CN117650561A - Multi-energy complementation method and system for rail transit power supply - Google Patents
Multi-energy complementation method and system for rail transit power supply Download PDFInfo
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Abstract
The invention provides a multi-energy complementary method and system for rail transit power supply, and belongs to the rail power supply technology. The power supply is compensated by the photovoltaic generator, the energy storage power supply and the train brake feedback, the energy storage capacitor stores energy fluctuation, and the compensation capacitor compensates power in a power supply section, so that stable power supply of rail transit is realized. The power supply section is divided into a plurality of traction branches by utilizing the self-coupling windings, the number of trains of the traction branches, the working states of the circuit breakers and the like are detected, the compensation power supply effect of the photovoltaic and energy storage power supply in rail transit is improved, and the energy consumption is saved. Further, the access state of the energy storage capacitor is adjusted according to the current compensation parameters, and the service life of the energy storage capacitor is prolonged.
Description
Technical Field
The invention relates to the technical field of rail transit power supply, in particular to a multi-energy complementary method and system for rail transit power supply.
Background
The multi-energy complementary technology generally adopts equipment such as photovoltaic, wind energy, braking energy feedback, storage batteries and the like as a complementary power supply of a power grid, so that dependence of rail transit on the power grid can be reduced, and the energy utilization rate is improved. The Chinese patent with publication number CN106411144B discloses a railway traction power supply system based on photovoltaic power generation, which comprises a photovoltaic power generation device, a photovoltaic inverter, a step-up transformer, a traction transformer and a traction power supply system. The system adopts a power generation mode of self-power-consumption and residual power internet surfing to ensure the normal operation of a traction power supply system. The output power of the photovoltaic power generation equipment fluctuates greatly, the system lacks of effective energy supply management, and the electric energy utilization rate is low. The Chinese patent application with the application number of CN202111424103.7 discloses a train energy-saving control method based on a ground energy storage device. The method obtains running state data of each running train in a target line interval, and stores energy for a ground energy storage device or supplies power for the train by utilizing the net regenerated energy of the trains according to the relation between the net regenerated energy power of each train in the target line interval and the charge-discharge power threshold value of the ground energy storage device. The method can realize the recycling of train braking energy and can compensate electric energy to the power grid when the power supply of the line section of the power supply network is insufficient. In a multi-energy power supply system, in addition to braking the feedback of regenerated energy, photovoltaic power output fluctuations are another factor that leads to voltage fluctuations. It is necessary to adjust various operating parameters of the system according to power supply data of different power supply devices to provide a stable operating environment for the train. In addition, in the power supply system in the prior art, voltages among different line intervals are mutually influenced, and the running state data is difficult to accurately reflect the current power supply data. In view of this, there is a need for further improvements in the art.
Disclosure of Invention
In order to solve the defects in the prior art, the invention provides a multi-energy complementary method and a system for rail transit power supply, which realize multi-energy compensation power supply through a photovoltaic generator, an energy storage power supply and train brake feedback, complete temporary storage of energy supply fluctuation by an energy storage capacitor, complete power compensation of a power supply section by the compensation capacitor, and finally realize stable power supply of rail transit. Furthermore, the invention utilizes the autotransformer winding to divide the power supply interval into a plurality of traction branches, monitors the voltage data of the traction branches, adjusts the working parameters of the traction device, the photovoltaic generator and the energy storage power supply, and improves the utilization rate of energy under the condition of ensuring the stable working of the traction device.
