PWM-based Sliding-mode Controller Research Articles

A PWM-based Sliding Mode Control Scheme for Isolated Solar Photovoltaic Systems

A PWM-based Sliding Mode Control Scheme for Isolated Solar Photovoltaic Systems

Analysis, design and implementation of a fixed frequency PWM-based sliding-mode controller for quadratic buck converter

The DC-DC converters are well-known due to their nonlinear and time-variant nature. This paper addresses the investigation of a fixed frequency pulse width modulation (PWM) based sliding mode current controller applied to quadratic buck converter (QBC). The QBC is well-suited for very low voltage central processing unit (CPU) voltage regulator applications with high-step-down DC-DC conversion ratios. The sliding mode current control features the reference current profile generation, satisfaction of hitting, existence and stability conditions besides the selection of sliding surface parameters. The simulation of QBC is realised for 19 V~8 V/1V at 50 KHz using PSIM software. The experimental results are presented in order to validate the simulation results. The strength of this control strategy is analysed for both line and load regulations.

Robust control of mismatched buck DC–DC converters by PWM-based sliding mode control schemes

In this paper, two control methods are proposed to control mismatched dc–dc buck converters. In the first method, called Method I, a multiple surface sliding mode control is proposed to handle mismatched load uncertainty. A major problem associated with multiple surface sliding mode control viz. ‘explosion of terms’ is handled by a disturbance observer. Another method, Method II, based on simultaneous state and disturbance observer is proposed as a further improvement over Method I in terms of sensor requirement. The practical stability of the proposed schemes is proved. The performance of both the methods are assessed for regulation and tracking of output voltage under various uncertainties and is compared with a method based on extended state observer. It is shown by simulation and experimentation that the transient and steady state performance of both the controllers are satisfactory.

Design of Fixed-Frequency Pulsewidth-Modulation-Based Sliding-Mode Controllers for the Quadratic Boost Converter

The steady-state regulation error in power converters that use the pulsewidth-modulation (PWM)-based sliding-mode (SM) controllers can be alleviated via the use of a double-integral term of the state variables in the sliding surface. However, this not only increases the order of the controller but may also require more variables like two currents in feedback. Ideally, the controller should be of a lower order to reduce the cost and for ease of implementation. The main objective of this brief is to design a fixed-frequency PWM-based SM controller for the quadratic boost converter using a reduced number of state variables. The SM controller used in this brief requires only one current for its implementation while enjoying the advantages offered by both fixed-frequency and double-integral approaches. Apart from this, two SM controllers using the input and output inductor currents of the converter are separately designed to find the most suitable inductor current for the controller design. Such study is especially required for the higher order converters wherein more than one inductor currents are available for feedback purposes. It is shown that the controller using the input inductor current is preferred over the controller using the output inductor current. Some simulation and experimental results are also provided to validate the theoretical conclusions.

PWM-Based Sliding Mode Controller for Three-Level Full-Bridge DC-DC Converter that Eliminates Static Output Voltage Error

This paper proposes a pulse width modulation (PWM)-based sliding mode controller (SMC) for a full-bridge DC-DC converter that can eliminate static output voltage error. Hysteretic SMC in DC-DC converter does not have a fixed switching frequency, and applying hysteretic SMC to full-bridge converters is difficult. Fixed-frequency SMC, which is also called PWM-based SMC, based on equivalent control overcomes these shortcomings. However, the controller order reduction in equivalent control in PWM-based SMC causes static output voltage error. To resolve this issue, an integral item is added to the PWM-based SMC. Sliding mode coefficients are designed by applying a standard second-order system to the sliding mode surface. The effect of adding an integral item on the controller is analyzed, and an integral coefficient design method is proposed. Experiment results on a three-level full-bridge DC-DC converter verify the control scheme and design method proposed in this paper.

Matlab-Based Modeling and Simulations to Study the Performance of Different MPPT Techniques Used for Photovoltaic Systems under Partially Shaded Conditions

A pulse-width-modulator- (PWM-) based sliding mode controller is developed to study the effects of partial shade, temperature, and insolation on the performance of maximum power point tracking (MPPT) used in photovoltaic (PV) systems. Under partially shaded conditions and temperature, PV array characteristics become more complex, with multiple power-voltage maxima. MPPT is an automatic control technique to adjust power interfaces and deliver power for a diverse range of insolation values, temperatures, and partially shaded modules. The PV system is tested using two conventional algorithms: the Perturb and Observe (P&O) algorithm and the Incremental Conductance (IncCond) algorithm, which are simple to implement for a PV array. The proposed method applied a model to simulate the performance of the PV system for solar energy usage, which is compared to the conventional methods under nonuniform insolation improving the PV system utilization efficiency and allowing optimization of the system performance. The PWM-based sliding mode controller successfully overcomes the issues presented by nonuniform conditions and tracks the global MPP. In this paper, the PV system consists of a solar module under shade connected to a boost converter that is controlled by three different algorithms and is generated using Matlab/Simulink.

Monolithic quasi-sliding-mode controller for SIDO buck converter with a self-adaptive free-wheeling current level

An analog implementation of a novel fixed-frequency quasi-sliding-mode controller for single-inductor dual-output (SIDO) buck converter in pseudo-continuous conduction mode (PCCM) with a self-adaptive freewheeling current level (SFCL) is presented. Both small and large signal variations around the operation point are considered to achieve better transient response so as to reduce the cross-regulation of this SIDO buck converter. Moreover, an internal integral loop is added to suppress the steady-state regulation error introduced by conventional PWM-based sliding mode controllers. Instead of keeping it as a constant value, the free-wheeling current level varies according to the load condition to maintain high power efficiency and less cross-regulation at the same time. To verify the feasibility of the proposed controller, an SIDO buck converter with two regulated output voltages, 1.8 V and 3.3 V, is designed and fabricated in HEJIAN 0.35 μm CMOS process. Simulation and experiment results show that the transient time of this SIDO buck converter drops to 10 μs while the cross-regulation is reduced to 0.057 mV/mA, when its first load changes from 50 to 100 mA.