WO2023043371A2

WO2023043371A2 - A power controller

Info

Publication number: WO2023043371A2
Application number: PCT/SG2022/050655
Authority: WO
Inventors: Bih Hian KOH; Glen Ghias FARIVAR; Josep POU
Original assignee: Nanyang Technological University
Priority date: 2021-09-17
Filing date: 2022-09-14
Publication date: 2023-03-23
Also published as: WO2023043371A3

Abstract

This document describes a power controller comprising a first and a second power bus whereby each power bus is provided with a passive current limiting circuit. The passive current limiting circuits in both power buses are communicatively coupled to an energy management module which in turn is configured to dynamically allocate and set maximum load currents at output terminals of the first and second power buses. The energy management module is configured to do so by dynamically setting constant currents, iL of each of the passive current limiting circuits, whereby the dynamic allocation of the maximum load currents is done based on a set of one or more factors.

Description

A POWER CONTROLLER

Cross-Reference to Related Application

This application claims the benefit of Singapore Patent Application No. 10202110281X, titled “AC Line Current Limiting Circuit” which was filed on 17 September 2021 , which is expressly incorporated by reference herein in its entirety.

Field of the Invention

This invention relates to a power controller comprising one or more power buses such as a first and a second power bus whereby each power bus is provided with a passive current limiting circuit. The passive current limiting circuits in both power buses are communicatively coupled to an energy management module which in turn is configured to dynamically allocate and set maximum load currents at output terminals of the first and second power buses. The energy management module is configured to do so by dynamically setting constant currents, i of each of the passive current limiting circuits, whereby the dynamic allocation of the maximum load currents is done based on a set of one or more factors. By doing so, the energy management module is able to monitor and control the currents flowing in the power buses in real time and to adjust the maximum load currents as required.

Background

Due to the increase in the adoption of electric vehicles (EVs), charging infrastructures for these EVs will need to be made available at more locations and in large numbers. The deployment of EV charging infrastructures will be challenging as they would have to comply with various infrastructural and power requirements. For example, before a charging infrastructure may be installed at a new location, certain considerations will have to be carefully evaluated: such as the availability of parking spaces at the location; space for the installation of EV charging posts; compliance with existing safety regulations etc.

The most obvious solution would be for EV charging infrastructures to utilize the power infrastructures of existing buildings. Unfortunately, such power infrastructures are not designed to support a large EV charging facility or multiple individual EV supply equipment as each EV supply equipment draws a significant amount of power. For example, a Type 1 EV supply equipment may draw up to 32 Amperes, a Type 2 EV supply equipment may draw between 40 and 50 Amperes while DC chargers such as a Combined Charging System (Combo 1 or 2) may draw as much as 200 Amperes. As such, if a large EV charging facility were to be deployed at an existing building, a substantial amount will have to be invested into the overhaul or expansion of the building’s power distribution infrastructure, and feeder cables (for the power intake from the grid) to prevent the electrical network within the building from overloading. Due to this high cost, it is not feasible for a large charging facility to be deployed based on existing building infrastructures and as a result, only one to three EV charging systems may be deployed at each building.

If the building were configured to provide just a few parking lots with EV charging stations, certain issues would arise. First, all the EV owners staying at the building would be competing for use of the limited EV charging stations. Secondly, due to the limited availability of parking lots with EV charging stations, such lots will have to be designated for EVs only and this in turn would reduce the number of parking lots available for internal- combustion-engine (ICE) cars.

Smart charging or load management systems could possibly address issues caused by power supply and power network limitations as such systems could dynamically allocate the supply of existing power to a network of EV charging stations thereby effectively minimising the burden on existing power supply and network infrastructure.

As known in the art, existing smart charging solutions typically connect a cluster of EV charging stations to a control platform which may reside in the cloud or in a control room. The control platform communicates with individual EV charging stations to determine the amount of charging current that should be drawn by each charging station as the amount of power made available to these charging stations in the cluster are determined by the feed power supply provided by the grid or building. The smart charging platform is also configured to communicate with the battery management system (BMS) that resides in each EV.

In operation, when an EV is connected to a charging station, the control platform will determine the charging current that is available at the charging station and the control platform will then inform the BMS in the EV of the amount of charging current that is available. Based on this information, the BMS is then configured to charge the EV’s battery based on the amount of charging current that is available at the connected charging station. However, when another EV is connected to another charging station that is in the same cluster of charging stations as the original charging station, the amount of charging current available to the original charging station would have to be reduced to accommodate for the introduction of the additional load. In conventional power distribution systems, current flow from the main feed line to the various branches is usually uncontrolled. In other words, every branch’s current (e.g., current drawn by a charging station) is determined by the branch’s load (e.g., an EV). No issues would arise in such power distribution systems if the total current demanded by all the loads can be handled by the main feed line. Circuit breakers and fuses are provided at each branch to cut off the supply to the branch’s loads to prevent a branch’s current from exceeding a certain predefined limit. These limit-breakers typically comprise circuits that are fixed and set based on the electrical wires’ current ratings.

Traditional power distribution systems offer no flexibility to distribute available power among multiple branches irrespective of the loads of the branches. In fact, smart distribution management systems can only rely on the actively controllable loads and generators to achieve their control objectives. Therefore, communication links are established between the management system and the controllable assets such as the BMS of the EVs. Nevertheless, the management system has no mean of enforcing its commands and individual assets may decide to disobey the command or miscommunication may occur and as a result, certain lines may be overloaded thereby pushing the main feeder above its limit. Situations such as overshoots and/or spikes in energy consumption of EVs occur frequently in real-world situations due to the non-compliance of BMS in the EVs.

This undesirable scenario is more likely to occur when the main feeder is operating close to its capacity and a relatively large misbehaving load comes online, e.g., an electric vehicle in a multi-storey apartment carpark decides to charge around a peak load period. A fair distribution of the available current capacity among different branches is a desirable requirement in many scenarios.

For the above reasons, those skilled in the art are constantly striving to come up with a power controller that is able to dynamically allocate and set the maximum amount of current that may be drawn at each branch of a power distribution system.

Summary of the Invention

The above and other problems are solved and an advance in the art is made by systems and methods provided by embodiments in accordance with the invention.

A first advantage of embodiments of systems and methods in accordance with the invention is that the power controller is able to dynamically allocate and set the maximum amount of current that may be drawn at each branch. A second advantage of embodiments of systems and methods in accordance with the invention is that the power controller is able to independently set the maximum amount of current that may be drawn at each branch thereby negating the need for ensuring that its commands are enforced by active loads connected to each branch.

A third advantage of embodiments of systems and methods in accordance with the invention is that through the use of the power controller, more charging stations may be installed at a single location as the power controller allows the current at each branch to be carefully controlled as required.

A fourth advantage of embodiments of systems and methods in accordance with the invention is that unlike existing power distribution systems, when a branch’s current exceeds a predefined limit, the branch’s current will not be cut off. Instead, the power controller will cause the branch’s current to saturate at the predefined current limit thereby ensuring that the provision of the current to the load remains uninterrupted.

