FIELD OF THE INVENTION

[001] The present invention relates to power regulation, and more particularly to a power regulating device for regulating supply of power between multiple electrical systems.

BACKGROUND OF THE INVENTION

[002] An electrical network typically has various hardware such as switches, power sources, loads, and power regulating devices such as inverters, rectifiers etc. In order to operate a load such as solar pump or other loads (e.g. conveyors, winders, combination of loads etc.), one or multiple such hardware can be used.

[003] There may be multiple converters performing the same / similar job while feeding power to one or more electrical systems. For instance, there may be a line side converter for controlling feeding of power to a Grid and a motor side converter for controlling feeding of power to a motor. Each piece of hardware comes with a cost. Accordingly, the larger the number of hardware, the higher the cost and complexity, which in turn affects reliability.

[004] An additional concern arises in the utilization of the power sources. Due to the variation in the availability and capability of different power sources, connecting different power sources to one or more loads has a challenge of its own.

[005] Accordingly, there is a need for an improved power regulating device which utilizes minimal hardware and efficiently connects different power sources and loads. SUMMARY OF THE INVENTION

[006] An aspect of the invention provides a power regulating device. The power regulating device comprises a power stage and a control board. The power stage has a rectifier stage, a DC link and an inverter stage. Further, the power stage has a topology in which the rectifier stage is coupled with the DC link and the DC link is coupled with the inverter stage. In one embodiment, the rectifier stage is a diode rectifier stage. The inverter stage may have a switching component such as, but not limited to, an Insulated Gate Bipolar Transistor (IGBT) bridge.

[007] Additionally, the rectifier stage is connected with one of a first electrical system and a second electrical system. This depends on which one of the two electrical systems is acting as the source. The corresponding electrical system acting as the source is connected with the rectifier stage. The inverter stage is connected with one of the first electrical system and the second electrical system. This depends on which of the two electrical system acts as the load. Each of the first electrical system and the second electrical system acts as one of a source and a load respectively.

[008] The first electrical system can be one of, but not limited to, a Grid and a motor. The second electrical system can accordingly be one of, but not limited to, the motor and the Grid respectively. In the scenarios wherein the motor is one of the two electrical systems, the motor acts as one of an AC source and a load. The motor acts as the AC source in a regenerative mode and as a load in a motoring mode. Accordingly, in the regenerative mode, the motor is connected with the rectifier stage as the AC source, and the grid is connected with the inverter stage as the load. Similarly, in the motoring mode, the grid is connected with the rectifier stage as the AC source and the motor is connected with the inverter stage as the load.

[009] Optionally, the power regulating device is also connected with a third electrical system. The third electrical system may be one of a photovoltaic array, a battery and DC generator. In this topology, the DC link is connected with the third electrical system.

[0010] One or more components of the power stage are controlled through the control board of the power regulating device. The control board comprises an I/O module, a switching logic and a control module. The I/O module receives input from a sensor and sends commands for operating one or more switches connecting the power stage with the first electrical system and the second electrical system.

[0011] The sensor can be a sensor associated with a mode selection switch, or a sensor associated with a load (e.g. conveyor, winder) operated through one of the first electrical system and the second electrical system. In case the third electrical system is also connected, the one or more switches connect the rectifier stage, the DC link and the inverter stage with the first, second and third electrical systems. In such a case as well, the switches are also operated through the I/O module.

[0012] The switching logic defines one or more connections between the rectifier stage, the inverter stage, the first electrical system and the second electrical system through the one or more switches. In case there is the third electrical system, the switching logic defines one or more connections between the rectifier stage, the DC link, the inverter stage and the first, second and third electrical systems. The switching logic and accordingly the connection varies depending on which of the electrical systems act as a source and which acts as a load. Accordingly, which switches need to connect which electrical systems to corresponding components of the power stage is defined by the switching logic.

[0013] The control module processes the input received from the sensor for determining a corresponding connection from the one or more connections defined by the switching logic. Based on the processing, the control module transmits signals to the I/O module, which in turn sends the commands for operating the one or more switches as per the signals. The control module also provides control logic to the inverter stage based on the determination from the input received from the sensor and the corresponding connection for feeding power to one of the first electrical system and the second electrical system. The control logic can have one or more of, but not limited to, a logic for feeding power to the grid and a logic for feeding power to the motor. In the scenario having the third electrical system, the control logic comprises a logic for feeding of power to one of the first electrical system and the second electrical system based on a power demand of the corresponding electrical system and a power available at one or more of the third electrical system and one of the first electrical system and the second electrical system.

[0014] In case where there is the third electrical system, the control board can control the supply of power from the third electrical system to one of the first electrical system and the second electrical system. This can be based on the input of the sensor. Further, the power supply from the third electrical system may be switched from the first electrical system to the second electrical system based on a new input. The control logic that is provided correspondingly to the inverter stage may be changed from the logic for controlling supply to the rid to the logic for controlling supply to the motor loads.

