KR101249939B1 - Back to back converter comprising of edlc and wind power generation system using thereof - Google Patents

Abstract

PURPOSE: A back to back converter including an EDLC and a wind power generation system applying the same are provided to reduce an amount of power loss by omitting a power conversion apparatus such as a DC/DC converter and an inverter. CONSTITUTION: A generator side converter(220) converts poly-phase AC power to DC power. An EDLC unit(230) stores all or a part of the DC power converted in the generator side converter. The EDLC unit outputs DC power in a predetermined size. A system side converter(240) converts the DC power transferred from the EDLC unit to AC power. A control unit(250) controls the system side converter using system side standard active power and system side standard reactive power. [Reference numerals] (210) Permanent magnet synchronizing machine; (220) Generator side converter; (230) EDLC unit; (240) System side converter; (250) Control unit;

Description

Back to back converter including of EDLC and wind power generation system using

The present invention relates to a back-to-back converter including an electric double layer capacitor (EDLC) and a wind power generation system using the same. More specifically, in a wind power generation system using EDLC as an energy storage device, a back-to-back converter for simplifying the entire system by placing an EDLC on a DC link in a back-to-back converter and a wind power generation system using the same will be.

Wind power is a pollution-free energy source in the natural state and is the most economical energy source among alternative energy sources. The wind power generation system refers to a power generation system that converts wind energy into mechanical energy using various types of windmills, and generates electric power by driving a generator with the mechanical energy. Since the wind power generation system uses the wind power of infinite clean energy as the power source, it is a pollution-free power generation method without problems such as heat pollution, air pollution, and radioactive leakage due to heat generation, unlike the existing power generation method using fossil fuel or uranium. As a result, wind power generation is currently recognized as the most promising alternative energy source. In addition, the use of wind power generation systems is increasing worldwide because the structure or installation is simple, easy to operate and manage, unmanned and automated operation is possible.

However, the wind energy used in the wind power generation system has a lot of variability depending on the weather conditions. Larger wind speed variations can cause frequency fluctuations in the power generated by wind turbines. In order to link the wind power generation system having this problem to the existing power grid, a back-to-back converter composed of two sets of voltage source converters having a shared DC stage is required.

The back-to-back converter consists of a generator-side converter, a DC link capacitor, and a grid-side converter. Generator-side converter serves to control the active power generated through the power generation system, DC link capacitor is disposed between the generator-side converter and the grid-side converter to apply a constant DC voltage, the grid-side converter is DC The DC voltage across the link capacitor is used to convert it into AC power with a constant frequency component appropriate for the system.

1 is a view showing a conventional wind power generation system having a separate energy storage unit.

As shown in Figure 1, in the conventional wind power generation system, the permanent magnet synchronous generator is connected to the back-to-back converter to transfer the power generated from the wind to the grid, the separate energy storage unit charge / discharge process, It is connected with a DC / DC converter and inverter to carry out grid linkage. At this time, there was a power loss by connecting a separate DC / DC converter and an inverter which is a power conversion device for the connection and operation of the separate energy storage unit.

Korea Patent Publication No. 10-2010-001594

The present invention has been made to solve the above problems, to provide a back-to-back converter and a wind power system using the same that can simplify the configuration of the wind power system using the EDLC as an energy storage device.

In addition, through the simplification of the wind power generation system, there is no need for a separate power converter to provide a back-to-back converter and a wind power generation system using the same to reduce the amount of power loss.

A back-to-back converter according to an aspect of the present invention is connected to a power generation system, the back-to-back converter for converting the multi-phase AC power generated by the power generation system to AC power having a constant frequency component, generated in the power generation system A generator-side converter for converting the multi-phase AC power into DC power; An EDLC unit which stores all or part of the DC power converted by the generator-side converter and outputs DC power with reduced variability; And a grid-side converter for converting the DC power transferred from the EDLC unit into AC power.

In this case, the generator may further include a control unit for controlling the generator-side converter by using the generator-side reference active current and the generator-side reference reactive current.

