JP6368456B2 - Power fluctuation component output suppression device - Google Patents

Description

  The present invention relates to a power fluctuation component output suppression device capable of suppressing the output power of a distributed power source from causing or increasing power fluctuation of a power system.

  The Western Japan power system (60 Hz system) is a skewered system that exceeds 1000 km from east to west by connecting the power systems of each power company with a 500 kV transmission line. It is known that in a skew-shaped system, weakly-damping long-period power fluctuations (period 2 to 5 seconds) are generated in the entire power system due to its structure. Hereinafter, the long-period power fluctuation is simply referred to as “power fluctuation”. In addition, the instability of power fluctuations may increase due to heavy power flow and the liberalization of power due to power trading. A system monitoring method has been developed for accurately grasping the state of the power fluctuation and performing operation and control of the power system (see Non-Patent Document 1).

  In recent years, research using natural energy has progressed. Since the electric power generated by the solar cell is DC power, when it is supplied to the power system, it is necessary to convert it into AC power by an inverter circuit. A grid-connected inverter system has been developed as a system that converts DC power output from a DC power source into AC power by an inverter circuit and supplies the AC power to the power system (see, for example, Patent Document 1).

“Estimation of Inertial Center Frequency Based on Multipoint Synchronous Measurement Data”, Hashiguchi et al., Denki Theory B, Vol. 130, No. 1, 2010, pp. 106-113

JP2011-188665A

  Since the solar cell changes the output power depending on the solar radiation state, the output power of the inverter circuit also changes. This output change may increase the power fluctuation of the power system. In addition, when a large number of grid-connected inverter systems are connected to the power system, power fluctuations may be caused by these output changes. Further, not only the grid-connected inverter system but also the output power from the distributed power source, which is a small-scale power source that is distributed, may increase the power fluctuation of the power system or cause the power fluctuation.

  The present invention has been conceived under the circumstances described above, and is a power fluctuation component output suppression device capable of suppressing the output power of a distributed power source from causing or increasing the power fluctuation of a power system. Its purpose is to provide.

  In order to solve the above problems, the present invention takes the following technical means.

The power fluctuation component output suppression device provided by the first aspect of the present invention is connected to a connection line between a distributed power source and a power system, and the power system outputs power from the distributed power source to the power system. and removing only components of frequencies inherent power upset.

In a preferred embodiment of the present invention, there is provided DC power storage means for storing DC power, an inverter circuit for converting DC power and AC power, and a control circuit for controlling the inverter circuit by a PWM signal. The control circuit outputs a PWM signal for controlling the power fluctuation frequency component of the power downstream of the connection point with the connection line to zero.

In a preferred embodiment of the present invention, the control circuit calculates the power from a voltage and current detected downstream of the connection point, and outputs power as a power signal; and A power control means for generating a power compensation signal for controlling the frequency component of the power fluctuation to zero, and a current compensation signal for controlling the output current of the inverter circuit with the power compensation signal as a current target Current control means for generating and PWM signal generation means for generating the PWM signal based on the current compensation signal.

In a preferred embodiment of the present invention, the power control means performs signal processing by a transfer function designed using a frequency weight W (s), and the frequency weight W (s) is a frequency of the power fluctuation. _Is f _SW and the gain is k,
W (s) = k · s / {s ² + (2π · f _SW ) ² }
It is.

  In a preferred embodiment of the present invention, the inverter circuit outputs three-phase alternating current power, and the current control means is for a three-phase current signal respectively detecting the three-phase output current of the inverter circuit. Conversion means for performing three-phase / two-phase conversion and rotational coordinate conversion to convert two axis component signals, and two for controlling the deviation signal between the two axis component signals and the respective target signals to zero Two-phase control means for generating a signal, and inverse conversion means for performing a stationary coordinate transformation and a two-phase / three-phase transformation on the two signals to convert them into the three-phase current compensation signal. The power compensation signal is set as one target signal of the two axis component signals.

In a preferred embodiment of the present invention, the frequency of the power fluctuation is input from the outside.

In a preferred embodiment of the present invention, frequency detection means for detecting a system frequency of the power system and a system frequency signal continuously detecting the system frequency are input, and components other than a predetermined frequency band are attenuated. Predetermined band pass means for outputting, FFT processing means for calculating an output level for each frequency of the signal output from the predetermined band pass means, and predetermined frequency detection means for detecting a frequency at which the output level is equal to or higher than a threshold value. And the frequency detected by the predetermined frequency detecting means is used as the frequency of the power fluctuation .

