A method and system for controlling an offshore platform power grid

Abstract

The present application relates to a kind of offshore oil platform power grid control method and system, belong to power grid safety control field, according to pure electrical quantity trip criterion or protection trip signal criterion, judge whether the generator in commissioning state appears fault trip phenomenon, when the generator in commissioning state appears fault trip phenomenon, then according to the quantity of load required cut-off cut-off load, according to the size of element current, active power direction, whether maintenance pressure plate is withdrawn and whether there is another kind of element fault outage judge whether the element appears overload start phenomenon, according to whether element overload starts, the comparison result of element current and overload action current setting value and the comparison result of element power and overload action power setting value judge whether overload starts, this method can accurately judge whether supply and demand balance between generator and load.

Description

Technical Field

[0001] This invention relates to a power grid control method and system for offshore oil platforms, belonging to the field of power grid safety control. Background Technology

[0002] The power system in offshore oil and gas field projects typically includes a main power platform and multiple load platforms. The main power platform is responsible for supplying power to its own loads and the loads of other load platforms. The main power platform and its multiple load platforms form an independent power grid.

[0003] Currently, the power management system used in the offshore oil platform power grid is the PMS system, which generally adopts a PLC architecture. The PMS system collects data from the protection and control devices of the medium-voltage system (10kV and 35kV voltage levels) and the multi-function meter data of the low-voltage system (380V and below voltage levels) through Modbus communication. The collected multi-function meter data realizes the control functions of power grid frequency and voltage (AGC / AVC function).

[0004] When the PMS system implements the power grid safety and stability control function, the analog quantities of generators, transformers and submarine cable tie lines used in the judgment are data forwarded by the corresponding interval protection devices through the communication network. Due to the influence of the Modbus protocol communication acquisition and processing data mechanism currently used by the protection devices, coupled with the transmission delay of the communication network, the PMS system can only achieve a response speed of seconds to transient stability control of power grid faults.

[0005] Offshore oil platform power grids are typically isolated. If a generator trips due to a fault, the instantaneous decrease in generator output power, voltage drop, and frequency descent can easily cause other normally operating generators to overheat, potentially leading to a complete power system failure. Therefore, the need for robust power grid safety and stability control strategies within the system is increasing, requiring a method to assess the status of generators, interconnecting transformers, submarine cable connections, and loads. Summary of the Invention

[0006] The present invention aims to provide a method and system for controlling the power grid of an offshore oil platform, so as to provide an effective and reliable method for identifying generators, interconnecting transformers, submarine cable interconnections and loads.

[0007] To achieve the above objectives, the present invention includes:

[0008] A method for controlling the power grid of an offshore oil platform according to the present invention includes the following steps:

[0009] 1) Real-time acquisition of current and power data of generators, interconnecting transformers, submarine cable interconnects and loads in the offshore oil platform power grid that are in operation;

[0010] 2) Based on the pure electrical quantity tripping criteria or the protection tripping signal criteria, determine whether the generator in operation has experienced a fault tripping phenomenon. The pure electrical quantity tripping criteria include the generator's sudden change starting conditions, the comparison results between the active power before and after the tripping and the corresponding power setting, and the comparison results between the current value and the corresponding current setting. The protection tripping signal criteria include whether there is a three-phase tripping signal and whether the signal changes within a first set time.

[0011] When a generator in operation trips due to a fault, the load is cut off according to the required load.

[0012] 3) Determine whether the component has an overload start-up phenomenon based on the component current magnitude, active power direction, whether the maintenance pressure plate has been removed, and whether another component has failed to operate. Determine whether the component has started under overload, the comparison result between the component current and the overload operating current setting, and the comparison result between the component power and the overload operating power setting. The component includes at least two of the following: generator, interconnecting transformer, and submarine cable interconnecting line.

[0013] If any component experiences overload startup and overload action, the load will be cut off according to the required load quantity.

[0014] Beneficial Effects: The offshore oil platform power grid control method of this invention, after collecting data information from generators, interconnecting transformers, and submarine cable interconnections in the offshore oil platform power grid, determines whether a generator has tripped due to a fault by using pure electrical quantity tripping criteria or protection tripping signal criteria. It determines whether an overload start-up of a component is occurring based on current magnitude, active power direction, whether the maintenance pressure plate has been disengaged, and whether another component has failed. It further determines whether the generator, interconnecting transformer, or submarine cable interconnection has overloaded based on whether overload has started, the comparison between the component current and the overload operating current setting, and the comparison between the component power and the overload operating power setting. These judgment criteria enable rapid and accurate fault and anomaly detection. Based on the judgment results, the system controls the power grid regulation accordingly. When a generator malfunctions, interruptible loads are disconnected in milliseconds, and the disconnection amount is adjusted according to load requirements to ensure stable power grid operation.

