Device and method for improving the sinusoidal degree of the current of a traction power supply network

Abstract

The application provides a device and method for improving the sinusoidal degree of traction power supply network current, which comprises a traction transformer, a current sensor, at least one pulse rectifier, at least one pulse rectifier controller, a current compensation unit and a current compensation controller; the traction transformer comprises a primary winding, at least one first secondary winding and one second secondary winding; two ends of each first secondary winding are connected to one pulse rectifier; each pulse rectifier is connected with one pulse rectifier controller; the current compensation unit is connected to two ends of the second secondary winding; the current compensation controller is connected with the current compensation unit, the current sensor and each pulse rectifier controller, respectively. The device provided by the application effectively improves the sinusoidal degree of traction power supply network current, reduces the current distortion rate, improves the traction power supply network current performance and the stability of the traction power supply network.

Description

Technical Field

[0001] The present invention belongs to the field of power electronics, and in particular relates to a device and method for improving the sinusoidality of current in a traction power supply network in a rail transit electric traction AC drive system. Background Art

[0002] The electric traction AC drive system primarily consists of the traction power grid, pantograph, traction transformer, traction converter, and traction motor. The traction converter comprises a rectifier and inverter. Current train rectifiers are typically pulse rectifiers. Their performance characteristics include bidirectional energy flow, unity power factor operation, a near-sinusoidal current waveform, and stable DC-side voltage that meets inverter requirements. The pulse rectifier topology includes an inductor and fully controlled switching devices. The switching of the switching devices causes the inductor current path to switch, which in turn causes the inductor to switch between energy storage and energy release states. In the energy storage state, the inductor current rises, while in the energy release state, the inductor current falls. Both rising and falling inductor current waveforms are straight line segments. The pulse rectifier current waveform consists of multiple rising and falling straight line segments, approaching a sine wave. Even with multiple rectification, the current waveform of the traction transformer's primary winding still consists of multiple straight line segments.

[0003] Although the pulse rectifier current waveform is close to a sine wave, it still has the following shortcomings:

[0004] The current waveform of the traction power supply network is essentially composed of multiple straight lines, and the current distortion of the traction power supply network is still obvious. Summary of the Invention

[0005] The present invention addresses the drawback that the current waveform of the existing traction power supply network is composed of multiple straight line segments. It provides a device for improving the sinusoidality of the traction power supply network current. Based on the pulse rectifier, the waveform of the traction power supply network current is made closer to a sine wave. The device for improving the sinusoidality of the traction power supply network current includes:

[0006] a traction transformer, a current sensor, at least one pulse rectifier, at least one pulse rectifier controller, a current compensation unit, and a current compensation controller;

[0007] The traction transformer comprises:

[0008] a primary winding, one end of which is connected to the traction power supply network, and the other end of which is connected to the grounding device via the current sensor;

[0009] at least one first secondary winding; and

[0010] a second secondary winding;

[0011] Both ends of each first secondary winding are connected to one of the pulse rectifiers;

[0012] Each of the pulse rectifiers is connected to a pulse rectifier controller;

[0013] The current compensation unit is connected to both ends of the second secondary winding;

[0014] The current compensation controller is connected to the current compensation unit, the current sensor and each of the pulse rectifier controllers respectively.

[0015] In one embodiment, one end of at least one of the first secondary windings is connected to the corresponding pulse rectifier via an inductor.

[0016] In one embodiment, the current compensation unit includes:

[0017] a first diode, a second diode, a third diode, a fourth diode, a fixed resistor, and an impedance adjustable component;

[0018] Wherein, the first diode, the fixed resistor, the impedance adjustable component and the second diode are connected in sequence; the third diode, the fixed resistor, the impedance adjustable component and the fourth diode are connected in sequence;

[0019] The anode of the first diode and the cathode of the second diode are connected to one end of the second secondary winding through a first terminal; the anode of the third diode and the cathode of the fourth diode are connected to the other end of the second secondary winding through a second terminal;

[0020] The impedance adjustable component is used to adjust the impedance value of the current compensation unit to adjust the current of the second secondary winding.

[0021] In one embodiment, the impedance adjustable component is connected to a current compensation controller and is configured to adjust the impedance value of the current compensation unit according to control of the current compensation controller.

[0022] In one embodiment, the impedance adjustable component is a semiconductor device.

