Hybrid energy storage topological structure control method of energy router for urban rail transit

Abstract

The invention relates to a hybrid energy storage topological structure control method of an energy router for urban rail transit, and the energy router is provided with an energy supply end and four special ports, and has extremely high flexibility. The energy router supports dual energy storage solutions, battery and supercapacitor, to effectively manage energy requirements and capture braking energy from the train. In addition, the use of renewable energy sources is promoted by introducing a photovoltaic system. The energy router is designed to operate in conjunction with existing infrastructure, ensuring continuous power supply even under low energy storage conditions. And for two groups of different energy storage modules, improved model prediction control is adopted to realize power distribution under different conditions, so that the service life of the energy storage system is prolonged.

Description

Technical Field

[0001] The present invention relates to the field of home park energy technology, and in particular to a hybrid energy storage topology structure control method for an energy router for urban rail transit. Background Art

[0002] With the rapid development of modern science and technology, economic growth has also brought a heavy burden to the environment. Therefore, clean energy power generation methods such as photovoltaics and wind power have been widely promoted. Photovoltaic power generation has been rapidly developed in homes and parks due to its low cost and environmental protection advantages. At the same time, with the advancement of science and technology and the popularization of smart homes, the global reserves of fossil fuels are difficult to meet future energy needs, and it is particularly important to promote the application of new energy.

[0003] Improving the energy utilization rate of home parks can not only reduce energy waste, but also effectively reduce carbon emissions, helping to achieve the goals of a low-carbon society and green development. In addition, with the popularization of electric vehicles (EVs) and home energy storage devices, the energy demand and supply patterns in home parks have become more complex. How to reasonably dispatch and manage these energy resources to improve overall efficiency has become a hot topic in current research. Through the application of intelligent energy management systems (such as energy routers, load forecasting algorithms, demand response and other technologies), the energy flow in the home park can be optimized, thereby improving energy efficiency and promoting the realization of sustainable development of the home park, thereby solving the current problem of low energy utilization in the home park.

[0004] For the home campus system structure, the use of energy router system is a good solution. As an important part of the energy Internet, the energy router has superior multi-port characteristics and energy scheduling functions that can be better combined with the house power supply. At the same time, unlike the distributed structure of the DC microgrid, its integrated structure can save space as much as possible and has more advantages in control. Considering the frequent fluctuations in house power, the use of a dual energy storage system combining supercapacitors and energy storage batteries can effectively improve energy utilization and extend the service life of the system. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a hybrid energy storage topology structure control method for an energy router for urban rail transit, which adopts a dual energy storage system combining supercapacitors and energy storage batteries to effectively improve energy utilization and extend system service life.

[0006] To achieve the above object, the present invention adopts the following technical solution: a hybrid energy storage topology structure control method for an energy router for urban rail transit, step S1: constructing an energy router system with a hybrid energy storage structure of supercapacitors and energy storage batteries;

[0007] Step S2: realize the integration of the energy router system and the home power supply system, keep the original power supply system unchanged, and add a new power supply structure;

[0008] Step S3: setting the working requirements and dividing the working modes of the energy router according to the photovoltaic power and the load power;

[0009] Step S4: Determine the control strategy of the energy router according to the defined energy router working mode division;

[0010] Step S5: According to the specific characteristics of the hybrid energy storage structure set by the energy router, the control strategy is improved, the energy storage part is optimized, and the hybrid energy storage scheduling is achieved reasonably.

[0011] In a preferred embodiment, the energy router contains energy storage batteries and super capacitors.

[0012] In a preferred embodiment, the energy router has 7 ports; 3 ports are connected to the photovoltaic power supply and the hybrid pure energy control system at the energy supply end, and 4 ports are connected to the power consumption ports of different voltage levels of the electric vehicle.

