Reactive power compensation device at tail end of ship emergency fire pump

Abstract

The utility model belongs to the related technical field of shipbuilding, and particularly discloses a reactive power compensation device at the tail end of a ship emergency fire pump, which comprises two groups of capacitors with different capacities, the capacitors are respectively marked as high-capacity capacitors and low-capacity capacitors according to the capacities, and each group of capacitors is provided with a built-in reactor and a corresponding protection fuse. Two circuit breakers, two contactors and a time relay are also configured; the capacity of a small-capacity capacitor is calculated according to the power factor of the emergency fire pump in normal operation and the target power factor, the compensation value of the small-capacity capacitor is determined through the capacity of the small-capacity capacitor, and when the power factor of the emergency fire pump is compensated to the target power factor when the motor is started, the compensation value of the small-capacity capacitor is subtracted. And calculating to obtain the capacity of the high-capacity capacitor.

Description

Technical Field

[0001] This utility model relates to the technical field of shipbuilding, specifically to a reactive power compensation device at the end of a ship emergency fire pump. Background Technology

[0002] Conventional star-delta starting marine emergency fire pumps are at risk of starting failure during ship mooring, sea trials, and operation. To address this potential starting failure, the main solutions are: 1) Adjusting the starting circuit protection settings to avoid motor starting current and starting inrush current; 2) Replacing the starter from a conventional star-delta starter with another type of starter with lower starting current, such as a closed-loop star-delta starter, autotransformer, soft starter, or even a frequency converter; and 3) Connecting a capacitor in parallel at the end of the emergency fire pump's power supply circuit for local reactive power compensation.

[0003] Option 1, which avoids starting current and starting inrush current by adjusting the starting circuit settings, has the advantages of convenient adjustment and no hardware cost. However, the starting inrush current occurs at the moment of motor startup or during star-delta switching, and its duration is very short, making it difficult to measure. Motor protection settings include undervoltage protection, overload protection, short-delay protection, long-delay protection, and short-circuit protection, which are difficult to set. During sea trials or operation, technicians may not have the ability or resources to adjust the protection settings, and improper adjustment may lead to switch malfunctions or even grid disconnection. Furthermore, the circuit breaker in the general protection circuit is selected based on the motor's rated current, and the protection setting of the associated trip unit can only be adjusted within a certain range; even at its maximum, it may not be possible to avoid the starting inrush current.

[0004] The main drawback of Option 2 is its high cost. Since the probability of a ship's emergency fire pump failing to start is not high, and considering cost factors, star-delta starters are typically chosen during the design phase, using a starter with better starting performance would further increase ship construction costs. Furthermore, if a starting failure occurs during mooring, sea trials, or operation, there are no readily available spare parts, making it impossible to resolve the problem promptly.

[0005] Option 3 involves directly connecting a capacitor in parallel with the motor for reactive power compensation. This option is simple in structure and low in cost. Its main drawback is that the power factor during motor startup is difficult to predict, while the power factor of an emergency fire pump typically stabilizes between 0.7 and 0.9 during stable operation. If the parallel capacitor is too large, overcompensation may occur after startup, leading to overvoltage. If the parallel capacitor is too small, reactive power compensation will be insufficient, failing to effectively reduce starting current and inrush current. Grouped switching capacitors or static reactive power compensators typically have large capacities and high costs, and are usually used for centralized and decentralized compensation on the grid side, generally not for end-point compensation.

[0006] In view of this, the present invention provides a reactive power compensation device at the end of a ship emergency fire pump. Utility Model Content

[0007] The purpose of this utility model is to provide a reactive power compensation device at the end of a ship emergency fire pump. This device addresses the issue that the capacitor directly connected in parallel at the end of the motor is configured according to the power factor during the motor's startup process, which may lead to over-compensation and overvoltage after startup.

[0008] To achieve the above objectives, this utility model provides the following technical solution: a reactive power compensation device at the end of a ship's emergency fire pump, comprising two sets of capacitors with different capacities, labeled as a large-capacity capacitor and a small-capacity capacitor according to their capacity.

[0009] Each capacitor bank is equipped with a built-in reactor and corresponding protective fuses, as well as two circuit breakers, two contactors and a time relay.

[0010] The capacity of the small-capacity capacitor is calculated based on the power factor and target power factor of the emergency fire pump during normal operation. The compensation value of the small-capacity capacitor is then determined based on its capacity. When the power factor of the emergency fire pump is compensated to the target power factor during motor startup, the compensation value of the small-capacity capacitor is subtracted, and the capacity of the large-capacity capacitor is calculated.

