USING INPUT INVARIANCE AS A METHOD TO FACILITATE SYSTEM DESIGN IN DPS APPLICATIONS

Dynamic analysis of the interconnected regulated systems is commonly based on the minor-loop gain which composes of the ratio between the output and input impedances defined at an arbitrary interface within the system. The stability of the system is guaranteed, when the minor-loop gain satisfies Nyquist stability criterion. Usually, the stability conditions are expressed as a certain forbidden region in a complex plane out of which the minor-loop gain should stay for stability to exist. The robustness of the stability is guaranteed requiring certain phase and gain margins to exist. It is also natural to assume that the existence of robust stability means also the existence of acceptable transient behavior. The paper investigates the validity of those expectations. According to the investigations, the system-level minor-loop gain measured at an arbitrary interface does not necessarily contain any other information than the existence of stability. The theoretical analyses are based on a set of transfer functions describing the dynamics of a switched-mode converter. Practical evidence is provided based on a small-scale industrial prototype system composing of voltage-mode-controlled buck converters.

The stability and performance of a regulated converter is analysed based on its closed-loop output impedance. System theory is used to obtain a set of transfer functions that define the internal stability of an interconnected system consisting of source and load converters. The internal stability is described in terms of the ratio of the output impedance of the source converter and the input impedance of the load converter known as the minor-loop gain. Thus, the closed-loop output impedance of a source converter can be used to define safe operating areas that avoid instabilities in the load impedance. It is shown that the margins associated with the minor-loop gain (i.e. the gain and phase margins) do not generally match the margins of the output-voltage loop gain. The relationship is especially weak at frequencies close to and beyond the crossover frequency of the loop gain. This means that the margins given to the minor-loop gain should be gradually increased as the voltage-loop-gain crossover frequency is approached so as to avoid performance degradation (i.e. changes in margins and crossover frequency) in the supply converter. Experimental evidence is provided based on a buck converter under voltage- and peak-current-mode control.

A systematic review of supply and demand side optimal load scheduling in a smart grid environment

A low voltage, high current, modular 50 V, 700 A dc power supply has been developed to bias 35 number of 500 W, 505.8 MHz solid state RF amplifiers. This power supply incorporates 7 number of 50 V, 100 A ac-dc power modules, operating in parallel to share the load current. This power supply has two unique attributes namely modular hot swappability and active redundancy. Hot swappable feature incorporated in power modules enables isolation of faulty power modules and facilitates their online replacement without affecting the operation of RF amplifiers and remaining power modules. Active redundancy increases reliability of the power supply significantly. Both these features reduce the down time and increase the availability of the overall system significantly. This paper presents comparison of system reliability of this modular dc power supply with other modular dc power supplies of same output voltage and current rating and having different number of power modules. Suitable mathematical expressions for system reliability of these modular dc power supplies have been evaluated. This power supply also has a digital controller for monitoring the status of 35 number of RF amplifiers and 7 number of power modules as well as controls load current sharing among the power modules. This power supply achieves current THD ≤ 6.2%, input power factor ≥ 0.98, output voltage stability ≤ 0.4% and peak to peak output ripple ≤ 0.2% with overall system reliability and availability approaching near 100%.

This paper studies the conducted electromagnetic interference (EMI) problems in a DC/DC switched-mode power supply (SMPS) with semi-isolated topology. A high frequency circuit simulation model is firstly established to predict the conducted emissions of this power supply. Then the common mode (CM) and the differential mode (DM) conducted emission mechanisms of this power supply are analyzed in detail according to its working principle and structure. The voltage of the rectifier diodes at the transformer's secondary is founded to be the main CM EMI sources. A DM noise coupling phenomenon from the voltage ripple of output port is discovered and its role on EMI emission is explained too. Based on conduced emission paths analysis, three kinds of EMI filters, including traditional input EMI filter, high frequency input and output port EMI filters and a new DM topology filter are proposed to restrain the conducted emissions respectively. Their effectiveness is verified with experiments and the merits and drawbacks of different designs are also introduced.

