Power control method and system for hybrid excavator

Abstract

This invention discloses a power control method for a hybrid excavator, comprising: acquiring load demand; determining the valley filling threshold and peak shaving threshold of the engine based on the state of charge (SOC) of the power battery; determining the working mode of the motor based on the SOC of the power battery, load demand, and the valley filling and peak shaving thresholds of the engine; and controlling the motor torque according to the working mode of the motor. This invention uses the peak shaving and valley filling effect of the ISG motor to limit the engine torque to a low-energy consumption range at a certain speed, and adjusts the response speed of the ISG motor and the engine according to the load change rate, thereby avoiding transient changes in engine power and saving fuel consumption.

Description

Technical Field

[0001] This invention belongs to the field of new energy construction machinery technology, and in particular relates to a power control method and system for a hybrid excavator. Background Technology

[0002] Excavators are multi-purpose construction machinery capable of performing various tasks such as digging, leveling, loading, and crushing. The most common operating condition for excavators is digging, which involves a process of lowering, digging, lifting, rotating, releasing the shovel, and rotating back to its original position. This work cycle is highly cyclical, and the output power fluctuates dramatically. Under these transient conditions, the engine's fuel consumption increases significantly. This is especially true for large excavators, which have long working cycles throughout the year and high digging power, resulting in a significant impact on the customer's operating costs due to increased overall energy consumption.

[0003] The most common operating condition for excavators is digging, which includes the process of lowering, digging, lifting, rotating, releasing the shovel, and rotating back to its original position. This work cycle is highly cyclical and experiences significant power fluctuations, leading to a marked increase in fuel consumption under these transient conditions. This is especially true for large excavators, which have long working cycles and high digging power throughout the year; reducing overall fuel consumption significantly lowers operating costs for customers. By introducing an ISG motor to create a hybrid power system for the excavator, the peak-shaving and valley-filling effect of the ISG motor helps maintain the engine in a low-energy-consumption range for extended periods.

[0004] However, when the ISG motor operates in electric or generator mode for extended periods, it can cause the battery's State of Charge (SOC) to become too high or too low, thereby affecting the battery's charge and discharge power limits. This can lead to overcharging or over-discharging of the battery, increasing the probability of safety hazards. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a power control method and system for hybrid excavators, which can reduce excavator energy consumption while reducing the probability of safety hazards.

[0006] The technical problem to be solved by the present invention is achieved through the following technical solution:

[0007] In a first aspect, a power control method for a hybrid excavator is provided, characterized by comprising:

[0008] Obtain load requirements;

[0009] The valley filling threshold and peak shaving threshold of the engine are determined based on the state of charge (SOC) of the power battery.

[0010] The operating mode of the motor is determined based on the SOC of the power battery, load demand, and the valley filling and peak shaving thresholds of the engine.

[0011] The motor torque is controlled according to the motor's operating mode.

[0012] In conjunction with the first aspect, further details include:

[0013] Determine whether the power battery meets the conditions for forced charging. If it does, then force charge the power battery.

[0014] In conjunction with the first aspect, the forced charging conditions further include:

[0015] 3) The time threshold since the last forced charging or the cumulative charge / discharge amount has reached the charge / discharge threshold;

[0016] 4) The current SOC of the power battery is not 100%;

[0017] The forced charging includes: if conditions 1) and 2) are both met, the motor enters the power generation mode, and exits the forced charging after the power battery SOC reaches 100%.

[0018] In conjunction with the first aspect, further, obtaining the engine load requirements includes:

[0019] The actual flow rate Q1 of the radiator pump is calculated based on the actual pressure P1 and actual current I1 of the radiator pump in the hybrid system.

[0020] The actual flow rate Q2 of the hydraulic main pump is calculated based on the actual pressure P2 and actual current I2 of the hybrid system hydraulic main pump.

[0021] The load demand power is calculated according to equation (1).

[0022] P r =P1Q1+P2Q2 (1)

[0023] Among them, P r Power required by the load;

[0024] The load demand torque is obtained from the load demand power using equation (2).

[0025]

[0026] Among them, T r Where n is the torque required by the load and n is the current engine speed.