The grid-side converter may further include a controller using the grid-side reference effective power and the grid-side reference reactive power obtained through the grid-side reference power delivered to the grid-side converter.

In this case, the grid-side reference power delivered to the grid-side converter may be a power obtained by applying a low pass filter (LPF) to the power generated by the power generation system.

Alternatively, the grid-side reference power delivered to the grid-side converter may be power in which power generated in the power generation system is limited by the state of charge of the EDLC unit.

According to another aspect of the present invention, there is provided a wind power generation system including at least three phase permanent magnet synchronizers for converting rotational force into electrical energy; A generator-side converter connected to the permanent magnet synchronous to convert the multi-phase AC power generated by the permanent magnet synchronous to DC power; An EDLC unit which stores all or part of the DC power converted by the generator-side converter and outputs a DC current with reduced variability; And a grid-side converter for converting the DC power transferred from the EDLC unit into AC power.

At this time, the generator side reference active current and the generator side reference reactive current are controlled, and the system side reference effective power and system side reference reactive power obtained through the grid side reference power delivered to the grid side converter are used. And a control unit for controlling the grid-side converter, wherein the grid-side reference power delivered to the grid-side converter includes power generated by the power generation system passing through a low pass filter (LPF) and charged by the EDLC unit. May be limited power.

In the back-to-back converter and the wind power generation system using the same, the EDLC is located at the DC link in the back-to-back converter, so that a power converter such as a DC / DC converter and an inverter is not required separately, thereby reducing power loss. This has the effect of reducing the overall system cost.

1 is a view showing a conventional wind power generation system having a separate energy storage;
2 illustrates a back-to-back converter according to an embodiment of the present invention;
3 is a control block diagram of a generator-side converter according to an embodiment of the present invention;
4 is a control block diagram of a grid-side converter according to an embodiment of the present invention;
5 is a view showing a wind power generation system according to another embodiment of the present invention;
6 is a control block diagram of a generator-side converter in a wind power generation system according to still another embodiment of the present invention; and
7 is a control block diagram of a grid-side converter in a wind power generation system according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, when it is determined that a detailed description of related known functions or configurations may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

2 is a diagram illustrating a back-to-back converter according to an exemplary embodiment of the present invention. As shown in FIG. 2, a back-to-back converter according to an exemplary embodiment of the present invention is connected to a power generation system 10 so that the multi-phase AC power generated by the power generation system 10 has a constant frequency component. A back-to-back converter for converting AC power, comprising: a generator-side converter (20) for converting multi-phase AC power generated in the power generation system (10) into DC power; An EDLC unit 30 for storing all or part of the DC power converted by the generator-side converter 20 and outputting DC power with reduced variability; A grid-side converter 40 for converting DC power transferred from the EDLC unit 30 into AC power; Control unit 50 for controlling the operation of the generator-side converter 20 and the grid-side converter 40.

The generator-side converter 20 converts the polyphase AC power generated by the power generation system 10 into DC power. In one embodiment applicable to the present invention, the power generation system 10 may be a wind power generation system having a permanent magnet synchronous generator that is a multi-phase alternating current generator of at least three phases. In the case of a wind power generation system, electrical energy is produced using wind energy, and thus has a lot of variability according to weather conditions. In particular, when the degree of change of the wind power in the location where the wind power generation system is installed becomes large, the amount of power generated in the wind power generation system has great variability. This causes the frequency fluctuation problem of the power generated in the wind power generation system. In order to solve this problem, the generator-side converter 20 converts the AC power generated in the power generation system 10 into DC power before performing the task of making the variable power constant.

The controller 50 performs a task of maximizing the effective power of the power generated by the power generation system 10 and minimizing the reactive power, and the generator-side reference effective current i _{qr _ ref} and the generator obtained through the operation. The generator-side converter 20 is controlled to obtain the maximum power by using the side reference reactive current i _{dr _ ref} . In more detail, the controller 50 may obtain the generator-side reference power amount P _max by Equation 1 below.

