CN112659922A - Hybrid power rail vehicle and direct current bus voltage control method and system thereof - Google Patents
Hybrid power rail vehicle and direct current bus voltage control method and system thereof Download PDFInfo
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Abstract
The invention discloses a hybrid power rail vehicle and a direct current bus voltage control method and a system thereof.A target voltage at the output end of a direct current chopper is regulated through speed, so that the real-time voltage/energy of a rear-end energy storage power supply is regulated. When the vehicle is in a high-speed traction working condition, the voltage/energy of the rear-end energy storage power supply is controlled to be at a lower value, and when the whole vehicle enters a regenerative braking working condition, the rear-end energy storage power supply can absorb more regenerative braking energy, so that the absorption rate and the utilization rate of the regenerative braking energy are improved; when the vehicle is in a low-speed traction working condition, the voltage/energy of the rear-end energy storage power supply is controlled to be at a higher value, and when the whole vehicle enters a regenerative braking working condition, the regenerative braking energy at a low speed is less than that at a high speed, so that the rear-end energy storage power supply can still absorb the regenerative braking energy.
Description
Technical Field
The invention belongs to the technical field of hybrid power rail vehicle control, and particularly relates to a hybrid power rail vehicle and a direct current bus voltage control method and system thereof.
Background
With the continuous development of the rail transit energy storage technology, the vehicle-mounted energy storage technology is used as a power supply to be applied more and more in the field of rail transit. Due to the development limitation of energy storage technology, the performance of a single energy storage device is difficult to meet the requirements of the whole vehicle on power exertion and endurance mileage, and the energy type energy storage device and the power type energy storage device are mixed and matched in an electricity-electricity hybrid energy storage mode so as to meet the requirements of the whole vehicle on power and energy.
The electric-electric mixing is to mix and match the two energy storage devices electrically, and the power device is usually selected from a battery or a super capacitor. The battery or the super capacitor is used as a common vehicle-mounted energy storage device, is usually directly connected with a direct current bus of the whole vehicle in parallel, can directly provide energy required by traction for the vehicle, quickly absorbs regenerative braking energy, and improves energy efficiency and corresponding speed of the power of the whole vehicle.
Fig. 1 to 3 show structural schematic diagrams of three electric-electric hybrid power devices, fig. 1 is a structural schematic diagram of a diesel generator set + battery or super capacitor hybrid power device, fig. 2 is a structural schematic diagram of a fuel cell set + battery or super capacitor hybrid power device, and fig. 3 is a structural schematic diagram of a battery set + super capacitor hybrid power device. As shown in FIGS. 1-3, power regulation and energy regulation are usually performed between two mixed energy storage elements (referring to energy storage devices at the left and right ends of a direct current chopper).
The battery or the super capacitor is generally directly connected in parallel with a direct current bus (a direct current input end of the traction inverter and the auxiliary inverter) to obtain higher use efficiency (no additional direct current chopper and other devices are needed), and the investment of the battery or the super capacitor is also faster and more efficient. When the whole vehicle is in a traction working condition, the battery or the super capacitor can be used as an energy output unit to provide high-power output, so that the battery or the super capacitor is required to have high available energy to ensure that the whole vehicle can continuously output high power and energy; in a braking working condition, from the energy-saving perspective, the battery or the super capacitor is required to be used as an energy recovery unit to absorb regenerative braking energy, and the utilization rate of energy can be effectively improved, so that the available energy value of the battery or the super capacitor is required to be as low as possible to absorb more regenerative energy.
The battery or the super capacitor is directly connected with the direct current bus in parallel, so that the use voltage range of the battery or the super capacitor is consistent with the direct current bus. The energy of the battery or the super capacitor generally decreases with the decrease of the voltage, and the available energy of the super capacitor is more linearly proportional to the voltage. Meanwhile, the power characteristics of the battery or the super capacitor are related to the energy state of the battery or the super capacitor in real time, and when the energy of the battery or the super capacitor reaches the lower limit of the energy, the battery or the super capacitor cannot be discharged; when the energy of the battery or the super capacitor reaches the upper limit, the charging cannot be carried out.