[0013] In a preferred embodiment, the working state of the energy router is divided according to the working mode of the hybrid energy storage system and the specific working state of the energy router. The specific judgment basis is as follows:

[0014] If the power of photovoltaic power source is P PV >Total power of the park load P LOAD , then the working mode of the hybrid energy storage system is in the first mode Mode I;

[0015] In the first mode Mode I:

[0016] If 20 < SOC of the energy storage battery B <60, the specific working state of the energy router is in the first working state case 1;

[0017] If the state of charge SOC of the energy storage battery B >60, the specific working state of the energy router is in the second working state case 2;

[0018] If the state of charge SOC of the energy storage battery B >60, and the super battery's state of charge SOC S >95, the specific working state of the energy router is in the third working state case 3;

[0019] If the power of photovoltaic power source is P PV <Total power of the park load PLOAD , then the working mode of the hybrid energy storage system is in the second mode Mode II;

[0020] In the first mode Mode II:

[0021] If 20 < SOC of the energy storage battery B <60, the specific working state of the energy router is in the fourth working state case 4;

[0022] If the state of charge SOC of the energy storage battery B >60, the specific working state of the energy router is in the fifth working state case 5;

[0023] If the state of charge SOC of the energy storage battery B ≤20, the specific working state of the energy router is in the sixth working state case 6;

[0024] If the state of charge SOC of the energy storage battery B ≤20, and the super battery's state of charge SOC S ≤20, the specific working state of the energy router is in the seventh working state case 7.

[0025] In a preferred embodiment, the reference power of the system is first calculated using a model prediction method, and then the power is divided by a low-pass filter, and then the PI controller and PWM output determine the mode of the battery and supercapacitor switch tube.

[0026] Compared with the prior art, the present invention has the following beneficial effects: the energy router system of the present invention is closely integrated with the original home park power supply system, and is provided with a photovoltaic port, so as to introduce new energy for house use and reduce energy consumption. In addition to providing energy for the house, the energy router also has the function of energy recovery and can assume the role of an energy feedback device. The device body is provided with two groups of energy storage in different forms, namely supercapacitors and energy storage batteries, which respectively respond to energy of different frequencies, thereby increasing the life of the energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a topological diagram of an energy router in an embodiment of the present invention;

[0028] Figure 2 is a topological circuit diagram of an energy router in an embodiment of the present invention, wherein (a) is an energy supply end, and (b) is an energy consumption end;

[0029] Figure 3 is a control diagram of a hybrid energy storage system in an embodiment of the present invention;

[0030] Figure 4is a state division rule diagram (state of charge and input power) in an embodiment of the present invention;

[0031] Figure 5 : is the port power curve in the embodiment of the present invention, wherein (a) is the power flow curve of the energy storage battery, (b) is the power flow curve of the supercapacitor, and (c) is the photovoltaic power;

[0032] Figure 6 is a DC voltage curve in an embodiment of the present invention, wherein (a) is the DC bus voltage, and (b) is the DC bus voltage after boosting. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0034] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0035] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application; as used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations.

[0036] Please refer to Figure 1-6 The present invention provides a hybrid energy storage topology control strategy for a home park, comprising the following steps:

[0037] Step S1: constructing an energy router system with a hybrid energy storage structure of supercapacitors and energy storage batteries;

[0038] Step S2: realize the integration of the energy router system and the home power supply system, keep the original power supply system unchanged, and add a new power supply structure;

[0039] The present invention designs a 7-port small-scale energy router. It includes a photovoltaic power source at the energy supply end and 3 ports of a hybrid pure energy control system, as well as 4 power consumption ports with different voltage levels for electric vehicles. The energy supply end is composed of a photovoltaic power source and a hybrid energy storage system. Since a single energy storage will seriously damage the battery life under long-term or high-load charge and discharge, and the response speed of a single energy storage is limited, resulting in unstable efficiency provided for the system. Therefore, this research adopts a hybrid energy storage device combining a battery and a supercapacitor for household appliances with high power requirements. At the same time, because the supercapacitor has a fast response speed, but it is not suitable for long-term energy storage, combining the two devices can better stabilize the system voltage, thereby enhancing the stability of the entire system.

