JP2017189028A - Control method and controller for distributed power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method and controller that suppress voltage variations at an interconnection point by controlling a power converter by calculating an optimum power factor without varying effective power.SOLUTION: A distributed power supply control method controls reactive power output from a power converter interconnected with a system to suppress voltage variations at an interconnection point. The method suppresses voltage variations at the interconnection point by controlling the reactive power output from the power converter by: calculating an interconnection point voltage variation amount, interconnection point effective power, and interconnection point power factor from the interconnection point's voltage and current in a given period of time; approximating relation between the interconnection point effective power and the interconnection point voltage variation amount by a linear function to calculate its inclination using a least square method; setting a power factor variation amount depending on increase/decrease in the interconnection point power factor and increase/decrease in the inclination that are calculated according to a predetermined period; adding the power factor variation amount to the newest interconnection point power factor to calculate a power factor instruction that makes the inclination be approximately zero; and driving the power converter on the basis of the power factor instruction.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a control method and a control apparatus for a distributed power source composed of a solar power generation system, a wind power generation system, and the like, and more particularly to a technique for suppressing voltage fluctuations at a connection point between a distributed power source and a power system. is there.

In recent years, solar power generation systems and wind power generation systems have been put into practical use, and power conditioners including inverters and their controllers are usually used to connect these distributed power sources to the power system. . In this case, the active power output from the distributed power source fluctuates depending on weather conditions, etc., and the fluctuation of the active power may cause the voltage at the connection point with the power system to fluctuate, which may hinder the stabilization of the system. Become.
In view of the above points, various techniques have been conventionally provided to suppress voltage fluctuations at the interconnection point.

For example, FIG. 8 is an overall configuration diagram of a wind power generation system described in Patent Document 1.
In FIG. 8, 30 is a distributed power source having a wind power generator, 31 is a windmill blade, 32 is a generator, 33 is a power converter comprising a converter and an inverter, 34 is a voltage detector, 35 is a current detector, and 36 is controller, 37 windmill controller, 40 tie-line expressed by the resistance component _{R 1} and reactor components _{X 1,} 50 is a power system, 60 common load expressed by the resistance component _{R 2} and reactor components _{X 2,} A is This is an interconnection point between the distributed power supply 30 and the system side.

FIG. 9 is a block diagram showing the internal configuration of the controller 36.
The controller 36 receives a voltage detection value V and a current detection value I at the connection point A, calculates a valid power P and a voltage amplitude value V _p, and a fluctuation component ΔP of the active power P. a variation detector 36b for detecting the reactive power for calculating the fluctuation detector 36d for detecting a fluctuation component [Delta] V _p of the voltage amplitude value V _p, active power P and variation component [Delta] P, the reactive power command value Q ^* from [Delta] V _p A command calculator 36c and a power controller 36e that generates a gate pulse command G ^* using the active power command value P ^* and the reactive power command value Q ^* input from the windmill controller 37 of FIG. 8 are provided. . Then, the reactive power Q is controlled by turning on and off the semiconductor switching element of the power converter 33 by the gate pulse command G ^* , and the fluctuation component ΔV _p of the voltage amplitude value V _p generated with the fluctuation of the active power P is obtained. It is approaching zero.

The reactive power command calculator 36c converges the control parameter α to the ratio of the resistance component and reactance component of the combined impedance on the power system side by multiplying the fluctuation components ΔP and ΔV _p and integrating the result. The reactive power command value Q ^* is obtained by multiplying the control parameter α by the active power P and (−1).

Next, FIG. 10 is an overall configuration diagram of the photovoltaic power generation system described in Patent Document 2.
In FIG. 10, a plurality of photovoltaic power generation devices 80 are connected in parallel to the interconnection point A on the interconnection line 40 via a transformer 71 and a premises wiring 72. These photovoltaic device 80, the solar cell 81 includes a power converter 82 and controller 85, the output current I of the entire detected by the detectors 73,83,84, own output currents _{I 1} and The controller 85 to which the output voltage V ₁ is input is configured to generate a gate pulse signal G ₁ for the power converter 82.

