Method for controlling the operation of a track-bound vehicle with two energy sources

Abstract

A method for controlling the operation of a track-bound vehicle that can be operated alternatively and simultaneously with a first and a second energy source provides for dividing a required total power between the energy sources in such a way that the value of an evaluation criterion is optimized.

Description

The invention relates to a method for controlling the operation of a track-bound vehicle, wherein the vehicle is operable with a first and a second energy source, and to a track-bound vehicle.The term track-bound vehicle includes rail vehicles and non-rail-bound electrically operable vehicles which draw motive power from an electrical grid via current collectors. An example of this is a overhead bus. Hybrid concepts are increasingly being used to drive track-bound vehicles, that is to say the vehicle can be operated with energy from different energy sources. In the case of an electric drive, an energy supply network, an accumulator (usually referred to as a battery) and / or a fuel cell can be used as energy source. The energy sources supply the track-bound vehicle with energy via a respective feed unit.Modern hybrid track-bound vehicles usually have, on the one hand, a power supply unit with a transformer or filter and, if appropriate, a converter and further components. Power can be provided for the vehicle from the energy supply network via the network feed unit for the traction system or other consumers, and power can be fed back into the network. In addition, such vehicles have one or more energy stores, for example an accumulator which is usually referred to as a battery and which can output power to the traction equipment or other loads via a suitable battery feed unit or absorb it when feeding back. A further option for supplying energy in non-electrified route sections is a fuel cell, which is also usually coupled to a battery. The drive and further consumers, referred to as auxiliary operations (HBU), receive the power from one of the available energy sources or output it to these.The track-bound vehicle can thus be operated in different supply modes: In gridless track sections, the battery or the fuel cell serves as an energy source. In line-supplied line sections, the energy supply network serves as an energy source. The vehicle is powered via the power supply and the battery may be further charged. Such operation enables the use of track-bound vehicles with an electric drive even on tracks which are not continuously electrified. However, the required energy is high.It is an object of the invention to specify an improved method for the operation of a track-bound vehicle having at least two energy sources.Another object is to provide a track-bound vehicle that has low energy consumption when operating with at least two energy sources.These objects are achieved by a method having the features of claim 1 and by an arrangement according to claim 7.Advantageous embodiments of the invention are specified in the dependent claims.The invention provides for the operation of a track-bound vehicle which can be operated both alternatively and simultaneously with a first energy source and with a second energy source to specify an evaluation criterion for the operation. The total power required is determined. The value of the evaluation criterion is determined for operation with a predetermined distribution of the total power required among the energy sources. A proportion for the first energy source is set in the range 0%-100%, i.e., an operation only with the second energy source, an operation with both energy sources or an operation only with the first energy source is considered. This value is optimized by varying the distribution of the required total power among the energy sources. That distribution of the total power is therefore determined at which the evaluation criterion assumes an optimum value. It is within the scope of the invention to calculate the value of the evaluation criterion in advance for different distributions to the energy sources and to store the result. During operation, these stored results can then be used. However, the calculation can also be carried out during operation.The operation of the track-bound vehicle comprises driving, feeding back, rolling and / or holding, wherein auxiliary operations can be in operation in each case. The term feedback includes feedback to a network or to a battery or similar energy source.For the first and the second energy source, in particular an electrical energy supply network, a battery or a fuel cell can be used. It is also possible to use more than two energy sources.In one embodiment, the power loss is used as the evaluation criterion. In this case, in particular, the power loss can be determined in the feed unit of the respective energy source, which comprises, for example, in the case of a mains feed, an input controller with transformer and a cooling system. The optimization is effected in particular in such a way that the total power loss is minimized. Therefore, in the case of a specific split of the total power both for the power supply system and for the battery supply system, the power loss is calculated and then the split of the total power between the partial powers is selected such that the total loss-that is to say the sum of the individual power losses-is the lowest. In addition, grid losses, i.e. losses in the grid outside the vehicle, can also be taken into account and an overall system consideration can thus be carried out.In another embodiment, the energy costs are used as the evaluation criterion. In a further embodiment, the total loss energy can serve as the evaluation criterion. In particular, the power losses are calculated for specific time intervals and then integrated or added over these time intervals. In further embodiments, one of the variables listed below as a further evaluation criterion can be used as an evaluation criterion.If the power loss is considered