JP2010071159A - Device for smoothing electric power generated by wind power generation using wind mill and storage battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for smoothing electric power generated by wind power generation using a wind mill and a storage battery, suppressing variation in output power supplied to a system by the lower-capacity storage battery, in a wind power generation system provided with the wind mill and storage battery. <P>SOLUTION: In a wind power generation device including a wind power generator 1 controlling a pitch angle, the storage battery 4, an output terminal 2, and a control device, with respect to wind speed fluctuation, the pitch angle of the wind power generator 1 is controlled so that a variation in electricity caused by low-frequency fluctuation of not more than an optional frequency is suppressed, and the pitch angle of the wind power generator 1 and the charging/discharging of the storage battery 4 are controlled so that generated power supplied to the output terminal 2 and the remaining amount of energy of the storage battery become constant by compensating high-frequency fluctuation of not less than the optional frequency only by the charging/discharging of the storage battery 4. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wind power generation smoothing device that smoothes system output power of a wind power generation system, and in particular, wind power generation by a wind turbine and a storage battery that uses a wind turbine and a storage battery in a coordinated manner to smooth the power output to the system. The present invention relates to a power smoothing device.

In recent years, from the viewpoint of global warming prevention and depletion of fossil fuel resources, a large number of natural energy power generation facilities using wind energy and solar energy have been connected to the power system.
Wind power generation is being actively built around the world as a power generation system that uses wind energy, which is non-depleting clean energy. In addition, it is considered to deploy a wind power generation system as a distributed power source in a microgrid, which is a small-scale power distribution network that supplies power to a remote island or a limited area.

However, since natural energy fluctuates irregularly, when a natural energy power generation facility is introduced into a power system, the power system frequency and the system voltage will fluctuate. In particular, the wind energy is irregular, and the output power of the wind power generator fluctuates greatly in proportion to the third power of the wind speed, so that the system frequency is likely to be disturbed. When installed in a microgrid, the scale of the power system is small, so the effect on the system becomes more prominent.
Since there is a demand from the consumer to maintain the power quality, the power system in which the wind power generation facility is introduced needs to maintain the system frequency and system voltage constant.

  In order to compensate for fluctuations in the amount of power generated due to fluctuations in wind power, a method has been devised that suppresses fluctuations in system output by inserting a storage battery into a wind power generation system. In recent years, storage battery systems using NaS batteries and the like have attracted attention. By installing the storage battery system in the wind power generation facility, it is possible to smooth the power fluctuation that does not adversely affect the power system and increase the interconnection capacity to the system. In addition, since the energy density of the storage battery is increasing, it is easy to install it in the wind power generation facility if the restriction on the installation area is reduced. However, the installation cost increases due to the addition of the storage battery, and the maintenance cost is also required due to the deterioration of the performance of the storage battery.

For example, Patent Literature 1 discloses a wind power generation system that suppresses output fluctuations to the system by using a wind power generator equipped with a laser-type anemometer and a storage battery in combination.
The invention disclosed in Patent Document 1 observes the wind before reaching the windmill with a laser-type anemometer and optimizes the power generation amount of the windmill by predicting and controlling the pitch angle of the windmill accordingly. The amount of power supplied to the system is leveled by controlling the charge / discharge amount of the storage battery according to the amount of power generated.

  However, in the conventional windmill / storage battery cooperation system including the technology described in Patent Document 1, a large-capacity storage battery is required to continuously supply power even when wind power decreases. Storage batteries are repeatedly charged and discharged frequently, resulting in reduced storage efficiency and longevity.Large-capacity storage batteries are not only expensive to introduce, but are also expensive to maintain. There is a need for a wind power generation system that can do this.

JP 2004-301116 A

  Therefore, the problem to be solved by the present invention is to smooth the wind power generated by a wind turbine and a storage battery that can suppress fluctuations in output power supplied to the system with a small capacity storage battery in the wind power generation system including the wind turbine and the storage battery. It is to provide a device.

