JP2014176136A - Automatic power factor control system and automatic power factor control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a power factor at a power-receiving point while minimizing a total loss in a plurality of power generators installed in the premises of a customer.SOLUTION: A automatic power factor control system comprises: a reactive power detector 4 for detecting reactive power at a power-receiving point 2; active power detectors 5-5for detecting active power generated by power generators 3-3; a power factor arithmetic unit 6 for calculating, on the basis of the reactive power at the power-receiving point 2 and the active power generated by the power generators 3-3, an optimum value of the reactive power of the power generators 3-3for minimizing a sum total of loss costs of the power generators 3-3; and automatic power factor regulators 7-7for controlling, on the basis of the reactive power to be generated by the power generators 3-3as calculated by the power factor arithmetic unit 6, the field current of each of the power generators.

Description

  The present invention relates to an automatic power factor control system and an automatic power factor control method for a generator.

  In general, power generated by a generator installed on a customer's premises is apparent power including active power and reactive power. The active power is the power that is actually consumed by the load, and the reactive power is the power that is not consumed only by reciprocating between the load and the power source. In addition, reactive power causes power loss even though it is not consumed by the load. Therefore, although it seems that there is no need to generate reactive power, it is inevitable that many electric devices that are loads that consume power have a coil component inside, and the generator generates reactive power. .

  On the other hand, the power transmitted by the power company to the customer is apparent power including active power and reactive power. Accordingly, the electric power company transmits apparent power including reactive power that is not actually consumed by the customer to the customer. As a result, the power company is equipped with generators, transformers, and other transmission facilities with capacities that allow for apparent power, including reactive power, and bears the generation of power loss associated with reactive power transmission. There is reality.

  By the way, if the power factor (ratio of active power to apparent power) at the power receiving point of the consumer can be improved, the cost of power transmission equipment and the like from the power company to the consumer and the occurrence of power loss can be suppressed. . And one of the methods of improving the power factor in a consumer's power receiving point is generating a reactive power positively with the generator installed in a customer's premises. In other words, this power factor improvement method reduces the reactive power transmitted from the power company to the customer by covering the reactive power required by the load on the customer's premises with the generator on the premises. Is the method.

  From the above viewpoint, several techniques are known for maximizing reactive power in a generator installed in a customer's own premises and improving the power factor at a power receiving point. For example, Patent Document 1 describes a method for controlling the power factor of electric power generated by a generator according to the intake temperature of a gas turbine. Patent Document 2 discloses a method for controlling the power factor of power generated by a generator by detecting active power and reactive power from a power receiving power source and reactive power and reactive power from other generators that perform parallel operation. Have been described.

Japanese Unexamined Patent Publication No. 64-16300 JP-A-6-14466

  However, the method described in Patent Document 1 uses a phenomenon peculiar to a gas turbine generator and cannot be applied to a boiler generator or the like. In addition, the method described in Patent Document 2 detects active power and reactive power from the power receiving power source and other generators that perform parallel operation. When the reactive power output is increased, the field current of the generator increases. Since the loss of the generator increases, maximizing the reactive power of the generator alone is not always the most economical.

  The present invention has been made in view of the above, and an object thereof is to improve the power factor at the power receiving point while minimizing the total loss in a plurality of generators installed in the customer premises. An object is to provide an automatic power factor control system and an automatic power factor control method.

  In order to solve the above-described problems and achieve the object, an automatic power factor control system according to the present invention detects reactive power detecting means for detecting reactive power at a power receiving point and active power generated by each generator. Based on the active power detection means, the reactive power at the power receiving point, and the active power generated by each generator, the optimum value of the reactive power of each generator that minimizes the total loss cost of each generator Power factor calculating means for calculating the power factor, and power factor adjusting means for controlling the field current of each generator based on the reactive power to be generated by each of the generators calculated by the power factor calculating means. Features.

  In order to solve the above-described problems and achieve the object, an automatic power factor control method according to the present invention detects a reactive power detecting step for detecting reactive power at a power receiving point, and detects active power generated by each generator. Based on the active power detection step, the reactive power at the power receiving point, and the active power generated by each generator, the optimum value of the reactive power of each generator that minimizes the total loss cost of each generator And a power factor adjustment step of controlling the field current of each generator based on the reactive power that each of the generators calculated by the power factor calculation means should generate. Features.

