KR102142288B1 - System for controlling grid-connected apparatus for distributed generation - Google Patents

Abstract

The present invention relates to a control system for a distributed power grid connection device.
The control system for a distributed power grid connection device according to the present invention includes: an inverter converting a DC voltage into an AC voltage for linking to a grid power system and performing power synchronization with the grid power system; To attenuate the harmonics mixed in the AC voltage output from the inverter, comprising a first inductor at the output of the inverter, a second inductor at the input of the grid power system, and a capacitor connected between the first and second inductors. LCL filter; A system current sensor measuring a system current input to the system power system through the second inductor of the LCL filter; A grid voltage sensor for measuring a grid voltage supplied to the grid power system through the second inductor of the LCL filter; A pre-state observer for estimating an inverter-side current and a capacitor voltage of the LCL filter by using the grid current and grid voltage information measured by the grid current sensor and the grid voltage sensor, respectively; Inverter-side current and capacitor voltage of LCL filter are adjusted to maintain fast transient response and system stability in grid-connected mode, and to minimize load voltage fluctuations in independent operation mode by receiving output from full-state observer. It includes an integrated controller to control.

Description

System for controlling grid-connected apparatus for distributed generation

The present invention relates to a control system for a distributed power grid-connected device, and more particularly, by combining an integral sliding mode controller using a discrete time model and a resonance type controller, transient response in the existing resonance type controller during grid-connected operation. The present invention relates to a control system of a distributed power system interconnection device capable of improving characteristics and improving system stability and robustness.

Recently, the demand for grid-connected inverters and devices is increasing significantly due to the increase in the amount of distributed power generation using microgrid configuration and renewable energy.

The grid-connected inverter must be designed to ensure stable operation in a grid-connected environment, reduce the harmonics of the grid inflow current, and ensure that the distributed power facility meets the grid-connected regulations. In addition, stable bidirectional power control between the system and the microgrid must be possible, and it must be able to operate in an independent operation mode to supply stable and continuous power to critical loads in case of a system accident.

However, the control output in each operation fluctuates according to the load of the connection point or changes in an instantaneous operation state. In order to reduce voltage fluctuations occurring in the load, seamless transfer must be possible between the grid-connected mode and the independent operation mode, thereby minimizing damage to the load.

To this end, a non-sequential switching function or a multi-loop indirect current control method has been applied to the grid-connected inverter, but these techniques separately measure the grid-side current, capacitor-side voltage, and inverter-side current, thereby increasing the cost of the system. And complicates the structure of the controller.

In addition, when the distributed power facility operates in the grid-connected mode, the harmonics of the grid injection current may increase beyond the level specified in the grid-connected regulations due to the influence of the distortion system. have.

In the conventional grid-connected inverter system, a resonant controller capable of suppressing a specific harmonic component was applied to reduce the influence of the distortion system. However, although the conventional resonant controller has excellent compensation effect for a specific harmonic component, the transient response of the current is very slow, and there is a problem that the vibration is very severe during the initial grid connection or in a transient state such as a change in the current command value.

On the other hand, Korean Patent Application Publication No. 10-2017-0123021 (Patent Document 1) discloses a "distributed power microgrid system and a non-disruptive transfer method thereof". Accordingly, a non-disruptive transfer method of a distributed power microgrid system In a distributed power microgrid system that supplies power from grid power and distributed power to a load, sensing the current of the grid power in an independent operation mode in which the distributed power supplies power to the load while the grid power is cut off. Step to do; If the sensed current of the grid power is normal, calculating a deviation between the frequency of the grid power and the frequency of the distributed power; calculating a deviation between the phase of the grid power and the phase of the distributed power; Calculating an offset for the frequency of the grid power and the frequency of the distributed power; Calculating an offset for the phase of the grid power and the phase of the distributed power; Calculating a reference phase using the offset for the frequency and the offset for the phase; Calculating a deviation between the voltage of the grid power supply and the voltage of the distributed power supply;

Calculating an offset for the deviation of the calculated voltage; And calculating a current reference using the offset of the voltage deviation, and determining a current reference output from the distributed power supply using the calculated reference phase and the current reference.

