• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    Dynamic overcurrent protection system and method for power converters. A dynamic overcurrent protection system and method (1) is disclosed for power converters. The system is connectable to the output of a power stage (5) and comprises: a comparator (4) that measures an output current (IOUT) of the power stage; a control device (2) that measures a voltage (VDC) of the power stage; a pattern generator (3) comprising pairs of voltage-current values (VDC -IREF) that relate voltage values to current values of the power stage, where the pattern generator receives the measured voltage value from the control device and sends the corresponding current value of the voltage-current value pairs to the comparator, which stops the power stage if the output current of the Power is greater than or equal to the value of the current associated with the measured voltage. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2717341A1
    申请号:ES201731435
    申请日:2017-12-20
    公开日:2019-06-20
    发明作者:Lerma Antonio Poveda；Lillo Abelardo Salvo；Lillo David Salvo
    申请人:Power Electronics Espana SL；
    IPC主号:
    专利说明:

    [0001] SYSTEM AND METHOD OF DYNAMIC PROTECTION AGAINST OVERCURRENT
    [0002]
    [0003] FIELD OF THE INVENTION
    [0004] The present invention relates to a system and method of dynamic overcurrent protection for power converters.
    [0005] The technical field of the invention is framed within the field of power converters, motor controllers and solar and wind power generation systems.
    [0006]
    [0007] BACKGROUND OF THE INVENTION
    [0008] All power converters have as common elements at least one DC voltage bus and a power converter bridge, formed by switching devices whose tripping is controlled so that the voltage / current at the output has the characteristics required by the application. Thus, if the power converter is a solar inverter, the equipment will function as an AC current source of the same frequency as the network (typically 50/60 Hz). If the power converter is a speed variator, the power frequency will be modified in order to vary the rotation speed of three-phase asynchronous electric motors.
    [0009] The power stage is formed by one or more power modules. Each power module is formed, as a minimum, by a DC bus and a series of switching devices. The simplest case (DC / DC converters) would be composed of a single switching device, while in the variable speed drives or DC / AC converters will implement bridges formed by several switching devices (six if the bridge power converter is of Two levels). For power converters with AC output, the power stage incorporates a filter necessary to adapt the output waveform to that of the motor. If the input of the equipment is an AC source, the power stage would also include a rectifier bridge that rectifies the polarity of the input AC voltage, so that it is stable. The rectifier can be formed by diodes or by transistors. This second option incorporates the ability to move electrical energy bi-directionally, allowing the discharge of excess energy at the source.
    [0010] To ensure the correct operation of the power stage of the converter of power as well as to avoid damage by overvoltages or overcurrents, the power converter incorporates protection devices connected to the power stage. The necessary protection for the power converter is mainly determined by the characteristics of the switching devices.
    [0011] Currently, the protection incorporated in the power converters is "hardware." The protection system consists of setting a threshold of protection current, so that, if exceeded, the control of the power converter orders the stop , thus avoiding damage to the switching devices.
    [0012] This threshold is calculated taking into account that, when the switching device is stopped, a voltage peak occurs due to the associated dispersion inductances. This voltage peak is determined by the energy stored in these dispersion inductances and by the electrical capacity of the switching device itself and its parasitic elements. The failure detection threshold is determined based on the maximum voltage that the terminals of the switching device can withstand when the protection current flows through it.
    [0013] The hardware protection system uses a reference current less than or equal to the maximum current to ensure protection. The reference current in the current state of the art is fixed, that is, it has a constant value and its value is established as a function of the DC bus voltage.
    [0014] The main drawback of this mode of operation is that the maximum power is fixed and is determined by the value of the reference current defined above to carry out the comparison. Therefore, if it is desired to increase the range of use in voltage of a power converter, that is, if a gradual approach to its electrical limit (maximum voltage) is desired, it is not possible to set the protections at the same level as the one mentioned above. , since, in the event of a short circuit, the protection would stop the power stage. In addition, the peak voltage produced during the stop would destroy the switching devices. For this reason, the protection setting value is defined by the maximum voltage (VDC = DC bus voltage) of the power stage. As mentioned, this value can vary with time, but to calculate the protection it is considered fixed and maximum.
    [0015] Static protection circuits of the state of the art are, for example, the circuit disclosed in the European patent application with publication number EP2800260A1 disclosing a semiconductor protection circuit connected in parallel to a converter.