  The automatic power factor control apparatus and the automatic power factor control method according to the present invention can improve the power factor at the power receiving point while minimizing the total loss in the plurality of generators installed in the customer premises. Play.

FIG. 1 is a block diagram showing a schematic configuration of an automatic power factor control system according to an embodiment of the present invention. FIG. 2 is a functional block schematically showing the function of the power factor calculation device. FIG. 3 is a graph showing an example of a possible output curve. FIG. 4 is a flowchart showing an automatic power factor control method according to the embodiment of the present invention.

  Hereinafter, an automatic power factor control apparatus and an automatic power factor control method according to embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments described below.

[Automatic power factor control system]
FIG. 1 is a block diagram showing a schematic configuration of an automatic power factor control system according to an embodiment of the present invention. As shown in FIG. 1, an automatic power factor control system 1 according to an embodiment of the present invention generates power at a power receiving point 2 that receives power supply from a higher power system to a customer premises, and at the customer premises. It is for use in a power system comprising _N parallel generators 3 _{1 to} 3 _N.

The automatic power factor control system 1 according to the embodiment of the present invention detects reactive power among reactive power detector 4 that detects reactive power at a power receiving point 2 and power generated by each of the generators 3 _{1 to} 3 _N. enable the power detector ₅ 1 to 5 _N, based on the reactive power at the receiving point 2 and the active power each generator ₃ 1 to 3 _N is power, reactive power to be power generation each generator ₃ 1 to 3 _N The power factor calculation device 6 for calculating the power factor, and the field current of each of the generators 3 _{1 to} 3 _N based on the reactive power to be generated by the generators 3 _{1 to} 3 _N calculated by the power factor calculation device 6 are automatically Automatic power factor regulators (APFR) 7 _{1 to} 7 _N that are controlled via regulators (AVR) 8 ₁ to 8 _N are provided.

The reactive power detector 4 detects reactive power among the apparent power at the power receiving point 2. For example, the reactive power detector 4 measures the reactive power at the power receiving point 2 by measuring an AC voltage and an AC current at the power receiving point 2 by combining a current transformer and a transformer. The magnitude of the reactive power in the receiving point 2 and Q _L.

The active power detectors 5 _{1 to} 5 _N provided in the generators 3 _{1 to} 3 _N measure the AC voltage and the AC current at the power receiving point 2, thereby generating electric power generated by the generators 3 _{1 to} 3 _N. The active power is detected. The magnitudes of these active powers are defined as P _{1 to} P _N , respectively.

Power factor calculation device 6, the magnitude P ₁ to P _N of size Q _L and respective active power of the reactive power in the power receiving point 2 obtained as described above as an input value, each generator 3 ₁ to 3 _N calculates reactive power to be generated. The calculation performed by the power factor calculation device 6 will be described in detail later. Each generator ₃ 1 to 3 _N is the size of each _Q 1 to Q _N of the reactive power to be power.

The automatic power factor adjusters 7 _{1 to} 7 _N are arranged so that each of the generators 3 _{1 to} 3 _N generates power with the magnitudes Q _{1 to} Q _N of reactive power calculated by the power factor calculation device 6. a device for adjusting the power factor of ₁ to 3 _N. Automatic voltage regulator ₈ 1 to 8 _N is a device for varying the power factor of the generator ₃ 1 to 3 _N by varying the field voltage of the generator ₃ 1 to 3 _N. The automatic power factor regulators 7 _{1 to} 7 _N and the automatic voltage regulators 8 ₁ to 8 _N cooperate to adjust the power factor of each of the generators 3 _{1 to} 3 _N.

Each of the generators 3 _{1 to} 3 _N is a general generator that generates electric power synchronized with the rotation speed at which the armature winding traverses the magnetic field generated by the field, and has a field current that excites the field. It is a generator that can control the power factor of generated power by control. Accordingly, each of the generators 3 _{1 to} 3 _N has a reactive power calculated by the power factor calculation device 6 through the automatic power factor adjusters 7 _{1 to} 7 _N and the automatic voltage adjusters 8 ₁ to 8 _N. It is possible to generate electricity.

[Power factor calculation device]
Details of the function of the power factor calculation device 6 will be described below.

