A diesel generator parallel management system and power switching control method

Abstract

This invention discloses a diesel generator parallel operation management system and power switching control method, belonging to the field of power system automation technology. It collects voltage, current, phase difference, and active and reactive power data from the power grid, diesel generator, and parallel operation system; it also collects test load temperature, personnel intrusion data from the work area, and power grid reactive power demand data. An improved FFT spectrum analysis algorithm is used to process the voltage and current signals to calculate the total harmonic distortion (THD). An improved coordinate partitioning method is used to obtain the phase sequence components, and the three-phase imbalance value is calculated based on these components. This invention combines diesel generator parallel operation power switching with test load air intake control and personnel safety monitoring, achieving automatic opening and closing of the air intake damper and graded alarm linkage for personnel intrusion. This reduces manual intervention and lowers operational safety hazards. Simultaneously, a closed-loop correction mechanism dynamically adjusts compensation parameters and switching timing to ensure the stability of power output during power switching.

Description

Technical Field

[0001] This invention relates to the field of power system automation technology, and in particular to a diesel generator parallel management system and a power switching control method. Background Technology

[0002] In power distribution systems, diesel generator parallel operation systems are crucial for ensuring continuous power supply to loads during grid failures. Traditionally, the control systems and sub-control cabinets for diesel generator parallel operation sections are often provided by different manufacturers, resulting in inconsistencies in equipment interfaces and communication protocols. This necessitates extensive hardwiring for signal transmission, increasing construction costs and manpower requirements for on-site commissioning and maintenance. Furthermore, traditional systems suffer from low fault location efficiency and cumbersome troubleshooting processes, leading to long system construction cycles and slow deployment.

[0003] In terms of power quality management, traditional power compensation methods employ fixed capacitor banks with tiered switching, which is a passive compensation mode that follows voltage fluctuations. It only provides single reactive power compensation near the rated voltage and cannot achieve coordinated control of harmonic mitigation and three-phase imbalance correction. Furthermore, traditional FFT spectrum analysis algorithms are prone to spectral leakage when calculating total harmonic distortion (THD), and the calculation of three-phase imbalance relies on phase angle calculations, making it difficult to meet the real-time requirements of diesel-generator parallel switching in terms of response speed and calculation accuracy.

[0004] In the test load management phase, the air intake dampers of existing test loads require manual opening and closing. During the operation, dedicated personnel must be assigned to the site to keep irrelevant personnel away, which not only increases labor costs but also leads to lagging safety monitoring and poses a safety hazard of personnel accidentally entering the work area. At the same time, the traditional diesel generator parallel power switching, power quality management, and safety monitoring are independent of each other, lacking a coordinated control mechanism. This results in large fluctuations in power quality during the switching process, and insufficient reliability and safety of the system operation. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a diesel generator parallel operation management system and a power switching control method. The technical solution adopted is as follows: A method for switching power supplies between diesel generators and parallel generators includes the following steps: Step 1: Build a dual-ring redundant communication network, preset power switching, power compensation and safety monitoring thresholds, and complete the redundant configuration of the controller and communication link; Step 2: Collect voltage, current, phase difference, and active and reactive power data of the power grid, diesel generator, and parallel system; collect test load temperature, personnel intrusion data of the work area, and reactive power demand data of the power grid; use an improved FFT spectrum analysis algorithm to process the voltage and current signals and calculate the total harmonic distortion (THD) value; use an improved coordinate partitioning method to obtain the phase sequence components, and combine the phase sequence components to calculate the three-phase unbalance value. Step 3: Compare the total harmonic distortion (THD) value and three-phase imbalance value obtained in Step 2 with the preset power compensation threshold. Based on the comparison results, construct a three-phase imbalance compensation mathematical model, solve it through an intelligent optimization algorithm to obtain the optimal power compensation strategy, and generate a harmonic mitigation strategy at the same time. Step 4: Compare the collected grid electrical parameters with the preset power switching threshold to generate diesel generator parallel start-up and power switching commands; generate air intake damper control commands based on test load temperature data; and generate safety alarm commands based on personnel intrusion data in the work area. Step 5: Each instruction is transmitted to the execution module. Zero-crossing switching technology is used to achieve inrush-free switching between the diesel generator and the power grid. Based on the optimal power compensation strategy and harmonic mitigation strategy, the power devices and filter network are controlled to complete power quality management. The actuator is driven to open and close the air intake damper.

[0006] Optionally, the operating status of the diesel generator parallel operation and the power output quality are monitored in real time. The actual power output parameters are compared with the analysis results of step 2 and the preset thresholds, and the power compensation parameters and power switching sequence are dynamically corrected. If a communication or controller failure is detected, the system automatically switches to the redundant link or redundant controller. If intrusion is detected and a security alarm is triggered, the power switching operation of non-critical loads will be suspended and an audible and visual alarm will be activated. After the test is completed, the air intake damper will be closed, and the power quality data, switching timing data, and compensation strategy data of this operation will be archived.

[0007] Optionally, the specific process of calculating the total harmonic distortion (THD) value using the improved FFT spectrum analysis algorithm in step 2 is as follows: A BN cross-convolution window function is constructed and an improved FFT correction formula for three spectral lines is derived. The acquired three-phase voltage and current signals are windowed, and FFT transformation is performed on the windowed signals. The spectral leakage problem is eliminated by interpolation correction. The amplitudes of the fundamental wave and each harmonic are extracted. The total harmonic distortion (THD) value is calculated based on the THD calculation criteria and the amplitudes of the fundamental wave and harmonics.

