A High-Performance Controllable AC Load

Controllable AC loads are used to test AC sources, inverters and uninterruptible power supplies. They are designed to simulate constant-current, constant-resistance, constant-power, variable power factor, and nonlinear loads. They are also used to emulate variable AC load profiles in test-bench study of stand-alone energy conversion systems in research labs. High speed of response to the electronic control signal, high fidelity, high power density and low cost are among the desired characteristics of such loads. In this paper, a high-performance controllable AC load featuring simple structure, scalability, fast response and low cost, is introduced. The load can be configured to operate in single- or three-phase mode. It can be programmed to operate in controlled-current, impedance, active power, active and reactive power, as well as active power and power factor modes. The load can also emulate controlled-current diode-rectifier loads with a dc-side filter capacitor. The proposed controllable AC load can be easily configured as a controllable DC load, resulting in a compact controllable AC/DC load. The analytical expectations about the performance of the proposed controllable AC load have been verified through simulation.