A method and system for coordinated control of oilfield off-grid micro-grid energy storage main network and gas engine unit constant power energy supplement

Abstract

The application relates to a coordination control method and system for an oilfield off-grid micro-grid energy storage main network and a gas unit constant power energy compensation, relates to oilfield production type micro-grid and distributed energy control technology, and comprises the following specific control strategies: an energy storage unit is used as a main network source to establish the frequency and voltage of a 6KV bus; an energy storage converter in the energy storage unit executes primary frequency regulation, reactive power support and oil pumping machine impact compensation according to frequency deviation and voltage deviation; a gas unit is connected to the 6KV bus in a current source or grid-connected mode according to a constant power setting value; an energy management system is used to decompose fast and slow power, distribute the fast variable power component to the energy storage converter, and distribute the slow variable power component to the gas unit; when the energy storage unit is unavailable, the gas unit is switched to an emergency network source and executes load grading and power reduction to ensure power supply. The scheme can improve the frequency and voltage stability of the oilfield off-grid micro-grid, and reduce the risk of frequent speed regulation and inefficient operation of the gas turbine.

Description

Technical Field

[0001] This invention relates to oilfield production microgrids and distributed energy control technology, specifically a coordinated control method and system for an off-grid microgrid energy storage main network and constant power supplementation by a gas turbine unit. Background Technology

[0002] With the increasing demands for electrification, cleaner energy supply, and autonomous power generation in oilfields and remote well sites, photovoltaics, energy storage, gas turbine units, and EMS (Energy Management Systems) are being gradually introduced into oil production systems. However, most solutions remain at the level of power supply combination, economic dispatch, or single-equipment control, failing to adequately consider practical issues such as the cyclical impact of oilfield production loads, 6kV production feeder boundaries, communication degradation, network priority transfer, and the actual dynamic characteristics of gas turbine units. This results in the following problems with existing technologies:

[0003] 1. Long-term grid connection of gas turbine units leads to frequency and voltage fluctuations;

[0004] 2. The rapid regulation capability of energy storage has not been fully utilized for primary frequency regulation and transient support;

[0005] 3. Gas turbine units suffer from inefficiency and oscillations due to rapid load surges. Summary of the Invention

[0006] The purpose of this invention is to solve the problems of frequency and voltage fluctuations caused by long-term grid connection of gas turbine units in off-grid microgrids of oil fields, the insufficient use of energy storage rapid regulation capabilities for primary frequency regulation and transient support, and the inefficiency and oscillation caused by gas turbine units following rapid load impacts.

[0007] The technical problem solved by this invention is achieved by the following technical solution:

[0008] A coordinated control method for the energy storage main grid and constant power supplementation of gas turbine units in an off-grid microgrid for oil fields is applied to the off-grid microgrid for oil fields. The off-grid microgrid for oil fields includes photovoltaic power generation units, energy storage units, gas turbine units and oil well production loads connected to a 6KV bus, as well as an energy management system, protection equipment and switchgear. The specific control strategies include the following:

[0009] When the energy storage grid construction capability is effective, the energy storage converter is used as the only effective grid construction reference to establish and maintain the 6KV bus frequency and voltage in the grid construction working mode.

[0010] The energy storage converter in the energy storage unit provides power support for primary frequency regulation, reactive power support and pumping unit impact compensation based on frequency and voltage deviations.

[0011] The gas turbine unit is connected to the 6KV bus in grid-connected operation mode with constant power setpoint.

[0012] The power demand of the oil well production load is divided into fast-changing power components and slow-changing power components through the energy management system. The fast-changing power components are allocated to the energy storage converter, and the slow-changing power components are allocated to the gas turbine unit.

[0013] When energy storage is unavailable, the gas turbine unit will be switched to an emergency grid source and load grading and derated supply will be implemented.

[0014] As a preferred embodiment, the primary frequency regulation power of the energy storage converter is determined by the 6KV bus frequency deviation, the energy storage SOC margin, the available power of the energy storage converter, and the predicted impact of oil well production load.

[0015] As a preferred embodiment, the constant power setpoint of the gas turbine unit is determined by the target range of energy storage SOC, the predicted slow-varying power component, the minimum stable output of the gas turbine unit, the maximum output of the gas turbine unit, and the gas turbine unit ramp rate constraint.

[0016] As a preferred embodiment, the rapidly changing power component includes power changes caused by the pumping unit start-up impact, the superposition of the pumping unit stroke cycle, the second-level abrupt change in photovoltaic power, and the recovery of pumping between oil wells.

