JP2009273210A - Method of controlling distributed power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of controlling a distributed power supply that improves the stability of a frequency of a microgrid system in autonomous operation by making the distributed power supply having quick responsiveness compensate an output variation of the distributed power supply which generates a voltage and a frequency being bases at the autonomous operation. <P>SOLUTION: The method of controlling the distributed power supply integrally controls a plurality of the distributed power supplies different in following performance with respect to a load variation. The method performs autonomous operation control for stably maintaining the frequency without detecting the frequency by making the distributed power supply having the highest load following performance among the plurality of kinds of distributed power supplies compensate the output variation of the distributed power supply which generates the base, the voltage and the frequency at the autonomous operation, and an integrated value of the output variation. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for controlling a distributed power source.

  In recent years, the introduction of distributed power sources (solar power generation, wind power generation, etc.) has been promoted as a national strategy. However, natural energy-derived power sources such as solar power generation and wind power generation have a problem in that the output is greatly influenced by the weather, so the supply reliability is low, and it is difficult to balance the supply and demand of power in commercial systems . As a means to solve this problem, a distributed power source capable of adjusting output is used to generate power according to demand within a specific range (hereinafter referred to as load following operation), thereby reducing the burden on the commercial system. Mitigation has been done.

  Methods for realizing the load following operation can be roughly divided into two methods. The first is a method (distributed control) in which each distributed power source autonomously measures load power and performs load following operation like the system stabilization device described in Patent Document 1, and this method is used. Follow-up operation for high-speed load fluctuation can be realized. However, in cases where multiple distributed power sources are introduced, each distributed power source simultaneously performs load following operation for the same load fluctuation, resulting in output interference, resulting in load following operation. There is a risk of failure.

  As a second method, there is a distributed power control method (integrated control) described in Patent Document 2. Based on the measured load power, load follow-up operation is realized by combining a plurality of types of distributed power sources (see FIG. 9) having different follow-up performance and sharing the frequency band. Therefore, in order to perform integrated output adjustment, it is necessary to construct a control system (the brain of control) that has a "load, power purchase, distributed power output measurement system" and a "distributed power output control system". is there.

On the other hand, as one of means for realizing load following operation, there is a microgrid aiming at building a cooperative relationship by reducing the burden on the commercial system. In an energy supply system (hereinafter referred to as a microgrid) using a distributed power supply that incorporates the idea of a microgrid, the following two merits can be obtained by the load following operation of the distributed power supply.
(1) It is possible to suppress an adverse effect on a commercial system of a natural energy-derived power source whose output is unstable.
(2) When a commercial system abnormality such as a power failure occurs, the independent operation with stable power quality (frequency and voltage) can be continued for the load in the area by separating the microgrid from the commercial system.

As a method of performing load following operation of a distributed power source in order to realize a self-sustained operation with stable power quality by using a microgrid, the applicant has proposed a control method of the distributed power source “Japanese Patent Application No. 2007-189697”. Yes. In this control method, when performing load following operation using multiple types of distributed power supplies with different follow-up performance against load fluctuations, high-speed autonomous control via analog dedicated signal lines according to the follow-up performance of distributed power supplies and A control method is proposed that combines low-speed integrated control by a control system via a versatile low-speed digital communication network (for example, a LAN line). In high-speed autonomous control, a compensation amount is determined by extracting a high-speed load fluctuation component that cannot be followed by load control by a control system using a high-pass filter.
JP 2007-020361 A JP 2006-246484 A

  However, in a microgrid that uses a synchronous generator as a main power source, the frequency of the microgrid system that is operating independently depends on the rotational speed of the synchronous generator, so a distributed power source that compensates for high-speed load fluctuations Compensating the integrated value of the output deviation of the synchronous generator rather than the load following operation can realize power supply at a more stable frequency. The reason will be described below using mathematical expressions.

