Three-level flexible excitation dynamic regulation and control method and system for large hydroelectric generating set

Abstract

The invention discloses a three-level flexible excitation dynamic regulation and control method and system for a large-scale hydroelectric generating set, and relates to the technical field of flexible excitation control of the large-scale hydroelectric generating set, and the method comprises the steps: setting a DC bus voltage, and initializing a mapping relation between a capacitor voltage and an excitation output level; collecting operation parameters of a machine end, constructing a disturbance identification model and outputting a disturbance level; the excitation voltage output gear is set according to the disturbance level, the capacitor voltage difference is controlled, and dynamic voltage sharing is achieved by modulating the midpoint duty ratio. According to the method, through setting a bus target voltage and constructing excitation voltage output mapping, in combination with a disturbance level identification mechanism and a dynamic voltage-sharing strategy, closed-loop linkage of disturbance perception-voltage regulation-voltage difference control is realized. According to the method, the identification precision of the system on light disturbance and strong disturbance is effectively improved, the voltage stability and capacitance symmetry of the excitation system are enhanced, the overshoot risk is reduced, and the control robustness and safety of the system under extreme working conditions are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flexible excitation control of large hydroelectric generating units, in particular to a three-level flexible excitation dynamic regulation method and system for large hydroelectric generating units. BACKGROUND

[0002] With the continuous development of large hydroelectric generating units towards high capacity, high reliability and high stability, the excitation system as the core part of the generator operation control, its performance is directly related to the grid voltage regulation, system stability and grid quality. The traditional excitation system mostly adopts two-level structure, the regulation speed and accuracy are limited, and it is difficult to adapt to the dynamic demand of modern hydroelectric generating units under multi-working condition switching, high frequency disturbance and large range power fluctuation. In order to improve the excitation regulation response efficiency, three-level flexible excitation structure is gradually introduced, which realizes finer granularity regulation ability through multi-gear voltage control and dynamic current limiting. However, the dynamic coordination control and voltage balance management of three-level system still face engineering difficulties, especially in disturbance identification, gear switching and energy storage unit voltage balance control, there is a lack of systematic and robust regulation method.

[0003] The existing three-level excitation control technology mainly relies on static threshold or preset strategy for excitation voltage gear switching under multi-working condition operation condition, and cannot accurately identify and adaptively adjust according to the system disturbance characteristics, resulting in response lag or over-control, and there are problems of low disturbance identification granularity and fuzzy classification. At the same time, the fixed PWM strategy is mostly used for voltage balance regulation of energy storage capacitor voltage difference, and there is a lack of midpoint modulation mechanism linked with the running state, especially in the strong excitation or excitation state, the capacitor voltage imbalance of upper and lower bridge arms is easy to occur, which causes waveform distortion or device stress aggravation. The traditional control scheme does not construct a quantitative model of disturbance evolution trend, and cannot realize the mapping reasoning between voltage, frequency, reactive power change and disturbance level, so as to lack enough identification accuracy to support multi-gear excitation regulation logic. In actual application, there are often problems such as insufficient excitation voltage regulation granularity, long-term deviation accumulation of capacitor voltage and unstable excitation response coupling, which seriously restricts the high reliable regulation ability of flexible excitation system. Therefore, a dynamic regulation method combining disturbance identification and midpoint bias control mechanism is urgently needed to improve the adaptability of excitation control system to disturbance, the real-time of voltage balance and the stability of overall operation. SUMMARY

[0004] In view of the above problems, the present application is proposed.

[0005] Therefore, the technical problem solved by the present application is that the existing three-level excitation regulation method has problems of low disturbance identification granularity, non-adaptive voltage regulation mode switching, and difficulty in real-time regulation of capacitor voltage imbalance, and how to construct a three-level excitation dynamic regulation method combining disturbance identification and voltage balance linkage.

