Rectifier Control System

Abstract

The present disclosure relates to a method for varying the power consumption of a direct current (DC) powered industrial process by a control circuit (306), which uses a load modulation set point (δP) and one or more feedback signals (i line ,u line ) and based on the load modulation setpoint and the feedback signal, a direct current (i c ) current setting value (δi c ) and the current setting value (δi c A control unit (304) configured to control at least the saturation level of the saturable reactor (120) based on a current set value (δi c ) to supply.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates generally to the field of power management systems, and more particularly to circuits and methods for controlling rectifiers for DC applications. Summary of the Invention [Problem to be solved by the invention]

[0002] Some industrial processes require the application of direct current (DC) to one or more elements that carry out the process, for example, electrolysis processes require the flow of DC current through the lines of a manufacturing cell.

[0003] Balancing services for the grid are proposed. The grid frequency is the most important indicator of the power imbalance at a given moment in the grid. Indeed, an increase in consumption increases the power demand of the synchronous machines, which in turn slows down their rotation speed. Conversely, a decrease in the power demand at a given moment leads to overproduction and therefore to an increase in frequency.

[0004] In Europe, it is the role of the Transmission System Operator (TSO) to guarantee the stability of the grid by organizing and overseeing the implementation and mechanisms related to frequency control. In other countries, there are entities that fulfill a similar role. In relatively large grids, there are generally three layers of frequency control used to deal with frequency deviations: primary frequency control, secondary frequency control, and tertiary frequency control. Primary frequency control (PFC), also known as frequency control reserve (FCR), is mainly given by the droop characteristics of large generators. However, with the advent of demand response (DR) in today's smart grid development, the demand side has become a new actor in the stability of the grid. In fact, industrial sites are often willing to allow flexibility in their electricity consumption in exchange for financial incentives such as reduced energy costs.

[0005] It would be advantageous to make the power consumption of an electrolysis process, or other similar industrial processes based on direct current, variable, thereby enabling demand-side balancing of the power grid. However, the implementation of such a solution presents technical challenges.

[0006] It is an aim of embodiments of the present disclosure to at least partially address one or more problems in the prior art. [Means for solving the problem]

[0007] According to one embodiment, there is provided a method of modifying power consumption of an industrial process powered by a direct current, comprising receiving by a control circuit a load modulation setpoint indicative of an amount of modification to be applied to power of the industrial process and one or more feedback signals indicative of a power level supplied to the industrial process, generating by the control circuit a first current setpoint of a first direct current supplied to the industrial process by a first rectifier circuit having a first transformer and a saturable reactor based on the load modulation setpoint and the one or more feedback signals, and providing the first current setpoint to a first controller configured to control at least a saturation level of the saturable reactor based on the first current setpoint.

[0008] According to one embodiment, the first controller is further configured to control a tap position of a first transformer of the first rectifier circuit based on the first current set value.

[0009] According to one embodiment, the first current set point indicates an amount of change to be applied to a first process set point of current provided by the first rectifier circuit.

[0010] According to one embodiment, the method further comprises generating, by the control circuit, a second current set point for a second direct current supplied to the industrial process by one or more second rectifier circuits, each having a second transformer, and providing the second current set point to a second controller configured to adjust a tap position of a second transformer of each of the one or more second rectifier circuits based on the second current set point.

[0011] According to one embodiment, the second current set point indicates an amount of change to be applied to a second process set point of current provided by the one or more second rectifier circuits.

[0012] According to one embodiment, the control circuit is configured to generate the first current setpoint based on an equivalent admittance κ of the second rectifier circuit, the control circuit being configured to calculate the equivalent admittance κ, for example, based on the following formula:

[0013]

number

[0014] Here, K q is the estimated droop of each of the first and second rectifier circuits, q, and l is the number of first and second rectifier circuits.

[0015] According to one embodiment, the control circuit is further configured to generate the first current setpoint based on a group factor Γ representative of a sum of currents through the second rectifier circuits, the control circuit being configured to calculate the group factor Γ, for example, based on the following formula:

[0016]

number

[0017] Here, u rk,q is the output voltage q of each of the first rectifier circuit and the second rectifier circuit.

[0018] According to one embodiment, the control circuit is configured to generate the first current set point based on the following formula:

[0019]

number

[0020] where R is an estimate of the load resistance of the industrial process, E is an estimate of the back EMF voltage of the industrial process, and i c,0 is the first process setpoint and ΔP is the load modulation setpoint.

[0021] According to one embodiment, the industrial process is an electrolysis process comprising a line of production cells through which a direct current flows.

[0022] According to a further aspect, there is provided a control circuit for modifying power consumption of an industrial process powered by direct current, comprising: receiving a load modulation setpoint indicative of an amount of change to be applied to power of the industrial process and one or more feedback signals indicative of a power level delivered to the industrial process; generating a first current setpoint of a first direct current supplied to the industrial process by a first rectifier circuit having a first transformer and a saturable reactor based on the load modulation setpoint and the one or more feedback signals; A first current setting value is provided to a first control unit configured to control a saturation level of at least a saturable reactor of the first rectifier circuit based on the first current setting value. A control circuit is provided that is configured to:

[0023] According to yet another aspect, there is provided a power supply system for an industrial process, the power supply system comprising the above control circuit, the first rectifier circuit, and the first control unit.

[0024] According to one embodiment, the power supply system further comprises the one or more second rectifier circuits and a second controller, wherein the control circuit is further configured to generate a second current set point for a second direct current supplied to the industrial process by one or more second rectifier circuits each having a second transformer, and to provide the second current set point to the second controller configured to adjust a tap position of a second transformer of each of the one or more second rectifier circuits based on the second current set point.

