Hybrid energy storage control method for urban rail transit energy router

Abstract

The invention relates to a hybrid energy storage control method for an urban rail transit energy router. The method comprises the following steps: S1, carrying out topological structure design and system compatibility configuration on the energy router; s2, impedance modeling and frequency division power distribution of the hybrid energy storage system are carried out; s3, fuzzy controller design and super capacitor SOC dynamic management are carried out; s4, carrying out membership function optimization and fuzzy control parameter setting; s5, multi-mode cooperative control and system operation optimization are carried out; according to the structure of the energy router and the power utilization characteristics of the rail transit system, working modes are divided, the working state of the system is optimized, and the system is kept in a reasonable working state. The method can effectively improve the utilization rate of energy and prolong the service life of the system.

Description

Technical Field

[0001] The present invention relates to the technical field of urban rail transit power supply, and particularly relates to a hybrid energy storage control method for an urban rail transit energy router. Background Art

[0002] With the acceleration of the urbanization process, urban rail transit, as an important part of urban public transportation, has a huge power consumption problem that cannot be ignored. Introducing renewable energy into the traction power supply system and making full use of braking energy are important research directions for the rail transit power supply system. In addition, due to the complex structure and large power fluctuations of the traction power supply system itself, it will also pose challenges to the power supply system. Therefore, it is urgent to design a new and environmentally friendly power supply structure.

[0003] To improve energy utilization efficiency, the most widespread method currently is through energy feedback devices. According to statistics, nearly 1 / 3 of the traction energy can be recovered and reused. However, in fact, energy feedback devices only consider energy conservation and do not change the characteristics of the existing traction system with a single power supply form and insufficient environmental friendliness. At the same time, the traditional power supply structure has a high dependence on the power system. Once a traction substation fails, the traction power supply system will stop operating, thus reducing reliability. Therefore, the ultimate development direction of the traction power supply system should be to incorporate new energy such as wind and light into the urban rail transit power supply system, build a new energy Internet system, enhance the robustness of the system, and reduce the consumption of traditional energy.

[0004] For the power supply system structure of the subway, adopting an energy router system is a good solution. As an important part of the energy Internet, the superior multi-port characteristics and energy scheduling functions of the energy router can be better combined with the subway power supply. At the same time, different from 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 characteristics of frequent and large power fluctuations in rail transit, adopting a dual energy storage system combining supercapacitors and energy storage batteries can effectively improve energy utilization efficiency and extend the service life of the system. Summary of the Invention

[0005] The purpose of the present invention is to provide a hybrid energy storage control method for an urban rail transit energy router, which can effectively improve energy utilization efficiency and extend the service life of the system.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is: a hybrid energy storage control method for an urban rail transit energy router, including:

[0007] Step S1: Design the topology structure of the energy router and configure the system compatibility; construct the basic structure of the energy router according to the structure of the urban rail transit power supply system, the train operation status, and the required new energy power supply status. At the same time, keep the original power supply system structure unchanged, and directly expand the newly added energy router on the original power supply system;

[0008] Step S2: Model the impedance of the hybrid energy storage system and allocate the power by frequency; according to the constructed basic structure of the energy router, model the energy storage part to determine the power distribution;

[0009] Step S3: Design the fuzzy controller and dynamically manage the SOC of the supercapacitor; considering the power supply characteristics of the rail transit energy router, construct a new fuzzy controller to monitor the capacity status of the supercapacitor in real time, and at the same time perform subsequent power distribution to keep the supercapacitor always in a reasonable SOC range;

[0010] Step S4: Optimize the membership function and tune the fuzzy control parameters; according to the fuzzy filtering rules, construct the membership function of the fuzzy controller suitable for the urban rail transit energy router;

[0011] Step S5: Perform multi-modal cooperative control and optimize the system operation; according to the structure of the energy router and the power consumption characteristics of the rail transit system, divide the working modes, optimize the working state of the system, and keep the system in a reasonable working state.

[0012] Furthermore, the energy router contains two power supply structures, namely energy storage batteries and supercapacitors. At the same time, the energy router is combined with the rail transit power supply; the energy router is provided with two groups of DC1500V ports, which are respectively connected to the power supply of the subway up and down lines. Both groups of DC1500V ports are bidirectional ports, which can realize power supply and can also realize the recovery of train braking energy; when the energy router fails, the system is switched, and the original system supplies power.