[0027] In conjunction with the first aspect, further, determining the valley filling threshold and peak shaving threshold of the engine based on the power battery SOC includes:

[0028] Based on the current gear, query the engine's fuel consumption map to determine the torque range of the engine's optimal fuel consumption point at that gear speed [T]. min ,T max ];

[0029] Let the recommended charge / discharge range of the power battery be [S].d2 ,S c2 ], and S d2 S is set as the second discharge threshold of the power battery. c2 Set S as the second charging threshold for the power battery. c1 Set S as the first charging threshold for the power battery. d1 Let S be the first discharge threshold. c1 =S c2 -S g S d1 =S d2 +S g S g For interval transition values;

[0030] At each gear, when the SOC of the power battery is located at [0, S... d1 ), [S d1 ,S c1 ]、[S c1 When the range is 100%, set the corresponding peak-shaving threshold T for each range. x Valley filling threshold T t T min <T t <T x <T max .

[0031] In conjunction with the first aspect, further, determining the motor's operating mode based on the power battery's SOC, load demand, and the engine's valley filling and peak shaving thresholds includes:

[0032] If the SOC of the power battery is higher than the second charging threshold S c2 If the load demand T is at this time, then the motor is prohibited from generating electricity. r Greater than the peak reduction threshold T x If the peak reduction threshold T is less than the motor's operating threshold, the motor will enter drive mode. x The motor then enters zero torque mode;

[0033] If the SOC of the power battery is lower than the second discharge threshold S d2 If the motor is not driven, it will enter generator mode.

[0034] If the SOC of the power battery is between the second charging threshold S c2 Second discharge threshold S d2 Between, when the load demand T r Greater than the peak reduction threshold T x When the load demand T is reached, the motor enters drive mode. r Less than the valley filling threshold T t Then the motor enters generation mode when the load demand is at the peak shaving threshold T. x Valley filling threshold Tt The motor enters zero torque mode during this period.

[0035] In conjunction with the first aspect, further, the adjustment of motor torque according to the motor's operating mode includes:

[0036] When the motor enters zero torque mode, the motor torque output is 0;

[0037] When the motor enters generator mode, it generates electricity with a negative torque, and the generated torque must not be less than the minimum generated torque T. a and the minimum torque T of the motor min The minimum generating torque is obtained through equation (3):

[0038]

[0039] Among them, P chg Where n is the minimum allowable charging power of the power battery, and n is the current speed of the motor.

[0040] When the motor enters drive mode, the motor torque is positive and it drives the motor; the drive torque must not exceed the maximum drive torque T. b and the maximum torque T of the motor max The maximum driving torque is obtained through equation (4):

[0041]

[0042] Among them, P dis This refers to the maximum allowable discharge power of the power battery.

[0043] Secondly, a power control system for a hybrid excavator is provided, comprising:

[0044] The load requirement acquisition module is used to acquire load requirements;

[0045] The peak shaving and valley filling threshold determination module is used to determine the valley filling threshold and peak shaving threshold of the engine based on the SOC of the power battery.

[0046] The working mode determination module is used to determine the working mode of the motor based on the SOC of the power battery, load demand, and the valley filling threshold and peak shaving threshold of the engine.

[0047] The torque control module is used to control the motor torque according to the motor's operating mode.

[0048] In conjunction with the second aspect, the operations performed by the load demand acquisition module further include:

[0049] The actual flow rate Q1 of the radiator pump is calculated based on the actual pressure P1 and actual current I1 of the radiator pump in the hybrid system.

[0050] The actual flow rate Q2 of the hydraulic main pump is calculated based on the actual pressure P2 and actual current I2 of the hybrid system hydraulic main pump.

[0051] The load demand power is calculated according to equation (1).

[0052] P r =P1Q1+P2Q2 (1)

[0053] Among them, P r Power required by the load;

[0054] The load demand torque is obtained from the load demand power using equation (2).

[0055]

[0056] Among them, T r Where n is the torque required by the load and n is the current engine speed.