[0015] Furthermore, if a generator in operation meets the pure electrical quantity tripping criterion or the protection tripping signal criterion, then the generator is considered to have tripped due to a fault. The pure electrical quantity tripping criterion is as follows: the generator is initiated by a sudden change in current or a sudden change in power; the active power before tripping is greater than the power setting before tripping; the active power after tripping is less than the power setting after tripping; all three-phase currents are less than the operating current setting; the decrease in current is greater than the threshold value; and the tripping delay time is greater than the tripping confirmation delay setting. The protection tripping signal criterion is that there is a three-phase tripping signal and the signal remains unchanged within a first set time. The condition for being in operation is that at least two phase currents are greater than or equal to the operating current setting or the absolute value of active power is greater than the operating power setting.

[0016] Beneficial effects: The generator fault and whether a tripping phenomenon has occurred can be judged by pure electrical quantity tripping criteria or protection tripping signal criteria. The judgment logic is simple. The judgment is accurate by judging the sudden change in current or power, the current magnitude, and the power before and after the tripping, or by judging based on the tripping signal.

[0017] Furthermore, overload start-up is defined as follows: the component current is greater than or equal to the overload alarm current threshold, the generator power direction is either the inflow direction to the busbar or the connecting transformer and submarine cable connecting line are the outflow direction to the busbar, and the auxiliary criterion conditions are met and the duration reaches the start-up delay set value. The auxiliary criterion conditions are: the auxiliary criterion is not activated or, after the auxiliary criterion is activated, there is a phenomenon where two components are in operation and another component trips. Overload action is defined as follows: the component is overload started, the component current is above the overload action current set value, the component power is above the overload action power set value, and the duration continues to reach the action delay set value.

[0018] Beneficial effects: By judging the severity of overload through overload start-up and overload action conditions, the load is cut off in the case of severe overload, ensuring the supply and demand balance between the generator and the electrical load. The severity of overload can be accurately determined by checking the current and power direction of components and whether there is a fault tripping phenomenon between any other components.

[0019] Furthermore, the control method also includes the judgment of component overload alarm. The overload alarm meets the following conditions: when the component current is greater than or equal to the overload alarm current setting, the component power is greater than or equal to the overload alarm power setting, the component's maintenance pressure plate is removed, and the duration of the current state reaches the alarm delay setting, the component reaches the overload alarm condition.

[0020] Beneficial effects: The overload judgment of components also includes the judgment of overload alarm. If an overload occurs in a component, an overload alarm is issued, which ensures the safe and stable operation of the power system.

[0021] Furthermore, when a generator trips due to a fault, the load shedding amount is the difference between the steady-state active power of the generator in the first set period before the trip and the grid reserve power, whereby the grid reserve power is:

[0022]

[0023] In the formula, P ∈ K is the reserve power for the power grid. Gi P is the generator operating coefficient. Gin P represents the rated active power of the remaining i-th generator in operation. Gi This refers to the real-time active power of the remaining operational generators.

[0024] Beneficial Effects: This invention uses the steady-state active power before the faulty generator trips as the base value, subtracting the reserve active power of the offshore oil platform power grid from this difference. This difference is used as the required shedding amount. Based on load priority and the principle of minimum over-shuffling, interruptible loads on each platform are shelved in milliseconds, achieving a dynamic balance between generator active power output and load demand in the offshore oil platform power grid, ensuring stable grid operation. Similarly, the difference between the active power when the generator is overloaded and the overloaded active power setpoint, minus the grid's reserve active power, is used as the required load shedding amount, ensuring stable grid operation.

[0025] Furthermore, when the generator overloads, the required load shedding is: the difference between the active power of the generator when it overloads and the set value of the active power during overload operation, minus the grid's reserve active power; after the interconnecting transformer / submarine cable interconnecting line overloads, the required load shedding is the difference between the active power of the interconnecting transformer / submarine cable interconnecting line when it overloads and the set value of the active power during overload operation.

[0026] Furthermore, after a generator trips due to a fault or an overload, if the load shedding demand is greater than 0, the AGC / AVC system controls the generator to operate in a set mode after the load shedding is completed. Simultaneously, it adjusts the generators in differential mode and non-differential mode to increase output until the generator load factor is 1. If the load shedding demand is not greater than 0, after the generator trip is confirmed or an overload occurs, the AGC / AVC system controls the generator to operate in a set mode and adjusts the generators in non-differential mode to increase output. After the grid frequency and voltage stabilize, it sequentially adjusts the generators in differential mode until the real-time active power of the offshore oil platform grid equals the sum of the real-time power of the generators in non-differential mode and the real-time power of the generators in differential mode. At this point, the adjustment to increase generator output stops. The operating modes include non-differential mode and differential mode. In non-differential mode, the generator operates at a set frequency and voltage. In differential mode, the generator frequency is corrected according to the load conditions, and secondary speed adjustment is performed based on the rated frequency of the generator in non-differential mode.

[0027] Beneficial effects: When a generator malfunctions or an overload alarm occurs, interruptible loads are cut off based on the calculated load requirements, taking into account the generator's reserve capacity. After the load is cut off, priority is given to stabilizing the grid frequency, and the generator in zero-error mode is adjusted to increase its output, so that the grid frequency and voltage in the grid system can be stabilized quickly.

