Portable mobile power generation grid-connected vehicle and uninterrupted power grid-connected transfer method

Abstract

The present application relates to the technical field of power emergency power supply, in particular to a portable mobile power generation grid-connected vehicle and a non-stop power grid-connected transfer method, comprising a mobile carrier and a fuel power generation unit, an energy storage unit, a power conversion unit, a medium voltage switch protection unit, a quick access unit and a coordination controller arranged thereon; low voltage alternating current output by the fuel power generation unit is connected to a direct current bus through a rectifier, the energy storage unit is connected to the same direct current bus through a bidirectional direct current conversion circuit, and an isolation voltage boost conversion circuit isolates and boosts the direct current bus power to medium voltage alternating current for grid connection; the transfer method realizes non-stop power supply of users in the whole maintenance process through pre-synchronization with live loop closing, gradual load transfer, split transfer to island, and reverse rotation after power restoration.

Description

Technical Field

[0001] This invention relates to the field of emergency power supply technology, specifically to a portable mobile power generation vehicle and an uninterrupted grid connection and transfer method. Background Technology

[0002] There are two types of emergency power supplies commonly used in power distribution network maintenance and power supply protection operations.

[0003] One type is the 10kV medium-voltage generator truck, whose diesel generator sets directly output 10kV voltage. Single-unit capacities range from 500kVA to 2000kVA. These large vehicles are heavy and long, requiring connection to the distribution network via fixed cable channels or pole-mounted bridging. Connection work necessitates a power outage, and the process from arrival to power restoration typically takes about 120 minutes. In mountainous distribution networks, narrow roads, steep slopes, and sharp bends often prevent these large generator trucks from reaching faulty or maintenance areas. Even if they can reach these areas, the direct-load operation of the unit results in significant voltage drops during sudden load changes—the voltage dip tolerance time for sensitive users such as data centers and medical equipment is often shorter than the recovery time of the unit's speed control system.

[0004] Another type is the 0.4kV low-voltage generator vehicle, which is small in size and highly mobile, but can only carry loads on the low-voltage side of the distribution area and does not have the ability to supply power to 10kV medium-voltage lines; it does not have its own relay protection configuration, cannot be directly connected to high-voltage lines, and cannot automatically disconnect in the event of a short circuit or grounding fault.

[0005] Due to these restrictions, power line maintenance in mountainous areas can only be carried out by shutting down the power first and then carrying out the work. The loss of the number of households caused by power outages during maintenance accounts for more than 60% of the total pressure on power supply targets in some mountainous areas. Power supply for major events requires the deployment of large generator trucks and the closure of roads dozens of hours in advance, which brings about traffic management conflicts. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a portable mobile power generation vehicle and an uninterrupted grid connection and transfer method, as well as an emergency power supply equipment capable of entering narrow mountain roads, quickly and safely connecting to medium-voltage lines, and ensuring uninterrupted power supply to users throughout the connection process.

[0007] This invention is achieved through the following technical solution:

[0008] A portable mobile power generation and grid connection vehicle includes a mobile carrier and a fuel-fired power generation unit mounted on the mobile carrier, and also includes an energy storage unit, a power conversion unit, a medium-voltage switch protection unit, a fast access unit, and a coordination controller; the power conversion unit includes a rectifier, a bidirectional DC-DC converter circuit, and an isolated boost converter circuit;

[0009] The low-voltage AC power output by the fuel-fired power generation unit is rectified by the rectifier and then connected to the DC bus. The energy storage unit is connected to the DC bus via the bidirectional DC-DC converter circuit. The isolation boost converter circuit isolates and boosts the power of the DC bus into medium-voltage AC power.

[0010] The medium-voltage switch protection unit is connected to the output side of the isolation boost converter circuit; the fast access unit is connected to the medium-voltage switch protection unit and is used for detachable connection with the medium-voltage line;

[0011] The coordination controller is used to allocate power commands and perform pre-synchronization grid connection control;

[0012] Specifically, the power allocation input is frequency decomposed according to the frequency division cutoff frequency, the low-frequency component of the power allocation input is used as the power command of the fuel-fired power generation unit, the high-frequency residual is used as the power command of the energy storage unit, and a feedforward compensation is superimposed on the power command of the energy storage unit.

[0013] Optionally, the carriage is divided into a front compartment, a middle compartment, and a rear compartment along the longitudinal direction. The fuel-powered generator unit is located in the front compartment, the energy storage unit and the power conversion unit are located in the middle compartment, and the medium-voltage switch protection unit and the quick access unit are located in the rear compartment.

