JP6207427B2 - Method for determining preferred rotational speed, control method for power generation system, and power generation system using the control method - Google Patents

Description

  The present invention includes a secondary excitation induction generator having a stator having a primary winding and a rotor having a secondary winding, an engine as a drive source for driving the rotor, and an AC side having the primary winding A first power converter connected to the second power converter, an AC side connected to the secondary winding, a DC side of the first power converter and a DC side of the second power converter. The present invention relates to an operation technique of a power generation system including a power storage device connected to a DC unit to be connected and a changeover switch that selectively connects the primary winding and a power load.

  Conventionally, secondary excitation induction that can change the frequency of the output power with respect to the shaft input rotation speed, such as wind power generation and pumped-storage power generation, which changes the shaft input rotation speed input to the generator A power generation system that can control the frequency of output power to a target frequency (50 [Hz] or 60 [Hz]) by using it together with a generator has been proposed (see, for example, Patent Document 1). This Patent Document 1 only discloses a power generation system that uses a secondary excitation induction generator for wind power generation and pumped storage power generation. For example, as a drive source for driving a rotor of a secondary excitation induction generator If the engine can be used (corresponding to the power generation system of the present application), the rotation speed of the engine can be freely selected while the frequency of the output power can be controlled to the target frequency (50 [Hz] or 60 [Hz]), and the power generation efficiency Can be improved.

  On the other hand, conventionally, an engine cogeneration system using a synchronous generator as a generator is known as a power generation system using an engine as a drive source of the generator.

  In an engine cogeneration system using a synchronous generator, the frequency of the output power is affected by the rotational speed of the drive source, so the gas engine that is the drive source is operated at a constant rotational speed synchronized with the system frequency of the power system. There is a need. For example, in an area where the system frequency is 60 Hz, operation is performed at discrete rotational speeds such as 900 rpm (15 Hz), 1200 rpm (20 Hz), and 1800 rpm (30 Hz), which is an integer of 60 Hz, according to the number of poles of the synchronous generator. There is a need to. Therefore, in the engine cogeneration system, the engine speed for outputting the target frequency (50 [Hz] or 60 [Hz]) by the synchronous generator is restricted to a constant speed, so the output is reduced from the rating. In doing so, the power generation efficiency is greatly reduced.

In addition, when using an engine cogeneration system as a power generation system, it is important to be able to operate independently as an emergency power source that can supply power to a power load even when power is not supplied from the power system. is there. In autonomous operation, in order to supply output power of a desired target frequency to the power load, the engine is driven at a predetermined target rotation speed, and then connected to the power load, and the output power of the target frequency is connected to the power load. Supply.
Here, when the engine cogeneration system is connected to an electric power load, the load on the engine increases, so the rotational speed of the engine temporarily decreases. As the rotational speed decreases, the frequency of output power decreases.

  Therefore, the inventors have explained the secondary excitation described above for the purpose of preventing the frequency of the output power from decreasing when connecting to the power load during the self-sustaining operation while preventing the power generation efficiency from decreasing. As a control for an induction generator, an engine as a drive source, a first power converter, a second power converter, a power storage device, and a changeover switch, the engine as a drive source is driven at a target rotational speed, When shifting to a self-sustained operation that allows the output power of the desired target frequency to be freely supplied to the power load by supplying power from the power storage device without receiving power supply from outside, the target engine is rotated in the no-load state. Drive at a no-load rotation speed faster than the speed, execute a standby operation process to control the output power to the target frequency, and then execute a load connection process to connect to the power load Have proposed (Patent Document 2).

JP 2009-027766 A JP 2012-1000047 A

In the system disclosed in Patent Document 2, it is possible to prevent a decrease in frequency at the stage of shifting to a self-sustained operation. As to whether it is advantageous for the power generation system to operate at the target rotational speed), the technology has not yet been established.
In other words, at present, only a technology for using a gas engine at a high rotational speed at which the efficiency of the gas engine is high, for example, operating the engine in a rated state where the efficiency is originally high has been established.
Accordingly, in a power generation system including a secondary excitation induction generator having a stator having a primary winding and a rotor having a secondary winding, and an engine as a drive source for driving the rotor, a power load In view of the above, there is room for improvement with respect to the operating point at which the driving speed is high and the driving speed is high.

  The present invention has been made in view of the above problems, and its purpose is to provide a secondary excitation induction generator, and to generate power that satisfies the power load by obtaining a driving force from the engine in response to a predetermined power load. In a power generation system to be performed, a method for determining a suitable rotation speed of an engine, which can increase the overall efficiency of the system, and a control method for a power generation apparatus that performs power generation at a suitable rotation speed obtained by the method and a power generation system Is to provide

In order to achieve the above object, a first characteristic configuration of a method for determining a suitable rotational speed according to the present invention is as follows:
A secondary excitation induction generator having a stator with a primary winding and a rotor with a secondary winding;
A drive source for driving the rotor;
A first power converter having an AC side connected to the primary winding;
A second power converter having an AC side connected to the secondary winding;
A power storage device connected to a direct current unit connecting the direct current side of the first power converter and the direct current side of the second power converter;
A changeover switch for selectively connecting the primary winding and the power load,
A method for determining a suitable rotational speed of the engine when a predetermined power load Pload is supplied to the power load in a power generation system including an engine with an adjustable rotational speed as the drive source,
Using the generator loss index indicating the relationship of the generator loss Ploss, which is the loss of the secondary excitation induction generator, to the arbitrary rotation speed ω and the arbitrary power load amount Pload, the predetermined power load amount Pload and the temporary rotation A generator loss derivation step for determining a generator loss Ploss when the power generation system is operated at a speed ω;
Based on the generator loss Ploss derived in the generator loss deriving step, the generator efficiency ηd and the generator efficiency Pm for deriving the mechanical input Pm for driving input from the engine to the secondary excitation induction generator A machine input derivation process;
A torque deriving step of deriving a torque T applied to the secondary excitation generator from the machine input Pm derived in the generator efficiency / machine input deriving step and the temporary rotational speed ω;
An engine efficiency deriving step for obtaining an engine efficiency ηe from the torque T derived in the torque deriving step and the temporary rotational speed ω;
A total generation efficiency η as a product value ηd × ηe is derived from the generator efficiency ηd derived in the generator efficiency / machine input derivation step and the engine efficiency ηe derived in the engine efficiency derivation step. The efficiency deriving step is sequentially executed at the predetermined power load Pload and different temporary rotational speeds ω,
The temporary rotational speed ω that maximizes the power generation system overall efficiency η with respect to the temporary rotational speed ω that is sequentially derived is the preferred rotational speed ω when the predetermined power load amount is supplied to the power load.

Moreover, the first characteristic configuration of the power generation system according to the present invention for achieving the above object is as follows:
A secondary excitation induction generator having a stator with a primary winding and a rotor with a secondary winding;
A drive source for driving the rotor;
A first power converter having an AC side connected to the primary winding;
A second power converter having an AC side connected to the secondary winding;
A power storage device connected to a direct current unit connecting the direct current side of the first power converter and the direct current side of the second power converter;
A changeover switch for selectively connecting the primary winding and the power load,
As the drive source, a power generation system including an engine with adjustable rotation speed,
The relationship between the generator loss index indicating the relationship of the generator loss Ploss, which is the loss of the secondary excitation induction generator, to the arbitrary rotational speed ω and the arbitrary power load Pload, and the relationship of the engine efficiency to the rotational speed and torque of the engine A storage unit storing an engine efficiency index indicating
A generator loss deriving unit for determining a generator loss Ploss when operating at the predetermined power load Pload and the temporary rotational speed ω using the generator loss index stored in the storage unit;
Based on the generator loss Ploss derived by the generator loss deriving unit, the generator efficiency ηd and the generator efficiency Pd for deriving the mechanical input Pm for driving input from the engine to the secondary excitation induction generator A machine input deriving unit;
A torque deriving unit for deriving a torque T applied to the secondary excitation generator from the machine input Pm derived by the generator efficiency / machine input deriving unit and the temporary rotational speed ω;
An engine efficiency deriving unit for obtaining an engine efficiency ηe from the torque T derived by the torque deriving unit and the temporary rotational speed ω using an engine efficiency index stored in the storage unit;
Total generation efficiency η derived as a product value ηd × ηe from the generator efficiency ηd derived by the generator efficiency / machine input deriving unit and the engine efficiency ηe derived by the engine efficiency deriving unit An efficiency deriving unit,
While determining the power generation system overall efficiency at the predetermined power load Pload and different temporary rotational speed ω,
Determining a preferred rotational speed, which is a preferred rotational speed ω when the predetermined power load is supplied to the power load, with the temporary rotational speed ω at which the power generation system overall efficiency η is maximized with respect to the provisional rotational speed ω sequentially derived. It is in the point provided with a part.

  According to the above characteristic configuration, since the engine having a freely adjustable rotation speed is provided as a drive source, a secondary excitation induction generator is used, and a system using the engine as a drive source for the generator is provided. it can. Therefore, since the frequency of the output power can be changed with respect to the shaft input rotation speed of the secondary excitation induction generator by controlling the operation of the second power converter, the frequency of the output power is set to the target frequency (50 While controlling at [Hz] or 60 [Hz]), the rotational speed of the engine can be freely selected. As a result, the power generation efficiency can be improved.