    [0016] It would therefore be desirable to find an overcurrent protection system that, in addition to protecting the power converter, would allow to increase the power of the converter (its performance) up to its maximum operative limit, that is, up to the maximum value of the VDC of the power converter .
    [0017]
    [0018] DESCRIPTION OF THE INVENTION
    [0019]
    [0020] In a first aspect of the invention, a dynamic overcurrent protection system for power converters is disclosed. The dynamic overcurrent protection system for power converters is connectable to the output of the power stage included in the power converter. The overcurrent protection system for power converters of the present invention comprises:
    [0021] • a comparator connectable to the output of the power stage, which measures an output current (IOUT) of the power stage;
    [0022] • a control device connected to the comparator and connectable to the power stage, where the control device measures a voltage (VDC) of the power stage;
    [0023] • a pattern generator connected to the control device and to the comparator; wherein the pattern generator comprises pairs of voltage-current values (VDC-IREF) that relate voltage values (VDC) of the power stage with current values between zero and a preset current limit (IRMS);
    [0024] in such a way that the pattern generator receives the measured voltage value (VDC) from the control device and sends the corresponding current value (IREF) of the voltage-current value pairs to the comparator, which stops the power stage if the output current (IOUT) of the power stage is greater than or equal to the value of the current (IREF) associated with the measured voltage (VDC).
    [0025] The power stage comprises a DC bus and a power converter circuit. The power converter circuit comprises at least one switching device (for example: IGBT transistors).
    [0026] The switching device has an equivalent circuit which is formed by at least one capacitor, one coil and one switch.
    [0027] The pairs of voltage-current values (VDC-IREF) are calculated by applying Eq. 2 on the equivalent circuit.
    [0028] The pattern generator comprises the pairs of voltage-current values (VDC-IREF) where the pairs of voltage-current values (VDC-IREF) are calculated by:
    [0029]
    [0030]
    [0031]
    [0032] where:
    [0033] VDC: is the voltage in continuous of the power stage, which may vary with time; Vmax: maximum voltage that the terminals of the switching device can withstand the opening of the same when the protection current flows through it.
    [0034] L: dispersion inductance of the switching device;
    [0035] C: capacity of the parasitic elements of the switching device.
    [0036] In one embodiment, the control device comprises at least one voltage meter for measuring the DC voltage of the power stage.
    [0037] In another embodiment, the control device additionally comprises a processor and a memory for storing and processing control slogans that modify the voltage value (VDC) of the power stage. The control device receives from the comparator the value of the output current (IOUT) of the power stage, the voltage of the power stage (VDC) and the value of the reference current (IREF) that it stores in the memory. The control device, based on the three previous values (VDC, IOUT, IREF) can calculate new values of the direct voltage (VDC) that it sends (by means of setpoints) to the power stage in such a way that the power stage it increases its power (by increasing the VDC voltage) towards the maximum available power of the power stage depending on the source to which the power stage is connected. The gradual increase of the voltage value (VDC) implies an increase in the output current of the power stage (IOUT) that the protection device allows until the value of the output current is less than or equal to the current value Reference (IREF) dynamically calculated by the pattern generator.
    [0038] In one embodiment, the preset current limit (IRMS) is corresponds to the current limit of the switching devices included in the power stage. Normally, the transistors included in the power stage are the elements that limit the current of the same. Therefore, it will be the transistors (switching devices) that determine the maximum current value (IRMS).
    [0039] In a second aspect of the invention, a power converter comprising the dynamic protection system according to the first aspect of the invention and for any of its embodiments is disclosed.
    [0040] In a third aspect of the invention, a dynamic overcurrent protection method for power converters is disclosed. The dynamic overcurrent protection method for power converters comprises the following steps:
    [0041] • generate pairs of voltage-current values (VDC-IREF) that relate voltage values (VDC) of the power stage with values of current between zero and a current limit (IRMS) of switching devices included in the stage of power;
    [0042] • measure the DC voltage (VDC) and the output current (IOUT) of the power stage;
    [0043] • compare the value of the output current (IOUT) with the current value (IREF) corresponding to the measured voltage (VDC) in the pairs of voltage-current values (V dc -I ref );
    [0044] • Stop the power converter if the value of the output current (IOUT) is greater than or equal to the current value (IREF) corresponding to the measured voltage (VDC) in the voltage-current value pairs (VDC-IREF).
