Fixed frequency current controller applied to shunt active filters with UPF control in four-wire power systems

Current Control of the Isolated Self-Excited Induction Generator using Shunt Active Filter

Permanent magnet synchronous motor (PMSM) is the most widely used motor in electric vehicles (EV) due to its high power density and high efficiency. Conventional direct torque control (DTC) is developed to improve the performance of speed response of the PMSM drive but it suffers from higher torque ripples. Therefore a space vector modulation (SVM) based DTC has been developed to enhance the speed response. Due to the use of flux comparator and torque comparator conventional DTC has disadvantages such as higher torque and current ripples at steady state. To improve the performance of PMSM drive a space vector pulse width modulation is used with 3 level NPCI. To improve the performance of 2 level inverter in the PMSM drive is replaced with a neutral point clamped inverter (NPCI). Also, the switching selection strategy of SVM is modified using nearest three space vector pulse width modulation to reduce the total harmonic distortion (THD) in the inverter output. The simulation outcome proves that the SVM technique implementation in DTC for 3 level NPCI yields good performance for PMSM.KeywordsElectric vehicles (EV),voltage source inverter (VSI)Direct torque control (DTC)Neutral point clamped inverter (NPCI)Permanent magnet synchronous motor (PMSM)Space vector modulation (SVM)Total harmonic distortion (THD)

Active power filters have been used in practice to suppress the harmonic interference in power systems. To compensate for harmonic currents of loads active power filters are usually connected to power systems in parallel with the loads. These filters which are called shunt active filters here are very effective to loads that can be considered as current sources, such a thyristor rectifiers with large DC reactances. Many papers have covered the shunt active filters applied to these currentsource loads. No paper, however, has discussed characteristics of the shunt active filters when they are applied to voltage-source loads.On the other hand, since more and more diode rectifiers with capacitive DC filters are used recently, harmonics generated by which become an issue.The diode rectifier with capacitive DC filters behaves like a voltage source rather than a current source. When a shunt active filter is applied to such a diode rectifier, the current injected from the shunt active filter may flow into the diode rectifier. As a result, harmonics of the source current cannot be reduced effectively, and harmonic current flowing into the diode rectifier increases largely.This paper reveals the above-mentioned problem of shunt active filters analytically and experimentally. Then a series active filter is proposed to suppress harmonic current of the diode rectifiers. The features, operating conditions, and considerations of shunt active filters and series active filters are described analytically and demonstrated experimentally. Taking a diode rectifier with capacitive DC filter as a typical voltage-source load, compensation characteristics of shunt active filters and series active filters are discussed by experiment and simulation. The validity of the series active filters is illustrated experimentally.

This paper present the mitigation of line current harmonics using control of shunt active power filter (SAPF). The three phase system is connected to nonlinear load which cause harmonics to affect the power system. The control of shunt active power filter is not only compensating harmonics but also compensate reactive power. Voltage source inverter(VSI) at using SAPF reference current control strategies; instantaneous real and reactive power theory (p-q theory), modified synchronous rotating reference frame theory(Modified d- q theory) with PI control and current control method at using hysteresis current control and SPWM controller. The different control technique of SAPF is based on reference current generation and current control method simulated by using MATLAB Simulink.

This chapter focuses on pulse width modulation (PWM) schemes for the highpower two‐level inverter, where the device switching frequency is normally below 1 kHz. A carrier based sinusoidal PWM (SPWM) scheme is reviewed, followed by a detailed analysis of space vector modulation (SVM) algorithms. The conventional SVM scheme usually generates both even‐ and odd‐order harmonic voltages. The chapter analyses mechanism of even‐order harmonic generation, and presents a modified SVM scheme for even‐order harmonic elimination. The primary function of a voltage source inverter (VSI) is to convert a fixed DC voltage to a three‐phase AC voltage with variable magnitude and frequency. The dwell time for the stationary vectors essentially represents the duty‐cycle time of the chosen switches during a sampling period. The dwell time calculation is based on 'volt‐second balancing' principle, the product of the reference voltage and sampling period equals the sum of the voltage multiplied by the time interval of chosen space vectors.