(R: blade radius, w _opt optimal angular velocity, ρ: air density, C _pmax : wind turbine maximum power factor, λ _opt : optimal peripheral speed ratio)

The controller 50 controls the active power of the power generation system 10 to be maximum through the generator side reference effective current i _{qr _ ref} . In addition, the control unit is controlled to minimize the reactive power of the power generation system 10 through the generator side reference reactive current i _{dr _ ref} . The generator side reference effective current i _{qr _ ref} and the generator side reference reactive current i _{dr _ ref} are controlled by a PI (Proportional Integral) controller which is a linear integral controller, and the generator side reference voltage obtained through the PI controller. The generator controls the generator-side converter 20 through a pulse width modulation (PWM) generator. Hereinafter, the control algorithm of the generator-side converter 20 will be described in detail with reference to FIG. 3.

3 is a control block diagram of the generator-side converter 20 according to an embodiment of the present invention. As shown in FIG. 3, in a preferred embodiment of the present invention, the controller 50 is an operation for maximizing the effective power of the power generated by the power generation system 10 and minimizing the reactive power, MPPT (Maximum Power Point Tracking). Control can be performed. In the case of the wind power generation system, it is easy to become turbulent, and the wind direction and the wind speed change at intervals of several tens of seconds, so that the MPPT control can be performed to maximize the energy of the wind. Generator-side reference power that can be obtained through the MPPT control according to an embodiment applicable to the present invention is shown in Equation 1 above.

The controller 50 may obtain the generator side of the reference power (P _e ^*) and the active power (P _e) applying a PI controller to (i _{qr _ ref),} the generator side based on the effective current for the acquired through the MPPT control. In addition, the controller 50 may obtain a generator side reference reactive current (i _{dr _ ref} ) by applying a PI controller to the generator side reference reactive power (Q _ref ^* ) and the stator reactive power (Q _stator ).

Here, it is known to those skilled in the art in view of the technical spirit of the present invention that the PI controller can be variously configured using a known technique to perform the above object.

The controller 50 is a value obtained by applying the PI controller to the generator side reference effective current (i _{qr _ ref} ) and the generator side active current (i _qr ), the generator side set voltage (v _qr ), and ω _r * L _dr * i _dr The reference effective voltage value of the generator side can be calculated by using. In this case, ω _r may be preset as a generator side frequency or may be input from the outside. In addition, L _dr is a d-axis inductance value, which can be obtained from the induction coefficient of the generator-side reactor.

In addition, the controller 50 uses the PI controller applied to the generator side reference reactive current i _{dr _ ref} and the generator side reactive current i _dr , and the generator side reference invalid using ω _r * L _qr * i _qr . The voltage value can be calculated. In this case, ω _r may be preset as a generator side frequency or may be input from the outside. In addition, L _qr is a q-axis inductance value, which can be obtained from the induction coefficient of the generator-side reactor.

The controller 50 controls the generator-side converter 20 through a PWM generator using the generator-side reference effective voltage value and the generator-side reference reactive voltage value obtained through the above method.

EDLC unit 30 is located in the DC link between the generator-side converter 20 and the grid-side converter 40. The EDLC unit 30 applicable to the present invention has a structure in which an electrolyte is placed between two collector electrodes of a porous conductor having a very large surface area. When the electrolyte is immersed in the conductor of the electrode rods, an inner layer of molecules pressed by the conductor is formed on the interface between the conductors, and an outer layer (diffusion) is formed on the outer side (electrolyte side) in which the diffusion is caused by charge charge. . The EDLC unit 30 is almost completely insulated because no current flows in a range in which the externally applied voltage is lower than the voltage at which electrolysis occurs in the electrolyte. Thus, two capacitors having positive and negative poles in series are used as an insulating film. The structure is connected, and the electrolyte solution is weakly covered therebetween.

