Diesel generator parallel operation sudden unloading load cooperative protection method and system based on energy storage PCS power buffering

Abstract

The invention relates to the technical field of diesel generator set control, discloses a diesel generator set parallel operation sudden load unloading cooperative protection method based on energy storage PCS power buffering, and provides a diesel generator set parallel operation sudden load unloading cooperative protection strategy based on energy storage PCS power buffering. The strategy aims at forming a multi-level and active defense system through instantaneous power absorption of an energy storage PCS, cooperative power reduction of a diesel generator speed regulator and shutdown of a part of diesel generators, and therefore zero-interruption power supply of key loads is achieved on the premise that the safety of power generation equipment is guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of diesel generator set control technology, specifically relating to a collaborative active protection strategy for sudden load unloading faults in a parallel operation system of diesel generator sets by utilizing the fast power response characteristics of a power conversion system (power conversion system). Background Technology

[0002] Parallel operation of diesel generator sets (hereinafter referred to as "diesel generators") is a key technology for ensuring power supply reliability in scenarios such as data centers, hospitals, and island microgrids. However, if a large-capacity load is suddenly unloaded during system operation (sudden load shedding), the prime mover (diesel engine) cannot keep up with the sudden change in electromagnetic power due to mechanical inertia. This results in a huge excess power being converted into the kinetic energy of the unit, causing a sharp increase in speed (i.e., "runaway"). If not effectively suppressed, this will trigger overspeed protection shutdown, and in severe cases, it can lead to mechanical damage to the engine.

[0003] Existing protection measures mainly rely on the protective devices of the diesel generator itself:

[0004] 1. Electronic overspeed protection: Upon detecting excessive speed, it will trip and stop the machine;

[0005] 2. Mechanical overspeed protection: This acts as the final mechanical barrier.

[0006] These traditional methods are essentially "passive protection after a fault," and their actions inevitably lead to power outages, failing to meet the stringent requirements of primary loads (such as servers and operating rooms) for power continuity.

[0007] Energy storage systems, especially their core component, the power conversion system (PCS), possess millisecond-level bidirectional power regulation capabilities. Currently, PCS in diesel generator systems are mostly used as backup power or for steady-state energy management, and their powerful transient power buffering capabilities are not fully utilized in short-term impact conditions such as sudden load shedding. Therefore, how to deeply coordinate the PCS, diesel generator speed control system, and tiered loads to construct a proactive and preventative protection strategy has become a pressing technical problem in this field. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a collaborative protection strategy for sudden load unloading during diesel-generator parallel operation based on power buffering of energy storage PCS. This strategy aims to form a multi-layered, proactive defense system through instantaneous power absorption by PCS, coordinated power reduction by diesel-generator speed governor, and partial shutdown of diesel generators, thereby achieving zero-interruption power supply to critical loads while ensuring the safety of power generation equipment.

[0009] To achieve the above objectives, the present invention adopts the following core technical solutions:

[0010] The diesel-generator parallel operation and sudden load unloading collaborative protection strategy based on power buffering of energy storage PCS is characterized by the following steps:

[0011] Step 1: Fault detection and power calculation.

[0012] Real-time monitoring of the frequency change rate (df / dt) of the common connection point of the system. When df / dt > the preset threshold K in the positive direction. df When a sudden load shedding fault is detected, the sudden load shedding power ΔP is calculated. load The expression is:

[0013] (1-1)

[0014] In the formula, ΔP load P represents the total power of the unloaded load (kW). gen_before P is the sum of the total power output (kW) of all parallel diesel generators at the instant before the sudden unloading. load1 The primary load power (kW) that still needs to be supplied after a sudden load shedding.

[0015] Step 2: PCS priority power buffer.

[0016] Within milliseconds after the fault is determined (e.g., t) delay (≤20ms), issue an instruction to the PCS to enable it to operate at maximum capacity P pcs_ch_max Charge the system to quickly absorb excess power. The power P that PCS needs to absorb is... pcs_ref Determined by the following formula:

[0017] (1-2)

[0018] This step aims to take advantage of the speed of PCS to suppress frequency increases in the first instance.

