KR20090126127A - Apparatus and method of voltage control - Google Patents

Abstract

PURPOSE: A voltage control method and an apparatus thereof are provided to prevent voltage drop and rise caused by a system fault by using reactive power. CONSTITUTION: An electric power converting unit(20) is connected to a generator and changes generated power . A voltage comparator(40) produces an error voltage by using a measured voltage and a reference voltage. A controller(60) receives an error voltage and produces a first reactive power value. A driver(70) controls the electric power converting unit in response to the reactive power standard value. A drive comparator produces an error signal by using the total of the first reactive power value and the total of the reactive power standard value. An accumulation controller prevents the accumulation of the controller by using the error signal and the error voltage.

Description

 Voltage control method and apparatus {Apparatus and Method of Voltage control}

The present invention relates to a voltage control method and apparatus, and more particularly, to a voltage control method and apparatus of a power generation system that performs voltage control at the grid connection point by using the reactive power of the power conversion unit of the power generation system.

Wind power generation uses no-pollution and infinite wind scattered everywhere, so there is little impact on the environment and the land can be used efficiently.

In addition, wind power generation is a new energy generation technology that can compete with existing power generation in the case of large-scale power generation.

With the recent increase in energy costs, the market expansion of distributed power generation distributed in consumer areas such as wind power generation is accelerating. In the case of distributed power supply, controlling each distributed power supply is very important for efficient power generation system operation.

The voltage control method applied to the conventional wind power generation system is based on power factor control (Qref) using a reactive power compensation device (capacitor bank).

Wind power generation systems supply power in conjunction with existing commercial power systems. In this case, the stability and efficiency of grid connection is very important.

However, in the conventional wind power generation system, generators using a distributed power source, which were operated in conjunction with a commercial system at the time of power failure, were simultaneously cut off. In this case, a change in the voltage and frequency of the system caused a serious problem in the stability of the power system. Will result.

In order to solve these problems and to improve the stability of grid operation, the wind power generation system is installing an additional device called a capacitor bank to solve the voltage drop at the grid connection point.

However, the method of using the capacitor bank in the conventional wind power generation system has a problem in that it does not compensate for the sudden voltage fluctuation due to not only the responsiveness and precision but also the continuous control.

In addition, in the conventional wind power generation system, a dynamic capacitor bank may be installed and supplemented, but this also requires a high cost and has a problem in that it is not a realistic solution due to complicated control.

Therefore, it is difficult to solve the problems described above by using the method of the conventional wind power generation system and there is a problem that it is difficult to ensure the commercial system linkage conditions of power generation systems using distributed power sources that have been recently strengthened.

The present invention is to solve the above problems of the prior art, by using the reactive power of the power conversion unit provided for each generator, performing voltage control at the grid connection point ultimately for stable system operation of the power generation system Its purpose is to provide a voltage control method for a power generation system.

According to one aspect of the present invention, a power control device in a power generation system is provided.

An apparatus for controlling voltage in a power generation system including a generator and a power converter converting power produced by being connected to the generator according to an embodiment of the present invention is measured at a grid connection point of a power system network connected to the power converter. A voltage comparator for calculating an error voltage using the measured voltage and the reference voltage of the grid connection point, a controller for receiving the error voltage and calculating a first reactive power value, and the first reactive power value and the power converter. The apparatus may include a driver configured to calculate a reactive power reference value using the measured second reactive power value and to control the power converter in accordance with the calculated reactive power reference value.

According to another aspect of the present invention, a power control method in a power generation system is provided.

In a power generation system including a generator and a power converter converting power produced by connecting to the generator according to an embodiment of the present invention, a power control method includes a measurement measured at a grid connection point of a power system network connected to the power converter; Calculating an error voltage by comparing a voltage with a reference voltage of the grid connection point, a controller configured to calculate a first reactive power value by receiving the error voltage, and a first reactive power value measured by the power converter. Calculating a reactive power reference value using a reactive power value and controlling the power converter according to the calculated reactive power reference value.

Therefore, the present invention can prevent the voltage drop and the voltage rise due to the system accident by using the reactive power of the power conversion unit and further prevent the generators from being blocked at the same time.

In addition, the present invention can implement a reliable, efficient power generation system without additional equipment or processes to obtain stable power quality and reliability of system operation.

