• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The present invention discloses a method and system for diagnosing open-circuit fault of a boost chopper micro-inverter for photovoltaic panels. According to the present invention, the current in any one branch can be evaluated through an observer, and the evaluated current is compared with an actual current so as to obtain a current residual. With the amount of the current residual, it can be timely determined whether the branch involves faults, so that the branch with faults can be cut off accordingly. Therefore, any fault can be handled in time, and the stableness of the system can be enhanced.
    公开号:NL2017875A
    申请号:NL2017875
    申请日:2016-11-28
    公开日:2017-03-29
    发明作者:Dong Mi；Wang Shuo；Yang Jian；Li Li；Li Yulin；Su Mei；Han Hua；Nie Yuwen；Tian Xiaoyu
    申请人:Univ Central South；
    IPC主号:
    专利说明:

    METHOD AND SYSTEM FOR DIAGNOSING OPEN-CIRCUIT FAULT IN A BOOST CHOPPER MICRO-INVERTER FOR PHOTOVOLTAIC PANELS
    Technical Field
    The present invention relates to the field of circuit failure diagnosis, and in particular, to a method and a system for diagnosing open-circuit fault of a boost chopper micro-inverter for photovoltaic panels.
    Technical Background
    With a wide use of renewable energy, solar power becomes more and more important. To increase the efficiency of photovoltaic generation, a kind of micro-inverter assembly is proposed. Compared with traditional inverters, each micro-inverter in the micro-inverter assembly is separately connected to one photovoltaic panel of a photovoltaic panel array, so that each photovoltaic panel can be controlled by a separate maximum power point tracking control, as shown in Fig. 1. Moreover, modular design can be realized through integrating the micro-inverter with the photovoltaic component, thus achieving the surveillance of the whole system, which simplifies the structure of the system significantly.
    The boost chopper converter for photovoltaic panels is an important part of the micro-inverter. When there is one failure in one switch circuit, other photovoltaic inverters will consume energy, resulting in loss of energy and simultaneously influencing stableness of the whole system. Accordingly, there is a need for providing a solution of detecting the photovoltaic boost chopper micro-inverter, so as to timely determine whether the failure in the micro-inverter occurs, and thus prolong life of the micro-inverter system.
    Summary of the Invention
    The present invention aims to provide a solution for timely detecting the failure occurring in the micro-inverter to prolong life of the inverter system.
    In order to achieve the above objective, the present invention provides a method for diagnosing open-circuit failure occurred in the photovoltaic boost chopper micro-inverter for photovoltaic panels, wherein current of any one branch is estimated by an observer, and the estimated value of the current is compared with the actual value of the current so as to obtain a current residual. The amount of the current residual can be used to determine whether a fault occurred in the branch. In this manner, it can be timely determined whether a failure occurs in the branch, so that said branch can be cut off in time, thus improving stableness of the system.
    Moreover, when there is a fault, the fault can be handled timely and thus the fault circuit can be cut off in time through using PLC control technology. In addition, the boost chopper micro-inverter for photovoltaic panels of the present invention has advantages of less switches, simple structure, and high efficiency. Therefore, the time required for diagnosing the fault is less than that in traditional inverters, and thus the fault point can be found in a short time.
    Other features and advantages of the present invention will be further explained in the following description, and will partly become self-evident therefrom, or be understood through the implementation of the present invention. The objectives and advantages of the present invention will be achieved through the structures specifically pointed out in the description, claims, and the accompanying drawings.
    Brief Description of the Drawings
    The accompanying drawings, together with the embodiments, are provided for a further understanding of the present invention. The drawings constitute a part of the description, and are not intended to limit the present invention.
    Fig. 1 shows a structure of a boost chopper micro-inverter for photovoltaic panels according to an embodiment of the present invention;
    Fig. 2 shows an equivalent circuit of the boost chopper micro-inverter for photovoltaic panels according to the embodiment of the present invention;
    Fig. 3 is a block diagram of a system for diagnosing open-circuit fault in the boost chopper micro-inverter for photovoltaic panels according to the embodiment of the present invention;
    Fig. 4 is a wave graph of an actual current i,, an estimated current iL, and a current residual r of one branch when the boost chopper micro-inverter for photovoltaic panels operates normally; and
    Fig. 5 is a wave graph of an actual current iL, an estimated current iL, and current residual r of one branch when the open-circuit fault occurs therein.
    Detailed Description of the Embodiments
    The present invention will be explained in detail below with reference to the accompanying drawings, so that the objective, technical solutions and advantages thereof can be understood more clearly.
    Fig. 1 shows a structure of a boost chopper micro-inverter for photovoltaic panels according to an embodiment of the present invention. It should be noted that a converter according to the embodiment includes the structure of the micro-inverter with the high frequency part thereof being removed, and the diagnosis of the open-circuit fault in the micro-inverter mainly relates to switch fault in the converter.
    Fig. 2 shows an equivalent circuit of one branch of the boost chopper micro-inverter for photovoltaic panels, wherein uac is voltage of power grid across output ends of the boost chopper micro-inverter, d is turn-on time in one duty cycle of each switch element, L is an inductor of the boost chopper circuit in one single branch of the boost chopper micro-inverter, VD is an after-flow diode, Ro, Lo, Co are respectively filter resistant, filter inductor, and filter capacitor on the output ends, io is current in the filter inductor, iL is current in the inductor of the boost chopper circuit, uo is voltage across the filter capacitor, and upyis voltage on the DC side of the photovoltaic panels in the boost chopper micro-inverter.
    The following is an illustration on how to diagnose open-circuit fault in the boost chopper micro-inverter for photovoltaic panels, with reference to Fig. 3.
    As shown in Fig. 3, the open-circuit fault diagnosis system 300 includes an observer 310, a current residual module 320, a comparison module 330, and a fault point cutting-off module 340.
