MMC hybrid energy storage system
The series topology and energy management system of the MMC hybrid energy storage system solves the problem of high cost and low efficiency of the hybrid energy storage system, realizes efficient and reliable grid frequency regulation and auxiliary frequency regulation of thermal power units, and improves equipment stability and efficiency.
Patent Information
- Application Number
- CN202422246936.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-12
- Publication Date
- 2025-09-05
- Estimated Expiration
- 2034-09-12
AI Technical Summary
Existing hybrid energy storage systems are costly and inefficient, especially in terms of manufacturing and operating costs of energy storage equipment, which limits the development of the industry. In addition, the application of hybrid energy storage of lithium batteries and supercapacitors in grid frequency regulation has the problem of low efficiency.
The MMC hybrid energy storage system is adopted, which combines supercapacitors and lithium batteries through a series topology and bridge arm series method, and uses an energy management system and control system to monitor energy consumption and unified scheduling, reducing costs and improving system efficiency.
The high efficiency and reliability of the hybrid energy storage system are achieved, costs are reduced, the service life of lithium batteries and supercapacitors is increased, the frequency regulation capability of the power grid is optimized, and the frequency regulation performance and equipment stability of thermal power units are improved.
Smart Images
Figure CN223309593U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of power grid control, in particular to an MMC hybrid energy storage system. Background Art
[0002] As the proportion of wind and photovoltaic power generation capacity in the power system continues to increase, the centralized access of large-scale, random, and unpredictable power is increasingly complex in areas such as power balance and stability control, posing significant challenges to the safe operation of the power system. The integration of fast-response energy storage technologies can effectively balance power and energy across the power system under various operating conditions, thereby ensuring safe and economical grid operation and improving the utilization efficiency of wind and photovoltaic power generation.
[0003] At present, thermal power units generally have problems such as long response time lag, poor regulation accuracy, and reverse regulation during the frequency regulation process, making it difficult to meet the frequency regulation needs of the power grid. At the same time, the frequent increase and decrease of loads by thermal power units during the frequency regulation process will aggravate equipment fatigue and wear.
[0004] From the power supply side, it refers to a new type of energy storage system in which the energy storage device is connected to the inside of the power plant or the collection station. Its main functions are to combine renewable energy power generation and grid-connected operation, combine peak and frequency regulation of thermal power units, and independently regulate peak and frequency. The energy storage system configured in the new energy power station can smooth the output of new energy, and at the same time achieve transient active power output response and transient voltage emergency support. The energy storage system configured in the thermal power plant can improve the frequency regulation performance indicators of the thermal power units by jointly regulating the frequency of the thermal power units and energy storage facilities.
[0005] Lithium batteries offer advantages such as fast response, high short-term power throughput, and flexible regulation, enabling full power output within milliseconds to seconds. Using lithium battery energy storage systems to assist thermal power units in frequency regulation can effectively improve the units' frequency regulation capabilities and alleviate the pressure on grid frequency regulation assessments. Using lithium battery energy storage systems to assist thermal power units in frequency regulation can avoid frequent power increases and decreases, enabling stable operation near economic operating conditions and achieving energy conservation and emission reductions.
[0006] Supercapacitors, with their high power density, long cycle life, and fast response times, can also assist renewable energy stations and thermal power generators in grid frequency regulation. Under small grid frequency modulation commands, using supercapacitor energy storage systems to assist thermal power generators in frequency regulation can avoid frequent lithium-ion battery activation, significantly extending their service life.
[0007] Hybrid energy storage systems combine lithium batteries and supercapacitors at a specific power / capacity ratio to form a hybrid energy storage system. To fully leverage the advantages of hybrid energy storage systems, the optimal capacity ratio must be determined based on application requirements and system performance. Generally speaking, batteries account for 70% to 80% of the hybrid energy storage system's energy storage capacity, while supercapacitors account for 20% to 30%. This ensures that the system can maintain a stable charge while meeting high power output requirements. Leveraging the respective advantages of these two different types of energy storage to assist in the frequency regulation of thermal power units is a technology with great development potential. In-depth research on the key technologies for hybrid energy storage and supercapacitor-assisted frequency regulation is of great significance for promoting the development of related technologies and the implementation of projects related to hybrid energy storage-assisted frequency regulation.