FIG. 11 is a block diagram showing the internal configuration of the controller 85.
The controller 85 receives the voltage V ₁ and the currents I and I _{1 and} outputs the voltage V ₁ , the d of the current I ₁ , the q-axis components V _1d , V _1q , I _1d , I _1q and the total effective power P. A voltage / current / power calculator 85a to be calculated, a voltage estimation calculator 85b to estimate the voltage amplitude V _S of the interconnection point A, a fluctuation detector 85c to detect a fluctuation component ΔV _S of the voltage amplitude V _S , and the total effective power A fluctuation detector 85d for detecting a fluctuation component ΔP of P, a dead band encoder 85e for generating a sign signal ΔP _SIGN indicating the increase / decrease direction of the fluctuation component ΔP of the active power P, a fluctuation component ΔV _S and a sign signal ΔP _SIGN a multiplier 85f for multiplying the reactive power compensation using an integrator 85g to obtain the same control parameter α Patent Document 1 by integrating its output, the effective power P ₁ of the interconnection node a and the control parameter α No calculation of quantity Q ₁ ^* An active power compensation calculator 85h and an output fluctuation generator 85i that calculates an active power fluctuation command ΔP ₁ ^* using the fluctuation component ΔP of the active power P and the control parameter α are provided.

The reactive power compensation amount Q ₁ ^* and the active power fluctuation command ΔP ₁ ^* are input to the power controller 85j together with the voltage V ₁ and the current I ₁ . Power controller 85j generates a gate pulse signal G ₁ as reactive power Q equal to the reactive power compensation amount Q ₁ ^* under the active power variation command [Delta] P ₁ ^* is output semiconductor power converter 82 The switching element is turned on / off to bring the fluctuation component ΔV _S of the voltage amplitude V _S close to zero.

  As described above, the principle of suppressing the voltage fluctuation at the interconnection point A by adjusting the reactive power with an appropriate power factor based on the control parameter α is described in detail in Non-Patent Document 1.

Japanese Patent No. 4575272 (paragraphs [0025] to [0034], FIG. 1, FIG. 2, etc.) Japanese Patent No. 5329603 (paragraphs [0022] to [0033], FIG. 1, FIG. 2, etc.)

Tomoyuki Uchiyama and three others, "Voltage fluctuation suppression by reactive power control of large-scale photovoltaic power generation system", IEEJ Transaction B, Vol.130, No.3, 2010

With the techniques described in Patent Documents 1 and 2, the optimal control parameter α cannot be obtained unless the output of the distributed power source 30 or the solar power generation device 80 fluctuates. For this reason, for example, in Patent Document 2, the active power P is intentionally changed by giving an active power change command to the power controller.
However, fluctuating the active power P also decreases the generated power that can be output inherently, which leads to loss of power generation opportunities and is not preferable from the viewpoint of system stabilization.

  Therefore, the problem to be solved by the present invention is that the voltage fluctuation at the interconnection point is controlled by optimizing the power factor and controlling the power converter without changing the active power output from the distributed power source such as the photovoltaic power generation device. It is an object of the present invention to provide a distributed power supply control method and control device that suppresses the above.

In order to solve the above problems, the invention according to claim 1 is a control method of a distributed power source including a power converter connected to a power generation facility and operated in conjunction with a power system, wherein the power In a control method of a distributed power source that controls reactive power output from a converter to suppress voltage fluctuation at a connection point between the power system and the power converter,
A connection point voltage fluctuation amount, a connection point active power and a connection point power factor are calculated from the voltage and current of the connection point for a certain period, and the connection point active power and the connection point voltage fluctuation amount are calculated. By approximating the relationship with a linear function, the slope of the linear function is obtained by the least square method,
The power factor fluctuation amount is set according to the increase / decrease of the interconnection point power factor and the inclination increase / decrease calculated according to a predetermined calculation cycle, and the power factor fluctuation amount is added to the latest interconnection point power factor to While calculating a power factor command that makes the slope almost zero,
By driving the semiconductor switching element of the power converter based on the power factor command, the reactive power output from the power converter is controlled to suppress voltage fluctuation at the linkage point.