The aim of the invention can be achieved by the following technical means:
a multi-energy complementary method for rail transit power supply, comprising the steps of:
step 1: connecting two ends of the substation to the contact line and the positive feeder, respectively connecting two ends of the self-coupling winding to the contact line and the positive feeder, connecting the steel rail to the midpoint of the self-coupling winding, and connecting the traction device of the train to the contact line and the steel rail;
step 2: the power substation, the contact line and the positive feeder line form a power supply section, the power supply section is divided into a plurality of traction branches by the self-coupling winding, the power supply section is provided with a power regulator, the traction branches are provided with a load controller, and the power regulator is connected to the load controller of each traction branch;
step 3: the power regulators of at least two groups of power supply intervals are connected in parallel through compensation capacitors, the energy storage capacitors are connected in parallel to an energy storage power supply through a circuit breaker, and the energy storage power supply and the photovoltaic generator are connected in parallel to the power regulators through converters respectively;
step 4: detecting the number of trains in a traction branch, if the number of trains is greater than zero, entering an energy supply period by the traction branch, and restraining amplitude U according to the number of trains in the traction branch and voltage 1 Determining a discharge voltage threshold U 2 And a charging voltage threshold U 3 ；
Step 5: if the power supply voltage of the contact line is smaller than the discharge voltage threshold U 2 The load controller discharges to the corresponding traction branch, if the power supply voltage of the contact line is greater than the charging voltage threshold U 3 The load controller charges from the corresponding traction branch;
step 6: measuring a first power ratio lambda of a photovoltaic generator in a power supply section where a traction branch is located 1 According to the first power ratio lambda 1 Setting the starting voltage U of the braking resistor of the traction device 4 ；
Step 7: if the number of trains in the traction branch is equal to zero, ending the energy supply period and calculating the load controllerSecond power ratio lambda to traction device 2 According to the second power ratio lambda 2 Adjusting the voltage constraint amplitude U of the next energy supply period 1 ；
Step 8: detecting instantaneous current and instantaneous voltage of at least one converter, calculating charge compensation ripple C 1 If the charge compensates for fluctuations C 1 Rated capacity C smaller than compensation capacitance 0 Disconnecting the energy storage capacitor C 2 And returning to the step 4.
In the invention, in step 1, the traction device comprises a braking resistor, a chopper, a traction motor, a variable frequency speed regulator and a filter inductor, and the traction device is connected to a contact line and a steel rail through a pantograph and a power receiving shoe respectively.
In the present invention, in step 4,，/>，U 0 is the no-load voltage of the contact net, M is the number of trains of the traction branch, P 1m Rated traction power of mth train, R mL Is the equivalent resistance of the traction branch relative to the mth train.
In the invention, in step 6, the photovoltaic generator is connected to the power grid through a voltage controller, and the total power generation power of the photovoltaic generator is P 21 The photovoltaic power supply power output by the photovoltaic generator to the power regulator is P 22 A first power ratio lambda 1 = P 22 / P 21 。
In the present invention, in step 6, U 5 =U 0 +U C (1-λ 1 ) 2 ，U 0 Is no-load voltage of contact net, U C Is the chopping adjustment quantity of the chopper.
In the invention, in step 7, a second power ratio lambda is determined from the sum of the output powers of the traction devices and the average output power of the load controller during the power supply period 2 Voltage constraint amplitude of next energy supply period。
In the present invention, in step 8, the converter connected to the energy storage power source and the energy storage capacitor is a bidirectional converter, and the instantaneous current i (T) and the instantaneous voltage u (T) of the bidirectional converter during the operation period T' are detected, and the charge compensation fluctuation is compensatedMax (i (t)/u (t)) is the maximum value of the ratio of instantaneous current to instantaneous voltage.
