PWM Rectifier Model with Hysteresis Control Using Hysteresis Comparator

The hysteresis comparator application in PWM rectifiers represents a classic current control strategy primarily used for achieving high dynamic response power factor correction (PFC). The core concept involves real-time adjustment of switching device states through the hysteresis comparator, enabling input current to closely track the reference current waveform, thereby achieving low harmonic distortion and high power factor. In code implementation, this typically requires ADC sampling of actual current, generation of sinusoidal reference signals, and hysteresis boundary calculations using conditional statements.

The hysteresis control implementation logic proceeds as follows: First, the rectifier's input current is sampled and compared with the reference current (typically a sine wave). The hysteresis comparator sets an allowable error band (hysteresis width) - when the actual current exceeds the upper reference limit, the switching device activates to reduce current; conversely, when current falls below the lower limit, it increases current. This "two-point" control doesn't require fixed switching frequency and naturally adapts to load variations, but results in switching frequency fluctuations with input voltage and load changes. Algorithm implementation involves continuous comparison operations and switch state updates without requiring precise timer interrupts.

In PWM rectifiers, hysteresis control directly operates on the current loop, demonstrating superior dynamic performance compared to traditional PI control, particularly suitable for applications with strict harmonic suppression requirements. However, hysteresis width requires careful design - excessive width increases current ripple, while insufficient width may cause excessively high switching frequency and increased device losses. Practical applications often combine it with voltage outer loops (such as DC bus voltage stabilization) to form dual-closed-loop structures that balance steady-state accuracy and dynamic response. Code implementation typically uses interrupt service routines for current sampling and PWM updates, with separate voltage PI controllers for DC link regulation.

Extension consideration: To optimize the non-fixed switching frequency issue, adaptive hysteresis control or combinations with space vector modulation (SVM) can be introduced, maintaining hysteresis rapidity while constraining switching frequency ranges. Software implementation would require additional frequency detection algorithms and dynamic hysteresis width adjustments based on operating conditions.