  In order to solve the above problems, a wind power generation smoothing device using a windmill and a storage battery according to the present invention includes a wind generator capable of pitch angle control, a storage battery, an output terminal, and a control device, and has a predetermined frequency against wind speed fluctuations. The pitch angle of the wind power generator is controlled so as to suppress the power generation fluctuation due to the following low frequency fluctuations, and the generated power supplied to the output terminal is compensated only by the charge / discharge operation of the storage battery for the high frequency fluctuations above the frequency. The pitch angle of the wind power generator and the charge / discharge operation of the storage battery are controlled so as to be constant. The device according to the present invention controls and suppresses generated power fluctuations caused by wind speed fluctuations in a low frequency range and a high frequency range.

  The wind power generation smoothing device of the present invention is used by connecting the output terminal to the power system. The generated power of the wind power generator fluctuates nonlinearly in proportion to the cube of the wind speed. However, in the wind power generation smoothing device of the present invention, the wind power fluctuation is controlled by the pitch angle control of the windmill blade and the charge / discharge operation of the storage battery. Are coordinated to smooth out fluctuations in the amount of power generation and supply stable power to the grid.

  By controlling the pitch angle of the windmill blade, the fluctuation of the power generation due to the low frequency component of the wind fluctuation is suppressed, and the fluctuation of the power generation is compensated by the charge / discharge operation of the storage battery without following the pitch angle for the high frequency component. . As a result, since the wind power generator does not operate with respect to a change in a high frequency range, a sharp and frequent control operation of the pitch angle becomes unnecessary, and mechanical stress applied to the wind turbine blade is reduced. Further, since the low frequency fluctuation is suppressed by the pitch angle control, the storage battery does not need to compensate for the low frequency fluctuation having a large fluctuation range, so that the kWh capacity of the storage battery can be reduced.

  If the wind energy generator pitch angle is controlled so that the remaining energy of the storage battery is added to the control input so that the remaining energy becomes constant, if the remaining energy of the storage battery is sufficient, the pitch angle is increased to suppress the power generation amount. By doing so, since overcharge can be suppressed, the power capacity of the storage battery can be further reduced.

  When the wind power generator smoothing device of the present invention calculates the pitch angle of the wind power generator and the operation amount of the charge / discharge operation of the storage battery by H∞ control, the followability and robustness to parameter fluctuations are improved, and the entire frequency band In addition, the operation amount of the pitch angle control and the charge / discharge operation can be minimized.

Hereinafter, the wind power generation smoothing apparatus by the windmill and storage battery of this invention is demonstrated in detail based on an Example using drawing.
FIG. 1 is a configuration diagram showing an outline of a wind power generation smoothing device of the present embodiment. A bidirectional inverter 3 and a storage battery 4 are inserted in parallel in the wiring of the output terminal 2 that connects the wind power generator 1 to the power system. Output terminal 2 for power system. Output power P _c synthesized from charge-discharge electric power P _b of generated power P _g and the storage battery 4 of the wind power generator 1 is output to the power grid. The bidirectional inverter 3 is controlled by the PWM method.

The wind power generator 1 includes a windmill blade capable of controlling the pitch angle and a rugged and inexpensive squirrel-cage induction generator. The pitch angle is controlled so that the generated power does not exceed the rated power, as shown in FIG. It shall be operated with the pitch angle control law. Also, the storage battery 4 when excess power generation amount P _g of the wind power generator 1 will absorb power by the charging operation, when the power generation amount P _g of the wind power generator 1 is insufficient to release the power by the discharge operation, The power _Pc supplied from the output terminal 2 to the system is smoothed.

The power generation amount of the wind power generator 1 is expressed by the following model.
When the wind speed Vw is given, the wind turbine output Pw that can be taken out from the wind turbine is given by the following equation.

(1) Pw (Vw, β, ωw) = Cp (λ, β) Vw3ρA / 2
Here, ρ is the air density, A is the rotational cross-sectional area of the windmill, and Cp is approximated by the pitch angle β and the blade tip speed ratio λ = Rω / Vw (R: the radius of the windmill, ω: the rotational angular speed of the windmill). Output coefficient. The angular velocity ω of the windmill is given by the dynamic characteristic equation of the windmill below, where J is the moment of inertia of the windmill.