[0025] According to a further aspect, there is provided a system for carrying out an electrolysis process, comprising a power supply system as described above and a line of production cells through which a direct current flows. [Brief description of the drawings]

[0026] The above and other features and advantages are explained in detail below with reference to specific embodiments, given by way of illustration and not of limitation, with reference to the accompanying drawings, in which: FIG.

[0027] [Figure 1] FIG. 2 is a schematic diagram illustrating an example of a voltage conversion circuit in an industrial site according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a schematic diagram illustrating the rectifier circuit of FIG. 1 in further detail, in accordance with an embodiment of the present disclosure. [Diagram 3] FIG. 1 illustrates a schematic diagram of a rectifier control system according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is a schematic diagram illustrating a control circuit of the rectifier control system of FIG. 3 in further detail in accordance with an embodiment of the present disclosure. [Diagram 5] FIG. 1 shows a schematic diagram of a simple model of a rectifier with a load. [Figure 6] 2 is a diagram illustrating the operation of a rectifier with a load, showing voltage versus current. [Figure 7] FIG. 1 shows a schematic of a simple model of a pair of rectifiers with a load. [Figure 8] 1 is a diagram showing voltage versus current illustrating operation with varying loads; [Figure 9] 1 is a diagram illustrating the operation of a pair of rectifiers with current control using tap changing, showing voltage versus current. [Figure 10] 1 is a diagram illustrating operation of a pair of rectifiers with current control using tap changing after process modification, showing voltage versus current. [Figure 11] FIG. 1 shows a schematic diagram of a simple model of a pair of rectifiers with a load, where one of the rectifiers has a saturable reactor. [Figure 12] 1 is a diagram illustrating the operation of a pair of rectifiers with current control using a saturable reactor, showing voltage versus current. [Figure 13] 1 is a diagram showing an example of active power as a function of group factor and controllable current; [Figure 14] 1 is a chart showing an example of active power as a function of group factor and controllable positive current; [Figure 15] 4 is a graph illustrating an example of load modulation in the rectifier control system of FIG. 3, showing voltage versus current. [Figure 16] FIG. 1 is a schematic diagram illustrating a power supply system according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] In the various figures, like features are designated by like reference numerals, and in particular, structural and / or functional features common to various embodiments may have the same structural, dimensional and material characteristics with the same reference numerals.

[0029] Unless otherwise specified, when referring to two elements connected together, this means a direct connection without any intermediate elements other than conductors, and when referring to two elements coupled together, this means that the two elements can be connected or coupled through one or more other elements.

[0030] In the following disclosure, unless otherwise indicated, when reference is made to terms that qualify absolute positions, such as "front", "back", "top", "bottom", "left", "right", or relative positions, such as "upper", "lower", "high", "low", or orientations, such as "horizontal", "vertical", etc., this term refers to the orientation of the drawings.

[0031] Unless otherwise specified, the terms "about," "approximately," "substantially," and "to the extent of" refer to within 10%, preferably within 5%, of the relevant value.

[0032] FIG. 1 shows a schematic diagram of an example of a power supply circuit 100 in an industrial site according to an embodiment of the present disclosure. A high voltage busbar (HIGH V BUSBAR) 102 receives, for example, an AC voltage supplied to the industrial site. In an embodiment, this voltage is at least 50 kV, for example in the range of 200 kV to 250 kV, for example about 220 kV. The power supply circuit 100 of FIG. 1 comprises a variable power system 104 for supplying a DC current to a corresponding industrial process, such as an electrolysis process. In an embodiment, the variable power system 104 receives an intermediate voltage level, for example in the range of 10 kV to 50 kV, in one example about 30 kV, generated by a corresponding transformer 108 coupled between the high voltage busbar 102 and a medium voltage busbar (MED V BUSBAR) 110 of the variable power system 104.

[0033] The variable power system 104 comprises, for example, one or more rectifier circuits 112 arranged in parallel between a medium voltage busbar 110 and a further DC busbar (DC busbar) 115, through which power is supplied to an industrial process. Each rectifier circuit 112 comprises, for example, a transformer 116 with an on-load tap changer, coupled in series with a diode-based rectifier 118. In the example of FIG. 1, four such rectifier circuits 112 are arranged in parallel with one another. Furthermore, the variable power system 104 comprises, for example, at least one rectifier circuit 114 coupled between the medium voltage busbar 110 and the further DC busbar 115. The rectifier circuit 114 is similar to the rectifier circuit 112, but further comprises, for example, at least one saturable reactor 120 arranged between the transformer 116 and the diode-based rectifier 118. It is further possible that at least one saturable reactor 120 is arranged between the transformer 116 and the medium voltage busbar 110 .

[0034] 1, the variable power system 104 has four rectifier circuits 112 arranged in parallel, however, the number of these rectifier circuits may vary depending on the current level supplied to the industrial process. Furthermore, rather than the variable power system 104 having one rectifier circuit 114, in alternative embodiments, the variable power system 104 may be provided with two or more such rectifier circuits.

[0035] In the example of FIG. 1, a further transformer 108 and a further busbar 110 are provided, for example to supply auxiliary systems via a further transformer 122 and a low voltage busbar 124 .

[0036] FIG. 2 illustrates in schematic form the rectifier circuit 114 of FIG. 1 in more detail according to an embodiment.

[0037] For ease of explanation, Figure 2 shows the circuitry associated with a signal AC phase, hereafter referred to as Phase 1. In practice, there may be, for example, three AC phases, and the circuitry of the AC domain of the rectifier circuit 114 is replicated for each phase.

