Harmonic Suppression Strategy of Photovoltaic Grid Connected Inverter Based on Repetitive and PI Control

To address the serious harmonic problem of grid connected current in photovoltaic grid-connected inverter, a harmonic suppression strategy based on Repetitive and PI control is proposed in this thesis. According to this strategy, the mathematical model of LCL photovoltaic grid-connected inverter is established with the harmonic mechanism analyzed, the repetitive and PI control is added into the current controller, and the capacitive-current feedback is added to enhance the system damping. Furthermore, it puts PI control on the inner loop and the repetitive control on the outer loop to improve the dynamic performance and achieve the harmonic suppression of the system. Moreover, the simulation results show that this method improves the dynamic response ability of the system, and effectively suppress the grid-connected current harmonics as THD of grid-connected current is 19.65% lower than that of PI controller.

Nontrivial solutions to the p-harmonic equation with nonlinearity asymptotic to |t| p–2 t at infinity

We consider the following p-harmonic problem Δ ( | Δ u | p − 2 Δ u ) + m | u | p − 2 u = f ( x , u ) , x ∈ R N , u ∈ W 2 , p ( R N ) , $$\begin{array}{} \displaystyle \left\{ \displaystyle\begin{array}{ll} \displaystyle {\it\Delta} (|{\it\Delta} u|^{p-2}{\it\Delta} u)+m|u|^{p-2}u=f(x,u), \ \ x\in {\mathbb R}^N, \\ u \in W^{2,p}({\mathbb R}^N), \end{array} \right. \end{array}$$ where m > 0 is a constant, N > 2p ≥ 4 and lim t → ∞ f ( x , t ) | t | p − 2 t = l $\begin{array}{} \displaystyle \lim\limits_{t\rightarrow \infty}\frac{f(x,t)}{|t|^{p-2}t}=l \end{array}$ uniformly in x, which implies that f(x, t) does not satisfy the Ambrosetti-Rabinowitz type condition. By showing the Pohozaev identity for weak solutions to the limited problem of the above p-harmonic equation and using a variant version of Mountain Pass Theorem, we prove the existence and nonexistence of nontrivial solutions to the above equation. Moreover, if f(x, u) ≡ f(u), the existence of a ground state solution and the nonexistence of nontrivial solutions to the above problem is also proved by using artificial constraint method and the Pohozaev identity.

Exact Solution of the Harmonic Problem for a Rectangular Plate in Flat Deformation by the Method of Initial Functions

A wide range of applications is based nowadays on analytical developments which allow a precise and effective approach and short time of computations compared with the time required for numerical methods; in this way these developments are suitable for calculations in real time. This work proposes an approach for solving a two-dimensional harmonic problem of a rectangular plate under local surface loading using Vlasov’s symbolic method of initial functions and a general solution of the harmonic equation for a rectangle. Substituting the harmonic functions in symbolic form for the corresponding solutions allows us to give the exact solution of the problem in trigonometric form.

Harmonic Load Mitigation Using the Optimal Double Tuned Passive Filter Technique

Harmonic is one of the power quality disturbances customarily imminent in an unbalanced electrical system. Harmonic represents as the multiple integral of fundamental frequency of voltage and current inflicting towards the shifting in system frequency causing to a disruptive operation of electrical devices. This paper investigates on the performance of passive filter intrinsically by utilizing the inductor and capacitor electrical components to mitigate harmonic problem emanating from an unbalanced electrical system. In particular, explication in this paper will focus on the optimal parameters specification for the double tuned passive filter that used to overcome the phenomenon of harmonic issue. The two case studies constituting with different number of harmonic orders injected in a system were introduced to distinguish effectiveness of double tuned passive filter in solving the aforesaid problems. The parameters configuration of the passive filter are automatically tuned by the MATLAB® software to reduce the total harmonic distortion incurred in a system designed under the Simulink® software.

Generation of Hydroacoustic Waves by an Oscillating Ice Block in Arctic Zones

The time harmonic problem of propagating hydroacoustic waves generated in the ocean by a vertically oscillating ice block in arctic zones is discussed. The generated acoustic modes can result in orbital displacements of fluid parcels sufficiently high that may contribute to deep ocean currents and circulation. This mechanism adds to current efforts for explaining ocean circulation from a snowball earth Neoproterozoic Era to greenhouse earth arctic conditions and raises a challenge as the extent of ice blocks shrinks towards an ice-free sea. Surprisingly, unlike the free-surface setting, here it is found that the higher acoustic modes exhibit a larger contribution.