The present invention, distributed power from the power output to the power system, to remove components of the frequency of the specific power oscillations in the power system. Therefore, it is possible to suppress the output of the power fluctuation frequency component to the power system. Thereby, it is possible to suppress the output power of the distributed power source from causing or increasing the power fluctuation of the power system.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

It is a figure for demonstrating the electric power fluctuation component output suppression apparatus which concerns on 1st Embodiment. It is a functional block diagram for demonstrating the internal structure of the control circuit which concerns on 1st Embodiment. It is a figure for demonstrating the design of the control system of the inverter circuit which concerns on 1st Embodiment. 4 is a Bode diagram showing characteristics of a controller K. FIG. It is a functional block diagram for demonstrating the internal structure of the current control part which concerns on 1st Embodiment. It is a figure for demonstrating the model for simulation. It is a figure which shows a simulation result (when the power fluctuation component output suppression device is not provided). It is a figure which shows a simulation result (when the electric power fluctuation component output suppression apparatus is provided). It is a functional block diagram for demonstrating the internal structure of the control circuit which concerns on 2nd Embodiment. It is a figure for demonstrating the high capacity | capacitance system which concerns on 3rd Embodiment. It is a functional block diagram for demonstrating the internal structure of the control circuit which concerns on 4th Embodiment.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings, taking as an example the case where the power fluctuation component output suppression device according to the present invention is connected to a distribution line connecting a distributed power source and a power system. To do.

  FIG. 1 is a diagram for explaining the power fluctuation component output suppressing device according to the first embodiment.

  In the same figure, the electric power fluctuation component output suppression apparatus A has shown the state connected to the distribution line D which connects the distributed power supply C and the electric power grid | system B by the connection point a. The distributed power source C is a grid-connected inverter system including a DC power source such as a solar battery. The distributed power source C converts DC power generated by the DC power source into AC power and supplies it to a load (not shown). AC power is also supplied from the power system B to the load. The distributed power source C is a system with a reverse power flow and outputs AC power to the power system B. The power fluctuation component output suppression device A absorbs the frequency component of the power fluctuation of AC power output from the distributed power source C to the power system B. The distributed power source C only needs to generate electric power, and may be a diesel engine generator or the like. Further, the distributed power source C may be connected to the power system B by a transmission line.

  The power fluctuation component output suppression device A detects the active power on the power system B side (hereinafter referred to as “downstream side”) from the connection point a of the distribution line D, and the frequency of the detected power fluctuation of the active power. Feedback control is performed so that the component becomes “0”. As shown in the figure, the power fluctuation component output suppression device A includes a storage battery 1, an inverter circuit 2, a control circuit 3, a current sensor 4, a voltage sensor 5, and a current sensor 6. In this embodiment, the case where the power system B and the distributed power source C are three-phase and the power fluctuation component output suppression device A is also three-phase is described. Hereinafter, the three phases are referred to as a U phase, a V phase, and a W phase.

  The storage battery 1 stores DC power. The storage battery 1 outputs DC power to the inverter circuit 2 or DC power converted by the inverter circuit 2 from AC power is input. A capacitor may be used instead of the storage battery 1.

  The inverter circuit 2 performs conversion between DC power and AC power. The inverter circuit 2 converts DC power input from the storage battery 1 into AC power and outputs it to the distribution line D, or converts AC power input from the distribution line D into DC power and outputs it to the storage battery 1. The inverter circuit 2 includes a PWM control inverter and a filter (not shown). The PWM control inverter is a three-phase inverter provided with three sets of six switching elements (not shown). By switching on and off each switching element based on the PWM signal input from the control circuit 3, the DC power And AC power conversion. The filter removes high frequency components due to switching.

The current sensor 4 is disposed on the downstream side of the connection point a of the distribution line D, and detects an instantaneous value of a three-phase current flowing through the distribution line D. The current sensor 4 converts the detected instantaneous value into a digital signal and controls it as current signals i _1u , i _1v , i _1w (the three current signals may be collectively described as “current signal i ₁ ”). 3 is output. The voltage sensor 5 is disposed on the downstream side of the connection point a of the distribution line D, and detects the instantaneous values of the three-phase voltages of the distribution line D, respectively. The voltage sensor 5 converts the detected instantaneous value into a digital signal and outputs it as a voltage signal v _u , v _v , v _w (the three voltage signals may be collectively described as “voltage signal v”). Output to. The current sensor 6 is disposed between the inverter circuit 2 and the connection point a, and detects the instantaneous value of the three-phase output current of the inverter circuit 2. The current sensor 6 converts the detected instantaneous value into a digital signal and controls it as current signals i _2u , i _2v , i _2w (the three current signals may be collectively described as “current signal i ₂ ”). 3 is output.