The insulating film is naturally obtained, and the film thickness is as thin as one molecule, so that a large capacitance capacitor can be manufactured. The EDLC unit 30 has a very fast charge / discharge rate, and the energy storage capability is also superior to other energy storage devices.

The EDLC unit 30 is freely charged / discharged according to the power condition of the DC link. When the capacity of the EDLC unit 30 reaches a limit, the supply and demand relationship with the system is performed to maintain the power balance of the entire system. .

The grid-side converter 40 converts the DC power transferred from the EDLC unit 30 to AC power. More specifically, the grid-side converter 40 converts the output voltage of the EDLC unit 30 to an AC voltage usable in the grid. In this case, the output voltage of the grid-side converter 40 may be an AC voltage having a predetermined magnitude and a predetermined frequency. In addition, harmonics may be removed from the output voltage by a low pass filter (LPF) as necessary. In one preferred embodiment of the present invention, the output voltage may be an AC voltage having a frequency of 60 Hz.

The controller 50 obtains the grid-side reference power amount (P _u ^* ) from the power delivered to the grid-side converter 40 through the EDLC unit 30, through which the grid-side reference effective current (i _{q _ ref} ) and the grid Obtain the side reference reactive current i _{d_ref} . The controller 50 controls the grid-side converter 40 by using the grid-side reference active current and the grid-side reference reactive current. In more detail, the variation of the generator output is stabilized through the grid-side reference effective current (i _{q _ ref} ) obtained through the grid-side reference power amount (P _u ^* ), and the active power for power transmission is controlled. In addition, the grid-side reference reactive current (i _{d _ ref} ) stabilizes the generator output variation, and controls the reactive power for power transfer. The grid-side reference effective current i _{q _ ref} and the grid-side reference reactive current i _{d _ ref} are controlled by a PI controller, and the grid-side reference voltage obtained through the PI controller is a pulse width modulation (PWM) generator. The grid side converter 40 is controlled via the control. Hereinafter, the control algorithm of the grid-side converter 40 will be described in detail with reference to FIG. 4.

4 is a control block diagram of the grid-side converter 40 according to an embodiment of the present invention. The controller 50 controls the grid-side converter 40 through the control algorithm of FIG. 4 to stabilize the output variation of the wind power generation system. As shown in FIG. 4, in a preferred embodiment of the present invention, the grid-side converter 40 uses LPF for the power _Pe generated by the power generation system 10 to convert the power _Pe . Remove high frequency components. In addition, in order to make the direction of the power constant according to the direction of the power _Pe , a scale conversion of −1 may be performed.

Then, the voltage and current of the power is limited according to the state of charge of the EDLC unit 30 located in the DC link of the back-to-back converter. More specifically, the EDLC unit 30 has a much larger capacity than the capacitor and the electrolyte capacitor, and requires a short time when charging, but when dissipating energy, it may emit energy for a longer time than when charging. Can be. By using such a characteristic, the EDLC unit 30 may adjust the amount of power supplied to the actual system, even if the wind speed changes rapidly and the amount of power produced through the wind power generation system increases rapidly.

When the state of charge of the EDLC unit 30 is charged above the threshold value, the amount of power supplied through the generator-side converter 20 is not limited, and may be entirely transmitted to the grid-side converter 40. More specifically, in order to prevent overcharging of the EDLC unit 30, when the EDLC unit 30 is charged for a predetermined time or more, the amount of power delivered to the grid-side converter 40 is limited by the EDLC unit 30. It may not be. Those skilled in the art to which the present invention pertains implement a modified form of the reference charge state of the EDLC unit 30 to prevent overcharging of the EDLC unit 30 without departing from the essential characteristics of the present invention. It can be understood.

In an applicable embodiment of the present invention, when the state of charge of the EDLC unit 30 is less than the threshold value, part of the power supplied from the generator-side converter 20 is used to recharge the EDLC unit 30 to supply to the actual system. The amount of power to be used can be limited by a certain amount. Those skilled in the art to which the present invention pertains can implement the modified ratio within a range that does not deviate from the essential characteristics of the present invention in the ratio of the amount of power supplied through the generator-side converter 20 You will understand.

