Space vector modulation based proportional resonant current controller with selective harmonics compensation for matrix converter systems

This paper proposes a modified proportional-integral (PI) controller and compares it with a proportional-resonant (PR) controller. These controllers are tested on a three-phase direct matrix converter (MC). The modified PI controller involves current feedforward together with space vector modulation (SVM) to control the MC output currents. This controller provides extra control flexibility in terms of the current error reduction, and it gives improved steady-state tracking performance. When the coefficient of current feedforward is equal to the load resistor (K = R), the steady-state error is effectively minimized even when regulating sinusoidal variables. The total harmonic distortion is also reduced. In order to comparatively evaluate the modified PI controller, a PR controller is designed and tested. Both the modified PI and PR controllers are implemented in the natural frame (abc) in a straightforward manner. This removes the coordinate transformations that are required in the stationary (αβ) and synchronous (dq) reference frame based control strategies. In addition, both controllers can handle the unbalanced conditions. The experimental and simulation results verify the feasibility and effectiveness of the proposed controllers.

The Current control of voltage source inverters are realized by many techniques such as Proportional Integral (PI), Proportional Resonant (PR) and Hysteresis Current Control. The PR control works on an αβ frame and it involves less calculation process comparing to PI control. The αβ frame should be converted to dq frame in PI control. The PR control can easily implemented with digital control techniques due to the slow sampling frequency. PR control has very high proportional and integral gain at resonance frequency where it can mitigate low order harmonics. PR control can be implemented with other digital control techniques. In this study, a Seven-Level asymmetric cascade multilevel inverter simulation is realized with PR control. As a result of structure developed, the Total Harmonic Distortion (THD) is more lowered with respect to the structure without using PR control.

Integration of photovoltaic (PV) power to the grid is achieved using three-phase inverters with high-quality current waveforms. The new grid codes impose a limit on the total harmonic distortion (THD) value of the inverter’s current waveforms. Due to simple structure and ease of design, proportional integral (PI) controllers are the most widely adopted methods to control three-phase grid-connected inverters; however under abnormal grid conditions, PI controllers may suffer from instability problems. To address the aforementioned problem, this article proposes an expert knowledge-based proportional resonant (PR) control for the integration of PV power to the grid under abnormal grid conditions. The proposed control method adjusts the control parameters based on rules generated from expert knowledge. Initially, parameters of the proposed control methods are optimized using particle swarm optimization (PSO) method. The proposed control is tested with a 100 kW grid-tied three-phase inverter unit under normal and abnormal grid conditions and its performance are compared with PI and fixed gain PR control methods. Moreover, the proposed control is tested experimentally with a scaled down 300 W grid-tied inverter lab prototype module. From the simulation and experimental results, it is verified that the proposed adaptive PR control technique is capable of providing low THD in the injected current under abnormal grid conditions compared with fixed gained PR controllers.

Recent technological advances in power electronics has led to a substantial increase in nonlinear loads. This has led to deterioration in quality of power in distribution networks and sparked interest in power quality issues and its solutions. This paper discusses the issue of harmonics, which is a power quality problem: their estimation and subsequent control and mitigation using a shunt compensator. The control of shunt compensator using proportional-resonant (PR) controllers has been designed and implemented. Literature review presents a wide range of control techniques and proportional-integral (PI) controllers are the simplest and most commonly used in industries. Recently introduced PR controllers have been presented as an alternative to PI controllers. These controllers are believed to overcome the shortcomings of the conventional PI controller, which include the presence of steady-state errors and the need for transformation in three-phase systems using the synchronous dq frame. The added advantages of PR controllers include the possibility of implementation for simultaneous detection and extraction of harmonic components without requiring excessive computational efforts. This paper highlights the application of PR controller for harmonic estimation and their reduction in the utility grid using shunt compensator. Closed loop control using PR controllers as filters has been demonstrated using simulation as well as experimental results. Extensive results are presented for different loading conditions, and they demonstrate the application of PR controllers in grid-interfaced converter for power quality improvement.

The performance analysis of a proportional-resonant (PR) controller for single-phase inverter is presented in this paper. One of the most important issues in inverter control is the load current regulation. In literature, proportional-integral (PI) controller has been used in current-controlled of voltage source inverter (VSI) in various applications such as grid-connected and stand-alone systems. The PI current control of a single-phase inverter has well-known drawbacks which are steady-state magnitude error, phase error and also it has a very limited disturbance rejection capability. Proportional-resonant (PR) controller has been introduced to overcome these problems. As compared with the conventional PI controller, the PR controller can introduce an infinite gain at the fundamental frequency hence, it can achieve zero steady-state error without requiring a complex transformation and a dc-coupling technique. Performance analysis of PR controller in both steady-state and transient conditions has been carried out in this study by simulation and experiment and compared with the conventional PI controller. Both controllers were implemented on a floating-point TMS320F28335 digital signal controller and tested at 250W output power using a resistive load. Simulation and experimental results verified the controller performances.