The control circuit 3 controls the inverter circuit 2 and is realized by, for example, a microcomputer. The control circuit 3 generates a PWM signal based on the current signal i ₁ input from the current sensor 4, the voltage signal v input from the voltage sensor 5, and the current signal i ₂ input from the current sensor 6. To the inverter circuit 2.

  FIG. 2 is a functional block diagram for explaining the internal configuration of the control circuit 3.

  The control circuit 3 includes an active power calculator 31, an active power controller 32, a current controller 33, and a PWM signal generator 34.

The active power calculation unit 31 calculates the active power downstream of the connection point a (see FIG. 1) of the distribution line D. The active power calculation unit 31 continuously calculates active power based on the current signal i ₁ input from the current sensor 4 and the voltage signal v input from the voltage sensor 5, and outputs it as an active power signal. Instead of providing the active power calculation unit 31, an active power detection device that detects active power may be provided on the downstream side of the connection point “a” of the distribution line D and input to the control circuit 3.

The active power control unit 32 is for controlling active power downstream of the connection point a of the distribution line D. The active power control unit 32 generates an active power compensation signal for making the component of the power fluctuation frequency f _SW of the active power signal output from the active power calculation unit 31 zero, and outputs the active power compensation signal to the current control unit 33.

  FIG. 3 is a diagram for explaining the design of the control system of the inverter circuit 2.

The target values of the active power P and the reactive power Q output from the inverter circuit 2 are P ^* and Q ^* , respectively. The d-axis component and the q-axis component of the output current of the inverter circuit 2 are Id and Iq (the target value is Id ^* and Iq ^* ), and assuming that the d-axis component and the q-axis component of the output voltage of the inverter circuit 2 are Vd and Vq, the control system of the inverter circuit 2 can be expressed as shown in FIG. The d-axis component and the q-axis component are two-phase components of the rotating coordinate system after being converted by a three-phase / two-phase converting process and a rotating coordinate converting process described later. Further, assuming that the output voltage of the inverter circuit 2 completely follows the system voltage, Vq = 0.
P = Vd · Id + Vq · Iq = Vd · Id
Q = Vd · Iq−Vq · Id = Vd · Iq
It has become.

  Since the power oscillation period is several seconds, the current minor loop is on the order of milliseconds, so the dynamics of the current minor loop and the inverter main circuit can be ignored. Also, the reactive power control system can be ignored. Therefore, FIG. 3A can be considered as shown in FIG.

  The power fluctuation component output suppression device A outputs the active power P2 with respect to the active power P1 output from the distributed power source C, thereby reducing the power fluctuation of the active power P3 (= P1 + P2) downstream of the connection point a. The frequency component is removed. Therefore, it is only necessary to detect P3 and adjust P2 so that the frequency component of the power fluctuation becomes “0”, which is considered as shown in FIG.

In FIG. 3C, when the active power control system controller is K and Vd is the control object G, the transfer function S from P1 to P3 is
S = 1 / (1 + GK)
It is. Since removal of a specific frequency component is considered, it is understood that a controller based on the internal model principle may be designed as the controller K. Therefore, the controller K may be designed using the frequency weight W (s) shown in the following equation (1). ω ₀ is the central angular frequency of the component to be controlled, and k is the gain.
W (s) = k · s / (s ² + ω ₀ ² ) (1)

  FIG. 4 is a Bode diagram showing the characteristics of the controller K with W (s) shown in the above equation (1) as a transfer function.

This figure shows the case where the center angular frequency ω ₀ = 2π [rad / sec] and the gain k is “0.1”, “1”, “10”. The amplitude characteristic shown in the figure has a peak at the central angular frequency ω ₀ , and the amplitude characteristic increases as the gain k increases. In addition, the phase characteristic shown in the figure becomes 0 degree at the central angular frequency ω ₀ . That is, the transfer function W (s) amplifies and passes the signal having the central angular frequency ω ₀ without changing the phase.

