阅读说明：本技术 基于变门限值的混合动力有轨电车能量管理方法 (Hybrid power tramcar energy management method based on variable threshold value ) 是由 王子豪 曹慧坤 杨斌辉 滕凯 邢宗义 于 2019-09-03 设计创作，主要内容包括：本发明公开了一种基于变门限值的混合动力有轨电车能量管理方法,该方法为：首先基于有轨电车运行状态,计算有轨电车运行功率需求；然后根据不同区间运行功率需求,动态调整对应区间功率门限值；在不同的功率门限值下,针对混合储能元件选择相应的工作模式。本发明具有满足工况变化下的有轨电车功率需求、充分发挥不同储能元件工作特性、延长储能元件使用寿命的优点。(The invention discloses a hybrid power tramcar energy management method based on a variable threshold value, which comprises the following steps: firstly, calculating the running power requirement of the tramcar based on the running state of the tramcar; then dynamically adjusting the power threshold value of the corresponding interval according to the operating power requirements of different intervals; and under different power threshold values, selecting a corresponding working mode aiming at the hybrid energy storage element. The invention has the advantages of meeting the power requirement of the tramcar under the condition of working condition change, fully playing the working characteristics of different energy storage elements and prolonging the service life of the energy storage elements.)

1. A hybrid power tramcar energy management method based on a variable threshold value is characterized by comprising the following steps:

step 1, calculating the running power requirement of the tramcar based on the running state of the tramcar;

step 2, dynamically adjusting the power threshold value of the corresponding interval according to the operating power requirements of different intervals;

and 3, selecting a corresponding working mode aiming at the hybrid energy storage element under different power threshold values.

2. The variable threshold-based hybrid streetcar energy management method according to claim 1, wherein the tram operating power requirement is calculated based on the tram operating state in step 1, and specifically comprises the following steps:

in an operation interval, the tramcar comprises four operation conditions in an automatic driving mode: full-force traction, constant-speed cruise, coasting and full-force braking, determining the relation between the running speed and the running mileage of the tramcar according to an ATO curve, and analyzing the running power requirement of the tramcar on the basis that the tramcar is in an interval (x)₀,x_end) Operating according to an ATO curve, wherein the power required by the operation is as follows:

P_need(x)＝η₁ ^σ1η₂ ^σ1η₃ ^σ1P_Ft(x)+P_aux

the operation requires energy as follows:

in the formula: p_need、E_needThe power demand and the energy demand are respectively required by the tramcar during operation; p_Ft(x) Is the circumferential traction power of the tramcar; x is the kilometer post of the tramcar; eta₁、η₂、η₃Efficiency of the drive train, traction motor, and traction inverter, respectively, σ 1 ═ sgn (-P)_Ft(x))；P_auxRepresenting tramcar auxiliary equipment power; v (x) is the desired speed of the tram at x; x is the number of₀、x_endThe starting point kilometer post and the end point kilometer post of the operation interval are respectively.

3. The variable threshold-based hybrid streetcar energy management method according to claim 1, wherein the step 2 dynamically adjusts the corresponding section power threshold according to the different section operation power requirements, specifically as follows:

during operation, on the premise of ensuring that the tramcar runs at a target speed, the power battery and the super capacitor are matched to supply power according to a power threshold value, namely when the power requirement is less than or equal to the power threshold value, the power battery supplies power independently; when the power demand is higher than the power threshold value, the power battery and the super capacitor supply power together, and the power is suppliedThreshold value P_bIs determined by the discharge power of the power battery, and the maximum discharge power P of the power battery_maxThe power threshold value is an initial value, the minimum energy consumption of the power battery is taken as a target, and the current I is limited through optimization_bTo optimize the power threshold value P_bAnd finally obtaining the optimal power threshold value of each operation interval, wherein the specific steps are as follows:

1) using maximum allowable charging and discharging current I_maxInitial limiting current I_bI.e. satisfy I_b＝I_max；

2) In limiting the current I_bDetermined power threshold value P_bJudging whether the running target speed requirement of the tramcar is met or not;