In the present invention, in step 8, the no-load current U is corrected based on the instantaneous current of the contact line at a plurality of sampling moments 0 。
A multi-energy complementary system according to the multi-energy complementary method for rail transit power supply, characterized by comprising: contact line, positive feed line, steel rail, train, substation, auto-coupling winding, energy storage power supply, photovoltaic generator and energy storage capacitor,
the traction device of the train is connected to the contact line and the steel rail;
the two ends of the substation are connected to the contact line and the positive feeder line, the power substation, the contact line and the positive feeder line form a power supply section, a power regulator is arranged in the power supply section, and the power regulators in at least two groups of power supply sections are connected in parallel through compensation capacitors;
the two ends of the self-coupling winding are respectively connected with a contact line and a positive feeder, the self-coupling winding divides a power supply interval into a plurality of traction branches, and the traction branches are provided with a load controller;
the energy storage power supply is connected in parallel to the power regulator through the bidirectional converter;
the photovoltaic generator is connected in parallel to the power regulator through the unidirectional converter;
the energy storage capacitor is connected in parallel to the energy storage power supply through the breaker, if the charge compensation fluctuation of the bidirectional converter is smaller than the rated capacity of the compensation capacitor, the breaker is disconnected, wherein,
after the traction branch enters an energy supply period, determining the working state of a load controller according to the number of trains in the traction branch and the voltage constraint amplitude, and determining the working state of a brake resistor of the traction device according to the first power ratio of the photovoltaic generator;
and after the traction branch circuit finishes the energy supply period, adjusting the voltage constraint amplitude according to the second power ratio.
The multi-energy complementary system of the multi-energy complementary method for supplying power to the rail transit has the following beneficial effects: the photovoltaic and energy storage power supply is integrated into the contact line through the power regulator, and the compensation capacitor is adopted to reduce voltage fluctuation, so that complementary power supply of the power grid, the photovoltaic, the storage battery and the braking mechanical energy is realized. According to the invention, the power supply section is divided into a plurality of traction branches through the autotransformer, the number of trains of the traction branches, the power supply voltage of the overhead contact system and the output power of the photovoltaic generator are monitored to determine the working states of the load controller, the circuit breaker and the like, so that the compensation power supply effect of the photovoltaic and energy storage power supply in rail transit is improved, and the energy consumption is saved. Furthermore, the connection state of the energy storage capacitor is adjusted according to the current compensation parameter, so that the high-capacity energy storage capacitor is prevented from being repeatedly charged and discharged in a low-charge state, and the service life of the energy storage capacitor is prolonged.
Drawings
FIG. 1 is a flow chart of a multi-energy complementary method of rail transit power supply of the present invention;
FIG. 2 is a schematic diagram of electrical connections of a multi-energy complementary method of rail transit power supply of the present invention;
FIG. 3 is a schematic diagram of a tow branch of the present invention;
FIG. 4 is a schematic power take-off view of the train of the present invention;
FIG. 5 is a schematic diagram of the electrical configuration of the parallel power conditioner, bi-directional converter and unidirectional converter of the present invention;
FIG. 6 is a schematic diagram of a traction device of the train of the present invention;
FIG. 7 is a graph showing the relationship between the starting voltage of a traction branch and the power supply efficiency;
fig. 8 is a system block diagram of the multi-energy complementary system of the present invention.
Detailed Description
For a clearer understanding of the objects, technical solutions and advantages of the present application, the present application is described and illustrated below with reference to examples.
The invention adopts the voltage-reducing power supply principle of an autotransformer, the reference voltage provided by the power grid through the substation to the contact line and the positive feeder line is 2 multiplied by 900V, and the load voltage of the contact line and the steel rail is 900V. In addition to the grid, photovoltaic, stored energy power and braking mechanical energy also provide electrical energy to the contact wires and positive feed lines. The power regulator adopts an MMC-RPC (Multi-modular railway power condition) structure to control the output power of the photovoltaic generator and the energy storage power supply, so that the stable operation of the equipment is realized. The load controller adjusts the charge and discharge states of the energy storage power supply, and main control parameters comprise the number of trains, the voltage constraint amplitude and the power supply voltage of the contact line. The recovery efficiency of the braking mechanical energy is regulated by a chopper of the braking resistor, and the main control parameter is the starting voltage of the braking resistor. According to the multi-energy complementary method and system for rail transit power supply, the photovoltaic generator and the energy storage power supply are combined into the contact line through the power regulator, voltage fluctuation is reduced by adopting the compensation capacitor, and complementary power supply of the power grid, the photovoltaic power, the energy storage power supply and the braking mechanical energy is realized.