[0019] Step 3: Diesel and generator power coordinated adjustment.

[0020] After the energy storage converter PCS operates, the remaining power ΔP remaining The diesel-generator system will absorb this energy by slowing down (releasing kinetic energy), and will ultimately achieve balance through active power reduction. Calculate the remaining power ΔP. remaining The expression is:

[0021] ΔP remaining =ΔP load - P pcs_ref (1-3)

[0022] The power station management system (PMS) is based on the power absorbed by the PCS, P. pcs_ref and Level 1 load P load1 To meet the demand, calculate and issue a new target power command P. gen_ref The speed governors of each diesel generator are adjusted to ensure that the total output power decreases smoothly to P. gen_ref ,Right now

[0023] P gen_ref = P load1 +P pcs_ref - P loss (1-4)

[0024] Ultimately, the diesel generator system only guarantees normal power supply to the primary load, and its total output target power P gen_ref for

[0025] P gen_ref = P load1 + P loss ≈ P load 1 (1-5)

[0026] In the formula, P loss The system loss (kW) is usually negligible. The power distribution of each parallel diesel generator unit should follow the droop control principle to achieve automatic, stable, and proportional load distribution to the unit capacity.

[0027] Droop control simulates the natural frequency regulation characteristics of synchronous generators in a power grid: when the frequency decreases, the generator is required to increase power output; conversely, when the frequency increases, the generator is required to decrease power output. In parallel operation, by setting a frequency-power (fP) droop characteristic curve with an appropriate slope, the system can automatically achieve proportional load distribution. Its core formula is:

[0028] f - f0 = -K droop ×(P gen_i - P 0_i (1-6)

[0029] In the formula, f is the actual system frequency (Hz); f0 is the rated system frequency (50Hz or 60Hz); K droop The droop coefficient is usually expressed as a percentage, such as 5% droop; P gen_i P represents the actual output power (kW) of the i-th diesel generator. 0_i This is the reference power setpoint (kW) for the i-th diesel generator at its rated frequency. In this invention, this value is uniformly set by the PMS in the power reduction command.

[0030] Sag coefficient Kdroop This defines the relationship between the frequency variation of a generator and its output power variation. It is usually expressed as a percentage, and its physical meaning is: how much the system frequency needs to change in order to produce 100% of the rated power variation.

[0031] Sag coefficient K droop The calculation expression is:

[0032] K droop = (Δf / f rated ) × 100% / (ΔP / P rated (1-7)

[0033] In the formula, Δf is the frequency deviation (Hz); f rated The system's rated frequency (50 Hz or 60 Hz); ΔP is the power change (kW); P rated This refers to the generator's rated power (kW).

[0034] Step 4: System steady-state recovery.

[0035] After the coordinated adjustment in steps 2 and 3, the system frequency stabilized at the rated value, entering a new stable operating state. The total output of the diesel generator first decreased to P. load1 +P pcs_ref Level 1 load with P load1 The power is operating normally, and the PCS is at P pcs_ref The power of the charging process; the final total output of the diesel generator is approximately P. load1 (Supply only to Tier 1 load P) load1 At this point, the energy storage converter PCS stops charging and enters standby mode. The frequency returns to stability, and the power supply to the primary load is uninterrupted.

[0036] Step 5: Backup and protection.

[0037] If the energy storage converter PCS fails to fully engage or has insufficient power (i.e., the charging power is insufficient to consume excess system power), causing the system frequency f to continuously rise and exceed the first-level warning threshold f1 (e.g., 51.0Hz), the backup protection process is initiated: Diesel Generator 2 continuously reduces its power output until it shuts down, while Diesel Generator 1 reduces its output to supply only the core load, eventually restoring frequency stability. If the output power of Diesel Generator 1 is insufficient, it will proceed according to a preset priority (e.g., first the third-level load P). load3 The secondary load P load2 Non-critical loads are gradually cut off, and finally the diesel generator output is used to supply only the core loads.

