On-board intelligent power supply power pack system for electrified railway

Abstract

The application discloses a kind of intelligent power supply power packs for electrified railway of vehicle, the system includes converter, traction inverter, auxiliary inverter and power supply power pack;The converter is connected traction inverter and auxiliary inverter respectively by high-voltage DC bus, and provides DC power supply for it;The power supply power pack is connected with high-voltage DC bus, and converter provides DC power supply for power supply power pack by high-voltage DC bus, and power supply power pack provides DC power supply for traction inverter and auxiliary inverter by high-voltage DC bus.The beneficial effects of the present application are: without large-scale reconstruction to the original traction power supply system, realize locomotive not power loss, safe and stable overpass, and also auxiliary realization to secondary pulsating power compensation;Intelligent power supply power pack can provide emergency power for locomotive when traction network fails, improve the safety and reliability of locomotive system;Its converter is small in size, light in weight and low in cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrified railway power supply, and in particular to a vehicle-mounted intelligent power supply power pack system suitable for electrified railways. BACKGROUND

[0002] With the continuous development and long-term practice of electrified railways, manual power-off neutral sections have gradually been eliminated. At present, there are three relatively mature automatic neutral section schemes, namely, ground automatic neutral section, vehicle-mounted automatic neutral section and column switch automatic switching neutral section. Among the neutral section schemes commonly used in domestic and foreign high-speed railway traction power supply systems, the vehicle-mounted automatic type needs the locomotive to frequently open and close the vehicle-mounted resistor, and has high requirements for the location of the electric neutral section. The ground switch type needs the ground sensor to accurately identify the position of the locomotive, and has long response time, slow switching process and limited service life. The column switch type needs frequent maintenance, and has strict requirements for the speed of the locomotive passing through the neutral section, and is difficult to adapt to the locomotive with multi-bow movement. Among the new neutral section schemes, the use of through-type same-phase traction power supply devices and catenary continuous power supply devices needs to revolutionize the structure of the existing traction power supply system, and has high cost and maintenance cost. The gradual phase shift type needs complex converter control circuit and locomotive matching mode, and has poor reliability and high implementation cost. The flexible automatic type needs a large-capacity converter device when matching the operating power of the locomotive, greatly increasing the construction investment cost. Therefore, the conventional vehicle-mounted energy storage scheme occupies a large area, has high cost and large operating loss, and is not suitable for electric locomotives which have high requirements for device size and efficiency.

[0003] With the popularization of new energy equipment and the application of a large number of power electronic devices, although the power electronic devices have the advantage of fast response, they lack inertia and damping characteristics, which reduces the stability of the entire system. The grid-side suppression measures are mostly to use compensators to realize dynamic compensation by detecting the real-time changes of voltage and current. However, the above measures all need large-scale investment and reconstruction of the existing traction power supply system infrastructure, so in terms of economic cost and practicality, further research is still needed to find a more optimal solution to effectively suppress low-frequency oscillation at the lowest cost and with the highest practicality. The existing suppression methods on the locomotive side are all to modify the control parameters and characteristics of the traction converter, which is difficult to unify for different vehicle types, and may cause higher power loss of the system or change the structure of the original controller, affecting the dynamic performance of the system during normal operation. Moreover, low-frequency oscillation will cause negative damping behavior of the system, so if passive control is used, the energy function matrix cannot be maintained in the low-frequency range. Therefore, it is necessary to study a more efficient and easy-to-implement suppression scheme to improve the dynamic and steady-state performance of the system.

[0004] For the converter power secondary fluctuation suppression, the existing hardware scheme can overcome the disadvantages of large size, parameter drift and other passive hardware schemes, but the scheme also has problems such as cost increase and circuit complication. The software scheme needs a high-bandwidth current loop, and for a megawatt-level high-power traction converter, the switching frequency is not high, and it is difficult to realize a high-bandwidth current loop; when the DC bus voltage fluctuates sharply, a larger error will be generated, and a satisfactory compensation effect cannot be achieved. At present, there are not many cases that the existing compensation methods can be successfully applied to the condition of severe fluctuation of DC bus voltage, so it is a direction worth studying.

