Converters for Supplying Pulsed Power Loads

Modern military aircraft are developing larger pulsed power loads varying from new weapon technologies to advanced avionics and other electrical equipment. Pulsing power loads emulate a pulse width modulated signal which have non-linear destabilizing effects on the electrical system. Additionally, these devices have thermal properties that can induce electrical stability issues at low and high temperatures and various pulsing load conditions. These non-linear electrical stability issues carry through to the mechanical and thermal systems of the aircraft and can damage components. The MATLAB/Simulink workspace is used to simulate a non-linear model of an aircraft’s electrical-mechanicalthermal (EMT) system. This system includes electrical generation with constant and pulsing power loads, mechanical fluid pumping, and thermal cooling systems. The goal of the EMT model is to demonstrate the destabilizing effects caused by both the thermal coupling of the pulsing load and the large signal analysis of the PWM signal. An operational boundary of the power pulsed device is found by varying the duty cycle for a given pulse period and power load based on bus voltage transients and voltage drop limits. The system is defined metastable for a given set of parameters if the system experiences periods of stability and instability based on varying operating points. Regions of complete stability, metastability, marginal metastability, and instability are determined based on bus voltage transient tolerances. Analyzing the marginally metastable boundary layer, thermal analysis is performed at different points of equivalent average power and varying pulse energy. Post processing the results determines the most efficient operational region of the system given thermal and electrical requirements.

Compared with the capacitive pulsed power supply (CPPS), the inductive pulsed power supply (IPPS) is considered to have broader prospects because of its theoretically higher energy densities. Most recent researches focus on characteristics of the IPPS with a fixed load, which is rather different from practical applications from the engineering point of view. In this paper, with the purpose of preliminarily verifying the IPPS’s feasibility, the performance of the novel meat grinder circuit with a dynamic load model is presented and analysed under PSpice environment. The analysis model is based on the parameters of the four-module IPPS and the pulsed power load built in Institute of Electrical Engineering. Finally, the comparison between the IPPS and the CPPS with same initial energy is carried out.

Keeping in the mind of pulsed power applications, especially in defence sectors, the Superconducting Magnetic Energy Storage (SMES) system is proposed for a smooth and reliable power flow in the grid. Power Converter Unit (PCU) of the SMES system consists of a DC-DC converter and a three-phase voltage source converter along with a DC-link capacitor which couples both the converters. Particularly, the voltage across the DC-link capacitor is tightly regulated using a dynamic evolution based control strategy in the DC-DC converter. Consequently, the DC-link voltage is maintained almost constant with a voltage regulation of ± 5.26% during pulsed power load condition. Moreover, an effective pulsed power load compensation, and uniform voltage distribution across the SMES coil are achieved due to the precise solid-state control. Nevertheless, the performance of the proposed SMES system is conducted in the MATLAB software.

Characterizing rapid capacity fade and impedance evolution in high rate pulsed discharged lithium iron phosphate cells for complex, high power loads

For pulsed power load (PPL) accommodation in a medium‐voltage DC (MVDC) shipboard power system (SPS), the charging control of energy storage systems (ESSs) and the generation control of distributed generators (DGs) need to be properly coordinated. Targeting the important but not well‐studied problem, an optimal output‐constrained control algorithm for the offline PPL accommodation strategy is presented. Three control objectives including realising the generation and charging control references, maintaining the DC bus and supercapacitor voltages within the safe operating ranges, and minimising the total generation cost of DGs, are fulfilled concurrently. First, an SPS model with multiple DGs, a supercapacitor ESS, and regular loads is developed. By restricting the DC bus and supercapacitor voltages within pre‐defined constraints, both the transient‐ and steady‐state performances of the SPS are guaranteed. Furthermore, by incorporating the cost minimisation objective into designed virtual control signals, the third control objective on energy efficiency is realised. The stability of the presented algorithm is rigorously proven based on the Lyapunov method. Finally, detailed case studies are conducted to validate the performance of the designed algorithm.

Pulsed power loads are widely used in electric power system, such as electrical brake system, laser radar and so on, which bring about significant harmonic pollution. The harmonic pollution will decline the power quality, damage sensitive load, and even cause system instability. To decrease the impact of pulsed power loads, effective measures should be taken to absorb these harmonics. In this paper, different power storage units are compared first. Then, several solutions are proposed and designed. Finally, based on a case-study, the simulation results of each solution are provided and compared and the weights of each solution are estimated. With these results, the advantages and disadvantages of each solution are concluded.

Technological advancements have been made in the field of electrochemistry leading to the development of energy storage devices that are more power dense than ever before. Coupled with their already modestly high energy density, this makes them well suited for use as the prime power source of many high pulsed and continuous power AC and DC loads operated within MicroGrid architectures. The energy storage devices of interest as well as the MicroGrid concept are both technologically immature. Their independent performance characteristics as well as the manner in which they can be integrated with one another need further research in order to understand their limitations and how they will perform in an extreme environment where high pulsed and continuous power loads are sourced simultaneously. With support from the US Office of Naval Research (ONR), a novel MicroGrid test-bed at UTA is being used to characterize how the power quality of different generation sources, including various low impedance energy storage technologies, solar panels, wind turbines, fuel cells, and fossil fuel based generators, are impacted when they are interconnected and used to source these types of high power loads. A description of the experimental setup and some experimental results obtained will be presented.

