Three-phase Input Currents Research Articles

Design and Implementation of Input AC Filters and Predictive Control for Matrix-Converter Based PMSM Drive Systems

Matrix converters have many advantages, including high-efficiency, single-stage AC/AC energy conversion, bidirectional power flow, a near-unity input power factor, sinusoidal three-phase input currents, and sinusoidal three-phase output currents. However, matrix converters have 360 Hz voltage pulsations at the virtual DC-bus, which produce input harmonic currents and output harmonic currents, which cause unsatisfactory responses. To solve the problem of the input harmonic currents, a systematic design of an input three-phase current modulation method and an input three-phase AC filter that uses two different design methods are proposed. In addition, to improve dynamic responses, two predictive speed controllers are investigated and compared, and a predictive current controller is studied to reduce the output harmonic currents. A digital signal processor and an FPGA are used to execute the control algorithms. Several experimental results validate the theoretical analysis and show that the proposed methods effectively improve the power quality of the PMSM drive system and its input power-source quality.

A novel filter for three-phase power factor correction voltage feedback loop under heavy DC voltage ripple condition

THD and the amplitude balance of three-phase input current are an important index for the performance of three-phase power factor correction (PFC). In general, when the hardware and the load of three-phase PFC are confirmed, the THD and amplitude balance of three-phase input current mainly depend on voltage and current feedback loop of PFC. Firstly, this paper designs the traditional voltage and current feedback loop for three-phase PFC according to traditional small signal theory. Secondly, this paper studies the designing difficulty of large dc voltage ripple for PFC voltage controller and puts forward a new dc voltage ripple filter which can eliminate the ac component of sampling dc bus voltage. Finally, this paper proposes a novel filter with dc voltage ripple frequency adaption function to copy with the frequency variety of the voltage ripple caused by the change of the output inverter frequency. With the help of the proposed algorithm the distortion of three-phase 3 input current reference decreases rapidly, therefore, the low THD and good amplitude balance of three phase input current will be achieved.

Three-Phase Three-Level Neutral Point Clamped Rectifier with Predictive Control Method without Employing Weighting Factor

A predictive control method using injected offset voltage to achieve neutral point (NP) voltage balance of three-phase three-level neutral point clamped (NP) rectifiers, without employing a weighting factor, is proposed in this study. One of the biggest problems with the three-level NP rectifiers is the dc link capacitor voltage imbalance. Therefore, it is necessary to maintain the balance of the NP voltage in addition to synthesize the three-phase sinusoidal input current by control methods. Conventional predictive control methods for the NP rectifiers have used a weighting factor in a cost function that determines the control ratio of the input currents and the capacitor voltage balance. As a result, it is burdensome to empirically redesign the weighting factor when the rectifiers’ parameter values and control conditions change. Unlike the conventional methods, the proposed approach without the weighting factor can significantly eliminate differences between two DC capacitor voltages by utilizing an offset voltage, which is generated by using the difference between the upper and lower capacitor voltages. Consequently, the proposed approach using the offset voltage injection can control the input currents and retain the balance of NP voltage. Simulation and experiments are presented to verify the correctness of the NP voltage balancing of the proposed control method.

Comparative analysis of two different interphase reactors applied in 36‐pulse diode rectifier

This study presents a comparative analysis of two different interphase reactors (IPRs) applied in a 36-pulse diode rectifier. One is traditional triple-tapped IPR; the other is unconventional IPR (UIPR) composed of the primary winding and secondary winding. The primary winding is double-tapped conventionally and the secondary winding is connected with a single-phase full-wave rectifier. The operation modes and optimal parameters of both IPRs are analysed. The effect of different operation modes on output currents of the two three-phase diode-bridge rectifiers, input currents and load voltages is also analysed. Under the optimal parameters, both rectifiers operate as 36-pulse diode rectifiers and reduce the total harmonic distortion of input line currents to be 5%. Especially, the proposed rectifier using UIPR is easy and simple to implement. Some experiments are provided to validate the theoretical analysis.