[0008] Hybrid energy storage currently faces challenges of high costs and low efficiency, particularly in the manufacturing and operating costs of energy storage equipment, which have limited the industry's development. This is primarily due to high R&D and production costs, as well as energy losses during storage and release, which reduce overall efficiency. Summary of the Invention
[0009] The utility model provides an MMC hybrid energy storage system, which realizes supercapacitor energy storage of MMC, adopts an energy management system to improve the efficiency and reliability of the hybrid energy storage system, adopts a series topology structure, changes the previous phase-shifting wiring, adopts a bridge arm series connection method, greatly reduces the cost, and uses the energy management system to realize the monitoring and unified scheduling of various energy consumption.
[0010] In order to achieve the above purpose, the present invention adopts the following technical solutions:
[0011] An MMC hybrid energy storage system includes an energy management system, a control system, an MMC converter valve, and a hybrid energy storage system. The hybrid energy storage system includes a supercapacitor cluster and a lithium battery pack. The AC side of the MMC converter valve is connected to the AC bus, and the DC side is connected to the supercapacitor cluster and the lithium battery pack respectively. The lithium battery pack is connected to the energy management system via a bus. The communication port of the energy management system and the output end of the MMC converter valve are connected to the control system.
[0012] Furthermore, the MMC converter valve includes three upper bridge arms and three lower bridge arms, the upper bridge arms are a plurality of H-bridge power units connected in series, and the H-bridge power unit is composed of four IGBTs, a voltage-equalizing resistor and a DC capacitor.
[0013] Furthermore, the control system includes a bus board, a CPU board, a controller, a PWM board, a digital board, an analog board, a communication board and a display board. The CPU board is connected to the bus board, the bus board is connected to the PWM board, the digital board, the analog board, the communication board and the display board, the controller is connected to the input end of the H-bridge power unit, and the controller is connected to the PWM board of the control system via an optical fiber.
[0014] Furthermore, the energy management system includes an all-in-one monitoring machine, an energy storage converter PCS, a configuration screen, a battery management unit BMU, a battery cluster management unit BCU, a battery array management unit BAU and a bus. The lithium battery pack is evenly divided into several groups, each group is connected to a battery management unit BMU, and multiple battery management units BMU are connected to corresponding battery cluster management units BCU. The interconnected battery packs, battery management units BMU and battery cluster management units BCU are arranged in the same battery cabinet. The battery cluster management units BCU in different battery cabinets are connected to the battery array management unit BAU through a bus. The battery array management unit BAU is connected to the energy storage converter PCS and the configuration screen through a communication line. The all-in-one monitoring machine is connected to the energy storage converter PCS, the battery array management unit BAU and the control system through a LAN bus.
[0015] Furthermore, it also includes a power indicator, an isolation knife switch, a current transformer, a circuit breaker, a charging resistor and a lightning arrester. The isolation knife switch and the circuit breaker are connected in series between the AC bus and the MMC converter valve, the power indicator is connected in parallel on the three-phase power line between the isolation gate and the AC bus, the current transformer is connected in series on the three-phase power line between the isolation knife switch and the circuit breaker, the charging resistor is connected in parallel at both ends of the circuit breaker, and a lightning arrester is arranged on the three-phase power line between the circuit breaker and the MMC converter valve.