In this case, the state of charge of the EDLC unit 30 may be measured by the controller 50.

The controller 50 obtains the grid-side reference effective current (i _{q _ ref} ) by applying a PI controller to the grid-side reference power amount (P _u ^* ) and the grid-side effective power amount (P _u ) obtained through the above method. Can be. In addition, the controller 50 may apply the PI controller to the grid-side reference reactive power Q _ref and the reactive power Q to obtain the grid-side reference reactive current i _{d _ ref} .

Here, it is known to those skilled in the art in view of the technical spirit of the present invention that the PI controller can be variously configured using a known technique to perform the above object.

The control unit 50 calculates the values obtained by applying the PI controller to the grid-side reference active current (i _{q _ ref} ) and the grid-side active current (i _q ), the grid-side set voltage (v _qs ), and ω * L _d * i _d . The system-side reference effective voltage value can be calculated. In this case, ω may be preset as the system side frequency or may be input from the outside. L _d is the d-axis inductance value and can be obtained from the induction coefficient of the system-side reactor.

In addition, the controller 50 uses the system side reference reactive current (i _{d _ ref} ) and the system side reactive current (i _d ) by applying a PI controller and the system side reference reactive voltage using ω * L _q * i _q . The value can be calculated. In this case, ω may be preset as the system side frequency or may be input from the outside. In addition, L _q is a q-axis inductance value, which can be obtained from the induction coefficient of the system-side reactor.

The controller 50 controls the grid-side converter 40 via a PWM generator using the grid-side reference effective voltage value and the grid-side reference reactive voltage obtained through the above method.

5 is a view showing a wind power generation system according to another embodiment of the present invention.

As shown in FIG. 5, the wind power generation system according to an exemplary embodiment of the present invention includes at least three phase permanent magnet synchronizer 210 for converting rotational force into electrical energy; A generator-side converter 220 connected to the permanent magnet synchronizer 210 and converting the multi-phase AC power generated by the permanent magnet synchronizer 210 into DC power; An EDLC unit 230 for storing all or part of the DC power converted by the generator-side converter 220 and outputting a variably relaxed DC current; A grid-side converter 240 for converting DC power transferred from the EDLC unit 230 into AC power; And a controller 250 that controls the operation of the generator-side converter 220 and the grid-side converter 240.

Wind power generation system is a system for producing electrical energy using wind energy. In the wind power generation system, the blade (not shown) has a rotational force by the wind energy, the permanent magnet synchronizer 210 converts the rotational force of the blade into electrical energy. Therefore, the output of the permanent magnet synchronizer 210 is dependent on the wind. Therefore, the amount of power generated by the permanent magnet synchronizer 210 is not constant. The variable amount of power is converted into AC suitable for a system by a back-to-back converter composed of a generator-side converter 220, an EDLC unit 230, and a grid-side converter 240.

The generator-side converter 220 converts the multi-phase AC power generated by the permanent magnet synchronizer 210 into DC power. In one embodiment applicable to the present invention, the permanent magnet synchronizer 210 may be a permanent magnet synchronous generator, which is a multiphase alternator of at least three phases. In the case of a wind power generation system, electrical energy is produced using wind energy, and thus has a lot of variability according to weather conditions. In particular, when the degree of change of the wind power in the location where the wind power generation system is installed becomes large, the amount of power generated in the wind power generation system has great variability. This causes the frequency fluctuation problem of the power generated in the wind power generation system. In order to solve this problem, the generator-side converter 220 converts the AC power generated in the power generation system into DC power before performing the task of making the variable power constant.

The control unit 250 performs a task of maximizing the effective power of the power generated by the permanent magnet synchronizer 210 and minimizing the reactive power, and the generator-side reference effective current i _{qr _ ref} obtained through the operation and The generator-side converter 220 is controlled to obtain the maximum power using the generator-side reference reactive current i _{dr _ ref} . In more detail, the controller 250 may obtain a generator-side reference power amount P _max by Equation 2 below.