Details of the above objects and technical configurations and the effects thereof according to the present invention will be more clearly understood by the following detailed description with reference to the drawings showing preferred embodiments of the present invention.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all transformations, equivalents, and substitutes included in the spirit and technical scope of the present invention. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a power generation system according to an embodiment of the present invention, Figure 2 is a block diagram of a voltage control device according to an embodiment of the present invention.

1 and 2, the voltage control system of the power generation system according to the present invention is connected to a plurality of generators 10, generator 10, a plurality of power converter 20 for converting the power provided, The error voltage ev is calculated at the grid connection point of the power system network 30 and the power system network 30 connected to the power converter 20, and the control signal is supplied to the power converter 20 by using the power voltage. The voltage control device 50 is included.

Hereinafter, the voltage control system according to the present invention is preferably a power control system of the wind power generation system, in addition, it is apparent to those skilled in the art that can be applied to the power generation system using a natural force.

The voltage control device 50 includes a voltage comparator 40 for calculating an error voltage ev at a grid connection point of the power system network 30, a controller 60 for calculating a reactive power value Qp, and power conversion. And a driver 70 for supplying a control signal to the unit 20.

More specifically, the generator 10 according to the present invention is provided with n pieces (n is a natural number) as an electric generator for generating electric power. The generator may be a squirrel cage generator or a permanent magnet generator, and any generator that can be used as a generator may be applied to those skilled in the art.

Next, the power conversion unit 20 is provided for each generator 10, is a power conversion device that can stably supply the power generated by the generator (10).

The power converter 20 may include a converter (not shown) for converting AC into DC and an inverter (not shown) for converting DC into AC.

The power converter 20 may convert unstable power generated by the generator 10 into a constant output by using a converter and an inverter to obtain more reliable power quality.

Next, the power system network 30 is a means for supplying power from the generator 10 to the commercial power system (not shown) for the power supplied through the power converter 20 to be substantially supplied to the user.

The power system network 30 performs voltage control of the grid connection point by using the reactive power Qp, j provided from the power converter 20.

The voltage comparator 40 has a voltage difference error based on a difference between the measured voltage Vm measured at the grid connection point of the power system network 30 and the reference voltage Vs at the grid connection point of the power system network 30. The voltage ev is calculated. Here, the reference voltage Vs may be preset by the operator as a voltage for stably supplying power.

The controller 60 performs linear control on the error voltage ev to prevent the controller 61 and the cumulative saturation of the controller 61 which calculates the reactive power value Qp necessary for voltage control of the grid connection point. Accumulation preventer 62 is included.

The driver 70 divides the reactive power value Qp calculated by the controller 61 of the controller 60 into the driver 72, and the reactive power value Qp provided by the distributor 71. ) And a driver for calculating the reactive power reference value (Q ^set _{j, s} ) by performing comparison of the reactive power values (Q ^max _{j, c} ) measured for each of the power converters 20 and Q ^set _{j ,} and a drive comparator for calculating a deviation signal es based on a difference between the sum of the sums and the reactive power value Qp output from the divider.

Such a power generation system using the voltage control according to the present invention will be more clearly understood by the following detailed description with reference to FIGS. 3 to 5 showing preferred embodiments.

3 is a diagram illustrating a controller and a driver of a power generation system using voltage control according to an embodiment of the present invention.

Referring to FIG. 3, the controller 60 of the present invention includes a controller 61 and a cumulative preventer 62.

First, the controller 61 may be any one of a proportional integral (PI) controller, a proportional differential (PI) controller, or a proportional integral differential (PID) controller, which is a controller for feeding back and controlling an output value. As shown in FIG. 3, a proportional integral derivative controller having all the advantages of the proportional controller P, the integral controller I for improving the steady state response, and the differential controller D for improving the response speed may be configured. .

Next, the cumulative preventer 62 controls the controller 61 of the controller 60 based on the deviation signal es fed back through the driver 70.

The accumulation preventer 62 prevents accumulation due to a difference between an input terminal and an output terminal during operation of a controller including an integral controller I, such as a proportional differential (PI) controller or a proportional integral differential (PID) controller. This cumulative phenomenon reduces the transient response characteristics and the steady state response characteristics, thereby degrading the performance of the controller 61.

Therefore, in the present invention, a cumulative preventer 62 of an anti-windup technique may be additionally configured to provide a cumulative preventive function, thereby preventing malfunction of the controller 61 including an integral controller.