    The observer 310 is configured to evaluate current in a branch including any switch in the boost chopper micro-inverter for photovoltaic panels on line (in real time), so as to obtain an evaluated current. A branch current in the example is the current l/ in the inductor of the boost chopper circuit of the micro-inverter.
    It is necessary to establish the observer in advance, which includes the following steps.
    In step A, the boost chopper micro-inverter for photovoltaic panels is modeled through using average switching period method, so as to create a three-order non-linear model based on the average switching period with respect to one single branch of the converter, which is expressed as follows:
    (1) wherein reference can be made to the above explanations on Fig. 2 for the meaning represented by each parameter.
    In step B, small deviation at steady state points with respect to the three-order non-linear model are processed by linearization, so as to obtain linear small signal model of the single branch of the converter.
    Assume that n , and are respectively current in the inductor of the boost chopper circuit, current in the filter inductor, and voltage on the filter capacitor, ^pv is voltage on the DC side of the photovoltaic panels of the steady boost chopper micro-inverter, D is steady state duty cycle, is voltage on the AC side of the steady state, and Δ//, Δ/'°, Δ^°, 9 Διίργ ^ Δuac are reSpectiveiy smaii disturbances introduced into state variables and input variables at steady state points, which will be expressed as follows:
    (2)
    Through combining equation (2) into equation (1), the following equation can be obtained:
    (3)
    By using steady relationship and approximating the two-order AC term to be zero, Equation (3) can be simplified as follows:
    (4)
    The linear small signal model of the single branch of the converter can be obtained as follows:
    (5) wherein, ,
    , and y = ^ ] are respectively state variables, control inputs, and measurable outputs;
    , and C [l O O] arc respectively state matrix, control matrix, and output matrix, and
    wherein h is steady state current of inductor L at steady state,is the first derivative of the state variables.
    In step C the observer is established, which is expressed as follows:
    (6) wherein x , ^ are respectively the evaluated values of the state variables and measurable outputs, and H is error compensation matrix for output of the observer, and x is the evaluated value for x.
    In step D, with respect to the linear small signal model for the boost chopper micro-inverter, if the evaluation error of the states is made to be e ~ x~x, then
    ( ) £ . £. wherein ‘L is evaluated error of the current in the inductor of the boost chopper circuit, £ is evaluated error of the current in the filter inductor, and is evaluated error of the voltage on the filter capacitor.
    By subtracting the expression of the observer from the expression of the linear small signal model, the following equation can be obtained:
    (8)
    By combining equation (7) and equation (8), the following error equation can be obtained: 'e = (A-HC)e (9)
    The feedback gain matrix H of output error of the observer is selected to enable (A-HC) to be steady, so as to determine the observer.
    In this example, if the feedback gain matrix H of output error of the observer is made to H_h Η Η T 1 1 2 ’ J , wherein Hl, H2, and H3 are respectively ratios of output error feedback values to input values, then
    (10)
    Subsequently, the evaluated current l/ can be calculated according to equation (6).
    The current residual module 320 is configured to create the current residual based on the evaluated current and the actual current measured at the same point.
    Specifically, the current residual can be calculated by using the following equation,
    (11) wherein v= 1.2, ll is the actual current in the inductor of the boost chopper circuit, >L is the evaluated current in the inductor of the boost chopper circuit, and t is the time. The robustness of the system can be increased by using equation (11), thus the system is more sensitive to the fault.
    The comparison module 330 is configured to compare norm H2 of the current residual with the residual threshold, determining whether the branch including the switch involves open-circuit faults.
    Firstly, the residual threshold is calculated, which is ^th ~SUPH wherein
    is H2 norm of the current residual , and
    , wherein T is transposition of the matrix. In this example, ^,h =0.5.
    If H2 norm of the current residual is less than ^jh, there is no open-circuit fault occurred, and continuing to monitor the circuit is performed. If H2 norm of the current residual is larger than or equal to ^,h, it is determined that the branch involves an open-circuit fault.
    The fault point cutting-off module 340 is connected with comparison module 330 and configured to cut off the fault branch including the switch by using PLC technology where there is a fault.
    In practice, by using PLC technology, the open-circuit position can be determined by the parameter resulted in diagnosis of the fault position. Therefore, the fault can be timely handled, and the switch is turn off.
    The following provides an example of an actual circuit. The actual parameters are listed in Table 1.
    Table 1 Actual parameters
    In the simulation diagram as shown in Fig. 4, waves of the actual current ll in the inductor of the boost chopper circuit, the evaluated current 1l in the inductor of the boost chopper circuit, and the current residual r thereof are shown from top to bottom. From Fig. 4 it can be seen that the evaluated current can follow the actual current closely, thus implementing better evaluation.
    In Fig. 5, waves of the actual current 1l , the evaluated current 1l in the inductor of the boost chopper circuit, and the current residual r when there is a fault occurred in one branch of micro-inverter are shown in order from top to bottom. According to these waves, the branch which involves faults can be determined by comparing the current residual with the residual threshold.
    According to the present invention, the current in any one branch can be evaluated through an observer, and the evaluated current is compared with the actual current so as to obtain the current residual. With the amount of the current residual, it can be timely determined whether the branch involves faults, so that the branch with faults can be cut off accordingly. Therefore, any fault can be handled in time, and the stableness of the system can be enhanced.
    It should be noted that the above embodiments are described only for better understanding, rather than limit the present invention. Anyone skilled in the art can make any amendments to improvements on the implementing forms or details without departing from the scope of the present invention. The protection scope of the present invention shall still be determined by the claims.
    权利要求:
    Claims (10)
    [1]

