Adaptive power grid power supply protection method suitable for ship working condition change

Abstract

The application relates to a self-adaptive power grid power supply protection method suitable for ship working condition changes, and establishes a direction overcurrent protection system based on composite voltage locking, which is used for self-adapting system working condition changes under the conditions of power flow direction changes and large-capacity different power ratio of grid units, and realizes protection sensitivity and selectivity. Power direction discrimination elements and voltage discrimination elements are added to the lines of large-capacity different power ratio units to judge whether overcurrent protection is enabled to be put into operation, so that self-adaptive direction overcurrent protection and self-adaptive composite voltage overcurrent protection of large-capacity different power ratio units under different operation modes are realized, and the power grid power supply protection problem of the complex power supply network structure of a ship is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power supply system protection, in particular to a self-adaptive power grid power supply protection method suitable for ship working condition changes. BACKGROUND

[0002] The traditional ship power grid adopts a dry feed power supply network. In this network, the power supply path of the load device is single, the topology structure changes little under different working conditions, and the power grid power supply protection is mainly based on the current time principle. The current setting value determined based on the current time principle is usually selected according to the maximum operating mode to ensure the selectivity of protection action, and the sensitivity of protection action is verified according to the minimum operating mode. The protection scheme needs to consider the selectivity and sensitivity of protection action, but if the system operating mode changes greatly, it will be difficult to meet the requirements of selectivity and sensitivity, especially under the minimum operating mode, the protection may refuse to act and other consequences.

[0003] The dry feed power grid arrangement is feasible when the network scale is small. However, with the continuous development of ships and the increase of electrical equipment, its disadvantages gradually appear, such as the problem of air tightness between cabins caused by too many cabin cables. Therefore, the ring power grid emerges as the times require, which greatly improves the power supply continuity of the ship power supply system and the vitality and combat effectiveness of the ship. However, the overcurrent protection based on the current time principle cannot completely adapt to the ring power supply network, and a new protection strategy suitable for complex power supply network structure needs to be proposed.

[0004] Self-adaptive protection can follow the changes of power grid structure and operating mode, and adjust the protection performance in real time. It has been developed for many years in land power grid. Ships have multiple operating modes such as docking, cruising, fighting and anchoring. Moreover, the original power grid topology structure may be damaged due to fighting. In order to ensure that the ship protection system can normally perform protection functions under multiple operating modes, it is particularly important to implement and use the self-adaptive protection idea of land power grid in the ship protection system. SUMMARY

[0005] In view of the above power grid power supply protection problem of complex power supply network structure, a self-adaptive power grid power supply protection method suitable for ship working condition changes is proposed.

[0006] The technical scheme of the present application is as follows: a self-adaptive power grid power supply protection method suitable for ship working condition changes, specifically comprising

[0007] 1) Power supply state, under normal circumstances, the power direction of the emergency cross connection line is from the main busbar to the emergency busbar; under the emergency mode, the power direction is from the emergency busbar to the main busbar; a short-circuit power direction element is installed in the protection device of the emergency cross connection line, so that whether the protection setting value is put into operation can be determined, so as to realize adaptive overcurrent protection of different setting value groups to adapt to the change of system operation mode, specifically: under the condition that the single-phase current setting determination and the corresponding direction determination in the protection device of the emergency cross connection line are both satisfied and the PT disconnection is not locked, the action time accumulation is outputted, and the tripping action is performed when the action time of any one of the three phases reaches.

[0008] 2) Line state during fault, when a short-circuit fault occurs during the power supply of the high-power generating module to the system, the voltage on the main cross connection and busbar line decreases, and the current increases; when a short-circuit fault occurs during the power supply of the emergency ordinary generating module to the system, the voltage on the main cross connection and busbar line decreases, and the current increases; a composite voltage element is installed in the protection device of the main cross connection and busbar line, so that the setting value group is unified to realize adaptive composite voltage direction overcurrent protection to adapt to the system operation mode, specifically: under the condition that the single-phase current setting determination and the composite voltage criterion in the protection device of the non-emergency cross connection line are both satisfied and the PT disconnection is not locked, the action time accumulation is outputted, and the tripping action is performed when the action time of any one of the three phases reaches.

