Current protection method for power distribution network containing distributed photovoltaic power supply

Abstract

The invention provides a current protection method for a power distribution network containing a distributed photovoltaic power supply. The current protection method comprises the steps of arranging a longitudinal differential current protection device at an upper-stage circuit of a photovoltaic access point, and arranging three segmental adaptive current protection devices I / II / III at a system power supply side; judging whether a fault type is in two-phase circuit short or three-phase circuit short and correspondingly determining a coefficient Kd of the fault type by the adaptive current protection device after a fault occurs in the power distribution network; judging a two-phase or three-phase fault and protecting back-side impedance of the device and an electromotive force of a back-side equivalent power supply by the adaptive current protection device; and calculating protection action setting values of three segments I / II / III on line, taking corresponding protection action, and respectively judging a fault direction and taking corresponding protection action by each longitudinal differential current protection device. The protection method is free from a system running mode, each protection device can be enabled to accurately act, and the working reliability is high.

Description

technical field [0001] The invention relates to a distribution network protection method, in particular to a current protection method suitable for a distribution network containing distributed photovoltaic power sources. Background technique [0002] Although distributed photovoltaic power grid connection can improve the stability of the system and reduce the use of fossil fuels, it will have a certain impact on the existing protection, causing the traditional current protection in the distribution network to malfunction or refuse to operate. Therefore, Research on the protection of distribution network with distributed photovoltaic power access has gradually become a hot topic in domestic and foreign research. [0003] Photovoltaic grid-connected power generation has developed rapidly. With the access of a large number of distributed photovoltaic power sources, the traditional single-power radial distribution network has become a multi-power distribution network. When the ...

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Problems solved by technology

[0002] Although distributed photovoltaic power grid connection can improve the stability of the system and reduce the use of fossil fuels, it will have a certain impact on the existing protection, causing the traditional current protection in the distribution network to malfunction or refuse to operate. Therefore, Research on the protection of distribution network with distributed photovoltaic power access has gradually become a hot topic in domestic and foreign research.

[0003] Photovoltaic grid-connected power generation has developed rapidly. With the access of a large number of distributed photovoltaic power sources, the traditional single-power radial distribution network has become a multi-power distribution network. When the distribution network fails, the magnitude of its short-circuit current and The direction will change greatly, which will have a great impact on the current protection method adopted by the traditional distribution network, causing the current protection device in the traditional distribution network to malfunction or refuse to operate. Specifically, for distributed power For the current protection device upstream of the access point, due to the shunting effect of the distributed power supply, the current flowing into the current protection device will decrease, thereby reducing the protection range of the original current protection device, and even causing the original current protection device to refuse to operate; The downstream protection of the distributed power access point, due to the boosting effect of the photovoltaic power source, will increase the current flowing through the current protection device, increasing the protection range, which may extend the protection range to the next line, so that the current Malfunction of the protection device

At the same time, because the photovoltaic power generation system has no rotating parts, there is no damping effect caused by inertia, which makes it different from the failure characteristics of traditional synchronous motors. The output of photovoltaic power sources during a fault is generally a symmetrical three-phase current, and The capacity of the photovoltaic power source is much smaller than the capacity of the system. This weak power source characteristic will make the current protection device in the traditional distribution network unable to operate correctly after being connected to the distributed photovoltaic power source.

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