Control system for a power transmission system

Abstract

The invention relates to a control system (10) for regulating the transmission of electrical energy from a power generator (1) and an energy storage device to a DC bus (3) connected to a load. The control system (10) comprises: - a first control loop, configured to regulate a current (isc, ifc), via at least one first regulator (ST1, ST2) having a first response time; - a second control loop, configured to regulate a DC bus voltage (Vbus), via a second regulator (P1) having a second response time; - a third control loop, configured to regulate a voltage of the energy storage device (Vsc), via a third regulator (P2) having a third response time, the first response time being shorter than the second response time, and the second response time being shorter than the third response time. Figure 2

Description

Title of the invention: Control system for a power transmission system Technical field of the invention

[0001] The present invention relates to a control system for regulating the transmission of electrical energy from an energy generator and an energy storage device to a DC bus connected to a load. State of the art

[0002] The rise of electric vehicles has led to significant advances in managing the power supplied to these vehicles, particularly for systems that combine various energy sources such as fuel cells and storage devices. These systems must provide a stable voltage adapted to the vehicle while delivering the power required for the vehicle's proper operation.

[0003] The fuel cell, although efficient in providing continuous energy, must be complemented by energy storage elements, such as batteries or supercapacitors, in order to meet instantaneous power requirements and compensate for fluctuations in power demand.

[0004] In general, each energy source is coupled to an electrical converter, allowing precise control of the power flow to the vehicle. However, this type of energy management system presents challenges, notably the losses associated with the converters.

[0005] It is therefore important to implement a control strategy that ensures not only that the required power is supplied to the vehicle, but also that the electrical signal supplied is stable. The control strategy must manage the dynamics of the various components, such as the state of charge of the storage devices, while maintaining a stable voltage to guarantee vehicle performance.

[0006] Another challenge for energy management systems combining multiple energy sources lies in the complexity of these systems, which requires sophisticated control systems and significant computing power. Finally, the robustness of the entire system must be continuously verified in real time to ensure its stability, particularly in the face of rapid variations in power demand and voltage fluctuations.

[0007] Object of the invention

[0008] The present invention aims to provide a solution that addresses all or part of the aforementioned problems.

[0009] This goal can be achieved through the implementation of a control system to regulate the transmission of electrical energy from an energy generator and an energy storage device to a DC bus connected to a load, the control system comprising: - a first control loop, called the fast loop, configured to regulate a current supplied by the energy generator and the storage device, via at least one first regulator having an initial response time, - a second control loop, called the intermediate loop, configured to regulate a DC bus voltage, via a second regulator having a second response time, - a third control loop, called the slow loop, configured to regulate a voltage of the energy storage device, via a third regulator having a third response time, the first response time being less than the second response time, and the second response time being less than the third response time.

[0010] Advantageously, the control system provides the required power to the load and supplies the DC bus with the required voltage precisely while reducing disturbances and ensuring increased stability.

[0011] The control system may also have one or more of the following characteristics, taken alone or in combination.

[0012] According to one feature, at least one first regulator is a higher-order sliding mode control regulator, and the second and third regulators are each a proportional regulator.

[0013] Advantageously, the use of at least one higher-order sliding mode control regulator or super-twisting regulator makes it possible to reduce computational complexity in the control system, in particular by reducing the number of differential control equations to be solved in the control system.

[0014] Advantageously, the use of at least one control regulator makes it possible to compensate for an effect of the non-minimum phase behavior of the electrical converters.

[0015] In other words, this means that the control system can correct or adjust undesirable effects caused by the way in which the electrical converters react to changes.

[0016] According to one feature, the fast loop uses two higher-order sliding mode control regulators, and the intermediate loop and the slow loop each use a proportional regulator.

[0017] By "the fast loop uses two higher-order sliding mode control regulators, and the intermediate loop and the slow loop each use one regulator "proportional" means that the fast loop includes two higher-order sliding mode control regulators, and the intermediate and slow loops each include one proportional regulator.

[0018] According to one feature, the DC bus voltage is used to calculate an input of the intermediate loop and the voltage of the storage device is used to calculate an input of the slow loop.

[0019] According to one characteristic, an output of the intermediate loop and an output of the slow loop serve as a setpoint for the fast loop.

[0020] Advantageously, this allows for cross-control, ensuring robustness of the control system and providing a stable voltage to the DC bus.

[0021] According to one feature, an output of the fast loop is a control signal intended to control an electrical converter disposed between the load on one side, and the energy generator and the energy storage device on the other.

