BACKGROUND

This disclosure relates to renewable energy systems and further relates to the renewable energy systems operating independently from the electrical power grid, herein after the “grid.”

Electricity supplied to a home can come from various sources, for example, an electrical grid and a local secondary energy source (renewable energy source), such as a solar panel or a wind turbine, to maintain a reliable electricity supply. The local secondary energy source can be tied to the electrical grid, which is called a grid tied system. Because of constant connection between the local secondary energy source and the electrical grid, the grid tied system de-energizes and ceases production and distribution of power from the local secondary energy source to the electrical grid or its associated facility whenever the electrical grid goes down. This shutdown requirement for all grid tied inverters is defined in National Electric Code, ANSI/UL 1741, California Rule 21, and IEEE 1547.

The electricity from the electrical grid is supplied with a predetermined frequency, for example, approximately 50 Hz in Europe and approximately 60 Hz in North America. However, some appliances and equipment in the home or business can be operated with a frequency over or below the predetermined frequency. Thus, the frequency of the electricity supplied to the home or business can vary from the predetermined frequency.

SUMMARY

The innovations described in the claims each have several aspects, no single one of which is solely responsible for the desirable attributes. Without limiting the scope of the claims, some prominent features of this disclosure will now be briefly described.

Any combination of features described in provisional applications can be implemented in combination with aspects described herein. Moreover, any combination of features described in two or more of the provisional applications can be implemented together. As a non-limiting example, any of the features included in one of the provisional applications can be combined with any of the features included in one or more of the other appendices, as appropriate.

During a grid energy outage, even a facility equipped with the local secondary energy source will be without power because an inverter to which the local secondary energy source is connected cannot produce power without the presence of an electrical grid reference voltage and frequency to prevent back feeding the de-energized grid. This shutdown requirement for all grid tied inverters is defined in National Electric Code, ANSI/UL 1741, California Rule 21, and IEEE 1547.

Aspects of a micro grid in a box (MIB) or adapter that can be used in a grid tied solar or storage (battery) or grid tied solar and battery system with a utility meter, including the smart meter, with or without a remotely or automatically controlled grid “Service Disconnect” switch are described herein. The MIB can be located electrically and physically behind the utility or energy provider's electric meter. The MIB or adapter can isolate a secondary power system, such as grid-tied solar system or a battery system from the electric grid, prevent the isolated or islanded secondary power system from feeding power back into the grid, and permit the secondary power system to supply power to the facility. The advantages are that the facility can continue to receive power from the secondary power source associated with the facility when the electric grid is not supplying power.

An aspect of a micro grid system can comprise an adapter, a power controller, and a secondary energy source. The adapter is in communication with an electric grid and configured to connect and disconnect a connection between the electric grid and a micro grid. The power controller is in communication with the adapter and is configured to receive first AC power from the electric grid via the adapter, obtain grid information, and control the adapter to connect and disconnect the connection between the electric grid and the micro grid. The power controller comprises a processor and a memory configured to store instructions that, when executed, cause the processor to control the adapter to disconnect the connection in response to determining that the electric grid is abnormal based on the grid information. The secondary energy source is in communication with the power controller and configured to generate DC power and to supply the DC power to the power controller. The power controller is further configured to convert the generated DC power from the secondary energy source to second AC power and to supply the second AC power to loads in communication with the power controller responsive to a determination that the electric grid is abnormal.

The adapter can comprise a connection switch and a safety switch, the connection switch being configured to connect and disconnect the connection between the electric grid and the micro grid based on one or more control signals from the power controller and the safety switch being configured to send a connection status signal to the power controller to notify the power controller of grid status, wherein the grid status indicates i) that the electric grid is in electrically connected to the micro grid or ii) that the electric grid is electrically disconnected from the micro grid.

The connection switch and the safety switch can be mechanically linked to cause the connection switch and the safety switch operate together.

The power controller can be further configured to check the connection between the electric grid and the micro grid using the safety switch after controlling the adapter to disconnect the connection.

The micro grid system can further comprise a sensor configured to sense the grid information including at least one of current, voltage, and energy on a path between the electric grid and the micro grid.

The adapter can comprise the sensor. The adapter can comprise a connector, the connector being configured to be coupled with a grid meter. The power controller can comprise an inverter configured to convert the DC power from the secondary energy source to the second AC power and to modify frequency of the second AC power. The micro grid system can further comprise a wireless communication device configured to communicate with an external device and wherein the power controller obtains the grid information using the wireless communication device.

