Background
With the rapid development of urban rail transit construction in China, the rail train transmission control technology also makes remarkable progress. The urban rail transit basically adopts an alternating current variable frequency voltage regulation (VVVF) speed regulation system and a regenerative braking mode. The maximum advantage of regenerative braking is energy conservation, and regenerative braking energy is fed back to the traction power grid and can be used by adjacent trains. The regenerative braking energy generated by the train every year is considerable, statistics shows that the regenerative braking energy of some traction power grids accounts for about 30% of the total electric energy of the train traction, but the regenerative braking energy cannot be completely absorbed by other adjacent vehicles, and if the regenerative braking energy is not effectively processed, the voltage of the traction power grids exceeds a normal range, so that the overvoltage protection of a vehicle traction system is triggered, and the system operation is influenced. In order to solve the problem of recycling regenerative braking energy of rail transit, energy recycling methods adopted at home and abroad generally comprise four types, namely a resistance energy consumption type, a flywheel energy storage type, a capacitor energy storage type and an inversion feedback type.
The resistance energy consumption type comprises two regenerative energy absorption modes of a vehicle-mounted resistor and a ground resistor. The vehicle-mounted resistor absorption mode is characterized in that the resistor absorption device is mounted on a train, and when the energy fed back to the direct-current traction network is not completely absorbed by adjacent vehicles, and the voltage of the traction network reaches a set value, redundant energy is consumed by a vehicle-mounted brake resistor mounted on a carriage. The vehicle-mounted resistance braking mode is not energy-saving, the generated heat can cause the temperature in the tunnel to rise, and the operation cost and the construction cost of urban rail transit are increased. The ground resistance absorption mode is that the resistance absorption device is installed in a traction substation, and when the regenerative braking energy cannot be completely absorbed by the electric equipment of the vehicle and other adjacent vehicles, the ground resistance energy absorption device can be started immediately, so that the voltage of the traction power grid is maintained within a set range, and redundant energy is consumed in a heat energy mode. The main problem of the mode is that the energy is not saved, but the mode is applied to a plurality of domestic subway lines due to mature technology, simplicity, reliability and lower manufacturing cost. In the aspect of the resistance energy consumption type technical scheme, a constant voltage resistance absorption device is mainly adopted at present in China, and the scheme has the following defects: the regenerative braking energy is dissipated in a thermal energy mode, and is not recycled, so that energy is not saved; regenerative braking energy is concentrated on the absorption resistor to generate heat consumption, so that the ambient temperature of the equipment space where the resistor cabinet is placed is increased, measures are needed to ensure enough ventilation to dissipate heat, and extra energy consumption is increased.
The method for recycling the regenerative braking energy of the rail transit by flywheel energy storage is a good solution, and is more and more widely applied in recent years. The flywheel energy storage device is connected to a direct current bus of the traction power supply network, when a train brakes, regenerative braking energy is stored through kinetic energy of the flywheel, and when the train starts or accelerates, the kinetic energy stored by the flywheel is converted into electric energy to be output, so that the regenerative braking energy is recycled. The flywheel energy storage device has long service life and low operation and maintenance cost; regenerated energy is directly converted in the direct current system, the alternating current system is not influenced, the energy utilization efficiency is high, the energy-saving effect is good, and the initial investment cost is high.
In order to solve the problem of recycling regenerative braking energy of rail transit, the technical performance and the economic index are difficult to achieve the optimal effect only by a single product.
In view of the above, it is an urgent technical problem in the art to provide a new regenerative energy recovery system and control method based on flywheel energy storage and resistance braking to overcome the above drawbacks in the prior art.
Disclosure of Invention
The present invention aims to overcome the above defects in the prior art and provide a regenerative energy recovery system and a control method based on flywheel energy storage and resistance braking.