[0038] Compared with the prior art, the present invention has the following significant advantages:

[0039] (1) Revolutionary improvement in power supply continuity.

[0040] By transforming passive shutdown into active power balancing, power outages caused by diesel generator protection are fundamentally avoided, achieving "zero-interruption" protection for critical loads.

[0041] (2) Resource synergy and efficiency maximization.

[0042] The application scenarios of the energy storage converter PCS have been creatively expanded from "backup power supply" to "transient power buffer", and it has been deeply integrated with the diesel generator speed control system to achieve efficient utilization of resources within the system.

[0043] (3) Construct a defense-in-depth system.

[0044] This forms a multi-layered, degradeable protection defense system consisting of "energy storage converter PCS instantaneous buffer (main) - diesel generator stable regulation (coordination) - diesel generator shutdown (backup)", which is extremely robust.

[0045] (4) Extend equipment life.

[0046] Smooth power regulation replaces drastic emergency shutdowns, reducing mechanical and electrical shocks to the diesel generator and helping to extend equipment lifespan. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of the system structure and information flow of the present invention.

[0049] Figure 2 This is the overall flowchart of the method of the present invention.

[0050] Figure 3 This is a schematic diagram comparing the system frequency response under traditional protection methods and the method of this invention. Detailed Implementation

[0051] The technical solution of the present invention will now be clearly and completely described with reference to specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0052] This invention focuses on "responding to sudden load shedding and ensuring system stability and critical power supply," presenting a systematic, collaborative, and proactive technical architecture that can be analyzed in depth from both system hierarchy and workflow perspectives.

[0053] (1) System hierarchical structure: four-layer division of labor to build a complete response system.

[0054] The architecture is clearly divided into four layers: perception, collaborative control, execution, and load balancing. Each layer has a clearly defined function and works closely together. The analysis is as follows:

[0055] ① Sensing Layer. Composed of frequency / power sensors, this layer serves as the "eyes" and "data entry point" of the entire protection strategy. It continuously collects key parameters of the system's real-time operation, such as system frequency, total power, and graded load power, providing accurate and real-time data support for subsequent collaborative control layer decisions. It is the fundamental data source for the entire process.

[0056] ② Collaborative Control Layer. Centered on the PMS / EMS (Power Plant / Energy Management System), this layer acts as the "brain" of the entire architecture. It incorporates three key logics: fault detection, power calculation, and collaborative control. It receives data from the perception layer, determines whether a system fault has occurred, calculates the sudden power unloading, and formulates subsequent control schemes accordingly, thus guiding the entire process of responding to sudden load unloading impacts.

[0057] ③ Execution Layer. This layer includes the energy storage PCS (energy storage converter), the diesel generator electronic speed governor (EGOV), and load switches, serving as the system's "hands and feet." It strictly executes the instructions issued by the collaborative control layer, translating the collaborative control layer's "decision" into "actual actions," directly impacting power regulation and load on / off management. It is a crucial link in the implementation of the solution.

[0058] ④ Load Layer. Loads are divided into Level 1, Level 2, and Level 3 loads according to their importance, following the principle of "prioritizing key loads and responding in stages". Level 1 loads are the most critical and their uninterrupted power supply is guaranteed first; Level 2 and Level 3 loads are considered "sacrificial items" and are used to assist in stabilizing the system when the main solution is insufficient.

[0059] (2) Work process: closed-loop control to achieve stability and power supply guarantee.

[0060] The system forms a closed-loop control process of "data acquisition - fault diagnosis and decision generation - command execution - power balancing and power supply assurance" through information flow and actions at each stage.

[0061] ① Data Acquisition, Fault Diagnosis, and Decision Generation. Sensors in the perception layer upload real-time data such as frequency and total power to the fault detection and power calculation logic in the collaborative control layer. This logic determines whether a system fault has occurred; if a fault occurs, it calculates the sudden power reduction (ΔP). load Then, the fault signal and sudden power unloading are transmitted to the collaborative control logic to initiate the formulation of the control scheme and complete the transformation from "data analysis" to "decision generation".