  The invention according to claim 2 is the distributed power supply control method according to claim 1, except when the interconnection point voltage fluctuation amount is in a predetermined voltage range before and after the rated voltage of the power system. The power factor command calculation process is executed.

The invention according to claim 3 is a control device for a distributed power source including a power converter that is connected to a power generation facility and is operated in conjunction with a power system, and is an ineffective output from the power converter In the control device of the distributed power source that controls the power to suppress the voltage fluctuation at the connection point between the power system and the power converter,
Means for calculating the connection point voltage fluctuation amount, the connection point active power and the connection point power factor from the voltage and current of the connection point for a certain period;
An inclination calculating means for approximating a relation between the interconnection point active power and the interconnection point voltage fluctuation amount by a linear function and obtaining an inclination of the linear function by a least square method;
The power factor fluctuation amount is set according to the increase / decrease of the interconnection point power factor and the inclination increase / decrease calculated according to a predetermined calculation cycle, and the power factor fluctuation amount is added to the latest interconnection point power factor to Power factor calculation means for calculating a power factor command that makes the slope substantially zero;
A controller to which the power factor command is given,
The controller controls the reactive power output from the power converter by driving the semiconductor switching element of the power converter by the drive signal generated based on the power factor command, thereby changing the voltage at the linkage point. It suppresses.

  The invention according to claim 4 is the distributed power supply control device according to claim 3, except when the amount of fluctuation of the interconnection point voltage is in a predetermined voltage range before and after the rated voltage of the power system. Calculation processing by the power factor calculation means is executed.

According to the present invention, the reactive power is controlled according to the power factor optimized based on the voltage fluctuation amount and the active power at the interconnection point without changing the active power output from the distributed power source. Voltage fluctuations at the system point can be suppressed.
For this reason, it is possible to effectively use the power generated by the distributed power source and stabilize the system.

It is a whole lineblock diagram at the time of applying an embodiment of the present invention to a photovoltaic power generation system. It is a conceptual diagram which shows the relationship between the active power of a connection point, and the amount of voltage fluctuations. It is a conceptual diagram which shows the relationship between a power factor and the inclination of a linear function. It is a functional block diagram of the power factor calculator in the embodiment of the present invention. It is a flowchart of the process which changes the power factor instruction | command in embodiment of this invention. It is operation | movement explanatory drawing of the power factor calculation execution determination means in embodiment of this invention. It is a conceptual diagram which shows the relationship between the active power of a connection point, and the amount of voltage fluctuations. 1 is an overall configuration diagram of a wind power generation system described in Patent Literature 1. FIG. It is a block diagram which shows the internal structure of the controller in FIG. It is a whole block diagram of the solar energy power generation system described in patent document 2. It is a block diagram which shows the internal structure of the controller in FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram when this embodiment is applied to a photovoltaic power generation system.

In FIG. 1, reference numeral 20 denotes a photovoltaic power generation system as a distributed power source.
This solar power generation system 20 includes a solar cell 21, a power converter 22 such as an inverter that converts the DC output voltage into an AC voltage, a controller 23 for driving a semiconductor switching element of the power converter 22, It has. A plurality of series circuits of the photovoltaic power generation system 20 and the interconnection transformer 26 configured as described above are connected in parallel, and the primary side of the interconnection transformer 26 is connected to the interconnection point A.

  The output voltage (PV voltage) and output current (PV current) of the solar cell 21 are detected by the voltage / current detection means 24, and the output voltage and output current of the power converter 22 are detected by the voltage / current detection means 25. The controller 23 generates a drive signal (gate signal) based on each detected value and a power factor command to be described later, and controls on / off of the semiconductor switching element of the power converter 22.

