CN111934284A - Protection design method based on closed-loop ship power system - Google Patents
Protection design method based on closed-loop ship power system Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/06—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric generators; for synchronous capacitors
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/06—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric generators; for synchronous capacitors
- H02H7/062—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric generators; for synchronous capacitors for parallel connected generators
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/22—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for distribution gear, e.g. bus-bar systems; for switching devices
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/22—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for distribution gear, e.g. bus-bar systems; for switching devices
- H02H7/226—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for distribution gear, e.g. bus-bar systems; for switching devices for wires or cables, e.g. heating wires
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/22—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for distribution gear, e.g. bus-bar systems; for switching devices
- H02H7/228—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for distribution gear, e.g. bus-bar systems; for switching devices for covered wires or cables
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
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Abstract
The invention relates to a protection design method based on a closed-loop ship power system, which aims to realize the re-networking operation of at least two generator sets and provide power supply for as long as possible. The system has the obvious advantages that when a system fault occurs, only one fault generator set is isolated or one section of busbar is isolated, and the influence range of the fault is greatly reduced.
Description
Technical Field
The invention relates to a power system control technology, in particular to a protection design method based on a closed-loop ship power system.
Background
The dynamic positioning vessel utilizes variable frequency drive thrusters to maintain position during operations such as oil and gas drilling operations, positioning, mooring, and port maneuvering. One of the requirements for safe operation of a vessel is that no malfunction should occur which could lead to a serious loss of vessel position. DP3 level is the highest dynamic positioning level of the current international maritime organization, and the requirement of a ship adopting DP3 level dynamic positioning on a power system is higher.
In recent years, the requirement for emission is higher and higher at home and abroad, and the power supply mode of a power positioning system of high-end ocean engineering equipment adopts a bus-coupled closed loop type operation mode, so that the power generation efficiency can be greatly improved, the energy can be saved, the emission can be reduced, and the overall safety and the reliability of a power system are greatly challenged.
However, operating the system in the buscouple closed loop mode has the disadvantage that the system may be susceptible to faults, such as a short circuit fault in the system or a potential fault in the generator, which may result in a power loss from the ship. For dynamic positioning ships with high risk of operation for ships, human life and the environment, it is necessary to try to avoid power failure. For a long time, the domestic DP2/DP3 closed-loop power system is in an exploration stage on a plurality of technical problems, no mature application case can be used for reference, and especially a protection design scheme of the closed-loop power system is a core problem of system design.
Disclosure of Invention
The invention provides a protection design method based on a closed-loop ship power system, aiming at the problem that the protection requirement of the ship power positioning system adopting the closed-loop power operation system on the power system is improved.
The technical scheme of the invention is as follows: a protection design method based on a closed-loop ship power system divides the power system into a plurality of areas, each area comprises 1 generator, 1 propeller or 1 electric equipment, and each area has an independent detection and protection scheme; each zone is paired with a bus-section, each bus-section is connected with a circuit breaker CB through a bushR、CBiLConnected with the left bus section thereof through a bus coupler circuit breaker CBiR、CBiLIs connected with the right bus section; a generator circuit breaker, a propulsion transformer circuit breaker and a main transformer circuit breaker are respectively arranged on each bus section corresponding to the generator, the propeller and the electric equipment and bus connecting section; the bus-tie power system short-circuit protection configuration is as follows:
wherein t is1Setting a protection action time for a branch of a propulsion or main transformer; t is t2Comparing a pilot protection action time setting value for the bus coupling direction; the generator timing time limit overcurrent protection action time setting value is t1+ Δ t; the bus-coupled timing time limit over-current protection time setting value can be set as t1+2 Δ t; meanwhile, in order to satisfy the condition that the comparative pilot protection in the bus coupling direction is prior to the timing limit overcurrent protection action, the relation t exists2<t1+2Δt。
The generator speed regulator fault monitoring and fault judging:
based on a voting system, continuously comparing load distribution set points of the model and deviations between estimated values obtained through calculation and actual measured active power, rotating speed, rack positions and power grid frequency of the system through a built internal generator model, and monitoring the relevant parameter states of a distribution board where each generator is located and the states of other generator protection devices in real time; the generator protection device adjusts the generator according to the droop characteristic or the constant frequency characteristic of the power system distribution data, if the actual measurement parameters of the system do not conform to the internal generator model at the moment, the generator protection device sends state signals to the energy management system to send alarm signals and start a standby generator set, and sends the estimated active power of the generator and the power grid frequency to the internal speed regulator fault model for judgment, and if the deviation between the estimated data and the actual measurement parameters exceeds the limit specified by the speed regulator fault model, the generator protection device sends a generator circuit breaker tripping instruction or sends a bus-coupled jumper circuit breaker tripping instruction;
the generator voltage regulator fault monitoring and fault judging method comprises the following steps:
based on a voting system, continuously comparing load distribution set points of an internal generator model and deviations between calculated estimated values and actually measured reactive power, exciting current and grid voltage of the system through the built internal generator model, and monitoring the relevant parameter state of a distribution board where each generator is located and the states of other generator protection devices in real time; the generator protection device adopts droop characteristics to adjust the generator according to power system distribution data, if actual measurement parameters of the system do not conform to an internal generator model at the moment, state signals are sent to an energy management system to send alarm signals and start a standby generator set, estimated generator reactive power, exciting current and grid voltage at the moment are sent to an internal automatic voltage regulating device fault model to be judged, and if deviation between the estimated data and the actual measurement parameters exceeds the limit specified by the automatic voltage regulating device fault model, the generator protection device sends a generator breaker tripping instruction or sends a bus-tie bridging breaker tripping instruction.
