Power Split Hybrid Vehicle System

This PLECS demo model shows a Lithium-ion (Li-ion), battery-powered, series-parallel hybrid vehicle system. The simulation shows the startup for an electrically and mechanically coupled hybrid system.

Power Circuit

The electrical system of the series-parallel hybrid vehicle consists of a bi-directional DC/DC converter connecting the Li-ion battery to the DC-bus. A boost converter is connected on the front end of the drive to step up the 200 V battery to a 400 V DC-link. The boost stage is controlled with an outer voltage regulator, which generates a current setpoint for the DC-link current (high-side current). The current regulator in this controller is used to control the inductor current (low-side current). Thus the high-side current setpoint must first be transformed into a low-side current setpoint. The transformation is based on the approximation that the input power is equal to the output power. The derived low-side current setpoint is fed into a current regulator that is used to generate a voltage setpoint for the output of the boost stage. This setpoint value and the measured DC-link voltage are fed into a modulator, which sets the duty cycle for the symmetrical PWM generator. These gating signals control the IGBT pair, and a small dead time is also included to prevent the shorting of the DC bus.

Battery Modeling

The Li-ion battery is based on a resistor-only electrical model. This model enables users to take information from the battery datasheet to represent the current and voltage characteristics of a Li-ion battery pack as it is charged and discharged. Application notes on Li-ion battery modeling in PLECS can be found here.

Drive Systems

The series-parallel hybrid consists of two permanent-magnet synchronous machines (MG1 and MG2), inverters and associated controls. The DC-side of the inverters of both MG1 and MG2 are connected the DC-bus. MG2 is primarily used as a motor to aid the engine during acceleration. MG1 is used both as a motor and a generator. Both MG1 and MG2 system controllers consist of an outer speed loop and an inner current loop to regulate the rotor speed to a desired speed. The outer speed loop produces the torque setpoint for each machine. These torque set points are converted into dq-current set points. A digital synchronous frame regulator is used to regulate the current in each MG system.

Mechanical System

MG1 and MG2 are mechanically coupled to the engine via a planetary gear set (PGS). The PGS module has three mechanical ports to connect it to the sun, ring, and carrier gears. The PLECS PGS module internally consists of a ring-planet gear and sun-planet gear implementation. This allows users to introduce non-idealities into the planet gear to observe the effects on the overall system.

The ring gear is connected to both the rotor shaft of MG2 and the wheel. The engine is connected to the carrier shaft and MG1 is connected to the sun gear. This configuration allows the engine and MG2 to provide the driving torque for the wheel, while MG1 is controlled to maintain the engine speed at the desired level.

Try it

This model is available in the PLECS Demo Model library provided in both versions of PLECS.

Categories: 
Automotive
Controls
Mechanical Domain