The object of the invention can be achieved by the following technical measures:
the invention provides a regenerative energy recovery system based on flywheel energy storage and resistance braking, which comprises: the system comprises a power supply network for outputting electric energy to supply power to a rail, a direct current bus for outputting electric energy to supply power to a train, a rectifier and a transformer, wherein the rectifier and the transformer are arranged between the direct current bus and the power supply network, the direct current side of the rectifier is connected with the direct current bus, the alternating current side of the rectifier is connected with one end of the transformer, the other end of the transformer is connected with the power supply network, the electric energy output by the power supply network is matched with the direct current bus after being converted by the transformer and the rectifier, and the system also comprises:
the flywheel energy storage feedback device is connected with the direct current bus and is used for converting regenerative energy generated during train braking into kinetic energy to be stored or converting the stored kinetic energy into electric energy to be released for the train to use;
the resistance absorption device is connected with the direct current bus and can controllably consume the residual energy absorbed by the flywheel energy storage feedback device;
the voltage sensor is arranged on the direct current bus and used for detecting the voltage of the direct current bus;
the flywheel energy storage feedback device and the resistance absorption device change the running state according to the detection result of the voltage sensor.
Preferably, the flywheel energy storage feedback device comprises a bidirectional converter for dc-ac conversion and ac-dc conversion and a flywheel energy storage unit for electric energy-kinetic energy conversion and kinetic energy-electric energy conversion, a dc side of the bidirectional converter is connected to the dc bus, and an ac side of the bidirectional converter is connected to the flywheel energy storage unit.
Preferably, the resistance absorption device includes a first dc switch, a second dc switch, a filtering module, a chopper, a resistance, and a freewheeling diode, and the filtering module includes: the chopper is also connected with the resistor and the freewheeling diode respectively, and the capacitor, the freewheeling diode and the resistor are all connected with the second direct current switch.
Preferably, the rated voltage of the direct current bus is 750V or 1500V.
The invention also provides a control method applied to the regenerative energy recovery system based on flywheel energy storage and resistance braking, and the control method comprises the following steps:
the voltage sensor detects the voltage of the direct current bus;
and the flywheel energy storage feedback device and the resistance absorption device change the running state according to the detection result of the voltage sensor.
Preferably, the operation state of the flywheel energy storage feedback device comprises: charging, discharging and standby, wherein the operation state of the resistance absorption device comprises: absorbing and waiting.
Preferably, when the train brakes, when the dc bus voltage is greater than or equal to the first absorption threshold, the flywheel energy storage feedback device charges, and when the dc bus voltage is less than the first absorption threshold, the flywheel energy storage feedback device stands by.
Preferably, when the dc bus voltage is greater than or equal to the first absorption threshold, if the dc bus voltage is less than the second absorption threshold, the resistance absorption device is in standby; and if the direct current bus voltage is greater than or equal to the second absorption threshold value, the resistance absorption device absorbs the direct current bus voltage.
Preferably, the resistance absorption device adjusts the absorbed power by changing the conduction ratio of the chopper.
Preferably, when the train is started or accelerated, and when the voltage of the direct current bus is less than or equal to the discharge threshold, the flywheel energy storage feedback device discharges, and the resistance absorption device is in standby; when the voltage of the direct current bus is larger than the discharging threshold value, the flywheel energy storage feedback device is in standby state, and the resistance absorption device is in standby state.
The resistance absorption device and the flywheel energy storage feedback device in the system work in a coordinated mode, the regenerated energy is mainly stored and fed back by the flywheel, the resistance absorption is assisted, the flywheel energy storage feedback device provides most absorption power and absorbs most regenerated energy, and the resistance absorption device is used under the condition that the power of the flywheel energy storage feedback device is not enough to absorb the regenerated energy, so that the power configuration of the flywheel energy storage feedback device does not need to be configured according to the requirement of the maximum absorption power of the system, the regenerated energy can be fully utilized, the energy is saved, the emission is reduced, the overall investment can be saved, the economic benefit of the system is effectively improved, and the overall economy and the energy-saving effect of the system are better than those of the single resistance absorption device and the single flywheel energy storage feedback device; according to the system control method provided by the invention, the flywheel energy storage feedback device and the resistance absorption device are decoupled in control, mutual communication is not needed, the complexity of system control is reduced, and the system control method has expandability and is convenient to construct, operate and maintain.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In order to make the description of the present disclosure more complete and complete, the following description is given for illustrative purposes with respect to the embodiments and examples of the present invention; it is not intended to be the only form in which the embodiments of the invention may be practiced or utilized. The embodiments are intended to cover the features of the various embodiments as well as the method steps and sequences for constructing and operating the embodiments. However, other embodiments may be utilized to achieve the same or equivalent functions and step sequences.