Variable frequency and variable voltage are increasingly supplied by a three-level voltage source inverter for variable speed applications. The appropriate output voltage at the line side of the inverter is obtained using a suitable pulse width modulation technique. This chapter investigates the three-level Diode Clamped or Neutral Point Clamped topology, which is a popular multi-level topology. The modulation wave is generated using two Sine-triangle methods and two Space Vector Pulse Width Modulation methods. To produce the PWM signals for the three phases, these modulation waves are compared to a triangular carrier. Instead of the three phase modulating waves used in SPWM, a rotating reference voltage vector is used as a voltage reference in SVPWM methods. The magnitude and frequency of the line side's fundamental variable are controlled by the magnitude and frequency of the reference vector, respectively. Because of its higher dc bus utilization and lower harmonic distortion than SPWM, Space Vector Modulation has become a common PWM technique for three-phase Voltage Source Inverters. In MATLAB/SIMULINK software, the four PWM methods are simulated and compared for THD and Capacitor Balance. Embedded Editor and Matlab Editor Functions are used to build the programs. As compared to Sine PWM, simulation results show that Space vector PWM better utilizes dc bus voltage, produces less THD, and improves capacitor balance.

This chapter focuses on pulse width modulation (PWM) schemes for the highpower two???level inverter, where the device switching frequency is normally below 1 kHz. A carrier based sinusoidal PWM (SPWM) scheme is reviewed, followed by a detailed analysis of space vector modulation (SVM) algorithms. The conventional SVM scheme usually generates both even??? and odd???order harmonic voltages. The chapter analyses mechanism of even???order harmonic generation, and presents a modified SVM scheme for even???order harmonic elimination. The primary function of a voltage source inverter (VSI) is to convert a fixed DC voltage to a three???phase AC voltage with variable magnitude and frequency. The dwell time for the stationary vectors essentially represents the duty???cycle time of the chosen switches during a sampling period. The dwell time calculation is based on 'volt???second balancing' principle, the product of the reference voltage and sampling period equals the sum of the voltage multiplied by the time interval of chosen space vectors.

This paper proposes the modified space vector pulse width modulation (SVPWM) control algorithm for the three-phase voltage source inverter (VSI), which consists of traditional six switches VSI and three bidirectional switches for creating the ac decoupling circuit. This topology has some advantages such as the ability to reduce the leakage ground current from PV panel and therefore improve the efficiency of photovoltaic (PV) energy conversion based on the principle of decoupling when the zero space vectors occur. Likewise, no current flows through six traditional switches in zero space vectors, thus they operate at lower average temperature. In this case, the conduction losses are reduced. For avoiding shoot-through states between six traditional switches and three bidirectional switches, a delay time has been added to switching time and managed carefully to guarantee THD of output voltage. Operating of the inverter with the modified SVPWM method is simulated by using Matlab/Simulink software and implemented in the experimental prototype by using FPGA Virtex 5 (Xilinx).

This paper describes a novel control strategy for shunt active filters the sinusoidal Fryze currents control strategy. The control strategy considers the presence of harmonics in the system voltage and load current simultaneously. Although the fundaments of the pq theory is used to better explain the proposed control strategy, it is not directly used, since the Clarke transformation (abc to /spl alpha//spl beta/0 transformation) is avoided. In fact, the fundaments of the pq theory is inserted in a minimization method - the generalized Fryze currents, which together with a robust synchronizing circuit (PLL control circuit), form a concise controller for shunt active filter. The shunt active filter provides current compensation, such that the compensated current drawn from the network is sinusoidal and balanced, corresponding to the fundamental positive-sequence component of the load current, plus an additional fundamental positive-sequence component to cover losses in the power circuit of the shunt active filter. Simulation results are presented to validate the control strategy.

This paper shows the method of improving the power quality using voltage source inverter based shunt active power filter. The procedure uses a simple method named synchronous reference current generation for reference current extraction .The proposed topic comprises of PI controller, high pass filter, phase locked loop, dc link capacitor. The switching signal generation for filter is from hysteresis current controller techniques. With the all these element shunt active power filter reduce the total harmonic distortion. This paper represents the simulation and analysis of the using three phase three wire system active filter to compensate harmonics .The proposed shunt active filter model uses balanced non-linear load. This paper successfully lowers the THD within IEEE norms and satisfactorily works to compensate harmonics. The model is made in MATLAB / SIMULINK and successfully reduces the harmonic in the source current.