In the case of Patent Document 1 as described above, when the distributed power microgrid system is operated in the independent operation mode and then switched to the grid connection mode, the voltage and frequency supplied from the distributed power supply to the load are adjusted according to the grid power, and then the grid is connected. Since it is switched to mode, it will have the effect of non-stepping transition from independent operation mode to grid-connected mode, but it does not take into account the control of system control variables during non-stepless switching operation, so it is high quality in case of system distortion and load fluctuation. It has a problem that it is difficult to supply power to

Korean Patent Application Publication No. 10-2017-0123021 (published on November 7, 2017)

The present invention was created to improve the problems of the prior art, as described above, by constructing a control system for a grid-connected inverter in which an integral sliding mode controller using a discrete time model and a resonant controller are combined. Its purpose is to provide a control system for a distributed power system interconnection device capable of improving the transient response characteristics of the existing resonant controller and improving system stability and robustness.

In addition, by applying a full-state observer in a discrete-time state space, it estimates the control variable required by each inner loop controller during non-stepless switching operation, and uses it as a feedback signal, greatly increasing the hardware design cost and digital signal processing complexity of the system. Another object is to provide a control system for a distributed power grid-connected device that can be reduced.

In order to achieve the above object, the control system of the distributed power system interconnection device according to the present invention,

An inverter that receives DC voltage from a DC power source and converts it into AC voltage for connection to the grid power system, and performs power synchronization with the grid power system by on/off operations of a number of internal semiconductor switch elements. ;

It is located between the inverter and the grid power system, for weakening the harmonics mixed in the AC voltage output from the inverter, the first inductor connected to the output terminal of the inverter, and connected to the input terminal of the grid power system An LCL filter including a second inductor that is configured and a capacitor connected between the first inductor and the second inductor;

A system current sensor for measuring a system current input to the system power system through the second inductor of the LCL filter;

A grid voltage sensor for measuring a grid voltage supplied to the grid power system through a second inductor of the LCL filter;

A full-state observer for estimating the inverter-side current and the capacitor voltage of the LCL filter by using the grid current and grid voltage information measured by the grid current sensor and the grid voltage sensor, respectively; And

The inverter-side current and the capacitor of the LCL filter are input to receive the output from the full-state observer and maintain fast transient response and system stability in the grid-connected mode, and to minimize the load voltage fluctuation in the independent operation mode. It is characterized in that it includes an integrated controller to control the voltage.

=

의 행렬식이 영(zero)이 아니고, 시스템(분산전원 계통연계 장치)이 완전 관측 가능하면, 추적 오차가 점근적으로 안정하게 되는 다음과 같은 행렬 G를 찾음으로써, 상기 인버터측 전류와 상기 LCL 필터의 커패시터 전압을 추정할 수 있다.Here, the full-state observer estimates the inverter-side current and the capacitor voltage of the LCL filter, the observability matrix

=

If the determinant of is not zero and the system (distributed power grid interconnection device) is fully observable, the following matrix G is found, where the tracking error becomes asymptotically stable, and the inverter current and the LCL filter You can estimate the capacitor voltage of

G =

In addition, the integrated controller,

When the grid voltage is distorted due to an accident or an abnormal phenomenon, a proportional resonant controller (PR controller) for compensating for a distortion voltage including harmonic frequencies that appears;

A sliding mode controller for improving the transient response of the resonance controller and responding to changes in system impedance;

) 값을 제어 명령치로 사용하여 부하에 흐르는 전압을 제어하는 LCL 필터 커패시터측 전압 제어기(PI-v_c); 및In the grid-connected mode, the capacitor side voltage control command of the LCL filter is generated by using the command value obtained through the resonance controller and the sliding mode controller, and in the independent operation mode in which the connection to the grid is cut off, the full-state observer The estimated capacitor voltage of the LCL filter (

) LCL filter capacitor side voltage controller (PI-v _c ) for controlling the voltage flowing through the load using the value as a control command value; And

It is characterized in that it includes an inverter-side current controller (PI-i ₁ ) that controls the output current of the inverter by using the inverter output current command value obtained through the LCL filter capacitor-side voltage controller (PI-v _c ). .

In addition, as the resonance controller, a discrete time resonance controller may be used.