Further, a voltage detector 27 and a current detector 28 are connected between the connection point A and the primary side of the connection transformer 26, and the connection point voltage and the connection point current detected thereby are the power factor. It is input to the calculator 29. The power factor calculator 29 sends a power factor command generated based on the connection point voltage and the connection point current to the controller 23.
In the above configuration, it is assumed that the photovoltaic power generation system 20 has a three-phase output and is connected to the three-phase power system 50 and the interconnection line 40.

Next, the operation principle of the power factor calculator 29 will be described.
In the power factor calculator 29, the relationship between the active power at the connection point A and the amount of voltage fluctuation is a linear function based on the connection point voltage and the connection point current measured for a fixed time (for example, 10 minutes) when the power factor is not changed. The power factor command (= power factor moving average value + power factor fluctuation amount) is optimized and output so that the slope of the linear function becomes zero.

Here, FIG. 2 is a conceptual diagram showing the relationship between the active power at the interconnection point A and the voltage fluctuation amount.
As shown in the figure, when the connection point voltage fluctuation amount is approximated by a linear function of the connection point active power, if the slope of the linear function is positive, the power factor is too high, and the slope is negative The power factor is considered to be too low.
Accordingly, the linear function slope (indicated by Δ) in FIG. 3 is converged to almost zero, that is, the interconnection point voltage fluctuation amount is almost zero regardless of the fluctuation of the interconnection point active power. Optimize the rate.

The slope of the linear function is obtained by the least square method on the assumption that the amount of voltage fluctuation becomes 0 when the active power at the interconnection point A is 0. As a method for optimizing the power factor, a local search is used. We decided to use the hill-climbing method, which is a kind of law.
The power factor calculator 29 uses the previous value without changing the power factor when the variation in the voltage at the interconnection point A is within a predetermined voltage range centered on the rated voltage. .

FIG. 4 is a functional block diagram of the power factor calculator 29.
In FIG. 4, the connection point calculation means 1 calculates the effective voltage of each phase of the three phases from the voltage and current (both instantaneous values) of the connection point A detected at a predetermined sampling period for a predetermined time (for example, 10 minutes). The average value V _{s of} the values, the active power P _{s of} the connection point A, and the power factor φ of the connection point A are calculated and output.

Next, the moving average means 2 calculates a moving average value V _save from the average value V _s , and outputs this moving average value V _save as a rated voltage (for a base for determining the amount of voltage fluctuation). However, when the power determination unit 4 determines that the active power P _s is at a level that does not cause voltage fluctuation, a sample hold unit 3 is provided that updates and outputs the input moving average value V _save . .

The subtracting means 5 calculates the difference between the V _save output from the sample hold means 3 and the average value V _s, and obtains the voltage fluctuation amount V _sval (= V _save −V _s ) at the _connection point A.
This voltage fluctuation amount V _sval is input to the ring buffer 6 for storing data for 10 minutes, for example. That is, the data (voltage fluctuation amount V _sval ) up to 10 minutes before is always stored in the ring buffer 6, and the old data after 10 minutes has been discarded in order.
Also for the active power P _{s at the} interconnection point A, the data up to 10 minutes before (active power P _s ) is always stored by the ring buffer 7.

Here, _assuming that the voltage fluctuation amount V _sval is a function y (i) and the active power P _s is a function x (i), the slope calculating means 8 represents the relationship between the two as a linear function: y (i) = ax (i). The slope a where the partial differential value (∂S / ∂a) of the residual sum of squares S is 0 is calculated by the least square method, as shown in the following equations 1-3. The calculation of the slope a according to Equation 3 is performed on the data y (i) and x (i) for the past 10 minutes stored in the ring buffers 6 and 7.

[Formula 1]
S = Σ (y (i) −ax (i)) ²
[Formula 2]
∂S / ∂a = 0
[Formula 3]
a = Σx (i) y (i) / Σx (i) ²

On the other hand, the power factor φ of the connection point A calculated by the above-described connection point calculation means 1 is input to the moving average means 9, and the current value of the moving average value of the power factor φ and the sample hold means 11 is input to the power factor calculation means 16.
Further, the current value of the inclination a calculated by the inclination calculating means 8 and the previous value of the inclination a held by the sample hold means 13 are input to the power factor calculating means 16.
Reference numerals 10 and 12 denote fixed-cycle timers that generate clock signals input to the sample-and-hold means 11 and 13 and an AND gate 15 described later.