Example 1
As shown in fig. 1 to 6, the present embodiment discloses a multi-energy complementary method for supplying power to rail transit, which includes the following steps.
Step 1: the two ends of the transformer substation are connected to the contact line and the positive feeder, the two ends of the self-coupling winding are respectively connected to the contact line and the positive feeder, the steel rail is connected to the midpoint of the self-coupling winding, and the traction device of the train is connected to the contact line and the steel rail. The traction transformer of the substation adopts a v/v connection mode, converts three-phase current of a power grid into direct current, introduces the direct current into a contact line and then flows back to the substation through a positive feeder. In fig. 2, the current directions of the contact line and the positive feeder are opposite, so that the interference of the current on the train communication signal can be reduced. Adjacent autotransformer windings are spaced apart, for example, by 10km, and the step down ratio of the autotransformer windings is 2:1. In an ideal state, the train current flows back to the autotransformer winding from the steel rail between the autotransformer windings adjacent to the two sides, the steel rail at the far end of the autotransformer winding has no current, and the stray current flowing to the ground from the steel rail is reduced. In another embodiment, the power grid and the contact wires may also use single-phase power, which is not limited by the present invention.
Step 2: the power substation, the contact line and the positive feeder line form a power supply section, the power supply section is divided into a plurality of traction branches by the self-coupling winding, the power supply section is provided with a power regulator, the traction branches are provided with a load controller, and the power regulator is connected to the load controller of each traction branch. Dividing the whole rail transit power supply system into a plurality of power supply sections according to the position of the substation. As shown in fig. 3 and 4, each power supply section is provided with a plurality of groups of auto-coupling windings, and each two groups of auto-coupling windings form a traction branch. Each traction branch consists of a high-voltage loop positioned on the power grid side and a low-voltage loop positioned on the train side. Each power supply section is provided with a power regulator. The power regulator can adopt a plurality of groups of bridge arms, and the output voltage and the power can be regulated according to the number of the input bridge arms. The power conditioner using a single-phase full-bridge arm as shown in fig. 5 includes four switching devices and four freewheel diodes.
Step 3: the power controllers of at least two groups of power supply intervals are connected in parallel through compensation capacitors, the energy storage capacitors are connected in parallel to an energy storage power supply through a circuit breaker, and the energy storage power supply and the photovoltaic generator are connected in parallel to the compensation capacitors through converters respectively. In fig. 2, the stored energy power source supplies power to the contact wire via a bi-directional converter and the photovoltaic generator supplies power to the contact wire via a unidirectional converter. The energy storage power supply of the embodiment is a storage battery, and the storage battery is externally connected with a water cooling machine to realize temperature control. The photovoltaic cell is monocrystalline silicon photovoltaic cell, solar energy is converted into electric energy through a large-area planar diode, and photovoltaic power generation is achieved. As shown in fig. 5, the unidirectional converter comprises an inductor, a rectifier diode, a switching tube and a capacitor. The circuit breaker is an on-off switch for example, and controls the access state of the super capacitor. The rated capacity of the supercapacitor is, for example, 12000F. The rated capacity of the compensation capacitor is, for example, 1000F. The super Capacitor can adopt an electric double Layer Capacitor (Electrical Double-Layer Capacitor) structure, and is high in price but faster in charge and discharge.