The power system hidden fault protection design method comprises the following steps: monitoring and backup protection are carried out on breaker faults, tripping faults of a tripping loop of the breaker and sensor faults, and the determined hidden faults are isolated in time.
The fault ride-through capability design is carried out on the generator, the propulsion frequency converter and the low-voltage auxiliary equipment in the power system, so that the maximum fault ride-through capability can continuously work in the system, and the continuous time exceeds the maximum clearing time required by various short-circuit faults of the system.
The design method for rapidly recovering the power system after the power grid loses power comprises the following steps:
through the voltage sensor signal that detects direct current bus, if the electric wire netting takes place to lose the electric fault this moment, voltage transformer's voltage signal can drop to 0V fast, and generator circuit breaker, bus tie cross-over connection circuit breaker all are in the branch position simultaneously, and daily transformer inlet wire circuit breaker and important equipment auxiliary power supply equipment's circuit breaker do not have the undervoltage dropout and will keep losing the preceding state of electricity, are in the closing position, and control system will automatic quick start loses the electric restart logic this moment.
The power system protection scheme builds a hardware-in-the-loop test system, the protection function in the protection scheme is verified, and meanwhile, the action current of each protection function is set according to the calculation result of the system short circuit;
the construction method comprises the following steps: the ship power system is used as a virtual object, and a model of the ship power system is built in a simulation environment and loaded into a real-time simulator to operate; the comprehensive relay protection device and the generator protection device are used as actual controllers, and current signals output by all current transformers in the system are sampled and analyzed to execute a protection function.
The invention has the beneficial effects that: the invention relates to a protection design method based on a closed-loop ship power system, which aims to realize the re-networking operation of at least two generator sets and provide power supply for as long as possible. The system has the obvious advantages that when a system fault occurs, only one fault generator set is isolated or one section of busbar is isolated, and the influence range of the fault is greatly reduced.
Drawings
FIG. 1 is a schematic diagram of the area protection of a closed loop power system according to the present invention;
FIG. 2 is a single DP group schematic of the DP2/DP3 class DP medium voltage power system of the present invention;
FIG. 3 is a schematic view of a jumper cable protection arrangement according to the invention;
FIG. 4 is a schematic diagram of the generator circuit breaker fault protection of the present invention;
fig. 5 is a diagram of an exemplary fault clearing and fault timing for the circuit breaker of the present invention;
FIG. 6 is a schematic diagram of the trip circuit monitoring function of two digital input signals of the present invention;
FIG. 7 is a logic block diagram of the trip circuit monitoring function of two digital input signals of the present invention;
FIG. 8 is a diagram of a fault detection control strategy for a generator protection device in accordance with the present invention;
FIG. 9 is a schematic diagram of a closed loop power system hardware-in-loop test platform according to the present invention;
FIG. 10 is a schematic diagram of a simulated fault point location selection for a closed loop power system according to the present invention;
FIG. 11a is a waveform diagram of the secondary side current of the generator current transformer under the action of busbar differential protection under the busbar short circuit fault according to the present invention;
FIG. 11b is a waveform diagram of the secondary side current of the generator current transformer when the busbar differential protection fails under the busbar short circuit fault according to the present invention;
fig. 11c is a waveform diagram of the secondary side current of the bus-coupled current transformer when the differential protection of the busbar fails under the busbar short-circuit fault according to the invention.
