SeHwan Kim

Maximum Voltage Utilization of IPMSMs Using Modulating Voltage Scalability for Automotive Applications

A hybrid maximum voltage utilization controller is developed for interior permanent-magnet synchronous motors over a wide operating range. The structure of the controller combines the current vector control (CVC)-type maximum torque per ampere controller and the modulating voltage-scaled controller (MVSC). The hybrid structure provides a smooth transition from the CVC to the proposed MVSC mode by deactivating the current regulator in the flux weakening region. A seamless transition to a full six-step modulation can be realized by adjusting the scaling gain, which is a significant merit in terms of power utilization for wide flux weakening applications. This paper also examines the torque control accuracy under motor parameter drifts to determine how to decouple its effect using a voltage disturbance state-filter design.

Voltage disturbance state-filter design for precise torque-controlled interior permanent magnet synchronous motors

This paper presents the development and implementation of an online voltage disturbance estimator to achieve the precise torque control of interior permanent magnet synchronous motors (IPMSMs) over a wide operating region. Different design methodologies for disturbance extraction are analyzed using a complex vector frequency-response function (FRF) and evaluated in terms of estimation accuracy. The proposed design has a form of the state-filter based on a Luenburger-style closed-loop stator current vector observer. We provide an accurate torque control strategy with the estimated disturbance, which is based on a torque command manipulation. In addition, the developed estimator is proven to work with any torque control schemes incorporating even with numerous lookup tables. The proposed disturbance estimation scheme has the advantage of being general and readily applicable to a wide range of other systems, such as PWM converters and symmetric machines.

Finite-Settling-Steps Direct Torque and Flux Control for Torque-Controlled Interior PM Motors at Voltage Limits

This paper proposes a voltage-limited finite-settling-step direct torque and flux control (FSS-DTFC) method with a constant switching frequency for torque-controlled interior permanent-magnet synchronous motors (IPMSMs). The proposed control law dynamically scales the voltage vectors on the hexagonal voltage boundary to ensure the maximum torque capabilities under the given operating conditions while simultaneously regulating the stator flux linkage magnitude under flux-weakening operation. Instead of relying on classical overmodulation methods at voltage limits, this paper developed two independent voltage truncation rules to facilitate the possible voltage vector choices. The analytical solution led to the dynamic voltage modification at each time step with respect to the available inverter voltage. The voltage-limited FSS-DTFC approach has potential advantages in achieving a fast transient torque trajectory and direct manipulation of the stator flux linkage while exploiting the maximum voltage excitation.

Induction Motor Control With a Small DC-Link Capacitor Inverter Fed by Three-Phase Diode Front-end Rectifiers

This paper presents a small film capacitor inverter-based induction motor control approach to enhance with reliability and power density of three-phase variable speed drive applications. A robust hybrid motor controller is developed to prevent performance degradation caused by the electrolytic capacitor-less inverter fed by front-end diode rectifiers. The structure of the controller combines a model-based controller (MBC) and a hexagon voltage manipulating controller (HVC). The MBC determines the command output voltage with the intersection of the torque and rotor flux linkage command. In the HVC mode, the command voltage vector is determined simply by the torque command and the hexagon-shaped inverter voltage boundary. Successful application of the control approach is corroborated by a graphical and analytical means that naturally lead to a single voltage selection rule. This paper also examines the operation sensitivity under motor parameter drifts to determine how to decouple its effect using a voltage disturbance state-filter design.

Hexagon Voltage Manipulating Control (HVMC) for AC Motor Drives Operating at Voltage Limit

This paper proposes a hexagon voltage manipulating control (HVMC) method for ac motor drives operating at voltage limit. The command output voltage can be determined simply by the torque command and the hexagon voltage boundary in the absence of motor current-regulating proportional-integral (PI) control gains, additional flux weakening (FW) controllers, and observers for closed-loop control. These attributes reduce the time and effort needed for calibration of the controller in the nonlinear voltage-limited region. The proposed HVMC accomplishes the “true” maximum available voltage utilization, allowing for higher efficiency than that of the current vector controller (CVC) alone in the FW domain. In addition, a voltage selection rule was proposed to determine the unique HVMC solution between two possible voltage vectors. The successful application of the control approach was corroborated by a graphical and analytical analysis. The proposed control approach is potentially applicable to a wide range of control designs for ac drives.