The single-phase inverters with higher-order filters are popular for grid interface of photovoltaic (PV) systems. Increasing penetration of these systems coupled with nonlinear loads impact grid voltage quality. The grid code restricts the injection of harmonic currents into the grid. To reduce the harmonic distortions in the current that is fed to the grid, this article presents a Proportional-Resonant (PR) controller for a HERIC inverter topology with an integrated input side dc-dc converter. The traditional controllers cannot restrict the injected current harmonic content when the grid voltage is polluted. To solve this problem a PR controller with Harmonic Compensators (HC) has been presented to limit the harmonic distortions. A 1.5kVA single-phase grid-tied inverter with an LCL filter on the output side has been simulated in MATLAB. Simulation studies on a grid-tied PV inverter have been carried out, and performance has been investigated and compared with other controllers for different levels of the injected grid current. The developed grid-tied inverter with a PR controller with HC is suitable for achieving low total harmonic distortion which guarantees that the system provides satisfactory performance according to the grid standards.

Loss minimization of a Quadratic Boost Converter (QBC) for Multilevel inverter (MLI) fed Induction Motor (IM) is intended so that the efficiency can be optimized. QBC with MLI is placed between the DC-source & the induction motor. This work proposes QBC-between the DC source and inverter. The DC output is boosted by QBC and fed to the inverter. The inverter output activates the induction motor. This work deals with loss minimization of closed loop Quadratic boost converter multilevel inverter (QBCMLI) system using Proportional Integral (PI), Fractional Order PID (FOPID) and Proportional Resonant (PR) controllers. The objective of the proposed system is to maximize the efficiency of the induction motor drive modules incorporating PI, FOPID and PR controllers. The investigations are done in closed loop systems. Voltage mode PRC algorithm is proposed to optimize the performance of QBCMLIIM system. The outcome illustrates minimization of losses by utilizing PR controlled QBCMLIIM system.

Aiming at the output current of grid-connected inverter of LCL filter, this paper put forward a PR (Proportion Resonant) control technology based on BP (Back Propagation) neural network. Combining the traditional digital PID control technology and the novel PR control technology, an increment PR controller algorithm as well as its parameter self-tuning method based on BP neural network were proposed, Simulation experiment, confirmed that the output current of gird-connected inverter controlled by PR control technology based on BP neural network had better steady state adaptive ability and self-learning ability. Trained results turn out to be a good effect of control of grid-connected current.

This paper proposed a control method for output and circulating currents of modular multilevel converter (MMC). The output and circulating current are controlled with the help of arm currents, which contain DC, fundamental frequency, and double frequency components. The arm current is transformed into a stationary reference frame (SRF) to isolate the DC and AC components. The AC component is controlled with a conventional proportional resonant (PR) controller, while the DC component is controlled by a proportional controller. The effective control of the upper arm and lower arm ultimately controls the output current so that it delivers the required power to the grid and circulating current in such a way that the second harmonic component is completely vanished leaving behind only the DC component. Comparative results of leg-level control based on PR controller are included in the paper to show the effectiveness of the proposed control scheme. A three-phase, five-level MMC is developed in MATLAB/Simulink to verify the effectiveness of the proposed control method.

The proportional–integral (PI) control is usually applied in synchronous reference frame to regulate the output voltage of three-phase voltage source inverter (VSI). However, the PI controller is constrained by the capability of suppressing harmonic and negative sequence components; besides, its direct application in single-phase VSI is limited. While the proportional–resonant (PR) control can track ac reference and achieve harmonic suppression in stationary frame for both single-phase and three-phase VSI. Due to the high order of the resonant controller, lots of efforts are needed during the parameter design to get a satisfactory performance, such as trial-and-error. In this article, the way to approximately reduce the order of the resonant controller in the discrete time domain is presented, and then a method of selective pole placement and cancellation for the PR control design used in VSI is proposed. With the proposed method, the closed-loop pole-zero distribution of the PR control structure used in the VSI is well handled, and the parameters of the feedback controller and the reference feedforward controller are directly calculated by placing the selected poles and zeros in desired positions. The procedure of the parameter design is facilitated, and the performance of the VSI with PR control is improved.