[0023] The present invention also provides a method for improving the sinusoidality of current in a traction power supply network using the above-mentioned device, the method comprising:

[0024] The current compensation controller obtains the expected current and actual current of the corresponding pulse rectifier from each pulse rectifier controller;

[0025] The current compensation controller obtains the target current of the primary winding of the traction transformer according to the expected current of each pulse rectifier;

[0026] The current compensation controller obtains the current actual current of the primary winding from the current sensor;

[0027] When the current actual current of the primary winding is not equal to the target current of the primary winding, the current compensation controller adjusts the compensation current generated by the current compensation unit until the current actual current of the primary winding is equal to or closest to the target current of the primary winding.

[0028] In one embodiment, obtaining the target current of the primary winding of the traction transformer according to the expected current of each pulse rectifier includes:

[0029] Substitute the expected current of each pulse rectifier into the preset primary current calculation formula

[0030] Target current of the primary winding = k × the sum of the expected currents of each pulse rectifier / n

[0031] Among them, n is the primary-to-secondary transformation ratio of the traction transformer; when in traction working condition, k is a constant that makes the target current of the primary winding not less than the current on the primary winding corresponding to the sum of the actual currents of each pulse rectifier; when in regenerative braking working condition, k is a constant that makes the target current of the primary winding not more than the current on the primary winding corresponding to the sum of the actual currents of each pulse rectifier.

[0032] In one embodiment, when in traction mode, the compensation current generated by the regulating current compensation unit includes:

[0033] adjusting the compensation current generated by the current compensation unit according to a preset first current compensation formula;

[0034] The first current compensation formula is:

[0035] The actual current of the primary winding = (the sum of the actual currents of each pulse rectifier + compensation current) / n

[0036] Wherein, n is the primary-to-secondary transformation ratio of the traction transformer;

[0037] When the current actual current of the primary winding is less than the target current of the primary winding, increasing the compensation current;

[0038] When the current actual current of the primary winding is greater than the target current of the primary winding, the compensation current is reduced.

[0039] In one embodiment, when in a regenerative braking state, the compensation current generated by the regulating current compensation unit includes:

[0040] adjusting the compensation current generated by the current compensation unit according to a preset second current compensation formula;

[0041] The second current compensation formula is:

[0042] The actual current of the primary winding = (the sum of the actual currents of each pulse rectifier - compensation current) / n

[0043] Wherein, n is the primary-to-secondary transformation ratio of the traction transformer;

[0044] When the current actual current of the primary winding is less than the target current of the primary winding, reducing the compensation current;

[0045] When the current actual current of the primary winding is greater than the target current of the primary winding, the compensation current is increased.

[0046] The present invention also provides a second device for improving the sinusoidality of current in a traction power supply network, the device comprising: a traction transformer and at least one current compensation device;

[0047] One end of the primary winding of the traction transformer is connected to the traction power supply network, and the other end of the primary winding is connected to the grounding device; the current compensation device includes: a current sensor, an inductor, a pulse rectifier, a pulse rectifier controller, a current compensation unit, and a current compensation controller; the inductor and the pulse rectifier are connected in series to form a parallel circuit with the current compensation unit, one end of the parallel circuit is connected to one end of the secondary winding of the traction transformer through the current sensor, and the other end of the parallel circuit is connected to the other end of the secondary winding;

[0048] A first terminal of the current compensation controller is connected to the current compensation unit, a second terminal is connected to the current sensor, and a third terminal is connected to the pulse rectifier controller.

[0049] In one embodiment, the current compensation unit includes:

[0050] a first diode, a second diode, a third diode, a fourth diode, a fixed resistor, and an impedance adjustable component;

[0051] Wherein, the first diode, the fixed resistor, the impedance adjustable component and the second diode are connected in sequence; the third diode, the fixed resistor, the impedance adjustable component and the fourth diode are connected in sequence;

[0052] The anode of the first diode and the cathode of the second diode are connected to one end of the secondary winding of the traction transformer through a first terminal; the anode of the third diode and the cathode of the fourth diode are connected between the current sensor and the parallel circuit through a second terminal;

[0053] The impedance adjustable component is used to adjust the impedance value of the current compensation unit to adjust the current of the secondary winding.

[0054] In one embodiment, the impedance adjustable component is connected to a current compensation controller and is configured to adjust the impedance value of the current compensation unit according to control of the current compensation controller.

[0055] In one embodiment, the impedance of the adjustable impedance component is continuously adjustable.

[0056] In one embodiment, the impedance adjustable component is a semiconductor device.

