CN101734249A - Steady state operational control method of fuel cell engine - Google Patents

Abstract

A fuel cell engine steady-state operation control method belongs to the technical field of new energy fuel cell hybrid power. According to the information provided by the navigation system, the method establishes a prediction model based on stochastic process description to estimate the demand power of the fuel cell engine; by predicting the driving power of the next road section, combined with the state detection of the power battery, the dynamic The power demand is decomposed into the steady-state average power provided by the fuel cell, and the instantaneous auxiliary power provided by the traction battery; the passive output energy mode of the fuel cell is adjusted to the active predictive output through the DC-DC converter; thus realizing the steady-state operation of the fuel cell engine. The rate of change is achieved by setting limits or change curves. The invention reduces the dynamic load borne by the fuel cell engine and effectively improves the durability of the fuel cell engine. The coordinated control of various components inside the fuel cell engine and the output energy of the engine is realized, and the system cost is greatly reduced.

Description

A fuel cell engine steady-state operation control method

technical field

A control method for a fuel cell hybrid power system based on predictive control is applicable to an electric hybrid drive power system composed of a fuel cell engine and an energy storage device operating under fixed public transport conditions, and belongs to the technical field of new energy fuel cell hybrid power.

Background technique

The two major problems of energy crisis and environmental pollution are becoming more and more prominent, seriously affecting the sustainable development of human society, so they are getting more and more attention from governments and people of all countries. Petroleum resources account for more than 35% of the world's energy consumption, a considerable portion of which is consumed in the transportation industry. The traditional energy structure and its utilization methods are increasingly difficult to meet the needs of human survival and development. Facing the dual challenges of energy crisis and environmental pollution, many countries are trying to find new forms of transportation energy utilization. Electric energy is considered to be the most promising source of vehicle power energy in the 21st century.

The key to the electric drive system is the battery. At present, there are conventional storage forms such as lead-acid, nickel-metal hydride, and lithium-ion. The fuel cell (Fuel cell) that has appeared in recent years uses an electrochemical method to realize the reaction of hydrogen and oxygen in the air to generate electricity. , so it has the advantages of high efficiency, energy storage (through hydrogen), high energy density, and no pollution. It solves the problems of low energy density, dependence on charging devices, and battery pollution in traditional vehicle power batteries. Therefore, fuel cells It is considered to be an ideal clean and efficient power battery in the future.

Due to the high cost of fuel cell systems, compared with small passenger vehicles, urban buses are the most likely platform for the commercialization of fuel cell power systems. Also because of their high price, improving the durability of vehicle fuel cells is the key to reducing the cost of use. And ultimately the key to commercialization. How to ensure the stable operation of the fuel cell and good dynamic characteristics through the effective use and control of the fuel cell to prolong the life of the fuel cell is one of the core technologies in the control of the fuel cell engine for vehicles.

Contents of the invention

The purpose of the present invention is to solve the existing problems in the control of fuel cell hybrid city buses, and propose a new control system and control strategy based on predictive control to meet the needs of fuel cell hybrid control and effectively reduce the fuel cell engine. complex transient loads.

The operating conditions of urban buses have the characteristics of fixed lines, frequent start and stop, long-term idling, and predictable operating conditions. In view of this feature, the fuel cell engine can be controlled to work under relatively stable operating conditions with the assistance of power batteries , so as to avoid the adverse effects on the fuel cell caused by factors such as excessively severe load changes, frequent start-stops, and long-time idling, so as to improve the durability of the fuel cell engine.

The present invention is characterized in that: Aiming at the structure of the city bus hybrid power system composed of a fuel cell system, a DC-DC converter, a power storage battery and a drive motor, a control method for a fuel cell hybrid power system based on predictive control is proposed, which This method operates the fuel cell engine under quasi-steady-state conditions to improve its durability, also known as Soft-run technology, including the following steps:

(1) According to the information provided by the navigation system, such as the GPS positioning system, a prediction model based on stochastic process description is established to estimate the required power of the fuel cell engine. The model is based on the statistical basis of a large number of prior data, through the identification of the characteristics of the vehicle's operating conditions, to estimate the power change trend on a fixed route.

