CN108674195A - A kind of contactless net power supply city railway vehicle method for recovering brake energy - Google Patents

Abstract

The invention discloses a method for recovering braking energy of an urban rail vehicle with no catenary power supply. Excellent braking speed curve operation; in the braking process, the method of segmented resistance input is adopted to consume excess braking power and ensure the stability of the bus voltage. The invention enables the vehicle to recover more braking energy under the speed curve operation; changes the distribution of braking power over time during the braking process of the vehicle, and realizes braking under the premise of meeting the braking distance requirements and other indicators. The braking energy absorbed by the supercapacitor is maximized; the operating mileage of the hydrogen fuel cell rail vehicle is greatly improved, and the service life of the vehicle braking components will be extended.

Description

A method for recovering braking energy of urban rail vehicles with catenary-free power supply

technical field

The invention belongs to the technical field of hybrid power, and in particular relates to a method for recovering braking energy of an urban rail vehicle with no catenary power supply.

Background technique

Low-carbon, energy-saving, high-efficiency, and green have become the themes of global development in the 21st century. The development of low-carbon emissions, energy-saving, and clean vehicles in the transportation field is a development trend. Hydrogen fuel cell hybrid rail vehicles are a developing The vehicle that consumes hydrogen emits water, so it is more environmentally friendly and cleaner than other vehicles. However, due to the short distance between rail vehicles during operation, there are frequent start-brakes during the operation of the vehicle. During the braking process, a large amount of mechanical energy in the vehicle can be recovered and reused. However, the current rail vehicles During the braking process of the vehicle, a large amount of mechanical energy is consumed by braking resistors and other equipment, and only a small part is absorbed and reused. Not only the energy utilization rate is low, but also a large amount of heat is discharged to the surrounding environment, which has an impact on the surrounding environment. Improving the braking energy recovery rate of rail vehicles has become an urgent problem to be solved.

In the current research on hybrid battery braking, less consideration is given to the optimization strategy in the braking process, mostly based on the driver’s experience in braking the vehicle, which cannot maximize the absorption of the braking power in the braking process. Affected the mileage of the vehicle.

Contents of the invention

In order to solve the above problems, the present invention proposes a braking energy recovery method for urban rail vehicles with no catenary power supply, so that vehicles can recover more braking energy under the speed curve operation; The distribution of power over time maximizes the braking energy absorbed by the supercapacitor under the premise of meeting the braking distance requirements and other indicators; it greatly improves the operating mileage of hydrogen fuel cell rail vehicles, and will extend the vehicle Service life of brake components.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A method for recovering braking energy of an urban rail vehicle with catenary-free power supply, comprising the steps of:

S100, setting the braking distance of the vehicle;

S200. Obtain an optimal braking speed curve according to a speed optimization algorithm before braking, and the vehicle runs according to the optimal braking speed curve;

S300, in the braking process, adopts the method of segmented resistance input to consume excess braking power and ensure the stability of the bus voltage.

Further, the speed optimization algorithm includes steps:

S201: When the vehicle brakes, first brake according to the braking characteristic curve of the vehicle motor;

S202: Change the braking state of the motor after the speed drops to the power conversion point, so that the output power of the motor braking meets the requirements of the maximum absorbed power of the super capacitor and the braking distance of the vehicle meets the required value, and an optimal braking speed curve is obtained.

Further, the step S202 includes the steps of:

When the speed is reduced to the power conversion point, the braking state of the motor is changed, so that the power set by the motor emits braking power;

During the braking process of the vehicle according to the braking curve of the motor, the braking power of the motor is the maximum output braking power; during this process, the motor decelerates at the maximum deceleration, the vehicle speed decreases rapidly, and the vehicle brakes according to the braking curve of the motor. short distance;

The vehicle brakes according to the preset braking power, so that the output power of the motor brake meets the energy absorbed by the super capacitor; the power conversion point in the braking process is changed to make the braking distance meet the required value.