[0057] The present invention also provides a method for improving the sinusoidality of current in a traction power supply network using the second device described above, the method comprising:

[0058] The current compensation controller obtains the expected current and actual current of the corresponding pulse rectifier from the pulse rectifier controller;

[0059] The current compensation controller obtains the target current of the secondary winding according to the expected current of the pulse rectifier;

[0060] The current compensation controller obtains the actual current of the secondary winding from the current sensor;

[0061] When the actual current of the secondary winding is not equal to the target current of the secondary winding, the current compensation controller adjusts the compensation current generated by the current compensation unit until the actual current of the secondary winding is equal to or closest to the target current of the secondary winding.

[0062] In one embodiment, obtaining the target current of the secondary winding according to the expected current of the pulse rectifier includes:

[0063] Substitute the expected current of the pulse rectifier into the preset secondary current calculation formula

[0064] Target current of secondary winding = k × expected current of pulse rectifier

[0065] Among them, when in traction working condition, k is a constant that makes the target current of the secondary winding not less than the actual current of the pulse rectifier; when in regenerative braking working condition, k is a constant that makes the target current of the secondary winding not greater than the actual current of the pulse rectifier.

[0066] In one embodiment, when in traction mode, the compensation current generated by the regulating current compensation unit includes:

[0067] adjusting the compensation current generated by the current compensation unit according to a preset third current compensation formula;

[0068] The third current compensation formula is:

[0069] Actual current of secondary winding = (actual current of pulse rectifier + compensation current)

[0070] When the actual current of the secondary winding is less than the target current of the secondary winding, increasing the compensation current;

[0071] When the actual current of the secondary winding is greater than the target current of the secondary winding, the compensation current is reduced.

[0072] In one embodiment, when in a regenerative braking state, the compensation current generated by the regulating current compensation unit includes:

[0073] adjusting the compensation current generated by the current compensation unit according to a preset fourth current compensation formula;

[0074] The fourth current compensation formula is:

[0075] Actual current of secondary winding = (actual current of pulse rectifier - compensation current)

[0076] When the actual current of the secondary winding is less than the target current of the secondary winding, reducing the compensation current;

[0077] When the actual current of the secondary winding is greater than the target current of the secondary winding, the compensation current is increased.

[0078] Compared with the existing technology, the device and method for improving the sinusoidality of the current in the traction power supply network provided in this application effectively improve the sinusoidality of the current in the traction power supply network, reduce the current distortion rate, and improve the current performance and stability of the traction power supply network; at the same time, it is beneficial to improve the economy of electricity billing in the traction power supply network. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0080] Figure 1 Schematic diagram of the electric traction AC drive system.

[0081] Figure 2 This is a first circuit structure diagram of a first device for improving the sinusoidality of current in a traction power supply network.

[0082] Figure 3 This is the circuit structure diagram of the current compensation unit.

[0083] Figure 4 This is the second circuit structure diagram of the first device for improving the sinusoidality of the current in the traction power supply network.

[0084] Figure 5 Schematic diagram of a method for improving the sinusoidality of current in the traction power supply network using the first device.

[0085] Figure 6 Schematic diagram of the current waveform of the pulse rectifier 4QC1.

[0086] Figure 7 Schematic diagram of the current waveform of the pulse rectifier 4QC2.

[0087] Figure 8 This is a schematic diagram of the current in the primary winding under the traction condition of the first device.

[0088] Figure 9 This is a schematic diagram of the current in the primary winding under the regenerative braking condition of the first device.

[0089] Figure 10 This is a circuit diagram of the second device for improving the sinusoidality of the current in the traction power supply network.

[0090] Figure 11 Schematic diagram of a method for improving the sinusoidality of the current in the traction power supply network using the second device.

[0091] Figure 12 This is a schematic diagram of the current in the secondary winding of the second device under traction conditions.

[0092] Figure 13 This is a schematic diagram of the current in the secondary winding of the second device under regenerative braking conditions.

