Patent Description:
To supply an AC load (i.e. electrical equipment) from a DC source, a controller can be applied. They are used, for example, to control induction motors.

A stand-alone motor controller does not behave as a grid tie controller (with or without islanding capabilities).

A motor controller (<NUM>) usually switches the voltage from the energy source (<NUM>) into its arms (<NUM>), see <FIG>. The switched voltage on its arms (<NUM>) is filtered by the motor or load's internal inductance (<NUM>), limiting the current variation for the duration of the pulse.

For motors with nominal frequency at mains frequency (<NUM>/<NUM>), a motor controller can start the motor with lower voltage, current and frequency than when connecting directly to the mains. This way, a smoother motor start is achieved.

On the other side, a grid tie controller has filters that make its output (approximately) sinusoidal even without load. The three most common modulation schemes are square-wave, modified square-wave and sinusoidal modulation.

If the output is generated through a square-wave or modified square-wave modulation, the output filter must be tuned for the mains frequency (<NUM>/<NUM>). This fact limits the start of motors with reduced frequency.

The electrical supply of auxiliary loads in heavy-duty vehicles or reefer units, is either by a dedicated generator coupled to a combustion engine or directly by mains. The electrical power can be supplied by the electrical distribution network or by a controller. If the loads have large starting currents, either the inverter power is increased or a soft-starter or Variable Frequency Driver (VFD) is necessary.

These auxiliary systems may be on board of vehicles (including heavy-duty), trailers or even containers for cargo. In these cases, whenever it is not possible to supply them through mains, these systems use a combustion engine coupled to the auxiliary mechanisms.

Document <CIT>, for which the preamble of claim <NUM> relates, discloses a power converter which can be controlled to generate a target output power based on a reactive power reference and an active power reference. Document <CIT> also discloses a control process which may include monitoring a time-varying power signal (e.g., a power grid voltage signal from a power grid), and filtering the time-varying power signal to derive a filtered sine component of the time-varying power signal and a filtered cosine component of the time-varying power signal. Document <CIT> discloses how a sine coefficient and cosine coefficient each based on at least the reactive power reference and the active power reference can be determined, and applied to the filtered sine component and filtered cosine component of the time-varying power signal, respectively; a target current reference of the power converter can then be set to include a sum of the current reference sine component and the current reference cosine component.

These facts are described in order to illustrate the technical problem solved by the embodiments in the present document.

The invention is defined by a system for a direct-current to alternating-current power-supply bidirectional system for vehicles or transport containers with an electrical equipment as defined in claim <NUM>; the invention being characterised by the features recited in the characterising part of claim <NUM>.

Some vehicles, industrial machinery, trains or even intermodal containers (hereby referred to as load systems) are equipped with electrical loads that can feed from mains. The main caveat is they can only be supplied from mains when parked.

The present disclosure comprises a supply system which can be mounted on the load systems mentioned above, feeding them in electrical mode from a DC energy source, just as if they were connected to mains. The disclosure uses the already present standard plug in the load systems to interface between the energy source, mains and load systems simultaneously. This way any load system can be supplied from the energy source or mains without changing neither the load nor its functionalities.

A standard plug/socket can be defined such as that plug/socket combination that is commonly found or standardized to be found in household, industrial, or in particular, transport facility settings. For example, what is commonly referred as "Schuko"™ or a CEE <NUM>/<NUM> or <NUM>/<NUM>, or a CEE <NUM>/<NUM> or <NUM>/<NUM>, or a British Type G, Swiss Type J, Danish Type K, or Italian type L. , or equivalent triphasic versions, namely industrial versions such as IEC <NUM>. These are found in the industrial and transport settings where such electrical load equipments normally need to be plugged in.

To achieve such goal, a controller with its filters and derivations is necessary to allow the load system to be supplied by either mains or the DC energy source without any functional difference.

According to the disclosure, besides being able to feed any load electrical equipment of a vehicle or transport container with mains connection (i.e. with an AC electrical supply), the disclosed system itself can transfer energy from energy source to mains bidirectionally through the same plug while the load is still fully operative. This way, when the load system is connected to mains, not only its electrical load is connected but also the disclosed system is automatically connected (which can then decide to charge or inject energy on mains).