Detailed Description
The protection design method based on the closed-loop ship power system divides the power system into a plurality of regions, as shown by dotted line regions in fig. 1, each region comprises a generator set DG, an 11kV distribution board, a transformer, a propulsion frequency converter and a propulsion motor M, each region is provided with an independent system detection and protection scheme, and each region forms a complete system protection design scheme.
Advanced short circuit and ground fault protection:
for DP2/DP3 class dynamic positioning ships, the normal working condition provided by classification societies such as DNV is the mode of opening the bus-tie breaker. When the closed-loop bus coupler is adopted for operation, in order to achieve proper protection and isolation effects, the design method provides an additional protection method and device.
The technical scheme introduces a regional protection concept of bus with differential protection and directional fault protection. As shown in fig. 1: in the system area, there are several power generation devices and electric equipment with different quota and function. The protection area divided in the system is taken as a sub-part, and the protection area of one sub-part of the system comprises 1 generator, 1 propeller or 1 electric equipment (consisting of a well drilling driving feeder or a distribution feeder). The other 3 sub-sections of the system are configured similarly to this section.
The main system protection functions proposed by the design method are as follows:
and (3) feeder protection: overcurrent, short circuit, ground protection, etc.;
protection of jumper cables: overcurrent, short circuit, ground and cable differential protection, directional protection, etc.;
protection of the generator: overcurrent, short circuit, differential, grounding, reverse power, negative sequence, excitation fault protection and the like;
busbar: differential protection, directional protection, short delay protection, ground protection, etc
Pre-magnetizing a transformer and pre-charging a frequency converter: the integrity detection function before the transformer and the frequency converter are put into use is realized;
in addition to the above protection functions, several other protection functions are included: breaker fault protection and breaker trip circuit trip supervision.
1. Design of main protection scheme
The DP2/DP3 grade dynamic positioning marine medium voltage power system single bus section configuration is shown in FIG. 2. The bus section passes through the bus coupler circuit breaker CBhR、CBiLConnected with the left bus section thereof through a bus coupler circuit breaker CBiR、CBiLTo its right sideThe bus-sections are connected. The system mainly comprises a generator G, a busbar, a propulsion transformer, a main transformer and the like, and CBiG、CBiT、CBiDRespectively a generator circuit breaker, a propulsion transformer circuit breaker and a main transformer circuit breaker on the bus section.
1) Generator and busbar protection
The current differential protection of the design scheme has complete selectivity and only acts on faults in a protection area, so the current differential protection cannot be used as backup protection. In the system shown in fig. 2, it is assumed that only the generator is provided with current differential protection for short-circuit faults and that the protection is performed in CBiGTripping, pushing transformer circuit breaker CB when short-circuit fault occurs in pushing transformeriTSince the hidden fault is not active, the differential protection will not be active since the fault point is outside the generator differential protection area, which makes the generator unable to be isolated from the fault point and continuously contribute to the short circuit current. Therefore, the short-circuit protection corresponding to the generator should also be combined with other short-delay protection functions besides current differential.
2) Propulsion and main transformer branch protection
According to the analysis in 1), and considering certain economical efficiency, the propulsion and main transformer branches can adopt timing-limited overcurrent protection as main protection of short-circuit faults. The selection of the action time setting value needs to consider the selective cooperation with the lower-level circuit breaker.
3) Jumper cable protection
According to the analysis in 1), the jumper cable can adopt current differential protection as its main protection. Another more economical scheme is that direction comparison type pilot protection is adopted, the two-side protection device of the jumper cable transmits a judgment result of whether the power direction of the side is the specified direction to the opposite side, and the two-side protection device distinguishes the fault as an in-zone fault or an out-of-zone fault of the jumper cable according to the respective judgment result and carries out corresponding protection action. The directional comparison pilot protection is selected herein as the jumper cable primary protection.
2. Design of backup protection scheme
In the system shown in fig. 2, if a short-circuit fault occurs at any position of the medium-voltage side and cannot be cut off smoothly due to a hidden fault of the protection device or the switch, the fault will spread to the busbar. To prevent a fault from affecting other bus segments for a long time, backup protection is required to isolate the faulty busbar from the other bus segments. One simple way is to have the power system partition run in this case, i.e. enter Open Bus-ties mode, to ensure that the other Bus-sections are not affected after the fault has been removed. The backup protection function can be realized by configuring the bus coupler with timing over-current protection.