  Further, the preferred rotational speed determination method or the power generation system includes a generator loss index that is a relationship of a generator loss when the engine is operated at a predetermined rotational speed and a predetermined amount of power is generated. In addition, regarding the engine, an engine efficiency index is provided which is an index of engine efficiency when the engine is operated at a predetermined rotational speed to generate a predetermined torque.

  In addition, the generator loss in that state is taken into account with respect to the power load amount that is known in advance, taking into account the generator loss when the engine is operated at a rotational speed that can generate power corresponding to the power load amount. The efficiency and engine efficiency are obtained, and the product value is defined as the total efficiency of the power generation system. The total efficiency of the power generation system derived through such a derivation process is that the rotational speed of the engine is temporarily set, and thus it is necessary to optimize the rotational speed.

  On the other hand, in the present application, the output of the engine (machine input in the present application) that is required when the generator generates power corresponding to a certain amount of power load can be derived by the procedure described above.

  The engine efficiency index is, for example, a three-dimensional mountain-shaped index as shown in FIGS. 5B and 6B with respect to the rotational speed and torque. The optimal solution is derived by, for example, a hill-climbing method by iterative calculation while following the engine output (machine input in the present application, indicated by a thick broken line in FIGS. 5 (b) and 6 (b)). It becomes possible.

Therefore, in the method for determining the preferred rotational speed according to the present application, the generator loss derivation step, the generator / machine input derivation step, the torque derivation step, the engine efficiency derivation step, and the overall efficiency derivation step are executed repeatedly in order. The rotational speed that maximizes the total efficiency of the power generation system as the product of the engine efficiency is derived.
As a result, it is possible to obtain a rotation speed capable of generating the power of the power load amount with the highest efficiency, and to operate the power generation system satisfactorily.

  Further, the power generation system includes a storage unit, a generator loss deriving unit, a generator efficiency / machine input deriving unit, a torque deriving unit, an engine efficiency deriving unit, and an overall efficiency deriving unit, and a suitable rotational speed determining unit is provided. By providing the desired rotational speed determined as the target rotational speed (target rotational speed command value) for the engine, the power generation system can be operated with high efficiency commensurate with the amount of power load.

The first characteristic configuration of the control method of the power generation system according to the present invention is the preferred rotational speed determined by the preferred rotational speed determining method of claim 1 as a target rotational speed,
The engine is driven at the target rotational speed, and the power supply from the power storage device supplies power output at a desired target frequency to the power load without receiving power from an external power system. Regarding driving
The engine is driven at a no-load rotational speed faster than the target rotational speed in an unloaded state where the changeover switch is open and the primary winding is not connected to the power load, and the primary winding A standby operation step of controlling the output power of the target frequency to the output power of the target frequency,
Thereafter, a load connecting step of connecting the primary winding to the power load with the changeover switch closed is performed.

In addition, the second characteristic configuration of the power generation system according to the present invention is:
The preferred rotational speed determined by the preferred rotational speed determining unit according to claim 3 is set as a target rotational speed,
The engine is driven at the target rotational speed, and the power supply from the power storage device supplies power output at a desired target frequency to the power load without receiving power from an external power system. A self-sustaining operation control unit that operates
The engine is driven at a no-load rotational speed faster than the target rotational speed in an unloaded state where the changeover switch is open and the primary winding is not connected to the power load, and the primary winding A standby operation control unit that executes a standby operation step of controlling the output power of the target frequency to the output power of the target frequency;
Then, the load switch control part which performs the load connection process which makes the said changeover switch a closed state and connects the said primary winding to the said electric power load is provided.

According to the above characteristic configuration, in the self-supporting operation, the load connection process is performed after performing the standby operation process. Therefore, when performing the load connection process in which the primary winding is connected to the power load, the engine rotation speed is reduced. Set to a no-load rotation speed that is faster than the target rotation speed (Note that because the generator uses a secondary excitation induction generator, the frequency of the output power can be changed relative to the shaft input rotation speed, Even when the rotation speed is set to the no-load rotation speed, the frequency of the output power can be controlled to a predetermined target frequency). And, by setting the rotation speed to the no-load rotation speed and storing the kinetic energy in the engine flywheel, the drastic decrease in the rotation speed when the power load is connected is suppressed, and the fluctuation of the output power frequency is suppressed. Can be suppressed.
That is, according to the above characteristic configuration, it is possible to suppress a decrease in the frequency of the output power when connected to the power load during the self-sustained operation while utilizing the characteristics of the secondary excitation induction generator. And suppression of the fall of this frequency contributes to making the frequency of output electric power converge the target frequency in a short time. As a result, it is possible to prevent a decrease in the frequency of the output power while preventing a decrease in power generation efficiency, so that it is possible to connect to a larger power load, and the value as an emergency power supply is improved.

Schematic configuration diagram of a power generation system using a secondary excitation induction generator The control block diagram of the control apparatus of the electric power generation system which concerns on this invention Diagram showing simulation model for calculating generator loss Flow chart showing the procedure for determining the rotational speed by the hill-climbing method The figure which shows the example of a pattern of the rotational speed determination by the hill-climbing method The figure which shows the example of a pattern of the rotational speed determination by the hill-climbing method The flowchart which shows control of the independent operation of the electric power generation system which concerns on this invention The graph which shows control of the gas rotation speed of the electric power generation system which concerns on this invention The graph which shows the fluctuation | variation of the frequency of the output electric power of the electric power generation system which concerns on this invention The graph which shows the relationship between a load factor and the no-load rotation speed of a suitable gas engine

  An embodiment of a power generation system according to the present invention will be described with reference to the drawings. In addition, this invention is not limited to the structure described in embodiment and drawing demonstrated below, A various modification | change is possible if it is a structure with the same effect.

1. Overall Configuration of Power Generation System FIG. 1 shows a power generation system 1 to be controlled by a control device 100 (see FIG. 2). This power generation system 1 includes a secondary excitation induction generator (double-feed winding induction generator) 2, a gas engine 3, a first power converter 11, a second power converter 12, and a power storage device 5. , A first switch 21, a second switch 22, and a third switch 23. The secondary excitation induction generator 2 generates power (three-phase AC power) having the same frequency (for example, 50 [Hz] or 60 [Hz]) as the power system (commercial power system) 4, and the power Can be supplied to the load 7 and the power system 4 that consume power. The gas engine 3 is driven in response to the target rotational speed ω * (target rotational speed command) from the rotational speed control unit 103. Examples of the load 7 include an indoor unit, an outdoor unit, an electric lamp, and the like included in the air conditioning equipment. In the present embodiment, the third switch 23 and the load 7 correspond to the “changeover switch” and the “power load” in the present invention, respectively.

  The power generation system 1 can start the system in a state in which power is supplied from the power system 4 and is in a state in which power is not supplied from the power system 4 (the second switch 22 is opened). In this state, the system can be activated (independently activated) by the electric power supplied from the power storage device 5.

  The secondary excitation induction generator 2 includes a stator 2b (stator) having a primary winding (not shown) and a rotor 2a (rotor) having a secondary winding (not shown). Yes. The primary winding included in the stator 2 b is connected to the power system 4 via the first switch 21 and the second switch 22. The primary winding provided in the stator 2 b is also connected to the load 7 via the first switch 21 and the third switch 23. On the other hand, the secondary winding included in the rotor 2 a is connected to the filter circuit 10, the second power converter 12, the DC unit 13, the first power converter 11, the filter circuit 10, the transformer 6, and the second switch 22. Connected to the power system 4. The secondary winding included in the rotor 2 a is connected to the filter circuit 10, the second power converter 12, the DC unit 13, the first power converter 11, the filter circuit 10, the transformer 6, and the third switch 23. The load 7 is also connected.

  In the following description, the primary winding side included in the stator 2b is referred to as “primary side of the secondary excitation induction generator”, and the secondary winding side included in the rotor 2a is referred to as “secondary side of the secondary excitation induction generator”. " Therefore, the frequency of power (voltage, current) generated on the primary side of the secondary excitation induction generator 2 is the frequency of power supplied to the load 7 and the power system 4.

  The gas engine 3 is mechanically connected to the rotor 2a of the secondary excitation induction generator 2, and rotationally drives the rotor 2a. In this example, the output shaft of the gas engine 3 is directly connected so as to rotate integrally with the rotor 2a, and the rotational speed of the gas engine 3 and the rotational speed of the rotor 2a are equal. Note that a gear mechanism may be provided between the output shaft of the gas engine 3 and the rotor 2a. The gas engine 3 is an engine that uses city gas as fuel. In this example, the gas engine 3 serves as a corner of a cogeneration facility that can supply heat in addition to electric power in parallel in addition to electric power. In the present invention, for example, a gas engine 3 having a rated output of 1 [kW], several tens [kW], several [MW], or the like can be used.

  The first power converter 11 is connected to the stator 2b (primary winding) of the secondary excitation induction generator 2 via the first switch 21 on the AC side (the right side in FIG. 1), and the second switch 22 is connected to the electric power system 4 through the third switch 23, and is further connected to the load 7 through the third switch 23. The first power converter 11 is connected to the DC unit 13 on the DC side (left side in FIG. 1). The second power converter 12 is connected to the rotor 2a (secondary winding) of the secondary excitation induction generator 2 on the AC side (left side in FIG. 1). The second power converter 12 is connected to the DC unit 13 on the DC side (right side in FIG. 1). Each of the first power converter 11 and the second power converter 12 has a function as an inverter that converts DC power on the DC side into AC power (reverse conversion) and supplies it to the AC side, and an AC side. It is configured to be able to perform both of the function as a converter that converts (forward-converts) AC power into DC power and supplies it to the DC side.