A fifth advantage of embodiments of systems and methods in accordance with the invention is that the power controller is able to balance the current obtained from a three- phase feed current and is also able to eliminate harmonics found within the feed current.

The above advantages are provided by embodiments of a system and a method in accordance with the invention operating in the following manner.

According to a first aspect of the invention, a power controller is disclosed, the power controller comprising: a first power bus having an input terminal connectable to a power source, an output terminal connectable to a first electrical load, and a first passive current limiting circuit provided between the input and output terminals of the first power bus; a second power bus having an input terminal connectable to the power source, an output terminal connectable to a second electrical load, and a second passive current limiting circuit provided between the input and output terminals of the second power bus; and an energy management module coupled to the first and second passive current limiting circuits, wherein the energy management module is configured to dynamically allocate and set maximum load currents at the output terminals of the first and second power buses by dynamically setting a first constant current, i _i of the first passive current limiting circuit and a second constant current, i_L2, of the second passive current limiting circuit, whereby the dynamic allocation of the maximum load currents are done based on a set of one or more factors. With regard to the first aspect of the invention, the set of one of more factors comprises one or more of: maximum feed currents made available to the input terminals of the first and second power buses, types of electrical loads that are connected to the output terminals of the first and second power buses, and statuses of electrical loads that are connected to the output terminals of the first and second power buses.

With regard to the first aspect of the invention, the first passive current limiting circuit comprises a current source converter (CSC) having a reference current terminal coupled to an input terminal of the first power bus, an inductive load coupled to an input terminal of the CSC and an output terminal of a diode bridge rectifier (REC), a transformer with a turn ratio of Ni and having a primary side coupled to an output terminal of the first power bus and a secondary side coupled to a biasing terminal of the REC, and an output terminal of the CSC being coupled to the input terminal of the REC, whereby the circuit is configured to: generate the first constant current, i i, across the inductive load using the CSC; cause a short circuit at the secondary side of the transformer when a load current, iioad, at the output terminal of the first power bus is less than a product of the first constant current, i _i with turn ratio Ni; cause the load current, iioad, at the output terminal of the first power bus to saturate at the product of the first constant current, i_Li with turn ratio Ni , when the load current, iioad, at the output of the first power bus is equal the product of the first constant current, i _i with turn ratio Ni; and whereby the second passive current limiting circuit comprises a current source converter (CSC) having a reference current terminal coupled to an input terminal of the second power bus, an inductive load coupled to an input terminal of the CSC and an output terminal of a diode bridge rectifier (REC), a transformer with a turn ratio of N2 and having a primary side coupled to an output terminal of the second power bus and a secondary side coupled to a biasing terminal of the REC, and an output terminal of the CSC being coupled to the input terminal of the REC, whereby the circuit is configured to: generate the second constant current, i_L2, across the inductive load using the CSC; cause a short circuit at the secondary side of the transformer when a load current, iioad, at the output terminal of the second power bus is less than a product of the second constant current, ii_2 with turn ratio N2; cause the load current, iioad, at the output terminal of the second power bus to saturate at the product of the second constant current, ii_2 with turn ratio N2, when the load current, iioad, at the output of the second power bus is equal the product of the second constant current, ii_2 with turn ratio N2.

With regard to the first aspect of the invention, the current source converter of the first and second passive current limiting circuits comprises one of: a three-phase CSC, a two-phase CSC or a single-phase CSC. With regard to the first aspect of the invention, the generation of the first constant current, i_Li using the CSC of the first passive current limiting circuit comprises the energy management module that is communicatively coupled to the CSC of the first passive current limiting circuit being configured to modulate gate voltages of transistor-diode pairs of the CSC of the first passive current limiting circuit to generate the first constant current, i _i .

With regard to the first aspect of the invention, the generation of the second constant current, ii_2 using the CSC of the second passive current limiting circuit comprises the energy management module that is communicatively coupled to the CSC of the second passive current limiting circuit being configured to modulate gate voltages of transistor-diode pairs of the CSC of the second passive current limiting circuit to generate the second constant current, ii_2.

With regard to the first aspect of the invention, the first passive current limiting circuit further comprises an energy storage circuit that is coupled between an output terminal of the CSC and the input terminal of the REC whereby the energy storage circuit comprises: a fullbridge current converter having an input terminal coupled to the output terminal of the CSC, an output terminal coupled to the input terminal of the REC, and a biasing terminal coupled to an inductor-capacitor ladder circuit, whereby a battery is connected in series with the inductor of the inductor-capacitor ladder circuit.

With regard to the first aspect of the invention, the second passive current limiting circuit further comprises an energy storage circuit that is coupled between an output terminal of the CSC and the input terminal of the REC whereby the energy storage circuit comprises: a full-bridge current converter having an input terminal coupled to the output terminal of the CSC, an output terminal coupled to the input terminal of the REC, and a biasing terminal coupled to an inductor-capacitor ladder circuit, whereby a battery is connected in series with the inductor of the inductor-capacitor ladder circuit.

With regard to the first aspect of the invention, the first and second passive current limiting circuits comprise a combined current limiting circuit, the combined current limiting circuit comprising a current source converter (CSC) having a reference current terminal coupled to an input terminal of the first power bus, an inductive load coupled between an input terminal of the CSC and an output terminal of a first diode bridge rectifier (REC), a first transformer with a turn ratio of Ni and having a primary side coupled to an output terminal of the first power bus and a secondary side coupled to a biasing terminal of the first REC, a second transformer with a turn ratio of N2 and having a primary side coupled to an output terminal of the second power bus and a secondary side coupled to a biasing terminal of a second REC, an input terminal of the first REC being coupled to an output terminal of the second REC, and an output terminal of the CSC being coupled to an input terminal of the second REC, and whereby the first constant current i _i equals the second constant current i_L2, and whereby the combined current limiting circuit is configured to: generate the first constant current, i_Li, across the inductive load using the CSC; cause a short circuit at the secondary side of the first transformer when a load current, ii_Oad_i , at the output terminal of the first power bus is less than a product of the first constant current, i_Li with turn ratio Ni; cause the load current, ii_Oad_i , at the output terminal of the first power bus to saturate at the product of the first constant current, i_Li with turn ratio Ni , when the load current, iioad, at the output of the first power bus is equal the product of the first constant current, i _i with turn ratio Ni; cause a short circuit at the secondary side of the second transformer when a load current, ii_oad_2, at the output terminal of the second power bus is less than a product of the first constant current, i_Li with turn ratio N2; cause the load current, ii_Oad_2, at the output terminal of the second power bus to saturate at the product of the first constant current, i _i with turn ratio N2, when the load current, ii_Oad_2, at the output of the second power bus is equal the product of the first constant current, i_Li with turn ratio N2.