(2) By predicting the driving power of the next road section, combined with the state detection of the power battery, the dynamic power demand of the vehicle is decomposed into the steady-state average power provided by the fuel cell, and the instantaneous auxiliary power provided by the power battery.

(3) Adjust the passive output energy mode of the fuel cell to the active predictive output through the DC-DC converter. Here, an intelligent active auxiliary power unit IAAPU is composed of a fuel cell engine and a DC-DC converter, which actively controls the state of the fuel cell engine so that its power output is relatively stable or changes slowly (the change rate is realized by setting a limit value or a change curve. ), so as to realize the quasi-steady-state operation of the fuel cell engine.

The power system configuration is composed of a fuel cell system (also known as a fuel cell engine), a DC-DC converter, a power storage battery and a drive motor (Fig. 1). The fuel cell engine is used as the power source, and the output power is controlled by DC-DC according to the control instructions built into the vehicle controller (Figure 2), and is reasonably distributed to the power battery (charging) and the drive motor. When the power demand of the vehicle is small or the state of charge (SoC) of the power battery is low, the fuel cell charges the power battery; when the power demand of the vehicle is high, the fuel cell and the power battery output simultaneously to provide the required power. The vehicle management system reasonably adjusts the output power to ensure that the SoC of the power battery is basically stable.

The vehicle controller is the main control unit of the vehicle. Due to the large amount of data exchange between the components of the power system, high real-time performance, and high reliability requirements, the entire system adopts distributed control, and CAN bus is used for communication between the controllers. The vehicle controller realizes the energy management of the entire system and the coordinated control of each component through the CAN bus.

The fuel cell controller is the executive component of the fuel cell engine control system, responsible for comprehensively judging the current vehicle driving conditions according to the commands of the vehicle controller, and comprehensively and uniformly controlling each component of the fuel cell, so that the fuel cell can achieve the best performance. The working performance of the fuel cell and the fault diagnosis of the fuel cell are carried out to ensure the safety of the fuel cell engine.

The DC-DC converter is a power component for regulating the output power of the fuel cell engine in the fuel cell hybrid power system, including but not limited to unidirectional, bidirectional, constant current, constant voltage and other types.

The power storage battery is a high-power storage device in a hybrid power system, including but not limited to different types of power storage batteries such as nickel-metal hydride batteries, lead-acid batteries, and lithium iron phosphate batteries. When the output power of the fuel cell engine is greater than the actual power required for driving, the fuel cell engine charges the battery; when the power demand of the vehicle suddenly increases, the battery and the fuel cell engine jointly output energy to drive the motor to rotate.

The prediction model or GPS positioning system is an auxiliary tool for predicting the power demand of the whole vehicle, including a prediction model based on past driving information, or a prediction model based on past and current driving information, and obtaining the current vehicle position coordinates and Driving information, comparing electronic maps, and various auxiliary tools to estimate vehicle driving power in advance.

The present invention realizes the active control of the output energy of the fuel cell by integrating the control of the fuel cell and DC-DC in the fuel cell engine, and predicts the driving power demand in advance through the predictive model or GPS positioning system, so as to satisfy the vehicle driving power At the same time as the demand, the quasi-steady-state operation of the fuel cell engine can be achieved. Compared with traditional control methods, its main advantages are:

(1) The dynamic load borne by the fuel cell engine is reduced, and the durability of the fuel cell engine can be effectively improved.

(2) The coordinated control of the internal components of the fuel cell engine and the output energy of the engine is realized, and the adverse effects caused by the lack of gas, water flooding, overload, etc.

(3) The fuel cell engine is mainly responsible for providing steady-state power, and its rated power can be reduced (for example, from 80kw to 60kw), so that the original high-power fuel cell engine can be replaced by a small fuel cell engine to greatly reduce the system cost.