Step 4: detecting the number of trains in a traction branch, if the number of trains is greater than zero, entering an energy supply period by the traction branch, and restraining amplitude U according to the number of trains in the traction branch and voltage 1 Determining a discharge voltage threshold U 2 And a charging voltage threshold U 3 . The method for detecting the number of trains is, for example, a method for positioning a train route, a method for detecting a contact point of a pantograph, and the like.If the number of trains is equal to zero, no load exists in the traction branch, the steps are repeated, and the trains in the branch are continuously detected. In the present embodiment, the discharge voltage threshold valueCharging voltage threshold>。U 0 Is the no-load voltage of the contact net, M is the number of trains of the traction branch, P 1m Rated traction power of mth train, R mL Is the equivalent resistance of the traction branch relative to the mth train. The equivalent resistance of the traction branch can be based on the resistance R of the unit length of the steel rail, the length L of the traction branch and the resistance R of the power receiving boot without considering the resistances of the contact line and the positive feeder 0 And (5) calculating to obtain the product. For example, the train is arranged in the middle of the traction circuit, R of the traction circuit mL = R 0 +Lr/4, more generally, the mth train is at a distance L' from the autotransformer, R of the traction loop mL =R 0 +L'(L-L')r/L。
Step 5: if the power supply voltage of the contact line is smaller than the discharge voltage threshold U 2 The load controller discharges to the corresponding traction branch, if the power supply voltage of the contact line is greater than the charging voltage threshold U 3 The load controller charges from the corresponding traction leg. If the power supply voltage of the contact line is greater than or equal to the discharge voltage threshold U 2 And is less than or equal to the charging voltage threshold U 3 The load controller does not operate. In the invention, the photovoltaic generator and the energy storage power supply play a role in compensation, and when the voltage drop or the voltage is obviously raised, the load controller enters a working state. Discharge voltage threshold U 2 And a charging voltage threshold U 3 The management of the working state of the load controller can be realized. The load controller of the embodiment can be a circuit controller with a reversing switch and a diode, and can set a buck mode and a boost mode, and the discharging state and the charging state are controlled according to the on-off direction of current.
Step 6: measuring a first power ratio lambda of a photovoltaic generator in a power supply section where a traction branch is located 1 According to the first power ratio lambda 1 Traction is arrangedStarting voltage U of braking resistor of device 4 . And a brake resistor in the traction device feeds back regenerated electric energy generated by train braking to the contact line. The photovoltaic generator can be connected to a power grid through a voltage controller except for finishing power supply compensation, and the voltage controller mainly comprises an inverter, a three-phase step-up transformer and the like. The total power of the photovoltaic generator is P 21 Photovoltaic power supply P of photovoltaic generator output to power controller 22 A first power ratio lambda 1 = P 22 / P 21 。
The structure of the traction device referring to fig. 6, the traction device includes a braking resistor, a chopper, a traction motor, a traction variable frequency speed regulator and a filter inductor, and the traction motor is connected to a contact line and a steel rail through a pantograph and a power receiving shoe, respectively. When the input voltage of the traction device is greater than the starting voltage U 4 The chopper is turned on, and a feedback current generated by braking mechanical energy is consumed by the braking resistor. U (U) 4 =U 0 +U C (1-λ 1 )，U 0 Is no-load voltage of contact net, U C The chopper adjustment of the brake resistor is achieved. The no-load voltage of the catenary can be measured after the end of the power supply cycle, typically 900V. U (U) C Typically 80V. First power ratio lambda through photovoltaic generator 1 When the power supply power of the photovoltaic generator is high, the starting voltage is regulated, the braking voltage can be increased, the braking mechanical energy is increased to feed back to the threshold value of the contact net, the braking mechanical energy fully compensates the electric energy, and voltage fluctuation caused by insufficient power supply of the photovoltaic generator is avoided. When the power supply power of the photovoltaic generator is low, the braking voltage is reduced, braking mechanical energy is consumed in the braking resistor, and the rapid lifting of the power grid voltage caused by braking of a plurality of groups of trains is avoided.
Step 7: if the number of trains in the traction branch is equal to zero, ending the energy supply period, and calculating a second power ratio lambda of the load controller to the traction device 2 According to the second power ratio lambda 2 Adjusting the voltage constraint amplitude U of the next energy supply period 1 . Determining a second power ratio lambda of the load controller to the traction device based on the sum of the output powers of the traction device and the average output power of the load controller during the power supply period 2 . In this embodiment, the average output power is calculated from the instantaneous power integration of the load controller. In another embodiment, the average output power may be calculated from a weighted sum of the instantaneous powers. Second power ratio，P 1m Rated traction power of mth train, t 1m For the time when the mth train is located in the traction branch, p t The output power of the load controller at the moment T is the duration of the energy supply period. Voltage constraint amplitude of next energy supply period +.>. The preset voltage constraint amplitude is 31V, and the voltage constraint amplitude U is used for 1 The regulation of the system improves the compensation power supply effect of the photovoltaic and the storage battery in the rail transit, increases the voltage constraint amplitude when the output power of the load controller is low, and expands the working voltage interval of the load controller. The iteration is performed step by step, and the accuracy of the voltage constraint amplitude is improved.
