Extended Operation Range of Photovoltaic Inverters by Current Waveform Shaping

The grid connection of photovoltaic voltage source inverters depends on the dc-link voltage level that can be supplied by the maximum power tracking of the photovoltaic system. The inverter disconnects from the grid, if the minimum required dc link voltage level is violated, which leads to unwanted energy curtailments implying losses to the system owner. This paper proposes to apply current waveform shaping to the inverter current in order to reduce the peak value of the voltage waveform at the point of common coupling by which the minimum required dc-link voltage level for power injection is reduced. This extended operation range of photovoltaic inverters is achieved through third harmonic current injection and can be applied to single-phase and three-phase, four-wire inverters without additional converter stages. A control structure for harmonic current injection and harmonic phase determination is presented and validated by simulations and the analysis is verified by experiments

Voltage-Dependent Load Levelling Approach by means of Electric Vehicle Fast Charging Stations

Intermittent generation and load demand are one of the major challenges for grid operators. Caused for example by renewables power variability or electric vehicle charging, it can create mismatches between the realtime and forecasted demand, affecting frequency regulation. To alleviate this mismatch, operators have to resort either on the balancing market or on extensive use of energy storage systems, which increases operation costs. This paper introduces a load levelling approach exploiting the voltage dependency of the loads. With a controlled reactive power injection, the converters of fast charging stations can influence the voltage profile, and consequently the power consumption of voltage-dependent loads. The approach has two main goals: minimizing the mismatches with respect to the demand forecast and reducing the grid losses. Fast charging stations are particularly suited for this approach. Being employed with full capacity for charging only for short-time, their spare capacity can be exploited to apply the load levelling approach. This proposed approach is discussed theoretically and analyzed in a modified distribution network in Northern Germany. Parameters variation analysis has been performed to thoroughly demonstrate the effectiveness of the approach under different load/grid conditions. Its feasibility has been evaluated by means of power-hardware-in-the-loop tests

Generation of an NCS1 gene knockout human induced pluripotent stem cell line using CRISPR/Cas9

NCS1 (Neuronal calcium sensor protein 1) encodes a highly conserved calcium binding protein abundantly expressed in neurons. It modulates intracellular calcium homeostasis, calcium-dependent signaling pathways as well as neuronal transmission and plasticity. Here, we generated a NCS1 knockout human induced pluripotent stem cell (hiPSC) line using CRISPR-Cas9 genome editing. It shows regular expression of pluripotent markers, normal iPSC morphology and karyotype as well as no detectable off-target effects on top 6 potentially affected genes. This newly generated cell line constitutes a valuable tool for studying the role of NCS1 in the pathophysiology of various neuropsychiatric disorders and non-neurological disease