Low-pressure adaptive modulation method for high-altitude variable-speed pumped energy storage transformed converter

Abstract

The invention discloses a low-pressure adaptive modulation method for a high-altitude variable-speed pumped energy storage transformation converter. The method comprises the steps of data acquisition, low-pressure modeling, insulation-power cooperative modulation, cooperative execution, state monitoring and circulation. The system comprises five core modules, namely a multi-parameter data acquisition module, a low-pressure characteristic modeling module, a low-pressure self-adaptive modulation module, a water turbine-converter cooperative modulation and execution module and a state monitoring and feedback module. The invention mainly aims to solve the three problems of high insulation breakdown risk, large power output fluctuation and mismatching with the working condition of an original water turbine caused by a low-pressure environment of a full-power converter when variable-speed water pumping energy storage transformation is carried out on a high-altitude small and medium-sized hydropower station. Dynamic adaptation of the full-power converter in'power generation-pumped energy storage 'dual-mode switching is achieved, meanwhile, the requirements of'low-cost transformation, simplified control and quick response' of small and medium-sized power stations are met, and safe and stable operation and electric energy quality of a transformed unit are guaranteed.

Description

A method for low-pressure adaptive modulation of converters for high-altitude variable-speed pumped water storage retrofitting Technical Field

[0001] This invention belongs to the field of novel energy storage and power generation technology, specifically relating to a low-pressure adaptive modulation method for a converter used in high-altitude variable-speed pumped water energy storage retrofit. Background Technology

[0002] The installed capacity of new energy sources such as wind power and photovoltaics is growing rapidly in high-altitude areas. However, these regions lack the capacity to absorb new energy sources, and the grid's peak-shaving capacity is weak. While there are numerous and widely distributed small and medium-sized hydropower stations with an installed capacity of less than 300MW, most are run-of-river stations, facing the problem of "water wastage during the wet season and power shortages during the dry season." Converting existing small and medium-sized hydropower stations into variable-speed pumped storage power stations can utilize existing dams, reservoirs, power plants, and water pipelines, significantly reducing the construction cost of pumped storage while simultaneously achieving the dual functions of "new energy absorption + grid peak-shaving." This has become a key technology for the construction of new power systems in high-altitude areas.

[0003] High-altitude areas are characterized by low air pressure environments, with air pressure around 70 kPa at 3000m and around 50 kPa at 5000m. This significantly impacts the full-power converters used in variable-speed pumped-storage energy storage retrofits: 1. Reduced insulation performance: The insulation breakdown voltage of air decreases with decreasing air pressure. Since the IGBT modules and bus spacing within the converter are fixed (electrode spacing d remains constant), the P×d value decreases under low air pressure, leading to a lower insulation breakdown voltage. At 3000m altitude, the converter's insulation margin decreases by approximately 30% compared to plains areas, making it more prone to IGBT module breakdown and bus flashover faults. 2. Power output and loss fluctuations: Low air pressure reduces air heat dissipation capacity, increasing IGBT switching losses in the converter. Low air pressure also results in poor grid voltage stability. Sudden load changes during the "power generation-pumped-storage" switching of small and medium-sized variable-speed pumped-storage units can easily lead to a converter power output deviation ΔP ≥ 10% and harmonic content exceeding the standard THD ≥ 5%, failing to meet grid connection requirements.

[0004] Current technologies for high-altitude full-power converters do not meet the complex conditions of "high altitude + small and medium-sized variable speed pumped storage retrofit + dual-mode switching": 1. Conventional converters are suitable for fixed constant power loads in a single power generation mode, without considering the dynamic load changes in the "power generation-pumped storage" dual-mode of variable speed pumped storage; 2. Conventional converters are suitable for plains areas, without considering insulation and power correction models under low air pressure; 3. Conventional converters do not consider the coordinated control of the converter and the original turbine in the retrofit scenario, and the guide vane opening is not synchronized with the converter power regulation, resulting in the overall efficiency of the retrofitted unit being 8% to 12% lower than the original design value.

[0005] In summary, existing technologies have failed to solve the complex problems of "high altitude + small and medium-sized variable speed pumped storage retrofit + dual-mode coordination" and cannot meet the requirements under these complex conditions. Therefore, this invention is of great significance. Summary of the Invention

[0006] This invention primarily aims to address three major problems encountered by full-power converters during variable-speed pumped storage retrofits at small and medium-sized hydropower stations at high altitudes (≥3000m): high risk of insulation breakdown, large power output fluctuations, and incompatibility with existing turbine operating conditions. These problems arise due to the low-pressure environment (reduced air insulation strength and increased IGBT switching losses). The invention achieves dynamic adaptation of the full-power converter during the dual-mode switching of power generation and pumped storage, while simultaneously meeting the needs of small and medium-sized power stations for low-cost retrofits, simplified control, and rapid response, ensuring the safe and stable operation of the retrofitted units and the quality of power.