Step 8: detecting instantaneous current and instantaneous voltage of at least one converter, calculating charge compensation ripple C 1 If the charge compensates for fluctuations C 1 Rated capacity C smaller than compensation capacitance 0 Disconnecting the energy storage capacitor C 2 And returning to the step 4. The rated capacity of the compensation capacitor of this embodiment is preset to 1000F. The sampling period is preset, for example, 1s, the instantaneous current i (t) and the instantaneous voltage u (t) of the bidirectional converter in the working period are detected every sampling period, and the ratio i (t)/u (t) of the instantaneous current and the instantaneous voltage is calculated. Charge compensation rippleThe duty cycle T' of the bi-directional converter is typically composed of a plurality of energization cycles. max (i (t)/u (t)) is the maximum value of the ratio of instantaneous current to instantaneous voltage during the duty cycle. According to the embodiment, the connection state of the energy storage capacitor is adjusted according to the current compensation parameters, when the low-charge compensation fluctuates, only the low-cost compensation capacitor is connected, the high-capacity energy storage capacitor is prevented from being repeatedly charged and discharged in the low-charge state, and the service life of the energy storage capacitor is prolonged.In this embodiment, the air load current is calculated and determined according to the voltage reduction ratio of the power grid. The no-load current is not strictly maintained at 900v due to the changes of the internal resistance of the line and the power supply environment. In another embodiment, the invention can correct the no-load current U according to the instantaneous current of the contact line at a plurality of sampling moments after the end of the power supply period 0 。
Example two
According to the invention, through adjusting the working states of the load controller, the brake resistor and the like, the power supply management in the case of multi-energy complementation is realized, and the power supply efficiency is improved on the premise of keeping the voltage of the power grid stable. Voltage constraint amplitude U 1 Chopper control value U of braking resistor C The advantages and disadvantages of the preset values influence the improvement of the working efficiency of the system. Wherein, the optimized voltage constraint amplitude U 1 Can accelerate the iteration efficiency, so that the voltage constraint amplitude U 1 The optimal value of the current working condition is more quickly approximated. Embodiment one discloses a voltage constraint amplitude U 1 Is better to take value 31V and chopper regulating quantity U of brake resistor C Is preferably 80V. The embodiment also further discloses that the voltage constraint amplitude U is optimized in combination with specific application conditions 1 And chopper adjustment U C Is a method of (2). Firstly, setting an algorithm formula of a charging voltage threshold value and a discharging voltage threshold value, U 1 = U 0 +△U 1 ，U 2 = U 0 +△U 2 . Then, an optimization function f is defined by adopting a heuristic search algorithm obj (U1，U2)=max (ω 1 J 1 + J 2 ω 2 )，J 1 To provide energy efficiency omega 1 Weight of energy supply efficiency, J 2 Omega for energy exchange rate 2 Is the weight of the energy exchange rate. Omega 1 Can be 0.3, omega 2 0.7 may be taken. Setting the crossover probability of the genetic algorithm to be 0.5 and the variation probability to be 0.05, and obtaining DeltaU through iteration 1 =520v, Δu1= -10V. Finally according to U 1 =(△U 1 -△U 2 ) 2 determining the preferred value of the voltage constraint amplitude, U 1 =31V。
In addition, the chopping adjustment quantity U of the braking resistor can be optimized through a target optimization analysis method C Is a value of (a). First preset the target first workRatio of rate lambda 1 0.8. And then measuring the relation between the starting voltage and the system efficiency under the current traction branch length. As shown in fig. 7, the relationship between the starting voltage and the system efficiency is that the no-load voltage is 900v, and the power supply efficiency is the maximum value when the starting voltage 916v is shown in the figure. The starting voltage continues to increase, and the influence of the brake resistance on the contact network voltage increases. Finally according to U 4 =U 0 +U C (1-λ 1 ) And determining that the chopper adjustment optimization value of the current traction branch is 80V.