    Method for diagnosing an open-circuit error in a boost chopper micro-inverter for photovoltaic panels, comprising the steps of: establishing an observer for evaluating a current in a branch of the boost chopper micro-inverter comprising a switch in an on-line manner for obtaining an evaluated current; obtaining a current residue based on the evaluated current and an actual current measured at said branch; comparing an H 2 standard of the current remainder with a residual threshold value for determining whether an open circuit error occurs in the branch containing the switch; and cutting off the branch containing the switch by using PLC technology when the open chain error occurs in said branch.
    [2]
    The method of claim 1, wherein if the H 2 standard of the current remainder is less than the residual threshold value, it is determined that no open chain error occurs; in other cases, it is determined that an open chain error occurs.
    [3]
    The method according to claim 1 or 2, wherein the step of establishing the observer further comprises sub-steps of: performing modeling for the boost chopper microinverter for photovoltaic panels, for obtaining a third order not -linear model based on average switching period with regard to a single converter branch; processing small deviation at points of stable operation with respect to the third-order non-linear model via linearisation, to obtain a linear small signal model of the single branch of the converter; constructing an expression for the observer, and obtaining an error calculation expression based on the linear small signal model of the single branch of the converter and the expression for the observer; and selecting a feedback gain matrix of output error from the observer that makes the error stable for determining the observer.
    [4]
    The method of claim 3, wherein an expression for the third-order non-linear model of the single branch of the converter is as follows:

    ti where ac is a mains voltage across output ends of the boost chopper microinverter, Xi Pr is a voltage on a DC side of the photovoltaic panels in the boost chopper microinverter, d is a switch-on time of each switch during one cycle, L is a self-induction of a boost chopper chain in a single branch of the boost chopper microinverter, RL is C 0, 0, and 0, respectively, a filter resistor and filter self-induction, and a filter capacity of the output ends, * ° is a current in a filter inductor, lp is a current in an inductor of the boost chopper circuit, and li is a voltage on a filter capacitor.
    [5]
    The method of claim 4, wherein the expression for the linear small signal model of the single branch of the converter is as follows:

    at which

    and y ~ W are respectively a state variable, a control input and a measurable output;

    3n C - [10 O] are respectively a state matrix, a control matrix and an output matrix,

    is a first derivative of the state variable,

    D is a power factor in stable operation, AC is a voltage on an AC side in stable operation, IL is a current in stable operation in the inductor in stable operation.
    [6]
    The method of claim 4 or 5, wherein the expression for the observer is as follows:

    wherein x, y are evaluated values of the state variable and the measurable output, respectively, Fault error matrix for output from the observer, and x is an evaluated value for x.
    [7]
    The method of any one of claims 4-6, wherein error ^ can be calculated by the following equation: e = (A - HC) e where

    "L is an evaluated error of the current in the inductor of the boost chopper chain, is an evaluated error of the current in the filter inductor, and is an evaluated error of the voltage in the filter capacitor. A method according to claim 7, wherein if the selected M = h m m "F is feedback amplification matrix H of the output error of the observer L 1 2 3 j, wherein H 1, H 2, and Ht, respectively, are ratios of output error feedback values to input values, then


    [9]
    The method according to any of claims 4-8, wherein the current remainder is calculated by the following equation: r (t) = v * (iL-LL) where r (t) is the current residue, v = 1.2, ÏL a actual current in the inductor of the boost chopper chain, 11 is an evaluated current in the inductor of the boost chopper chain, and t is time.
    [10]
    The method of any one of claims 4-9, wherein the residual threshold value is calculated by the following equation:

    where Jth is the residual threshold value, H ^ is an H2 standard of the current residue, and

    , where T is the transposition of the matrix.
    [11]
    A system for diagnosing an open-circuit error in a boost chopper microinverter for photovoltaic panels, comprising: an observer configured to evaluate a current in a branch of the boost chopper microinverter comprising a switch on an -line method for obtaining an evaluated current, a current residual module, configured to obtain a current residual based on the evaluated current and an actual current measured at said branch, a comparison module configured for comparing the H2 standard of the current remainder with a residual threshold value for determining whether an open chain error occurs in the branch containing the switch, and an error point cut module configured to cut off the branch containing the switch by using PLC technology when the open chain error occurs in that branch.
    类似技术:
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    同族专利:
    公开号 | 公开日
    NL2017875B1|2017-05-23|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US20110018578A1|2009-07-21|2011-01-27|Gm Global Technology Operations, Inc.|Methods, systems and apparatus for detecting abnormal operation of an inverter sub-module|
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    CN103208815A|2013-04-02|2013-07-17|清华大学|d-q axis parameter identification method for grid-connected inverter of photovoltaic power generation system|
    CN108445340B|2018-02-28|2021-04-20|江苏大学|Method for detecting open-circuit fault of five-phase permanent magnet synchronous motor inverter|
    CN110635686B|2019-11-14|2021-10-01|东北电力大学|Control and fault detection method of boost circuit based on switching system|
    法律状态:
    2021-08-11| PD| Change of ownership|Owner name: CHANGSHA VICTORY ELECTRICITY TECH CO LTD; CN Free format text: DETAILS ASSIGNMENT: CHANGE OF OWNER(S), ASSIGNMENT; FORMER OWNER NAME: CENTRAL SOUTH UNIVERSITY Effective date: 20210716 |
    优先权:
    申请号 | 申请日 | 专利标题
    CN201610841041|2016-09-22|
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