Referring to fig. 1, fig. 1 shows a regenerative energy recovery system based on flywheel energy storage and resistance braking, which includes: the power supply system comprises a power supply network 10 for outputting electric energy to supply power to a rail, a direct current bus 20 for outputting electric energy to supply power to a train, a rectifier 30 and a transformer 40 which are arranged between the direct current bus 20 and the power supply network 10, wherein the direct current side of the rectifier 30 is connected with the direct current bus 20, the alternating current side is connected with one end of the transformer 40, the other end of the transformer 40 is connected with the power supply network 10, the electric energy output by the power supply network 10 is matched with the direct current bus 20 after being converted by the transformer 40 and the rectifier 30, and the system further comprises: at least one flywheel energy storage feedback device 50, at least one resistance absorption device 60 and a voltage sensor (not shown).
Further, referring to fig. 1, the flywheel energy storage feedback device 50 is connected to the dc bus 20, the resistance absorption device 60 is connected to the dc bus 20, the voltage sensor is disposed on the dc bus 20 for detecting the voltage of the dc bus 20, and the flywheel energy storage feedback device 50 and the resistance absorption device 60 change the operation state according to the detection result of the voltage sensor.
Further, the flywheel energy storage feedback device 50 can be configured according to application requirements, and a plurality of flywheel energy storage feedback devices 50 work in parallel to improve power and energy storage capacity. The flywheel energy storage feedback device 50 is used for converting the regenerative energy generated during the braking of the train into kinetic energy for storage, and converting the stored kinetic energy into electric energy for the train to use when the train is started or accelerated.
Further, the resistive absorber 60 may be configured according to application requirements, and a plurality of resistive absorbers 60 may be operated in parallel to improve power configuration. When the train brakes, the resistance absorption device 60 controllably consumes the residual energy absorbed by the flywheel energy storage feedback device 50 in the form of heat energy, so as to ensure that the voltage of the direct current bus 20 is stabilized within a set value range.
Further, the rated voltage of the dc bus 20 is 750V or 1500V.
In this embodiment, when a train is braked, the generated regenerative energy is fed back to the dc bus 20, the voltage of the dc bus 20 is increased to stabilize the voltage of the dc bus 20 within a set value range, so as to ensure normal and safe operation of the train, when the voltage sensor detects that the voltage of the dc bus 20 is greater than or equal to the first absorption threshold, the flywheel energy storage and feedback device 50 converts the regenerative energy into kinetic energy for storage, when the train is started or accelerated, the voltage of the dc bus 20 is decreased, and when the voltage of the dc bus 20 is less than or equal to the discharge threshold, the flywheel energy storage and feedback device 50 converts the stored kinetic energy into electric energy for release, so as to provide for train operation, fully utilize the regenerative energy, and save resources. During the braking process of the train, when the flywheel energy storage feedback device 50 reaches the maximum absorption power and cannot absorb the regenerative energy, along with the increase of the voltage of the direct current bus 20, when the voltage of the direct current bus 20 is greater than or equal to the second absorption threshold, the resistance absorption device 60 consumes the residual energy in the form of heat energy.
In this embodiment, the resistance absorption device 60 and the flywheel energy storage feedback device 50 work in coordination with each other, the regenerated energy is mainly stored and fed back by the flywheel, the resistance absorption is assisted, the flywheel energy storage feedback device 50 provides most of absorption power to absorb most of the regenerated energy, the resistance absorption device 60 is used only when the power of the flywheel energy storage feedback device 50 is not enough to absorb the regenerated energy, so that the power configuration of the flywheel energy storage feedback device 50 does not need to be configured according to the requirement of the maximum absorption power of the system, the regenerated energy can be fully utilized, energy is saved, emission is reduced, the overall investment can be saved, the economic benefit of the system is effectively improved, and the overall economy and the energy saving effect of the system are better than those of the single resistance absorption device 60 and the flywheel energy storage feedback device 50.
