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The capability of a distributed renewable generator (DRG) in providing load low-voltage ride-through (LVRT) is examined. The harnessed renewable power, load demand, and the occurrences of low-voltage incidents are treated as random variables. The probability of successful load LVRT is assessed through the use of a copula function to quantify the stochastic dependency between the load and the renewable power. The analysis is then applied to the case of a series-connected photovoltaic DRG incorporated with capacitor energy storage, wherein the focus is to establish the analytical relationship between the probability of successful load LVRT and the rated power/energy capacities of the DRG capacitor. Determination of the optimal capacities of the DRG capacitor is achieved through maximization of the expected economic benefits obtained from the renewable energy harness and load LVRT minus the cost of the DRG capacitor.

Active ripple current reduction method is proposed for isolated DC/AC dual active bridge (DAB) converter to reduce the double grid frequency ripple in the DC current. Unlike those active methods that require extra switches to construct separate ripple reduction circuit, in this method, one or two branches of LC ripple steering circuits are used along with existing full bridge switches in a multiplexing manner. For the purpose of the ripple elimination, unsymmetrical phase shift modulation and duty cycle regulation methods are proposed and applied to both legs of the converter on the primary side of DAB converter. Also a current sharing (CS) scheme is presented to balance the current on both LC ripple steering circuits.

A frequency modulation scheme is proposed for a Capacitor-Inductor-Inductor-Capacitor (CLLC) Resonant Dual Active Bridge (RDAB) that relies on dynamic retuning of the resonant capacitors to the switching frequency as it is modulated. The proposed modulation scheme greatly reduces the circulating reactive currents in the High Frequency Link (HFL) by operating at a range of fixed discrete switching frequencies. A Triple Phase Shift (TPS) modulation scheme is used in between the discrete steps of switching frequencies and capacitances. In this paper, a mathematical analysis is presented of the RDAB and the proposed modulation scheme is compared to all of the existing modulation schemes. The CLLC RDAB is implemented in simulation and the simulation results demonstrate the effectiveness of the proposed modulation scheme at decreasing the circulating reactive currents, and therefore, greatly decreasing the conduction losses of the converter at light load, while maintaining its soft switching capability.

Several power converter topologies have been presented for Inductive Power Transfer (IPT) systems to generate high frequency current to cite the primary side inductive coils/tracks. This paper proposed the neutral point clamped (NPC) and flying capacitor (FC) multilevel converters based IPT systems which are suitable for high power IPT applications. The modulation strategies for single phase as well as three phase converters are carried out. The simulation results are presented to demonstrate the feasibility of the proposed system.

This paper presents a novel topology for the generation of high voltage pulses that uses both slow and fast solid-state power switches. This topology includes diode-capacitor units in parallel with commutation circuits connected to a positive buck-boost converter. This enables the generation of a range of high output voltages with a given number of capacitors. The advantages of this topology are the use of slow switches and a reduced number of diodes in comparison with conventional Marx generator. Simulations performed for single and repetitive pulse generation and experimental tests of a prototype hardware verify the proposed topology.

PurposeMulti‐level diode‐clamped inverters have the challenge of capacitor voltage balancing when the number of DC‐link capacitors is three or more. On the other hand, asymmetrical DC‐link voltage sources have been applied to increase the number of voltage levels without increasing the number of switches. The purpose of this paper is to show that an appropriate multi‐output DC‐DC converter can resolve the problem of capacitor voltage balancing and utilize the asymmetrical DC‐link voltages advantages.Design/methodology/approachA family of multi‐output DC‐DC converters is presented in this paper. The application of these converters is to convert the output voltage of a photovoltaic (PV) panel to regulate DC‐link voltages of an asymmetrical four‐level diode‐clamped inverter utilized for domestic applications. To verify the versatility of the presented topology, simulations have been directed for different situations and results are presented. Some related experiments have been developed to examine the capabilities of the proposed converters.FindingsThe three‐output voltage‐sharing converters presented in this paper have been mathematically analysed and proven to be appropriate to improve the quality of the residential application of PV by means of four‐level asymmetrical diode‐clamped inverter supplying highly resistive loads.Originality/valueThis paper shows that an appropriate multi‐output DC‐DC converter can resolve the problem of capacitor voltage balancing and utilize the asymmetrical DC‐link voltages advantages and that there is a possibility of operation at high‐modulation index despite reference voltage magnitude and power factor variations.

There is a trade off between a number of output voltage levels and the reliability and efficiency of a multilevel converter. A new configuration of diode-clamped multilevel inverters with a different combination of DC link capacitors voltage has been proposed in this paper. Two different symmetrical and asymmetrical unequal arrangements for a four-level diode-clamped inverter have been compared, in order to find an optimum arrangement with lower switching losses and optimised output voltage quality. The simulation and hardware results for a four-level inverter show that the asymmetrical configuration can obtain more output voltage levels with the same number of components compared with a conventional four-level inverter and this will lead to the reduction of the harmonic content of the output voltage. A new family of multi-output DC-DC converters with a simple control strategy has been utilised as a front-end converter to supply the DC link capacitor voltages for the optimised configuration.