In the present embodiment, the transfer function of the active power control unit 32 is W (s) shown in the above equation (1). The gain k is appropriately determined based on actual machine verification based on the stability of the control system. For the center angular frequency ω ₀ , “2πf _SW ” is set using the frequency f _{SW of} power fluctuation. In the present embodiment, the frequency f _SW is received from the electric power company that manages the power system B. If the power fluctuation frequency f _SW is known in advance, it may be set in advance. In this case, the active power control unit 32 may be an adaptive filter so as to cope with a change in the frequency f _SW . Note that the transfer function of the active power control unit 32 is not limited to the case of W (s) in the above equation (1), and may be a transfer function designed using W (s) as a frequency weight. Further, the active power control unit 32 may be configured by connecting controllers corresponding to the respective frequencies f _SW in parallel so that the case where there are a plurality of power fluctuation frequencies f _SW can be dealt with.

Returning to FIG. 2, the current control unit 33 is for controlling the output current of the inverter circuit 2. The current control unit 33 generates a compensation signal based on the current signal i ₂ input from the current sensor 6 and outputs the compensation signal to the PWM signal generation unit 34.

  FIG. 5 is a functional block diagram for explaining the internal configuration of the current control unit 33.

  The current controller 33 includes a three-phase / two-phase converter 33a, a rotation coordinate converter 33b, an LPF 33c, an LPF 33d, a PI controller 33e, a PI controller 33f, a stationary coordinate converter 33g, and a two-phase / three-phase converter. 33h.

The three-phase / two-phase conversion unit 33a performs a so-called three-phase / two-phase conversion process (αβ conversion process). The three-phase / two-phase conversion process is a process that converts a three-phase AC signal into an equivalent two-phase AC signal. The three-phase AC signal is a stationary orthogonal coordinate system (hereinafter referred to as “static coordinate system”). In this case, the signals are decomposed into orthogonal α-axis and β-axis components and the components of the respective axes are added to each other, thereby converting into an AC signal of the α-axis component and an AC signal of the β-axis component. The three-phase / two-phase converter 33a converts the three-phase current signals i _2u , i _2v , i _2w input from the current sensor 6 into an α-axis current signal iα and a β-axis current signal iβ, and rotates coordinates. It outputs to the conversion part 33b.

The conversion process performed in the three-phase / two-phase conversion unit 33a is represented by a determinant represented by the following equation (2).

The rotation coordinate conversion unit 33b performs a so-called rotation coordinate conversion process (dq conversion process). The rotation coordinate conversion process is a process of converting a two-phase signal in the stationary coordinate system into a two-phase signal in the rotation coordinate system. The rotating coordinate system is an orthogonal coordinate system having orthogonal d-axis and q-axis and rotating in the same rotational direction at the same angular velocity as the fundamental wave of the system voltage of the power system B. The rotation coordinate conversion unit 33b converts the α-axis current signal iα and β-axis current signal iβ of the stationary coordinate system input from the three-phase / two-phase conversion unit 33a into the rotation coordinates based on the phase θ of the fundamental wave of the system voltage. System d-axis current signal i _d and q-axis current signal i _q are converted and output.

The conversion process performed by the rotation coordinate conversion unit 33b is represented by a determinant represented by the following expression (3).

LPF33c and LPF33d is a low-pass filter, to pass only the DC component of the d-axis current signal i _d and the q-axis current signal i _q, respectively. By rotating the coordinate transformation process, the fundamental wave component of the α-axis current signal iα and β-axis current signal iβ has been converted into a DC component of the d-axis current signal i _d and the q-axis current signal i _q, respectively. That is, the LPF 33c and the LPF 33d remove the unbalanced component and the harmonic component and pass only the fundamental wave component.

The PI control unit 33e performs PI control (proportional integration control) based on the deviation between the DC component of the d-axis current signal i _d and the target signal, and outputs a compensation signal x _d . The active power compensation signal input from the active power control unit 32 is used as the target signal i _d ^* of the d-axis current signal i _d . The PI control unit 33f performs PI control based on the deviation between the DC component of the q-axis current signal i _q and the target signal i _q ^*, and outputs a compensation signal x _q .

The stationary coordinate conversion unit 33g converts the compensation signals x _d and x _q respectively input from the PI control unit 33e and the PI control unit 33f into the compensation signals xα and xβ of the stationary coordinate system, and the rotational coordinate conversion unit This is the reverse of the conversion process of 33b. The stationary coordinate conversion unit 33g performs a so-called stationary coordinate conversion process (inverse dq conversion process). The compensation signal x _d , x _q of the rotating coordinate system is converted into a compensation signal x α of the stationary coordinate system based on the phase θ. , convert to xβ.