[0006] To solve the above technical problems, the application provides the following technical scheme: a three-level flexible excitation dynamic regulation method for large hydroelectric generating units, comprising setting a DC bus voltage, initializing a capacitor voltage and an excitation output level mapping relationship; collecting machine end operation parameters, constructing a disturbance identification model and outputting a disturbance level; setting an excitation voltage output gear according to the disturbance level and controlling a capacitor voltage difference, and realizing dynamic voltage balancing through modulation of a midpoint duty cycle; the construction of the disturbance identification model comprises collecting machine end operation parameters, outputting a change between the machine end operation parameters and a steady-state reference value, constructing a disturbance identification model, dividing a disturbance level in combination with an instantaneous amplitude of the change, and outputting a disturbance level identification value; the realization of dynamic voltage balancing through modulation of the midpoint duty cycle comprises, in the process of excitation voltage output, real-time collection of voltage values of upper and lower end capacitors of an energy storage capacitor bank, output of a capacitor voltage difference and a relative voltage difference ratio, judgment of whether the voltage difference ratio exceeds a safety threshold, and if yes, entering a dynamic voltage balancing state and controlling a duty cycle offset of a midpoint bridge arm of a PWM modulator.

[0007] As a preferred scheme of the three-level flexible excitation dynamic regulation method for large hydroelectric generating units, the setting of the DC bus voltage comprises that the set DC bus voltage is not lower than twice the rated excitation output voltage, and the capacitor bank voltage is initialized in the excitation system starting stage to make the upper and lower bridge arm capacitor voltages equal, and a proportional mapping relationship between the excitation output voltage and the target bus voltage is constructed.

[0008] As a preferred scheme of the three-level flexible excitation dynamic regulation method for large hydroelectric generating units, the collection of the machine end operation parameters comprises collection of a generator end voltage, a frequency, active power and reactive power.

[0009] As a preferred scheme of the three-level flexible excitation dynamic regulation method for large hydroelectric generating units, the disturbance level comprises output of a disturbance level identification value through construction of a disturbance identification model based on multi-parameter threshold comparison.

[0010] As a preferred scheme of the three-level flexible excitation dynamic regulation method for large hydroelectric generating units, the setting of the excitation voltage output gear according to the disturbance level comprises, in each control period, selection of a preset excitation voltage output gear parameter according to the disturbance level.

[0011] As a preferred scheme of the three-level flexible excitation dynamic regulation method for large hydroelectric generating units, the realization of dynamic voltage balancing through modulation of the midpoint duty cycle comprises, through real-time sampling of upper and lower bridge arm energy storage capacitor voltages and output of a voltage difference, adjustment of the midpoint duty cycle to realize dynamic voltage balancing when the voltage difference exceeds a set threshold.

[0012] As a preferred scheme of the three-level flexible excitation dynamic regulation method for large hydroelectric generating units, the modulation midpoint duty cycle comprises adaptive adjustment according to the differential ratio, and the control range is between the set minimum and maximum duty cycles.

[0013] Another object of the present application is to provide a three-level flexible excitation dynamic regulation system for large hydroelectric generating units, which can set the excitation voltage output gear according to the disturbance level and control the capacitor voltage difference, and realize dynamic voltage balancing through modulation midpoint duty cycle, thereby solving the problem that the current three-level excitation regulation method contains capacitor voltage imbalance which is difficult to adjust in real time.

[0014] As a preferred scheme of the three-level flexible excitation dynamic regulation system for large hydroelectric generating units, the system comprises an excitation initial voltage configuration module, a disturbance level identification modeling module, and an excitation voltage dynamic regulation and voltage balancing control module; the excitation initial voltage configuration module is used to set the voltage reference standard of the starting state of the excitation system; the disturbance level identification modeling module is used to judge the operating state of the generator and classify the disturbance level, construct a disturbance identification model and output a disturbance level identification by sampling parameters, and serve as the trigger basis for control strategy switching; and the excitation voltage dynamic regulation and voltage balancing control module is used to select the excitation voltage output gear according to the disturbance level and maintain the symmetry of the capacitor voltage.

[0015] A computer device comprises a memory and a processor, the memory stores a computer program, and the processor executes the computer program to implement the steps of the three-level flexible excitation dynamic regulation method for large hydroelectric generating units.

[0016] A computer readable storage medium stores a computer program, and the computer program is executed by a processor to implement the steps of the three-level flexible excitation dynamic regulation method for large hydroelectric generating units.

[0017] The application provides a three-level flexible excitation dynamic regulation method for a large-scale hydroelectric generating set. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0019] Fig. 1 A three-level flexible excitation dynamic regulation method for a large-scale hydroelectric generating set provided by the embodiment 1 of the present application.