This paper presents a sensorless direct torque control (DTC) scheme for interior permanent magnet synchronous motors (IPMSMs) drives over a wide speed range including very low speeds. The stator flux observer comprises the voltage model augmented by the current model. The position information required by the current model is derived from the examination of the stator current response due to machine saliency. Unlike the signal injection method, the proposed method utilizes only the applied voltage vectors to the machine stator windings. The simulation results presented verify the effectiveness of the proposed approach.

A switch-mode assisted linear amplifier (SMALA) combining a linear (Class B) and a switch-mode (Class D) amplifier is presented. The usual single hysteretic controlled half-bridge current dumping stage is replaced by two parallel buck converter stages, in a parallel voltage controlled topology. These operate independently: one buck converter sources current to assist the upper Class B output device, and a complementary converter sinks current to assist the lower device. This topology lends itself to a novel control approach of a dead-band at low power levels where neither class D amplifier assists, allowing the class B amplifier to supply the load without interference, ensuring high fidelity. A 20 W implementation demonstrates 85% efficiency, with distortion below 0.08% measured across the full audio bandwidth at 15 W. The class D amplifier begins assisting at 2 W, and below this value, the distortion was below 0.03%. Complete circuitry is given, showing the simplicity of the additional class D amplifier and its corresponding control circuitry.

A high-frequency-link micro-inverter is proposed for integrating a single photovoltaic panel to a local load or utility grid. The number of power switches is minimized in addition to reduced magnetic components in order to design a low cost, light weight, compact and efficient inverter. A front-end current-fed isolated boost converter is used to integrate the photovoltaic panel to the rest of micro-inverter that consists of a half-wave cycloconverter and half-bridge inverter. The two basic building modules are interconnected via a high voltage DC-link capacitor. A series resonant tank is used to implement soft-switching in the half-bridge inverter and in the half-wave cycloconverter at the grid side. A highly optimized switching scheme is proposed to have soft-switching in all possible power conversion stages. The proposed micro-inverter is simulated using the MATLAB/Simulink Simpower block-set and with PSIM in order to verify the feasibility of the proposed converter and the effectiveness of the proposed switching control scheme.

An electronically-controlled series resonant circuit based micro-inverter with a full-bridge inverter and a half-wave cycloconverter is proposed for single phase distributed photovoltaic (PV) systems rated up to 400W. A series resonant circuit and a high frequency transformer are used to couple the full-bridge inverter and the half-wave cycloconverter. Inductor of the series resonant circuit is used to control output current of the micro-inverter. The proposed current control strategy of the micro-inverter is mathematically analyzed. The proposed micro-inverter is simulated using the MATLAB/PLECS block set in order to verify feasibility of the proposed current control method in series resonant circuit based DC-AC converters. Experimental results are obtained to further validate the proposed current control method.

The IEC 61850 family of standards for substation communication systems was released in the early 2000s and includes IEC 61850-8-1 and IEC 61850-9-2 that enable Ethernet to be used for process-level connections between transmission substation switchyards and control rooms. This paper presents an investigation of process bus protection performance, since the inservice behavior of multifunction process buses is largely unknown. An experimental approach was adopted that used a Real Time Digital Simulator and "live" substation automation devices. The effect of sampling synchronization error and network traffic on transformer differential protection performance was assessed and compared to conventional hard-wired connections. Ethernet was used for all sampled value measurements, circuit breaker tripping, transformer tap-changer position reports, and precision time protocol synchronization of sampled value merging unit sampling. Test results showed that the protection relay under investigation operated correctly with process bus network traffic approaching 100% capacity. The protection system was not adversely affected by synchronizing errors significantly larger than the standards permit, suggesting that these requirements may be overly conservative. This "closed loop" approach, using substation automation hardware, validated the operation of protection relays under extreme conditions. Digital connections using a single shared Ethernet network outperformed conventional hard-wired solutions. Refereed/Peer-reviewed

This paper proposes an improved control of rotor side and load side converters with repetitive control in order to compensate the harmonic components in the stator voltage and current of the doubly-fed induction generator (DFIG) when connected with non-linear loads. The non-linear loads results in distorted stator voltage and current with subsequent power quality degradation and electromagnetic torque pulsations of DFIGs. The distorted stator voltage and current are compensated by the proposed hybrid control scheme with repetitive control (RC) based PI controller (PIRC). The harmonic components of different orders and negative sequence component of the stator voltage can be rejected using a single PIRC while most of the other alternative harmonic compensators require separate controllers for damping these components. The PIRC is applied in rotor side converter (RSC) for the purpose of stator voltage compensation and in line side converter (LSC) for stator current compensation, respectively. The simulation results are given and they show that the PIRC control scheme can eliminate stator voltage and current harmonic of stand-alone DFIG effectively.

