Optimization and Comparative Evaluation of Multiloop Control Schemes for Controllable AC Sources With Two-Stage <inline-formula> <tex-math notation="LaTeX">$LC$</tex-math> </inline-formula> Output Filters
Abstract:This work investigates the control system design and its small-signal properties for the output stage of a high bandwidth, four-quadrant three-phase switch-mode controllable AC voltage source (CVS) with an output power of 10 kW, a switching frequency of 48 kHz, and a two-stage LC output filter. Each output phase of the CVS is operated individually, i.e. the phase voltages are generated with reference to the DC inputvoltage midpoint, to allow maximum flexibility in the generation of the output-voltage waveforms… Show more
“…In order to obtain a compact EMI filter, it is sufficient to limit the switching frequencies that are considered during the design process to a set of discrete values, f s ∈ {24, 36, 48, 72, 144} kHz [21]. From these, f s = 48 kHz has been considered, as this choice provides acceptable switching losses and a compact design of the boost inductor [22,23].…”
Section: Switching Frequency and Current Ripplementioning
A new universal front-end PFC rectifier topology of a battery charger for Electric Vehicles (EVs) is proposed, which allows fast charging at rated and/or full power level in case of 3-phase (Europe) as well as 1-phase (USA) mains supply. In this regard, a conventional 3-phase PFC rectifier would facilitate only one-third of the rated power in case of 1-phase operation. The new topology is based on a two-level six-switch (2LB6) 3-phase boost-type PFC rectifier, which is extended with a diode bridge-leg and additional windings of the Common-Mode (CM) chokes of the EMI filter. Besides this extension of the power circuit, the general design of the new converter is explained, and the generated Differential Mode (DM) and Common Mode (CM) EMI disturbances are investigated for 3-phase and 1-phase operation, resulting in guidelines for the EMI filter design. The EMI performance (CISPR 11 class-B QP) is experimentally verified for 1-phase and 3-phase operation at an output power of 4.5 kW, using a full-scale hardware prototype that implements the proposed extensions for a 2LB6 3-phase boost-type PFC rectifier and that is designed for output power levels of 22 kW and 19 kW in case of 3-phase and 1-phase operation, respectively. Compared to a conventional 2LB6 PFC rectifier, the volume of the extended system increases from 2.7 dm3 to 3.4 dm3, of which 0.5 dm3 is due to the additional dc-link capacitance for buffering the power pulsation with twice the mains frequency occurring for 1-phase operation.
“…In order to obtain a compact EMI filter, it is sufficient to limit the switching frequencies that are considered during the design process to a set of discrete values, f s ∈ {24, 36, 48, 72, 144} kHz [21]. From these, f s = 48 kHz has been considered, as this choice provides acceptable switching losses and a compact design of the boost inductor [22,23].…”
Section: Switching Frequency and Current Ripplementioning
A new universal front-end PFC rectifier topology of a battery charger for Electric Vehicles (EVs) is proposed, which allows fast charging at rated and/or full power level in case of 3-phase (Europe) as well as 1-phase (USA) mains supply. In this regard, a conventional 3-phase PFC rectifier would facilitate only one-third of the rated power in case of 1-phase operation. The new topology is based on a two-level six-switch (2LB6) 3-phase boost-type PFC rectifier, which is extended with a diode bridge-leg and additional windings of the Common-Mode (CM) chokes of the EMI filter. Besides this extension of the power circuit, the general design of the new converter is explained, and the generated Differential Mode (DM) and Common Mode (CM) EMI disturbances are investigated for 3-phase and 1-phase operation, resulting in guidelines for the EMI filter design. The EMI performance (CISPR 11 class-B QP) is experimentally verified for 1-phase and 3-phase operation at an output power of 4.5 kW, using a full-scale hardware prototype that implements the proposed extensions for a 2LB6 3-phase boost-type PFC rectifier and that is designed for output power levels of 22 kW and 19 kW in case of 3-phase and 1-phase operation, respectively. Compared to a conventional 2LB6 PFC rectifier, the volume of the extended system increases from 2.7 dm3 to 3.4 dm3, of which 0.5 dm3 is due to the additional dc-link capacitance for buffering the power pulsation with twice the mains frequency occurring for 1-phase operation.
“…In contrast to the conventional PI control implementation, in this variation the control output is updated multiple times per switching period. A common variance of this control structure is the PI controller that updates its reference duty ratio twice per switching period [31]. In this study, however, the control output is updated at every sampling period (i.e.…”
Section: B Pi Controller With a Fast Update Ratementioning
Several current control concepts for non-isolated interleaved DC-DC converters are systematically evaluated in terms of their dynamic and steady state performance, based on defined performance evaluation indicators. Various current control structures suitable for multi-phase interleaved systems are studied: i) a conventional PI controller with a single update per switching period, ii) a PI controller with a fast execution rate, equal to the sampling frequency instead of the switching frequency iii) a LQR-based state feedback controller (SFC), iv) a model predictive controller (MPC), and v) an adaptive hybrid controller that consists of a hysteretic controller during transient and a PI controller during steady state. Each of these control structures is optimized based on the same multi-objective optimization routine and a defined cost function. After the optimal controller design for each control structure is identified, the optimized designs are compared to identify the advantages and disadvantages of each structure. Additionally, a high current prototype current source based on a multi-phase interleaved converter with 6 interleaved modules switching at 60kHz is used to verify the most promising control structures, the developed models, and the results presented in this paper. Among the different studied structures, the adaptive hybrid controller is shown to exhibit the best performance to step transients and the MPC shows great potential following arbitrary waveforms, but also striking shortcomings in the presence of measurement noise.INDEX TERMS Current control, interleaved converter, optimal control, multi-objective optimization, high dynamic performance, high power DC-DC converters.
“…Thus, a megawatt test bench is necessary, which can adjust the amplitude, phase, frequency and harmonic content of the output voltage [4]. However, the large filter is needed due to low switching frequency when two-level or three-level topologies are used in megawatt field [5][6][7], even with two-stage inductorcapacitor (LC) filters [8,9]. Besides, the peak value of output voltage will be very high when the test bench output rated voltage and a certain harmonic voltage at the same time.…”
This study describes a megawatt test bench based on the cascaded converter for the stability test of renewable energy generation system under different grid disturbances. The test bench is composed of two cascaded converters, which are used to control the output of fundamental voltage and harmonic voltage. Aiming at the defects of the traditional repetitive controller (RC) and hybrid pulse-width modulation (HPWM) method, configurable RC (CRC) and novel HPWM (NHPWM) method are presented. By flexibly configuring the zeros and poles of CRC, the harmonic order that can be tracked accurately and the time delay of CRC can be easily changed. Besides, with NHPWM, the number of modules modulated by carrier phaseshifted PWM can be arbitrarily configured according to the output voltage quality and switching loss. Therefore, the flexible CRC and NHPWM are beneficial to achieve high control accuracy of fundamental and harmonic voltage and fast dynamic response while considering the switching loss, which is verified by simulation. The detailed harmonic analysis and calculation method of NHPWM are given, which are also proved correct by comparison of theoretical calculation and simulation results.
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