Abstract
To prevent the passengers from electric shock, the DC-bus capacitor voltage of the high-voltage permanent magnet synchronous machine (PMSM)-based drives in electric vehicles (EVs) is required to decline to safe voltage as quickly as possible when emergency occurs. Considering that the discharge time for small safe current limit powertrain systems will be longer than required, this paper proposed a maximum power discharge strategy to accelerate the dissipating process and meanwhile avoid the voltage surge. Firstly, the PMSM discharge model as a generator is established on the basis of analyzing the discharge course. Secondly, the feasible reference current trajectory is presented by drawing the trajectories of the voltage, current, and power constraints. Then the maximum power discharge strategy is achieved by following the extreme points in the reference trajectory. Finally, simulation and experiment are conducted on a three-phase SPMSM powertrain system to validate the proposed algorithm can effectively shorten the discharge process.
Highlights
Since permanent magnet synchronous machines (PMSMs) have brilliant advantages of high efficiency, high power density, wide speed range, and compact structure, they have been widely applicated as main power source in electric vehicle (EV) powertrain systems [1]–[9]
An accurate PMSM phasor diagram model as a generator is established on basis of analyzing the different stages of the discharge process
This paper proposes a novel maximum power discharge strategy based on the internal windings to meet the discharge requirement as quickly as possible without voltage surge for EV-PMSM powertrain system
Summary
Since permanent magnet synchronous machines (PMSMs) have brilliant advantages of high efficiency, high power density, wide speed range, and compact structure, they have been widely applicated as main power source in electric vehicle (EV) powertrain systems [1]–[9]. For EV-PMSM powertrain system with large inertia and small safe current, the back EMF cannot be pulled down to safety voltage in most cases, even the current has reached the limit In view of this situation, [20] concentrates no more on the stability of the DC-bus voltage but comes up with a strategy of giving a large negative d-axis current and a negative q-axis current to consume the residual energy. This paper proposes a new control strategy for the EV-PMSM powertrain system with low safe current limit, discharging the DC-bus and dissipating the system energy as soon as possible without the DC-bus voltage surge. Since the method considers the friction and the maximum system safe current, the powertrain system will dissipate the remanent energy in maximum discharge power, decreasing the DC-bus voltage and rotor speed in the fastest way.
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