  The power factor calculation means 16 generates a power factor command according to the flowchart of FIG. The power factor command is a value obtained by adding the power factor fluctuation amount to the moving average value of the power factor as described above.

  First, after the previous change of the power factor command (step S1), the current value of the inclination a, that is, the sign of a (i) is determined (S2). As shown in FIG. 2 and FIG. 3, the power factor φ is too high when the inclination a is large on the positive side (Yes in S2). Next, the increase / decrease tendency of the power factor φ is determined (S3). ).

The current value φ (i) of the power factor has decreased from the previous value φ (i-1) (S3 Yes), and the current value a (i) of the slope has decreased from the previous value a (i-1). (S4 Yes), it is only necessary to adjust the power factor φ in that direction (the direction in which the power factor φ is reduced and the inclination a is made close to 0), so the power factor fluctuation amount is (−Δφ). (S5), and this is added to the current value φ (i) of the power factor to change the power factor (S1).
Even if the current value φ (i) of the power factor is smaller than the previous value φ (i−1) (S3 Yes in the same), the current value of the slope is increased by increasing the voltage fluctuation amount V _sval or decreasing the active power P _s. If a (i) is greater than the previous value a (i-1) or does not change from the previous value a (i-1) (No in S4), in order to change the power factor φ in the opposite direction The power factor fluctuation amount is set to (+ Δφ) (S6), and this is added to the current value φ (i) of the power factor to change the power factor (S1).

When the current value φ (i) of the power factor has increased from the previous value φ (i−1) or does not change from the previous value φ (i−1) in the above-described step S3 (No in S3), It is determined whether the inclination a increases or decreases (S7). When the current value a (i) of the slope is increased from the previous value a (i-1) due to the increase in the voltage fluctuation amount V _sval or the decrease in the active power P _s (S7 Yes in the same), the power factor φ Must be changed in the opposite direction.
Therefore, the power factor fluctuation amount is set to (−Δφ) so that the power factor becomes low (S8), and this is added to the current value φ (i) of the power factor to change the power factor (S1).

  If the current value a (i) of the slope is less than the previous value a (i-1) or is not different from the previous value a (i-1) (No in S7), the power factor φ is reversed. In order to change the power factor, the power factor variation is set to (+ Δφ) (S9), and this is added to the current value φ (i) of the power factor to change the power factor (S1).

  Further, as shown in FIGS. 2 and 3, when the slope a is large on the negative side, the power factor φ is too low (No in S2). The increase / decrease tendency of a is determined (S10, S11, S14), and the power factor is changed by setting the amount of power factor fluctuation opposite to steps S5, S6, S8, S9 according to the increase / decrease of the inclination a ( (S12, S13, S15, S16, S1).

Here, the power factor calculation execution determination unit 14 in FIG. 4 is configured such that the voltage fluctuation amount V _sval is included in a voltage range of ± ΔV _s (ΔV _s is, for example, 2 [%] of the rated voltage) around the rated voltage. A logic value “1” or “0” is generated as shown in FIG. 6 so that the power factor calculation means 16 does not execute the power factor calculation, and this logic value together with the clock signal from the fixed period timer 12 is AND gate 15. Has been entered.

As described above, in the present embodiment, even if the fluctuation amount of the active power P _s is small, as shown in FIG. 7, the linear function y (i) = ax (i) passing through the origin serves as the linkage point active power. The relationship with the system point voltage fluctuation amount is approximated. For this reason, the power factor calculation means 16 in FIG. 4, in other words, the power factor calculator 29 in FIG. 1 has a slope a based on y (i) and x (i) (voltage fluctuation amount V _sval and active power P _s ). It is possible to optimize the power factor command so that the inclination a approaches zero.