[0013] Furthermore, in step S2, by analyzing the impedance structure differences between the energy storage batteries and supercapacitors in the energy router, the filter is designed directionally, and then the decomposition and control of different frequency powers are realized, so as to more effectively realize the stable control of the DC bus voltage; from the perspective of the energy storage battery, the input impedance of the system is Z bat and Z DCDC in two parts; from the perspective of the supercapacitor, the input impedance of the system is Z sc and Z DCDC ;

[0014] Construct a multi-path cascaded bidirectional Buck-Boost converter. The multi-path cascaded bidirectional Buck-Boost converter has two operating modes, namely the Boost mode and the Buck mode, corresponding to the discharge state and the charge state of the supercapacitor respectively;

[0015] First, calculate the impedance function of the supercapacitor branch in the Boost mode; in the Boost mode, the system impedance is as follows:

[0016]

[0017] In the formula:

[0018]

[0019] Z ln (s) = L n s + r n

[0020] r n = D n r dsn +(1 - D n )r fn + r Ln

[0021]

[0022] In the formula, N SC-series and N SC-paralle are the number of parallel groups and the number of series groups of the supercapacitors respectively, C sc , R sc are the internal capacitance and the resistance parameter values of the supercapacitor respectively, C ci , R ci are the input capacitance and the parasitic resistance value respectively, L i , r i are the input inductance and the parasitic resistance value respectively, C o , R co are the output capacitance and the parasitic resistance value respectively, N sc is the total number of parallel circuits of the DCDC converter at the supercapacitor end;

[0023] Assume that in terms of control, the duty cycle of each path is the same, only phase-shift control is adopted, and the parameters of all circuits are the same, that is:

[0024]

[0025] At this time, there is

[0026]

[0027] Similarly, the system impedance of the supercapacitor in the Buck mode is obtained as follows:

[0028]

[0029] Similarly, for the energy storage battery, the system impedance in the boost mode is obtained respectively:

[0030]

[0031] In the formula, N Bat-series and N Bat-paralle are the number of parallel groups and the number of series groups of the energy storage battery respectively, and N Bat is the total number of parallel circuits of the DCDC converter at the energy storage battery terminal;

[0032] Considering that the duty cycle corresponding to different SOCs of the supercapacitor is different, multiple groups of typical duty cycle values are selected corresponding to the boost mode and the buck mode respectively; by constructing the Bode plot of the transfer function, the intersection points in the two different cases are found, so as to determine the corresponding cut-off frequency and the frequency division value. Through this frequency division value, the supercapacitor processes the high-frequency components on the DC bus in most cases, and the remaining low-frequency components are processed by the energy storage battery.

[0033] Furthermore, in step S3, there are two input quantities of the fuzzy controller, which are the total power minus the power after passing through the low-pass filter, denoted as P FIN and the state of charge SC of the supercapacitor soc .

[0034] Furthermore, for the membership function of SC SOC , three parts are defined respectively, namely Low, Medium and High, corresponding to three different levels of the state of charge of the supercapacitor; for the membership function of P FIN , seven parts are defined respectively, namely P zero , and , corresponding to the high, medium and low charging powers respectively, the middle 0 state P zero , and the high, medium and low discharging powers; the output of the fuzzy control is the reference power of the supercapacitor They are HighC, MedC, SlowC, Zero, SlowD, MedD, and HighD respectively, representing the seven states of the reference power of the supercapacitor: fast charging, medium-speed charging, slow charging, the middle 0 state, slow discharging, medium-speed discharging, and fast discharging; assume the following situation analysis: The train in the left power supply section is in an emergency acceleration state. At this time, the energy router receives a high-frequency and large discharge power demand, and this power demand is first considered to be met by the supercapacitor; in this case, the state of charge of the supercapacitor is divided into three situations: high, medium, and low; when the state of SC SOC is High, at this time, through the fuzzy controller, the signal transmitted to the converter at the SC end tends to fast discharge HighD, that is, the supercapacitor meets the output load demand with a large power; if SC SOC is Medium, then the supercapacitor meets the output load demand with a medium-sized power; as the state of SC SOC decreases, the supercapacitor tends not to discharge, the output power decreases, and the final load power is met by the energy storage battery; if the discharge power demand is not large and the SOC of the supercapacitor is in the Low state, at this time, the system output state tends to slow charging SlowC, that is, slowly charge the supercapacitor to increase the SOC of the supercapacitor to cope with future high-power output demands.

