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A Microgrid Protection Method Based on Impedance Characteristics
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A technology of impedance characteristics and micro-grid, applied in the direction of emergency protection circuit devices, electrical components, etc., can solve the problems of high data synchronization requirements and poor anti-transition resistance ability
Active Publication Date: 2021-09-17
UNIV OF JINAN
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[0011] In summary, the existing micro-grid protection schemes have problems such as being greatly affected by the system operation mode and load current, high requirements for data synchronization, and poor anti-transition resistance. Therefore, it is urgent to study micro-grid protection that can solve the above problems. Program
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Embodiment 1
[0077] Set the fault point f in the area 1 , the fault type is BC phase-to-phase fault, and the fault time is t=1.0s.
[0078] (1) In the microgrid, the protection devices on both sides of the protected line L2, that is, the M side and the N side, respectively collect the three-phase voltage and three-phase current in real time, and record the obtained three-phase voltage sampling value sequence of the M side as u MA (k), u MB (k), u MC (k), the M-side three-phase current sampling value sequence is respectively denoted as i MA (k), i MB (k), i MC (k); denote the obtained N-side three-phase voltage sampling value sequence as u NA (k), u NB (k), u NC (k), the N-side three-phase current sampling value sequence is respectively denoted as i NA (k), i NB (k), i NC (k). The value of the sequence number k above is 1 to 1440.
[0079] (2) The protection device on the M side extracts the positive sequence voltage sampling value and the positive sequence current sampling valu...
Embodiment 2
[0105] Set the out-of-area fault point f 2 , the fault type is BC phase-to-phase fault, and the fault time is t=1.0s.
[0106] The steps (1) to (7) in Example 2 are consistent with the steps (1) to (7) in Example 1, and only the differences will be described below.
[0107] Step (6), after calculation, Z CM =-0.4001-j0.2598Ω, Z CN =0.3155+j0.2947Ω.
[0108] Step (7), after calculation, arg(Z CM )=216.51°, arg(Z CN )=41.78°, Protective devices on both sides do not need to be calculated|Z CM +Z CN The value of |. arg(Z CN )∈(0°,180°], arg(Z CM )∈[90°,360°], the result of the discrimination in the present invention is an out-of-area fault.
Embodiment 3
[0110] Set the out-of-area fault point f 3 , the fault type is BC phase-to-phase fault, and the fault time is t=1.0s.
[0111] Steps (1) to (7) in Example 3 are consistent with the processes of Steps (1) to (7) in Example 1, and only the differences will be described below.
[0112] Step (6), after calculation, Z CM =0.0019+j0.0166Ω, Z CN =-0.0816+j0.0272Ω.
[0113] Step (7), after calculation, arg(Z CM )=83.54°, arg(Z CN )=198.41°, arg(Z CN )∈(180°,270°), the protective devices on both sides need to calculate |Z CM +Z CN | to distinguish between internal and external faults. After calculation, |Z CM +Z CN |=0.080Ω,|Z CM +Z CN |<0.096Ω, the judgment result of the present invention is an out-of-area fault.
[0114] Table 2 is the discrimination result of 3 examples, wherein "—" indicates that this content does not need to be calculated.
[0115] The discrimination result of table 2 embodiment
[0116] fault location arg(Z CM )
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Abstract
The invention discloses a micro grid protection method based on impedance characteristics. This method collects the three-phase voltage and three-phase current on both sides of the protected line in the microgrid in real time. When the protected line fails, the protection on both sides calculates the positive-sequence fault component voltage and positive-sequence fault component current respectively, and respectively according to The measured impedance is calculated from the positive sequence fault component voltage and the positive sequence fault component current. Both guards receive the measured impedance transmitted from the opposite side. The protection on either side judges the internal and external faults of the protected line according to the phase angle and amplitude characteristics of the measured impedance on the local side and the received phase angle and amplitude characteristics of the measured impedance on the opposite side. If the protection on both sides of the protected line is judged to be an internal fault, the respective circuit breakers will be tripped. The invention is suitable for line protection in a microgrid, does not rely on stepped coordination to achieve selectivity, and can adapt to the situation of multiple distributed power sources in the microgrid being connected.
Description
technical field [0001] The invention belongs to the field of relay protection of electric power systems, and in particular relates to a method for protecting micro-grids based on impedance characteristics. Background technique [0002] With the development of distributed generation (Distributed Generation, DG), a variety of distributed power sources, energy storage devices, loads and control devices are combined into an independent power supply system, which is connected to the large power grid in the form of a micro grid, taking advantage of the flexibility of control It can support the power supply capacity and power quality of the large power grid. The microgrid contains a large number of distributed power sources. Different from the structure of the traditional distribution network, the microgrid has become a complex multi-power system. The distribution of power flow in the microgrid and the short-circuit current in the line during the fault are different from the tradit...
Claims
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Application Information
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