[0014] The middle compartment is equipped with a series-reused air duct. The air inlet of the series-reused air duct is located on the side of the carriage. The cooling airflow flows through the air duct of the energy storage unit first, then through the radiator of the power conversion unit, and is then discharged from the carriage by the top-mounted fan, in the order of allowable temperature rise from low to high. The rear compartment adopts natural ventilation.

[0015] Optionally, the isolated boost converter circuit includes multiple intermediate frequency isolated DC-DC converter modules, with the input side of each intermediate frequency isolated DC-DC converter module connected in parallel to the DC bus; the output side of each intermediate frequency isolated DC-DC converter module is connected in series and synthesized into medium-voltage AC power by cascading H-bridge.

[0016] A method for uninterrupted grid connection and power transfer, employing the portable mobile power generation and grid connection vehicle described above, includes:

[0017] The portable mobile power generation and grid connection vehicle is connected to the medium-voltage line of the section to be inspected via the fast access unit.

[0018] The output voltage of the portable mobile power generation vehicle is pre-synchronized with the grid voltage, and the grid-connected switch is controlled to close after the closing criterion is met.

[0019] The load is gradually transferred from the grid side to the portable mobile power generation and grid connection vehicle according to the ramp-up command;

[0020] When the vehicle-to-grid switching power drops below a set threshold and the upstream switch of the section to be inspected is tripped, the undervoltage is detected and the output stage of the isolation boost converter circuit is switched from current source control to voltage source control, and it enters islanded operation to independently supply power to the load.

[0021] After the line is energized, reverse pre-synchronization is performed and the loop is closed again to return the load to the grid side, and the portable mobile power generation vehicle is disconnected and withdrawn.

[0022] Furthermore, it also includes a power allocation step: determining the power allocation input quantity, where the power allocation input quantity is taken as the measured load power during islanded operation, and the given value of the ramp command during the load transfer stage;

[0023] The power command of the fuel-fired power generation unit takes the low-frequency component of the power allocation input, and the power command of the energy storage unit takes the high-frequency residual and is superimposed with the feedforward compensation amount determined according to the rotational speed of the fuel-fired power generation unit.

[0024] Optionally, the power command of the fuel-fired power generation unit is: ;

[0025] The power command for the energy storage unit is: ,in, Assign input amount to the power. The frequency division time constant, This is the cutoff frequency for the frequency division. The measured rotational speed of the fuel-fired power generation unit is... For the rated speed, This is the speed deviation compensation coefficient. For virtual inertia coefficient, Used after low-pass filtering;

[0026] The frequency division cutoff frequency is adaptively adjusted according to the state of charge of the energy storage unit: ,in, The state of charge of the energy storage unit. This is a reference value for the state of charge. , These are the lower and upper limits of the frequency division cutoff frequency, respectively. The slope coefficient is used; a hysteresis dead zone is set for the charged state, and a rate of change limit is applied to the frequency division cutoff frequency.

[0027] Optionally, the closing criterion is based on the predicted phase difference, which is: ,in, The instantaneous phase difference between the two sides of the grid connection point. The frequency difference between the two sides of the grid connection point. The closing delay of the grid-connected switch;

[0028] When the voltage amplitude difference, frequency difference, and predicted phase difference on both sides of the grid connection point all meet the preset range and remain for a set duration, a closing command is issued.

[0029] Optionally, the closing delay is corrected according to the ambient temperature: ,in, Reference temperature The calibrated closing time is below. For ambient temperature, This is the temperature correction factor.

[0030] Furthermore, it also includes steps for handling unplanned pressure loss:

[0031] During grid-connected operation, when the positive sequence voltage at the grid connection point is lower than a set threshold and remains below it for a set time, a voltage failure is determined. The output stage of the isolation boost converter circuit is switched from current source control to voltage source control. During the switching period, the power deficit is made up by the energy storage unit through the DC bus, and the grid-connected switch is then tripped.

[0032] Optionally, when the load exceeds the capacity of a single vehicle, multiple portable mobile power generation and grid connection vehicles can be connected in parallel to provide power:

[0033] The first vehicle operates as the main source of voltage and frequency, and subsequent vehicles operate in controlled current source mode after pre-synchronization and paralleling.

[0034] The first vehicle broadcasts the total load and rated capacity of each vehicle, with each vehicle sharing the power proportionally according to its capacity: ,in, For the first The rated capacity of the trolley Total load;

[0035] When communication is interrupted, subsequent vehicles switch to frequency-power droop control: ,in, The power command value was retained before the communication interruption. This is the locally measured frequency. For the rated frequency, This is the droop coefficient.