It is disclosed a direct current to alternated current power supply system for vehicles, containers or transport modules with electrical apparatus with mains supply, comprising: Direct current energy source; DC-AC controller connected to said direct current energy source; Filter with inductance and capacitance, to connect between the DC-AC controller and said connection for mains supply, in order to limit the current variation in the controller when it is on. It comprises switch or switches such that the flows of energy, between the DC energy source and the electrical equipment, between the DC energy source and the charger electrical grid connection, and between the electrical equipment and the electrical equipment electrical grid connection are bidirectional and independently switchable. The system may be retrofittable to an electrical equipment having a standard power plug, using said standard power plug as the single connection between the system and the electrical equipment.

The system is for connecting to any load system prepared to connect to mains because the system is prepared to emulate mains characteristics; said load system being an electrical equipment of a vehicle or a transport container.

It is disclosed a direct current to alternating current power supply bidirectional system for vehicles or transport containers with electrical equipment having an electrical grid connection for connecting to the electrical grid, comprising:.

In an embodiment, the filter with a series inductance and a parallel capacitance, connecting between the DC-AC controller and said electrical grid connection of the electrical equipment, comprises an additional series inductance forming an L-C-L filter.

The invention comprises switch or switches such that the flows of energy, between the DC energy source and the electrical equipment, and between the electrical equipment and the electrical grid connection are bidirectional and independently switchable.

The invention comprises a charger, mains, electrical grid connection (i.e. an electrical grid connector for connection to a mains electrical grid) for charging the DC energy source, comprising switch or switches such that the flows of energy, between the DC energy source and the electrical equipment, between the DC energy source and the charger, mains, electrical grid connection, and between the electrical equipment and the electrical equipment electrical grid connection are bidirectional and independently switchable.

In an embodiment, the system is retrofittable to an electrical equipment having a standard power plug as the electrical equipment electrical grid connection, using said standard power plug as the single connection between the system and the electrical equipment.

The invention comprises connection switches for mains electrical grid connection for bidirectional energy flow connection from mains electrical grid to the DC source.

An embodiment comprises additional connection switches for bidirectional energy flow connection between the mains electrical grid and the electrical equipment.

An embodiment comprises safety switches between said filter and a common connection to said connection switches.

In an embodiment, the capacitance comprises one or more capacitors, and/or one or more varistors. In an embodiment, the inductance comprises one or more inductors, in particular one or more inductor coils.

In an embodiment, the capacitance is connected either in delta or wye or delta-wye.

In an embodiment, system and filter, and switches if existing, are three-phase, for connection to a three-phase electrical equipment standard plug. In an embodiment, system and filter, and switches if existing, are single-phase, for connection to a single-phase electrical equipment standard plug.

An embodiment comprises a socket for connecting with the electrical equipment plug, in particular a standard power socket.

It is also disclosed a system for vehicles or transport containers with electrical equipment having an optional electrical power generator, comprising a bypass electrical connection for connecting with said generator such that the generator is able to independently, or jointly with powering the electrical equipment, charge the DC power source. In an embodiment, said bypass connection is connected to the electrical power generator to receive energy to charge the DC power source.

An embodiment comprises switch or switches such that the flow of energy, between the DC energy source and the optional electrical power generator, is bidirectional and independently switchable.

The invention comprises an electronic data processor according to claim <NUM> which is configured for switching between operating modes which comprise:.

In an embodiment, said operating modes further comprise:.

Derating is the operation of a device at less than its rated maximum capability. Typical examples include operation below the maximum power rating, current rating, or voltage rating. In the present disclosure, derating is used to reducing the amount of power for battery charging to take into account the power limit of the power supply. For example, for the two cases above, respectively:.

The electrical equipment is normally on-board electrical equipment like a refrigerator. In an embodiment, the vehicle or transport container electrical equipment is refrigeration equipment; in particular the electrical equipment is an electrical compressor motor for refrigeration equipment.

In an embodiment, the electrical power generator is a combustion motor (e.g. diesel or gasoline). In an embodiment, the DC energy source is a battery, super-capacitor, or combination of batteries, fuel cells and/or super-capacitor.

For better illustrating the disclosure, the attached figures represent preferential embodiments that are not to be considered limitative.

It is described a system (<NUM>) composed of a DC-AC controller (<NUM>) according to the present embodiments, which is capable of grid tied or off grid operation, as well as capable of controlling electrical loads such as motors (<NUM>), syncing with the grid (<NUM>) for charging an energy source (<NUM>) or injecting on the grid (<NUM>) with energy from the energy source (<NUM>) simultaneously, see <FIG> for a schematic representation.

It is also comprised of a set of filters and derivations (<NUM>) which allow the integration and interface of the energy source (<NUM>), mains (<NUM>) and AC loads (<NUM>) in an independent and bidirectional fashion.