[0008] Optionally, the three-spectral-line improved FFT correction formula is as follows: ; ; ; Where A is the corrected fundamental or harmonic amplitude. Let the amplitude of the spectral line preceding the frequency point to be determined be . Let be the amplitude of the spectral line corresponding to the frequency point to be determined. Let be the amplitude of the spectral line following the frequency point to be determined.

[0009] Optionally, the specific process of obtaining the phase sequence components and calculating the three-phase unbalance value by improving the coordinate partitioning method in step 2 is as follows: the phasor coordinates of the three-phase voltage and current are divided into six sector partitions. The amplitude and phase relationship of the phase sequence components are directly determined by the partition matching method. The positive sequence, negative sequence and zero sequence components can be extracted without calculating the phase angle. Based on the amplitude ratio of the negative sequence component and the positive sequence component, the three-phase unbalance value is obtained in combination with the three-phase unbalance calculation specification.

[0010] Optionally, the specific process of generating a harmonic mitigation strategy based on the THD total harmonic distortion value in step 3 is as follows: when the THD total harmonic distortion value exceeds the preset power compensation threshold, the operating frequency of the multi-stage LC filter network is determined according to the harmonic frequency distribution corresponding to the THD total harmonic distortion value, and the filtering parameters of the filter network are set for the 3rd, 5th, and 7th major harmonics to form a harmonic mitigation strategy adapted to the harmonic frequency.

[0011] Optionally, the specific process of constructing the three-phase imbalance compensation mathematical model in step 3 is as follows: the system side is equivalent to the Thevenin model, the system admittance characteristics are considered, the negative sequence current component is allocated to the three-phase positive sequence circuit through negative sequence weighting, the operating characteristics and compensation capacity limits of the power compensation device are incorporated, and a dual-objective mathematical model including the three-phase current imbalance degree and the number of times the compensation device operates is established.

[0012] Optionally, the specific process of solving the optimal power compensation strategy through intelligent optimization algorithm in step 3 is as follows: initialize the particle parameters and iteration parameters of the particle swarm algorithm, use the output result of the three-phase unbalance compensation mathematical model as the calculation basis of the particle fitness function, select the Pareto optimal solution set through non-dominated sorting, and select the optimal power compensation strategy that meets the power compensation threshold from the optimal solution set using the hierarchical sequence method. The optimization objective of finding the optimal power compensation strategy is to make the corrected three-phase imbalance value less than or equal to 1%, while reducing the number of operation times of the power compensation device by more than 30% compared with the traditional compensation strategy, and matching the reactive power compensation amount of the system with the reactive power demand of the power grid during the correction process.

[0013] A diesel generator parallel operation management system is provided to implement a diesel generator parallel operation power switching control method. The system includes a multi-source data acquisition module, a redundant communication module, an intelligent decision-making module, an execution control module, a safety monitoring module, and a closed-loop correction module. The multi-source data acquisition module is used to collect electrical parameters, environmental parameters, and safety monitoring data; The redundant communication module uses a dual-ring network redundancy architecture built with network cables or optical fibers and integrates a GOOSE communication unit. The intelligent decision-making module receives data collected by the multi-source data acquisition module and performs improved FFT spectrum analysis, three-phase imbalance calculation and optimal compensation strategy solution. The execution control module communicates with the intelligent decision-making module to perform power switching, power quality management, and air intake control operations.

[0014] Optionally, the decision module has a built-in power quality analysis unit and a compensation strategy solution unit. The power quality analysis unit is equipped with an embedded program of an improved FFT spectrum analysis algorithm and a calculation program of an improved coordinate partitioning method, which outputs the total harmonic distortion (THD) value and the three-phase imbalance value. The compensation strategy solution unit has a built-in particle swarm optimization algorithm calculation program and a three-phase imbalance compensation mathematical model, which outputs the optimal power compensation strategy based on the power quality analysis results.

[0015] In summary, the present invention has at least one of the following beneficial technical effects: This invention provides a diesel generator parallel operation management system and a power switching control method. It adopts an improved FFT spectrum analysis algorithm and an improved coordinate partitioning method to achieve high-precision and fast-response calculation of total harmonic distortion (THD) and three-phase imbalance, respectively. It eliminates the spectrum leakage problem of the traditional FFT algorithm, simplifies the extraction process of phase sequence components, and provides accurate data support for power quality management.

[0016] By constructing a three-phase imbalance compensation mathematical model and combining it with an intelligent optimization algorithm to solve the optimal power compensation strategy, the coordinated control of reactive power compensation, harmonic control and three-phase balance correction was achieved. The corrected three-phase imbalance can be controlled within 1%, and the number of operation times of the power compensation device is reduced by more than 30% compared with the traditional strategy, thus improving the efficiency and economy of power quality management.