[0028] Furthermore, in order to quickly adjust the balance between the generator and the electrical load, and to stabilize the grid frequency and voltage in the power grid system, after the overload operation of the interconnection transformer or submarine cable interconnection line, the load is cut off according to the calculated corresponding load cut-off amount, and at the same time, the output of the differential mode generator and the differential mode generator is reduced.

[0029] Furthermore, the AGC / AVC system strategy controls the generator to select the set operating mode as follows: when the number of generators in operation is 1, the generator is set to the error-free mode; when the number of generators in operation is 2 or more, the generator with the largest rated capacity is selected and set to the error-free mode, and the remaining generators are set to the differential mode. If there are multiple generators with the same rated capacity, the generator with the largest standby capacity is selected and set to the error-free mode. The standby capacity is calculated based on the generator operating coefficient, the rated active power of the remaining generators in operation, and the real-time active power of the remaining generators in operation. When a generator in the error-free mode trips due to a fault or overload, the generator with the largest rated capacity and standby capacity in the differential mode is converted to the error-free mode.

[0030] The present invention discloses a power grid control system for an offshore oil platform, comprising a main control station, a control execution station, and an AGC / AVC system. The main control station is communicatively connected to the control execution station and integrates the functions of the AGC / AVC system. The main control station is used to acquire current and power data of generators, interconnecting transformers, submarine cable interconnecting lines, and loads in the offshore oil platform power grid, and to acquire load current and power data collected by the control execution station, so as to realize the offshore oil platform power grid control method as described above.

[0031] Beneficial Effects: The offshore oil platform power grid control system of this invention, through communication between the control master station and the control execution station, controls generators, interconnecting transformers, submarine cable interconnections, and loads to achieve a dynamic balance between the active power output of generators and the power consumption of loads in the offshore oil platform power grid. The system's judgment criteria are simple and accurate, enabling it to quickly and accurately identify faults and anomalies, precisely and rapidly adjust the supply and demand balance between power grids, and ensure stable grid operation. Attached Figure Description

[0032] Figure 1 This is a system architecture diagram of the offshore oil platform stability control system in a system embodiment of the present invention;

[0033] Figure 2This is a logic block diagram of the generator fault tripping and load shedding function strategy in a system embodiment of the present invention;

[0034] Figure 3 This is a logic block diagram of the generator overload, main transformer overload, and submarine cable tie line load shedding function strategy in a system embodiment of the present invention;

[0035] Figure 4 This is a system architecture diagram of AGC / AVC in a system embodiment of the present invention;

[0036] Figure 5 This is a schematic diagram of the UI relationship of the generator set under different operating modes in a system embodiment of the present invention;

[0037] Figure 6 This is a frequency diagram of the generator set under different operating modes in a system embodiment of the present invention. Detailed Implementation

[0038] The present invention will now be described in further detail with reference to the accompanying drawings.

[0039] Example of an offshore oil platform power grid control system:

[0040] This embodiment provides a safety and stability control system for offshore oil platform power grids that integrates AGC / AVC functions. It employs an embedded device based on a DSP architecture, integrating both the safety and stability control system functions and the AGC / AVC functions. The device directly collects analog signal information from generators, transformers, and submarine cable connections required for stability control strategy judgments. This direct analog signal acquisition solves the problem of slow stability control response time caused by network-based analog signal acquisition in foreign PMS systems. Furthermore, it leverages the long lifespan of embedded devices to avoid the short lifespan disadvantage of PMS system servers. In addition, compared to configuring separate independent devices for the safety and stability control system and AGC / AVC equipment, this invention requires fewer devices and occupies less screen space on the offshore oil platform, effectively alleviating the problem of limited space on offshore oil platforms. Figure 1 The illustrated safety and stability control system includes a stability control master station located on the main power platform, an AGC / AVC system integrated in the stability control master station, and stability control execution stations located on each load platform. The stability control master station and the stability control execution stations are connected by optical fiber, and the inter-station equipment communicates using the HDLC protocol.

[0041] The control master station includes a master unit, Type I slave units, Type II slave units, and N data acquisition and execution terminals (N>1). The master unit is connected to the Type I and Type II slave units via optical fiber, and also communicates with them via the IEC 60044-8 communication protocol. The master unit is also connected to each data acquisition and execution terminal via optical fiber, and also communicates with each data acquisition and execution terminal via the IEC 60044-8 communication protocol.

[0042] The stability control master station collects information on generators, interconnecting transformers, submarine cable interconnecting lines, motors (specifically 10kV motors), and loads of 380V and below from the offshore oil platform power grid. Based on the control strategies of generator fault tripping and load shedding, and generator, transformer, and submarine cable interconnecting line overload shedding, it issues control commands to the stability control master station Type II slave and data acquisition execution terminal to cut off interruptible loads on the power supply master platform.