但し、Ｊ：原動機及び同期発電機の回転子の合成慣性モーメント
Ｂ：粘性抵抗 ω：回転子の角速度
Ｔ_Ｍ：機械入力トルク Ｔ_Ｅ：電気出力トルク
Ｐ_Ｍ：機械入力 Ｐ_Ｅ：電気出力 When the synchronous generator is simulated by a single inertia system, the following equation can be obtained with respect to the rotational speed of the synchronous generator that determines the frequency of the system.

However, J: Synthetic moment of inertia of the rotor of the prime mover and the synchronous generator B: Viscous resistance ω: Angular velocity of the rotor T _M : Machine input torque T _E : Electric output torque P _M : Machine input P _E : Electric output

Here, from the steady state where the machine input P _M0 = electric output P _E0 and the rotor is operating at a constant speed ω ₀ , only the electric output changes to P _E0 + ΔP, and the rotor It is assumed that the rotation speed has changed to ω ₀ + Δω. Since slow changes in mechanical input P _M as compared to the change in the instantaneous electrical output, P _M can be considered to be constant. Further, assuming that Δω << ω ₀ , the following approximate expression is obtained from the expression (1).

  This formula shows that the angular acceleration of the synchronous generator can be reduced by suppressing the fluctuation of the electric output of the synchronous generator.In other words, the output fluctuation of the synchronous generator can be achieved by performing load following operation using a distributed power source. As a result, the frequency fluctuation of the microgrid system is also reduced.

However, according to this equation, the angular acceleration of the synchronous generator can be made zero, but the reference deviation Δω of the angular velocity cannot be made zero. That is, there is no function for forcibly returning the changed frequency to the reference value when the load following operation cannot completely compensate for the load change. Therefore, equation (2) is integrated on both sides to create an equation for Δω.

  If the integrated value of the output fluctuation of the synchronous generator is kept at zero from this equation, it is possible to immediately return the frequency to the reference value even if the frequency fluctuates. In general, the function of returning the frequency of the microgrid system during the self-sustaining operation to the reference value has been realized by adjusting the machine input by a governor incorporated in the motor of the synchronous generator. However, since the response speed of the governor is as low as several tens of seconds to several hundreds of seconds, in order to perform high-speed frequency maintenance management, it is necessary to integrate the output fluctuation of this synchronous generator using a distributed power source with high-speed response performance. It is desirable to compensate the value.

  On the other hand, an electric double layer capacitor, a superconducting power storage device, a secondary battery, etc. can be considered as a distributed power source capable of realizing the above function. Since the above function compensates the integrated value of the output fluctuation of the synchronous generator, the compensation time tends to be long. However, the electric double layer capacitor and the superconducting power storage device have low energy density, and are not suitable for control that performs long-time compensation from the viewpoint of capacity. Therefore, when the electric double layer capacitor or the superconducting power storage device has the above function, the limited capacity is obtained by gradually sharing the compensation to the secondary battery having load following performance according to these power sources. It is also necessary to operate the power supply within the range.

  DISCLOSURE OF THE INVENTION The present invention has been made in view of such circumstances, and a distributed power source having a high-speed response performance based on output fluctuations of a distributed power source that generates a voltage and a frequency serving as a base during independent operation and an integrated value of the output fluctuations. It is an object of the present invention to provide a control method for a distributed power source that can improve the frequency stability of a microgrid system that is operating independently without detecting the frequency.

  The present invention is a control method for a distributed power source that integrally controls a plurality of distributed power sources having different follow-up performance with respect to load fluctuations. The self-sustained operation control that keeps the frequency stable without detecting the frequency is achieved by compensating the output fluctuation of the distributed power supply that generates the output and the integrated value of the output fluctuation with the distributed power supply with the highest load following performance. Features.

  According to the present invention, the compensation of the output fluctuation by the distributed power source having the highest load following performance has a load following performance according to the distributed power source having the highest load following performance and the dispersion having the highest load following performance. A distributed power source having a capacity larger than that of a power source is gradually shared.

