Solid heat storage system based on green electricity consumption and power factor compensation control method thereof

Abstract

This invention discloses a solid-state thermal energy storage system based on green electricity consumption and its power factor compensation control method, belonging to the field of high-voltage energy storage and power quality management. The system includes a green electricity power supply bus, a high-voltage power control cabinet, and a solid-state thermal energy storage device connected in sequence, as well as an SVG (Static Var Generator) and a comprehensive controller connected in parallel to the incoming side of the power control cabinet. The method includes: the controller calculating the target active power based on the real-time output of wind and solar power and adjusting the firing angle of the power control cabinet; high-speed sampling of the bus voltage and current, extracting the lagging reactive power component generated by phase-shift control based on instantaneous reactive power theory; and controlling the SVG to output an equal and opposite phase capacitive reactive current for local compensation within 5ms. This invention solves the problem of the power factor plummeting to 0.5–0.7 due to thyristor phase-shift power control, stabilizing the power factor at the grid connection point above 0.98 across the entire power control range, while suppressing voltage flicker and harmonics, achieving efficient and economical green electricity consumption and thermal storage.

Description

Technical Field

[0001] This invention belongs to the field of high-voltage, large-capacity energy storage and power quality management technology, specifically involving a system and control method for utilizing solid thermal storage devices to absorb green electricity such as wind and solar power, and combining them with static var generators for dynamic power factor compensation. Background Technology

[0002] Driven by the "dual carbon" goals, the installed capacity of green electricity, represented by wind and solar power, has grown rapidly. However, wind and solar power generation is characterized by strong intermittency, volatility, and anti-peak-shaving features, leading to difficulties in grid absorption and frequent instances of wind and solar curtailment. Solid-state thermal storage devices, such as solid-state electric thermal storage boilers, can convert surplus green electricity into high-temperature heat energy for storage, representing an important technological path for large-scale absorption of green electricity and the realization of clean heating and industrial steam supply.

[0003] To keep pace with the random fluctuations in wind and solar power output, solid-state thermal energy storage systems commonly employ high-voltage power control cabinets based on thyristor phase-shift control to continuously adjust heating power. These cabinets typically operate at 6kV, 10kV, or 35kV. However, phase-shift trigger control introduces a serious drawback while regulating power: as the thyristor conduction angle decreases, the current waveform becomes distorted and lags behind the voltage, generating significant amounts of lagging reactive power. Especially under light load or deep power regulation conditions, the system's power factor can plummet to below 0.5-0.7, far below the grid-specified standard of 0.9.

[0004] Low power factor can trigger a series of problems: businesses face hefty power factor penalties; reactive power circulation increases transformer and line losses, reducing the actual utilization efficiency of green electricity; and it can also cause grid voltage fluctuations and flicker, endangering equipment safety. Traditional compensation methods using fixed capacitors or mechanically switched reactors have slow response times, cannot match the rapid changes in wind and solar power output on a second- or minute-by-minute basis, and are prone to resonance with the phase-shift control of the power control cabinet, thus failing to meet requirements. Summary of the Invention

[0005] This invention aims to solve the core problems of low power factor and lagging reactive power compensation in existing solid thermal energy storage devices due to the use of phase-shifting power regulation. It provides a solid thermal energy storage system based on green electricity consumption and its power factor compensation control method.

[0006] To achieve the above objectives, this invention proposes a system scheme comprising a high-voltage power control cabinet, a solid-state thermal storage device, a static var generator (SVG), and a comprehensive controller. The input terminal of the high-voltage power control cabinet is connected to the green power supply bus, and its output power is adjusted using a thyristor phase-shift triggering method. The solid-state thermal storage device is connected to its rear end, converting electrical energy into thermal energy for storage. The SVG is installed in parallel on the same incoming bus of the power control cabinet. The comprehensive controller serves as the control core, connecting and coordinating the two sets of equipment.