  Such first power converter 11 and second power converter 12 are configured to include a plurality of (for example, six) switching elements. As the switching element, power transistors having various structures such as a metal oxide semiconductor field effect transistor (MOSFET) and an insulated gate bipolar transistor (IGBT) can be employed. The first power converter 11 and the second power converter 12 receive a PWM (pulse width modulation) signal, and the switching element performs a switching operation (on / off operation) based on the PWM signal. The PWM signal for operating the first power converter 11 and the second power converter 12 is generated by the control device 100 (see FIG. 2).

  As shown in FIG. 1, a filter circuit 10 including an inductance and a capacitor is provided on both the AC side of the first power converter 11 and the AC side of the second power converter 12. The filter circuit 10 is a filter that removes high-frequency components generated by switching of the switching element, and the output voltage waveform from the first power converter 11 and the second power converter 12 is sinusoidal by the filter circuit 10. Converted.

  Further, as shown in FIG. 1, a transformer 6 is provided on the secondary excitation induction generator 2 side (power system 4 side) from the filter circuit 10 provided on the AC side of the first power converter 11. Yes. In the following description, “the primary side of the transformer” refers to the first power converter 11 side of the transformer 6 (the side labeled with “# 1” in FIG. 2), and “the secondary side of the transformer”. Indicates the secondary excitation induction generator 2 side of the transformer 6 (the power system 4 side, the side labeled “# 2” in FIG. 2).

  The DC unit 13 is a part that connects the DC side of the first power converter 11 and the DC side of the second power converter 12. The DC unit 13 includes a capacitor 8 and a power storage device 5. The power storage device 5 supplies electric power required when the power generation system 1 is activated independently. It is also possible to suppress fluctuations in the power supplied to the load 7 and the power system 4 using the power storage device 5. The power storage device 5 is configured by, for example, a storage battery, an electric double layer capacitor, or the like, and can supply and discharge power to the direct current unit 13 and can be charged by receiving power from the direct current unit 13. Composed. A switch may be interposed between the power storage device 5 and the DC unit 13.

  The first switch 21 selectively connects the stator 2 b (primary winding) of the secondary excitation induction generator 2 and the first power converter 11. The second switch 22 selectively connects the power system 4 and the first power converter 11. The first switch 21 cooperates with the second switch 22 to selectively connect the stator 2b (primary winding) of the secondary excitation induction generator 2 and the power system 4, and to the third switch 23. In cooperation, the stator 2b (primary winding) of the secondary excitation induction generator 2 and the load 7 are selectively connected. The second switch 22 selectively connects the power system 4 and the load 7 in cooperation with the third switch 23.

  Each of the first switch 21, the second switch 22, and the third switch 23 is controlled to open / close based on an open / close signal generated by the switch control unit 104 (see FIG. 2) of the control device 100. These switches can be, for example, electromagnetic contact type switches that open and close by the operation of an electromagnet.

The power generation system 1 having the above configuration is a system with a high degree of freedom with respect to the frequency (voltage, current frequency) of the generated power. Although a detailed description is omitted (for details, see, for example, Patent Document 1), the frequency of the output power of the generated power of the power generation system 1 (the primary side voltage v1 induced on the primary side of the secondary excitation induction generator 2). The frequency (see FIG. 4)) is f1, the rotational frequency of the rotor 2a is f0, and the alternating current (alternating voltage) supplied to the secondary winding to excite the secondary winding of the rotor 2a If the frequency of f2 is f2, then “f1 = f0 + f2”.
Here, the rotation frequency f0 of the rotor 2a is obtained from “f0 = m × n / 120” where the rotation speed of the rotor 2a is m [rpm] and the number of magnetic poles of the secondary excitation induction generator 2 is n. .

  For example, when the rotation speed of the rotor 2a is 1100 [rpm] and the number of magnetic poles of the secondary excitation induction generator 2 is “6”, the rotation frequency f0 of the rotor 2a is 55 [Hz]. Therefore, in this case, if the second power converter 12 is controlled to supply an AC current (AC voltage) having a frequency of 5 [Hz] to the secondary winding (f2 = 5 [Hz]), the frequency is the target. AC power with a frequency of 60 [Hz] can be obtained. Conversely, if the second power converter 12 is controlled to extract an AC current (AC voltage) having a frequency of 5 [Hz] from the secondary winding (f2 = −5 [Hz]), the frequency will be the target frequency. AC power of 50 [Hz] can be obtained. Note that any rotation speed other than the synchronous rotation speed can be selected as the rotation speed of the rotor 2a (that is, the rotation speed of the gas engine 3). The synchronous rotation speed is 1200 [rpm] when the frequency of the power system 4 is 60 [Hz], which is the target frequency, and the number of magnetic poles of the secondary excitation induction generator 2 is “6”. .

  Thus, even if the rotation speed of the rotor 2a (that is, the rotation speed of the gas engine 3) is the same, the frequency f2 of the alternating current supplied to the secondary winding of the rotor 2a (as described above, The frequency f1 of the output power can be changed by changing a negative value when AC current is extracted from the secondary winding. Therefore, for example, there is an advantage that the gas engine 3 having the same specification can be used in an area where the target frequency is 50 [Hz] and an area where the target frequency is 60 [Hz]. Further, as will be described in detail later, by appropriately selecting the rotation speed of the gas engine 3 according to the electric power load, it is possible to perform an appropriate operation in a state where the overall efficiency of the power generation system 1 referred to herein is high.

2. Configuration of Control Device Next, the configuration of the control device 100 will be described in detail based on FIG. Here, as shown in FIG. 2, active power and reactive power generated on the primary side of the secondary excitation induction generator 2 are referred to as first active power P1 and first reactive power Q1, respectively. The active power and reactive power supplied to the secondary side of the secondary excitation induction generator 2 are referred to as second active power P2 and second reactive power Q2, respectively. Further, active power and reactive power supplied from the primary side of the secondary excitation induction generator 2 to the first power converter 11 side are referred to as third active power P3 and third reactive power Q3, respectively. And the arrow which shows the flow of these electric power in FIG. 2 has shown the flow direction in case the value of the said electric power is positive. In this example, regarding the positive and negative of the reactive power, the case where the delayed reactive power (reactive power in the delayed phase) is positive is positive, and the case where the delayed reactive power is negative is negative. Here, “the delayed reactive power is positive” means that the phase of the current is advanced with respect to the voltage, and “the delayed reactive power is negative” means that the phase of the current is delayed with respect to the voltage. Means the case. If the resistance component can be ignored, the phase difference between the current and voltage is 90 degrees.

  As shown in FIG. 2, the control device 100 includes a first control unit 101 that controls the operation of the first power converter 11, a second control unit 102 that controls the operation of the second power converter 12, A switch control unit 104 that controls the open / closed state of the switch 21, the second switch 22, and the third switch 23. Further, the control device 100 includes a suitable rotational speed determining unit 150 for determining the rotational speed of the engine for generating power in accordance with the amount of electric power load, and the suitable rotational speed determined by the suitable rotational speed determining unit 150. A rotation speed control unit 103 that instructs the engine 3 as a target rotation speed is provided. These functional units have a hardware or software (program) or a functional unit for performing various processes on the input data, with an arithmetic processing unit such as a CPU common to each other or independent from each other as a core member. Implemented and configured by both. These functional units are configured to exchange information with each other via a communication line such as a digital transfer bus. Here, when these functional units are configured by software (program), the software is stored in a storage unit such as a RAM or a ROM that can be referred to by the arithmetic processing unit.

  The control device 100 operates the first control unit 101 and the second control unit 102, and does not receive the supply of power from the power system 4 (the second switch 22 (see FIG. 1) is opened). ), The system can be activated (independently activated) by the electric power supplied from the power storage device 5. Hereinafter, the configurations of the second control unit 102 and the first control unit 101 will be described in order.

2-1. Configuration of Second Control Unit The second control unit 102 is a functional unit that controls the operation of the second power converter 12 (specifically, the switching operation of the switching element included in the second power converter 12). The second control unit 102 is configured to control the operation of the second power converter 12 and to supply the AC power generated by the second power converter 12 to the secondary winding included in the rotor 2a. Yes. That is, the second control unit 102 serves as secondary-side excitation means for performing a step of exciting the secondary winding of the rotor 2a by the second power converter 12 (hereinafter referred to as “secondary-side excitation step”). Function.

  In the present embodiment, the second control unit 102 performs voltage feedback control based on the primary side voltage v1 as the secondary side excitation process. Therefore, the power generation system 1 includes a voltage sensor (not shown) that detects the primary side voltage v1. And the 2nd control part 102 performs this voltage feedback control at the time of the independent starting of the electric power generation system 1, so that it may mention later.

  Specifically, the second control unit 102 includes a functional unit as shown in FIG. 2, and performs voltage feedback control using the primary side voltage v1 as a feedback value and the primary side voltage command value V1 * as a command value. Run. Note that the flow of the voltage feedback control process executed by the second control unit 102 is clear from the block diagram shown in FIG. 2, and therefore the flow will be briefly described here. In the following description of the control processing, characters described in each function unit in FIG. 2 are enclosed in square brackets (“”) and represent a function unit corresponding to the character. In the present embodiment, the primary side voltage command value V1 * corresponds to the “target voltage value” in the present invention.

