Measuring the small-signal response of diode rectifier loads using a DSP controlled switching converter system
The assumption that non-linear rectifier loads contribute only to the steady state of a power system is commonly made in the design and analysis of power conditioners such as the shunt active filter. This tacitly assumes that the non-linear rectifier load is less sensitive than the AC system. This paper presents experimental measurements of the sensitivity of non-linear rectifiers made by injecting a perturbing current into the point of coupling of the rectifier. The perturbing current is generated with a DSP controlled switching power converter typically used in shunt active filters. The DSP system also measures the change in the load current. Results are presented for both single-phase and three-phase rectifiers. These show that both these rectifiers are sensitive to the perturbing current, that the response is measurable with relatively unsophisticated hardware and that the response has a well defined pattern in the frequencies that occur.