Example III
As shown in fig. 8, the embodiment discloses a multi-energy complementary system according to the multi-energy complementary method for supplying power to rail transit, which comprises: the system comprises a contact line, a positive feeder, a steel rail, a train, a substation, an autotransformer, an energy storage power supply, a photovoltaic generator and an energy storage capacitor. The traction means of the train are connected to the contact line and the rail. The two ends of the substation are connected to the contact line and the positive feeder. The whole power supply system is divided into a plurality of power supply areas by the power substation, and the power substation comprises a traction transformer for converting and distributing voltage.
The power substation, the contact line and the positive feeder line form a power supply section, the power supply section is provided with a power regulator, and at least two groups of power regulators in the power supply section are connected in parallel through a compensation capacitor. The two ends of the self-coupling winding are respectively connected with a contact line and a positive feeder, the self-coupling winding divides a power supply section into a plurality of traction branches, and the traction branches are provided with a load controller. The energy storage power supply is connected in parallel to the compensation capacitor through the bidirectional converter. The photovoltaic generator is connected in parallel to the compensation capacitor through the unidirectional converter. The energy storage capacitor is connected in parallel to the energy storage power supply through the breaker, and if the charge compensation fluctuation of the bidirectional converter is smaller than the rated capacity of the compensation capacitor, the breaker is disconnected.
The energy storage power supply of this embodiment is a storage battery. The energy storage device can simultaneously realize the supplementary power supply of the train, the electric energy storage of the photovoltaic generator and the suppression of harmonic current. Furthermore, in order to ensure the stable operation of the energy storage power supply, the invention further predicts the charge state of the energy storage power supply and controls the access state of the energy storage power supply according to the charge state. For example, if the current charge amount is lower than 20% of the capacity of the energy storage power supply, the energy storage power supply is controlled by the bidirectional converter to only charge and not discharge. And if the current charge quantity is higher than 80% of the capacity of the energy storage power supply, controlling the energy storage power supply to only perform discharging and not charging through the bidirectional converter.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.
Claims (9)
1. A multi-energy complementary method for rail transit power supply, comprising the steps of:
step 1: connecting two ends of the substation to the contact line and the positive feeder, respectively connecting two ends of the self-coupling winding to the contact line and the positive feeder, connecting the steel rail to the midpoint of the self-coupling winding, and connecting the traction device of the train to the contact line and the steel rail;
step 2: the power substation, the contact line and the positive feeder line form a power supply section, the power supply section is divided into a plurality of traction branches by the self-coupling winding, the power supply section is provided with a power regulator, the traction branches are provided with a load controller, and the power regulator is connected to the load controller of each traction branch;
step 3: the power regulators of at least two groups of power supply intervals are connected in parallel through compensation capacitors, the energy storage capacitors are connected in parallel to an energy storage power supply through a circuit breaker, and the energy storage power supply and the photovoltaic generator are connected in parallel to the power regulators through converters respectively;
step 4: detecting the number of trains in a traction branch, if the number of trains is greater than zero, entering an energy supply period by the traction branch, and restraining amplitude U according to the number of trains in the traction branch and voltage 1 Determining a discharge voltage threshold U 2 And a charging voltage threshold U 3 ；
Step 5: if the power supply voltage of the contact line is smaller than the discharge voltage threshold U 2 The load controller discharges to the corresponding traction branch, if the power supply voltage of the contact line is greater than the charging voltage threshold U 3 The load controller charges from the corresponding traction branch;
step 6: measuring the power supply area of the traction branchFirst power ratio lambda of the photovoltaic generator 1 According to the first power ratio lambda 1 Setting the starting voltage U of the braking resistor of the traction device 4 ；
Step 7: if the number of trains in the traction branch is equal to zero, ending the energy supply period, and calculating a second power ratio lambda of the load controller to the traction device 2 According to the second power ratio lambda 2 Adjusting the voltage constraint amplitude U of the next energy supply period 1 ；
Step 8: detecting instantaneous current and instantaneous voltage of at least one converter, calculating charge compensation ripple C 1 If the charge compensates for fluctuations C 1 Rated capacity C smaller than compensation capacitance 0 Disconnecting the energy storage capacitor C 2 And returning to the step 4.
