3-phase step-up resonant dc-dc converter for medium power applications

The topology of LCC in the RTN comprises three reactive elements, the capacitor Crp that is connected to the load in parallel represents the third element. Thus, the topology contains two resonant frequencies: firstly, the series resonant frequency fr1 depending on the series elements Lr Cr and secondly, the parallel resonant frequency fr2 depending on the entire three tank elements Lrp, Cr, and Lr as illustrated in as they are shown in Eqs.

In the LCC converters, the proportion of resonant capacitors AC should be chosen prudently to be equal to the targeted peak gain. It is seen that the light load voltage gain advances across the converter properties and parallel resonant frequency fr2 acts as a parallel resonant converter PRC.

Voltage gain property of LCC converter. The topology structure comprises parallel resonant capacitor Crp, parallel resonant inductance Lrp, and a series elements Lr Cr, which implies that the topology contains two proportions whereby the inductance AL and capacitance AC must be appraised in the design. Moreover, the topology comprises three frequencies: two parallel frequencies frp1, frp2, and one series resonant frequency frs.

Voltage gain property of LCLC converter. The controlled strategies of the resonant converter is a bit disparate from the pulse width modulated PWM converters. A lot of parameters should be considered to attain a soft switching at a certain segment to fabricate the precise controller that can achieve the desired results like load condition, energy storage elements, frequency range, and among others.

There were several controlled topologies, which had been applied in the previous studies to manage the series resonant converters. For example, the pulse density modulation, voltage and current control, diode conduction control, and frequency control [ 24 ].

The full bridge resonant converter voltage had been regulated through the phase shift control; this phenomenon can be referred to as the switching signal primary control. In addition, to enhance the outcome of a control system, several improved techniques through adaptive controls had been reported [ 25 ], which include the passivity-based control and auto disturbance-rejection control ADRC. A phase shift control had been used to control the current of resonant [ 26 ].

Because of this, the control outcome was increased in relative to the traditional PSRC control system. From the previous studies, the controlled techniques can be categorized into their implementation technique either through analog or digital.

The digital controls are used because of their flexibility features in compact, programming, and light in comparison to analog controllers, they are also more resistant to inferences and noise. A three element DC-DC resonant converter type LLC has been discussed in this part, in order to compare the performance of frequency duty-cycle with variable frequency control, in terms of wide load variation.

Moreover, to ensure the expansion range of ZVS for entire inverter switches S1—S4 , and to improve the converter voltage gain. From Figure 14 , the LLC resonant converter gain M is evaluated using voltage divider law by considering the load quality factor Q and transformer step-up ratio as shown in Eq. The purpose of using this technique is that the voltage output is being influenced by changing the duty-cycle to attain a targeted voltage output.

Thus, the controlled signal pertained to the PWM generator through the utilization of the switching frequency in generating a gate signal for the entire switches. From Eq. Therefore, a duty cycle is the only factor that measures the output voltage. Because the voltage ripple can vary by changing the load, then, the duty cycle will react to the variation of load variation relative to the estimated output voltage ripple.

This control varies the switching frequency in adjusting the output voltage so as to reach the targeted load stage and save the output voltage of converter stable in any situation as illustrated in Figure 5. Therefore, the controller increases or decreases the switching frequency based on the targeted output voltage if any variation occurs from the required output or error sign.

Thus, a signal will be sent to the entire device switches. Depending on the magnetizing inductance and resonant impedance, the tank response needs to be saved inductively to appraise the attainment of the ZVS in the entire switches. A simplified illustration of full-bridge LLC resonant converter. The AC equivalent circuit between the rectifier and inverter. Simulation waveforms of the resonant tank input voltage V AB , resonant inductor current i L , resonant capacitor voltage V cr , and transformer primary voltage V pri.

The dynamic response of the output voltage, output current, and controlled duty-cycle signal with respect to the load changes. The dynamic response of output voltage, output current, and controlled frequency signal as the function of load change from full to half load.

In this frequency control, the controlled signal is used for the PWM generator in generating the gate signals for the entire switches.

Then, the switches S 1 and S 4 are enhanced concurrently and replace the S 2 and S 3 switches to generate the input voltage for the resonant tank V AB. Therefore, the resonant elements generate the voltage V Cr and sinusoidal current i Lr as illustrated in Figure It was observed that the output voltage ripple is enormous at full load condition in relative to the half load state that reflects a direct duty cycle changes within the entire load conditions.