    [0045] In one embodiment, the dynamic overcurrent protection method for power converters additionally comprises increasing the DC voltage of the power stage until the condition that the value of the output current (IOUT) is satisfied. it is lower at a pre-established value than the current value (IREF) corresponding to the measured voltage (VDC) at the voltage-current value pairs (VDC-IREF). The pre-established value can be chosen as small as a user wishes in such a way that the output current (IOUT) approaches that of the reference current (IREF) without reaching the same value.
    [0046] BRIEF DESCRIPTION OF THE FIGURES
    [0047] Figure 1 shows a circuit of the power stage of a power converter whose output is connected to a surge protection system.
    [0048] Figure 2.- Shows the voltage peak produced in the terminals of a switching device (IGBT transistor) when the switching device is stopped.
    [0049] Figure 3.- Shows the equivalent circuit of a switching device.
    [0050] Figure 4 shows a protection system against overvoltages of the state of the art.
    [0051] Figure 5.- Shows a surge protection system according to the present invention.
    [0052] Figure 6 shows the reference current (protection level) calculated according to the present invention with respect to the voltage (VDC) of the power stage.
    [0053]
    [0054] PREFERRED EMBODIMENT OF THE INVENTION
    [0055] The following is an illustrative and non-limiting example of an embodiment of the invention.
    [0056] Fig. 1 shows a power stage 5 of the state of the art comprised in a power converter. The power stage 5 comprises the DC bus 51 and the power converter circuit 52 . The power converter circuit 52 is formed primarily by switching devices 52A . A power source (not shown) is connected to the input of the power stage. At the output of the power stage, a protection device 1 is connected.
    [0057] Fig. 2 shows the voltage peak VMAX produced at the terminals of a switching device (for example switching device 52A ) when the switching device is stopped. The voltage peak is necessarily taken into account to set a current threshold with which the protection system protects the power converter in situations of overvoltage or overcurrent.
    [0058] Fig. 3 shows the equivalent circuit of a switching device 52A . The switching device limits the performance of the power stage. The equivalent circuit shown in Fig. 3 comprises two capacitors 13 , two switches 11 and an inductor 12 . In order to calculate the protection current threshold it is it is necessary to know the voltage peak of the switching device at the time of its arrest. The voltage peak Vmax (Fig. 2) is determined by the energy stored in the dispersion inductances (L) and by the electrical capacity of the switching device itself and its parasitic elements (C), so that the following is verified energy balance:
    [0059]
    [0060]
    [0061]
    [0062] Where V is the DC voltage of the power stage, which can vary with time. The fault detection threshold (Imax) is determined based on the maximum voltage (Vmax) that the terminals of the switching device can support when the switching device opens through the protection current.
    [0063]
    [0064]
    [0065]
    [0066] The hardware protection system uses a reference current (Iref) less than or equal to the maximum current (I max ) to ensure protection. The reference current (Iref) in the current state of the art is fixed, that is, it has a constant value. In Figure 6, the constant I ref according to the state of the art would be the value 200 amps.
    [0067] Taking into account the above, Fig. 4 shows an overcurrent protection system of the state of the art. The protection system consists of a comparator 4 with two inputs and one output. The output is connected to a control device 2 , one input is connected to the output of the power stage 5 to measure the output current of the power stage and the other input receives the reference current value for adequate protection of the power stage. With this configuration, the comparator compares the value of the current to the output of the power stage 5 and the reference current value Ire f. The comparator sends the result of the comparison to the control device 2 . The control device 2 stops the power stage, and consequently the power converter when the value of the current at the output of the power stage Iout is greater than or equal to the reference current value Ire f.