An aspect of method of operating a micro grid system can comprise obtaining grid energy information, determining a status of the electrical grid based on the grid energy information, in response to determining that the grid status is abnormal, disconnecting the connection between the electric grid and the micro grid, and operating the secondary energy source to supply the second AC power to loads associated with the micro grid system responsive to disconnecting the connection between the electric grid and the micro grid. The micro grid system comprising an adapter connected to an electric grid and configured to connect and disconnect a connection between the electric grid and a micro grid, a power controller connected to the electric grid via the adapter and configured to receive first AC power from the electric grid via the adapter, a secondary energy source connected to the power controller and configured to generate DC power and supply the DC power to the power controller for conversion into second AC power,

The grid energy information can be obtained by sensing at least one of current, voltage and energy on a path between the electric grid and the power controller. The grid energy information can be obtained by receiving grid information via wireless communication.

The adapter can comprise a connection switch configured to connect and disconnect the connection between the electric grid and the micro grid and wherein the safety switch is configured to send signals to notify the power controller of a status of the connection, the status being that the electric grid and the micro grid are electrically connected or that the electric grid and the micro grid are electrically disconnected.

The method can comprises using the safety switch to verify the status of the connection between the electric grid and the micro grid after controlling the adapter to disconnect the connection. The method can comprises changing frequency of the second AC power supplied to the loads.

An aspect of an adapter can be configured to connect and disconnect connection between an electric grid and a micro grid system. The adapter can comprise a first connector, a second connector, a connection switch, a driver and a safety switch. The first connector can be configured to couple to the electric grid. The second connector can be configured to couple to a utility meter for measuring energy supplied from the electric grid. The connection switch can be configured to connect and disconnect electrical communication between the electric grid and the power controller based at least in part on the measured energy. The driver can be configured to drive the connection switch to connect or disconnect the connection. The safety switch can be mechanically linked to the connection switch, the mechanical linkage causing the safety switch operate in conjunction with the connection switch, a state of the safety switch associated with grid safety relative to operation of the micro grid system.

The adapter can further comprise a sensor configured to sense at least one of current, voltage and energy on a path between the electric grid and a power controller that can be configured to receive AC power from the electric grid via the adapter.

The adapter can be configured to disconnect the connection in response to determining that the at least one of the sensed current, the voltage and the energy is below a predetermined threshold.

The adapter can further comprise a processor and memory configured to store instructions that, when executed, cause the processor to control the driver.

The adapter can comprise a motor mechanically connected to the connection switch and the safety switch, and configured to be driven by the driver, and wherein the driver comprises H motor control circuitry.

Aspects of a variable frequency electronics that can be used in conjunction with a micro grid to supply the load on the micro grid with variable frequency power are described herein. The variable frequency electronics can modify the frequency of the power from the secondary power source that is supplying power to the facility load. Advantageously, reducing the frequency of the power supplied to the load on the facility reduces the power consumed by the load. This increases the efficiency and effectiveness of the secondary power source to provide power to the facility loads. For example, the energy stored in a battery storage system will last longer before it need to be replenished because it is being used more efficiently and more effectively. The variable frequency electronics continuously monitors the variable frequency power and provides adjustments to the frequency for optimum operation as the loads from the facility change. It is important to note that the variable frequency electronics is monitoring and modifying the frequency of the electrical energy supplied from a secondary power source to all of the loads drawing power from the secondary power source. This is different from a variable frequency motor that operates using variable frequency power because the variable frequency electronics monitors and adjusts the frequency based on the varying cumulative load on a facility, as well as attributes of the secondary power, such as current, voltage, and harmonics.

An aspect of a micro grid system can comprise a secondary energy source and a power controller. The secondary energy source can be associated with the micro grid, the secondary energy source configured to generate first DC power signal. The power controller can be in communication with the secondary energy source and an electric grid, and configured to receive first AC power signal from the electric grid and the first DC power signal from the secondary energy source and to output a second AC power signal to loads in communication with the power controller. The power controller can comprise a frequency converter configured to change frequency of the second AC power signal, a processor, and a memory configured to store instructions that, when executed, cause the processor to control the frequency converter to change the frequency of the second AC power signal.

The power controller can be configured to obtain information related to at least one of current, voltage, frequency and harmonic contents of the second AC power signal and to control the frequency converter to change the frequency of the second AC power signal based on the information.

The frequency converter can comprise a first stage comprising an AC-DC converter for converting the first AC power signal into a second DC power signal, and a second stage comprising a bus bar configured to receive the first DC power signal and the second DC power signal, and a first inverter configured to convert at least one of the first and second DC power signals into the second AC power signal for distribution to the loads.

The first stage can comprise a second inverter that is configured to receive the second DC power signal, convert the second DC power signal into a third AC power signal, and supply the third AC power signal into the electric grid.

The power controller can be configured to sense at least one of current, voltage and power on the bus bar, allocate electrons on the bus bar into the secondary energy source, the first inverter, the loads, and the electric grid based at least on the sensing result.