[0017] As a preferred option, when the energy storage SOC is higher than the upper warning value, the photovoltaic power limiting, flexible load (wellhead heater, etc.) absorption and the reduction of the constant power setting value of the gas turbine unit are executed in sequence; when the energy storage SOC is lower than the lower warning value, the constant power setting value of the gas turbine unit is increased, non-critical load is reduced and the oil well recovery queue is delayed in sequence, so that the gas turbine unit can maintain the operation of the core load.

[0018] As a preferred option, the gas turbine unit does not use the 6KV bus frequency deviation as the rapid active power regulation input of the energy management system in the grid-connected working mode, but only responds to the constant power setpoint and safety protection commands issued by the energy management system.

[0019] As a preferred embodiment, the energy storage unavailability includes at least one of the following: energy storage converter failure, energy storage battery management system failure, energy storage circuit breaker disconnection, protection or maintenance lockout, invalid critical local measurements or hard contacts, and energy storage SOC reaching the hard exit condition for grid deployment.

[0020] This invention also provides a coordinated control system for the off-grid microgrid energy storage main network and the constant power supplementation of gas turbine units in oil fields, comprising:

[0021] The operation mode recognition module is used to receive switch position, energy storage converter status, energy storage battery status, energy storage SOC margin, gas turbine status, 6KV bus frequency and voltage, protection signals, hard contacts and energy management system plans, and output operation status code, network construction permission and protection lockout flag.

[0022] The energy storage grid control module is used to control the energy storage converter to establish and maintain the frequency and voltage of the 6KV bus as the main grid source under normal working mode. Based on the frequency deviation and voltage deviation, it generates active and reactive commands constrained by the energy storage SOC, battery management system and the P / Q feasible domain of the energy storage converter.

[0023] The power decomposition module is used to generate fast-changing power components and slow-changing power components based on the net load power, and to allocate the fast-changing power components to the energy storage branch, and to allocate the predicted slow-changing power components and the energy storage SOC recovery power demand to the gas turbine branch.

[0024] The constant power supplementation module for gas turbine units is used to generate the constant power setpoint and its dynamic feasible range of gas turbine units based on the predicted slow variable power component and the correction amount of the energy storage SOC target range.

[0025] The source-load coordinated protection module is used to coordinate with the gas turbine unit to make corresponding adjustments, flexible load absorption, photovoltaic power limiting control, non-critical load reduction and load graded recovery according to instantaneous surplus, continuous surplus, instantaneous deficit, continuous deficit and energy storage SOC boundary.

[0026] The emergency grid transfer module is used to read the aforementioned permission and lockout flags, distinguish between planned grid transfer, sudden grid failure, re-voltage establishment, safety isolation, and energy storage restoration synchronization, and execute controlled back-switch when conditions are met. If any step fails, it maintains the current safe grid source or enters safe isolation.

[0027] The beneficial effects of this invention are:

[0028] 1. Using energy storage as the sole effective grid reference and having the gas turbine unit operate at constant power in grid-following mode for slow energy replenishment (compared to the rapid response of energy storage) helps reduce grid reference competition and the pressure on the gas turbine unit to adjust quickly.

[0029] In existing technologies, most oilfield microgrids use gas turbine units as the main grid source. Theoretically, this scheme has the capability to support synchronous machine voltage sources. However, in production practice, oil well production loads are characterized by pumping unit periodic impacts, intermittent pumping recovery, photovoltaic fluctuations, and low inertia of small systems. Gas turbine unit grid construction is easily affected by mechanical speed regulation, excitation response, and low load operation constraints.

[0030] This solution prioritizes long-term grid connection for energy storage, with gas turbine units only providing emergency grid connection during energy storage maintenance or failures. By entrusting grid connection responsibilities to faster and more controllable power electronic energy storage, the frequency and voltage quality of the off-grid system are improved from the source, and the amplified impact of the gas turbine unit's mechanical speed regulation on the pumping unit is reduced. After long-term grid connection of energy storage, the stability of the 6kV bus can be maintained through virtual inertia, droop control, rapid reactive power support, and energy storage SOC boundary control; the gas turbine unit, operating in grid-connected mode, provides constant power supplementation, primarily undertaking the responsibilities of energy continuity and energy storage SOC recovery.

[0031] When energy storage is unavailable, the gas turbine unit can operate with the core load for a short period, but the system will simultaneously perform load grading, photovoltaic power limiting control, and recovery switching. This utilizes the stability of the energy storage network while preserving the reliability of the gas turbine unit as an emergency backup, achieving a balance between long-term stable operation and fault coverage.

[0032] 2. Effectively improves the stability of the oilfield microgrid power supply system.

[0033] Unlike off-grid solutions that only configure the main power supply for energy storage and the start-up and shutdown of the standby unit, in this solution, the energy storage converter in the energy storage unit performs primary frequency regulation, reactive power support, and pumping unit impact compensation based on frequency and voltage deviations; the gas turbine unit is connected to the 6KV bus in a grid-connected operating mode with constant power setpoints.