[0057] In conjunction with the second aspect, the operations performed by the working mode determination module further include:

[0058] If the SOC of the power battery is higher than the second charging threshold S c2 If the load demand T is at this time, then the motor is prohibited from generating electricity. r Greater than the peak reduction threshold T x If the peak reduction threshold T is less than the motor's operating threshold, the motor will enter drive mode. x The motor then enters zero torque mode;

[0059] If the SOC of the power battery is lower than the second discharge threshold S d2 If the motor is not driven, it will enter generator mode.

[0060] If the SOC of the power battery is between the second charging threshold S c2 Second discharge threshold S d2 Between, when the load demand T r Greater than the peak reduction threshold T x When the load demand T is reached, the motor enters drive mode. r Less than the valley filling threshold T t Then the motor enters generation mode when the load demand is at the peak shaving threshold T. x Valley filling threshold T t The motor enters zero torque mode during this period.

[0061] The beneficial effects of this invention are:

[0062] (1) By using the peak shaving and valley filling effect of the ISG motor, the engine torque is limited to the low energy consumption range at a certain speed. The response speed of the ISG motor and the engine is adjusted according to the load change rate, which avoids the transient change of engine power and saves fuel consumption.

[0063] (2) Considering the impact of battery SOC, a safety threshold is set. At low SOC, to prevent battery over-discharge, the ISG motor drive is prohibited. At high SOC, to prevent battery over-charging, the ISG motor power generation is prohibited. At the same time, the valley filling threshold and peak shaving threshold are dynamically adjusted according to the SOC.

[0064] (3) In order to ensure the accuracy of battery SOC estimation, after the battery has been working for a period of time or has completed a certain amount of charging and discharging, the ISG motor will be controlled to generate electricity to charge the battery SOC to 100%. Attached Figure Description

[0065] Figure 1 This is a flowchart of the present invention;

[0066] Figure 2 This is a schematic diagram of the motor's operating mode in this invention;

[0067] Figure 3 This is a schematic diagram of the engine's minimum fuel consumption torque in this invention;

[0068] Figure 4 This is a schematic diagram illustrating the calculation of power generation torque in this invention;

[0069] Figure 5 This is a schematic diagram illustrating the calculation of driving torque in this invention;

[0070] Figure 6 This is a schematic diagram of the hybrid system in this invention. Detailed Implementation

[0071] The present invention will now be described in further detail with reference to the accompanying drawings.

[0072] Example 1

[0073] like Figures 1-6As shown, this invention provides a power control method for a hybrid excavator. When the engine operates at a fixed speed, the load demand is calculated by detecting the parameters of the cooling pump and the main pump. When the load demand is lower than the valley filling threshold, the ISG motor operates in generator mode, acting as an additional load to increase the engine torque to the lower limit of the low-energy consumption zone. When the load demand is higher than the peak shaving threshold, the ISG motor operates in drive mode, assisting the engine drive and limiting the engine torque to the upper limit of the low-energy consumption zone. When the load power changes too much, the motor response speed is increased while the engine response speed is decreased, reducing the transient changes of the engine when following load changes. Simultaneously, considering the impact of battery SOC, when the battery SOC is lower than the first discharge threshold, the valley filling threshold and peak shaving threshold are increased, causing the ISG motor to generate more electricity and drive less, preventing further SOC decrease. When the battery SOC is higher than the first charging threshold, the valley filling threshold and peak shaving threshold are decreased, causing the ISG motor to generate less electricity and drive more, preventing further SOC increase. The specific process includes:

[0074] S1. Collect data to obtain load requirements.

[0075] The hybrid controller collects voltage data signals from the pressure and current sensors of the cooling pump, converts them into the actual pressure P1 and actual current I1 of the cooling pump, and then calculates the actual flow rate Q1 = f(I1) of the cooling pump based on the current and flow conversion formula of the cooling pump (obtained by experiment).

[0076] The hybrid controller collects the voltage signals from the pressure and current sensors of the hydraulic main pump, converts them into the actual pressure P2 and actual current I2 of the hydraulic main pump, and calculates the actual flow rate Q2 = f(I2) of the hydraulic main pump based on the current and flow conversion formula of the hydraulic main pump (obtained by experiment).

[0077] Therefore, the load power demand P is calculated. r =P1Q1 + P2Q2;

[0078] The hybrid controller collects the speed signal n sent by the engine to the CAN bus, which is the speed of the engine and the motor. In this architecture, the engine and the motor are coaxial.