(R: blade radius, ω _opt optimal angular velocity, ρ: air density, C _pmax : wind turbine maximum power factor, λ _opt : optimal peripheral speed ratio)

The controller 250 controls the active power of the permanent magnet synchronizer 210 to be maximum through the generator side reference effective current i _{qr _ ref} . In addition, the control unit is controlled to minimize the reactive power of the permanent magnet synchronizer 210 through the generator side reference reactive current i _{dr _ ref} . The generator side reference effective current i _{qr _ ref} and the generator side reference reactive current i _{dr _ ref} are controlled by a PI (Proportional Integral) controller which is a linear integral controller, and the generator side reference voltage obtained through the PI controller. The generator controls the generator-side converter 220 through a pulse width modulation (PWM) generator. Hereinafter, the control algorithm of the generator-side converter 220 will be described in detail with reference to FIG. 6.

6 is a control block diagram of a generator-side converter 220 according to an embodiment of the present invention. As shown in FIG. 6, in one preferred embodiment of the present invention, the control unit 250 is an operation of maximizing the effective power of the power generated by the permanent magnet synchronizer 210 and minimizing the reactive power, MPPT (Maximum Power Point). Tracking) control can be performed. In the case of the wind power generation system, it is easy to become turbulent, and the wind direction and the wind speed change at intervals of several tens of seconds, so that the MPPT control can be performed to maximize the energy of the wind. Generator-side reference power amount obtained through the MPPT control according to an embodiment applicable to the present invention is shown in Equation 2.

Controller 250 may obtain the generator side of the reference power (P _e ^*) and the active power (P _e) applying a PI controller to (i _{qr _ ref),} the generator side based on the effective current for the acquired through the MPPT control. In addition, the controller 250 may obtain a generator side reference reactive current (i _{dr _ ref} ) by applying a PI controller to the generator side reference reactive power (Q _ref ^* ) and the stator reactive power (Q _stator ).

Here, it is known to those skilled in the art in view of the technical spirit of the present invention that the PI controller can be variously configured using a known technique to perform the above object.

The controller 250 applies a PI controller to the generator side reference effective current (i _{qr _ ref} ) and the generator side active current (i _qr ), the generator side set voltage (v _qr ), and ω _r * L _dr * i _dr The reference effective voltage value of the generator side can be calculated by using. In this case, ω _r may be preset as a generator side frequency or may be input from the outside. In addition, L _dr is a d-axis inductance value, which can be obtained from the induction coefficient of the generator-side reactor.

In addition, the controller 250 uses the PI controller applied to the generator side reference reactive current (i _{dr _ ref} ) and the generator reactive current (i _dr ) and the generator side reference invalid using ω _r * L _qr * i _qr . The voltage value can be calculated. In this case, ω _r may be preset as a generator side frequency or may be input from the outside. In addition, L _qr is a q-axis inductance value, which can be obtained from the induction coefficient of the generator-side reactor.

The controller 250 controls the generator-side converter 220 through a PWM generator using the generator-side reference effective voltage value and the generator-side reference reactive voltage obtained through the above method.

The EDLC unit 230 is located at the DC link between the generator-side converter 220 and the grid-side converter 240. The EDLC unit 230 applicable to the present invention has a structure in which an electrolyte is placed between two collector electrodes of a porous conductor having a very large surface area. When the electrolyte is immersed in the conductor of the electrode rods, an inner layer of molecules pressed by the conductor is formed at the interface between the conductors, and an outer layer (diffusion) is formed on the outer side (electrolyte side) in which the diffusion is caused by charge charge. . Since the EDLC unit 230 is almost completely insulated because no current flows in a range where the externally applied voltage is lower than the voltage at which electrolysis occurs in the electrolyte, two capacitors having positive and negative poles in series are used as an insulating film. The structure is connected, and the electrolyte solution is weakly covered therebetween.