[0009] Further, the adaptive overcurrent protection implementation method in 1) is: overcurrent short-time delay protection detects overcurrent and gradually disconnects through timing limit step delay, starting from the power supply end according to the power supply direction, sequentially passing through the protection switches along the line, and finally gradually disconnecting through the delay of the unit main switch, so as to realize the coordination between the upper and lower protection.

[0010] Further, the composite voltage element in 2) is composed of a negative sequence voltage element and a phase-to-phase low voltage element, and the two constitute or logic, wherein the negative sequence voltage element can sensitively reflect two-phase asymmetric short circuit of the system, and the low voltage element can sensitively reflect three-phase symmetric short circuit of the system.

[0011] Further, the adaptive composite voltage direction overcurrent protection implementation method in 2) is: the adaptive composite voltage and overcurrent protection of the busbar and the main cross connection are unified through the following table for the protection current setting value group under the power supply of the high-power generating module and the emergency ordinary generating module, wherein, I DG is the rated current of the diesel generator unit, U is the voltage between any two phases of the system, U n is the rated voltage of the power supply system, and U2 is the negative sequence voltage of the system.

[0012]

[0013]

[0014] The beneficial effects of the present invention are as follows: the present invention is applicable to an adaptive power grid power supply protection method for changing ship operating conditions, establishing a directional overcurrent protection system based on composite voltage blocking, which is used to adapt to system operating conditions under power flow direction changes and large-capacity and low-power ratio conditions for on-grid units, thereby achieving protection sensitivity and selectivity. By adding power direction discriminating elements and voltage discriminating elements to the circuits of large-capacity and low-power ratio units to determine whether overcurrent protection is enabled, adaptive directional overcurrent protection and adaptive composite voltage overcurrent protection are achieved for large-capacity and low-power ratio units under different operating modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of an exemplary power supply network and adaptive directional overcurrent protection according to the present invention;

[0016] Figure 2 This is a schematic diagram of the adaptive directional overcurrent protection principle of the present invention;

[0017] Figure 3 This is a schematic diagram of the composite voltage overcurrent protection principle of the present invention. DETAILED DESCRIPTION

[0018] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0019] This invention describes an adaptive protection technology suitable for changing ship operating conditions. Based on a directional overcurrent protection system with composite voltage blocking, it adapts to system operating conditions under varying power flow direction and large power ratios of grid-connected units, achieving protection sensitivity and selectivity. By adding power direction and voltage discrimination elements to the circuitry of units with large power ratios, the technology determines whether overcurrent protection is enabled. This technology implements adaptive directional overcurrent protection and composite voltage overcurrent protection for units with large power ratios in different operating modes.

[0020] Take the power supply network structure of a ship as an example. Figure 1 As shown, the power supply network is equipped with two high-power generator modules, each equipped with two high-power generator modules (TGs) and two medium-voltage main switchboard control panels. To improve power supply continuity, the main busbar of each high-power generator module is connected to the emergency busbar of the emergency general generator module (DG) via an emergency jumper line. This allows for power supply to the entire ship's emergency loads in the event of a loss of power from the high-power generator module. The capacity of the emergency general generator module is much smaller than that of the high-power generator module. Given the same voltage level, the current of the emergency general generator module is much lower than that of the high-power generator module.

[0021] (1) In normal mode, the entire ship's load is powered by the high-power power generation module; in emergency mode, the entire ship's emergency load is powered by the emergency general power generation module.

[0022] (2) If the power supply network only adopts the overcurrent protection based on the current-time principle, the protection setting value cannot be unified when different power units supply power to the power supply network in normal mode and emergency mode.

