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The purpose of this paper is to present a influences of parameter deviations on operation of a novel current sensorless AC-DC converter are discussed. The off time is calculated based on the equations of each operating state for boundary current control mode. The relationship among the THD, power factor and efficiency, and circuit parameter errors are discussed. When the circuit parameter varies from...
This paper presents an analysis of two algorithms used to control the active and reactive powers in three phase inverters for grid-tied photovoltaic systems under unbalanced voltages in the Point of Common Coupling (PCC). The algorithms are focused on injecting balanced currents to the grid despite the voltage unbalances. The analysed algorithms are composed of two control loops: the reference signal...
The recently proposed Hexverter topology belongs to the group of modular multilevel direct AC/AC converters. For its operation, a so-called adjacent compensating power is essential. This paper introduces a new method for composing the adjacent compensating power, which optimises the efficiency. The importance of the adjacent compensating power for branch energy control is shown and the differences...
In this paper, a nonlinear control method called flatness-based control (FBC) is proposed to manage the delivered wind turbine (WT) energy to the grid. The studied system includes a three-bladed horizontal wind turbine and a permanent magnet synchronous generator (PMSG) which is connected to the grid through a back to back converter. The proposed control method is carried out by planning the appropriate...
Since the demand of energy with high quality and reliable power is growing and temporary faults in the grid are common, the analysis of unbalanced voltage conditions has become increasingly important. Power converters can control the instantaneous active and reactive power and manage them in order to improve the voltage conditions at the point of common coupling. The current reference generation strategies...
This paper presents a high performance control strategy for a single phase photovoltaic system based on cascaded multilevel converter. The concept of single phase d-q vector control is introduced into the system and a general control scheme for arbitrary number of modules is proposed. The proposed method can not only track the maximum power point at panel level but also ensures a high performance...
This paper presents the flexible dc capacitor voltages balancing control method for star-connected cascaded H-bridge converters. In this paper, the power flows are analysed by investigating all the converter's control freedoms. Based on the analyses, users can accomplish dc capacitor voltage balancing with both negative-sequence current and zero-sequence voltage. These two kinds of control options...
This paper introduces the use of machine saliency as one of the parameters for the sizing of a three level inverter dc-link capacitor. A new nearest three vector (NTV) balancing algorithm is also introduced for the dc-link capacitors. A comparison between a two and three level inverter was conducted whereby the inverter input dc current for the two level inverter registered higher ripples than that...
It has always been believed that power-flow analysis should precede any power system problem solution. Consequently, loading conditions are presumed to be the most critical for solving power system problems. This notion is investigated further in this paper by revisiting the problem of Static Var Compensators' (SVCs) placement in a power system network for reactive power augmentation from three perspectives:...
The induction machine in the operating mode of generator is a very valuable alternative to the synchronous machines. Especially in lower nominal power rating range, such solution can be more cost effective. Induction machine with a squirrel-cage rotor cannot generate a reactive power and even more it is a permanent consumer of the reactive power. In this paper, we strive to define theoretical limits...
This paper discusses a control technique that allows for controlling the bi-directional flow of active and reactive power using the DQ theory. Traditionally, this theory is used for three phase systems. Its use in single-phase converters presents a challenge due to the lack of degrees of freedom required for orthogonal systems. In this paper, a few methods for orthogonal system generation are presented...
In this paper a vernier motor with a spoke PM structure instead of a surface PM is proposed in order to obtain higher power factor and flux density. However, upon investigating this structure with a single gap, unique effects which virtually eliminate the vernier effect are identified. To avoid these effects the spoke PM vernier motor with a double gap is then proposed. Analytic equations for back...
Unified Power Flow Controllers (UPFCs) are the most versatile Flexible AC Transmission (FACTS) devices. Yet, they are seldom used for power flow control owing to the high cost and size of the Zig-Zag transformers. Recently, a transformer-less UPFC concept has been introduced that uses cascaded multilevel inverters to match the line voltage levels and the configuration does not need isolation. Thus,...
In recent years, interest in the application of the Power Factor Corrector has grown considerably. This paper gives a comprehensive account of Critical Conduction Mode (CrM) in the Power Factor Corrector. The Critical Conduction Mode technique is newer than Continuous Conduction Mode (CCM). The analysis shows the principle which are based on structural schema and mathematical description of the waveforms...
Uplink sum power minimization problem with required Quality of Service (QoS) under statistical Channel State Information (CSI) and probabilistic constraints in solved for a multicell multiuser scenario. To handle the probabilistic constraints and analyze the system performance, financial risk management measures Value at Risk (VaR) and Conditional Value at Risk (CVaR) are applied. The resulting expressions...
In process control, a key of acquiring desired control performance is making good use of information that is included in operation data. Direct controller adjustment methods without the knowledge of a process model, and techniques for diagnosing control performance, which is control performance monitoring / assessment (CPM / CPA) have been proposed. The present work proposes a direct control parameter...
Virtual impedance (VI) loops are frequently employed in droop based controllers for grid-connected inverters so as to improve the dynamic response which can be very oscillatory when large droop factors are used. They neither yield active power losses nor reactive power demand but they tend to create a drop in the bus voltage. This paper discusses an approach based on phase shifting the reference voltage,...
Voltage instability is caused by the inability of the system to meet reactive power demand. The problem of voltage instability is even more critical for an isolated microgrid, which only has generators with limited reactive power capacities. In this paper, we investigated what happens if all generators in the system hit their reactive power limit. To simplify the analysis, a simple two-bus example...
In this paper, we address the problem of semi-blind parameter estimation of linear systems driven by chaotic signal. We propose an on-line expectation maximization (EM) based extended fixed-lag Kalman smoothing (EM-EFLKS) estimator to simultaneously estimate parameters of system along with the chaotic signal. The performance of the proposed estimator is compared to its offline counterpart, EM-EKS...
In this paper we show an alternative mathematical interpretation of the error propagation law for complex quantities established in supplement 2 of the GUM [1]. We use this interpretation to study VNA's one port reflection measurement which includes several terms that represent complex quantities. We show two different approaches to solve the problem that arises when trying to establish the variance...
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