    [0068] Fig. 5 shows the protection system 1 of the present invention which is composed of a control device 2 , a pattern generator 3 and a comparator 4 . The control device comprises a processor 21 , a memory 22 and a voltage meter 23 connected to the DC BUS 51 of the power stage 5 . The comparator 4 has two inputs and one output. The output is connected to the control device 2 , one input is connected to the output of the power stage 5 for measuring the output current IOUT of the power stage and the other input receives the reference current value IREF for the protection adequate of the power stage. With this configuration, the comparator 4 compares the value of the current IOUT to the output of the power stage 5 and the reference current value IREF. The comparator sends the result of the comparison to the control device and also the values of the output current IOUT and reference current IREF. The control device 2 stops the power stage 5 if the value of the current IOUT at the output of the power stage 5 is greater than or equal to the reference current value IREF. Unlike the state of the art, the IREF value calculated by the pattern generator 3 is a function of the DC voltage (voltage in the DC BUS, Fig. 1) measured in the power stage 5 and the rated current IRMs of the switching device. The current limitation of the power stage 5 is determined by the maximum current that the switching devices (IRMS) are capable of supporting. The pattern generator 3 has pairs of associated VI values (VDC, I) which relate for all possible current values between zero and the current limit (IRMS) of the switching devices, with the possible VDC voltage of the stage of power (see Fig. 6). The pairs of VI values are calculated by applying the equation Ec.2 described above. Once the value pairs VI have been calculated, the pattern generator 3 is able to calculate the value of the IREF current for the voltage value VDC measured in the power stage, thus avoiding the risk of overcurrents. This is so because the value of the current at the output of the pattern generator (IREF) is always less than or equal to the current limit (IRMS) of the switching device. As shown in Figure 6, by means of the present invention, it is possible to increase the current (IOUT) to the output of the power stage 5, which would increase the power of the power stage, maintaining the protection of the stage of power. Taking the values of figure 6 as a reference, according to the state of the art, the power stage could never supply output current values (IOUT) greater than 200 amps because the protection device according to the state of the art would not allow it . In contrast with the protection device of the present invention, it would be possible, for example, to increase the output current (IOUT) up to 950 amps for voltage values (VDC) between 1000 Volts and 1250 Volts.
    [0069] The control device 2 has several functionalities. One functionality is to protect the power converter as it is conventional. Another function is to measure the voltage in the DC BUS to provide the voltage value to the pattern generator.
    [0070] The control device 2 can optionally also comprise a user interface (not shown) with which a user can enter the maximum current value (IRMs) of the switching devices and the values of the VI value pairs, where all subsequently the values (IRMS, VI) are sent to the pattern generator. Optionally, the pattern generator may comprise
    [0071] a user interface with which a user can enter the maximum current value (IRMS) of the switching devices and the values of the pairs of values V-I.
    [0072] Additionally and independently, the control device 2 , by control command sent to the power stage, is capable of gradually increasing the voltage of the power stage and, therefore, the power of the power stage (power of the power unit). power converter), also adjusting the value of the protection current, IREF. It is recalled that the power Sout at the output of the power stage is defined as:
    [0073]
    [0074]
    [0075]
    [0076]
    [0077] An example of how the control device 2 increases the VDC potential and decreases the protection current IREF is shown in Fig. 6. The control device 2 is capable of increasing the power by increasing the values of VDC maintaining the current value IREF up to 1250 VDC and decreasing the value of
    [0078] IREF up to 1500 VDC, voltage limit for power stage 5 and for which the reference current IREF is equal to the IRMS current. That is, in the state of the art the protection current IREF (200) is calculated as if the power stage always had a voltage of 1500V, at which point the current coincides
    [0079] IREF reference with the IRMS current. In contrast, by the present invention, the reference current IREF is calculated from the maximum current that can be supported by the switching devices (hence, also the power stage 5)
    [0080] for each voltage value in which the power stage 5 operates. The ratio (VDC,
    [0081] IREF) shown in Figure 6 can be not only discrete points, but also
    [0082]
    [0083]
    [0084] a continuous graph, table pairs of values and any other type of relationship that meets Iref (t) = f (VDo (t)).
    权利要求:
    Claims (10)
    [1]
    1. - Dynamic protection system (1) against overcurrent for power converters, where the protection system is connectable to the output of a power stage (5) included in the power converter; The protection system is characterized because it includes:
    • a comparator (4) connectable to the output of the power stage (5), which measures an output current (IOUT) of the power stage;
    • a control device (2) connected to the comparator (4) and connectable to the power stage (5), wherein the control device (2) measures a voltage (VDC) of the power stage;
    • a pattern generator (3) connected to the control device (2) and to the comparator (4); wherein the pattern generator (3) comprises pairs of voltage-current values (VDC-IREF) that relate voltage values (VDC) of the power stage with current values between zero and a preset current limit (IRMS);
    in such a way that the pattern generator (3) receives the measured voltage value (VDC) from the control device (2) and sends the corresponding current value (IREF) of the voltage-current value pairs to the comparator (4) , which stops the power stage if the output current (IOUT) of the power stage is greater than or equal to the current value (IREF) associated with the measured voltage (VDC).
    [2]
    2. - Protection system according to claim 1, characterized in that the power stage comprises a DC bus (51) and a power converter circuit (52); and wherein the power converter circuit (52) comprises at least one switching device (52A).