When the energy of the battery or the super capacitor is insufficient (the voltage is reduced to the minimum value), the direct current bus voltage is possibly too low, so that the problems of overcurrent faults of the traction inverter and the auxiliary inverter and traction blockage are caused, and further the parking fault of the whole vehicle is caused. On the contrary, when the energy of the battery or the super capacitor is close to the full value (the voltage reaches the maximum limit), the direct current bus may reach or approach the maximum voltage, so that the regenerative braking energy cannot be absorbed under the regenerative braking condition. At this time, the whole vehicle is required to generate heat through the brake resistor to consume the residual electric brake energy, so that the regenerative brake energy is wasted, extra heat (generated by the brake resistor) is generated to be consumed, and the regenerative brake power of the whole vehicle is limited.
In the regulation of a hybrid power system, it is very important to balance the real-time energy of a battery or a super capacitor, and the energy control (namely the voltage of a direct-current bus) of the real-time regulation of the battery or the super capacitor (directly connected with the direct-current bus) in a proper range can effectively ensure the energy requirement of the whole vehicle operation and improve the recycling efficiency of the braking energy.
Disclosure of Invention
The invention aims to provide a hybrid power rail vehicle and a direct current bus voltage control method and system thereof, and aims to solve the problems that the direct current bus voltage is too low due to too low energy of a battery or a super capacitor, so that an over-current fault can be generated and traction is blocked by a traction inverter under the condition of vehicle traction, and the problem that the regenerative braking energy of the vehicle cannot be effectively absorbed due to too high energy of the battery or the super capacitor, so that the utilization rate of the regenerative braking energy is low.
The invention solves the technical problems through the following technical scheme: a DC bus voltage control method for a hybrid rail vehicle comprises the following steps:
acquiring a speed signal of a vehicle traction motor;
under the traction working condition, the target voltage at the output end of the direct current chopper is adjusted according to the speed signal, so that the voltage of the rear-end energy storage power supply follows the target voltage at the output end of the direct current chopper, and the adjustment of the direct current bus voltage is realized;
the rear end refers to the output end of the direct current chopper.
In the invention, the target voltage at the output end of the direct current chopper is regulated through speed, so that the real-time voltage/energy of a rear-end energy storage power supply (such as a battery and/or a super capacitor) is regulated. When the vehicle is in a high-speed traction working condition, the target voltage at the output end of the direct-current chopper is reduced, so that the voltage of the rear-end energy storage power supply is controlled to be reduced (namely the available power consumption is reduced), the voltage/energy of the rear-end energy storage power supply is controlled to be at a lower value, and the whole vehicle has large regenerative braking energy (needs to absorb more regenerative braking energy) under the high-speed traction working condition, so that the rear-end energy storage power supply can absorb more regenerative braking energy when the vehicle subsequently enters the braking working condition, and the absorption rate and the utilization rate of the regenerative braking energy are improved; when the vehicle is in a low-speed traction working condition, the target voltage at the output end of the direct current chopper is increased, so that the voltage increase (namely the increase of available power consumption) of the rear-end energy storage power supply is controlled, the voltage/energy of the rear-end energy storage power supply is in a higher value, and the regenerative braking energy of the whole vehicle is small at a relatively high speed under the low-speed traction working condition (more regenerative braking energy does not need to be absorbed), so that the rear-end energy storage power supply can still absorb less regenerative braking energy when the vehicle subsequently enters a braking working condition. Meanwhile, the rear-end energy storage power supply keeps higher available power so as to meet the continuous power requirement of the whole vehicle after the traction working condition, and the problem that the traction is blocked due to overcurrent faults of the traction converter caused by overlarge current due to overlow voltage is solved.
Further, the specific adjusting process of the target voltage at the output end of the direct current chopper is as follows:
when V is less than or equal to VaThe target voltage U of the output end of the direct current chopper0Is a first voltage threshold value Ua；
When V isa＜V＜VbThe target voltage U of the output end of the direct current chopper0Comprises the following steps:
when V is more than or equal to VbThe target voltage U of the output end of the direct current chopper0Is a second voltage threshold Ub；
Wherein V is the speed of the traction motor, VaFor the lowest speed, V, when applying electric brakesbAt an overcurrent critical speed, U0Is a target voltage, U, at the output of the DC chopperaIs a first voltage threshold, UbIs a second voltage threshold, Ua＞Ub。
Further, the first voltage threshold and the second voltage threshold are set according to the voltage of the back-end energy storage power supply, the first voltage threshold is 850V, and the second voltage threshold is 650V.