The second stage can comprise pulse width modulation circuitry configured to change a duty cycle of the first DC power signal, the frequency converter configured to change the frequency of the second AC power signal based on the duty cycle of the first DC power signal, and the first inverter is in communication with the secondary energy source via the bus bar and the pulse width modulation circuitry.

The secondary energy source can comprise a first energy source and a second energy source. The pulse width modulation circuitry can comprise first pulse width modulation circuitry configured to change a duty cycle of the first DC power signal from the first energy source and second pulse width modulation circuitry configured to change a duty cycle of the first DC power signal from the second energy source. The processor can be configured to control the first pulse width modulation circuitry and the second pulse width modulation circuitry to synchronize the duty cycles of the first DC power signals from the first and second energy sources.

The micro grid system can comprises an adapter configured to be connected between the electric grid and the micro grid, and configured to connect and disconnect a connection between the electric grid and the micro grid. The power controller can be further configured to control the adapter to disconnect the connection in response to determining that the electric grid is abnormal.

The system can comprise a rechargeable battery connected to the bus bar and configured to store DC energy and to supply the DC energy to the frequency converter via the bus bar.

An aspect of a method of operating a micro grid system can comprise generating a first DC power signal with the secondary energy source, outputting, with the power controller that is configured to receive the first DC power signal from the secondary energy source and a first AC power signal from the electric grid, a second AC power signal to be supplied to loads associated with the micro grid system, modifying frequency of the second AC power signal. The modifying the frequency of the second AC power signal can include obtaining characteristics of the second AC power signal on a path between the power controller and the loads, calculating load to be operated based on the characteristics, generating, with the power controller, a control signal based on the calculated load, and modifying, with a frequency converter, the frequency of the second AC power signal supplied to the loads based on the control signal. The micro grid can comprise a secondary energy source and a power controller in communication with the secondary energy source and an electric grid.

The characteristics of the second AC power signal can comprise at least one of current, voltage, frequency and harmonic contents.

The characteristics of the second AC power signal can be obtained by receiving the characteristics of the second AC power signal via wireless communication.

The frequency of the second AC power signal can be modified by changing a duty cycle of the first DC power signal with pulse width modulation.

The secondary energy source can comprise a first energy source and a second energy source. The frequency converter can comprise first pulse width modulation circuitry configured to change a duty cycle of the first DC power signal from the first energy source and second pulse width modulation circuitry configured to change a duty cycle of the first DC power signal from the second energy source. The method can further comprise synchronizing the duty cycles of the first DC power signals from the first and second energy sources.

The method can further comprise obtaining grid energy information associated with the electric grid, determining a state of the electric grid based on the electric grid information, the state being one of normal or abnormal, and in response to an abnormal determination, disconnecting an electrical connection between the electric grid and the micro grid system.

The method can further comprise converting the second AC power signal into the second DC power signal and supplying the second DC power signal to the electric grid.

An aspect of a power controller for operating a micro grid system comprises a frequency converter, a process, and a memory. The micro grid system can comprise a secondary energy source can be configured to generate a first DC power signal, the power controller in communication with the electric grid and the secondary energy source. The frequency converter can comprise an AC-DC inverter configured to receive a first AC power signal from the electric grid and to convert the first AC power signal to a second DC power signal, and a first inverter configured to convert at least one of the first and the second DC power signals into the second AC power signal and to supply the second AC power signal to loads associated with the micro grid system. The memory is configured to store instructions that, when executed, cause the processor to control the frequency converter to change frequency of the second AC power signal supplied to the loads associated with the micro grid system.

The power controller can further comprises a sensor configured to sense at least one of current, voltage, frequency and harmonic contents of the second AC power signal, and the processor can be configured to control the frequency converter to change the frequency of the second AC power signal based on the at least one of the sensed current, voltage, frequency and harmonic contents.

The frequency converter can further comprise a bus bar in communication with the secondary energy source, the electric grid, and the first inverter, the bus bar being configured to receive the first DC power signal and the second DC power signal and to deliver the first and the second DC power signals to the first inverter.

The controller can further comprise pulse width modulation circuitry configured to change a duty cycle of the first DC power signal, the frequency converter configured to change the frequency of the second AC power signal based on the duty cycle of the first DC power signal, the first inverter in communication with the secondary energy source via the bus bar and the pulse width modulation circuitry.

For purposes of summarizing the disclosure, certain aspects, advantages and novel features are discussed herein. It is to be understood that not necessarily all such aspects, advantages or features will be embodied in any particular embodiment of the invention, and an artisan would recognize from the disclosure herein a myriad of combinations of such aspects, advantages or features.

