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This paper proposes a frequency observer based control of a solar energy conversion system (SECS). The proposed control eliminates the DC offset and harmonics current and provides fundamental component of load current. The mathematical analysis of the control is corroborated and discussed in terms of filtering capabilities. Besides, capability of maximum power extraction, it integrates maximum extracted...
A novel discrete sinusoidal signal integrator (DSSI) structure is proposed in this paper for single grid-tied inverters. The DSSI provides an adjustable gain and bandwidth at the expected frequency and a highly attenuated gain at other frequencies which make the DSSI based controllers obtain the zero steady-state error tracking performance of arbitrary frequencies. The performance of the conventional...
With the increasing penetration of renewable energy generations such as solar and wind power, negative impacts of the large-scale integration of renewable energy on the bulk grid cannot be ignored. Thus, grid integration testing of inverter-coupled renewable energy is essential. For this reason, a high power gird simulator capable of emulating various types of realistic grid conditions is needed for...
The MMC is an emerging and highly attractive multilevel converter topology for medium and high voltage applications. Various modulation strategies are being used to control the MMC system. Balancing the cascaded submodule voltages and eliminating the second order circulating current in the leg of the MMC system are the main concerns of many researchers in the area of MMC system. Mostly, for circulating...
This paper presents a proportional harmonic power sharing (PHPS) control scheme to improve the voltage quality at point of common coupling (PCC) and share harmonic power simultaneously for an islanded microgrid. The proposed control strategy employs P+ multiple resonant controller, and P+ plus Q+-based improved droop control scheme to improve the voltage quality at the load bus. Additionally, the...
The trends in power DC/DC conversion are not only size and weight reduction together with a good efficiency; EMI and mass production are a must as well. In this context, piezoelectric transformers seem to be the ideal solution, since they allow higher switching frequencies (size and weight reduction) while also providing high efficiencies. Additionally, they are not magnetic devices, which facilitates...
Harmonic power can be shared by controlling the equivalent harmonic impedance of distributed generation (DG) units in islanded microgrids. This paper firstly reviews several methods for controlling the equivalent harmonic impedance of DGs and adopts the method based on resistive active power filter (R-APF). Then, a droop relationship between the equivalent harmonic impedance of DGs and their remaining...
Medium/High power converters usually employ low switching frequency to reduce power loss, resulting in large system delay in their control system. The multi-sampling technique is an effective method to reduce the system delay while this will make the system a Linear Periodic Time Varying (LPTV) system. Modeling this kind of system by using LTI modeling method, such as Laplace transform, Z-transform,...
The appearance of harmonics in the grid voltage is an issue for the generation systems and grid connected consumers. This paper presents the basic control strategy to be implemented in Synchronous Power Control (SPC) based power converters, which contributes to reduce the harmonic content in the voltage by means of injecting different harmonic current to the grid using a separated virtual admittance...
This paper presents a grid-side current controller for grid-tied inverters with LCL filter, including harmonic current elimination. Contrarily to previously proposed harmonic-current controllers, the presented solution offers a generalized method that gives a consistent and stable performance irrespectively of the number of current harmonics to be canceled and of the resonant frequency of the LCL...
This paper proposes a frequency adaptive discrete Fourier transform (DFT) based repetitive control (RC) scheme for DC/AC converter. DFT-based RC is an improved RC scheme aiming to eliminate waveform distortion on selected harmonics without influencing the overall system stability. However, the traditional DFT-based RC is insufficient to accommodate frequency fluctuation as fractional delay period...
The active power filter (APF) has already established itself as a prominent means of addressing harmonic pollution and other power quality issues. Current control of an APF is a key in achieving a good compensation performance. Generally, PI control is used owing to its simplicity and ease of implementation. However, using a proportional resonant (PR) controller can give an added advantage in tracking...
In order to test the renewable energy grid-connect converters, a grid simulator is in need which is able to simulate grid transition such as voltage sags, unbalanced voltages, flicker and low-order harmonics. The main concern of this paper is on the harmonics generation. A compound control strategy is proposed on the basis of three-phase inverter to generate precise controllable required voltage harmonics...
Kidney cancer is a severe disease which can be treated by using a non-invasive, controllable and focused ultrasound surgery method-histotripsy. Previously, histotripsy produced by hundred-microsecond-long focused ultrasound pulses has been proposed by us, which generates mechanical homogenized lesion by employing boiling bubbles and high duty cycle compared with conventional methods. However, the...
In this paper, a novel supply voltage harmonic mitigation method using a simple DVR without harmonic detection is proposed. In contrast to the conventional DVRs control methods, the proposed method realizes two independent control objectives at fundamental and harmonic frequencies without couplings, with the adoption of the proposed voltage controller with two independent inputs focusing on different...
The matrix converter has emerged as a direct AC/AC converter and has attracted research attention. This work proposes a Proportional Resonant (PR) controller based on the Space Vector Modulation (SVM) method for the three-phase direct matrix converter and its application systems. The PR controller, compared with the widely used PI controller, has better steady-state error performance, specific harmonics...
Due to the existence of mass unbalance and sensor runout, magnetically suspended rotor (MSR) system will generate harmonic current. The ratio of sampling frequency to fundamental frequency of the harmonic current is not always an integer. However, the existing repetitive controller (RC) for harmonic current suppression of MSR can only compensate for the cases where the ratio is an integer, so the...
The current tracking control strategy is the key technology to realize dynamic reactive power regulation and harmonic current compensation in D-STATCOM system. In order to improve the precision and dynamic response speed of the D-STATCOM, a direct current control algorithm based on proportional vector proportional integral (PVPI) was proposed. The principle, performance and parameters of the controller...
The modular multi-level converter (MMC) is considered as the state of the art converter among multilevel topologies. The harmonic suppression of circulating current is the inherent problem needed to be solved. In this paper, a new control strategy is proposed. The strategy includes the double fundamental frequency, negative sequence rotating coordinate transformation and the four fundamental frequency,...
Phase-locked loops (PLLs) are commonly used for the synchronization of grid connected power converters. However, the standard PLL structures are not able to reject grid disturbances such as voltage harmonics, unbalances or DC components in the measured voltage. Since the response of the power converters depends on the grid phase tracking, it is necessary to ensure an accurate synchronization even...
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