[0036] This invention utilizes an integrated power generation and grid connection architecture combining low-voltage power generation, a dual-source architecture with a common DC bus, and isolated voltage boosting. Combined with a pre-synchronized live-loop transfer method, it achieves uninterrupted power transfer during maintenance and power supply protection scenarios in mountainous distribution networks. Compared with existing technologies, it offers the following advantages:

[0037] This invention replaces the direct generation of medium-voltage generator units with a low-voltage power generation plus vehicle-mounted isolation boost architecture, which reduces the weight and size of the vehicle and allows it to travel on narrow mountain roads and steep slopes, solving the problem of poor terrain adaptability of large medium-voltage generator vehicles; through the cooperation of the fast access unit and pre-synchronized live loop closing, the operation time from arrival to completion of load transfer is shortened, and the user is not interrupted during the transfer process, reducing the number of users lost during maintenance periods;

[0038] In this invention, the fuel-fired power generation unit and the energy storage unit share a DC bus. Power is distributed in segments according to frequency and superimposed with speed feedforward. The energy storage compensates for the initial impact of load step in real time, suppresses low-frequency coupling oscillations between DC bus voltage and unit speed, and reduces voltage dips experienced by sensitive users. At the same time, the frequency division cutoff frequency is adaptively adjusted according to the state of charge. The fuel-fired power generation unit operates in the high-efficiency load range for a long time, and can be shut down during light load periods and powered independently by the energy storage, reducing fuel consumption under low load conditions. Attached Figure Description

[0039] The accompanying drawings illustrate exemplary embodiments of the present invention and, together with the description thereof, serve to explain the principles of the invention. These drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, but do not constitute a limitation on the embodiments of the present invention.

[0040] Figure 1 This is an overall electrical architecture diagram of the portable mobile power generation and grid connection vehicle provided in an embodiment of the present invention;

[0041] Figure 2 This is a main circuit topology diagram of the power conversion unit provided in an embodiment of the present invention;

[0042] Figure 3 This is a block diagram of frequency band decoupling power allocation control provided in an embodiment of the present invention;

[0043] Figure 4 A flowchart illustrating the uninterrupted power grid connection and transfer method provided in an embodiment of the present invention;

[0044] Figure 5 This is a schematic diagram of the three-compartment layout and series reuse air duct provided in an embodiment of the present invention;

[0045] Figure 6 This is a schematic diagram comparing the DC bus voltage and unit speed response before and after frequency band decoupling. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0047] It should also be noted that, for ease of description, only the parts relevant to the present invention are shown in the accompanying drawings.

[0048] Where there is no conflict, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0049] Example 1

[0050] This embodiment provides an overall solution for a portable mobile power generation and grid connection vehicle. For example... Figure 1 As shown, the power generation vehicle includes a mobile carrier and fuel-fired power generation unit, energy storage unit, power conversion unit, medium-voltage switch protection unit, fast connection unit and coordination controller installed on the mobile carrier.

[0051] Medium voltage refers to the distribution voltage level of 6kV to 35kV, typically 10kV; low voltage refers to the voltage level below 1kV, typically 0.4kV.

[0052] Fuel-fired power generation units include, but are not limited to, diesel generator sets, gasoline generator sets, gas generator sets, and other generator sets that use internal combustion engines as prime movers.

[0053] The power conversion unit includes a rectifier, a bidirectional DC-DC converter circuit, and an isolated boost converter circuit.

[0054] The low-voltage AC power output from the fuel-fired power generation unit is rectified by a rectifier and then connected to the DC bus; the energy storage unit is connected to the DC bus via a bidirectional DC-DC converter circuit, sharing the same DC bus with the fuel-fired power generation unit, and can exchange power bidirectionally; the isolation boost converter circuit isolates and boosts the power from the DC bus to medium-voltage AC power.

[0055] By using a common DC bus architecture, the two power sources, power generation and energy storage, converge on the DC side, while the output side only needs one set of boost and switching equipment. The millisecond-level power response capability of energy storage can also directly contribute to the power balance on the output side.

[0056] In this embodiment, the rectifier is a three-phase AFE rectifier with a rated DC bus voltage of 750V (selectable within the range of 600V to 900V). The energy storage unit uses a lithium iron phosphate battery pack with a capacity of 200kWh (configurable within the range of 100kWh to 400kWh), a system voltage of approximately 650V, a continuous discharge rate of 1C, a short-time pulse discharge rate of 2C, and a charge rate of 0.5C.

[0057] The fuel-fired power generation unit uses a 400kW diesel generator set, outputting 0.4kV / 50Hz three-phase AC power. In other embodiments, the energy storage unit may also employ lithium titanate batteries or a hybrid energy storage form combining supercapacitors and lithium batteries.