  FIG. 2 is a functional block schematically showing the function of the power factor calculation device 6. As shown in FIG. 2, the power factor calculation device 6 includes power factor calculation means 6a and calculation condition storage means 6b.

The power factor calculation means 6a refers to the constraint condition stored in the calculation condition storage means 6b, and uses the reactive power magnitude Q _L and the active power magnitudes P _{1 to} P _N as input values to each generator. The magnitudes of reactive power Q _{1 to} Q _N to be generated by 3 _{1 to} 3 _N are calculated.

The calculation condition storage unit 6b, the data relating to power chart of the generator 3 ₁ to 3 _N is stored. The possible output curve represents a constraint condition for operation determined for each of the generators 3 _{1 to} 3 _N. FIG. 3 is a graph showing an example of a possible output curve. Each of the generators 3 _{1 to} 3 _N can generate power only by a combination of active power and reactive power within the possible output curve as shown in FIG.

Accordingly, the reactive power magnitudes Q _{1 to} Q _N that the generators 3 _{1 to} 3 _N can tolerate are determined for the magnitudes P _{1 to} P _{N of the} active powers that are input values, and the power factor calculation means 6a refers to the stored in the calculation condition storage unit 6b constraints to obtain the magnitude Q ₁ to Q _N of reactive power each generator 3 ₁ to 3 _N is acceptable. This is the first constraint condition.

As a first constraint condition, the range of reactive power that can be output from each of the generators 3 _{1 to} 3 _N is expressed by the following equation (1). However, in the following formula (1), Q _i is the magnitude of reactive power of the i-th generator 3 _i , and Q _imax is the maximum reactive power magnitude determined from the possible output curve.

When the above formula (1) is represented by a power factor setting value, it is represented as the following formula (2). However, in the following formula (2), P _i is the magnitude of the active power of the i-th generator 3 _i , and f _i is a function representing a possible output curve.

On the other hand, the total sum of the reactive power magnitudes Q _{1 to} Q _N of the generators 3 _{1 to} 3 _N must be equal to the reactive power magnitude Q _L supplied from the upper power system. This is the second constraint condition and is expressed as the following expression (3).

  Next, calculation of the optimum value of reactive power performed by the power factor calculation means 6a will be described.

In each of the generators 3 _{1 to} 3 _N , loss costs for the magnitudes of reactive power Q _{1 to} Q _N are determined. This loss cost is a loss cost specific to each of the generators 3 _{1 to} 3 _N , and the loss cost of each of the generators 3 _{1 to} 3 _N is also stored in the calculation condition storage unit 6 b. Hereinafter, the magnitude of the loss cost with respect to the magnitudes Q _{1 to} Q _N of reactive power is assumed to be F (Q ₁ ) to F (Q _N ).

  Here, a Lagrange undetermined multiplier method will be described as a method for calculating a reactive power set that minimizes the sum of loss costs.

  When Lagrange's undetermined multiplier is λ, the Lagrangian function is expressed by the following equation (4).

Then, the following equation (5) is obtained by differentiating the above equation (4) with respect to Q _i .

  That is, from the above equation (5), the following equation (6) is established.

Therefore, the sum of the loss costs of the generators 3 _{1 to} 3 _N is minimized by selecting the magnitudes Q _{1 to} Q _N of the reactive power that satisfy the above formula (6).

However, the reactive power magnitudes Q _{1 to} Q _N satisfying the above equation (6) may not satisfy the equation (1) as the first constraint condition. Therefore, when any of the reactive power magnitudes Q _{1 to} Q _N does not satisfy the expression (1), Q _i not satisfying the expression (1) is set as Q _i = 0 or Q _i = Q _imax . It performs recalculation of the reactive power of the magnitude _Q 1 to Q _N. That is, if the i-th Q _i is Q _imax <Q _i and does not satisfy the equation (1), recalculation is performed with Q _i = Q _imax , and the i-th Q _i becomes Q _i <0, If 1) is not satisfied, recalculation is performed with Q _i = 0.