The conversion process performed by the stationary coordinate conversion unit 33g is represented by a determinant represented by the following expression (4).

The two-phase / three-phase converter 33h converts the compensation signals xα, xβ input from the stationary coordinate converter 33g into three-phase compensation signals x _u , x _v , x _w . The two-phase / three-phase conversion unit 33h performs a so-called two-phase / three-phase conversion process (reverse αβ conversion process), and performs a reverse conversion process to the three-phase / two-phase conversion unit 33a.

The conversion process performed by the two-phase / three-phase conversion unit 33h is represented by a determinant represented by the following equation (5).

Returning to FIG. 2, the PWM signal generation unit 34 generates a PWM signal. The PWM signal generator 34 is a command signal for commanding the waveform of the output voltage of each phase of the inverter circuit 2 based on the three-phase compensation signals x _u , x _v , x _w input from the current controller 33. And a PWM signal is generated by a triangular wave comparison method based on the command signal and the carrier signal. For example, a pulse signal that is high when the command signal is larger than the carrier signal and low when the command signal is equal to or less than the carrier signal is generated as a PWM signal. The generated PWM signal is output to the inverter circuit 2. Note that the PWM signal generation unit 34 is not limited to the case where the PWM signal is generated by the triangular wave comparison method, and the PWM signal may be generated by a hysteresis method, for example.

  In the present embodiment, the case where the control circuit 3 is realized as a digital circuit has been described, but it may be realized as an analog circuit. Further, the processing performed by each unit may be designed by a program, and the computer may function as the control circuit 3 by executing the program. The program may be recorded on a recording medium and read by a computer.

In the present embodiment, the active power control unit 32 generates and outputs an active power compensation signal for making the component of the power fluctuation frequency f _SW of the active power signal output from the active power calculation unit 31 zero. The current control unit 33, the active power compensation signal output from the active power control unit 32 as a target signal of the d-axis current signal i _d, generates and outputs a compensation signal for controlling the output current. The PWM signal generation unit 34 generates a PWM signal based on the compensation signals x _u , x _v , and x _w generated by the current control unit 33 and outputs the PWM signal to the inverter circuit 2. The inverter circuit 2 performs power conversion based on the PWM signal. That is, the control circuit 3 performs control to make the component of the power fluctuation frequency f _SW of the active power downstream of the connection point a of the distribution line D (see FIG. 1) zero. Therefore, also include components of power fluctuation of the frequency f _SW output power of the distributed power supply C, the component of the frequency f _SW of the power input to the power system B is suppressed. Thereby, the power oscillation component output suppression device A can suppress the output power of the distributed power source C from causing or increasing the power oscillation of the power system B.

  A simulation for confirming that power fluctuation is generated by the frequency component of the power fluctuation output from the distributed power source C and that the power fluctuation component output suppression device A suppresses this power fluctuation will be described below.

FIG. 6A is a diagram showing a model obtained by adding a model indicating the distributed power source C to the one-machine infinite bus model. The one-machine infinite bus model is a model in which one generator E is connected to a large power system (infinite bus F) via a transmission line. A model indicating the distributed power source C is connected to the power transmission line. Using the model shown in FIG. 6A, a simulation was performed to see how the rotational speed of the generator E changes when the active power P1 output from the distributed power source C changes greatly in a stepped manner. . The rated capacity of the generator E is 60 [MVA], the rated output is 50 [MW], the system frequency is 60 [Hz], and the system voltage is 33 [kV _rms ].

  FIG. 7A shows the amount of change in active power P1 output from the distributed power source C from the steady state (hereinafter referred to as “active power output change amount”) ΔP and the reactive power from the steady state. A change amount (hereinafter referred to as “reactive power output change amount”) ΔQ is shown. Since the reactive power of the distributed power source C is controlled to “0”, the active power output change amount ΔP indicates the output fluctuation. When the time Time is 1 [s], the effective power P1 is increased by 2 [MW], so that the effective power output change ΔP is changed from 0 [MW] to 2 [MW] as shown in FIG. ] Is greatly changed stepwise.

  FIG. 7B shows a change in the rotational speed of the generator E, and the difference between the rotational speed and the reference is based on the rotational speed corresponding to the reference frequency (for example, 60 [Hz]) of the power system. Is expressed as a percentage of the reference. As shown in FIG. 7B, the rotational speed of the generator E has changed since the time Time is 1 [s]. This fluctuation was due to power fluctuation, and the frequency of fluctuation (frequency of power fluctuation) was about 0.918 [Hz] (period about 1.09 [s]). That is, when the output of the distributed power source C changes in a step shape, the frequency component of the power oscillation is output and the power oscillation occurs, which appears as a fluctuation in the rotational speed of the generator E.