[0058] The medium-voltage switch protection unit is connected to the output side of the isolation step-up converter circuit and includes a grid-connected switch and a protection device. The protection device can be a microprocessor-based protection device, configured with overcurrent, instantaneous overcurrent, and zero-sequence protection functions. The settings are adjusted according to the vehicle capacity and the parameters of the transformer substations it supports. In case of a fault, the grid-connected switch is tripped, achieving selective coordination with the existing protection of the distribution network.

[0059] The quick-connect unit connects to the medium-voltage switch protection unit and is designed for detachable connection to the medium-voltage line.

[0060] The coordination controller collects output power, DC bus voltage, unit speed, energy storage state of charge, and voltage phasors on both sides of the grid connection point. It distributes power commands between the fuel-fired power generation unit and the energy storage unit according to frequency segments and performs pre-synchronization grid connection control. The coordination controller can run on an onboard industrial computer, and the control cycle can be 0.5ms to 2ms.

[0061] The mobile carrier can be a complete vehicle chassis or a combination of a tractor and a trailer. In a specific example, the mobile carrier uses a 12t-class 4×4 off-road chassis, with a cargo box that is 4.6m long, 2.3m wide, and 2.6m high. It has a maximum gradeability of no less than 30%, a vehicle width of no more than 2.3m, and can pass through narrow alleys with a width of 4m.

[0062] The estimated weight of the entire vehicle is as follows: diesel generator set including daily fuel tank: approximately 3.0t; energy storage battery pack: approximately 1.8t; power conversion and medium-voltage switchgear: approximately 1.8t; vehicle body, cable reel and accessories: approximately 1.4t; chassis weight: approximately 4.0t; totaling approximately 12t.

[0063] In another embodiment, the power generation unit and the other units are placed separately in the tractor and the trailer body. The bottom of the trailer body is equipped with a transport skid to facilitate hoisting and transfer. This is suitable for scenarios where small-tonnage vehicles are used for segmented transfer on ultra-narrow roads, and the electrical architecture remains unchanged.

[0064] Example 2

[0065] This embodiment, based on Embodiment 1, describes the cabin layout and heat dissipation structure of the carriage.

[0066] like Figure 5 As shown, the carriage is divided longitudinally into a front compartment, a middle compartment, and a rear compartment. The fuel-fired power generation unit is located in the front compartment, adjacent to the driver's cab; the energy storage unit and power conversion unit are located in the middle compartment; and the medium-voltage switch protection unit and quick-connect unit are located in the rear compartment. The compartments are separated by partitions, which can be made of 2mm thick galvanized steel plates, with only cable penetration holes and fireproof seals.

[0067] The middle compartment is equipped with a series-reused air duct. Ambient air enters through the air intake louvers on the side of the compartment, first flowing through the air duct of the energy storage unit, then converging into the radiator air duct of the power conversion unit, and finally being discharged from the compartment by the top-mounted fan. The cooling airflow flows in order of increasing allowable temperature rise—the battery, with the lowest allowable temperature rise and the most stringent requirements for the intake air temperature, is upstream; the power module, with a larger temperature rise margin, is downstream. The same airflow is utilized twice in a tiered manner. Compared with the conventional practice of configuring independent fans and air ducts for each cabinet, the total power consumption of the fans and the number of openings in the compartment are reduced, and the compartment protection rating can be easily achieved at IP54.

[0068] The airflow is designed based on the total loss in the middle compartment. The total loss in the middle compartment is generally 4% to 6% of the rated power. Based on a temperature rise of 15K, the airflow can be selected within the range of 3500 m³ / h to 5500 m³ / h, with 4500 m³ / h being preferred. A centrifugal fan can be used for the top-mounted fan. The stern compartment does not have a forced air duct; it uses natural ventilation and is equipped with an anti-condensation heating belt.

[0069] In terms of vibration reduction, the fuel-fired power generation unit is installed on the underframe of the carriage via 4-point shear type rubber vibration isolators. The natural frequency of the vibration isolation system is designed to be 6Hz to 9Hz to avoid the first-order excitation frequency of the unit. The power conversion cabinet and energy storage rack are connected to the underframe of the carriage via steel wire rope vibration isolators with limiters to adapt to the impact conditions of mountain roads.

[0070] In addition, this embodiment also briefly describes the configuration of the fast access unit.

[0071] The quick access unit includes a vehicle-mounted cable reel, a detachable connector, and a three-position switch. The three-position switch has three positions: closed, isolated, and connected. The detachable connector can be an elbow connector, which can be plugged into and unplugged with the equipment bushing at the medium-voltage line access point to achieve a detachable connection.

