Method for operating parallel bypass thyristors under low load

Abstract

A system for switching on a thyristor is presented, the system comprising: an input configured to be coupled to a power source; an output configured to be coupled to a load; a first branch coupled between the input and the output and including a first thyristor having a first threshold voltage; a second branch coupled between the input and the output and coupled in parallel with the first branch, the second branch including a second thyristor having a second threshold voltage higher than the first threshold voltage; and at least one controller configured to control the system to selectively generate a bias voltage across the second thyristor to cause a voltage across the second thyristor to change from a first voltage to a second voltage, the first voltage being less than a second threshold voltage, the second voltage being greater than the second threshold voltage.

Description

Technical Field

[0001] At least one example according to the present disclosure generally relates to a power system having a bistable switching element, such as a thyristor. Background Art

[0002] Power devices such as uninterruptible power supplies (UPS) can be used to provide stable, uninterrupted power to sensitive and / or critical loads such as computer systems and other data processing systems. Existing UPS include online UPS, offline UPS, line interactive UPS and others. UPS can provide output power to the load. The output power can come from a main power source, such as a mains power source, and / or from a backup power source, such as an energy storage device. Summary of the invention

[0003] According to at least one aspect of the present disclosure, a system for turning on a thyristor is proposed, the system comprising: an input configured to be connected to a power supply; an output configured to be connected to a load; a first branch connected between the input and the output and comprising a first thyristor having a first threshold voltage; a second branch connected between the input and the output and connected in parallel with the first branch, the second branch comprising a second thyristor having a second threshold voltage higher than the first threshold voltage; and at least one controller configured to control the system to selectively generate a bias voltage across the second thyristor to cause the voltage across the second thyristor to change from the first voltage to the second voltage, the first voltage being less than the second threshold voltage, and the second voltage being greater than the second threshold voltage.

[0004] In some examples, a bias voltage is provided in response to the system receiving an input voltage at an input. In various examples, the system further includes a transformer connected in series with the second thyristor. In many examples, when the system is controlled to generate the bias voltage, at least one controller is also configured to control the transformer to cause a change in the voltage across the second thyristor from a first voltage to a second voltage. In some examples, the transformer includes a secondary winding, and wherein controlling the transformer includes controlling a voltage source to supply power to the secondary winding. In various examples, the system further includes at least one bus, wherein the transformer includes a magnetic core surrounding the at least one bus, the magnetic core being electromagnetically coupled to the primary winding and the secondary winding. In many examples, the voltage change across the second thyristor is equal to or greater than the sum of the voltage changes across one or more other thyristors connected to one or more branches, each branch of the one or more branches being connected in parallel with the second branch between the input and the output.

[0005] In some examples, the system also includes a first current source connected in a parallel configuration relative to the first thyristor and the reference node; and a second current source connected in a parallel configuration relative to the second thyristor and the reference node. In various examples, at least one controller is also configured to: control the first current source to output a first current having a first phase and amplitude; control the second current source to output a bias current having a second phase and amplitude, wherein the bias current is generated to offset the first current at the output. In many examples, the bias current is generated to cause the voltage across the second thyristor to change from the first voltage to the second voltage by an amount equal to the bias voltage. In various examples, the first phase is 180 degrees out of phase with the second phase. In some examples, the input is configured to receive an input current from a power supply, and at least one controller is also configured to: request the power supply output to increase the input current provided at the input; control the first current source to provide a first current having a first phase and a first amplitude; and control the second current source to provide a bias current having a second phase and a second amplitude.

[0006] In many examples, the sum of the first amplitude and the second amplitude is equal to an increase in input current provided at the input. In some examples, the first current source is a first inverter and the second current source is a second inverter. In various examples, the controller controls the current source to generate a bias current to cause a voltage change equal to a bias voltage across the second thyristor such that a new voltage across the second thyristor is greater than a second threshold voltage.

[0007] According to at least one aspect of the present disclosure, a method for operating a first thyristor and a second thyristor connected in parallel is provided. The method includes providing a voltage associated with a current to the first thyristor and the second thyristor; and providing a bias voltage across the second thyristor to cause the voltage across the second thyristor to change from a first voltage to a second voltage, wherein the first voltage is less than a threshold voltage of the second thyristor and the second voltage is greater than the threshold voltage.

[0008] In some examples, providing the bias voltage includes controlling a power supply to provide a time-varying voltage to a secondary winding of a transformer coupled in series with the second thyristor. In various examples, providing the bias voltage across the second thyristor includes operating a current source to provide a bias current to the second thyristor. In many examples, the method also includes providing a first current to a first node coupled between the first thyristor and the output; providing the bias current to a second node coupled between the second thyristor and the output; and setting a first amplitude and phase of the first current, and setting a second amplitude and phase of the bias current, such that the first current and the bias current cancel each other at the output.

[0009] In some examples, the method further includes providing a first current to the first thyristor; directing a first portion of the first current to a reference node and through a first impedance associated with a first branch of a circuit including the first thyristor; and directing a second portion of the first current to the reference node and through a second impedance associated with a second branch of the circuit. In various examples, a sum of the first portion of the first current and the second portion of the first current is less than the first current.

[0010] According to at least one aspect of the present disclosure, a non-transitory computer-readable medium containing computer-readable instructions for a power system is provided. The instructions instruct at least one processor to control a first thyristor to draw an input current through the first thyristor; and in response to controlling the first thyristor to draw the input current through the first thyristor, control a circuit element to provide a bias voltage across a second thyristor, thereby causing a voltage across the second thyristor to change from a first voltage to a second voltage, the second voltage being greater than a threshold voltage of the second thyristor.

[0011] In various examples, the instructions further instruct at least one processor to: control the power supply to provide a time-varying voltage to the secondary winding of the transformer connected in series with the second thyristor. In some examples, controlling the transformer to provide a bias voltage across the second thyristor includes controlling a current source to provide a bias current to a node connected between the second thyristor and the output. In many examples, the instructions instruct at least one processor to select a value of the bias current provided to the node so that the corresponding voltage drop across the second thyristor is greater than the threshold voltage of the second thyristor. In various examples, the node is a second node, and the instructions further instruct at least one processor to: control the first current source to provide a first current to the first node, the first node is connected between the output and the first thyristor; and control the second current source to provide a bias current to the second node. In some examples, the instructions also instruct at least one processor to: control the first current source to provide a first current, and control the second current source to provide a bias current, so that the first current and the bias current cancel each other at the output.

[0012] In various examples, the instructions further instruct the at least one processor to control the input power supply to increase the input current by an additional amount, and provide the increased input current by the additional amount to the first thyristor, wherein a sum of the first current and the bias current is equal to the additional amount of the input current.

[0013] In some examples, an uninterruptible power supply for providing uninterruptible power to a load is provided. The uninterruptible power supply includes an input configured to draw input power from a power supply; an output configured to provide output power to the load; a thyristor having a threshold voltage and a first connection coupled to the input and a second connection coupled to the output; a bias element coupled to the thyristor; and at least one controller configured to: select a bias voltage applied across the thyristor to increase the voltage across the thyristor from a first voltage to a second voltage, the bias voltage being selected so that the second voltage is greater than the threshold voltage of the thyristor; and in response to drawing input power at the input, control the bias element to provide the bias voltage across the thyristor.