  Next, it will be described that power oscillation is suppressed by the power oscillation component output suppression device A.

FIG. 6B is a diagram illustrating a model obtained by adding a model indicating the power fluctuation component output suppression device A to the model illustrated in FIG. A model indicating the power fluctuation component output suppression device A is connected to a connection point a of the distribution line that connects the distributed power source C and the transmission line of the one-machine infinite bus model. A simulation similar to that performed on the model shown in FIG. 6A was performed using the model shown in FIG. The power fluctuation component output suppression device A is set with the frequency f _SW (= 0.918 [Hz]) of the power fluctuation detected in the simulation shown in FIG. Other conditions are common to the model shown in FIG.

  FIG. 8A shows the active power output change amount ΔP and the reactive power output change amount ΔQ of the distributed power source C, as in FIG. 7A. When the time Time is 1 [s], by increasing the active power P1 by 2 [MW], the effective power output change ΔP is changed from 0 [MW] to 2 [MW] as shown in FIG. ] Is greatly changed stepwise.

FIG. 8B shows the active power output change amount ΔP of the active power P2 output from the power fluctuation component output suppression device A and the reactive power output change amount ΔQ of the reactive power. FIG. 8C shows the active power output change amount ΔP of the active power P3 (= P1 + P2) downstream of the connection point a and the reactive power output change amount ΔQ of the output reactive power. The power fluctuation component output suppression device A outputs the active power P2 so that the component of the power fluctuation frequency f _SW of the active power P3 becomes “0”.

FIG. 8D shows a change in the rotational speed of the generator E, as in FIG. As shown in FIG. 8D, the fluctuation of the rotational speed that occurred when the time Time is 1 [s] is immediately settled. That is, by providing the power fluctuation component output suppression device A and controlling the frequency f _SW component of the active power P3 to “0”, the power fluctuation is suppressed.

  As described above, it was confirmed that the use of the power fluctuation component output suppression device A can suppress the occurrence of power fluctuation.

In addition, in the said 1st Embodiment, although the case where the power fluctuation component of active power was suppressed was demonstrated, it is not restricted to this. The q-axis side of the current control unit 33 may have the same configuration so as to suppress the power fluctuation component of the reactive power. That is, reactive power is calculated based on the current signal i ₁ and the voltage signal v, a reactive power compensation signal for controlling the reactive power is generated, and the target signal i _q ^* of the q-axis current signal i _q is generated. It may be used. Further, the active power calculation unit 31 may calculate the apparent power instead of the active power and output it to the active power control unit 32.

In the first embodiment, the control is performed after the current control unit 33 performs the three-phase / two-phase conversion of the current signal i ₂ and the rotational coordinate conversion, but is not limited thereto. For example, the α-axis current signal iα and the β-axis current signal iβ output from the three-phase / two-phase conversion unit 33a may be controlled. In this case, the target signal i _d ^* and the target signal i _q ^* may be converted into stationary coordinates and used as the target signal. Further, the three-phase current signal i ₂ may be directly controlled. In this case, the target signal i _d ^* and the target signal i _q ^* may be subjected to stationary coordinate conversion, two-phase / three-phase conversion, and used as the target signal.

In the first embodiment, the case where the frequency f _{SW of} power fluctuation is given from the outside has been described, but the present invention is not limited to this. For example, the frequency f _SW may be detected and used. A case where the frequency f _SW is detected and set will be described below as a second embodiment.

  FIG. 9 is a functional block diagram for explaining the internal configuration of the control circuit according to the second embodiment. In the figure, the same or similar elements as those of the control circuit 3 (see FIG. 2) according to the first embodiment are denoted by the same reference numerals. As shown in FIG. 9, the control circuit 3 ′ is different from the control circuit 3 according to the first embodiment in that it includes a power fluctuation frequency detection unit 35.

The power oscillation frequency detection unit 35 detects the power oscillation frequency f _SW from the system frequency of the power system B and sets it in the active power control unit 32. The power fluctuation frequency detection unit 35 includes a frequency detection unit 35a, a bandpass filter 35b, an FFT processing unit 35c, and a comparison unit 35d.