Further, the specific following mode that the voltage of the rear-end energy storage power supply follows the target voltage at the output end of the direct current chopper is as follows:
when the voltage of the rear-end energy storage power supply is larger than the target voltage of the output end of the direct-current chopper, the rear-end energy storage power supply discharges to a direct-current bus to meet the power requirement of the direct-current bus, so that the voltage of the rear-end energy storage power supply is reduced until the voltage is equal to the target voltage of the output end of the direct-current chopper;
when the voltage of the rear-end energy storage power supply is smaller than the target voltage of the output end of the direct current chopper, the front-end power supply charges the rear-end energy storage power supply to increase the voltage of the rear-end energy storage power supply until the voltage is equal to the target voltage of the output end of the direct current chopper;
the front end refers to the input end of the direct current chopper.
Further, the rear-end energy storage power supply is a storage battery pack or a super capacitor pack.
The invention also provides a hybrid rail vehicle dc bus voltage control system, comprising:
the speed acquisition unit is used for acquiring a speed signal of a vehicle traction motor;
and the adjusting unit is used for adjusting the target voltage of the output end of the direct current chopper according to the speed signal under the traction working condition so that the voltage of the rear-end energy storage power supply follows the target voltage of the output end of the direct current chopper.
Further, the adjusting unit includes:
a first regulating unit for regulating V when V is less than or equal to VaThen, the target voltage U of the output end of the DC chopper is adjusted0Is a first voltage threshold value Ua；
A second adjusting unit for adjusting Va＜V＜VbThen, the target voltage U of the output end of the DC chopper is adjusted0Comprises the following steps:
a third regulating unit for regulating when V is greater than or equal to VbThen, the target voltage U of the output end of the DC chopper is adjusted0Is a second voltage threshold Ub；
Wherein V is the speed of the traction motor, VaFor the lowest speed, V, when applying electric brakesbAt an overcurrent critical speed, U0Is a target voltage, U, at the output of the DC chopperaIs a first voltage threshold, UbIs a second voltage threshold, Ua＞Ub。
The invention also provides a hybrid rail vehicle which comprises the direct-current bus voltage control system of the hybrid rail vehicle.
Advantageous effects
Compared with the prior art, the voltage of the rear-end energy storage power supply is adjusted according to the speed of the vehicle, so that on one hand, regenerative braking energy can be absorbed and utilized to the maximum extent, the absorption rate and the utilization rate of the regenerative braking energy are improved, and the utilization efficiency of the regenerative braking energy is improved; on the other hand, the high available electric quantity can be kept while a small amount of regenerative braking energy is absorbed, the continuous power requirement of the whole vehicle after the whole vehicle enters a traction working condition can be met, and the problem that the traction is blocked due to overcurrent faults of a traction converter caused by overlarge current due to too low voltage is solved.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only one embodiment of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a schematic diagram of a hybrid power plant of a diesel generator set and a battery or a super capacitor in the background of the invention;
FIG. 2 is a schematic diagram of a fuel cell stack + battery or super capacitor hybrid power plant according to the background of the invention;
FIG. 3 is a schematic diagram of a hybrid power device of a battery pack and a super capacitor according to the background art of the present invention;
FIG. 4 is a flow chart of the hybrid rail vehicle DC bus voltage control in an embodiment of the present invention;
FIG. 5 is a schematic diagram of a main traction system of an embodiment of the present invention, which is a hybrid power of a storage battery and a super capacitor;
wherein, 1-battery or super capacitor, 2-traction motor, 3-super capacitor, 4-traction motor speed feedback signal.
Detailed Description
The technical solutions in the present invention are clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 4, the method for controlling dc bus voltage of a hybrid rail vehicle according to the present embodiment includes the following steps:
1. a speed signal of a vehicle traction motor is obtained.