[0014] In some examples, the biasing element is a current source coupled between the thyristor and the reference node. In various examples, the at least one controller is further configured to control the current source to generate a current from the second connection to the reference node. In many examples, the biasing element is coupled to the first connection of the thyristor; and the biasing element is a transformer having a primary winding and a secondary winding. In various examples, the at least one controller is further configured to control the transformer power supply to provide a time-varying voltage to the secondary winding of the transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Various aspects of at least one embodiment are discussed below with reference to the accompanying drawings, which are not intended to be drawn to scale. The accompanying drawings are included to provide illustration and further understanding of the various aspects and embodiments, and are incorporated into and constitute a part of the specification, but are not intended as a definition of the limits of any particular embodiment. The accompanying drawings, together with the rest of the specification, serve to explain the principles and operation of the described and claimed aspects and embodiments. In the drawings, each identical or nearly identical component shown in various figures is represented by the same number. For clarity, not every component is labeled in every figure. In the drawings:

[0016] Figure 1 shows a schematic diagram of a power system according to an example;

[0017] Figure 2 shows a schematic diagram of a power system according to an example;

[0018] Figure 3 shows a schematic diagram of a power system according to an example;

[0019] Figure 4 shows a schematic diagram of a power system according to an example;

[0020] Figure 5A A process for switching on a thyristor according to an example is shown;

[0021] Figure 5B A process for switching on a thyristor according to an example is shown;

[0022] Figure 6 shows a schematic diagram of a power system according to an example;

[0023] Figure 7 A process for switching on a thyristor according to an example is shown;

[0024] Figure 8 shows a schematic diagram of a power system according to an example;

[0025] Fig. 9 shows a schematic diagram of a control circuit according to an example; and

[0026] Fig.10 A procedure for switching on a thyristor according to an example is shown. DETAILED DESCRIPTION

[0027] The examples of the methods and systems discussed herein are not limited in application to the details of the construction and arrangement of components set forth in the following description or shown in the accompanying drawings. These methods and systems can be implemented in other embodiments and can be practiced or executed in various ways. The examples of specific implementations provided here are for illustrative purposes only and not for limitation. Specifically, the actions, components, elements, and features discussed in conjunction with any one or more examples are not intended to be excluded from similar roles in any other examples.

[0028] In addition, the wording and terminology used herein are for the purpose of description and should not be considered as restrictive. Any reference to the example, embodiment, parts, element or action of the system and method mentioned in the singular form herein may also cover the embodiment comprising multiple, and any reference to any embodiment, parts, elements or action mentioned in the plural form herein may also cover the embodiment comprising only the singular. Reference in the singular or plural form is not intended to limit the currently disclosed system or method, their parts, actions or elements. "Including", "comprising", "having", "including", "involving" and variants thereof used herein are meant to include the project and its equivalent and additional items listed thereafter.

[0029] References to "or" may be interpreted as inclusive, such that any term described using "or" may mean any of the described terms singly, more than one, and all. Furthermore, in the event of inconsistencies in the usage of terms between this document and documents incorporated herein by reference, the usage of the term in the incorporated features is supplemental to this document; for irreconcilable differences, the usage of the term in this document controls.

[0030] In some parallel power systems, due to the differences in thyristors, silicon controlled rectifiers (SCRs), thyristors, and / or other types of bistable switches (collectively referred to as "thyristors") may be turned on at different times. For example, thyristors may have different threshold voltages. The threshold voltage of a thyristor may refer to the minimum forward voltage (e.g., the voltage from the anode to the cathode of the thyristor) applied to the thyristor before the thyristor begins to conduct a considerable forward current. Once turned on (i.e., once the thyristor begins to conduct a considerable amount of current), the thyristor may remain turned on as long as the forward voltage remains above the minimum voltage value corresponding to the voltage at which the thyristor will turn off. In some examples, the term turn-on voltage may refer to the forward voltage across the thyristor when the thyristor conducts a considerable amount of current. In some examples, the turn-on voltage may be lower than and / or may drop below the threshold voltage. That is, in some examples, the thyristor may continue to conduct a considerable amount of current even if the turn-on voltage is less than the threshold voltage. Similarly, thyristors may have different breakdown voltages. The breakdown voltage of a thyristor may refer to the minimum reverse voltage applied to the thyristor (ie, the voltage from the cathode to the anode of the thyristor) before the thyristor breaks down and conducts reverse current.

[0031] For example, a first thyristor connected in parallel with the second thyristor between the input and output may turn on (ie, start conducting a non-negligible amount of current) before the second thyristor if the threshold voltage of the first thyristor is lower than the threshold voltage of the second thyristor.

[0032] Furthermore, in some power systems using parallel thyristors, a lag may occur between the power source providing the input voltage and each parallel thyristor turning on. This lag may cause disturbances and / or irregularities in the power provided by the power system. For example, a power system may include two or more power devices connected in parallel, such as an uninterruptible power supply (UPS). Each parallel-connected UPS may include a respective thyristor, which may be referred to herein as a "parallel thyristor".

[0033] By providing a bias voltage and / or current to at least one thyristor via a bias element, parallel thyristors, such as individual thyristors in a parallel UPS, can be turned on simultaneously or with less hysteresis. The bias voltage and / or current can cause the forward voltage across the respective thyristor to exceed the threshold voltage of the thyristor by a sufficient amount to ensure that the thyristor conducts in the desired direction. The bias element can include a circuit element, such as a current or voltage source, that is capable of changing the voltage drop across a thyristor or a circuit branch containing the thyristor.

[0034] Compared to existing systems and methods, the present disclosure provides systems and methods that enable parallel thyristors to be turned on simultaneously and / or nearly simultaneously. Some examples of systems and methods use a current source as a biasing element to generate a bias voltage that increases the voltage across the thyristor. Some systems and methods use a transformer as a biasing element to generate a bias voltage across the thyristor. By generating a bias voltage across the thyristor, the system can ensure that the breakdown voltage and / or threshold voltage of the thyristor is exceeded when necessary, thereby turning the thyristor on (i.e., turned on).

[0035] Figure 1 A schematic diagram of an electric power system 100 according to an example is shown. The electric power system 100 facilitates the first thyristor 120a and the second thyristor 120b to be turned on simultaneously or nearly simultaneously. In some examples, the electric power system 100 can use one or more current sources to induce a current and / or voltage in the electric power system 100 so that the voltage across the thyristors 120a, 120b exceeds the threshold voltage of both the thyristors 120a, 120b for at least a time interval.

[0036] The power system 100 includes a reference node 102, an input power source 104 ("power source 104"), a first impedance 106, a second impedance 108, a third impedance 110, a fourth impedance 112, one or more loads 114 ("load 114"), and at least two power devices, including a first power device 116a ("first device 116a") and a second power device 116b ("second device 116b"). In at least one example, each of the devices 116a, 116b may be or include at least a portion of a UPS. The first impedance 106, the first device 116a, and the third impedance 110 may be collectively referred to as a "first branch" of the power system 100. The second impedance 108, the second device 116b, and the fourth impedance 112 may be collectively referred to as a "second branch" of the power system 100. The first and second branches may be connected in parallel to each other.

[0037] The first device 116a includes a first input impedance 118a, a first thyristor 120a, a first resistor 122a, a first line impedance 124a, a first source impedance 126a, a first output impedance 128a, a first current source 130a, and at least one first controller 132a ("first controller 132a"). The second device 116b includes a second input impedance 118b, a second thyristor 120b, a second resistor 122b, a second line impedance 124b, a second source impedance 126b, a second output impedance 128b, a second current source 130b, and at least one second controller 132b ("second controller 132b").

[0038] The power source 104 is coupled to the reference node 102 at a first connection and to the first and second impedances 106, 108 at a second connection. The first impedance 106 is coupled to the power source 104 at a first connection and to the first device 116a at a second connection. In some examples, the first impedance 106 is coupled to a first input impedance 118a at the second connection. The second impedance 108 is coupled to the power source 104 at a first connection and to the second device 116b at a second connection. In some examples, the second impedance 108 is coupled to a second input impedance 118b at the second connection.

[0039] The third impedance 110 is coupled to the load 114 at a first connection and to the first device 116a at a second connection. In some examples, the third impedance 110 is coupled to the first output impedance 128a at the second connection. The fourth impedance 112 is coupled to the load 114 at a first connection and to the second device 116b at a second connection. In some examples, the fourth impedance 112 is coupled to the second output impedance 128b at the second connection. The load 114 is coupled to the third impedance 110 and the fourth impedance 112.

[0040] The first input impedance 118a is coupled to the input of the first device 116a at a first connection and to the first thyristor 120a at a second connection. The first thyristor 120a is coupled to the first input impedance 118a at a first connection and to the first resistor 122a at a second connection. The first resistor 122a is coupled to the first thyristor 120a at a first connection and to the first line impedance 124a at a second connection. The first line impedance 124a is coupled to the first resistor 122a at a first connection and to the first source impedance 126a and the first output impedance 128a at a second connection. The first source impedance 126a is coupled to the first current source 130a at a first connection and to the first line impedance 124a and the first output impedance 128a at a second connection. The first current source 130a is coupled to the first source impedance 126a at a first connection and to the reference node 102 at a second connection. Because the first current source 130a is coupled to the reference node 102, it can be said that the first current source 130a is coupled in a parallel configuration relative to the series configuration of the first input impedance 118a, the first thyristor 120a, the first resistor 122a, the first line impedance 124a, and the first output impedance 128a.