[0016] Compared with the prior art, the beneficial effects of the present invention are:
[0017] 1) The hybrid energy storage system connects to the AC busbar through the MMC converter valve to achieve power regulation and grid connection for renewable energy power generation equipment;
[0018] 2) Through supercapacitor energy storage and lithium battery energy storage, the efficiency of the hybrid energy storage system is improved, the response is quickly improved, and the low efficiency of the hybrid energy storage of supercapacitors and battery packs in the existing technology is avoided. The energy management system collects energy consumption and operation information of each energy consumption monitoring point and key equipment, which plays an important role in unified energy scheduling, optimizing energy medium balance, improving environmental protection management level, reducing enterprise comprehensive energy consumption and improving labor productivity, helping customers use energy more effectively, thereby achieving "energy-saving management and green energy efficiency."
[0019] 2) Through the energy management system and control system of this system, the equipment is refined to the equipment level or production line level. Through signal acquisition, communication, protocol conversion and other technical means, the collection of energy medium parameters is isolated from the production control system, providing continuous, real and reliable data basis, realizing the integration of energy management and control, and accurately calculating the energy consumption of each product series, providing a basis for accurate product series cost evaluation;
[0020] 3) Through the control system, the target information is collected and processed, and the automatic control process is carried out, thereby achieving a more efficient and reliable control effect. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 This is a schematic diagram of the connection between the MMC and the AC busbar described in the present invention.
[0022] Figure 2 This is a schematic diagram of the lithium battery energy storage and supercapacitor energy storage system architecture described in this utility model.
[0023] Figure 3 It is a schematic diagram of the communication structure between the control system and the controller of the power unit of the utility model.
[0024] Figure 4 It is a structural diagram of the energy management system described in this utility model. DETAILED DESCRIPTION
[0025] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:
[0026] The utility model discloses an MMC hybrid energy storage system, comprising an energy management system, a control system, an MMC converter valve, and a hybrid energy storage system. The hybrid energy storage system comprises a supercapacitor cluster and a lithium battery pack. The AC side of the MMC converter valve is connected to the AC bus, and the DC side is respectively connected to the supercapacitor cluster and the lithium battery pack. The lithium battery pack is connected to the energy management system via a bus. The communication port of the energy management system and the output end of the MMC converter valve are connected to the control system.
[0027] See Figure 1 In the cascade energy storage system, the MMC converter valve includes three upper bridge arms and three lower bridge arms. The upper bridge arm is a series connection of several H-bridge power units. The H-bridge power unit is composed of four IGBTs, a voltage-equalizing resistor and a DC capacitor. An isolation knife switch and a circuit breaker are connected in series between the AC bus and the MMC converter valve. A power indicator is connected in parallel on the three-phase power line between the isolation knife switch and the AC bus. A current transformer is connected in series on the three-phase power line between the isolation knife switch and the circuit breaker. A charging resistor is connected in parallel at both ends of the circuit breaker. A lightning arrester is arranged on the three-phase power line between the circuit breaker and the MMC converter valve.
[0028] The control system includes a bus board, a CPU board, a controller, a PWM board, a digital board, an analog board, a communication board and a display board. The CPU board is connected to the bus board, and the bus board is connected to the PWM board, the digital board, the analog board, the communication board and the display board. The controller is connected to the input end of the H-bridge power unit. Figure 3 , the controller is connected to the PWM board of the control system through an optical fiber.
[0029] See Figure 4 The energy management system includes an all-in-one monitoring machine, an energy storage converter PCS, a configuration screen, a battery management unit BMU, a battery cluster management unit BCU, a battery array management unit BAU, and a bus. The lithium battery pack is evenly divided into several groups, each group is connected to a battery management unit BMU, and multiple battery management units BMU are connected to corresponding battery cluster management units BCU. The interconnected battery packs, battery management units BMU, and battery cluster management units BCU are arranged in the same battery cabinet. The battery cluster management units BCU in different battery cabinets are connected to the battery array management unit BAU via a bus. The battery array management unit BAU is connected to the energy storage converter PCS and the configuration screen via a communication line. The all-in-one monitoring machine is connected to the energy storage converter PCS, the battery array management unit BAU, and the control system via a LAN bus.