Further, the speed optimization algorithm includes steps:

(1) Calculate the maximum absorbed power P _sc (t) of the supercapacitor according to the braking distance s ^* of the vehicle; set the sampling time as T, the maximum deceleration a _max and the comfort limit value difa _max ;

(2) The vehicle first brakes according to the motor braking characteristic curve, and absorbs power P _sc (t) according to the supercapacitor after the vehicle speed drops to the power conversion point; through the motor efficiency η ₁ and the bidirectional DC/DC inverter efficiency η ₂ , DC/AC inverter efficiency η ₃ , operating resistance sharing power P _f (t) and speed v, calculate the deceleration a;

(3) Take v(i)=Vs, Vs is the speed corresponding to the maximum power point, the formula for calculating deceleration a: (mv(i)a(i)-P _f (i))η ₁ η ₂ η ₃ = P _sc (i);

(4) Optimizing restrictions on the deceleration a;

(5) Calculate the comfort degree difa, and optimize the comfort degree difa limit for deceleration;

(6) Calculation speed v(i+1)=v(i)-aT;

(7) Judging whether the speed v(i+1) reaches 0; if it is executed step (8); if not, then make i=i+1 and execute step (3);

(8) Recalculate the braking distance s; if the braking distance satisfies |ss ^* |<ε, then end, otherwise adjust the power conversion point and re-execute step (3).

Further, the method for absorbing energy by the supercapacitor is:

The supercapacitor voltage U changes continuously with the current inflow during the braking process, and the current flowing into the supercapacitor is limited by bidirectional DC/DC. The maximum current is I ^* , so the supercapacitor absorption capacity Psc(t) varies with the The change of the capacitor voltage changes;

The supercapacitor absorption capacity Psc(t) is determined according to the supercapacitor voltage at the braking moment; during the braking process of the vehicle, the supercapacitor voltage U ₀ is measured at the initial moment t ₀ of braking, and U ₀ is used as the voltage at the initial moment to iteratively calculate the following At one moment, the supercapacitor voltage U(i+1), the charge stored in the supercapacitor and the open circuit voltage are linearized;

Calculate the absorbed power of the supercapacitor according to the following formula:

Q(i+1)=C×U(i)-I ^* ×T;

U(i+1)=Q(i+1)/C;

P _SC (t)=U(i)×I*;

Among them: U(i) is the terminal voltage of the supercapacitor, I ^* is the bidirectional DC/DC limited charging current, Q(i) is the amount of charge stored in the supercapacitor, and T is the sampling time.

Further, the comfort degree difa is defined as the derivative of the deceleration, and the calculation formula is:

Where: T is the sampling time;

The optimization limit of the comfort degree and its method: compare the calculated comfort degree difa with the comfort limit value, if the comfort degree difa does not exceed the comfort limit value difa _max , the deceleration value remains unchanged; if the comfort value exceeds If the comfort limit value is difa _max , then change the deceleration a value to ensure that the comfort level does not exceed the comfort limit value difa _max .

Further, the calculation of the deceleration a includes the steps of:

Before the power conversion point of the vehicle, the motor brakes according to the maximum braking power during the braking process, the motor works in the constant power characteristic curve or constant torque characteristic curve, and the braking torque generated by the motor is the largest;

After the vehicle is at the power conversion point, the motor works inside the motor torque characteristic curve, and the torque of the motor is calculated by the following formula:

The total braking force suffered by the vehicle during braking includes various running resistances in addition to the braking torque provided by the motor. The deceleration a of the vehicle is calculated as follows:

For the motor to brake according to the braking characteristic curve before the power change point,

(mv(i)a(i)-P _f (i))η ₁ η ₂ η ₃ ＝P _sc (i), is the braking of the motor after the power conversion point,

Among them: P _moter (t) is the electrical braking power of the motor, and P _f (t) is the braking power shared by the resistance;

The optimal limiting method of the vehicle deceleration a comprises the steps of:

Since the deceleration is limited by the wheel-rail creep factor during the deceleration process, the deceleration a cannot exceed the limit value of the maximum deceleration; compare the calculated deceleration a with the limited maximum deceleration a _max , if a does not exceed the maximum deceleration a _max , then a remains unchanged; if the deceleration a exceeds the maximum deceleration a _max , take a as the maximum deceleration a _max .