[0017] By combining the power switching of the diesel generator parallel unit with the air intake control of the test load and personnel safety monitoring, the automatic opening and closing of the air intake damper and the hierarchical alarm linkage for personnel intrusion are realized, reducing manual intervention and lowering operational safety hazards. At the same time, the closed-loop correction mechanism dynamically adjusts the compensation parameters and switching sequence to ensure the stability of power output during power switching. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating a diesel generator parallel power supply switching control method according to the present invention; Figure 2 This is a schematic diagram of the architecture of a diesel generator parallel management system according to the present invention. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to the accompanying drawings.

[0020] This invention discloses a diesel generator parallel management system and a power switching control method.

[0021] Reference Figure 1 and Figure 2 Example 1: A method for switching power supplies between diesel generators and parallel generators, comprising the following steps: Step 1: Build a dual-ring redundant communication network, preset power switching, power compensation and safety monitoring thresholds, and complete the redundant configuration of the controller and communication link; Step 2: Collect voltage, current, phase difference, and active and reactive power data of the power grid, diesel generator, and parallel system; collect test load temperature, personnel intrusion data of the work area, and reactive power demand data of the power grid; use an improved FFT spectrum analysis algorithm to process the voltage and current signals and calculate the total harmonic distortion (THD) value; use an improved coordinate partitioning method to obtain the phase sequence components, and combine the phase sequence components to calculate the three-phase unbalance value. Step 3: Compare the total harmonic distortion (THD) value and three-phase imbalance value obtained in Step 2 with the preset power compensation threshold. Based on the comparison results, construct a three-phase imbalance compensation mathematical model, solve it through an intelligent optimization algorithm to obtain the optimal power compensation strategy, and generate a harmonic mitigation strategy at the same time. Step 4: Compare the collected grid electrical parameters with the preset power switching threshold to generate diesel generator parallel start-up and power switching commands; generate air intake damper control commands based on test load temperature data; and generate safety alarm commands based on personnel intrusion data in the work area. Step 5: Each instruction is transmitted to the execution module. Zero-crossing switching technology is used to achieve inrush-free switching between the diesel generator and the power grid. Based on the optimal power compensation strategy and harmonic mitigation strategy, the power devices and filter network are controlled to complete power quality management. The actuator is driven to open and close the air intake damper.

[0022] Example 2: Real-time monitoring of the diesel generator parallel operation status and power output quality; comparison of actual power output parameters with the analysis results of step 2 and preset thresholds; dynamic correction of power compensation parameters and power switching sequence; if a communication or controller failure is detected, automatic switching to redundant link or redundant controller. If intrusion is detected and a security alarm is triggered, the power switching operation of non-critical loads will be suspended and an audible and visual alarm will be activated. After the test is completed, the air intake damper will be closed, and the power quality data, switching timing data, and compensation strategy data of this operation will be archived.

[0023] By adopting the above technical solution, a dual-ring redundant communication network is built and redundant controllers and communication links are configured. The high-speed transmission characteristics of GOOSE communication technology unify device interfaces and protocols, replacing the traditional hard-wiring method. When the main communication link or controller fails, the system automatically switches to the redundant link or controller. Relying on the fault tolerance of the redundant architecture, the continuity of command transmission and system control is ensured, avoiding control interruptions caused by single-point failures.

[0024] The system synchronously collects electrical parameters from the power grid, diesel generator, and parallel generator systems, as well as environmental and safety monitoring data from the test load using multi-source sensors. For THD (Total Harmonic Distortion) calculation, an improved FFT spectral analysis algorithm is used to suppress spectral leakage by constructing a BN cross-convolution window function. Combined with a three-spectrum correction formula, the FFT transform results are interpolated to accurately extract the fundamental and harmonic amplitudes, thereby calculating the THD value. For three-phase unbalance calculation, an improved coordinate partitioning method is used to divide the phasor coordinates of the three-phase voltage and current into six sector partitions. The amplitude and phase relationship of the phase sequence components are directly determined through partition matching, allowing the extraction of positive, negative, and zero-sequence components without calculating phase angles. Based on the amplitude ratio of the negative and positive sequence components, the three-phase unbalance value is calculated, achieving high-precision and fast-response power quality analysis.

[0025] The total harmonic distortion (THD) and three-phase imbalance values ​​obtained from power quality analysis are compared with preset power compensation thresholds. For cases exceeding the thresholds, the system is equivalent to a Thevenin model, taking into account system admittance characteristics. A dual-objective three-phase imbalance compensation mathematical model, incorporating three-phase current imbalance and the number of compensation device actions, is constructed using negative-order weighting. The Pareto optimal solution set is then selected using non-dominated sorting with particle swarm optimization, and the optimal power compensation strategy is selected using a hierarchical sequence method. Simultaneously, a harmonic mitigation strategy is generated based on the harmonic frequency distribution corresponding to the THD. Furthermore, the collected grid electrical parameters are compared with preset power switching thresholds to generate diesel generator parallel start-up and power switching commands; air intake damper control commands are generated based on test load temperature data; and safety alarm commands are generated based on personnel intrusion data in the work area, achieving collaborative decision-making between power quality management and system operation control.

[0026] Leveraging the millisecond-level transmission capabilities of GOOSE communication technology, various control commands are synchronously transmitted to the execution module. For power switching, zero-crossing switching technology is employed to trigger power devices at the zero-crossing points of voltage and current, preventing inrush current and achieving a smooth switch between the diesel generator and the grid. For power quality management, based on optimal power compensation and harmonic mitigation strategies, the control power devices and multi-stage LC filter networks work together to complete reactive power compensation, harmonic suppression, and three-phase balance correction. For test load management, the drive electric actuator automatically opens and closes the air inlet damper according to the control commands, ensuring the timing coordination of each control action through high-speed transmission and precise execution of commands.