(2) ω2 = ∫2 / J · (Pw−Pg) dt
A squirrel-cage induction generator is used as the wind power generator, and the generated power Pg when the slip s is given is given by the following equation.
(3) Pg = -3V2s (1 + s) R2 / {(R2-sR1) 2 + s2 (X1 + X2) 2}
Here, V: phase voltage, R1: stator resistance, R2: rotor resistance, X1: stator reactance, X2: rotor reactance.

The operation of the storage battery 4 is represented by the model shown in FIG. When the command charge / discharge power PB ^* is given from the control device, the operation delay of the storage battery 4 and the bidirectional inverter 3 is simulated by the transfer function 1 / (TBs + 1) of the primary delay of the time constant TB = 0.5 s. Discharge power PB is obtained. Further, the remaining amount of energy ξ of the storage battery 4 is calculated from the integration of the charge / discharge power PB. Since the discharging operation is positive and the charging operation is negative, the sign is reversed.

The wind power generation smoothing device of the present embodiment achieves both H∞ with smoothing of the output power _Pc to the system by pitch angle control and charge / discharge power control of the storage battery and constant control of the remaining energy ξ of the storage battery 4. Realized by control.

In the closed-loop system shown in FIG. 4, an H _∞ controller having the following equation (4) as a design specification is designed in an open-loop plant for P, K as a controller, and W1 and W2 as weight functions. . The purpose of the control is to minimize the sensitivity function S = (I + PK) −1 that compensates for disturbance suppression and tracking, and the complementary sensitivity function T = PKS that handles robustness against parameter variations in the model.

Here, γ is the boundary of the H∞ norm.

The sensitivity function S is related to the response (sensitivity) to the disturbance and the tracking characteristic, and T is related to the robust stability. Robust stability refers to the strength against uncertainty so that the stability of the system is not lost even when the simulation model is inaccurate or the set parameters fluctuate.
By making the sensitivity function S related to the tracking characteristic smaller in the low frequency range, the complementary sensitivity function T related to the robust stability is made smaller in the high frequency range where the influence of dynamics such as dead time becomes relatively large. The system can be stabilized over the belt.

Therefore, the frequency function W ₁ as the gain is increased in a low frequency band, the frequency function W ₂ as the gain increases in the high frequency band, the S significant penalty in the low frequency range, the T RF band The system is designed so that a large penalty is imposed, and control is performed so as to satisfy equation (4). Equation (4) represents the design specifications for these mixed sensitivity problems.
For a closed loop transfer function including a weighting function between the disturbance w and the control amount z, an H∞ controller for internal stabilization can be designed by using an LMI (linear matrix inequality) approach.

The wind power generator has a strong non-linearity depending on the parameters of the pitch angle β, the wind speed Vw, and the rotational angular speed ω, but uses the linearization model shown in FIG. 5 as having a linearity in the vicinity of the operating point. Pitch angle β, and the response from the wind speed Vw to the generated power P _g is approximated by a first-order lag system. The model shown in FIG. 5 has a large linearization error in a wide range other than the vicinity of the operating point. However, the linearization error is regarded as a parameter variation, and the weight function is selected and designed so as to maintain sufficient robust stability. Control performance is secured.

As shown in FIG. 6, the _H∞ controller of the wind power generation smoothing device of the present embodiment can be a centralized controller that controls the windmill and the storage battery with a single controller. The generated power Pg of the wind power generator, the remaining energy ξ of the storage battery, and the combined output power Pc are input to the controller to obtain the pitch angle command value βCMD and the charge / discharge power command value PB ^* of the storage battery. A prefilter is used so that the pitch angle is not operated in a high frequency band. Thereby, the sharing of the wind power generator and the storage battery in the frequency domain can be performed more smoothly.