as an evaluation criterion, this is strongly dependent on the current through the energy sources. The current through, for example, the mains supply and the battery supply enters approximately square-law into the power loss. The optimized value, i.e. the minimum of the total loss power, thus depends strongly on the current power.In one specific embodiment, a further evaluation criterion is taken into account in defining the distribution of the total power among the energy sources. The optimization then takes place taking into account both evaluation criteria, which can be suitably weighted. Examples of the further evaluation criterion are: lifetime of components, temperature or compliance with setpoint temperatures of components, state of charge of the battery. For example, due to aging or acute heating of a component, its internal resistance can change in such a way that the optimum power distribution to the energy sources changes. The further evaluation criterion can therefore comprise in particular operating data of components (temperature, internal resistance and the like). The term operating data also includes variable parameters which can be calculated in advance.Alternatively or additionally, the state of charge of the battery can be taken into account since the battery energy is required in route sections not supplied with the grid. In addition, the storage device can be charged during grid operation, in particular when the contents are kept longer; such charging is also necessary in many cases. This energy consumption or feeding back into the battery is likewise encompassed by the term "operation". Using route data of the route to be traveled or predictive logic, the required state of charge and thus the usable energy of the battery can be determined, wherein the route can consist of a plurality of network-supplied and network-free partial routes. The usable energy of the battery in sections supplied with the grid, i.e. as a support for the grid supply, and the required charge are determined by a predictive logic, taking into account the necessary energy or the required battery state of charge, in particular at the end of the sections supplied with the grid. It is advantageous if for this purpose the driving profiles and necessary performance profiles are known and the current loading state, loading inlets and outlets, weather data (wind, temperature, among others), slopes in the course of the route and the like are also known. If an excessively low state of charge is detected, the optimum of the division is deviated in that the battery outputs less power during driving and / or receives more power during holding and / or receives more power during braking (regenerative). If a higher state of charge than required is determined, the optimum of the division can be deviated in that the battery outputs more power during driving and / or absorbs less power during holding and / or absorbs less power during braking (regenerative).The consideration of the further evaluation criterion (in particular of the state of charge) can be carried out in such a way that the optimum of the evaluation criterion (in particular the minimum power loss) is deviated during the division. More weight can also be given to the further evaluation criterion than to the evaluation criterion.The usable energy of the battery in grid-supplied sections can be distributed in such a way that the total energy requirement occurring over a specific route or over a specific time is minimized.For example, in particular in situations with a large power requirement of the drive and / or of the auxiliary operations in which the absolute losses during the feeding are excessively large, the feeding through the energy store can be reduced. In contrast, in situations with low power requirements, in which a deviation from the optimum has a quantitatively less pronounced effect, it is possible to deviate from this energy-reasonable optimum in order to conserve the state of charge of the battery.In one embodiment, provision is made for optimizing the charging of the battery. The charge required for a route is calculated accordingly taking account of travel times and standstill times and is designed such that the evaluation criterion is optimized, that is to say, for example, the total losses of the energy sources are as low as possible, and at the same time the described necessary charge is ensured. It is calculated which losses occur when charging the storage device during times of weak load power (e.g. standstill times) and, in contrast, during strong load power (e.g. acceleration times), and the charging power is determined in all phases such that the total losses of the energy sources integrated over time or over the section are as small as possible. In particular, with longer holding times, the charging power can be reduced such that the losses on the feed side and on the side of the battery are low.The battery can be charged in particular when the power requirement is low as a result of operation. The relatively high power loss that usually occurs when the power is drawn low can thus be avoided or reduced.This results in a reduction in the maximum power for the grid feed, since the charge of the energy store is distributed predictively over the entire region of the grid-supplied route section. In addition, as already described, the grid feed power is reduced in that a portion of the total power required is supplied by the second energy source, in particular the battery. Compared to a later spontaneous increase in the recharging power due to a state of charge falling below a threshold value, the method brings about an early recharging with better efficiency and lower input power.The components of the feed units can therefore also be designed to be smaller, because the losses are smaller and the energy drawn is distributed more uniformly over time. Both reduce the demands on the thermal load capacity of the components of the feed (in particular of winding products such as transformer). This