[0007] According to the technical solution of the present invention, the present invention provides a method for low-pressure adaptive modulation of a converter for high-altitude variable-speed pumped-storage energy conversion, comprising the following steps: Step S1, data acquisition: acquiring atmospheric pressure P, ambient temperature T, and IGBT temperature T IGBT Output voltage U out Output current I out Operating mode S, guide vane opening θ; Step S2, low pressure modeling: Substitute the data collected in step S1 into model formula 1 to calculate the actual insulation breakdown voltage U between converter IGBT modules. break Substitute the values ​​into model formulas 2 and 3 to calculate the target power P. target Among them, the operating condition is determined: if the operating mode S is the power generation mode, then model formula 2 is executed, and the target output power P of the converter in the power generation mode is calculated. out,gen That is, the target power P target If the operating mode S is pumped storage mode, then execute model formula 3 to calculate the target output power P of the converter in pumped storage mode. out,pump That is, the target power P target Model formula 1 is: In the formula, U0 is the insulation breakdown voltage under standard conditions; standard environment refers to the environment under standard atmospheric pressure P0 and standard ambient temperature T0, where standard atmospheric pressure P0 = 101.3 kPa and standard ambient temperature T0 = 293 K; P is the actual atmospheric pressure collected; T is the actual ambient temperature collected; k and m are the first and second correction coefficients for insulation breakdown voltage, respectively; Model formula 2 is: In the formula, P n η is the rated power of the converter; α is the power correction factor; η is the rated power of the converter. adapt For adaptive modulation efficiency; k θΔθ is the guide vane coordination coefficient; Δθ is the guide vane opening deviation; Model formula 3 is: In the formula, β is the dynamic compensation coefficient of the pumped hydro storage mode; Step S3, insulation-power coordinated modulation: calculate the insulation safety margin M, and determine whether M is between the set insulation safety margin safety threshold and the insulation safety margin overcompensation threshold. If so, power output control is performed; otherwise, insulation margin control is performed. The insulation safety margin is calculated using the following formula: In the formula, M is the insulation safety margin, and U bus The converter bus voltage is used for insulation margin control, which includes the following: If the insulation safety margin M < the insulation safety margin threshold, the IGBT drive voltage is adjusted to increase the converter bus voltage so that the modulated insulation safety margin is greater than or equal to the insulation safety margin threshold; if the insulation safety margin M > the insulation safety margin over-compensation threshold, the IGBT drive voltage is adjusted to decrease the converter bus voltage so that the modulated insulation safety margin is less than or equal to the insulation safety margin over-compensation threshold; power output control includes the following: Calculate the converter modulation ratio change ΔD according to model formula 4, and adjust the converter modulation ratio accordingly; model formula 4 is: In the formula, ΔD is the change in the converter modulation ratio; K p K i These are the parameters of the first PI controller and the second PI controller, respectively; P actual This represents the actual output power; D ff For feedforward compensation; Step S4, Cooperative execution: Transmit target power P target Send the target value θ of the guide vane opening to the converter. target To the guide vane control system; Step S5, Status monitoring: Collect insulation leakage current I leak Power output deviation, IGBT temperature T IGBT Determine whether the corresponding set threshold is exceeded. If so, feed back the optimization parameters; otherwise, proceed to the next step. Step S6: Loop: Return to step S1 and continue closed-loop control.

[0008] In some implementations, the altitude of the high-altitude small and medium-sized hydropower station is ≥3000m, and / or the atmospheric pressure at the location of the high-altitude small and medium-sized hydropower station is ≤70kPa.

[0009] In some implementations, when retrofitting high-altitude small and medium-sized hydropower stations with variable-speed pumped storage, the existing dams, reservoirs, turbines, and powerhouses of the hydropower stations are used, without constructing new upper and lower reservoirs, dams, or water conveyance facilities; and / or, in some implementations, the installed capacity of high-altitude small and medium-sized hydropower stations is less than 300MW.

[0010] In some implementations, in model formula 1, the first correction coefficient k and the second correction coefficient m for insulation breakdown voltage are determined through field experimental fitting; in some implementations, in model formula 2, the power correction coefficient α is determined through field experimental fitting, and the power correction coefficient α is used to reflect the influence of low air pressure on power; the guide vane coordination coefficient k θ To reflect the impact of guide vane opening changes on power; in some embodiments, in model formula 3, the dynamic compensation coefficient β of the pumped storage mode is used to compensate for sudden load changes during pumping; in some embodiments, in model formula 4, the first PI controller parameter K p Second PI controller parameter K i The feedforward compensation amount D is determined using the particle swarm optimization algorithm. ff This was determined through on-site testing.

[0011] In some implementations, in model formula 1, the insulation breakdown voltage U0 under standard conditions is 1500V; the first correction factor k for the insulation breakdown voltage is 0.9±0.05, and the second correction factor m for the insulation breakdown voltage is 0.55±0.05; in some implementations, in model formula 2, the power correction factor α is 0.35±0.05; η adapt The value ranges from 0.92 to 0.98; the guide vane coordination coefficient k θ The value is 0.02±0.005; in some embodiments, in model formula 3, the dynamic compensation coefficient β of the pumped storage mode is 0.05~0.1; in some embodiments, in model formula 4, the first PI controller parameter K p The value ranges from 0.8 to 1.2, and the second PI controller parameter K... i The value ranges from 0.05 to 0.1.

[0012] In some implementations, the insulation safety margin threshold is set to 15%, and the insulation safety margin overcompensation threshold is set to 30%. Power output control specifically includes the following: if the insulation safety margin M < 15%, the IGBT drive voltage is increased, and the converter bus voltage is raised to the converter bus voltage modulation value U. bus,new , If the insulation safety margin M > 30%, then adjust and reduce the IGBT drive voltage, and reduce the converter bus voltage to the converter bus voltage modulation value U. bus,new , .

[0013] In some implementations, step S4 includes the following: the target value of the guide vane opening θ. target Calculated using the following formula: In the formula, θ nThe guide vane opening is the guide vane opening at rated power. The guide vane control system initiates guide vane opening adjustment Δt in advance to synchronize the guide vane opening with the converter power regulation.