A novel concept of producing high dc voltage for pulsed-power applications is proposed in this paper. The topology consists of an LC resonant circuit supplied through a tuned alternating waveform that is produced by an inverter. The control scheme is based on the detection of variations in the resonant frequency and adjustment of the switching signal patterns for the inverter to produce a square waveform with exactly the same frequencies. Therefore the capacitor voltage oscillates divergently with an increasing amplitude. A simple one-stage capacitor-diode voltage multiplier (CDVM) connected to the resonant capacitor then rectifies the alternating voltage and gives a dc level equal to twice the input voltage amplitude. The produced high voltage appears then in the form of high-voltage pulses across the load. A basic model is simulated by Simulink platform of MATLAB and the results are included in the paper.

Ethernet is a key component of the standards used for digital process buses in transmission substations, namely IEC 61850 and IEEE Std 1588-2008 (PTPv2). These standards use multicast Ethernet frames that can be processed by more than one device. This presents some significant engineering challenges when implementing a sampled value process bus due to the large amount of network traffic. A system of network traffic segregation using a combination of Virtual LAN (VLAN) and multicast address filtering using managed Ethernet switches is presented. This includes VLAN prioritisation of traffic classes such as the IEC 61850 protocols GOOSE, MMS and sampled values (SV), and other protocols like PTPv2. Multicast address filtering is used to limit SV/GOOSE traffic to defined subsets of subscribers. A method to map substation plant reference designations to multicast address ranges is proposed that enables engineers to determine the type of traffic and location of the source by inspecting the destination address. This method and the proposed filtering strategy simplifies future changes to the prioritisation of network traffic, and is applicable to both process bus and station bus applications. © 2011 IEEE. Refereed/Peer-reviewed

This paper presents a high-voltage pulsed-power system based on low-voltage switch-capacitor units that are connected to a current source for several applications such as plasma systems. A modified positive buck-boost converter topology is used to utilize the current source concept, and a series of low-voltage switch-capacitor units is connected to the current source in order to provide a high voltage with a high voltage stress (dv/dt) as demanded by the loads. This pulsed-power converter is flexible in terms of energy control because the stored energy in the current source can be adjusted by changing the current magnitude to significantly improve the efficiency of various systems with different requirements. The output-voltage magnitude and stress (dv/dt) can be controlled by a proper selection of components and control algorithm to turn on and off the switching devices.

This paper presents a novel topology to generate high voltage with utilization of slow and fast power switches. New concepts used in this topology include numbers of diode-capacitor units in parallel with resonant circuits which are connected to a positive buck-boost converter. The resonant circuit reverses the voltage polarity of the capacitors. This configuration has capability of generating a flexible high voltage with certain number of capacitors. The advantage of this topology is to use slow switches, less number of diodes and capacitors compare to Marx generator. Simulations have been performed to verify the proposed topology.

This paper proposes a linear state-space model for a phase-controlled resonant dual active bridge with a tuned capacitor-inductor-inductor-capacitor network. The proposed model is useful for fast simulation and for the estimation of state variables under large signal variation. The model is also useful for control design because the slow changing dynamics of the dq variables are relatively easy to control. Using the proposed model, a decoupled control scheme was designed which allows for the control of the high frequency link currents while also improving the soft switching range of the converter. Using steady-state relationships between state variables and the system inputs, the controller was simplified from three proportional integral (PI) controllers to a single PI controller. The controller was implemented on a low cost digital signal processor and verified experimentally. The experimental and simulation results showed the proposed model's usefulness for control design and fast simulation.

One of the issues faced by manufacturers of fluorescent luminaires is the vast number of models they have to contemplate in the light of an EMC compliance regime. By modelling the luminaire's electrical circuit with lumped elements, this paper investigates the insertion loss performance of a number of fluorescent luminaires, and the effects of the power-factor correction capacitor on the insertion loss performance, to enable a quick evaluation of each luminaire model.

The new configuration proposed in this paper for Marx Generator (MG) aims to generate high voltage for pulsed power applications through reduced number of semiconductor components with a more efficient load supplying process. The main idea is to charge two groups of capacitors in parallel through an inductor and take advantage of resonant phenomenon in charging each capacitor up to a double input voltage level. In each resonant half a cycle, one of those capacitor groups are charged, and eventually the charged capacitors will be connected in series and the summation of the capacitor voltages can be appeared at the output of the topology. This topology can be considered as a modified Marx generator which works based on the resonant concept. Simulated models of this converter have been investigated in Matlab/SIMULINK platform and a prototype set up has been implemented in laboratory. The acquired results of either fully satisfy the anticipations in proper operation of the converter.