[0062] ② Issuance and execution of main control commands (main scheme). The collaborative control logic issues main control commands to the execution layer, mainly in two ways: one is to issue "charging commands (P)" to the energy storage PCS. pcs_ref The system allows the energy storage PCS to absorb power and assists the system in power regulation; on the other hand, it issues a "power reduction command (P)" to the diesel generator. gen_ref Adjusting the power output of the diesel generator to match the total output of the diesel generator with the load requirements, the system power is adjusted from two dimensions: "energy storage absorbing power" and "diesel generator reducing power output".

[0063] ③ Backup control commands (standby scheme) provide supplementary protection. If the main scheme is not effective enough in regulating system stability, the collaborative control logic will activate the standby scheme. The diesel generator 2 will continuously reduce its power output until it shuts down. If the remaining diesel generator power is insufficient, a "shutdown command" can be sent to the switches of secondary and tertiary loads to actively disconnect these secondary loads (reducing the total power demand of the system), further assisting the system in restoring stability. This reflects the design concept of "combining main and standby schemes to provide dual protection for system stability".

[0064] ④ Power Balancing and Power Supply Guarantee. The energy storage PCS absorbs power according to instructions, and the diesel generator adjusts its output accordingly. Together, they work at the point of common coupling (AC 400V) to achieve power balance at the point of common coupling, fundamentally ensuring the stability of the system's voltage and frequency. Once the system stabilizes, power will continue to be supplied to the primary loads, achieving the ultimate goal of "coping with sudden load shedding and ensuring uninterrupted power supply to core loads."

[0065] (3) Overall core value: three major advantages.

[0066] Figure 1 The architecture shown in the document accurately reflects the three core advantages of this technology strategy:

[0067] ① The system is systematic, with clear division of labor and close connection among the four levels, forming a complete system of "perception-decision-execution-service (ensuring power supply to the load)", without any functional gaps, ensuring the continuity of the response process.

[0068] ② Synergy: With PMS / EMS as the core, it coordinates the three types of execution units: energy storage PCS, diesel generator, and load, to achieve multi-device linkage rather than single-device operation, which greatly improves the efficiency of coping with sudden load unloading impact.

[0069] ③ Proactive: The system can not only passively detect faults, but also proactively calculate the sudden load shedding power and formulate main and backup control schemes, transforming "passive response to faults" into "proactive prevention and control of fault impacts", effectively and timely responding to the impact of sudden load shedding.

[0070] The overall process of the method of this invention can be divided into several steps: normal operation and monitoring, fault identification and main strategy startup, main strategy execution and system steady state, backup protection startup and degraded operation, namely...

[0071] Step 1: Normal operation and monitoring.

[0072] The system is operating normally, with the diesel generator in parallel operation and under load. Simultaneously, the system monitors the system frequency change rate (df / dt) in real time to determine if a sudden load shedding fault has occurred. When df / dt is less than a set threshold, it indicates stable system operation, and monitoring continues; when df / dt is greater than or equal to the threshold, the system enters the fault identification phase.

[0073] Step 2: Fault identification and main strategy startup.

[0074] If the detected df / dt is greater than the threshold, the system will perform fault identification, determine it as a sudden load shedding fault, and calculate the sudden load shedding power ΔP. load Subsequently, a collaborative protection strategy is activated, allowing the energy storage PCS to charge at maximum power, with the charging power command P... pcs_ref Take the sudden unloading power ΔP load and PCS maximum charging power P pcs_ch_max The smaller value in the range is used to absorb power through energy storage to help stabilize the system.

[0075] Step 3: Execution of the main strategy and steady state of the system.