3) if the condition requirement is met, limiting the current I_bOn the basis of subtracting a certain variable DeltaI, i.e. satisfying I_b＝I_b- Δ I, and go to decision in 2);

4) if the condition requirement is not met, the circulation is exited, and the limiting current I in the last circulation is taken_bAs an optimum limiting current I_bmThe limiting current determines an optimum power threshold value P_bm。

4. The variable threshold-based hybrid streetcar energy management method according to claim 1, wherein the step 3 selects a corresponding operating mode for the hybrid energy storage element under different power threshold values, specifically as follows:

the working mode of the hybrid energy storage system of the power battery and the super capacitor is divided into: A. a low power traction mode of operation; B. a high power traction mode of operation; C. a regenerative braking mode of operation; D. a regenerative braking + mechanical braking mode of operation;

A. low power traction mode of operation: 0 < P_need≤P_bm，SOC_btmin＜SOC_bt＜SOC_btmax

In the low-power traction mode, the power demand of the tramcar is less than or equal to the power threshold value, namely 0 < P_need≤P_bmState of charge SOC of power battery_btIn the normal operating state, i.e. SOC_btmin＜SOC_bt＜SOC_btmaxIf the power battery is used for supplying power alone, the power balance relationship in the mode is as follows:

in the formula, P_btoRepresenting the output power of the power battery; p_cmoRepresenting the output power of the power battery; eta₄Representing the working efficiency of a DC-DC converter of the power battery;

B. high power traction operating mode: p_need＞P_bm，SOC_btmin＜SOC_bt＜SOC_btmax，SOC_cmmin＜SOC_cm＜SOC_cmmax

In the high-power traction working mode, the power demand of the tramcar is higher than a power threshold value, namely P_need＞P_bmAnd the state of charge SOC of the power battery_btSOC of super capacitor_cmAre all in normal operating condition, i.e. SOC_btmin＜SOC_bt＜SOC_btmax、SOC_cmmin＜SOC_cm＜SOC_cmmaxAnd the power battery and the super capacitor are used for supplying power together, and the power balance relationship in the mode is as follows:

P_need＝η₄P_bto+η₅P_cmo

in the formula eta₅The working efficiency of the DC-DC converter representing the super capacitor;

C. regenerative braking mode of operation: p_need＜0，SOC_cmmin＜SOC_cm＜SOC_cmmax

In the regenerative braking mode of operation, the tram power demand P_needThe braking energy is regenerated when the voltage is less than 0, and the super capacitor is in a normal working mode, namely SOC_cmmin＜SOC_cm＜SOC_cmmaxIf so, the regenerative braking energy is recovered by the super capacitor, and the power balance relationship in the mode is as follows:

η₅P_need＝P_cmi

in the formula, P_cmiRepresenting the input power of the super capacitor;

D. regenerative braking + mechanical braking mode of operation: p_need＜0，SOC_cm≥SOC_cmmax

In the regenerative braking + mechanical braking operating mode, when the regenerative braking energy exceeds the maximum recovery capacity of the super capacitor, namely the charge state of the super capacitor exceeds the maximum value, the braking resistor begins to consume the regenerative braking energy, namely the over-regenerative braking energy is converted into heat energy, and the power balance relationship in the mode is as follows:

η₅P_need＝P_cmi+P_mch

in the formula, P_mchRepresenting the brake resistor dissipating power.

Technical Field

The invention belongs to the technical field of tramcar energy management, and particularly relates to a hybrid tramcar energy management method based on a variable threshold value.

Background

The energy storage type tramcar has the advantages of small influence on landscape, small dependence on a power grid, convenience in maintenance and the like, and is widely popularized in urban rail transit. Because the single energy storage element with high energy density and high power density is lacked to meet the operation requirement of the tramcar at present, different energy storage elements are mostly adopted to form a hybrid power system. In each energy storage element, the power battery has high energy density and strong cruising ability, and the super capacitor has high power density to meet the requirement of the tramcar on traction for short time and high power and can realize the recovery of braking energy, so the hybrid power of the power battery and the super capacitor is mostly adopted as an energy storage system of the energy storage type tramcar.