In this case, the discrete time resonance controller may be expressed by the following equation.

Here, a and b denote constant values for compensating for a specific frequency, respectively, and u and y denote input values and output values of the discrete time resonance controller, respectively.

In addition, as the sliding mode controller, a discrete time integral sliding mode controller may be used.

According to the present invention, the system control variable (the current on the inverter and the voltage on the capacitor side of the LCL filter) is estimated using a state-of-the-art observer, and the estimated control variable is an internal current controller on the inverter side and the voltage controller on the LCL filter capacitor side. By controlling the system, it is possible to improve the hardware design cost and the complexity of the CPU implementation of the grid-connected system, supply high-quality power even to system distortion and parameter changes, and to improve the transient response and robustness of the controller. have.

1 is a view schematically showing the configuration of a control system of a conventional distributed power grid connection device.
2 is a diagram schematically showing the configuration of a control system for a distributed power grid connection device according to an embodiment of the present invention.
3 is a view showing the internal configuration of the integrated controller of the control system of the distributed power grid connection device shown in FIG.
4 is a diagram showing a simulation waveform by a conventional PI controller when the system voltage is distorted.
5 is a diagram showing a system current waveform using a discrete time resonance controller.
6 is a diagram showing a system current waveform in which a discrete time integral sliding mode controller is added to the discrete time resonance controller.

The terms or words used in the specification and claims should not be interpreted as being limited to the ordinary or dictionary meanings, and the inventor can appropriately define the concept of terms in order to best describe his or her invention. Based on the principles, it should be interpreted as meanings and concepts consistent with the technical spirit of the present invention.

Throughout the specification, when a part “includes” a certain component, it means that the component may further include other components, not to exclude other components, unless otherwise stated. In addition, terms such as “…unit”, “…group”, “module”, and “device” described in the specification mean a unit that processes at least one function or operation, which is hardware or software or a combination of hardware and software. Can be implemented as

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

Here, prior to a full description of the embodiments of the present invention, a description will be given of an existing control system related to the present invention in order to aid understanding of the present invention.

1 is a view schematically showing the configuration of a control system of a conventional distributed power grid connection device.

Referring to FIG. 1, the control system 100 of a conventional distributed power grid connection device receives a DC voltage from a DC power source and converts it into an AC voltage for connection to the grid power system 180. It is located between the PWM inverter 110 that performs power synchronization with the grid power system 180 by the on/off operation of the semiconductor switch device, and the PWM inverter 110 and the grid power system 180, and the PWM inverter ( To attenuate harmonics mixed in the AC voltage output from 110), a first inductor L ₁ connected to the output terminal of the PWM inverter 110 and a second inductor L ₁ connected to the input terminal of the grid power system 180 from the inductor (L _2), and a first inductor (L ₁₎ and second inductor (L ₂₎ LCL filter 120, and a PWM inverter (110) having a capacitor (C) connected to a three-phase line between the The current controller 130 generates a reference voltage for controlling the output current of the PWM inverter 110 by receiving feedback input of the output current of the output current and the voltage and current applied to the grid power system 180 and providing it to the PWM inverter 110 side. ).

In order to solve the complexity of the controller design, the control system 100 of the conventional distributed power grid-connected device as described above includes the current of the second grid-side inductor (L ₂ ), the voltage of the capacitor (C) of the LCL filter 120, and PWM. Each of the currents of the first inductor L ₁ on the inverter 110 side is separately controlled in a dependent structure. That is, two inverter current sensors 140 on the side of the PWM inverter 110, two grid current sensors 150 on the side of the grid power system 180, and two capacitors on the capacitor (C) side of the LCL filter 120. By installing each of the voltage sensors 170, the current and voltage measured from these sensors are input from the current controller 130 to generate a reference voltage for controlling the output current of the PWM inverter 110, and the PWM inverter 110 It is taking the way of supplying it to the side.

Although the above-described control method has its own advantages, such as non-interrupted switching, as described above, two inverter current sensors 140 on the PWM inverter 110 side and two grid current sensors on the grid power system 180 side. (150) As the two capacitor voltage sensors 170 are installed on the capacitor (C) side of the LCL filter 120, there is a disadvantage of increasing the cost of the system and complicating the design of the circuit and the controller.