[0022] Advantageously, modifying the duty cycle of the control signal allows the power supplied to the load to be controlled.

[0023] According to one feature, the first response time is at least ten times shorter than the second response time, and the second response time is at least eight times shorter than the third response time.

[0024] Advantageously, it is thus possible to ensure that the first loop evolves at a sufficiently rapid dynamic compared to the second loop and that the second loop evolves at a sufficiently rapid dynamic compared to the third loop, which makes it possible to ensure the stability of the control system.

[0025] According to one characteristic, the energy generator is chosen between a fuel cell and a renewable energy source, for example a solar panel, and the energy storage device is chosen between a supercapacitor and a battery.

[0026] Brief description of the drawings

[0027] Other aspects, objectives, advantages and features of the invention will become clearer upon reading the following detailed description of preferred embodiments thereof, given by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0028] [Fig-1] is a schematic representation of a power transmission system including a power generator and an energy storage device.

[0029] [Fig.2] is a block diagram which represents a control system of the transmission system of the [Fig.1]. Detailed description

[0030] In the figures and in the rest of the description, the same reference numerals represent identical or similar elements. Furthermore, the various elements are not shown to scale in order to prioritize the clarity of the figures.

[0031] Fig. 1 presents an example of an energy transmission system comprising an energy generator and an energy storage device.

[0032] The transmission system comprises an energy storage device 2 connected to a first DC power converter 1 and an energy generator 1 connected to a second DC power converter 2. The first DC power converter 1 and the second DC power converter 2 are connected to a DC bus 3 which is connected to a load 4.

[0033] The energy generator 1 can for example be a fuel cell or a renewable energy source, for example a solar panel.

[0034] The energy storage device 2 can be a supercapacitor or a battery.

[0035] The load 4 can be an electric machine of an electric vehicle connected to a DC bus 3.

[0036] The first DC1 electrical converter can be a buck-boost converter for example and the second DC2 converter can be a boost type converter.

[0037] The first DC1 electrical converter includes a switch or transistor controlled by a control signal having a first duty cycle 1-dl and the second DC2 converter includes a switch or transistor controlled by a control signal having a second duty cycle l-d2.

[0038] By controlling the first duty cycle 1-dl and the second duty cycle l-d2, it is possible to act on the electrical power delivered to the load 4. It is important to deliver the power required by the load 4 while maintaining a stable DC bus voltage 3.

[0039] Fig. 2 presents a control system 10 for regulating the transmission of electrical energy in the energy transmission system described above.

[0040] The control system 10 comprises: - a first control loop, called the fast loop, configured to regulate an isc, ifc current supplied by the energy generator 1 and the storage device 2, via at least one first regulator STI, ST2 having a first response time, - a second control loop, called the intermediate loop, configured to regulate a DC bus voltage (Vbus), via a second PI regulator having a second response time, - a third control loop, called the slow loop, configured to regulate a voltage of the energy storage device Vsc, via a third regulator P2 having a third response time.

[0041] The first response time is shorter than the second response time, and the second response time is shorter than the third response time. For example, the first response time may be at least ten times shorter than the second response time, and the second response time may be at least eight times shorter than the third response time.

[0042] Advantageously, it is thus possible to ensure that the first loop evolves at a sufficiently rapid dynamic compared to the second loop and that the second loop evolves at a sufficiently rapid dynamic compared to the third loop, which makes it possible to ensure the stability of the control system 10.

[0043] For example, the first response time may be equal to 0.022 seconds, the second response time may be equal to 0.29 seconds and the third response time may be equal to 2.5 seconds.

[0044] The third response time can be calculated so as to limit a current pulse to less than 4 Amperes / second.

[0045] Advantageously, a current pulse of less than 4 Amperes / second makes it possible to extend the life of the components.

[0046] Current and voltage regulation in the control system 10 can be done in real time.

[0047] In [Fig.2], we can see, for each block, an input signal or an input and an output signal or an output.

[0048] In the example of [Fig.2], the fast loop uses two higher-order sliding mode control STI, ST2 controllers. By "higher-order sliding mode control controllers," we mean a super-twisting controller in Anglo-Saxon terminology.

[0049] The STI regulator has as input a difference ei-sc between a measured current of the storage device isc and a current setpoint of the storage device i*sc, and as output a signal having a duty cycle of 1 -dl and intended to control the DC1 converter.