[0020] Fig. 2 A three-level flexible excitation dynamic regulation method for a large-scale hydroelectric generating set provided by the embodiment 1 of the present application. DETAILED DESCRIPTION

[0021] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the drawings in the specification. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the protection scope of the present application.

[0022] Embodiment 1, refer to Figs. 1-2 For an embodiment of the present application, a three-level flexible excitation dynamic regulation method for a large-scale hydroelectric generating set is provided, which comprises: S1: Set the DC bus voltage, initialize the capacitor voltage and the mapping relationship of the excitation output level.

[0023] Further, in view of the actual demand of the excitation system of large hydroelectric generating units for strong excitation, de-excitation and bidirectional switching, the target voltage of the DC bus of the excitation system is first set . The target voltage should meet the maximum voltage output demand covering the normal operation voltage, the fault strong excitation output voltage and the reverse de-excitation, and therefore needs to be set to more than 2 times the rated excitation voltage, with a certain dynamic control margin, which is expressed as: , Among them, is the rated excitation voltage of the generator excitation winding; is the margin voltage for supporting the strategy adjustment of rapid voltage rise under fault conditions, and the recommended value range is .

[0024] If there is a low-frequency resonance risk in the system, the may be increased to leave a damping margin for oscillation. The target voltage is provided by the front three-level PWM converter, and the controller adjusts the output through a linear boost slope controller, to ensure that the DC voltage is smoothly boosted to the target value at the initial stage of system power-on, avoiding the non-steady-state start phenomenon caused by capacitor overcharging or dramatic changes in the magnetic field.

[0025] It should be noted that, considering that the three-level topology needs to provide multiple output voltages of positive, negative, half and zero at both ends of the chopper, two groups of energy storage capacitors (C1, C2) are used in series to form a voltage dividing structure of the DC bus voltage. After the system is powered on, active voltage balancing adjustment of the capacitors is started, which is expressed as: , Among them, is the DC bus voltage of capacitor C1, is the DC bus voltage of capacitor C2.

[0026] The controller samples the voltages across C1 and C2 in real time, controls the midpoint conduction behavior of the front PWM through differential comparison, and makes the two capacitor groups maintain a voltage difference of no more than in the initial steady state. In engineering implementation, the following control logic can be used: If , increase the conduction duty cycle of the C2 branch to allow it to absorb more charge; If , adjust the midpoint offset to moderately increase the charging rate of C1; If (recommended ), where The capacitor voltage difference control threshold, i.e. the maximum voltage deviation limit between the allowed upper and lower bridge arm energy storage capacitors C1 and C2, remains unchanged, and the current PWM strategy is unchanged, entering the voltage stabilization lock state.

[0027] In addition, an alarm mechanism needs to be triggered when the capacitor voltage difference fluctuates sharply to prevent voltage distortion caused by midpoint deviation.

[0028] It should be noted that after the bus voltage and capacitor voltage initialization is completed, the system enters the initialization configuration phase of the excitation output gear. To meet various operating requirements, the chopper output end is preset with multiple excitation voltage gears, and a mapping relationship table between them and the bus voltage is constructed, as shown in Table 1: Table 1 Mapping relationship table

[0029] The controller presets the above gears as state diagram nodes, and sets the following state transition rules: in the initial stage of normal power-on, it defaults to "zero voltage gear"; after the bus voltage difference stabilizes, it enters "half voltage gear" for maintenance; when the state recognition module outputs a fault signal or the frequency jumps, it can jump to "strong excitation gear" or "reverse gear"; the holding time or duty cycle of any gear is constrained by the protection logic to prevent long-term one-way output from damaging the chopper devices.

[0030] S2: Collect machine end operating parameters, construct a disturbance recognition model and output the disturbance level.

[0031] Further, during the operation of the hydroelectric generating set, the excitation system needs to have high-speed sensing capability for the state changes of the external power grid and its own excitation circuit. This step first constructs a high-frequency operating state sampling framework, with a sampling period set to 10-50 ms, which can be adjusted according to the system response characteristics.

[0032] It should be noted that the collected machine end operating parameters include generator terminal voltage, system frequency, generator electrical power angle, excitation current, generator port reactive power, rotor mechanical angular velocity, and energy storage capacitor temperature. After each sampling period ends, the system writes the sampling values into a buffer area for the state judgment module to call.