In addition, the control system 100 of the conventional distributed power system interconnection device as described above applies a resonance type controller capable of suppressing a specific harmonic component in order to reduce the influence of the distortion system. However, although the conventional resonant controller has excellent compensation effect for a specific harmonic component, the transient response of the current is very slow, and there is a problem that the vibration is very severe during the initial grid connection or in a transient state such as a change in the current command value. In FIG. 1, reference numeral 160 denotes a system voltage sensor for measuring a voltage applied to the system side.

The present invention was created to solve various problems of the control system 100 of a conventional distributed power grid interconnection device as described above, and an embodiment of the present invention will be described below based on the above matters. .

2 is a diagram schematically showing the configuration of a control system for a distributed power grid connection device according to an embodiment of the present invention.

2, the control system 200 of the distributed power grid connection device according to the present invention includes an inverter 210, an LCL filter 220, a grid current sensor 230, a grid voltage sensor 240, and a full state observer. (full-state observer) 250, is configured to include an integrated controller 260.

The inverter 210 receives a DC voltage from a DC power supply (V _DC ) and converts it into an AC voltage for connection to the grid power system 290, and a plurality of internal semiconductor switch elements (eg, MOSFET, IGBT, etc.) performs power synchronization with the system power system 290 by an on/off operation. As such inverter 210, a pulse width modulation (PWM) inverter may be used.

The LCL filter 220 is located between the inverter 210 and the grid power system 290 and is for attenuating the harmonics mixed in the AC voltage output from the inverter 210. The first inductor L ₁ connected to the phase line, the second inductor L ₂ connected to the three-phase line of the input terminal of the grid power system 290, and the first inductor L ₁ and the second It includes a capacitor (C) connected in parallel to the three-phase line between the inductor (L ₂ ).

The system current sensor 230 measures the system current input to the system power system 290 through the second inductor L ₂ of the LCL filter 220. Here, the system current sensor 230 may be used as long as it can measure current on a three-phase line, and is not particularly limited. Here, two system current sensors 230 as described above may also be installed.

The grid voltage sensor 240 measures the grid voltage supplied to the grid power system 290 through the second inductor L ₂ of the LCL filter 220. Here, the system voltage sensor 240 can be used as long as it can measure the voltage between the three-phase lines, and there is no particular limitation.

The full-state observer 250 uses the grid current and grid voltage information measured by the grid current sensor 230 and the grid voltage sensor 240, respectively, to the inverter 210 side current and the The capacitor voltage of the LCL filter 220 is estimated.

Here, the full-state observer 250 as described above will be described again later.

The integrated controller 260 receives the output from the full-state observer 250 to maintain fast transient response and system stability in the grid-connected mode, and to perform non-stop switching to minimize load voltage fluctuations in the independent operation mode. The current on the inverter 210 side and the capacitor voltage of the LCL filter 220 are controlled.

) 값을 제어 명령치로 사용하여 부하에 흐르는 전압을 제어하는 LCL 필터 커패시터측 전압 제어기(PI-v_c)(263); 및 LCL 필터 커패시터측 전압 제어기(PI-v_c)(262)를 통해 획득된 인버터 출력 전류 명령치를 이용하여 인버터(210)의 출력 전류를 제어하는 인버터측 전류 제어기(PI-i₁)(264)를 포함하여 구성될 수 있다. Here, the integrated controller 260 is a resonance controller (proportional resonant controller) for compensating for a distortion voltage including a harmonic that appears when the grid voltage is distorted due to an accident or an abnormal phenomenon, as shown in FIG. 3. : PR controller) 261; A sliding mode controller 262 for improving the transient response of the resonance controller 261 and responding to changes in system impedance; In the grid-connected mode, a capacitor-side voltage control command of the LCL filter 220 is generated using the command values obtained through the resonance controller 261 and the sliding mode controller 262, and the system (system power system 290) The capacitor voltage of the LCL filter estimated by the pre-state observer 250 in the independent operation mode in which the connection with) is cut off (

) LCL filter capacitor side voltage controller (PI-v _c ) 263 for controlling the voltage flowing through the load by using the value as a control command value; And an inverter-side current controller (PI-i ₁ ) 264 that controls the output current of the inverter 210 by using the inverter output current command value obtained through the LCL filter capacitor side voltage controller (PI-v _c ) 262. It can be configured to include.