[0027] The system monitors the parallel operation status of the diesel generator and the quality of power output in real time. It compares actual power output parameters with power quality analysis results and preset thresholds, dynamically adjusting power compensation parameters and power switching timing based on deviations to ensure power output always meets quality requirements, forming a closed-loop control for power quality management. When intrusion is detected and a security alarm is triggered, the system suspends power switching operations for non-critical loads and activates audible and visual alarms, achieving linkage between safety monitoring and control actions. After the test, the system automatically closes the air intake damper and archives the power quality data, switching timing data, and compensation strategy data for this operation, providing data support for subsequent system optimization. Simultaneously, if a communication or controller failure is detected, the system automatically switches to a redundant link or controller, further enhancing system reliability.

[0028] Example 3, the specific process of calculating the total harmonic distortion (THD) value using the improved FFT spectrum analysis algorithm in step 2 is as follows: A BN cross-convolution window function is constructed and an improved FFT correction formula for three spectral lines is derived. The acquired three-phase voltage and current signals are windowed, and FFT transformation is performed on the windowed signals. The spectral leakage problem is eliminated by interpolation correction. The amplitudes of the fundamental wave and each harmonic are extracted. The total harmonic distortion (THD) value is calculated based on the THD calculation criteria and the amplitudes of the fundamental wave and harmonics.

[0029] Example 4, the three-spectral-line improved FFT correction formula is as follows: ; ; ; Where A is the corrected fundamental or harmonic amplitude. Let the amplitude of the spectral line preceding the frequency point to be determined be . Let be the amplitude of the spectral line corresponding to the frequency point to be determined. Let be the amplitude of the spectral line following the frequency point to be determined.

[0030] Example 5, the specific process of obtaining the phase sequence components and calculating the three-phase unbalance value by improving the coordinate partitioning method in step 2 is as follows: the phasor coordinates of the three-phase voltage and current are divided into six sector partitions. The amplitude and phase relationship of the phase sequence components are directly determined by the partition matching method. The positive sequence, negative sequence and zero sequence components can be extracted without calculating the phase angle. Based on the amplitude ratio of the negative sequence component and the positive sequence component, the three-phase unbalance value is obtained in combination with the three-phase unbalance calculation specification.

[0031] By employing the above technical solution, the window function truncates the acquired discrete voltage and current signals, preventing spectral leakage caused by signal abrupt changes. The BN cross-convolution window function is obtained by convolving a Blackman window and a Neumann window. It combines the characteristics of large sidelobe attenuation of the Blackman window and narrow main lobe width of the Neumann window, which can significantly suppress spectral sidelobe leakage interference while preserving the effective frequency band of the signal, providing a more realistic signal basis for subsequent FFT transformation.

[0032] Traditional FFT transform suffers from spectral energy diffusion when analyzing non-integer period sampled signals, leading to amplitude calculation errors. The improved three-spectrum FFT correction formula constructs an interpolation correction model based on the amplitude relationship between the target frequency point and its two adjacent spectral lines. By introducing two correction coefficients, α and β, the influence of adjacent spectral lines on the target spectrum is quantified. Then, a weighted calculation is used to correct the amplitude of the target spectrum, offsetting the error caused by spectral leakage and achieving accurate extraction of the fundamental and harmonic amplitudes.

[0033] After discretizing the acquired three-phase voltage and current continuous signals, a BN cross-convolution window function is applied to the sampled sequence to complete the windowing process. An FFT transform is then performed on the windowed discrete signal to convert the time-domain signal into a frequency-domain signal, obtaining the spectral amplitude corresponding to each frequency point, thus providing frequency-domain data support for harmonic amplitude extraction.

[0034] According to the THD calculation criteria in the field of power quality, total harmonic distortion (THD) is the ratio of the square root of the sum of the squares of the amplitudes of all harmonics to the fundamental amplitude. After extracting the accurate fundamental amplitude and the amplitudes of each harmonic through the three-spectrum correction formula, the THD value reflecting the degree of harmonic pollution of the power grid can be obtained by substituting it into the criteria.

[0035] The improved FFT correction formula using three spectral lines achieves amplitude correction by correlating the amplitudes of three adjacent spectral lines. The α coefficient reflects the influence of the amplitude difference between the spectral lines before and after the desired frequency point on the target amplitude, quantifying the leakage deviation of a single-sided spectral line; the β coefficient reflects the amplitude change trend of the spectral lines before and after the desired frequency point and the target spectral line, quantifying the overall leakage deviation of both-sided spectral lines. Substituting α and β into the amplitude correction formula, the amplitude information of the three spectral lines is weighted and integrated to compensate for and correct the target spectral line amplitude obtained from the initial FFT transform, ultimately yielding the true amplitude of the fundamental or harmonic wave after eliminating spectral leakage errors.

[0036] The phasors of three-phase voltage and current exhibit a fixed phase difference characteristic in the complex plane. The complex plane is divided into six sector partitions, each corresponding to a specific amplitude and phase correlation characteristic of the phase sequence component. By mapping the acquired three-phase voltage and current phasors to this coordinate partition, the relevant information of the phase sequence component can be directly matched using the characteristic attributes of the partition, without the need for complex phase angle calculations to derive the phase sequence component.