7 is a singular value plot from the smoothing command value to the generated power fluctuation Pg, FIG. 8 is a singular value plot from the remaining battery energy command value (constant 50%) to the remaining energy ξ, and FIG. 9 is the combined output power. It is a singular value plot concerning. 7-9, the case where there is an H∞ controller is shown by a solid line, and the case where there is no controller is shown by a dotted line. When attention is paid to the dotted line graph in FIG. 7, it can be seen that the loop from the target pitch angle value to the fluctuation of the generated power has an integral characteristic at a low frequency component of 0.1 rad / s or less. From the dotted line graph of FIG. 8, the integration operation is performed in the loop from the remaining energy command value of the storage battery to the remaining energy amount. Further, from the dotted line graph in FIG. 9, a high gain is confirmed in the vicinity of 1 rad / s in the mixed output power loop.
From these results, in the design of the H∞ controller, the weight was selected so as to eliminate the integral characteristic and remove the high gain.

In this embodiment, the weight function obtained by the LMI approach using the control model is as follows.
(5) W11 = 0.0214 / (s2 + 0.0304s + 0.00294)
W12 = 0.16 / (s + 0.001)
W13 = 61.8312 / (s + 0.6183)
W21 = (0.0105s-0.0016) / (s + 97.5197)
W22 = (0.0193s−0.2041) / (s + 8390.5)
W23 = (0.0064s + 0.0365) / (s + 5646.2)

  10 and 11 are singular value plots of sensitivity function weights W11 to W13 and complementary sensitivity function weights W21 to W23, respectively. The sensitivity function was set so that the fluctuation of the low frequency component was suppressed on the wind power generator side, and the fluctuation of the high frequency component and the remaining energy of the storage battery were made constant in the storage battery. In the complementary sensitivity function, the gain is set high up to a high frequency region in order to obtain robustness.

The solid line graphs in FIGS. 7 to 9 are singular value plots when the H∞ controller using W11 to W23 in the equation (5) is applied.
FIG. 7 shows that the integration operation can be removed by applying the H∞ controller, and the characteristics are such that the fluctuation is suppressed by the low frequency component. In FIG. 8, it can be seen that the gain characteristic of the low frequency component is improved and the residual energy constant control is achieved. Moreover, it can be confirmed from FIG. 9 that the high gain in the low frequency region is removed and the high frequency component fluctuation is suppressed.
As shown in FIGS. 7 to 9, when no controller is used, the integral characteristic with a gain of 0 dB or more is shown in the low frequency region, whereas when the H∞ controller is used, the integral operation is removed over the entire region. It can be seen that the H∞ controller is effective for stabilization at low frequency components.

12-17 is a figure explaining the simulation result which compared the effect of the Hinfinity controller of the wind power generator smoothing apparatus of a present Example with the conventional method. In the figure, the solid line is the control result by the _H∞ controller used in this embodiment, and the broken line is the control result by the conventional method to be compared. FIG. 18 is a block diagram showing a conventional method used for comparison.
As shown in FIG. 18, the PI controller controls the wind power generator and the storage battery with separate controllers. The PI controller of the storage battery has a 2-input 1-output configuration in which the difference between the command values for ξ and Pc is calculated and the sum is input as the deviation e for controlling the remaining energy of the storage battery.

The control law of the wind power generator and storage battery controller is expressed by the following equation.
(6) u (t) = KPe (t) + KI∫0te (τ) dτ + KDde (t) / dt
Here, u: control amount, e: deviation, and KP, KI, and KD are proportional, integral, and differential gains, respectively. The parameters used are as shown in the PI control parameter table of FIG. PI controller parameters are tuned according to the limit sensitivity method. The differential gain was 0. In the conventional method, a pre-filter that deletes high frequency components is not applied.

The parameters of the wind turbine, induction generator, and selected operating point used in the simulation are as shown in the simulation parameter table of FIG.
FIG. 12 is a drawing showing changes in wind speed given to the wind power generator in this simulation. Note that the wind speed given in this simulation increases from 8 m / s selected as the operating point, and fluctuates around 10 m / s. Further, power generation, command value used for the smoothing of the combined output power is constant at 96.5kW operating point P _g0 generated power.