The accumulator preventer 62 is a setpoint limiting method for preventing the output of the controller 61 from exceeding a setpoint change amount, an incremental algorithm method for controlling the operation of the controller 61 by calculating an increment of a control signal at every sampling moment, and a controller ( The cumulative phenomenon of the controller 61 can be prevented by using any one of a tracking type method of controlling the integrator by feedbacking the difference between the output of the driver 61 and the output of the driver 71.

Hereinafter, the accumulation preventer 62 will be described in more detail.

First, the controller 61 tracks the tracking time constant (kt) to the deviation signal (es) calculated by comparing the sum of the reactive power value Qp output distributed by the divider 71 and the sum of the driver 72 output. Multiply by) to get input.

Therefore, the accumulation preventer 62 does not affect the normal operation at all in the range where the saturation of the driving unit 70 does not occur since the deviation signal es is zero when there is no saturation of the driving unit 70.

On the other hand, when the driving unit 70 is saturated, the accumulation preventer 62 generates a deviation signal es ≠ 0, and prevents accumulation by reducing the input of the integral controller I of the controller 61 by the feedback path. can do.

The drive unit 70 of the present invention includes a distributor 71, a driver 72 and a drive comparator 73 is configured.

First, the distributor 71 distributes a reactive power value Qp, which is an output of the controller 60, and provides a control signal to the power converter 20, which is connected to each of the plurality of generators 10, and provides a control signal. To supply.

Next, the driver 72 performs a process by comparing the measured reactive power value Q ^max _{j, c} of the power converter 20 with the reactive power value Qp provided by the divider 71, respectively. The reactive power reference values Q ^set _{j and s} corresponding to the power converter 20 are calculated.

The driver 72 provides a control signal for each power converter 20 to the calculated reactive power reference value Q ^set _{j, s} . Here, the reactive power reference value Q ^set _{j, s} calculates a margin of reactive power in preparation for the effective power for each power converter 20, and satisfies Equation 1 below.

<Equation 1>

Here, the Q ^set _{j, s} is a reactive power reference value that is a control signal provided to the j-th power converter 20 by the driver 72 of the driver 70,

Q ^max _{j, c} is a measured reactive power value of the j-th power converter 20,

은 1부터 j까지의 전력변환부(20)의 측정된 무효 전력 값의 합이며, 상기 Qp는 제어부(60)에 의해 출력되는 무효 전력 값이다. remind

Is the sum of the measured reactive power values of the power converter 20 from 1 to j, and Qp is the reactive power value output by the controller 60.

In the above Equation 1, min {a, b} means to take a smaller value of a and b, and the subscript j is 1,2,3, ..., n as the generator 10 and the generator ( 10 is a natural number indicating the number of power conversion units 20 provided, and the superscript max means a maximum value.

Next, the drive comparator 73 has a sum of the reactive power value Qp which is the output of the controller 60 distributed by the divider 71 and the reactive power reference value Q ^set _{j, s} which is the output of the driver 72. ), The deviation signal es is calculated, and the feedback signal is fed back to the cumulative preventer 62 of the controller 60.

The voltage control method of the power generation system according to the present invention having the above configuration will be described in more detail with reference to FIG. 4.

4 is a flowchart illustrating a voltage control method of a power generation system according to an exemplary embodiment of the present invention, and FIG. 5 is a diagram illustrating a maximum reactive power value Q ^max _j, which is measured by a power converter according to an exemplary embodiment of the present invention _{. It} is a figure for demonstrating _c ).

In step S410, the voltage comparator 40 measures the voltage at a grid connection point of the power system network 30 that receives power from the power converter 20 connected to the plurality of generators 10 to measure the measured voltage Vm. Get

In operation S420, the voltage comparator 40 calculates an error voltage ev in the voltage comparator 50 based on the difference between the measured measurement voltage Vm and the reference voltage Vs of the grid connection point.

In step S430, the controller 60 receives the error voltage ev calculated from the voltage comparator 40, and performs the preceding control with the controller 61 provided in the controller 60 to calculate the reactive power value Qp. do.

In this case, the error voltage ev is input to the proportional controller P to multiply the error voltage ev by the proportional gain kp.

In addition, the error voltage ev is input to the integral controller I of the controller 61 to integrate the error voltage ev and multiply the integral gain ki.

At the same time, the measured voltage (Vm) measured at the grid connection point of the power system network 30 is input to the differential controller (D) to be differentiated, and the process of multiplying the differential gain (kd).