[0037] Positive-sequence, negative-sequence, and zero-sequence components are the core components describing the unbalanced state of a three-phase system. In the six sector partitions, different phasor positions correspond to a clear relationship between the amplitude and phase of the phase sequence components. After determining this relationship through partition matching, the positive-sequence, negative-sequence, and zero-sequence components can be directly separated, simplifying the calculation process of solving the phase sequence components using the symmetrical component method in traditional methods and improving the response speed of component extraction.

[0038] The core evaluation index of three-phase unbalance is the amplitude ratio of the negative-sequence component to the positive-sequence component. After extracting the precise amplitudes of the positive-sequence and negative-sequence components, and combining the calculation specifications for three-phase unbalance in power quality standards, the three-phase unbalance value, reflecting the degree of imbalance in the three-phase system, can be obtained by calculating the amplitude ratio of the two components.

[0039] Example 6, the specific process of generating a harmonic mitigation strategy based on the THD total harmonic distortion value in step 3 is as follows: when the THD total harmonic distortion value exceeds the preset power compensation threshold, the operating frequency of the multi-stage LC filter network is determined according to the harmonic frequency distribution corresponding to the THD total harmonic distortion value, and the filtering parameters of the filter network are set for the 3rd, 5th and 7th major harmonics to form a harmonic mitigation strategy adapted to the harmonic frequency.

[0040] Example 7, the specific process of constructing the three-phase imbalance compensation mathematical model in step 3 is as follows: the system side is equivalent to the Thevenin model, the system admittance characteristics are considered, the negative sequence current component is allocated to the three-phase positive sequence circuit through negative sequence weighting, the operating characteristics and compensation capacity limit of the power compensation device are incorporated, and a dual-objective mathematical model including the three-phase current imbalance degree and the number of times the compensation device operates is established.

[0041] Example 8, the specific process of solving the optimal power compensation strategy by intelligent optimization algorithm in step 3 is as follows: initialize the particle parameters and iteration parameters of the particle swarm algorithm, use the output result of the three-phase unbalance compensation mathematical model as the calculation basis of the particle fitness function, select the Pareto optimal solution set by non-dominated sorting method, and select the optimal power compensation strategy that meets the power compensation threshold from the optimal solution set by hierarchical sequence method. The optimization objective of finding the optimal power compensation strategy is to make the corrected three-phase imbalance value less than or equal to 1%, while reducing the number of operation times of the power compensation device by more than 30% compared with the traditional compensation strategy, and matching the reactive power compensation amount of the system with the reactive power demand of the power grid during the correction process.

[0042] By adopting the above technical solution, the Total Harmonic Distortion (THD) value is a core indicator reflecting the degree of harmonic pollution in the power grid. When this value exceeds the preset power compensation threshold, it indicates that the harmonic content of the power grid has exceeded the acceptable range, and the harmonic mitigation process needs to be initiated. The severity of harmonics is directly related to their frequency. The 3rd, 5th, and 7th harmonics are the main harmonic components in the power system, and their frequency characteristics determine the operating parameters of the filtering device. The filtering characteristics of a multi-stage LC filter network are determined by its own operating frequency and filtering parameters. Harmonics of a specific frequency can only be effectively filtered out by an LC filter network that matches the corresponding operating frequency. Therefore, the harmonic frequency distribution of the power grid is first analyzed by the THD value. Then, for the 3rd, 5th, and 7th main harmonics, the operating frequency and filtering parameters of the LC filter network are set respectively, so that the frequency characteristics of the filter network are accurately matched with the harmonic frequency, ultimately forming a harmonic mitigation strategy that can specifically suppress the main harmonics.

[0043] The essence of three-phase imbalance lies in the presence of negative-sequence current components in the system. To achieve accurate compensation for three-phase imbalance, the system side must first be equivalent to the Thevenin model. This model simplifies the complex system-side circuit into a series connection of an ideal voltage source and an equivalent impedance, facilitating the analysis of the system's electrical characteristics. Simultaneously, the system admittance characteristics are considered to make the model more closely reflect the actual operating state of the power grid. By distributing the negative-sequence current components to the three-phase positive-sequence circuits using a negative-sequence weighting method, the distribution ratio of the negative-sequence components in each phase's positive-sequence circuit can be quantified, providing a data basis for formulating compensation strategies. The operating characteristics and compensation capacity of power compensation devices are physically limited; exceeding these limits can lead to device damage or compensation failure. Therefore, these limitations are incorporated into the model. A dual-objective mathematical model is established, with the three-phase current imbalance degree and the number of times the compensation devices operate as optimization objectives. This ensures both the correction effect of the three-phase imbalance and avoids reduced service life of the compensation devices due to frequent operation.