[0005] During the operation of the locomotive, the instantaneous power output by the power grid to the rectifier contains not only steady-state active power but also secondary fluctuation components. When these secondary fluctuation power components pass through the DC support capacitor, they will generate even harmonic voltages dominated by the second harmonic on the DC side. When the three-phase inverter is subjected to sinusoidal pulse width modulation under this fluctuating voltage, a sub-harmonic voltage, i.e., a beat frequency voltage or a beat frequency voltage, will be generated on the AC side. The low-frequency beat frequency voltage will generate a large beat frequency current on the stator side of the asynchronous motor. This beat frequency current may cause motor torque pulsation, excessive rotational noise, mechanical component resonance, and additional losses, reducing the stability of the system. Solving the secondary power fluctuation problem is of great significance to the safe and stable operation of the railway system.

[0006] The electric locomotive and the traction power supply system, which are the key components of the electrified railway, form a complex system that is interconnected and mutually influenced. The stability of the vehicle-grid coupling system formed by the traction power supply system and the electric locomotive directly affects the normal operation of the electrified railway, and harmonic oscillation is the most common phenomenon in unstable phenomena. With the development of heavy-haul railways and high-speed railways, harmonic oscillation has become an electric power quality problem that cannot be ignored in electrified railways, and it is necessary to improve this phenomenon to ensure the normal and safe operation of electrified railways.

[0007] In summary, future electrified railways will develop towards high speed and heavy load. In order to solve the problem of electric neutral section and power quality, two aspects need to be considered: on the one hand, without large-scale modification of the existing power supply and traction system, uninterrupted power supply through the neutral section is realized; on the other hand, the energy structure of electrified railways needs to be optimized to improve the comprehensive energy utilization efficiency, achieve energy-saving, efficient, low-carbon, green and safe and reliable power supply of electrified railways. Therefore, it is necessary to study the schemes of locomotive uninterrupted power supply through the neutral section with high efficiency, high flexibility, high safety, low loss, low cost, low carbon and environmental protection, and enhancement of the vehicle-grid coupling system. SUMMARY

[0008] This application is designed to adapt to the high-speed and heavy-load development of electrified railways, meet the higher reliability and stability requirements of traction power supply systems, and address the issues of locomotive power loss during phase transitions, secondary power pulsation compensation of single-phase converters, and improvement of the stability of the vehicle-grid coupling system. It is a vehicle-mounted intelligent power supply package system suitable for electrified railways.

[0009] The technical solution adopted by this application to solve its technical problem is:

[0010] An onboard intelligent power supply package system suitable for electrified railways, the system comprising a converter, a traction inverter, an auxiliary inverter, and a power supply package;

[0011] The converter is connected to the traction inverter and the auxiliary inverter respectively through the high-voltage DC bus, and provides DC power to the traction inverter and the auxiliary inverter.

[0012] The power supply pack is connected to the high-voltage DC bus. The converter provides DC power to the power supply pack through the high-voltage DC bus. The power supply pack provides DC power to the traction inverter and the auxiliary inverter through the high-voltage DC bus.

[0013] The on-board intelligent power supply pack system suitable for electrified railways includes a battery pack and an isolated DC / DC converter.

[0014] The positive terminal of the battery pack is connected to both the positive input terminal and the negative output terminal of the isolated DC / DC converter.

[0015] The negative terminal of the battery pack is simultaneously connected to the input negative terminal of the isolated DC / DC converter and the negative power supply line of the high-voltage DC bus.

[0016] The positive output terminal of the isolated DC / DC converter is connected to the positive power supply line of the high-voltage DC bus.

[0017] The on-board intelligent power supply package system applicable to electrified railways uses an isolated DC / DC converter that is a bidirectional isolated DC / DC converter. It employs dual closed-loop control, with the outer loop stabilizing the output voltage and the inner loop stabilizing the inductor current. The actual output voltage value is compared with the given output voltage value, and after passing through the voltage loop, it serves as a command for the inductor current. After being compared with the actual inductor current value, it generates a duty cycle signal through the current loop, which is then used for modulation.