[0076] While the PCS is charging at maximum power, the diesel generator speed controller will reduce its power accordingly. If the system frequency stabilizes, the system will enter a new steady state. At this point, the diesel generator drives a primary load, the PCS continues charging, the protection is successful, the power supply is not interrupted, and the process ends. After the new steady state, the charging power of the PCS gradually decreases, and the output power of the diesel generator decreases accordingly. Eventually, the diesel generator only drives a primary load, the PCS stops charging, and it enters a standby state.

[0077] Step 4: Backup protection and downgrade operation.

[0078] If the system frequency does not stabilize after the main strategy is executed, and the frequency exceeds the first-level warning threshold f1, then backup protection will be activated: Diesel generator 2 will continuously reduce its power output until it shuts down, and the power of diesel generator 1 will be adjusted to the first-level load power P. load1 +P pcs_ref At this time, the system is running under level one load, with PCS at P pcs_ref The power of the diesel generator is adjusted to the primary load power P. load1 The process ends with only a level 1 load (protection successful, but in a degraded operation state).

[0079] In traditional methods, after a fault occurs, the frequency spikes dramatically, exceeding the warning threshold and overspeed shutdown threshold consecutively within a very short time, reaching a maximum of approximately 65Hz. The generator set trips and shuts down due to protection device activation in about 1.0 second, causing the power supply system to collapse and all loads to lose power. In contrast, the method of this invention uses a PCS to absorb the impact power in milliseconds, limiting the frequency peak. The diesel generator speed control system then smoothly reduces the power, allowing the frequency to quickly return to and stabilize at the rated value, remaining within a safe range throughout the process without triggering a shutdown, ensuring zero interruption of power supply to critical loads. The core conclusion is that this invention, through active collaborative control, transforms the system frequency response from a "violent, uncontrolled disaster" to "tiny, controllable fluctuations," resolving the contradiction between "protecting equipment" and "ensuring power supply."

[0080] Example 1: Diesel generator parallel operation protection when PCS is normal

[0081] A data center microgrid system is configured with one 500kW diesel generator and another 300kW diesel generator operating in parallel, along with a 200kW / 200kWh energy storage system (PCS maximum charging power P). pcs_ch_max =200kW), the load is divided into first level 300kW, second level 200kW, and third level 100kW.

[0082] (1) Initial state description

[0083] Total load 600kW (sum of all loads), total output P of two diesel generators gen_before =600kW (less than the total output power of 800kW from 2 diesel generators).

[0084] (2) Explanation of the fault occurrence

[0085] The secondary and tertiary loads (total 300kW) are suddenly unloaded, i.e., ΔP load =600kW - 300kW = 300kW.

[0086] (3) Implementation process analysis

[0087] Step 1: The PMS (Power Plant Management System) detects that df / dt exceeds the limit and calculates ΔP.load =300kW.

[0088] Step 2: The PMS immediately instructs the PCS to charge at maximum power. pcs_ref = min(300kW, 200kW) = 200kW.

[0089] Step 3: Calculate the remaining power as: ΔPremaining = 300kW - 200kW = 100kW(s-1)

[0090] The PMS sends a power reduction command (i.e., 100kW) to the two diesel generators, causing their total output to smoothly decrease to P within a few seconds. gen_ref ≈ 300kW.

[0091] Next, we analyze the values ​​of the power reduction ΔP1 and ΔP2 for the two diesel generators. Common industry standard droop factors are 3%, 4%, or 5%. This invention patent chooses 5% as the benchmark for calculation. This value is a balance point: if the value is too small (e.g., 3%), the system adjustment is too sensitive and prone to oscillation; if the value is too large (e.g., 6%), the frequency deviation is large. 5% is a stable and widely used value. Assuming that the droop factors of the two diesel generators are equal and both are 5%, i.e., Kdroop1 = Kdroop2 = 5%, then the frequency variation range of both diesel generators is:

[0092] Δf1 =Δf2 =5% × 50 Hz = 2.5 Hz (S-2)

[0093] The power reduction ΔP1 of the diesel generator is:

[0094] ΔP1 = (P rated1 / (P rated1 + P rated2 )) × ΔP total = (500 / 800) ×100=62.5 kW(S-3)