[0040] The load end of the energy router mainly considers sharing high-power devices and daily lighting systems for the home park to reduce the household electricity demand. Among them, high-power devices mainly consider common appliances such as air conditioners and water heaters. At the same time, with the development of the times, electric vehicle technology has become increasingly mature, and there are more and more electric vehicle users. However, in some ordinary cities, electric vehicle charging piles have not been widely popularized, resulting in charging difficulties. Therefore, a household charging pile is of great significance. In order to reduce the number of power adapters for sensor devices, a 25V low-voltage DC port is configured through a DC / DC converter on the DC bus to meet the daily lighting needs.

[0041] Step S3: Set the working requirements and divide the working modes of the energy router according to the magnitudes of the photovoltaic power and the load power.

[0042]

[0043] In Model I, when the battery SOC satisfies 20 < SOCB ≤ 60, the battery is in a good working state, and the battery and the supercapacitor can jointly absorb the excess photovoltaic energy to stabilize the bus voltage. In Case 2, the battery is overcharged, and the battery needs to be disconnected from the system, and the supercapacitor alone undertakes the excess photovoltaic energy. In Case 3, the SOCs of the battery and the supercapacitor are too high, which may cause safety problems, and the photovoltaic module needs to be interrupted, and the battery and the supercapacitor supply power to the load. In Model 2, in Case 4, the battery and the supercapacitor are healthy, and the energy storage system needs to discharge to stabilize the bus voltage; in Case 5, the battery SOC is too high, and it needs to discharge and disconnect the supercapacitor, and the photovoltaic and the battery supply power; in Case 6, SOCB ≤ 20, and the battery power supply needs to be interrupted, and the supercapacitor discharges. When the SOC is too low, to save costs, the load end is disconnected, and the grid supplies power, and the photovoltaic energy is input into the HESS to restore the battery.

[0044] Step S4: Determine the control strategy of the energy router hybrid energy storage system according to the defined energy router working mode division;

[0045] Step S5: According to the specific characteristics of the hybrid energy storage structure set by the energy router, the control strategy is improved, the energy storage part is optimized, and the hybrid energy storage is reasonably scheduled to improve the service life.

[0046] This paper selects a scheme combining filtering control with new model predictive control for power distribution. The so-called new model predictive control is to combine model predictive control with PI control, which not only makes up for the long adjustment time of PI control, but also improves the large current ripple caused by model predictive control. Figure 2 The mathematical model of the dual energy storage system can be obtained:

[0047]

[0048] Discretize the continuous differential equation 1 to obtain:

[0049]

[0050] In the formula, the sampling period of the system is T, t is the sampling time of the system, and t+1 represents the sampling time of the next moment.

[0051] Order I es is the total current output by the hybrid energy storage system. According to the energy supply end topology, I es The expression is:

[0052]

[0053] The current at the load end can be simply expressed by the power required by the load end and the DC bus voltage. The expression is as follows:

[0054]

[0055] Where P LOAD , P L , P H are the ideal powers of the three port loads respectively. The differential form of the DC bus current can also be simply expressed as:

[0056]

[0057] Converting it into discrete form, we get:

[0058]

[0059] For V DC It can be assumed that after K cycles, the ideal voltage V can be reached. DCR, there is the following discrete relationship between the two:

[0060]

[0061] Substituting formula (7) into formula (6) and combining it with formula (3) yields:

[0062]

[0063] The corresponding energy storage port reference power at time t+1 should be:

[0064]

[0065] Since the energy and power characteristics of supercapacitors and batteries are different, a low-pass filter is used to distribute the high-frequency part to the supercapacitor, and the low-frequency part is realized by the battery. The battery power P BR , and supercapacitor power P CR The reference formula is as follows:

[0066]

[0067] P CR (t+1)=P es (t+1)-P BR (t+1) (11)

[0068] Single model predictive control will cause large current ripple, so this paper uses a combination of model prediction and PI control to reduce current ripple. Figure 4 As shown, the model is first used to predict the reference power of the calculation system, and then the power is divided by a low-pass filter. The PI controller and PWM output determine the mode of the battery and supercapacitor switch tube.