allows weight and costs to be saved and a further increase in energy efficiency may be obtained if necessary by the design of the components.In one embodiment, it is provided to take into account the lifetime of components in the distribution of the total power. For example, a battery has a longer service life if smaller discharge / charge cycles are preferred for a battery compared to deeper cycles or very high or very low charge states are avoided. Further, the division may be selected so that the temperature variation of components (particularly semiconductor components) is small, thereby increasing the durability. From a lifetime model of a component, a power reduction value can be determined from which a significant or a lifetime gain to be achieved for the component occurs. It can also be taken into account here that a power reduction for one of the energy sources is associated with a power increase of the other energy source. The power reduction or increase is associated with temperature swings. In this case, use can be made of the fact that smaller additional temperature swings in the battery converter are associated with a small lifetime shortening and at the same time the reduced large temperature swings in the feed converter bring about a relatively high lifetime extension. The service life thus represents a further evaluation criterion and is taken into account for distributing the total power among the energy sources. In this case, a suitable weighting of the two evaluation criteria can be carried out. Energy gain and loss of service life and vice versa are weighed against one another.In one specific embodiment, the temperature and / or the temperature development is taken into account as an evaluation criterion or a further evaluation criterion in the division of the total power. Since the losses also influence the temperature development of the internal resistors and the temperature in turn determines the value of the internal resistors and this in turn determines the loss energy, this aspect can also be included. The power distribution over time is designed such that the temperature development is controlled in such a way that, on the one hand, the predicted curves of the internal resistances over the total cycle lead to an overall optimized energy consumption, and, on the other hand, a reduction in the level due to overheating of individual components is prevented. For example, if a quick charge is predicted or planned in the case of short standstill times, the transformer can be thermally relieved in advance. As a result, it is preset thermally in an optimum manner for the possibly highly loading rapid charge, and disconnection due to overheating of the transformer is prevented. Predictively occurring cooling phases can be scheduled.In one exemplary embodiment, the battery temperature and / or the external temperature are taken into account when distributing the total power. The battery as a power source may have to be heated at cool external temperatures, in particular if its contribution to the overall power is small. It may be more advantageous in terms of energy to increase its contribution to the overall power, so that it is thus heated more strongly. Even if their power loss and the total power loss increase as a result, more favourable operation in terms of energy can be achieved by saving the battery heating.In one exemplary embodiment, it is provided that the battery is completely switched off, i.e. the proportion of the battery in the total power is 0%. The battery feed unit generates losses at low power and also in open circuit (in particular its converter part). With a low auxiliary operating power and without a drive, it can therefore be more advantageous in terms of energy to completely shut off the batteries at times and to draw the power only from the supply network. If, on the other hand, the state of charge is very high, the mains converter can be switched off--virtually vice versa--since there are also no-load losses at the converter and transformer here.The invention is explained in more detail below with reference to exemplary embodiments. They are shown in schematic representation FIG. 1 shows an arrangement for supplying energy to a track-bound vehicle which can be operated with two energy sources FIG. 2 shows a schematic illustration of an embodiment of the method sequence FIG. 3 shows a dependence of the total power loss on the proportion of an energy source in the total power FIG. 4 shows the state of charge of a battery at different route sections FIG. 5 is a power-time diagram illustrating an embodiment of the invention FIG. 6 is a power-time diagram illustrating another embodiment of the invention FIG. 7 is a power-time diagram illustrating another embodiment of the invention FIG. 8 is a temperature-time diagram illustrating another embodiment of the invention FIG. 9 shows two temperature-time diagrams to illustrate a further embodiment of the invention FIG. 10 shows a schematic illustration of an embodiment of the method sequenceFIG. 1 schematically shows an arrangement 1 for supplying energy to a track-bound vehicle. The vehicle is connected via a network infeed unit 3 to an energy supply network 2, in particular a railroad network, as a first energy source. A battery system 4 with a battery feed unit 5 in the vehicle is present as a second energy source. Both feed units 3, 5 are connected to a control unit 6. The control unit performs the calculation and optimization methods for distributing the total required power among the power sources and performs the distribution obtained thereby. On the output side, the control unit is connected via converters 7, 8 to the consumers, namely a traction drive 9 and auxiliary operations 10. In the figure, the control lines are shown in dashed lines.FIG. 2 illustrates a portion of the method for distributing total power performed in the controller. The total power loss is defined as the evaluation criterion. In step 20, the total power currently required is determined. In