    [3]
    3. - Protection system according to claim 2, wherein the switching device (52A) has an equivalent circuit that is formed by at least one capacitor (13), a coil (12) and a switch (11).
    [4]
    4. Protection system according to claim 2 or 3, characterized in that the pairs of voltage-current values (VDC-IREF) are calculated by:

    [5]
    5. - Protection system according to claim 1, characterized in that control device (2) comprises at least one voltage meter (23) for measuring the DC voltage (VDC) of the power stage (5).
    [6]
    6. - Protection system according to claim 1 or 5, characterized in that control device (2) additionally comprises a processor (21) and a memory (22) for storing and processing control slogans that modify the voltage value (VDC) ) of the power stage (5).
    [7]
    7. - Protection system according to claim 2, characterized in that the preset current limit (IRMs) corresponds to the current limit of switching devices (52A) included in the power stage (5).
    [8]
    8. - Power converter characterized in that it comprises the dynamic protection system according to any one of claims 1 to 7.
    [9]
    9. - Dynamic overcurrent protection method for power converters characterized in that it comprises:
    one
    • generate pairs of voltage-current values (VDC-IREF) that relate voltage values (VDC) of the power stage with values of current between zero and a current limit (IRMS) of switching devices included in the stage of power;
    • measure the DC voltage (VDC) and the output current (IOUT) of the power stage;
    • compare the value of the output current (IOUT) with the current value (IREF) corresponding to the measured voltage (VDC) in the pairs of volt-current values (Vdc-Iref);
    • stop the power converter if the value of the output current (IOUT) is greater than or equal to the current value (IREF) corresponding to the measured voltage (VDC) in the voltage-current value pairs (VDC-IREF).
    [10]
    10.- Dynamic overcurrent protection method for power converters according to claim 9, wherein the method additionally comprises increasing the DC voltage of the power stage until the condition that the current value of the current is satisfied. output (IOUT) is lower by a pre-established value than the current value (IREF) corresponding to the measured voltage (VDC) in the voltage-current value pairs (VDC-IREF).
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    同族专利:
    公开号 | 公开日
    EP3731391A4|2021-02-24|
    US20200328670A1|2020-10-15|
    ES2717341B2|2020-07-06|
    WO2019122469A1|2019-06-27|
    EP3731391A1|2020-10-28|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US20120075891A1|2008-10-21|2012-03-29|On-Bright Electronics Co., Ltd.|Systems and methods for constant voltage mode and constant current mode in flyback power converters with primary-side sensing and regulation|
    US20120020118A1|2010-07-21|2012-01-26|Sony Corporation|Switching power supply apparatus|
    US20120195076A1|2011-02-01|2012-08-02|On-Bright Electronics Co., Ltd.|Systems and methods for dynamic threshold adjustment with primary-side sensing and regulation for flyback power converters|
    WO2014070835A2|2012-10-30|2014-05-08|General Electric Company|System and method for over-current protection|
    US4415960A|1982-03-29|1983-11-15|Sperry Corporation|Line variable overcurrent protection for a voltage conversion circuit|
    DE102009055055A1|2009-12-21|2011-06-22|Robert Bosch GmbH, 70469|Method for fault detection in an electrical machine controlled by an inverter in a motor vehicle and device for monitoring an operation of the electric machine|
    KR101255959B1|2011-12-28|2013-04-23|주식회사 효성|Protection circuit for protecting voltage source converter|
    US9461559B2|2013-03-15|2016-10-04|Rockwell Automation Technologies, Inc.|Active front end power converter with boost mode derating to protect filter inductor|
    法律状态:
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    优先权:
    申请号 | 申请日 | 专利标题
    ES201731435A|ES2717341B2|2017-12-20|2017-12-20|DYNAMIC SYSTEM AND METHOD OF PROTECTION AGAINST OVERCURRENT FOR POWER CONVERTERS|ES201731435A| ES2717341B2|2017-12-20|2017-12-20|DYNAMIC SYSTEM AND METHOD OF PROTECTION AGAINST OVERCURRENT FOR POWER CONVERTERS|
    US16/956,119| US11283346B2|2017-12-20|2018-12-04|System and method for dynamic over-current protection for power converters|
    PCT/ES2018/070778| WO2019122469A1|2017-12-20|2018-12-04|System and method for dynamic over-current protection for power converters|
    EP18891528.4A| EP3731391A4|2017-12-20|2018-12-04|System and method for dynamic over-current protection for power converters|
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