One extreme case is a short circuit fault in the jumper cable, while a hidden fault occurs in the protection devices on either side of the jumper cable, causing the directional comparator pilot protection to fail correctly and affecting the backup protection function. In this case, it is necessary to provide timing overcircuit protection for both sides of the jumper cable so that even in the event of a hidden fault, one side of the protection will always act correctly to separate the different bus sections as shown in fig. 3.
The backup protection scheme ensures that the system loses at most one engine room and main switchboard room function under the worst condition, and the design index of the DP3 ship for short-circuit fault according to DNVGL regulation is met.
3. System short circuit protection arrangement
From the above analysis, it can be seen that if the DP3 ship power system shown in fig. 2 is expected to operate in Closed Bus-ties/Closed ring mode, the protection scheme for short-circuit fault in the system can be configured according to the DP3 ship Closed buscouple power system short-circuit protection configuration shown in table 1.
TABLE 1
The generator timing over-current protection is used as the superior level of protection, and has longer time delay compared with the timing over-current protection of the branch circuit of the propulsion/main transformer. Considering the time interval delta t required by the selective matching of the actual system protection, if the branch protection action time setting value of the propulsion/main transformer is t1Timing the generatorThe over-current limiting protection action time setting value is t1+Δt。
The bus-coupled timing-limited overcurrent protection is used as a far backup for all short-circuit faults in the subsystem, the action time of the bus-coupled timing-limited overcurrent protection is longer than that of all short-circuit protection in the subsystem, the time interval delta t required by selective protection matching is considered, and the setting value of the bus-coupled timing-limited overcurrent protection time can be set to t1+2 Δ t. Meanwhile, in order to satisfy the condition that the comparative pilot protection in the bus-coupled direction is prior to the timing-limited over-current protection action, the due relation t2<t1+2Δt。
4. Circuit breaker fault protection
According to the protection function configuration of fig. 2, the generator protection device, the bus tie jumper protection device and the breaker failure protection function in the load protection device can be assigned. The circuit breaker fault protection function is primarily used to monitor whether the associated circuit breaker is properly opened. As shown in fig. 4, the protection principle is described by taking breaker failure protection as an example in generator protection.
The method comprises the following steps that a generator protection device acquires corresponding current of an output side of a generator, when the generator detects faults such as short-circuit fault, under-over-frequency, under-over-voltage, grounding and the like, the protection device outputs a breaker tripping designation according to corresponding fault protection time, if the breaker does not trip after the output action of the protection device and the opening time of the breaker per se are exceeded, the protection device can continue to monitor the current at the generator end, and the protection device can determine that the breaker breaks down through the program setting of the protection device. The exemplary fault clearing and fault timing diagram for the circuit breaker shown in fig. 5.
5. Circuit breaker trip loop trip supervision
The circuit breaker trip circuit monitoring signal wiring schematic diagram is shown in fig. 6, namely, one switching value input signal is connected with the circuit breaker position auxiliary state contact in parallel, the other is connected with the protection trip contact in parallel through a digital value input signal, and when the circuit is interrupted, an alarm signal is sent out to remind the circuit breaker trip circuit of fault.
The trip circuit is monitored by means of digital input signals, it is possible not only to monitor the faults of the trip circuit and the disappearance of the control voltage, but also to monitor the operation of the circuit breaker by means of the circuit breaker position auxiliary status contacts. Depending on the open/closed state of the protective trip relay and the circuit breaker, the digital input signal is active ("H" logic state in table 2) or short-circuited ("L" logic state).
If the trip circuit is normal, the two digital input signals will appear at the same time low voltage only in a short transient situation (the protective trip relay has closed but the circuit breaker has not yet had time to open). If this condition is maintained, it may simply be a tripped open, short, control voltage fault or breaker position assist condition contact fault. This can therefore be used as an action criterion for trip circuit monitoring. Table 2 shows the relationship between the switching on/off state of the trip relay and the breaker and the input signal state.
TABLE 2
The protection device periodically checks the status of the two digital input signals with a polling period of 600 ms. If all three consecutive (after 1.8 s) state conditions are abnormal, a signal is issued (as shown in fig. 7). This repeated measurement process determines the delay time of the alarm signal and avoids the problem of false alarms during brief state transitions. If the fault in the trip circuit disappears, the alarm signal will automatically reset after the same time delay.