[0095] The power reduction ΔP2 of the diesel generator 2 is:

[0096] ΔP2 = (P rated2 / (P rated1 + P rated2 )) × ΔP total = (300 / 800) ×100=37.5kW(S-4)

[0097] The frequency droop ratio fdroop1 of the diesel generator 1 is:

[0098] f droop1 =Δf1 / ΔP1 =2.5Hz / 62.5 kW≈0.04Hz / kW(S-5)

[0099] The frequency droop ratio fdroop2 of the diesel generator is:

[0100] f droop2 =Δf2 / ΔP2 =2.5Hz / 37.5 kW≈0.07Hz / kW(S-6)

[0101] Check the droop ratio of the two power units, i.e.

[0102] The power droop ratio of Diesel Engine 1 is:

[0103] ΔP1 / P rated1 =62.5 / 500 =0.125 (12.5%) (S-7)

[0104] The power droop ratio of the Diesel Engine 2 is:

[0105] ΔP2 / P rated2 = 37.5 / 300 =0.125 (12.5%) (S-8)

[0106] Comparative analysis of expressions (S-7) and (S-8) reveals that the power droop ratios are almost identical! Therefore, when the system frequency drops by the same value, the two units will naturally share the load change at a ratio of 12.5%, perfectly achieving capacity-based allocation.

[0107] Step 4: The total output of the diesel generator is first reduced to 500kW, of which 300kW is used to power the primary load and 200kW is absorbed by the PCS charging power; finally, the total output of the diesel generator is reduced to 300kW, which is only used to power the primary load. The PCS stops charging to ensure frequency stability, and the power supply to the primary load is not affected in any way.

[0108] Step 5: If a PCS fault is known in advance and only 100kW of charging power can be provided, during step 2, ΔP remaining = 200kW, the frequency rises relatively quickly. When f1 > 51.0Hz, step 6 is triggered.

[0109] Step 6: The PMS commands the diesel generator 2 to continuously reduce its power output until it stops, the diesel generator 1 reduces its power output, and the PCS charges to ensure power balance. That is, after the final stabilization, the total output of the diesel generator 1 is 300kW, which supplies 300kW of power to the primary load. The PCS stops charging and is in standby mode. The power supply to the primary load is never affected.

[0110] Example 2: System resilience protection under extreme PCS complete failure scenario

[0111] Same as Example 1 (configured with one 500kW diesel generator and another 300kW diesel generator running in parallel, and a 200kW / 200kWh energy storage system (PCS maximum charging power P)). pcs_ch_max =200kW), the load is divided into first level 300kW, second level 200kW, and third level 100kW).

[0112] (1) Initial state of the system

[0113] On the power generation side: one 500kW and one 300kW diesel generator operate in parallel, with a total output P gen_before = 600 kW.

[0114] Load side: Level 1 load 300 kW (must be guaranteed), Level 2 load 200 kW, Level 3 load 100 kW.

[0115] Energy storage system: PCS is in a fault state, maximum charging capacity P pcs_ch_max = 0 kW.

[0116] System status: Total load 600 kW, power generation and load power are balanced.

[0117] (2) Explanation of the fault occurrence

[0118] A sudden unloading of the secondary and tertiary loads (totaling 300kW) occurred. The initial total load was 300 + 200 + 100 = 600kW. After the unloading, the remaining load was 300kW (primary load) = 300kW. Unloading power:

[0119] ΔP load = P gen_before - P load_after = 600 kW - 300 kW = 300 kW

[0120] (3) Implementation process

[0121] Step 1: Fault Identification. The PMS detects that df / dt exceeds the limit, indicating a sudden load shedding fault. Calculate the sudden load shedding power:

[0122] ΔP load = 300 kW

[0123] Step 2: PCS power buffer (complete failure). The PMS sends a command to the PCS, but there is no response (power returned is 0). Remaining excess power:

[0124] ΔP remaining =ΔP load = 300 kW (all remaining)

[0125] Step 3: Backup protection becomes the primary focus. The frequency rises rapidly due to the excess power of 300kW.

