read by the reading means 32 is set as the reference rotation speed of the engine 4.

The predicted temperature calculation means 36 calculates the temperature of the alternator 6 (that is, the predicted temperature) after a predetermined time, for example, 5 seconds, based on the temperature detected by the temperature detection means 24. Such calculation is performed as follows, for example. Done. The predicted temperature calculation means 36 first obtains the instantaneous temperature (T _a ) of the AC generator 6 at a predetermined time a from the detection signal of the detected temperature sent from the temperature detection means 24, and further, this instantaneous temperature (T _a ) To obtain the temperature change rate (T _a ′) of the alternator 6 at the instant of time a, and the instantaneous temperature (T _a ) and temperature change rate ( by performing the calculation according to equation (1) below on the basis of T _a '), it calculates t seconds after time a (predicted temperature of the alternator 6 in example 5 seconds) (T a _{+ t).} In Equation (1), α is a constant.

回転数補正手段３８は、予測温度演算手段３６により演算して得られた予測温度（Ｔ_ａ＋ｔ）と、上述の基準温度（Ｔ_ｂ）との温度差（Ｔ_ａ＋ｔ−Ｔ_ｂ）に基づき所定の演算を行うことにより、回転数設定手段３４により設定された基準回転数を補正する。予測温度（Ｔ_ａ＋ｔ）と基準温度（Ｔ_ｂ）との温度差と、基準回転数の補正量（すなわち、補正回転数）との関係は図４に示す通りである。回転数補正手段３８は、例えば予測温度が基準温度よりも低い場合には、交流発電機６の永久磁石（図示せず）の磁力の低下が少なく、且つコイルの抵抗の増大が小さく、従って所定時間後において交流発電機６の発電電圧が上昇すると判断し、基準回転数を低下させる補正を行い、また予測温度が基準温度を超える場合には、この永久磁石の磁力の低下が大きく、且つコイルの抵抗の増大が大きく、従って所定時間後において交流発電機６の発電電圧が低下すると判断し、基準回転数を上昇させる補正を行う。

The rotation speed correction means 38 is a predetermined number based on the temperature difference (T _{a + t} −T _b ) between the predicted temperature (T _{a + t} ) obtained by the calculation by the predicted temperature calculation means 36 and the reference temperature (T _b ). By performing the calculation, the reference rotational speed set by the rotational speed setting means 34 is corrected. The relationship between the temperature difference between the predicted temperature (T _{a + t} ) and the reference temperature (T _b ) and the reference rotation speed correction amount (that is, the correction rotation speed) is as shown in FIG. For example, when the predicted temperature is lower than the reference temperature, the rotation speed correction means 38 has a small decrease in magnetic force of a permanent magnet (not shown) of the AC generator 6 and a small increase in coil resistance. It is determined that the power generation voltage of the AC generator 6 will increase after a time, and correction is performed to decrease the reference rotational speed. If the predicted temperature exceeds the reference temperature, the magnetic force of the permanent magnet is greatly decreased, and the coil Therefore, it is determined that the power generation voltage of the AC generator 6 decreases after a predetermined time, and correction is performed to increase the reference rotational speed.

Next, a method for controlling the power generation system 2 will be described as follows. The case where the power generation system 2 is activated will be described. The temperature detection unit 24 detects the temperature of the AC generator 6 immediately before the engine 4 is activated, and outputs a detection signal of the detected temperature (T ₁ ) immediately before the engine 4 is activated. It is fed to the control means 28. The reading unit 32 reads the first rotation number data (N ₁ ) corresponding to the detected temperature (T ₁ ) based on the first set rotation number data stored in the storage unit 30 (see FIG. 2). The rotation speed setting means 34 sets the read rotation speed data (N ₁ ) as the initial setting rotation speed of the engine 4, sends a predetermined pulse signal to the motor 18 of the engine 4, and sets the throttle valve 16. The opening degree is adjusted to a predetermined opening degree, whereby the engine 4 is started at the initial set rotational speed (N ₁ ). In this manner, since the initial rotation speed of the engine 4 is set based on the temperature of the AC generator 6 immediately before the engine 4 is started, the generated voltage of the AC generator 6 at the time of startup becomes a predetermined generated voltage. The power generation system 2 can be started stably.