Advanced generator protection device:
for a generator set speed regulator fault, the generator protection device control system strategy is based on a voting system, as shown in the generator protection device fault detection control strategy diagram of fig. 8: through the built internal generator model, the generator protection device system continuously compares the load distribution set point of the internal generator model with the deviation between the calculated estimated value and the actual measured value of the speed control system, each generator is provided with the independent generator protection device system, and the system can monitor the relevant parameter state of a distribution board where each generator set is located and the state of other generator protection device systems in real time.
The generator protection device system adjusts a corresponding internal generator model when a droop characteristic or a constant frequency characteristic is adopted according to power system distribution data, if actual measurement parameters of the system do not accord with the internal generator model at the moment, the generator protection device system sends state signals to the energy management system to send alarm signals and start a standby generator set, and sends the active power of a generator and the grid frequency evaluated at the moment to the internal speed regulator fault model for judgment, if deviation between the evaluation data and the actual measurement parameters exceeds the limit specified by the speed regulator fault model, the generator protection device system sends a generator circuit breaker tripping instruction, and under certain fault conditions, a bus-coupled jumper circuit breaker tripping instruction can be sent, particularly when the load factor of the power system is very low.
For a generator set AVR (voltage regulator) fault, the control system strategy is based on a voting system, as shown in fig. 8: through the built internal generator model, the generator protection device system continuously compares the load distribution set point of the internal generator model and the deviation between the calculated estimated value and the actual measured value reactive power, exciting current and power grid voltage of the system, each generator set is provided with an independent generator protection device system, and the system can monitor the relevant parameter state of a distribution board where each generator set is located and the states of other generator protection device systems in real time.
If the actual measurement parameters of the system do not accord with the internal model at the moment, the generator protection device system sends a state signal to the energy management system to send an alarm signal and start a standby generator set, and sends the estimated reactive power of the generator, exciting current and grid voltage to the internal AVR fault model for judgment, if the deviation between the estimated data and the actual measurement parameters exceeds the limit specified by the AVR fault model, the generator protection device system sends a tripping instruction of a generator circuit breaker, and under the condition of model fault, a tripping instruction of a bus-coupled jumper circuit breaker can be sent, particularly when the load rate of the power system is very low.
Hidden fault processing: the present invention takes into account the general principle that all parts of a closed loop power system design should be protected against hidden faults, and that each system and subsystem must be designed with sufficient redundant equipment to ensure the safety and reliability of the system functions. Because the protection device is a main protection implementation device of the system, and the circuit breaker is a device for specifically executing protection actions, if the two devices have hidden faults due to equipment problems, the reliability of the whole system is influenced, so the hidden fault monitoring method and the backup protection implementation mode of the main equipment such as the comprehensive relay protection device, the circuit breaker, the sensor and the like are mainly considered in the design of the invention.
Hidden failures mainly represent two aspects: 1. hidden faults of the comprehensive relay protection device and the circuit breaker; 2. hidden fault protection of the sensor;
the invention provides a hidden fault solution for a comprehensive relay protection device and a circuit breaker, which comprises the following steps: the hidden fault protection scheme of the comprehensive relay protection device for the generator, the bus tie bridge and the load is mainly embodied in backup protection among all protection devices, the hidden fault protection of the circuit breaker is mainly realized by two modes, one mode is that the circuit breaker fault protection function and the tripping supervision function of the self-developed comprehensive relay protection device are used for realizing corresponding protection, the other mode is that the backup protection scheme is designed by depending on a system selective time principle, the specific design process of the part refers to the detailed introduction of the backup protection scheme in the previous section of advanced short circuit and ground fault protection, and the detailed description is omitted here.
The hidden fault solution about the sensor proposed by the invention is as follows: the current transformer and voltage transformer protection scheme is mainly characterized in that when a current signal and a voltage signal acquired by each comprehensive relay protection device have faults, the corresponding comprehensive relay protection device cannot judge the faults and send corresponding action instructions, and the backup protection is that the previous comprehensive relay protection device detects the faults (the current and voltage signals acquired by the previous comprehensive relay protection device are independent of the next comprehensive relay protection device) and isolates the faults; the hidden fault protection scheme for the transmitter mainly embodies that when an exciting current signal acquired by an advanced generator protection device and a sensor signal of a speed regulator rack position have faults, the advanced generator protection device can use reactive power and a voltage signal as criteria to perform fault judgment aiming at the AVR fault of a generator set, and can use active power and a frequency signal as criteria to perform fault isolation aiming at the speed regulator fault of the generator set so as to isolate a fault unit.