[0079] Calculate the engine load torque requirement based on the load power demand and the current engine speed n:

[0080]

[0081] S2. Determine the valley filling threshold and peak shaving threshold of the engine based on the SOC of the power battery.

[0082] Based on a specific operating gear, the engine's fuel consumption map is consulted to determine the torque range where the engine achieves optimal fuel consumption at that gear's RPM. min ,T max];

[0083] Let the recommended charge / discharge range of the power battery be [S]. d2 ,S c2 ], and S d2 S is set as the second discharge threshold of the power battery. c2 Set S as the second charging threshold for the power battery. c1 Set S as the first charging threshold for the power battery. d1 Let S be the first discharge threshold. c1 =S c2 -S g S d1 =S d2 +S g S g For the interval transition value, S in this example g Take 10%; S c1 S c2 S d1 S d2 The percentages are 60%, 70%, 40%, and 30%, respectively.

[0084] At each gear, when the SOC of the power battery is located at [0, S... d1 ), [S d1 ,S c1 ]、[S c1 When the range is 100%, set the corresponding peak-shaving threshold T for each range. x Valley filling threshold T t T min <T t <T x <T max Peak reduction threshold T x Valley filling threshold T t Based on experience and testing, the settings should be optimized to both smooth out peaks and valleys without causing SOC to change too quickly and become unstable during adjustments.

[0085] To ensure high battery safety and performance, the State of Charge (SOC) needs to be controlled within a suitable range. The permissible operating modes of the ISG motor should be determined based on the battery's SOC charge / discharge threshold, such as... Figure 2 As shown, the impact of battery SOC on the valley-filling threshold and peak-shaving threshold is as follows: when the battery SOC is below the first discharge threshold, the valley-filling threshold and peak-shaving threshold are increased, causing the ISG motor to generate more electricity and drive less, preventing the SOC from decreasing further. When the battery SOC is above the first charging threshold, the valley-filling threshold and peak-shaving threshold are decreased, causing the ISG motor to generate less electricity and drive more, preventing the SOC from increasing further.

[0086] Taking a certain engine as an example, at 1400 rpm in 7th gear, the lowest fuel consumption torque range is [1000-2000]. Figure 3 As shown, the first discharge threshold S of the battery SOC is set. d1 The second discharge threshold is 40%. d2 The first charging threshold is 30%. c1 The second charging threshold is 60%. c2 Set to 70%. When battery SOC < 40%, set T. t =1700, T x =2000; When the battery SOC is between 40% and 60%, set T. t =1300, T x =1700; When battery SOC>60%, set T t =1000, T x =2000.

[0087] S3. Determine the motor's operating mode based on the power battery's SOC, load demand, and the engine's valley filling and peak shaving thresholds.

[0088] If the battery SOC is higher than the second charging threshold S c2 If the load demand T is high, the ISG motor will be prohibited from generating electricity. r Greater than the peak reduction threshold T x If the torque is 1, the ISG motor enters drive mode; otherwise, the ISG enters zero-torque mode.

[0089] If the battery SOC is lower than the second discharge threshold S d2 If the battery level is too low, the ISG motor will be prohibited from driving. At this time, the ISG motor needs to enter the generator mode to replenish the battery power because the battery power is too low.

[0090] If the battery SOC is between the second charging threshold S c2 Second discharge threshold S d2 Between, when the load demand T r Greater than the peak reduction threshold T x When the load demand T is reached, the ISG motor enters drive mode. x Less than the valley filling threshold T t When the torque is applied, the ISG motor enters the generator mode; otherwise, the ISG motor enters the zero-torque mode.

[0091] S4. Control the motor torque according to the motor's operating mode.

[0092] When the ISG motor reaches zero torque, the torque output of the ISG motor is 0.

[0093] When the ISG motor enters the power generation mode, the ISG motor generates electricity with a negative torque, and the generated torque must not be less than the minimum generated torque T. a and the minimum torque T of the motor min Methods for calculating and limiting generator torque, such as Figure 4 As shown. The minimum torque T of the ISG motor is... min The minimum generating torque T is obtained directly from the CAN bus by the hybrid controller. a Through the minimum charging power P allowed by the battery chg Calculated.