BRIEF DESCRIPTION OF DRAWINGS

[0015] The subject matter of the invention will be explained in more detail in the following text with reference to exemplary embodiments which are illustrated in attached drawings in which:

[0016] Fig. 1 is a simplified representation of a power regulating device connected with a plurality of electrical systems; [0017] Fig. 2 is another simplified representation of the power regulating device connected with a DC source, a motor and a Grid;

[0018] Fig. 3 is a simplified representation of a connection between a power stage and an AC source, a DC source and a load;

[0019] Fig. 4 is a simplified representation of a power flow between the motor and the grid;

[0020] Fig. 5 is a simplified representation of another power flow between the grid and the motor;

[0021] Fig. 6 is another simplified representation of the connection between the power regulating device and the plurality of electrical systems; and

[0022] Fig. 7 is another simplified representation of the connection between the power regulating device, the Grid and the motor.

DETAILED DESCRIPTION

[0023] Referring to Fig. 1 , which is a simplified representation of a power regulating device (100) connected with a plurality of electrical systems including a first electrical system (120) and a second electrical system (122). The power regulating device has a power stage (102) and a control board (104).

[0024] The power stage has a rectifier stage (106), a DC link (108) and an inverter stage (110). The rectifier stage can be a three phase diode bridge. The DC link can be a DC capacitor link and the inverter stage can be a controlled switching component such as an Insulated Gate Bipolar Transistor (IGBT) bridge. [0025] The control board has an I/O module (112), a switching logic (114) and a control logic (116). The I/O module can have one or more of, but not limited to, one or more digital inputs, one or more digital outputs, one or more analog inputs and one or more analog outputs. The digital / analog inputs can receive input from a sensor (118). For example, there may be a sensor connected with a user interface of a load (e.g. a conveyor), which can pass on information as per user input. Taking another example, there may be a load such as a conveyor, and a sensor may be linked with a mode of operation of the load. Here, a change in mode (e.g. change from winder to unwinder or forward or reverse etc.), may be sensed and communicated to the digital / analog inputs. The digital outputs may be used for sending commands for operating switches (e.g. opening or closing of one or multiple switches). The I/O module may be provided as a separate board communicating with the control board.

[0026] The switching logic defines one or more connections between one or more of the rectifier stage, the DC link and the inverter stage, and one or more electrical systems.

[0027] In the embodiment illustrated in Fig. 1, the switching logic defines that the first electrical system is connected with the rectifier stage and the inverter stage through switches S 1 and S2. Depending on whether the first electrical system is a source or a load, only one of S 1 and S2 is closed, while the other is open. In a similar manner, the switching logic defines the connections between the second electrical system and the rectifier stage and the inverter stage through switches S3 and S4.

[0028] In the embodiment shown in Fig. 2, the switching logic defines the connections between the power regulating device, a DC source (202), a motor (204) and a Grid (206). Here, the DC source may be a photovoltaic array, which can supply power to the Grid or the motor. According to the embodiment, the switch S5 can be closed, connecting the DC source with the power regulating device (through the DC link shown in Fig. 1). In addition, one of switch S6 or S7 can be closed, connecting the motor or grid as a load. There could be a scenario where the load demand from the motor is higher than what could be supplied from the DC source. Accordingly, additional power can be pulled from the Grid by closing the switch S8 (switch S7 being open), which connects the Grid at the rectifier stage.

[0029] Another example of the connection between the sources and loads is shown in Fig. 3, wherein an AC source (302) is connected at the rectifier stage, a DC source (304) is connected with the DC link and a load (306) is connected with the inverter stage. The AC source may be a grid or a motor in a generation mode. The load may be a Grid or a motor in a motoring mode.

[0030] The control board process the input from the sensor and determines which connection defined by the switching logic is to be applied. Accordingly, the control board provides the control logic to the inverter stage. For example, depending on whether the motor is connected as a load or the power is fed to the Grid, the appropriate control logic to feed the power can be provided to the inverter stage. In case the DC source is used, the control board can determine the power demand of the load and how the different power sources should be connected to satisfy the power demand.

[0031] The following describes an example of operation of the power regulating device. The input would be a digital input via the I/O module, wherein the based on the input, the logic for motoring or generation would be switched in the control board.

[0032] During the motoring mode, the logic is switched to motor control logic and S 1 and S3 is switched (see Fig. 1 and Fig. 7). Based on the start command which is given via the I/O module (or fieldbus) and reference, the motor starts rotation based on the set speed. In this mode all the motor protection features are enabled. The powers flow from the diode bridge to DC link and then inverter stage to be converted to the AC power based on the reference set as shown in Fig. 4. The control board generates the switching pattern fed to the gate driver board to trigger the inverter stage to get desired voltage and frequency based on the reference.

