Caterpillar Inc.

Dachuan Yu

Gregory J Speckhart

Mahesh Sitaram Illindala

Jesse R Gerdes

Gregory Scott Hasler

Eric M Andris

Osama Mohammad Alkhouli

Jackson Wai

Joshua W Steffen

Suresh Baddam Reddy

Seok-hee Han

Kevin J Sergott

Michael Parry Liechty

Ronald C Gayles

John Joseph Votoupal

Basheer Qattum

Varsha Sunkara

Matthew Thomas Muller

Greg Speckhart

Techniques that eliminate the need for a dedicated pre-charge resistor by using the main power path of the AC/DC, DC/DC, or DC/AC converter. By eliminating the pre-charge resistor, the techniques increase the maximum allowable current rating of the converter as well as increase the impedance and inductance of the converter.

Resistor-less pre-charging techniques

An interface circuit to interface an energy source to a power bus of a microgrid includes a switching inverter circuit, an output filter circuit coupled between an output of the three-phase inverter circuit and the power bus, and a control circuit loop to control switching of the switching inverter circuit. The control circuit loop is coupled to the output filter circuit and the switching inverter and includes a proportional-integral oscillator-based repetitive (PIOR) controller.

Voltage source inverter control for unbalanced and nonlinear loads

An example transformer includes a controller that determines the currents on a power grid side of the transformer, as well as an inverter/load side of the transformer. The transformer may be of a delta-wye configuration. The controller compares the currents on the delta side of the transformer to the currents on the wye side of the transformer to determine whether the currents on either side are imbalanced. If the currents on the delta side are balanced, while the currents on the wye side are imbalanced, then the controller may determine that an open phase condition exists on the wye side of the transformer. Alternatively, if the currents on the delta side are imbalanced or if the currents on the delta side are balanced and the currents on the wye side are also balanced, then the controller determines that no open phase condition exists.

Open phase detection

The present disclosure discloses methods, systems, and non-transitory computer-readable medium for off-grid load stabilization. For instance, the method may include: receiving generator data from at least one generator and energy storage data from at least one energy store; determining, based on the generator data and/or the energy storage data, a moving average of a system load of the at least one generator; and determining, based on the generator data and/or the energy storage data, an instantaneous load value of the at least one generator. The method may further include: determining a first electronic storage dispatch (ESD) based on the moving average of the system load and the instantaneous load value of the at least one generator; and providing the first ESD to the at least one energy store.

Methods and systems for off-grid load stabilization of energy distribution systems

A method of allocating power across a microgrid having a plurality of energy storage systems with different power and/or energy capacities, and different states of charge. The method includes allocating a total charge request and/or a total discharge request across the energy storage systems; and limiting the charge and/or discharge of one or more energy storage systems to a submaximal value.

Methods and systems for charging or discharging energy storage systems

A hybrid micro-grid system for providing power to a load connected to a common bus. The system includes at least one renewable power source, at least one genset, at least one energy storage unit, and an asset management controller operatively coupled to the power sources supply power to the common bus. The AMC is configured to determine a renewable cost function, a genset cost function, and a storage cost function, then assigns a priority of each power source based on the corresponding cost function. The AMC determines a cascade of the power sources based on the determined priority and selectively distributes a power demand of the load between each power source based on the determined cascade.

System and method for diverse multi-source energy management

A micro grid power system includes a plurality of generator sets, a photovoltaic system, an external load, and a controller. Each generator set includes an engine and a sensor to determine a temperature of exhaust gases exiting the engine. The photovoltaic system includes a plurality of photovoltaic panels for generating power. The external load is powered by the plurality of generator sets and the photovoltaic system. The controller is configured to determine the external load, and control the plurality of generator sets to maintain the temperature above a threshold temperature. The controller is further configured to determine a remaining load which is the external load subtracted by a portion of the external load powered by the plurality of generator sets, and control the photovoltaic system to power the remaining load.

Micro grid power system

A method is provided to control the output voltage across an unbalanced load connected to a three-phase inverter, The method includes transformation of a set of three-phase voltage signals to a dq-coordinate system. Based on the transformation, a set of d-axis and a set of q-axis positive, negative and a set of zero sequence signals are generated. The method includes phase shifting of each of the zero sequence signals to generate 120 degrees and 240 degrees phase shifted zero sequence signals. Each of the zero sequence signals, the 120 degrees and the 240 degrees phase shifted zero sequence signals are transformed to a set of d-axis and q-axis zero sequence signals. A set of error signals, calculated based on the set of d-axis and q-axis zero, positive and negative sequence signals, are minimized and transformed to abc-coordinate system to obtain a three-phase control voltage signal.

