The_Effect_of_12_Pulse_Converter_Input_Transformer

The research focuses on the effect of the 12-pulse converter input transformer configuration on the input harmonic currents.

According to the standard, there are 5 transformer connection groups mentioned in the paper.

The THDi for the 12-pulse converter inputs side ranged from 11.59% to 13.6%.

The phase difference of 300 is significant as it is achieved by connecting two 6-pulse converters in series, which helps in reducing harmonic distortion.

The methodology used was a quantitative method involving theoretical analysis, simulations with PSIM software, and measurements.

The formula for calculating the DC output voltage of a 6-pulse converter is: VDCout = 3.Vm.√3 / π.

The current in the D winding is in phase with the current in the y phase winding, and the source current to the D winding is the result of subtracting phase 1 and phase 3 currents.

The primary winding has a Y connection.

In a delta connection, line currents and phase currents have a phase difference of 30°.

The input transformer connection Yd1 affects the phase position of the relevant input current, but the input current waveform remains the same for both Dy11 and Yd1 connections.

The input current in the phase D winding is in phase with the current in the phase W winding.

The approximation used for the waveform is that it is a square wave.

The use of a 12-pulse converter with an autotransformer input transformer can suppress harmonic input current orders 5, 7, and 11, leading to a reduction in total harmonic distortion (THD) values for both current and voltage.

The transformer configuration used in a 12-pulse converter can reduce input current harmonics and improve the power factor. Specifically, configurations like Dy11/d0 and Yy0/d1 can enhance the quality of electrical power and affect the required transformer capacity, which is about 40% of the DC load power.

A passive filter can further reduce the input current harmonics to the converter, complementing the effects of the transformer configuration and improving overall power quality.

In a 12-pulse converter, the input current waveform is typically a square wave, which is influenced by the load characteristics, such as inductance and resistance. For example, with a load inductance of 0.1 H and resistance of 15 Ohm, the waveform reflects these parameters.

The input current of the 12-pulse converter with the Dy11/d0 configuration has the same shape as that of the Yd1/y0 configuration, but the input current in the Yd1/y0 configuration is smaller.

In the Dy11/d0 configuration, the phase current in the Y winding is equal to I, while the current in the d winding is I/√3.

The current in the secondary winding y is calculated as I/ay, where ay = 400/32 = 12.5.

The current in the secondary winding d is calculated as I/ad, where ad = 400/55 = 7.27.

The input current in winding D can be stated as:

is(wt) = 2n=1 anSin nwt + bnCos nwt

The harmonic values of the order 3, 5, 7, and 9 are below 2% and can be ignored.

The effective current rating leff is calculated as:

leff = (2.9^2 + 0.3^2 + 0.2^2)^(1/2) = 2.9 Ampere.

The Total Harmonic Distortion (THD) is calculated as:

THD = (0.3^2 + 0.2^2)^(1/2) / 2.9 = 0.119 = 11.9%.

The harmonic order table shows the coefficients for different harmonic orders, indicating that the first harmonic has a significant amplitude while higher orders (3, 5, 7, 9) have negligible contributions.

The output voltage waveform for a 12-pulse converter with a Dy11/d0 transformer connection shows three distinct voltage waveforms labeled as Vinput1, Vinput2, and Vinput3, with voltage ranging from 0 to 175.00 over a time period from 20.00 to 90.00.

The input current waveform of the 12-pulse converter shows three charts with the x-axis representing time from 20 to 90 and the y-axis representing current. The first two charts range from -16 to 16, while the third chart ranges from -8 to 8.

The THD values and effective current values for the Dy11/d0 connection are as follows:

In the Yd1/y0 transformer configuration, the input current in each converter is I / √3. Therefore, the phase current in the Y winding is also I / √3, while in the d winding, the phase current is I / 3.

The input current equation for the Yd1 transformer connection can be expressed as:

i_(in,y)(ωt) = ∑_(n=1,3,5)^∞ c_n sin n(ωt + θ) where the values of harmonic currents of the order 3, 5, 7, and 9 are below 2% and can be ignored.

The effective value of the input current for the 12-pulse converter in the Yd1 transformer connection is calculated as:

I_(eff) = (0,99^2 + 0,1^2 + 0,09^2)^(1/2) = 1,00 Amp.

The Total Harmonic Distortion (THD) for the input current in the Yd1 transformer connection is calculated as:

THD_I = (0,1^2 + 0,09^2)^(1/2) / 0,99 = 0,136 = 13,6%.

The harmonic orders that have values below 2% and can be ignored in the analysis of the 12-pulse converter input current are the 3rd, 5th, 7th, and 9th harmonic orders.

The THD (Total Harmonic Distortion) and Irms (Root Mean Square Current) values for the harmonic spectrum are as follows:

• Irms: 1.00
• THD: 12.03%

The total harmonic distortion (THD) for the input side of the two 6 pulse converters is 27.9%.

The output current of the 12-pulse converter with Yd1_y0 configuration is 5.8 amperes or 1/√3, while the Dy11_d0 configuration output current is in accordance with the plan.

The harmonics of order 3, 5, 7, 11, 15, 17, 19, and 21 can be eliminated, leaving only the fundamental waves and harmonics of order 11 and 13.

The THD values for the two converters range from 11.9% to 13.6%.

The power sent by the converter with the 12 pulses configuration input transformer Yd1_y0 becomes 1/3 compared to the Dy11/d0 connection, indicating that the transformer configuration affects the power output.