KR101309287B1 - Apparatus and method for a fault diagnosis of direct current terminal voltage sensor of grid connected power transformer and fault-tolerant control - Google Patents

Abstract

A device for performing fault diagnosis and fault tolerance control of a DC link voltage sensor provided in a grid-connected power converter, the DC link voltage estimating the DC link voltage from the q-axis command current and the q-axis current detected from the grid. Estimator; A failure determination unit comparing the estimated DC terminal voltage with a measured value of the DC terminal voltage sensor and determining whether the DC terminal voltage sensor is broken; And a controller for outputting the estimated DC link voltage as a control voltage to the power converter in order to perform fault tolerance control for the power conversion, when the failure determination unit determines that the DC link voltage sensor is faulty. Provided are a DC link voltage sensor fault diagnosis and a fault tolerance control device of a grid-connected power converter including.

Description

Fault diagnosis and fault tolerance control device of DC link voltage sensor of grid-connected power converter and method thereof

The present invention relates to a device for diagnosing a failure of a DC-link voltage sensor and a fault-tolerant control device of a grid-connected power converter, and more particularly, to a two-dimensional current (i _d , i _q ) converted from a grid-linked power converter. Fault Diagnosis and Fault Tolerance Control of DC-Stage Voltage Sensors of Power Converters Using DC-based Voltage Converters, which can significantly reduce the time delay due to the calculation amount according to modeling. An apparatus and a method thereof are provided.

Recently, as the issue of climate change agreements and the depletion of energy resources are raised around the world, interest in solar energy is increasing. Accordingly, researches for efficiently using solar energy have been widely conducted in advanced countries.

In particular, in Korea, amendments to the Electricity Business Law, which allows the supply of electricity generated by using alternative energy to commercial systems, are in progress and research is being conducted.

Grid-connected power generation system using the solar energy has the advantage of reducing the burden of the existing thermal power plant during peak load in summer.

The types of grid-connected inverters that have been developed and used abroad are largely divided into a low frequency (60 Hz) transformer, a high frequency link using a high frequency transformer, and no isolation transformer. In the past, many low frequency transformers have been used. However, low frequency transformers have a disadvantage of increasing the size and weight of the entire system. Recently, high frequency link or no isolation transformers have been used.

The high frequency link method is electrically insulated from the system line by using a high frequency transformer, but because of the large number of switching elements and inverting at the same time, it is difficult to optimize the circuit and due to the leakage inductance of the high frequency transformer, The disadvantage is that voltage ringing occurs.

The transformerless method requires additional DC / DC converters for boosting when the output voltage of the solar cell is lower than the peak value of the grid line voltage. It is widely used in large capacity solar power system.

On the other hand, the power converter is an essential module for the control of not only the existing electric / power control system but also the renewable energy generation system that is in the spotlight due to the recent environmental problems. However, the failure of the DC terminal voltage sensor to measure the voltage applied to the DC terminal capacitor in the industrial field often occurs, which may cause performance and stability problems of the system and economic loss. Therefore, there is a need for techniques for minimizing the above problems and increasing the convenience of maintenance through fault diagnosis of the DC terminal voltage sensor.

In the conventional case, a phase current comparison method and a model-based method are used to diagnose a DC voltage sensor. The phase current comparison method can only diagnose faults, and the model-based method can even diagnose faults and control fault tolerance.

In the phase current comparison method, when a voltage sensor suddenly fails and an incorrectly sensed voltage value is used in the system, an unexpected strange phase current is output. Compare this to other phases, and if the difference is larger than the specified value, it is recognized as a failure. The phase current comparison method is simple, but it is only possible to diagnose the failure, and it is difficult to judge the DC voltage sensor correctly because it does not compare with DC voltage.

On the other hand, when comparing models based on accurate system modeling is required. Since direct DC link voltage is estimated and compared, it is relatively more accurate than phase current comparison, but there is a problem that a large amount of calculation is required according to modeling, and thus a time delay may occur.

The problem to be solved by the present invention, by using the two-dimensional current (i _d , i _q ) transformed in the grid-connected power converter device to perform the diagnosis of the DC terminal voltage sensor of the power converter and the fault tolerance control according to modeling The present invention provides a device and method for diagnosing a fault in the DC link voltage sensor of a grid-connected power converter that can significantly reduce the time delay due to a calculation amount, and a method for controlling the fault.