On the basis of the above embodiments, in the present embodiment, referring to fig. 1, the flywheel energy storage feedback device 50 includes a bidirectional converter 501 for dc-ac conversion and ac-dc conversion and a flywheel energy storage unit 502 for electric energy-kinetic energy conversion and kinetic energy-electric energy conversion, a dc side of the bidirectional converter 501 is connected to the dc bus 20, and an ac side of the bidirectional converter 501 is connected to the flywheel energy storage unit 502.
When a train is braked, the voltage of the direct current bus 20 rises, when the voltage sensor detects that the voltage of the direct current bus 20 is greater than or equal to a first absorption threshold value, the bidirectional converter 501 controls power to flow from the direct current bus 20 to the flywheel energy storage unit 502, regenerative energy is stored in the form of kinetic energy, when the train is started or accelerated, the voltage of the direct current bus 20 drops, when the voltage of the direct current bus 20 is less than or equal to a discharge threshold value, the bidirectional converter 501 controls power to flow from the flywheel energy storage unit 502 to the direct current bus 20, the stored kinetic energy is converted into electric energy to be released for the train to run, and the bidirectional converter 501 can adjust the power according to the change of the voltage of the direct current bus 20 to enable the voltage of the direct current bus 20 to be stabilized within a set value.
The flywheel energy storage unit 502 of this embodiment realizes the interconversion between kinetic energy and electric energy, and utilizes the flywheel body that rotates at a high speed in the flywheel energy storage unit 502 to store energy, belongs to physical energy storage, and is pollution-free to the environment, and the flywheel energy storage feedback device 50 has long service life, low operation and maintenance cost, and good energy-saving effect.
On the basis of the above embodiments, in the present embodiment, referring to fig. 1, the resistance absorption device 60 includes a first dc switch K1, a second dc switch K2, a filtering module 70, a chopper VT, a resistor R, and a freewheeling diode VD, and the filtering module 70 includes: the chopper VT comprises an inductor L and a capacitor C, wherein one end of the inductor L is connected with a first direct current switch K1, the other end of the inductor L is respectively connected with a chopper VT and the capacitor C, the chopper VT is also respectively connected with a resistor R and a freewheeling diode VD, and the capacitor C, the freewheeling diode VD and the resistor R are all connected with a second direct current switch K2. When the train is braked, the voltage of the direct current bus 20 rises, when the voltage sensor detects that the voltage of the direct current bus 20 is larger than or equal to a second absorption threshold value, the resistance absorption device 60 consumes the regenerated energy through the resistor R, and the resistance absorption device 60 adjusts the power consumption of the resistor R by changing the conduction ratio of the chopper VT so as to stabilize the voltage of the direct current bus 20 within a set value range.
The present invention also provides a control method applied to the above regenerative energy recovery system based on flywheel energy storage and resistance braking, please refer to fig. 2, fig. 2 shows a control method of a regenerative energy recovery system based on flywheel energy storage and resistance braking, the control method includes:
step S1: the voltage sensor detects the voltage of the direct current bus 20;
step S2: the flywheel energy storage feedback device 50 and the resistance absorption device 60 change the operation state according to the detection result of the voltage sensor.
Further, the operation states of the flywheel energy storage feedback device 50 include: the operation states of the resistance absorbing device 60, which are charging, discharging, and standby, include: absorbing and waiting.
Further, when the train brakes and the voltage of the direct current bus 20 is greater than or equal to the first absorption threshold value, the flywheel energy storage feedback device 50 charges;
when the voltage of the direct current bus 20 is smaller than the first absorption threshold, the flywheel energy storage feedback device 50 is in standby.