[0069] Figure 6 The experimental power is divided, mainly showing the total required power, photovoltaic power and energy storage battery power.

[0070] The figure shows the power flow in Model I state. In case 1, in order to share the bus voltage, the battery is in a charging state, so the power flow is negative. In case 2, P B is 0, that is, the battery has SOC B When the critical value is reached, the battery is disconnected from the system to maintain the battery life. In case 3, since the photovoltaic power is not working at this time, the power required by the system is all provided by the battery. At this time, the battery power flow shows a surge until it can meet the power required by the load. From the voltage flow and power flow of the system, it can be judged that in the case of Model I, H-ER can work stably in each state and has strong stability.

[0071] The present invention is an energy router for home campuses, and the seven-port structure is perfectly integrated with the existing home campus system. The dual energy storage structure used in the structure and the improved model predictive control method used can effectively extend the energy storage life, and the overall structure has strong controllability. Specifically, the present invention relates to a reliable home campus energy router structure, which provides a new solution for the power supply structure of the house. The dual energy storage system used in the energy router structure adopts improved model predictive control and hierarchical control, which effectively meets the house structure and realizes better power supply function.

Claims

1. A hybrid energy storage topology control method for an energy router for urban rail transit, characterized in that: Step S1: construct an energy router system with a hybrid energy storage structure of supercapacitors and energy storage batteries; Step S2: realize the integration of the energy router system and the home power supply system, keep the original power supply system unchanged, and add a new power supply structure; Step S3: setting the working requirements and dividing the working modes of the energy router according to the photovoltaic power and the load power; Step S4: Determine the control strategy of the energy router according to the defined energy router working mode division; Step S5: According to the specific characteristics of the hybrid energy storage structure set by the energy router, the control strategy is improved, the energy storage part is optimized, and the hybrid energy storage scheduling is achieved reasonably.

2. According to claim 1, a hybrid energy storage topology control method for an energy router for urban rail transit is characterized in that: The energy router contains energy storage batteries and supercapacitors.

3. According to claim 1, a hybrid energy storage topology control method for an energy router for urban rail transit is characterized in that: The energy router has 7 ports; 3 ports are connected to the photovoltaic power supply and hybrid pure energy control system at the energy supply end, and 4 ports are connected to the power consumption ports of different voltage levels of electric vehicles.

4. According to claim 1, a hybrid energy storage topology structure control method for an energy router for urban rail transit is characterized in that: According to the working mode of the hybrid energy storage system and the specific working state of the energy router, the working state of the energy router is divided. The specific judgment basis is as follows: If the power of photovoltaic power source P PV >Total power of the park load P LOAD , then the working mode of the hybrid energy storage system is in the first mode Mode I; In the first mode Mode I: If 20 < SOC of the energy storage battery B <60, the specific working state of the energy router is in the first working state case 1; If the state of charge SOC of the energy storage battery B >60, the specific working state of the energy router is in the second working state case 2; If the state of charge SOC of the energy storage battery B >60, and the super battery's state of charge SOC S > 95, the specific working state of the energy router is in the third working state case 3; If the power of photovoltaic power source P PV <Total power of the park load P LOAD , then the working mode of the hybrid energy storage system is in the second mode Mode II; In the first mode Mode II: If 20 < SOC of the energy storage battery B <60, the specific working state of the energy router is in the fourth working state case 4; If the state of charge SOC of the energy storage battery B >60, the specific working state of the energy router is in the fifth working state case 5; If the state of charge SOC of the energy storage battery B ≤20, the specific working state of the energy router is in the sixth working state case 6; If the state of charge SOC of the energy storage battery B ≤20, and the super battery's state of charge SOC S ≤ 20, the specific working state of the energy router is in the seventh working state case 7.

5. The hybrid energy storage topology structure control method of an energy router for urban rail transit according to claim 1 is characterized in that: First, the reference power of the system is calculated using the model prediction method, and then the power is divided by a low-pass filter. The PI controller and PWM output determine the mode of the battery and supercapacitor switch tube.

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