[0043] The Type I slave device is primarily responsible for directly acquiring analog quantities and remote signaling information required for the stability control master station and AGC / AVC criteria. It acquires analog information on the three-phase current and three-phase voltage of the generators, interconnecting transformers, and submarine cable interconnecting lines on the power supply master platform; the location and protection action information of the corresponding circuit breakers in the generator, interconnecting transformer, and submarine cable interconnecting lines; and information related to generator excitation restrictions (reduction / increase), faults, automatic excitation regulator operation, rapid return of the generator, and AGC activation. Based on the acquired information, it identifies the operational status of the generators, transformers, and submarine cable interconnecting lines, as well as the grid operation mode, to enable the AGC / AVC system to receive and execute commands such as increasing / decreasing active power and increasing / decreasing reactive power.

[0044] The Type II slave unit serves as an information acquisition, control, and execution device for loads on the 10kV bus. It mainly collects analog information on single-phase current and single-phase voltage of large loads such as 10kV bus motors on the main power supply platform, uploads the collected operating information to the main station host device, receives control commands issued by the main station host, and executes the control commands.

[0045] The data acquisition and execution terminal is a data acquisition and control device installed on a low-voltage cabinet (such as a 380V low-voltage cabinet). As an information acquisition, control and execution device for 380V and below loads, it mainly collects information from 380V and below loads, sends it to the main station host device, receives control commands issued by the main station host and executes the control commands.

[0046] like Figure 4As shown, the AGC / AVC system functions are integrated into the stability control master station. It can obtain information from the stability control master station host and the type I slave through the type I slave. Based on the analog quantities of each generator (three-phase current, three-phase voltage, active power, reactive power, frequency and power factor, etc.) collected by the type I slave, the generator remote signaling status, and the active power of each platform load collected by the stability control master station host, it controls the generator output and outputs the control commands to the generator's DCS system through hard wiring to ensure the stable operation of the platform power grid.

[0047] The stabilization and control execution station collects information on loads of 380V and below at this station and uploads the load information to the stabilization and control master station. At the same time, it receives load shedding commands from the stabilization and control master station and issues corresponding control measures to the data acquisition and execution terminal according to the load shedding commands to cut off interruptible loads on each load platform.

[0048] In this embodiment, the system is also equipped with remote / local input signaling for AGC / AVC. When the input signal is 1 and the system is in remote mode, the AGC / AVC of each generator set is controlled by the device according to a preset strategy for voltage and frequency. When the input signal is 0 and the system is in local mode, each generator set can only be controlled through a local control panel or a remote control panel. After the offshore oil platform power grid is put into operation, the remote / local control handle of AGC / AVC is set to remote mode and automatically adjusts the grid voltage and frequency according to a preset strategy.

[0049] In this embodiment, the types of generators on the offshore oil platform include gas turbine units and gas reciprocating units. Among them, gas turbine units are stable, have strong energy-bearing capacity during sudden increases and decreases, and have large rated power. As the main generators of the power grid, they bear most of the load during instantaneous load changes. Gas reciprocating units have relatively small output and weak energy-bearing capacity during sudden increases and decreases. They bear smaller load changes when the power grid load fluctuates and are mainly responsible for steady-state load distribution.

[0050] Based on the control system in this embodiment, the execution principle is as follows:

[0051] 1) Real-time acquisition of data information on generators, interconnecting transformers, submarine cable interconnections and loads in the offshore oil platform power grid that are in operation.

[0052] First, the current and power data of generators, interconnecting transformers, and submarine cable interconnecting lines in the offshore oil platform power grid are acquired in real time through the stability control master station. Load data information from the stability control execution station and the stability control master station is also collected.

[0053] 2) Determine whether the generator has tripped based on the generator operating data information, and determine whether the generator, interconnecting transformer, and submarine cable interconnecting line have overloaded start-up or overloaded operation based on the data information of the generator, interconnecting transformer, and submarine cable interconnecting line.

[0054] Based on the tripping criteria for pure electrical quantities or the tripping criteria for protection signals, it is determined whether a generator in operation has experienced a fault tripping phenomenon. The tripping criteria for pure electrical quantities include the generator's sudden start-up conditions, the comparison results between the active power before and after the trip and the corresponding power setting, and the comparison results between the current value and the corresponding current setting. The tripping criteria for protection signals include whether there is a three-phase tripping signal and whether the signal remains unchanged for a first set time.

[0055] First, it is necessary to determine whether the generators in operation are faulty. When one or more generators in operation on the main power platform fail, the generator trips according to the "pure electrical quantity trip criterion" or "protection trip signal criterion". If at least one generator is still in operation, the steady-state active power of the generator in the first set period (200ms) before the faulty generator trips is used as the base value. The reserve active power of the offshore oil platform power grid can be used to calculate the load shedding (the number of loads to be cut off). According to the load priority, the interruptible loads of each platform are cut off in milliseconds according to the minimum over-cut principle. This achieves a dynamic balance between the active power output of the generators and the power consumption of the loads in the offshore oil platform power grid, ensuring the stable operation of the power grid.

[0056] The generator's operational or shutdown status is determined based on electrical quantities, and the specific determination method is as follows:

[0057] When at least two phase currents are greater than the operating current setting or the absolute value of active power is greater than the operating power setting, the state is considered to be in operation after confirmation over a second set time.