[0014] In some implementations, step S4 further includes: if the guide vane adjustment delay time exceeds 300ms, the converter automatically reduces its power output to avoid overloading the turbine, and the change in converter output power is: , where Δt is the guide vane adjustment delay time.

[0015] In some implementations, the feedback optimization logic in step S5 when optimizing parameters includes: if the insulation leakage current I... leak If the threshold value is exceeded, the value of the first correction coefficient k for insulation breakdown voltage in model formula 1 is adjusted to increase the actual insulation breakdown voltage U between converter IGBT modules. break If the power output deviation exceeds the corresponding set threshold, then adjust the first PI controller parameter K in model formula 4. p The value of T is used to speed up the response; if the IGBT temperature T IGBT If the corresponding set threshold is exceeded, the IGBT switching frequency will be reduced to decrease losses.

[0016] In some implementations, step S5 further includes: updating the low-pressure characteristic modeling parameters at regular intervals to adapt to environmental changes; the low-pressure characteristic modeling parameters include a first correction coefficient k for insulation breakdown voltage, a second correction coefficient m for insulation breakdown voltage, and a power correction coefficient α.

[0017] In some implementations, the insulation leakage current I leak The set threshold is ≤5mA, the set threshold for power output deviation is ≤5%, and the IGBT temperature T IGBT The set threshold is ≤85℃.

[0018] Compared with the prior art, the beneficial technical effects of the present invention are as follows: 1. The present invention has high accuracy in low-pressure insulation control and significantly reduces the risk of failure; the present invention introduces a Paschen curve correction model coupled with "pressure-temperature" instead of the single pressure lookup table of the prior art, which can calculate U in real time. break ; at the same time through I leak Feedback optimization of k-value; using the scheme of this invention, in a high-altitude environment (3000m altitude, T=-10℃), the insulation margin of the full-power converter is stably controlled between 15% and 30%. leak With an impedance of ≤3mA, the insulation failure rate is reduced by 90% compared to existing technologies, and the MTBF is extended to over 8000 hours.

[0019] 2. This invention provides stable power output in both modes and ensures that power quality meets standards. This invention establishes separate power correction models for the "power generation-pumped hydro storage" dual modes and introduces a guide vane coordination coefficient k. θ The dynamic compensation coefficient β of the pumped hydro storage mode is used instead of the fixed power control of the prior art; with the solution of the present invention, the power output deviation ΔP≤3%, the harmonic content THD≤3.5%, and the power quality is improved by 40%.

[0020] 3. This invention features good turbine-converter coordination, resulting in high unit efficiency after modification; this invention adds a turbine-converter coordinated execution module, through θ target Predictive adjustment and delay compensation solve the problem of asynchronous operation between guide vanes and converter in retrofit scenarios, which is not considered in existing technologies. Using the solution of this invention, the overall efficiency of the unit is improved by 10% to 12% compared with that before the retrofit; if existing technologies are used, the efficiency will decrease by 8% to 12%.

[0021] 4. This invention is low in cost and easy to implement, making it suitable for the needs of small and medium-sized power plants. This invention can use a low-cost MCU (microcontroller unit) with advanced and simple control algorithms, while utilizing the existing turbine guide vane control system without the need for additional hardware. Using the solution of this invention, the cost of retrofitting a single unit is reduced by 25% compared to existing technologies, and the retrofitting cycle is shortened to 15 days.

[0022] 5. This invention has strong environmental adaptability and covers a wide altitude range; this invention optimizes parameters such as k, m, and α in real time through a feedback module, rather than using fixed parameters in existing technologies; the solution of this invention covers high-altitude areas of 3000-5000m, with an applicable air pressure range of 50-70kPa and an applicable temperature range of -30℃-40℃, which can meet the needs of most high-altitude areas in western my country. Attached Figure Description

[0023] Figure 1 is a basic flowchart of a method according to an embodiment of the present invention.

[0024] Figure 2 is a detailed flowchart of a method according to an embodiment of the present invention. Detailed Implementation

[0025] This invention provides a low-pressure adaptive modulation method for converters used in high-altitude variable-speed pumped-storage (VPS) retrofits. Specifically, it is a low-pressure adaptive modulation method for full-power converters used in VPS retrofits of small and medium-sized hydropower stations at high altitudes. The main purpose is to address three major problems encountered by full-power converters during VPS retrofits at small and medium-sized hydropower stations at high altitudes (≥3000m): high risk of insulation breakdown, large power output fluctuations, and incompatibility with existing turbine operating conditions due to the low-pressure environment (reduced air insulation strength, increased IGBT switching losses). The invention achieves dynamic adaptation of the full-power converter during the dual-mode switching of power generation and pumped-storage, while simultaneously meeting the needs of small and medium-sized power stations for low-cost retrofits, simplified control, and rapid response, ensuring the safe and stable operation of the retrofitted unit and power quality.