When a power load (for example, two power loads among the power loads 14a to 14d) is applied after the engine 4 is activated, the load power detection means 26 detects the load power (W ₂ ), and the reading means 32 is the storage means 30. The second rotation speed data (for example, 1900 rpm) corresponding to the detected load power (W ₂ ) detected by the load power detection means 26 is read based on the second set rotation speed data stored in (see FIG. 3). The rotation speed setting means 34 sets the read second rotation speed data (for example, 1900 rpm) as the reference rotation speed of the engine 4. Further, the temperature detection unit 24 sends a detection signal to the control unit 28, and the predicted temperature calculation unit 36 performs the above-described calculation based on this detection signal, so that t seconds after the current time a (for example, The predicted temperature (T _{a + t} ) of the AC generator 6 after 5 seconds) is calculated. Then, the rotation speed correction means 38 calculates a correction rotation speed by performing a predetermined calculation based on the temperature difference between the predicted temperature (T _{a + t} ) and the reference temperature (Tb), and uses this correction rotation speed as a reference rotation speed. Correct. For example, when the predicted temperature (T _{a + t} ) is lower than the reference temperature (T _b ), the rotation speed correction means 38 changes the reference rotation speed (for example, 1900 rpm) to the correction rotation speed (−ΔT ₂ ) corresponding to the temperature difference (−ΔT ₂ ). performs correction to decrease by -N _2), the rotational speed setting unit 34 sets the corrected reference rotational speed (1900-N ₂₎ as the rotation speed of the engine 4 at t seconds after the current time a. As a result, the engine 4 is rotated at a reference rotational speed (1900-N ₂ ) corrected by predicting the temperature of the AC generator 6 at that time, particularly the permanent magnet, at t seconds after the current time a. By controlling the rotational speed of the engine 4, the DC voltage on the DC side of the converter 8 is controlled to be constant at 400 V in consideration of the temperature fluctuation of the AC generator 6.

Further, for example, when the predicted temperature (T _{a + t} ) is higher than the reference temperature (T _b ), the rotation speed correction means 38 changes the reference rotation speed (for example, 1900 rpm) to the correction rotation speed (ΔT ₃ ) corresponding to the temperature difference (ΔT ₃ ). perform N ₃₎ by a correction of increasing the rotational speed setting unit 34 sets the corrected reference rotational speed (1900 + N ₃₎ as the rotation speed of the engine 4 at t seconds after the current time a. As a result, the engine 4 is rotated at a reference rotational speed (1900 + N ₃ ) that is corrected by predicting the temperature of the AC generator 6 at that time t seconds after the current time a. Thus, the DC voltage on the DC side of the converter 8 is controlled to be constant at 400 V in consideration of the temperature fluctuation of the AC generator 6.

  As described above, the temperature of the alternator 6 after a predetermined time from the current time is predicted until the temperature of the alternator 6 reaches the saturation temperature after the engine 4 is started, and the engine is based on the predicted temperature. By controlling the rotational speed of 4, the control of the rotational speed of the engine 4 is not delayed, and the DC voltage on the DC side of the converter 8 can be accurately controlled at a constant level. Even after the temperature of the AC generator 6 reaches the saturation temperature, the rotational speed of the engine 4 is controlled in the same manner as described above.

In such an operating state of the power generation system 2, for example, when the remaining two power loads are input and the load power increases from W ₂ to W ₄ , the reading unit 32 determines the load based on the second set rotational speed data. The second rotational speed data (for example, 2000 rpm) corresponding to the electric power (W ₄ ) is read, and the rotational speed setting unit 34 sets the read second rotational speed data as the reference rotational speed of the engine 4. In the same manner as described above, the predicted temperature calculating means 36 calculates the predicted temperature of the AC generator 6 after a predetermined time from the current time, and the rotation speed correcting means 38 is based on this predicted temperature. Correct. In this way, the engine 4 is rotated at the corrected reference rotational speed, and the DC voltage on the DC side of the converter 8 is controlled to be constant at 400V. Thus, even when load fluctuations occur in the power loads 14a to 14d, fluctuations in the DC voltage on the DC side of the converter 8 can be suppressed and held constant, and the power generation system 2 can be operated stably. It becomes possible to make it.