Further, when the voltage of the DC bus 20 is greater than or equal to the first absorption threshold,
if the voltage of the dc bus 20 is less than the second absorption threshold, the resistance absorption device 60 is in standby, and if the voltage of the dc bus 20 is greater than or equal to the second absorption threshold, the resistance absorption device 60 absorbs the voltage.
Further, the resistance absorbing device 60 adjusts the magnitude of the absorbed power by changing the on-ratio of the chopper VT.
Further, when the train starts or accelerates, when the voltage of the dc bus 20 is less than or equal to the discharge threshold, the flywheel energy storage feedback device 50 discharges, and the resistor absorption device 60 is in standby, and when the voltage of the dc bus 20 is greater than the discharge threshold, the flywheel energy storage feedback device 50 is in standby, and the resistor absorption device 60 is in standby.
Specifically, the control method of the system in the working state and the corresponding state is as follows:
referring to fig. 3, when the voltage of the dc bus 20 is within the range of the set value, as shown in state 2, that is, the voltage of the dc bus 20 is smaller than the first absorption threshold and larger than the discharge threshold, the resistance absorption device 60 and the flywheel energy storage feedback device 50 are both in the standby state and do not perform energy conversion.
When a train is braked, regenerative energy is fed back to the direct current bus 20, the voltage of the direct current bus 20 is increased, when the voltage of the direct current bus 20 is greater than or equal to a first absorption threshold, the flywheel energy storage feedback device 50 starts charging firstly, the magnitude of charging power is controlled through the bidirectional converter 501, and then the voltage of the direct current bus 20 is controlled to be stabilized within a set value range, if the flywheel energy storage feedback device 50 can stabilize the voltage of the direct current bus 20 within the maximum absorption power range, as shown in a state 3 shown in fig. 3, that is, the voltage of the direct current bus 20 is smaller than a second absorption threshold, the resistance absorption device 60 is in a standby state and does not need to be put into operation, as shown in a first peak T1 shown in fig. 4, the situation that only an absorption part of the flywheel energy storage feedback device 50 exists in the system or as shown in a third peak T3 shown in fig.; if the flywheel energy storage feedback device 50 is already operated at the maximum absorption power and still is not enough to absorb the regenerative energy, the voltage of the dc bus 20 continues to rise, see fig. 3, state 4 shown in fig. 3, when the voltage of the dc bus 20 is greater than or equal to the second absorption threshold, the resistance absorption device 60 automatically starts to operate, and adjusts the magnitude of the absorption power by controlling the on-state ratio of the chopper VT, so as to stabilize the voltage of the dc bus 20, as shown by the second peak T2 shown in fig. 4, which indicates that not only the absorption part of the flywheel energy storage feedback device 50 but also the absorption part of the resistance absorption device 60 exist in the system. With the development of the braking process of the train, the regenerated energy gradually decreases, the voltage of the direct current bus 20 also decreases, and when the voltage of the direct current bus 20 is smaller than the second absorption threshold value, the resistance absorption device 60 automatically quits the operation and enters a standby state. When the train braking is finished and the voltage of the direct current bus 20 is smaller than the first absorption threshold, the flywheel energy storage feedback device 50 also exits the charging state and enters the standby state.
Referring to fig. 3, when the train starts or accelerates, the voltage of the dc bus 20 decreases, as shown in state 1, when the voltage of the dc bus 20 is less than or equal to the discharge threshold, the flywheel energy storage feedback device 50 automatically enters the discharge state to convert the stored kinetic energy into electric energy, the power is controlled by the bidirectional converter 501 to flow from the flywheel energy storage unit 502 to the dc bus 20, the voltage of the dc bus 20 is controlled to be stabilized within the set value range, and the resistance absorption device 60 is in the standby state.
In the control method of the system in this embodiment, the flywheel energy storage feedback device 50 and the resistance absorption device 60 are decoupled in control, and do not need to rely on mutual communication, so that the complexity of system control is reduced, and the system has expandability and is convenient to construct and operate and maintain.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.