According to a second aspect of the invention, a method for setting maximum load currents of a first and a second power bus using an energy management module, whereby the first power bus has an input terminal connectable to a power source, an output terminal connectable to a first electrical load, and a first passive current limiting circuit provided between the input and output terminals of the first power bus, whereby the second power bus has an input terminal connectable to the power source, an output terminal connectable to a second electrical load, and a second passive current limiting circuit provided between the input and output terminals of the second power bus, and whereby the energy management module is coupled to the first and second passive current limiting circuits is disclosed, the method comprising: dynamically setting a first constant current, i _i of the first passive current limiting circuit and a second constant current, i_L2, of the second passive current limiting circuit to dynamically allocate and set the maximum load currents at the output terminals of the first and second power buses, whereby the dynamic allocation of the maximum load currents are done based on a set of one or more factors.

With regard to the second aspect of the invention, the set of one of more factors comprises one or more of: maximum feed currents made available to the input terminals of the first and second power buses, types of electrical loads that are connected to the output terminals of the first and second power buses, and statuses of electrical loads that are connected to the output terminals of the first and second power buses.

With regard to the second aspect of the invention, the first passive current limiting circuit comprises a circuit that has a current source converter (CSC) having a reference current terminal coupled to an input terminal of the first power bus, an inductive load coupled to an input terminal of the CSC and an output terminal of a diode bridge rectifier (REC), a transformer with a turn ratio of Ni and having a primary side coupled to an output terminal of the first power bus and a secondary side coupled to a biasing terminal of the REC, and an output terminal of the CSC being coupled to the input terminal of the REC, and whereby the second passive current limiting circuit comprises a circuit that has a current source converter (CSC) having a reference current terminal coupled to an input terminal of the second power bus, an inductive load coupled to an input terminal of the CSC and an output terminal of a diode bridge rectifier (REC), a transformer with a turn ratio of N2 and having a primary side coupled to an output terminal of the second power bus and a secondary side coupled to a biasing terminal of the REC, and an output terminal of the CSC being coupled to the input terminal of the REC, the method comprising: generating, using the first passive current limiting circuit, the first constant current, i _i , across the inductive load using the three-phase CSC and generating, using the second passive current limiting circuit, the second constant current, i_L2, across the inductive load using the three-phase CSC; causing, using the first passive current limiting circuit, a short circuit at the secondary side of the transformer when a load current iioad, at the output terminal of the power bus is less than a product of the first constant current, i_Li with turn ratio N1 and causing, using the second passive current limiting circuit, a short circuit at the secondary side of the transformer when a load current i load, at the output terminal of the power bus is less than a product of the second constant current, ii_2 with turn ratio N2; causing, using the first passive current limiting circuit, the load current, iioad, at the output terminal of the power bus to saturate at the product of the first constant current, i_Li with turn ratio N1 , when the load current, iioad, at the output of the power bus is equal the product of the first constant current, i _i with turn ratio N1 and causing, using the second passive current limiting circuit, the load current, iioad, at the output terminal of the power bus to saturate at the product of the second constant current, ii_2 with turn ratio N2, when the load current, iioad, at the output of the power bus is equal the product of the second constant current, ii_2 with turn ratio N2. With regard to the second aspect of the invention, the current source converter of the first and second passive current limiting circuits comprises one of: a three-phase CSC, a two-phase CSC or a single-phase CSC.

With regard to the second aspect of the invention, the generating of the first constant current, i_Li using the CSC of the first passive current limiting circuit comprises the steps of: modulating, using the energy management module that is communicatively coupled to the CSC of the first passive current limiting circuit, gate voltages of transistor-diode pairs of the CSC of the first passive current limiting circuit to generate the first constant current, i _i .

With regard to the second aspect of the invention, the generating of the second constant current, ii_2 using the CSC of the second passive current limiting circuit comprises the steps of: modulating, using the energy management module that is communicatively coupled to the CSC of the second passive current limiting circuit, gate voltages of transistordiode pairs of the CSC of the second passive current limiting circuit to generate the second constant current, ii_2.

With regard to the second aspect of the invention, the first passive current limiting circuit further comprises an energy storage circuit that is coupled between an output terminal of the CSC and the input terminal of the REC whereby the energy storage circuit comprises: a full-bridge current converter having an input terminal coupled to the output terminal of the CSC, an output terminal coupled to the input terminal of the REC, and a biasing terminal coupled to an inductor-capacitor ladder circuit, whereby a battery is connected in series with the inductor of the inductor-capacitor ladder circuit.

With regard to the second aspect of the invention, the second passive current limiting circuit further comprises an energy storage circuit that is coupled between an output terminal of the CSC and the input terminal of the REC whereby the energy storage circuit comprises: a full-bridge current converter having an input terminal coupled to the output terminal of the CSC, an output terminal coupled to the input terminal of the REC, and a biasing terminal coupled to an inductor-capacitor ladder circuit, whereby a battery is connected in series with the inductor of the inductor-capacitor ladder circuit.

With regard to the second aspect of the invention, the first and second passive current limiting circuits comprise a combined current limiting circuit, the combined current limiting circuit comprising a current source converter (CSC) having a reference current terminal coupled to an input terminal of the first power bus, an inductive load coupled between an input terminal of the CSC and an output terminal of a first diode bridge rectifier (REC), a first transformer with a turn ratio of Ni and having a primary side coupled to an output terminal of the first power bus and a secondary side coupled to a biasing terminal of the first REC, a second transformer with a turn ratio of N2 and having a primary side coupled to an output terminal of the second power bus and a secondary side coupled to a biasing terminal of a second REC, an input terminal of the first REC being coupled to an output terminal of the second REC, and an output terminal of the CSC being coupled to an input terminal of the second REC, and whereby the first constant current i _i equals the second constant current i_L2, the method comprising: generating, using the combined current limiting circuit, the first constant current, i_Li , across the inductive load using the CSC; causing, using the combined current limiting circuit, a short circuit at the secondary side of the first transformer when a load current, ii_Oad_i , at the output terminal of the first power bus is less than a product of the first constant current, i _i with turn ratio N1; causing, using the combined current limiting circuit, the load current, ii_Oad_i , at the output terminal of the first power bus to saturate at the product of the first constant current, i_Li with turn ratio N1, when the load current, iioad, at the output of the first power bus is equal the product of the first constant current, i_Li with turn ratio N1; causing, using the combined current limiting circuit, a short circuit at the secondary side of the second transformer when a load current, ii_Oad_2, at the output terminal of the second power bus is less than a product of the first constant current, i_Li with turn ratio N2; causing, using the combined current limiting circuit, the load current, iioad_2, at the output terminal of the second power bus to saturate at the product of the first constant current, i_Li with turn ratio N2, when the load current, ii_Oad_2, at the output of the second power bus is equal the product of the first constant current, i_Li with turn ratio N2.