  The primary voltage v1 detected by the voltage sensor is input to “PLL”. “PLL” detects the angular velocity (angular frequency) ω of the primary side voltage v1 by performing PLL (Phase Locked Loop) processing, and outputs the information to “1 / s”. “1 / s” performs an integration process for integrating the angular velocity sent from “PLL”, and derives a first reference phase θ1 as a reference for three-phase to two-phase conversion.

  The primary side voltage v1 detected by the voltage sensor is also input to “dq ← abc”. In “dq ← abc”, based on the first reference phase θ1, the primary side voltage v1 is changed from a three-phase (a-phase, b-phase, c-phase) AC coordinate system (abc coordinate system) to a two-phase rotational coordinate system ( dq coordinate system) to derive the d-axis component v1d and the q-axis component v1q of the primary voltage v1. In this example, the first reference phase θ1 is set so that the q-axis component v1q of the primary side voltage v1 is zero.

  The d-axis component v1d and the q-axis component v1q of the primary voltage v1 obtained by “dq ← abc” are sent to “v1dq = √ (v1d2 + v1q2)”, and the amplitude value v1dq of the primary voltage v1 is calculated. The Then, the amplitude value v1dq is compared with V1 * which is the command value (target value) of the output voltage of the secondary excitation induction generator 2, and proportional integral control is performed by “PI” so that the difference becomes zero. Calculation (PI control calculation) is performed. The primary voltage command value V1 * is multiplied by a coefficient as necessary (according to the winding connection method or the like), and then compared with the amplitude value v1dq. For example, when the primary side voltage command value V1 * is expressed by the effective value of the line voltage, the coefficient can be set to “√ (2/3)”.

  “PI” performs a PI control calculation and derives a d-axis component urd and a q-axis component urq of the voltage command value. Then, the d-axis component urd and the q-axis component urq of the voltage command value are sent to “dq → abc”, and two-phase three-phase conversion from the dq coordinate system to the abc coordinate system is executed. As described above, in this example, since the first reference phase θ1 is set so that the q-axis component v1q of the primary side voltage v1 becomes zero, the q-axis component urq of the voltage command value becomes zero. . Therefore, in this example, “PI” obtains only the d-axis component urd of the voltage command value, the d-axis component urd is input to “dq → abc”, and the voltage command value of “dq → abc” “0” is input as the q-axis component urq.

  Further, “1 / s” derives the second reference phase θ2 based on the difference (ω0−ωr) between the angular velocity ω0 of the primary side voltage v1 and the angular velocity ωr of the rotor 2a (the above rotation frequency f0 × 2π). The angular velocity ωr of the rotor 2a can be detected by a magnetic pole position sensor (such as a resolver) (not shown). “Dq → abc” performs two-phase three-phase conversion on the d-axis component urd and the q-axis component urq of the voltage command value based on the second reference phase θ2, and sets the execution result to “PWM”. Output. “PWM” is a PWM signal (gate drive signal) for switching control of the switching element included in the second power converter 12 based on the three-phase voltage command value sent from “dq → abc”. Generate.

  The above is the flow of voltage feedback control executed by the second control unit 102. Although not described in detail, the first active power P1 and the first reactive power Q1 generated by the second control unit 102 on the primary side of the secondary excitation induction generator 2 during normal operation of the power generation system 1 are described. It can be configured to perform feedback control (power feedback control) using as a feedback value. In such a configuration, in a steady state where the resistance component can be ignored, the first active power P1 is converted into the d-axis component (secondary component) of the secondary current i2 that is the current flowing through the secondary side of the secondary excitation induction generator 2. Side d-axis current), and the first reactive power Q1 can be controlled by the q-axis component (secondary q-axis current) of the secondary current i2. That is, the first active power P1 and the first reactive power Q1 can be controlled independently of each other.

2-2. Configuration of First Control Unit The first control unit 101 is a functional unit that controls the operation of the first power converter 11 (specifically, the switching operation of the switching element included in the first power converter 11). The first control unit 101 is configured to control the operation of the first power converter 11 and to supply the AC power generated by the first power converter 11 to the primary winding included in the stator 2b. Yes. That is, the first control unit 101 functions as a primary side excitation unit that executes a step of exciting the primary winding of the stator 2b by the first power converter 11 (hereinafter referred to as “primary side excitation step”).

  In this embodiment, the 1st control part 101 performs the current feedback control based on the electric current (this example transformer secondary side current ig) which flows into the alternating current side of the 1st power converter 11 as a primary side excitation process. . Therefore, the power generation system 1 includes a current sensor 30 that detects the transformer secondary current ig. And the 1st control part 101 performs this electric current feedback control at the time of the independent starting of the electric power generation system 1, so that it may mention later.

  Specifically, the first control unit 101 includes a functional unit as shown in FIG. 2, and current feedback control is performed using the transformer secondary current ig as a feedback value and the current command value Ig * as a command value. Execute. Note that the flow of the current feedback control process executed by the first control unit 101 is clear from the block diagram shown in FIG. 2, and therefore the flow will be briefly described here. In the following description of the control process, as in the description of the second control unit 102, the characters described in each function unit in FIG. 2 are enclosed in square brackets, and the function unit corresponding to the character is Represent.

  The transformer secondary current ig detected by the current sensor 30 is input to “dq ← abc”. The above-mentioned first reference phase θ1 is also input to “dq ← abc”. Then, “dq ← abc” performs three-phase two-phase conversion on the transformer secondary current ig based on the first reference phase θ1, and the d-axis component igd of the transformer secondary current ig and A q-axis component igq is derived.

  Then, the d-axis component “igd” of the transformer secondary current “igd” is compared with the d-axis component “Igd *” of the current command value Ig *, and the PI control calculation is executed at “PI” so that the difference becomes zero. Then, non-interference control for improving controllability is executed on the result. Specifically, the sum of the output of “PI” multiplied by (−1) and ω0 × Lg × igq is derived. Then, the d-axis component v1d of the primary side voltage v1 is added to the derivation result to derive the d-axis component ugd of the voltage command value. Here, Lg is an inductance obtained by converting the positive phase reactance of the transformer 6 to the secondary side.

  Similarly, the q-axis component igq of the transformer secondary current ig and the q-axis component Igq * of the current command value Ig * are compared, and the PI control calculation is performed at “PI” so that the difference becomes zero. The non-interference control for improving the controllability is executed on the result. Specifically, a value obtained by subtracting ω0 × Lg × igd from the output of “PI” multiplied by (−1) is derived. Then, the q-axis component v1q (“0” in this example) of the primary side voltage v1 is added to the derivation result, and the q-axis component ugq of the voltage command value is derived.

  “Abc ← dq” performs two-phase three-phase conversion on the d-axis component ugd and the q-axis component ugq of the voltage command value based on the first reference phase θ1, and outputs the execution result to “PWM”. “PWM” is a PWM signal (gate drive signal) for switching control of the switching element included in the first power converter 11 based on the three-phase voltage command value sent from “abc ← dq”. Generate.

  The above is the flow of current feedback control executed by the first control unit 101. As will be described later, the first control unit 101 controls the third reactive power Q3 when the power generation system 1 is independently activated. In this example, as described above, the q-axis component v1q of the primary side voltage v1 is zero. Therefore, the third reactive power Q3 can be controlled by the q-axis component igq of the transformer secondary current ig. In this case, the current command value Ig * has at least its q-axis component Igq *. On the other hand, since the third active power P3 can be controlled by the d-axis component igd of the transformer secondary current ig, when the third active power P3 is positively controlled, the current command value Ig * is And d-axis component Igd *.

  Although not described in detail, during the normal operation of the power generation system 1, the first control unit 101 performs feedback control so that the voltage Vdc is constant with the voltage Vdc of the DC unit 13 as a feedback value. It can be constituted as follows.

3. Self-sustained operation control Self-sustained operation means that the gas engine 3 is driven at the target rotational speed and the load 7 is supplied with power from the power storage device 5 without being supplied with power from the power system 4. [Hz] or 60 [Hz]). About this independent operation, it is comprised so that the control apparatus 100 as an independent operation control part may perform.
In the following, referring to FIG. 4, in order to operate the power generation system 1 at its suitable efficiency (almost the highest efficiency) corresponding to the load 7 to be supplied with electric power, the rotation speed unique to the present application is determined. A description will be given of the method, and with reference to FIG. 7, control (self-sustained operation control) from self-sustained activation of the power generation system 1 to connection to the load 7 executed in the control device 100 will be described. Here, the description will be made assuming that the power load amount of the load 7 connected in the self-sustained activation is known in advance. As this type of power load amount, a so-called “important load” power load amount is exemplified.

  Hereinafter, the self-sustained operation control described below is executed by hardware or software (program) or both constituting each functional unit of the control device 100. When each of these functional units is configured by a program, the arithmetic processing unit included in the control device 100 operates as a computer that executes the program that configures each functional unit. Regarding the control of the self-sustained operation, the parts that perform the main functions in the control device 100 are a rotation speed control unit 103 and a suitable rotation speed determination unit 150 described below.

3-0. Determination of Target Rotation Speed ω * Hereinafter, the configuration of the power generation system 1 of the present application will be described in order to operate the power generation system 1 in the state with the highest overall power generation efficiency corresponding to a predetermined power load amount.

As shown in FIG. 1 and FIG. 2, the power generation system 1 according to the present application is provided with a suitable rotational speed determining unit 150 as a functional part attached to the rotational speed control unit 103, An engine for operating the power generation system 1 in the most efficient state (a state where the secondary excitation generator efficiency and the engine efficiency are maximized in a comprehensive manner) with respect to the power load Pload that has been known in advance. The rotational speed of the rotor 2a is determined by subtracting the rotational speed of the rotor 2a.
The preferred rotational speed ω * determined by the preferred rotational speed determining unit 150 is the “target rotational speed ω *” commanded from the rotational speed control unit 103 to the gas engine 3.