  The frequency detector 35a detects the system frequency of the power system B. The frequency detector 35 a detects the frequency of the voltage signal v input from the voltage sensor 5. The voltage signal v is obtained by detecting the voltage on the downstream side of the connection point a of the distribution line D, that is, the system voltage of the power system B. Therefore, the system frequency of the power system B can be detected by detecting the frequency of the voltage signal v. The frequency detector 35a continuously detects the system frequency and outputs it as a frequency signal f to the band-pass filter 35b.

  The band pass filter 35b extracts a component in a predetermined frequency band (0.2 [Hz] to 1 [Hz]). The band pass filter 35b passes a predetermined frequency band component of the frequency signal f input from the frequency detector 35a as it is, attenuates other frequency components, and outputs the attenuated frequency component to the FFT processor 35c. It is known that the frequency of power fluctuation is 0.2 [Hz] to 1 [Hz], and the frequency of power fluctuation accompanying changes in power demand is known to be included in 0.2 [Hz] or less. ing. The band-pass filter 35b removes the frequency component of fluctuation due to power demand and extracts only the frequency component of power fluctuation.

  The FFT processing unit 35c performs a fast Fourier transformation process. The FFT processing unit 35c performs a fast Fourier transform process on the signal input from the bandpass filter 35b (extracting a frequency component of a predetermined frequency band from the frequency signal f), and calculates an output level for each frequency. To the comparison unit 35d.

The comparison unit 35d compares the output level of each frequency input from the FFT processing unit 35c with a threshold value. The comparison unit 35d outputs the frequency at which the output level is equal to or higher than the threshold to the active power control unit 32 as the power fluctuation frequency _fSW .

The configuration of the power fluctuation frequency detection unit 35 is not limited to this. For example, a fast Fourier transform process may be performed on the frequency signal f output from the frequency detection unit 35a, and only the output level of a frequency in a predetermined frequency band may be input to the comparison unit 35d. Further, the comparison unit 35d may detect the frequency having the maximum output level among the frequencies at which the output level is equal to or higher than the threshold as the frequency f _SW .

Also in the second embodiment, as in the first embodiment, the active power control unit 32 performs control to make the component of the power fluctuation frequency f _SW of the active power signal output from the active power calculation unit 31 zero. Therefore, also in 2nd Embodiment, there can exist an effect similar to 1st Embodiment.

The power fluctuation component output suppression device A may not detect the power fluctuation frequency f _SW , but a remote monitoring control device that monitors the distributed power source C may detect the frequency f _SW . A case where the remote monitoring control device detects the frequency f _SW and transmits it to the power fluctuation component output suppression device A will be described below as a third embodiment.

  FIG. 10 is a diagram for explaining a large-capacity system according to the third embodiment.

The large-capacity system G includes a plurality of distributed power sources C connected in parallel, a remote monitoring control device H that remotely monitors each distributed power source C, and a power fluctuation component output suppression device A. The remote monitoring control device H monitors the power generation state of each distributed power source C and includes a power fluctuation frequency detection unit 35. The power oscillation frequency detection unit 35 is the same as the power oscillation frequency detection unit 35 (see FIG. 9) according to the second embodiment, and the power oscillation frequency f is based on the voltage signal v input from the voltage sensor 5. _SW is detected and transmitted to the power fluctuation component output suppression device A. The power fluctuation component output suppression device A sets the received frequency f _SW in the active power control unit 32 (see FIG. 2).

  In the third embodiment, the same effect as that of the first embodiment can be obtained.

  In the first to third embodiments, the case where the distributed power source C is a three-phase system has been described. However, a single-phase system may be used. The case of a single-phase system will be described below as a fourth embodiment.

  FIG. 11 is a functional block diagram for explaining an internal configuration of a control circuit according to the fourth embodiment. In the figure, the same or similar elements as those of the control circuit 3 (see FIG. 2) according to the first embodiment are denoted by the same reference numerals. The control circuit 3 ″ differs from the control circuit 3 according to the first embodiment in that the active power calculation unit 31 ′, the current control unit 33 ′, and the PWM signal generation unit 34 ′ use single-phase signals. However, the current sensor 4, the voltage sensor 5, and the current sensor 6 each detect a single-phase current (voltage) signal.

The active power calculation unit 31 ′ continuously calculates active power based on the current signal i ₁ input from the current sensor 4 and the voltage signal v input from the voltage sensor 5 and outputs it as an active power signal. .