[0034] The technical effects of this distinction are mainly reflected in two aspects:

[0035] On the one hand, conventional solutions do not clearly define who will bear the impact of oilfield pumping unit shocks or who will provide rapid support for the 6KV bus frequency and voltage. This solution clearly defines that energy storage will be responsible for primary frequency regulation, reactive power support, and pumping unit shock compensation, which can directly suppress second-level frequency and voltage fluctuations.

[0036] On the other hand, the gas turbine unit operates stably at constant power, no longer frequently climbing uphill following the impact of the oil pumping unit, which can reduce the risks of governor oscillation, low-load instability, reverse power, and energy consumption deterioration.

[0037] 3. By using fast and slow power stratification, the risk of frequency drop, voltage sag and protection malfunction caused by the second-level impact of the oil pumping unit on the 6KV bus is reduced.

[0038] This invention employs fast and slow power decomposition control. Minute-level changes in oil well production load (slow power component) can be used by the energy management system for the gas turbine unit's PQ baseline value (constant power setpoint) and energy storage SOC plan. Second-level disturbances such as pumping unit upstroke, start-up impact, and intermittent pumping recovery (fast power component) are rapidly handled by the energy storage converter within the available boundary. The energy storage converter establishes the frequency and voltage of the 6KV bus in a grid-type operating mode. When short-term impacts cause a drop in the 6KV bus frequency and a voltage sag, the energy storage unit provides active and reactive power support at the millisecond level. The gas turbine unit only adjusts the constant power setpoint based on the predicted slow power component and the SOC target range correction. Through fast and slow power layered control, inefficient operation and oscillations of the gas turbine unit following rapid load impacts are avoided.

[0039] 4. In the control logic of this invention, different operating conditions are not simply merged into a fixed action. Instead, a unified state machine, a unified set of grid connection weighting criteria, and a unified set of power stratification principles are used to uniformly judge and execute operating conditions such as complete grid disconnection, energy storage maintenance, energy storage failure, emergency grid connection of gas turbine units, and recovery switching. In other words, a unified switching logic is used for each operating condition. The advantages are:

[0040] 1) Reduce control strategy fragmentation. Instead of writing independent control strategies for each operating condition, different branches are entered through the same state machine, reducing logical conflicts between the energy management system, edge controller, and protection interlocks.

[0041] 2) Avoid dual voltage source conflicts. Ensure that there is only one long-term grid reference at any given time to prevent the simultaneous hard paralleling of energy storage VF / VSG and gas turbine VF, which would cause competition for voltage phase angle, frequency reference, and reactive power distribution.

[0042] 3) Improve the predictability of the switching process. All switching is performed in the same sequence, which is easy for on-site operators to understand and also facilitates the unification of protection settings, switch operations and emergency plans.

[0043] 4) Improve the continuity of off-grid power supply. When the energy storage is normal, its rapid response capability is used to maintain frequency and voltage; when the energy storage grid is unavailable, the gas turbine unit only undertakes emergency power supply, and the core load will not lose power due to the chaos of the control mode.

[0044] 5) Reduce the mechanical speed regulation pressure of the gas turbine unit. Under normal off-grid conditions, the gas turbine unit does not follow the rapid oscillation of the pumping unit, which can reduce the efficiency loss caused by governor oscillation, low load instability and frequent uphill climbing. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the off-grid microgrid in an oil field.

[0046] Figure 2It is a flowchart of the coordination control and abnormal branch operation of the main energy storage network off-grid.

[0047] Figure 3 This is a schematic diagram of the net load fast and slow power decomposition and the coordinated control of energy storage and gas turbine units.

[0048] Figure 4 This is a flowchart of emergency grid construction and controlled switchback when the energy storage grid is unavailable.

[0049] Figure 1 In the middle, 100-off-grid microgrid for oil fields, 110-photovoltaic power generation unit, 120-energy storage unit, 130-gas turbine unit, 140-6 kV busbar and switch protection interface, 150-oil well production load, 160-energy management system, 170-local controller, 175-busbar measurement and data validity unit, 180-flexible load interface. Detailed Implementation

[0050] The following is in conjunction with the appendix Figure 1-4 The present invention will be described in further detail as follows:

[0051] This implementation method specifies:

[0052] Discharging energy from the energy storage to the 6kV bus is considered positive active power, while charging is negative active power. Providing positive reactive power support to the 6kV bus is considered positive reactive power. Bus frequency deviation only enters the active power Pf branch (active power-frequency control branch, existing technology), and bus voltage deviation only enters the reactive power QU branch (reactive power-voltage control branch, existing technology). Both generate separate requests, which are then arbitrated by the active / reactive power feasible domain of the energy storage converter.