[0035] Furthermore, according to the working mode of the train and the specific working state of the energy router, the working state of the energy router is divided; the energy router is divided into two working modes, namely Mode I and Mode II, and the division basis is the energy storage SOC in the initial state. When the value of SOC bat is higher than the lowest threshold, the system enters Mode I, otherwise it enters Mode II; after entering Mode I, the powers of the two catenary ports (P cat1 and P cat2 ) and the power of the photovoltaic port (P pv ) are compared to obtain the current system working state case 1 or case 2, and different divisions under case 1; after entering Mode II, different divisions under the current system working state case 3 are obtained.

[0036] Furthermore, in the working mode Mode I, it means that the SOC state of the energy router is relatively high, and all the energy for the train operation is provided by the energy router, and the original traction system of the subway does not work; case 1 means that the energy provided by the photovoltaic is not enough to support the train operation, and additional energy needs to be provided by the energy storage part, and the SOC bat decreases; there are multiple possibilities in case 1:

[0037] Case 1-1 indicates that the catenary ports of both groups of trains consume energy, and the required energy is jointly provided by the battery and the photovoltaic system.

[0038] Case 1-2 indicates that the photovoltaic system generates energy, the catenary port 1 consumes energy, and the catenary port 1 recovers energy. However, Pcat1 > Pcat2 + Ppv, and the energy storage part still needs to provide energy.

[0039] Case 1-3 indicates a lightless state where the photovoltaic system does not generate energy, the catenary port 1 consumes energy, and the catenary port 1 recovers energy. However, Pcat1 > Pcat2, and the energy storage part still needs to provide energy.

[0040] Furthermore, case 2 indicates that when the photovoltaic energy is sufficient and can supply power to the two catenary ports, the energy storage battery is charged simultaneously.

[0041] Furthermore, in operating mode Mode II, it indicates that the SOC of the energy router is at a relatively low level and needs to be charged, so it does not serve as a power supply system for trains. There are multiple possibilities in case 3:

[0042] Case 3-1 indicates that the energy of both groups of trains is provided by the upper-level rectifier transformer, and the energy generated by the PV port charges the energy storage battery.

[0043] Case 3-2 indicates that one train is in the braking state and one train is in the normal state. The train running normally is provided by the rectifier transformer, and the feedback energy generated by the braking train is recovered by the energy router to charge the energy storage battery.

[0044] Case 3-3 indicates that both trains are in the charging state to charge the battery.

[0045] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a hybrid energy storage control method for an energy router for urban rail transit. The energy router constructed by this method supports a dual-energy storage solution - battery and supercapacitor to effectively manage the energy demand and capture the braking energy from the train. In addition, the use of renewable energy is promoted by introducing a photovoltaic system. The energy router provided by this method is designed to operate in combination with the existing infrastructure and can ensure continuous power supply even under low energy storage conditions. For the two different energy storage modules, low-pass fuzzy filtering control is adopted to achieve power distribution in different situations, thereby extending the life of the energy storage system. Description of the Drawings

[0046] Figure 1 is the topological structure diagram of the energy router in the embodiment of the present invention;

[0047] Figure 2 It is a schematic diagram of the hybrid energy storage system modeling in the embodiment of the present invention;

[0048] Figure 3 It is the overall system control diagram in the embodiment of the present invention;

[0049] Figure 4 It is the membership function (state of charge and input power) based on fuzzy control in the embodiment of the present invention;

[0050] Figure 5 It is the membership function (output power) based on fuzzy control in the embodiment of the present invention;

[0051] Figure 6 It is the schematic diagram of the working mode division in the embodiment of the present invention;

[0052] Figure 7 It is the port power curve diagram in the embodiment of the present invention;

[0053] Figure 8 It is the DC bus and catenary voltage curve diagram in the embodiment of the present invention. Detailed implementation manners

[0054] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0055] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0056] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary implementation manners according to the present application. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0057] This embodiment provides a hybrid energy storage control method for an urban rail transit energy router, and its specific implementation steps are as follows.

[0058] Step S1: Conduct the topology structure design of the energy router and the system compatibility configuration; construct the basic structure of the energy router according to the structure of the urban rail transit power supply system, the train operation state, and the required new energy power supply state, while keeping the original power supply system structure unchanged, and directly expand the newly added energy router on the original power supply system.