With the increasing scale and penetration of inverter-type power supplies, the network structure of the distribution network has changed, making it vulnerable to reclosing malfunctions and arc reignition during grid faults. In this paper, we propose an inverter-based distributed generation handling method during grid fault that eliminates the adverse effects of reclosing and automatic input device for backup. By reconstructing the external fault characteristics of the distributed power supply so that it does not output short-circuit current during low voltage periods and automatically restores power to the distributed power supply after a successful reclosing or automatic input device for backup, we use a finite state machine model to implement distributed power supply fault handling switching control. Simulation results verify that the method is simple and easy to implement and can improve the level of active distribution self-healing during grid fault.

This paper focuses on the outstanding issue of whether distributed power supplies can effectively distribute reactive loads, specifically by incorporating the corresponding sag characteristics of load Q/V, and effectively incorporating the voltage amplitude feedback and transmission line voltage drop method for distributed power supplies on the basis of traditional reactive sag control, so as to effectively track the voltage change at the access point, which can effectively improve the output voltage amplitude inequality, and ensure that all distributed power supplies can output the same voltage amplitude when the microgrid system reaches the stable operation state. This ensures that all distributed power supplies can output the same voltage amplitude when the microgrid system reaches a stable operating state, thus ensuring that the distributed power supplies can distribute the reactive load equally and ensuring the stability and reliability of the microgrid system. Finally, the improved reactive power sag control is simulated on the TR-LAB platform and compared with the pre-improved microgrid operation characteristics to verify the feasibility and effectiveness of the improved sag control method proposed in this paper, i.e. whether it can improve and optimise the steady-state performance of the microgrid system.

Active electromagnetic interference (EMI) filter is a feasible and effective suppression technology for switching mode power supply (SMPS) system. The traditional active EMI filter (AEF) suppresses EMI by sensing EMI signal and generating cancelation EMI by the controlled high-frequency operational amplifier. The filtering performance not only depends on the high-open-loop gains of the operational amplifier but also on its low-output impedance of AEF. However, obtaining sufficiently low-output impedance of AEF is very difficult in a controlled filtering frequency band. To cope with it, a filtering topology of AEF based on impedance modulation for SMPS is proposed in this article. The proposed active trap EMI filter (ATEF) can trap the EMI current at the filtering frequency band with a sufficiently low-output impedance by introducing a negative impedance circuit. Finally, the impedance and the filtering performance are evaluated on a 48 W SMPS, and experimental results show that the proposed ATEF can effectively suppress the conducted EMI generated by SMPS.

In order to reduce the impact of scaled distributed power access on the original grid and improve the multiple utilization efficiency of the source grid. In this paper, by analyzing the multi-stage energy interaction scene with distributed power supply, the multi space scale of main network, distribution network, feeder and platform area, and short-term, ultra short term, quasi real time multi time scale interaction mechanism are formulated, a multi-source interactive coordinated optimal control model for distributed power supply including large wind power plants, gas turbines and centralized large capacity energy storage is established. The objective function of the model is the minimum active power fluctuation, the closest network loss and the largest economic benefit. The model sets constraints such as node power flow, wind power, and so on. Taking Chongming Island in Shanghai as an example, the multi intelligence coordinated optimization control application scene of source network is set up to simulate and verify the short-term, super-short-term and quasi-real-time optimization effects of multiple spatial scales, and to provide optimized control basis for the access of large-scale distributed power supply.

With a large number of distributed power sources connected to the distribution network, power supply reliability has always been one of the most concerned indicators for power supply companies. Fault mode and effect analysis (FMEA) can predict the impact of fault isolation and load switching diversity in active intelligent distribution networks. In this paper, a standardized model of reliability system evaluation is constructed by FEMA table, and the reliability index is solved by combining Monte Carlo analysis method. The simulation with IEEE-RBTS BUS6 as an example shows that the method can quantify the effect of distributed power supply on the reliability of active distribution network, which proves that the proposed method is effective and feasible to solve the index.

The bi-channel voltage regulator proposed in this paper has been specifically developed for smart cards. Its purpose is to protect the supplied system against power analysis attacks. It generates the internal power supply voltage from the external power supply voltage provided by card readers, while ensuring the uncorrelation between the external power supply current and the internal power supply current. The power supply current of an electronic system can be decomposed into a DC component, which contains little information, and an AC component, which handles considerably more. In order to reach a good compromise between regulation and security, while respecting the smart card stringent technological constraints, these two components are treated separately by a bi-channel power structure. The presented implementation has been simulated from the process parameters of a STMicroelectronics $$0.18\,\upmu\hbox{m}$$ CMOS technology. It provides a 1.8 V output voltage from a 2 to 5.5 V input voltage range. The structure has been sized to handle a 25 mA DC current while hiding a 20 MHz AC current presenting 75 mA peaks. Its estimated area is approximatively $$0.8\,\hbox{mm}^2$$ .