[0053] like Figure 1 As shown, this embodiment describes a coordinated control method for the energy storage main grid and constant power supplementation of a gas turbine unit 130 in an off-grid microgrid 100 in an oilfield, applied to the off-grid microgrid 100 in an oilfield. The off-grid microgrid 100 in the oilfield includes a photovoltaic power generation unit 110, an energy storage unit 120, a gas turbine unit 130, and an oil well production load 150 connected to a 6KV bus, as well as an energy management system (EMS) 160, a local controller 170 (prior technology), protection equipment, and switching equipment. Among them, the energy storage unit 120 includes an energy storage battery, an energy storage converter (PCS), and an energy storage battery management system (BMS); the energy management system (EMS) 160 performs prediction of slow power components and calculation of the constant power setpoint of the gas turbine unit 130, and the local controller 170 performs power distribution and grid right interlocking at the station end.

[0054] In this embodiment, the coordinated control method includes the following specific control strategies:

[0055] First, when the energy storage grid connection capability is effective, the energy storage converter serves as the sole effective grid connection reference, establishing and maintaining the 6KV bus frequency and voltage in a grid-connected operating mode. The gas turbine unit 130, operating in a grid-connected mode (PQ mode), provides constant power supplementation, undertaking the responsibilities of energy continuity and energy storage SOC recovery.

[0056] Secondly, the energy storage converter (PCS) performs primary frequency regulation, reactive power support, and pumping unit impact compensation based on frequency and voltage deviations, which can directly suppress second-level frequency and voltage fluctuations.

[0057] Specifically, a primary frequency regulation feedback component is formed based on the frequency deviation, and a feedforward compensation component is formed based on the predicted impact power of the oil well production load of 150. These two components are combined to form the energy storage rapid active power regulation power. After combination, the power is limited according to the energy storage SOC (State of Charge) directional soft derating factor, the BMS allowable charging and discharging power, the PCS apparent power constraint, and the rate of change constraint. A reactive power support command is independently formed from the voltage deviation, and active and reactive power requests are projected onto the active / reactive power feasible domain, which is limited by the energy storage SOC, BMS, PCS apparent power, and protection. The frequency deviation forms a primary frequency regulation feedback through the Pf branch, and the voltage deviation forms a reactive power support through the QU branch. The two types of requests are calculated separately and then arbitrated by the active / reactive power feasible domain of the energy storage converter to avoid undefined superposition of voltage terms into the active power command.

[0058] Third, the gas turbine unit 130 does not participate in rapid grid-connected regulation. Instead, it operates as a current source or in grid-connected mode (PQ mode) with a constant power setting on the 6KV bus, providing slow energy replenishment. This eliminates the need for frequent ramp-up following the pumping unit's surges, reducing the risks of governor oscillation, low-load instability, reverse power, and energy consumption deterioration. The energy management system 160 does not use bus frequency deviation to generate rapid active power settings for the gas turbine unit 130; therefore, the equipment-level protection, speed regulation, and safety inner loop of the gas turbine unit 130 remain effective.

[0059] Fourth, the net load is measured to obtain the slow-changing power component via a low-pass filter, and the difference between the measured net load and the slow-changing power component is used to obtain the fast-changing power component. The fast-changing power component and frequency deviation are fed back into the energy storage branch, while the slow-changing power component and SOC target range correction are fed into the gas turbine unit's 130 branch. The actual instantaneous power of the grid-connected energy storage still varies with the bus power balance and local grid control, and is not forcibly tracked by the energy management system 160 point by point according to the planned value.

[0060] The energy management system (EMS) 160 decomposes fast and slow power, allocating the fast-changing power component to the power storage converter (PCS) and the slow-changing power component to the gas turbine unit 130. This invention employs fast and slow power decomposition control. Minute-level changes in the oil well production load 150 (slow-changing power component) can be used by the energy management system 160 for the gas turbine unit 130's PQ baseline (constant power setpoint) and energy storage SOC plan. Second-level disturbances such as pumping unit upstroke, start-up impact, and intermittent pumping recovery (fast-changing power component) are quickly handled by the energy storage converter within the available boundary. The energy storage converter establishes the frequency and voltage of the 6KV bus in a grid-type operating mode. When short-term impacts cause a drop in the 6KV bus frequency and a voltage dip, the energy storage unit 120 provides active and reactive power support at the millisecond level. The gas turbine unit 130 only adjusts the constant power setpoint based on the predicted slow-changing power component and the SOC target range correction.

[0061] Fifth, when energy storage is unavailable, the gas turbine unit 130 can operate with the core load for a short period of time, but the system will simultaneously implement load grading, photovoltaic power curtailment, and recovery switching. This utilizes the stability of the energy storage network while preserving the reliability of the gas turbine unit 130 as an emergency backup, forming a balance between long-term stable operation and fault coverage.