According to an aspect of the present invention, a device for performing fault diagnosis and fault tolerance control of a DC-link voltage sensor provided in a grid-connected power converter, DC from the q-axis command current and q-axis current detected from the grid A DC stage voltage estimator for estimating the stage voltage; A failure determination unit comparing the estimated DC terminal voltage with a measured value of the DC terminal voltage sensor and determining whether the DC terminal voltage sensor is broken; And a controller for outputting the estimated DC link voltage as a control voltage to the power converter in order to perform fault tolerance control for the power conversion, when the failure determination unit determines that the DC link voltage sensor is faulty. Provided are a DC link voltage sensor fault diagnosis and a fault tolerance control device of a grid-connected power converter including.

The DC stage voltage estimator may use a deadbeat current controller to obtain the q-axis command current and the q-axis current. The deadbit current controller is a current controller that selects a voltage vector command to zero the current error at the end of the sampling period.

The DC link voltage estimator may estimate the DC link voltage from the q-axis command current and the q-axis current using a proportional integrator.

The failure determination unit may compare the estimated DC terminal voltage with a measured value of the DC terminal voltage sensor and determine that the DC terminal voltage sensor is out of order when the difference value is out of a set reference range.

The power converter may be a voltage inverter of a grid-tied photovoltaic power generation system.

The DC stage voltage sensor fault diagnosis and fault tolerance control apparatus of the grid-connected power converter further includes a current axis converting unit converting a 3-phase current into a 2-phase current from the grid and outputting the 3-phase current to the DC-link voltage estimating unit. Can be.

The DC link voltage sensor fault diagnosis and fault tolerance control device of the grid-associated power changer further includes a voltage axis converting unit converting a 3-phase voltage into a 2-phase voltage from the grid and outputting the 3-phase voltage to the DC link voltage estimating unit. Can be.

According to another aspect of the present invention, a method for performing fault diagnosis and fault tolerance control of a DC-link voltage sensor provided in a grid-connected power conversion device, the method comprising a direct current from the q-axis command current and q-axis current detected from the grid Estimating a short voltage; Comparing the estimated DC terminal voltage with a measured value of the DC terminal voltage sensor to determine whether the DC terminal voltage sensor is faulty; And outputting the estimated DC link voltage as a control voltage for the power conversion device and performing fault tolerance control for the power conversion when it is determined that the DC link voltage sensor is faulty. Provided are a method for diagnosing a fault in a DC-stage voltage sensor and a fault-tolerant control method of a power converter.

The DC stage voltage estimating step may use a dead bit current controller to obtain the q-axis command current and the q-axis current. The deadbit current controller is a current controller that selects a voltage vector command to zero the current error at the end of the sampling period.

The DC link voltage estimating step may estimate the DC link voltage from the q-axis command current and the q-axis current using a proportional integrator.

The failure determining step may be determined as a failure of the DC terminal voltage sensor when comparing the estimated DC terminal voltage and the measured value of the DC terminal voltage sensor when the difference value is out of the set reference range.

The power converter may be a voltage inverter of a grid-tied photovoltaic power generation system.

The DC link voltage sensor fault diagnosis and fault tolerance control method of the grid-connected power converter may further include the step of converting a 3-phase current into a 2-phase current from the grid to estimate the DC link voltage.

The DC link voltage sensor fault diagnosis and fault tolerance control method of the grid-connected power converter may further include the step of converting a 3-phase voltage from the grid into a 2-phase voltage to estimate the DC link voltage.

According to the present invention, the two-dimensional current is expressed through the axis conversion process in the three-phase current for fault diagnosis and fault tolerance control of the DC-link voltage sensor of the grid-connected photovoltaic system. DC voltage is estimated with q-axis command current and q-axis current. If the fault of the DC voltage sensor is diagnosed by the estimated voltage value and the actual voltage value, and the fault is detected, the fault tolerance control may be implemented by replacing the actual value with the estimated value.

Accordingly, the fault diagnosis and fault tolerance control of the DC-link voltage sensor of the grid-connected photovoltaic power generation system are implemented by estimating the fault diagnosis and fault tolerance with an estimated value through a proportional integral controller without complicated mathematical modeling. It can provide the effect of significantly reducing the time delay caused by the calculation amount.

In addition, according to the present invention, it is possible to determine the failure of the DC-stage voltage sensor to reduce the maintenance cost and to improve reliability and stability with a fault-tolerant control that does not require a system stop immediately.

