Efficient State Reference Generation for Torque Control in Externally Excited Synchronous Machines

Abstract

A relevant challenge in hybrid electric vehicles (HEVs) and full EVs is the torque control of externally excited synchronous machines (EESMs). Effective torque control requires an efficient solution to the state reference generation problem, which is a nonlinear nonconvex optimization problem. The goal of this paper is to develop a state reference generation algorithm based on the gridding of the state and output spaces. First, an approximation defined over a cubic partition of the torque function with a piecewise affine (PWA) function is made. As a result, the state reference generation problem is reduced in each cube to solving a convex optimization problem. Moreover, this approach provides guarantees about the error bound introduced by the state reference generation procedure for the full operational state-space. To illustrate the effectiveness and robustness of the proposed algorithm, several real-time results obtained on an industrial hardware-in-the-loop (HIL) test-bench are presented. The obtained results show significant improvement compared with existing state-of-the-art reference generation methods.

Predictive DC-link voltage control of permanent magnet synchronous machine drives for hybrid electric vehicles

“…The proof of the Lemma IV.2 is omitted here for brevity and the interested reader is referred to [12]. It suffices to mention here that Lemma IV.2 states that the approximation of (27) with an affine function in any S i can be done by using only the vertices of S i .…”

“…T max , p ∈ Z [0,s −2] . It should be noted that the error introduced by the gridding of the torquespace can be maximally the distance between two grid points [12]. In what follows the goal is to find the set of indexes that correspond to squares where the desired value T e,ref ∈ T is contained, i.e., …”

Low-computational-complexity algorithm for current predictive control of an externally excited synchronous machine

“…The state-space model of the electrical subsystem of EESMs is obtained from (8), using the same reasoning as in [9], by introducing the stator currents in the rotor reference frame and the excitation current as state variables, i.e.,…”

“…Then, the electromagnetic torque can be obtained using the description of the input power in the rotor reference frame as follows, i.e., (9) where P p denotes the number of pole pairs.…”

“…Therefore, the control strategy has to compute also the current references in the rotor reference frame. For an overview of the state-of-the-art techniques to compute current references for EESMs the interested reader is referred to [8], [9] and the references therein.…”