[0094]

[0095] When the ISG motor enters drive mode, the ISG motor torque is positive and it drives the motor; the drive torque must not exceed the maximum drive torque T. b and the maximum torque T of the motor max The methods for calculating and limiting driving torque are as follows: Figure 5 As shown. The maximum torque T of the ISG motor is... max The maximum drive torque T is obtained directly from the CAN bus by the hybrid controller. b The maximum allowable discharge power P of the battery dis Calculated.

[0096]

[0097] Where n is the motor speed.

[0098] The excavator experiences highly variable loads with significant power fluctuations. During these fluctuations, the ISG motor needs to respond first, while the engine's response speed is reduced. This ensures the excavator can adapt to the changing load while slowing down engine torque fluctuations and minimizing transient changes in engine torque. The parameters affecting the response speed of the ISG motor and engine are the proportional gain K of the current regulator. p-m and speed regulator proportional gain K p-e .

[0099] Calculate the rate of change of required torque

[0100] When the rate of change a is less than or equal to the threshold a1, the proportional gain K of the current regulator p-m and speed regulator proportional gain K p-e The value is set to the default value.

[0101] When the rate of change 'a' is greater than the threshold 'a1', the proportional gain K of the current regulator of the ISG motor... p-m =f1(a), is a monotonically increasing function. The proportional gain K of the engine's speed governor. p-e =f2(a), which is a monotonically decreasing function.

[0102] The above values ​​can be determined through experimental testing.

[0103] The hybrid excavator system used in this method is as follows: Figure 6 As shown, it includes:

[0104] Sensor 1 is used to measure the pressure of the radiator pump;

[0105] Cooling pump 2 is used to power the excavator's cooling system;

[0106] Sensor 3 is used to measure the current of the radiator pump;

[0107] Engine 4, used to power the entire vehicle;

[0108] Engine controller 5, used to control the engine's response to speed commands;

[0109] Hybrid controller 6 for acquiring data and executing control methods;

[0110] ISG motor 7 is used to assist engine drive or charge the battery;

[0111] Motor controller 8 for controlling the response torque command of the ISG motor;

[0112] Power battery 9 used to provide electrical energy to ISG motors or to recover electrical energy;

[0113] Hydraulic main pump 10 is used to provide power to the hydraulic system;

[0114] Sensor 11 is used to measure the current of the hydraulic main pump;

[0115] Pressure sensor 12 is used to measure the pressure of the hydraulic main pump.

[0116] The engine, ISG motor, and hydraulic main pump are mechanically coaxially connected, and the cooling pump is mechanically connected to the engine's PTO port. The power battery, motor controller, and ISG motor are connected via high-voltage connections. The hybrid controller, engine controller, motor controller, and power battery are connected via CAN communication for information exchange. The pressure sensor, current sensor, and hybrid controller are connected via low-voltage connections. The hybrid controller collects pressure and current signals from the cooling pump and hydraulic main pump, converts the current signal into a flow signal, and then calculates the current power based on the pressure and flow rate.

[0117] Example 2

[0118] The present invention also provides a power control system for a hybrid excavator, comprising:

[0119] The load requirement acquisition module is used to acquire load requirements;

[0120] The peak shaving and valley filling threshold determination module is used to determine the valley filling threshold and peak shaving threshold of the engine based on the SOC of the power battery.

[0121] The working mode determination module is used to determine the working mode of the motor based on the SOC of the power battery, load demand, and the valley filling threshold and peak shaving threshold of the engine.

[0122] The torque control module is used to control the motor torque according to the motor's operating mode.

[0123] The operations performed by the load demand acquisition module include:

[0124] The actual flow rate Q1 of the radiator pump is calculated based on the actual pressure P1 and actual current I1 of the radiator pump in the hybrid system.

[0125] The actual flow rate Q2 of the hydraulic main pump is calculated based on the actual pressure P2 and actual current I2 of the hybrid system hydraulic main pump.

[0126] The load demand power is calculated according to equation (1).