Although a motor controller apparently satisfies the needs to supply auxiliary loads, if a motor is coupled with a capacitor bank (<NUM>) before the motor inductance (<NUM>) (for various reasons), then the current variation during a pulse is no longer limited by the inductance of the motor and the maximum current is limited by the resistance of the electrical path. As a direct consequence, the current that flows through the controllers will be several times larger than the nominal load current, which may incur in system damage.

There is also the possibility of the operation start being externally controlled, for example with switches (<NUM>), see <FIG> for a schematic representation. These switches will only conduct in case energy is detected. In this situation, the motor controller won't be able to generate a voltage similar to mains and consequently the switches will never conduct. A Carrier or a Thermo King reefer unit are examples of said systems. The voltage is read to the left of the switches (<NUM>) and the reefer temperature is measured. If there is voltage at the switches (<NUM>) and the temperature is below its setpoint, the switches (<NUM>) start conducting.

This description enables the retrofitting of loads supplied by mains in a transparent fashion for the user as explained next.

For a load (<NUM>) supplied by mains (<NUM>) through a plug/socket such as socket (<NUM>) and plug (<NUM>), see <FIG>: From the functional point of view, the load can be seen as the set (<NUM>) and (<NUM>). The mains is then (<NUM>) and (<NUM>).

It is possible to integrate the disclosure in a transparent way for the user (which will operate only the plug/socket (<NUM> and <NUM>) ), see <FIG>.

The loads are connected internally through the filters and derivations (<NUM>) detailed next. As will be demonstrated, the filter variations can be placed in (<NUM>). As long as the plug (<NUM>) is placed in the point where the filters and derivations (<NUM>) connect to mains (<NUM>), then the load can be directly connected to the filters and derivations as in the shown schemes (without the plugs), keeping the transparency to the user.

The user will plug in the socket (<NUM>) as he has always been doing and been trained to do, and the proposed disclosure is responsible for the energy management between energy source, loads and mains.

From the functional point of view, the "load", as seen from the user, is now the energy source (<NUM>), DC-AC controller (<NUM>), filters and derivations (<NUM>), loads (<NUM>) and plug (<NUM>).

The present description presents a configuration of an inductive filter at switching frequency that makes the DC-AC controller (<NUM>) see an inductance before the capacitive elements. In its simpler configuration, it is made only of <NUM> inductors (<NUM>) and <NUM> capacitors (<NUM>), see <FIG> for a schematic representation. Several modifications can alter its behavior, but their function is similar to the proposed filter in this description (<NUM>).

This filter solves the problems described and provides the following advantages:.

Furthermore, an input capacitor at the electrical equipment to be powered, in parallel with the load, would short-circuit the DC-AC switches (IGBTS). The LC filter is used to limit the peak current that could be generated due to the capacitors connected across the electrical equipment, avoiding the short-circuit. A further additional series inductance results on a LCL filter, which increases the noise attenuation capability. This ensures that the voltage generated by the DC-AC controller to feed the electrical equipment is sufficiently filtered in order to guarantee more compatibility with the load (ex: refrigerated units), namely avoiding problems of voltage detection by the electrical equipment.

The capacitors (<NUM>) can be connected in delta (as in the picture) or wye.

Exemplifying, if the converter operates at a <NUM> frequency, the L and C value must be calculated such as to place the resonant frequency between switching frequency and maximum load frequency operation.

L and C can be designed in many ways, namely:.

Taking L=2mH and C=10uF (with the capacitors (<NUM>) with a wye connection: <MAT>.

Consequently, being possible to operate loads with frequency lower than this value, switching at frequencies higher than this value.

The current ripple can be calculated, with some approximations, through: <MAT> Where V is the voltage drop between controller and capacitor. The waveform (and consequently applied voltage) is dependent on both controller modulation and voltage on the capacitor at the given moment.

The voltage ripple on the capacitor can be calculated, with some approximations, through: <MAT> Where I is equal to the difference between current through the inductor and current into the load.

The load variations will disturb the voltage on the capacitors (<NUM>). The maximum rate at which this variation occurs (in time) can be calculated once more though the inductor formula: <MAT>.

<FIG> describes an example of the application of the present description when the load (<NUM>+<NUM>) is made of switches (<NUM>) and a motor (<NUM>), which may or may not have capacitive elements at its terminals. Any combination of load can be supplied through the filters (<NUM>).

The controller (<NUM>), when connected to the filters (<NUM>), shares all the advantages described above and more:.

Instead of the LC filter, other solutions can be implemented, replacing the capacitors by other elements able to absorb electrical energy, as is the case of varistors, see <FIG>.