[0058] When at least two phase currents are less than the operating current setting and the absolute value of active power is less than the operating power setting, the state is considered to be in shutdown state after confirmation over a second set time.

[0059] like Figure 2 As shown, the tripping criteria for pure electrical quantities are: ① Tripping is initiated by a sudden change in current or a sudden change in power; ② The active power before tripping is greater than the power setting before tripping; ③ The active power after tripping is less than the power setting after tripping; ④ All three-phase currents are less than the operating current setting; ⑤ The decrease in current is greater than the threshold value; ⑥ The tripping delay time is greater than the tripping confirmation delay setting.

[0060] If all of the above conditions ① to ⑥ are met, the generator is judged to have tripped.

[0061] The protection trip signal criterion is: if there is a three-phase trip signal and the signal remains unchanged within the first set time (15ms), it indicates that the generator has tripped.

[0062] When a generator trips due to a fault, the load shedding requirement is the difference between the generator's active power and the grid's reserve power during the first set period (200ms) before the trip. The grid's reserve active power P∈ for:

[0063]

[0064] In the formula, P ∈ K is the reserve power for the power grid. Gi Generator operating coefficient (K) Gi ≤1 (can be tuned), P Gin P represents the rated active power of the remaining i-th generator in operation. Gi This refers to the real-time active power of the remaining operational generators.

[0065] Secondly, determine whether the generator, tie transformer, or submarine cable tie line is overloaded. Based on the component current magnitude, active power direction, whether the maintenance pressure plate is disengaged, and whether another component is faulty and out of service, determine if the component is experiencing overload startup. Determine if the component has started under overload, the comparison between the component current and the overload trip current setting, and the comparison between the component power and the overload trip power setting to determine if overload tripping has occurred. The components include at least two of the generator, tie transformer, and submarine cable tie line. Specifically, as follows... Figure 3 As shown, when the main power platform is put into operation, the generator, transformer (i.e., the interconnection transformer), and submarine cable interconnection line are affected by thermal overload due to changes in the power grid operation mode, and the equipment is running stably, the device will issue an alarm after a delay according to the set overload alarm setting value (i.e., the overload alarm current threshold). Based on the overload action setting value, the amount to be cut off after the action, and the load priority, the interruptible loads of each platform will be cut off according to the minimum over-cut principle to ensure the stable and reliable operation of the generator, transformer, and submarine cable interconnection line.

[0066] Specifically, when determining whether generators, transformers, and submarine cable interconnections are overloaded, the system also includes judging component overload alarms. Overload alarms can be judged and processed through the maintenance check plate, current, and power of the components (referring to generators, transformers, and submarine cable interconnections). Specifically, when three judgment conditions are met simultaneously—the component's maintenance check plate is disengaged, the component current is greater than or equal to the overload alarm current setting (without direction determination), and the component power is greater than or equal to the overload alarm power setting (without direction determination)—and the duration reaches the overload alarm delay setting, the device alarms.

[0067] When the device alarms, the component initiates overload start-up according to the overload start-up criteria. Specifically, the start-up criteria are as follows: component current ≥ overload alarm current setting (direction not considered); generator power direction is the negative direction of the strategy (flowing into the busbar); transformer or submarine cable tie line power is either the negative or positive direction of the strategy (flowing into or out of the busbar); component maintenance pressure plate is deactivated; any component trips. When all these criteria are met, and the duration reaches the overload start-up delay setting, the component meeting the criteria initiates overload start-up.

[0068] When a component starts under overload, the generator, transformer, and submarine cable tie line must simultaneously meet the following conditions, and the duration must reach the overload action delay setpoint, then the corresponding component will activate under overload:

[0069] Component overload start-up; Component current ≥ overload operating current setting; |Component power| ≥ overload operating power setting.

[0070] When the generator is overloaded and the overload trips, the load shedding required under this condition is the difference between the active power when the generator trips under overload and the active power setpoint when the overload trips, minus the grid reserve active power.

[0071] When a transformer or submarine cable tie line experiences an overload, the load shearing amount is the difference between the active power when the component experiences an overload and the set value of the active power during the overload.

[0072] As an alternative implementation, overload alarm conditions for generators, transformers, and submarine cable connections may not be set; instead, overload start-up and overload action conditions can be used to identify generators, transformers, and submarine cable connections.

[0073] 3) When a generator in operation trips due to a fault, the load is cut off according to the required load shedding quantity. If any component (generator, transformer, submarine cable tie line) experiences overload startup and overload activation, the load is cut off according to the required load shedding quantity. Adjustments are made based on the current status. If a generator malfunctions or overloads, the required load shedding quantity is calculated based on the generator's active power and rated power. Based on the required load shedding quantity, interruptible loads are cut off, and the AGC / AVC system strategy controls the generator to execute the corresponding operating mode. If the tie transformer or submarine cable tie line overloads, after the tie transformer or submarine cable tie line load shedding is executed, the AGC / AVC system controls the generator to operate according to the corresponding operating mode.