[0127] P r =P1Q1+P2Q2(1)

[0128] Among them, P r Power required by the load;

[0129] The load demand torque is obtained from the load demand power using equation (2).

[0130]

[0131] Among them, T r Where n is the torque required by the load and n is the current engine speed.

[0132] The operations performed by the working mode determination module include:

[0133] If the SOC of the power battery is higher than the second charging threshold S c2 If the load demand T is at this time, then the motor is prohibited from generating electricity. r Greater than the peak reduction threshold T x If the peak reduction threshold T is less than the motor's operating threshold, the motor will enter drive mode. x The motor then enters zero torque mode;

[0134] If the SOC of the power battery is lower than the second discharge threshold S d2 If the motor is not driven, it will enter generator mode.

[0135] If the SOC of the power battery is between the second charging threshold S c2 Second discharge threshold Sd2 Between, when the load demand T r Greater than the peak reduction threshold T x When the load demand T is reached, the motor enters drive mode. r Less than the valley filling threshold T t Then the motor enters generation mode when the load demand is at the peak shaving threshold T. x Valley filling threshold T t The motor enters zero torque mode during this period.

[0136] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0137] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0138] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0139] The operations performed when exiting the heating module include:

[0140] Get the engine coolant temperature, excavator hydraulic oil temperature, engine oil temperature, engine compartment temperature, excavator radiator temperature, excavator air filter intake temperature, and engine intercooler temperature at the current ambient temperature.

[0141] If any of the following temperature parameters exceed the corresponding vehicle thermal balance qualification limit: engine coolant temperature, excavator hydraulic oil temperature, engine oil temperature, engine compartment temperature, temperature difference between the excavator radiator and the current environment, temperature difference between the excavator air filter intake temperature and the current environment, or temperature difference between the engine intercooler temperature and the current environment, the cooling fan's heat dissipation performance will be improved.

[0142] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A power control method for a hybrid excavator, characterized in that, include: Obtain load requirements; The valley filling threshold and peak shaving threshold of the engine are determined based on the state of charge (SOC) of the power battery. The operating mode of the motor is determined based on the SOC of the power battery, load demand, and the valley filling and peak shaving thresholds of the engine. The motor torque is controlled according to the motor's operating mode; The determination of the engine's valley filling threshold and peak shaving threshold based on the power battery's SOC includes: Based on the current gear, query the engine's fuel consumption map to determine the torque range where the engine achieves optimal fuel consumption at that gear speed. ; Let the recommended charge / discharge range of the power battery be... and will Set as the second discharge threshold for the power battery. Set as the second charging threshold for the power battery, Set as the first charging threshold for the power battery, Set as the first discharge threshold. = - , = + ,in For interval transition values; At each gear, when the SOC of the power battery is respectively located , , When dealing with intervals, set the corresponding peak-shaving threshold for each interval. Valley filling threshold , ; When the battery SOC is lower than the first discharge threshold, the valley filling threshold and peak shaving threshold are increased; when the battery SOC is higher than the first charging threshold, the valley filling threshold and peak shaving threshold are decreased.

2. The power control method for a hybrid excavator according to claim 1, characterized in that, Also includes: Determine whether the power battery meets the conditions for forced charging. If it does, then force charge the power battery.

3. The power control method for a hybrid excavator according to claim 2, characterized in that, The forced charging conditions include: 1) The time threshold since the last forced charging or the cumulative charge / discharge amount has reached the charge / discharge threshold; 2) The current SOC of the power battery is not 100%; The forced charging includes: if conditions 1) and 2) are both met, the motor enters the power generation mode, and exits the forced charging after the power battery SOC reaches 100%.

4. The power control method for a hybrid excavator according to claim 1, characterized in that, The acquisition of engine load requirements includes: Based on the actual pressure of the hybrid system's cooling pump and actual current Calculate the actual flow rate of the cooling pump ; Based on the actual pressure of the hybrid system's hydraulic main pump and actual current The actual flow rate of the hydraulic main pump was calculated. ; The load demand power is calculated according to equation (1). （1） in, Power required by the load; The load demand torque is obtained from the load demand power using equation (2). （2） in, For the required torque of the load, This is the current engine speed.