[0041] The second input impedance 118b is coupled to the input of the second device 116b at a first connection and to the second thyristor 120b at a second connection. The second thyristor 120b is coupled to the second input impedance 118b at a first connection and to the second resistor 122b at a second connection. The second resistor 122b is coupled to the second thyristor 120b at a first connection and to the second line impedance 124b at a second connection. The second line impedance 124b is coupled to the second resistor 122b at a first connection and to the second source impedance 126b and the second output impedance 128b at a second connection. The second source impedance 126b is coupled to the second current source 130b at a first connection and to the second line impedance 124b and the second output impedance 128b at a second connection. The second current source 130b is coupled to the second source impedance 126b at a first connection and to the reference node 102 at a second connection. Because the second current source 130b is coupled to the reference node 102, it can be said that the second current source 130b is coupled in a parallel configuration relative to the series configuration of the second input impedance 118b, the second thyristor 120b, the second resistor 122ba, the second line impedance 124b, and the second output impedance 128b.

[0042] The node connecting the third impedance 110, the fourth impedance 112, and the load 114 may be referred to as "node A". The node connecting the power source 104, the first impedance 106, and the second impedance 108 may be referred to as "node B". The node connecting the first line impedance 124a, the first source impedance 126a, and the first output impedance 128a may be referred to as "node C". The node connecting the second line impedance 124b, the second source impedance 126b, and the second output impedance 128b may be referred to as "node D".

[0043] The impedance and thyristor of each of the first device 116a and the second device 116b need not be the same. Differences may arise due to, for example, manufacturing-induced differences. For example, the threshold voltages of the first thyristor 120a and the second thyristor 120b may not be the same, even though in some examples, components are selected to match as closely as possible during the manufacturing process. In some examples, the threshold voltage of the first thyristor 120a may be greater than the threshold voltage of the second thyristor 120b.

[0044] The first impedance 106 may be a line impedance of a connection between the power source 104 and the first device 116a. The second impedance 108 may be a line impedance of a connection between the power source 104 and the second device 116b. The third impedance 110 may be a line impedance of a connection between the first device 116a and the load 114. The fourth impedance 112 may be a line impedance of a connection between the second device 116b and the load 114. The line impedance may be an impedance attributed to conductors connecting the power devices 116a, 116b to the load 114 and / or the power source 104.

[0045] With respect to the first device 116a, the first input impedance 118a may be the impedance of an internal bus or similar conductor. The first resistor 122a may be the resistance of the first thyristor 120a. In some examples, the first resistor 122a may have a resistive component and a reactive component (i.e., the first resistor 122a may be an impedance). The first line impedance 124a may be the impedance of an internal bus or similar conductor. The first source impedance 126a may be the impedance of the first current source 130a and / or an internal cable or other conductor connecting the first current source 130a to the first line impedance 124a and / or the first output impedance 128a. The first output impedance 128a may be the impedance of an internal bus or similar conductor.

[0046] With respect to the second device 116b, the second input impedance 118b may be the impedance of an internal bus or similar conductor. The second resistor 122b may be the resistance of the second thyristor 120b. In some examples, the second resistor 122b may have a resistance component and a reactance component (i.e., the second resistor 122b may be an impedance). The second line impedance 124b may be the impedance of an internal bus or similar conductor. The second source impedance 126b may be the impedance of an internal cable or other conductor that connects the second current source 130b to the second line impedance 124b and / or the second output impedance 128b. The second output impedance 128b may be the impedance of an internal bus or similar conductor.

[0047] With respect to the first device 116a, the first current source 130a may be an inverter or a converter (e.g., a DC / DC converter, an AC / DC converter, or a DC / AC inverter controlled by the first controller 132a to operate as a current source). The first current source 130a may be unidirectional or bidirectional. The first current source 130a may provide current to the reference node 102 or the first source impedance 126a. The first current source 130a may provide a constant or variable current, and may provide the current as a DC or AC current.

[0048] With respect to the second device 116b, the second current source 130b may be an inverter or a converter (e.g., a DC / DC converter, an AC / DC converter, or a DC / AC inverter controlled by a second controller 132b to work as a current source). The second current source 130b may be unidirectional or bidirectional. The second current source 130b may provide current to the reference node 102 or the second source impedance 126b. The second current source 130b may provide a constant or variable current, and may provide a current as a DC or AC current.

[0049] With respect to the first device 116a, the first thyristor 120a can act as a switch, allowing current to pass through the first thyristor 120a in either direction. The first thyristor 120a can have a threshold voltage and a breakdown voltage. In some examples, the threshold voltage can include a voltage that needs to be overcome to allow a non-negligible current to pass from the power source 104 through the first thyristor 120a to the first output impedance 128a. In some examples, the second threshold voltage can include a voltage that needs to be overcome to allow a non-negligible current to pass from the load 114 through the first thyristor 120a to the first input impedance 118a.

[0050] With respect to the second device 116b, the second thyristor 120b can act as a switch, allowing current to pass through the second thyristor 120b in either direction. The second thyristor 120b can have a threshold voltage and a breakdown voltage. In some examples, the threshold voltage can include a voltage that needs to be overcome to allow current to pass from the power source 104 to the second output impedance 128b through the second thyristor 120b, and the second threshold voltage can include a voltage that needs to be overcome to allow current to pass from the load 114 to the second input impedance 118b through the second thyristor 120b.

[0051] The power source 104 may be any power source, including a power source capable of providing AC or DC power. For example, the power source 104 may be an AC mains grid. The load 114 may be any load rated to receive power from the power devices 116a, 116b.

[0052] The first controller 132a can be configured to control the operation of at least the first current source 130a and provide communication and interface functions to the first device 116a. The first controller 132a can be configured to determine the current provided by the power supply 104 to the load 114, and can be configured to communicate with other controllers (e.g., the second controller 132b).

[0053] The second controller 132b can be configured to control the operation of at least the second current source 130b and provide communication and interface functions to the second device 116b. The second controller 132b can be configured to determine the current provided by the power supply 104 to the load 114, and can be configured to communicate with other controllers (e.g., the first controller 132a).

[0054] The current sources 130a, 130b may be configured to output current. For example, the current sources 130a, 130b may include an inverter. In some examples, the controllers 132a, 132b may control the current sources 130a, 130b to bias the thyristors 120a, 120b, as discussed in more detail below. In other examples, in addition to or in place of the current sources 130a, 130b, the power device may include an alternative source to bias the thyristors 120a, 120b. For example, the power device may include a transformer with an associated control circuit to deliver a controllable bias voltage and / or current to the thyristors 120a, 120b.

[0055] Figure 2 Schematic diagram of a power system 200 according to an example of implementing a transformer and a control circuit is shown. Figure 1 Compared to the topology of power system 100 , power system 200 has an alternative topology and will be discussed in more detail below.

[0056] Figure 3 The first operating mode is shown according to an example Figure 1 Schematic diagram of an electric power system 100 . Figure 3 The first trace 302, the second trace 304 and the third trace 306 are included. The first trace 302 indicates the current provided by the power supply 104 to the load 114 via the first device 116a. The second trace 304 indicates the current provided by the first current source 130a to the node A. The third trace 306 indicates the current drawn from the node A by the second current source 130b.

[0057] In the first operating mode, the power supply 104 supplies power to the first device 116a and the second device 116b. For example, the first thyristor 120a has a lower turn-on voltage and / or threshold voltage than the threshold voltage of the second thyristor 120b. In this example, the first thyristor 120a conducts the current indicated by the first trace 302. Therefore, the first trace 302 shows the current originating from the power supply 104 and reaching the load 114 through the first thyristor 120a. In this example, the voltage across the second thyristor 120b is less than the threshold voltage of the second thyristor 120b; therefore, the second thyristor 120b does not conduct significant current (i.e., is not turned on).

