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This paper introduces a low complexity implementation of the voltage balancing sorting algorithm to reduce the switching frequency of the power devices in modular multilevel converters (MMCs). Two modulation techniques are evaluated; staircase modulation and phase-disposition pulse-width modulation (PD-PWM) under the conventional and the proposed algorithm. Using a circulating current controller in...
As the development and installation of photovoltaic (PV) systems are still growing at an exceptionally rapid pace, relevant grid integration policies are going to change consequently in order to accept more PV systems in the grid. The next generation PV systems will play an even more active role like what the conventional power plants do today in the grid regulation participation. Requirements of...
Cell capacitor energy control of a Modular Multilevel Converter (MMC) is conventionally done by controlling leg current and modulation strategy. In most of literatures, leg current transient is analyzed under an assumption that the DC bus is a stiff DC voltage source. In a real MMC-based HVDC transmission system, however, there's no such virtual stiff DC voltage source and the conventional regulation...
A traditional half-bridge three-phase inverter topology can achieve zero voltage switching by implementing BCM operation which requires no additional power devices or magnetic components. In this paper a variable boundary dualmode current modulation method that combines ZVS and ZCS is proposed in order to improve the efficiency of the BCM current controlled micro-inverter. Decreasing output current...
In this paper, it is shown that in the three-phase six-switch boost PFC rectifier with average-current control and unbalanced input-voltage and/or input-current sensing gains, the current controller with proportional (P) compensation exhibits lower total harmonic distortion (THD) and higher power factor (PF) compared with that of proportional and integral (PI) compensation. It is also shown that the...
This paper proposes a novel current control method for reducing the rms current of converters in the distorted grid. The proposed strategy can reduce the conduction losses of both the local converter itself and the overall power system. In practical, the grid voltage may be distorted by various nonlinear loads. However, the present standards on the current harmonics of individual equipment under the...
This paper proposes a new hysteresis current control technique for a grid connected single-phase three-level quasi-Z-source inverter. This control algorithm could be applied in any three-level inverter with Z- or quasi-Z-source network where reference current control signal along with shoot-through states is used. To explain the operation principle of the algorithm the steady state analysis is presented...
This paper presents a method for current controller design in a single phase grid-connected inverter (GCI). The proposed controller addresses the following items: transient performance; steady state tracking; output current distortions and dc; active damping; and start-up transient. The proposed controller is based on various extensions of the linear quadratic regulator (LQR) method and it inherits...
The bridgeless power-factor-correction (PFC) converter possesses higher efficiency than the conventional boost-type PFC converter due to its reduced conduction voltage drop and conduction loss. The conventional multiloop control needs to sense the input current to yield the desired sinusoidal current waveform. This paper presents a control method for bridgeless PFC converter to provide sinusoidal...
A modular approach for DC/DC converters to obtain desired voltages and currents is presented in this paper. A high efficiency low switch count isolated push-pull DC/DC converter is used as a unit module. The converters are connected in input series or parallel and output series, or parallel configuration to meet the desired power level. The aim is to obtain a flexible DC/DC converter block which can...
This paper presents an optimal negative current control for four-phase interleaved bi-directional converters to achieve soft-switching features. Four-phase buck/boost converters with bi-directional operation and in discontinuous conduction mode (DCM) are designed and implemented. The optimal negative current is determined and controlled to reduce reactive power loss, while achieves ZVS and ZCS turn-on...
A single-phase Dual Active Half Bridge (DAHB) DC-DC converter topology is evaluated for medium voltage (MV) application. A 15kV SiC-IGBT based three-level half-bridge is connected to the high voltage (HV) primary side of a high frequency (HF) transformer operating at 10kHz link-frequency. A 1200V SiC-MOSFET based two-level H-bridge is connected on the low voltage (LV) secondary side. This topology...
In this paper, we discuss the principles of operating the electric spring (ES) as a reactive power compensator and as a power factor corrector. The theory on electric springs with capacitors for voltage stabilization is reviewed to present a general idea on the behavior of ES. Further discussion focuses on the principle of ES with batteries to cover its eight possible operating modes and their usefulness...
The paper proposes a computationally efficient finite state model based current control of a three-level neutral point clamped (NPC) five-phase voltage source inverter. The space vector model of a five-phase voltage source inverter (VSI) yields 243 space vectors, with 240 active and three zero vectors. The presented technique utilizes a modified switching algorithm to reduce the computation time while...
A two-stage single-phase grid-connected inverter has 120Hz component in input current as influence of pulsating output power at double of the grid frequency. The 120Hz component of input current has to be reduced or eliminated because low frequency current can damage a source or reduce efficiency in the photovoltaic, fuel cell and battery systems. Prior studies which deal with reduction of the 120Hz...
LCL filter control design is challenging because of presence of a resonant pole in the LCL filter transfer function. This paper presents a guideline for LCL filter design, which are often used in grid connected applications, with compensation based on complex poles and zeros. A Software Frequency Response Analyzer (SFRA) is integrated in the control software of the power converter. This enables periodical...
A primary side controlled offline Flyback LED driver is an very attractive LED driver solution due to its low component cost and high efficiency. However, as any other single-stage LED driver, it produce significant low frequency ripple current. In this paper, an innovative primary side controlled Flyback LED driver with low frequency ripple cancellation has been proposed. The low frequency ripple...
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