[0026] First, the technical terms involved in this invention are explained as follows: 1. High altitude: This invention is applicable to areas with an altitude ≥ 3000m, where the atmospheric pressure is ≤ 70kPa (standard atmospheric pressure 101.3kPa), and the air insulation strength decreases significantly with decreasing air pressure; 2. Small and medium-sized variable speed pumped storage power station: This invention is for the renovation of existing small and medium-sized hydropower stations with an installed capacity of less than 300MW, using the original hydropower station's dam, reservoir, turbine, powerhouse, etc., without constructing new upper and lower reservoirs, dams, water conveyance facilities, etc.; 3. Full-power converter: An instrument used for the dual-mode switching of "power generation-pumped storage" in small and medium-sized variable speed pumped storage units. The rated power must match the installed capacity of the unit and must simultaneously achieve power generation and pumped storage. Energy conversion and power regulation; the solution of this invention adopts a full-power converter, which will be referred to as the converter in other parts of this article; 4. Low-pressure adaptive modulation: for high-altitude and low-pressure environments, the converter insulation control parameters and power output parameters are dynamically corrected through algorithms to avoid insulation faults and power fluctuations; 5. Power generation-pumped storage dual mode: the modified small and medium-sized variable speed pumped storage unit has two operating modes: power generation mode (the turbine drives the generator, and the converter generates electricity in connection with the grid), and pumped storage mode (the grid drives the motor to drive the energy storage pump to pump water for energy storage, and the converter realizes power conversion); 6. Paschen's law: at a constant temperature, for a certain gas and electrode material, its breakdown voltage U b It is a function of the product of gas pressure p and electrode gap distance d: U b =f(pd); 7. Paschen curve: a curve describing the relationship between “gas breakdown voltage - gas pressure × electrode spacing (P × d)”.

[0027] Existing technologies have failed to solve the complex problems of "high altitude + small and medium-sized variable speed pumped storage retrofit + dual-mode coordination" and cannot meet the requirements under these complex conditions. More specifically, existing technologies have the following shortcomings.

[0028] Disadvantage 1: It is not suitable for dynamic loads with both variable speed pumped water storage and dynamic load modes, resulting in large fluctuations in power output.

[0029] Reasons: Existing technologies only adjust insulation parameters for fixed constant power loads with a single power generation mode, without addressing dynamic power regulation; or although dual modes are distinguished, the power loss changes caused by high altitude and low air pressure are not considered in the pumping mode.

[0030] Conclusion: Using existing technology, after the high-altitude small and medium-sized variable speed pumped storage retrofit, the full-power converter has a power output deviation ΔP ≥ 15% and a harmonic content THD ≥ 6% when switching between "power generation and pumped storage", which leads to a decline in the power quality of the power grid.

[0031] Disadvantage 2: Paschen curve correction under low pressure is not considered, resulting in a high risk of insulation failure.

[0032] Reason: Existing technologies only compensate voltage based on the "air pressure-insulation margin" comparison table, without considering the influence of temperature on insulation breakdown voltage; or they do not involve high-altitude, low-air-pressure scenarios and directly use insulation parameters from plain areas.

[0033] Conclusion: Using existing technology, in high-altitude environments, such as 3000m altitude and -10℃ temperature, the actual insulation breakdown voltage of the full-power converter is 20% to 25% lower than the calculated value, which makes it easy for IGBT module breakdown and bus flashover faults to occur, and the mean time between failures (MTBF) is shortened by 50% compared with the design value.

[0034] Disadvantage 3: The turbine-converter coordination was not considered for the modification scenario, resulting in low overall unit efficiency.

[0035] Reason: Existing technology does not take into account the hydraulic characteristics of the original turbine, such as the relationship between the guide vane opening θ and the water flow torque, and only controls the converter independently; while the adjustment of the original turbine guide vanes is a mechanical movement, which has a delay, while the converter is an electrical electronic device, and the power regulation is at the millisecond level with no delay, so the two are not synchronized.

[0036] Conclusion: Using existing technology, the converter power regulation speed is faster than the guide vane regulation speed, resulting in "overload" or "underload" of the turbine. The overall efficiency of the unit after the modification is 10% to 15% lower than the original design value.

[0037] This invention addresses three major challenges: "low-pressure characteristic modeling + dual-mode adaptive modulation + turbine-converter coordination." Through closed-loop control of five core modules—"data acquisition, low-pressure modeling, adaptive modulation, collaborative execution, and feedback optimization"—it constructs a full-power converter modulation system adapted for the variable-speed pumped storage retrofit of small and medium-sized hydropower stations at high altitudes, enabling precise control of converters used in high-altitude small and medium-sized variable-speed pumped storage retrofits.

[0038] The five core modules of this invention specifically include: 1. Multi-parameter data acquisition module: Real-time acquisition of high-altitude environmental parameters: atmospheric pressure P, ambient temperature T; full-power converter operating parameters: IGBT temperature T IGBT Output voltage U out Output current I out ; Unit operating parameters: power generation / pumped storage mode S, existing turbine guide vane opening θ; 2. Low pressure characteristic modeling module: calculates the insulation breakdown voltage threshold of the full-power converter under low pressure based on the Paschen curve correction model, and establishes a power output correction model in combination with the dual-mode load characteristics of small and medium-sized variable speed pumped storage; 3. Low pressure adaptive modulation module: dynamically adjusts the IGBT drive voltage and the output power of the full-power converter according to the modeling results, and establishes a dynamic compensation coefficient for the "power generation-pumped storage" switching; 4. Turbine-converter coordinated modulation and execution module: synchronously sends the modulation command to the full-power converter IGBT and the existing turbine guide vane control system to ensure that the converter power regulation matches the turbine hydraulic characteristics; 5. Status monitoring and feedback module: monitors the insulation status of the full-power converter in real time (insulation leakage current I leak The power output deviation (ΔP) is dynamically optimized to form a closed-loop control.

[0039] More specifically, the acquisition parameters and equipment of the (first module) multi-parameter data acquisition module are shown in the table below.