[0062] In this embodiment, the primary frequency regulation power of the energy storage converter (PCS) is determined by the 6KV bus frequency deviation, energy storage SOC margin, available power of the energy storage converter (energy storage PCS), and the predicted impact of the oil well production load of 150.

[0063] In this embodiment, the constant power setpoint of the gas turbine unit 130 is synthesized from the predicted slow-varying power component and the correction amount of the energy storage SOC target range, and a dynamic feasible range is formed based on the minimum stable output of the gas turbine unit 130, the maximum allowable output of the gas turbine unit 130, and the rate of increase / decrease in power (ramp rate) relative to the previously confirmed output. When the gas turbine unit 130 is in an online PQ permitted state and the dynamic feasible range is not empty, the synthesized result is restricted to the dynamic feasible range.

[0064] In this embodiment, the rapidly changing power components include the starting impact of each pumping unit in the pumping unit well group, the superposition of the stroke cycles of each pumping unit, the second-level sudden change of photovoltaic power (cloud shadow shading, etc.), and the power change caused by the recovery of pumping between oil wells.

[0065] In this embodiment, when the energy storage SOC is higher than the upper limit warning value, the photovoltaic power limiting, flexible load (wellhead heater, etc.) absorption and reduction of the constant power setting value of the gas turbine unit 130 are executed in sequence; when the energy storage SOC is lower than the lower limit warning value, the constant power setting value of the gas turbine unit 130 is increased, non-critical load is reduced and the oil well recovery queue is delayed in sequence, so that the gas turbine unit 130 can maintain the operation of the core load.

[0066] In this embodiment, the gas turbine unit 130 does not use the 6KV bus frequency deviation as the fast active power regulation input of the energy management system 160 under the grid-connected working mode (PQ mode), but only responds to the constant power setpoint and safety protection commands issued by the energy management system (EMS) 160.

[0067] In this embodiment, the unavailability of energy storage includes at least one of the following: energy storage converter failure, energy storage battery management system (BMS) failure, energy storage circuit breaker tripping, protection or maintenance lockout, invalid critical local measurements or hard contacts, and energy storage SOC reaching the hard exit condition for grid deployment. It should be noted that, if, after confirmation by composite criteria, the energy management system (EMS) 160 or upper-level communication fails while local critical measurements and equipment status remain valid, the energy storage converter (PCS) maintains its grid-connected operating mode and freezes or downgrades its execution of the upper-level plan, and is not treated as an unavailable state for energy storage grid deployment alone.

[0068] In this embodiment, a coordinated control system for an off-grid microgrid 100 in an oilfield and a gas turbine unit 130 for constant power supplementation includes:

[0069] The operation mode recognition module is used to receive switch position, energy storage converter status, energy storage battery status, energy storage SOC margin, gas turbine 130 status, 6KV bus frequency and voltage, protection signals, hard contacts and energy management system 160 plan, and output operation status code, network construction permission and protection lockout flag.

[0070] The energy storage grid control module is used to control the energy storage converter to establish and maintain the frequency and voltage of the 6 kV bus as the main grid source under normal working mode. Based on the frequency deviation and voltage deviation, it generates active and reactive commands constrained by the energy storage SOC, battery management system and the P / Q feasible domain of the energy storage converter.

[0071] The power decomposition module is used to form fast-changing power components and slow-changing power components based on the net load power, and to allocate the fast-changing power components to the energy storage branch, and to allocate the predicted slow-changing power components and the energy storage SOC recovery power demand to the gas turbine 130 branch.

[0072] The 130 constant power energy replenishment module for the gas turbine unit is used to generate the 130 constant power setpoint and its dynamic feasible range for the gas turbine unit based on the predicted slow variable power component and the correction amount of the energy storage SOC target range.

[0073] The source-load coordination protection module is used to coordinate with the gas turbine unit 130 to make corresponding adjustments, flexible load absorption, photovoltaic power limiting control, non-critical load reduction and load graded recovery according to instantaneous surplus, continuous surplus, instantaneous deficit, continuous deficit and energy storage SOC boundary.

[0074] The emergency grid transfer module is used to read the aforementioned permission and lockout flags, distinguish between planned grid transfer, sudden grid failure, re-voltage establishment, safety isolation, and energy storage restoration synchronization, and execute controlled back-switch when conditions are met. If any step fails, it maintains the current safe grid source or enters safe isolation.

[0075] like Figure 2 As shown, implementing the technical solution described in this embodiment includes the following steps:

[0076] S1 identifies the initialization / local security, normal energy storage main network, SOC-limited / pre-transfer, planned network transfer, sudden network failure, gas turbine 130 emergency network construction, restoration of synchronization / controlled back-cut and safety isolation / re-pressurization status.