[0018] The on-board intelligent power supply power pack system suitable for electrified railways is composed of an isolated DC / DC converter, an H-bridge converter and a high-voltage lithium battery pack; in order to meet the use requirements of high voltage and high power, a plurality of input sides of the isolated DC / DC converters are connected in series to adapt to the high voltage of the high-voltage battery pack, and the output sides of the plurality of isolated DC / DC converters are connected in parallel and connected with the input end of the H-bridge converter, and the output end of the H-bridge converter outputs direct current.

[0019] The on-board intelligent power supply power pack system suitable for electrified railways is composed of a bidirectional isolated DC / DC converter, an H-bridge converter and a high-voltage lithium battery pack; an over-phase uninterrupted power supply control strategy is adopted to realize compensation for secondary power pulsation.

[0020] The on-board intelligent power supply power pack system suitable for electrified railways is composed of a bidirectional isolated DC / DC converter, an H-bridge converter and a high-voltage lithium battery pack; an over-phase uninterrupted power supply control strategy is adopted to realize compensation for secondary power pulsation. HL , negative feedback is given to the PI regulation of the set current, and then the duty cycle is changed, so that the output current is close to the expected set current I HLref .

[0021] The on-board intelligent power supply power pack system suitable for electrified railways adopts a vehicle network low-frequency oscillation suppression method, releases energy opposite to fluctuating power to suppress fluctuations, realizes the equivalent function of "peak clipping and valley filling", and thus suppresses the oscillation signal of the direct current side voltage.

[0022] The on-board intelligent power supply power pack system suitable for electrified railways is composed of a bidirectional isolated DC / DC converter, an H-bridge converter and a high-voltage lithium battery pack; an over-phase uninterrupted power supply control strategy is adopted to realize compensation for secondary power pulsation.

[0023] The above at least one technical scheme adopted by the embodiment of the application can achieve the following beneficial effects:

[0024] (1) In the face of a series of problems caused by the loss of power of the locomotive over-phase, the present subject matter proposes an over-phase uninterrupted power supply scheme based on on-board energy storage batteries and partial power compensation conversion, which realizes the safe and stable over-phase of the locomotive without power loss without large-scale modification of the original traction power supply system. At the same time, the DC / DC converter only transmits a small part of the power of the battery pack charging and discharging, so the converter is small in size, light in weight and low in cost; and the intelligent power supply power pack composed of the DC / DC converter and the high-voltage lithium battery pack can also provide emergency power for the locomotive in the case of failure of the traction network, and continue to maintain the operation of the locomotive to the safe area.

[0025] (2) Aiming at the secondary power ripple of the single-phase four-quadrant converter of the locomotive, a secondary power ripple active compensation scheme is proposed, and the corresponding control strategy is designed, so that the intelligent power supply power pack composed of the DC / DC converter and the high-voltage lithium battery can compensate the secondary power ripple while the locomotive does not lose power over the phase.

[0026] (3) According to the generation mechanism of the vehicle-network oscillation, an active damping compensation based on the vehicle-mounted energy storage is proposed, the virtual inertia and damping characteristics are introduced, the power fluctuation compensation of the energy storage converter on the DC side is enhanced, the stability of the vehicle-network coupled system is enhanced, and the safety and reliability of the locomotive system are improved. BRIEF DESCRIPTION OF DRAWINGS

[0027] The drawings described herein are used to provide further understanding of the present application, and form a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application, and do not constitute an improper limitation on the present application. In the drawings:

[0028] Figure 1 Fig. 1 is a topology structure diagram of the intelligent power supply power pack scheme for the vehicle-mounted;

[0029] Fig. 2(a) is a topology structure diagram of the energy storage module of the intelligent power supply power pack based on series compensation;

[0030] Fig. 2(b) is an equivalent schematic diagram of the intelligent power supply power pack based on series compensation;

[0031] Fig. 3 is a double-loop control block diagram;

[0032] Fig. 4 is a topology structure diagram of the high-efficiency DC / DC converter;

[0033] Fig. 5 is a topology structure diagram of the input series output parallel ISOP+H bridge converter;