In order to ensure the energy storage elements with different characteristics to work cooperatively, an efficient energy management method is more important besides selecting proper parameter configuration. The research of China in the aspect of hybrid power energy management is late, at present, the research is mostly concentrated in the field of electric automobiles, for the hybrid power energy management of tramcars, a strategy of fixing a power threshold value is mostly adopted in engineering, the selection of the power threshold value depends on engineering experience, the power threshold value cannot adapt to working condition change, the characteristics of different energy storage elements cannot be fully exerted, and the selection of the power threshold value is not reasonable, so that the overcharge and the overdischarge of the energy storage elements are caused, and the service life of the energy storage elements is further influenced. Therefore, adapting to working condition changes and ensuring the coordination work of different energy storage elements are the difficult problems and the key in the research of the hybrid power energy management method.

Disclosure of Invention

The invention aims to provide a hybrid power tramcar energy management method based on a variable threshold value, so that the running characteristics of the tramcar are met, and the coordinated work of different energy storage elements is realized.

The technical solution for realizing the purpose of the invention is as follows: a hybrid power tramcar energy management method based on a variable threshold value comprises the following steps:

step 1, calculating the running power requirement of the tramcar based on the running state of the tramcar;

step 2, dynamically adjusting the power threshold value of the corresponding interval according to the operating power requirements of different intervals;

and 3, selecting a corresponding working mode aiming at the hybrid energy storage element under different power threshold values.

Compared with the prior art, the invention has the following remarkable advantages: (1) the invention sets different power threshold values in different intervals, and can adapt to the power requirement of the tramcar under the condition change; (2) the matching of the proper working mode is beneficial to the maximum working characteristics of each energy storage element, the problems of over-charging and over-discharging of the energy storage elements are avoided, and the service life of the energy storage elements is prolonged.

Drawings

Fig. 1 is a schematic flow chart of a variable threshold value-based hybrid tramcar energy management method according to the present invention.

Fig. 2 is a schematic diagram of the operation condition of the ATO curve of the tramcar.

Fig. 3 is a schematic diagram of the tramcar system structure and energy flow according to the present invention.

Fig. 4 is a schematic diagram of an equivalent model of the power battery of the invention.

Fig. 5 is a schematic diagram of the expected operation speed and position of the tramcar according to the embodiment of the invention.

Fig. 6 is a schematic diagram of the power demand and the power threshold of the tramcar according to the embodiment of the invention.

Fig. 7 is a schematic diagram illustrating state of charge changes of a power battery and a super capacitor according to an embodiment of the present invention.

Detailed Description

The invention will be further explained and analyzed with reference to the drawings.

With reference to fig. 1, the hybrid tramcar energy management method based on the variable threshold value of the invention firstly calculates the running power requirement of the tramcar based on the running state of the tramcar; then dynamically adjusting the power threshold value of the corresponding interval according to the operating power requirements of different intervals; finally, under different power threshold values, selecting a corresponding working mode for the hybrid energy storage element, and specifically comprising the following steps:

step 1, calculating the running power requirement of the tramcar based on the running state of the tramcar, and specifically comprising the following steps:

in an operation interval, the automatic driving (ATO) operation process of the tramcar is divided into four working conditions: the operating conditions of the full-force traction (I), the constant-speed cruise (II), the coasting (III) and the full-force brake (IV) are schematically shown in FIG. 2, wherein:

1) in the I working condition interval, the tramcar starts from the speed 0 and starts with the maximum traction force to reach the interval maximum speed V_max；

2) In the II working condition interval, the tramcar has the interval maximum speed V_maxThe uniform motion is carried out, and the traction force is equal to the comprehensive resistance;

3) in the working condition interval of III, the tramcar performs coasting, and the traction force is 0;

4) and in the IV working condition interval, the tramcar brakes with the maximum braking force.