[0072] To ensure the safety of the access operation, the fast access unit can be configured with conventional interlocking mechanisms:

[0073] The mechanical interlock prevents the three-position switch from rotating out of the contact position when the detachable connector is not properly inserted, and prevents the detachable connector from being pulled out when the three-position switch has not returned to the contact position.

[0074] The electrical interlock releases the closing circuit after the phase and phase sequence verification of the connected circuit passes; if the verification fails, the closing circuit is locked and an alarm is issued. All of the above interlocks can be implemented using existing interlocking mechanisms, which will not be elaborated upon here.

[0075] Example 3

[0076] This embodiment, based on Embodiment 1, illustrates the specific topology of the isolated boost converter circuit.

[0077] like Figure 2As shown, the isolated boost converter circuit includes multiple intermediate frequency isolated DC-DC converter modules. The input side of each intermediate frequency isolated DC-DC converter module is connected in parallel to the DC bus, and the output side is connected in series. The medium-voltage AC power is synthesized by cascaded H-bridges, forming a power electronic transformer architecture with parallel inputs and series outputs.

[0078] In a specific example, the intermediate frequency isolated DC-DC converter module adopts a dual active bridge topology with a switching frequency of 10kHz (selectable in the range of 5kHz to 20kHz), uses SiC devices, and has a single module capacity of 20kVA. A total of 24 modules are configured, with 8 modules connected in series on the output side. The DC voltage on the output side of each module is 1.2kV, and the voltage synthesis capability of each phase cascaded H-bridge is 9.6kV, covering the peak phase voltage of the 10.5kV system of 8.6kV with a modulation margin of about 10%.

[0079] In other embodiments, the isolation boost converter circuit can also be implemented in the form of a three-phase inverter with a frequency boost transformer: the DC bus outputs 0.4kV / 50Hz AC power through a three-phase PWM inverter, and then the voltage is boosted by a 0.4 / 10.5kV, Dyn11 connected, 400kVA boost transformer before being connected to a medium-voltage switch protection unit. The boost transformer can be oil-immersed or dry-type.

[0080] Example 4

[0081] This embodiment provides an uninterrupted grid connection and power transfer method based on the aforementioned portable mobile power generation and grid connection vehicle. For example... Figure 4 As shown, the overall process of this method is as follows:

[0082] After the vehicle arrives at the transformer substation where the section to be inspected is located, the operators release the cable and plug the detachable connector into the access point of the medium voltage line. After the interlocking verification is passed, the three-position switch is switched from the connected position to the closing preparation position to complete the connection.

[0083] The fuel-powered generator unit is started and a medium-voltage output is established. The controller is coordinated to pre-synchronize the vehicle output voltage with the grid voltage. After the closing criteria are met, the grid-connected switch is closed to achieve live loop closing.

[0084] After the loop is closed, the load is gradually transferred from the grid side to the vehicle according to the ramp-up command. The ramp-up rate can be 20kW / s to 100kW / s to avoid impacting the power flow of the line during the transfer process.

[0085] When the vehicle-to-grid switching power drops below a set threshold and the upstream switch of the section under maintenance trips, the vehicle detects a voltage loss. The coordinating controller switches the output stage of the isolation boost converter circuit from grid-connected current source control to V / f voltage source control, switching to islanded operation and independently supplying power to the load in the distribution area. The set threshold can be 3% to 10% of the vehicle's rated power.

[0086] During the maintenance work, the user is continuously powered by the vehicle. After the maintenance is completed and the line is re-energized, the coordination controller performs reverse pre-synchronization, closes the loop again, and returns the load to the grid side according to the ramp command. The vehicle is then disconnected and removed from the grid. Subsequently, the grid connection switch is opened, the three-position switch returns to the connected position, the detachable connector is disconnected, and the disengagement is completed. The user's power supply remains uninterrupted throughout the entire maintenance process.

[0087] Handling of boundary situations: If the pre-synchronization fails to meet the closing criteria within 60 seconds, an alarm will be issued and a manual inspection will be requested; when the load exceeds the vehicle's capacity during islanded operation, non-critical load branches will be cut off according to the preset priority.

[0088] During operation, the coordinating controller continuously performs power allocation: determining the power allocation input; when islanded, the power allocation input is taken from the actual load power measured on the vehicle output side; during the load transfer phase, it is taken from the ramp command setpoint; when switching from loop to island, it is seamlessly connected to the actual load value with the command value before the switch as the initial value; the power command of the fuel-fired power generation unit is taken from the low-frequency component of the power allocation input; the power command of the energy storage unit takes the high-frequency residual and is superimposed with the feedforward compensation amount determined according to the unit speed.

[0089] Example 5

[0090] This embodiment, based on embodiment four, explains the specific algorithm for frequency band decoupling power allocation.