The preferred rotation speed determination unit 150 includes a generator loss index M1 indicating a relationship between the generator loss Ploss, which is a loss of the secondary excitation induction generator 2, with respect to an arbitrary rotation speed ω and an arbitrary power load Pload, A storage unit 151 that stores an engine efficiency index M2 indicating a relationship of engine efficiency to engine rotation speed and torque;
Using the generator loss index M1 stored in the storage unit 151, a generator loss deriving unit 152 for obtaining a generator loss Ploss when the power generation system is operated at the predetermined power load Pload and the temporary rotational speed ω. When,
Based on the generator loss Ploss derived by the generator loss deriving unit 153, the generator efficiency ηd for deriving the generator efficiency ηd and the mechanical input Pm for driving input from the engine to the secondary excitation induction generator A deriving unit 154;
A torque deriving unit 155 for deriving a torque T applied to the secondary excitation generator from the machine input Pm derived by the generator efficiency / machine input deriving unit 154 and the temporary rotational speed ω;
An engine efficiency deriving unit 156 for determining an engine efficiency ηe from the torque T derived by the torque deriving unit 155 and the temporary rotational speed ω using the engine efficiency index M2 stored in the storage unit 151;
From the generator efficiency ηd derived by the generator efficiency / machine input deriving unit 154 and the engine efficiency ηe derived by the engine efficiency deriving unit 156, a total generation system efficiency η as a product value ηd × ηe is derived. And an overall efficiency deriving unit 157.

[Generator loss index M1]
Table 1 below shows an example of the generator loss index M1.
In the table, the column indicates the rotation speed [rpm], and the row indicates the power load [W]. Each internal element indicates a generator loss [W].

In order to derive the generator loss, the model shown in Fig. 3 is used, and the control of the secondary excitation induction generator is described in the literature ("Power-off start control and independent operation of a gas engine cogeneration system using a wound-type induction generator"). Examination of time control method ”The method shown by Tetsuo Ohmichi, Tomofumi Miura, Toshifumi Ito, Yuki Sato Semiconductor Power Conversion Study Group SPC-11-029 (2011)) was used.
Further, calculation was performed using “PSCAD / EMTDC” (manitoba HVDC Research Center Inc.) as simulation software.

  The basic simulation algorithm receives the power load Pload and the rotational speed ω of the power generation system, and outputs a rotational speed command value ω * to the engine.

[Engine efficiency index M2]
An example of the engine efficiency index M2 is an index as shown in FIGS. 5B and 6B, where the horizontal axis indicates the rotational speed [rpm] and the vertical axis indicates the torque [N · m]. It corresponds. The engine efficiency ηe (ηe <ηeb <ηec <ηd ·) is shown as a region within the approximate ellipse in the figure, and indicates a region where the engine efficiency increases as the alphabet advances.

  The generator loss deriving unit 153 obtains the generator loss Ploss when the power generation system is operated at the predetermined power load Pload and the temporary rotation speed ω using the generator loss index M1 described above. When the generator loss index M1 shown in Table 1 is used, the surface element is generated by using the data of the generator loss Ploss of the four points on the table surrounding the operating point of the predetermined power load Pload and the temporary rotational speed ω. The generator loss Ploss in the operation state is derived by the four-point interpolation method.

  The generator efficiency / machine input deriving unit 154 derives the generator efficiency ηd as ηd = (Pload−Ploss) / Pload based on the generator loss Ploss derived by the generator loss deriving unit 153. On the other hand, the driving mechanical input Pm input from the gas engine 3 to the secondary excitation induction generator 2 is derived as Pm = Pload + Ploss.

  Further, the torque deriving unit 155 calculates the torque T applied to the secondary excitation generator from the mechanical input Pm derived by the generator efficiency / mechanical input deriving unit 154 and the temporary rotational speed ω by T = Pm / (2π × ω / 60 ).

  In this example, the engine efficiency deriving unit 156 uses the index M2 configured as an engine efficiency map as shown in FIGS. 5B and 6B, and uses the torque T derived by the torque deriving unit 155. Then, the engine efficiency ηe is obtained from the temporary rotational speed ω.

  The total efficiency deriving unit 157 calculates the product value ηd × ηe from the generator efficiency ηd derived by the generator efficiency / machine input deriving unit 154 and the engine efficiency ηe derived by the engine efficiency deriving unit 156. The power generation system overall efficiency η = ηd × ηe is derived.

  Therefore, the preferred rotational speed determination unit 150 employs a configuration in which the power generation system total efficiency is sequentially obtained at a predetermined power load Pload and different temporary rotational speeds ω, and the temporary rotational speed ω that maximizes the total efficiency η. Is configured to find a provisional rotation speed ω that maximizes the overall efficiency η by satisfying a predetermined convergence condition. Yes. Then, the temporary rotation speed ω at which the power generation system overall efficiency η with respect to the temporarily derived temporary rotation speed ω is maximized is determined as a suitable rotation speed ω when a predetermined amount of power load is supplied to the load 7.

  As a result, in the power generation system 1 including the driving engine 3 and the secondary excitation induction generator 2 with respect to the predetermined power load amount Pload, the total efficiency is maximized with respect to the predetermined power load amount Pload. And you can drive.

Hereinafter, the procedure for determining the target rotational speed will be described with reference to FIGS. 4, 5, and 6.
FIG. 4 shows a processing flow executed upon determination.
First, the power load amount Pload to be determined is fetched (step # 1).
As this power load amount Pload, for example, a power supply amount for only an important load that needs to be supplied in the event of a power failure, or an expected power supply amount that is expected to be supplied every predetermined time period is used. Applicable.

An initial provisional rotational speed ω ₀ is set for the power load Pload captured in step # 1 (step # 2). For this setting, a table of the initial temporary rotation speed ω ₀ is prepared in advance, and the initial temporary rotation speed ω ₀ corresponding to the power load amount Pload can be set in advance from the table.

  The power generator loss deriving unit 153 derives the generator loss Ploss with respect to the power load Pload and the temporary rotational speed ω set in this way (step # 3: generator loss deriving step).

  Next, the generator efficiency / machine input deriving unit 154 inputs the generator efficiency ηd and the drive input from the engine to the secondary excitation induction generator 2 based on the generator loss Ploss derived in the generator loss deriving step. Machine input Pm is derived (step # 4: generator efficiency / machine input derivation step). Here, the machine input Pm corresponds to the driving force that the gas engine 3 should generate.

  Next, the torque deriving unit 155 derives the torque T applied to the secondary excitation generator from the machine input Pm derived in the generator efficiency / machine input deriving step and the temporary rotational speed ω (step # 5: torque deriving step). ).

  Next, the engine efficiency deriving unit 156 obtains the engine efficiency ηe according to the engine efficiency index M2 from the torque T derived in the torque deriving step and the temporary rotational speed ω (step # 6: engine efficiency deriving step).

  Further, the total efficiency deriving unit 157 generates the product value ηd × ηe from the generator efficiency ηd derived in the generator efficiency / machine input deriving step and the engine efficiency ηe derived in the engine efficiency deriving step. The total efficiency η is derived (step # 7: total efficiency deriving step).

Then, the search calculation processing function unit 152 determines whether or not the power generation system overall efficiency η satisfies a certain convergence condition according to the hill-climbing method (step # 8: convergence determination step).
When it is determined that the determination condition is satisfied (step # 8: yes), the temporary rotation speed ω at the determination stage is set as a preferable rotation speed ω * when the predetermined power load is supplied to the load 7. (Step # 10).
On the other hand, if it is determined that the determination condition is not satisfied (step # 8: no), the temporary rotational speed ω is corrected (ω = ω + Δω), and step # 3 to step # 8 are repeated again according to the hill climbing method. .
As a result, the rotational speed ω * that maximizes the overall efficiency η can be obtained by the hill-climbing method. This rotational speed ω * becomes a rotational speed command value ω * for the gas engine 3.

  FIG. 5 and FIG. 6 show the processing by the hill-climbing method (pattern A: FIG. 5) when the set value of the initial temporary rotational speed ω0 is set on the larger side with respect to a suitable rotational speed, and the smaller side. The process (pattern B: FIG. 6) by the hill-climbing method when set is shown. In FIG. 5, the search proceeds in the order of operating points 1, 1 ′, 2, 3, 4, 5, 6. In FIG. 6, the search proceeds in the order of operating points 1, 2, 3, 4, and 5.

The pattern A corresponds to the case where the efficiency increases when Δω is changed. When the efficiency decreases by performing + Δω from the state 1 shown in FIG. 5A (1 → 1 ′), the sign of Δω is changed. Replace (-ω). The rotational speed is changed with a search range of 1 → 2 → 3 and Δω (change by −ω). Since the efficiency decreases as 2 → 3, the sign is reversed from the rotational speed of 3, and the rotational speed is changed with a search width of Δ0.5ω (changed by + 0.5ω). Since the efficiency decreases from 4 to 5, the sign is reversed from the rotational speed of 5, and the rotational speed is changed with a search width of Δ0.5 × 0.5ω (changed by + 0.25ω).
Further, the search is repeated while narrowing the search width by 0.5 times, and the maximum efficiency point in the search until the predetermined number of times (for example: 20 times) or the previous sign is inverted is set. As the convergence condition, the current efficiency is compared, and the efficiency improvement width is less than a certain value Δη (eg, Δη <+1
. 0%), it can be judged that it has converged.