The tramcar runs according to the ATO curve, the running condition of the tramcar can be determined, namely the relation between the running speed and the running mileage is known, and the running power requirement of the tramcar is analyzed on the basis. In the running process of the tramcar, the energy requirement is embodied on the traction force and the resistance, namely the traction force realizes the energy conversion into the mechanical energy to finish the vehicle running, and the resistance consumes the energy to block the vehicle running.

The system structure and energy flow schematic diagram of the power battery + super capacitor hybrid power tramcar are shown in fig. 3. In the figure, a hybrid energy storage power supply consisting of a power battery and a super capacitor is connected with one side of a direct current bus, and a traction inverter, a traction motor, a transmission system and a vehicle are connected in series and then connected with auxiliary equipment and a brake resistor in parallel at the other side of the direct current bus. When the traction motor works in a motor mode, the energy flow direction of a power system is as follows: hybrid energy storage power supply>DC bus>Traction inverter>Traction motor>Transmission system>A vehicle; when the traction motor works in a generator mode, the energy flow direction of the power system is as follows: vehicle (vehicle)>Transmission system>Traction motor>Traction inverter>Hybrid energy storage power supply (DC/DC converter-)>A super capacitor). Wherein eta is₁、η₂、η₃、η₄、η₅Respectively representing the efficiencies of the transmission system, the traction motor, the traction inverter, the power battery DC-DC converter and the super capacitor DC-DC converter, P_Ft、P_aux、P_mch、P_needRespectively representing tramcarsCircumferential traction power, auxiliary equipment power, brake resistance consumed power and operation required power.

Traction force F of driving wheel of tramcar_t(x) Satisfies the following conditions:

F_t(x)＝(1+γ)Ma(x)+f_t(x)

in the formula: x is the kilometer post of the tramcar, and x is an element (x)₀,x_end)；F_t(x)、f_t(x) Respectively represents the traction force and the resistance force of the tramcar at x, when F_t(x) When the force is more than 0, the acting force on the driving wheel is traction force, and when F is greater than 0_t(x) When < 0, the acting force on the driving wheel is braking force, F except for special description_t(x) Is greater than 0; m is tramcar mass; gamma is the rotational inertia of the tramcar; and a (x) is the tram expected acceleration.

The expected acceleration a (x) of the tramcar satisfies:

in the formula: v (x) is the desired speed of the tram at x.

During the running of the tramcar, the resistance f_t(x) From a basic resistance f₀(x) Additional resistance f₁(x) Composition in which the resistance f is added₁(x) Adding resistance f from the ramp_i(x) Curve additional resistance f_r(x) Air additional resistance f_w(x) Composition, resistance f_t(x) Satisfies the following conditions:

f_t(x)＝f₀(x)+f₁(x)

basic resistance f₀(x) Produced by friction between tram machines, satisfies:

f₀(x)＝Mg(A+Bv(x)+Cv(x)²)

in the formula: g is the gravitational acceleration and A, B, C is the basic drag coefficient.

Additional resistance f₁(x) The resistance generated by the tramcar when the tramcar runs through a specific line (ramp, curve) comprises the following components: adding resistance f from the ramp_i(x) Curve additional resistance f_r(x) Air attachmentResistance f_w(x) And satisfies the following conditions:

f₁(x)＝f_i(x)+f_r(x)+f_w(x)

additional resistance f of ramp_i(x) The component force of the dead weight along the ramp direction that tram received when the ramp operation, it is less to consider the actual operation route slope, satisfies:

f_i(x)＝Mgi

in the formula: i is a tangent value of the slope angle theta, namely a gradient value of the tramcar at the x position, and satisfies i ═ tan theta.

Curve additional resistance f_r(x) Caused by the increase of friction between wheel and the track that the tram wheel transversely slides, satisfy:

in the formula: r is the current position curve radius; d is the curve additional drag coefficient.