Comprehensive PM motor controller design for electrically assisted turbo-charger systems

A hybrid position sensorless motor control strategy is developed to meet the challenges of electrically assisted turbo-charger (EATC) systems integrated into an automotive engine plant. The proposed controller has a straightforward structure with properties that combines the conventional current vector controller (CVC) and the proposed hexagon voltage modulation controller (HVMC). The proposed HVMC accomplishes the maximum available voltage utilization, allowing a larger motor torque generation per ampere than that of current control alone in the 2nd flux weakening region. This feature leads to a higher PM flux linkage of the motor design, which lets us capture the reliable back-EMF information at the starting speed. In addition, setting a lower bound of the base speed can be achieved to avoid non-ideal current regulation problems at higher speeds. The proposed structure can offer further flexibilities in motor design and drive control, beyond a conventional turbo-charger.

Wide-speed direct torque and flux control of torque-controlled IPMSM drives

This paper proposes a voltage-limited finite-settling-step direct torque and flux control (FSS-DTFC) method with a constant switching frequency for torque-controlled interior permanent-magnet synchronous motors (IPMSMs). The proposed control law dynamically scales voltage vectors on the hexagonal voltage boundary to ensure maximum torque capabilities at given operating conditions, while simultaneously regulating the stator flux linkage magnitude under flux-weakening operation. Instead of evaluating control performance based on intuitive voltage selection rule, this paper focuses on developing a discrete time function of the rate of change of an air-gap torque for facilitating optimal voltage vector choices. Then, this analytical solution leads to optimal voltage modification at each time step with respect to the available inverter voltage. The voltage-limited FSS-DTFC approach has potential advantages of achieving fastest transient torque trajectories and direct manipulation of the stator flux linkage while exploiting maximum voltage excitation.

Active Mechanical Vibration Control of Rotary Compressors for Air-conditioning Systems

Recent power electronics and variable-frequency motor drive technologies have been applied to air conditioners to improve efficiency and power density. However, the mechanical vibrations and acoustic noise resulting from the compressor still remain as a serious problem. This paper presents the development and implementation of an online disturbance state-filter for the suppression of multiple unknown and time-varying vibrations of air conditioning systems. The proposed design has a form of the state-filter based on a Luenburger-style closed-loop speed observer. An active vibration decoupling strategy with an estimated disturbance is provided, which manipulates a motor torque command. Since the proposed estimation does not require any additional transducers or hardware for obtaining real-time information upon disturbances, it is suitable for retrofitting industrial air conditioners.

Disturbance decoupling control of voice coil motors for precise automated manufacturing processes

In this paper, a controller design of a voice coil motor (VCM) with enhanced disturbance input decoupling performance, especially for precise automated manufacturing processes, is proposed. To enhance the force control accuracy, a disturbance state filter for force control is applied to estimate and compensate for the varying dynamics of VCM systems, such as nonlinearly variable loads and other uncertainties. The state filter estimation accuracy in the presence of system parameter errors is fully analyzed. In addition, the proposed disturbance decoupling method is computationally efficient and robust to other parameter errors. The proposed algorithm is implemented in a developed VCM actuator and verified to be appropriate for a VCM drive system with unknown disturbances.

Soft-restarting of free-run induction motors driven by small DC-link capacitor inverters

This paper presents a small film capacitor inverter-based induction motor control approach to enhance with reliability and power density of three-phase variable speed drive applications. A robust hybrid motor controller is developed to prevent performance degradation caused by the electrolytic capacitor-less inverter fed by front-end diode rectifiers. The structure of the controller combines a model-based voltage controller (MVC) and a hexagon voltage manipulating controller (HVMC). The MVC determines the command output voltage with the intersection of the torque and rotor flux linkage command. In HVMC mode, the command voltage vector is determined simply by the torque command and the hexagon-shaped inverter voltage boundary. Successful application of the control approach is corroborated by a graphical and analytical means that naturally lead to a single voltage selection rule. This paper also examines the operation sensitivity under motor parameter drifts to determine how to decouple its effect using a voltage disturbance state-filter design.