[0034] Fig. 6 is a topology structure diagram of the secondary power ripple compensation scheme of the intelligent power supply power pack;

[0035] Fig. 7 is a topology structure diagram of the secondary ripple compensation control strategy of the intelligent power supply power pack;

[0036] Fig. 8 is a principle diagram of the low-frequency oscillation suppression of the intelligent power supply power pack;

[0037] Fig. 9 is an equivalent control model diagram of the low-frequency oscillation suppression method of the vehicle-network;

[0038] Fig. 10 is a control block diagram of the active damping compensation. DETAILED DESCRIPTION

[0039] In order to make the purposes, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be clearly and completely described below in combination with specific embodiments of the present application and corresponding drawings. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0040] The technical solutions provided by the embodiments of the present application will be described in detail below in combination with the drawings.

[0041] In order to adapt to the high-speed and heavy-load development of electrified railways, meet the higher reliability and stability requirements of traction power supply systems, and solve the problems of non-failure of locomotive over-phase, secondary power pulsation compensation of single-phase converter and improvement of stability of vehicle-network coupling system, the present application proposes an over-phase uninterrupted power supply scheme based on on-board energy storage battery and series power compensation conversion, as shown in Figure 1

[0042] An on-board intelligent power supply power pack system suitable for electrified railways, the system comprising a converter, a traction inverter, an auxiliary inverter and a power supply power pack;

[0043] The converter is connected to the traction inverter and the auxiliary inverter through a high-voltage DC bus and provides DC power for the traction inverter and the auxiliary inverter; the traction inverter provides power for the traction motor, and the auxiliary inverter provides power for the AC load;

[0044] The power supply power pack is connected to the high-voltage DC bus, the converter provides DC power for the power supply power pack through the high-voltage DC bus, and the power supply power pack provides DC power for the traction inverter and the auxiliary inverter through the high-voltage DC bus. The power supply power pack is an energy storage device, which can be charged by the converter from the catenary power supply, or can provide power for the traction inverter and the auxiliary inverter in the form of independent power supply or supplementary power supply.

[0045] The on-board intelligent power supply power pack system suitable for electrified railways, the power supply power pack comprises a battery pack and an isolation type DC / DC converter;

[0046] The positive electrode of the battery pack is connected to the input positive electrode of the isolation type DC / DC converter and the output negative electrode of the isolation type DC / DC converter at the same time;

[0047] The negative electrode of the battery pack is connected to the input negative electrode of the isolation type DC / DC converter and the negative power supply line of the high-voltage DC bus at the same time;

[0048] The output positive electrode of the isolation type DC / DC converter is connected to the positive power supply line of the high-voltage DC bus. ​

[0049] The battery pack serves as an energy source, and a DC / DC converter is connected between the high-voltage DC bus and the battery pack, and the DC / DC converter only processes a small part of the power between the battery pack and the high-voltage DC bus, so that the over-division uninterruptible solution has the advantages of small size, low cost, high efficiency and no need to make large-scale modification to the existing traction power supply system.

[0050] (1) Analysis of intelligent power supply power pack technology based on series compensation

[0051] The intelligent power supply power pack based on series compensation provided by the application only processes a small part of the power of battery charging and discharging, thereby reducing the size of the converter and reducing the design cost. As shown in FIG. 2(a), the battery is connected to the input end of the converter, and the output end of the converter is connected in series with the battery to form a new voltage output connected to the load or the DC bus. By controlling the output voltage of the converter, the equivalent battery voltage and the current flowing into the battery can be controlled. The converter can be equivalent to a controlled current source I s and a controlled voltage source V s in series with the battery pack. I s can be understood as the input current of the converter, and V s can be understood as the output voltage of the converter, both of which are controlled by the battery voltage V b , and the equivalent circuit shown in FIG. 2(b) is obtained accordingly, wherein V b and I b are the voltage and current of the equivalent battery pack, respectively. Through the equivalent circuit diagram, it can be clearly seen that under such grouping mode, the power flowing through the converter is only a part of the total power output by the battery, and the size is determined by the voltage difference between the battery and the DC bus, that is, the ratio of the output voltage of the converter to the battery voltage. The smaller the compensation voltage is, the smaller the power of the converter is, and the lower the system size and cost are, and the higher the operation efficiency is.