In this work, an optimal power sharing controller for a three-phase Inverter-based Generator (IG) in a synchronous d-q reference frame is presented. The optimization of this controller is computed using a Linear-Quadratic (LQ) tracking index that measures the tracking error. This approach has many advantages regarding to stability and robustness over classical Proportional-Integral (PI) or Proportional-Resonant (PR) controllers that use droop functions for power sharing. In addition, a comprehensive model that represents a grid-connected IG sharing power to the main grid is developed using the superposition principle. This model integrates the Voltage-Current (V-I) and power sharing dynamics in a single state space expression. To the best of our knowledge, although there have been approaches in V-I and power sharing control that improve microgrid stability and transient response, there are no formal methods that integrate both controllers as a single entity. The results of this method were compared against a known Proportional-Resonant controller that use droop functions for power sharing. Results show that the optimal power sharing controller improves transient response, improves power decoupling, and also reduces the quadratic cost associated with microgrid states and inputs.

In order to solve the problem of 3rd, 5th and 7th harmonics in the inverter modulation process of Open-Winding Permanent Magnet Synchronous Motor with Common DC Bus (OW-PMSM-CDCB). In this paper, with the help of traditional Proportional-Integral (PI) and Proportional-Resonant (PR) control, an improved Proportional-Integral-Resonant (QPIR) harmonic suppression method which can be applied to different speed conditions is studied. The 3rd, 5th and 7th harmonics tracking are realized to solve the problem that PR control cannot change with the speed change. The stability proof and parameter selection of QPIR are given. Finally, an OW-PMSM-CDCB drive system experimental platform was built for verification. Simulation and experimental results show that the QPIR control strategy can effectively suppress the 3rd, 5th and 7th harmonics of the OW-PMSM system at different speeds.

Parallel operation of inverters is one method to increase power ratings of motor drives for high power applications. This paper proposes a novel variation of Field-Oriented Control for parallel inverters driving AC machines. The proposed strategy is implemented directly in the natural (abc) reference frame and overcomes many issues faced by conventional controllers for parallel motor drives. At the core of this control strategy is a proposed Resonant Proportional Integral (RPI) controller, which uses integrated plant dynamics to achieve the functionality of a second-order Proportional Resonant (PR) controller using only a first-order Proportional Integral (PI) controller. Hence the proposed control strategy is very simple, requiring only an inner first-order RPI controller for the the stator currents, and an outer PI controller for motor speed and maximum torque per ampere (MTPA) operation. A theoretical analysis of the RPI controller is given, which is supported by simulation and experimental results.

Single-phase Static Var Generator (SVG) is widely used in fields like electrified railway and Distribution Generation (DG) etc. However, it has special requirements and difficulties, e.g. a single-phase SVG is not easy to achieve satisfactory performance of tracking the AC reference comparing with the three-phase one. In three-phase system, a PI controller can track the reactive current without steady-state error theoretically because it is converted to DC component in synchronous rotating coordination. What's more, because of the constraints of device switching capacity and grid voltage disturbances like low-order harmonic distortion, the harmonic characteristics of device output current is poor. Aiming at improving the accuracy of reactive power compensation, ability of anti-disturbance of grid voltage and the distortion performance of the output current, this paper presents a Proportional Resonant (PR) controller with multiple resonant frequencies for single-phase SVG. The controller design is taken in z-domain for convenient digital implementation. The superiority of control strategy is verified through created simulation models and experimental prototype.

The off-grid village electrification is made viable by utilizing the full potential offered by renewable energy sources (RESs). Integrating more than one resource i.e. wind and solar, offers self-sufficiency of power due to their complementary nature. The intermittency issues raised by RESs are overcome by using a battery as the storage. The battery reduces the uncertainty during demand rise, power deficiency and overloading with its faster response than diesel generators and micro-turbines. This work deals with the wind energy/solar photovoltaic (PV)/battery energy storage (BES) operating in coordinated manner to meet the high power residential loads at village scale. For the required speed regulation of a wind turbine driven generator, the traditional proportional integral (PI) controller is replaced by evolution inspired biogeography based optimization control (BBO) based PI controller. The relevant issues identified by a use of fixed gain PI controller such as, unsuitable regulation due to incorrect tuning are addressed by the use of BBO tuned speed controller providing fine-tuning of the weighting factors. Whereas, in the voltage control, the performance degradation issue of PI controller while dealing with AC quantities, is dealt with adaptive proportional resonant (PR) controller along with disturbance observer based phase locked loop (DO-PLL). The DO control filters the load current component and improves the power quality at point of common coupling (PCC). The battery is deployed through a bidirectional converter, acts as a residential storage for backing up the power firming RESs production. Performance improvement obtained from a laboratory developed test setup verifies the microgrid effectiveness at RESs generation variability and load changes.