[0033] During the regeneration mode, the logic is switched to grid side control logic and S2 and S4 (refer Fig. 1 and Fig. 7) are switched. Now motor, which is acting as generator will connect to the diode bridge and inverter stage will get connected to grid side. Once the start command is given the motor which is acting as a generator, the motor will produce AC power, which will be rectified by the diode bridge and provided to charge the DC capacitor. Also, inverter modulation is started and power is fed back to the Grid. So the power flows from the generator from the diode bridge to DC capacitor and then to the inverter stage to be converted to AC power, which is fed to the Grid as shown in Fig. 5. In this mode the DC voltage reference is set via a keypad, AI or fieldbus and based on the reference set, the control board generates the switching pattern fed to the gate driver board to trigger the inverter stage to get the desired voltage and frequency based on the reference. In this mode, there are four controllers working together: torque and flux hysteresis controller and dc voltage and reactive power control. Also, the Grid side auto identification is done to synchronize with the Grid.

[0034] The following describes another example of operation of the power regulating device. Here, the same topology could be used with other source, wherein the DC link could be powered from a PV Panel or other DC Source as shown in Fig. 6. In this case, the sensor is actuated to connect to motor for driving a connected load (e.g. conveyor or winder). Accordingly, the motor control logic is loaded. At the same time, S5 and S6 (refer Fig. 5) are closed and the motor is connected to be run for a different application like pump or conveyor. [0035] When the motor load demand is high and the DC source (e.g. PV) is not able to generate the required power, then additional power could be supplied from the Grid or other AC source via the Diode Bridge by switching S8 (see Fig. 2, Fig. 6).

[0036] When grid control mode is selected via digital input or other sensor, the S5 and S7 contactors are switched and the grid side control logic is switched in the control board. Also, the DC source, which can be a PV panel or a DC generator driven via an active load (e.g. pump storage), will get connected for feeding power at the DC link. This connection can be from a brushless DC motor with blades driven by water falling from the storage tank. Water from the top of tank is used to drive the blades which are coupled to the DC generator, which generates the DC power, which is fed to intermediate DC circuit and the Grid control logic is switched to feed the power back to the network via the inverter stage.

[0037] In the above scenario, the switches S6 and S7 are cross interlocked to ensure that either motor side control or Grid control is connected. This would be replacement for battery storage, wherein this small hydro plant can be setup with the existing infrastructure in an apartment. Here, it is assumed that an overhead tank exists and an additional tank can be constructed. The existing pump, which would be run by the same inverter after switching to motor control mode to pump the water from below to refill the overhead tank when the solar power is available. During night time, this tank is emptied and drives the DC motor as generator. This output DC is connected to the DC link. Prior to connecting the output DC, the inverter logic is switched to grid control mode and start command is given to the inverter, which starts feeding power to the Grid or internal load.

[0038] Consider a case of an active load motor (e.g. a downhill conveyor or unwinder). The downhill conveyor is an inclined conveyor where it is driven by the gravitational force and this motor will be in continuous regeneration. The motor acts as generator and is fed via a diode bridge which creates the DC Voltage across the DC Bus which would be feed to the Inverter and which feed the power to the network. Typically, regenerative drives may be used, which has line side converter and motor side converter, which increase the cost. With this invention, since it is known that in some cases, the motor is always regenerating (e.g. downhill conveyor). In such cases, the motor is connected to the diode bridge and this generates the DC bus voltage, which in turn feeds the power to Grid via the inverter stage or to a load like pump, centrifuge or other conveyor instead of feeding to the Grid.

[0039] In a fixed unwinder / winder or a coiled / uncoiled line, this invention can be used to reduce the cost. In such cases, the motors act in either regeneration or motoring modes. There, the switching of logic and connections can be performed to control feeding of power generated to a network or load and optimize utilization of energy from the Grid and the generator.

[0040] The power regulating device disclosed herein can be utilized in situations where there are multiple electrical systems, each of which may act as a source or load. Depending on the mode of each of the multiple electrical systems, and the power requirements, the connections between the multiple electrical systems and the components of the power stage can be determined. Further, the appropriate control logic can be selected and provided for feeding of power to the loads.

[0041] The power regulating device may also have communication abilities. In such a case, the power regulating device can obtain the switching logic and / or the communication logic through a network depending on the mode of operation of the electrical systems and the power requirements.

[0042] Thus, the invention provides various advantages. One of the most significant advantages given by the invention is that the same hardware is used for connecting different power sources and loads. Also, the power regulating device regulates switching the connections between various sources and loads based on sensor inputs, thereby optimally utilizing power from different sources. In addition, the control logic is selected dynamically based on the load(s) profile, thereby the cost optimization is achieved with a higher reliability.