AVR fault identification method suitable for marine diesel generating set

Abstract

The invention relates to an AVR fault identification method suitable for a marine diesel generating set, the fault types of the marine AVR comprise an excitation loss fault and a mistaken switching and forced excitation fault, the fault characteristics of the marine AVR are analyzed, the fault state of the AVR is identified only through the characteristics of the system voltage and the reactive power of the set, an additional sensor does not need to be additionally arranged, and the fault identification efficiency is improved. And meanwhile, the problem of unit parallel inverse reactive protection misoperation is solved, the reliability of power supply of a marine power system is improved, and potential safety hazards caused by excitation loss of a generator and mis-switching and forced excitation are avoided.

Description

Technical Field

[0001] This invention relates to the field of marine electrical system protection technology, and in particular to a method for fault identification of AVR in marine diesel generator sets. Background Technology

[0002] Automatic voltage regulators (AVRs) play a crucial role in marine synchronous generators, maintaining stable generator terminal voltage by controlling the generator's excitation current. AVR failure can lead to generator demagnetization or voltage regulation failure. Traditional protection systems monitor the AVR's excitation current and output voltage, immediately isolating the generator unit if the deviation exceeds a preset value.

[0003] Currently, the excitation current of marine generator AVRs is transmitted via a communication interface, which has poor reliability. Acquiring the excitation current requires pre-setting a current sensor within the AVR, necessitating design modifications, which most current marine AVRs cannot meet. Furthermore, when multiple generators are connected in parallel within a marine power station, a large voltage difference between the connected unit and the grid can cause reverse reactive power in the original grid-connected unit, triggering a false trip of the loss-of-excitation protection. In summary, current fault diagnosis and protection strategies for AVRs still have reliability issues, and there is room for optimization in the protection system design. Summary of the Invention

[0004] To address the above issues, a fault diagnosis method for AVR systems in marine diesel generator sets is proposed.

[0005] The technical solution of the present invention is: a fault identification method for AVR of marine diesel generator sets, including identification of demagnetization fault and accidental forced excitation fault; The demagnetization fault identification: The AVR demagnetization fault protection criteria are as follows: 1) and 2). When both criteria are met, the system is identified as experiencing an AVR demagnetization fault. 1) The reactive power of the faulty unit is greater than Q. set Qset is the reverse reactive power setting value, which is adjusted according to the actual system capacity for demagnetization reverse reactive power, and is greater than the instantaneous reverse reactive power value when the unit is paralleled. 2) System voltage < 1.1 times rated voltage; The identification of erroneous forced excitation faults: The AVR false start fault protection criteria are as follows: A and B. A false start fault is identified when both of the following criteria are met. A: System voltage > 1.1 times rated voltage; B: The reactive power output of the faulty unit shows a continuous increasing trend, while the reactive power output of other normal units shows a decreasing trend, and even reverse reactive power occurs.

[0006] Furthermore, through a centralized control device, the grid voltage and reactive power of each unit are collected to form a two-dimensional voltage-reactive power coordinate system. Then, combined with the protection criteria for AVR demagnetization fault and AVR erroneous excitation fault, a voltage-power curve of AVR fault characteristics is constructed. By comparing it with the voltage-reactive power curve of AVR fault characteristics, the protection logic judgment is executed.

[0007] The beneficial effects of this invention are as follows: This invention is applicable to the AVR fault identification method of marine diesel generator sets. It identifies the fault state of AVR only by the characteristics of system voltage and generator set reactive power, without the need for additional sensors. At the same time, it solves the problem of false tripping of parallel reverse reactive power protection of generator sets. While identifying faults quickly, it improves the reliability of marine power supply system and avoids safety hazards caused by generator demagnetization and accidental activation of forced excitation. Attached Figure Description

[0008] Figure 1 This is a UQ curve diagram illustrating the fault characteristics of the AVR in this invention. Detailed Implementation

[0009] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0010] This invention applies to the AVR fault identification method for marine diesel generator sets: 1. The AVR demagnetization fault protection criteria are as follows: an AVR demagnetization fault is identified when both of the following criteria are met: (1) The reactive power of the faulty unit is greater than Q. set (Qset is the reverse reactive power setting value, which is adjusted according to the actual system capacity for reverse reactive power after loss of excitation, and is greater than the instantaneous reverse reactive power value when the unit is connected to the grid.) (2) The system voltage is less than 1.1 times the rated voltage.