[0038] The transformer 116 has two output terminals for each phase, and the rectifier 118 has two input terminals for each phase. Furthermore, at least one saturable reactor 120 includes, in the example of FIG. 2, a pair of saturable reactors 120A, 120B for the first phase. The saturable reactor 120A is coupled, for example, connected, between one of the output terminals of the transformer 116 for the first phase and one of the input terminals of the rectifier 118 for the first phase. The saturable reactor 120B is coupled, for example, connected, between the other of the output terminals of the transformer 116 for the first phase and the other of the input terminals of the rectifier 118 for the first phase.

[0039] The rectifier 118 has, for example, two output terminals, an output terminal 212A that is coupled, for example connected, to the positive busbar 115+ of the busbars 115, and an output terminal 212B that is coupled, for example connected, to the negative busbar 115- of the busbars 115. These output terminals 212A, 212B are, for example, common to all phases.

[0040] The saturable reactors 120A, 120B are, for example, respectively controlled by a saturation control signal SAT_CTRL, which is, for example, an analog control signal. As known to those skilled in the art, a saturable reactor is a type of inductor having a magnetic core that can be purposely saturated by a DC control current applied to a control winding. The inductance of the magnetic core limits the level of AC current before saturation. Once saturated by the DC control current, the inductance decreases and the level of AC current through the magnetic core can increase. The saturation control signal SAT_CTRL, for example, sets the level of the DC control current in the control winding.

[0041] The transformer 116 comprises, for example, a high voltage (HV) circuit breaker 202 coupled, for example, connected, for the first phase, between the busbar 110 and one terminal of an on-load tap changer (OLTC) 204. The high voltage circuit breaker 202 comprises, for example, a switch, having one terminal coupled, for example, connected, to the busbar 110 and another terminal coupled, for example, connected, to the OLTC 204 and, via a further switch, to earth. The other terminal of the OLTC 204 is coupled, for example, connected, for the first phase, to two parallel branches each comprising a star transformer 206 and a delta transformer 208. These transformers 206, 208 are arranged to provide AC voltages offset, for example, by a phase difference of 30°. These transformers 206, 208 provide, for example, separate outputs of the transformer 116, respectively. Star transformer 206 has output terminals that are coupled, e.g., connected, e.g., to saturable reactor 120A, and delta transformer 208 has output terminals that are coupled, e.g., connected, e.g., to saturable reactor 120B.

[0042] As known to those skilled in the art, an On-Load Tap Changer (OLTC) is a mechanism in a transformer that allows the turns ratio to be selected in discrete steps without interrupting the supply during tap changing. The OLTC 204 is, for example, controlled by a control signal TAP_CTRL, which is a digital signal that controls an actuator of the OLTC to adjust, for example, the tap position and thus the turns ratio of the transformer. For example, this digital control signal TAP_CTRL is in the form of two binary control signals, one signal being an UP signal that is set when increasing the tap and the other signal being a DOWN signal that is set when decreasing the tap.

[0043] The rectifier 118 is, for example, a diode-based 12-pulse rectifier as known to those skilled in the art. In Fig. 2, two pairs of diodes for the first phase are shown. Each diode of one of the two pairs has an anode coupled, for example connected, to a corresponding one of the input terminals 210A, 210B of the rectifier 118 and a cathode coupled, for example connected, via a corresponding switch, to the output terminal 212A of the rectifier 118. Each diode of the other pair has a cathode coupled, for example connected, to a corresponding one of the input terminals 210A, 210B of the rectifier 118 and an anode coupled, for example connected, via a corresponding switch, to the output terminal 212B of the rectifier 118. Each of the four switches is, for example, an electrically operated switch (M).

[0044] In the example of FIG. 2, the industrial process is represented by a back emf (electromotive force) voltage E and a load resistance R coupled in series between busbar 115+ and busbar 115-.

[0045] The rectifier circuit 112 of the conversion system 104 of Fig. 1 is implemented, for example, by a circuit similar to that of Fig. 2, but does not include the saturable reactors 120A, 120B. For example, the output terminal of the transformer 206 is connected to the input terminal 210A of the rectifier 118, and the output terminal of the transformer 208 is connected to the input terminal 210B of the rectifier 118.

[0046] According to embodiments described herein, at least one saturable reactor 120 of the rectifier circuit 114, and possibly an OLTC 204 of either or both of the rectifier circuits 112, 114, may be advantageously used to regulate power consumption of an industrial process for power grid balancing applications, as described in more detail with reference to FIGS. 3 and 4.

[0047] Figure 3 illustrates generally a rectifier control system 300 arranged to control the variable power systems 104 of Figure 1. In the case of a site such as the example of Figure 1 where more than one variable power system is provided, each variable power system may be controlled, for example, by a similar rectifier control system 300.

[0048] The rectifier control system 300 includes a controller 302 configured to control the OLTC of the transformer 116 of the rectifier circuit 112, and a controller 304 configured to control the OLTC of the one or more saturable reactors 120 of the rectifier circuit 114, and possibly the transformer 116 of the rectifier circuit 114. The rectifier control system 300 further includes, for example, a control circuit 306.

[0049] The control circuit 306 is configured to receive, for example, a load modulation setpoint δP indicative of the amount of change to be applied to the power of the industrial process, and one or more feedback signals from the industrial process indicative of the power level consumed by the industrial process. In the example of FIG. 3, these feedback signals include a line current i line , and the line voltage u, which corresponds to the voltage applied to the line of the manufacturing cell line It is in the form of:

[0050] For example, in an electrolysis process, the lines of electrolysis cells are known as pot lines, and an equal amount of direct current flows through each of the electrolysis cells. The total voltage in the pot lines is the sum of the ohmic and back emf voltages of the electrolysis cells. For example, in an electrolysis process, the back emf is generated by, for example, the dissociation reaction of the electrolyte.