[0052] The intelligent power supply power pack system suitable for electrified railways, the isolation type DC / DC converter is a bidirectional isolation DC / DC converter, adopts double closed loop control, the outer ring stabilizes the output voltage, and the inner ring stabilizes the inductance current; the actual value of the output voltage is compared with the given value of the output voltage, and after the voltage ring, it is used as the instruction of the inductance current, and after comparing with the actual value of the inductance current, the duty cycle signal is generated after the current ring, and the duty cycle signal is used for modulation.

[0053] Isolated DC / DC converter due to the increase of high frequency transformer, the topology is relatively complex, the efficiency is usually lower than the non-isolated type, but because of the existence of high frequency transformer, there is no direct electrical connection between the input and output ports, which can be used for battery group. In order to stabilize the voltage at the DC side, the bidirectional isolated DC / DC converter can adopt double closed loop control, the outer ring stabilizes the output voltage, and the inner ring stabilizes the inductance current. The actual value of the output voltage is compared with the given value of the output voltage, and the inductance current is compared with the inductance current after the voltage ring. After the current ring, the duty cycle signal is generated, and then the modulation is carried out. The double closed loop control block diagram is shown in Figure 3 ; The stable inductance current control only includes the current inner loop. The duty cycle signal is generated by comparing the actual value of the inductance current with the given value of the inductance current through the current ring, and the controller usually adopts PI regulator.

[0054] The intelligent power supply power pack system suitable for electrified railway is composed of isolated DC / DC converter, H bridge converter and high voltage lithium battery pack; in order to meet the use demand of high voltage and high power, a plurality of isolated DC / DC converters are connected in series at the input side, so as to adapt to the high voltage of the high voltage battery pack, and the output side of the plurality of isolated DC / DC converters is connected with the input end of the H bridge converter in parallel, and the output end of the H bridge converter outputs direct current.

[0055] In order to realize the positive and negative voltage regulation of the output, it is also necessary to add H bridge conversion circuit after the isolated DC / DC converter. Therefore, the DC / DC converter topology of the present application adopts the topology structure composed of front-stage isolated DC / DC converter and rear-stage H bridge conversion circuit, as shown in Figure 4 .

[0056] A single DC / DC converter usually cannot meet the requirements of high voltage and high power system. At this time, a plurality of DC / DC converters can be combined in series and parallel. In order to meet the use demand of high voltage, the present application uses input series output parallel (ISOP). As shown in Figure 5 , the topology uses a plurality of isolated DC / DC converters at the input, which are connected in series at the input and in parallel at the output, so as to adapt to the voltage of the high voltage battery pack, obtain low voltage internal DC bus, and provide isolation at the same time. The converter works near the resonant frequency, so as to ensure the stability of the internal DC bus voltage. The output uses H bridge converter, which can provide positive and negative compensation voltage. Through the voltage and current control of H bridge, the functions of charging and voltage stabilization of high voltage DC bus during power failure are realized.

[0057] (2) Secondary power pulsation compensation scheme based on intelligent power supply power pack

[0058] The intelligent power supply power pack system suitable for electrified railway is an intelligent power supply power pack composed of a bidirectional isolation DC / DC converter, an H-bridge converter and a high-voltage lithium battery pack; an over-phase uninterrupted power supply control strategy is adopted to realize compensation for secondary power pulsation.

[0059] The application proposes that the bidirectional isolation DC / DC converter and the high-voltage lithium battery pack form an intelligent power supply power pack to compensate for secondary power pulsation, and the topology is as shown in Figure 6 If the line resistance is ignored, the specific expression of the pulsating current can be obtained as shown in formula (1).