In addition, a discrete-time PR controller may be used as the resonance controller 261.

In this case, the discrete time resonance controller may be expressed by the following equation.

Here, a and b denote constant values for compensating for a specific frequency, respectively, and u and y denote input values and output values of the discrete time resonance controller, respectively.

In addition, a discrete-time integral sliding mode controller may be used as the sliding mode controller 262.

In FIG. 2, reference numeral 270 denotes a pulse width modulation process by receiving the q-axis and d-axis reference voltages (v ^* _q , v ^* _d ) from the integrated controller 260, and a plurality of semiconductor switch elements in the inverter 210 A space vector pulse width modulator (SVPWM) that outputs a signal for control of the inverter 210 to the inverter 210, 280 is the grid side voltage measured by the grid voltage sensor 240 (e _q , e _d ) To generate a system voltage phase angle (θ) and provide a phase locked loop (PLL) to the space vector pulse width modulator 270, respectively.

Here, a further explanation will be given in relation to the full-state observer 250.

As described above, the full-state observer 250 uses the grid current and grid voltage information measured by the grid current sensor 230 and the grid voltage sensor 240, respectively, to the inverter 210 side. The current and the capacitor voltage of the LCL filter 220 are estimated. In this regard, we will explain in more detail.

The grid-connected device, that is, the grid-connected inverter 210 may be expressed by the following equation of state.

로 정의된다.In this case, x, u, e are each

Is defined as

는 각각 계통측 전류, 인버터측 전류, 커패시터 전압을 나타낸다. 그리고 u와 e는 시스템 입력값과 계통측 전압값을 각각 나타낸다. 위에 언급된 모든 값은 고정 좌표계로 표현된다. here,

Represents the grid-side current, inverter-side current, and capacitor voltage, respectively. And u and e represent the system input value and the grid side voltage value, respectively. All values mentioned above are expressed in a fixed coordinate system.

In addition, A is a system matrix, B is an input matrix, D is a system input matrix, and C is an output matrix, and can be expressed as follows.

C =

C =

Finally, the equation of state of the inverter system can be expressed by discretizing it as follows.

The equation below is a system equation including a full-state observer.

In the above equation, G is the full-state observer gain matrix, which is determined during the design of the full-state observer.

이다. (u는 시스템 입력값, y는 시스템 출력값이다) 전상태 관측기의 목적은 t >

에 따라

> x 가 되도록 추정값

를 제공하고자 하는 것이다.The inputs of the prestate observer are u and y, and the output is

to be. (u is the system input, y is the system output) The purpose of the full-state observer is t>

Depending on the

Estimate so that> x

Is to provide.

=

의 행렬식이 영(zero)이 아닐 때, 시스템(분산전원 계통연계 장치)을 완전히 관측할 수 있게 된다. 시스템(분산전원 계통연계 장치)이 완전 관측 가능하면, 추적 오차가 점근적으로 안정하게 되는 행렬 G를 항상 찾을 수 있다. 위의 시스템 이득 행렬과 유사한 방식으로 다음의 특성 방정식

= 0 가 좌반평면에 모든 근을 가지면 t >

에 따라

x 를 만족하도록 하는 행렬 G를 찾을 수 있다. 이때, 행렬 G는 다음과 같이 나타낼 수 있다.Prestate observer is an observability matrix

=

When the determinant of is not zero, the system (distributed power grid connection device) can be fully observed. If the system (distributed power grid connection device) is fully observable, then you can always find a matrix G where the tracking error becomes asymptotically stable. In a manner similar to the system gain matrix above, the following characteristic equation

= 0 has all roots in the left half plane, then t>

Depending on the

We can find the matrix G that satisfies x. In this case, the matrix G can be expressed as follows.