[0033] Based on the machine end operating parameters, the system defines the disturbance index change as: , wherein, represents the parameter change (difference) in the time window , represents the transient deviation amplitude of the current change trend, represents the real-time value of a certain operating parameter (such as voltage, frequency, reactive power, etc.) collected at the current time ​denotes the sliding time window or the lag time amount, in seconds (s), usually taking values such as 0.5s, 1s, 2s, etc. denotes the current time point traces back to seconds ago.

[0034] It should also be noted that the disturbance trend integral function is introduced as a comprehensive disturbance measurement index: , wherein, denotes the disturbance trend integral value at the current time point , indicating the cumulative intensity of the comprehensive disturbance of the system in the near future, denotes the disturbance observation time window length, in seconds (s), such as 1s or 2s, indicating the cumulative evaluation of the disturbance in the past seconds, denotes the change in terminal voltage at time point , denotes the change in frequency at time point , denotes the change in reactive power at time point , is an empirical weight factor, used to balance the contribution of voltage, frequency, and power to the disturbance trend;

[0035] When , the disturbance level is determined to be steady-state operation; when , the disturbance level is determined to be light disturbance; when , the disturbance level is determined to be strong disturbance; and when , the disturbance level is determined to be extreme disturbance (strong excitation, de-excitation).

[0036] In addition, the system can call the disturbance evolution prediction module to forward infer the voltage and frequency change trend in the future periods, to assist in entering the strong excitation or de-excitation mode in advance.

[0037] The identified disturbance type is bound to the excitation control state machine to construct a state-action mapping structure table, as shown in Table 2:

[0038] Table 2 State-Action Mapping Structure Table

[0039] When the system identifies state changes, it also records the following information: state switching timestamp; state duration; main cause analysis of the triggering disturbance; and difference vector from the previous state.

[0040] S3: According to the disturbance level, set the excitation voltage output gear, control the capacitor voltage difference, and realize dynamic voltage sharing by modulating the midpoint duty cycle.

[0041] Further, the system determines the current excitation control mode according to the disturbance identification result of S2 in each control cycle (typically 5-10 ms).

[0042] It should be noted that the excitation output control is based on the set target voltage , the current output voltage is adjusted to realize fast tracking. The basic control model is as follows: , wherein, is the output voltage gear coefficient set according to the current mode; In the strong excitation mode, if there is a bus voltage drop (for example, caused by dynamic load of the chopper), a voltage drop compensation needs to be introduced: , wherein, the voltage drop compensation term can be estimated by the voltage deviation model: , wherein, is an empirical gain coefficient (usually ), which is used to quickly compensate for the weakening effect of the bus voltage drop on the excitation voltage output.

[0043] To avoid current overshoot damage to the excitation winding or chopper device in the strong excitation state, the current limiting controller is introduced in the present application, the current limiting threshold is set, and the limiting adjustment function based on the output voltage feedback is established: , wherein, is the equivalent impedance of the excitation circuit (which can be measured or calibrated).

[0044] If is measured, is temporarily weakened, the output gear is lowered, and then it is slowly raised after the current drops; the current limiter has a differential first prediction mechanism to avoid transient current peak over-limiting when the voltage is rapidly raised.

[0045] The minimum holding time limit is introduced, as shown in Table 3:

[0046] Table 3 Time Limit Table

[0047] In addition, to improve the smoothness of dynamic switching, a step transition buffer is set: any switching between two different voltage levels must be controlled by a linear slope, with a time constant of 20-50 ms to avoid system instability caused by large excitation disturbances.

[0048] The system synchronously collects the current voltage values of the two capacitors in each control cycle With , the voltage difference is calculated: , And compared with half of the bus reference voltage , the relative voltage difference ratio is established: , Where, represents the relative voltage difference ratio.

[0049] If , it is considered that the voltage difference enters the controllable range, where the voltage difference threshold is usually set to , and exceeds this value, it enters the asymmetric voltage sharing control state.

[0050] It should also be noted that once , the control system enters the active voltage sharing state, and by adjusting the PWM midpoint bias pulse width, the charging and discharging path of C1 and C2 is changed, the target is to converge If , increase the conduction time of the midpoint to C2, and increase the duty cycle to . If , increase the conduction ratio of the midpoint to the C1 branch, and handle symmetrically; the midpoint offset adjustment is constrained within to avoid frequent bias causing output waveform distortion.