The insulating film is naturally obtained, and the film thickness is as thin as one molecule, so that a large capacitance capacitor can be manufactured. The EDLC unit 230 has a very fast charge / discharge rate, and the energy storage capability is also superior to other energy storage devices.

The EDLC unit 230 is freely charged / discharged according to the power condition of the DC link. When the capacity of the EDLC unit 230 reaches a limit, the supply and demand relationship with the system is performed to maintain the power balance of the entire system. .

The grid-side converter 240 converts the DC power transferred from the EDLC unit 230 to AC power. More specifically, the grid-side converter 240 converts the output voltage of the EDLC unit 230 to an AC voltage usable in the grid. In this case, the output voltage of the grid-side converter 240 may be an AC voltage having a predetermined magnitude and a predetermined frequency. In addition, harmonics may be removed from the output voltage by a low pass filter (LPF) as necessary. In one preferred embodiment of the present invention, the output voltage may be an AC voltage having a frequency of 60 Hz.

The controller 250 obtains the grid-side reference power amount (P _u ^* ) from the power delivered to the grid-side converter 240 through the EDLC unit 230, through which the grid-side reference effective current (i _{q _ ref} ) and the grid Obtain the side reference reactive current i _{d_ref} . The controller 250 controls the grid-side converter 240 by using the grid-side reference active current and the grid-side reference reactive current. In more detail, the variation of the generator output is stabilized through the grid-side reference effective current (i _{q _ ref} ) obtained through the grid-side reference power amount (P _u ^* ), and the active power for power transmission is controlled. In addition, the grid-side reference reactive current (i _{d _ ref} ) stabilizes the generator output variation, and controls the reactive power for power transfer. The grid-side reference effective current i _{q _ ref} and the grid-side reference reactive current i _{d _ ref} are controlled by a PI controller, and the grid-side reference voltage obtained through the PI controller is a pulse width modulation (PWM) generator. Control the grid-side converter 240 via. Hereinafter, the control algorithm of the grid-side converter 240 will be described in detail with reference to FIG. 7.

7 is a control block diagram of the grid-side converter 240 according to an embodiment of the present invention. The controller 250 controls the grid-side converter 240 through the control algorithm of FIG. 7 to stabilize the output variation of the wind power generation system. 7, the said power (P _e) using the LPF on the grid side converter 240. In one preferred embodiment of the present invention, the electric power (P _e) generated by the permanent magnet synchronous machine (210) Remove high frequency components. In addition, in order to make the direction of the power constant according to the direction of the power _Pe , a scale conversion of −1 may be performed.

Thereafter, the voltage and current of the power are limited according to the state of charge of the EDLC unit 230 located in the DC link of the back-to-back converter. More specifically, the EDLC unit 230 has a much larger capacity than the capacitor and the electrolyte capacitor, and requires a short time when charging, but when dissipating energy, it may emit energy for a longer time than when charging. Can be. By using such a characteristic, the EDLC unit 230 may adjust the amount of power supplied to the actual system even if the wind speed changes rapidly and the amount of power produced through the wind power generation system increases rapidly.

When the state of charge of the EDLC unit 230 is charged above a threshold value, the amount of power supplied through the generator-side converter 220 is not limited, and may be entirely transmitted to the grid-side converter 240. More specifically, in order to prevent overcharging of the EDLC unit 230, when the EDLC unit 230 is charged above a certain amount, the amount of power delivered to the grid-side converter 240 is limited by the EDLC unit 230. It may not be. Those skilled in the art to which the present invention pertains implement a modified form of the reference charge state of the EDLC unit 230 to prevent overcharging of the EDLC unit 230 without departing from the essential characteristics of the present invention. It can be understood.