Fault-ride-through capability of important devices: for a DP2/DP 3-level power constant-force closed-loop power system, a generator and a propulsion frequency converter are the most important devices according to the related requirements of DNV classification society, and when the 11kV bus has short circuit, grounding and other faults to cause the system to lose power from the whole ship, the devices have fault ride-through capability, namely the maximum fault ride-through capability of the main devices continuously exceeds the maximum clearing time required by the system for various short-circuit faults, so that the purpose of stable and reliable operation of the system is achieved.
The solution for generator fault ride-through capability is as follows:
aiming at the problems that the traditional generator selection method cannot solve, such as rated power, voltage, power factors and the like, the contents of a generator data table, an attenuation curve, a capacity curve, a rotating shaft torque, AVR design and the like must be fully analyzed to provide support for the design of a closed-loop power system.
The solution provided by the invention is that under the conditions of sudden load shedding, synchronous switching-on faults and the like of the system through Matlab or other simulation work, the characteristic change ranges of voltage, current, rotating shaft torque and the like of the generator meet the design requirements of the system, and the reliability and safety of the system cannot be influenced.
The solution for the fault ride-through capability of the propulsion frequency converter is as follows:
for conventional inverter designs, the dc voltage fault level would drop to less than 80% after 100ms without inverter-driven motor power feedback. The load torque Tm will drop from 60% to about 20% within a measurement time of 1000ms (1 sec). The motor flux will also drop to zero in 1 sec. If a special control strategy is not considered to be applied to the selected frequency converter, when the main power grid (11kV) breaks down, the frequency converter is locked due to the fact that the voltage of a direct-current bus is too low, and therefore even if the system is clear of short-circuit faults, the power supply of the frequency converter cannot be recovered, at the moment, a ship cannot operate a dynamic positioning system, the position of the dynamic positioning system is lost, and great loss is caused to the use of the ship.
The solution proposed by the invention is to make the inverter-driven motor power-regenerative when the main grid (11kV) fails, by optimizing the propulsion control system control strategy, while the asynchronous/synchronous rotating machine, in which the motor propeller inertia effect operates even if the propeller is decelerating, provides sufficient energy for feeding the drive and compensating the motor losses. Therefore, the voltage drop of the direct current link of the frequency converter is reduced. By adjusting the control system to the optimum controller gain, the maximum power available can be achieved, allowing the propeller to remain operational after the power supply interruption for the next 2000ms (2 sec).
Low voltage auxiliary device fault ride through capability: for a DP2/DP 3-level power constant-force closed-loop power system, according to related requirements of DNV classification society, when faults such as short circuit and grounding of an 11kV bus lead to the fact that the system loses power of the whole ship, molded case circuit breakers configured by equipment such as a propeller, a steering engine, a lubricating oil pump of a generator set, a cooling water pump and a fuel pump on a 400V/690V low-voltage distribution board cannot be disconnected, and otherwise the power supply recovery time of the system cannot meet the requirements of the classification society, the invention provides a solution that an undervoltage trip is not arranged for the inlet line circuit breakers for auxiliary power supply of important equipment, and in addition, a set of redundant power supply is arranged for power supply of motor starters of the pumps, and power is supplied by an external UPS, so that the motors of the pumps can be ensured to be started quickly even if a loop for normal power supply.
The power system is quickly recovered after the power grid loses power;
according to the requirement of the DNV classification society, when the power grid has a power failure, important equipment needs to be restored to power supply within 45 seconds and has a state before power failure, and at the moment, after the power positioning system receives a signal that the power system has an operation state, the power positioning system can directly perform related power positioning operation without influencing the normal operation capacity of the power positioning ship.
The invention provides a rapid power restoration control strategy.A self-developed control system detects a voltage sensor signal of a direct current bus, if a power failure fault occurs in a power grid, the voltage signal of a voltage transformer can rapidly drop to 0V, a generator circuit breaker and a bus-tie bridging circuit breaker are positioned separately, the incoming line circuit breaker of a daily transformer and the circuit breakers of important equipment auxiliary power supply equipment are not provided with undervoltage tripping, the incoming line circuit breaker of the daily transformer and the circuit breakers of the important equipment auxiliary power supply equipment are kept in a state before power failure and are positioned at a switching-on position, and at the moment, the control system automatically and rapidly starts power failure restart logic.