Generally, since the energy value of the battery pack or the super capacitor pack is not related to the speed, and is generally a fixed value, the average value of the energy of the battery pack or the super capacitor pack is basically kept unchanged no matter the speed of the vehicle. When the vehicle runs at a high speed, electric braking is applied, the absorption capacity of the super capacitor to braking energy is low, so that the braking resistor is used for consuming electric energy too early to generate heat energy, the kinetic energy of the vehicle is wasted, and the absorption rate and the utilization rate of regenerative braking energy are reduced. The present embodiment relates speed to the energy of the battery pack or ultracapacitor pack to improve the rate of absorption and utilization of regenerative braking energy while avoiding the problem of the traction inverter possibly creating over-current faults and blocking traction.
The speed of the traction motor reflects the speed of the hybrid rail vehicle, according toFormula of energy
It can be known that the higher the speed of the whole vehicle is, the larger the kinetic energy of the whole vehicle is, which means that more regenerative braking energy can be converted during braking; on the contrary, the lower the speed of the whole vehicle is, the smaller the kinetic energy of the whole vehicle is, that is, the smaller the energy can be converted into regenerative braking energy during braking, so that the voltage or the electric quantity (equivalent to the voltage of a direct current bus) of the energy storage power supply at the output end of the direct current chopper is adjusted according to the speed signal of the traction motor, and preparation is made for subsequent possible braking, so that the regenerative braking energy is fully absorbed, and the absorption rate and the utilization rate of the regenerative braking energy are improved.
The collected speed signal of the traction motor can be fed back to the direct current chopper through the network control system TCMS, so that the direct current chopper can adjust the target voltage at the output end of the direct current chopper according to the speed signal.
2. And when the tractor is in a traction working condition, the voltage of the rear-end energy storage power supply is regulated according to the speed signal.
Under the traction working condition, the direct current chopper adjusts the target voltage at the output end of the direct current chopper according to the speed signal, so that the voltage of the rear-end energy storage power supply follows the target voltage at the output end of the direct current chopper, and the adjustment of the direct current bus voltage is realized. The back-end energy storage power source refers to an energy storage power source at the output end of the dc chopper, for example, as shown in fig. 5, taking a hybrid power of a storage battery and a super capacitor as an example, the front-end power source is the storage battery, and the back-end energy storage power source is the super capacitor.
The storage battery or the super capacitor is not frequently put into use in the normal use process, the storage battery or the super capacitor is basically put into use once in a normal operation period, meanwhile, the power regulation speed of the direct current chopper is high, and full power regulation can be basically completed within 3-5 seconds, so that the input speed of the storage battery or the super capacitor is not greatly influenced by the direct current chopper. Because two different energy storage devices of the hybrid power rail vehicle have characteristic difference, the direct parallel connection can cause faults of overcharge, heating and the like, and therefore the direct current chopper is a device which cannot be cancelled.
Vehicle electricBraking energy EbExpressed by formula (1):
wherein k is a kinetic energy conversion coefficient, m is the whole vehicle mass, and v is the braking initial speed. According to the approximation of the formula (1), when the mass m is constant, the regenerative braking energy of the whole vehicle is in direct proportion to the square of the speed, and the larger the speed is, the more the regenerative braking energy is.
The power of the rail vehicle is high when the rail vehicle runs in the stages of starting acceleration and heavy load climbing, the rail vehicle has low traction power under the working conditions of straight road, light load and low speed running, and meanwhile, the energy can be fed back under the working condition of regenerative braking.
As shown in fig. 1-3, the link of connecting the hybrid power and the whole vehicle traction/auxiliary system is a direct current bus, and the direct current bus is closest to the hybrid power link, so that the total power and energy change condition of the hybrid power system is directly reflected, as shown in formula (2-5):
the relation between the exerted power of the whole vehicle and the power of the direct current bus of the whole vehicle is as shown in the formulas (2) and (3):
when the whole vehicle is in a traction working condition: pVehicle＝PDClink×ηTraction system×ηTraction motor×ηTraction drive (2)
When the whole vehicle is in a regenerative braking working condition: pVehicle＝PDClink/ηTraction system/ηTraction motor/ηTraction drive (3)
The relation between the power of the direct current bus of the whole vehicle and the power of the hybrid energy storage system is as shown in the formulas (4) and (5):
when the whole vehicle is in a traction working condition: pDClink＝P1×ηDCDC+P2 (4)
When the whole vehicle is in a regenerative braking working condition: pDClink＝P1/ηDCDC+P2 (5)
Wherein, PVehicleThe actual power of the whole vehicle; pDClinkIs the power of the direct current bus; etaTraction systemTo the efficiency of the traction system; etaTraction motorIs the efficiency of the traction motor; etaTraction driveTo gear train efficiency; p1Real-time power for the front-end power supply; p2Storing real-time power of a power supply for the back end; etaDCDCIs the efficiency of the dc chopper.