[0059] Figure 1This is the topology structure diagram of the energy router in this embodiment. Figure 2 This is the schematic diagram of the hybrid energy storage system modeling in this embodiment.

[0060] The energy router contains two power supply structures, namely energy storage batteries and supercapacitors. At the same time, the energy router is combined with the rail transit power supply. The energy router is provided with two groups of DC1500V ports, which are respectively connected to the power supplies of the subway up and down lines. Both groups of DC1500V ports are bidirectional ports, which can supply power and can also recover the braking energy of the train. When the energy router fails, the system switches, and the original system supplies power.

[0061] The electric energy of the traditional urban rail transit traction power supply system comes from the AC35KV urban power grid, and DC1500V is obtained after passing through the traction rectifier transformer for the train to use.

[0062] The energy router system proposed in this embodiment is a full DC system, and 5 groups of ports are provided in terms of structure. The functions are described as follows. Ports 1 and 2 supply power to the trains in two sections respectively, and these two ports adopt bidirectional DCDC converters. This port can not only undertake the power supply function, but also recover the energy generated by the train braking, and at the same time undertake the role of the energy feedback device. Ports 3 and 4 also adopt the structure of bidirectional DCDC converters, and these two groups of ports are used to connect the energy storage system. There are two energy storage structures in the energy router, namely energy storage batteries and supercapacitors. The two different forms of energy storage respectively play the advantages of large capacity and fast response speed to reflect the energy fluctuation requirements of different forms. Port 5 adopts a unidirectional DCDC port, which is connected to the photovoltaic system to connect new energy into the energy router system for the train to use. This energy router can be compatible with the original power supply system. B1 and B2 are the isolation circuit breakers of the original 24-pulse rectifier transformer. When both groups of energy storage systems are in a power-deficient state, B1 and B2 are closed, and the train can be powered by the original system. The energy router undertakes the role of the energy feedback device, recovers the train braking energy, and at the same time uses the photovoltaic system to charge the energy storage system. When the energy storage part reaches the threshold, B1 and B2 are turned off again, and the train power supply is provided by the energy router.

[0063] Step S2: Conduct impedance modeling and frequency-divided power distribution of the hybrid energy storage system; according to the basic structure of the constructed energy router, model the energy storage part to determine the power distribution.

[0064] By analyzing the impedance structure differences between the energy storage batteries and supercapacitors in the energy router, design the filter directionally, and then realize the decomposition and control of different frequency powers, so as to more effectively realize the stable control of the DC bus voltage. From the perspective of the energy storage battery, the input impedance of the system is Z bat and Z DCDCTwo parts; from the perspective of the supercapacitor, the input impedance of the system is Z sc and Z DCDC . The energy storage battery pack is a source with a slow response and a large impedance value, while the supercapacitor has a fast response and a small impedance value. This characteristic can be utilized to study the frequency characteristics of the system and set an appropriate filter to achieve power decomposition.

[0065] Construct a multi-path cascaded bidirectional Buck-Boost converter. The multi-path cascaded bidirectional Buck-Boost converter has two operating modes, namely the Boost mode and the Buck mode, corresponding to the discharge state and the charge state of the supercapacitor respectively.

[0066] First, calculate the impedance function of the supercapacitor branch in the Boost mode; in the Boost mode, the system impedance is as follows:

[0067]

[0068] In the formula:

[0069]

[0070] Z ln (s) = L n s + r n

[0071] r n = D n r dsn +(1 - D n )r fn + r Ln

[0072]

[0073] In the formula, N SC-series and N SC-paralle are the number of parallel groups and the number of series groups of the supercapacitors respectively, C sc , R sc are the internal capacitance and resistance parameter values of the supercapacitor respectively, C ci , R ci are the input capacitance and parasitic resistance values respectively, L i , r i are the input inductance and parasitic resistance values respectively, C o , R co are the output capacitance and parasitic resistance values respectively, N sc is the total number of parallel circuits of the DCDC converter at the supercapacitor end.