[0058] If only the current and power corresponding to the first trace 302 are provided to the power system 100, the second thyristor 120b may be turned on after the first thyristor 120a, or may not be turned on at all, because the voltage drop across the second thyristor 120b may never exceed the threshold voltage of the second thyristor 120b. To ensure that the thyristors 120a, 120b are turned on at almost the same time, the first controller 132a and / or the second controller 132b may control the first current source 130a and the second current source 130b to generate a current from the first device 116a and provided to the reference node 102 by the second current source 130b. In some examples, one or more of the controllers 132a, 132b may control the first current source 130a to generate a first current pulse having a first phase angle, and control the second current source 130b to generate a second current pulse having a second phase angle. In some examples, the second phase angle may differ from the first phase angle by 180 degrees. In some examples, at least the first pulse and the second pulse can be equal in magnitude.The first and second pulses can contribute to generating a current from the first current source 130a through the second current source 130b to the reference node 102 .

[0059] The current generated by the pulses may be "invisible" to the load 114. That is, because the first pulse is equal and opposite to the second pulse, no portion of the current generated by the pulses is provided to the load 114. For example, the current entering node A must be equal to the current leaving node A. The current entering node A via the third impedance 110 is equal to the sum of the current indicated by the first trace 302 and the current indicated by the second trace 304. The current flowing out of node A via the fourth impedance 112 is equal to the current shown by the third trace 306.

[0060] Because the current in the third trace 306 is equal in magnitude and 180 degrees out of phase with the current indicated by the second trace 304, the currents indicated by the second and third traces 304, 306 are equal but opposite in direction (i.e., the current indicated by the second trace 304 enters node A, while the current indicated by the third trace 306 leaves node A). As a result, the current provided to the load 114 is equal to the current in the first trace 302, and the load 114 does not see the effects of the currents indicated by the second trace 304 and the third trace 306.

[0061] The current indicated by the second and third traces 304, 306 contributes to the change in the voltage drop across the second thyristor 120b. Because the second current source 130b is providing a current that flows from the second source impedance 126b to the reference node 102, in at least some examples, when the current indicated by the third trace 306 is applied, the voltage at the node D may drop. The voltage drop at the node D may correspond to the change in the voltage drop across the second thyristor 120b. In particular, the voltage drop across the second thyristor 120b may increase to a value greater than the threshold voltage of the second thyristor 120b, thereby causing the second thyristor 120b to turn on.

[0062] In some examples, based on the foregoing examples, the following equation may indicate a voltage relationship in the power system 100 when the second thyristor 120 b is not conducting:

[0063] (1) V1 = V th +I1·(Z c1 +R a1 +Z a1 +Z a2 )

[0064] (2) V2 = (I1 + I2) · (Z a3 +Z c3 )

[0065] (3) V3 = -I2·(Z c4 +Z b3 )

[0066] (4) V4 = V1 + V2 - V3

[0067] Where V1 is the voltage across nodes B and C, V2 is the voltage drop across nodes C and A, V3 is the voltage drop across nodes A and D, and V4 is the voltage drop across nodes B and D (which may be equal to the voltage drop across the second thyristor 120b when the second thyristor 120b is not conducting). I1 is the current represented by the first trace 302, and I2 is the current represented by the second and third traces 304, 306. V th is the voltage drop across the first thyristor 120a. c1 is the impedance of the first impedance 106. a1 is the resistance of the first resistor 122a. a1 is the impedance of the first input impedance 118a. a2 is the impedance of the first line impedance 124a. a3 is the impedance of the first output impedance 128a. c3 is the impedance of the third impedance 110. c4 is the impedance of the fourth impedance 112. b3 is the impedance of the second output impedance 128b.

[0068] In some examples, at least one of the controllers 132a, 132b may control the first current source 130a to provide a "positive" first pulse at a first time, and control the second current source 130b to provide a "negative" first pulse at a first time. The amplitude of the "positive" first pulse may be equal to the amplitude of the "negative" first pulse. At a second time, the controllers 132a, 132b may control the first current source 130a to provide a "negative" second pulse, and control the second current source 130b to provide a "positive" second pulse. The terms "positive" and "negative" may indicate the direction of current relative to a circuit node (e.g., node A). "Positive" may indicate that current flows into node A, and "negative" may indicate that current flows out of node A, and vice versa.

[0069] In some examples, the controllers 132a, 132b control the current sources 130a, 130b to provide these pulses at consecutive zero crossings of the voltage of the input power provided by the power supply 104. In this manner, the controllers 132a, 132b can control the current sources 130a, 130b to generate equal but opposite current oscillation pulses to generate an AC current from the first current source 130a to the second current source 130b.

[0070] As described above, in some examples, power devices 116a, 116b may illustrate at least a portion of respective UPSs coupled in parallel. Although two power devices 116a, 116b are shown, the principles of the present disclosure are applicable to power systems having more than two parallel-connected power devices, which may be parallel-connected UPSs.

[0071] For example, Figure 4 A block diagram of an electric power system 400 according to an example is shown, the electric power system 400 having more than two power devices (which in some examples may be UPS) connected in parallel between a power source and a load. The electric power system 400 includes a reference node 402, a power source 404, a first power device 406 ("first device 406"), a second power device 408 ("second device 408"), a third power device 410 ("third device 410"), a load 412, and at least one controller 418 ("controller 418"). Each of the power devices 406-410 may also include a current source. The first device 406 may include a first current source 406a. The second device 408 may include a second current source 408a. The third device 410 may include a third current source 410a. Figure 4 Also included is a first trace 414 indicating a first current path and a second trace 416 indicating a second current path. The power devices 406-410 may be connected to Figure 1 and 3 The power devices 116a, 116b are similar or identical. Figure 4 Two nodes are also shown, including node A (representing a node between power source 404 and devices 406 - 410 ) and node B (representing a node between devices 406 - 410 and load 412 ).

[0072] In the power system 400, a power source 404 is coupled to a reference node 402 at a first connection and to each power device 406-410 at a second connection. A first device 406 is coupled to the power source 404 at a first connection, to a load 412 at a second connection, and to the reference node 404 at a third connection. A second device 408 is coupled to the power source 404 at a first connection, to a load 412 at a second connection, and to the reference node 402 at a third connection. A third device 410 is coupled to the power source 404 at a first connection, to a load 412 at a second connection, and to the reference node 402 at a third connection.

[0073] The first trace 414 indicates the path of the first current provided by the power source 404. The current provided by the power source 404 enters the node A, passes through the first and second devices 406, 408 to the node B, and is then provided to the load 412. In this example, the third device 410 may include a non-conductive thyristor; therefore, no significant portion of the first current passes through the third device 410. In particular, a portion of the first current passes through the first device 406, and a portion of the first current passes through the second device 408.

[0074] The second trace 416 depicts the path of the second current provided by the current sources 406a, 408a, 410a of the devices 406-410. The second current corresponding to the second trace 416 is provided by the current sources 406a, 408a of the first and second devices 406, 408 to the third device 410 via the node B. The second current proceeds from the node B to the reference node 402 through the current source of the third device 410. When a portion of the second current is provided to the node B by the first device 406 and the second device 408, the second current is split. At the node B, the second current is combined into a single current that reaches the reference node 402 through the third device 410.

[0075] The third current source 110a can provide a current that is equal to the sum of the currents provided by the first device 406 and the second device 408, but in the opposite direction, because otherwise the load 412 will see the second current. In some examples, when there are an odd number of power devices, at least one power device can provide a current that is equal to and opposite to the sum of the currents provided by two (or more) other power devices. In some examples, when there are an even number of power devices, each power device can provide a current of equal magnitude. Half of the power devices can provide current in one direction, while the other half of the power devices can provide current in the other direction. In some examples, assuming that the net current is zero from the perspective of the load 412, a single power device can provide pulses of equal magnitude and opposite polarity to more than two other power devices.

[0076] In some examples, at least one controller may control one or more power devices to generate a first pulse having a first polarity, while also controlling one or more other power devices to generate simultaneous pulses having opposite polarities. At least one controller may include a controller 418, which may be part of any, some or all of the power devices 406-410, or may be independent of the power devices 406-410. After providing the first pulse, the controller 418 may control one or more power devices to generate a second pulse having a polarity opposite to the polarity of the first pulse, and may control one or more other power devices to generate simultaneous pulses having the polarity of the first pulse (i.e., a polarity opposite to the polarity of the second pulse). The power devices selected to generate the first and second pulses may be randomly selected. The power devices selected to generate simultaneous pulses may also be randomly selected, or may be a group of power devices that are not selected to generate the first and second pulses. In other examples, the power devices that generate pulses may be selected based on which devices are conducting or not conducting.