[0091] After the fuel-fired power generation unit and the energy storage unit are coupled to the same DC bus, a new problem arises that does not exist in a separate power generation vehicle:

[0092] The power response of an energy storage converter is in the millisecond range, while the speed regulation of an internal combustion engine is in the second range, with a difference of about two orders of magnitude in their response time scales. If no coordination is provided during sudden load changes, the DC bus voltage fluctuation will be reflected by the rectifier as electromagnetic torque disturbance of the unit, forming a low-frequency coupled oscillation of 0.5Hz to 2Hz with the unit speed fluctuation, which manifests as alternating swings in the bus voltage and the unit speed. Figure 6 The comparison of the DC bus voltage and unit speed response before and after frequency band decoupling is shown.

[0093] like Figure 3 As shown, let For the power distribution input, the power command of the fuel-fired generator unit is taken from its low-frequency component: ,in, The frequency division time constant, This is the cutoff frequency for the frequency division.

[0094] The power command of the energy storage unit carries the high-frequency residual and is superimposed with the speed feedforward term: ,in, The measured speed (rad / s) of the diesel engine. Rated speed; This is the speed deviation compensation coefficient, with a value ranging from 5kW / (rad / s) to 20kW / (rad / s); This is the virtual inertia coefficient, with a value ranging from 2 kg·m² to 8 kg·m². It is used after first-order low-pass filtering, and the filtering time constant can be taken from 10ms to 30ms.

[0095] Compared to energy storage mitigation methods that rely on fixed ratios or simple filtering, this embodiment explicitly incorporates the physical quantity of diesel engine speed into the energy storage command: when the engine speed drops, energy storage is adjusted accordingly. Items instantly increase output, according to The simulated additional rotational inertia is equivalent to the unit bearing the initial impact of the load step, thus breaking the coupling loop of "bus voltage disturbance → torque disturbance → speed fluctuation → bus re-disturbance" from the mechanism.

[0096] Frequency division cutoff frequency There are potential failure scenarios when the energy storage is in a fixed state of charge (SOC). When the SOC is low, the diesel engine will still bear all the high-frequency power at a fixed frequency, which will accelerate the depletion of the energy storage. When the SOC is high, the diesel engine will still bear a lot of variable load, resulting in higher fuel consumption and mechanical wear.

[0097] to this end Adaptive adjustment based on state of charge: ,in, 0.05Hz is acceptable. 1Hz is acceptable. A slope coefficient of 0.5 can be used. The value range is from 8 to 15.

[0098] When the state of charge is higher than the reference value Automatic adjustment, the diesel engine only follows extremely low frequency trends, with more fluctuations handled by energy storage; when the state of charge is low The frequency band of the diesel engine is increased, allowing for recovery of energy storage.

[0099] Adaptive adjustment itself introduces new problems: when the state of charge fluctuates slightly around the reference value... Frequent changes cause power command jitter on both sides. The corresponding measure is to set a hysteresis dead zone for the state of charge, with a dead zone width of ±2% to ±5%; and to... Apply a rate of change limit, with the limit value ranging from 0.02 Hz / s to 0.1 Hz / s.

[0100] Example 6

[0101] This embodiment, based on Embodiment 4, explains the pre-synchronization closing criteria.

[0102] Live-loop closure requires that the amplitude, frequency, and phase of the vehicle's output voltage and the grid voltage be basically consistent at the moment of closure. Conventional synchronizing devices determine this based on the phase difference at the current moment, but there is an inherent mechanical delay of 30ms to 60ms between the issuance of the closing command and the actual closure of the circuit breaker contacts, during which the frequency difference between the two sides will continue to widen the phase difference.

[0103] In this embodiment, the predicted phase difference is used instead of the instantaneous phase difference as the criterion: ,in, The instantaneous phase difference between the two sides of the grid connection point. The frequency difference between the two sides of the grid connection point is given by both phase-locked loops, and the frequency difference is taken as the 100ms moving average. This refers to the closing delay of the grid-connected switch.

[0104] The closing criterion is: voltage amplitude difference. Frequency difference not exceeding 5% of rated voltage (3% to 10% is acceptable) Predicted phase difference not exceeding 0.2Hz (can be 0.1Hz to 0.5Hz). When the three conditions are met simultaneously and maintained for no less than 3° (1° to 5° is acceptable), and the closing command is issued, the closing command is issued.

[0105] Closing delay Preset according to the circuit breaker's factory settings, and correct for ambient temperature: ,in, Reference temperature The calibrated closing time is below. 20℃ is acceptable. For example, 45ms; This is a temperature correction factor, ranging from 0.2 ms / ℃ to 0.5 ms / ℃. At low temperatures, the viscosity of the lubricating grease in the operating mechanism increases, and the movement slows down. Without correction, this will cause an increase in the phase deviation during winter closing.