1 is a view illustrating a DC terminal voltage sensor fault diagnosis and fault tolerance control apparatus according to an embodiment of the present invention.
2 is a block diagram illustrating a fault diagnosis and a fault tolerance control unit according to an exemplary embodiment of the present invention.
3 is a block diagram illustrating a voltage stage estimator according to an exemplary embodiment of the present invention.
4 is a flowchart illustrating a DC-stage voltage sensor fault diagnosis and fault tolerance control method according to an embodiment of the present invention.
5 is a flowchart of a method for diagnosing a fault and controlling a fault tolerance of a DC terminal voltage sensor of a grid-connected power converter according to an embodiment of the present invention.
6 is a graph of simulation results for explaining fault diagnosis of a DC terminal voltage sensor according to an exemplary embodiment of the present invention.
7 is a simulation graph for explaining fault tolerance control of a DC terminal voltage sensor according to an exemplary embodiment of the present invention.
8 is a simulation graph illustrating a tracking value according to a change in a DC voltage according to an embodiment of the present invention.
FIG. 9 is a graph showing IV and PV characteristic curves of a solar cell equivalent circuit for simulation according to an embodiment of the present invention. FIG.
10 is a graph illustrating MPPT control during fault tolerance control according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the width, length, thickness, and the like of the components may be exaggerated for convenience. Like numbers refer to like elements throughout.

1 is a view illustrating a DC terminal voltage sensor fault diagnosis and fault tolerance control apparatus according to an embodiment of the present invention.

Referring to FIG. 1, a system including a DC terminal voltage sensor fault diagnosis and a fault tolerance control apparatus according to an embodiment includes a voltage inverter 10 connected to a grid, a phase locked loop 20, and a current. It may be configured to include an axis conversion unit 30, voltage axis conversion unit 40, fault diagnosis and fault tolerance control unit 50, SVPWM (60).

The voltage inverter 10 is a power converter connected to the grid. The voltage inverter 10 includes a capacitor element, and is provided with a DC terminal voltage sensor for measuring a DC voltage across both ends of the capacitor element. The voltage inverter 10 performs power conversion in accordance with a fault diagnosis and a control signal from the fault tolerance control unit 50.

The phase locked loop unit 20 is a loop circuit for performing phase synchronization between three phase voltages. The current axis converting unit 30 performs the axis conversion of the three-phase current to a two-phase current. The voltage conversion unit 40 performs the axis conversion of the three-phase voltage to a two-phase voltage.

The fault diagnosis and fault tolerance control unit 50 compares the DC terminal voltage estimated from the grid with the measured value of the DC terminal voltage sensor, diagnoses whether the DC terminal voltage sensor is faulty, and checks the estimated DC terminal voltage when the fault occurs. Fault tolerance control is performed by outputting a control voltage to the power converter.

The SVPWM 60 is a switch unit that switches the control signals of the fault diagnosis and fault tolerance control unit 50. Here, the SVPWM 60 is described as SVPWM, but the present invention is not limited thereto, and PWM may be used.

2 is a block diagram illustrating a fault diagnosis and a fault tolerance control unit according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the fault diagnosis and fault tolerance controller 50 may include a dead bit current controller 51, a DC link voltage estimator 52, a failure determiner 53, and a controller 54. Can be.

The deadbeat current control section 51 is a current controller that selects a voltage vector command to zero the current error at the end of the sampling period. In order to diagnose a fault and tolerate fault control according to an exemplary embodiment of the present invention, a dead bit current controller is used because a controller having very fast dynamic characteristics is required.

The DC stage voltage estimator 52 estimates the DC stage voltage from the q-axis command current and the q-axis current sensed by the grid.

The failure determining unit 53 compares the estimated DC terminal voltage with the measured value of the DC terminal voltage sensor to determine whether the DC terminal voltage sensor is faulty. The failure determining unit 53 may compare the estimated DC terminal voltage with the measured value of the DC terminal voltage sensor and determine that the DC terminal voltage sensor is out of order when the difference value is out of the set reference range.

When the failure determination unit 53 determines that the DC terminal voltage sensor is faulty, the control unit 54 converts the estimated DC terminal voltage to perform the fault tolerance control for the voltage inverter 10. To the control voltage.

The operation of the dead bit current controller 51 will be described.