[0023] (3) In the power supply state, under normal circumstances, the power direction of the emergency jumper line flows from the main busbar to the emergency busbar. In the emergency mode, the power direction flows from the emergency busbar to the main busbar.

[0024] (4) Line status at the time of fault: when a short circuit occurs when the high-power power generation module supplies power to the system, the voltage on the main jumper and bus tie lines decreases and the current increases; when a short circuit occurs when the emergency ordinary power generation module supplies power to the system, the voltage on the main jumper and bus tie lines decreases and the current increases.

[0025] (5) According to the situation in (3), a short-circuit power direction element can be added to the protection device of the emergency jumper line to enable the protection setting value to be put into use, so as to realize adaptive overcurrent protection with different setting value groups to adapt to the changes in the system operation mode. The protection principle of adaptive directional overcurrent protection is as follows: Figure 2 As shown, when the single-phase current setting judgment and the corresponding direction judgment in the protection device of the emergency jumper line are both satisfied (and), and the PT line is broken and not locked, the output is output to accumulate the action time, and the tripping action is performed when the action time of any one of the three phases is reached (or).

[0026] (6) Based on the situation in (4), the protection devices of the main jumper, busbar and other lines can be equipped with composite voltage elements on the basis of (5) to realize the adaptive composite voltage direction overcurrent protection that can adapt to the system operation mode by unifying the setting group. The principle of adaptive composite voltage direction overcurrent protection is as follows: Figure 3 As shown, in the protection device of the non-emergency jumper line, both the single-phase current setting judgment and the composite voltage judgment criteria are satisfied (and), and the PT line is broken and not locked, the output is output to accumulate the action time, and the tripping action is performed when the action time of any one of the three phases is reached (or).

[0027] Specific implementation of (5) and (6):

[0028] Adaptive directional overcurrent protection:

[0029] The overcurrent short-time delay protection detects overcurrent and disconnects it step by step through a time-limited ladder delay. It starts from the power supply end according to the power supply direction, passes through the protection switches in sequence along the line, and finally disconnects the main switch of the unit step by step to achieve coordination between the upper and lower protections. After the emergency jumper switch is equipped with adaptive directional overcurrent protection, the coordination between the upper and lower protections of the system can be achieved through Figure 1 Further description:

[0030] a. The short-circuit power direction from the medium-voltage main bus to the line is defined as the positive direction (as shown by the blue arrow), and the overcurrent protection of the emergency cross connection QF1 is enabled only when the positive direction power supply is determined, thereby forming the "emergency cross connection switch t+Δt→bus tie switch t+2Δt→main cross connection switch t+3Δt→high-power generating module switch t+4Δt" step time limit characteristic in the high-power generating module power supply mode;

[0031] b. The short-circuit power direction from the medium-voltage emergency bus to the line is defined as the positive direction (as shown by the red arrow), and the overcurrent protection of the emergency cross connection QF2 is enabled only when the positive direction power supply is determined, thereby forming the "load screen tie switch t+Δt→main cross connection switch t+2Δt→bus tie switch t+3Δt→emergency cross connection switch t+4Δt→emergency ordinary generating module switch t+5Δt" step time limit characteristic in the emergency ordinary generating module power supply mode.

[0032] Adaptive composite voltage overcurrent protection:

[0033] The adaptive composite voltage and overcurrent protection of the bus tie and the main cross connection can be illustrated by Table 1 (adaptive protection-fixed value group), and the protection current fixed value groups in the high-power generating module and the emergency ordinary generating module are unified, wherein, I DG is the rated current of the diesel generator set, U is the voltage between any two phases of the system, U n is the rated voltage of the power supply system, and U2 is the negative sequence voltage of the system.

