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Telecom rectifier power system. (a) Telecom distributed rectifiers. (b) Basic telecom rectifier topology.
Source publication
Modern telecommunication power supply systems have several parallel-connected switch-mode rectifiers to provide -48 V DC. A typical switch-mode rectifier configuration includes a three-phase diode rectifier followed by a DC-DC converter. Such a system draws significant harmonic currents for the utility, resulting in poor input power factor and high...
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... telecommunication systems require a higher dc power. An example system requirement consists of 48 Vdc and 800 A (38.4 kW) [14]. All of the equipment runs on dc voltage generated by ac-fed redundant rectifiers of which the purpose is to supply power to the equipment. Fig. 1(a) shows a distributed rectifier system where a three-phase utility power is transferred into 48 Vdc. 1 The telecom rectifiers consist of a rectifier stage, a dc-to-dc converter, and a battery backup system. The major portion of the load is the logic circuitry in board-mounted power (BMP) converter units used to convert 48 V to 5 V and 12 ...
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... high dc-link voltage to lower voltage 48 V and provide isolation. Each paralleled dc-dc converter module requires a current-sharing mechanism to ensure even current distribution. A battery backup system on the 48-V dc bus is required to support the critical loads in case of utility failure. The basic topology of the telecom rectifier is shown in Fig. 1(b). The boost stage is used only to regulate dc-link voltage for a wide input voltage range. Since the power supply employs diode rec- tifiers because of economic reasons, the high-power rectifiers result in more serious problems related to harmonic currents. Such a typical rectifier may have more than 30% THD of input current. Fig. 2 ...
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... the other hand, the power factor angle between utility voltage and rectifier load current is calculated from Fig. 10 ...
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... from (14). The dc com- ponent in represents phase angle . Fig. 8(b) shows the block diagram of harmonic reference current generator to compensate for reactive power as well as load harmonics. The final fundamental current of the AHR is generated from the dc quantity (21) where , and the current flowing out of the AHR has a leading angle . Fig. 11 shows the current waveforms in terms of reactive power compensation on the stationary ref- erence frame. It is clear that the expected utility current with reactive power compensation is synchronized with the utility voltage. The AHR current is calculated by an inverse transformation of harmonic reference current . Two APF currents are ...
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... AHR design is based on the telecommunication rectifier system shown in Fig. 2(a) (9) and (10) reference frame and SVPWM technique is employed for the voltage-source inverter. Fig. 12(a) shows the control perfor- mance of the proposed scheme from experimental results without reactive power compensation. The AHR compensates for load harmonics and supplies active power. The APF results are shown in Fig. 12(b). The AHR current contains a fundamental component and load harmonics while the APF generates only load harmonic ...
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... system shown in Fig. 2(a) (9) and (10) reference frame and SVPWM technique is employed for the voltage-source inverter. Fig. 12(a) shows the control perfor- mance of the proposed scheme from experimental results without reactive power compensation. The AHR compensates for load harmonics and supplies active power. The APF results are shown in Fig. 12(b). The AHR current contains a fundamental component and load harmonics while the APF generates only load harmonic ...
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Citations
... Four complete BMS units have been built and the hardware setup is shown in Fig. 6. The system features four BMS units connected in series to support a 48 VDC bus, which is widely used in telecommunication applications [31]. The input and output voltages to the dc-dc converter are shown on two Fluke 289 multimeters from left to right, respectively. ...
This paper presents the design and implementation of an advanced battery management system (BMS). The basic concept is to divide each series battery array into sub-arrays where each battery is individually monitored and managed. The proposed BMS continuously monitors the voltage, current, and energy of each battery. Based on these measurements, the BMS can calculate individual state of charge (SoC) levels and Crates. Furthermore, the system has the capability to isolate each individual battery to apply different charging profiles and advanced diagnostics to detect the correct problems. Pulsed charging is deployed using different duty cycles for SoC balancing. The isolated battery is bypassed to maintain uninterrupted supply to the load despite reduced series array voltage. An unidirectional dc–dc boost converter maintains a constant output voltage level to the load, regardless of the number of batteries connected, until the problem is corrected. A hardware implementation of the proposed BMS is explained in detail. The performance of the system is tested experimentally under different loading conditions, including heavy pulsed loads. Index Terms—Battery management system (BMS), energy storage, lead acid battery, microgrids, pulsed load, smart grid.
... Therefore, 48 V DC distribution power system is widely used in telecommunication central offices. The reliability of that system is 99.999% [140][141][142][143][144]. ...
... This type of arrangement draws nonlinear and unbalanced load currents from the utility. Obviously, there are PQ issues, such as unbalance, deprived power factor, and harmonics produced by telecom equipment in power distribution networks as reported [7]. Therefore, the functionalities of the traditional DSTATCOM should be increased in order to lessen PQ problems and to give away the de loads from its de link capacitor as well. ...