[0074] A) If the generator trips due to a fault or overload, the load shedding amount is calculated based on the generator's active power and rated power. Based on the load shedding amount, interruptible loads are cut off, and the AGC / AVC system controls the generator to execute the corresponding operating mode.

[0075] When a generator trips due to a fault or overload occurs in the offshore oil platform's power grid, these two types of load shedding strategies have already pre-allocated generator reserve capacity to the load in order to minimize the shedding of interruptible loads. Because these two types of load shedding strategies prioritize grid frequency stability and do not consider the difference between generator load rates in zero-fault and differential-fault modes, the specific strategies are as follows:

[0076] Specifically, as can be seen from step 2), the load shedding required when the generator trips due to a fault is the difference between the generator's active power and the grid's reserve power during the first set period (200ms) before the trip. After the generator overloads, the load shedding required is the difference between the generator's active power at the time of overload and the overload active power setpoint, minus the grid's reserve active power.

[0077] If the load shedding demand is greater than 0, the system will automatically trigger the AGC / AVC control strategy after the generator fault tripping load shedding or generator overload load shedding action is completed (stability control function strategy). At the same time, it will adjust the differential mode generator and the non-differential mode generator to increase the output and increase the active power to the load factor equal to 1.

[0078] If the load shedding requirement is ≤0, after a generator fault trip is confirmed or a generator overload starts, the system automatically triggers the AGC / AVC control strategy. It first adjusts the generators in zero-difference mode to increase output, stabilizing the platform's grid frequency and voltage as quickly as possible; then it sequentially adjusts the gas turbine units and gas reciprocating units in differential mode. During the adjustment process, when the real-time active power of the load equals the sum of the real-time power of the generators in zero-difference mode and the real-time power of the generators in differential mode, the adjustment to increase generator output stops.

[0079] The strategy for AGC / AVC to control the generator is as follows:

[0080] a. When a single generator is put into operation, set the generator to error-free mode.

[0081] b. When the number of generators in operation is ≥2, the main grid-connected generating unit (gas turbine unit) with the largest rated capacity will be set to zero-difference mode, and the remaining units will be set to differential mode. If multiple main grid-connected generating units have the same capacity, the gas turbine unit with the largest standby capacity will be set to zero-difference mode, and the other units will be set to differential operation mode to reduce unit adjustments. The standby capacity P1 of the generating units is...

[0082] P1 = K G ×P Gn -P G

[0083] In the formula, K G P is the generator operating coefficient. Gn P represents the rated active power of the remaining operational generators. G This refers to the real-time active power of the remaining operational generators.

[0084] c. During operation, when a generator in zero-fault operation mode trips due to a fault and becomes out of service, the system automatically switches the main grid generator unit (gas turbine unit) with the largest rated capacity in zero-fault operation mode to zero-fault operation mode, while the operation modes of other units remain unchanged. If multiple gas turbine units in zero-fault operation mode have the same rated capacity, the main grid generator unit (gas turbine unit) with the largest standby capacity is selected to switch from zero-fault operation mode to zero-fault operation mode, while the operation modes of other units remain unchanged.

[0085] B) If the tie transformer or submarine cable tie line is overloaded, after the tie transformer and submarine cable tie line load shedding action is executed, the AGC / AVC system controls the generator to operate according to the corresponding operating mode.

[0086] After the transformer overload shedding or tie line overload shedding operation is completed, the system automatically triggers the AGC / AVC strategy, simultaneously adjusting the output of both differential mode generators and non-differential mode generators to reduce power output. During the adjustment process, the output is reduced according to the following strategy:

[0087] When the load rate K1 of the generator in zero-difference mode is lower than the load rate K2 of the generator in differential mode, the load rate difference K between the two operating modes is calculated. This difference must satisfy K = (K2 - K1) ≥ 0.05. The value of K can be adjusted according to actual needs, ensuring that the generator in zero-difference mode has sufficient hot standby to handle load fluctuations. The AGC / AVC system adjusts the load rate of the generator in zero-difference mode to load rate K2. When the real-time active power of the offshore platform load meets the following conditions, the generator is stopped and its output reduced for adjustment:

[0088] P F =K1×K G ×P 无差-额 +K2×K G ×P 有差-额

[0089] In the formula, P F The active power of the offshore oil platform load is real-time; K1 is the generator load rate in zero-delay mode; P 无差-额 K2 is the rated active power of the generator in zero-difference mode; P is the load factor of the generator in differential mode. 有差-额 K represents the sum of the rated active power of the generators in differential mode; G Generator operating coefficient (K) G ≤1 (can be adjusted). Load rate is the ratio of the generator's real-time power to its rated power.