Additional resistance f to air_w(x) The air resistance that receives when tram moves promptly satisfies:

f_w(x)＝0.5ESρv_r(x)²

wherein E is the coefficient of air resistance, S is the frontal area, ρ is the air density, v_r(x) Is the relative speed between the tramcar and the wind speed.

Thus, the resistance force f_t(x) Satisfies the following conditions:

tramcar circumference traction power P_Ft(x) Satisfies the following conditions:

tramcar is in the interval (x)₀,x_end) The tramcar runs at the expected speed completely, and the required power P of the tramcar runs_need(x) Satisfies the following conditions:

P_need(x)＝η₁ ^σ1η₂ ^σ1η₃ ^σ1P_Ft(x)+P_aux

in the formula eta₁、η₂、η₃Represents the efficiency of the transmission system, the traction motor and the traction inverter respectively, and sigma 1 is sgn (-P)_Ft(x))；P_auxRepresents the power of auxiliary equipment of the tramcar, and the auxiliary equipment comprises an air conditioner and lighting. Furthermore, when F_t(x) < 0 i.e. P_Ft(x) When < 0, F_t(x) For braking force, brake recovery energy is generated.

Tramcar is in the interval (x)₀,x_end) Energy requirement for operation E_need(x) Satisfies the following conditions:

step 2, dynamically adjusting the power threshold value of the corresponding interval according to the operating power requirements of different intervals, which is as follows:

the hybrid power tramcar comprises a power battery and a super capacitor, wherein the power battery does not recover braking energy and adopts a first-station and last-station charging mode; the super capacitor is responsible for recovering braking energy and adopts a station charging mode. Because the power battery adopts a first-station and last-station charging mode, the power battery is ensured to be in a proper state of charge (SOC) and supply energy as little as possible in consideration of element performance and running characteristics of the tramcar; the super capacitor adopts a station charging mode, and in order to recover the braking energy to the maximum extent, the super capacitor needs to supply more energy in the traction and cruise stages as much as possible, so that the braking energy is efficiently recovered in the braking stage.

During operation, on the premise of ensuring that the tramcar runs at a target speed, the power battery and the super capacitor are matched to supply power to meet the power energy requirement, a power threshold value is set, and when the power requirement is smaller than or equal to the power threshold value, the power battery supplies power independently; when the power demand is higher than the power threshold value, the power battery and the super capacitor are used for supplying power together.

And the optimal power threshold value of each operation interval is obtained by taking the minimum energy consumption of the power battery as a target, so that the power distribution between the power battery and the super capacitor is dynamically adjusted according to the actual condition, and the system performance is optimal.

For facilitating the determination of the discharge power of the power battery, R is adopted_intInternal resistance model, as shown in fig. 4.

The power battery terminal voltage U satisfies:

U＝U_oc-IR₀

in the formula of U_ocIs the power cell open circuit voltage, related to the state of charge SOC; i is a charge-discharge current; r₀Is the equivalent internal resistance of the power battery, neglects the temperature and SOC to R for simplifying the model₀Of (2), i.e. R₀Is a constant value.

SOC of power battery_btSatisfies the following conditions:

in the formula, Q_ini、Q_btThe initial capacity and the rated capacity of the power battery are respectively; t is t₀、t₁Respectively, the start time and the end time of the discharge current I.

Discharge power P of power battery_bAnd satisfies the following conditions:

in the formula I_bThe power battery is charged and discharged to limit current, and is positive during discharging and negative during charging; SOC_btmin、SOC_btmaxThe lowest and highest states of charge of the power battery during normal operation are respectively. From the formula, the state of charge SOC_btAnd limiting the current I_bDetermining discharge power P_bAnd state of charge SOC_btBy limiting the current I_bDetermine, therefore, the discharge power P_bBy limiting the current I_bDetermining, i.e. limiting, the current I by optimization_bCan optimize the discharge power P_b。

The power threshold value is discharged by a power batteryElectric power determination, with maximum discharge power P of the power battery_maxLimiting the current I by optimizing the power threshold value_bTo optimize the discharge power P_bI.e. power threshold value, to finally obtain the optimum limiting current I_bmAnd an optimum power threshold value P_bm。

Limiting the current I_bSatisfies the following conditions:

I_b≤I_max

in the formula I_maxThe maximum allowable charge and discharge current.