[0051] The PWM modulator can use adaptive dead zone adjustment logic to adjust the delay time of the midpoint bridge arm in real time according to to achieve microsecond-level voltage sharing control accuracy.

[0052] Considering that the charging and discharging cycle and amplitude of C1 and C2 differ greatly under different excitation modes, the voltage sharing control needs to have mode adaptability. Introduce the mode linkage coefficient to dynamically enhance the voltage sharing rate in strong excitation and de-excitation modes: , Where, represents the effective voltage regulation coefficient, represents the basic voltage regulation coefficient, is steady state, is light disturbance, For strong excitation, gray magnetic.

[0053] This mechanism ensures that under short-time high-current impact, the voltage symmetry of C1 and C2 can be quickly restored, improving the stability of gear output and avoiding unilateral capacitor overcharge or breakdown.

[0054] If the system continuously detects If the pressure difference exceeds 100 ms, the system enters an abnormal pressure difference alarm state and performs the following protection actions: reducing the excitation output level, switching from the strong excitation gear to the half-pressure gear or zero-pressure gear, outputting a fault event code, starting the bypass discharge branch or reserving redundant capacitors for voltage balancing, and if the imbalance still cannot be restored, issuing a high-level protection shutdown signal and recording waveform data.

[0055] In addition, the system allows reading the recent pressure difference record during the shutdown and restart process, and delaying the initialization of the strong excitation gear to avoid the re-excitation of the imbalance amplification effect under the power-on overshoot state.

[0056] In Example 2, an embodiment of the present application provides a three-level flexible excitation dynamic regulation method for large hydroelectric generating units. In order to verify the beneficial effects of the present application, economic benefit calculation and simulation experiments are used for scientific demonstration.

[0057] Firstly, an excitation system comparative experiment framework based on a simulation platform and a semi-physical experimental device is constructed. The test objects include two types of systems: a traditional double-level excitation control system and a three-level flexible excitation system designed by the present application. The test platform includes an excitation system controller, a chopper module, an energy storage capacitor group, a PWM modulator, and a simulation generator model. The system is connected with a high-precision data acquisition unit through a PLC, and the sampling period is set to 10 ms to simulate the response characteristics under different disturbance levels.

[0058] Firstly, the initialization settings of the two types of systems are completed respectively. The traditional system is set with a single rated bus voltage, while the system of the present application sets the bus target voltage according to twice the rated excitation voltage of the generator, and initializes the capacitor voltage difference threshold and the midpoint modulation control logic. In the start-up stage, the system of the present application activates the linear boost slope adjustment mechanism to realize dynamic voltage balancing of C1 and C2, and completes the preset mapping of the voltage gear.

[0059] In the disturbance simulation stage, three types of disturbances are injected: light disturbance (such as small amplitude grid voltage sag), strong disturbance (such as main transformer fault, electrical angle mutation), and de-excitation (artificially triggered loss-of-step protection). The collected operating parameters include voltage, frequency, current, reactive power, power angle, etc. The disturbance level is automatically judged by the disturbance identification model, and different excitation output gears are dispatched. In the experiment, the trigger threshold (for example, Δf ≥ 0.3 Hz is judged as strong disturbance) is set, and the response time, voltage recovery process, capacitor voltage difference, and midpoint offset are recorded according to the corresponding rules.

[0060] During the experiment, the key indicators such as current overshoot limiting effect, voltage recovery time and voltage equalization success rate were observed, and the system response and stability under three disturbance levels were recorded to build a basis for comparison and evaluation. The experimental data are shown in Table 4.

[0061] Table 4 Experimental data table

[0062] From the experimental data, it can be observed that under the three types of disturbance, the three-level flexible excitation system of the present application is superior to the traditional excitation system in various performance indicators. For example, under light disturbance, the average excitation response time of the traditional system is 74.2 ms, while that of the present application is shortened to 48.7 ms, indicating that the disturbance identification mechanism has a significant advantage in response speed; and under strong disturbance, the response time is shortened from 128.9 ms to 91.5 ms, reflecting that the dynamic regulation mechanism based on disturbance level can effectively speed up the regulation process.