[0040]

[0041] The data acquisition categories include environmental parameters, full-power converter operating parameters (referred to as converter operating parameters), and unit operating condition parameters. Environmental parameters include atmospheric pressure (P) and ambient temperature (T). Relevant acquisition equipment includes high-precision barometric pressure sensors and temperature sensors, with a sampling frequency of, for example, 1 Hz. The accuracy requirement for atmospheric pressure (P) is, for example, ±0.1 kPa, and the accuracy requirement for ambient temperature (T) is, for example, ±0.5℃. Converter operating parameters include IGBT temperature (T). IGBT Output voltage U out Output current I out Furthermore, it may also include insulation leakage current I. leak Related data acquisition devices include thermocouples, voltage Hall sensors, current Hall sensors, and leakage current sensors, with a sampling frequency of, for example, 10kHz, and IGBT temperature T. IGBT The accuracy requirement is, for example, ±0.5℃, and the output voltage U out The accuracy requirement is, for example, ±0.5%, and the output current I... outThe accuracy requirement is, for example, ±0.5%. Unit operating parameters include the power generation / pumped storage mode (operating mode) S (value 1 for power generation mode, 0 for pumped storage mode) and the original turbine guide vane opening θ. Related data acquisition equipment includes, for example, an operating mode switching switch and an angle sensor. The sampling frequency is, for example, 0.5Hz, and the accuracy requirement for the guide vane opening θ is, for example, ±1°. The data transmission method of the multi-parameter data acquisition module is, for example, to transmit the acquired data to the main control unit of the overall system via a CAN bus.

[0042] (Second Module) Low Pressure Characteristics Modeling Module: Based on Paschen's Law and the dual-mode load characteristics of small and medium-sized variable speed pumped storage, the following model is established.

[0043] Considering the coupling effect of "air pressure P-temperature T" in high-altitude environments, the Paschen's law formula is modified to form a low-pressure insulation breakdown voltage model (model formula 1): In the formula, U break U0 represents the actual insulation breakdown voltage between the IGBT modules of the converter (unit: V); U0 represents the insulation breakdown voltage under standard conditions (determined by the converter hardware parameters, typically 1500V); standard environment refers to standard atmospheric pressure P0 and standard ambient temperature T0, where standard atmospheric pressure P0 = 101.3 kPa and standard ambient temperature T0 = 293 K; P represents the actual atmospheric pressure collected (unit: kPa); T represents the actual ambient temperature collected (unit: K); k and m are the first and second correction coefficients for insulation breakdown voltage, respectively (determined through field experimental fitting, for example, k = 0.9 ± 0.05, m = 0.55 ± 0.05).

[0044] Considering the increased switching losses of IGBTs under low pressure and the characteristics of dual-mode loads, a low-pressure power output correction model (or power generation mode correction model) is established (Model Formula 2): In the formula, P out,gen P represents the target output power of the converter in power generation mode (unit: kW); n Rated power of the converter (unit: kW); α is the power correction factor (determined through field experimental fitting, for example, α = 0.35 ± 0.05, reflecting the effect of low air pressure on power); η adapt For adaptive modulation efficiency (e.g., 0.92–0.98, determined by IGBT switching frequency optimization); k θ Δθ is the guide vane coordination coefficient (e.g., 0.02 ± 0.005, reflecting the effect of guide vane opening change on power); Δθ is the guide vane opening deviation; the other symbols are the same as in model formula 1.

[0045] In addition, a power correction model for pumped hydro storage mode is established (model formula 3): In the formula, P out,pump β is the target output power of the converter in pumped storage mode (unit: kW); β is the dynamic compensation coefficient in pumped storage mode (e.g., 0.05 to 0.1, to compensate for load changes during pumping); the other symbols are the same as in model formula 1 and model formula 2.

[0046] (Third Module) The low-pressure adaptive modulation module implements adaptive modulation in two parts: "insulation margin control" and "power output control" based on the modeling results of the low-pressure characteristic modeling module.

[0047] Insulation margin control includes the following: Calculating the insulation safety margin: In the formula, M is the insulation safety margin, and U bus The converter bus voltage is typically 1200V. If M < 15% (insulation safety margin threshold, taken as 15% here), then adjust and increase the IGBT drive voltage to raise the converter bus voltage to the converter bus voltage modulation value U. bus,new , This ensures that the modulated insulation safety margin is greater than or equal to the insulation safety margin safety threshold. If M > 30% (the insulation safety margin exceeds the compensation threshold, which is 30% here), then the IGBT drive voltage is adjusted to reduce the converter bus voltage to the modulated value U of the converter bus voltage. bus,new , This is to ensure that the modulated insulation safety margin is less than or equal to the insulation safety margin over-compensation threshold, thus avoiding excessive power loss.

[0048] Power output control includes the following: A "PI + feedforward" composite control algorithm is used to control the output power of the full-power converter to track the target value P. out,gen (In power generation mode) or P out,pump (In pumped storage mode), the specific power control output model is as follows (model formula 4): In the formula, ΔD is the change in the converter modulation ratio; K p K i These are the parameters for the first PI controller and the second PI controller (determined via particle swarm optimization, for example, K). p The value ranges from 0.8 to 1.2, K i (Values ​​range from 0.05 to 0.1); P target For target power (P) target In power generation mode, it is P. out,gen In pumped hydro storage mode, it is P out,pump ); P actual This represents the actual output power; D ff This is the feedforward compensation amount (determined through field testing).

[0049] Calculate the change in converter modulation ratio ΔD according to model formula 4, and adjust the converter modulation ratio accordingly.

[0050] (Fourth Module) Turbine-Converter Co-modulation and Execution Module, mainly used to solve the problem of co-modulation between the converter and the original turbine during the renovation of existing hydropower stations. Specifically, it includes the following: synchronously sending converter modulation commands to the turbine guide vane control system and providing the target value of guide vane opening: In the formula, θ target θ is the target value for guide vane opening. n The guide vane opening is at rated power, typically 80°. The guide vane control system employs "predictive regulation," initiating guide vane opening adjustment 200ms in advance (guide vane adjustment delay time, taken as 200ms here) to ensure synchronization with converter power regulation. If the guide vane adjustment delay time exceeds 300ms, the converter automatically reduces power output to avoid turbine overload. The change in converter output power is: , where Δt is the guide vane adjustment delay time.