Firstly, the control system sends a breaker closing instruction to the generator, the control system sends a starting instruction to the generator set after receiving a breaker closing feedback signal, the generator is started at the moment, and the control system sends an excitation starting signal to the AVR of the generator set when the generator set sends a signal that the engine speed exceeds 90% to the control system. The AVR will increase the voltage and cause the generator and all connected transformers and busbars to "soft start", automatically starting each motor based on "last run conditions" or by restart of the control system when 90% of the nominal voltage has been reached; secondly, carry out main propulsion transformer circuit breaker closing operation, in order to avoid main propulsion transformer closing to be the heavy current impact, can carry out and magnetize the operation this moment, treat after pre-magnetizing, with main propulsion transformer inlet wire circuit breaker closing. Finally, when 90% of the voltage on the secondary coil of the thruster transformer is reached, the thruster frequency converter can be started (pre-charging of the thruster drive dc bus is started by the drive itself), and when the thruster drive dc voltage has reached 85% of the nominal voltage, the drive is ready to start and close the incoming line breaker. At this point all power restoration operations are complete and the drive is now ready for power positioning.
Short circuit test verification: in order to verify the selective protection scheme of the system, according to the DNV classification society specification, the verification of a real ship or hardware-in-loop short circuit test needs to be completed, the invention provides a set of test room hardware-in-loop (HIL) test verification system method, which can verify the complete selective design scheme of the system and the design methods such as backup protection of hidden faults.
A principle verification is carried out on the protection scheme by using a Hardware-in-the-loop (HIL) test system built by an RT-LAB platform, as shown in FIG. 9. The ship power system is used as a virtual object, and a model of the ship power system is built in a simulation environment Simulink and loaded into a real-time simulator to run; the comprehensive relay protection device and the generator protection device are used as actual controllers, current signals output by current transformers in the system are sampled and analyzed, a protection function is executed, and the whole simulation system is composed of semi-virtual semi-real hardware. And setting the action current of each protection function according to the short circuit calculation result of the system.
As shown in fig. 10, fault points K1, K2, K3 and K4 are selected from the busbar, the generator outlet terminal, the propulsion transformer inlet terminal and the busbar cable respectively to perform a three-phase short circuit test. The specific test steps are as follows:
1) the system is enabled to run in real time under the DP working condition;
2) selecting a fault point to perform a short-circuit test, observing the condition of a main protection action, and recording the action time;
3) disabling the corresponding main protection function to simulate the hidden fault of the protection device;
4) and (3) carrying out a short circuit test on the same short circuit point in the step 2), observing the backup protection action condition, and recording the action time.
According to the test steps, a three-phase short circuit test is carried out on a fault point K1 on the busbar, and secondary side current waveforms (represented by voltage signals) of related transformers are recorded by an oscilloscope.
When a short-circuit fault occurs at the K1 point, the busbar comprehensive protection device detects a differential current larger than a setting value, the differential protection instantaneously acts, and CBiL、CBiR、CBiG、CBiT、CBiDTripping, the current waveform of the secondary side of the transformer at the outlet end of the generator is shown in fig. 11 a; under the condition of differential protection failure, the generator is isolated from a fault point by the timing over-current protection of the generator comprehensive protection device, a fault busbar is isolated from other busbar sections by the timing over-current protection of the bus-coupled cross-over comprehensive protection device, so that the fault is prevented from spreading, and the current waveforms of the secondary sides of the generator outlet end mutual inductor and the bus-coupled mutual inductor are respectively shown in fig. 11b and 11 c.
The above test procedure was repeated for the remaining failure points. When a short-circuit fault occurs at the point K4, the backup protection test method is to disable the bus tie right comprehensive protection device to simulate the hidden fault. The protective action was recorded as shown in the HIL test record in table 3.
TABLE 3
According to the test results, the protection configuration scheme designed in the text can correctly act on short-circuit faults of all parts of the system in the HIL test, and the faults are isolated.