[0030] Working Principle: The voltage level of the energy storage frequency modulation system connected to the grid is usually 6-35kV. Therefore, hundreds or thousands of lithium battery and supercapacitor cells are connected in parallel and used in groups. The energy storage form adopts a cascade energy storage system. By connecting multiple small-capacity, distributed PCS units in series to boost the voltage directly to 6-35kV, the system is directly connected to the grid without passing through a step-up transformer.
[0031] The high-voltage cascade energy storage system does not have parallel connection of battery clusters, nor does it have capacity and efficiency loss caused by current circulation. It is suitable for medium-voltage and high-voltage energy storage systems. The structure of the cascade energy storage system is as follows: Figure 1 As shown in the results, it was found that under different H-bridge power unit numbers and cascade power modules per phase in the high-voltage cascade energy storage system, the comprehensive efficiency of the high-voltage cascade energy storage system (the product of the battery cluster energy utilization rate and the PCS power conversion efficiency) was between 92.66% and 92.84%. The efficiency of the high-voltage cascade energy storage system was significantly improved. The high-voltage cascade structure energy storage system has the advantages of high comprehensive efficiency, strong coordinated control capability, short response time and high reliability. It can be used to assist thermal power units in participating in grid frequency regulation. The DC / DC converter can suppress the DC side second harmonics in the high-voltage cascade energy storage system and avoid the impact of the current second harmonics on the life of the energy storage battery.
[0032] See Figure 2In the hybrid energy storage system, the lithium battery energy storage system and the supercapacitor energy storage system are connected to the power grid system in parallel on the DC bus side. Multiple lithium battery groups constitute the lithium battery energy storage system, which is energy-type energy storage, and multiple supercapacitor clusters constitute the supercapacitor energy storage system, which is power-type energy storage. They are coupled on the DC side, and the converter can connect the DC system and the AC system to realize energy transfer in any direction between the AC and DC systems and the energy storage system. The supercapacitor energy storage system and the lithium battery energy storage system are connected to the AC bus in parallel through their own DC / AC converters and need to be controlled separately. This operation greatly simplifies the system components, improves the efficiency of the hybrid energy storage system, and responds quickly. In addition, MMC has good power quality and high modular integration, and is suitable for high-voltage, large-capacity power transmission and distribution fields. The energy storage system with this topology has been widely used in electric locomotive braking systems and power fluctuation suppression of new energy stations.
[0033] The structure of the MMC cascade hybrid energy storage system can fully utilize the respective advantages of the lithium battery energy storage system and the supercapacitor energy storage system, and optimize the power output of the energy storage system. When a fault occurs in the DC side or AC side system of the MMC, as long as the faulty part of the equipment is removed, the rest of the system equipment can still operate normally, greatly enhancing the reliability of the entire hybrid energy storage system.
[0034] The control system includes a bus board, a CPU board, a controller, a PWM board, a digital board, an analog board, a communication board and a display board. Figure 3 , each H-bridge power unit input is connected to a controller, and each controller is connected to the PWM board via optical fiber. After the control program of the on-site working conditions is downloaded to the control system, the control system generates multi-level PWM control waveforms, realizes fast protection and network communication and other control functions to meet user requirements.
[0035] The all-in-one monitoring machine can display the relationship between energy input, conversion and use, clearly showing what energy the company has purchased, what conversions have been made, what energy is used in each workshop, and how much is used. It can monitor the energy consumption, real-time flow, and quality parameters of key process links in real time, and detect production operating parameters. It can accurately calculate the production capacity of each product series, provide a basis for accurate product series cost evaluation, and also provide a basis for scientific energy consumption cost allocation.
[0036] The integrated monitoring machine can detect the energy transmission network and equipment operating status in real time. It can use current, power, instantaneous flow rate of energy consumption medium, pressure, temperature and other parameters as the basis for equipment diagnosis and operation efficiency analysis, such as Figure 4 As shown, by monitoring key equipment, it is possible to determine the operating status, such as shutdown, standby, normal operation, overload, etc. Different colors of parameters mark the operating conditions of different equipment, timely discover leakage, find energy-saving space, and realize the possibility of energy saving from the management method.