Brief Description of the Drawings

The above advantages and features in accordance with this invention are described in the following detailed description and are shown in the following drawings:

Figure 1 illustrating a block diagram representative of a smart centralised electric vehicle charging system in accordance with embodiments of the invention;

Figure 2 illustrating a block diagram representative of a power controller that may be utilized in the smart centralised electric vehicle charging system illustrated in Figure 1 in accordance with embodiments of the invention;

Figure 3 illustrating a circuit diagram of a passive current limiting circuit that may be utilized by the power controller illustrated in Figure 2 in accordance with embodiments of the invention; Figure 4 illustrating a circuit diagram of the passive current limiting circuit that is configured with an energy storage circuit in accordance with embodiments of the invention;

Figure 5 illustrating a block diagram representative of a processing system providing embodiments in accordance with embodiments of the invention;

Figure 6 illustrating a simulated waveform of the load current at a power bus in accordance with embodiments of the invention;

Figure 7 illustrating a simulated waveform of the input feed current at a power bus in accordance with embodiments of the invention;

Figure 8 illustrating a simulated waveform of the input feed current at a power bus and the energy storage current in an energy storage circuit provided within the passive current limiting circuit in accordance with embodiments of the invention;and

Figure 9 illustrating a block diagram representative of another embodiment of the power controller that may be utilized in the smart centralised electric vehicle charging system illustrated in Figure 1 in accordance with embodiments of the invention.

Detailed Description

This invention relates to a power controller comprising a first and a second power bus whereby each power bus is provided with a passive current limiting circuit. The passive current limiting circuits in both power buses are communicatively connected to an energy management module which in turn is configured to dynamically allocate and set maximum load currents at output terminals of the first and second power buses. The energy management module is configured to do so by dynamically setting constant currents, i of each of the passive current limiting circuits, whereby the dynamic allocation of the maximum load currents is done based on a set of one or more factors. By doing so, the energy management module is able to monitor and control the currents flowing in the power buses in real time and to adjust the maximum load currents as required.

The present invention will now be described in detail with reference to several embodiments thereof as illustrated in the accompanying drawings. In the following description, numerous specific features are set forth in order to provide a thorough understanding of the embodiments of the present invention. It will be apparent, however, to one skilled in the art, that embodiments may be realised without some or all the specific features. Such embodiments should also fall within the scope of the current invention. Further, certain process steps and/or configurations in the following may not have been described in detail and the reader will be referred to a corresponding citation so as to not obscure the present invention unnecessarily.

Further, one skilled in the art will recognize that many functional units in this description have been labelled as modules throughout the specification. The person skilled in the art will also recognize that a module may be implemented as circuits, logic chips or any sort of discrete component, and multiple modules may be combined into a single module or divided into sub-modules as required without departing from the invention. Still further, one skilled in the art will also recognize that a module may be implemented in software which may then be executed by a variety of processors. In embodiments of the invention, a module may also comprise computer instructions or executable code that may instruct a computer processor to carry out a sequence of events based on instructions received. The choice of the implementation of the modules is left as a design choice to a person skilled in the art and does not limit the scope of this invention in any way.

Figure 1 illustrates a block diagram representative of a smart centralised electric vehicle charging system in accordance with embodiments of the invention. The system is configured to dynamically utilize a building’s available shadow power (i.e., a building’s excess power) for charging active loads such as, but not limited to, electric vehicles. This ensures that the building’s power supply will not be interrupted as only the building’s excess power will be utilized for these purposes.

The system comprises a centralised power system 101 that is communicatively coupled, using data bus 118, to an electric vehicle charging management platform 112 that may reside in the cloud or on-location with power system 101. One skilled in the art will recognize that all data exchanged between the modules of the system may take place through the various data buses 118.

Management platform 112 may be configured to carry out both artificial intelligence and operator control functions such as, but are not limited to, the authentication of users, the processing of transactions, the provision of a display interface for users and operators, the scheduling of charging service, the determination of charging rate patterns, billings etc.

Power system 101 also contains smart control modules such as smart charging controller module 104, gateway controller module 102 and power controller module 150 that are communicatively connected through data bus 118. Gateway controller 102 is configured to coordinate the communication between the modules in power system 101 , smart energy management platform 112 and building load meter 106 while power controller 150 has the primary function of regulating the power supply to each individual load, e.g., loads 121 or 122. One skilled in the art will recognize that any number of loads may be connected to power controller 150 without departing from the invention.

In a typical operation, gateway controller 102 will receive the building’s electrical meter data from building load meter 106. Based on this information, controller 102 will then update smart charging controller 104 and platform 112 so that platform 112 may dynamically control the supply of power flowing through power bus 116 from building distribution network 108 to a series of loads 121, 122 (connected to power controller 150), which may comprise, but are not limited to, wall plugs or EV charging stations I EV supply equipment. In embodiments of the invention, instead of updating both controller 104 and platform 112, controller 102 may be configured to update only smart charging controller 104. Smart charging controller 104 may then be configured to dynamically control the supply of power flowing through power bus 116 from building distribution network 108 to the series of loads 121, 122. This ensures that the system may operate normally when communications between controller 104 and platform 112 are disrupted due to connectivity issues. Building distribution network 108 is also connected via power bus 116 to grid 110.

In operation, the smart centralised electric vehicle charging system may be configured to evaluate the total electrical load at an estate or building, and to calculate the excess power capacity available from building distribution network 108. This may be done by taking the difference of peak power limit allowable by the estate’s/building’s electrical infrastructure and the estate’s/building’s current total power load. The system then calculates, based on a combination of parameters including but not limited to the priority of users, state of charge, charging duration, and the availability of the power supply. Based on this calculation, the system then allocates and regulates the supply of power to each connected load, through power controller 150, to ensure that the total accumulated power delivered to all the connected loads 121 , 122 (e.g., wall plugs/EV supply equipment) does not exceed the excess power capacity of the building.

In embodiments of the invention, an energy storage system (ESS) 114 may be connected, via power bus 116, to building distribution network 108 to augment the amount of power available to power controller 150 when charging demand is high and/or when the building does not have sufficient excess power for loads 121, 122. ESS 114 may also be configured to supply power to the building during peak loading periods. In this embodiment, ESS 114 is configured to communicate with platform 112 and smart charging controller 104 via gateway controller 102.

Figure 2 illustrates a block diagram representative of power controller 150 that may be utilized in the smart centralised electric vehicle charging system illustrated in Figure 1 whereby power controller 150 is configured to limit the power that is available to a load connected to the power controller by regulating the current and/or voltage flowing to the load. In accordance with embodiments of the invention, power controller 150 may comprise of energy management module 201 that is communicatively coupled to a plurality of current limiters 202.

Each of the current limiters are in turn connected to a power bus or feeder branch and are used to regulate the current flowing across the power bus/feeder branch. As for the power buses, each end of each power bus is connected to supply feed 210 while the other end of each power bus is connected to one of corresponding loads 204a-c. Although Figure 2 illustrates power controller 150 as comprising of only three power buses 203a-c that each have their corresponding passive current limiters 202a-c, and their corresponding loads 204a-c, one skilled in the art will recognize that any number of such power buses, current limiters and loads may be used without departing from the invention.

In operation, feed current provided to supply feed 210 from building distribution network 108 (see Figure 1) will be divided across uncontrolled branch 212 and power buses 203a-c, i.e. , the controlled branch. It should be noted that the current flowing in uncontrolled branch 212 is not regulated by power controller 150 and its regulation is left as a design choice to one skilled in the art. Energy management module 201 (which is communicatively connected to smart charging controller 104) then determines the amount of current that is to be made available to each of the loads on the controlled branch, i.e., loads 204a-c, based on the amount of power that is available from supply feed 210.