[0093] Figure Number:

[0094] L: Traction power supply network PT: Pantograph

[0095] TR: Traction transformer P: Primary winding

[0096] S1, S2, SX: secondary winding CS: current sensor

[0097] G: Grounding device Z: Track

[0098] 4QC1, 4QC2: Pulse rectifiers QT1, QT2: Pulse rectifier controllers

[0099] CP, CP1: Current compensation unit CTR, CTR1: Current compensation controller

[0100] T1, T2: terminals I1, I2: inductors

[0101] D1, D2, D3, D4: diodes R: fixed resistor

[0102] SD: Impedance adjustable component isr1, isr2: Actual current of pulse rectifier

[0103] ist1, ist2: expected current of pulse rectifier

[0104] ipr: The sum of the actual currents of each pulse rectifier corresponds to the current on the primary winding

[0105] ipe: target current of the primary winding ipcpr: compensation current corresponding to the current on the primary winding

[0106] ise1: target current of secondary winding icpr1: compensation current

[0107] S501-S204, S110-S113: Steps DETAILED DESCRIPTION

[0108] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0109] Figure 1 Figure 1 is a schematic diagram of an electric traction AC transmission system. Figure 1 As shown, the electric traction AC drive system primarily consists of a traction power grid, pantograph, traction transformer, traction converter, and traction motor. The traction converter typically includes a rectifier and inverter. All components except the traction power grid are located on the train. The traction power grid provides single-phase sinusoidal AC power. The train draws high-voltage AC from the traction power grid via the pantograph, which is then stepped down to a lower voltage by the traction transformer and supplied to the traction converter. The traction converter performs AC-DC-AC conversion to drive the traction motor, which then drives the wheels through a gearbox, enabling the train to move. The AC-DC conversion process is called rectification, and the device that performs this rectification is called a rectifier. The rectifier is connected to the secondary winding of the traction transformer. The DC-AC conversion process is called inversion, and the device that performs this inversion is called an inverter. The inverter is connected to the traction motor. During traction operation, the traction power grid serves as the power source, and the train serves as the load. During regenerative braking, the traction power grid serves as the load, and the train serves as the power source.

[0110] Whether operating under traction or regenerative braking conditions, the current performance of the traction power grid is a critical indicator. Current performance impacts the performance of the traction system, and severe degradation can even affect the safe operation of the traction power grid. Power factor and current distortion ratio are the most fundamental indicators of traction power grid current performance. Typically, the traction power grid is required to operate at unity power factor and have a current distortion ratio less than a set value. In practice, the lower the current distortion ratio, the better. The higher the sinusoidality of the traction power grid current and the lower the current distortion ratio, the better the current performance. The traction power grid current is the sum of the primary winding currents of the traction transformers of all trains in the traction power grid. The rectifier current is coupled to the primary winding of the traction transformer through the secondary winding of the traction transformer. Therefore, the rectifier current performance directly affects the current performance of the traction power grid. Furthermore, the current performance of the traction power grid also factors in electricity billing. Generally, better current performance results in more economical electricity billing.

[0111] In order to make the waveform of the traction power supply network current closer to a sine wave on the basis of a pulse rectifier, the present invention provides two devices for improving the sinusoidality of the traction power supply network current. Figure 2 This is a schematic diagram of the first circuit structure of the first device for improving the sinusoidality of the current in the traction power supply network of the present invention. Figure 2 As shown, the first device for improving the sinusoidality of the current in the traction power supply network includes:

[0112] Traction transformer TR, current sensor CS, pulse rectifiers 4QC1 and 4QC2, pulse rectifier controllers QT1 and QT2, current compensation unit CP, and current compensation controller CTR; wherein, there is at least one pulse rectifier, and this application uses two pulse rectifiers as an example for illustration. In actual applications, more or fewer pulse rectifiers may be included, and this application is not limited to this; there is also at least one pulse rectifier controller. Generally speaking, the number of pulse rectifier controllers is the same as the number of pulse rectifiers, so this application also uses two pulse rectifier controllers as an example for illustration. In actual applications, the number of pulse rectifier controllers can be adjusted according to the actual number of pulse rectifiers included, and this application is not limited to this.

[0113] The traction transformer TR includes a primary winding P, first secondary windings S1 and S2, and a second secondary winding SX. One end of the primary winding P is connected to the traction power supply network L through a pantograph PT, and the other end of the primary winding P is connected to the grounding device G through a current sensor CS, and the grounding device G is connected to the track Z. Among them, the number of first secondary windings is at least one, and this embodiment is described as including two first secondary windings. In practical applications, more or less than two first secondary windings may be included, and this application is not limited to this. Usually, the number of first secondary windings, pulse rectifiers, and pulse rectifier controllers are the same, and the number of pulse rectifiers and pulse rectifier controllers can be flexibly adjusted according to the number of first secondary windings.