FIG. 13 is a graph showing the pitch angle variation obtained in this simulation. According to the _H∞ controller of the present embodiment, it can be seen that minute fluctuations are reduced as compared with the conventional PI controller. When the PI controller is used, minute fluctuations occur. However, if the proportional gain is set smaller than this in order to suppress the minute fluctuations, the generated power fluctuations increase. In the method of the present invention, since the pitch angle control for the fluctuation of the high frequency component is suppressed by the weighting function of the prefilter and the _H∞ control, the minute fluctuation is reduced. In addition, since the pitch angle is abrupt and frequent operation is not performed, mechanical stress applied to the wind turbine blade can be reduced.

FIG. 14 is a graph showing changes in generated power fluctuations. From FIG. 14, the generated power fluctuation of the wind power generator is larger when the _H∞ controller is used. This is because the pitch angle has low sensitivity to high-frequency fluctuations in wind speed. This generated power fluctuation does not cause a problem because it is not directly output to the power system.
15 to 17 are graphs showing transitions of the storage battery output, the remaining energy amount, and the combined output power. The output of the storage battery is output so as to suppress the generated power fluctuation. From FIG. 15 to FIG. 17, when the PI controller is used, the residual energy control is achieved, but the fluctuation of the combined output power is large, and the smoothing is not sufficiently achieved. On the other hand, in the _H∞ controller, it can be seen that the output from the storage battery smoothes the combined output power by compensating for fluctuations in the wind turbine generated power. Further, it can be confirmed that the control performance of the storage battery is improved and the combined output power is sufficiently smoothed.

  Thus, according to the wind power generation smoothing device of the present embodiment, the combined output power supplied to the system is smoothed by compensating for the power generation amount variation of the wind power generator due to the wind speed variation by the charge / discharge operation of the storage battery. At the same time, by reducing the sensitivity to the high-frequency component of the wind speed fluctuation, abrupt pitch angle control can be suppressed, and mechanical stress applied to the windmill blade can be reduced.

Moreover, in order to confirm the influence on storage battery capacity, the result of the simulation which gave another wind speed fluctuation | variation as a wind speed disturbance is shown in FIGS. 21-25 and FIGS. 26-30. In the figure, the dotted line indicates the result of the conventional storage battery control, and the solid line indicates the result of the harmonization control of the present invention.
21 to 25 show the second simulation result assuming the case where the wind speed swells, FIG. 21 shows the wind speed given as a disturbance, FIG. 22 shows the pitch angle of the windmill blade as the simulation result, and FIG. 23 shows the windmill power generation. FIG. 24 shows the output power of the storage battery, and FIG. 25 shows the remaining energy of the storage battery.
The wind speed pattern given to the windmill is set to descend from the operating point of 8 m / s and then rise. The control of the conventional method achieves smoothing with only the storage battery, and uses the transfer function Kpib on the storage battery side of the distributed PI controller shown in FIG. The command value used for smoothing the combined output power is calculated using an LPF (low-pass filter) having a time constant of 100 s for the maximum generated power obtained from the wind speed.

The simulation results show that when the wind speed drops from 8 m / s, the pitch angle is fixed at 10 degrees to generate the maximum power for both _H∞ control and the conventional method. The storage battery is discharged for smoothing. Therefore, the remaining amount of energy of the storage battery decreases monotonously.
On the other hand, when the wind speed increases and exceeds 8 m / s, the remaining energy increases by more than 50% in the conventional method, whereas in H _∞ control, the remaining energy is maintained at 50%. Then, the pitch angle control is performed to control the generated power, thereby suppressing an increase in the remaining amount of storage battery energy. Therefore, the capacity of the storage battery can be reduced.
Thus, according to the wind power generation smoothing device of the present embodiment, by controlling the pitch angle of the wind power generator according to the remaining amount of energy of the storage battery, the remaining energy of the storage battery is simultaneously smoothed with the combined output power. A constant amount control can be performed.

FIG. 26 to FIG. 30 show the change for 10 minutes as a result of the third simulation assuming the case where the wind speed shows a fluctuation in the upward trend. 26 shows the wind speed given as a disturbance, FIG. 27 shows the pitch angle of the windmill blade, FIG. 28 shows the wind turbine power generation, FIG. 29 shows the output power of the storage battery, and FIG. 30 shows the remaining energy of the storage battery.
From FIG. 27, it can be seen that the pitch angle operates when the wind speed exceeds the rated wind speed in the control of only the storage battery. By using the controller of the present invention, as shown in FIG. 28, the pitch angle is controlled so that the generated power follows the command value, and as shown in FIG. It is suppressed. As a result, as shown in FIG. 30, the residual energy amount is controlled to be constant. Thereby, it turns out that the capacity | capacitance reduction of a storage battery can be aimed at.

