Shiyan Yang

A MultiWinding Transformer Cell-to-Cell Active Equalization Method for Lithium-Ion Batteries With Reduced Number of Driving Circuits

The bidirectional cell-to-cell equalization methods perform well to prevent the series-connected batteries from overcharging and undercharging. However, it remains a challenge to achieve fast equalization and high equalization efficiency with low complexity. To address the issue, we propose a new bidirectional cell-to-cell active equalization method using a multiwinding transformer. The new method allows the energy to transfer directly from the highest voltage cell to the lowest one by fly-back operation or forward operation which gives a short balancing path and guarantees a fast equalization speed. We adopt the bidirectional switches of low conduction loss for high equalization efficiency. Since the bidirectional switches are turned on or off simultaneously, a common driving circuit for the bidirectional switch has been designed to reduce the number of the driving circuits by half. The experiments with a six 50-Ah Lithium-ion battery strings are conducted and the results have demonstrated that our new approach has achieved a good overall performance of equalization in terms of speed, efficiency, and complexity of the circuit.

Optimum Design of Interphase Reactor With Double-Tap Changer Applied to Multipulse Diode Rectifier

In this paper, the optimum turns ratio of an interphase reactor (IPR) with a double-tap changer is presented with mathematical analysis. The relation between the total harmonic distortion (THD) of the input current and the turns ratio is introduced, and based on the relation, the optimum turns ratio when the THD is minimal is obtained. Via another relation between the ripple coefficients of the output voltage and the turns ratio, the optimum turns ratio is derived when the ripple coefficient is minimal. Meanwhile, using the optimum turns ratio, a new formula to calculate the critical value of IPR is written. Some computer simulation results and experiments are included to support the theoretical analysis of optimum design.

Effect of Voltage Transformation Ratio on the Kilovoltampere Rating of Delta-Connected Autotransformer for 12-Pulse Rectifier System

This paper presents the effect of voltage transformation ratio on the kilovoltampere rating of delta-connected autotransformer for 12-pulse rectifier system and gives an optimal configuration of the autotransformer with minimal kilovoltampere rating and the least windings. According to the phasor diagrams and the relation between the output voltage and input voltage of the autotransformer under different connection ways, the effect of voltage transformation ratio on current through windings is analyzed, and corresponding expressions and waveforms of the currents are also obtained. Consequently, a relation between the position parameter and output power is established, and based on the relation, the effect of winding configuration on the kilovoltampere rating of the autotransformer is analyzed, which can be used to obtain the optimal configuration. From the theoretical analysis, an autotransformer with optimal configuration and minimal equivalent kilovoltampere rating is designed. Some simulated and experimental results show the correctness of the theoretical analysis.

Load Adaptability of Active Harmonic Reduction for 12-Pulse Diode Bridge Rectifier With Active Interphase Reactor

In order to improve the harmonic reduction ability of 12-pulse rectifier, an active interphase reactor (AIPR) and corresponding auxiliary circuit are often used to produce circulating current resulting in harmonic reduction. This paper analyzes the load adaptability of 12-pulse rectifier with AIPR. The loads are classified into three types, RL-type load, RC-type load, and RLC-type load. Load currents and circulating currents are calculated under different load types. According to the calculation results, the THD of input line current and ripple coefficient of load voltage are also described by figures under RL-type load and RLC-type load. The appropriate amplitude of the circulating current under RL -type load and the LC filter under RLC-type load are presented. Simulation and experimental results validate the theoretical analysis.

Modeling for a Multitap Interphase Reactor in a Multipulse Diode Bridge Rectifier

This paper presents a new mathematical model for tapped interphase reactor (IPR) in a six-phase diode bridge rectifier. On the basis of coupling circuit principle and phase coordinate method, the proposed model, which reduces the mutual inductance coupling completely, describes the IPR by an admittance matrix containing the information about the connection way and electrical quantities. To double-tap IPR as an example, and using the proposed method, the full-decoupling model is set up. Compared with the model built by Kirchhoffs law, the proposed model is easier to realize in simulation software. The proposed method can well be extended to the multitap IPR. Some theoretical analysis, computer simulation, and experiments are included to verify the correctness of the model.