For example, when smart energy management platform 112 receives a charging request from a load 204a that is connected to an end of power bus 204a, platform 112, using energy management module 201 , then allocates a maximum limit on the current that may be drawn through power bus 203a. Platform 112 then informs load 204a of the reference charging current that has been assigned to it. If load 204a ignores the current limit that has been set and tries to draw more current from power bus 203a, current limiter 202a that is provided at power bus 203a then causes the current flowing to load 204a to be saturated at the set current limit. When smart energy management platform 112 receives another charging request from a newly connected load such as load 204b, that is connected to an end of power bus 204b, platform 112 then arbitrates and dynamically allocates the maximum amount of current that is to be made available to loads 204a and 204b. It does so by causing energy management module 201 to allocate maximum limits on the currents that may be drawn through power bus 203a and 203b.

Through the use of the current limiters provided at each of the power buses, smart energy management platform 112 is able to ensure that the loads connected to the power buses will not be able to draw excessive current I power from supply feed 210, regardless of the number or type of loads that are connected to the system.

Figure 3 illustrates a circuit diagram of passive current limiter 202 in accordance with embodiments of the invention. In the embodiment illustrated in Figure 3, it is assumed that the branch line that current limiter 202 is connected to branched off from the main supply line connected to supply feed 210 and may be known as a three-phase branch, a three-phase power bus, a three-phase lateral tap or a three-phase branch line. For brevity, this branch line will be defined as power bus 301 in the remainder of the description. An input terminal of power bus 301 is then in turn coupled to a reference current terminal of three-phase current source converter 302.

In other embodiments of the invention, power bus 301 that current limiter 202 is connected to may instead comprise a single-phase or a two-phase branch/power bus that branches off from the main feeder line that is connected to supply feed 210. The singlephase or two-phase power bus is then in turn coupled to a single-phase or two-phase current source converter accordingly. In the remainder of the description, while reference is only made to the three-phase power bus and three-phase current source converter, one skilled in the art will recognize that these components may be replaced with the single-phase or two-phase power bus and their corresponding single-phase or two-phase current source converters without departing from the invention.

As illustrated in Figure 3, an input terminal of the three-phase power bus is coupled to a reference current terminal of three-phase AC-DC current source converter 302 (which comprises three input terminals) while an output terminal of the three-phase power bus is coupled to an active load 204 through a primary side 311 of transformer 308. The secondary side 312 of transformer 308 is coupled to biasing terminals of diode bridge rectifier 304 and it should be noted that transformer 308 comprises a N:1 transformer that is known in the art, whereby the turn ratio N of transformer 308 is left as a design choice to one skilled in the art. An inductor 306 is coupled to the output terminal of rectifier 304 and the input terminal of converter 302. Three-phase current source converter 302 is used to regulate the constant current i flowing through inductor 306 and the value of inductor 306 is selected such that there is minimal ripple that occurs at the constant current i . The value of inductor 306 is left as a design choice to one skilled in the art. Further, as it can be seen, the output terminal of converter 302 is coupled to the input terminal of rectifier 304.

In embodiments of the invention, three-phase current source converter 302 may comprise transistor-diode pairs that are configured in series whereby each of these transistor-diode pairs may be communicatively coupled to energy management module 201. Module 201 may then be configured to regulate the constant current i flowing through inductor 306 by varying the voltage provided to the gates of the transistor-diode pairs in three-phase current source converter 302, which in turn regulates the amount of current, i.e. , lref_a-c, flowing through the reference current terminal of converter 302 from the input terminal of power bus 301. By doing so, module 201 would be able to dynamically allocate and set the constant current i flowing through inductor 306 as required. Decoupling capacitors C are also provided at the inputs to three-phase current source converter 302 to decouple converter 302 from the input terminal of the three-phase power bus.

In operation, energy management module 201 will cause convertor 302 to set the constant current i flowing through inductor 306 at a required current level. In embodiments of the invention, the required current level may be determined by a set of one or more factors such as maximum feed currents that are available at the input terminal of the power bus, the types of electrical loads that are connected to the output terminal of the power bus, and/or statuses of electrical loads that are connected to the output terminal of the power bus.

When load 204 draws a load current ii_oad that is less than a product of the constant current i (that is flowing through inductor 306) with turn ratio N, (Lx N), secondary side 312 of transformer 308 will be short circuited. As a result, the load current ii_oad may flow freely from the power bus to load 204.

However, when load 204 attempts to draws a load current ii_oad that is more than the product of the constant current i , with turn ratio N, (L x N), the product of the constant current i with turn ratio N will prevent this from happening and will cause the load current iioad to saturate at the product of the constant current i with turn ration N, (ii_ x N),. This happens because from the circuit diagram in Figure 3, when the current flowing across inductor 306 is set at a constant current level L, any currents flowing into node 320 may not exceed the constant current level i set earlier. By doing so, the current limiting circuit is able to set the maximum load current oad at the output terminal of the power bus effectively limiting the current drawn by load 204 without the need for sending any commands or instructions to load 204.

Hence, when two power buses are each provided with passive current limiting circuits as described above, energy management module 201 may be configured to dynamically allocate and set maximum load currents at the output terminals of the two power buses by dynamically setting a first constant current, i _i of a first passive current limiting circuit associated with one of the power buses and a second constant current, i_L2, of a second passive current limiting circuit associated with the other power bus.

Figure 4 illustrates an embodiment of the invention whereby current limiting circuit 202 is provided with an energy storage circuit. The energy storage circuit is connected in series with inductor 306 and converter 302. In this embodiment, the energy storage circuit comprises batteries 402 that are connected to the middle nodes of full-bridge current converter 408 (or the biasing terminals of convertor 408) through an LC ladder circuit comprising inductor 406 and capacitor 404. In other words, batteries 402 are connected in series with inductor 406 of the LC ladder circuit. The positive terminals of the diodes in converter 408 (or the input terminals of convertor 408) are coupled to the output terminals of converter 302 and the output terminals of converter 408 are coupled to the input terminals of diode bridge rectifier 304. Full-bridge current converter 408 is also communicatively coupled to energy management module 201 such that module 201 may modulate the charging of battery 402 and capacitor 404 through the selective switching of the transistor-diode pairs in convertor 408.

In further embodiments of the invention, harmonic components of the currents at the output terminal, i.e. , l_Out_a-c, of power bus 301 may be measured, extracted and subsequently utilized by energy management module 201 to alter harmonic components of currents l_ref_a-c drawn by convertor 302. When operated in a harmonic compensation operation, module 201 will superpose the harmonic components obtained from currents l_Out_a-c with the initial reference currents l_ref_a-c. Module 201 will then use the superposed currents to selectively modulate currents l_ref_a-c that are drawn by converter 302 from the input terminal of power bus 301. By doing so, the system is able to partially compensate for the harmonic components originally found in output currents l_Out_a-c thereby effectively reducing harmonic components of the currents at the supply feed 210. For completeness, it should be noted that the measurement of the currents l_Out_a-c at the output terminal of power bus 301 may be done using current sensors provided at the output terminal. Sequence analysers may be then utilized to extract the harmonic components of currents l_Out_a-c. In embodiments of the invention, the current sensors may be provided at power bus 301 while the sequence analysers may be provided at power bus 301 or module 201.