  Here, the excellent effect in the power generation system 2 of the present invention, that is, the effect that the fluctuation of the DC voltage on the DC side of the converter 8 can be suppressed when the engine 4 is started and when the load fluctuates is compared with the conventional power generation system. While explaining.

First, a conventional power generation system 100 (see FIG. 7) will be described with reference to FIG. FIG. 5 is a waveform diagram showing the DC voltage on the DC side of the converter from when the engine is started until the temperature of the AC generator reaches the saturation temperature. In conventional power generation system 100, the DC voltage on the DC side of converter 106 varies as shown in FIG. When the engine 102 is started up, the generated voltage of the AC generator varies slightly depending on the environmental conditions. Therefore, the generated voltage of the AC generator fluctuates due to DC voltage control, and accordingly, the DC voltage on the DC side of the converter 106 also changes. fluctuate. Further, when the power load increases to W ₂ after t ₁ second after starting the engine 102, the control cannot catch up with the instantaneous load increase, and the DC voltage on the DC side of the converter 106 decreases. When the DC voltage decreases in this way, control for increasing the rotation speed of the engine 102 is performed, and the generated voltage increases, thereby increasing the DC voltage on the DC side of the converter 106. On the other hand, when the temperature of the AC generator gradually increases due to an increase in the power load, the generated voltage decreases, and thereby the DC voltage on the DC side of the converter 106 decreases. When the DC voltage decreases, control for increasing the rotational speed of the engine 102 is performed again, and the power generation voltage of the AC generator increases, and thereby the DC voltage on the DC side of the converter 106 also increases. Since the DC voltage of converter 106 varies in this way, the DC voltage of converter 106 does not stabilize until the temperature of the AC generator is stabilized (see the region surrounded by the dotted line indicated by arrow P in FIG. 5).

In contrast, in the above-described power generation system 2 (power generation system shown in FIG. 1), the DC voltage on the DC side of converter 8 varies as shown in FIG. FIG. 6 is a waveform diagram showing the DC voltage on the DC side of the converter from when the engine is started until the temperature of the AC generator reaches the saturation temperature. In the power generation system 2 described above, the engine 4 is started. At this time, since the initial rotation speed is set in consideration of the ambient temperature, the DC voltage on the DC side of the converter 8 becomes almost constant at 400 V after rising from 0 V to 400 V, and the DC voltage at the start is stabilized. . In addition, when t ₁ second after the engine 4 is started and a power load is applied and the load power becomes W ₂ , the DC voltage on the DC side of the converter 8 once rises after dropping from 400 V, but the AC Since the rotational speed of the engine 4 is set in consideration of the predicted temperature of the generator 6, particularly the predicted temperature of the permanent magnet, the peak when this rises is significantly smaller than that of the conventional one (indicated by the arrow Q in FIG. 6). After that, the DC voltage repeatedly rises and falls and converges to 400V.

  As described above, in the power generation system 2 of the present invention, when the engine 4 is started, the engine 4 is rotated at the initial rotation speed corresponding to the temperature of the AC generator 6 immediately before the engine 4 is started. And the DC voltage on the DC side of the converter 8 can be stabilized. When the power load after the engine 4 is activated, the reference rotational speed is corrected based on the predicted temperature of the AC generator 6, and the engine 4 is rotated at the corrected reference rotational speed. There is no control delay in the number control, and the DC voltage on the DC side of the converter 8 can be controlled to be constant with high accuracy. In particular, the fluctuation of the DC voltage on the DC side of the converter 8 is suppressed even after the engine 4 is started until the temperature of the AC generator 6 reaches the saturation temperature or even when a load fluctuation occurs. Therefore, the power generation system 2 can be operated stably.

  As mentioned above, although one Embodiment of the electric power generation system according to this invention was described, this invention is not limited to this Embodiment, A various deformation | transformation thru | or correction | amendment are possible without deviating from the scope of the present invention.

  For example, in the above-described embodiment, the rotation speed setting unit 34 is configured to control the rotation speed of the engine 4 by adjusting the opening degree of the throttle valve 16 of the engine 4. The number of revolutions of the engine 4 may be controlled by adjusting the opening of a fuel supply valve (not shown) for controlling the amount of fuel supplied to the engine.

