Heat pumps are often mandated and installed in new construction. Further, existing air conditioning units are now being replaced with heat pumps for winter heating use. There are a variety of options from straight heat pump use for heating to augmentation with carbon-based fuel heaters as well as simple resistive heating. The temperature data and energy price for a particular region will determine the basic cost profile and breakpoints for transitioning or augmentation. However, carbon minimization will likely not align with the minimizing of operational costs. This paper first examines a number of scenarios utilizing data gathered from two facilities which gives the reader some options based on desired parameters of optimization. This may be particularly useful if there are government energy credits available for all-electric and solar or carbon mandates that must be met. The paper places much of its emphasis on practical solutions.

Diode “oring” (or steering) is often used to provide battery backup power for many consumer products. For higher power dc microgrids such as those found on commercial or military maritime vessels, auctioneering diodes may be used for no-break power from multisource paths to vital loads. This paper addresses the following two issues: (a) the observed uneven distribution of negative bus current when employing only positive auctioneering diodes with multiple loads on the same circuit, and (b) the observed double load voltage discovered during one possible double ground fault scenario. An arrangement with anti-parallel diodes on the negative rail provides both balanced rail impedances and a path for fault current.

This chapter presents a brief discussion of solid-state dc circuit breakers followed by a description of the Z-source circuit breaker. The primary distinction of this breaker is that it automatically responds to a fault, not requiring fault sensing circuitry. This is accomplished by a Z-source impedance network which was introduced in the power electronics arena in the early 2000s. The basic principle of operation is described followed by popular variations that have appeared in the literature. Z-source breakers with coupled inductors are then illustrated. It turns out that the coupled-inductor versions have many advantages such as the ability to tune the sensitivity to a fault using the turns ratio and also require fewer passive components. Finally, the incorporation of the Z-source breaker into power converters is shown. Examples of a buck and boost converter with built-in Z-source breakers are presented.

This paper describes and displays an advanced demonstration model of a medium-voltage dc reduced order system which contains six partial electrical zones of a ship. The model has two anticipated purposes; to assist in the determination of necessary high-speed breaker locations and to be considered a baseline for future medium-voltage dc integrated power systems with pulse loads and energy storage. The model is suited for system analysis and contains the global apparatus for reconfiguration control. The system model was constructed using average-value power electronic components with minimized controls. The impedances between subsystems as well as the internal component impedances were kept intact to assist in the evaluation of high-speed breaker placement, and utilization.

This paper presents the attributes, benefits, and characteristics of a series load resonant converter for use as an interface converter within a Navy combatant power system. The closed-form equations for three typical modes of operation are developed and presented. The equations for operation below resonant frequency are used to evaluate component stress in an effort to optimize existing hardware. The authors tabulate several methods of minimizing component stress via shifting the steady-state operating point from discontinuous to continuous. While evaluating the results from a modeling effort and proof-of-principle hardware, two undesirable sub-modes were uncovered and documented. The authors present avoidance strategies for these two sub-modes. Finally, the paper recommends the series load resonant topology for use as an interface converter between the high-power medium-voltage bus and the low-voltage ship service bus for the next generation Naval combatant.

The future naval combatant ships will feature a fully integrated power system. These systems will allow unprecedented control of shipboard power to propel the ship, sense the battlespace, and engage the enemy. One crucial enabling technology is robust power conversion modules like the hybrid dc to ac inverter. This paper is a further exploration of the hybrid inverter scheme consisting of a six-step voltage-source inverter and a hysteresis-controlled current-regulated inverter. In this implementation, the six-step controller was designed to be independent of the hysteresis controller. The hysteresis controller is fed a reference signal extracted from the total output current going to the load. The signal is filtered and modified by a closed-loop system such that the total output current approaches a perfect sine wave; the quality of which is limited only by the bandwidth of the hysteresis converter. The modified closed-loop controller was compared to previous efforts and found to improve current total harmonic distortion from 3.2% to 1.8%. This paper proves that existing power electronic technology can be used to produce high-fidelity waveforms for high-power Naval propulsion drives which have a power range of 50 MW to 100 MW.

This paper documents the requirements, modeling, design and testing of a 400kW 1kV full-bridge water-cooled power electronics building block for use as a low frequency current injector for an industrial load. The evolution of the buss bar, buss capacitance and gate driver mother-board are discussed. Both modeling and hardware test results are presented.

Generally, drive manufacturers include input filters and/or output filters to meet system requirements. Depending on damping, these filters have the potential to introduce resonant conditions. Often the switching frequency changes with the rotational speed of the drive machine leading to the possibility that switching harmonics align with the resonant peak of the filters. As the frequency of the drive decreases, the number of pulses per half cycle of the output fundamental can increase to maintain a reasonably constant switching frequency. For drives that utilize interleaving, another possibility investigated in this paper is to dynamically alter the phase angle between interleaved converters. This allows selective elimination of harmonics near the filter resonance while reducing losses due to a lower switching frequency. Typically, the phase shift is based on the number of system inverters and is used to increase the effective switching frequency. The phase-shifting strategy in this paper differs from the traditional method by targeting specific harmonics of interest. This paper 1 describes the details of implementing strategies to dynamically alter the phase shift between interleaved converters to eliminate harmonics.