[0007] This invention also proposes a control method, the core logic of which is as follows: The integrated controller first calculates the target active power of the thermal storage device based on the real-time output of wind and solar power, and controls the firing angle of the power regulating cabinet. Simultaneously, the controller samples the bus voltage and current at high speed, extracts the fundamental reactive component generated by phase-shift control in real time based on instantaneous reactive power theory, and instructs the SVG to immediately output an equal and opposite capacitive reactive current for local cancellation. This dynamic tracking error-free compensation process is completed within milliseconds, ensuring that the power factor at the system grid connection point remains stable above 0.98 regardless of changes in the power regulation depth.

[0008] Solid thermal energy storage systems based on green electricity consumption include the following devices:

[0009] The high-voltage power control cabinet has its input end connected to the green power supply bus, and is used to adjust the active power output to the back end through thyristor phase-shift triggering.

[0010] A solid thermal energy storage device, the input end of which is connected to the output end of the high-voltage power control cabinet, is used to convert electrical energy into thermal energy and store it.

[0011] A static var generator (SVG) is connected in parallel to the incoming busbar of the high-voltage power control cabinet to generate dynamic reactive current.

[0012] The integrated controller is connected to both the high-voltage power control cabinet and the SVG signal.

[0013] The integrated controller is used to calculate the target active power of the solid thermal energy storage device based on the real-time output data of green electricity, thereby controlling the thyristor firing angle of the high-voltage power control cabinet, and detecting the electrical quantity of the incoming bus in real time. It controls the SVG to generate a capacitive reactive current that is opposite in direction and equal in magnitude to the lagging reactive power generated by the high-voltage power control cabinet, so as to maintain the power factor of the system grid connection point above the preset target value.

[0014] As a further improvement, the solid heat storage device includes a high-temperature alloy resistance element, a solid heat storage body, an insulation layer, and a steam heat exchanger; the solid heat storage body is a magnesia brick or a corundum brick, and its heat storage temperature can reach over 600℃. The structure and materials (magnesia brick / corundum brick) of the solid heat storage device are clearly defined, improving the high-temperature resistance and heat storage capacity, and enhancing the system stability and service life.

[0015] As a further improvement, the SVG adopts a fully controlled inverter bridge structure based on IGBT and outputs reactive current through PWM pulse width modulation. By adopting a fully controlled SVG based on IGBT and PWM control, the reactive power regulation accuracy and response speed are improved, and a better dynamic compensation effect is achieved.

[0016] As a further improvement, the integrated controller adopts the PQ method based on instantaneous reactive power theory to extract the fundamental reactive current component of the incoming bus in real time and calculate the reactive power required for compensation. The PQ theory is introduced for reactive power detection to improve the accuracy of reactive power calculation and provide a theoretical basis for accurate compensation.

[0017] As a further improvement, the preset target value is 0.98. The system maintains a power factor of 0.98 or higher at the grid connection point within the full operating range of the solid thermal energy storage device, from 10% to 100% of the rated power. This limits the target value of the power factor and the operating range, ensuring that the system has excellent power quality performance under all operating conditions.

[0018] As a further improvement, the response time of the SVG is less than 5ms, which is used to suppress bus voltage flicker caused by phase shift control of the power control cabinet and sudden changes in green power output, so as to reduce the total harmonic distortion rate of voltage to below 3%. The SVG fast response and harmonic and voltage indicators are specified to significantly improve the power quality and dynamic stability of the system.

[0019] As a further improvement, the high-voltage power control cabinet operates at 6kV, 10kV, or 35kV, limiting the voltage level range, improving the applicability of the system engineering, and facilitating its widespread application.

[0020] A power factor compensation control method for solid thermal energy storage systems based on green electricity consumption, applied to the aforementioned system, is characterized by comprising the following steps:

[0021] Step S1: The integrated controller calculates the target active power P required by the solid thermal energy storage device based on the real-time output of the connected wind farm, photovoltaic power station or hybrid microgrid and the grid dispatch instructions.

[0022] Step S2: The integrated controller calculates and outputs the thyristor firing angle α to the high-voltage power control cabinet based on the target active power P, so as to adjust its output power.

[0023] Step S3: Real-time high-speed sampling of the voltage and current signals of the incoming bus of the high-voltage power regulating cabinet; extraction of the fundamental reactive current component based on instantaneous reactive power theory; calculation of the current reactive power Q and power factor; comparison with the preset target value; and determination of the reactive power ΔQ to be compensated.