Further, the motor efficiency calculation method is as follows: when the actual speed of the asynchronous motor is greater than the synchronous speed of the magnetic field, the motor is in a braking state, and the motor converts mechanical energy into electrical energy;

Motor synchronous speed: f ₀ is the three-phase power frequency of the stator winding, and p is the number of pole pairs;

Motor braking electric power, torque and speed during braking: P _motor is the power generated by the motor, Ω is the motor speed, T is the motor torque;

When the actual speed of the asynchronous motor is lower than the synchronous speed, the motor runs normally, and the motor converts electrical energy into mechanical energy; when the actual speed of the asynchronous motor is greater than the synchronous speed, the motor is in a braking state, and the motor converts mechanical energy into electrical energy; During the motion process, the energy flow calculation formula is:

The motor power relation of the motor: PP _CU1 -P _Fe -P _CU2 =P _mec ,

Motor power relationship in generator: P+P _CU1 +P _Fe +P _CU2 ＝P _mec ;

The electric energy generated by the motor includes stator winding copper loss P _CU1 , stator winding iron loss P _Fe , stator winding copper loss P _CU2 and output power P;

Therefore, the efficiency calculation during motor braking is:

Further, the calculation method of braking power shared by various running resistances during the braking process is: there are various running resistances during the braking process of the vehicle, including air resistance, rolling resistance, bearing resistance, sliding resistance and slope resistance; At low speeds, rolling resistance and air resistance account for the main part. Therefore, by calculating the rolling resistance and air resistance, and assuming that the vehicle is running on a straight track, calculate the braking power shared by the resistance during the braking process. The calculation formula is:

F _f =mgn+csρv ² ,

P _f =F _f v =(mgn+csρv ² )v,

Among them: F _f is resistance, P _f is resistance power, m is vehicle mass, n is rolling resistance coefficient, c is drag coefficient, S is windward area, ρ is air density.

Further, in step S300, the method of inputting segmented resistors is used to consume excess braking power to ensure the stability of the bus voltage, including steps:

S301: measure the bus voltage;

S302: Compare the measured bus voltage signal with a reference value, where the reference value includes an incremental multi-level voltage reference value;

S303: When the bus voltage exceeds the primary voltage reference value, the first group of braking resistors are put into operation, and if the bus voltage continues to rise, perform step S304; the primary voltage reference value is 825V;

S304: When the bus voltage exceeds the secondary voltage reference value of 875V, the second set of braking resistors is put into operation, and if the bus voltage continues to rise, perform step S305; the secondary voltage reference value is 875V;

S305: When the bus voltage exceeds the reference value of the third-level voltage, the third group of braking resistors is used; if the bus voltage is still rising after the three groups of braking resistors are connected, the value of the braking resistors is reduced; the second-level voltage reference The value is 925V.

The beneficial effect of adopting this technical solution:

The method of the invention essentially changes the distribution of braking power over time during the braking process of the vehicle, so that the vehicle can recover more braking energy under the speed curve operation; it changes the distribution of braking power over time during the braking process of the vehicle distribution, which maximizes the braking energy absorbed by the supercapacitor under the premise of meeting the braking distance requirements and other indicators; greatly improves the operating mileage of hydrogen fuel cell rail vehicles, and will prolong the service life of vehicle braking components. service life;

The vehicle of the present invention adopts the mode of non-catenary power supply and supercapacitor common power supply, and the energy recovery method of the hybrid rail vehicle vehicle of the present invention is as follows: according to the known vehicle motor braking characteristic curve, maximum deceleration requirement, maximum The braking distance, the maximum absorption capacity of the super capacitor and the comfort level are considered to optimize a vehicle braking speed curve, so that the vehicle can recover more braking energy under this speed curve.