[0051] The control circuit 306 may, for example, determine a current setpoint δi of the DC current supplied to the industrial process by the rectifier circuit 112 and a current setpoint δi of the DC current supplied to the industrial process by the rectifier circuit 114 based on the load modulation setpoint δP and one or more feedback signals. cIn the example of FIG. 3, the current setpoint δi is in the form of a change applied to the original setpoint i0, and the current setpoint δi c is the original setting value i c0 The form of the change applied to the set value i0 and the set value i c0 are provided, for example, from a setpoint memory (setpoint) 308 that stores setpoints entered, for example, by an operator. However, in alternative embodiments, these current setpoints δi and δi c Either or both of may directly represent the applied current or may correspond to the amount of change in the set point relative to its previous value.

[0052] The control unit 302 may, for example, add the setting value δi to the original setting value i0 to obtain a changed setting value i tap and a line current i indicative of the current flowing through a line of the manufacturing cell of the industrial process. line the changed setting value i tap and a subtractor 310 configured to subtract from the OLTC of the transformer 116 of the rectifier circuit 112. The subtraction result ε indicates the amount of adjustment applied by the OLTC of the transformer 116 of the rectifier circuit 112. For example, the signal ε is a digital signal provided to a group control (OLTC GROUP CTRL) 312. In an embodiment, the group control 312 is further configured to receive as an input signal a current signal corresponding to the output current of the transformer 116 of the rectifier circuit 112. The group control 312 is configured, for example, to compare the signal ε to one or more thresholds to determine the change to be applied to one or more of the OLTCs of the transformer 116 of the rectifier circuit 112. The group control 312 is configured, for example, to provide a control signal to an individual OLTC control (OLTC CTRL) 314 associated with the transformer 116 of each rectifier circuit 112. Each individual OLTC control 314 is configured, for example, to receive the current state of the OLTC of the corresponding transformer 116 and generate a control signal for controlling the tap position of the corresponding transformer 116 .

[0053] The control unit 304, for example, sets the set value δi c the original setting value i c0 Add to the changed setting value i c and an adder 316 configured to generate a modified set value i c is provided to a saturable reactor control (SR CTRL) 318. The saturable reactor control 318 is configured to generate digital control signals for controlling, for example, one or more saturable reactors 120 of the rectifier circuit 114. In one embodiment, the saturable reactor control 318 is further configured to receive a current state of an OLTC of a transformer 116 of the rectifier circuit 114 and generate a control signal for controlling a tap position of the transformer 116.

[0054] The control circuit 306, for example, generates a current signal i line and voltage signal u line The feedback signal i may include a multiple linear regression module (MLR) 320 configured to process one or more feedback signals, such as the feedback signal i, to generate an estimate R of the load resistance of the industrial process, and an estimate E of the back emf voltage of the industrial process. line and the feedback signal u line The estimated values ​​R and E are provided to, for example, a load modulation control unit (LM CTRL) 322, which, for example, - load modulation setpoint δP, - Current setting value i c0 , A tap index vector {TI k,q}, A vector {K q},and A vector {u rk,q} Further receive.

[0055] FIG. 4 illustrates generally the control circuit 306 and the set point generation circuit 402 of FIG. 3 in more detail.

[0056] The set point generation circuit 402 is configured to generate a load modulation set point δP based on, for example, a frequency offset δf and a signal TSO indicative of the level of load modulation applied by the rectifier circuits 112, 114. For example, the signal TSO may be provided by a grid operator or the like. In one embodiment, the frequency offset δf is captured locally, for example by a sensor (not shown) at the industrial site. The signal δf is derived from, for example, the frequency of the mains supply as seen at the industrial site and a given target frequency f of, for example, 50 Hz. mains Signal TSO indicates a frequency offset with respect to signal δf and is used to apply a primary reserve or FCR (frequency recovery reserve). Signal TSO is, for example, a secondary reserve signal or aFRR (automatic frequency recovery reserve) signal indicating a power set point. The secondary reserve has a longer response time compared to, for example, the primary reserve. Set point generation circuit 402 includes, for example, transfer functions K and H applied to signals δf and TSO, respectively, and a summer 404 configured to sum together the power adjustments caused by the transfer functions to generate a load modulation set point δP.

[0057] The control circuit 322 may, for example, calculate the vector {K q}. For example, the module 406 is configured to calculate the equivalent admittance κ based on the following equation:

[0058]

number

[0059] Here, l is the number of the rectifier circuits 112 and the rectifier circuits 114.

[0060] The control circuit 322 may, for example, calculate the vector {urk,q}, vector {K q} and vector {TI k,q The system further includes a module 408 (group factor) configured to generate a group factor Γ based on {}. The group factor Γ quantifies the state of the rectifier circuits and tap settings. For example, the module 408 is configured to calculate the group factor Γ based on the following equation:

[0061]

number

[0062] The control circuit 322 controls, for example, the current setting value δi and the current setting value δi c For example, the calculation module 410 may further include a calculation module 410 configured to generate a transfer function f(i c,0 ,Γ,δP,κ,R,E) based on the current setting value δi c It is configured to calculate

[0063] In one example, the current setting value δi c is calculated based on the following formula:

[0064]

number

[0065] This formula can be used to determine, for example, the setpoints of the controllable rectifiers i to achieve a power change of δP given a particular load state {R,E} and the current configuration of the remaining rectifier tap changers. c,0 gives the instantaneous value to be added to