[0024] In step S4, the integrated controller controls the SVG to respond immediately and generate a capacitive reactive current that is equal in magnitude and opposite in direction to the current reactive power Q, so as to offset the lagging reactive power generated by the phase shift control of the high-voltage power control cabinet.

[0025] Step S5: When fluctuations in green power output cause changes in the target active power P, repeat steps S1 to S4 to achieve dynamic error-free compensation.

[0026] As a further improvement, in step S3, the preset target value is 0.98; in step S4, the SVG completes the response compensation in less than 5ms, further limiting the response time and power factor targets in the method, and enhancing the feasibility and performance assurance of the control method.

[0027] As a further improvement, the method further includes: when the grid voltage fluctuates abnormally, the integrated controller controls the SVG to output corresponding inductive or capacitive reactive power to assist in grid voltage stability, increase voltage support function, so that the system not only has absorption capacity, but also has the ability to assist the grid in stable operation, thus expanding application value.

[0028] The beneficial effects of this invention are as follows: it achieves dynamic power factor compliance across the entire power regulation range of the solid thermal energy storage device, completely eliminating the risk of grid penalties; it significantly reduces reactive current in lines and transformers, and can increase active heating capacity by more than 15% under the same access capacity, directly increasing the amount of green electricity absorbed; the millisecond-level response of the SVG effectively suppresses voltage fluctuations and flicker, reducing the total harmonic distortion (THD) rate to below 3%, improving the equipment operating environment; the overall system loss is extremely low, and the saved electricity costs and increased green electricity revenue can shorten the investment payback period by 2 to 3 years, and transform the thermal energy storage device from a source of grid disturbance into a friendly and flexible load that can assist in supporting the voltage. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0030] Figure 1 This is a block diagram of a solid thermal energy storage system based on green electricity consumption. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0032] This invention provides a solid thermal energy storage system based on green electricity consumption, including a high-voltage power control cabinet, a solid thermal energy storage device, an SVG, and a comprehensive controller.

[0033] The high-voltage power control cabinet is connected to the green power supply bus and adjusts the output active power through thyristor phase-shift triggering. Its output is connected to a solid thermal storage device. The solid thermal storage device is equipped with high-temperature alloy resistance elements to convert electrical energy into heat energy and store it in a solid thermal storage body made of magnesium bricks or corundum bricks. Its operating temperature can reach over 600℃, and the heat energy is utilized through a steam heat exchanger.

[0034] The SVG is connected in parallel to the incoming bus of the high-voltage power control cabinet. It adopts a fully controlled inverter bridge structure based on IGBT and outputs dynamic reactive current through PWM modulation.

[0035] The integrated controller is communicatively connected to the high-voltage power control cabinet and the SVG, and its core control logic is as follows:

[0036] Calculate the target active power P based on the real-time output and dispatch instructions of wind power, photovoltaic power or microgrid;

[0037] Calculate the thyristor firing angle α based on P, and control the output of the power control cabinet;

[0038] Real-time acquisition of bus voltage and current signals, and extraction of fundamental reactive components based on instantaneous reactive power theory (pq method);

[0039] Calculate the current reactive power Q and the required compensation ΔQ;

[0040] Control the SVG output to produce an equivalent reverse reactive current to achieve error-free compensation.

[0041] During operation, when the green electricity output fluctuates, the system automatically cycles through the above control process to achieve dynamic coordinated adjustment of active and reactive power. Simultaneously, when an abnormal grid voltage is detected, the system controls the SVG to output corresponding inductive or capacitive reactive power to support voltage stability.

[0042] The system is suitable for voltage levels of 6kV, 10kV or 35kV and can maintain a high power factor operation across the entire load range.