The Distribution Static Compensator (DSTATCOM) is used for development of power
quality in power distribution network with various loads such as linear, nonlinear and variable load. The dc link capacitor voltage is directly affected by any alteration made in the load. Proper operation of DSTATCOM requires maintenance of capacitor voltage within the limits. Right from the beginning, conventional controller has been used to maintain the converter dc-link capacitor voltage. In spite of it, the transient response of the PI and Hysteresis controller is still slow. In this paper, an adaptive hysteresis band current controller is proposed for DSTATCOM to eliminate harmonics and compensate the reactive power of three-phase converter. The adaptive hysteresis band current controller is varied from the hysteresis bandwidth with respect to modulation frequency, source voltage, dc link voltage and slope of the reference compensator current wave. Mathematical expressions are given to design the adaptive hysteresis band current controller to achieve the fast transient response. The results of simulation study of the proposed method have been carried out using MATLAB simulation software.
... Different operating voltages need to provide simultaneously, especially for mixed-signal application specific integrated circuit (ASIC) and I/O interfaces. Furthermore, various requirements are imposed on power supplies for industry applications including multi-outputs, tight voltage regulation, fast dynamic responses, high efficiency etc. [2,3]. ...
An improved soft-switching post-regulator topology for multi-outputs dual forward DC/DC converter is presented. A delay-trailing modulation method is proposed. ZVSZCS on/zero-current-switching off conditions can be realised on both the primary MOSFETs and the secondary rectifying diodes. Excellent decoupling among different outputs and tight output voltage regulation are achieved. The efficiency is improved due to single power-conversion stage and share in the primary components. The operating principle and main feature of this improved topology are analysed. Key design issue including zero-voltage-switching operation, maximum duty ratio of the primary side MOSFETs and parameter determination for the primary magnetising inductor and the secondary additional redistribution capacitor are discussed. Finally, an experimental prototype with two outputs (300–400 V input, 48 V, 6.5 A and 24 V, 11 A outputs) is built to verify the theoretical analysis. The measured efficiency at normal operation input voltage (400 V) is improved by about 0.5–2%, and the measured efficiency under light loads is improved by more than 2%.
... This type of arrangement draws nonlinear and unbalanced load currents from the utility. Obviously, there are PQ issues, such as unbalance, deprived power factor, and harmonics produced by telecom equipment in power distribution networks as reported [7]. Therefore, the functionalities of the traditional DSTATCOM should be increased in order to lessen PQ problems and to give away the de loads from its de link capacitor as well. ...
The distribution static compensator (DSTATCOM) is used for enhancement of power quality in power distribution network with unbalanced, nonlinear and variable loads. The dc link capacitor voltage is directly affected by any alteration made in the load. The sudden decrease of load would result in an increase in the converter dc link voltage above the reference value, where as a sudden increase in the load would reduce the dc link capacitor voltage below its reference value. For proper operation of DSTATCOM requires variation of the DC link capacitor voltage within the prescribed limits. Right from the beginning, a proportional integral (PI) controller has been used to maintain the converter dc-link capacitor voltage to the reference value. Despite of it, the transient response of the conventional PI controller is still slow. In this paper, a fast acting dc-link voltage controller based on energy of the converter dc-link capacitor is proposed. Reference current is generated based on instantaneous symmetrical component theory for improving power quality in the power distribution network. Mathematical expressions are given to design the fast-acting dc-link controllers to achieve the fast transient response. A simulation study of the proposed method has been carried out using MATLAB simulation software.
... The ease in the calculation of the proportional and integral gains is an additional advantage. The value of the proportional controller gain can be given as = /2 (12) For example, if the value of dc link capacitor is 2200µF and the capacitor voltage ripple period is 0.01 s, then is computed as 0.11 by using (12). The selection of depends up on the tradeoff between the transient response and overshoot in the compensated source current. ...
... The ease in the calculation of the proportional and integral gains is an additional advantage. The value of the proportional controller gain can be given as = /2 (12) For example, if the value of dc link capacitor is 2200µF and the capacitor voltage ripple period is 0.01 s, then is computed as 0.11 by using (12). The selection of depends up on the tradeoff between the transient response and overshoot in the compensated source current. ...
The Transient response of the distribution static compensator (DSTATCOM) is very important while compensating rapidly varying unbalanced and nonlinear loads. Any change in the load affects the dc link voltage directly. The sudden removal of load would result in an increase in the dc link voltage above the reference value where as a sudden increase in the load would reduce the dc link voltage below its reference value. The proper operation of DSTATCOM requires variation of the DC link voltage within the prescribed limits. Conventionally, a proportional-integral (PI) controller is used to maintain the dc-link voltage to the reference value. It uses the deviation of the capacitor voltage from its reference value as its input. However, the transient response of the conventional PI dc-link voltage controller is slow. In this paper, a fast acting dc-link voltage controller based on the energy of the dc-link capacitor is proposed and proposed shunt controller method by using PQ-Theory. Mathematical equations are given to compute the gains of the conventional controller based on the fast-acting dc-link controllers to achieve similar fast transient response. The detailed simulation studies are carried out to validate the proposed controller. Index Terms—DC-link voltage controller, distribution static compensator (DSTATCOM), fast transient response, harmonics, load compensation, power factor, power quality, unbalance and voltage-source inverter (VSI) , PQ-Theory. _________________________________________________________________________________________
... Alternatively, a more elegant approach employs a shunt connected active power filter (APF) at the uncontrolled rectifier input, supplying the reactive current to the diode rectifier, thus achieving both near unity power factor (PF) and near zero total harmonic distortion (THD) by letting the utility to supply the active current only, which is in phase with the utility voltage and of the same shape. The use of either one three phase [34]- [37] or three single phase [38]- [40] APF configurations are potentially feasible for implementing a three phase PFC stage. The additional advantage of the approach is the fact that because of the shunt connection, the APF rating is less than one-third of the bridge rectifier rating, since the APF supplies the reactive and harmonic power only, while the series connected PFC converter rating is equal to the load kVA rating. ...