[0050] The ST2 regulator has as input a difference ei-fc between a measured current of the energy generator ifc and a setpoint of energy generator current i*fc, and as output a signal having duty cycle l-d2 and intended to control the DC2 converter.

[0051] The intermediate loop uses a first proportional PL regulator. The PI regulator has as input a difference ev-bus between a measured DC bus voltage Vbus and a DC bus voltage setpoint V*bus, and as output the storage device current setpoint i*sc. The PI regulator therefore transforms the difference ev-bus into the current setpoint i*sc.

[0052] The slow loop uses a second proportional regulator P2. Regulator P2 takes as input a difference ev-sc between a measured voltage of the storage device Vsc and a voltage setpoint of the storage device V*sc, and as output the current setpoint i*fc of the energy generator. Regulator P2 therefore transforms the difference ev-sc into the current setpoint i*fc.

[0053] The ifc energy generator current and the isc energy storage device current are supplied to the DC bus 3.

[0054] The fast loop has a shorter response time than the intermediate loop. In other words, the intermediate loop does not perceive the regulation performed by the fast loop because the fast loop operates at a significantly faster rate, for example ten times faster, than the intermediate loop.

[0055] Similarly, the intermediate loop has a shorter response time than the slow loop. In other words, the slow loop does not perceive the regulation performed by the intermediate loop because the intermediate loop operates at a significantly faster rate, for example ten times faster, than the slow loop.

[0056] The control system blocks 10 operate independently and it is therefore advantageous to modify a control block without modifying the entire control system 10.

[0057] The control system 10 can be stored in an on-board computer intended to control the transfer of electrical energy from the energy generator 1 and the energy storage device 2 to the vehicle.

[0058] Advantageously, the control system 10 allows a singular perturbation strategy to be applied to said control system 10 so as to simplify the analysis of the control system 10 by decomposing the control system 10 into different control loops evolving at different time scales.

[0059] Advantageously, the singular perturbation strategy treats the fast loop as a stable control loop, and simplifies the slow loop by replacing a complex model of the fast loop with an approximation to a first-order system.

[0060] Advantageously, the control system 10 ensures robust and precise control to provide a constant Vbus voltage to the DC bus and prevent oscillations in said Vbus voltage. This makes it possible to power the electric vehicle stably, thereby extending the service life of the various components of the power transmission system.

Claims

Demands

1. Control system (10) for regulating the transmission of electrical energy from an energy generator (1) and an energy storage device (2) to a DC bus (3) connected to a load (4), the control system (10) comprising: - a first control loop, called the fast loop, configured to regulate a current (isc, ifc) supplied by the energy generator (1) and the storage device (2), via at least one first regulator (STI, ST2) having a first response time, - a second control loop, called the intermediate loop, configured to regulate a voltage of the DC bus (Vbus), via a second regulator (PI) having a second response time, - a third control loop, called the slow loop, configured to regulate a voltage of the energy storage device (Vsc), via a third regulator (P2) having a third response time, the first response time being less than the second response time,and the second response time being shorter than the third response time.

2. Control system (10) according to claim 1, wherein at least one first controller (STI, ST2) is a higher-order sliding mode control controller, and the second controller (PI) and the third controller (P2) are each a proportional controller.

3. Control system (10) according to any one of claims 1 or 2, wherein the fast loop uses two higher-order sliding mode control regulators (STI, ST2), and the intermediate loop and the slow loop each use a proportional regulator (PI, P2).

4. Control system according to any one of the preceding claims wherein the DC bus voltage (Vbus) is used to calculate an input of the intermediate loop (ev-bus) and the storage device voltage (Vsc) is used to calculate an input (ev-sc) of the slow loop.

5. Control system (10) according to any one of the preceding claims wherein an output of the intermediate loop (i*sc) and an output of the slow loop (i*fc) serve as setpoints for the fast loop.

6. Control system (10) according to any one of the preceding claims wherein an output of the fast loop (1-dl, l-d2) is a control signal intended to control an electrical converter disposed between the load (4) on the one hand, and the power generator (1) and the power storage device (2) on the other hand.

7. Control system (10) according to any one of the preceding claims wherein the first response time is at least ten times less than the second response time, and the second response time is at least eight times less than the third response time.

8. Control system (10) according to any one of the preceding claims wherein the power generator (1) is selected from a fuel cell and a renewable energy source, for example a solar panel, and the energy storage device (2) is selected from a supercapacitor and a battery.

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