Analytical Modeling of Neutral Point Current in T-type Three-level PWM Converter

Since a T-type three-level PWM converter has several intrinsic advantages, it has been researched for various applications such as grid-connected converter systems. However, it necessarily requires an additional voltage control loop for balancing the upper and the lower DC-link voltage. To satisfy this requirement, an offset voltage is widely used to provide a neutral point current without affecting other variables such as total DC-link voltage and three-phase input current. However, these methods are mostly based on the averaged value between the applied offset voltage and the neutral point voltage or current, and there is no exact analytical model. Therefore, in this paper, the exact theoretical relationship between the offset voltage and the neutral point current is analyzed. This result can be expected to be useful for an effective voltage balancing control loop design as well as the better understanding of the whole system operation. The validity of the obtained analytical model is verified by simulation and experimental results.

A Two-Switch, Isolated, Three-Phase AC–DC Converter

A new, three-phase, single-stage, isolated ac–dc converter (rectifier) that employs only two switches and achieves less than 5% total harmonic distortion of the three-phase input currents and provides a tightly regulated, isolated, output voltage is introduced. The rectifier features zero-voltage-switching of both switches over the entire input and load range without any additional soft-switching circuitry. The rectifier is derived by combining the three-phase, power-factor-correction, discontinuous-current-mode boost rectifier that is also known as Taipei rectifier with the conventional LLC resonant half-bridge converter. The introduced rectifier requires single feedback loop with frequency control to regulate the output voltage. The evaluation was performed on a 1-kW prototype operating with a three-phase line-voltage range from 180 to 264 $V_{\text{L}-\text{L}}$ and delivering a tightly-regulated, isolated, output voltage of 54 V. The measured efficiency of the prototype at nominal line voltage V IN = 208 VL-L is above 95% from 90% of full load down to 50% of full load. The maximum voltage stress is approximately 430 V.

Six-Step Mode Control of IPMSM for Railway Vehicle Traction Eliminating the DC Offset in Input Current

In the six-step mode control of the interior permanent-magnet machine (IPMSM), inequality of the positive half-cycle length and the negative half-cycle length will bring about dc offset in the three-phase input current. This paper proposes a six-step mode control scheme of IPMSM for railway vehicle traction to eliminate the dc offset in input current. An approximately continuous rotor position signal is reconstructed in the field-programmable gate array chip. This position signal is used to generate the square drive signal for IPMSM in the flux-weaken region. Rotor position signal error of the resolver will also cause dc offset in the three-phase input current. A novel scheme using phase-locked loop to decrease the rotor position signal error is proposed. And using this scheme, the dc offset is eliminated from the three-phase input current. A seamless transition scheme from six-step mode control to space vector pulse width modulation (SVPWM) mode is proposed. The effectiveness of this six-step mode control scheme is proved by the experimental results.

Hybrid Control Scheme for Three-Phase Multilevel Unidirectional Rectifier Under Unbalanced Input Voltages

In this paper, a hybrid control scheme for three-phase Y-connected multilevel bridgeless rectifier (TMBR) under unbalanced input voltages is presented, based on the mathematical model of the TMBR topology, with the emphasis on the discussion for power fluctuation suppression, dc-link capacitor voltages balancing and input current zero-crossing distortion elimination. With the hybrid control scheme, the power fluctuation can be suppressed and three-phase input currents can flow with a purely sinusoidal waveform, besides, three-phase dc-link capacitor voltages can be controlled to be equal to each other under unbalanced input voltages. Moreover, the proposed hybrid control scheme is applicable to all other three-phase three wire multilevel unidirectional rectifiers under unbalanced input voltages. The validity of the proposed control scheme is demonstrated by the mathematical deduction. The simulations and experimental results verify that, with the proposed control scheme, TMBR can stably operate not only under balanced input voltages but also under unbalanced input voltages.

Compensation of DC Offset and Scaling Errors in Voltage and Current Measurements of Three-Phase AC/DC Converters

The dc offset and scaling errors in the voltage and current measurements cause the injection of undesired dc and unbalanced currents into the three-phase input currents and subsequently lead to voltage ripple at the dc output voltage of the ac/dc converter. This paper proposes a compensation scheme for current measurement error where the dc offset and scaling errors in the current measurement are estimated from the voltage ripple characteristics of the dc output voltage ripple combining with simple band-pass and low-pass filters. Meanwhile, the dc offset and scaling errors in the voltage measurement can be rejected by using an advanced current controller developed with a proportional resonant plus a repetitive controller designed in the synchronous ( d–q ) reference frame. The proposed control algorithm is able to effectively reject the impact of both voltage and current measurement error so that the three-phase input currents are regulated to be balanced and sinusoidal with ultralow dc current component. Meanwhile, the dc output voltage is also well regulated to be pure dc with a negligibly small voltage ripple. The proposed compensation method is developed without the need of extra hardware circuit, sensor, or precise information of system parameters so that it can be considered as more cost effective and robust solution. The effectiveness of the proposed solution is verified by experimental results.