Description of drawings

Fig. 1 is a kind of non-catenary power supply urban rail vehicle brake energy recovery method flow diagram of the present invention;

Fig. 2 is a schematic flow chart of the speed optimization algorithm in the embodiment of the present invention;

Fig. 3 is a schematic flow chart of a method for optimizing and limiting comfort in an embodiment of the present invention;

Fig. 4 is the schematic diagram of motor torque characteristic curve in the embodiment of the present invention;

Fig. 5 is a schematic flow chart of an optimal limiting method for deceleration in an embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further elaborated below in conjunction with the accompanying drawings.

In the present embodiment, referring to Fig. 1, the present invention proposes a method for recovering braking energy of an urban rail vehicle with no catenary power supply, comprising the steps of:

S100, setting the braking distance of the vehicle;

S200. Obtain an optimal braking speed curve according to a speed optimization algorithm before braking, and the vehicle runs according to the optimal braking speed curve;

S300, in the braking process, adopts the method of segmented resistance input to consume excess braking power and ensure the stability of the bus voltage.

1. As the optimization scheme of above-mentioned embodiment, described speed optimization algorithm comprises steps:

S201: When the vehicle brakes, first brake according to the braking characteristic curve of the vehicle motor;

S202: Change the braking state of the motor after the speed drops to the power conversion point, so that the output power of the motor braking meets the requirements of the maximum absorbed power of the super capacitor and the braking distance of the vehicle meets the required value, and an optimal braking speed curve is obtained.

The step S202 includes the steps of:

When the speed is reduced to the power conversion point, the braking state of the motor is changed, so that the power set by the motor emits braking power;

During the braking process of the vehicle according to the braking curve of the motor, the braking power of the motor is the maximum output braking power; during this process, the motor decelerates at the maximum deceleration, the vehicle speed decreases rapidly, and the vehicle brakes according to the braking curve of the motor. short distance;

The vehicle brakes according to the preset braking power, so that the output power of the motor brake meets the energy absorbed by the super capacitor; the power conversion point in the braking process is changed to make the braking distance meet the required value.

The speed optimization algorithm is specifically, as shown in Figure 2:

(1) Calculate the maximum absorbed power P _sc (t) of the supercapacitor according to the braking distance s ^* of the vehicle; set the sampling time as T, the maximum deceleration a _max and the comfort limit value difa _max ;

(2) The vehicle first brakes according to the motor braking characteristic curve, and absorbs power P _sc (t) according to the supercapacitor after the vehicle speed drops to the power conversion point; through the motor efficiency η ₁ and the bidirectional DC/DC inverter efficiency η ₂ , DC/AC inverter efficiency η ₃ , operating resistance sharing power P _f (t) and speed v, calculate the deceleration a;

(3) Take v(i)=Vs, Vs is the speed corresponding to the maximum power point, the formula for calculating deceleration a: (mv(i)a(i)-P _f (i))η ₁ η ₂ η ₃ = P _sc (i);

(4) Optimizing restrictions on the deceleration a;

(5) Calculate the comfort degree difa, and optimize the comfort degree difa limit for deceleration;

(6) Calculation speed v(i+1)=v(i)-aT;

(7) Judging whether the speed v(i+1) reaches 0; if it is executed step (8); if not, then make i=i+1 and execute step (3);

(8) Recalculate the braking distance s; if the braking distance satisfies |ss ^* |<ε, then end, otherwise adjust the power conversion point and re-execute step (3).