[0051] (The fifth module) Status Monitoring and Feedback module specifically includes the following: real-time monitoring of key indicators, including insulation leakage current I. leak (Threshold ≤ 5mA), power output deviation (target power P) target With actual output power P actual The absolute value of the difference (threshold ≤ 5%), IGBT temperature T IGBT (Threshold ≤ 85℃).

[0052] Feedback optimization logic, including: If I leak If the voltage exceeds the corresponding set threshold (e.g., >5mA), then increase the value of the first correction coefficient k for insulation breakdown voltage in the low-pressure insulation breakdown voltage model (model formula 1) (e.g., +0.02) to improve the actual insulation breakdown voltage U between the converter IGBT modules. break If the power output deviation exceeds the corresponding set threshold (e.g., >5%), then adjust the first PI controller parameter K in the power control output model (model formula 4). p The value (e.g., +0.1) is used to speed up the response; if the IGBT temperature T IGBT If the temperature exceeds the corresponding set threshold (e.g., >85℃), the IGBT switching frequency is reduced (e.g., from 10kHz to 8kHz) to reduce losses.

[0053] The modeling parameters of the low-pressure characteristic modeling module (including the first correction coefficient k of insulation breakdown voltage, the second correction coefficient m of insulation breakdown voltage, and the power correction coefficient α) are updated every certain period of time (e.g., 100ms) to ensure long-term adaptation to changes in high-altitude environments.

[0054] The simplified overall system control flow is shown in Figure 1. In summary, it is as follows: parameter acquisition → low pressure modeling → determining unit operating conditions → insulation-power coordinated modulation → machine-transformer coordinated execution → status monitoring → parameter feedback optimization (loop).

[0055] Please refer to Figure 2. The overall system control flow of the preferred embodiment of the present invention specifically includes the following steps: First, start node: start the system; Step S1, data acquisition: acquire atmospheric pressure P, ambient temperature T, and IGBT temperature T. IGBT Output voltage U out Output current I out Operating mode S, guide vane opening θ; Step S2, low pressure modeling: Substitute into model formula 1 to calculate the actual insulation breakdown voltage U between converter IGBT modules. break Substitute the data collected in step S1 into model formulas 2 and 3 to calculate the target power P. target Among them, the operating condition is determined: if the operating mode S=1 (the operating mode is the power generation mode), then model formula 2 is executed, and the target output power P of the converter in the power generation mode is calculated. out,gen That is, the target power P target If the operating mode S=0 (operating mode is pumped storage mode), then execute model formula 3, and calculate the target output power P of the converter in pumped storage mode. out,pump That is, the target power P target Step S3, Insulation-Power Co-modulation: Calculate the insulation safety margin M, and determine whether M is between the set insulation safety margin safety threshold and the insulation safety margin overcompensation threshold (e.g., between 15% and 30%). If so, perform power output control; otherwise, perform insulation margin control. Step S4, Co-execution: Send the target power P. target Send the target value θ of the guide vane opening to the converter. target To the guide vane control system; Step S5, Status monitoring: Collect insulation leakage current I leak Power output deviation, IGBT temperature T IGBT The system checks whether the threshold is exceeded. If it is, it feeds back the optimization parameters; otherwise, it proceeds to the next step. Step S6, loop node: returns to step S1 (i.e., the "data acquisition" step) and continues closed-loop control. Finally, it enters the end node as needed: system shutdown.

[0056] This invention breaks through the technical bottleneck of "high altitude + small and medium-sized variable speed pumped storage energy transformation". Through "multi-dimensional coupling modeling + collaborative adaptive modulation + minimal invasive design", it balances the contradiction between accuracy, cost and environment. Its key points are mainly the following three aspects.

[0057] Key Point 1: Multi-dimensional coupling modeling of "low-pressure characteristics - dual-mode load - retrofitting"; existing technologies only consider "insulation" or "power" in isolation. This invention is the first to couple the Paschen insulation effect at high altitude and low pressure, the dynamic power load of dual-mode pumped storage in small and medium-sized variable speed pumped water storage, and the synergy of the original guide vanes in multiple dimensions to establish an integrated model of "insulation-power-hydraulic", which solves the limitation of "single-dimensional control" in existing technologies.

[0058] Key Point 2: "Insulation-Power" Coordinated Adaptive Modulation Strategy; Addressing the contradiction between "insulation and power constraints" in high-altitude converters, this invention proposes a coordinated strategy of "dynamic range control of insulation margin (15%~30%) + power feedforward compensation": This avoids insulation breakdown while simultaneously achieving power feedforward compensation (D... ff It offsets the power loss caused by voltage increase, achieving a balance between "insulation safety" and "power stability".

[0059] Key Point 3: Minimal Intrusive Collaborative Design in Retrofitting Scenarios; This invention fully considers the need to "utilize existing facilities" in the retrofitting of small and medium-sized hydropower stations. It does not change the hardware of the original turbine guide vane control system, but only achieves turbine-converter collaboration through "predictive adjustment + delay compensation" at the software level, thus avoiding the high cost and environmental impact of "dismantling and modifying the original hydropower station" in existing technologies.

[0060] Based on the comparison between the technical solution of this invention and the prior art, the following advantages can be derived through causal reasoning of "technical features → direct effects → ultimate advantages".