[0074] To simplify the analysis, it is assumed that, in terms of control, the duty cycle of each path is the same, only phase-shift control is adopted, and the parameters of all loops are the same, that is:

[0075]

[0076] At this time, there is

[0077]

[0078] Using the same simplification method, the system impedance of the supercapacitor in Buck mode is obtained as:

[0079]

[0080] Similarly, for the energy storage battery, the system impedance in boost mode is obtained respectively:

[0081]

[0082] In the formula, N Bat-series and N Bat-paralle are the number of parallel groups and the number of series groups of the energy storage battery respectively, and N Bat is the total number of parallel loops of the DCDC converter at the energy storage battery terminal.

[0083] Considering that the duty cycle corresponding to different SOCs of the supercapacitor is different, multiple groups of typical duty cycle values are selected for the boost mode and the buck mode respectively; by constructing the Bode plot of the transfer function, the intersection points in the two different cases are found, so as to determine the corresponding cut-off frequency, determine the frequency division value, and through this frequency division value, make the supercapacitor handle the high-frequency components on the DC bus in most cases, and the remaining low-frequency components are handled by the energy storage battery.

[0084] Step S3: Design a fuzzy controller and dynamically manage the SOC of the supercapacitor; considering the power supply characteristics of the rail transit energy router, a new fuzzy controller is constructed to monitor the capacity status of the supercapacitor in real time and perform subsequent power distribution, so as to keep the supercapacitor always in a reasonable SOC range.

[0085] As Figure 3 shown, there are two input quantities of the fuzzy controller, which are the total power minus the power after passing through the low-pass filter, denoted as P FIN and the state of charge SC soc of the supercapacitor.

[0086] Step S4: Optimize the membership function and tune the fuzzy control parameters; according to the fuzzy filtering rules, construct a membership function of the fuzzy controller suitable for the urban rail transit energy router.

[0087] As Figure 4Shown is the membership function of SC soc , as shown Figure 5 is the membership function of P FIN . The shapes of the membership functions are all Gaussian. For the membership function of SC SOC , three parts are defined, namely Low, Medium, and High, corresponding to three different levels of the charge state of the supercapacitor; for the membership function of P FIN , seven parts are defined, namely P zero , and , corresponding to high, medium, and low charging power respectively, and the 0 state P zero in the middle, as well as high, medium, and low discharging power; the output of the fuzzy control is the reference power of the supercapacitor , namely HighC, MedC, SlowC, Zero, SlowD, MedD, HighD respectively, representing seven states of the reference power of the supercapacitor: fast charging, medium-speed charging, slow charging, the middle 0 state, slow discharging, medium-speed discharging, and fast discharging.

[0088] Now analyze a possible mode: The train in the left power supply section is in an emergency acceleration state. At this time, the energy router gets a high-frequency and large discharging power demand, and this power demand is first considered to be met by the supercapacitor; in this case, the charge state of the supercapacitor is divided into three situations: high, medium, and low; when the state of SC SOC is High, at this time, through the fuzzy controller, the signal transmitted to the converter at the SC end tends to fast discharge HighD, that is, the supercapacitor meets the output load demand with a large power; if the state of SC SOC is Medium, then the supercapacitor meets the output load demand with a medium-sized power; as the state of SC SOC decreases, the supercapacitor tends not to discharge, the output power decreases, and the final load power is met by the energy storage battery; if the discharging power demand is not large and the SOC of the supercapacitor is in the Low state, at this time, the system output state tends to slow charging SlowC, that is, slowly charge the supercapacitor to increase the SOC of the supercapacitor to cope with future high-power output demands.

[0089] Step S5: Perform multi-modal collaborative control and system operation optimization; according to the structure of the energy router and the power consumption characteristics of the rail transit system, divide the working modes, optimize the working state of the system, and keep the system in a reasonable working state.

[0090] The energy storage port, as the core control port, plays a role in stabilizing the DC bus voltage. The realization of the energy router function relies on the coordinated scheduling of the high-power bidirectional DC port and the energy storage port. According to the working mode of the ports, the energy router can be briefly divided into two working modes.

[0091] According to the working mode of the train and the specific working state of the energy router, the working state of the energy router is divided; the energy router is divided into two working modes, namely Mode I and Mode II. The division basis is the energy storage SOC in the initial state. When the value of SOC bat is higher than the lowest threshold, the system enters Mode I, otherwise it enters Mode II; after entering Mode I, the powers of the two catenary ports (P cat1 and P cat2 ) and the power of the photovoltaic port (P pv ) are compared to obtain the current system working state case 1 or case 2, and different divisions under case 1; after entering Mode II, different divisions under the current system working state case 3 are obtained. The working mode division is as Figure 6 shown.