In pattern B, when the efficiency is necessarily lowered by performing ± Δω from the state 1 shown in FIG. 6A (1 → 2 or 1 → 3), the search width Δω is multiplied by 0.5. If the efficiency is always reduced by changing ± Δ0.5ω, the search width is further increased by 0.5 (1 → 4 or 1 → 5). Repeat until the efficiency increases. When a rotational speed with increased efficiency is found (5 in the figure), the previous search width is multiplied by 0.5 from the rotational speed of 5, and a search similar to pattern A is further performed.
As a result, it is possible to satisfactorily search for (converge) a suitable rotation speed by the hill climbing method.

This completes the description of the search process for the preferred engine speed.
Hereinafter, the standby operation process and the load connection process before setting the target rotation speed will be described with reference to FIGS.

  FIG. 7 shows a state in which the first switch 21 is closed and the second switch 22 is opened in a no-load state in which the rotor 2a is driven by the gas engine 3 and the third switch 23 is opened. From this state, the flow of processing from when the power generation system 1 (secondary excitation induction generator 2) starts up independently and power is supplied to the load 7 is shown. In addition, although the 2nd switch 22 is made into the closed state instead of an open state, also when it exists in the state which cannot supply electric power from the electric power grid | system 4, the process demonstrated here can be performed similarly. The gas engine 3 is accelerated to a predetermined rotational speed without being connected to a load 7 (excluding energy necessary for rotating the rotor 2a) after being started by a cell motor, for example, and is connected to the load 7. It is assumed that the motor is stable at the predetermined rotation speed in a no-load state. Further, when the power generation system 1 is autonomously started, the power storage device 5 is in a state in which power can be supplied to the DC unit 13, and the secondary winding included in the rotor 2 a or It supplies to the primary winding with which stator 2b is provided.

3-1. Independent start-up (step-up process, primary side excitation process)
As shown in FIG. 7, the control device 100 operates only the second power converter 12 of the first power converter 11 and the second power converter 12 by the second control unit 102 and executes the boosting step. (Step # 1). Here, the “boosting step” is a step of performing a boosting process for boosting the primary side voltage v1 to the primary side voltage command value V1 * by the secondary side excitation step. That is, after the “boost process” is performed, the primary side voltage v1 and the primary side voltage command value V1 * become equal. In this boosting step, the second control unit 102 executes the voltage feedback control described above.

  Here, the primary-side voltage command value V1 * is a voltage that determines the output voltage (primary-side voltage v1) of the secondary excitation induction generator 2 as described above. It can be set to 200 [V], 3300 [V], 6600 [V], or the like. The primary voltage command value V1 * is preferably configured to increase in a slope shape toward the set value (soft start), and the amplitude of the primary voltage v1 is preferably increased in a slope shape from the viewpoint of stability. . For example, the primary voltage command value V1 * can be raised to the set value at a rate of 400 [V / sec] in terms of the effective value of the line voltage.

  Note that the maximum value (peak value) of the amplitude when the primary side voltage v1 is expressed by a phase voltage (for example, a phase voltage of the a phase) is v1am (unit [V]), and the primary side voltage command value V1 * is between the lines. Assuming that the voltage is an effective value (unit [V]), in this embodiment, the state of v1am = V1 * × √ (2/3) is the primary voltage v1 and the primary voltage command value V1 *. Are equal. Thus, “the state where the primary side voltage v1 is boosted to the primary side voltage command value V1 *” and “the state where the primary side voltage v1 and the primary side voltage command value V1 * are equal”, and the same meaning as these, This means a state in which the value of v1 and the value of V1 * are equal to each other after being multiplied by a coefficient if necessary (according to a method for connecting windings or the like).

  After execution of the boosting step by the second control unit 102, that is, after the primary side voltage v1 has been boosted to the primary side voltage command value V1 *, the first control unit 101 of the control device 100 turns the first power converter 11 on. Operate and execute the primary side excitation process (step # 2). In addition, the 1st control part 101 performs the electric current feedback control mentioned above as a primary side excitation process. Specifically, the first control unit 101 controls the first power converter 11 so that the first power converter 11 generates reactive power (in this example, positive delayed reactive power). In this case, since the third reactive power Q3 is a negative value and the third switch 23 is in the open state, the first reactive power Q1 is also a negative value (a value substantially equal to the third reactive power Q3). Thereby, positive delayed reactive power is supplied from the first power converter 11 to the primary winding included in the stator 2b of the secondary excitation induction generator 2. That is, the 1st control part 101 performs control which supplies reactive power (in this example, positive delay reactive power) to the primary winding from the 1st power converter 11 as a primary side excitation process.

  When performing the primary side excitation process, the first control unit 101 sets a current command value Ig * corresponding to the desired delayed reactive power (third reactive power Q3). As described above, in this example, the third reactive power Q3 can be controlled by the q-axis component igq of the transformer secondary current ig. Therefore, the first control unit 101 sets at least the q-axis component Igq * having a value other than zero as the current command value Ig *. When the active power is positively generated in the first power converter 11 together with the positive delayed reactive power, the current command value Ig * is set so that the d-axis component Igd * also has a value other than zero. To do.

  It is preferable from the viewpoint of stability that the current command value Ig * is configured to increase in a slope shape toward the set value (soft start), and the amplitude of the transformer secondary side current ig is increased in a slope shape. It is. For example, the current command value Ig * is obtained by multiplying the maximum value (unit [V]) of the line current iga of a phase (for example, a phase) of the transformer secondary current ig by √ (3/2). If it is, the current command value Ig * can be raised to the set value at a rate of 6 [V / sec].

  Note that the second control unit 102 executes the secondary side excitation process even after the primary side voltage v1 is boosted to the primary side voltage command value V1 *, and maintains the primary side voltage v1 at the primary side voltage command value V1 *. The second power converter 12 is controlled as described above. That is, in step # 2, the first control unit 101 executes current feedback control, and the second control unit 102 executes voltage feedback control. In this state, since a part of the power required by the secondary excitation induction generator 2 is supplied as reactive power from the first power converter 11, the primary side voltage v1 is changed to the primary side voltage command value V1 *. The power (at least the second reactive power Q2) that needs to be supplied to the secondary winding in order to maintain it is less than when the boosting step (step # 1) is completed. Therefore, the power generated by the second power converter 12 (from the second power converter 12 to the secondary winding) in accordance with the increase of the positive delay reactive power supplied from the first power converter 11 to the primary winding. The second control unit 102 controls the second power converter 12 so that the power supplied) decreases. By setting it as such a structure, it is possible to suppress that the electric power supplied to the secondary winding from the 2nd power converter 12 becomes excessive.

  In this example, when the positive delay reactive power supplied from the first power converter 11 to the primary winding is increased, the power supplied from the second power converter 12 to the secondary winding is decreased. The current flowing through the secondary winding (secondary current i2) is reduced. In addition, it can also be set as the structure which also reduces the secondary side voltage v2 which is the voltage induced by the secondary side of the secondary excitation induction generator 2 with the reduction | decrease of the secondary side electric current i2.

  After execution of the primary side excitation step (step # 2), the primary side voltage v1 is set to the primary side voltage command value V1 * and the reactive power supplied to the primary winding of the secondary excitation induction generator 2 Or the electric power supplied to the secondary winding of the secondary excitation induction generator 2 has a desired value. This state is a primary voltage established state in which connection with the load 7 is possible.

  As described above, the control device 100 (the first control unit 101 and the second control unit 102) performs both the primary side excitation process and the secondary side excitation process in a no-load state, in other words, Both the primary power converter 11 and the secondary power converter 12 are operated to establish the primary side voltage v1 generated on the primary side of the secondary excitation induction generator 2 as the primary side voltage command value V1 *. A process (primary side voltage establishment process) is executed. In this example, as described above, after the boosting step, the positive voltage supplied from the first power converter 11 to the primary winding in the state where the primary voltage v1 is maintained at the primary voltage command value V1 *. The delay reactive power is increased, and the power supplied from the second power converter 12 to the secondary winding is decreased. That is, in this example, the primary side voltage establishment process is a delayed primary side voltage establishment process (delayed primary side voltage establishment process) in which the primary side excitation process is started after the boosting process is executed.

3-2. Standby operation and connection to load 7 (standby operation process, load connection process)
When the primary voltage v1 is established by executing the delay-type primary voltage establishing step (step # 1 and step # 2) and the control device 100 is in a self-sustaining operation state, the third switch 23 is opened and connected to the load 7 In an unloaded state, the gas engine 3 is driven at a no-load rotation speed faster than the target rotation speed, and the output power of the primary winding of the secondary excitation induction generator 2 is controlled to the output power of the target frequency. A standby operation step is executed (step # 3). The control device 100 including the rotation speed control unit 103, the first control unit 101, and the second control unit 102 of the control device 100 is configured to execute a standby operation process. A control function part that executes a standby operation step provided in the control device 100 is referred to as a “standby operation control unit 110”.