Quasi-Z-Source Three-to-Single-Phase Matrix Converter and Ripple Power Compensation Based on Model Predictive Control

A quasi-Z-source three-to-single-phase matrix converter is proposed with low-frequency ripple power compensation. The employed impedance network between the source grid and the matrix converter extends the voltage gain; meanwhile, it has filtering function. Therefore, voltage step-up devices and an additional input filter are avoided. In addition, for a conventional three-to-single-phase matrix converter, input current of the source grid contains high harmonic components because of double-line-frequency pulsating power produced in single-phase side. A model predictive control-based ripple power compensation system is proposed in this paper to eliminate the low-order harmonic components from the three-phase input currents and voltages. Thus, the impedance parameters could be small in size and value. Simulation and experimental results verify the analysis and control of the proposed topology.

A duty cycle generation scheme for the three‐phase single‐stage full‐bridge PFC in balanced‐grid

In this Letter, the duty cycle generation scheme is presented and implemented, which can improve the input performances of the three-phase single-stage full-bridge power factor correction (PFC) converter. The analysis and discussion is aiming at the operation of the PFC converter in balanced grid condition. On the basis of the instantaneous expression of the three-phase input current, the ideal duty cycle of each phase is obtained. To achieve a good PF for each phase, a simplified duty cycle generation scheme is presented and implemented in the three-phase PFC converter. The simulating and experimental results based on a 500 W prototype show that after adoption of the presented duty cycle generation scheme, a higher PF has been achieved for each phase of the three-phase PFC converter.

An Improved Control Strategy of Three-Phase PWM Rectifiers Under Input Voltage Distortions and DC-Offset Measurement Errors

This paper proposes an enhanced current control strategy to reject the impact of dc-offset measurement error and the distortion in the supply voltage on the dc output voltage and the input current performance of three-phase pulse-width modulation rectifiers. The proposed current controller designed in the synchronous reference frame is developed with a proportional integral (PI) and two vector PI (VPI) controllers. The PI controller regulates the fundamental current to follow its reference generated from outer dc-link voltage control, meanwhile two VPI controllers tuned at the fundamental grid frequency ( $\omega _{s}$ ) and $6\omega _{s}$ are employed to eliminate the dc and harmonic components in the input current. Compared with the standard resonant controllers, the proposed VPI controller offers some advantages such as simpler and straightforward tuning process for controller gains and more robust control system against control delay time and frequency variations. Thanks to the effectiveness of the VPI controllers, the dc output voltage is controlled at a stable manner without any ac ripple, and the three-phase input currents are controlled to be balanced, sinusoidal, and extremely low dc component despite the presence of the dc-offset measurement error and distorted supply voltage conditions. Various experimental tests are provided to verify the effectiveness of the proposed control algorithm.

Control of Three-to-Five-Phase Matrix Converter Using Carrier-Based PWM Algorithm

Abstract - This paper proposes a simple Carrier-Based PWM (CBPWM) technique to control the three- to five-phase Direct Matrix Converter (3×5 DMC). The proposed technique uses the indirect modulation approach to control the 3×5 DMC such as a three-phase bidirectional rectifier followed by five-phase voltage source inverter (VSI). Based on this approach, it is possible to synthesize the desired five-phase output voltages with sinusoidal three-phase input currents and unity input power factor. A CBPWM method is suggested for each stage independently including both linear and overmodulation operating modes. By the proposed technique, in both operating modes, the maximum possible overall Voltage Transfer Ratio (VTR) are achieved. Moreover, this technique allows the input power factor to be controlled by controlling the input current displacement angle. The feasibility of the proposed technique has been verified by a series of simulation and experimental results based on Matlab/Simulink and dSPACE-DS1104 platform. The results show that, a sinusoidal output and input waveforms can be achieved with a maximum possible VTR in the linear region. However, in the overmodulation region, a maximum possible VTR is achieved at the cost of some distortion of output and input waveforms. Therefore, this technique can be used for the application where a higher VTR is essential.