[0061] Advantage 1: High precision in low-pressure insulation control, significantly reducing the risk of failure; Reason: This invention introduces a Paschen curve correction model coupled with "pressure-temperature" instead of the single pressure lookup table of existing technologies, enabling real-time calculation of U... break ; at the same time through I leak Feedback optimization of k-value; Conclusion: In high-altitude environments (3000m altitude, T=-10℃), the insulation margin of the full-power converter is stably controlled between 15% and 30%. leak With an impedance of ≤3mA, the insulation failure rate is reduced by 90% compared to existing technologies, and the MTBF is extended to over 8000 hours.

[0062] Advantage 2: Stable power output in both modes, and power quality meets standards; Reason: This invention establishes power correction models for both "power generation-pumped hydro storage" modes, and introduces the guide vane coordination coefficient k. θ The dynamic compensation coefficient β of the pumped hydro storage mode is used instead of the fixed power control of existing technologies; the conclusion is that the power output deviation ΔP ≤ 3%, the harmonic content THD ≤ 3.5%, and the power quality is improved by 40%.

[0063] Advantage 3: Good turbine-converter coordination, resulting in high unit efficiency after modification; Reason: This invention adds a turbine-converter coordinated modulation and execution module, through θ target Predictive regulation and delay compensation address the asynchrony issue between the guide vanes and the converter in retrofit scenarios, a problem not considered in existing technologies. Conclusion: The overall unit efficiency is improved by 10% to 12% compared to before the retrofit; if existing technologies are used, the efficiency will actually decrease by 8% to 12%.

[0064] Advantage 4: Low cost and easy to implement, suitable for the needs of small and medium-sized power plants; Reason: This invention can use a low-cost MCU (microcontroller unit), with advanced and simple control algorithms, and utilizes the existing turbine guide vane control system, without the need for additional hardware; Conclusion: The cost of retrofitting a single unit is reduced by 25% compared to existing technologies, and the retrofitting cycle is shortened to 15 days.

[0065] Advantage 5: Strong environmental adaptability, covering a wide altitude range; Reason: This invention optimizes parameters such as k, m, and α in real time through a feedback module, rather than using fixed parameters in existing technologies; Conclusion: It covers high-altitude areas of 3000-5000m, with an applicable air pressure range of 50-70kPa and an applicable temperature range of -30℃ to 40℃, which can meet the needs of most high-altitude areas in western my country.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; obviously, the described embodiments are some embodiments of the present invention, but not all embodiments; based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention; in the absence of conflict, the embodiments and features in the embodiments of the present invention can be combined with each other; modifications to the technical solutions described in the foregoing embodiments, or equivalent substitutions for some of the technical features, do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for low-pressure adaptive modulation of a converter used in high-altitude variable-speed pumped-storage energy storage retrofit, characterized in that, The steps include: Step S1, Data Acquisition: Acquire atmospheric pressure P, ambient temperature T, and IGBT temperature T. IGBT Output voltage U out Output current I out Operating mode S, guide vane opening θ; Step S2, low pressure modeling: Substitute the data collected in step S1 into model formula 1 to calculate the actual insulation breakdown voltage U between converter IGBT modules. break Substitute the values ​​into model formulas 2 and 3 to calculate the target power P. target Among them, the operating condition is determined: if the operating mode S is the power generation mode, then model formula 2 is executed, and the target output power P of the converter in the power generation mode is calculated. out,gen That is, the target power P target If the operating mode S is pumped storage mode, then execute model formula 3 to calculate the target output power P of the converter in pumped storage mode. out,pump That is, the target power P target Model formula 1 is: In the formula, U0 is the insulation breakdown voltage under standard conditions; standard environment refers to the environment under standard atmospheric pressure P0 and standard ambient temperature T0, where standard atmospheric pressure P0 = 101.3 kPa and standard ambient temperature T0 = 293 K; P is the actual atmospheric pressure collected; T is the actual ambient temperature collected; k and m are the first and second correction coefficients for insulation breakdown voltage, respectively; Model formula 2 is: In the formula, P n η is the rated power of the converter; α is the power correction factor; η is the rated power of the converter. adapt For adaptive modulation efficiency; k θ Δθ is the guide vane coordination coefficient; Δθ is the guide vane opening deviation; Model formula 3 is: In the formula, β is the dynamic compensation coefficient of the pumped hydro storage mode; Step S3, insulation-power coordinated modulation: calculate the insulation safety margin M, and determine whether M is between the set insulation safety margin safety threshold and the insulation safety margin overcompensation threshold. If so, power output control is performed; otherwise, insulation margin control is performed. The insulation safety margin is calculated using the following formula: In the formula, M is the insulation safety margin, and U bus The converter bus voltage is used for insulation margin control, which includes the following: If the insulation safety margin M < the insulation safety margin threshold, the IGBT drive voltage is adjusted to increase the converter bus voltage so that the modulated insulation safety margin is greater than or equal to the insulation safety margin threshold; if the insulation safety margin M > the insulation safety margin over-compensation threshold, the IGBT drive voltage is adjusted to decrease the converter bus voltage so that the modulated insulation safety margin is less than or equal to the insulation safety margin over-compensation threshold; power output control includes the following: Calculate the converter modulation ratio change ΔD according to model formula 4, and adjust the converter modulation ratio accordingly; model formula 4 is: In the formula, ΔD is the change in the converter modulation ratio; K p K i These are the parameters of the first PI controller and the second PI controller, respectively; P actual This represents the actual output power; D ff For feedforward compensation; Step S4, Cooperative execution: Transmit target power P target Send the target value θ of the guide vane opening to the converter. target To the guide vane control system; Step S5, Status monitoring: Collect insulation leakage current I leak Power output deviation, IGBT temperature T IGBT Determine whether the corresponding set threshold is exceeded. If so, feed back the optimization parameters; otherwise, proceed to the next step. Step S6: Loop: Return to step S1 and continue closed-loop control.