[0066] In one embodiment, the calculation module 410 may calculate, for example, a transfer function f(i c,0 ,Γ,δP,κ,R,E) based on the current setting value δi c ', which is then configured to generate a current setpoint δi cFor example, the error value Err is processed by a proportional-integral (PI) block and then added to the current setpoint δi by an adder 412. c The error value Err is generated, for example, based on the power value P0, which indicates a real-time performance control baseline. For example, the multiplier 414 multiplies the feedback signal i line and the feedback signal u line to generate a power value P, which is provided to a real-time performance control baseline calculator (RT PERF CTRL) 416, which generates a power value P0 based on the power value P, for example by applying a low-pass filter. In one embodiment, a subtractor 417 is used to determine the difference between the power value P0 and the voltage value P, and a subtractor 418 subtracts this difference from the load modulation setpoint δP to obtain the current setpoint δi c The current setting value δi c '.

[0067] In one embodiment, the set value δi c The change in DC current δ i applied to the industrial process taking into account the adjustment of is calculated by the control circuit 306 based on the following equation:

[0068]

number

[0069] This change amount δi is applied to, for example, a current setting value for controlling the rectifier circuit 112. In particular, the setting value δi c Adjusting the operation of rectifier circuit 114 by adjusting, for example, the operating point of other rectifier circuits 112 will change, causing deviations from the expected adjustments. It is advantageous to generate and apply a signal δi to counteract some of these deviations.

[0070] The calculation module 410 calculates the current setpoint δi and the current setpoint δi based on a model of the rectifier circuit, for example as described in more detail with reference to FIGS. c is configured to generate

[0071] FIG. 5 shows a simplified model of a rectifier including a load but not including a saturable reactor. For example, the simplified model of FIG. 5 represents one of the rectifier circuits 112 of FIG. 1 passing a DC current i_fp through a load corresponding to an industrial process such as an electrolysis process. As previously mentioned, the load is represented by an impedance R and a back emf voltage E, and the voltage across the load is represented by u. The rectifier circuit 112 generates a no-load voltage u r and its droop K. In fact, the rectifier circuit can be modeled as having a droop, since an increasing level of the direct current i supplied to the load causes a decrease in the voltage level u at its output.

[0072] FIG. 6 is a diagram showing the output voltage u of the rectifier circuit 112 as a function of the current i. Curves 601 to 608, each having substantially the same negative slope, represent the response of the rectifier circuit 112 based on different tap positions. Curve 606 represents an example of a selected tap position. Curve 610 represents the voltage across the load as a function of the DC current flowing through the load. This curve intersects the voltage axis at the back emf voltage E and has a slope equal to the impedance R of the load. The operating point of the system based on one rectifier circuit 112 corresponds to the intersection point 611 between the two curves 606 and 610 associated with the DC current i_fp.

[0073] However, the values ​​of E and R are not constant, but change over time due to the progression of processes in the cells of an industrial process, e.g., in the case of an aluminum smelter, due to changes in the amount of material fed and / or extracted, the consumption of cathodes, anodes and / or crusts, temperature, magnetic field, etc. A change in R changes the curve 610, for example, between a curve 612 with a higher slope relative to the curve 610 and a curve 614 with a lower slope relative to the curve 610. A change in E shifts the curve 610 along the voltage axis, for example, as represented by the curve 616. In order to maintain a given operating point when the values ​​of E and R are changing over time, the OLTC of the rectifier circuit 112 can be controlled to change the tap position. For example, the current i can be calculated by the following two equations: u=u r -K×i and u=E+R×i, so i=(u r -E) / (K+R), where E and R are varying due to the physical characteristics of the process, and K and u r is constant. r can be adjusted, but only between discrete values.

[0074] To increase the DC current delivered to the load, two rectifier circuits can be connected in a parallel mode, each providing an amount of current depending on the respective UI curves and load characteristics, as described with reference to Figures 7 and 8.

[0075] FIG. 7 shows a simplified model of a pair of rectifiers with a load, where one rectifier circuit has a droop K1 and a no-load voltage u r1 The other rectifier circuit has a droop K2 and a no-load voltage u r2 5 except that

[0076] Figure 8 is a current versus voltage diagram illustrating the operation of the pair of rectifier circuits of Figure 7. For a given tap index combination, a unique configuration of rectifier currents is applied to the load, and the current i delivered to the load is the sum of current i1 and current i2 provided by each rectifier circuit.

[0077] From the model in Figure 7, i1+i2=i, u=u r1 -K1i1, u=u r2 A system of equations can be set up with four equations for -K2i2, and u=E+Ri and four unknown factors. Therefore, the equation for the current can be extracted from the system of equations as follows:

[0078]

number

[0079] Fig. 9 is a voltage versus current diagram illustrating the operation of a pair of rectifiers with current control using tap changing. In particular, when the tap position of each rectifier circuit is in a first position, a first operating point of current i_fp is obtained. After changing the taps to increase the current of both rectifier circuits, a new operating point i_fp' is obtained, resulting in an increase in power consumption ΔP corresponding to the difference between the initial power, which is equal to the product of the initial voltage u and the initial current i_fp, and the new power, which is equal to the product of the new voltage u' and the new current i_fp'.

[0080] FIG. 10 is a voltage versus current diagram illustrating the operation of a pair of rectifiers with current control using tap changing. In particular, FIG. 10 illustrates the case where a process change causes the current operating point to change from current i_fp to a higher current i_fp'. A step-down of one tap of one of the rectifier circuits is applied, for example, to return to a current operating point closer to the original current i_fp.