In accordance with embodiments of the invention, a block diagram representative of components of processing system 500 that may be provided within modules 112, 104, 102, 201 and any other modules in the system (as shown in any of the figures) for implementing embodiments in accordance with embodiments of the invention is illustrated in Figure 5. One skilled in the art will recognize that the exact configuration of each processing system provided within these modules may be different and the exact configuration of processing system 500 may vary and Figure 5 is provided by way of example only.

In embodiments of the invention, each of the modules in system 500 may comprise controller 501 and user interface 502. User interface 502 is arranged to enable manual interactions between a user and each of these modules as required and for this purpose includes the input/output components required for the user to enter instructions to provide updates to each of these modules. A person skilled in the art will recognize that components of user interface 502 may vary from embodiment to embodiment but will typically include one or more of display 540, keyboard 535 and trackpad 536.

Controller 501 is in data communication with user interface 502 via bus 515 and includes memory 520, processor 505 mounted on a circuit board that processes instructions and data for performing the method of this embodiment, an operating system 506, an input/output (I/O) interface 530 for communicating with user interface 502 and a communications interface, in this embodiment in the form of a network card 550. Network card 550 may, for example, be utilized to send data from these modules via a wired or wireless network to other processing devices found in loads, or to receive data via the wired or wireless network. Wireless networks that may be utilized by network card 550 include, but are not limited to, Wireless-Fidelity (Wi-Fi), Bluetooth, Near Field Communication (NFC), cellular networks, satellite networks, telecommunication networks, Wide Area Networks (WAN) etc.

Memory 520 and operating system 506 are in data communication with CPU 505 via bus 510. The memory components include both volatile and non-volatile memory and more than one of each type of memory, including Random Access Memory (RAM) 520, Read Only Memory (ROM) 525 and a mass storage device 545, the last comprising one or more solid- state drives (SSDs). Memory 520 also includes secure storage 546 for securely storing secret keys, or private keys. One skilled in the art will recognize that the memory components described above comprise non-transitory computer-readable media and shall be taken to comprise all computer-readable media except for a transitory, propagating signal. Typically, the instructions are stored as program code in the memory components but can also be hardwired. Memory 520 may include a kernel and/or programming modules such as a software application that may be stored in either volatile or non-volatile memory.

Herein the term “processor” is used to refer generically to any device or component that can process such instructions and may include: a microprocessor, microcontroller, programmable logic device or other computational device. That is, processor 505 may be provided by any suitable logic circuitry for receiving inputs, processing them in accordance with instructions stored in memory and generating outputs (for example to the memory components or on display 540). In this embodiment, processor 505 may be a single core or multi-core processor with memory addressable space. In one example, processor 505 may be multi-core, comprising — for example — an 8 core CPU. In another example, it could be a cluster of CPU cores operating in parallel to accelerate computations.

Figure 6 illustrates a simulated waveform of the load current of the power bus of the circuit illustrated in Figure 3. As illustrated in this plot, when the passive current limiting circuit is not used with the power bus between 0 and 0.1 seconds of the simulation, the root- mean-square (RMS) value of the load current is 20.64 ampere. However, when the passive current limiting circuit is deployed between 0.1 and 0.4 seconds of the simulation, it can be seen that the RMS value of the load current is reduced to 15.76 ampere.

Figure 7 illustrates a simulated waveform of the load current of the power bus of the circuit illustrated in Figure 3. Between 0 and 0.3 seconds of the simulation, when the current limiting circuit is limiting the load current without harmonic compensation, the total harmonic distortion (THD) of the grid current was found to be 9.27%. Between 0.3 and 0.4 seconds of the simulation, when the current limiting circuit is configured to compensate for the current harmonics, the THD of the grid current was found to be 2.76%. This shows the effectiveness of the harmonic compensation functionality of the circuit.

Figure 8 illustrates a simulated waveform of the load current of the power bus of the circuit illustrated in Figure 4, that is when the current limiting circuit is integrated with energy storage. Between 0 and 0.2 seconds of the simulation, the energy storage is idle, hence the energy storage current IES is zero. Between 0.2 and 0.4 seconds of the simulation, the energy storage is discharging, hence its current iss becomes negative. Accordingly, the magnitude of the input current i_in decreases, which indicates less power is required from the grid side. This simulation shows that energy may be stored by the energy storage circuit illustrated in Figure 4.

Figure 9 illustrates a circuit diagram of another embodiment of a passive current limiter 900 in accordance with embodiments of the invention. As illustrated in Figure 9, an input terminal of the three-phase power bus 203b is coupled to a reference current terminal of three-phase AC-DC current source converter 302 (which comprises three input terminals). An output terminal of the three-phase power bus 203b is coupled to an active load 902 through a primary side 911 of transformer 914 and an output terminal of another three-phase power bus 203a is coupled to an active load 904 through a primary side 921 of transformer 924.

The secondary side 912 of transformer 914 is coupled to biasing terminals of diode bridge rectifier 901 and similarly, the secondary side 922 of transformer 924 is coupled to biasing terminals of diode bridge rectifier 903. It should be noted that transformers 914 and 924 comprise a Ni : 1 and N2:1 transformer respectively that is known in the art, whereby the turn ratios Ni and N2 are left as design choices to one skilled in the art.

As described in the previous sections, an inductor 306 is coupled to the output terminal of rectifier 901 and the input terminal of converter 302. In operation, energy management module 201 will cause convertor 302 to set the constant current i flowing through inductor 306 at a required current level. In embodiments of the invention, the required current level may be determined by a set of one or more factors such as maximum feed currents that are available at the input terminal of the power bus, the types of electrical loads that are connected to the output terminal of the power bus, and/or statuses of electrical loads that are connected to the output terminal of the power bus.

When load 902 draws a load current ii_Oad_i that is less than a product of the constant current i (that is flowing through inductor 306) with turn ratio Ni, (ii_ x Ni), secondary side 912 of transformer 914 will be short circuited. As a result, the load current ii_Oad_i may flow freely from the power bus to load 902.

However, when load 902 attempts to draws a load current ii_Oad_i that is more than the product of the constant current i , with turn ratio Ni, (ii_ x Ni), the product of the constant current i with turn ratio Ni will prevent this from happening and will cause the load current iioad to saturate at the product of the constant current i with turn ration Ni , (ii_x Ni).

Similarly, when load 904 draws a load current ii_oad_2 that is less than a product of the constant current i (that is flowing through inductor 306) with turn ratio N2, (ii. x N2), secondary side 922 of transformer 924 will be short circuited. As a result, the load current iioad_2 may flow freely from the power bus to load 904.