2. As an optimization scheme of the foregoing embodiment, the method for absorbing energy by the supercapacitor is:

The supercapacitor voltage U changes continuously with the current inflow during the braking process, and the current flowing into the supercapacitor is limited by bidirectional DC/DC. The maximum current is I*, so the supercapacitor absorption capacity Psc(t) varies with the supercapacitor The change of the capacitor voltage changes;

The supercapacitor absorption capacity Psc(t) is determined according to the supercapacitor voltage at the braking moment; during the braking process of the vehicle, the supercapacitor voltage U ₀ is measured at the initial moment t ₀ of braking, and U ₀ is used as the voltage at the initial moment to iteratively calculate the following At one moment, the supercapacitor voltage U(i+1), the charge stored in the supercapacitor and the open circuit voltage are linearized;

Calculate the absorbed power of the supercapacitor according to the following formula:

Q(i+1)=C×U(i)-I*×T;

U(i+1)=Q(i+1)/C;

P _SC (t)=U(i)×I*;

Among them: U(i) is the terminal voltage of the supercapacitor, I ^* is the bidirectional DC/DC limited charging current, Q(i) is the amount of charge stored in the supercapacitor, and T is the sampling time.

3. As the optimization scheme of the above-mentioned embodiment, the definition of the comfort degree difa is the derivative of the deceleration, and the calculation formula is:

Where: T is the sampling time;

The optimization limit of the comfort degree and its method: as shown in Figure 3, comparing the calculated comfort degree difa with the comfort limit value, if the comfort degree difa does not exceed the comfort limit value difa _max , the deceleration value remains unchanged ; If the comfort value exceeds the comfort limit value difa _max , then change the deceleration a value to ensure that the comfort level does not exceed the comfort limit value difa _max .

4. As an optimization scheme of the foregoing embodiment, the calculation of the deceleration a includes the steps of:

Before the power conversion point of the vehicle, the motor brakes according to the maximum braking power during the braking process, and the motor works in the constant power characteristic curve or constant torque characteristic curve, as shown in Figure 4, curve 1, the braking torque generated by the motor maximum;

After the vehicle is at the power conversion point, the motor works inside the motor torque characteristic curve, as shown in area 2 in Figure 4, and the torque of the motor is calculated by the following formula:

The total braking force suffered by the vehicle during braking includes various running resistances in addition to the braking torque provided by the motor. The deceleration a of the vehicle is calculated as follows:

For the motor to brake according to the braking characteristic curve before the power change point,

(mv(i)a(i)-P _f (i))η ₁ η ₂ η ₃ ＝P _sc (i), is the braking of the motor after the power conversion point,

Among them: P _moter (t) is the electrical braking power of the motor, and P _f (t) is the braking power shared by the resistance;

The optimal limiting method of the vehicle deceleration a, as shown in Figure 5, includes the steps:

Since the deceleration is limited by the wheel-rail creep factor during the deceleration process, the deceleration a cannot exceed the limit value of the maximum deceleration; compare the calculated deceleration a with the limited maximum deceleration a _max , if a does not exceed the maximum deceleration a _max , then a remains unchanged; if the deceleration a exceeds the maximum deceleration a _max , take a as the maximum deceleration a _max .

5. As an optimization scheme of the above embodiment, the motor efficiency calculation method is as follows: when the actual speed of the asynchronous motor is greater than the synchronous speed of the magnetic field, the motor is in a braking state, and the motor converts mechanical energy into electrical energy;

Motor synchronous speed: f ₀ is the three-phase power frequency of the stator winding, and p is the number of pole pairs;

Motor braking electric power, torque and speed during braking: P _motor is the power generated by the motor, Ω is the motor speed, T is the motor torque;

When the actual speed of the asynchronous motor is lower than the synchronous speed, the motor runs normally, and the motor converts electrical energy into mechanical energy; when the actual speed of the asynchronous motor is greater than the synchronous speed, the motor is in a braking state, and the motor converts mechanical energy into electrical energy; During the motion process, the energy flow calculation formula is:

The motor power relation of the motor: PP _CU1 -P _Fe -P _CU2 =P _mec ,

Motor power relationship in generator: P+P _CU1 +P _Fe +P _CU2 ＝P _mec ;

The electric energy generated by the motor includes stator winding copper loss P _CU1 , stator winding iron loss P _Fe , stator winding copper loss P _CU2 and output power P;