[0081] 11 shows a schematic of a simple model of a pair of rectifier circuits with a load, one without a saturable reactor, such as rectifier circuit 112, and the other with a saturable reactor, such as rectifier circuit 114. In particular, the model shows a voltage u t1 11 is similar to the model of Fig. 7, except that the saturable reactor SR is placed inside the voltage source. In Fig. 11, the saturable reactor can be considered as a changeable impedance. The input of the reactor control system is considered here as the current set point.

[0082] The provision of a saturable reactor in one of the rectifier circuits has the advantage that the rectifier current can be changed smoothly. The other rectifier circuit, however, maintains its normal behavior, e.g. constant droop and tap voltage. An increase in the current i1 from the saturable reactor not only increases the output current through the load, but also reduces the current i2 supplied by the other rectifier circuit. In particular, part of the increase in the rectifier current i1 is "consumed" to discharge the current i2 drawn by the other rectifier circuit.

[0083] The set of equations is the same as in the previous case, only i1 is considered as a purely controllable current. The overall current and voltage response is obtained as follows:

[0084]

number

[0085] The current i2 of the second rectifier can for example be derived from the current i1.

[0086]

number

[0087] FIG. 12 is a voltage versus current diagram illustrating the operation of a pair of rectifiers with current control using saturable reactors. In particular, a saturable reactor is used to control the voltage u to u t1 It can be seen that by adjusting the operating point by an amount, ΔP, the operating point can be changed resulting in a change in power consumption.

[0088] The above technique can be generalized to n rectifier circuits, where l rectifier circuits are simple diode-based rectifier circuits such as rectifier circuit 112, and m rectifier circuits are diode-based rectifier circuits with saturable reactors such as rectifier circuit 114. Thus, n=l+m.

[0089] The following system of n+2 equations with n+2 unknown factors can be extracted from the electrical model, where the n+2 unknown factors are {i, u, i1, . . . , i n}. The system of equations {Eq.} is as follows:

[0090]

number

[0091] Variables {E,R,u r1 ,···,u rn ,K1,···,K n} are known or can be estimated as certain characteristics of, for example, electrical hardware and processes.

[0092] This system of equations is potentially a Cramer system of equations and may therefore be solved from a matrix inversion as described in more detail below. However, as will be explained in more detail, an analytical solution is also possible, taking advantage of having model equations for the unknown factors. This provides improvements in speed and ease of implementation. In particular, an advantage of a solution based on analytical principles is that it is relatively easy to code and perform on-site, and provides results continuously. Conversely, matrix inversion requires the use of a solution each time a result is to be produced.

[0093] The line current can be expressed as (Equation 1) as follows:

[0094]

number

[0095] The line voltage can be expressed as (Equation 2) as follows:

[0096]

number

[0097] Each current supplied by the rectifier circuit q can be expressed as (Equation 3) as follows:

[0098]

number

[0099] Two constant factors κ and Γ can be introduced into these equations, simplifying them.

[0100] - κ corresponds to the negative admittance (or negative conductance) that characterizes the rectifier assemblies (units [Ω -1 ] or [S] (Siemens). (Equation 4)

[0101]

number

[0102] - Γ is the tap-related group factor that characterizes the rectifier group in a given configuration. The ratio (u rq / K q ) is the "virtual" current at no voltage (unit: [A] (ampere)). (Equation 5)

[0103]

number

[0104] Consider now the use of controllable rectifiers to convey load modulation to the grid, e.g. as an FCR (Frequency Control Reserve) or aFRR (Automatic Frequency Recovery Reserve) solution. The current setpoints of one or more controllable current rectifiers 114 are derived, e.g., from a controllable voltage tap rectifier 112.

[0105]

number

[0106]

number

[0107] It should be noted in Equations 6-8 above that the droop and tap voltages of the current controllable rectifier are no longer taken into account in the equations.

[0108] From Equation 6 and Equation 7, the active power delivered to the load according to the tap voltage setting and the current control setting can be expressed and simplified as follows:

[0109]

number

[0110] Therefore, if expressed differently, it would look like this:

[0111]

number

[0112] As shown in FIG. 13, which is a diagram showing an example of active power as a function of group factor and controllable current, the function P=p(Γ,i c ) resembles the surface of a "hammock."

[0113] FIG. 14 is a chart showing an example of active power as a function of group factor and controllable positive current restricted to the positive quadrant.

[0114] The active power P is a combination of the group factor of the diode-based rectifier circuit 112 and the current setpoint from one or more rectifier circuits 114 with saturable reactors. In real operation, R and E are also changing, so the surface is constantly moving. Classical regulation of the load tries to keep the overall current i as stable as possible.

[0115] FIG. 15 is a current vs. voltage plot illustrating an example of load modulation in the rectifier control system of FIG. 3. In particular, FIG. 15 shows the initial operation (bold line) and the load modulation configuration (dashed line). The current setpoint δi c is constantly changing due to the load modulation setpoint δP. The complete set of other rectifiers is changing accordingly without changing the taps. The current in each rectifier is mechanically reduced, but the overall voltage and current are increased. In particular, in the example of FIG. 15, the current setpoint δi c causes a corresponding increase in the current generated by the rectifier circuit with the saturable reactor. Part of this change is compensated for by other regulation circuits, but the overall result is that the DC current increases by δ i The amount of

[0116] Fig. 16 illustrates a schematic diagram of an electricity supply system 1600 according to an embodiment of the present disclosure. In the example of Fig. 16, the electricity supply system 1600 includes two client sites 1602, 1604, a central electricity management system 1606, a market server (market) 1607, and a grid operator server (grid operator) 1608.