[0106] Example 7

[0107] This embodiment provides handling for two unconventional situations: unplanned pressure loss and multi-vehicle parallel expansion.

[0108] The islanding handover in Example 4 is a planned handover: the switching power is first reduced below a set threshold, and then the upstream switch is tripped, resulting in a seamless handover. Unplanned power outages (such as upstream line fault tripping) do not have this preparation process.

[0109] During grid-connected operation, the coordinating controller detects a voltage loss based on the following criteria: the positive sequence voltage at the grid connection point is lower than a set threshold for a set duration. The threshold can be 0.8 to 0.9 times the rated voltage, and the duration can be 5ms to 20ms. After detecting a voltage loss, the output stage of the isolation boost converter circuit is directly switched from current source control to voltage source control. This switch is a pure control mode switch, which does not rely on mechanical switch action and can be completed within 20ms. The power deficit during the switch is immediately compensated by the energy storage unit via the DC bus, and the vehicle-mounted grid-connected switch then trips, completing electrical isolation.

[0110] When the load exceeds the capacity of a single vehicle, two or more portable mobile generator vehicles are connected in parallel to supply power. The first vehicle operates according to the algorithm in Example 5 and serves as the main source of V / f voltage frequency in islanded mode; subsequent vehicles are connected to the islanded microgrid according to the pre-synchronization criterion in Example 6 and operate in controlled current source (PQ) mode—the inner current loop directly limits the output current, and the workshop circulating current is naturally suppressed.

[0111] The first vehicle broadcasts the total load via CAN bus or wireless channel. According to the rated capacity table for each vehicle, each vehicle shares power proportionally based on its capacity: ,in, For the first Rated capacity of the trolley.

[0112] In the event of a communication interruption, subsequent vehicles automatically switch to local frequency-power droop control as a fallback. ,in, The power command value was retained before the communication interruption. This is the locally measured frequency. Rated frequency 50Hz; droop factor The frequency difference should be set to 2% to 5% of the vehicle's rated power for every 0.1Hz frequency difference.

[0113] In a specific example, a single vehicle has a rated power of 400kW, which is supported by 2C pulse discharge for short-term output of 600kW. A single vehicle can achieve continuous stepless adjustment from 50kW to 400kW. Two 400kW vehicles can be connected in parallel according to their capacity ratio and can be expanded to 800kW.

[0114] Those skilled in the art should understand that the above embodiments are merely for illustrating the present invention and are not intended to limit the scope of the invention. Those skilled in the art can make other changes or modifications based on the above invention, and these changes or modifications still fall within the scope of the present invention.

Claims

1. A portable mobile power generation and grid connection vehicle, comprising a mobile carrier and a fuel-fired power generation unit mounted on the mobile carrier, characterized in that, It also includes an energy storage unit, a power conversion unit, a medium-voltage switch protection unit, a fast access unit, and a coordination controller; the power conversion unit includes a rectifier, a bidirectional DC-DC converter circuit, and an isolated boost converter circuit; The low-voltage AC power output by the fuel-fired power generation unit is rectified by the rectifier and then connected to the DC bus. The energy storage unit is connected to the DC bus via the bidirectional DC-DC converter circuit. The isolation boost converter circuit isolates and boosts the power of the DC bus into medium-voltage AC power. The medium-voltage switch protection unit is connected to the output side of the isolation boost converter circuit; the fast access unit is connected to the medium-voltage switch protection unit and is used for detachable connection with the medium-voltage line; The coordination controller is used to allocate power commands and perform pre-synchronization grid connection control; Specifically, the power allocation input is frequency decomposed according to the frequency division cutoff frequency, the low-frequency component of the power allocation input is used as the power command of the fuel-fired power generation unit, the high-frequency residual is used as the power command of the energy storage unit, and a feedforward compensation is superimposed on the power command of the energy storage unit.

2. The portable mobile power generation and grid connection vehicle according to claim 1, characterized in that, The carriage is divided into a front compartment, a middle compartment and a rear compartment along the longitudinal direction. The fuel power generation unit is located in the front compartment, the energy storage unit and the power conversion unit are located in the middle compartment, and the medium-voltage switch protection unit and the quick access unit are located in the rear compartment. The middle compartment is equipped with a series-reused air duct. The air inlet of the series-reused air duct is located on the side of the carriage. The cooling airflow flows through the air duct of the energy storage unit first, then through the radiator of the power conversion unit, and is then discharged from the carriage by the top-mounted fan, in the order of allowable temperature rise from low to high. The rear compartment adopts natural ventilation.