However, when load 904 attempts to draws a load current ii_Oad_2 that is more than the product of the constant current i_L, with turn ratio N2, (ii_ x N2), the product of the constant current i with turn ratio N2 will prevent this from happening and will cause the load current iioad_2 to saturate at the product of the constant current i with turn ration N2, (ii_ x N2).

In this embodiment, as the output terminals of three-phase power buses 203a and 203b both share the same constant current, i_L, transformers 914 and 924 may comprise tap changing transformers with variable turn ratios, Ni and N2, to allow the respective maximum load current magnitudes to be adjusted as required, i.e., Nik and N2ii_. Numerous other changes, substitutions, variations, and modifications may be ascertained by the skilled in the art and it is intended that the present invention encompass all such changes, substitutions, variations, and modifications as falling within the scope of the appended claims.

Claims

22 CLAIMS:

1. A power controller comprising: a first power bus having an input terminal connectable to a power source, an output terminal connectable to a first electrical load, and a first passive current limiting circuit provided between the input and output terminals of the first power bus; a second power bus having an input terminal connectable to the power source, an output terminal connectable to a second electrical load, and a second passive current limiting circuit provided between the input and output terminals of the second power bus; and an energy management module coupled to the first and second passive current limiting circuits, wherein the energy management module is configured to dynamically allocate and set maximum load currents at the output terminals of the first and second power buses by dynamically setting a first constant current, i _i of the first passive current limiting circuit and a second constant current, i_L2, of the second passive current limiting circuit, whereby the dynamic allocation of the maximum load currents are done based on a set of one or more factors.

2. The power controller according to claim 1 wherein the set of one of more factors comprises one or more of: maximum feed currents made available to the input terminals of the first and second power buses, types of electrical loads that are connected to the output terminals of the first and second power buses, and statuses of electrical loads that are connected to the output terminals of the first and second power buses.

3. The power controller according to claims 1 or 2, whereby the first passive current limiting circuit comprises a current source converter (CSC) having a reference current terminal coupled to an input terminal of the first power bus, an inductive load coupled between an input terminal of the CSC and an output terminal of a diode bridge rectifier (REC), a transformer with a turn ratio of Ni and having a primary side coupled to an output terminal of the first power bus and a secondary side coupled to a biasing terminal of the REC, and an output terminal of the CSC being coupled to an input terminal of the REC, whereby the circuit is configured to: generate the first constant current, i_Li , across the inductive load using the CSC; cause a short circuit at the secondary side of the transformer when a load current, iioad, at the output terminal of the first power bus is less than a product of the first constant current, i_Li with turn ratio Ni; cause the load current, iioad, at the output terminal of the first power bus to saturate at the product of the first constant current, i_Li with turn ratio Ni, when the load current, iioad, at the output of the first power bus is equal the product of the first constant current, i_Li with turn ratio Ni; and whereby the second passive current limiting circuit comprises a current source converter (CSC) having a reference current terminal coupled to an input terminal of the second power bus, an inductive load coupled between an input terminal of the CSC and an output terminal of a diode bridge rectifier (REC), a transformer with a turn ratio of N2 and having a primary side coupled to an output terminal of the second power bus and a secondary side coupled to a biasing terminal of the REC, and an output terminal of the CSC being coupled to an input terminal of the REC, whereby the circuit is configured to: generate the second constant current, i_L2, across the inductive load using the

