The present invention relates to the supply of electrical power, and in particular to a multi-phase electrical transformer and a multi-phase electrical power control apparatus.
The electricity system is undergoing a change of scale not seen for decades. The traditional model of centralised large-scale generation providing electricity and inertia is changing to allow for carbon-free generation technologies such as solar and wind to supply a greater percentage of our electricity needs. This, combined with an increasing uptake in electric vehicles and electrification of heating systems is resulting in a system where the way we generate and use electricity has changed to a more decarbonised, decentralised, digitised and democratised system, but the way we transport it has not evolved and is no longer fit for purpose.
Energy System Challenges
The fundamental design of the electricity grid has not changed in more than 100 years. It is based on a hub and spoke delivery system, with electricity flowing one way from large generators to tranched consumers. The distances travelled are generally quite large, spanning hundreds and sometimes thousands of kilometres, resulting in significant energy losses. The entire system is generator-centric in that generators act to balance the grid by controlling the amount of power that is generated to match the amount of power that is consumed. The traditional generators provide both the real power consumed, as well as other services such as inertia to the grid to maintain stability.
Traditional generation such as coal fire power plants use a spinning turbine to generate electricity. The spinning mechanical inertia stored in the spinning turbine provides immediate acting synchronous power reserves for the system when an imbalance occurs.
Electricity generated from renewable sources such as wind and solar still provide the real power required, however they do not provide any inertia. This is primarily due to the fact that the generating elements are not physically connected to the system. The properties of these renewable generators are also volatile: the voltage, harmonics and phase can change rapidly, but the electricity system cannot cope with these rapid changes.
Renewable energy generation is becoming cheaper than traditional generators because the marginal cost of production is very low. In particular, whereas coal power plants require a consumable input of coal to generate power, wind and solar only require the wind and the sun, which are freely available. However, because of the volatile nature of generation as described above, the electricity grid must be provided with balancing services to maintain the fragile balance of supply and demand in real time to provide a reliable power supply. As the percentage of renewable energy generation increases, so does the balancing services requirement. This has led to higher energy prices, for example in the USA the cost of energy is made up of 40% non-wholesale costs, and in some states such as New York this rises to 90% (source EIA). In Germany, the non-wholesale cost of energy accounts for 80.7% of the price of energy (source BDEW 2017).
Energy System Pricing Models
Most electricity systems globally operate in an energy market where generators bid to provide energy at a cost. The market operator then selects a mix of the cheapest generation to supply the predicted demand for a specified period, which is usually 30 minutes.
However, the changes to the electricity system described above significantly affect this practice in a number of ways. First, renewable generation is not dispatchable like traditional generation: it is dependent on the weather, which is outside the generators' control. This means the generators at times do not meet their generation requirements, or affect the short-term system stability by immediately starting or stopping generation. Renewable generators often underestimate the amount of energy they will produce in order to avoid undersupply and the associated financial penalties, which means these generators have to curtail excess energy.
Additionally, geographically distributed power generation means that the power flows within the electricity grid are changing, both in quantity and sometimes direction. The grid owner and operator generally have no insight as to what is happening within the system, as monitoring instrumentation was not previously required in these locations. This makes it more challenging for the grid to be kept operating effectively and efficiently.
It is desired to overcome or alleviate one or more difficulties of the prior art, or to at least provide a useful alternative.
In accordance with some embodiments of the present invention, there is provided an electrical power control apparatus, including:
In some embodiments, each of the phase limbs is interconnected to the other phase limbs only at respective ends of the phase limb.
In other embodiments, the magnetic core further includes coupling limbs that interconnect the phase limbs, wherein each phase limb is connected to adjacent ones of the other phase limbs at a location of the phase limb between the ends of the phase limb.
In some embodiments, the limbs of the magnetic core have a circular cross-section. In some embodiments, the limbs of the magnetic core have a square or rectangular cross-section.
In some embodiments, each of the control windings constitutes a portion of the corresponding secondary winding.
In some embodiments, the electrical power control apparatus includes one or more rectifier windings around respective portions of the magnetic core to generate electric power for the control windings. In some embodiments, each of the rectifier windings constitutes a portion of the corresponding primary winding.