The filter (<NUM>) described above is compatible and useful to variations the allow the mains connection.

Below are described some of the possibilities, having in common the filter (<NUM>), to which are added switches (to allow the independent connection of loads and mains). It is even possible the add power line filters to the mains connection in the topology, improving it without compromising its operation.

The addition of switches (<NUM>) allows the connection to mains in a controlled fashion, see <FIG>.

This variation has the following advantages:.

The addition of switches (<NUM>) adds an additional safety layer to the present description, isolating the controller from mains (<NUM>) and load (<NUM>), see <FIG>.

The topology shown has the additional advantage and functionality:.

The addition of power line filters (<NUM>) placed on a branch that doesn't affect controller impedance to the load enables the control of the impedance of mains connection without compromising the control of the load, see <FIG>.

This variation as the additional advantage:.

This alternative shows an implementation of the concept present in the description, exemplifying with the electrical connections. The connection to motor and mains is made with only <NUM> groups of switches (a single pole single throw (SPST) group and a single pole double throw (SPDT) group), see <FIG>.

This topology has the additional advantages:.

The same concept can be applied to single-phase systems, with or without mains connection, see <FIG>. One or two inductors can be used.

As in the picture above, all presented variations are also valid for single-phase systems, adapted by removing one of the arms and filter elements (<NUM>) that were connected to that arm.

<FIG> shows an alternative embodiment applied to a refrigerated trailer that includes an electrical generator (<NUM>). This generator is normally powered by an included diesel engine, but other engines or mechanical power inputs may be used to power the generator.

<FIG> shows an alternative embodiment also applied to a refrigerated vehicle that also includes an electrical generator (<NUM>), but in this case the refrigerated part is a container which is transported by a trailer (<NUM>) that is adapted for transporting containers. The system is particularly advantageous as it allows the uncoupling of the two parts, keeping the disclosed elements in the trailer which can be connected when needed with the refrigeration equipment of the container, in particular using a standard power socket/plug combination.

When the load includes an electrical generator, these systems will normally include an internal switch that connects or disconnects the generator from the load. This can be used advantageously by having a direct connection between the generator and the power input (mains connection) of the disclosed embodiments. This connection is preferably connected by means of a switch (<NUM>).

This is advantageous because the generator can power and charge the energy source (<NUM>) independently, if switches <NUM> are disconnected. Furthermore, if switches <NUM> are connected, the remaining power from the generator powering the load can be used to power (albeit with less power) and charge the energy source (<NUM>).

With these alternatives, the mains connection can be generalized to any power source with adequate electrical parameters (i. , respecting the system's components electrical limits).

The generic power source can be either controlled by the system through switches <NUM> or switches <NUM>, or externally through switches <NUM>. It may even be the case where the generic power source is also a load.

An example for a data processor suitable for controlling the disclosed system is a STM32 series (ARM cortex M4). An example for the switches comprises IGBTs and relays - using mechanical switches has the advantage that disconnection can be guaranteed in a power-off state. An example for a DC-AC controller comprises a controller which converts the DC current into AC current, operationally it may comprise a stage with a buck-boost to convert the voltage level and a stage with an inverter to convert the DC current into AC current.

Claim 1:
Direct current to alternating current power supply bidirectional system for vehicles or transport containers with an electrical equipment (<NUM>), said electrical equipment being adapted to be supplied by an AC electrical supply, the system comprising:
an electrical grid connector for connection to a mains electrical grid;
a direct current, DC, energy source (<NUM>);
a bidirectional direct current to alternating current, DC-AC, controller (<NUM>) connected to the direct current energy source; and
a filter (<NUM>) with a series inductance (<NUM>) and a parallel capacitance (<NUM>), arranged to be connected between the DC-AC controller and said AC electrical supply, for limiting the DC-AC
controller current variation when the system is supplying the electrical equipment;
characterized by the system further comprising switches (<NUM>, <NUM>, <NUM>) which are bidirectional and independently switchable; and
the system further comprising an electronic data processor configured for switching said switches between operating modes which comprise:
supplying the electrical equipment with the AC electrical supply from the DC energy source through the DC-AC controller and the filter;
charging the DC energy source from the mains electrical grid via the electrical grid connector;
injecting energy from the DC energy source into the mains electrical grid via the electrical grid connector;
supplying the electrical equipment directly from the mains electrical grid via the electrical grid connector; and
simultaneously, supplying the electrical equipment directly from the mains electrical grid via the electrical grid connector while the DC energy source charges with power derating by the DC-AC controller.