[0011] As a preferred technical solution of this utility model, a large-capacity capacitor C1 and a small-capacity capacitor C2 are connected in parallel at the outlet of the emergency fire pump, and a protective fuse and a contactor are connected to the circuit to achieve timely circuit disconnection.

[0012] As a preferred technical solution of this utility model, when the emergency fire pump is not working, contactor KM1 is closed, contactor KM2 is open, and reactor-type capacitors are connected to the emergency distribution board for centralized reactive power compensation.

[0013] When the emergency fire pump starts, contactor KT1 is activated, contactor KM2 is closed, contactor KM1 is opened, and inductor L1 and capacitor C1 are connected in parallel with inductor L2 and capacitor C2 at the outlet of the emergency fire pump for reactive power compensation.

[0014] After startup, time relay KT1 stops timing, contactor KM2 opens, contactor KM1 closes, inductor L1 and capacitor C1 continue to provide centralized reactive power compensation for the emergency power distribution network, while inductor L2 and capacitor C2 continue to be connected in parallel with the emergency fire pump for end-point compensation.

[0015] As a preferred technical solution of this utility model, overload and short circuit protection are provided by circuit breakers and fuses; time relays are used to control the closing and opening of contactors to realize automatic switching of compensation strategies.

[0016] As a preferred technical solution of this utility model, a monitoring system is set up to monitor the power factor and current, and the capacitance or control logic of the capacitor is fine-tuned according to the actual operating conditions.

[0017] As a preferred technical solution of this utility model, the switching of capacitors is dynamically adjusted in real time using a PLC programmable logic controller.

[0018] Compared with the prior art, the beneficial effects of this utility model are:

[0019] This invention addresses the risk of start-up failure of ship emergency fire pumps during mooring, sea trials, and operation. It consists of two sets of capacitors, one large and one small. When the emergency fire pump starts, they work together to compensate for reactive power. When the emergency fire pump stops running or returns to normal operation, the larger set of capacitors connects to the ship's emergency power distribution network to provide centralized reactive power compensation for other loads, while the smaller set provides end-point reactive power compensation for the normally operating emergency fire pump. Connecting to the ship's emergency power distribution board outside of motor start-up time improves the power factor of the emergency power distribution network, increases the utilization rate of the emergency generator, and also increases the power supply capacity of the emergency power distribution network. Attached Figure Description

[0020] Figure 1 A schematic diagram of reactive power compensation at the end of a ship's emergency fire pump.

[0021] Figure 2 Circuit diagram of the reactive power compensation device at the end of a ship's emergency fire pump; Detailed Implementation

[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0023] This embodiment uses a local parallel capacitor connected to the motor for end-of-line reactive power compensation. However, if the capacitor directly connected to the motor end is configured according to the power factor during motor startup, overcompensation may occur after startup, leading to overvoltage. Conversely, selecting a capacitor that is too small will result in insufficient reactive power compensation. Group switching or static reactive power compensators are not suitable for end-of-line compensation. The proposed end-of-line reactive power compensation device for marine emergency fire pumps can provide reactive power compensation during emergency fire pump startup, limiting starting current and inrush current to prevent startup failure. When the emergency fire pump starts, it provides local reactive power compensation for the emergency fire pump while simultaneously providing centralized reactive power compensation for the emergency power supply system. Furthermore, it can also provide centralized reactive power compensation for the emergency power supply system when the emergency fire pump is not running.

[0024] Please see Figure 1-2 This utility model provides a reactive power compensation device at the end of a ship emergency fire pump, including a reactive power compensation device. One end of the reactive power compensation device is connected in parallel with the output end of the emergency fire pump, and the other end is connected to the emergency distribution board. The reactive power compensation device includes two sets of built-in reactor capacitors and a protective fuse. The protective fuse is connected to the emergency fire pump and the emergency distribution board respectively through a circuit breaker.

[0025] Specifically, the reactor-type capacitor consists of a capacitor and an inductor connected in series, with two sets of capacitors of different capacities, labeled as large-capacity capacitor C1 and small-capacity capacitor C2 respectively; each set of capacitors is equipped with built-in reactors L1 and L2, as well as corresponding protective fuses FU1 and FU2; two circuit breakers QF1 and QF2 are configured, as well as two contactors KM1 and KM2, and one time relay KT1.

[0026] The reactor-type capacitor includes a first reactor-type capacitor composed of capacitor C1 and inductor L1, and a second reactor-type capacitor composed of capacitor C2 and inductor L2; the protective fuses include FU1 and FU2, the circuit breakers include QF1 and QF2, which provide protection based on the circuit breakers, the contactors include KM1 and KM2, and the time relay KT1; its built-in reactor has the functions of limiting the high-order harmonic current flowing into the capacitor, suppressing harmonic amplification, and reducing the inrush current of the sluice gate.