[0063] In addition, in terms of maximum capacitor voltage difference, the traditional system has a voltage difference of 12.5% under de-excitation state, while the present application system, by introducing the midpoint duty cycle modulation mechanism and voltage equalization threshold judgment mechanism, controls the voltage difference within 3.9%, proving that the dynamic voltage equalization regulation strategy can realize fast voltage difference convergence and significantly improve the symmetry of the capacitor bank. The improvement of voltage equalization success rate also proves the practicality of the strategy: from 73.6% to 96.8% under de-excitation state.

[0064] In terms of current overshoot control, the present application system automatically suppresses the current peak value through the current limiting regulation function, and under strong disturbance, the maximum current is suppressed from 76.4 A to 49.7 A, which reflects the effectiveness of the amplitude limiting mechanism based on feedback current closed-loop regulation in protecting equipment. The improvement of voltage recovery time further proves the regulation advantage of flexible voltage gear setting.

[0065] In summary, by establishing a three-step collaborative mechanism of bus voltage initial control, disturbance level identification and dynamic voltage output and voltage equalization integrated control, the present application method shows superior performance in response speed, voltage equalization accuracy and system stability. The core innovation lies in: firstly introducing a disturbance trend integral function as a disturbance level identification criterion, combining PWM midpoint duty cycle offset adjustment to realize microsecond-level capacitor voltage equalization, and establishing a pressure difference closed loop and fault redundancy protection linkage mechanism, which fills the coupling bottleneck problem between asymmetric capacitor control and multi-gear excitation regulation in the prior art. The test results fully demonstrate the engineering feasibility and practical value of the present application.

[0066] Embodiment 3 provides a three-level flexible excitation dynamic regulation system for large hydroelectric generating units according to an embodiment of the present application, comprising an initial excitation voltage configuration module, a disturbance level identification modeling module, and an excitation voltage dynamic regulation and voltage equalization control module.

[0067] The initial excitation voltage configuration module is used to set the voltage reference standard of the starting state of the excitation system, initialize the bus voltage and the capacitor voltage division structure. The initial excitation voltage configuration module sets the target voltage of the DC bus covering the normal operation and fault response according to the rated voltage of the excitation winding and the fault strong excitation / de-excitation requirement, and reserves a regulation margin. The initial excitation voltage configuration module further controls the linear boost slope of the front-stage three-level PWM converter, realizes the slow rise of the bus voltage to the target value, and prevents capacitor overcharging and excitation mutation. After the voltage initialization is completed, the module establishes a midpoint symmetric regulation structure for the energy storage capacitor groups C1 and C2, monitors the voltages of the two groups in real time, adjusts the midpoint duty ratio through capacitor voltage difference feedback control, ensures that the voltage difference between C1 and C2 is stable within the preset threshold, and outputs the excitation voltage reference curve and the voltage difference equalization state to the disturbance level identification modeling module and the excitation voltage dynamic regulation and voltage equalization control module as the basis for subsequent strategies.

[0068] The disturbance level identification modeling module is used to collect the operating state parameters of the generator and make disturbance level discrimination, and provides a basis for control strategy switching. The disturbance level identification modeling module takes the initialization parameters output by the initial excitation voltage configuration module as the input premise, collects the key indicators such as generator terminal voltage, system frequency, reactive power, and electrical power, constructs a sliding window difference model and a disturbance trend integral model, and extracts the parameter change trend and the comprehensive disturbance degree. The disturbance level identification modeling module judges the current operating state according to the set steady state, light disturbance, strong disturbance, and extreme disturbance threshold, outputs the disturbance level identification, and is accompanied by state switching timestamp, main cause field, disturbance evolution prediction value, and other diagnostic information. The disturbance level identification will be transmitted to the excitation voltage dynamic regulation and voltage equalization control module as an input signal, guiding the selection of excitation voltage gear and the scheduling of voltage equalization behavior.

[0069] The excitation voltage dynamic regulation and voltage equalization control module is configured to receive the disturbance level identification and dynamically adjust the excitation output voltage and control the voltage difference of the energy storage capacitor under different working conditions to realize stable and efficient excitation response. The module automatically selects the voltage output gear (such as strong excitation gear, half voltage gear, de-excitation gear, etc.) based on the input information of the disturbance level identification modeling module, and adjusts the output voltage curve according to the current mode to realize fast voltage tracking and voltage drop compensation. At the same time, the module obtains the terminal voltage of the energy storage capacitor C1 and C2 in real time, constructs a voltage difference feedback model, calculates the relative voltage difference ratio, and judges whether to enter the active voltage equalization control state. When the voltage difference exceeds the preset threshold, the module starts PWM midpoint bias adjustment, changes the branch conduction duty cycle, realizes voltage difference convergence control, and sets the midpoint offset slope and minimum holding time according to the excitation state to avoid frequent switching and output distortion. The voltage equalization control logic supports adaptive adjustment of the regulation rate and control strategy under different disturbance levels to improve the system stability under high dynamic states such as strong excitation and de-excitation.