The power factor command generated in this way is sent to the controller 23 in FIG. The controller 23 generates a drive signal for the semiconductor switching element and performs on / off control so that the power converter 22 outputs predetermined reactive power in accordance with the input power factor command. Thereby, the voltage fluctuation of the connection point A can be suppressed without intentionally changing the active power output from the power converter 22.
Therefore, the power generation capacity of the solar power generation system 20 can be used effectively and contributes to the stabilization of the system.

  In the embodiment of FIG. 1, a plurality of photovoltaic power generation systems 20 are connected in parallel. However, the present invention can also be applied to a case where a single distributed power source is connected to the power system 50. It is.

  The present invention can be used not only for a solar power generation system but also for a distributed power source including various power generation facilities such as a wind power generation system and a fuel cell power generation system.

A: Linkage point 1: Linkage point calculation means 2, 9: Moving average means 3, 11, 13: Sample hold means 4: Power determination means 5: Subtraction means 6, 7: Ring buffer 8: Inclination calculation means 10, 12: Periodic timer 14: Power factor calculation execution determination means 15: AND gate 16: Power factor calculation means 20: Solar power generation system (distributed power supply)
21: Solar cell 22: Power converter 23: Controller 24, 25: Voltage / current detection means 26: Interconnection transformer 27: Voltage detector 28: Current detector 29: Power factor calculator 40: Interconnection line 50 : Power system

Claims (4)

A method for controlling a distributed power source including a power converter connected to a power generation facility and operated in conjunction with a power system, wherein the power system controls a reactive power output from the power converter In the control method of the distributed power source so as to suppress the voltage fluctuation at the linkage point between the power converter and the power converter,
A connection point voltage fluctuation amount, a connection point active power and a connection point power factor are calculated from the voltage and current of the connection point for a certain period, and the connection point active power and the connection point voltage fluctuation amount are calculated. By approximating the relationship with a linear function, the slope of the linear function is obtained by the least square method,
The power factor fluctuation amount is set according to the increase / decrease of the interconnection point power factor and the inclination increase / decrease calculated according to a predetermined calculation cycle, and the power factor fluctuation amount is added to the latest interconnection point power factor to While calculating a power factor command that makes the slope almost zero,
A dispersion characterized by controlling a reactive power output from the power converter by driving a semiconductor switching element of the power converter based on the power factor command to suppress a voltage fluctuation at the linkage point. Control method of mold power The control method of the distributed power supply according to claim 1,
The distributed power supply control method, wherein the power factor command calculation process is executed except when the interconnection point voltage fluctuation amount is in a predetermined voltage range before and after the rated voltage of the power system is included. A control device for a distributed power source including a power converter connected to a power generation facility and operated in conjunction with a power system, wherein the power system controls the reactive power output from the power converter In a control device for a distributed power source that suppresses voltage fluctuations at a connection point between the power converter and the power converter,
Means for calculating the connection point voltage fluctuation amount, the connection point active power and the connection point power factor from the voltage and current of the connection point for a certain period;
An inclination calculating means for approximating a relation between the interconnection point active power and the interconnection point voltage fluctuation amount by a linear function and obtaining an inclination of the linear function by a least square method;
The power factor fluctuation amount is set according to the increase / decrease of the interconnection point power factor and the inclination increase / decrease calculated according to a predetermined calculation cycle, and the power factor fluctuation amount is added to the latest interconnection point power factor to Power factor calculation means for calculating a power factor command that makes the slope substantially zero;
A controller to which the power factor command is given;
With
The controller controls the reactive power output from the power converter by driving the semiconductor switching element of the power converter by the drive signal generated based on the power factor command, thereby changing the voltage at the linkage point. A control device for a distributed power supply characterized by suppressing the above. In the distributed power supply control device according to claim 3,
A control device for a distributed power supply, wherein the power factor calculation means performs a calculation process except when the interconnection point voltage fluctuation amount is in a predetermined voltage range before and after the rated voltage of the power system is included. .

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