CSC; cause a short circuit at the secondary side of the transformer when a load current, iioad, at the output terminal of the second power bus is less than a product of the second constant current, ii_2 with turn ratio N2; cause the load current, iioad, at the output terminal of the second power bus to saturate at the product of the second constant current, ii_2 with turn ratio N2, when the load current, iioad, at the output of the second power bus is equal the product of the second constant current, ii_2 with turn ratio N2. The power controller according to claim 3 wherein the current source converter of the first and second passive current limiting circuits comprises one of: a three-phase CSC, a two-phase CSC or a single-phase CSC. The power controller according to claim 3, whereby the generation of the first constant current, i_Li using the CSC of the first passive current limiting circuit comprises the energy management module that is communicatively coupled to the CSC of the first passive current limiting circuit being configured to modulate gate voltages of transistor-diode pairs of the CSC of the first passive current limiting circuit to generate the first constant current, i_Li. The power controller according to claims 3 or 5, whereby the generation of the second constant current, ii_2 using the CSC of the second passive current limiting circuit comprises the energy management module that is communicatively coupled to the CSC of the second passive current limiting circuit being configured to modulate gate voltages of transistor-diode pairs of the CSC of the second passive current limiting circuit to generate the second constant current, ii_2. The power controller according to claim 3, whereby the first passive current limiting circuit further comprises an energy storage circuit that is coupled between an output terminal of the CSC and the input terminal of the REC whereby the energy storage circuit comprises: a full-bridge current converter having an input terminal coupled to the output terminal of the CSC, an output terminal coupled to the input terminal of the REC, and a biasing terminal coupled to an inductor-capacitor ladder circuit, whereby a battery is connected in series with the inductor of the inductor-capacitor ladder circuit. The power controller according to claims 3 or 7, whereby the second passive current limiting circuit further comprises an energy storage circuit that is coupled between an output terminal of the CSC and the input terminal of the REC whereby the energy storage circuit comprises: a full-bridge current converter having an input terminal coupled to the output terminal of the CSC, an output terminal coupled to the input terminal of the REC, and a biasing terminal coupled to an inductor-capacitor ladder circuit, whereby a battery is connected in series with the inductor of the inductor-capacitor ladder circuit. The power controller according to claim 1 or 2, 25 whereby the first and second passive current limiting circuits comprise a combined current limiting circuit, the combined current limiting circuit comprising a current source converter (CSC) having a reference current terminal coupled to an input terminal of the first power bus, an inductive load coupled between an input terminal of the CSC and an output terminal of a first diode bridge rectifier (REC), a first transformer with a turn ratio of Ni and having a primary side coupled to an output terminal of the first power bus and a secondary side coupled to a biasing terminal of the first REC, a second transformer with a turn ratio of N2 and having a primary side coupled to an output terminal of the second power bus and a secondary side coupled to a biasing terminal of a second REC, an input terminal of the first REC being coupled to an output terminal of the second REC, and an output terminal of the CSC being coupled to an input terminal of the second REC, and whereby the first constant current i _i equals the second constant current i_L2, and whereby the combined current limiting circuit is configured to: generate the first constant current, i _i , across the inductive load using the CSC; cause a short circuit at the secondary side of the first transformer when a load current, ii_Oad_i , at the output terminal of the first power bus is less than a product of the first constant current, i_Li with turn ratio N1; cause the load current, ii_Oad_i, at the output terminal of the first power bus to saturate at the product of the first constant current, i_Li with turn ratio N1, when the load current, iioad, at the output of the first power bus is equal the product of the first constant current, i_Li with turn ratio N1; cause a short circuit at the secondary side of the second transformer when a load current, ii_oad_2, at the output terminal of the second power bus is less than a product of the first constant current, i_Li with turn ratio N2; cause the load current, ii_oad_2, at the output terminal of the second power bus to saturate at the product of the first constant current, i_Li with turn ratio N2, when the load current, ii_Oad_2, at the output of the second power bus is equal the product of the first constant current, i _i with turn ratio N2. 26 A method for setting maximum load currents of a first and a second power bus using an energy management module, whereby the first power bus has an input terminal connectable to a power source, an output terminal connectable to a first electrical load, and a first passive current limiting circuit provided between the input and output terminals of the first power bus, whereby the second power bus has an input terminal connectable to the power source, an output terminal connectable to a second electrical load, and a second passive current limiting circuit provided between the input and output terminals of the second power bus, and whereby the energy management module is coupled to the first and second passive current limiting circuits, the method comprising: dynamically setting a first constant current, i _i of the first passive current limiting circuit and a second constant current, i_L2, of the second passive current limiting circuit to dynamically allocate and set the maximum load currents at the output terminals of the first and second power buses, whereby the dynamic allocation of the maximum load currents are done based on a set of one or more factors. The method according to claim 10 wherein the set of one of more factors comprises one or more of: maximum feed currents made available to the input terminals of the first and second power buses, types of electrical loads that are connected to the output terminals of the first and second power buses, and statuses of electrical loads that are connected to the output terminals of the first and second power buses. The method according to claims 10 or 11 , whereby the first passive current limiting circuit comprises a circuit that has a current source converter (CSC) having a reference current terminal coupled to an input terminal of the first power bus, an inductive load coupled between an input terminal of the CSC and an output terminal of a diode bridge rectifier (REC), a transformer with a turn ratio of Ni and having a primary side coupled to an output terminal of the first power bus and a secondary side coupled to a biasing terminal of the REC, and an output terminal of the CSC being coupled to an input terminal of the REC, and 27 whereby the second passive current limiting circuit comprises a circuit that has a current source converter (CSC) having a reference current terminal coupled to an input terminal of the second power bus, an inductive load coupled between an input terminal of the CSC and an output terminal of a diode bridge rectifier (REC), a transformer with a turn ratio of N2 and having a primary side coupled to an output terminal of the second power bus and a secondary side coupled to a biasing terminal of the REC, and an output terminal of the CSC being coupled to an input terminal of the REC, the method comprising: generating, using the first passive current limiting circuit, the first constant current, i_Li, across the inductive load using the three-phase CSC and generating, using the second passive current limiting circuit, the second constant current, i_L2, across the inductive load using the three-phase CSC; causing, using the first passive current limiting circuit, a short circuit at the secondary side of the transformer when a load current iioad, at the output terminal of the power bus is less than a product of the first constant current, i_Li with turn ratio N1 and causing, using the second passive current limiting circuit, a short circuit at the secondary side of the transformer when a load current iioad, at the output terminal of the power bus is less than a product of the second constant current, ii_2 with turn ratio N₂; causing, using the first passive current limiting circuit, the load current, iioad, at the output terminal of the power bus to saturate at the product of the first constant current, i_Li with turn ratio N1 , when the load current, iioad, at the output of the power bus is equal the product of the first constant current, i _i with turn ratio N1 and causing, using the second passive current limiting circuit, the load current, iioad, at the output terminal of the power bus to saturate at the product of the second constant current, ii_2 with turn ratio N₂, when the load current, iioad, at the output of the power bus is equal the product of the second constant current, ii_2 with turn ratio N₂. The method according to claim 12 wherein the current source converter of the first and second passive current limiting circuits comprises one of: a three-phase CSC, a two- phase CSC or a single-phase CSC. 28 The method according to claim 12, whereby the generating of the first constant current, i_Li using the CSC of the first passive current limiting circuit comprises the steps of: modulating, using the energy management module that is communicatively coupled to the CSC of the first passive current limiting circuit, gate voltages of transistor-diode pairs of the CSC of the first passive current limiting circuit to generate the first constant current, i_Li. The method according to claims 12 or 14, whereby the generating of the second constant current, ii_2 using the CSC of the second passive current limiting circuit comprises the steps of: modulating, using the energy management module that is communicatively coupled to the CSC of the second passive current limiting circuit, gate voltages of transistor-diode pairs of the CSC of the second passive current limiting circuit to generate the second constant current, ii_2. The method according to claim 12, whereby the first passive current limiting circuit further comprises an energy storage circuit that is coupled between an output terminal of the CSC and the input terminal of the REC whereby the energy storage circuit comprises: a full-bridge current converter having an input terminal coupled to the output terminal of the CSC, an output terminal coupled to the input terminal of the REC, and a biasing terminal coupled to an inductor-capacitor ladder circuit, whereby a battery is connected in series with the inductor of the inductor-capacitor ladder circuit. The method according to claims 12 or 16, whereby the second passive current limiting circuit further comprises an energy storage circuit that is coupled between an output terminal of the CSC and the input terminal of the REC whereby the energy storage circuit comprises: a full-bridge current converter having an input terminal coupled to the output terminal of the CSC, an output terminal coupled to the input terminal of the REC, and a biasing terminal coupled to an inductor-capacitor ladder circuit, whereby a battery is connected in series with the inductor of the inductor-capacitor ladder circuit. The method according to claims 10 or 11 , 29 whereby the first and second passive current limiting circuits comprise a combined current limiting circuit, the combined current limiting circuit comprising a current source converter (CSC) having a reference current terminal coupled to an input terminal of the first power bus, an inductive load coupled between an input terminal of the CSC and an output terminal of a first diode bridge rectifier (REC), a first transformer with a turn ratio of Ni and having a primary side coupled to an output terminal of the first power bus and a secondary side coupled to a biasing terminal of the first REC, a second transformer with a turn ratio of N2 and having a primary side coupled to an output terminal of the second power bus and a secondary side coupled to a biasing terminal of a second REC, an input terminal of the first REC being coupled to an output terminal of the second REC, and an output terminal of the CSC being coupled to an input terminal of the second REC, and whereby the first constant current i _i equals the second constant current i_L2, the method comprising: generating, using the combined current limiting circuit, the first constant current, i_Li , across the inductive load using the CSC; causing, using the combined current limiting circuit, a short circuit at the secondary side of the first transformer when a load current, ii_Oad_i, at the output terminal of the first power bus is less than a product of the first constant current, i _i with turn ratio N1; causing, using the combined current limiting circuit, the load current, ii_Oad_i , at the output terminal of the first power bus to saturate at the product of the first constant current, i_Li with turn ratio N1, when the load current, iioad, at the output of the first power bus is equal the product of the first constant current, i _i with turn ratio N1; causing, using the combined current limiting circuit, a short circuit at the secondary side of the second transformer when a load current, ii_Oad_2, at the output terminal of the second power bus is less than a product of the first constant current, i_Li with turn ratio N2; causing, using the combined current limiting circuit, the load current, ii_Oad_2, at the output terminal of the second power bus to saturate at the product of the first constant current, i _i with turn ratio N2, when the load current, ii_Oad_2, at the output of the second power bus is equal the product of the first constant current, i_Li with turn ratio N2.