When the voltage equation is established in FIG. 1, it may be expressed as Equation (1).

식 (1)

Formula (1)

 In order to convert the continuous-time voltage equation into a discrete-time voltage equation, the current value is approximated as shown in equations (2) and (3).

식(2)

Equation (2)

식(3)

Equation (3)

 If equation (2) and (3) are substituted into equation (1) and expressed as a discrete time voltage equation, it can be expressed as equation (4).

식 (4)

Equation (4)

 In order to perform the dead bit control in Eq.

식(5)

Equation (5)

Substituting equation (5) into equation (4) is the same as in equation (6).

식 (6)

Equation (6)

 Here, an integration controller such as equation (7) is added to follow the command value more accurately.

식 (7)

Equation (7)

 The completed equation can be expressed as Equation (8).

식(8)

Equation (8)

If Equation (8) is expressed as a block diagram, the functional block diagram shown in FIG. 4 may be implemented.

The operation of the DC-stage voltage estimator 52 will be described.

와 비례적분 제어기

을 넣어서 식 (9)과 같은 비선형 방정식으로 표현할 수 있다.To apply DC-stage voltage sensorless control technique

And proportional integral controller

Can be expressed as a nonlinear equation such as (9).

식 (9)

Equation (9)

 Simply substituting Eq. (8) into Eq. (9) can be expressed as Eq. (10).

식 (10)

Equation (10)

을 기준으로 q축 성분만 식으로 정리하면 식 (11)와 같이 표현될 수 있다.Because we set the q axis as the active ingredient

If only the q-axis component can be summarized as an expression, it can be expressed as Equation (11).

식(11)

Equation (11)

에 대한 함수로 나타낼 수 있다는 것을 의미하며 비례적분 제어기 출력이 0이라면 추정값과 실제값이 같다는 것을 의미한다. 이런 관계에서 데드비트 제어를 적용하면 도 3과 같이 제안된 직류단 전압 추정 비례적분 제어기와 식 (12)로 정리된다.This equation gives an estimate

It can be expressed as a function of. If the proportional integral controller output is 0, it means that the estimated value and the actual value are the same. Applying the dead bit control in this relationship is summarized by the proposed DC stage voltage estimation proportional integral controller and equation (12) as shown in FIG.

식 (12)

Equation (12)

The failure determination unit 53 and the control unit 54 will be described to perform the DC terminal voltage sensor fault diagnosis and fault tolerance control.

The failure determination unit 53 may compare the estimated DC terminal voltage with the measured value of the DC terminal voltage sensor to determine whether the voltage sensor is faulty. The error rate calculation formula for determining the failure may be expressed as in Equation (13).

식 (13)

Equation (13)

The failure determining unit 53 compares the error rate calculated from Equation (13) with a preset voltage error range value K to determine whether the voltage sensor has failed as in Equation (14). That is, when the difference value is out of the set voltage error range K by comparing the estimated DC terminal voltage and the measured value of the DC terminal voltage sensor, it may be determined as a failure of the DC terminal voltage sensor.

식(14)

Formula (14)

에

값을 대입하여 고장 허용 제어를 구현할 수 있다. 즉, 직류단 전압 센서의 측정값 대신에 추정된 직류단 전압을 전압형 인버터(10)에 대한 제어 전압으로 출력하여 고장 허용 제어를 구현할 수 있다.When the failure of the DC terminal voltage sensor is diagnosed by the failure determination unit 53, the controller 54

on

You can implement fault tolerance control by assigning values. That is, the fault-tolerant control may be implemented by outputting the estimated DC terminal voltage as a control voltage for the voltage inverter 10 instead of the measured value of the DC terminal voltage sensor.

5 is a flowchart of a method for diagnosing a fault and controlling a fault tolerance of a DC terminal voltage sensor of a grid-connected power converter according to an embodiment of the present invention.

Referring to FIG. 5, a step of estimating a DC stage voltage from the q-axis command current and the q-axis current sensed by the system in order to perform fault diagnosis and fault tolerance control of the DC terminal voltage sensor included in the voltage inverter 10 is performed. (S10) is performed.

In the DC stage voltage estimation step S10, the DC stage voltage estimator 52 estimates the DC stage voltage from the q-axis command current and the q-axis current detected from the grid. For this purpose, the deadbit current control unit 51 is used because a controller with very fast dynamic characteristics is required. The dead bit current control section 51 selects the voltage vector command to zero the current error at the end of the sampling period.