[0092] Mode I:

[0093] In the working mode of Mode I, it means that the SOC state of the energy router is relatively high, and all the energy for the train operation is provided by the energy router, and the original traction system of the subway does not work; case 1 means that the energy provided by the photovoltaic is not enough to support the train operation, and the energy storage part needs to provide additional energy, and the SOC bat decreases.

[0094] In the case of case 1, there are multiple possibilities:

[0095] case 1-1 means that both catenary ports of the two trains consume energy, and the required energy is provided by the battery and the photovoltaic together;

[0096] case 1-2 means that the photovoltaic generates energy, the catenary port 1 consumes energy, the catenary port 1 recovers energy, but Pcat1 > Pcat2 + Ppv, and the energy storage part still needs to provide energy;

[0097] case 1-3 means that in the dark state, the photovoltaic does not generate energy, the catenary port 1 consumes energy, the catenary port 1 recovers energy, but Pcat1 > Pcat2, and the energy storage part still needs to provide energy.

[0098] case2 means that the photovoltaic energy is sufficient, and on the premise of being able to supply power to the two catenary ports, it also charges the energy storage battery at the same time.

[0099] Mode II:

[0100] In the working mode of Mode II, it indicates that the SOC of the energy router is at a relatively low level and needs to be charged. Therefore, it does not serve as a power supply system for the train.

[0101] In case 3, there are multiple possibilities:

[0102] Case 3-1 means that the energy of both trains is provided by the superior rectifier transformer, and the energy generated by the PV port charges the energy storage battery;

[0103] Case 3-2 means that one train is in the braking state and one train is in the normal state. The normally operating train is powered by the rectifier transformer, and the feedback energy generated by the braking train is recovered by the energy router to charge the energy storage battery;

[0104] Case 3-3 means that both trains are in the charging state to charge the battery.

[0105] Figure 7 For the experimental power division, the three figures respectively show the total required power, the power of the supercapacitor after filtering, and the power of the energy storage battery. It is obvious that after low-pass filtering, the high-frequency power is transmitted to the supercapacitor, and the low-frequency part is transmitted to the energy storage battery. Through this method, the final power division is achieved.

[0106] When the capacity of the energy storage part is sufficient, the system mode is Mode I. The transformation of the photovoltaic and port power leads to the mode switching, but the system does not use the rectifier transformer for power supply. The energy router simultaneously undertakes the dual roles of power supply and energy feedback. The initial setting of the photovoltaic power is 1 MW, which decreases at time A1 and drops to 0.1 MW at time A2. Figure 7 As shown in (b), it is the catenary power, that is, the train power. The train experiences processes such as zero power, increasing forward power, decreasing forward power, zero power, increasing reverse braking power, decreasing reverse braking power, and zero power. Train 2 experiences increasing forward power, increasing braking reverse power, decreasing braking reverse power until zero power, re-braking, increasing reverse power, decreasing power to zero, and then consuming forward power, increasing, and then decreasing to zero. The system power is balanced, corresponding to Figure 7 the power fluctuation of the energy storage part shown in (c).

[0107] Figure 7 In (a), it is the DC bus power diagram and the corresponding mode division. Figure 7 As shown in (b), it is the catenary voltage of the two groups. At this time, all states of the system are circulating within Mode I, and the catenary voltage is preferably stabilized at about 1600 V. All the obvious points of the system power switching can be obtained fromFigure 8 Obtained by observation in (a), that is, the fluctuations of the DC bus voltage can reflect the power states of all ports and the converter voltage mode switching. For the catenary port 1, the catenary port between B1 - B4 provides energy, and the catenary port between B8 - B12 undertakes the energy feedback function, which is reflected in Figure 7 In (c), the energy storage power starts to increase reversely from C7.

[0108] The hybrid energy storage control method for an urban rail transit energy router provided in this embodiment constructs an energy router for urban rail transit, and the five - port structure is perfectly combined with the existing traction power supply system. The dual - energy storage structure adopted in the structure and the fuzzy control strategy adopted can effectively extend the service life of the energy storage, and at the same time, the overall structure has strong controllability. This method provides a reliable structure for the urban rail transit energy router, and provides a new solution idea for the urban rail transit power supply structure. The dual - energy storage system adopted in the energy router structure adopts a fuzzy control strategy and hierarchical control at the same time, which effectively meets the subway working conditions and realizes a better power supply function.