Modulation techniques for current source inverters (CSIs) have traditionally been derived from those used for voltage source inverters (VSIs), with space vector modulation (SVM) and pulse width modulation (PWM) being the most popular. Among these, PWM is the preferred choice due to its simplicity and ability to offer the same benefits as SVM, such as increased phase voltage. Ideally, PWM from VSIs could be directly applied to CSIs, but this is not feasible because CSIs require a holistic consideration of all switches on the upper (positive) and lower (negative) rails. In contrast, VSIs allow for per-phase modulation, which enables the straightforward use of a PWM modulator. In this paper, a PWM method tailored specifically for CSIs without any requirements typical for SVM, such as sector identification, is proposed. Using linear algebra, a technique for generating duty cycles averaged over a switching frequency period is derived. These duty cycles are then fed into a specially for CSIs proposed multi-threshold pulse width modulator, which finally produces the gate signals. To validate our method, both simulation and extensive experimental results are presented. The proposed approach is general and applicable to CSIs with any number of phases.

Usage of Active power filters is increased in this moderen era as they are capable to reduce harmonics effectively. Shunt Active Filters are proven to diminish harmonics compared to all other devices. Many control strategies has been developed till date to control Shunt Active Power filter. In soft computing techniques generally fuzzy logic has been used with mamdani type of fuzzy logic controller. This paper presents comparison of mamdani and TS type fuzzy logic controller to control the three-phase shunt active power filter. Fuzzy logic method is used to tune PID controller to autotune controller. Instantaneous Reactive Power theory is implemented to generate reference currents. Simulation is done in MATLAB to verify the results.

A new switching scheme, which combines conventional space vector modulation (SVM) and carrier-based pulse width modulation (CBPWM), is proposed for a three-phase four-leg voltage source inverter (VSI). The proposed algorithm is simpler than conventional three-dimensional space vector modulation (3-D SVM) and easy in implementation in a real-time DSP system, it avoids the selection of a prism and tetrahedron in a 3-D SVM, therefore alleviates the computation burden of the DSP. Also, the concept of near-state pulse width modulation (NSPWM) method, which is used in a three-phase three-leg inverter to reduce the common mode voltage (CMV) noises, can be adopted in this algorithm so as to reduce the common mode voltage for a three-phase four-leg VSI. The feasibility of the proposed modulation technique is verified by both computer simulation and experimental results.

This paper describes a single-phase modified packed U-cell seven-level multilevel inverter (MPUC7) with finite control set model predictive control (FCS-MPC) for a single phase shunt active power filter application. The shunt active filter can directly inject the harmonic load current and compensate for the reactive power of the load and thus, make the grid current sinusoidal and in-phase with the grid voltage. The active filter improves the power factor and THD of current at point of common coupling (PCC). The MPUC7 is a six switch seven level inverter with only two dc-link capacitors. The mathematical model of shunt connected MPUC7 converter is explained for derivation of the next sample prediction required for FCS-MPC. The cost function for the constraint of tracking current and regulating the two dc-link voltage is mentioned. The filter reference currents are derived using direct control method. The single-phase active filter application is simulated in the Matlab/Simulink to validate the operation and robustness of the FCS-MPC current controller. Various non-linear load changes are simulated to verify the effect on dynamic operation.

This paper presents a modeling and a nonlinear control of three-phase voltage source shunt active filter. The modeling is based on the abc/dq transformation of the AC system variables. The currents injected by the active filter are controlled in the synchronous orthogonal dq frame using a decoupled nonlinear control strategy. The reference harmonic components are extracted from the sensed nonlinear load currents by applying the synchronous reference frame method, where a three-phase thyristor bridge rectifier with R-L load is taken as the nonlinear load. The voltage level of the DC side is regulated using a linearizing feedback control. The reference current needed to maintain a regulated DC voltage is added to the current loop reference. The transfer functions of the two loops are developed and synthesized to obtain the desired stability and dynamic response. Simulation results confirm the performances considered theoretically for the shunt active filter topology.