[0077] S2, under normal energy storage main grid conditions, enables PCS to operate in grid-type working mode, generates primary frequency regulation feedback based on bus frequency deviation, generates reactive power support based on bus voltage deviation, and forms final commands within the feasible domains of SOC, BMS, and PCS P / Q.

[0078] S3 decomposes the oil well load and photovoltaic fluctuations into fast-changing power components and slow-changing energy components. The fast-changing component is absorbed by the energy storage, and the slow-changing constant power is supplemented by the gas turbine unit 130.

[0079] S4 generates the original constant power base value of gas turbine 130 based on the energy storage SOC target range, slow variable power component prediction, and gas turbine 130 ramping constraints. The final constant power setpoint of gas turbine 130 is then formed when the online PQ permit for gas turbine 130 is valid and the dynamic feasible range is not idle. Gas turbine 130 is connected to the grid in a grid-connected operating mode (PQ mode) and its direct rapid oscillation at the bus frequency is prohibited.

[0080] S5. When photovoltaic power generation suddenly increases, load suddenly decreases, or energy storage SOC approaches the upper limit, it shall be handled in the order of energy storage absorption, flexible load absorption, and photovoltaic power curtailment; when photovoltaic power generation suddenly decreases, load suddenly increases, or energy storage SOC approaches the lower limit, it shall be handled in the order of energy storage discharge, gas turbine slow-up at 130 rpm, and non-critical load reduction.

[0081] S6, when energy storage is unavailable, planned events are executed with controlled transfer according to ready, synchronizing, switching, protection, P / Q ramp and mutual exclusion permission; emergency events are taken over by gas turbine unit 130 only if a verified quick takeover permission is valid, otherwise they enter repressurization or safety isolation and are restored according to load level.

[0082] A few points to note:

[0083] First, after energy storage is restored, it will not directly switch to grid-connected power sources. The energy storage converter (PCS), battery management system (BMS), insulation, energy storage SOC, critical local measurements, and protection status will be verified first. Frequency, voltage, and phase angle synchronization will be completed during the grid connection of the gas turbine unit 130's maintenance bus. Once synchronization, switching, and protection permissions are continuously met, active and reactive power loads will be transferred according to a preset ramp. Energy storage grid connection permission will only be granted after the gas turbine unit 130's grid connection permission is released. If any condition fails, the switchback will stop and the current safe state will be maintained.

[0084] Second, the grid connection permits for energy storage and gas turbine units 130 are mutually exclusive, allowing both to be invalid during safe isolation, but not allowing both to be used simultaneously as valid grid connection references for 6 kV busbars.

[0085] Third, the planned transfer and sudden failure network are respectively set with trigger, permission, action, confirmation and failure rollback; the synchronization threshold, opening and closing interlock, P / Q ramp and gas turbine unit 130PQ to VF capability must be confirmed by equipment data, protection logic or field test.

[0086] During implementation, each control threshold should be stored as a configurable parameter in the EMS or station-side edge controller. Specific capacities, thresholds, and time windows can be adjusted based on the on-site equipment capacity, well production schedule, protection settings, and scheduling procedures.

[0087] Explanation of calculation relationships and variables:

[0088] The following calculation relationships are used to illustrate the executable processes of power decomposition, active and reactive power control of energy storage, 130 slow-cycle energy replenishment of gas turbine units, data validity, grid right interlocking, photovoltaic power limiting control, and controlled back-off in this embodiment. Each threshold, gain, cycle, and equipment boundary is a configurable parameter, and its specific values ​​are determined based on equipment data, protection settings, operating procedures, and field tests.

[0089] 1. Frequency difference, voltage difference, and net load

[0090]

[0091]

[0092]

[0093] In the formula:

[0094] Δf(k) is the power grid frequency deviation at time k, and fN is the rated power grid frequency (50 Hz in Chinese standard).

[0095] k is the discrete-time index (representing the kth sampling time); f(k) is the measured frequency at the grid connection point at time k; ΔU(k) ​​is the grid connection point voltage deviation at time k; UN is the grid connection point rated voltage; U(k) is the measured voltage at the grid connection point at time k; P(net)(k) is the net load power of the system at time k (i.e., the power that the grid actually needs to absorb or inject from the outside); PL(k) is the power consumed by the load at time k (electrical load); P(PV)(k) is the photovoltaic power generation power (new energy power generation) at time k; P(loss)(k) is the line loss power at time k.

[0096] Load consumption, photovoltaic power generation, and grid losses are calculated according to the symbols in the formula; energy storage discharges to the bus in the positive direction and charging in the negative direction.