  Then, after the standby operation process (step # 3) is performed, a load connection process is performed in which the third switch 23 is closed and the primary winding is connected to the load 7 (step # 4). As described above, the control device 100 includes the switch control unit 104 that controls the open / close state of the third switch 23, and includes the switch control unit 104, the first control unit 101, and the second control unit 102. The control device 100 is configured to execute the load connection process. Thereby, the electric power generated by the secondary excitation induction generator 2 is supplied to the load 7 that requires electric power. By enabling such self-sustained operation, it is possible to supply power to the important load (load 7) from the power generation system 1 even when it is disconnected from the power system 4, and serve as an emergency power source in the event of a power failure It becomes possible to bear. A control function part that executes a load connection process provided in the control device 100 is referred to as a “load connection waiting control unit 120”.

  Hereinafter, the control in the standby operation process (step # 3) and the effect of the control will be described with reference to FIGS.

  FIG. 8 is a graph showing the control of the rotational speed of the gas engine 3 in the power generation system 1. In FIG. 8, the state of control of the rotational speed of the gas engine 3 in the power generation system 1 is indicated by a solid line, and the state of control when a conventional synchronous generator is used as a generator is indicated by a broken line. The target rotational speed of the gas engine 3 in FIG. 8 is 1200 [rpm]. However, in the power generation system 1 according to the present embodiment, in the range shown in FIG. The gas engine 3 is operated at 1500 [rpm] (no-load rotation speed) higher than the target rotation speed 1200 [rpm]. This target rotation speed is an example of a suitable rotation speed commensurate with the power load amount of the important load (load 7) described above.

  8B, the third switch 23 is closed, and the power generation system 1 is connected to the load 7 that is 30% of the rated load. As can be seen in FIG. 8C, the rotational speed of the gas engine 3 also decreases in this embodiment due to the connection to the load 7 (solid line), but the decrease in rotational speed per hour is conventional (dashed line). It is moderate compared to

  FIG. 9 shows a change in the frequency f1 of the output power of the power generation system 1 when the rotation speed of the gas engine 3 is controlled as shown in FIG. FIGS. 9A, 9B, and 9C correspond to the timings of FIGS. 8A, 8B, and 8C, respectively.

  In FIG. 9, in the range of (A) before connection to the load 7, as shown in FIG. 8A, the gas engine 3 is operated at a no-load rotational speed 1500 [rpm higher than the target rotational speed 1200 [rpm]. ]. In the range of FIG. 9A, the control device 100 controls the secondary excitation induction generator 2 to stabilize the frequency f1 of the output power of the power generation system 1 at the target frequency of 60 [Hz]. In other words, the control device 100 controls the frequency f2 of the alternating current supplied to the secondary winding in order to excite the secondary winding of the rotor 2a based on the rotational frequency f0 of the rotor 2a. The frequency f1 of power is stabilized at the target frequency of 60 [Hz].

  When connected to the load 7 in FIG. 9B, the frequency f1 of the output power of the power generation system 1 is once lowered in this embodiment (solid line) as in the conventional technique (broken line) (FIG. 9C )). However, the decrease in the frequency f1 of the output power in the present embodiment (solid line) is smaller than that in the conventional technique (broken line). That is, as seen in FIG. 8 (C), immediately after connection to the load 7, since the change in the rotational speed of the gas engine 3 is large, the frequency f1 of the output power slightly decreases in this embodiment as well. In the present embodiment, since the subsequent change in the rotational speed of the gas engine 3 is more gradual than in the prior art, fluctuations in the frequency f1 of the output power when the power load is connected can be suppressed, as shown in FIG. As described above, it can be controlled at a target frequency of 60 [Hz].

  As described above, according to the control method and the control device of the power generation system according to the present invention, it is possible to suppress the decrease in the frequency of the output power when the power load is connected as compared with the case where the conventional control method and the control device are used. Therefore, it becomes possible to connect to a larger power load.

  In FIG. 8C, after the connection to the load 7, the rotational speed of the gas engine 3 is set to a rotational speed 1250 [rpm] near the target rotational speed, which is different from the target rotational speed 1200 [rpm]. This is because the power of the target frequency is supplied to the load 7 while always controlling the frequency supplied to the secondary winding by the second power converter 12. Therefore, it is not always necessary to control the rotation speed as described above, and the frequency control may not be performed after connection to the load 7 and the rotation speed may be set to the target rotation speed 1200 [rpm].

3-3. Setting of a preferred no-load rotation speed in the standby operation process A preferred setting of the no-load rotation speed in the standby operation process will be described with reference to FIG. FIG. 10 is a graph showing a preferred no-load rotation speed of the gas engine 3 when the reduction in the frequency f1 of the output power of the power generation system 1 when the power load is connected is targeted to be within 5%. is there. In the power generation system 1 according to FIG. 10, the maximum rotation speed of the gas engine 3 is 1500 [rpm].

  When the load factor is 0% in the range of FIG. 10 (i) where the load factor, which is the ratio of the connected load power of the load 7 connected to the primary winding to the total power consumed by the power load, is 30% or less The power load starts at a rotational speed of 1500 [rpm] or less, which is the maximum rotational speed of the gas engine 3, starting from a rotational speed of 1250 [rpm] to a rotational speed of 1500 [rpm] when the load factor is 30%. The decrease in the frequency f1 of the output power of the power generation system 1 at the time of connection can be kept within the target range of 5%. Accordingly, in the range of FIG. 10 (i), the no-load rotation speed becomes faster as the load factor (the size of the connected load 7) increases, and the frequency f1 of the output power when connected to the load. It is preferable to set the rotation speed so that the decrease can be kept within the target range of 5%.

  On the other hand, in the range of FIG. 10 (iii) where the load factor is 30% to 60% of the rated load, in order to suppress the decrease in the frequency f1 of the output power of the power generation system 1 when the power load is connected to within 5%, It is necessary to drive the gas engine 3 at a rotational speed exceeding the maximum rotational speed 1500 [rpm]. However, due to mechanical constraints, the gas engine 3 cannot be driven at a rotational speed exceeding the maximum rotational speed 1500 [rpm]. Therefore, in the range of FIG. 10 (iii), in order to suppress the decrease in the frequency f1 of the output power of the power generation system 1 when the power load is connected as much as possible, the no-load rotation speed is the maximum rotation speed of the gas engine 3. It is preferable to set it to 1500 [rpm].

  As described above, in order to suppress the decrease in the frequency f1 of the output power of the power generation system 1 when the power load is connected to the target range as much as possible while suppressing the increase in size of the power generation system 1, the rotational speed at no load is Depending on the size (load factor) of the load 7 to be connected, the reduction in the frequency f1 of the output power when connected to the load 7 is not less than the rotation speed at which the reduction in the frequency f1 can be kept within the target range and not more than the maximum rotation speed It is preferable to set either the rotation speed or the maximum rotation speed of the gas engine 3.

  In addition, as described above, by setting the no-load rotation speed according to the load factor, the frequency range of the output power when the power load is connected can be reduced as much as possible while suppressing the enlargement of the power generation system as much as possible. A suitable no-load rotation speed can be set.

  It should be noted that it is preferable to set the no-load rotation speed faster according to the increase in the load factor, and the load factor range in FIG. 10 (i) is suitable, and the no-load rotation speed is a constant value regardless of the increase in the load factor. The load factor in FIG. 10 (ii), which is a boundary with the range of the load factor in FIG. 10 (iii) that is preferably set to (maximum rotation speed), is a reference value for switching the setting method of the no-load rotation speed. By setting as a certain set load factor, the control device 100 can set a suitable no-load rotation speed.

10 (iv) is a load factor indicating the limit of the power load that can be connected to the power generation system 1. FIG. For the connected power load, it is not preferable that the frequency f1 of the supplied power fluctuates greatly. Therefore, the upper limit of the load 7 that can be connected to the power generation system 1 is set as an allowable limit depending on the degree of decrease in the frequency f1 of the output power of the power generation system 1 when the load 7 is connected.
In FIG. 10, in the range of FIG. 10 (iii) where the rotational speed is limited due to mechanical constraints, the frequency f1 of the output power of the power generation system 1 when the power load is connected increases as the load factor increases. Decreases beyond the range (5%).
In FIG. 10 (iv) in which the load factor is 60%, the decrease in the frequency f1 of the output power of the power generation system 1 when the power load is connected reaches 15%, which is an allowable limit. For this reason, in the electric power generation system 1, the connection of the electric power load in which a load factor exceeds 60% is not recognized. Therefore, in the range exceeding FIG. 10 (iv), the rotation speed is not described (FIG. 10 (v)), and FIG. 10 (iv) serving as the boundary indicates the limit of the power load that can be connected to the power generation system 1. Load factor.

4). Other Embodiments Finally, other embodiments according to the present invention will be described. Note that the features disclosed in each of the following embodiments can be used only in that embodiment, and can be applied to other embodiments as long as no contradiction arises.

(1) In the above embodiment, as a preferred setting of the no-load rotation speed during self-sustained operation, in FIG. 10, the decrease in the frequency f1 of the output power of the power generation system 1 when the power load is connected is kept to 5%. The case where the target is set as an example has been described. However, the embodiment of the present invention is not limited to this, and the target range of reduction in the frequency f1 of the output power is set to 3% or 10%, for example, depending on the nature of the connected load 7. You can also. Further, in FIG. 10, as an example of the limit of the connectable power load, the limit of the power load that can be connected is described as an example of the limit of the power load that can be connected. However, the embodiment of the present invention is not limited to this, and the limit of the power load that can be connected according to the nature of the connected load 7, for example, the power at which the frequency of the output power is reduced by 10% or 20%. It can also be a load.