As described above, the magnitude _Q 1 to Q _N of reactive power power factor calculation means 6a has been calculated is transmitted to the automatic power factor regulator ₇ 1 to _7-N, the automatic power factor regulator ₇ 1 to _7-N and The power factor is adjusted by the automatic voltage regulators 8 ₁ to 8 _{N so} that each of the generators 3 _{1 to} 3 _N generates power with the magnitudes Q _{1 to} Q _N of reactive power. As a result, according to the automatic power factor control system according to the embodiment of the present invention, the power factor at the power receiving point can be improved while minimizing the total loss in the plurality of generators installed in the customer premises.

[Automatic power factor control method]
Next, an automatic power factor control method according to an embodiment of the present invention will be described with reference to FIG. FIG. 4 is a flowchart showing an automatic power factor control method according to the embodiment of the present invention.

As shown in FIG. 4, in the automatic power factor control method according to the embodiment of the present invention, the reactive power detector 4 first detects the reactive power magnitude Q _L at the power receiving point 2 (step S1). . On the other hand, each generator ₃ 1 to 3 active power provided to the _N detectors ₅ 1 to 5 _N, the magnitude _P 1 to P _N of active power each generator ₃ 1 to 3 _N to generate electricity is detected (Step S2).

Then, the power factor calculation unit 6, each generator ₃ 1 based on to 3 _N of possible output curve, the magnitude _P 1 to P _N of active power each generator ₃ 1 to 3 _N is power, each generator The first constraint condition that should be satisfied by the magnitudes Q _{1 to} Q _{N of} the reactive power generated by 3 _{1 to} 3 _N is acquired (step S3). In addition, the second constraint condition is acquired that the sum of the reactive power magnitudes Q _{1 to} Q _N generated by the generators 3 _{1 to} 3 _N is equal to the reactive power magnitude Q _L at the power receiving point 2. (Step S4).

Then, the power factor calculation unit 6, under the second constraint, the size Q of the reactive power of each generator 3 ₁ to 3 _N each generator 3 ₁ to 3 _N where the sum of the loss cost is minimal ₁ to Q _N is calculated (step S5). For example, the Lagrange undetermined multiplier method is used to calculate the optimum reactive power magnitudes Q _{1 to} Q _N in this step, as described above.

Thereafter, the power factor calculation device 6 determines whether or not the calculated reactive power magnitudes Q _{1 to} Q _N of the generators 3 _{1 to} 3 _N satisfy the first constraint condition (step S 6). ). When the calculated magnitudes Q _{1 to} Q _N of the generators 3 _{1 to} 3 _N do not satisfy the first constraint condition (step S6; No), the first constraint condition is not satisfied. Reactive power magnitudes Q _{1 to} Q _N are recalculated with reactive power magnitude Q _{i set} to Q _i = 0 or Q _i = Q _imax (step S 7). On the other hand, when the calculated magnitudes Q _{1 to} Q _N of the generators 3 _{1 to} 3 _N satisfy the first constraint condition (step S6; Yes), the calculated generators 3 ₁ to 3 of _N reactive power magnitude _Q 1 to Q _N is transmitted to the automatic power factor regulator ₇ 1 to _7-N, the automatic power factor regulator ₇ by 1 to _7-N and the automatic voltage regulator ₈ 1 to 8 _N The power factor is adjusted so that each of the generators 3 _{1 to} 3 _N generates power with the magnitude of reactive power Q _{1 to} Q _N (step S8).

  This completes the automatic power factor control method according to the embodiment of the present invention.

〔Example〕
Hereinafter, an example of the optimum value calculation of the reactive power by the automatic power factor control device and the automatic power factor control method according to the embodiment of the present invention will be described. In the embodiment described below, a case where there are three generators is considered. That is, the magnitude of reactive power of each generator is Q _{1 to} Q ₃ , and the loss cost is F ₁ (Q ₁ ) to F ₃ (Q ₃ ).

It is assumed that loss costs F ₁ (Q ₁ ) to F ₃ (Q ₃ ) with respect to the reactive power magnitudes Q _{1 to} Q ₃ of each generator are given by the following equation (7).

  Further, it is assumed that the first constraint condition determined from the possible output curve of each generator is determined as in the following equation (8).

Under the above conditions, the reactive power magnitudes Q _{1 to} Q ₃ that minimize the sum of the loss costs F ₁ (Q ₁ ) to F ₃ (Q ₃ ) of each generator are determined by the Lagrange multiplier method described above. The following equation (9) is satisfied.