[0060]

[0061] It can be seen from the formula that if the DC bus voltage is a stable DC, only the secondary pulsation component is contained in the pulsating current. If the DC bus voltage is not a stable DC, as described above, the secondary pulsation component is contained. The formula is expanded according to Taylor's first order, and formula (2) is obtained. It can be seen that the pulsating current not only contains the secondary pulsation component, but also contains the fourth pulsation component. Therefore, the DC side current of the secondary pulsation passes through the DC bus capacitor to generate the DC voltage of the secondary pulsation. The DC voltage of the secondary pulsation passes through the coupling modulation to generate the DC side current of the fourth pulsation, and then the DC side current of the fourth pulsation passes through the DC capacitor to generate the DC voltage of the fourth pulsation. By analogy, the even components of the eighth, tenth and the like can be obtained.

[0062]

[0063] By controlling the DC / DC converter to output a compensation current i c to the DC side, the pulsating current represented by formula (2) can be completely compensated, that is, i c =-i r , so that the current output to the DC bus capacitor end only contains a DC component and does not contain any pulsation component, and therefore will not be affected by the secondary pulsation power. Because the DC side voltage is a stable DC at this time and does not contain a low-frequency pulsation component, the pulsating current represented in formula (2) also only contains a secondary component. Therefore, only the secondary pulsation current needs to be compensated to the DC side in the steady state.

[0064] The over-phase uninterrupted power supply control strategy of the intelligent power supply power pack system suitable for electrified railway is a self-adaptive droop current control strategy, the innermost ring is an inductance current ring, the real-time current I HL on the resonant inductor of the H-bridge conversion circuit in the bidirectional isolation DC / DC converter is detected, PI regulation is performed on the set of the current through negative feedback, and then the duty cycle is changed, so that the output current is close to the expected set current I HLref .

[0065] As Figure 7 shown, the strategy is an adaptive droop control strategy, the innermost loop is the inductor current loop, by detecting the real-time current I HL on the H-bridge resonant inductor in the DC / DC converter, negative feedback to the set of the current for PI regulation, then change the duty cycle, so that the output current as close as possible to the expected set current I HLref , the operation is minimal, the fastest dynamic response. The second loop is the DC / DC converter output voltage loop, by detecting the output voltage of the DC / DC converter to carry out negative feedback PI regulation, its loop PI output is directly for the set current I HLref of the inductor current loop, so the voltage loop control contains the output voltage loop and the inductor current loop. On the basis of the second loop, the droop current loop is added, the battery charging and discharging current command value I Bref is subtracted from the actual battery charging and discharging current I B , and then the H-bridge output voltage compensation value ΔV H is obtained by the droop coefficient K2, and finally superimposed on the H-bridge output voltage command V Href to achieve compensation for the secondary pulsating current.

[0066] The instantaneous power expression (3) of the single-phase four-quadrant converter flowing into the DC side is:

[0067]

[0068] The instantaneous power p ac contains not only the DC component, that is, the average power p o , but also the secondary pulsating power p r . p o is used to power the DC side load, p r is the pulsating power that adversely affects the system, and the purpose of suppressing pulsation is to compensate for this power using an intelligent power supply power pack.

[0069] According to equation (3), when the pulsating power intelligent power supply power pack is compensated, the energy required for compensation can be represented by equation (4):

[0070]

[0071] Where C B is the energy storage capacity of the intelligent power supply power pack, and u Bis the instantaneous voltage of the intelligent power supply pack, and K (K ≥ 1) is the utilization coefficient of the intelligent power supply pack, representing the utilization rate of the energy that the intelligent power supply pack can store. For example, when represents the complete charging and discharging of the intelligent power supply pack in each working cycle, the higher the value of K = 1, the lower the utilization rate of the stored energy of the intelligent power supply pack. From equation (5), the voltage expression (5) can be derived as:

[0072]

[0073] For equation (4), setting sin(2ωt+φ) to -1 and 1 respectively yields the maximum and minimum stored energy of the intelligent power supply pack during operation. Similarly, for equation (5), setting sin(2ωt+φ) to -1 and 1 respectively yields the maximum and minimum voltage of the intelligent power supply pack during operation. These are expressed by equations (6) to (9) respectively:

[0074]