3. The portable mobile power generation and grid connection vehicle according to claim 1, characterized in that, The isolated boost converter circuit includes multiple intermediate frequency isolated DC-DC converter modules. The input side of each intermediate frequency isolated DC-DC converter module is connected in parallel to the DC bus. The output side of each intermediate frequency isolated DC-DC converter module is connected in series and synthesized into medium-voltage AC power by cascading H-bridge.

4. A method for uninterrupted grid connection and power transfer, characterized in that, The portable mobile power generation and grid connection vehicle according to any one of claims 1 to 3 includes: The portable mobile power generation and grid connection vehicle is connected to the medium-voltage line of the section to be inspected via the fast access unit. The output voltage of the portable mobile power generation vehicle is pre-synchronized with the grid voltage, and the grid-connected switch is controlled to close after the closing criterion is met. The load is gradually transferred from the grid side to the portable mobile power generation and grid connection vehicle according to the ramp-up command; When the vehicle-to-grid switching power drops below a set threshold and the upstream switch of the section to be inspected is tripped, the undervoltage is detected and the output stage of the isolation boost converter circuit is switched from current source control to voltage source control, and it enters islanded operation to independently supply power to the load. After the line is energized, reverse pre-synchronization is performed and the loop is closed again to return the load to the grid side, and the portable mobile power generation vehicle is disconnected and withdrawn.

5. The uninterrupted power grid connection and transfer method according to claim 4, characterized in that, It also includes a power allocation step: Determine the power allocation input. When operating in islanded mode, the power allocation input is taken from the measured load power. During the load transfer phase, the input is taken from the ramp command setpoint. The power command of the fuel-fired power generation unit takes the low-frequency component of the power allocation input, and the power command of the energy storage unit takes the high-frequency residual and is superimposed with the feedforward compensation amount determined according to the rotational speed of the fuel-fired power generation unit.

6. The uninterrupted power grid connection and transfer method according to claim 5, characterized in that, The power command for the fuel-fired power generation unit is: ; The power command for the energy storage unit is: ,in, For the Laplace operator, The power allocation input. The frequency division time constant, This is the cutoff frequency for the frequency division. The measured rotational speed of the fuel-fired power generation unit is... For the rated speed, This is the speed deviation compensation coefficient. For virtual inertia coefficient, Used after low-pass filtering; The frequency division cutoff frequency is adaptively adjusted according to the state of charge of the energy storage unit: ,in, The state of charge of the energy storage unit. This is a reference value for the state of charge. , These are the lower and upper limits of the frequency division cutoff frequency, respectively. The slope coefficient is used; a hysteresis dead zone is set for the charged state, and a rate of change limit is applied to the frequency division cutoff frequency.

7. The uninterrupted power grid connection and transfer method according to claim 4, characterized in that, The closing criterion is based on the predicted phase difference, which is: ,in, The instantaneous phase difference between the two sides of the grid connection point. The frequency difference between the two sides of the grid connection point. The closing delay of the grid-connected switch; When the voltage amplitude difference, frequency difference, and predicted phase difference on both sides of the grid connection point all meet the preset range and remain for a set duration, a closing command is issued.

8. The uninterrupted grid connection and power transfer method according to claim 7, characterized in that, The closing delay is corrected according to the ambient temperature: ,in, Reference temperature The calibrated closing time is below. For ambient temperature, This is the temperature correction factor.

9. The uninterrupted grid connection and power transfer method according to claim 4, characterized in that, It also includes unplanned pressure loss handling procedures: During grid-connected operation, when the positive sequence voltage at the grid connection point is lower than a set threshold and remains below it for a set time, a voltage failure is determined. The output stage of the isolation boost converter circuit is switched from current source control to voltage source control. During the switching period, the power deficit is made up by the energy storage unit through the DC bus, and the grid-connected switch is then tripped.

10. The uninterrupted grid connection and power transfer method according to claim 4, characterized in that, When the load exceeds the capacity of a single vehicle, multiple portable mobile power generation and grid connection vehicles are connected in parallel to provide power: The first vehicle operates as the main source of voltage and frequency, and subsequent vehicles operate in controlled current source mode after pre-synchronization and paralleling. The first vehicle broadcasts the total load and rated capacity of each vehicle, with each vehicle sharing the power proportionally according to its capacity: ,in, For the first The rated capacity of the trolley Total load; When communication is interrupted, subsequent vehicles switch to frequency-power droop control: ,in, The power command value was retained before the communication interruption. This is the locally measured frequency. For the rated frequency, This is the droop coefficient.

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