  Further, for example, in the above embodiment, the second set rotational speed data is configured in a table format. However, the second set rotational speed data may be configured in a map format in the same manner as the first set rotational speed data, or the first set rotational speed data is stored in a table. You may make it comprise in a format.

  Further, for example, in the above embodiment, the power consumed in each of the power loads 14a to 14d is configured to be equal. However, the present invention is not limited to this, and these powers can be set as appropriate. For example, the temperature detection unit 24 is configured to detect the temperature of the coil of the AC generator 6, but may detect the temperature inside the casing of the AC generator 6.

1 is a block diagram schematically showing a power generation system according to an embodiment of the present invention. It is a figure which shows the relationship between the temperature of an alternating current generator, and the rotation speed of an engine. It is a figure which shows the relationship between the magnitude | size of load electric power, and the engine standard rotation speed. It is a figure which shows the relationship between the temperature difference of prediction temperature and reference | standard temperature, and correction | amendment rotation speed. It is a wave form diagram which shows the DC voltage waveform in the DC side of the converter in the comparative experiment using the conventional power generation system. It is a wave form diagram which shows the direct-current voltage waveform in the direct current | flow side of the converter in the experiment using the electric power generation system of this invention. It is a block diagram which shows the conventional electric power generation system simply.

Explanation of symbols

2,100 Power generation system 4,102 Engine 6,104 AC generator 8,106 Converter 10,108 Inverter 12,114 Commercial power supply 14a-14d, 116a-116d Power load 24 Temperature detection means 26 Load power detection means 28 Control means 30 Storage means 32 Reading means 34 Rotation speed setting means 36 Predicted temperature calculation means 38 Rotation speed correction means

Claims (5)

An engine, an AC generator driven by the engine, a converter for converting the generated power from the AC generator into predetermined DC power, and for converting the DC power from the converter into predetermined AC power The AC power from the inverter is grid-connected to a commercial power source, and the AC power from the inverter and the commercial power source is supplied to a power load,
Temperature detecting means for detecting the temperature of the AC generator, and control means for controlling the rotational speed of the engine are provided,
When the engine is started, the control means sets the engine speed based on the temperature detected by the temperature detection means. The control means includes a rotational speed setting means for setting the rotational speed of the engine, a storage means in which set rotational speed data indicating a relationship between the temperature of the AC generator and the rotational speed of the engine is stored, Reading means for reading the set rotational speed data stored in the storage means,
At the time of starting the engine, the reading means reads rotation speed data corresponding to the detected temperature of the temperature detection means from the set rotation speed data, and the rotation speed setting means reads the read rotation speed data to the engine. The power generation system according to claim 1, wherein the power generation system is set as an initially set rotation speed. An engine, an AC generator driven by the engine, a converter for converting the generated power from the AC generator into predetermined DC power, and for converting the DC power from the converter into predetermined AC power The AC power from the inverter is grid-connected to a commercial power source, and the AC power from the inverter and the commercial power source is supplied to a power load,
Temperature detecting means for detecting the temperature of the AC generator, and control means for controlling the rotational speed of the engine are provided,
After starting the engine, the control means predicts the temperature of the AC generator after a predetermined time based on the temperature detected by the temperature detection means, and sets the engine speed based on the predicted temperature. Characteristic power generation system. In relation to the power load, load power detection means for detecting load power in the power load is provided,
The control means includes a rotation speed setting means for setting the rotation speed of the engine, a predicted temperature calculation means for calculating a predicted temperature of the AC generator, a magnitude of the power load, and a rotation speed of the engine. And storage means for storing the set rotational speed data indicating the relationship between and a reading means for reading the set rotational speed data stored in the storage means,
The predicted temperature calculating means calculates a predicted temperature of the AC generator after a predetermined time based on the temperature detected by the temperature detecting means, and the reading means is detected by the load power detecting means from set rotational speed data. 4. The power generation system according to claim 3, wherein rotation speed data corresponding to detected load power is read, and the rotation speed setting means sets the read rotation speed data as a reference rotation speed of the engine.   The control means includes a rotation speed correction means for correcting a reference rotation speed, the rotation speed correction means corrects the reference rotation speed based on the predicted temperature, and the rotation speed setting means sets the corrected reference rotation speed. The power generation system according to claim 4, wherein the power generation system is set as a rotational speed of the engine.

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