[0011] 2. The criteria for AVR false start-up fault protection are as follows: AVR false start-up fault is identified when both of the following criteria are met: (1) System voltage > 1.1 times rated voltage; (2) The reactive power output of the faulty unit shows a continuous increasing trend, while the reactive power output of other normal units shows a decreasing trend, and even reverse reactive power occurs.

[0012] The fault types of marine AVRs include demagnetization faults and accidental forced excitation faults. Their fault characteristics are analyzed as follows: 1. Fault characteristics after generator AVR loses excitation: 1) Reverse no-work: The de-excitation generator changes from outputting reactive power to absorbing reactive power, and the reactive power remains negative after reversal.

[0013] 2) Overcurrent in de-excitation generators and normal generators: The demagnetizing generator will absorb a large amount of reactive power from the system to establish an air gap magnetic field (to maintain the energy conversion channel from mechanical power to electrical power), which will cause overcurrent in the demagnetizing generator; Other normally operating generators, in addition to bearing all the original reactive load in the system, also need to bear the additional reverse reactive load required by the de-excitation generator, which will cause overcurrent in the normally operating generators and lead to a drop in the voltage of the entire system.

[0014] 2. Characteristics of generator AVR erroneous forced excitation fault: 1) The grid voltage increases.

[0015] 2) High reactive power output of faulty units: The AVR continuously outputs the maximum excitation current, causing the unit to generate reactive power beyond its share, becoming a "reactive power source" in the power grid.

[0016] 3) Normal units are forced to reverse reactive power: The grid voltage is forcibly raised by the faulty unit. In order to maintain the set voltage, the normal unit's AVR will reduce its excitation current in the opposite direction, which will result in a significant reduction in its output reactive power, or even absorb reactive power from the grid.

[0017] like Figure 1 The diagram shows the UQ curve of AVR fault characteristics. Through a centralized control device, grid voltage and reactive power of each generating unit are collected to form a two-dimensional coordinate system. This data, combined with protection criteria, is used to construct the UQ curve of AVR fault characteristics. Figure 1 A comparison is performed, and protection logic is executed to determine the cause. When the real-time acquired two-dimensional coordinate point is located in region ②, it indicates that the local generator AVR has a loss-of-excitation fault. When the two-dimensional coordinate point is located in region ⑤, and other grid-connected generators show a decrease in reactive power or reverse reactive power, it indicates that the local generator AVR has a fault of mistakenly switching on forced excitation.

[0018] The embodiments described above merely illustrate specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for fault identification of AVR in marine diesel generator sets, characterized in that, This includes the identification of demagnetization faults and accidental forced excitation faults; The demagnetization fault identification: The AVR demagnetization fault protection criteria are as follows: 1) and 2). When both criteria are met, the system is identified as experiencing an AVR demagnetization fault. 1) The reactive power of the faulty unit is greater than Q. set Qset is the reverse reactive power setting value, which is adjusted according to the actual system capacity for demagnetization reverse reactive power, and is greater than the instantaneous reverse reactive power value when the unit is paralleled. 2) System voltage < 1.1 times rated voltage; The identification of erroneous forced excitation faults: The AVR false start fault protection criteria are as follows: A and B. A false start fault is identified when both of the following criteria are met. A: System voltage > 1.1 times rated voltage; B: The reactive power output of the faulty unit shows a continuous increasing trend, while the reactive power output of other normal units shows a decreasing trend, and even reverse reactive power occurs.

2. The method for fault identification of AVR in marine diesel generator sets according to claim 1, characterized in that, The system collects grid voltage and reactive power of each generating unit through a centralized control device, forming a two-dimensional voltage-reactive power coordinate system. Then, it combines the protection criteria for AVR demagnetization fault and AVR erroneous excitation fault to construct a voltage-power curve of AVR fault characteristics. By comparing the voltage-reactive power curve of AVR fault characteristics with the voltage-reactive power curve of AVR fault characteristics, the system executes protection logic judgment.

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