US Navy investment in future warships is focused on DC integrated power systems (IPS). A naval DC IPS will include multiple power generation devices, energy storage devices, and layered power converters. Power converters coupled to high-bandwidth regulators exhibit constant power load (CPL) behavior. CPLs exhibit negative non-linear impedance which reduce stability margins and limit the efficacy of linear control methods. Incorporating megawatt level pulsed loads, such as laser weapons or railguns, challenges the limits of linear control methods. A recently introduced control scheme, Adaptive Select-Matrix LQR (LQR-SM), is a flexible and adaptable centralized control approach to multi-input, multi-rate, high order systems. This paper presents a comparative study of LQR-SM controller performance in a naval medium-voltage DC shipboard electric distribution system with CPLs. The four configurations studied are a full-order adaptive LQR-SM controller, two adaptive reduced-order controllers, and a non-adaptive full order controller. The controllers are compared on the basis of quality of regulation, size of region of attraction (ROA), computation load, and stored-energy efficiency.

Over the last two decades, the US Navy has invested significantly in developing Integrated Power Systems (IPS) on warships. Future warship classes equipped with IPS are expected to have Medium Voltage DC distribution. DC distribution systems are host to scores of power converters which provide tailored voltage, frequency, and power quality to connected loads. When coupled to high-bandwidth controllers, power converters appear as constant power loads to the distribution system. The negative non-linear impedance associated with constant power loads reduces stability margins and limits the efficacy of linear control methods. The inclusion of megawatt level pulsed loads, such as laser weapons or railguns, further exacerbates the challenge to designers. A recently introduced control scheme, Adaptive Select-Matrix LQR (LQR-SM), is a flexible and adaptable centralized control approach to multi-input, multi-rate, high order systems. This paper presents the design and implementation of the LQR-SM control scheme in a complex hypothetical naval zonal MVDC distribution system that includes: multiple power generating units, multiple active energy storage devices, multiple load zones, and pulsed loads.

Over the last two decades, the US Navy has invested significantly in developing Integrated Power Systems (IPS) on warships. IPSs present unique challenges to electrical distribution system designers. The inclusion of megawatt energy weapon systems, high-powered radars and increased computation capacity coupled with the planned use of a medium voltage DC (MVDC) architecture result in ever-greater utilization of power electronics within a shipboard electrical distribution system. The power converters used to provide tailored voltage and frequency to each load exhibit constant-power load profiles to the MVDC bus. Constant-power loads destabilize the MVDC bus by introducing non-linear negative impedance. Large pulsed loads, such as laser weapon systems and electromagnetic railguns, prevent the use of classical linear controls. Energy storage devices (ESDs), such as batteries or flywheels, coupled to bidirectional DC-DC converters, may be used as controlled sources in addition to generator voltages. This paper introduces a multi-input adaptive Linear Quadratic Regulator based control scheme using generator voltage and energy storage device current as control inputs to produce superior MVDC bus voltage regulation in a CPL dominated system while reducing the need for bulk stabilizing capacitance.

The future all-electric warship is expected to utilize medium-voltage DC (MVDC) main distribution to supply several load zones. The load zones will convert the MVDC power to lower voltage for use by local loads as well as contain local energy storage for casualty back-up power. A majority, if not totality, of loads are expected to exhibit constant-power load (CPL) behavior. While many papers have developed single-input control schemes to regulate MVDC bus voltage where CPLs are present, multi-input controller schemes have not been explored. This paper presents two implementations of adaptive, multi-rate LQR controllers to regulate system voltages during step load transients. Through coordinated use of switching converter based low-rate DC voltage sources and high-rate energy storage device currents, multi-rate LQR controllers can provide excellent bus regulation by leveraging of all available control input devices. A periodic discrete-time multi-rate LQR controller (LQR-P) is described and compared to a selective-feedback, multi-rate LQR controller (LQR-SM). Both are designed and implemented in MATLAB software using a hypothetical multi-machine, multi-zone shipboard MVDC electric distribution system with CPLs and energy storage devices.

A novel type of circuit breaker is introduced for application in medium-voltage dc power systems. The breaker utilizes a z-source L-C circuit in order to automatically commutate a main-path SCR during a fault. Compared to existing dc circuit breakers, the z-source breaker features faster turn-off, simpler control, and the source does not experience the fault current. The operation and analysis of the new breaker is presented. Component sizing is carried out for three medium-voltage power levels. The new concept is verified with detailed simulation. Incorporation of the new breaker within a drive system is also explored.