[0077] Figure 5A and 5B Processes 500 , 550 are shown for ensuring that two or more thyristors connected in parallel between a power source and a load are turned on, according to respective examples.

[0078] for Figure 5AIn the process 500, in at least one example, a controller (e.g., controller 418) randomly selects two or more power devices (e.g., power devices 406-410), and creates a first group and a second group based on the selected power devices. At a given time, such as a zero crossing of the voltage or current of the input power, the controller 418 controls the first group to generate a pair of pulses, including a first pulse of a first polarity and a second pulse of an opposite polarity. The first pulse can be generated at a first time (e.g., at the aforementioned zero crossing), and the second pulse can be generated immediately after the first pulse (e.g., a very short time after the aforementioned zero crossing). At the same time, the controller 418 controls the second group to generate a pair of pulses, wherein the first pulse (which can be generated at the first time) is of opposite polarity and the second pulse (which can be generated immediately after the first pulse) is of the first polarity. At the next zero crossing, the controller 418 can control the first group to generate a second pair of pulses, this time of opposite polarity after the first polarity, and control the second group to generate a second pair of pulses, this time of opposite polarity after the first polarity.

[0079] In contrast, in process 550, the controller 550 may select two or more power devices 406-410 and divide these devices into a first group and a second group. The first group may include one or more power devices in the power devices 406-410 with conducting thyristors, and the second group may include one or more power devices in the power devices 406-410 with non-conducting thyristors. At a given time, such as a zero crossing of the voltage or current of the input power, the controller 418 may control the first group to generate a single pulse of a first polarity and control the second group to generate a single pulse of the opposite polarity. At a subsequent time (e.g., the next zero crossing), the controller 418 may control the first group to generate a single pulse of the opposite polarity and control the second group to generate a single pulse of the first polarity. Therefore, in at least some examples, the process 500 is characterized in that a pulse pair is generated for each of the selected power devices 406-410 at a given time, and the process 550 is characterized in that a single pulse is generated for each of the selected power devices 406-410 at a given time.

[0080] Figure 5A A process 500 for ensuring that two or more thyristors connected in parallel between a power source and a load are turned on is shown according to an example. Figure 4 The process 500 is described with reference to the components of FIG. 5 , however, the process 500 may also be applied to Figure 1 For example, while in some examples the actions of process 500 may be performed by controller 418, in other examples the process 500 may be performed by one or both of controllers 132a, 132b.

[0081] At act 502, controller 418 receives a signal or other indication that power source 404 is supplying power to two or more power devices 406-410 connected in parallel between power source 404 and load 412. The signal may be sent from power source 404 or may be received from a sensor or other device configured to detect whether power source 404 is supplying power to power devices 406-410 and / or load 412. Process 500 may continue to act 504.

[0082] At action 504, the controller 418 randomly selects two or more power devices from the power devices 406-410. The controller 418 may use any random or pseudo-random algorithm to select the power devices. The controller 418 may select an odd or even number of power devices 406-410. The controller 418 may allocate a first group of selected power devices 406-410 to generate a first pair of current pulses, and allocate a second group of selected power devices 406-410 to generate a second pair of current pulses. The process 500 may then continue to action 506.

[0083] In action 506, the controller 418 controls and / or instructs the first group to generate a first pair of current pulses. The controller 418 may control and / or instruct at least one current source, such as an inverter or a converter, to generate the first pair of current pulses. In some examples, the at least one current source may include one or more corresponding current sources 406a, 408a, 410a of each power device 406-410. The controller 418 may instruct the power devices of the first group to each generate a "positive" current pulse, followed by a "negative" current pulse. The sum of the positive pulses of the current generated in this manner may be referred to as a first positive current, and the sum of the negative pulses generated in this manner may be referred to as a first negative current. The controller 418 may instruct the second group to generate a "negative" current pulse, followed by a "positive" current pulse. The sum of the negative current pulses generated in this manner may be referred to as a second negative current, and the sum of the positive pulses generated in this manner may be referred to as a second positive current.

[0084] In some examples, controller 418 can determine the amount of current produced by each power device 406-410 such that the sum of the first positive current and the first negative current is zero from the perspective of load 412 and / or the sum of the first negative current and the second positive current is zero from the perspective of load 412. Process 500 can then continue to act 508.

[0085] In action 508, the controller 418 determines whether a delay period has passed after the first current pulse is generated. This amount of time may vary according to characteristics such as the frequency of the power system. The delay may be determined according to a phase angle relative to the first current pulse. In some examples, a delay may be provided to prevent the pulse from being generated until shortly after or immediately after the zero crossing. In some examples, the delay is zero, i.e., ignored. If the controller 418 determines that the delay has not expired (508 is no), the controller 418 may wait. If the controller 418 determines that the delay has expired (508 is yes), the process 500 may continue to action 510.

[0086] In action 510, the controller 418 controls and / or instructs the selected power devices 406-410 to generate a second pair of current pulses. The controller 418 can control and / or instruct at least one current source, such as an inverter or a converter, to generate the second pair of pulses. The controller 418 can control the first group, which previously generated a positive pulse followed by a negative pulse, to now generate a negative pulse followed by a positive pulse. The controller 418 can instruct the second group that previously generated a negative pulse followed by a positive pulse to generate a positive pulse followed by a negative pulse. As previously described, the sum of the currents generated by the first group and the second group can be zero, at least from the perspective of the load 412. In some examples, the selected power devices 406-410 can generate pulses of equal size but opposite direction compared to the pulses generated during action 506.

[0087] Figure 5B A process 550 is shown for ensuring that two or more thyristors in two or more respective power devices connected in parallel between a power source and a load are turned on, according to an example. Figure 5A The process 500 is the opposite, Figure 5B The process 550 does not randomly select power devices. Figure 4 The process 550 is described as a component of Figure 1 For example, while in some examples the actions of process 550 may be performed by controller 418, in other examples the process 550 may be performed by one or both of controllers 132a, 132b.

[0088] At act 552 , controller 418 determines that power source 404 is providing power to powered devices 406 - 410 . Process 550 may then continue to act 554 .

[0089] In action 554, the controller 418 selects two or more of the power devices 406-410 to generate current pulses. At least one of the selected power devices 406-410 is a device with a non-conducting thyristor, and at least one of the selected power devices 406-410 is a device with a conducting thyristor. In some examples, the controller 418 can select a plurality of power devices 406-410 with non-conducting thyristors and / or a plurality of power devices 406-410 with conducting thyristors. Any number of power devices 406-410 can be selected as long as the currents generated by the first and second groups (the first group is a power device with a conducting thyristor and the second group is a power device with a non-conducting thyristor) are equal in magnitude and opposite in polarity. The process 550 can then continue to action 556.

[0090] At act 556, the controller 418 instructs and / or controls the first group to generate a "positive" first current pulse, and instructs and / or controls the second group to generate a "negative" first current pulse. The "positive" and "negative" pulses of the current are equal in amplitude but opposite in polarity (i.e., the phase angle of the "negative" first pulse is 180 degrees different from the phase angle of the "positive" first pulse). The process 550 can then continue to act 558.

[0091] At action 558, the controller 418 determines whether the delay period has expired. The delay period may be based on the power source 404 (e.g., Figure 1 The delay period may also be based on a phase angle or angle, a preset or configurable time period, etc. If the delay period has expired (yes at 558), the process may proceed to action 560. If the delay period has not expired (no at 558), the process may wait for the delay period to expire.

[0092] In action 560, the controller 418 instructs and / or controls the first group to generate a "negative" second current pulse, and instructs and / or controls the second group to generate a "positive" second current pulse. The "positive" and "negative" pulses of the current are equal in amplitude but opposite in polarity (i.e., the phase angle of the "negative" second pulse is 180 degrees different from the phase angle of the "positive" second pulse).

[0093] about Figure 5A and 5B , "negative" and "positive" do not necessarily refer to the polarity of a voltage relative to neutral. For example, a "positive" pulse of current is not necessarily associated with a voltage greater than zero. Rather, "positive" and "negative" mean that the "positive" and "negative" pulses are opposite to each other relative to at least one circuit node (e.g., node A).