Therefore, the efficiency calculation during motor braking is:

6. As an optimization scheme of the above-mentioned embodiment, the calculation method of braking power shared by various running resistances in the braking process is as follows: there are various running resistances in the braking process of the vehicle, including air resistance, rolling resistance, bearing resistance, sliding resistance, etc. Resistance and slope resistance; at low speeds, rolling resistance and air resistance account for the main part, so by calculating the rolling resistance and air resistance, and assuming that the vehicle is running on a straight track, calculate the resistance to share the braking power calculation during the braking process , the calculation formula is:

F _f =mgn+csρv ² ,

P _f =F _f v =(mgn+csρv ² )v,

Among them: F _f is resistance, P _f is resistance power, m is vehicle mass, n is rolling resistance coefficient, c is drag coefficient, S is windward area, ρ is air density.

7. As the optimization scheme of the above-mentioned embodiment, the excess braking energy is consumed by using the braking resistor in sections during the braking process to ensure the stability of the bus voltage, and multiple sets of braking resistors are connected in parallel in the braking resistor section In the connection mode of the direct busbar, each set of braking resistors judges whether to put it into use according to the change of the busbar voltage. The rated value of the busbar voltage is 750V. The voltage will increase; the resistance value of the braking resistor is determined according to the maximum braking power generated during the braking process, and the maximum braking power can be absorbed. Each set of braking resistors measures and judges the bus voltage.

In step S300, use segmented resistors to consume excess braking power to ensure the stability of the bus voltage, including steps:

S301: measure the bus voltage;

S302: Compare the measured bus voltage signal with a reference value, where the reference value includes an incremental multi-level voltage reference value;

S303: When the bus voltage exceeds the primary voltage reference value, the first group of braking resistors are put into operation, and if the bus voltage continues to rise, perform step S304; the primary voltage reference value is 825V;

S304: When the bus voltage exceeds the secondary voltage reference value of 875V, the second set of braking resistors is put into operation, and if the bus voltage continues to rise, perform step S305; the secondary voltage reference value is 875V;

S305: When the bus voltage exceeds the reference value of the third-level voltage, the third group of braking resistors is used; if the bus voltage is still rising after the three groups of braking resistors are connected, the value of the braking resistors is reduced; the second-level voltage reference The value is 925V.

The basic principles and main features of the present invention and the advantages of the present invention have been shown and described above. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments, and that described in the above-mentioned embodiments and the specification only illustrates the principles of the present invention, and the present invention will also have other functions without departing from the spirit and scope of the present invention. Variations and improvements all fall within the scope of the claimed invention. The protection scope of the present invention is defined by the appended claims and their equivalents.

Claims (10)

1. The city railway vehicle method for recovering brake energy 1. a kind of contactless net is powered, which is characterized in that including step：

   S100 sets vehicle braking distance；

   S200 obtains optimal retro-speed curve before braking according to speed-optimization algorithm, and vehicle is according to the optimal system Dynamic rate curve operation；

   S300 consumes extra braking power, it is ensured that busbar voltage in braking process by the way of grading resistance input Stablize.
2. The city railway vehicle method for recovering brake energy 2. the contactless net of one kind according to claim 1 is powered, feature It is, the speed-optimization algorithm includes step：

   S201：First according to vehicular electric machine braking characteristic braking in a curve when vehicle braking；

   S202：Change motor braking state after speed drops to power conversion point, so that the output power of motor braking is met super The requirement of capacitance absorption maximum power and vehicle braking distance is made to meet the requirements value, obtains optimal retro-speed curve.
3. The city railway vehicle method for recovering brake energy 3. the contactless net of one kind according to claim 2 is powered, feature It is, the step S202 includes step：

   After speed is reduced to power conversion point, change the on-position of motor, the power production braking power for making motor set；

   Motor braking power is the maximum brake power exported during vehicle presses motor braking braking in a curve；It is electric in the process Machine is slowed down with maximum deceleration, and car speed quickly reduces, and vehicle presses motor braking braking in a curve vehicle, and braking distance is short；