[0097] 2. Decomposition of net load measurement speed

[0098]

[0099]

[0100]

[0101] In the formula:

[0102] αB is the smoothing coefficient; T_B is the local fast calculation period (sampling period); τB is the decomposition time constant; P(long)(k) is the slow power component at time k; P(long)(k−1) is the slow power component at time k−1 (previous time); P(net)(k) is the net load power at time k; P(short)(k) is the fast power component at time k (short-time component).

[0103] 3. Energy storage active power feedback and short-term disturbance feedforward

[0104]

[0105]

[0106]

[0107] In the formula:

[0108] Pf(k) is the active power feedback control quantity of energy storage; Kf is the active power-frequency droop coefficient (or feedback gain); D(Δf(k);Δfab) is a function based on the frequency deviation Δf(k) and the dead zone Δfab; P(ff)(k) is the active power feedforward control quantity of energy storage (for short-time disturbances); Ks is the short-time disturbance feedforward gain; P(short)(k) is the power of the short-time component of the net load at time k; ΔP(B,raw)(k) is the raw active power adjustment quantity output by energy storage unit 120 (before arbitration in the feasible region).

[0109] 4. Voltage deviation creates reactive power demand.

[0110]

[0111]

[0112] In the formula:

[0113] Q(B,raw)(k) is the raw reactive power demand of the energy storage output (before feasible domain arbitration); KU is the reactive power-voltage droop coefficient (or gain); D(ΔU(k);ΔUab) is a function based on voltage deviation ΔU(k) ​​and dead zone ΔUab; Sat() is the saturation limit function; Q(B,req)(k) is the final reactive power demand command of energy storage unit 120; QB∗(k−1) is the upper limit of reactive power command allowed by BMS or PCS at the previous time (k−1); R(Q,↑)TB is the command change due to reactive power rise rate limit; R(Q,↓)TB is the command change due to reactive power fall rate limit.

[0114] Voltage deviations only enter the QU branch; the final reactive upper and lower limits and apparent power constraints are determined by arbitration of the P / Q feasible domain.

[0115] 5. Predicted slow-variable power component of gas turbine unit 130

[0116]

[0117]

[0118]

[0119] In the formula:

[0120] P(net,pre)(k) is the net load slow-variable power component predicted at time k; P^L(k+HG) is the predicted load value after a time-domain step size of HG; P^(PV)(k+HG) is the predicted photovoltaic power generation value after a time-domain step size of HG; P^(loss)(k+HG) is the predicted grid loss value after a time-domain step size of HG; HG is the prediction step size (or dispatch cycle) of gas turbine unit 130; TG is the set update cycle (or ramp-up time constant) of gas turbine unit 130; τG is the time constant of slow-variable low-pass; αG is the forgetting factor calculated based on the time constants TG and τG (αG=exp(−TG / τG)). P(net,pre)(k) is the slow variable power component after low-pass filtering at the previous time (k−1); P(net,pre)(k) is the net load prediction slow variable power component at the current time (k).

[0121] 6. SOC target range correction

[0122]

[0123]

[0124]

[0125]

[0126] In the formula:

[0127] e(SOC)(k) is the SOC error correction amount at time k; SOCL∗ is the lower limit of the SOC target range set by the user or algorithm; SOCH∗ is the upper limit of the SOC target range set by the user or algorithm; SOC(k) is the actual battery state of charge at the current time (k); P(SOC)(k) is the final active power command (or correction amount) after SOC correction; Sat() is the saturation limit function; K(SOC)e(SOC)(k) is the correction gain (or proportional coefficient) based on the SOC error; PSOC,down,max is the maximum allowable downward adjustment power limit (to prevent over-discharge); PSOC,up,max is the maximum allowable upward adjustment power limit (to prevent overcharging).

[0128] Low SOC results in positive correction, increasing the slow compensation for gas turbine units by 130; high SOC results in negative correction. The target range should not be confused with soft derating or hard exit thresholds for grid construction.

Claims

1. A coordinated control method for the main energy storage grid and constant power supplementation of gas turbine units in an off-grid microgrid for oil fields, applied to an off-grid microgrid for oil fields, wherein the off-grid microgrid includes photovoltaic power generation units, energy storage units, gas turbine units and oil well production loads connected to a 6KV bus, as well as an energy management system, protection equipment and switching equipment, and the energy storage unit further includes energy storage batteries, energy storage converters and energy storage battery management systems, characterized in that... The specific control strategies include the following: When the energy storage grid construction capability is effective, the energy storage converter is used as the only effective grid construction reference to establish and maintain the 6KV bus frequency and voltage in the grid construction working mode. The energy storage converter in the energy storage unit provides power support for primary frequency regulation, reactive power support and pumping unit impact compensation based on frequency and voltage deviations. The gas turbine unit is connected to the 6KV bus in grid-connected operation mode with constant power setpoint. The power demand of the oil well production load is divided into fast-changing power components and slow-changing power components through the energy management system. The fast-changing power components are allocated to the energy storage converter, and the slow-changing power components are allocated to the gas turbine unit. When energy storage is unavailable, the gas turbine unit will be switched to an emergency grid source and load grading and de-rating will be implemented to ensure supply.