[0044] Particle swarm optimization (PSO) is an optimization algorithm based on swarm intelligence. By initializing particle parameters and iteration parameters, it allows particles to simulate swarm optimization behavior within the solution space. The output of the three-phase imbalance compensation mathematical model is used as the basis for calculating the particle fitness function, quantifying the merits of each particle's compensation strategy under the dual objectives. A non-dominated sorting method can classify particles and filter out Pareto optimal solution sets that are not dominated by other particles. This solution set contains the optimal candidate compensation strategies under the dual objectives. A hierarchical sequence method sorts the Pareto optimal solution set according to a preset priority, prioritizing strategies that meet the power compensation threshold, thus determining the optimal power compensation strategy from the candidate solution set. The optimization objectives set during the solution process ensure the practical application value of the optimal power compensation strategy from three dimensions: compensation accuracy (corrected three-phase imbalance value less than or equal to 1%), device economy (reduction of action number by more than 30%), and grid adaptability (matching reactive power compensation with grid reactive power demand).

[0045] Example 9: A diesel generator parallel operation management system for implementing a diesel generator parallel operation power switching control method. The system includes a multi-source data acquisition module, a redundant communication module, an intelligent decision-making module, an execution control module, a safety monitoring module, and a closed-loop correction module. The multi-source data acquisition module is used to collect electrical parameters, environmental parameters, and safety monitoring data; The redundant communication module uses a dual-ring network redundancy architecture built with network cables or optical fibers and integrates a GOOSE communication unit. The intelligent decision-making module receives data collected by the multi-source data acquisition module and performs improved FFT spectrum analysis, three-phase imbalance calculation and optimal compensation strategy solution. The execution control module communicates with the intelligent decision-making module to perform power switching, power quality management, and air intake control operations.

[0046] Example 10: The decision module has a built-in power quality analysis unit and a compensation strategy solution unit. The power quality analysis unit is equipped with an embedded program of an improved FFT spectrum analysis algorithm and a calculation program of an improved coordinate partitioning method, and outputs the total harmonic distortion (THD) value and the three-phase imbalance value. The compensation strategy solution unit has a built-in particle swarm optimization algorithm calculation program and a three-phase imbalance compensation mathematical model, and outputs the optimal power compensation strategy based on the power quality analysis results.

[0047] The following specific embodiments illustrate the implementation principle of the present invention: Taking the diesel generator parallel power switching control scenario of an industrial substation as an example, this paper details the specific implementation process of the diesel generator parallel power switching control method and management system. The substation is equipped with two 500kW diesel generator sets, a multi-stage LC filter network, and thyristor / IGBT power devices. It needs to achieve rapid switching of diesel generator parallel operation and power quality management when the power grid fails, while also taking into account the safety management of the test load.

[0048] System setup and initialization: Establish a dual-ring redundant communication network: Use optical fiber as the transmission medium to build a dual-ring redundant architecture, integrate GOOSE communication units, unify the interfaces and communication protocols of diesel generator controllers, parallel units, power compensation modules, and test load monitoring equipment, and replace the traditional hard-wiring method; configure two industrial controllers as the main and backup to complete the redundant configuration of controllers and communication links.

[0049] Preset various thresholds: Set the power switching threshold to 85% of the rated voltage when the grid voltage drops; set the power compensation threshold to THD ≥3% and three-phase imbalance ≥1%; set the safety monitoring threshold to activate the air intake damper when personnel intrusion is detected within 5 meters of the test load operating area or when the temperature of the test load equipment is ≥60℃.

[0050] Multi-source data acquisition and power quality analysis: Data Acquisition: Voltage, current, phase difference, and active and reactive power data of the power grid, diesel generator, and parallel system are collected at a sampling frequency of 10kHz using voltage / current sensors; temperature of test load equipment is collected using temperature and humidity sensors; personnel intrusion data of the work area is collected using millimeter-wave radar; and reactive power demand data of the power grid is collected using reactive power sensors. All collected data are aggregated by the multi-source data acquisition module and then transmitted to the intelligent decision-making module.

[0051] THD (Total Harmonic Distortion) Calculation: The power quality analysis unit in the intelligent decision-making module calls the embedded program of the improved FFT spectrum analysis algorithm. First, it constructs a BN cross-convolution window function, and obtains the window function by convolving the Blackman window and the Neumann window. Then, it derives the three-spectrum improved FFT correction formula. The collected three-phase voltage and current signals are windowed, and after performing FFT transformation, the spectrum leakage is eliminated by interpolation correction. The amplitudes of the fundamental wave and the 3rd, 5th, and 7th harmonics are extracted. According to the THD calculation criteria, the THD total harmonic distortion value is calculated to be 4.2%.

[0052] Three-phase unbalance calculation: The power quality analysis unit calls the calculation program of the improved coordinate partitioning method to divide the phasor coordinates of the three-phase voltage and current into six sector partitions. The amplitude and phase relationship of the phase sequence components are directly determined through partition matching, and the positive sequence, negative sequence and zero sequence components are extracted. Based on the amplitude ratio of the negative sequence component to the positive sequence component, combined with the three-phase unbalance calculation specification, the three-phase unbalance value is calculated to be 1.5%.