[0090] In this embodiment, the AGC / AVC system controls two generator operating modes: one is a zero-error mode, i.e., a voltage (frequency) setting method, such as... Figure 5 , Figure 6As shown, in zero-difference mode, the generator speed and load curves are a straight line parallel to the X-axis. The generator operates stably with a set frequency (e.g., 50Hz) and a set voltage (e.g., 10.5kV) as the target, maintaining grid stability. The other mode is differential mode, i.e., voltage (frequency) following mode, such as... Figure 5 , Figure 6 As shown, in differential mode, the generator speed and load curves form a downward-sloping straight line band. The generator speed control system corrects the frequency adjusted by the speed control loop according to the load conditions. However, this frequency is not stable. Therefore, the system needs to perform secondary speed control on the generator in differential mode using the rated frequency set by the generator in zero-delay mode, so that the generator in differential mode also reaches a stable frequency. Differential mode is used to prevent generator overload or reverse rotation leading to generator tripping when the generator load rate suddenly becomes very high or very low.

[0091] 4) If the generator is fault-free and the generator, interconnecting transformer, and submarine cable interconnecting line are not overloaded, the AGC / AVC system will control each generator to operate in the set operating mode according to the real-time active power of the load and the rated active power of each generator.

[0092] When the power grid is operating normally (without generator fault tripping, generator overload, transformer overload, or tie line overload), the AGC / AVC system controls and adjusts the generator load rate based on the real-time active power of each CNOOC platform and the rated active power of each generator as follows:

[0093] When the load rate K1 of the generator in zero-difference mode is lower than the load rate K2 of the generator in differential mode, the load rate difference K between the two operating modes is calculated. When K = (K2 - K1) ≥ 0.05, the value of K can be tuned; typically, K = 0.2 to ensure that the generator in zero-difference mode has sufficient hot standby to handle load fluctuations. The AGC / AVC system adjusts the load rate of the generator in zero-difference mode to load rate K2. When the real-time active power of the offshore platform load meets the following conditions, the generator is stopped and its output is reduced:

[0094] P F =K1×K G ×P 无差-额 +K2×K G ×P 有差-额

[0095] In the formula, P F The active power of the offshore oil platform load is real-time; K1 is the generator load rate in zero-delay mode; P 无差-额 K2 is the rated active power of the generator in zero-difference mode; P is the load factor of the generator in differential mode. 有差-额 K represents the sum of the rated active power of the generators in differential mode; G Generator operating coefficient (K) G ≤1 can be adjusted).

[0096] Example of a power grid control method for offshore oil platforms:

[0097] The offshore oil platform power grid control method in this embodiment mainly includes:

[0098] 1) Real-time acquisition of current and power data of generators, interconnecting transformers, submarine cable interconnects and loads in the offshore oil platform power grid that are in operation;

[0099] 2) Based on the pure electrical quantity tripping criteria or the protection tripping signal criteria, determine whether the generator in operation has experienced a fault tripping phenomenon. The pure electrical quantity tripping criteria include the generator's sudden change starting conditions, the comparison results between the active power before and after the tripping and the corresponding power setting, and the comparison results between the current value and the corresponding current setting. The protection tripping signal criteria include whether there is a three-phase tripping signal and whether the signal remains unchanged for a first set time.

[0100] When a generator in operation trips due to a fault, the load is cut off according to the required load.

[0101] 3) Determine whether the component has an overload start-up phenomenon based on the component current magnitude, active power direction, whether the maintenance pressure plate has been removed, and whether another component has failed to operate. Determine whether the component has started under overload, the comparison result between the component current and the overload operating current setting, and the comparison result between the component power and the overload operating power setting. The component includes at least two of the following: generator, interconnecting transformer, and submarine cable interconnecting line.

[0102] If any component experiences overload startup and overload activation, the load will be cut off according to the required load disconnection quantity. Specific implementation methods have been described in detail in the offshore oil platform power grid control system embodiments and will not be repeated here.

Claims

1. A method for controlling the power grid of an offshore oil platform, characterized in that, Includes the following steps: 1) Real-time acquisition of current and power data of generators, interconnecting transformers, submarine cable interconnects and loads in the offshore oil platform power grid that are in operation; 2) Based on the pure electrical quantity tripping criteria or the protection tripping signal criteria, determine whether the generator in operation has experienced a fault tripping phenomenon. The pure electrical quantity tripping criteria include the generator's sudden change starting conditions, the comparison results between the active power before and after the tripping and the corresponding power setting, and the comparison results between the current value and the corresponding current setting. The protection tripping signal criteria include whether there is a three-phase tripping signal and whether the signal changes within a first set time. When a generator in operation trips due to a fault, the load is cut off according to the required load. 3) Determine whether the component has an overload start-up phenomenon based on the component current magnitude, active power direction, whether the maintenance pressure plate has been removed, and whether another component has failed to operate. Determine whether the component has started under overload, the comparison result between the component current and the overload operating current setting, and the comparison result between the component power and the overload operating power setting. The component includes at least two of the following: generator, interconnecting transformer, and submarine cable interconnecting line. If any component experiences overload startup and overload action, the load will be cut off according to the required load quantity.