Although, the system generates a favorable outcome by controlling the output voltage equivalent to V, nevertheless, the resonant tank parameters mislaying the resonant concept during the changes in load changes as illustrated in Figure In the variable frequency control technique, the measured output voltage is used to detect frequency. Thereafter, the controlled signal is implemented on PWM to produce gate signals to the entire switches by considering the switching duration depending on the converter nature to generate enormous output voltage gain.

Moreover, the variation in load is being tested and applied to affirm the controller dynamic responses. Figure 18 illustrates the parameter frequency controller dynamic response of the output voltage, and the load is stepped up and down in the similar way of duty-cycle control.

It can also be observed that in this control technique, the full load condition results in enormous output voltage ripple as compared to half load state, and this affirms the significant variation in frequency with the entire load condition. Moreover, the parameter frequency control gives a significant response to the tank AC parameters as illustrated in Figure As the load varies, the AC parameters temporarily react by increasing or decreasing the voltage and resonant current values depending on the varied frequency and keeping a shape of the sinusoidal waveform.

Based on the sufficient demerit of RPCs as earlier stated in the above segments, they have uncommon application in modern industries. The summary of the noticeable implementations is discussed in this segment. The main areas of RPCs application are household applications like induction cookers, portable power supplies, network connection of renewable energy mains, and hybrid and electric vehicles.

In a case of the portable power supply, requirements of the converter include a low price tag, light-weight and small size, high efficiency, high reliability, and low electromagnetic interference EMI.

Soft switching is the way of ensuring higher efficiency; it can be implemented by utilizing RPCs. Based on the area of application, the topology can be chosen to ensure maximum efficiency, ideal cost, and size.

For example, the supply of power to an electron beam welding compartment uses a full bridge LLC resonant converter [ 16 ]. The soft switching technique and topology solves the problem associated with power utilization within the filament supply by staying away from the inverter heating challenge and ensures higher efficiencies.

RPCs are used in the electrostatic precipitator. This is a high-power appliance industrially utilized for removing smoke and dust from a flowing gas. The series-parallel RPC coupled with phase control suggested by [ 27 ] is negligible in size; it gives a faster temporary response and possesses a higher efficiency as compared to the traditional line frequency power supplies.

RPCs are known for charging hybrid vehicles whereby the batteries need to be charged either by wireless or wired. If the error persists, contact the administrator by writing to support infona. You can change the active elements on the page buttons and links by pressing a combination of keys:. I accept. Polski English Login or register account.

Robinson, J. Abstract This paper describes a 3-phase DC-DC resonant converter for medium or high power applications. The converter characteristics during discontinuous and continuous operation modes are derived.

A design procedure is given for component sizing and application examples are shown for the connection of two different types of wind turbines to a medium voltage DC bus. A preliminary evaluation of the converter switching losses for the wind turbine applications is shown. Authors Close. Assign yourself or invite other person as author. In the conventional boost converters, high voltage ratio is feasible without multistage cascading [ 8 ]. The voltage ratios in these are limited by the parasitic elements and switching control used [ 9 , 10 ].

Three-level boost converters have significant advantage as compared to conventional boost converter. The size of the inductor is reduced and switch voltage rating is half of the output voltage.

This reduces the overall size and improves the efficiency in three-level DC-DC converters. However, the voltage balancing across the DC bus capacitors is required due to nonidealities in the components. This is feasible by sensing the voltages across them with corrective feedback through controllers [ 11 , 12 ]. The current sensing of inductor by dispensing the voltage measurements is feasible to balance the voltages across the DC bus capacitors [ 13 ].

PV array in solar power conversion system operates at a point having maximum power transfer. It is necessary to track this operating point by using the MPPT control algorithms to maximize the utilization efficiency.

Various algorithms for MPPT are reported in the literature and used for the efficient energy conversion process [ 14 ]. These methods are derivative based and noise sensitive. This is having noise and signal fluctuation immunity with fast convergence as compared to many reported MPPT methods [ 15 , 16 ].