As described above, according to the wind power generation smoothing device using the windmill and the storage battery of the present embodiment, the pitch angle of the windmill and the charge / discharge operation of the storage battery are cooperatively controlled by the _H∞ controller, and output to the system. The smoothing of electric power, the reduction of the mechanical stress on the windmill blade by lowering the pitch angle operation, and the reduction of the storage battery capacity by constant control of the remaining amount of storage battery energy are achieved.

It should be noted that the PID controller can also eliminate the high-frequency component of the wind speed by the pre-filter, thereby suppressing a rapid change in pitch angle and reducing mechanical stress on the blade. Further, the combined output power can be leveled by controlling the charging / discharging operation of the storage battery according to the fluctuation of the wind turbine power generation amount. In this case, although the control performance is inferior to that of the _H∞ controller, it is possible to simultaneously reduce the mechanical stress on the wind turbine blade and smooth the power output to the system.

It is a block diagram which shows the outline | summary of the wind power generation electric power smoothing apparatus in one Example of this invention. It is a graph which shows the pitch angle control law in a present Example. It is a block diagram showing operation | movement of the electrical storage apparatus in a present Example. It is a block diagram of a closed loop system used for simulation. It is a block diagram which shows the linearization model of a wind generator. It is a singular value plot of the weight function. It is a singular value plot from pitch angle target value to generated electric power fluctuation (DELTA) Pg. It is a singular value plot from the remaining energy command value of the storage battery to the remaining energy. It is a block diagram which shows the control structure of a _Hinfinity controller. It is a singular value plot of the weight function. It is a singular value plot concerning synthetic output power. It is a graph which shows the wind speed given by simulation. It is a graph which shows the pitch angle response by simulation. It is a graph which shows the wind power generation electric power response by simulation. It is a graph which shows the storage battery output response by simulation. It is a graph which shows transition of the energy remaining amount by simulation. It is a graph which shows transition of synthetic output electric power by simulation. It is a block diagram of the PID controller used for simulation. It is a parameter table of the PID controller used for simulation. It is a table | surface of a simulation parameter. It is a graph which shows the wind speed given by the 2nd simulation. It is a graph which shows the pitch angle response by the 2nd simulation. It is a graph which shows the wind power generation electric power by a 2nd simulation. It is a graph which shows the storage battery output by a 2nd simulation. It is a graph which shows transition of the amount of remaining energy by the 2nd simulation. It is a graph which shows the wind speed given by the 3rd simulation. It is a graph which shows the pitch angle response by the 3rd simulation. It is a graph which shows the wind power generation electric power by a 3rd simulation. It is a graph which shows the storage battery output by a 3rd simulation. It is a graph which shows transition of the amount of remaining energy by the 3rd simulation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wind generator 2 Output terminal 3 PWM inverter 4 Storage battery

Claims (3)

  A wind power generation smoothing device including a wind power generator capable of pitch angle control, a storage battery, an output terminal, and a control device, wherein the control device generates power generated by low frequency fluctuations below a predetermined frequency with respect to wind speed fluctuations. The pitch angle of the wind power generator is adjusted so as to suppress fluctuations, and high-frequency fluctuations greater than or equal to the frequency are compensated only by the charge / discharge operation of the storage battery so that the generated power supplied to the output terminal is constant. A wind-generated power smoothing device using a windmill and a storage battery.   Furthermore, the wind power generator smoothing device by the windmill and storage battery of Claim 1 which controls the pitch angle of the said wind power generator so that the energy residual amount of the said storage battery may become fixed.   3. The wind power generation smoothing by the windmill and the storage battery according to claim 1, wherein the control device cooperatively operates a pitch angle of the wind power generator and a discharging / charging operation of the storage battery by H∞ control. apparatus.