[0027] Specifically, the capacity of the small-capacity capacitor is calculated based on the power factor and target power factor of the emergency fire pump during normal operation, and the compensation value of the small-capacity capacitor is determined by the capacity of the small-capacity capacitor. When the power factor of the emergency fire pump is compensated to the target power factor when the motor starts, the compensation value of the small-capacity capacitor is subtracted, and the capacity of the large-capacity capacitor is calculated.

[0028] More specifically, the formula for calculating the reactive power that the reactive power compensation device needs to compensate is as follows:

[0029]

[0030] Among them: C2 is designed to compensate the normal operating power factor of the emergency fire pump from approximately 0.7 to 0.9, Q c2 ≈0.5P e C1 is compensated to a power factor of approximately 0.3 at motor startup, reduced to 0.9 by the compensation value of C2. Q c1 ≈2.2P e .

[0031] When the emergency fire pump is not working, the normally closed contact of KM2 and the coil circuit of KM1 are connected, the contactor KM1 is closed, KM2 is opened, and L1 and C1 are connected to the emergency distribution board, which plays the role of centralized reactive power compensation for the emergency distribution network.

[0032] When the emergency fire pump starts, the normally closed coil of timer KT1 and the coil circuit of KM2 are connected, contactor KM2 is closed, the normally closed contact of KM2 and the coil circuit of KM1 are disconnected, and contactor KM1 is disconnected. At this time, L1, C1 and L2, C2 are connected in parallel at the outlet of the emergency fire pump.

[0033] After the emergency fire pump finishes starting, the timer KT1 circuit is activated, the normally closed coil of timer KT1 and the coil circuit of KM2 are deactivated, contactor KM2 is deactivated, the normally closed contact of KM2 and the coil circuit of KM1 are activated, contactor KM1 is closed, KM2 is deactivated, L1 and C1 are connected to the emergency distribution board to continue centralized reactive power compensation for the emergency power distribution network. L2 and C2 continue to be connected in parallel to the emergency fire pump for end-point compensation.

[0034] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the protection scope of the claims.

[0035] Finally: The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A reactive power compensation device at the end of a ship's emergency fire pump, characterized in that: It includes two sets of capacitors with different capacities, labeled as large-capacity capacitors and small-capacity capacitors according to their capacitance. Each capacitor bank is equipped with a built-in reactor and corresponding protective fuses, as well as two circuit breakers, two contactors and a time relay. The capacity of the small-capacity capacitor is calculated based on the power factor and target power factor of the emergency fire pump during normal operation. The compensation value of the small-capacity capacitor is then determined based on its capacity. When the power factor of the emergency fire pump is compensated to the target power factor during motor startup, the compensation value of the small-capacity capacitor is subtracted, and the capacity of the large-capacity capacitor is calculated.

2. The reactive power compensation device at the end of a ship emergency fire pump according to claim 1, characterized in that: A large-capacity capacitor C1 and a small-capacity capacitor C2 are connected in parallel at the outlet of the emergency fire pump, and a protective fuse and contactor are connected to the circuit to achieve timely circuit disconnection.

3. The reactive power compensation device at the end of a ship emergency fire pump according to claim 2, characterized in that: When the emergency fire pump is not working, contactor KM1 closes and contactor KM2 opens, and the reactor-type capacitor is connected to the emergency distribution board for centralized reactive power compensation. When the emergency fire pump starts, contactor KT1 is activated, contactor KM2 is closed, contactor KM1 is opened, and inductor L1 and large-capacity capacitor C1 are connected in parallel with inductor L2 and small-capacity capacitor C2 at the outlet of the emergency fire pump for reactive power compensation. After startup, time relay KT1 stops timing, contactor KM2 opens, contactor KM1 closes, inductor L1 and large-capacity capacitor C1 continue to provide centralized reactive power compensation for the emergency power distribution network, while inductor L2 and small-capacity capacitor C2 continue to be connected in parallel with the emergency fire pump for end-point compensation.

4. The reactive power compensation device at the end of a ship emergency fire pump according to claim 3, characterized in that: Overload and short-circuit protection is provided by circuit breakers and fuses; time relays are used to control the closing and opening of contactors to enable automatic switching of compensation strategies.

5. The reactive power compensation device at the end of a ship emergency fire pump according to claim 4, characterized in that: Set up a monitoring system to monitor power factor and current, and fine-tune the capacitor capacity or control logic according to the actual operating conditions.

6. The reactive power compensation device at the end of a ship emergency fire pump according to claim 5, characterized in that: The switching of capacitors is dynamically adjusted using real-time data from a PLC (Programmable Logic Controller).

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