2. The method of claim 1, wherein in step 1, the traction device comprises a brake resistor, a chopper, a traction motor, a variable frequency governor, and a filter inductor, and wherein the traction device is connected to the contact line and rail via a pantograph and a power receiving shoe, respectively.
3. The method of claim 1, wherein in step 4,，/>，U 0 is the no-load voltage of the contact net, M is the number of trains of the traction branch, P 1m Rated traction power of mth train, R mL Is the equivalent resistance of the traction branch relative to the mth train.
4. The method of claim 1, wherein in step 6, the photovoltaic generator is connected to the power grid via a voltage controller, and the total power generated by the photovoltaic generator is P 21 The photovoltaic power supply power output by the photovoltaic generator to the power regulator is P 22 A first power ratio lambda 1 = P 22 / P 21 。
5. The method of claim 1, wherein in step 6, U 5 =U 0 +U C (1-λ 1 ) 2 ，U 0 Is no-load voltage of contact net, U C Is the chopping adjustment quantity of the chopper.
6. The method according to claim 1, characterized in that in step 7, the second power ratio λ is determined from the sum of the output powers of the traction devices and the average output power of the load controller during the energy supply period 2 Voltage constraint amplitude of next energy supply period。
7. The method of claim 1, wherein in step 8, the converter connected to the energy storage source and the compensation capacitor is a bi-directional converter, and the instantaneous current i (T) and the instantaneous voltage u (T) of the bi-directional converter are detected during the working period T', and the charge compensation ripple is detectedMax (i (t)/u (t)) is the maximum value of the ratio of instantaneous current to instantaneous voltage.
8. The method according to claim 1, characterized in that in step 8, the no-load current U is corrected according to the instantaneous current of the contact line at a plurality of sampling instants 0 。
9. A multi-energy complementary system for a multi-energy complementary method for rail transit power supply according to claim 1, characterized by comprising: contact line, positive feed line, steel rail, train, substation, auto-coupling winding, energy storage power supply, photovoltaic generator and energy storage capacitor,
the traction device of the train is connected to the contact line and the steel rail;
the two ends of the substation are connected to the contact line and the positive feeder line, the power substation, the contact line and the positive feeder line form a power supply section, a power regulator is arranged in the power supply section, and the power regulators in at least two groups of power supply sections are connected in parallel through compensation capacitors;
the two ends of the self-coupling winding are respectively connected with a contact line and a positive feeder, the self-coupling winding divides a power supply interval into a plurality of traction branches, and the traction branches are provided with a load controller;
the energy storage power supply is connected in parallel to the power regulator through the bidirectional converter;
the photovoltaic generator is connected in parallel to the power regulator through the unidirectional converter;
the energy storage capacitor is connected in parallel to the energy storage power supply through the breaker, if the charge compensation fluctuation of the bidirectional converter is smaller than the rated capacity of the compensation capacitor, the breaker is disconnected, wherein,
after the traction branch enters an energy supply period, determining the working state of a load controller according to the number of trains in the traction branch and the voltage constraint amplitude, and determining the working state of a brake resistor of the traction device according to the first power ratio of the photovoltaic generator;
and after the traction branch circuit finishes the energy supply period, adjusting the voltage constraint amplitude according to the second power ratio.
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