Claims (6)
1. A protection design method based on a closed-loop ship power system is characterized in that the power system is divided into a plurality of areas, each area comprises 1 generator, 1 propeller or 1 electric equipment, and each area has an independent detection and protection scheme; each zone is paired with a bus-section, each bus-section is connected with a circuit breaker CB through a bushR、CBiLConnected with the left bus section thereof through a bus coupler circuit breaker CBiR、CBiLIs connected with the right bus section; a generator circuit breaker, a propulsion transformer circuit breaker and a main transformer circuit breaker are respectively arranged on each bus section corresponding to the generator, the propeller and the electric equipment and bus connecting section; the bus-tie power system short-circuit protection configuration is as follows:
wherein t is1Setting a protection action time for a branch of a propulsion or main transformer; t is t2Comparing a pilot protection action time setting value for the bus coupling direction; the generator timing time limit overcurrent protection action time setting value is t1+ Δ t; the bus-coupled timing time limit over-current protection time setting value can be set as t1+2 Δ t; meanwhile, in order to satisfy the condition that the comparative pilot protection in the bus coupling direction is prior to the timing limit overcurrent protection action, the relation t exists2<t1+2Δt。
2. The closed-loop marine vessel power system based protection design method of claim 1, wherein the generator governor fault monitoring and fault determination:
based on a voting system, continuously comparing load distribution set points of the model and deviations between estimated values obtained through calculation and actual measured active power, rotating speed, rack positions and power grid frequency of the system through a built internal generator model, and monitoring the relevant parameter states of a distribution board where each generator is located and the states of other generator protection devices in real time; the generator protection device adjusts the generator according to the droop characteristic or the constant frequency characteristic of the power system distribution data, if the actual measurement parameters of the system do not conform to the internal generator model at the moment, the generator protection device sends state signals to the energy management system to send alarm signals and start a standby generator set, and sends the estimated active power of the generator and the power grid frequency to the internal speed regulator fault model for judgment, and if the deviation between the estimated data and the actual measurement parameters exceeds the limit specified by the speed regulator fault model, the generator protection device sends a generator circuit breaker tripping instruction or sends a bus-coupled jumper circuit breaker tripping instruction;
the generator voltage regulator fault monitoring and fault judging method comprises the following steps:
based on a voting system, continuously comparing load distribution set points of an internal generator model and deviations between calculated estimated values and actually measured reactive power, exciting current and grid voltage of the system through the built internal generator model, and monitoring the relevant parameter state of a distribution board where each generator is located and the states of other generator protection devices in real time; the generator protection device adopts droop characteristics to adjust the generator according to power system distribution data, if actual measurement parameters of the system do not conform to an internal generator model at the moment, state signals are sent to an energy management system to send alarm signals and start a standby generator set, estimated generator reactive power, exciting current and grid voltage at the moment are sent to an internal automatic voltage regulating device fault model to be judged, and if deviation between the estimated data and the actual measurement parameters exceeds the limit specified by the automatic voltage regulating device fault model, the generator protection device sends a generator breaker tripping instruction or sends a bus-tie bridging breaker tripping instruction.
3. The protection design method based on the closed-loop ship power system according to claim 1 or 2, characterized in that the power system hidden fault protection design method comprises the following steps: monitoring and backup protection are carried out on breaker faults, tripping faults of a tripping loop of the breaker and sensor faults, and the determined hidden faults are isolated in time.
4. The method for designing protection based on closed-loop ship power system of claim 3, wherein the fault-ride-through capability of the generator, the propulsion frequency converter and the low-voltage auxiliary equipment in the power system is designed to make the maximum fault-ride-through capability continuous system work, and the continuous time exceeds the maximum clearing time required by the system to generate various short-circuit faults.
5. The protection design method based on the closed-loop ship power system according to claim 3, wherein the power system is quickly restored to the design method after power failure of a power grid:
through the voltage sensor signal that detects direct current bus, if the electric wire netting takes place to lose the electric fault this moment, voltage transformer's voltage signal can drop to 0V fast, and generator circuit breaker, bus tie cross-over connection circuit breaker all are in the branch position simultaneously, and daily transformer inlet wire circuit breaker and important equipment auxiliary power supply equipment's circuit breaker do not have the undervoltage dropout and will keep losing the preceding state of electricity, are in the closing position, and control system will automatic quick start loses the electric restart logic this moment.
6. The protection design method based on the closed-loop ship power system is characterized in that a hardware-in-loop test system is built in the power system protection scheme, the protection function in the protection scheme is verified, and meanwhile, the action current of each protection function is set according to the calculation result of the system short circuit;
the construction method comprises the following steps: the ship power system is used as a virtual object, and a model of the ship power system is built in a simulation environment and loaded into a real-time simulator to operate; the comprehensive relay protection device and the generator protection device are used as actual controllers, and current signals output by all current transformers in the system are sampled and analyzed to execute a protection function.
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