[0109] The above are only the preferred embodiments of the present invention, and are not limitations on the present invention in other forms. Any person skilled in the art may use the technical content disclosed above to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims

1. A hybrid energy storage control method for urban rail transit energy router, characterized in that: include: Step S1: Design the energy router topology and configure system compatibility; The basic structure of the energy router is constructed according to the structure of the urban rail transit power supply system, the train operation status and the required new energy power supply status. At the same time, the structure of the original power supply system remains unchanged, and the newly added energy router is directly expanded on the original power supply system. Step S2: Conduct impedance modeling and frequency-divided power distribution of the hybrid energy storage system; model the energy storage part according to the basic structure of the constructed energy router to determine the power distribution; Step S3: Designing a fuzzy controller and dynamically managing the supercapacitor SOC; Considering the power supply characteristics of the rail transit energy router, a new fuzzy controller is constructed to monitor the capacity state of the supercapacitor in real time and perform subsequent power allocation, so as to keep the supercapacitor always in a reasonable SOC range; Step S4: Optimizing the membership function and setting the fuzzy control parameters; constructing a fuzzy controller membership function suitable for the urban rail transit energy router according to the fuzzy filtering rule; Step S5: Perform multi-modal collaborative control and system operation optimization; divide the working modes according to the energy router structure and the power consumption characteristics of the rail transit system, optimize the system working state, and keep the system in a reasonable working state.

2. A hybrid energy storage control method for an urban rail transit energy router according to claim 1, characterized in that: The energy router contains two power supply structures, namely energy storage batteries and supercapacitors, and is combined with rail transit power supply. The energy router is provided with two sets of DC1500V ports, which are respectively connected to the power supply of the uplink and downlink of the subway. Both sets of DC1500V ports are bidirectional ports, which can realize power supply and recovery of train braking energy. When the energy router fails, the system is switched and the original system is used for power supply.

3. A hybrid energy storage control method for an urban rail transit energy router according to claim 1, characterized in that: In step S2, by analyzing the impedance structure differences between the energy storage battery and the supercapacitor in the energy router, the filter is designed in a targeted manner to achieve the decomposition and control of power at different frequencies, thereby more effectively achieving stable control of the DC bus voltage; from the perspective of the energy storage battery, the input impedance of the system is Z bat and Z DCDC Two parts; from the perspective of the supercapacitor, the input impedance of the system is Z sc and Z DCDC ; Constructing a multi-channel cascaded bidirectional Buck-Boost converter, wherein the multi-channel cascaded bidirectional Buck-Boost converter has two working modes, namely, a Boost mode and a Buck mode, which correspond to a discharge state and a charge state of a supercapacitor, respectively; First, calculate the supercapacitor branch impedance function in Boost mode; in Boost mode, the system impedance is as follows: Where: Z ln (s)=L n s+r n r n =D n r dsn +(1-D n )r fn +r Ln Where N SC-series and N SC-paralle are the number of supercapacitors in parallel and in series, respectively. sc , R sc They are the internal capacitance and resistance parameter values ​​of the supercapacitor, C ci , R ci are the input capacitance and parasitic resistance respectively, L i 、r i are the input inductance and parasitic resistance respectively, C o , R co are the output capacitance and parasitic resistance respectively, N sc is the total number of parallel circuits of DCDC converters at the supercapacitor end; Assume that the duty cycle of each circuit is the same, only phase shift control is used, and the parameters of all circuits are consistent, that is: At this time, there are Similarly, the system impedance of the supercapacitor in Buck mode is obtained as: Similarly, for the energy storage battery, the system impedance in boost mode is obtained: Where N Bat-series 、N Bat-paralle are the number of parallel and series energy storage battery groups, N Bat is the total number of parallel DCDC converter circuits at the energy storage battery end; Considering that different SOCs of supercapacitors correspond to different duty cycles, multiple groups of typical duty cycle values ​​are selected corresponding to boost mode and buck mode respectively; By constructing the Bode plot of the transfer function, we find the intersection point in two different situations, thereby determining the corresponding cutoff frequency and the division value. Through this division value, the supercapacitor handles the high-frequency components on the DC bus in most cases, and the remaining low-frequency components are handled by the energy storage battery.