step 21, this power is divided between the two energy sources supply network and battery, and the associated power losses in the network feed unit (VN) and in the battery feed unit (VB) are determined (step 22). By addition, the total loss power is calculated (step 23). It is then checked whether a minimum or sufficiently low value for the total loss power has been reached, and if applicable the calculation for changed distributions of the power is carried out (loop 24) until the minimum value of the total loss is present as the optimum of the evaluation criterion (step 25). In this exemplary embodiment, the loop 24 is passed through a plurality of times and the optimum is determined. The associated power split is set by the controller (step 26).FIG. 3 shows a result of the calculation described with reference to FIG. 2. The table shows the total power loss V= VN+ VB calculated in step 23 at different proportions A of the battery power to the total power. In this case, half division results in a minimum total loss power and is correspondingly adjusted by the control unit.FIG. 4 schematically shows the state of charge 31, 32, 33, 34 of the battery of the vehicle at different points of a route being traveled and thus at times lying one after the other. Starting from the charge state 31 present at t 1 and route data (slopes, distances, mains supply, charging possibilities, among others), the expected charge state is calculated at times t 2, t 3 and t 4. In the example, the following boundary conditions are used as the basis for the calculation: in the range t1-t2, track current is available, in the range t2-t3, a gridless section is traveled on, i.e. the total power required must be provided by the battery, between t3 and t4 there is, inter alia, a stopping point at which the battery can be charged. When distributing the total power between the grid and the battery, in addition to the lowest possible total loss power, it is also taken into account that at the beginning of the gridless section, that is to say at the time t2, the battery must have a minimum state of charge which corresponds to the lower value of the state of charge range 32.FIG. 5 shows an example of the calculated power L obtained from the grid (solid line 40) and from the battery (dashed line 41) with optimized sharing of the total power during a trip. Positive values mean an input to the vehicle, negative values mean a feedback to the network or to the battery (charging). The travel plug is constantly supplied with network. The total loss serves as the evaluation criterion.Between t0 and t1, a high total power, for example for traction, is required. The optimization of the evaluation criterion "total loss" results in the illustrated distribution of the total power among the energy sources.Between t1 and t2, an average traction power is required. Minimizing the total loss results in optimum operation in obtaining the power from the grid and at the same time charging the battery with low power. Between t2 and t3, the vehicle brakes, it can be fed back to the mains as well as the battery can be charged with high power. Between t 3 and t 4, it is provided that the vehicle is stopped but some auxiliary operations are in operation. Since only a low power is required for this, the optimization yields a reference of the power via the network feed unit and simultaneous charging of the battery.For the above example, FIG. 6 shows the power obtained from the network with (50) and without (51, dashed) optimization. Positive values mean an input to the vehicle, negative values mean a feedback to the grid. The travel plug is constantly supplied with network. The power supply by the battery is not shown.Without optimization (51), power is only drawn from the network or fed back to the network. Between t0 and t1, the entire, relatively high power is obtained from the network without optimization; with optimization, it is divided among the energy sources. Between t1 and t2, the charging of the battery is dispensed with without optimization, with the consequence that the power drawn by the grid is lower than when the optimization is carried out. Between t 3 and t 4, namely when holding at a stopping point with good network connection, charge of the battery is provided depending on the state of charge, which occurs spontaneously with very high power without optimization. Such a procedure is disadvantageous for the service life of the battery and is avoided by the optimized method ( 50).FIG. 7 shows an example of the calculated power obtained from the network (60) during an optimized split of the total power during a trip, compared to a method without optimization (61 shown in dashed lines). In this example, a constraint of optimizing that the battery should not be discharged is. Positive values mean an input to the vehicle, negative values mean a feedback to the grid. The travel plug is constantly supplied with network. The total loss serves as the evaluation criterion.Between t 0 and t 1, the calculated powers 60, 61 are the same (with and without optimization), since a possible power provision by the battery is not included in the optimization. Between t 1 and t 2, the battery is charged, so that the optimized scenario shows a higher power consumption from the network than the non-optimized scenario. Between t2and t3, the battery is also charged, which leads to a lower recovery to the grid. In the optimized method, charging with very high power between t 3 and t 4 can be avoided, since the battery has already been charged to the required extent between t 1 and t 3.FIG. 8 shows, using the example from FIG. 5, the temperature profile of a feed converter in the network feed unit ( 70, 71) and of a converter in the battery feed unit ( 72, 73, dashed lines), in each case with ( 70, 72) and without optimization ( 71, 73). By optimizing or distributing the power among two energy sources, the temperature peaks in the feed converter are significantly reduced, thereby increasing its service life. In contrast, the