[0114] The connection relationship between the various components in the first device for improving the sinusoidality of the current in the traction power supply network is as follows: the two ends of each first secondary winding are connected to a pulse rectifier; each pulse rectifier is connected to a pulse rectifier controller; the current compensation unit is connected to the two ends of the second secondary winding; the current compensation controller is respectively connected to the current compensation unit, the current sensor and each pulse rectifier controller.

[0115] Specifically, if Figure 2 As shown, the first secondary winding S1 is connected to the pulse rectifier 4QC1, and the first secondary winding S2 is connected to the pulse rectifier 4QC2; the pulse rectifier 4QC1 is also connected to the pulse rectifier controller QT1, and the pulse rectifier 4QC2 is also connected to the pulse rectifier control QT2; one end of the second secondary winding SX is connected to the first terminal T1 of the current compensation unit CP, and the other end of the second secondary winding SX is connected to the second terminal T2 of the current compensation unit CP; the current compensation controller CTR is respectively connected to the current compensation unit CP, the current sensor CS, the pulse rectifier control QT1, and the pulse rectifier controller QT2.

[0116] The current compensation unit in the first device for improving the sinusoidality of the current in the traction power supply network is used to adjust the current on the second secondary resistor SX. This application provides a possible structure of the circuit compensation unit. Figure 3 As shown, the current compensation unit includes:

[0117] A first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fixed resistor R, and an impedance adjustable component SD;

[0118] Among them, the first diode D1, the fixed resistor R, the impedance adjustable component SD and the second diode D2 are connected in sequence; the third diode D3, the fixed resistor R, the impedance adjustable component SD and the fourth diode D4 are connected in sequence;

[0119] The anode of the first diode D1 and the cathode of the second diode D2 are connected to one end of the second secondary winding SX via the first terminal T1. The anode of the third diode D3 and the cathode of the fourth diode D4 are connected to the other end of the second secondary winding SX via the second terminal T2. The adjustable impedance component SD is also connected to the current compensation controller CTR.

[0120] The working principle of the current compensation unit is as follows: the first terminal T1 and the second terminal T2 are the main circuit interfaces of the current compensation unit CP. When a voltage is applied between the first terminal T1 and the second terminal T2, the current compensation controller CTR can reduce the current passing through the current compensation unit CP by controlling the impedance of the adjustable impedance component SD to increase, and the current compensation controller CTR can increase the current passing through the current compensation unit CP by controlling the impedance of the adjustable impedance component SD to decrease. The current passing through the current compensation unit CP is the current passing through the second secondary winding SX.

[0121] Since the current passing through the current compensation unit CP is determined by the impedance of the adjustable impedance component SD, when the impedance of the adjustable impedance component SD can be continuously changed, more precise adjustment of the current passing through the current compensation unit CP can be achieved. The adjustable impedance component SD used in this application is a semiconductor device with continuously variable impedance characteristics.

[0122] Figure 2 The inductance of the pulse rectifier is implemented by the leakage inductance of the traction transformer TR. In one embodiment, the inductance of the pulse rectifier can also be implemented by a separate inductor device, and the inductor current is the current of the pulse rectifier. Therefore, this application also provides a second circuit structure diagram of the first device for improving the sinusoidality of the traction power supply network current.

[0123] like Figure 4 As shown, in the second circuit structure of the first device, one end of the first secondary winding S1 is connected to the pulse rectifier 4QC1 via an inductor I1, and one end of the first secondary winding S2 is connected to the pulse rectifier 4QC2 via an inductor I2. Typically, the number of inductors equals the number of pulse rectifiers. Since this embodiment uses two pulse rectifiers as an example, this embodiment also includes two inductors. In actual applications, the number of inductors can be flexibly adjusted based on the number of pulse rectifiers.

[0124] In addition to the above-mentioned inductor devices, the structures of all components including the components of the current compensation unit in the second circuit structure of the above-mentioned first device for improving the sinusoidality of the current in the traction power supply network and the connection relationship between the components are the same as the first circuit structure of the first device, and will not be repeated here.

[0125] Based on the first circuit structure diagram of the apparatus for improving the sinusoidality of traction power supply network current and the second circuit structure diagram of the apparatus for improving the sinusoidality of traction power supply network current, the present application accordingly provides a method for improving the sinusoidality of traction power supply network current using the apparatus for improving the sinusoidality of traction power supply network current. Using this method, the current waveform of each secondary winding connected to the pulse rectifier approaches a sine wave, but the sum of the currents of all secondary windings is a sine wave, meaning that the current of the primary winding of the traction transformer is a sine wave.