A simple duty cycle based pulse width modulation PWM and capacitor voltage controller are suggested. The switching and reverse recovery losses are less in the three-level boost converter. The steady state and dynamic behavior of the system are presented. Both the simulation and hardware results are seen to have clear agreement with inherent robustness built using new MPPT algorithm.

In high power rating PV systems with high voltage gain requires boost converter with controller to maintain the DC bus voltage constant. The interfacing PV with wide range of voltages with boost converter having three-level is advantageous due to reduce input filter size and current ripple cancellation. In three-level boost converter, switching devices voltage rating is half of the output voltage; this leads to increase the power density, efficiency, and reduction in cost.

The three-level boost converter is shown in Figure 2. The voltage of the center point is as capacitors and are equal, which in turn reflects the voltage stress reduction across the switching devices in these converters. Symmetrical operation of three-level boost converter is explained with its operating modes. In this converter are the voltage across the capacitors , respectively.

The switch is upper switch and is lower switch and switching frequency is. Therefore, the converter operates in four distinct modes as shown in Figure 3. In this mode the inductor is always in charging mode and charged capacitors supply the current to the load. In this mode inductor may be in charging mode or discharging mode and charged capacitor supplies the current to the load while is in charging mode. Due to boosting operation , so in this mode inductor always is in discharging mode and both capacitors are in charging mode and input supplies the current to the load.

In modes 1 and 4 inductor is in charging mode and discharging mode, respectively, but in modes 2 and 3 inductor currents raising polarity depend on the voltages and , depending upon the relation between and half of the output voltage ; there exist two operating regions. In region 1, ; hence so inductor current raising polarity is positive in modes 3 and 2 as shown in Figure 3 a. This will occur only when duty ratios of upper switch and of lower switch are less than 0.

In region 2, ; input voltage is ; then, inductor current raising polarity is negative in modes 2 and 3 as shown in Figure 3 b. In this region both switches must not be OFF at the same time. In boost converter, maximum inductor current ripple occurs when duty ratio is 0. The inductor current ripple is given by.

In three-level boost converter, equivalent switching frequency is twice the switching frequency of conventional boost converter. In region 1 maximum ripple occurs at and is given by. From 1 and 2 , it is observed that the inductor current ripple is less for three-level boost converter for the same inductor value and inductor value is four times less than conventional boost converter.

The inductor loss due to the resistance is a major design parameter. The selection of the ratio and switching devices losses are the major contributors in the efficient operation of the converter. The golden section search is a technique for finding extremum minimum or maximum by sequentially narrowing the range of values inside which extremum exists. The main aim is to find maximum functional value of within the input interval. Two points and are selected in the interval and function is evaluated at these points.

Assume a line segment as shown in Figure 4 b. Then ; that is, ; hence. Consider ; that is, is 0. For a GSS based MPPT for photovoltaic system, the characteristics are the operating characteristics wherein corresponds to power, whose maximum value has to be tracked.

The range of operation is from zero to open circuit voltage ; that is, and as shown in Figure 4 b. The way of tracking maximum point is shown in Figure 4 a. The voltage corresponding to the maximum power is obtained and mapped into the characteristics to obtain the current reference. MPPT is used to track the maximum power under different atmospheric conditions; this method is robust and also has a fast response as compared to the conventional MPPT algorithms.

This algorithm has guaranteed convergence under continuous variable irradiance and temperatures. The algorithm for generating the PV characteristics is presented in Figure 5 a. The inductor current feedback is used to generate the error by comparing it with the reference current generated by the GSS algorithm and it is processed through proportional P controller. This P controller changes the duty ratio according to error and governs the PV to track the maximum power point on its characteristics.

Capacitors and are alternatively charged to their voltages and. Even though both capacitor values are equal, there is a voltage unbalance between output capacitors due to mismatch of two real capacitors and equivalent series resistance. The voltage balancing controller is required to maintain the equal voltages across these capacitors through duty cycle control and is implemented as shown in Figure 7.

In the three-level boost operation of the DC-DC converters with duty ration relates the fact that the input and output voltage are given as If , then where the input DC voltage is PV input voltage and varies with respect to varying environmental conditions. The duty ratio of the boost switch is determined by the MPPT control and duty ratio of the boost switch is determined by the additional controller. The PI generates the duty from the voltage error obtained from.