G =

=

의 행렬식이 영(zero)이 아니고, 시스템(분산전원 계통연계 장치)이 완전 관측 가능하면, 추적 오차가 점근적으로 안정하게 되는 행렬 G를 찾음으로써, 인버터(210)측 전류와 LCL 필터(220)의 커패시터 전압을 추정할 수 있게 된다.As described above, in estimating the current on the inverter 210 side and the capacitor voltage of the LCL filter 220, the observability matrix

=

If the determinant of is not zero and the system (distributed power grid interconnection device) is completely observable, the tracking error is asymptotically stable, and the matrix G is found, so that the current on the inverter 210 and the LCL filter 220 ) Can be estimated.

Here, further explanation will be given in relation to the discrete-time PR controller and the discrete-time integral sliding mode controller employed in the present invention.

4 is a diagram showing a simulation waveform by a conventional PI controller when the system voltage is distorted.

4, this shows a simulation waveform in which the inverter is controlled using an existing PI controller when the grid voltage is distorted, such as the right waveform (lower right waveform) due to an accident or an abnormal phenomenon. As can be seen, when the inverter is controlled using an existing PI controller, both voltage and current are distorted under the influence of grid voltage distortion.

5 is a diagram showing a system current waveform using a discrete-time PR controller.

Harmonics that may appear during system distortion are the 5th, 7, 11th, and 13th harmonics as shown in FIG. 4, and a PR controller is usually used to compensate for the distortion voltage including these harmonics. The PR controller compensates for these harmonics and satisfies the inverter output current harmonic limit requirements proposed by IEEE st.1547.

5 is an output waveform obtained by compensating for harmonics using a discrete-time PR controller in the same systemic distortion environment as the PI controller of FIG. 4. By compensating for the harmonics in this way, a high-quality output current waveform can be obtained, but it can be seen that the transient response is poor.

6 is a diagram showing a system current waveform in which a discrete time integral sliding mode controller is added to the discrete time resonance controller.

Referring to FIG. 6, this is a system current waveform in which a discrete-time integral sliding mode controller is added to the discrete time resonance controller of FIG. 5, and the transient response is improved and the sliding mode controller It can be seen that the characteristic toughness is maintained. In addition, the sliding mode controller can effectively respond to system disturbances due to its robustness, and can effectively follow existing command values even when system parameters are changed.

Meanwhile, as described above, the discrete time resonance controller is expressed as an equation as follows.

This is a transfer function obtained by discretizing the resonant controller transfer function of continuous time using a bilinear transform. Here, a and b denote constant values for compensating for a specific frequency, respectively, and u and y denote input values and output values of the discrete time resonance controller, respectively.

In addition, the discrete-time integral sliding mode controller is expressed as an equation as follows.

The discrete-time integral sliding mode controller satisfies the sufficient condition for the existence of the discrete-time sliding mode, and determines the reaching law so that the variable structure control feature is always satisfied in discrete time. Design to be the dynamic relationship of (k).

Here, a sufficient condition for the existence of the discrete time sliding mode is as follows.

A) In continuous time, the initial state trajectory of the sliding mode controller meets at the switching plane within a limited time, but in the case of the discrete time model, it passes through the sliding plane.

B) If the trajectory of the state passes the switching plane, it must return to the opposite side of the switching plane again at the next sampling moment. As a result, it vibrates in the switching plane.

C) The magnitude of continuous vibration is reduced and the trajectory of the state stays in a limited band.

-Reaching Law s(k +1)-s(k) =-qTs(k)-εT sgn(s(k))

-In the above equation, q>0, ε>0, 1-qT>0, and the sampling period T is greater than 0. Therefore, if 1-qT>0 is valid, s(k+1)<0 if s(k)>0, and s(k+1)>0 if s(k)<0. Features "A)" are guaranteed.

-sgn(s(k)) satisfies the features "B)" and "C)" of the discrete variable structure control.

Here, a little more explanation will be added to the derivation process of Equation 2 above.

First, the sliding function S(t) is defined as follows.

And E(t) is defined as follows.

을 이용하여 다음과 같이 표현될 수 있다.The sliding function is z transform,

It can be expressed as follows using.

Using the law of arrival approach (approximate),

는 다음과 같이 표현될 수 있다.

Can be expressed as

,

로 정의하기로 한다. 그러면, 최종적으로 이산 시간 적분형 슬라이딩 모드 제어기는 다음과 같은 수식 관계로 표현될 수 있다.here,

,

It will be defined as Then, finally, the discrete time integral sliding mode controller can be expressed by the following equation.