[0117] The client sites of the power supply system 1600 represent sites with industrial electrical loads and / or power storage where electrical energy is transferred from the grid to the client sites and / or from the client sites to the grid. For example, one or more power supply contracts are entered into involving the client sites 1602, 1604 and the grid operator to establish a business relationship between the entities. Although two client sites 1602, 1604 are shown in the embodiment of FIG. 16, in alternative embodiments there may be any number of client sites managed by a central power management system 1606.

[0118] The client sites 1602, 1604 are each provided with a flexible source of electrical energy, in other words electrical loads and / or electrical energy storage, that can be adapted to meet current and future needs.

[0119] In the example of Figure 16, client site 1602 is provided with an electrical energy storage and an electrical load, and client site 1604 is provided with a generator and an electrical load. However, it is further possible that sites are provided with both an electrical energy storage and a generator in addition to an electrical load, and further possible that some sites are provided with only an electrical load, a generator, or an electrical energy storage.

[0120] For example, the client site 1602 is provided with a large capacity battery bank 1610 capable of inputting or outputting, for example, up to 10 MW of electrical energy, and having, for example, a storage capacity of 10 kWh to 20 MWh or more. The battery bank 1610 is coupled to an on-site supervisory control interface (DR box) 1614, hereinafter referred to as a demand response (DR) box or simply a DR box, for example, via a battery management system (BMS) 1612. The DR box 1614 is, for example, a programmable logic controller (PLC), and is further configured to manage energy, for example, in a role similar to that of an energy management system (EMS).

[0121] The client site 1602 is further provided with one or more electrical loads 1618, represented for example by a factory in the example of Fig. 16, which are coupled to the DR box 1614 via a rectifier control circuit (RC) 1620, which may for example comprise the rectifier control system 300 of Fig. 3. For example, the electrical loads 1618 correspond to an industrial process as described herein. The DR box 1614 is configured to provide control signals to the rectifier control circuit 1620, such as for example a load modulation set point δP and / or a signal TSO and / or a signal δf.

[0122] The DR box 1614 is coupled to one or more on-site meters (meter(s)) 1616 for monitoring, for example, single-phase and / or three-phase active and reactive power and / or other electrical characteristics. For example, the on-site meters 1616 may include, as seen by the client site 1602, one or more electric meters for monitoring current supplied to and / or from the site, one or more electric meters for monitoring current supplied to or drawn from the battery bank 1610, one or more electric meters for monitoring the phase of the electrical signal, and one or more AC (alternating current) frequency meters for monitoring the frequency of the power grid supply voltage. Other characteristics that may be measured include electrical energy and power factor. The DR box 1614 is configured to collect meter data from these meters 1616, for example. Furthermore, the DR box 1614 is configured to provide a communication interface between, for example, the client site 1602 and the central power management system 1606.

[0123] The DR box 1614 can communicate with the central power management system 1606, for example, via the Internet, and possibly with client devices. For example, although not shown in FIG. 16, the DR box 1614 can be connected to the Internet via a switched network, for example, via an ADSL (Asymmetric Digital Subscriber Line) modem, or via a wireless connection, for example with a cellular network.

[0124] The client site 1604 is provided with a DR box 1614 and one or more meters 1616, which for example have a role similar to that of the client site 1602 and will not be described in detail again. The client site 1604 is further provided with one or more electrical loads 1618, for example similar to the electrical loads 1618 of the client site 1602, which are coupled to the DR box 1614 via a rectifier control circuit (RC) 1620. Furthermore, in the example of Fig. 16, the client site 1604 is provided with one or more generators (generators) 1622, for example photovoltaic generators, wind turbines, generator sets or other types of generators.

[0125] In the example of FIG. 16, one DR box 1614 is provided for each client site 1602, 1604, however, in alternative embodiments, two or more DR boxes 1614 may be provided for multiple sites.

[0126] The central power management system 1606 comprises a control and data acquisition system 1628, e.g. a supervisory control and data acquisition system (SCADA), which is responsible for receiving data from each DR box 1614 and for providing control signals to the client sites 1602, 1604 via the DR box 1614. In particular, the SCADA 1628 is responsible for sending control signals to the DR boxes of the client sites 1602, 1604, e.g. to control the power supplied to or supplied by the client sites and / or the power applied to or drawn from the battery bank 1610. Furthermore, the SCADA 1628 is responsible for obtaining and storing data measurements from the client sites 1602, 1604 as well as information regarding the status of the client sites, such as the state of charge of the battery bank 1610, if a battery is provided at the client site.

[0127] The central power management system 1606 further includes, for example, a distributed energy resource management system (DERMS) 1630, which is a computer platform configured to orchestrate resource operations, for example, in relation to loads or batteries at various client sites of the power supply system 1600. The DERMS 1630 further provides an interface, for example, with a market server 1607 and a grid operator server 1608.

[0128] The central power management system 1606 further comprises a monitoring and planning module (monitoring+planning) 1632 that communicates with the DERMS 1630 to receive data from the SCADA 1628 .

[0129] For example, the market server 1607 provides information about current and / or future electricity prices, as well as activation information required by the grid operator server 1608 .

[0130] The grid operator server 1608 corresponds to, for example, a computer platform of an operator of a grid that supplies power to client premises. In Europe, the grid operator corresponds to, for example, a transmission system operator (TSO) and / or a distribution system operator (DSO). For example, the grid operator server 1608 provides start-up orders to the DERMS 1630, which in turn provides monitoring data and / or control data such as load status to the grid operator server 1608.