Method to control three-phase inverter voltage

A variable speed genset system is provided that may include a primary power source, an electric machine, an energy storage device, a boost converter, and a controller. The electric machine may be coupled to the primary power source and electrically coupled to a load through a common bus. The boost converter may be in electrical communication with the common bus and the energy storage device. The controller may determine a State of Health (SOH) for the energy storage device, selectively engage the energy storage device to provide a first power amount to the common bus, and selectively change the operating speed of the primary power source to provide a second power amount to the common bus, the speed based on the SOH, a temperature of the energy storage device, and the load demand. The combination of the first and second power amounts substantially meet a load power demand.

Life degradation mitigation for transient response energy storage

A hybrid energy storage system (HESS) and method of controlling a HESS is provided. The HESS comprises a common direct current (DC) bus having a DC bus voltage, an energy storage device electrically coupled to the common DC bus, a power device electrically coupled to the common DC bus, and a controller in operable communication with the energy storage device, the power device and the common DC bus. The controller is configured to, when the energy storage device is charging, increase a power device charging current if an energy storage device charging current is greater than a charging limit for the energy storage device, and when the energy storage device is discharging, increase a power device discharging current if an energy storage device discharging current is greater than a discharging limit for the energy storage device. The HESS can be part of a power system.

Control of hybrid energy storage system for high pulse load

A system that manages a supplemental energy source connected to a power grid uses a two stage control strategy to manage power transfers in and out of the power grid as well as in and out of an energy storage system, such as a battery bank. One stage uses a non-linear transfer function to control an output frequency of a DC-to-AC inverter to limit undesired effects of power transients that occur on the grid. A second stage uses control strategy for transferring energy between the energy storage system and an internal DC link based on a relationship between a voltage on a DC link connecting the first and second stages and a DC link reference voltage, the voltage on the DC link, and a voltage at the energy storage system. The control strategy includes rapid charging, over-charging protection, and grid transient stabilization.

Control of energy storage system inverter system in a microgrid application

A hybrid power system is disclosed. The hybrid power system may include a primary power source configured to provide a primary power, and an energy storage device coupled to the primary power source, the energy storage device configured to store excess primary power provided by the primary power source. The hybrid power system may further include a variable speed genset, the variable speed genset including a secondary power source configured to operate at a variable rotor speed to provide a secondary power responsive to power requirements of a load. The hybrid power system may also include a central controller communicatively coupled to the primary power source, the energy storage device, and the variable speed genset, the central controller configured to control the primary power source, the energy storage device, and the variable speed genset based on the power requirements of the load.

Hybrid power system with variable speed genset

A method of determining an optimal operating speed of a variable speed genset is provided. The method may include determining whether an actual operating speed of the genset approximates a desired operating speed, the desired operating speed being predetermined based on a measured load value associated with the genset, the desired operating speed being associated with an applied offset value that is adjustable between a minimum offset value and a maximum offset value; incrementing the applied offset value of the desired operating speed to decrease the actual operating speed if the actual operating speed approximates the desired operating speed, and the applied offset value is less than the maximum offset value; and determining the desired operating speed as the optimal operating speed if the actual operating speed approximates the desired operating speed, and the applied offset value is equal to the maximum offset value.

Adaptive variable speed genset control

A control system for a power inverter is disclosed. The power inverter may be configured to supply power to a grid. The control system may include a plurality of output voltage sensors and a plurality of output current sensors configured to measure output line voltages and output line currents of the power inverter. The control system may further include a controller coupled to the power inverter. The controller may be configured to provide a control signal associated with a disturbance frequency to the power inverter. The controller may be further configured to determine an output power of the power inverter based on the output line voltages and output line currents, and determine an amplitude of oscillation in the output power caused by the disturbance frequency. The controller may also be configured to detect an islanding condition, if the amplitude of oscillation is below a threshold. The control system may further include an interface circuit coupled to the controller and configured to disconnect the grid from the power inverter if the islanding condition is detected.

Growing community of inventors

Dunlap, IL, United States of America

Dachuan Yu