   Vehicle is pressed default braking power and is braked, and so that the output power of motor braking is met super capacitor and absorbs energy；Change braking Power conversion point in the process, makes braking distance meet the requirements value.
4. The city railway vehicle method for recovering brake energy 4. the contactless net of one kind according to claim 3 is powered, feature It is, the speed-optimization algorithm includes step：

   (1) according to the vehicle braking distance s^*, calculate super capacitor absorption maximum power P_sc(t)；Set the sampling time as T, Deceleration maximum value a_maxWith comfort level limit value difa_max；

   (2) vehicle is first braked according to motor braking characteristic curve, according to super electricity after car speed drops to power conversion point Hold absorbed power P_sc(t)；Pass through electric efficiency η₁, two-way DC/DC inverter efficiencies η₂, DC/AC inverter efficiencies η₃, operation resistance Power shares power P_f(t) with speed v, deceleration a is calculated；

   (3) it is the corresponding speed of maximum power point to take v (i)=Vs, Vs, calculates the formula of deceleration a：(mv(i)a(i)-P_f(i)) η₁η₂η₃=P_sc(i)；

   (4) to deceleration a optimization limitations；

   (5) comfort level difa is calculated, and to the comfort level difa optimization limitations of deceleration；

   (6) calculating speed v (i+1)=v (i)-aT；

   (7) judge whether speed v (i+1) reaches 0；If executing step (8)；If it is not, then making i=i+1 and executing step (3)；

   (8) braking distance s is recalculated；If braking distance meets | s-s^*| ＜ ε then terminate, and otherwise adjust the Vs of power conversion point Re-execute step (3).
5. The city railway vehicle method for recovering brake energy 5. the contactless net of one kind according to claim 4 is powered, feature It is, the method that the super capacitor absorbs energy is：

   Super-capacitor voltage U is due to the continuous variation of electric current inflow in braking process, flowing into super capacitor electric current due to double It is I to the limitation maximum current of DC/DC^*, therefore super capacitor absorbability Psc (t) is electric with super capacitor in braking process The change of pressure and change；

   Super capacitor absorbability Psc (t) is determined according to braking moment super-capacitor voltage；It is being braked during vehicle braking Initial time t₀Measure super-capacitor voltage U₀, with U₀The super electricity of subsequent time is constantly iterated to calculate out as initial time voltage Hold voltage U (i+1), the quantity of electric charge of super capacitor storage is turned into linear relationship with open-circuit voltage；

   Super capacitor absorbed power is sought according to following formula：

   Q (i+1)=C × U (i)-I^*×T；

   U (i+1)=Q (i+1)/C；

   PSC (t)=U (i) × I*；

   Wherein：U (i) is super capacitor terminal voltage, I^*Charging current is limited for two-way DC/DC, Q (i) super capacitors store charge Amount, T is the sampling time.
6. The city railway vehicle method for recovering brake energy 6. the contactless net of one kind according to claim 5 is powered, feature It is, the comfort level difa is the derivative of deceleration, and calculation formula is：

   Wherein：T is the sampling time；

   The optimization limitation of the comfort level and its method：To the comfort level difa that is calculated compared with comfort level limit value, if Comfort level difa is not above comfort level limit value difa_max, then deceleration value is constant；If comfortable angle value is limited more than comfort level Value difa_max, then change deceleration a values, ensure that comfort level is no more than comfort level limit value difa_max。
7. The city railway vehicle method for recovering brake energy 7. the contactless net of one kind according to claim 6 is powered, feature It is, the calculating of the deceleration a, including step：

   Vehicle is before power conversion point, and motor is braked by maximum brake power in braking process, and motor is in constant output characteristic song Line or the work of constant torque characteristic curve, the braking moment that motor generates are maximum；

   For vehicle after power conversion point, motor is operated in the characteristic inside of motor torque, and the torque of motor is counted as the following formula It calculates：