[0131] The DERMS 1630 is configured to determine how power usage at the client site may be adapted in light of current and / or future power prices to reduce energy costs and / or increase revenue at the client site, e.g., by reducing operating costs or through grid balancing services. For example, the DERMS 1630 is configured to send control signals to the client site indicating periods during which charging of the battery bank 1610 from the power grid should be prioritized, e.g., in light of relatively low power prices, and periods during which discharging of the battery bank 1610 to the power grid should be prioritized, e.g., in light of relatively high power prices.

[0132] An advantage of the embodiments described herein is that demand side balancing of the power grid can be implemented relatively simply and effectively by relatively finely regulating the power consumption of industrial processes powered by DC current.

[0133] Various embodiments and variants are described. Those skilled in the art will understand that certain features of these embodiments may be combined, and other variants will readily occur to those skilled in the art. For example, although a solution is described in which the control circuit 306 is configured to generate a current setpoint based on an equation defining a system model, in alternative embodiments the control circuit 306 is configured to apply a different type of control mechanism. For example, the control circuit 306 may apply a closed loop control based on an error signal equal to the difference between an estimate of the power consumption of the industrial process and a load modulation setpoint δP. According to another example, a matrix solution may be applied as described in more detail below.

[0134] Below is an example based on five diode-based rectifier circuits, one of which has a saturable reactor: Of course, the same principle can be applied to a different number of rectifier circuits, and more than one rectifier circuit with a saturable reactor can be provided.

[0135] The following equations can be extracted from the diagram of the five rectifiers and the pot line:

[0136]

number

[0137] Therefore, we have a system of seven equations with seven unknown factors which can be rewritten as follows:

[0138]

number

[0139] So, under matrix form:

[0140]

number

[0141] If the determinant is different from zero, then we have a Cramer system of equations and A can be inverted.

[0142]

number

[0143] Without manual calculations, the system of equations {7eq.-7unk.} can be solved using a solver such as Python, as known to those skilled in the art.

[0144] This patent application claims priority from French Patent Application No. 21 / 05719, which is incorporated herein by reference.

Claims

1. 1. A method for modifying power consumption of an industrial process powered by direct current, comprising the steps of: receiving, by a control circuit, a load modulation set point indicative of an amount of change to be applied to power of the industrial process and one or more feedback signals indicative of a power level delivered to the industrial process; generating, by the control circuit, a first current setpoint of a first direct current supplied to the industrial process by a first rectifier circuit having a first transformer and a saturable reactor based on the load modulation setpoint and the one or more feedback signals; providing the first current set value to a first controller configured to control at least a saturation level of the saturable reactor and a tap position of a first transformer of the first rectifier circuit based on the first current set value; generating, by the control circuit, a second current set point for a second direct current supplied to the industrial process by one or more second rectifier circuits, each having a second transformer; providing the second current set point to a second controller configured to adjust a tap position of a second transformer of each of the one or more second rectifier circuits based on the second current set point.

2. 2. The method of claim 1, wherein the first current set point indicates an amount of change to be applied to a first process set point of current provided by the first rectifier circuit.

3. The method of claim 1 or 2, wherein the second current set point indicates an amount of change to be applied to a second process set point of current provided by the one or more second rectifier circuits.

4. the control circuit is configured to generate the first current set value based on an equivalent admittance κ of the one or more second rectifier circuits, the control circuit being configured to calculate the equivalent admittance κ based on the following equation: [0010] Here, K q 3. The method of claim 1, wherein: q is the estimated droop of each of the first and second rectifier circuits, and l is the number of first and second rectifier circuits.

5. The control circuit is further configured to generate the first current set point based on a group factor Γ representing a sum of currents through the second rectifier circuit, the control circuit being configured to calculate the group factor Γ according to the following formula: [0025] Here, u rk,q 5. The method of claim 4, wherein q is the output voltage of each of the first rectifier circuit and the second rectifier circuit.

6. The control circuit is configured to generate the first current set point based on the following equation: [0030] where δi c is the first current setpoint, R is an estimate of the load resistance of the industrial process, E is an estimate of the back EMF voltage of the industrial process, and i c,0 3. The method of claim 2, wherein: ΔP is the first process set point, δP is the load modulation set point, κ is an equivalent admittance of the one or more second rectifier circuits, and Γ is a group factor representing a sum of currents through the second rectifier circuits.

7. 3. The method according to claim 1 or 2, wherein the industrial process is an electrolysis process comprising a line of production cells through which a direct current flows.

8. 1. A control circuit for modifying power consumption of an industrial process powered by direct current, comprising: receiving a load modulation setpoint indicative of an amount of change to be applied to power of the industrial process and one or more feedback signals indicative of a power level delivered to the industrial process; generating a first current setpoint of a first direct current supplied to the industrial process by a first rectifier circuit having a first transformer and a saturable reactor based on the load modulation setpoint and the one or more feedback signals; providing a first current set value to a first control unit configured to control at least a saturation level of a saturable reactor of the first rectifier circuit and a tap position of a first transformer of the first rectifier circuit based on the first current set value; generating a second current set point for a second direct current supplied to the industrial process by one or more second rectifier circuits, each having a second transformer; providing the second current setpoint to a second controller configured to adjust a tap position of a second transformer of each of the one or more second rectifier circuits based on the second current setpoint; The control circuit is configured as follows.

9. 1. A power supply system for an industrial process, comprising: A control circuit according to claim 8; the first rectifier circuit; The first control unit; A power supply system comprising:

10. the one or more second rectifier circuits; The second control unit; The power supply system of claim 9 further comprising:

11. 1. A system for performing an electrolysis process, comprising: The power supply system according to claim 9 or 10, A line of manufacturing cells with direct current The system comprises:

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