  According to the present invention, among a plurality of types of distributed power sources, the distributed power source having the highest load follow-up performance is obtained by calculating the output fluctuation and the integrated value of the output fluctuation of the distributed power source that generates a voltage and frequency as a base during independent operation. Since the operation control is performed by compensating for the above, it is possible to improve the frequency stability of the microgrid system during the independent operation. Compensation of output fluctuations by the distributed power supply with the highest load following performance has load following performance equivalent to the distributed power supply with the highest load following performance, and the capacity is larger than the distributed power supply with the highest load following performance. Since the distributed power source is gradually shared, there is also an effect that the distributed power source can be operated in a stable state within a limited capacity range.

Hereinafter, a distributed power supply control method according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an energy supply system using a distributed power source in the embodiment. A distributed power source for supplying power to a load includes a secondary battery 1 connected through an inverter, a synchronous generator 2 driven by an engine, and an electric double layer capacitor 3 connected through an inverter. To do. The measuring instrument 11 measures the output voltage / current of the secondary battery 1, and A / D-converts the active power value (P _BES ) calculated based on the measured voltage / current value by the converter 12. To the control system 7 via. The measuring instrument 21 measures the output voltage / current of the synchronous generator 2, A / D-converts the active power value (P _G ) calculated based on the measured voltage / current value by the converter 22, and the LAN 6 To the control system 7 via. The measuring instrument 31 measures the output voltage / current of the electric double layer capacitor 3, and the converter 32 _performs A / D conversion on the active power value (P _EDLG ) calculated based on the measured voltage / current value. The data is output to the control system 7 via the LAN 6. The measuring instrument 51 measures the electric power (P _LOAD ) supplied to the load 6, A / D-converts this measured value by the converter 52, and outputs it to the control system 7 via the LAN 6.

The control system 7 outputs the output command value Ps for the secondary battery 1 and the control system 4 based on the active power values P _BES , P _G , P _EDLC , and P _LOAD measured by the measuring instruments 11, 21, 31, 51. Obtain _BES and Ps _G. Then, the obtained output command values Ps _BES and Ps _G are D / A converted by the converters 13 and 41 via the LAN 6 and output to the secondary battery 1 and the control system 4. Operation control of power supply performed by the secondary battery 1 is performed by the output command value Ps _BES .

On the other hand, the control system 4 inputs the active power value P _G output from the measuring instrument 21, the active power value P _EDLC output from the measuring instrument 31, and the output command value Ps _G output from the control system 7, From these values, an output command value Ps _EDLC for the electric double layer capacitor 3 is obtained and output to the electric double layer capacitor 3. Operation control of power supply performed by the electric double layer capacitor 3 is performed by the output command value.

In this way, the electric double layer capacitor 3 does not perform autonomous load following operation based on the measured load power, but outputs the output of the electric double layer capacitor 3 itself to the output target value (output) of the synchronous generator 2. Based on the output command value Ps _EDLC output from the control system 4 based on the command value Ps _G ), control is performed so as to supply stable power by performing output control of the electric double layer capacitor 3.

Next, the control operation of the control system 4 shown in FIG. 1 will be described with reference to FIG. FIG. 2 is a block diagram showing the configuration of the control system 4 shown in FIG. First, subtraction output target value of the synchronous generator 2 (output command value Ps _G) from the measured value P _G of the synchronous generator 2 by the computing unit 42. Then, the output of the computing unit 42 is integrated by the integrator 45. The integral gain K _{1 at} this time is a value adjusted according to the moment of inertia of the rotor of the synchronous generator 2. On the other hand, the computing unit 43 adds the output of the computing unit 42 and the measured value P _EDLC of the electric double layer capacitor 3. The computing unit 44 adds the output of the computing unit 43 and the output of the integrator 45 and outputs the result. The limiter 46 limits the amplitude of the output of the computing unit 44 and outputs the result. This output becomes the output command value Ps _EDLC for the electric double layer capacitor 3.