   Suffered total brake force further includes various running resistances, vehicle in addition to the braking moment that motor provides during vehicle braking Deceleration a be calculated as follows：

   Braking characteristic curve is pressed before power conversion point for motor Braking,

   (mv(i)a(i)-P_f(i))η₁η₂η₃=P_sc(i), it is that motor is braked after power conversion point,

   Wherein：P_moter(t) it is motor braking electrical power, P_f(t) it is drag contribution braking power；

   The optimization method for limiting of the vehicle deceleration a, including step：

   Since deceleration is limited by wheel track creep factor in moderating process, deceleration a is no more than maximum deceleration Limits value；Maximum deceleration a to the deceleration a and restriction that calculate gained_maxCompare, if a is not above maximum deceleration a_max, Then a is remained unchanged；If deceleration a has been more than maximum deceleration a_maxIt is maximum deceleration a then to take a_max。
8. The city railway vehicle method for recovering brake energy 8. the contactless net of one kind according to claim 7 is powered, feature It is, the electric efficiency computational methods are：When the actual speed of asynchronous machine is more than field synchronous rotating speed, motor is in system Dynamic state, motor convert mechanical energy to electric energy；

   Motor synchronous rotational speed：f₀For stator winding three phase mains frequency, p is number of pole-pairs；

   Motor braking electrical power and torque and rotating speed in braking process：P_motorFor the power that motor is sent out, Ω is Motor speed, T are motor torque；

   The motor normal operation when the actual speed of asynchronous machine is less than synchronous rotational speed, motor convert electrical energy into mechanical energy；It is different When walking the actual speed of motor more than synchronous rotational speed, motor is in on-position, and motor converts mechanical energy to electric energy；Motor exists With braking process, the flowing calculation formula of energy is electric motor state：

   Power of motor relationship when motor：P-P_CU1-P_Fe-P_CU2=P_mec,

   Power of motor relationship when generator：P+P_CU1+P_Fe+P_CU2=P_mec；

   The electric energy that motor is sent out includes stator winding copper loss P_CU1, stator winding iron loss P_Fe, stator winding copper loss P_CU2And output work Rate P；

   Therefore, efficiency calculation is during motor braking:
9. The city railway vehicle method for recovering brake energy 9. the contactless net of one kind according to claim 8 is powered, feature Be, in the braking process various running resistances share braking power calculate method be：Exist during vehicle braking each Kind running resistance includes air drag, rolling resistance, bearing resistance, resistance to sliding and gradient resistance；In low speed due to rolling Resistance accounts for major part with air drag, therefore by calculating rolling resistance and air drag, and assumes vehicle in straight track Upper operation calculates drag contribution braking power in its braking process and calculates, and calculation formula is：

   F_f=mgn+cs ρ v²,

   P_f=F_fV=(mgn+cs ρ v²) v,

   Wherein:F_fFor resistance, P_fFor resistance power, m is vehicle mass, and n is coefficient of rolling resistance, and c is air resistance coefficient, and S is windward Area, ρ are atmospheric density.
10. The city railway vehicle method for recovering brake energy 10. the contactless net of one kind according to claim 9 is powered, feature It is, the mode put into grading resistance in step S300 consumes extra braking power, it is ensured that the stabilization of busbar voltage, packet Include step：

    S301：Measure busbar voltage；

    S302：The bus voltage signal measured is compared with reference value, and the reference value includes that incremental multilevel voltage refers to Value；

    S303：First group of braking resistor is put into when busbar voltage is more than voltage order one reference value, if busbar voltage continues to increase, Then follow the steps S304

    S304：Second group of braking resistor is put into when busbar voltage is more than secondary voltage reference value 875V, if busbar voltage continues It increases, thens follow the steps S305；

    S305：Third group braking resistor is put into when busbar voltage is more than tertiary voltage reference value；If three groups of braking resistors are all thrown Enter rear busbar voltage also increasing, then reduces the value of braking resistor.