Photovoltaic Battery - Battery - Super Capacitor Composite Power Supply Design Principle

Photocoupler

Overview:
1 Introduction Rechargeable battery is one of the most mature and commonly used simple power supply devices. Commonly used battery types are lead-acid batteries, nickel-hydrogen batteries, lithium-ion batteries, etc., but they generally have large volumetric weight, low power density, and charging time. Shortcomings such as long length and short service life [1]-[3]. In recent years, supercapacitors have received extensive attention and research as a new type of energy storage device with good power characteristics. Compared with commonly used batteries, supercapacitors have the advantages of high power density, fast charge and discharge speed, high efficiency, long cycle life, etc., but their energy density is low, and generally cannot be used as a power supply device alone [4]. Related research combines the two to form a composite energy storage system. The performance of this composite power supply relies on reasonable and reliable control devices and energy management methods. However, these energy storage devices do not have an energy harvesting function and cannot supplement the power system. In some applications, such as mobile robots, smart sensor nodes, etc., the power supply is required to have maximum continuous working capability. Solar energy is an energy that can be generally used in the environment. Solar photovoltaic conversion and its control technology are relatively mature. The method based on solar energy acquisition has practical significance for many applications.
In this paper, a solar photovoltaic cell, a battery and a supercapacitor are combined to form a composite power supply [5]. The open dynamic architecture, system composition and design method of the complex power system are studied and applied to the mobile robot power supply. Good results.

2 The structure of the composite power system The composite power system consisting of photovoltaic cells, batteries and supercapacitors may have various structural forms. The simplest structure is to directly connect the three in parallel, but the solar energy cannot be fully utilized, the battery and the super capacitor The characteristics cannot be fully utilized. Figure 1 shows the composition principle of the composite power system used in this paper. In the presence of light, solar energy is an online supplemental source of robotic energy. As a composite energy storage device, batteries and supercapacitors can store excess energy for use when there is insufficient light. The solar panel is a non-linear DC power source that is affected by the light intensity and ambient temperature, and its output power also varies with the external load. At the same light intensity and ambient temperature, the maximum power output is only Appears when certain load conditions are met. To maximize solar energy, solar panels are connected to the system's DC bus through a Maximum Power Tracking (MPPT) controller. By connecting the battery and the supercapacitor to the DC bus through a DC/DC converter, the active control of the output power of the battery and the supercapacitor can be realized, and energy management can be realized. The battery is the main energy storage device. In order to reduce the power loss when the electric energy passes through the DC/DC converter, the battery can be directly connected to the DC bus without using the DC/DC converter between the battery and the DC bus.

Figure 1 shows the structure of a complete composite power system, which can be selected and tailored according to actual needs in different applications. The load in the figure includes not only the load of the conventional meaning that only consumes power, but also the load that can feed back power, such as a motor that operates in a regenerative braking state. In addition, the power of the load is usually dynamically changed, and the output power of the solar panel is also changed. The battery and the super capacitor may operate in a discharged state or a charged state. Therefore, the converter in the figure generally uses a bidirectional DC/DC converter.
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