[0037] See Figure 4 The EMS and its subordinate computers, including battery cabinets and other equipment, utilize the CAN communication protocol. The CAN bus uses serial data transmission and can also be connected using fiber optic cables. The bus protocol supports multiple master controllers. The subordinate computers are connected to five battery cabinets, each containing a high-voltage box, a BMU battery pack, and a CSC battery pack, forming an integrated monitoring system.
[0038] Choose an integrated monitoring system (EMS) with charging and discharging functions to monitor the battery pack charging and discharging process. Rationally arrange the charging and discharging operations of energy storage facilities to achieve efficient energy utilization and conservation. By optimizing energy operating efficiency, achieve integrated energy management and control, and reduce operating costs.
[0039] The above embodiments are implemented under the premise of the technical solution of the present utility model, and detailed implementation methods and specific operation processes are given, but the protection scope of the present utility model is not limited to the above embodiments. The methods used in the above embodiments are conventional methods unless otherwise specified.
Claims
1. An MMC hybrid energy storage system, characterized in that: It includes an energy management system, a control system, an MMC converter valve, and a hybrid energy storage system. The hybrid energy storage system includes a supercapacitor cluster and a lithium battery pack. The AC side of the MMC converter valve is connected to the AC bus, and the DC side is connected to the supercapacitor cluster and the lithium battery pack respectively. The lithium battery pack is connected to the energy management system through a bus. The communication port of the energy management system and the output end of the MMC converter valve are connected to the control system.
2. The MMC hybrid energy storage system according to claim 1, characterized in that: The MMC converter valve includes three upper bridge arms and three lower bridge arms. The upper bridge arms are a plurality of H-bridge power units connected in series. The H-bridge power unit is composed of four IGBTs, a voltage-equalizing resistor and a DC capacitor.
3. The MMC hybrid energy storage system according to claim 1, characterized in that: The control system includes a bus board, a CPU board, a controller, a PWM board, a digital board, an analog board, a communication board and a display board. The CPU board is connected to the bus board, and the bus board is connected to the PWM board, the digital board, the analog board, the communication board and the display board. The controller is connected to the input end of the H-bridge power unit, and the controller is connected to the PWM board of the control system via an optical fiber.
4. The MMC hybrid energy storage system according to claim 1, characterized in that: The energy management system includes an all-in-one monitoring machine, an energy storage converter PCS, a configuration screen, a battery management unit BMU, a battery cluster management unit BCU, a battery array management unit BAU and a bus. The lithium battery pack is evenly divided into several groups, each group is connected to a battery management unit BMU, and multiple battery management units BMU are connected to corresponding battery cluster management units BCU. The interconnected battery packs, battery management units BMU and battery cluster management units BCU are arranged in the same battery cabinet. The battery cluster management units BCU in different battery cabinets are connected to the battery array management unit BAU through a bus. The battery array management unit BAU is connected to the energy storage converter PCS and the configuration screen through a communication line. The all-in-one monitoring machine is connected to the energy storage converter PCS, the battery array management unit BAU and the control system through a LAN bus.
5. The MMC hybrid energy storage system according to claim 1, characterized in that: It also includes a power indicator, an isolating knife switch, a current transformer, a circuit breaker, a charging resistor and a lightning arrester. The isolating knife switch and the circuit breaker are connected in series between the AC busbar and the MMC converter valve, the power indicator is connected in parallel on the three-phase power line between the isolating gate and the AC busbar, the current transformer is connected in series on the three-phase power line between the isolating knife switch and the circuit breaker, the charging resistor is connected in parallel at both ends of the circuit breaker, and a lightning arrester is arranged on the three-phase power line between the circuit breaker and the MMC converter valve.