The electrical power control apparatus may include one or more rectifier components coupled to the rectifier windings, wherein each rectifier component receives an AC input from the corresponding rectifier winding, rectifies the received signal and charges at least one corresponding capacitor, wherein the at least one corresponding capacitor provides the electric power for at least one of the control windings. Each rectifier component may be configured to correct the power factor of the corresponding electrical phase.
The electrical power control apparatus may include one or more inverter components, each inverter component being coupled to the at least one corresponding capacitor and at least one of the corresponding control windings, and configured to generate the control signal for at least one of the control windings. The electrical power control apparatus may include a control component to control operation of the one or more inverter components.
The electrical power control apparatus may include control components to generate, for each of the phases of electric power, the corresponding control signal that is applied to the corresponding control winding to dynamically control the magnetic flux through the corresponding phase limb and consequently the corresponding output signal at the corresponding secondary winding.
The one or more electrical attributes may be selected from AC voltage and harmonic content or harmonic distortion.
Also described herein is an electrical power control apparatus, including:
In accordance with some embodiments of the present invention, there is provided a multiphase electric power transformer, including:
In some embodiments, the limbs of the magnetic core have a square or rectangular cross-section. In other embodiments, the limbs of the magnetic core may have a circular cross-section.
Also described herein is an electrical power control apparatus, including:
The electrical power control apparatus may include one or more rectifier windings around respective portions of the magnetic core to generate electric power for the control windings, wherein each of the rectifier windings constitutes a portion of the corresponding primary winding.
Some embodiments of the present invention are hereinafter described, by way of example only, with reference to the accompanying drawings, wherein:
International Patent Application No. PCT/AU2019/050246, entitled “An electrical power control apparatus and process” (referred to hereinafter as the “Faraday Exchanger application”), describes an electromagnetic apparatus or device, referred to in that application and herein as a “Faraday Exchanger”, that receives input electrical energy in the form of an AC input signal having some voltage waveform and root-mean-square (RMS) voltage amplitude, and converts that input electrical energy to output electrical energy in the form of an output signal having a desired or ‘target’ voltage waveform, and a desired or ‘target’ output RMS voltage. The input electrical energy typically varies over time (that is, its AC voltage waveform and/or its RMS voltage is time-dependent), and thus the apparatus operates to dynamically control the conversion so that the output electrical energy has the desired target voltage waveform and target RMS voltage independently of the input voltage waveform and RMS voltage, and dynamic variations of those input characteristics. The dynamic control is achieved by the dynamic control of magnetic flux coupling in a magnetic core.
Additionally and simultaneously, the output electrical energy of the Faraday Exchanger has a power factor determined by the downstream load drawing power from the Exchanger. The Faraday Exchanger determines that power factor on its output, and provides a unity power factor on its input, such that (the input of) the Exchanger appears as an ideal (i.e., purely resistive) load.
The Faraday Exchanger is thus able to provide voltage waveform and RMS voltage conversion while simultaneously providing power factor correction. The use of high-speed electromagnetic path modulation instead of the electronic circuit switching used in prior art power electronics devices enables the Faraday Exchanger to deliver improved efficiency and performance (while also electrically isolating the upstream and downstream components).
The Faraday Exchanger is particularly useful when multiple instances of the exchanger are distributed throughout an electric power distribution network to maintain a stable and clean sinusoidal AC waveform with reduced harmonic content and improved power factor throughout the network, particularly when unpredictable and highly variable renewable energy sources such as solar and wind power generators are distributed throughout the network. By dynamically storing and releasing energy to compensate for such variations throughout the network, the overall stability of the network can be maintained. The control of power factor reduces energy losses, and thus improves the power carrying capacity and productivity of the network. The reduction of harmonics increases the efficiency and security of the network. By being able to adjust output voltage in real time depending on grid frequency and rate of change of grid frequency, a change in demand of loads connected to the exchanger is created. Faraday Exchangers can hence support the grid frequency and Rate of Change of Frequency (“RoCoF”) protection within the parameters of grid operation by producing suitable demand response from the loads connected to the exchanger output.
When applied to three-phase power, a three-phase (“3P”) Faraday Exchanger includes three of the magnetic cores described above in parallel, one for each phase, with a single control component configured to dynamically control and coordinate the operation of all three magnetic cores, as illustrated schematically in
Although the three-phase Faraday Exchanger has been demonstrated to be extremely capable at maintaining a stable and clean supply of electric power in the face of unpredictable and highly variable injected power, there is nevertheless room for improvement. In particular, the magnetic cores are heavy and rather costly.