Assuming that the magnitude of reactive power at power receiving point 2 is Q _L , the following equation (10) is obtained from equation (9).

That is, if the reactive power magnitude Q _L at the power receiving point 2 is specified by Expression (10), λ is determined, and if λ is determined by Expression (9), the reactive power magnitudes Q ₁ to Q are determined. ₃ is determined.

Therefore, hereinafter, a calculation example in the case where the reactive power magnitude Q _L at the power receiving point 2 is specifically given will be described.

[Example 1] In the case of Q _L = 60 The following values are obtained by the equations (9) and (10).

However, since Q ₃ > 15 at the above value, the first constraint condition is not satisfied. Therefore, recalculation is performed for Q ₁ and Q ₂ with Q ₃ = 15. As a result, the following values are obtained.

Since the above value satisfies the first constraint condition, the reactive power is such that the sum of the loss costs F ₁ (Q ₁ ) to F ₃ (Q ₃ ) of each generator is minimized.

[Example 2] In the case of Q _L = 30 The following values are obtained by the equations (9) and (10).

Since the above value satisfies the first constraint condition, the amount of reactive power that minimizes the sum of the loss costs F ₁ (Q ₁ ) to F ₃ (Q ₃ ) of each generator without recalculation. It has become.

[Example 3] In the case of Q _L = 5 The following values are obtained by the equations (9) and (10).

However, since Q ₂ <0 at the above value, the first constraint condition is not satisfied. Therefore, recalculation is performed for Q ₁ and Q ₃ with Q ₂ = 0. As a result, the following values are obtained.

Since the above value satisfies the first constraint condition, the reactive power is such that the sum of the loss costs F ₁ (Q ₁ ) to F ₃ (Q ₃ ) of each generator is minimized.

DESCRIPTION OF SYMBOLS 1 Automatic power factor control system 2 Power receiving point 3 _{1 to} 3 _N generator 4 Reactive power detector 5 _{1 to} 5 _N Active power detector 6 Power factor calculation device 6a Power factor calculation means 6b Calculation condition storage means 7 _{1 to} 7 _N Automatic power factor adjuster (APFR)
8 ₁ to 8 _N automatic voltage regulator (AVR)

Claims (4)

Reactive power detection means for detecting reactive power at a power receiving point;
Active power detection means for detecting active power generated by each generator;
Based on the reactive power at the power receiving point and the active power generated by each of the generators, a power factor calculation that calculates an optimum value of the reactive power of each generator that minimizes the sum of the loss costs of the generators Means,
Power factor adjusting means for controlling the field current of each of the generators based on the reactive power to be generated by each of the generators calculated by the power factor calculating means;
An automatic power factor control system characterized by comprising: The power factor calculation means is
Obtaining the first constraint condition that the reactive power generated by each generator should satisfy based on the active power generated by each of the generators;
Obtaining a second constraint condition that the total of reactive power to be generated by each of the generators coincides with the reactive power at the power receiving point;
Calculating the reactive power of each generator that minimizes the total loss cost of each generator under the second constraint,
When the calculated reactive power of each generator satisfies the first constraint condition, the reactive power of each generator is set to the optimum value of reactive power to be generated by each generator,
The automatic power factor control system according to claim 1. A reactive power detection step for detecting reactive power at a power receiving point;
An active power detection step for detecting active power generated by each generator;
Based on the reactive power at the power receiving point and the active power generated by each of the generators, a power factor calculation that calculates an optimum value of the reactive power of each generator that minimizes the sum of the loss costs of the generators Steps,
A power factor adjustment step for controlling the field current of each generator based on the reactive power to be generated by each of the generators calculated by the power factor calculating means;
The automatic power factor control method characterized by including. The power factor calculation step includes:
Obtaining the first constraint condition that the reactive power generated by each generator should satisfy based on the active power generated by each of the generators;
Obtaining a second constraint condition that the total of reactive power to be generated by each of the generators coincides with the reactive power at the power receiving point;
Calculating the reactive power of each generator that minimizes the total loss cost of each generator under the second constraint,
When the calculated reactive power of each generator satisfies the first constraint condition, the reactive power of each generator is set to the optimum value of reactive power to be generated by each generator,
The automatic power factor control method according to claim 3.

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