The regulation of the target voltage at the output of the dc chopper during the traction condition is illustrated by taking the battery + supercapacitor hybrid shown in fig. 5 as an example. The maximum discharge power of a front-end power supply (namely the storage battery in figure 5) is 220KW, the voltage range of a rear-end energy storage power supply (namely the super capacitor in figure 5) is DC 600V-DC 900V, the total energy is 11kWh, and the speed range of the whole vehicle is 0 km/h-25 km/h. In this embodiment, the lowest speed V at the time of power-on braking of the facilitya5km/h, overcurrent critical speed Vb25km/h, a first voltage threshold Ua850V, and a second voltage threshold UbIs 650V.
According to the modern rail alternating-current transmission technology, a normal range exists in the voltage of a direct-current bus of the whole vehicle, so that the first voltage threshold value and the second voltage threshold value are relative values in the normal range, namely the first voltage threshold value and the second voltage threshold value are a high voltage value and a low voltage value which are set according to the voltage range of the rear-end energy storage power supply (or the normal range of the voltage of the direct-current bus). The high and low speeds are defined differently for different vehicles and cannot be defined by a value, for example, the high speed range of a high speed train may be 200km/h to 300km/h, the low speed range may be 100km/h to 160km/h, and for a tram the high speed range may be 50km/h to 70km/h, the low speed range may be 20km/h to 30km/h, so that the lowest speed V at which electric braking is appliedaAnd an overcurrent critical speed VbA low speed threshold and a high speed threshold are also set according to the speed range of the whole vehicle.
According to the equations (2) - (5), if the energy of the super capacitor (i.e. the back-end energy storage power supply) is not saturated, the power under the regenerative braking condition is absorbed by the super capacitor, i.e. PDClink＝P2U is the super capacitor voltage and I is the super capacitor current.
According to the formula of voltage calculation
The higher the speed is, the lower the target voltage (namely the target direct current bus voltage) at the output end of the direct current chopper is, and the current limit value of the super capacitor is set as ImaxThe regenerative braking power is also of limited value, corresponding to a power limit on the DC bus of PDClink_maxUnder the condition of constant power, the voltage drop of the super capacitor will cause the current to rise, but the current cannot exceed the corresponding current limit value ImaxThus, there are:
PDClink_max＝P2＝U×Imax (6)
when the voltage U of the super capacitor is reduced to a voltage limit value, the speed corresponding to the voltage limit value is the overcurrent critical speed.
In this embodiment, the target voltage U at the output terminal of the dc chopper0The specific adjusting process comprises the following steps:
2.1 when V is less than or equal to VaThe target voltage U of the output end of the direct current chopper0Is a first voltage threshold value Ua。
When the vehicle is in a low-speed traction working condition, the target voltage at the output end of the direct current chopper is adjusted to be a high voltage value U in the normal range of the direct current bus voltageaThe voltage of the super capacitor follows the UaChange and gradually approach to UaBecause the super capacitor is directly connected with the DC bus in parallel, the voltage of the DC bus is adjusted to approach to UaThe direct current chopper controls the direct current bus voltage to be at a higher value, when the whole vehicle enters a braking working condition, because the energy fed back by normal regeneration at a low speed is less, the regenerative braking energy which needs to be absorbed by the super capacitor correspondingly is less, at the moment, the super capacitor keeps higher available power (with higher voltage) to meet the continuous power requirement of the whole vehicle after the whole vehicle enters a traction working condition, and the condition that the current is overlarge due to overlow voltage is avoidedThe traction converter has overcurrent faults, so that the problem of blocking traction is caused.
2.2 when Va＜V＜VbThe target voltage U of the output end of the direct current chopper0Comprises the following steps:
when the vehicle is in a high-speed traction working condition and a low-speed traction working condition, the target voltage at the output end of the direct-current chopper is adjusted according to the formula (8), so that the voltage of the super capacitor and the voltage of the direct-current bus are adjusted, more regenerative braking energy can be absorbed, the continuous power requirement of the whole vehicle after the vehicle enters the traction working condition can be met, and the overcurrent fault of the traction converter caused by overlarge current due to overlow voltage is avoided.