The DC stage voltage estimator 52 may estimate the DC stage voltage from the q-axis command current and the q-axis current using a proportional integrator.

Thereafter, comparing the estimated DC terminal voltage with the measured value of the DC terminal voltage sensor, determining whether the DC terminal voltage sensor is broken or not (S20) is performed.

In the failure determination step (S20), the failure determination unit 53 compares the estimated DC terminal voltage and the measured value of the DC terminal voltage sensor to determine whether the DC terminal voltage sensor is faulty.

The failure determining unit 53 compares the estimated DC terminal voltage with the measured value of the DC terminal voltage sensor and determines that the DC terminal voltage sensor is out of order when the difference value is out of the set reference range.

If it is determined that the DC terminal voltage sensor is faulty, a step (S30) of performing the fault tolerance control for power conversion by outputting the estimated DC terminal voltage as a control voltage for the voltage inverter 10 is performed.

In the control step (S30), when the control unit 54 determines that the failure of the DC terminal voltage sensor is determined by the failure determination unit 53, the control unit 54 receives the estimated DC terminal voltage to perform the fault tolerance control for the voltage inverter 10. Output to the voltage inverter 10 as a control voltage.

Accordingly, the SVPWM 60 switches the control voltage of the controller 54 and outputs the voltage to the voltage inverter 10, and the voltage inverter 10 may perform power conversion accordingly.

 6 is a graph of simulation results for explaining fault diagnosis of a DC terminal voltage sensor according to an exemplary embodiment of the present invention.

이 된다. 오차 범위 K와 비교하면

가 되어 고장으로 판단한다. 도 5에서 고장신호의 레벨값이 0에서 1로 바뀌어 직류단 전압센서에서 고장이 발생되었음을 알 수 있다. Referring to Figure 6, it is a waveform for the failure diagnosis of the DC terminal voltage sensor. At 1.2 seconds, the DC link voltage sensor fails and you can see that the DC link voltage is less than the estimated value. Error rate

. Compared with the error range K

It is judged to be a failure. In FIG. 5, it can be seen that a failure occurs in the DC voltage sensor because the level value of the failure signal is changed from 0 to 1. FIG.

7 is a simulation graph for explaining fault tolerance control of a DC terminal voltage sensor according to an exemplary embodiment of the present invention.

에

값을 대입하여 고장 허용 제어를 구현하였다. 고장 허용 제어된

는 약 5㎳의 정착 시간 이후에 정상적인 값을 나타냈다.Referring to Figure 7, it can be seen the waveform of the fault-tolerant control of the DC terminal voltage sensor. After 1.2 seconds fault diagnosis

on

The fault tolerance control was implemented by assigning a value. Fault Tolerant Controlled

The normal value was obtained after a settling time of about 5 ms.

8 is a simulation graph illustrating a tracking value according to a change in a DC voltage according to an embodiment of the present invention.

Referring to FIG. 8, the waveform of the estimated value according to the change in the DC voltage is shown. The command voltage was changed from 600V to 700V in 2.5 seconds to see if the DC link voltage is well followed. As the actual DC link voltage changes, it can be confirmed that the estimated DC link voltage closely follows the actual voltage value after a settling time of about 40 mA.

9 is a graph showing I-V and P-V characteristics curves of a solar cell equivalent circuit for simulation according to an embodiment of the present invention.

Referring to FIG. 9, the maximum power point of the solar cell according to the voltage may be checked. That is, it can be seen that the maximum power is 6366W when the voltage is 257V. Thus, the current at the maximum power point is 24.77 A.

Due to the characteristics of the solar cell, the output may vary in various environmental conditions, so it is necessary to control the maximum output point tracking (MPPT) to follow the maximum output for each condition.

10 is a graph illustrating MPPT control during fault tolerance control according to an embodiment of the present invention.

Referring to Figure 10, it can be seen the power, current, voltage of the photovoltaic system. That is, it can be seen from the graph of FIG. 10 that the maximum power is 6124.89W when the voltage is 257.515V and the current is 24.7422A. From these results, it can be seen that a parameter coinciding with the maximum power point shown in FIG. 9 is shown. Through this, it can be seen that MPPT control can be performed without any trouble even in fault-tolerant control.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the equivalents of the claims and the claims.