Active Harmonic Reduction for 12-Pulse Diode Bridge Rectifier at DC Side With Two-Stage Auxiliary Circuit

A 12-pulse diode bridge rectifier is often used in high-power rectification. However, the total harmonic distortion (THD) of input line current in 12-pulse rectifier does not meet the IEEE-519 standard. In order to reduce the harmonics to an acceptable level, we use a two-stage auxiliary circuit at dc side of the 12-pulse rectifier to eliminate harmonics actively. The effect of the auxiliary circuits parameter on the system performance is analyzed first, which indicates the necessity of applying two-stage auxiliary circuit. The front-stage auxiliary circuit plays a role in producing circulating current to cancel harmonics, and the back stage adjusts the output voltage of the front stage and feeds the power absorbed by the front stage to load in accordance with load current and input voltage of 12-pulse rectifier. Besides the good performance in harmonic elimination, the proposed auxiliary circuit has low kilovolt ampere rating.

Effect of Single-Phasing on Multipulse Rectifier With Active Interphase Reactor

When one of the input terminals of multipulse rectifier (MPR) is open, MPR operates under single-phasing. This paper analyzes the effect of single-phasing on MPR with active interphase reactor (AIPR). The output voltages of phase shift transformer and the voltage across the secondary winding are calculated under single-phasing. Compared with the voltages under normal operation, the amplitude of ouput voltages are not equal to each other under single-phasing, and phase difference of arbitrary two phases are not equal to 120°. The MPR with AIPR is equivalent to two single-phase full-bridge rectifiers operating in parallel. Zero-phase difference of output voltages of the two bridge rectifiers leads to no harmonic power being absorbed by the AIPR. Some simulation and experiment are carried out to validate the theoretical analysis.

Effect of Phase-Shift Angle on a Delta-Connected Autotransformer Applied to a 12-Pulse Rectifier

The delta-connected autotransformer with π/6 phase-shift angle is widely used in the multipulse rectifier when the output voltage of the autotransformer is approximately equal to its input voltage. If its output voltage is slightly greater than its input voltage, the equivalent kilovoltampere (kVA) rating of the autotransformer increases rapidly, and each core limb of the autotransformer has five windings. The increase in winding number will increase the asymmetry and manufacture difficulty of the autotransformer. Therefore, the autotransformer with π/6 phase-shift angle is not suitable in the boost voltage application. This paper analyzes the effect of phase-shift angle of the autotransformer with three windings in each core limb on the input line current, output voltage, and equivalent kVA rating and proposes a new phase-shift angle. The equivalent kVA rating of the delta-connected autotransformer with the new phase-shift angle is slightly greater than that of the autotransformer with π/6 phase-shift angle under the same turn ratio, but the autotransformer with the new phase-shift angle has three windings in each core limb and is propitious to design and manufacture. Some simulation and experiment are carried out to verify the theoretical analysis.

Comments and further results on "A New Critical Formula and Mathematical Model of Double-Tap Interphase Reactor in a Six-Phase Tap-Changer Diode Rectifier

This paper presents some comments and further results concerning the mathematical model of double-tap interphase reactor (IPR) in a six-phase tap-changer diode rectifier. On the basis of coupling circuit principle and phase-coordinate method, the proposed model, which reduces the mutual inductance coupling completely, describes the double-tap IPR by an admittance matrix containing the information about the connection way and electrical quantities. Some computer simulation and experiments are included to support the theoretical analysis of the model.

A Novel 24-Pulse Diode Rectifier with an Auxiliary Single-Phase Full-Wave Rectifier at DC Side

A simple and robust 24-pulse diode rectifier for low-voltage and high-current applications is proposed in this paper. The proposed 24-pulse diode rectifier consists of a conventional four-star 12-pulse diode rectifier and an auxiliary single-phase full-wave rectifier (ASFR) installed at dc side. The low-power (3.4%Po) ASFR extracts two rectangular currents from the modified second-stage interphase transformer and injects a square current into the output of the rectifier system. This modification extends the conventional four-star 12-pulse operation to 24-pulse operation. The proposed 24-pulse rectifier draws near sinusoidal input line currents with the absence of 5th, 7th, 11th, 13th, 17th, and 19th harmonics. The average value of current through the ASFR has only 1.7% of load current, which means the current rating and conduction losses of ASFR are very small. The proposed scheme has low-diode conduction losses, and it is more suitable for low-voltage and large-current applications. Since only an additional ASFR is needed, the proposed scheme is low cost and simple to implement. The detailed analysis for the proposed rectifier is presented, and experimental results are provided to verify the proposed concept.