(2) In the above-described embodiment, the configuration in which the primary side voltage establishing step is the delayed primary side voltage establishing step has been described as an example. However, the embodiment of the present invention is not limited to this, and a configuration in which the primary-side excitation process is started before the boosting process by the secondary-side excitation process is completed is also preferable implementation of the present invention. One of the forms. That is, the primary side voltage v1 is boosted to the primary side voltage command value V1 * and the primary side voltage v1 is established while simultaneously executing the primary side excitation step and the secondary side excitation step in parallel. Can do. In this case, the primary side excitation process and the secondary side excitation process can be started simultaneously or substantially simultaneously. As described above, in the configuration in which the primary side excitation step and the secondary side excitation step are executed in parallel to boost the primary side voltage v1 to the primary side voltage command value V1 *, the secondary side current i2 is compared to the above embodiment. It is possible to keep the maximum value of the lower value lower and to keep the time during which the secondary current i2 is in an excessive state shorter.

(3) In the above embodiment, the configuration in which the current feedback control is executed based on the transformer secondary current ig in the primary side excitation process has been described as an example. However, the embodiment of the present invention is not limited to this. In the primary side excitation process, current feedback is based on the current on the primary side of the transformer 6 and the current on the stator 2b side with respect to the current sensor 30 in FIG. It can also be set as the structure which performs control.

(4) In the above embodiment, a configuration in which both the current feedback control by the first control unit 101 and the voltage feedback control by the second control unit 102 are based on proportional-integral control calculation (PI control calculation) is taken as an example. As explained. However, the embodiment of the present invention is not limited to this, and may be configured to execute a proportional integral differential control calculation (PID control calculation) instead of the proportional integral control calculation.

(5) In the above embodiment, in the primary side excitation process, current feedback control is performed based on the current flowing through the AC side of the first power converter 11 (transformer secondary side current ig), and in the secondary side excitation process, The configuration for performing voltage feedback control based on the primary side voltage v1 has been described as an example. However, the embodiment of the present invention is not limited to this, and at least one of the primary side excitation step and the secondary side excitation step is wound by a control method other than feedback control (for example, feedforward control). It is also possible to set it as the process of exciting a line.

(6) In the above embodiment, when the power supplied from the second power converter 12 to the secondary winding is reduced in the primary voltage establishing step, the current flowing through the secondary winding (secondary current i2 ) Is described as an example. However, the embodiment of the present invention is not limited to this, and may be configured to reduce only the secondary side voltage v2 without reducing the current flowing through the secondary winding (secondary side current i2). Is possible.

(7) In the above embodiment, a configuration in which the reference phase used by the first control unit 101 for controlling the first power converter 11 is the first reference phase θ1 derived by the second control unit 102 will be described as an example. did. However, the embodiment of the present invention is not limited to this, and the first control unit 101 includes a PLL function unit, and the reference phase used for the control of the first power converter 11 is, for example, two of the transformer 6. It can be set as the structure calculated | required by PLL process based on the voltage of the next side. In this case, the 1st control part 101 becomes a structure which controls by the dq coordinate system on the basis of the transformer secondary side voltage.

(8) In the above embodiment, in the primary side excitation step, positive delay reactive power is generated in the first power converter 11 and positive delay reactive power is supplied from the first power converter 11 to the primary winding. The configuration has been described as an example. However, the embodiment of the present invention is not limited to this, and depending on the configuration of the secondary excitation induction generator 2 and the power generation system 1 as a whole, a negative delay occurs in the first power converter 11 in the primary side excitation process. It is also possible to generate reactive power and supply negative delayed reactive power from the first power converter 11 to the primary winding.

(9) Regarding other configurations as well, the embodiments disclosed herein are illustrative in all respects, and embodiments of the present invention are not limited thereto. That is, as long as the configuration described in the claims of the present application and a configuration equivalent thereto are provided, a configuration obtained by appropriately modifying a part of the configuration not described in the claims is naturally also included in the present invention. Belongs to the technical scope.

DESCRIPTION OF SYMBOLS 1 Electric power generation system 2 Secondary excitation induction generator 2a Rotor 2b Stator 3 Gas engine 4 Electric power system 5 Power storage device 7 Load (electric power load)
11 1st power converter 12 2nd power converter 13 DC part 23 3rd switch (changeover switch)
100 Control device f1 Output power frequency v1 Primary voltage v2 Secondary voltage

Claims (4)

A secondary excitation induction generator having a stator with a primary winding and a rotor with a secondary winding;
A drive source for driving the rotor;
A first power converter having an AC side connected to the primary winding;
A second power converter having an AC side connected to the secondary winding;
A power storage device connected to a direct current unit connecting the direct current side of the first power converter and the direct current side of the second power converter;
A changeover switch for selectively connecting the primary winding and the power load,
A method for determining a suitable rotational speed of the engine when a predetermined power load Pload is supplied to the power load in a power generation system including an engine with an adjustable rotational speed as the drive source,
Using the generator loss index indicating the relationship of the generator loss Ploss, which is the loss of the secondary excitation induction generator, to the arbitrary rotation speed ω and the arbitrary power load amount Pload, the predetermined power load amount Pload and the temporary rotation A generator loss derivation step for determining a generator loss Ploss when the power generation system is operated at a speed ω;
Based on the generator loss Ploss derived in the generator loss deriving step, the generator efficiency ηd and the generator efficiency Pm for deriving the mechanical input Pm for driving input from the engine to the secondary excitation induction generator A machine input derivation process;
A torque deriving step of deriving a torque T applied to the secondary excitation generator from the machine input Pm derived in the generator efficiency / machine input deriving step and the temporary rotational speed ω;
An engine efficiency deriving step for obtaining an engine efficiency ηe from the torque T derived in the torque deriving step and the temporary rotational speed ω;
The total generation efficiency η as the product value ηd × ηe is derived from the generator efficiency ηd derived in the generator efficiency / machine input derivation step and the engine efficiency ηe derived in the engine efficiency derivation step. The efficiency deriving step is sequentially executed at the predetermined power load Pload and different temporary rotational speeds ω,
The temporary rotational speed ω that maximizes the power generation system overall efficiency η with respect to the temporary rotational speed ω that is sequentially derived is set to a preferable rotational speed ω when the predetermined power load is supplied to the power load. Decision method. The preferred rotational speed determined by the preferred rotational speed determining method of claim 1 is set as a target rotational speed,
The engine is driven at the target rotational speed, and the power supply from the power storage device supplies power output at a desired target frequency to the power load without receiving power from an external power system. Regarding driving
The engine is driven at a no-load rotational speed faster than the target rotational speed in an unloaded state where the changeover switch is open and the primary winding is not connected to the power load, and the primary winding A standby operation step of controlling the output power of the target frequency to the output power of the target frequency,
Then, the control method of the electric power generation system which performs the load connection process which makes the said changeover switch a closed state and connects the said primary winding to the said electric power load. A secondary excitation induction generator having a stator with a primary winding and a rotor with a secondary winding;
A drive source for driving the rotor;
A first power converter having an AC side connected to the primary winding;
A second power converter having an AC side connected to the secondary winding;
A power storage device connected to a direct current unit connecting the direct current side of the first power converter and the direct current side of the second power converter;
A changeover switch for selectively connecting the primary winding and the power load,
As the drive source, a power generation system including an engine with adjustable rotation speed,
The relationship between the generator loss index indicating the relationship of the generator loss Ploss, which is the loss of the secondary excitation induction generator, to the arbitrary rotational speed ω and the arbitrary power load Pload, and the relationship of the engine efficiency to the rotational speed and torque of the engine A storage unit storing an engine efficiency index indicating
A generator loss deriving unit for determining a generator loss Ploss when operating at the predetermined power load Pload and the temporary rotational speed ω using the generator loss index stored in the storage unit;
Based on the generator loss Ploss derived by the generator loss deriving unit, the generator efficiency ηd and the generator efficiency Pd for deriving the mechanical input Pm for driving input from the engine to the secondary excitation induction generator A machine input deriving unit;
A torque deriving unit for deriving a torque T applied to the secondary excitation generator from the machine input Pm derived by the generator efficiency / machine input deriving unit and the temporary rotational speed ω;
An engine efficiency deriving unit for obtaining an engine efficiency ηe from the torque T derived by the torque deriving unit and the temporary rotational speed ω using an engine efficiency index stored in the storage unit;
Total generation efficiency η derived as a product value ηd × ηe from the generator efficiency ηd derived by the generator efficiency / machine input deriving unit and the engine efficiency ηe derived by the engine efficiency deriving unit An efficiency deriving unit, and determining the power generation system overall efficiency η at the predetermined power load Pload and different temporary rotational speed ω,
Determining a preferred rotational speed, which is a preferred rotational speed ω when the predetermined power load is supplied to the power load, with the temporary rotational speed ω at which the power generation system overall efficiency η is maximized with respect to the provisional rotational speed ω sequentially Power generation system with parts. The preferred rotational speed determined by the preferred rotational speed determining unit according to claim 3 is set as a target rotational speed,
The engine is driven at the target rotational speed, and the power supply from the power storage device supplies power output at a desired target frequency to the power load without receiving power from an external power system. A self-sustaining operation control unit that operates
The engine is driven at a no-load rotational speed faster than the target rotational speed in an unloaded state where the changeover switch is open and the primary winding is not connected to the power load, and the primary winding A standby operation control unit that executes a standby operation step of controlling the output power of the target frequency to the output power of the target frequency;
And a load connection control unit configured to perform a load connection step of connecting the primary winding to the power load with the changeover switch closed.

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