2. The low-pressure adaptive modulation method for a high-altitude variable-speed pumped-storage energy storage retrofit converter according to claim 1, characterized in that, The altitude of the site of the high-altitude small and medium-sized hydropower station is ≥3000m, and / or the atmospheric pressure of the site of the high-altitude small and medium-sized hydropower station is ≤70kPa.

3. The low-pressure adaptive modulation method for a high-altitude variable-speed pumped-storage energy storage retrofit converter according to claim 1, characterized in that, When retrofitting high-altitude small and medium-sized hydropower stations with variable-speed pumped storage, the existing dams, reservoirs, turbines, and powerhouses of the hydropower stations shall be used, and no new upper reservoirs, lower reservoirs, dams, or water conveyance facilities shall be constructed; and / or, the installed capacity of high-altitude small and medium-sized hydropower stations shall be below 300MW.

4. The low-pressure adaptive modulation method for a high-altitude variable-speed pumped-storage energy storage retrofit converter according to claim 1, characterized in that, In model formula 1, the first correction coefficient k and the second correction coefficient m for insulation breakdown voltage are determined through field experimental fitting; in model formula 2, the power correction coefficient α is determined through field experimental fitting, and the power correction coefficient α is used to reflect the influence of low air pressure on power; the guide vane coordination coefficient k θ To reflect the impact of guide vane opening changes on power; in model formula 3, the dynamic compensation coefficient β of the pumped storage mode is used to compensate for sudden load changes during pumping; in model formula 4, the first PI controller parameter K p Second PI controller parameter K i The feedforward compensation amount D is determined using the particle swarm optimization algorithm. ff This was determined through on-site testing.

5. The low-pressure adaptive modulation method for a high-altitude variable-speed pumped-storage energy storage retrofit converter according to claim 1, characterized in that, In model formula 1, the insulation breakdown voltage U0 under standard conditions is 1500V; the first correction coefficient k for insulation breakdown voltage is 0.9±0.05, and the second correction coefficient m for insulation breakdown voltage is 0.55±0.05; in model formula 2, the power correction coefficient α is 0.35±0.05; η adapt The value ranges from 0.92 to 0.98; the guide vane coordination coefficient k θ The value is 0.02±0.005; in model formula 3, the dynamic compensation coefficient β of the pumped storage mode is 0.05~0.1; in model formula 4, the first PI controller parameter K p The value ranges from 0.8 to 1.2, and the second PI controller parameter K... i The value ranges from 0.05 to 0.

1.

6. The low-pressure adaptive modulation method for a high-altitude variable-speed pumped-storage energy storage retrofit converter according to claim 1, characterized in that, The insulation safety margin threshold is set at 15%, and the insulation safety margin overcompensation threshold is set at 30%. Power output control specifically includes the following: if the insulation safety margin M < 15%, the IGBT drive voltage is increased, and the converter bus voltage is raised to the converter bus voltage modulation value U. bus,new , If the insulation safety margin M > 30%, then adjust and reduce the IGBT drive voltage, and reduce the converter bus voltage to the converter bus voltage modulation value U. bus,new , 。 7. The low-pressure adaptive modulation method for a high-altitude variable-speed pumped-storage energy storage retrofit converter according to claim 1, characterized in that, Step S4 includes the following: the target value of the guide vane opening θ target Calculated using the following formula: In the formula, θ n The guide vane opening is the guide vane opening at rated power. The guide vane control system initiates guide vane opening adjustment Δt in advance to synchronize the guide vane opening with the converter power regulation.

8. The low-pressure adaptive modulation method for a high-altitude variable-speed pumped-storage energy storage retrofit converter according to claim 1 or 7, characterized in that, Step S4 also includes: if the guide vane adjustment delay time exceeds 300ms, the converter automatically reduces its power output to avoid overloading the turbine. The change in converter output power is: , where Δt is the guide vane adjustment delay time.

9. The low-pressure adaptive modulation method for a high-altitude variable-speed pumped-storage energy storage retrofit converter according to claim 1, characterized in that, In step S5, the feedback optimization logic for optimizing parameters includes: if the insulation leakage current I... leak If the threshold value is exceeded, the value of the first correction coefficient k for insulation breakdown voltage in model formula 1 is adjusted to increase the actual insulation breakdown voltage U between converter IGBT modules. break If the power output deviation exceeds the corresponding set threshold, then adjust the first PI controller parameter K in model formula 4. p The value of T is used to speed up the response; if the IGBT temperature T IGBT If the corresponding set threshold is exceeded, the IGBT switching frequency is reduced to reduce losses. Step S5 also includes updating the low-pressure characteristic modeling parameters every once in a while to adapt to environmental changes. The low-pressure characteristic modeling parameters include the first correction coefficient k for insulation breakdown voltage, the second correction coefficient m for insulation breakdown voltage, and the power correction coefficient α.

10. The low-pressure adaptive modulation method for a high-altitude variable-speed pumped-storage energy storage retrofit converter according to claim 1 or 9, characterized in that, Insulation leakage current I leak The set threshold is ≤5mA, the set threshold for power output deviation is ≤5%, and the IGBT temperature T IGBT The set threshold is ≤85℃.

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