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Nonlinear loads connected to the microgrid distort the voltage of the Point of Common Coupling (PCC) and the grid current. Therefore, A droop control based harmonic voltage compensation strategy of voltage controlled inverter in islanded/grid-connected mode is proposed in this paper. To compensate the PCC voltage distortion, fundamental and harmonic voltage components are controlled separately in...
When generators of a power system are subject to a large disturbance, their electromechanical oscillations (EOs) are essentially nonlinear as observed from their rotor angle waveforms due to the nonlinear power network. However, traditional modal analysis has not given enough considerations to nonlinearities in EOs. This paper analytically formulates the accurate oscillation frequency (OF) of an EO...
This paper proposes a new approach to estimate the non-constant nonlinear frequency of a power system electro-mechanical oscillation mode by deriving an approximate, analytic expression about the oscillation amplitude-frequency dependency. The approach uses the Harmonic Balance Method (HBM) together with one of three representative function approximation techniques, i.e. Taylor Expansion (TE), Chebyshev...
The grid-feeding voltage controlled inverter (GF-VCI) based on droop control is vulnerable to the harmonic voltages of the utility grid. Because of the equivalent impedance of system is small, the slight distorted grid voltage will result in the harmonic component increasing of GF-VCI output currents. Therefore, the reason of generation of distorted grid-feeding current of GF-VCI under the distorted...
For analysis of non-constant electro-mechanical oscillation frequency with a power system, this paper proposes an analytical approach integrating Differential Groebner Basis (Diff-GB) and the Harmonic Balance Method (HBM). This approach is illustrated in detail on a single-machine-infinite-bus system, whose oscillation frequency fluctuates with time due to its nonlinear-system nature. The Diff-GB...
To satisfy the need of high performance, a grid-connected hybrid cascaded H-bridge single-phase inverter is proposed. The topology of the inverter has different DC voltages, and a modulation method minimizing the switching loss is applied. In order to improve the control performance, the phase lock loop (PLL) based on generalized second-order integrator is adopted. A current controller based on Proportional-Resonant...
Power converter is the key element of the photovoltaic generation system. In order to improve the energy conversion efficiency and achieve an economic solution, hybrid cascade inverter (HCI) is employed and implemented to realize DC-AC conversion in this paper. HCI has a similar topology with conventional H-bridge cascade inverter, while the voltages of its DC buses are in a geometric sequence. In...
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