The current control unit 33 ′ generates a compensation signal based on the current signal i ₂ input from the current sensor 6, and outputs the compensation signal to the PWM signal generation unit 34 ′. The current control unit 33 ′ uses the active power compensation signal input from the active power control unit 32 as the target signal i ₂ ^* of the current signal i ₂ . That is, the current control unit 33 ′ performs PI control (proportional integration control) by the PI control unit 33e based on the deviation between the current signal i ₂ and the target signal i ₂ ^*, and outputs the compensation signal x.

  The PWM signal generation unit 34 ′ generates a PWM signal based on the compensation signal x input from the current control unit 33 ′ and outputs the PWM signal to the inverter circuit 2.

  In the fourth embodiment, the same effect as that of the first embodiment can be obtained.

  The power fluctuation component output suppressing device according to the present invention is not limited to the above-described embodiment. The specific configuration of each part of the power fluctuation component output suppression device according to the present invention can be varied in design in various ways.

A Power fluctuation component output suppression device 1 Storage battery (DC power storage means)
2 Inverter circuit 3, 3 ', 3 "Control circuit 31, 31' Active power calculation unit (power calculation means)
32 Active power control unit (power control means)
33, 33 'Current control unit 33a Three-phase / two-phase conversion unit (conversion means)
33b Rotating coordinate converter (converter)
33c, 33d LPF
33e, 33f PI controller (two-phase control means)
33g Static coordinate conversion unit (inverse conversion means)
33h Two-phase / three-phase converter (inverse conversion means)
34, 34 'PWM signal generation unit 35 Power oscillation frequency detection unit 35a Frequency detection unit 35b Band pass filter (predetermined band pass means)
35c FFT processing unit 35d comparison unit (predetermined frequency detection means)
4 Current sensor 5 Voltage sensor B Power system C Distributed power supply D Distribution line E Generator F Infinite bus G Large capacity system H Remote monitoring and control device

Claims (6)

It is connected to a connection line between a distributed power source that is a grid-connected inverter system and a power system, and removes a frequency component of power fluctuation inherent to the power system from the power that the distributed power source outputs to the power system. A power fluctuation component output suppression device,
DC power storage means for storing DC power;
An inverter circuit for converting DC power and AC power between the DC power storage means and the connection line;
A control circuit for controlling the inverter circuit by a PWM signal ;
With
The control circuit includes:
Power calculating means for calculating power from an electrical signal detected on the downstream side of the connection point with the connection line, and outputting it as a power signal;
Power control means for generating a power compensation signal for controlling the frequency component of the power fluctuation of the power signal to zero;
With
Controlling the inverter circuit based on the power compensation signal;
A power fluctuation component output suppression device characterized by that. The control circuit includes:
Current control means for generating a current compensation signal for controlling the output current of the inverter circuit with the power compensation signal as a current target;
A PWM signal generating means for generating the PWM signal based on the current compensation signal,
Further comprising
Controlling the inverter circuit by the PWM signal;
The power fluctuation component output suppression device according to claim 1. The power control means performs signal processing by a transfer function designed using the frequency weight W (s),
The frequency weight W (s) is, when the frequency of the power fluctuation is f _SW and the gain is k,
W (s) = k · s / {s ² + (2π · f _SW ) ² }
Is,
The power fluctuation component output suppression device according to claim 2. The inverter circuit outputs three-phase AC power,
The current control means includes
Conversion means for performing three-phase / two-phase conversion and rotational coordinate conversion on the three-phase current signals respectively detecting the three-phase output currents of the inverter circuit, and converting them into two axis component signals;
Two-phase control means for generating two signals for controlling the deviation signal between the two axis component signals and the respective target signals to zero;
Inverse conversion means for performing static coordinate conversion and two-phase / three-phase conversion on the two signals to convert the two signals into the three-phase current compensation signal;
With
The power compensation signal is set as one target signal of the two axis component signals.
The power fluctuation component output suppression device according to claim 2 or 3.   The power oscillation component output suppression device according to any one of claims 1 to 4, wherein the frequency of the power oscillation is input from the outside. A frequency detection means for detecting a system frequency of the power system;
A system band signal that continuously detects the system frequency is input, a predetermined band passing means that attenuates and outputs a component other than the predetermined frequency band, and
FFT processing means for calculating an output level for each frequency of the signal output from the predetermined band passing means;
Predetermined frequency detecting means for detecting a frequency at which the output level is equal to or higher than a threshold;
Further comprising
Using the frequency detected by the predetermined frequency detection means as the frequency of the power fluctuation,
The power oscillation component output suppression apparatus in any one of Claims 1 thru | or 4.