Claims

1. A three-level flexible excitation dynamic control method for large hydropower units, characterized in that: include: Set the DC bus voltage and initialize the mapping relationship between capacitor voltage and excitation output level; Collect machine-side operating parameters, build a disturbance identification model and output the disturbance level; The excitation voltage output gear is set according to the disturbance level, and the capacitor voltage difference is controlled, and dynamic voltage balancing is achieved by modulating the midpoint duty cycle; Constructing a disturbance identification model includes collecting machine-side operating parameters, outputting the variation between the machine-side operating parameters and a steady-state reference value, constructing a disturbance identification model, classifying disturbance levels based on the instantaneous amplitude of the variation, and outputting a disturbance level identification value; Dynamic voltage balancing is achieved by modulating the midpoint duty cycle. During the excitation voltage output process, the voltage values ​​of the upper and lower capacitors of the energy storage capacitor group are collected in real time, the ratio of the output capacitor voltage difference to the relative voltage difference is determined, and whether the voltage difference ratio exceeds the safety threshold is determined. If so, the dynamic voltage balancing state is entered to control the duty cycle offset of the midpoint bridge arm of the PWM modulator.

2. The three-level flexible excitation dynamic control method for large hydropower units according to claim 1, characterized in that: The setting of the DC bus voltage includes: The set DC bus voltage is not less than twice the rated excitation output voltage, and the capacitor bank voltage is initialized during the startup phase of the excitation system to make the upper and lower arm capacitor voltages equal, and establish a proportional mapping relationship between the excitation output voltage and the target bus voltage.

3. The three-level flexible excitation dynamic control method for large hydropower units according to claim 2, characterized in that: The operating parameters of the acquisition machine include: Generator terminal voltage, frequency, active power and reactive power.

4. The three-level flexible excitation dynamic control method for large hydropower units according to claim 3, characterized in that: The disturbance levels include: The disturbance level identification value is output by constructing a disturbance identification model based on multi-parameter threshold comparison.

5. The three-level flexible excitation dynamic control method for large hydropower units according to claim 4, characterized in that: The step of setting the excitation voltage output gear according to the disturbance level includes: In each control cycle, the preset excitation voltage output gear parameters are selected according to the disturbance level.

6. The three-level flexible excitation dynamic control method for large hydropower units according to claim 5, characterized in that: The method of achieving dynamic voltage balancing by modulating the midpoint duty cycle includes: By sampling the voltages of the upper and lower bridge arm energy storage capacitors in real time and outputting the pressure difference, the midpoint duty cycle is adjusted to achieve dynamic voltage balancing when the pressure difference exceeds the set threshold.

7. The three-level flexible excitation dynamic control method for large hydropower units according to claim 6, characterized in that: The modulation midpoint duty cycle includes: Adaptive adjustment is made based on the pressure difference ratio, and the control range is between the set minimum and maximum duty cycles.

8. A three-level flexible excitation dynamic control system for large hydropower units, using the three-level flexible excitation dynamic control method for large hydropower units according to any one of claims 1 to 7, characterized in that: It includes the excitation initial voltage configuration module, the disturbance level identification modeling module, the excitation voltage dynamic regulation and voltage equalization control module; The excitation initial voltage configuration module is used to set the voltage reference standard of the initial state of the excitation system; The disturbance level identification modeling module is used to determine the operating status of the generator and classify the disturbance level. By sampling the parameters, a disturbance identification model is constructed and a disturbance level identifier is output as a trigger basis for switching the control strategy. The excitation voltage dynamic regulation and voltage balancing control module is used to select the excitation voltage output gear according to the disturbance level and maintain the capacitor voltage symmetry.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the three-level flexible excitation dynamic control method for large hydropower units described in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the three-level flexible excitation dynamic control method for large hydropower units according to any one of claims 1 to 7 are implemented.

Images