[0075] For ease of analysis, we define the energy utilization rate η of the intelligent power supply package. B The energy fluctuations E during the operation of the intelligent power supply pack Bf The maximum energy fluctuation E when the intelligent power supply pack is working max The ratio is shown in equation (10):

[0076]

[0077] Similarly, the voltage utilization rate η of the intelligent power supply package is defined. U Voltage fluctuations U during the operation of the intelligent power supply pack Bf The maximum voltage fluctuation U when the intelligent power supply pack is working max The ratio is shown in equation (11):

[0078]

[0079] By eliminating the utilization coefficient K of the intelligent power supply pack from equations (10) and (11), the energy utilization rate η of the intelligent power supply pack can be obtained. B With intelligent power supply package voltage utilization η U The relationship between them is shown in equation (12):

[0080]

[0081] Energy utilization rate η of intelligent power supply pack B It can be viewed as an indicator of secondary pulsation compensation, η BThe greater the value, the more sufficient the energy utilization of the power pack, and the greater the power density of the bidirectional isolated DC / DC converter. The voltage utilization rate of the intelligent power supply power pack is η U The greater the value, the greater the current flowing through the bidirectional isolated DC / DC converter, which means that the switching device needs to withstand higher current stress. Especially when η U is close to 1, the current flowing through the converter is not only very large, but also the current value will suddenly change at some moments, because there is a parasitic capacitance and a parasitic inductance in series in the actual circuit, the current suddenly changes and thus causes the system to generate high voltage, so η U equal to or close to 1 is not suitable. However, too low voltage utilization rate will cause the power density of the whole system to decrease. Therefore, the selection of the voltage utilization rate of the intelligent power supply power pack η U should be moderate.

[0082] (3) Vehicle network low-frequency oscillation suppression scheme based on intelligent power supply power pack

[0083] The vehicle-mounted intelligent power supply power pack system suitable for electrified railways adopts a vehicle network low-frequency oscillation suppression method, releases energy opposite to fluctuating power to suppress fluctuations, realizes the equivalent function of "peak clipping and valley filling", thereby suppresses the oscillation signal of the DC side voltage, suppresses the power fluctuation, and maintains the stability of the DC side voltage, which will further expand and improve the application range of vehicle-mounted energy storage.

[0084] The principle of the intelligent power supply power pack is as shown in Figure 8 When low-frequency oscillation occurs, it will cause the output power of the DC side to oscillate as P load . In order to suppress this fluctuation, the energy storage device needs to output power opposite to the fluctuating power in real time. Since the energy storage converter is connected in parallel to the rectifier DC side, the fluctuating power of the two is superimposed and then balanced.

[0085] When the vehicle network system has low-frequency oscillation, the power fluctuation of the traction rectifier DC side, especially the short-time power impact, will have an adverse effect on the DC side voltage, and further cause the entire traction network to be locked. If a double closed-loop control is used, the voltage can be maintained stable, but since the system lacks inertia like a traditional synchronous motor, the DC side voltage is relatively sensitive to power disturbance, which is not conducive to the suppression and stability of the low-frequency oscillation of the vehicle network system.

[0086] Therefore, the application proposes a vehicle network low-frequency oscillation suppression method based on an intelligent power supply power pack, introduces virtual inertia and virtual damping coefficient according to the characteristics of the DC motor, and actively improves the voltage stability. The equivalent control model is as shown in Figure 9 . Figure 9 In the formula, E, R a and I aThe armature induced electromotive force, equivalent resistance and current are respectively denoted as E, R and I, and the virtual mechanical torque and electromagnetic equation are introduced, and their expressions are as follows:

[0087] In formula (14), C T is the torque coefficient, and Φ is the magnetic flux per pole. The active damping compensation control block diagram considering the mechanical torque and electromagnetic equation is shown in Figure 10 . Wherein, ΔP represents the power deviation, and the control utilizes the mechanical power deviation to construct a mechanical torque model, so as to simulate the torque inertia and damping of the DC motor.