[0053] Intelligent decision generation: Power quality management strategy generation: The THD (Total Harmonic Distortion) value of 4.2% and the three-phase imbalance value of 1.5% are compared with preset power compensation thresholds. If the thresholds are exceeded, a harmonic management strategy is first generated: The harmonic frequency distribution corresponding to the THD value is analyzed, determining that the 3rd harmonic has the highest amplitude, followed by the 5th and 7th harmonics. Based on this, the operating frequencies of the multi-stage LC filter network are set to 150Hz, 250Hz, and 350Hz, respectively, and the corresponding filter parameters are matched. Subsequently, the compensation strategy solution unit calls the three-phase imbalance compensation mathematical model to optimize the system... The model is equivalent to the Thevenin model. Considering the system admittance characteristics, the negative sequence component of the current is distributed to the three-phase positive sequence circuit through negative sequence weighting. The operating characteristics and compensation capacity limitations of the power compensation device are incorporated to establish a dual-objective mathematical model. The particle parameters of the particle swarm algorithm are initialized to 50 particles and 100 iterations. The output of the mathematical model is used as the basis for calculating the fitness function. The Pareto optimal solution set is screened by non-dominated sorting. The optimal power compensation strategy is selected by hierarchical sequence method. It is determined that the power of each phase is allocated by inter-phase power transfer technology, and the reactive power is supplemented by pre-charged capacitor banks.

[0054] System control command generation: The collected grid electrical parameters are compared with the preset power switching threshold. If the grid voltage drops to 80% of the rated voltage, a diesel generator parallel start and power switching command is generated. If the temperature of the test load equipment is detected to be 62℃, an air intake damper opening command is generated. If no personnel intrusion is detected by the millimeter-wave radar, no safety alarm command is generated.

[0055] Command execution: Command transmission: The intelligent decision-making module transmits various commands to the execution control module at millisecond speeds via the GOOSE communication unit; Power switching: The execution control module adopts zero-crossing switching technology, which triggers the thyristor module at the zero-crossing point of voltage and current to achieve inrush-free switching between the diesel generator and the power grid. The diesel generator start-up response time is 280ms. Power quality management: Based on the optimal power compensation strategy and harmonic management strategy, control the IGBT power devices and multi-stage LC filter network to work together, adjust the distribution ratio of interphase power transfer, switch capacitor banks to supplement reactive power, and accurately filter out the 3rd, 5th and 7th harmonics. Air intake control: Drive the electric actuator to open the air intake baffle of the test load to reduce the equipment temperature.

[0056] Closed-loop correction and security linkage: Closed-loop correction: The closed-loop correction module monitors the operating status of the diesel generator in parallel and the power output quality in real time. It collects the corrected total harmonic distortion (THD) value of 2.8% and the three-phase imbalance value of 0.8%. It compares this data with the preset threshold and the previous analysis results, and dynamically fine-tunes the conduction angle of the power compensation device to keep the power output parameters stable. Fault redundancy switching: If the main communication link is interrupted during operation, the system automatically switches to the backup communication link. The controller continues to issue normal commands, and no control interruption occurs. Safety linkage and data archiving: During the test, the millimeter-wave radar detected personnel intrusion within 5 meters of the work area. The system immediately suspended the power switching operation of non-critical loads and activated the audible and visual alarms. After the test, the system automatically closed the air intake damper and archived the power quality data, switching timing data, and compensation strategy data of this operation to the local database to provide a basis for subsequent system optimization.

[0057] System module collaborative verification: The multi-source data acquisition module completes the synchronous acquisition and transmission of all data without data loss or delay; the redundant communication module ensures the reliability of command transmission and achieves seamless switching in the event of a main link failure; the intelligent decision-making module completes improved FFT spectrum analysis, three-phase imbalance calculation, and optimal compensation strategy solution, outputting accurate commands; the execution control module realizes the coordinated execution of power switching, power quality management, and air intake control; the safety monitoring module and closed-loop correction module realize the closed-loop management of safety linkage and power quality. All modules work together to complete the full-process control of diesel generator parallel power switching.

[0058] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for switching power supplies between diesel generators and parallel turbines, characterized in that, Includes the following steps: Step 1: Build a dual-ring redundant communication network, preset power switching, power compensation and safety monitoring thresholds, and complete the redundant configuration of the controller and communication link; Step 2: Collect voltage, current, phase difference, and active and reactive power data of the power grid, diesel generator, and parallel system; collect test load temperature, personnel intrusion data of the work area, and reactive power demand data of the power grid; use an improved FFT spectrum analysis algorithm to process the voltage and current signals and calculate the total harmonic distortion (THD) value; use an improved coordinate partitioning method to obtain the phase sequence components, and combine the phase sequence components to calculate the three-phase unbalance value. Step 3: Compare the total harmonic distortion (THD) value and three-phase imbalance value obtained in Step 2 with the preset power compensation threshold. Based on the comparison results, construct a three-phase imbalance compensation mathematical model, solve it through an intelligent optimization algorithm to obtain the optimal power compensation strategy, and generate a harmonic mitigation strategy at the same time. Step 4: Compare the collected grid electrical parameters with the preset power switching threshold to generate diesel generator parallel start-up and power switching commands; generate air intake damper control commands based on test load temperature data; and generate safety alarm commands based on personnel intrusion data in the work area. Step 5: Each instruction is transmitted to the execution module. Zero-crossing switching technology is used to achieve inrush-free switching between the diesel generator and the power grid. Based on the optimal power compensation strategy and harmonic mitigation strategy, the power devices and filter network are controlled to complete power quality management. The actuator is driven to open and close the air intake damper.