A Low-Speed, High-Torque Motor Drive Using a Modular Multilevel Cascade Converter Based on Triple-Star Bridge Cells (MMCC-TSBC)

This paper provides experimental verification of a modular multilevel cascade converter based on triple-star bridge cells (MMCC-TSBC) for a low-speed, high-torque motor drive. The TSBC is one of direct ac-to-ac power converters capable of achieving bidirectional power flow and drawing/feeding three-phase sinusoidal input (supply-side) and output (motor-side) currents with any power factor at both sides. This paper designs, constructs, and tests a downscaled drive system combining a 400-V, 15-kW, phase-shifted-carrier PWM TSBC equipped with four bridge cells per cluster and a 320-V, 38-Hz, 6-pole, 15-kW induction motor loaded at the rated torque. Experimental waveforms obtained from the downscaled drive system verify stable operation across a broad range from a standstill to the rated speed, showing satisfactory start-up performance.

Modified one‐cycle‐controlled three‐phase pulse‐width modulation rectifiers under low‐output DC voltage conditions

The saddle pulse-width modulation (PWM) that can be obtained by injecting third harmonic current into sampled three-phase input currents is proposed to introduce in the conventional one-cycle control (OCC) strategy-based three-phase PWMrectifier on this study. In addition, for the three-level boost-type neutral-point-clamped structure rectifiers such as three-phase Vienna rectifier, the fluctuation in the neutral-point-potential (NPP) is analysed under modified OCC strategy. The proposed control scheme can not only improve the utilisation of DC bus voltage and the efficiency of converter without sacrificing the advantages of the conventional OCC scheme, such as no phase-locked loop and constant switching frequency, but also is beneficial to suppress the ripple in the DC-link voltage. Moreover, the neutral-point voltage loop is added in the proposed OCC scheme, and the neutral-point voltage controller is employed for controlling the unbalance DC voltage in the NPP which caused by the non-uniformity of parameters of components. The validity of the theoretical analysis and feasibility of the modified OCC strategy are verified by system simulation and experimental results based on a 5-kW prototype.

Active harmonic suppression of paralleled 12-pulse rectifier at DC side

In order to improve the ability of harmonic suppression, and reduce the loss of switching devices, this paper proposes an active harmonic suppression method at dc side of multi-pulse rectifier (MPR). The circulating current through secondary winding of active inter-phase reactor (AIPR) is derived from the current relation between the ac and dc sides of MPR when the three-phase input currents are sinusoidal simultaneously, and an applicable circulating current is presented. According to the relation between voltage across secondary winding of AIPR and the applicable current, it is confirmed that harmonic energy of input line current can be consumed by the resistor in series with the secondary winding. A half-bridge PWM rectifier is designed to abstract the harmonic power and to feed the load, which can realize the recycling of harmonic energy. Experimental results show that the power factor of the proposed system is approximately equal to one when the PWM rectifier operates normally, and that the proposed system has the ability of anti-variation of load and input voltage.

Three-Phase Single-Stage Four-Switch PFC Buck–Boost-Type Rectifier

This paper proposes a new three-phase single-stage power-factor corrector buck-boost-type rectifier topology. The typical topology uses a bridge configuration with six switches. This new topology only requires four switches, improving the rectifier efficiency as only one reverse-blocking power semiconductor conducts at any time. A vector-based sliding-mode control method for the three-phase input currents is also proposed. This fast and robust technique uses sliding mode to generate /spl alpha//spl beta/ space-vector modulation, which forces the input line currents to track a suitable sinusoidal reference. A near-unity power-factor operation of the rectifier is obtained using a sinusoidal reference in phase with the input source voltages. A proportional-integral controller is adopted to regulate the output voltage of the converter. This external voltage controller modulates the amplitude of the current references. The characteristics of the new rectifier are verified with experimental results.

Input power factor control of AC-DC series resonant DC link converter using PID operation

This paper proposes a method of power factor control for the three-phase input current of AC-DC series resonant DC link power converter systems. The proposed system has fast response, using high frequency resonance, soft switching (zero current switching), and natural commutation of thyristor switches. By implementing the PID operation strategy for switching control, the system performs reliable operation in the input power factor control, and the elimination of higher harmonic components can be achieved dramatically. The numerical and experimental results are presented in this paper.