[0126] Step 4: Backup Protection Action. When the frequency continues to rise sharply and approaches the first action threshold f1 (e.g., 51.0Hz), the PMS executes the ultimate backup measure, which instructs the smaller-capacity Diesel Generator 2 (300kW) to perform the shutdown procedure. After Diesel Generator 2 shuts down, the total power generation of the system is provided solely by Diesel Generator 1 (500kW).

[0127] Step 5: Diesel-generator power coordinated adjustment (final balance). During this process, the governor of Diesel Generator 1 also reduces its output in response to the rising frequency. The PMS sends an adjustment power command to Diesel Generator 1, requiring its output to decrease to match the first-level load. When the output of Diesel Generator 1 equals 300kW, the power generation and load power are balanced.

[0128] Step 6: New Steady State (Degraded Operation). The total output of the diesel generator is 300 kW (supplied solely by Diesel Generator 1), Diesel Generator 2 is shut down, PCS charging power is 0 kW (fault), the primary load (300 kW) is operating normally, the secondary and tertiary loads have been unloaded, and the power supply to the primary load is unaffected. The system achieves degraded steady state operation.

[0129] The system's resilience protection logic under extreme PCS failure scenarios: Starting with the most severe failure conditions, through the defense of "frequency triggering - shutdown to cure", it ultimately forms a new steady state of degraded operation with a single diesel generator carrying the core load, vividly illustrating the resilient nature of the system in ensuring core power supply by strategically sacrificing secondary functions.

[0130] This embodiment 2 introduces a shutdown mechanism as the final solution, constructing an extreme failure response strategy that conforms to the laws of physics, and achieving two innovations:

[0131] Innovation of Example 2: System resilience and degraded operation. This extremely verifies the multi-layered nature and ultra-high reliability of the protection strategy of this invention. Even if the core functional unit (PCS) completely fails, the system can still achieve the ultimate strategic goal of "ensuring power supply to the primary load" through degraded operation mode.

[0132] Innovation Point 2 of Example 2: Verification of a complete protection chain. The complete protection chain from "PCS buffer" to "diesel generator shutdown" is thoroughly implemented in this example, proving that the strategy has protective capabilities under any possible operating conditions, providing strong support for the patent.

[0133] The control method of this invention is automatic control through a controller. The control circuit of the controller can be implemented by programming by those skilled in the art. The power supply is also common knowledge in the art. Furthermore, this invention is mainly used to protect the method of dealing with sudden load shedding, so the control method and circuit connection will not be explained in detail.

[0134] This invention has been described through several embodiments. Those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of this invention, modifications can be made to these features and embodiments to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, this invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are protected by this invention.

Claims

1. A collaborative protection method for sudden load unloading during diesel-generator parallel operation based on power buffering of energy storage PCS, characterized in that: Sudden load shedding faults are determined by real-time monitoring of the frequency change rate df / dt at the microgrid's point of common coupling. When the df / dt value exceeds the preset threshold in the positive direction, a sudden load shedding fault is determined to have occurred, and the energy storage PCS is immediately triggered to enter the charging mode. The energy storage PCS performs power buffering, and then the power is reduced in coordination with the diesel generator droop control, and the system enters a new steady state.

2. The method for coordinated protection of sudden load unloading during diesel-generator parallel operation based on power buffering of energy storage PCS according to claim 1, characterized in that: When the energy storage PCS enters charging mode, the energy storage PCS uses P pcs_ref Charge at that power. P pcs_ref =min(ΔP load , P pcs_ch_max ); In the formula, ΔP load P is the total power of the load during sudden unloading. pcs_ch_max This represents the maximum charging power of the energy storage PCS.