10: voltage inverter 20: phase locked loop portion
30: current axis conversion unit 40: voltage axis conversion unit
50: fault diagnosis and fault tolerance control unit
51: dead bit current control unit 52: DC terminal voltage estimation unit
53: failure determination unit 54: control unit
60: SVPWM

Claims (14)

An apparatus for performing fault diagnosis and fault tolerance control of a DC link voltage sensor provided in a grid-connected power converter.
A DC stage voltage estimator for estimating a DC stage voltage from the q-axis command current and the q-axis current sensed by the system;
A failure determination unit comparing the estimated DC terminal voltage with a measured value of the DC terminal voltage sensor and determining whether the DC terminal voltage sensor is broken; And
And a controller for outputting the estimated DC link voltage as a control voltage for the power converter in order to perform fault tolerance control for the power conversion when the failure determination unit determines that the DC link voltage sensor is faulty. Fault diagnosis and fault tolerance control device of DC link voltage sensor of grid-connected power converter. The method according to claim 1,
And the DC terminal voltage estimator uses a deadbeat current controller to obtain the q-axis command current and the q-axis current. The method according to claim 1,
The DC link voltage estimator uses a proportional integrator to estimate the DC link voltage from the q-axis command current and the q-axis current, the DC-link voltage sensor fault diagnosis and fault tolerance control device of the grid-connected power converter. The method according to claim 1,
The failure determining unit compares the estimated DC terminal voltage and the measured value of the DC terminal voltage sensor, and determines that the DC terminal voltage sensor is a failure when the difference value is out of a set reference range. DC link voltage sensor fault diagnosis and fault tolerance control device of the device. The method according to claim 1,
The power converter is a DC-type voltage sensor fault diagnosis and fault tolerance control device of the grid-connected power converter, characterized in that the voltage-type inverter of the grid-connected photovoltaic power generation system. The method according to claim 1,
DC-axis voltage sensor fault diagnosis and fault tolerance control device of the grid-linked power conversion device further comprises a current-axis conversion unit for converting the three-phase current from the grid into a two-phase current to output to the DC terminal voltage estimator. The method according to claim 1,
DC-axis voltage sensor fault diagnosis and fault tolerance control device of the grid-connected power conversion device further comprises a voltage axis conversion unit for converting the three-phase voltage from the grid to a two-phase voltage to output the DC-link voltage estimator. A method for performing fault diagnosis and fault tolerance control of a DC link voltage sensor provided in a grid-connected power converter,
Estimating a DC terminal voltage from the q-axis command current and the q-axis current sensed by the system;
Comparing the estimated DC terminal voltage with a measured value of the DC terminal voltage sensor to determine whether the DC terminal voltage sensor is faulty; And
If it is determined that the DC link voltage sensor is faulty, outputting the estimated DC link voltage as a control voltage for the power converter and performing fault tolerance control for the power conversion. Diagnosis and fault tolerance control method of DC link voltage sensor of power converter. The method according to claim 8,
In the step of estimating the DC-stage voltage, the DC-stage voltage sensor fault diagnosis and fault tolerance control method of the grid-connected power converter, characterized in that for using the dead-bit current controller to obtain the q-axis command current and the q-axis current. The method according to claim 8,
In the step of estimating the DC-stage voltage, the DC-stage voltage sensor fault diagnosis and fault tolerance control method of the system-linked power converter, characterized in that for estimating the DC voltage from the q-axis command current and the q-axis current using a proportional integrator. The method according to claim 8,
The failure determination step is a grid-connected power converter, characterized in that the comparison of the estimated DC terminal voltage and the measured value of the DC terminal voltage sensor to determine the failure of the DC terminal voltage sensor when the difference value is out of the set reference range. DC link voltage sensor fault diagnosis and fault tolerance control method. The method according to claim 8,
The power converter is a voltage inverter of the grid-connected photovoltaic power generation system DC-link voltage sensor fault diagnosis and fault tolerance control method of the grid-linked power converter. The method according to claim 8,
A method for diagnosing and allowing fault control of a DC terminal voltage sensor of a grid-connected power converter further comprising the step of converting a 3-phase current into a 2-phase current from the system to estimate the DC terminal voltage. The method according to claim 8,
A method for diagnosing and allowing fault control of a DC link voltage sensor of a grid-connected power converter further comprising the step of converting a 3-phase voltage into a 2-phase voltage from the grid to estimate the DC link voltage.

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