Compensation effects of the active power filter based on PWM converters are mainly affected by two factors: ① time lagging of reference compensation current; ②The dynamic limit of switching device themselves, that is, the limit of max di/dt of filter power output. This paper has presented the error models which are used to evaluate the compensation errors of the two main limitations, and has studied various factors influencing the di/dt capability of converters by the experiments. The experiment results showed that the accurate compensation error models are different when the structure of the converter, the load type and the current controlling way are distinct. But the research work can be done by the similar methods: the size of the compensation errors can be determined by the actual compensation current curves, the area between average lagging reference current curves. Further more, the ideal compensation current can be observed as time function. Finally, the paper has verified the validity of the estimation error model by the experimental study changing the circuit parameters.