This paper proposes an enhanced Energy Management System (EMS) for hybrid DC microgrids in presence of pulse load. The proposed enhanced EMS employs instantaneous data acquisition technique to track pulse load behavior. By adopting this approach the proposed strategy is able to eliminate voltage drop in DC bus voltage due to presence of pulse load despite of simple load coordination. The proposed enhanced EMS is examined by several simulation studies in MATLAB/Simulink and obtained results verified effectiveness of the proposed EMS.

In this work we have demonstrated a hybrid system of a fuel cell and rechargeable battery with pulse power capability. It successfully ran a pulse power load simulation synonymous with military electronics and communications equipment. The hybrid consisted of a 35 W proton exchange membrane fuel cell (PEMFC) stack in parallel with a Li-ion battery. Two cyclic regimes were utilized. Each consisted of a baseline load for 9 min followed by a higher pulse load for 1 min. One regime consisted of 20 W (baseline)/40 W (pulse) load; whereas, the second was 25 W/50 W. Under both scenarios, the hybrid provided significantly enhanced performance over the individual components tested separately.

In this paper, we present the results of work with a hybrid power system made of a fuel cell and rechargeable battery with pulse power capability. This hybrid power source successfully ran pulse power load based on the power profile of the present and future manportable military electronics and communications equipment. The hybrid consisted of a 35 W proton exchange membrane fuel cell (PEMFC) stack in parallel with a Li-ion battery. In this work, two cyclic load scenarios were utilized. Each consisted of a baseline load for 9 minutes followed by a higher pulse load for 1 minute. One test profile consisted of 20 W (baseline)/40 W (pulse) load, whereas, the second was 25 W/50 W. Under both scenarios, the hybrid provided significant enhancements in performance over the individual components tested separately. These results are discussed and analyzed. Also discussed are possible future implications of such technology and approach.

Rapid capacitor chargers are typically used to charge a bank of capacitors with the purpose of discharging it into a pulsed power load [1,3]. Previous research shows that the charging voltage of the load can be accurately calculated in real-time using microcontroller software algorithms [1,5]. The objective of this paper is to report a hardware based approach to measure the charge transfer into the load capacitor and implicitly the capacitor charging voltage. The proposed circuit uses operational amplifiers in order to integrate the input charge. A microcontroller receives the integrated signal to compute the output voltage and stop the charging process when the target voltage has been reached. Failure to accurately detect the end of charge time could lead to an excessively large capacitor bank voltage. For this reason, the proposed method can be utilized as a primary means of end-of-charge detection in conjunction with a traditional voltage sensing scheme.

To isolate the negative impacts of pulsed power loads (PPL) in a shipboard power system (SPS), energy storage systems (ESS) are usually equipped for online ESS charging and offline ESS discharging for PPL deployment. In order to achieve fast and smooth ESS charging, the generation control and ESS charging control need to be well coordinated. In addition, control constraints, such as generation and charging current bounds and ramp rates, and changes of operating conditions during charging, should also be properly considered. To better solve this important but insufficiently investigated problem, two control algorithms are presented in this paper. The first PI-based control algorithm is designed based on analysis of the desired performance and rules for coordination. The second feedback linearization based control algorithm is designed based on a simplified SPS model and ramp rates difference of supply and demand. The algorithms are simple to implement and can effectively reduce the negative impacts during supercapacitor charging. The algorithms are tested with detailed single-generator and multiple-generator SPS models. Power hardware-in-the-loop and real-time digital simulation studies are performed to demonstrate the effectiveness of the proposed algorithms.

All-electric ship power systems include less generation capacity and smaller rotating inertia compared with large power systems. The systems include large portions of nonlinear loads and dynamic loads, which may reduce the stability margin. Moreover, various operational constraints, such as system frequency constraint, motor voltage constraint and dynamic cable constraint, need to be satisfied in operational real time. Further, pulse loads draw very high short-time power in an intermittent way, which may significantly deteriorate the power quality of the system. In this paper, a novel multi-agent system cooperative controller for a medium voltage AC (MVAC) system of all-electric ship power systems is developed to balance load and generation in real time while satisfying system's operational constraints and considering load priorities. The new method coordinates the pulse load and the propulsion load to reduce the impact of pulse load changes on the power quality of all-electric ship power systems. The dynamic behavior of the new method is evaluated using case studies in PSCAD software.

A proactive power compensation strategy applicable to achieving transient ride-through of ship microgrid (SM) under pulsed load is presented in this paper. The essence of this strategy can be summarized as the generator enters a transient process when a large portion of the pulsed load is connected to the islanded microgrid. Next, the pulsed load power is calculated and predicted over a 20 ms time scale based on the changes in stator current, stator voltage, excitation current and excitation voltage during the process. As a result, the predicted power is used as the control desired value of the compensation device to ensure that the microgrid recovers the power balance and achieves transient ride-through. Finally, the proposed control strategy not only replaces the one machine infinite bus (OMIB) with the transient model of the SG but also utilizes the energy storage device to actively guide the generator to output the differential power in the microgrid. The power response time of the compensation system is in the range of 6–20 ms, which is able to realize the transient ride-through of the SG within one cycle.

C/C composite, carbon nanotube and paraffin wax hybrid systems for the thermal control of pulsed power in electronics