As described above, the control system of the distributed power grid-connected device according to the present invention estimates the system control variable (current on the inverter and the voltage on the capacitor side of the LCL filter) using the pre-state observer, and calculates the estimated control variable internally. By controlling the inverter-side current controller and the LCL filter capacitor-side voltage controller, the hardware design cost of the grid-connected system and the complexity of implementing the CPU can be improved, and high-quality power can be supplied even in the case of system distortion and parameter changes. It has the advantage of improving transient responsiveness and toughness.

As described above, the present invention has been described in detail through preferred embodiments, but the present invention is not limited thereto, and various modifications and applications can be made without departing from the spirit of the present invention. It is obvious to the technician. Therefore, the true scope of protection of the present invention should be interpreted by the following claims, and all technical spirits within the equivalent scope should be interpreted as being included in the scope of the present invention.

100: (Conventional) Distributed power grid connection device control system
110: PWM inverter 120: LCL filter
130: current controller 140: inverter current sensor
150: grid current sensor 160: grid voltage sensor
170: capacitor voltage sensor 180: grid power system
200: (Invention) Distributed power grid connection device control system
210: inverter (PWM inverter) 220: LCL filter
230: grid current sensor 240: grid voltage sensor
250: full-state observer 260: integrated controller
261: resonance controller 262: sliding mode controller
263: LCL filter capacitor side voltage controller 264: Inverter side current controller
270: spatial vector pulse width modulator 280: phase locked loop (PLL)
290: grid power system

Claims (5)

An inverter that receives DC voltage from a DC power source and converts it into AC voltage for connection to the grid power system, and performs power synchronization with the grid power system by on/off operations of a number of internal semiconductor switch elements. ;
It is located between the inverter and the grid power system, for weakening the harmonics mixed in the AC voltage output from the inverter, the first inductor connected to the output terminal of the inverter, and connected to the input terminal of the grid power system An LCL filter including a second inductor that is configured and a capacitor connected between the first inductor and the second inductor;
A system current sensor for measuring a system current input to the system power system through the second inductor of the LCL filter;
A grid voltage sensor for measuring a grid voltage supplied to the grid power system through a second inductor of the LCL filter;
A full-state observer for estimating the inverter-side current and the capacitor voltage of the LCL filter by using the grid current and grid voltage information measured by the grid current sensor and the grid voltage sensor, respectively; And
The inverter-side current and the capacitor of the LCL filter are input to receive the output from the full-state observer and maintain fast transient response and system stability in the grid-connected mode, and to minimize the load voltage fluctuation in the independent operation mode. Including an integrated controller to control the voltage,
The full-state observer estimates the inverter-side current and the capacitor voltage of the LCL filter, wherein the observability matrix

=

If the determinant of is not zero and the system (distributed power grid connection device) is fully observable, by finding the following matrix G where the tracking error becomes asymptotically stable,
G =

And estimating the inverter current and the capacitor voltage of the LCL filter.
delete The method of claim 1,
The integrated controller,
When the grid voltage is distorted due to an accident or an abnormal phenomenon, a proportional resonant controller (PR controller) for compensating for a distortion voltage including harmonic frequencies that appears;
A sliding mode controller for improving the transient response of the resonance controller and responding to changes in system impedance;
In the grid-connected mode, the capacitor side voltage control command of the LCL filter is generated by using the command value obtained through the resonance controller and the sliding mode controller, and in the independent operation mode in which the connection to the grid is cut off, the full-state observer The estimated capacitor voltage of the LCL filter (

) LCL filter capacitor side voltage controller (PI-v _c ) for controlling the voltage flowing through the load using the value as a control command value; And
Distributed power grid connection device comprising an inverter-side current controller (PI-i ₁ ) for controlling the output current of the inverter by using the inverter output current command value obtained through the LCL filter capacitor-side voltage controller (PI-v _c ). Control system.
The method of claim 3,
The resonance controller is a control system of a distributed power system interconnection device, characterized in that the discrete time resonance controller.
The method of claim 3,
The sliding mode controller is a discrete time integral type sliding mode controller.

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