Lei Da

Analysis on grid-friendly microgrid economic operation

The ability of the grid-friendly microgrid responding the system operation demand is analyzed by exploiting potentialities of grid operation from the traditional load side. The volatility of DGs output is balanced by including controlling EVs the charging and discharging. The output of microgrid is scalable through coordinating all kinds of DGs based on which a microgrid economic operation model is built. The simulation result shows the microgrid can absorb internal intermittent power and achieve system dispatching well by coordinating kinds of powers. Its dispatching potentiality is sizable.

Study of the interaction between photovoltaic inverter and power quality harmonic and its suppression method

In the process of photovoltaic (PV) generator was connected to the grid, in order not to affect the power quality of grid, the current harmonic component from PV inverter needs to meet the relevant interconnection standards. This topic put-forwards a method based on impedance analysis, which analyses the harmonic interaction between the photovoltaic (PV) grid-connected inverter and power grid containing background harmonic. The basic reason of harmonic resonance problem caused by grid-connected PV system is duo to the existence of impedance intersection at the point of common connection (PoC), which is determined by the equivalent output impedance of the inverter and the equivalent impedance of the grid. At that intersection point, the sum of the impedance reduced to the minimum value and the current amplitude significantly increased, which leads to the harmonic resonance phenomenon. To analyze this problem, this paper established the NORTON equivalent model of the inverter, developed the expression for the equivalent output impedance of the inverter, and analyzed the reasonable range of the equivalent inverter output impedance based on the maximum limit of photovoltaic (PV) grid harmonic voltage, current and harmonic resonance conditions. On this basis, the PI control and the quasi PR control methods were used respectively to adjust the equivalent output impedance of inverter. Based on the simulation experiment, the equivalent output impedance was effectively suppressed, and the harmonic resonance phenomenon was avoided.