2.3 when V is more than or equal to VbThe target voltage U of the output end of the direct current chopper0Is a second voltage threshold Ub。
When the vehicle is in a high-speed traction working condition, the target voltage at the output end of the direct current chopper is adjusted to be a low voltage value U in the normal range of the direct current bus voltagebThe voltage of the super capacitor follows the UbChange and gradually approach to UbBecause the super capacitor is directly connected with the DC bus in parallel, the voltage of the DC bus is adjusted to approach to UbThe direct current chopper controls the direct current bus voltage to be at a lower value, when the whole vehicle enters a braking working condition, because more energy is normally regenerated and fed back at a high speed, more regenerative braking energy needs to be absorbed by the super capacitor correspondingly, and the direct current chopper has a low voltage value UbThe super capacitor can absorb more regenerative braking energy, and the absorption rate and the utilization rate of the regenerative braking energy are improved.
Wherein V is the speed of the traction motor, VaFor the lowest speed, V, when applying electric brakesbAt an overcurrent critical speed, U0Is a target voltage, U, at the output of the DC chopperaIs a first voltage threshold, UbIs a second voltage threshold, Ua＞Ub。
Under the traction working condition, if the target voltage at the output end of the direct current chopper is U0Then the voltage of the back-end energy storage power supply follows the target voltage U at the output end of the direct current chopper0There are three cases:
in the first case: the voltage of the super capacitor is higher than U0
Because the voltage of the super capacitor is higher than that of the DCDC (namely, the direct current chopper), the DCDC can not discharge and output power, and the relation (4) between the power of the whole vehicle direct current bus and the power of the hybrid energy storage system under the traction working condition is updated as follows: pDClink＝P2Meanwhile, the voltage of the dc capacitor gradually decreases with the discharging process (output power) and gradually approaches to U0。
In the second case: the voltage of the super capacitor is lower than U0
Because the voltage of super capacitor is lower than the voltage of DCDC, therefore super capacitor can't output power, and whole car direct current bus power and mixed energy storage system's under the traction operating mode power relational expression (4) are:
PDClink＝P1×ηDCDC……(PDClink＝P1max×ηDCDC)
PDClink＝P1×ηDCDC+P2……(PDClink＜P1max×ηDCDC)
wherein, P1maxIs P1If the power of the storage battery is excessive, the storage battery can be charged to the super capacitor at the same time, and at the moment, P is measured2Is negative (indicating that the battery is charging the super capacitor). The voltage of the super capacitor gradually rises along with the charging of the storage battery and gradually approaches to U0。
In the third case: the voltage of the super capacitor is equal to U0
Updating a relation (4) between the power of the direct-current bus of the whole vehicle and the power of the hybrid energy storage system into:
PDClink＝P1×ηDCDC……(PDClink＝P1max×ηDCDC)
PDClink＝P1×ηDCDC+P2……(PDClink＜P1max×ηDCDC)……P2is negative
PDClink＝P1×ηDCDC+P2……(PDClink＞P1max×ηDCDC)……P2Is positive
Wherein, P2Negative means that the accumulator charges the super capacitor, P2The discharge of the super capacitor is positively indicated, the power of the super capacitor is converted along with the power of a direct current bus of the whole vehicle (the corresponding voltage is also changed), and the super capacitor and the storage battery discharge simultaneously to output power under the high-power traction working condition of the whole vehicle; under the working condition of low-power traction of the whole vehicle, the storage battery can charge the super capacitor while meeting the power of the whole vehicle, and the voltage of the super capacitor is generally towards approaching U0The voltage direction is developed.
In summary, the voltage U is selected according to the speed0Then, the voltage of the super capacitor can gradually follow U0Whenever there is a relationship between the voltage and capacity of the super capacitor and the lithium battery. The general trend is that the higher the voltage, the higher the capacity, and vice versa. According to the discharge curve of the battery, as the discharge capacity increases, the voltage decreases and the available capacity decreases. The capacity of the super capacitor is calculated according to the formula
It can be further seen that the energy varies proportionally with the voltage. Therefore, when the voltage of the super capacitor is at a lower level, the super capacitor can absorb more regenerative energy under the regenerative braking condition. On the contrary, the voltage of the super capacitor is controlled to be at a higher level, so that the super capacitor can be ensured to output more energy under the traction working condition.