[0043] Through the above system and method, the present invention successfully solves the problems of reactive power impact and power quality in the process of flexibly absorbing green electricity in high-pressure solid thermal energy storage devices, and realizes efficient, economical and friendly green electricity absorption and thermal storage.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A solid thermal storage system based on green power accommodation, characterized in that, Includes the following devices: The high-voltage power control cabinet has its input end connected to the green power supply bus, and is used to adjust the active power output to the back end through thyristor phase-shift triggering. A solid thermal energy storage device, the input end of which is connected to the output end of the high-voltage power control cabinet, is used to convert electrical energy into thermal energy and store it. A static var generator (SVG) is connected in parallel to the incoming busbar of the high-voltage power control cabinet to generate dynamic reactive current. The integrated controller is connected to both the high-voltage power control cabinet and the SVG signal. The integrated controller is used to calculate the target active power of the solid thermal energy storage device based on the real-time output data of green electricity, thereby controlling the thyristor firing angle of the high-voltage power control cabinet, and detecting the electrical quantity of the incoming bus in real time. It controls the SVG to generate a capacitive reactive current that is opposite in direction and equal in magnitude to the lagging reactive power generated by the high-voltage power control cabinet, so as to maintain the power factor of the system grid connection point above the preset target value.

2. The green electricity consumption-based solid thermal storage system and its power factor compensation control method according to claim 1, characterized in that, The solid heat storage device includes a high-temperature alloy resistance element, a solid heat storage body, an insulation layer, and a steam heat exchanger; the solid heat storage body is a magnesium brick or a corundum brick, and its heat storage temperature can reach over 600℃.

3. The green power consumption based solid thermal storage system and its power factor compensation control method according to claim 1, characterized in that, The SVG adopts a fully controlled inverter bridge structure based on IGBT and outputs reactive current through PWM pulse width modulation.

4. The green power consumption based solid thermal storage system and its power factor compensation control method according to claim 1, characterized in that, The integrated controller uses the pq method based on instantaneous reactive power theory to extract the fundamental reactive current component of the incoming bus in real time and calculate the amount of reactive power to be compensated.

5. The green power consumption based solid thermal storage system and its power factor compensation control method according to claim 1, characterized in that, The preset target value is 0.98, and the system maintains a power factor of 0.98 or higher at the grid connection point within the full operating range of the solid thermal energy storage device from 10% to 100% of its rated power.

6. The green electricity consumption-based solid thermal storage system of claim 1, wherein, The SVG has a response time of less than 5ms and is used to suppress bus voltage flicker caused by phase shift control of the power control cabinet and sudden changes in green power output, so that the total harmonic distortion rate of the voltage is reduced to below 3%.

7. The green electricity consumption-based solid thermal storage system of claim 1, wherein, The operating voltage of the high-voltage power control cabinet is 6kV, 10kV or 35kV.

8. A power factor compensation control method for a solid thermal energy storage system based on green electricity consumption, applied to the system described in any one of claims 1 to 7, characterized in that, Includes the following steps: Step S1: The integrated controller calculates the target active power P required by the solid thermal energy storage device based on the real-time output of the connected wind farm, photovoltaic power station or hybrid microgrid and the grid dispatch instructions. Step S2: The integrated controller calculates and outputs the thyristor firing angle α to the high-voltage power control cabinet based on the target active power P, so as to adjust its output power. Step S3: Real-time high-speed sampling of the voltage and current signals of the incoming bus of the high-voltage power regulating cabinet; extraction of the fundamental reactive current component based on instantaneous reactive power theory; calculation of the current reactive power Q and power factor; comparison with the preset target value; and determination of the reactive power ΔQ to be compensated. In step S4, the integrated controller controls the SVG to respond immediately and generate a capacitive reactive current that is equal in magnitude and opposite in direction to the current reactive power Q, so as to offset the lagging reactive power generated by the phase shift control of the high-voltage power control cabinet. Step S5: When fluctuations in green power output cause changes in the target active power P, repeat steps S1 to S4 to achieve dynamic error-free compensation.

9. The method according to claim 8, characterized in that, In step S3, the preset target value is 0.98; in step S4, the SVG completes response compensation in less than 5ms.

10. The method according to claim 8, characterized in that, The method further includes: when the grid voltage fluctuates abnormally, the integrated controller controls the SVG to output corresponding inductive or capacitive reactive power to help support grid voltage stability.

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