[0094] Figure 6 A circuit diagram with three traces according to an example is shown. Figure 1 A schematic diagram of an electric power system 100 is shown. Figure 3 on the contrary, Figure 6 The power system 100 is shown providing current so that a bias current for turning on a non-conducting thyristor is drawn from the power supply 104. Figure 3 This version of the power system 100 may also facilitate the turning on of the parallel thyristors with simpler control than the system of FIG. 1 because it is not necessary to determine which parallel thyristors are conducting or not conducting before providing the bias current. In addition, the pulse amplitude of the bias current may also be smaller, but the power source 104 and the load 114 may experience some distortion due to the current pulses. In some examples, a reactive sinusoidal current may be implemented instead of a current pulse to facilitate the turning on of one or more parallel thyristors.

[0095] Figure 6 The first trace 602, the second trace 604, and the third trace 606 are included. The first trace 602 corresponds to the current ("I1") provided by the power supply 104 to the load 114. The second trace 604 corresponds to the current ("I2") consumed by the second current source 130b. The third trace 606 corresponds to the current ("I3") consumed by the first current source 130a. The first current source 130a directs the current to the reference node 102, and thus is Figure 3 Compared to the example of , a current in the opposite direction is provided.

[0096] In some examples, based on the foregoing examples, the following equation may indicate a voltage relationship in the power system 100 when the second thyristor 120 b is not conducting:

[0097] (5) V1 = V th +(I1+I2+I3)·(Z c1 +R a1 +Z a1 +Z a2 )

[0098] (6) V2 = (I1 + I2) · (Z a3 +Z c3 )

[0099] (7) V3 = -I2·(Z c4 +Z b3 )

[0100] (8) V4 = V1 + V2 - V3

[0101] Where V1 is the voltage across nodes B and C, V2 is the voltage drop across nodes C and A, V3 is the voltage drop across nodes A and D, and V4 is the voltage drop across nodes B and D (which in some examples may be equal to the voltage drop across the second thyristor 120b). I1 is the current represented by the first trace 602, I2 is the current represented by the second trace 604, and I3 is the current represented by the third trace 306. Vth is the voltage drop across the first thyristor 120a. c1 is the impedance of the first impedance 106. a1 is the resistance of the first resistor 122a, Z a1 is the impedance of the first input impedance 118a, Z a2 is the impedance of the first line impedance 124a. a3 is the impedance of the first output impedance 128a, Z c3 is the impedance of the third impedance 110. c4 is the impedance of the fourth impedance 112, Z b3 is the impedance of the second output impedance 128b.

[0102] and Figure 3 In contrast to the power system 100 in FIG. 1 , in which the load 114 and the power source 104 do not see the current generated by the current sources 130 a, 130 b, Figure 6 In the example of , the load 114 and the power supply 104 can see the current drawn by the current sources 130a, 130b. Figure 3 In the power system 100 of FIG. 1 , when the current sources 130 a, 130 b generate current pulses to turn on the second thyristor 120 b (which is assumed to be non-conductive for the purpose of explanation), these pulses appear in the current (and power) provided by the power supply 104. As a result, the input power from the input power supply 104 and the load 114 may experience distortion due to the pulses.

[0103] The current generated by the first current source 130a may be equal to the current generated by the second current source 130b. Figure 3 on the contrary, Figure 6 130a, 130b is not zero. The current at node A remains equal to the sum of I1 and I2. Only at node D does the current drop to equal I2. In other words, of the total current provided to load 114 from node B via nodes C and A, a first portion of the total current (equal to I3) is drawn by the first current source 130a at node C, and a second portion of the total current (equal to I2) is drawn by the second current source 130b at node A, while the remaining portion (equal to I1) is provided to load 114. The directions of I1, I2, and I3 indicate that the voltage will decrease from node B to node A and increase from node D to node A. In addition, because the second thyristor 120b is turned off, there is no voltage drop across impedances 108, 118b, 122b, and 124b. Therefore, increasing the voltage across the second thyristor 120 b from the node B to the node D may cause the second thyristor 120 b to turn on.

[0104] Figure 7A process 700 is shown for managing current in a power device to ensure that one or more thyristors are turned on. Figure 5A and 5B Compared to processes 500 , 550 , process 700 includes directing current from node B to C and from node B to node D so that bias current is drawn from power source 104 for turning on the non-conducting parallel thyristors 120 a , 120 b .

[0105] Specifically, with respect to process 700, the currents generated by current sources 130a, 130b of power devices 116a, 116b are now directed to reference node 102. Figure 3 and 6 As an example, in Figure 3 In the example, the first current source 130a directs the current from the reference node 102 to the node C, which is consistent with Figure 5A and 5B The processes 500 and 550 are consistent. In contrast, Figure 6 In FIG. 1 , current source 130 a directs current from node C to reference node 102 , which is consistent with process 700 . Figure 6 The current into node C is equal to I1+I2+I3, the current into node A is equal to I1+I2, and the current into node D is equal to I2. The load receives current I1, but also experiences distortion due to the current pulses generated by current sources 130a, 130b.

[0106] At act 702 , the controller 418 receives a signal or otherwise detects that the power source 404 is providing power to one or more power devices 406 - 410 . The process 700 may then continue to act 704 .

[0107] At action 704, the controller 418 selects one or more of the power devices 406-410 to provide the first current pulse. The power devices may be randomly selected according to a random or pseudo-random algorithm, or may be selected based on the conduction state of the thyristors associated with the respective power devices. In an example of selecting a power device based on the conduction state of the thyristors, at least one of the selected power devices may have a thyristor in a non-conducting state, and at least one of the selected power devices may have a thyristor in a conducting state. Process 700 may then continue to action 706.

[0108] At act 706, controller 418 controls and / or instructs the selected power devices to generate pulses. In some examples, the pulses generated by each power device can be equal to the pulses generated by each other power device. In some examples, a current source (e.g., an inverter or converter of a power device) can generate the corresponding pulses. The pulses can be generated so that the current of the pulses is directed to reference node 402 and away from load 412 (e.g., directed to Figure 6 The reference node 102 is far away from Figure 6 In some examples, the pulses may have a phase angle of 90 degrees relative to the input current provided by the power supply 104. As a result, the input Figure 4 The current at node B can be equal to the sum of the current to be provided to load 412 and the current drawn by power devices 406-410 with non-conducting thyristors. Power devices 406-410 with conducting thyristors can draw current from the current provided to node B from node A and provide this current to reference node 402, thereby reducing the total current entering node B.

[0109] As mentioned above, Figure 2 A schematic diagram of a power system 200 is shown according to one example. Figure 2 Similar to Figure 1 , with some exceptions, including transformer implementation, as described below. The power system 200 ensures that the thyristors of the power devices discussed below are turned on simultaneously (or nearly simultaneously).

[0110] The power system 200 includes a first transformer having a first primary winding (or coil) 202a ("first primary coil 202a") and a first secondary winding (or coil) 204a ("first secondary coil 204a"), and at least one first control circuit 206a ("first control circuit 206a") coupled to the first transformer. The power system 200 also includes a second transformer having a second primary winding (or coil) 202b ("second primary coil 202b") and a second secondary winding (or coil) 204b ("second secondary coil 204b"), and at least one second control circuit 206b ("second control circuit 206b") coupled to the second transformer.

[0111] Figure 2 The power system 200 and Figure 1 The power system 100 is different in at least one aspect. Figure 2In the power system 200 of FIG. 1 , the first input impedance 118a is coupled to the first thyristor 120a at the second connection and to the first primary coil 202a at the first connection. The first primary coil 202a is coupled to the first impedance 106 at the first connection, to the first input impedance 118a at the second connection, and is magnetically coupled to the first secondary coil 204a. In addition, the second input impedance 118b is coupled to the second thyristor 120b at the second connection and to the second primary coil 202b at the first connection. The second primary coil 202b is coupled to the second impedance 108 at the first connection, to the second input impedance 118b at the second connection, and is magnetically coupled to the second secondary coil 204b. The input impedances 118a, 118b are not directly coupled to the first impedance 106 or the second impedance 108. The source impedances 126a, 126b and the current sources 130a, 130b are optional and may be replaced with an open circuit and / or removed entirely.