The above disclosure is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of changes or modifications within the technical scope of the present invention, and shall be covered by the scope of the present invention.
Claims (8)
1. A DC bus voltage control method for a hybrid rail vehicle is characterized by comprising the following steps:
acquiring a speed signal of a vehicle traction motor;
under the traction working condition, the target voltage at the output end of the direct current chopper is adjusted according to the speed signal, so that the voltage of the rear-end energy storage power supply follows the target voltage at the output end of the direct current chopper, and the adjustment of the direct current bus voltage is realized;
the rear end refers to the output end of the direct current chopper.
2. The hybrid rail vehicle direct current bus voltage control method according to claim 1, wherein the specific adjustment process of the target voltage at the output terminal of the direct current chopper is as follows:
when V is less than or equal to VaThe target voltage U of the output end of the direct current chopper0Is a first voltage threshold value Ua；
When V isa＜V＜VbThe target voltage U of the output end of the direct current chopper0Comprises the following steps:
when V is more than or equal to VbThe target voltage U of the output end of the direct current chopper0Is a second voltage threshold Ub；
Wherein V is the speed of the traction motor, VaFor the lowest speed, V, when applying electric brakesbAt an overcurrent critical speed, U0Is a target voltage, U, at the output of the DC chopperaIs a first voltage threshold, UbIs a second voltage threshold, Ua＞Ub。
3. The hybrid rail vehicle dc bus voltage control method of claim 2, wherein the first voltage threshold is 850V and the second voltage threshold is 650V.
4. The method for controlling the voltage of the direct-current bus of the hybrid rail vehicle according to any one of claims 1 to 3, wherein the specific following manner of the voltage of the rear-end energy storage power supply following the target voltage at the output end of the direct-current chopper is as follows:
when the voltage of the rear-end energy storage power supply is larger than the target voltage of the output end of the direct-current chopper, the rear-end energy storage power supply discharges to a direct-current bus to meet the power requirement of the direct-current bus, so that the voltage of the rear-end energy storage power supply is reduced until the voltage is equal to the target voltage of the output end of the direct-current chopper;
when the voltage of the rear-end energy storage power supply is smaller than the target voltage of the output end of the direct current chopper, the front-end power supply charges the rear-end energy storage power supply to increase the voltage of the rear-end energy storage power supply until the voltage is equal to the target voltage of the output end of the direct current chopper;
the front end refers to the input end of the direct current chopper.
5. The hybrid rail vehicle dc bus voltage control method of claim 1, wherein the back-end energy storage power source is a battery pack or a super capacitor pack.
6. A hybrid rail vehicle DC bus voltage control system, comprising:
the speed acquisition unit is used for acquiring a speed signal of a vehicle traction motor;
and the adjusting unit is used for adjusting the target voltage of the output end of the direct current chopper according to the speed signal under the traction working condition so that the voltage of the rear-end energy storage power supply follows the target voltage of the output end of the direct current chopper.
7. The hybrid rail vehicle dc bus voltage control system of claim 6, wherein the regulating unit comprises:
a first regulating unit for regulating V when V is less than or equal to VaThen, the target voltage U of the output end of the DC chopper is adjusted0Is a first voltage threshold value Ua；
A second adjusting unit for adjusting Va＜V＜VbThen, the target voltage U of the output end of the DC chopper is adjusted0Comprises the following steps:
a third regulating unit for regulating when V is greater than or equal to VbThen, the target voltage U of the output end of the DC chopper is adjusted0Is a second voltage threshold Ub；
Wherein V is the speed of the traction motor, VaFor the lowest speed, V, when applying electric brakesbAt an overcurrent critical speed, U0Is a target voltage, U, at the output of the DC chopperaIs a first voltage threshold, UbIs a second voltage threshold, Ua＞Ub。
8. A hybrid rail vehicle characterized by: comprising a hybrid rail vehicle dc bus voltage control system according to claim 6 or 7.
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