In order to alleviate these difficulties, the inventors have developed a multi-phase magnetically coupled core that forms the basis of a new form of multi-phase Faraday Exchanger. For example, in the case of three-phase power, a three-phase Faraday Exchanger need include only one magnetic core, namely a three-phase magnetically coupled core as described herein, rather than the three separate magnetic cores described in the Faraday Exchanger application. The use of only one magnetic core not only provides substantial cost and weight savings, but also reduces iron losses, and enables the transfer of energy between phases to occur entirely in the magnetic domain. As described below, a magnetically coupled multi-phase core also provides other performance benefits.
Primary and secondary windings for each phase are arranged around the corresponding peripheral vertical limbs interconnecting the central layer with the top and bottom layers of the magnetic core. The rectifier and control windings for each phase are wound around the corresponding horizontal limb of the central Y-shaped layer of the magnetic core.
A particular advantage of the multi-phase magnetic cores described herein is the significant reduction in the total volume of core material required, relative to using multiple separate magnetic cores for respective electrical phases. This factor alone provides a significant reduction in volume, mass, and cost of a three-phase Faraday Exchanger. Additionally, magnetic modelling of this core configuration reveals that the magnetic flux flows effectively cancel each other in the central vertical limbs interconnecting the central layer to the top and bottom layers of the magnetic core, as illustrated schematically in
In this embodiment, the primary, secondary, and rectifier windings for each phase are wound concentrically in a stacked arrangement around the corresponding vertical limbs interconnecting the corresponding vertex of the central layer with the respective vertices of the top and bottom layers. That is, for each vertical limb the corresponding rectifier windings are wound directly onto the corresponding vertical limb, the corresponding secondary windings are wound over the rectifier windings, and the corresponding primary windings are wound over the secondary windings. The control windings for each phase are wound around a corresponding horizontal limb of the central layer.
The three-phase magnetic cores of
As shown in
Returning to the square form embodiment illustrated in
The three-phase magnetic core configurations described herein support considerable flexibility in the arrangement of windings around the various limbs of the magnetic core. For example,
The electromagnetic performance of the three-phase magnetic cores described herein can be simulated using an electromagnetic stimulator platform, in this instance Altair Flux3D, as described at https://www.altair.com/flux/. The simulations described below were generated for a signal frequency of 50 Hz at time steps of 300 μs (i.e., 60 steps per cycle), for a 10 kVA core with the following parameters:
Similarly,
Windings
In addition to the advantages resulting from the new multi-phase magnetic core configurations, the inventors have also devised improvements to the core windings. In particular, inventors have determined that is not necessary for the rectifier and control windings to be physically separate to the primary and secondary windings and to be wound around horizontal limbs of the core. In particular, as shown in
On the primary side, the relevant equations are as follows:
and on the secondary side:
This provides a significant reduction in the amount of copper wire required, reducing copper wire energy losses, and significantly reducing the size, weight and cost of the core. Moreover, this allows the central horizontal limbs to be entirely omitted, enabling new and simplified rectilinear and spherical core configurations as shown in
To demonstrate the performance of these three magnetic core configurations, the primary current, secondary voltage, and secondary current in each configuration was simulated as described above, and the results are shown in
Heavy: Large area around corner and limb; Medium: Area around 3-4 corners;
Light: Area around 1-2 corners
A transformer with the demi-torus magnetic core provides far superior performance, and with substantially lower mass and volume relative to the other configurations described herein. For example, a 500 kVA transformer can be made from a demi-torus core with a core volume of 0.087 m3 and weighing 666 kg. When used as the core of a three-phase Faraday Exchanger, the total weight of the core and windings is 984 kg. When used as the magnetic core of a conventional three-phase transformer, the total weight of the core and windings is 1250 kg.
Although embodiments of the present invention have been described above in the context of three-phase electric power, it should be understood that other embodiments of the invention may support multi-phase or polyphase electric power in which the number of phases is greater than three and the phase difference between respective phases is less than 120°. For example, the number of phases may be 5, 6, 7 or even greater.
Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention.
Number | Date | Country | Kind |
---|---|---|---|
2020902972 | Aug 2020 | AU | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/AU2021/050926 | 8/20/2021 | WO |