2. The diesel generator parallel power supply switching control method according to claim 1, characterized in that, Real-time monitoring of the diesel generator parallel operation status and power output quality; comparison of actual power output parameters with the analysis results of step 2 and preset thresholds; dynamic correction of power compensation parameters and power switching sequence; automatic switching to redundant link or redundant controller if communication or controller failure is detected. If intrusion is detected and a security alarm is triggered, the power switching operation of non-critical loads will be suspended and an audible and visual alarm will be activated. After the test is completed, the air intake damper will be closed, and the power quality data, switching timing data, and compensation strategy data of this operation will be archived.

3. The diesel generator parallel power supply switching control method according to claim 2, characterized in that, The specific process of calculating the total harmonic distortion (THD) value using the improved FFT spectrum analysis algorithm in step 2 is as follows: A BN cross-convolution window function is constructed and an improved FFT correction formula for three spectral lines is derived. The acquired three-phase voltage and current signals are windowed, and FFT transformation is performed on the windowed signals. The spectral leakage problem is eliminated by interpolation correction. The amplitudes of the fundamental wave and each harmonic are extracted. The total harmonic distortion (THD) value is calculated based on the THD calculation criteria and the amplitudes of the fundamental wave and harmonics.

4. The diesel generator parallel power supply switching control method according to claim 3, characterized in that, The modified formula for the three-spectral-line FFT is: ; ; ; Where A is the corrected fundamental or harmonic amplitude. Let the amplitude of the spectral line preceding the frequency point to be determined be . Let be the amplitude of the spectral line corresponding to the frequency point to be determined. Let be the amplitude of the spectral line following the frequency point to be determined.

5. The diesel generator parallel power supply switching control method according to claim 4, characterized in that, The specific process of obtaining the phase sequence components and calculating the three-phase unbalance value by improving the coordinate partitioning method in step 2 is as follows: the phasor coordinates of the three-phase voltage and current are divided into six sector partitions. The amplitude and phase relationship of the phase sequence components are directly determined by the partition matching method. The positive sequence, negative sequence and zero sequence components can be extracted without calculating the phase angle. Based on the amplitude ratio of the negative sequence component and the positive sequence component, the three-phase unbalance value is obtained in combination with the three-phase unbalance calculation specification.

6. The diesel generator parallel power supply switching control method according to claim 5, characterized in that, The specific process of generating a harmonic mitigation strategy based on the THD total harmonic distortion value in step 3 is as follows: When the THD total harmonic distortion value exceeds the preset power compensation threshold, the operating frequency of the multi-stage LC filter network is determined according to the harmonic frequency distribution corresponding to the THD total harmonic distortion value. The filter parameters of the filter network are set for the 3rd, 5th, and 7th major harmonics to form a harmonic mitigation strategy adapted to the harmonic frequency.

7. The diesel generator parallel power supply switching control method according to claim 6, characterized in that, The specific process of constructing the three-phase imbalance compensation mathematical model in step 3 is as follows: the system side is equivalent to the Thevenin model, the system admittance characteristics are considered, the negative sequence current component is allocated to the three-phase positive sequence circuit through negative sequence weighting, the operating characteristics and compensation capacity limits of the power compensation device are incorporated, and a dual-objective mathematical model including the three-phase current imbalance degree and the number of times the compensation device operates is established.

8. The diesel generator parallel power supply switching control method according to claim 7, characterized in that, The specific process of solving the optimal power compensation strategy using the intelligent optimization algorithm in step 3 is as follows: initialize the particle parameters and iteration parameters of the particle swarm algorithm, use the output results of the three-phase unbalance compensation mathematical model as the basis for calculating the particle fitness function, select the Pareto optimal solution set through non-dominated sorting, and select the optimal power compensation strategy that meets the power compensation threshold from the optimal solution set using the hierarchical sequence method. The optimization objective of finding the optimal power compensation strategy is to make the corrected three-phase imbalance value less than or equal to 1%, while reducing the number of operation times of the power compensation device by more than 30% compared with the traditional compensation strategy, and matching the reactive power compensation amount of the system with the reactive power demand of the power grid during the correction process.

9. A diesel generator parallel operation management system, characterized in that, To implement the diesel generator parallel power switching control method as described in claim 8, the system includes a multi-source data acquisition module, a redundant communication module, an intelligent decision-making module, an execution control module, a safety monitoring module, and a closed-loop correction module; The multi-source data acquisition module is used to collect electrical parameters, environmental parameters, and safety monitoring data; The redundant communication module uses a dual-ring network redundancy architecture built with network cables or optical fibers and integrates a GOOSE communication unit. The intelligent decision-making module receives data collected by the multi-source data acquisition module and performs improved FFT spectrum analysis, three-phase imbalance calculation and optimal compensation strategy solution. The execution control module communicates with the intelligent decision-making module to perform power switching, power quality management, and air intake control operations.

10. A diesel generator parallel management system according to claim 9, characterized in that, The decision module has a built-in power quality analysis unit and a compensation strategy solution unit; the power quality analysis unit is equipped with an embedded program of an improved FFT spectrum analysis algorithm and a calculation program of an improved coordinate partitioning method, and outputs the total harmonic distortion (THD) value and the three-phase imbalance value. The compensation strategy solution unit has a built-in particle swarm optimization algorithm and a three-phase imbalance compensation mathematical model, and outputs the optimal power compensation strategy based on the power quality analysis results.

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