[0112] In each transformer, the primary coils 202a, 202b are electromagnetically coupled to their respective secondary coils 204a, 204b. The first secondary coil 204a is coupled to a first control circuit 206a, and the second secondary coil 204b is coupled to a second control circuit 206b. In some examples, the transformer includes a magnetic core wound around a busbar and can be electromagnetically coupled to the corresponding primary coils 202a, 202b and / or secondary coils 204a, 204b.

[0113] The control circuits 206a, 206b may control one or more power supplies configured to provide current to the secondary coils 204a, 204b. In some examples, the control circuits 206a, 206b may include respective power supplies and may provide current to the secondary coils 204a, 204b. The control circuits 206a, 206b may control the power supplies to provide a sinusoidal signal, a square wave, a triangular wave, or any other type of AC power, current, and / or voltage to the secondary 204a, 204b. The control circuits 206a, 206b may include corresponding H-bridge circuits, which may be used to control the provision of power, current, and / or voltage to the secondary coils 204a, 204b. When the secondary coils 204a, 204b receive AC power, current, and / or voltage, corresponding voltages and currents are induced on the primary coils 202a, 202b.

[0114] Figure 8 Power system 200 is shown with trace 802 indicating current according to an example.

[0115] Trace 802 represents the current I1 provided from power source 104 to load 114. Figure 3 and Figure 6 In contrast to the example Figure 8Only a single trace is shown in . The following equations describe the relationship of certain voltages in the power system 200 .

[0116] (9) V1 = V t h+I1·(Z c1 +Z c3 +R a1 +Z a1 +Z a2 +Z a3 )+V T1

[0117] (10) V2 = V1 + V T2

[0118] Where V1 is the voltage across nodes B and C, and V2 is the voltage drop across the second thyristor 120b. I1 is the current represented by trace 802. th is the voltage drop across the first thyristor 120a. c1 is the impedance of the first impedance 106. a1 is the resistance of the first resistor 122a, Z a1 is the impedance of the first input impedance 118a, Z a2 is the impedance of the first line impedance 124a. a3 is the impedance of the first output impedance 128a, Z c3 is the impedance of the third impedance 110. T1 is the voltage across the first primary 202a, V T2 is the voltage across the second primary 202b.

[0119] The control circuits 206a, 206b can control the corresponding power provided to the corresponding secondary coils 204a, 204b to induce the corresponding voltage on the primary coils 202a, 202b. For simplicity, controlling the power provided to the secondary coils can be referred to as controlling the secondary coils. For example, the first control circuit 206a can control the first secondary coil 204a to induce a voltage on the first primary coil 202a by controlling the power provided to the first secondary coil 204a. Similarly, the second control circuit 206b can control the second secondary coil 204b to induce a voltage on the second primary coil 202b by controlling the power provided to the second secondary coil 204b. The control circuits 206a, 206b can use a power supply, a waveform generator, an H-bridge or any other suitable circuit to provide an AC or instantaneous current or voltage to the corresponding secondary coils 204a, 204b as a means of controlling the secondary coils 204a, 204b to induce a voltage on the primary coils 202a, 202b. The voltage induced on the primary coils 202a, 202b can change the voltage across the thyristors 120a, 120b, and thus can be used to make the thyristors 120a, 120b conduct in either direction (i.e., allowing current to flow from the input impedances 118a, 118b to the resistors 122a, 122b, or from the resistors 122a, 122b to the input impedances 118a, 118b).

[0120] As an example, consider the case where the first thyristor 120a is conducting in the direction from the first input impedance 118a to the first resistor 122a and the second thyristor 120b is not conducting. By controlling the H-bridge or other power supply, the control circuit 206b can induce a voltage on the second primary 202b via the second secondary 204b. According to equation (10), the voltage across the second thyristor 120b will increase or decrease V T2 , V T2 is the voltage induced on the second primary coil 202b. By adjusting the voltage across the second thyristor 120b in this way, the voltage across the second thyristor 120b can be made to exceed the threshold voltage of the second thyristor 120b, thereby turning on the second thyristor 120b. In some examples, the first primary coil 202a can be connected between the impedances 106 and 118a, such as Figure 8As shown. In other examples, the first primary coil 202a can be connected in series with the first thyristor 120a at any other location, such as between the first input impedance 118a and the first thyristor 120a, between the first resistor 122a and the first line impedance 124a, between the output impedance 128a and the third impedance 110, or between the first impedance 106 and the first input impedance 118a. Similarly, the second primary coil 202b can be connected in series with the second thyristor 120b at any other location, such as between the second input impedance 118b and the second thyristor 120b, between the second resistor 122b and the second line impedance 124b, between the output impedance 128b and the fourth impedance 112, or between the second impedance 108 and the second input impedance 118b.

[0121] Fig. 9 A control circuit 900 according to an example is shown. The control circuit 900 is an example implementation of the control circuits 206a, 206b. The control circuit 900 includes at least one controller 902 ("controller 902"), a first transistor 904, a second transistor 906, a third transistor 908, and a fourth transistor 910. The control circuit 900 can be coupled to a secondary winding 914, a primary winding 912, and a transformer core 916. The control circuit 900 includes two nodes A and B. Node A is a node between the first transistor 904, the third transistor 908, and the secondary winding 914. Node B is a node between the secondary winding 914, the second transistor 906, and the fourth transistor 910.

[0122] The controller 902 is coupled to each transistor 904-910 via a respective control connection of each transistor 904-910. For example, if the transistors 904-910 include field effect transistors (FETs), the controller 902 can be coupled to the respective gates of each FET. The first transistor 904 is coupled to the second transistor 906 and the controller 902 at a first connection, and to the third transistor 908 at a second connection. The second transistor 906 is coupled to the first transistor 904 and the controller 902 at a first connection, and to the fourth transistor 910 at a second connection. The third transistor 908 is coupled to the controller 902 and the fourth transistor 910 at a first connection, and to the first transistor 904 at a second connection. The fourth transistor 910 is coupled to the third transistor 908 and the controller 902 at a first connection, and to the second transistor 906 at a second connection. The secondary winding 914 is coupled to the first and third transistors 904, 908 at a first connection, and to the second and fourth transistors 906, 910 at a second connection.

[0123] The controller 902 can control the states of the transistors 904-910, which can operate as switches (i.e., the transistors 904-910 can conduct current or not). The controller 902 can control the conductive path on the secondary winding 914. For example, the controller 902 can control the first transistor 904 and the fourth transistor 910 to be in a conductive state. Therefore, the current can reach the node A through the first transistor 904, reach the node B through the secondary winding 914, and finally reach the controller 902 through the fourth transistor 910. The controller 902 can also control the second transistor 906 and the third transistor 908 to be in a conductive state, so that the current reaches the node B through the second transistor 906, reaches the node A through the secondary winding 914, and then reaches the controller 902 through the third transistor 908. The above examples illustrate how current through the secondary winding 914 can flow in either direction through the secondary winding 914, and therefore the voltage induced on the primary winding 912 by the secondary winding 914 can be positive or negative.

[0124] Fig.10 A process 1000 of connecting thyristors in parallel using a transformer according to an example is shown. Figure 2 shown.

[0125] At act 1002, controller 418 determines that power source 404 is providing current to load 412. For example, controller 418 may receive a signal or otherwise detect that power source 404 is providing power to load 412. Process 1000 may then continue to act 1004.

[0126] In action 1004, the controller 418 may select two or more power devices. The power devices may be randomly selected according to a random or pseudo-random algorithm, or may be selected based on the conduction state of the thyristors associated with the power devices 406-410. In an example where the power devices 406-410 are selected based on the conduction state of the thyristors, at least one of the selected power devices 406-410 may have a thyristor in a non-conducting state, and at least one of the selected power devices 406-410 may have a thyristor in a conducting state. The process 1000 may then continue to action 1006.

[0127] At act 1006, the controller 418 can control a transformer coupled to the thyristor to generate a bias voltage across the thyristor. In some examples, the controller 418 can control a power source (e.g., an H-bridge) to provide a time-varying current and / or voltage to the secondary of the transformer, thereby inducing a voltage across the primary coil of the transformer. The voltage across the primary coil of the transformer can then cause the voltage across the thyristor coupled to the transformer to change, increasing or decreasing the voltage, and allowing at least one thyristor to begin conducting in at least one direction. Process 1000 can then continue to act 1008.