Subsequently, the proportional controller P, the integral controller I, and the derivative controller D add up the respective output signals to calculate the reactive power value Qp.

In operation S440, the driving unit 70 receives the reactive power value Qp calculated from the controller 60, and powers the input reactive power value Qp to be connected to the plurality of generators 10 through the divider 71. The driver 20 supplies a control signal to the converter 20.

The driver 72 uses the reactive power value Q ^max _{j, c} measured in the operating range (FIG. 5) of the power converter 20 and the reactive power value Qp distributed and provided by the divider 71. By performing Equation 1, the reactive power reference values Q ^set _{j and s} are calculated for each power converter 20.

Here, referring to FIG. 5, P is the maximum effective power of the power converter 20, and P _{j and C} are measured power of the power converter 20.

In addition, + Q _max is the maximum reactive power that can be supplied by the power converter 20, -Q _max is the maximum reactive power that can be absorbed by the power converter 20, -Q ^max _{j , c} to + Q ^{Up to max} _{j and c} are reactive power values Q _{maxj and c} measured corresponding to the active power P _{j and C of} the power converter 20.

That is, the reactive power reference values Q ^set _{j and s for} each power converter 20 used for linear distribution of the driver 70 are effective power for each power converter 20 as shown in FIG. 5. Obtain the measured reactive power value (Q ^max _{j, c} ) in preparation for, but satisfies Equation 1.

In this case, Equation 1 described above is the same as described in the detailed description of the invention to avoid overlapping the detailed description.

In operation S450, the driver 72 controls the power converter 20 using the calculated reactive power reference value Q ^set _{j, s} . The power converter 20 may control the connected generator 10 to stably and easily control the driving of the entire power generation system according to the present invention.

Subsequently, in step S460, the driving comparator 73 determines the deviation signal es based on the difference between the sum of the reactive power reference values Q ^set _{j and s} and the sum of the reactive power values Qp distributed through the divider 71. To calculate.

Subsequently, in step S470, the accumulation preventer 62 uses the sum of the signal and the error voltage ev output by multiplying the tracking time constant (kt) by the tracking time constant (kt) and the integral controller of the controller 61. It is entered as (I).

Accumulation preventer 62 can reduce the integration controller (I) input by the feedback path to prevent the cumulative phenomenon of the controller (61).

Therefore, since the deviation signal es is zero when there is no saturation of the driving unit 70, the cumulative preventer 62 does not affect the normal operation at all in a range in which the saturation of the driving unit does not occur.

On the other hand, when the driving unit 70 is saturated, the accumulation preventer 62 reduces the input of the integral controller I by the feedback path through the kt which is the accumulation preventer 62 when the deviation signal es ≠ 0 occurs. Accumulation can be prevented.

As a result, the present invention can prevent the voltage drop, the voltage rise due to the system accident of the power generation system using grid connection point voltage control, and further prevent the generator from being blocked at the same time.

In particular, the present invention is not only applicable to the structure or scale of the power generation complex composed of the generators 10 having the power conversion unit 20, but also can pursue versatility.

Embodiments of the invention may include computer readable media containing program instructions for performing various computer-implemented operations. The computer readable medium may include program instructions, local data files, local data structures, or the like, alone or in combination. The media may be those specially designed and constructed for the purposes of the present invention, or they may be of the kind well-known and available to those having skill in the computer software arts.

The detailed description with reference to the drawings is not limited to the above-described embodiments, and various changes and modifications may be made by those skilled in the art without departing from the spirit of the present invention.

1 is a block diagram of a power generation system according to an embodiment of the present invention.

2 is a block diagram of a voltage control device according to an embodiment of the present invention.

3 is a view for explaining a control unit and a driving unit of a power generation system using voltage control according to an embodiment of the present invention.

4 is a flowchart illustrating a voltage control method of a power generation system according to an embodiment of the present invention.

