Ge Leijiao

Study on double modulation wave carrier-based PWM for three-level neutral-point-clamped inverters

Three-level neutral-point-clamped (NPC) inverters have been widely applied in power conversion device occasions of medium high voltage and power, and, most recently, increasing in occasions of the low-voltage low-power applications. The three-level inverters have the problems of low frequency ripple that appears in the neutral-point (NP) of the DC-link under some operating conditions because of its unique structure and the limitations of the existing modulation methods. The Low frequency ripple of the three-level NPC inverter PWM rectifier technology is an important problem. Conventional three-level carrier-based pulse width modulation (PWM), which has only one modulation wave per phase, cannot eliminate low-frequency neutral point(NP) potential ripple of three-level neutral point clamped (NPC)inverter completely under some modulation index and power factor. This paper analyzes the condition, which eliminated low-frequency voltage oscillation of three-level neutral-point-clamped (NPC) inverter completely, established the model of the low frequency ripple of the three-level NPC inverter. A double modulation wave carrier-based PWM (DMWPWM) was proposed in this paper. Based on voltage equivalent principle and NP potential balance principle, one modulation wave is decomposed into two modulation waves to implement modulation. The proposed DMWPWM can eliminate the low frequency ripple of the three-level NPC inverter completely. Fundamental principle of the proposed PWM was introduced in this paper. The effectiveness of the proposed method was verified by simulation.

Available Transfer Capacity calculation based on carbon emission reduction strategy

Increasingly serious issue of climate change proposed an urgent requirement of low-carbon development on the global challenges. The power industry mainly contributes to CO2 emissions. Available Transfer Capacity (ATC) reflects power generation, transmission, distribution, supply and demand situation in electricity transaction. In order to improve the energy efficiency of the power industry and promote carbon emission reduction, this article proposes a calculation method of ATC with minimum unit carbon emissions and fuel costs, considering the security, economic and environmental factors. It aims to reasonably schedule inter-regional resources and makes full use of the transfer capacity of the existing equipment. The results have shown that carbon emissions and ATC has a certain contradiction with each other and could not be optimal simultaneously. Sacrifice of a certain amount of ATC was needed to control the carbon emissions. The method proposed in the current imbalance state between economic development and environmental protection accords with the global carbon emission reduction targets and energy strategies for sustainable development.

Framework design of cloud computing technology application in power system transient simulation

In order to solve the power system transient simulation problem, which is caused by the contradiction between efficiency and accuracy due to insufficient calculation ability, this paper proposes a Cloud Computing technology application framework for power system transient simulation. Firstly, it expounds the characteristics and current situation of power system transient simulation, and points out the problems in its further development. Secondly, this paper introduces current research status of the cloud computing technology, and discusses the application of infrastructure as a service (IaaS), platform as a service (PaaS) and system as a service (SaaS) in power system transient simulation. Thirdly, it constructs the overall structure, software architecture and application mode of the power system transient simulation based on cloud computing technology. This paper can provide a reference for the cloud computing application in power system transient simulation.

Design of dual control and dual output constant current source for semi-conductor laser diode

To meet the high power and high stability requirements of BWT 915-10W and 915-30W pumped semiconductor laser (with adjustable current from 0 to 12A, current ripple factor less than 2%) a dual control and dual output circuit is designed to allow the power supply output current adjustable from 0 to 12A. It is called dual control because power can control manually by an external knob to achieve current continuously adjustable, and also through DSP28035 to achieve current digital regulation. Temperature detection with protection circuits is also designed, and so is highly reflective pulsed light detection with protection circuits. The output state of the DSP is controlled by signals from the control card. They communicate each other through A 25-pin parallel port. By designing schematics, producing PCB and repeated tests, it is indicated that this dual power supply is a small ripple, high stability and efficient, small volume and light weight switching power supply.

Automatic test platform for photovoltaic grid-connected inverters

Photovoltaic (PV) solar inverter is equipment that converts the DC output of solar batteries to the AC power which meets the requirements of the gird, its performance and quality are directly related to the photovoltaic effect on the public grid. Current national standard specifies only the requirements for protection and did not develop appropriate testing rules and procedures. This paper researched and developed the PV grid-connected inverter detects platform, analyzed the PV grid-connected inverter protective function and testing methods and procedures. We realized the PC integration of the system and the automatic test of the inverter by using Kingview software, to ensure the reliability and accuracy of test results, in addition, the host computer system has proved ease of use, stability and scalability.

Implementation of battery charging and discharging system in photovoltaic system

Nowadays, the photovoltaic system is widely used, but the charging and discharging controllers only provide protection to avoid overcharge and overdischarge. The poor charging ability leads the battery to have poor lifetime. The battery charging and discharging system in this paper can realize the three-stage charging, achieve the rapid charging of the battery, and make full use of the battery capacity. At the same time, the system can choose two modes of discharging to avoid overdischarge, also it can make the bus voltage stable to meet other applications.