[0128] At action 1008, the controller 418 determines whether the current level through the secondary winding of one of the transformers (preferably the transformer that accommodates the power device that does not conduct the thyristor) reaches a threshold level. In some examples, the threshold level can be based on when the transformer core of one of the transformers (preferably the transformer that accommodates the power device that does not conduct the thyristor) is saturated. If the controller 418 determines that the current level through the secondary winding of the transformer is below the threshold level (No at 1008), the process 1000 can continue to wait at action 1008 until the current reaches the threshold level. If the current reaches or exceeds the threshold level (Yes at 1008), the process 1000 can continue to act 1010.

[0129] In action 1010, the controller 418 controls the transformer to stop providing the bias voltage. In some examples, the controller 418 can control the power supply 404 (e.g., an H-bridge) to stop providing a time-varying current and / or voltage to the secondary winding of the transformer. Without a time-varying current or voltage, the secondary winding will no longer induce a voltage on the primary winding, thus eliminating the bias voltage.

[0130] In front Figure 1-10 In the embodiment, power devices 406-410 may be UPS or similar devices that provide uninterruptible power to one or more loads.

[0131] In general, especially in Figure 5A , 5B , 7 and 10, when a controller is referred to as performing an operation, the controller may perform the operation independently and completely independently, or the controller may perform the operation partially or in coordination with other controllers. More generally, although controllers are mentioned throughout, the controllers may act as a single controller that makes decisions together (peer-to-peer network) or may operate in a commander-subordinate manner, where one controller makes decisions and other controllers execute instructions.

[0132] Throughout the foregoing discussion, when pulses are generated, the controller may control the power device or the components of the power device to generate those pulses at a time that is consistent or approximately consistent with the zero crossing of the current and / or voltage of the input power. For example, the pulse may be generated starting from the zero crossing, or may be generated at the end of the zero crossing, or may be generated at another time based on the zero crossing.

[0133] Various controllers, such as controllers 132a, 132b, 418, 902, can perform the various operations described above. Using data stored in associated memory and / or storage devices, the controller can also execute one or more instructions stored on one or more non-transitory computer-readable media that the controller can include and / or be connected to, which can generate manipulated data. In some examples, the controller may include one or more processors or other types of controllers. In one example, the controller is or includes at least one processor. In another example, in addition to a general-purpose processor, or instead of a general-purpose processor, the controller uses a dedicated integrated circuit to perform at least a portion of the above operations, which is suitable for performing specific operations. As shown in these examples, many specific combinations of hardware and software can be used to perform the operations described herein according to examples of the present disclosure, and the present disclosure is not limited to any specific combination of hardware and software components. Examples of the present disclosure may include a computer program product configured to perform the above methods, processes, and / or operations. The computer program product may be or include one or more controllers and / or processors configured to execute instructions to perform the above methods, processes, and / or operations.

[0134] Thus, having described several aspects of at least one embodiment, it will be appreciated that various changes, modifications and improvements will readily occur to those skilled in the art. These changes, modifications and improvements are intended to be a part of this disclosure and are within the spirit and scope of this disclosure. Therefore, the foregoing description and drawings are merely exemplary.

Claims

1. A system comprising: an input configured to be connected to a power source; an output configured to be connected to a load; a first branch coupled between the input and the output and comprising a first thyristor having a first threshold voltage; a second branch coupled between the input and the output and coupled in parallel with the first branch, the second branch comprising a second thyristor having a second threshold voltage higher than the first threshold voltage; and At least one controller is configured to control the system to selectively generate a bias voltage across the second thyristor to cause the voltage across the second thyristor to change from a first voltage to a second voltage, wherein the first voltage is less than the second threshold voltage and the second voltage is greater than the second threshold voltage. 2 . The system of claim 1 , wherein the bias voltage is provided in response to the system receiving an input voltage at the input. 3 . The system of claim 1 , further comprising a transformer coupled in series with the second thyristor. 4 . The system of claim 3 , wherein when controlling the system to generate the bias voltage, the at least one controller is further configured to control the transformer to cause the voltage across the second thyristor to change from the first voltage to the second voltage.

5. The system of claim 4, wherein the transformer includes a secondary winding, and wherein controlling the transformer includes controlling a voltage source to supply power to the secondary winding.

6. The system of claim 3, further comprising at least one busbar, wherein the transformer comprises a magnetic core surrounding the at least one busbar, the magnetic core being electromagnetically coupled to the primary winding and the secondary winding.

7. The system of claim 1 , wherein a voltage change across the second thyristor is equal to or greater than a sum of voltage changes across one or more other thyristors coupled to one or more branches, each of the one or more branches being coupled in parallel with the second branch between the input and the output.

8. The system of claim 1, further comprising: a first current source coupled in a parallel configuration relative to the first thyristor and a reference node; and A second current source is coupled in a parallel configuration with respect to the second thyristor and the reference node.

9. The system of claim 8, wherein the at least one controller is further configured to: Controlling the first current source to output a first current having a first phase and an amplitude; The second current source is controlled to output a bias current having a second phase and amplitude, wherein the bias current is generated to offset the first current at the output.

10. The system of claim 9, wherein the bias current is generated to cause a voltage across the second thyristor to change from the first voltage to the second voltage by an amount equal to the bias voltage. The system of claim 9 , wherein the first phase is 180 degrees different from the second phase.

12. The system of claim 8, wherein the input is configured to receive an input current from the power source, and wherein the at least one controller is further configured to: requesting from the power supply output to increase an input current provided at the input; controlling the first current source to provide a first current having a first phase and a first amplitude; and The second current source is controlled to provide a bias current having a second phase and a second amplitude.

13. The system of claim 12, wherein the sum of the first amplitude and the second amplitude is equal to an increase in input current provided at the input.

14. The system of claim 8, wherein the first current source is a first inverter and the second current source is a second inverter.

15. The system of claim 1, wherein the controller controls the current source to generate a bias current to cause a voltage change equal to a bias voltage across the second thyristor so that a new voltage across the second thyristor is greater than the second threshold voltage.

16. A non-transitory computer-readable medium containing computer-readable instructions for a power system, the instructions directing at least one processor to: controlling the first thyristor to draw an input current through the first thyristor; and In response to controlling the first thyristor to draw input current through the first thyristor, a control circuit element provides a bias voltage across the second thyristor to cause a voltage across the second thyristor to change from a first voltage to a second voltage greater than a threshold voltage of the second thyristor.

17. The non-transitory computer readable medium of claim 16, wherein the instructions further instruct the at least one processor to: The control power supply provides a time-varying voltage to the secondary winding of the transformer connected in series with the second thyristor.

18. The non-transitory computer readable medium of claim 17, wherein controlling the transformer to provide the bias voltage across the second thyristor comprises controlling a current source to provide a bias current to a node coupled between the second thyristor and the output.

19. The non-transitory computer readable medium of claim 18, wherein the instructions instruct the at least one processor to select a bias current value provided to the node such that a corresponding voltage drop across the second thyristor is greater than a threshold voltage of the second thyristor.

20. The non-transitory computer-readable medium of claim 18, wherein the node is a second node and the instructions further instruct the at least one processor to: controlling a first current source to provide a first current to a first node, the first node being coupled between the output and the first thyristor; and The second current source is controlled to provide the bias current to the second node.

21. The non-transitory computer readable medium of claim 20, wherein the instructions further instruct the at least one processor to: The first current source is controlled to provide the first current and the second current source is controlled to provide the bias current, so that the first current and the bias current cancel each other at the output.

22. The non-transitory computer readable medium of claim 20, wherein the instructions further instruct the at least one processor to: controlling an input power source to increase an input current by an additional amount, and supplying the input current increased by the additional amount to the first thyristor, The sum of the first current and the bias current is equal to the additional amount of the input current.

23. A method of operating a first thyristor and a second thyristor connected in parallel, the method comprising: providing a voltage associated with current to the first thyristor and the second thyristor; and A bias voltage is provided across the second thyristor to cause a voltage across the second thyristor to change from a first voltage to a second voltage, the first voltage being less than a threshold voltage of the second thyristor and the second voltage being greater than the threshold voltage.

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