Description of drawings

Figure 1 is a schematic diagram of the hybrid power system of a fuel cell city bus.

Figure 2 is the control process of the joint output of fuel cell and DC-DC.

Figure 3 is the basic control method of the fuel cell engine "Soft-run".

Detailed ways

The present invention is illustrated below in conjunction with accompanying drawing.

Figure 1 shows the configuration of the hybrid power system of a fuel cell bus. When the fuel cell engine and DC-DC are combined together and viewed as a unified component, the fuel cell determines its own output power through cooperation with the DC-DC, thus realizing the management of the fuel cell's own output energy. From a unified point of view, the fuel cell and DC-DC form an independent energy supply unit, which can actively control its energy output according to various conditions such as vehicle driving conditions and power battery conditions, so it is called here It is an Intelligent Active Auxiliary Power Unit (IAAPU).

As shown in Fig. 2, it is a specific implementation manner of a fuel cell engine actively controlling its own energy output. The control of the fuel cell is indirectly coordinated with the DC-DC control through the vehicle controller, and the DC-DC control command issued by the fuel cell main control ECU is actually implemented by the vehicle controller, so it will not Destroy the TTCAN network of the vehicle and the control interface of the vehicle controller.

The schematic diagram of the quasi-steady-state control method of the fuel cell engine is shown in Fig. 3 . First, through the stochastic process estimation model based on statistical data, the vehicle's driving power is predicted and estimated by using the historical data of vehicle speed, historical data of driver acceleration, and demanded power data. During the forecasting process, the newly measured data continuously corrects the parameters in the model to ensure that the model can be adjusted according to the actual road conditions to better conform to the actual working conditions. The state estimation of the fuel cell is composed of the monolithic voltage of the fuel cell, the estimation of the humidity state, the internal resistance and other corresponding characteristics. According to different states of the fuel cell engine, the target power of the engine is corrected. After the actual vehicle test, in order to ensure the stability of the fuel cell engine within a certain period of time, it should have a suitable discrete gear value, and the gear value should be adaptively corrected according to the performance of the fuel cell and the actual road conditions. The optimal objective function of gear shifting is to minimize the probability of the fuel cell engine shifting gears within a period of time while meeting the power change requirements of the vehicle. For a fuel cell bus running on a fixed bus route, the shifting strategy and its gear value will be adaptively corrected by using the statistical data of the vehicle. The data basis is calculated and estimated offline and online by the data support system of the main control ECU of the fuel cell. For the estimation of the current shift power and the identification of road conditions, it is not only based on the current measurement value, but also through a period of data sequence, comprehensively considering the statistical results and location, for identification and prediction. The vehicle positioning information provided by the GPS auxiliary system enables the control process to comprehensively consider important factors such as stops on the driving route, traffic lights, and overpasses that affect the transient changes in vehicle power.

Claims (2)

1. A fuel cell engine steady-state operation control method, characterized in that the method steps are as follows: (1) According to the information provided by the navigation system, a prediction model based on stochastic process description is established to estimate the required power of the fuel cell engine; The prediction model identifies the characteristics of the vehicle's operating conditions through the statistics of prior data, and estimates the power variation trend on a fixed route; (2) By predicting the driving power of the next road section, combined with the state detection of the power battery, the dynamic power demand of the whole vehicle is decomposed into the steady-state average power provided by the fuel cell, and the instantaneous auxiliary power provided by the power battery; (3) Adjust the passive output energy mode of the fuel cell to an active predictive output through the DC-DC converter; here, an intelligent active auxiliary power unit IAAPU is composed of the fuel cell engine and the DC-DC converter to actively control the state of the fuel cell engine , so that its power output is relatively stable or changes slowly, so as to realize the steady-state operation of the fuel cell engine. 2. A method for controlling steady-state operation of a fuel cell engine according to claim 1, wherein the active control of the state of the fuel cell engine is a rate of change, and the rate of change is realized by setting a limit value or a change curve .

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