3. The method for coordinated protection of diesel generator parallel operation and sudden load unloading based on power buffering of energy storage PCS according to claim 2, characterized in that: Even after the energy storage PCS absorbs power during charging, the system still has residual power ΔP. remaining The power plant management system (PMS) determines the primary load power P based on the aforementioned power level P. load1 and the final absorbed power P of the energy storage PCS pcs_ref Calculate the target power P that decreases in the diesel generator system. gen_ref According to the droop control principle, the target power P is... gen_ref The power is distributed to each diesel generator, enabling second-level power adjustment of the diesel generators and further balancing the system power.

4. The diesel-generator parallel operation sudden load unloading collaborative protection method based on energy storage PCS power buffer as described in claim 3, characterized in that: When P gen >P load1 +P pcs_ref At that time, the charging power of the energy storage PCS remains at P pcs_ref With the total power output of the diesel generator system remaining unchanged, the calculated target power P is reduced. gen_ref The power is distributed to each diesel generator according to the droop principle, when the total output power P of the diesel generator system... gen Decrease to P gen =P load1 +P pcs_ref At this time, the charging power of the energy storage PCS begins to decrease and gradually decreases to 0. Simultaneously, the corresponding output power of the diesel generator system decreases, ultimately causing P... gen =P load1 This ensures the normal power supply to the most critical loads, namely the primary loads. Where P loss For system losses, P load1 This is the power requirement for a primary load. 5.P gen It is the sum of the total power output (kW) of all parallel diesel generators.

6. The method for coordinated protection of sudden load unloading during diesel-generator parallel operation based on power buffering of energy storage PCS according to claim 4, characterized in that: The total load power ΔP of the sudden unloading load The calculation method is as follows: ΔP load = P gen_before - P load1 ; In the formula, P gen_before P is the sum of the total power output of all parallel diesel generators at the instant before the sudden unloading. load1 This refers to the primary load power that still needs to be supplied after a sudden power outage.

7. The method for coordinated protection of sudden load unloading during diesel-generator parallel operation based on power buffering of energy storage PCS according to claim 5, characterized in that: The system's remaining power deficit ΔP remaining The calculation formula is: ΔP remaining = ΔP load - P pcs_ref ; Where ΔP load Calculate the total unloading power for the system.

8. The method for coordinated protection of sudden load unloading during diesel-generator parallel operation based on power buffering of energy storage PCS according to claim 6, characterized in that: When the state of charge (SOC) of the energy storage PCS battery reaches a set value, the maximum allowable charging power of the energy storage PCS is limited to P. pcs_avail And P pcs_avail < P pcs_ch_max The energy storage PCS ultimately absorbs power P pcs_ref In the calculation formula, P is used pcs_avail Replace P pcs_ch_max Recalculate the final absorbed power of the energy storage PCS, and simultaneously adjust the total power P of the diesel generator system as it decreases. gen_ref The computational logic.

9. The method for coordinated protection of sudden load unloading during diesel-generator parallel operation based on power buffering of energy storage PCS according to claim 7, characterized in that: If the system frequency f continues to rise and exceeds the first-level warning threshold f1, backup protection is activated. When the diesel generator system contains multiple diesel generators, and only the output power of a portion of the diesel generators can supply the load power, a shutdown command is issued to the diesel generator with smaller power, prioritizing the disconnection of low-capacity diesel generators, and then reducing the output power of the diesel generators operating in grid connection. The system frequency returns to stability, while ensuring continuous power supply to the core load. When the output power of only a portion of the diesel generators is insufficient to supply the load power, non-critical loads (other loads except for the first-level loads) should be disconnected step by step from low to high according to the preset load priority, until the output power of the diesel generators operating in grid connection can supply the load power.

10. The method for coordinated protection of sudden load unloading during diesel-generator parallel operation based on power buffering of energy storage PCS according to claim 3, characterized in that: When the energy storage PCS malfunctions and is unable to absorb power for charging, the remaining power ΔP remaining Equal to unloading power ΔP load The power reduction ΔP required by the diesel generator system gen =ΔP load Ultimately, a new balance was achieved where the diesel generator set only supplies the primary load.

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