This paper proposes a hybrid filter structure consisting of a passive power filter and a DC active power filter (DCAPF) applied in high current, high precision and low ripple accelerator power supplies. The configuration of the power system with the DCAPF is firstly introduced. Then four control schemes to obtain the reference signal for the DCAPF control circuit is presented. For each method, the basic operation principle of eliminating output voltage and current ripples is analyzed in detail. Furthermore, the compensation characteristics of each method is discussed and compared. To verify the proposed circuit configuration and the control methods, the testing results of the practical field operation of the DCAPF with a 120kW accelerator power supply is introduced. By adopting the control method of detecting the load ripple voltage, the output current ripple factor and tracking accuracy of the accelerator power supply achieve 8.87/spl times/10/sup -6/ (peak-to-peak) and 1/spl times/10/sup -4/ respectively, which is very satisfactory for this kind of power supplies. The dynamic response of the accelerator power supply is also greatly improved through the application of the DCAPF.

A novel passive integration structure based on flexible multi-layer foils was proposed for EMI filter in switching-mode power supply. Common mode (CM) inductors and capacitors, differential mode (DM) inductors and capacitors were all integrated in a single unit. This passive integration applied flexible multi-layer foils (FML). Prototypes were implemented for an 1 kW switching power supply. The conductive EMI testing result was presented. The temperature rising and efficiency curves of the integrated EMI filter were also presented. In comparison with the discrete EMI filter, the prototype in this paper can reduce the volume by 32%.

Objective: To study the problems and possible solutions in the introduction of an alternating current traction power supply system with catenary supports without rail grounding. Methods: To solve the set tasks, we used the statements and methods of the theory of power supply, experimental planning, mathematical and system analysis, and the theory of electrical measurements. In the experimental studies, the Trans-AURA Emergency Process Recorder and the Tektronix TDS 2014 Digital Oscilloscope were used, and the Aura2000 and MS Excel 2010 software products were used to process the experiment results. Results: The basic requirements for the AC traction power supply system grounding are presented. The flaws of the traditional grounding system of the catenary supports on the rail network are revealed. Two possible directions are described, which allow eliminating issues during the operation of the AC traction power supply system. The first direction requires the introduction of an additional stage into the traction network protection system, which makes it possible to identify short circuits through a high rail-to-earth resistance. The second suggests the need to revise the relay protection system itself, which includes changing the approach to grounding the catenary structures, the methodology for calculating the relay protection settings, a more detailed analysis of electrical safety conditions, etc. An equation has been formulated to determine support-groupto-earth resistance taking into account the group grounding cable and the existing requirements for ensuring the sensitivity of the main protection means, which allows ensuring reliable operation of feeders’ relay protection. The results of experimental tests of electrical safety conditions and electromagnetic influence are presented. The tasks are identified being the essential prerequisite to the widespread introduction of a system with supports without rail network grounding. Practical importance: The developed methodology for selecting the protection settings will make it possible to operate the AC catenary system without the supports’ rail grounding, as well as introduce the proposed additions to the instructions for grounding traction power supply devices at “Russian Railways”

The long-pulse power-supply system equipped for the 4 MW beam-power ion source is comprised of three units at ASIPP (Institute of Plasma Physics, Chinese Academy of Sciences): one for the neutral-beam test stand and two for the EAST neutral-beam injectors (NBI-1 and NBI-2, respectively). Each power supply system consists of two low voltage and high current DC power supplies for plasma generation of the ion source, and two high voltage and high current DC power supplies for the accelerator grid system. The operation range of the NB power supply is about 80 percent of the design value, which is the safe and stable operation range. At the neutral-beam test stand, a hydrogen ion beam with a beam pulse of 150 s, beam power of 1.5 MW and beam energy of 50 keV was achieved during the long-pulse testing experiments. The result shows that the power-supply system meets the requirements of the EAST-NBIs fully and lays a basis for achieving plasma heating.