[0088] When the intelligent power supply power pack and the traction rectifier work together, according to the proposed control strategy, the intelligent power supply power pack releases energy opposite to the fluctuating power to suppress the fluctuation, realizes the equivalent "peak clipping and valley filling" effect, and thus realizes the suppression of the DC side voltage oscillation signal. This method measures the oscillation signal of the DC side voltage through external additional equipment, and performs rapid suppression according to the oscillation signal, and then feeds back the suppressed DC voltage signal to the voltage loop controller, realizes the active damping compensation control of the system, and the control essentially provides positive damping for the system, which is also the fundamental solution to the low-frequency oscillation problem. In addition, this scheme is simple and convenient to realize, and does not need to make large-scale changes to the locomotive traction power supply topology and control. Moreover, in the case of abnormal situation of vehicle network fault, the intelligent power supply power pack can also provide emergency power for the locomotive, and continue to maintain the locomotive running to the safe area.

[0089] The on-board intelligent power supply power pack system suitable for electrified railways, the isolation type DC / DC converter can use LLC resonant converter, full-bridge converter, DAB converter, etc.

[0090] The above only describes the embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the scope of claims of the present application.

Claims

1. An onboard intelligent power supply package system suitable for electrified railways, characterized in that: The system includes a converter, a traction inverter, an auxiliary inverter, and a power supply pack; The converter is connected to the traction inverter and the auxiliary inverter respectively through the high-voltage DC bus, and provides DC power to the traction inverter and the auxiliary inverter. The power supply pack is connected to the high-voltage DC bus. The converter provides DC power to the power supply pack through the high-voltage DC bus. The power supply pack provides DC power to the traction inverter and the auxiliary inverter through the high-voltage DC bus. The power supply pack includes a battery pack and an isolated DC / DC converter; The positive terminal of the battery pack is connected to both the positive input terminal and the negative output terminal of the isolated DC / DC converter. The negative terminal of the battery pack is simultaneously connected to the input negative terminal of the isolated DC / DC converter and the negative power supply line of the high-voltage DC bus. The positive output terminal of the isolated DC / DC converter is connected to the positive power supply line of the high-voltage DC bus. Multiple isolated DC / DC converters are connected in series on their input sides to accommodate the high voltage of the high voltage battery pack. The output sides of multiple isolated DC / DC converters are connected in parallel and then connected to the input of the H-bridge converter. The output of the H-bridge converter is DC. The power supply pack is an intelligent power supply pack, consisting of a bidirectional isolated DC / DC converter, an H-bridge converter, and a high-voltage lithium battery pack. It adopts an over-phase uninterrupted power supply control strategy to compensate for secondary power pulsations and suppresses DC-side voltage oscillations through a vehicle-to-grid low-frequency oscillation suppression method.

2. The on-board intelligent power supply package system for electrified railways according to claim 1, characterized in that: The isolated DC / DC converter is a bidirectional isolated DC / DC converter, employing dual closed-loop control. The outer loop stabilizes the output voltage, while the inner loop stabilizes the inductor current. The actual output voltage value is compared with the given output voltage value, and after passing through the voltage loop, it serves as the command for the inductor current. This command is then compared with the actual inductor current value and passed through the current loop to generate a duty cycle signal, which is used for modulation.

3. The on-board intelligent power supply package system for electrified railways according to claim 1, characterized in that: The over-phase uninterruptible power supply control strategy is an adaptive droop current control strategy. The innermost loop is the inductor current loop, which detects the real-time current I on the resonant inductor of the H-bridge converter circuit in the bidirectional isolated DC / DC converter. HL The negative feedback is used to adjust the current setting via PI control, and then the duty cycle is changed to make the output current close to the expected set current I. HLref .

4. The on-board intelligent power supply package system for electrified railways according to claim 1, characterized in that: The intelligent power supply pack adopts a vehicle-to-grid low-frequency oscillation suppression method, which releases energy opposite to the fluctuating power to smooth out the fluctuations, achieving an equivalent "peak shaving and valley filling" effect, thereby suppressing the DC side voltage oscillation signal.

5. The on-board intelligent power supply package system for electrified railways according to claim 1, characterized in that: The isolated DC / DC converter is an LLC resonant converter, a full-bridge converter, or a DAB converter.

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