5. The power control method for a hybrid excavator according to claim 1, characterized in that, The method of determining the motor's operating mode based on the power battery's SOC, load demand, and the engine's valley filling and peak shaving thresholds includes: If the SOC of the power battery is higher than the second charging threshold If the load demand is high at this time, then the motor is prohibited from generating electricity. Greater than the peak reduction threshold If the peak load is less than the peak reduction threshold, the motor will enter drive mode. The motor then enters zero torque mode; If the SOC of the power battery is lower than the second discharge threshold If the motor is not driven, it will enter generator mode. If the SOC of the power battery is between the second charging threshold Second discharge threshold Between, when load demand Greater than the peak reduction threshold When the load demand is high, the motor enters drive mode. Less than the valley filling threshold Then the motor enters generation mode when the load demand is at the peak shaving threshold. Valley filling threshold The motor enters zero torque mode during this period.

6. The power control method for a hybrid excavator according to claim 5, characterized in that, The adjustment of motor torque according to the motor's operating mode includes: When the motor enters zero torque mode, the motor torque output is 0; When the motor enters generator mode, it generates electricity with a negative torque, and the generated torque must not be less than the minimum generated torque. and the minimum torque of the motor The minimum generating torque is obtained through equation (3): （3） in, The minimum allowable charging power for the power battery. This represents the current speed of the motor. When the motor enters drive mode, the motor torque is positive and it drives the motor; the drive torque must not exceed the maximum drive torque. and the maximum torque of the motor The maximum driving torque is obtained through equation (4): （4） in, This refers to the maximum allowable discharge power of the power battery.

7. A power control system for a hybrid excavator, characterized in that, include: The load requirement acquisition module is used to acquire load requirements; The peak shaving and valley filling threshold determination module is used to determine the valley filling threshold and peak shaving threshold of the engine based on the SOC of the power battery. The working mode determination module is used to determine the working mode of the motor based on the SOC of the power battery, load demand, and the valley filling threshold and peak shaving threshold of the engine. The torque control module is used to control the motor torque according to the motor's operating mode; The determination of the engine's valley filling threshold and peak shaving threshold based on the power battery's SOC includes: Based on the current gear, query the engine's fuel consumption map to determine the torque range where the engine achieves optimal fuel consumption at that gear speed. ; Let the recommended charge / discharge range of the power battery be... and will Set as the second discharge threshold for the power battery. Set as the second charging threshold for the power battery, Set as the first charging threshold for the power battery, Set as the first discharge threshold. = - , = + ,in For interval transition values; At each gear, when the SOC of the power battery is respectively located , , When dealing with intervals, set the corresponding peak-shaving threshold for each interval. Valley filling threshold , ; When the battery SOC is lower than the first discharge threshold, the valley filling threshold and peak shaving threshold are increased; when the battery SOC is higher than the first charging threshold, the valley filling threshold and peak shaving threshold are decreased.

8. The power control system for a hybrid excavator according to claim 7, characterized in that, The operations performed by the load demand acquisition module include: Based on the actual pressure of the hybrid system's cooling pump and actual current Calculate the actual flow rate of the cooling pump ; Based on the actual pressure of the hybrid system's hydraulic main pump and actual current The actual flow rate of the hydraulic main pump was calculated. ; The load demand power is calculated according to equation (1). （1） in, Power required by the load; The load demand torque is obtained from the load demand power using equation (2). （2） in, For the required torque of the load, This is the current engine speed.

9. The power control method for a hybrid excavator according to claim 7, characterized in that, The operations performed by the working mode determination module include: If the SOC of the power battery is higher than the second charging threshold If the load demand is high at this time, then the motor is prohibited from generating electricity. Greater than the peak reduction threshold If the peak load is less than the peak reduction threshold, the motor will enter drive mode. The motor then enters zero torque mode; If the SOC of the power battery is lower than the second discharge threshold If the motor is not driven, it will enter generator mode. If the SOC of the power battery is between the second charging threshold Second discharge threshold Between, when load demand Greater than the peak reduction threshold When the load demand is high, the motor enters drive mode. Less than the valley filling threshold Then the motor enters generation mode when the load demand is at the peak shaving threshold. Valley filling threshold The motor enters zero torque mode during this period.

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