4. A hybrid energy storage control method for an urban rail transit energy router according to claim 1, characterized in that: In step S3, the fuzzy controller has two inputs, which are the total power minus the power after passing through the low-pass filter, denoted as P FIN And the state of charge SC of the supercapacitor soc .

5. A hybrid energy storage control method for an urban rail transit energy router according to claim 4, characterized in that: For SC SOC The membership function of P is defined in three parts, namely Low, Medium and High, corresponding to the three different levels of charge state of the supercapacitor; FIN The membership function of is defined in 7 parts, which are and They correspond to high, medium and low charging power respectively, and the middle 0 state P zero , and high, medium and low discharge power; the output of fuzzy control is the reference power of the supercapacitor They are HighC, MedC, SlowC, Zero, SlowD, MedD, and HighD, which represent the reference power of the supercapacitor, namely, fast charging, medium charging, slow charging, the middle 0 state, slow discharge, medium discharge, and fast discharge. Assume the following analysis: the train in the left power supply section is in an emergency acceleration state. At this time, the energy router obtains a high-frequency and large discharge power demand, which is first considered to be met by the supercapacitor. In this case, the charge state of the supercapacitor is divided into three situations: high, medium, and low. When SC SOC When the state is High, the signal transmitted to the converter at the SC end through the fuzzy controller tends to be quickly discharged HighD, that is, the supercapacitor uses a larger power to meet the output load demand; if the SC SOC When the value is Medium, the supercapacitor meets the output load requirement with medium power. SOC When the SOC of the supercapacitor is low, the supercapacitor tends not to discharge, the output power is reduced, and the final load power is met by the energy storage battery; if the discharge power demand is not large and the SOC of the supercapacitor is in a Low state, the system output state tends to be slow charging SlowC, that is, slowly charging the supercapacitor to increase the SOC of the supercapacitor to cope with future high-power output needs.

6. A hybrid energy storage control method for an urban rail transit energy router according to claim 1, characterized in that: According to the working mode of the train and the specific working state of the energy router, the working state of the energy router is divided; the energy router is divided into two working modes, Mode I and Mode II, and the division is based on the energy storage SOC in the initial state. bat When the value of is higher than the minimum threshold, the system enters Mode I, otherwise it enters Mode II. After entering Mode I, the power (P cat1 and P cat2 ) and PV port power (P pv ) is compared to obtain the current system working state case 1 or case 2, and the different divisions under case 1; after entering Mode II, the different divisions under the current system working state case 3 are obtained.

7. A hybrid energy storage control method for an urban rail transit energy router according to claim 6, characterized in that: In working mode Mode I, it means that the SOC state of the energy router is high, the energy for train operation is all provided by the energy router, and the original traction system of the subway does not work; case 1 means that the energy provided by photovoltaics is not enough to support the operation of the train, and the energy storage part needs to provide additional energy. bat Reduce; case 1 is divided into several possibilities: Case 1-1 means that the overhead contact ports of both trains consume energy, and the required energy is provided by batteries and photovoltaics; Case 1-2 means that PV generates energy, overhead line port 1 consumes energy, and overhead line port 1 recovers energy, but Pcat1>Pcat2+Ppv, and the energy storage part still needs to provide energy; Case 1-3 indicates a no-light state, where photovoltaics do not generate energy, contact network port 1 consumes energy, and contact network port 1 recovers energy, but Pcat1>Pcat2, and the energy storage part still needs to provide energy.

8. A hybrid energy storage control method for an urban rail transit energy router according to claim 6, characterized in that: Case 2 means that the photovoltaic energy is sufficient and can provide power to two sets of contact network ports and charge the energy storage battery at the same time.

9. A hybrid energy storage control method for an urban rail transit energy router according to claim 6, characterized in that: In working mode Mode II, it means that the SOC of the energy router is at a low level and needs to be charged, so it is not used as a power supply system for trains. There are several possibilities in case 3: Case 3-1 means that the energy of both trains is provided by the upper rectifier transformer, and the energy generated by the PV port charges the energy storage battery; Case 3-2 means that one train is in braking state and the other train is in normal state. The normal running train is provided by the rectifier transformer, and the feedback energy generated by the braking train is recovered by the energy router to charge the energy storage battery; Case 3-3 means that both trains are in charging state and charging the batteries.

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