Traditional power supply is mostly analog control, although the technology has been quite mature, but there are many shortcomings: control circuit components are more complex, occupying a larger volume; flexibility is not enough, hardware circuit design is good, the control strategy can not be changed; inconvenient debugging, because of the differences in the characteristics of the devices used, resulting in poor consistency of power supply, and analog device work point drift, will lead to. Drift of system parameters. It is difficult to adopt some advanced control methods in analog mode, so the digital control of power supply is the trend of development. The designed power of the charger is 4.32 kW, which is mainly used in conjunction with a UPS. The maximum number of series batteries is 32, and the minimum number is 16. DSP is used for control and two-stage charging mode is adopted.
When cooperating with UPS, thermostatic element UPS will issue charging instructions to the controller through CAN communication, including setting parameters of charging voltage and charging current. Charger topology is composed of Boost circuit and Buck circuit cascade, as shown in Figure 1. When charging batteries, Boost circuit is started according to certain conditions, while Buck circuit is always in work. Boost circuit adopts double closed-loop PI control. When constant current charging, the output of voltage loop reaches the limit. Buck circuit adopts single current loop closed-loop control. When it is converted to constant voltage charging, double closed-loop control is adopted. Constant voltage and constant current can be automatically converted. Based on the simple embedded operating system of DSSP TMS320LF2802 produced by T I Company, the charger control program is programmed under the software development environment of CCS 3.3. The cut-off frequency of the current loop is less than 10% of the switching frequency, that is, about 12 kHz (rad/sec). We choose 8.21 kHz (rad/sec) with a phase margin of 43. Figure 3 shows the open-loop baud diagram after the current loop plus PI controller. The open-loop BOCLE diagram and root locus of the voltage loop with PI regulation are shown in Fig. 4.
As can be seen from Fig. 4, the closed-loop pole is in the left half plane, so the system is stable; the margin reaches 65.5, and the low-frequency gain is high, which basically meets the design requirements. The controller is designed in the sequence of continuous domain and discrete domain. The design tool is BODE diagram. To illustrate the system model, the Buck circuit topology is shown in Fig. 5. In the continuous domain design, the small signal model of the system must be established first, which is obtained by Kirchhoff’s law of voltage and current. According to the mathematical model deduction method of Boost circuit mentioned above, it can be obtained. Input voltage 650V (specific amplitude 50, frequency 300Hz ripple), output voltage 400V, constant current 10A, inductance 4mH, capacitance 110uF, load 43 (for example, setting PI controller parameters). There are many ways to tune the parameters of PI controller. A simple and easy-to-use system open-loop BODE diagram is adopted here. The parameters of voltage loop controller are Kp=0.05 and Ki_0.733. The parameters of current loop controller are Kp = 0.05, K, = 47. In order to achieve constant voltage and constant current, two kinds of loads, heavy load and light load, are adopted respectively. They are constant current mode under heavy load and constant voltage mode under light load. The constant current control effects of current 5A, 7A and 10A, output voltage 216-432V and BUS voltage 430-650V were tested respectively when three-phase rectifier bridge was used as input. Both light load and heavy load can be realized, and automatic conversion of constant current and constant voltage can be realized.
After changing the battery load to do experiments, the effect is basically the same as that of resistance load. The voltage ripple is about 5V and the current ripple is about 2A. A charger controller based on DSP is designed, which can automatically convert between constant voltage mode and constant current mode. Firstly, the mathematic model of the charger is deduced, and then the controller of the charger is designed by using the method of Bird diagram. Finally, the controller is verified by experiments. The experimental results show that the charger controller can achieve the desired function and meet the actual needs. Microsemi Corporation and Skippio Technologies have demonstrated the reverse power supply operation based on G. fast broadband access network infrastructure for the first time at the international CES exhibition. This is the first time that reverse power feeding is publicly demonstrated on real G. fast devices. G. fast is a newly approved ultra-wideband technology standard by the International Telecommunication Union (ITU). It is expected to provide residential users with up to lGbps speed, which will allow ultra-high-speed Internet access and support streaming media with multiple ultra-high definition television (4K) channels. G. fast is one of the key elements of UWB standard, which can be deployed near the user’s home where there is no power distribution point at present. Reverse power feeding enables operators to deploy these distribution points in more convenient locations without the need for dedicated AC power supply, thus achieving more efficient and cost-effective G.fast. deployment. Reverse power feeding is critical for many G. fast fiber to distribution point (FTTdp) deployments. Roger Holliday, Senior Vice President and General Manager of MGM Communications Products, said: “G. fast is an important new market for reverse power feeding technology, and Sckipio is the leading manufacturer in G. fast.
The joint demonstration of the two companies confirmed the feasibility and practicability of G. fast technology in FTTdp deployment. David Baum, chief executive of Sckipio, said: “Reverse power supply is important for many G. fast deployment scenarios. Through strong technical cooperation partners like MGM, we are speeding up G. fast’s listing, which will make service providers, equipment manufacturers and consumers happy. Now, they will gain the advantage of low-cost ultra-bandwidth technology at a faster pace than expected. This demonstration is based on MGM R, PF PSE chip PD81 001, which injects DC power into Sckipio CP1000-EVM G.fast client device, then transfers it to an eight-port power extraction and aggregation module based on MGM PD70201 RPF PD chip, and safely converts the average power distribution into 12V power supply for Sckipio DF3000-EVM G.fast distribution point device. TCL Multimedia and QD Vision announced that the new 55-inch 4K Ultra-high Definition Quantum Dot Television, which just landed in China in December last year, will soon be on the market in Europe, Asia and other target markets. The most leading quantum dot TV in the market now uses color IQ optical technology from QD Vision, showing excellent color performance. Compared with other LCD and OLED TV, this TV has more excellent performance and extraordinary value. The TV was shown at the International Consumer Electronics Show (CEs) in 2015.