The manuscript presents a 50KW vehicle battery fast charger prototype design. The charger is basically a two-stage controlled rectifier with power factor correction. The input stage consists of a three phase full bridge rectifier combined with a shunt active power filter. The input stage creates an uncontrolled pulsating DC bus while complying with the grid codes by regulating the THD and power factor according to the permissible limits. The output stage is formed by six interleaved parallel groups of two DC-DC converters, fed by the uncontrolled DC bus and performing the charging process. Two independent control boards are employed: active filter control circuitry and the DC-DC control circuitry. The former is operated according to the predetermined grid interfacing behavior, while the operation of the latter is dictated by the requests from the Battery Management System (BMS). The charger is capable of operating in any of the two typical charging modes: Constant Current and Constant Voltage. Control loops are briefly explained throughout the paper and extended simulation/experimental results are presented.
... Alternatively, a more elegant approach employs a shunt connected Active Power Filter (APF) at the rectifier input, supplying the reactive current to the diode rectifier and thus achieving both near unity power factor and near zero Total Harmonic Distortion (THD) by forcing the utility to supply the active current, which is in phase with the utility voltage and of the same shape [29]- [35]. The use of either one three phase [29] - [32] or three single phase [33]- [35] APF configurations are potentially feasible for implementing a three phase PFC. The additional advantage of the approach is the fact that because of the shunt connection, the APF rating is approximately 40% of the series-connected PFC circuit rating, since the APF supplies the reactive power only to the diode rectifier (which is around 40% of the active power, flowing through the rectifier), while the series connected PFC converter supplies the active power, demanded by the load. ...
Modeling and control of a 50KW Electric Vehicle battery fast charger Power Factor Correction stage, developed at Gamatronic Electronic Industries LTD, is presented in the paper. The charger topology may be referred as a two-stage controlled rectifier. The input stage consists of a three phase full bridge rectifier combined with an active power filter (three single stage power filters are actually employed). The input stage creates an uncontrolled DC bus while complying with the grid codes by keeping the THD and power factor within the permissible limits. The output stage is formed by twelve DC-DC converters and is perceived as a constant power load by the input stage. The active power filter is operated using all-analog control circuitry according to the predetermined grid interfacing behavior. Input stage hardware and control loops are explained throughout the paper and extended simulation/experimental results are presented.
... Thus, the harmonic detection becomes a matter of removing the dc-signal by means of a high pass filter [19]. The block diagram of the proposed control (Fig. 12) is a typical implementation of an APF having current controllers in the inner loop and the voltage controller in the outer loop [20]. The current control is realized in a combined structure with a classical proportional-integral (PI) controller for fundamental current and resonant controllers, one for each harmonic pair 6 1 [21]. ...
Classical discontinuous pulsewidth modulations (DPWMs) may not be efficiently applied in active power filters (APFs), because it is hard to predict the peak values of the inverter current, and consequently it is difficult to calculate the position of the clamped interval, that minimizes the switching losses in any operating point. This paper proposes a new DPWM strategy applied to shunt APFs. The proposed modulation strategy detects the current vector position relative to the inverter voltage reference and determines instantaneously the optimum clamped duration on each phase. It achieves a clamped voltage pattern, with variable lengths depending on the magnitude of the inverter current. This property adaptively reduces the current stress and minimizes the inverter switching losses, regardless of its application. The proposed modulation strategy is described, analyzed and validated on a three-phase voltage source inverter, rated at 7 kVA 400 V, controlled as an APF.
... The block diagram of the proposed control (Fig. 6) is a typical implementation of an APF having the current controller in the inner loop and the voltage controller in the outer loop [12]. The current control is realized in a combined structure with a classical proportional-integral (PI) controller for fundamental current and resonant controllers (Rez sixth in Fig. 6), one for each harmonic pair k = 6n ± 1 [6], [13]- [15] as in ...
This paper describes an adaptive method for compensating the reactive power with an active power filter (APF), which is initially rated for mitigation of only the harmonic currents given by a nonlinear industrial load. It is proven that, if the harmonic currents do not load the APF at the rated power, the available power can be used to provide a part of the required reactive power. Different indicators for designing such application are given, and it is proven that the proposed adaptive algorithm represents an added value to the APF. The algorithm is practically validated on a laboratory setup with a 7-kVA APF.