  In FIG. 2, the output of the computing unit 43 corresponds to an output for realizing the conventional load following operation function, and is for maintaining the frequency based on the equation (2). On the other hand, the output of the integrator 45 is for compensating the integrated value of the output fluctuation of the synchronous generator 2, and is for maintaining the frequency based on the equation (3). In this way, the electric double layer capacitor 3 can perform high-speed frequency maintenance management by compensating for the output of the computing unit 43 and the output added value of the integrator 45.

In the configuration shown in FIG. 1, since there is one synchronous generator 2, the output command value Ps _G of the synchronous generator 2 is input to the control system 2, but there are a plurality of generators in the microgrid. In order to apply equation (3) when a stand is installed, all the synchronous generators 2 need to be considered as a single synchronous generator. P _G and the output command value Ps _G may be used the sum of all of the synchronous generator 2.

Next, the control operation of the control system 7 shown in FIG. 1 will be described with reference to FIG. FIG. 3 is a block diagram showing the configuration of the control system 7 shown in FIG. First, the computing unit 71 subtracts the measured value P _BES of the secondary battery 1 from the output (measured value P _LOAD ) of the measuring device 51, and inputs this output to an LPF (low-pass filter) 75. Extract only. Then, the output of the LPF 75 is output by limiting the amplitude by the limiter 77. This output is the output command value Ps _G.

On the other hand, the arithmetic unit 72, and outputs the subtracted (measure _{P LOAD)} from the synchronous generator 2 measured value _{P G} output of the measuring device 51. The integrator 73 integrates the measured value P _EDLC of the electric double layer capacitor 3. The integral gain K _{2 at} this time is a value adjusted according to the capacitance of the electric double layer capacitor 3. The computing unit 74 adds the output of the computing unit 72 and the output of the integrator 73 and outputs the result. This output is input to an LPF (low pass filter) 76, and only the low frequency component is extracted by the LPF 76. Then, the output of the LPF 76 is output with the amplitude limited by the limiter 78. This output becomes the output command value Ps _BES .

  In this way, the integral value of the electrical output compensated by the electric double layer capacitor 3 is added to the difference between the load power and the power generation target value of the synchronous generator 2 (the power value that the secondary battery 1 should compensate in the load following operation). Thus, the output command value of the secondary battery 1 is determined. This means that the electric output compensated by the electric double layer capacitor 3 is gradually transferred to the secondary battery 1. As a result, the electric output of the electric double layer capacitor 3 converges to zero with time, so that the capacity of the electric double layer capacitor 3 can be managed using the secondary battery 1. Further, since the control for gradually sharing the compensation amount of the electric double layer capacitor 3 to the secondary battery 1 does not have to be performed at high speed, there is a problem even if it is realized using the control system 7 connected via the LAN 6. Absent.

  Note that the control method of gradually sharing the compensation amount of the electric double layer capacitor 3 to the secondary battery 1 is a function necessary when using the electric double layer capacitor 3 or the superconducting power storage device having a low energy density. This method may be omitted when a capacitor or a superconducting power storage device is not used.

  Further, in the configuration shown in FIG. 1, since there is one synchronous generator 2, the output command value of the synchronous generator 2 is not input to the synchronous generator 2. This is because when N (N is a natural number) distributed power sources exist in the microgrid, the power output of N-1 power sources is determined from the relationship that the power consumed by the demand always matches the power supplied by the power source. This is because the remaining output is uniquely determined. Therefore, in the case where there are a plurality of synchronous generators 2, the output command value may be transmitted from the control system 7 to the synchronous generator 2 except for one.