In an applicable embodiment of the present invention, when the state of charge of the EDLC unit 230 is less than the threshold value, a part of the power supplied from the generator-side converter 220 is used to recharge the EDLC unit 230 to supply the actual system. The amount of power to be used can be limited by a certain amount. Those skilled in the art to which the present invention pertains can be implemented in a modified form within a range that does not deviate from the essential characteristics of the present invention the ratio of the amount of power supplied through the generator-side converter 220 You will understand.

In this case, the state of charge of the EDLC unit 230 may be measured by the controller 250.

The controller 250 obtains the grid-side reference effective current (i _{q _ ref} ) by applying a PI controller to the grid-side reference power amount (P _u ^* ) and the grid-side effective power amount (P _u ) obtained through the above method. Can be. In addition, the controller 250 may apply the PI controller to the grid-side reference reactive power Q _ref and the reactive power Q to obtain the grid-side reference reactive current i _{d _ ref} .

Here, it is known to those skilled in the art in view of the technical spirit of the present invention that the PI controller can be variously configured using a known technique to perform the above object.

The control unit 250 calculates a value obtained by applying a PI controller to the grid-side reference active current (i _{q _ ref} ) and the grid-side active current (i _q ), the grid-side set voltage (v _qs ), and ω * L _d * i _d . The system-side reference effective voltage value can be calculated. In this case, ω may be preset as the system side frequency or may be input from the outside. L _d is the d-axis inductance value and can be obtained from the induction coefficient of the system-side reactor.

In addition, the control unit 250 uses the system side reference reactive current (i _{d _ ref} ) and the system side reactive current (i _d ) to apply the PI controller and the system side reference reactive voltage using ω * L _q * i _q . The value can be calculated. In this case, ω may be preset as the system side frequency or may be input from the outside. In addition, L _q is a q-axis inductance value, which can be obtained from the induction coefficient of the system-side reactor.

The controller 250 controls the grid-side converter 240 via a PWM generator using the grid-side reference effective voltage value and the grid-side reference reactive voltage obtained through the above method.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the appended claims rather than the foregoing description, and all differences within the equivalent scope are construed as being included in the present invention. Should be.

10: power generation system 20: generator-side converter
30: EDLC section 40: grid side converter
50: control unit 210: permanent magnet synchronizer
220: generator side converter 230: EDLC unit
240: grid-side converter 250: control unit

Claims (7)

A back-to-back converter connected to a power generation system for converting polyphase AC power generated by the power generation system into AC power having a constant frequency component,
A generator-side converter for converting the polyphase AC power generated in the power generation system into DC power;
An EDLC unit which stores all or part of the DC power converted by the generator-side converter and outputs DC power within a set size range;
A grid-side converter converting the DC power transferred from the EDLC unit into AC power; And
And a controller for controlling the grid-side converter using the grid-side reference effective power and the grid-side reference reactive power obtained through the grid-side reference power delivered to the grid-side converter.
The grid-side reference power delivered to the grid-side converter,
The power generated in the power generation system is a power limited by the state of charge of the EDLC unit.
The method of claim 1,
The control unit,
A back-to-back converter for controlling the generator-side converter by using the generator side reference effective current and the generator side reference reactive current.
delete The method of claim 1,
The grid-side reference power delivered to the grid-side converter,
And a low pass filter (LPF) applied to the power generated by the power generation system.
delete At least three phase permanent magnet synchronizer for converting rotational force into electrical energy;
A generator-side converter connected to the synchronizer and converting the polyphase AC power generated by the synchronizer into DC power;
An EDLC unit which stores all or part of the DC power converted by the generator-side converter and outputs a DC current with reduced variability;
A grid-side converter converting the DC power transferred from the EDLC unit into AC power; And
The generator side reference active power and the generator side reference reactive power are controlled using the system side reference active power and the system side reference reactive power obtained through the system side reference power delivered to the grid side converter. A control unit for controlling the grid-side converter,
The grid-side reference power delivered to the grid-side converter,
The power generated by the permanent magnet synchronizer is a power passing through a low pass filter (LPF), the power is limited by the state of charge of the EDLC unit. delete

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