5 is a view for explaining the maximum reactive power value (Q ^max _{j, c} ) measured by the power converter according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

 10: generator 20: power conversion unit

30: power system network 40: voltage comparator

50: voltage controller 60: control unit

61: controller 62: cumulative preventer

70: drive unit 71: distributor

72: drive 73: drive comparator

Claims (10)

An apparatus for controlling a voltage in a power generation system including a power generator for converting power generated by being connected to a generator and a generator, A voltage comparator for calculating an error voltage using a measured voltage measured at a grid link point of the power grid connected to the power converter and a reference voltage of the grid link point; A controller configured to receive the error voltage and calculate a first reactive power value; And And a driver configured to calculate a reactive power reference value using the first reactive power value and the second reactive power value measured by the power converter, and to control the power converter according to the calculated reactive power reference value. Voltage control device. The method of claim 1, A drive comparator configured to calculate a deviation signal using the sum of the first reactive power value and the calculated reactive power reference value; And And a cumulative controller for preventing accumulation of the controller by using the calculated deviation signal and the error voltage. The method of claim 2, The accumulation controller is characterized in that for using the calculated tracking time constant (kt) of the deviation signal. The method of claim 1, The controller is any one of a proportional integral (PI) controller, a proportional differential (PI) controller and a proportional integral differential (PID) controller for performing a linear control by receiving the error voltage (ev). The method of claim 1 The generator is j (j is a natural number), j power converters are respectively connected to the generator, the reactive power reference value is a margin of reactive power compared to the active power of the power converter calculated by the following equation Voltage control device. <Equation 1>

Here, the Q ^set _{j, s} is a reactive power reference value which is a control signal provided to the j-th power converter in the distribution unit, Q ^max _{j, c} is the measured second reactive power value of the j-th power converter, remind

Is the sum of the measured reactive power values of the power converter from 1 to j, Qp is a first reactive power value calculated by the controller, In Equation 1, min {a, b} means taking a smaller value of a and b, and subscript j is 1,2,3, ..., n, which is a power conversion connected to the generator and the generator. Natural number representing the number of negatives, superscript max means the maximum. The method of claim 1, The controller is a proportional integral differential (PID) controller for performing linear control by receiving the error voltage (ev), The proportional controller (P) of the proportional integral derivative (PID) controller outputs a first output value by inputting the error voltage and multiplying the error voltage by a proportional gain, The integral controller I of the proportional integral derivative (PID) controller inputs the error voltage to integrate the error voltage and multiplies the integral gain to output a second output value. The derivative controller (D) of the proportional integral derivative (PID) controller outputs a third output value by inputting the measured voltage and differentiating the error voltage to multiply the derivative gain (kd), And the first reactive power value is calculated using the first output value, the second output value, and the third output value. In the method for controlling the voltage in a power generation system comprising a generator and a power converter connected to the generator to convert the power produced, Calculating an error voltage using a measured voltage measured at a grid link point of a power grid connected to the power converter and a reference voltage of the grid link point; Calculating a first reactive power value by receiving the error voltage; Calculating a reactive power reference value using the first reactive power value and the second reactive power value measured by the power converter; And And controlling the power converter in accordance with the calculated reactive power reference value. The method of claim 7, wherein Calculating a deviation signal using the sum of the first reactive power value and the calculated reactive power reference value; And And preventing the accumulation of the controller by using the calculated deviation signal and the error voltage. The method of claim 7, wherein The method of claim 1, The controller is a proportional integral differential (PID) controller for performing linear control by receiving the error voltage (ev), A proportional controller (P) of the proportional integral derivative (PID) controller outputs a first output value by inputting the error voltage and multiplying the error voltage by a proportional gain; An integral controller (I) of the proportional integral derivative (PID) controller inputting the error voltage to integrate the error voltage and multiply the integral gain to output a second output value; A derivative controller (D) of the proportional integral derivative (PID) controller outputs a third output value by inputting the measured voltage and differentiating the error voltage to multiply the derivative gain (kd); And And calculating the first reactive power value using the first output value, the second output value, and the third output value. The method of claim 7, The generator is j (j is a natural number), j power converters are respectively connected to the generator, the reactive power reference value is a margin of reactive power compared to the active power of the power converter calculated by the following equation Voltage control method. <Equation 1>

Here, the Q ^set _{j, s} is a reactive power reference value that is a control signal provided to the j-th power converter in the driver, Q ^max _{j, c} is the measured second reactive power value of the j-th power converter, remind

Is the sum of the measured reactive power values of the power converter from 1 to j, Qp is a first reactive power value calculated by the controller, In Equation 1, min {a, b} means taking a smaller value of a and b, and subscript j is 1,2,3, ..., n, which is a power conversion connected to the generator and the generator. Natural number meaning the number of negative numbers, superscript max means the maximum value.

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