Limiting the current I_bOptimizing the process, specifically comprising the following steps:

1) using maximum allowable charging and discharging current I_maxInitial limiting current I_bI.e. satisfy I_b＝I_max；

2) In limiting the current I_bDetermined power threshold value P_bJudging whether the running target speed requirement of the tramcar is met or not;

3) if the requirement is met, limiting the current I_bOn the basis of subtracting a certain variable DeltaI, i.e. satisfying I_b＝I_b- Δ I and entering step 2) for a decision;

4) if the current does not meet the requirement, the circulation is exited, and the limiting current I in the last circulation is taken_bAs an optimum limiting current I_bmThe limiting current determines an optimum power threshold value P_bm。

And 3, selecting a corresponding working mode for the hybrid energy storage element under different power threshold values, wherein the working mode is as follows:

in order to adapt to the selection of the power threshold value, the working modes of the hybrid energy storage system of the power battery and the super capacitor are divided into: A. a low power traction mode of operation; B. a high power traction mode of operation; C. a regenerative braking mode of operation; D. regenerative braking + mechanical braking mode of operation.

A. Low power traction mode of operation (0 < P)_need≤P_bm，SOC_btmin＜SOC_bt＜SOC_btmax)

In the low-power traction mode, the power demand of the tramcar is smallEqual to or greater than the power threshold, i.e. 0 < P_need≤P_bmState of charge SOC of power battery_btIn the normal operating state, i.e. SOC_btmin＜SOC_bt＜SOC_btmaxIf the power battery is used for supplying power alone, the power balance relationship in the mode is as follows:

in the formula, P_btoRepresenting the output power of the power battery; p_cmoRepresenting the output power of the power battery; eta₄Representing the operating efficiency of the DC-DC converter of the power battery.

B. High power traction mode of operation (P)_need＞P_bm，SOC_btmin＜SOC_bt＜SOC_btmax，SOC_cmmin＜SOC_cm＜SOC_cmmax)

In the high-power traction working mode, the power demand of the tramcar is higher than a power threshold value, namely P_need＞P_bmAnd the state of charge SOC of the power battery_btSOC of super capacitor_cmAre all in normal operating condition, i.e. SOC_btmin＜SOC_bt＜SOC_btmax、SOC_cmmin＜SOC_cm＜SOC_cmmaxAnd the power battery and the super capacitor are used for supplying power together, and the power balance relationship in the mode is as follows:

P_need＝η₄P_bto+η₅P_cmo

in the formula eta₅And the working efficiency of the DC-DC converter of the super capacitor is represented.

C. Regenerative braking operating mode (P)_need＜0，SOC_cmmin＜SOC_cm＜SOC_cmmax)

In the regenerative braking mode of operation, the tram power demand P_needIf the voltage is less than 0, regenerative braking energy is generated, and when the super capacitor is in a normal working mode (SOC)_cmmin＜SOC_cm＜SOC_cmmax) The regenerative braking energy is recovered by the super capacitor, and the power balance is closed in the modeThe method comprises the following steps:

η₅P_need＝P_cmi

in the formula, P_cmiRepresenting the input power (charging power) of the super capacitor.

D. Regenerative braking + mechanical braking operating mode (P)_need＜0，SOC_cm≥SOC_cmmax)

In the regenerative braking + mechanical braking operating mode, when the regenerative braking energy exceeds the maximum recovery capacity of the super capacitor, namely the charge state of the super capacitor exceeds the maximum value, the braking resistor begins to consume the regenerative braking energy, namely the over-regenerative braking energy is converted into heat energy, and the power balance relationship in the mode is as follows:

η₅P_need＝P_cmi+P_mch

in the formula, P_mchRepresenting the brake resistor dissipating power.

The present invention will be described in detail with reference to examples.