  Next, referring to FIG. 4 and FIG. 5, the integrated value of the output fluctuation of the synchronous generator 2 is compensated for by a distributed power source having high-speed response performance, thereby stabilizing the frequency of the microgrid system during the independent operation. The effect of the control method for improving the performance will be described. FIG. 4 shows the output of each distributed power source when the autonomous operation is performed in the load following operation without performing the control for compensating the integrated value of the output fluctuation of the synchronous generator 2 to the distributed power source having high-speed response performance. It is a figure which shows a frequency. FIG. 5 shows a control for compensating the integrated value of the output fluctuation of the synchronous generator 2 to a distributed power source having high-speed response performance, and the output and frequency of each distributed power source when the autonomous operation is performed by load following operation. FIG. As the power source, a gas engine generator (indicated as ge in FIGS. 4 and 5) is used as the synchronous generator 2, and a nickel-metal hydride battery (indicated as nimh in FIGS. 4 and 5) is used as the secondary battery 1. Yes.

  Comparing the fluctuations of the frequency (Freq) in FIGS. 4 and 5, the maximum fluctuation width is reduced from 1.96 Hz to 1.16 Hz (40.8% performance improvement). In addition, the standard deviation is improved from 0.2 Hz to 0.14 Hz (30.0% performance improvement), and it can be seen that it is effective in suppressing frequency fluctuations during self-sustained operation using the control method according to the present invention. .

As a result, the following effects can be obtained by using the control method according to the present invention.
(1) Higher quality independent operation can be performed with respect to frequency without detecting the frequency.
(2) When a distributed power source that performs high-speed output control using an analog dedicated line uses a power source with a low energy density, the capacity can be managed by a power source that conforms to responsiveness. It becomes possible to continue the operation within the range.

  In this way, by compensating the output fluctuation of the synchronous generator 2 and the integrated value of the output fluctuation to the distributed power source (electric double layer capacitor 3) having a high-speed response performance, the frequency of the microgrid system during the independent operation can be reduced. Stability can be improved. In addition, when a power source having a low energy density such as an electric double layer capacitor or a superconducting power storage device is used as a distributed power source having high-speed response performance, the compensation amount is gradually transferred to the secondary battery 1 having a larger capacity. Since the load is shared, the distributed power source can be operated stably within a limited capacity range.

  Note that a program for realizing the functions of the control system 4 and the control system 7 shown in FIG. 1 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read by the computer system and executed. Therefore, the operation control may be performed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer system” includes a WWW system having a homepage providing environment (or display environment). The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, what is called a difference file (difference program) may be sufficient.

It is a block diagram which shows the structure of one Embodiment of this invention. It is a block diagram which shows the structure of the control system 4 shown in FIG. It is a block diagram which shows the structure of the control system 7 shown in FIG. It is a figure which shows the time change of the output and frequency of each distributed power supply at the time of performing independent operation by load following operation. It is a figure which shows the time change of the output and frequency of each distributed power supply at the time of performing independent operation by load following operation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Secondary battery, 2 ... Synchronous generator, 3 ... Electric double layer capacitor, 4 ... Control system (high-speed calculation), 5 ... Load, 6 ... LAN, 7 ..Control system (low speed calculation) 11, 21, 31, 51 ... measuring instrument 12, 22, 32, 52 ... A / D converter, 13, 41 ... D / A converter

Claims (2)

A control method for a distributed power source that integrally controls a plurality of distributed power sources having different follow-up performance to load fluctuations,
Among the plurality of types of distributed power supplies, by compensating the output fluctuation and the integrated value of the output fluctuation of the distributed power supply that generates the base, voltage and frequency during the self-sustained operation with the distributed power supply having the highest load following performance, A control method for a distributed power source, characterized by performing a self-sustained operation control that maintains a stable frequency without detecting the frequency.   Compensation of the output fluctuation by the distributed power source having the highest load following performance has a load following performance according to the distributed power source having the highest load following performance and has a capacity higher than that of the distributed power source having the highest load following performance. The distributed power supply control method according to claim 1, wherein the distributed power supply is gradually assigned to a large distributed power supply.

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