temperature increase of the battery converter is only moderate and is associated with a slight shortening of its service life. The optimization method uses the temperature or the service life as a further evaluation criterion in the distribution of the total power to the energy sources, wherein the criteria are weighed against one another in the desired manner.FIG. 9 shows in the upper part a time-dependent temperature profile 80 of the mains transformer and of the battery 81 without optimization. The temperature profile of the transformer 82 and of the battery 83 is shown in the lower part with optimization, i.e. with optimized distribution of the total power among the energy sources. The time profile of the corresponding internal resistances of these components is qualitatively the same or at least very similar to the temperature profile.Between t0 and t1 and between t2 and t3, network-supplied route sections are traversed; between t1 and t2, there is a network-free route section. Without optimization, the power is only drawn from the grid in the grid-supplied sections, so that the grid feed unit and in particular the grid transformer are strongly heated. Although the power is drawn from the battery between t1 and t2, the temperature of the mains transformer decreases only slightly as a result. This has the result that at t 3 the permitted maximum temperature Tmax of this component is exceeded.The predictively calculated temperature profile can be changed by the optimization method such that the allowed maximum temperature is not exceeded, as can be seen in the lower part of FIG. 9 from the temperature profile 82 of the mains transformer and the battery 83. The temperature of the components is taken into account as an evaluation criterion or as a further evaluation criterion in the method. As a result, the power distribution is controlled such that before t1, i.e. in the grid-supplied section, the total power is divided between the two power sources, whereby the temperature of the transformer only rises to a lower value. In the subsequent gridless section, cooling again takes place, and between t2 and t3, the total power is again divided between the two energy sources in such a way that the temperature does not rise above the permitted maximum temperature. It is also possible to plan fore-and-aft cooling phases in which the battery takes over a predominant proportion of the total power.FIG. 10 schematically shows the method sequence when further evaluation criteria are taken into account. After the start, the required energy for a route section i is determined in step 90. In step 91, the total energy is divided between the mains supply and the battery, and in step 92 the resulting individual losses and the total loss are determined. In step 93, a check is made as to whether the optimum of the total energy for the section of track i has been reached. If no, the total loss is minimized by varying the split (loop 94). If the optimum is reached, a check is made in step 95 as to whether all route sections are optimized and, if appropriate, the method is carried out for a further route section i+1 (loop 96).If all sections are optimized, one or more further evaluation criteria are checked (steps 97 a- c): for the method optimized to this extent, for example, the lifetime of a component, the temperature profile of a component and / or the current and / or the required battery state of charge is determined. If these are within a predetermined target range (step 98), the method optimized according to step 95 represents the final method with which the operation of the vehicle is controlled. If one of the parameters is outside the target range, the split is changed in step 91 and the method is run through again (loop 99) until the parameter or parameters are in the target range or are optimized. The division is preferably first changed for the sections i in which the optimum division between the energy sources changes the least.

Claims

Method for controlling the operation of a track-bound vehicle, wherein the vehicle can be operated alternatively and simultaneously with a first and with a second energy source, having the following steps: - determining a value of an evaluation criterion in the case of a predefined division of the total power required for the operation between the energy sources, wherein the proportion of the first energy source to the total power is in the range 0% - 100%, - dividing the required total power between the energy sources with the aid of an optimization of the value of the evaluation criterion when the proportion of the first energy source varies.Method according to the preceding claim, characterized in that the power loss or the energy costs or the total energy required for a route are used as evaluation criterion.Method according to Claim 1, characterized in that operating data of a component are used as evaluation criterion.Method according to one of the preceding claims, characterized in that a further evaluation criterion, in particular a lifetime of components and / or a state of charge of one of the energy sources and / or an energy required for a route, is taken into account in the division of the total power required.Method according to one of the preceding claims, characterized in that route data and / or operating data of components are additionally taken into account in the division between the energy sources.Method according to the preceding claim, characterized in that an energy of the battery available for grid-supplied routes is determined and, during operation in grid-supplied routes, the division is selected such that the evaluation criterion and / or the further evaluation criterion, in particular a total energy requirement for the grid-supplied route, is optimized.A track-bound vehicle which can be operated alternatively and simultaneously with at least two energy sources, having a control unit for carrying out the method according to one of claims 1 to 5.

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