[0034] Table 1

[0035]

[0036] a. The integrated protection device does not act when the high-power generating module is normally powered (the voltage criterion is not met, and the fixed value group is not put into operation), and the protection reliably does not act;

[0037] b. The integrated protection device acts when the high-power generating module power supply system has a short circuit, and the protection reliably acts;

[0038] c. The integrated protection device does not act when the emergency ordinary generating module is normally powered (the voltage criterion is not met, and the fixed value group is not put into operation), and the protection reliably does not act;

[0039] d. The integrated protection device acts when the emergency ordinary generating module power supply system has a short circuit, and the protection reliably acts.

[0040] The above analysis shows that the use of adaptive composite voltage overcurrent protection for busbars and main jumpers can ensure reliable operation in the event of a fault and reliable non-operation in normal power supply under different operating modes.

[0041] The composite voltage element is composed of a negative-sequence voltage element and a phase-to-phase low-voltage element, which form an OR logic. The negative-sequence voltage element can sensitively reflect the asymmetric short circuit of two phases in the system, and the low-voltage element can sensitively reflect the symmetrical short circuit of three phases in the system.

[0042] The above-described embodiments merely represent specific implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. An adaptive power grid power supply protection method suitable for changes in ship operating conditions, characterized in that: Specifically include 1) In the power supply state, under normal circumstances, the power direction of the emergency jumper line flows from the main busbar to the emergency busbar; in the emergency mode, the power direction flows from the emergency busbar to the main busbar; a short-circuit power direction element is added to the protection device of the emergency jumper line to enable the protection setting to be put into use, so as to realize adaptive overcurrent protection with different setting groups to adapt to changes in system operation mode. Specifically, if the single-phase current setting judgment and the corresponding direction judgment in the protection device of the emergency jumper line are both met and the PT line is not locked due to a break, the output is output to accumulate the action time, and a tripping action is performed when the action time of any one of the three phases expires; 2) Line status at the time of fault: when a short circuit occurs when the high-power generation module is supplying power to the system, the voltage on the main jumper and bus tie lines decreases and the current increases; when a short circuit occurs when the emergency ordinary generation module is supplying power to the system, the voltage on the main jumper and bus tie lines decreases and the current increases; Composite voltage elements are installed on the basis of the protection devices of the main jumper, busbar and other lines to realize the adaptive composite voltage directional overcurrent protection that unifies the setting group to adapt to the system operation mode. Specifically: when both the single-phase current setting judgment and the composite voltage judgment criteria in the protection device of the non-emergency jumper line are met, and the PT line is broken but not locked, the output is used to accumulate the action time, and the tripping action is performed when the action time of any one of the three phases is reached.

2. The adaptive grid power supply protection method applicable to changes in ship operating conditions according to claim 1 is characterized in that: The adaptive overcurrent protection implementation method in 1) is as follows: the overcurrent short-time delay protection detects overcurrent and disconnects it step by step through a time-limited step delay, starting from the power supply end according to the power supply direction, along the protection switch sequence passed by the line in sequence, and finally to the main switch of the unit, and disconnects it step by step with delay, so as to achieve coordination between the upper and lower protection levels.

3. The adaptive grid power supply protection method applicable to ship operating condition changes according to claim 1 is characterized in that: The composite voltage element in 2) is composed of a negative-sequence voltage element and an interphase low-voltage element, which form an OR logic. The negative-sequence voltage element can sensitively reflect the asymmetric short circuit of two phases in the system, and the low-voltage element can sensitively reflect the symmetrical short circuit of three phases in the system.

4. The adaptive grid power supply protection method applicable to changes in ship operating conditions according to claim 3 is characterized in that: The adaptive composite voltage direction overcurrent protection implementation method in 2) is as follows: The adaptive composite voltage and overcurrent protection of the busbar and main jumper is unified by the following table, which unifies the protection current setting groups of the two different power supply modes of the high-power generation module and the emergency ordinary generation module. DG is the rated current of the diesel generator set, U is the voltage between any phases of the system, U n is the rated voltage of the power supply system, U2 is the negative sequence voltage of the system,

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