2. The coordinated control method for the off-grid microgrid energy storage main network and the constant power supplementation of the gas turbine unit in an oilfield, as described in claim 1, is characterized in that: The primary frequency regulation power of the energy storage converter is determined by the 6KV bus frequency deviation, the energy storage SOC margin, the available power of the energy storage converter, and the predicted impact of oil well production load.

3. The coordinated control method for the main energy storage network of an off-grid microgrid in an oilfield and the constant power supplementation of a gas turbine unit according to claim 1, characterized in that: The constant power setpoint of the gas turbine unit is determined by the target range of energy storage SOC, the predicted slow-varying power component, the minimum stable output of the gas turbine unit, the maximum output of the gas turbine unit, and the gas turbine unit ramp rate constraint.

4. The coordinated control method for the main energy storage network of an off-grid microgrid in an oilfield and the constant power supplementation of a gas turbine unit according to claim 1, characterized in that: The rapidly changing power components include power variations caused by the pumping unit startup impact, the superposition of pumping unit stroke cycles, the second-level abrupt changes in photovoltaic power, and the recovery of pumping between oil wells.

5. The coordinated control method for the main energy storage grid of an off-grid microgrid in an oilfield and the constant power supplementation of a gas turbine unit according to claim 1, characterized in that: When the energy storage SOC is higher than the upper limit warning value, the photovoltaic power limiting, flexible load (wellhead heater, etc.) absorption and the reduction of the constant power setting value of the gas turbine unit are executed in sequence. When the energy storage SOC is lower than the lower limit warning value, the constant power setting value of the gas turbine unit is increased, non-critical load is reduced and the oil well recovery queue is delayed in sequence, so that the gas turbine unit can maintain the operation of the core load.

6. The coordinated control method for the main energy storage network of an off-grid microgrid in an oilfield and the constant power supplementation of a gas turbine unit according to claim 1, characterized in that: In grid-connected operation mode, the gas turbine unit does not use the 6KV bus frequency deviation as the rapid active power regulation input of the energy management system, but only responds to the constant power setpoint and safety protection commands issued by the energy management system.

7. The coordinated control method for the main energy storage network of an off-grid microgrid in an oilfield and the constant power supplementation of a gas turbine unit according to claim 1, characterized in that: The energy storage unavailability includes at least one of the following: energy storage converter failure, energy storage battery management system failure, energy storage circuit breaker tripping, protection or maintenance lockout, invalid critical local measurements or hard contacts, and energy storage SOC reaching the hard exit condition for grid deployment.

8. A coordinated control system for an off-grid microgrid energy storage main network and a gas turbine constant power supplementation unit in an oilfield, used to execute the method according to any one of claims 1 to 7, characterized in that, include: The operation mode recognition module is used to receive switch position, energy storage converter status, energy storage battery status, energy storage SOC margin, gas turbine status, 6KV bus frequency and voltage, protection signals, hard contacts and energy management system plans, and output operation status code, network construction permission and protection lockout flag. The energy storage grid control module is used to control the energy storage converter to establish and maintain the frequency and voltage of the 6KV bus as the main grid source under normal working mode. Based on the frequency deviation and voltage deviation, it generates active and reactive commands constrained by the energy storage SOC, battery management system and the P / Q feasible domain of the energy storage converter. The power decomposition module is used to generate fast-changing power components and slow-changing power components based on the net load power, and to allocate the fast-changing power components to the energy storage branch, and to allocate the predicted slow-changing power components and the energy storage SOC recovery power demand to the gas turbine branch. The constant power supplementation module for gas turbine units is used to generate the constant power setpoint and its dynamic feasible range of gas turbine units based on the predicted slow variable power component and the correction amount of the energy storage SOC target range. The source-load coordinated protection module is used to coordinate with the gas turbine unit to make corresponding adjustments, flexible load absorption, photovoltaic power limiting control, non-critical load reduction and load graded recovery according to instantaneous surplus, continuous surplus, instantaneous deficit, continuous deficit and energy storage SOC boundary. The emergency grid transfer module is used to read the aforementioned permission and lockout flags, distinguish between planned grid transfer, sudden grid failure, re-voltage establishment, safety isolation, and energy storage restoration synchronization, and execute controlled back-switch when conditions are met. If any step fails, it maintains the current safe grid source or enters safe isolation.

Images