Implementation of a Cubature Kalman Filter for Power Estimation of Non-ideal Constant Power Loads in a DC Microgrid

DC microgrids (MG) involve the integration of power electronic loads, which might behave as constant power loads (CPL). CPLs often degrade system stability due to their negative impedance characteristics. To maintain the voltage stability and safe operation of DC MGs, eliminating the undesired behavior of CPLs is a necessity. This aim requires the instantaneous power value of the time-varying uncertain CPLs. Since the integration of current sensors in DC MGs is costly and inefficient, estimation methods should be used to obtain the spontaneous power of CPLs. In this paper, a 3rd degree cubature Kalman filter (CKF) is developed to estimate the power of the CPLs alongside estimation of CPLs’ and source’s currents in a DC MG. By considering the CPLs powers as artificial states and augmenting them into the system states, not only the DC MG states but also the unknown values of the CPLs powers may be estimated. The proposed estimator is tested on a DC MG that feeds one CPL. The experimental results show that the proposed CKF is able to estimate instantaneous power consumption of the CPL as well as source and load currents. Key-Words: Estimation, Cubature Kalman filter, DC microgrid, Non-ideal Constant power load