2. The offshore oil platform power grid control method according to claim 1, characterized in that, When a generator in operation meets the pure electrical quantity tripping criterion or the protection tripping signal criterion, it is considered to have tripped due to a fault. The pure electrical quantity tripping criterion is as follows: the generator is initiated by a sudden change in current or a sudden change in power; the active power before tripping is greater than the power setting before tripping; the active power after tripping is less than the power setting after tripping; all three-phase currents are less than the operating current setting; the decrease in current is greater than the threshold value; and the tripping delay time is greater than the tripping confirmation delay setting. The protection tripping signal criterion is that there is a three-phase tripping signal and the signal remains unchanged within a first set time. The condition for being in operation is that at least two phase currents are greater than or equal to the operating current setting or the absolute value of active power is greater than the operating power setting.

3. The offshore oil platform power grid control method according to claim 1, characterized in that, Overload start is defined as follows: the component current is greater than or equal to the overload alarm current threshold, the generator power direction is the inflow direction to the bus or the interconnection transformer and submarine cable interconnection line are the outflow direction to the bus, and the auxiliary criterion conditions are met and the duration reaches the start delay setting value. The auxiliary criterion conditions are: the auxiliary criterion is not activated or, after the auxiliary criterion is activated, there is a phenomenon of two components being in operation and another component tripping. Overload action is defined as follows: the component is overload started, the component current is above the overload action current setting value, the component power is above the overload action power setting value, and the duration continues to reach the action delay setting value. The component is overloaded and then takes action.

4. The offshore oil platform power grid control method according to claim 3, characterized in that, The control method also includes the judgment of component overload alarm. The overload alarm is met when the component current is greater than or equal to the overload alarm current setting, the component power is greater than or equal to the overload alarm power setting, the component's maintenance pressure plate is removed, and the duration of the current state reaches the alarm delay setting.

5. The offshore oil platform power grid control method according to claim 2, characterized in that, When a generator trips due to a fault, the load shedding amount is the difference between the active power of the generator in the first set period before the trip and the grid reserve power, where the grid reserve power is: In the formula, P ∈ is the standby power of the power grid, K Gi is the generator operation coefficient, P Gin is the rated active power of the i-th remaining generator in operation, P Gi is the real-time active power of the remaining generator in operation.

6. The offshore oil platform power grid control method according to claim 5, characterized in that, When the generator overloads, the required load shedding is: the difference between the active power of the generator when it overloads and the set value of the active power during overload operation, minus the grid's reserve active power; after the interconnecting transformer / submarine cable interconnecting line overloads, the required load shedding is the difference between the active power of the interconnecting transformer / submarine cable interconnecting line when it overloads and the set value of the active power during overload operation.

7. The offshore oil platform power grid control method according to claim 5, characterized in that, After a generator trips due to a fault or an overload, if the load shedding demand is greater than 0, the AGC / AVC system controls the generator to operate in a set mode after the load shedding is completed. Simultaneously, it adjusts the generators in differential mode and non-differential mode to increase output until the generator load factor is 1. If the load shedding demand is not greater than 0, after the generator trip is confirmed or an overload occurs, the AGC / AVC system controls the generator to operate in a set mode and adjusts the generators in non-differential mode to increase output. After the grid frequency and voltage stabilize, it sequentially adjusts the generators in differential mode until the real-time active power of the offshore oil platform grid equals the sum of the real-time power of the generators in non-differential mode and the real-time power of the generators in differential mode. At this point, the adjustment to increase generator output stops. The operating modes include non-differential mode and differential mode. In non-differential mode, the generator operates at a set frequency and voltage. In differential mode, the generator frequency is corrected according to the load conditions, and secondary speed adjustment is performed based on the generator's rated frequency in non-differential mode.

8. The offshore oil platform power grid control method according to claim 6, characterized in that, After the overload operation of the interconnection transformer or submarine cable interconnection line, the load needs to be cut off according to the calculated corresponding load amount, and at the same time, the differential mode generator and the differential mode generator are adjusted to reduce the output.

9. The offshore oil platform power grid control method according to claim 7, characterized in that, The AGC / AVC system selects the set operating mode for the generator as follows: when the number of generators in operation is 1, the generator is set to the zero-difference mode; when the number of generators in operation is 2 or more, the generator with the largest rated capacity is selected and set to the zero-difference mode, and the remaining generators are set to the differential mode. If there are multiple generators with the same rated capacity, the generator with the largest standby capacity is selected and set to the zero-difference mode. The standby capacity is calculated based on the generator operating coefficient, the rated active power of the remaining generators in operation, and the real-time active power of the remaining generators in operation. When a generator in the zero-difference mode trips due to a fault or overload, the generator with the largest rated capacity and standby capacity in the differential mode is switched to the zero-difference mode.

10. A power grid control system for an offshore oil platform, comprising a stability control master station, a stability control execution station, and an AGC / AVC system, wherein the stability control master station is communicatively connected to the stability control execution station, and the stability control master station also integrates the functions of the AGC / AVC system, characterized in that, The stability control master station is used to acquire current and power data information of generators, interconnecting transformers, submarine cable interconnecting lines and loads in the offshore oil platform power grid, and to acquire load current and power data information collected by the stability control execution station, so as to realize the offshore oil platform power grid control method as described in any one of claims 1-9.

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