[0126] like Figure 5 As shown, the method includes steps S501 to S504:

[0127] In step S501 , the current compensation controller obtains the expected current and the actual current of the corresponding pulse rectifier from each pulse rectifier controller.

[0128] Figure 6 This is a schematic diagram of the current waveform of the pulse rectifier 4QC1. Please also refer to Figure 2 、 Figure 4 and Figure 6 The pulse rectifier controller QT1 controls the pulse rectifier 4QC1 so that the expected current ist1 of the pulse rectifier 4QC1 is a sine wave, while the actual current isr1 of the pulse rectifier 4QC1 is composed of multiple straight lines (see Figure 6 ). Among them, the pulse rectifier 4QC1 operates at unity power factor.

[0129] Figure 7 This is a schematic diagram of the current waveform of the pulse rectifier 4QC2. Please also refer to Figure 2 、 Figure 4 and Figure 7 The pulse rectifier controller QT2 controls the pulse rectifier 4QC2 so that the expected current ist2 of the pulse rectifier 4QC2 is a sine wave, while the actual current isr2 of the pulse rectifier 4QC2 is composed of multiple straight lines (see Figure 7 ). Among them, the pulse rectifier 4QC2 operates at unity power factor.

[0130] Step S502: The current compensation controller obtains the target current of the primary winding of the traction transformer according to the expected current of each pulse rectifier.

[0131] Specifically, the current compensation controller substitutes the expected current of each pulse rectifier into the preset primary current calculation formula, which is:

[0132] Target current of the primary winding = k × the sum of the expected currents of each pulse rectifier / n

[0133] Wherein, n is the primary-to-secondary transformation ratio of the traction transformer; when in traction operation, k is a constant that ensures that the target current of the primary winding is not less than the current corresponding to the sum of the actual currents of each pulse rectifier on the primary winding; when in regenerative braking operation, k is a constant that ensures that the target current of the primary winding is not more than the current corresponding to the sum of the actual currents of each pulse rectifier on the primary winding.

[0134] For example, see also Figure 2 、 Figure 4 、 Figure 6 、 Figure 7 、 Figure 8 and Figure 9 The actual current isr1 of the pulse rectifier 4QC1 and the actual current isr2 of the pulse rectifier 4QC2 are added together, and then the current ipr on the primary winding corresponding to the sum of the actual currents of each pulse rectifier is calculated based on the primary-to-secondary transformation ratio n of the traction transformer TR (see Figure 8 and Figure 9 ):

[0135] ipr=(isr1+isr2) / n

[0136] The expected current ist1 of the pulse rectifier 4QC1 and the expected current ist2 of the pulse rectifier 4QC2 are added together, and then the target current ipe of the primary winding is calculated based on the primary-to-secondary ratio n and the coefficient k of the traction transformer TR. The target current ipe is a sine wave (see Figure 8 and Figure 9 ):

[0137] ipe=k×(ist1+ist2) / n

[0138] In traction mode, the coefficient k makes the target current ipe of the primary winding not less than the current on the primary winding corresponding to the sum of the actual currents of all pulse rectifiers, that is, ipe ≥ ipr. Figure 8 As shown;

[0139] During regenerative braking, the coefficient k makes the target current ipe of the primary winding no greater than the current on the primary winding corresponding to the sum of the actual currents of all pulse rectifiers, that is, ipe≤ipr. Figure 9 shown.

[0140] Step S503: The current compensation controller obtains the current actual current of the primary winding from the current sensor.

[0141] See also Figure 2 and Figure 4The two ends of the current sensor CS are connected to the primary winding P of the traction transformer TR and the grounding device G, respectively. The current passing through the current sensor CS is the current passing through the primary winding P. Therefore, the current sensor CS can provide real-time feedback of the current actual current in the primary winding P to the current compensation controller CTR.

[0142] Step S504 , when the current actual current of the primary winding is not equal to the target current of the primary winding, the current compensation controller adjusts the compensation current generated by the current compensation unit until the current actual current of the primary winding is equal to or closest to the target current of the primary winding.

[0143] Specifically, when in the traction working state, the current compensation controller adjusts the compensation current generated by the current compensation unit according to a preset first current compensation formula; the first current compensation formula is:

[0144] The actual current of the primary winding = (the sum of the actual currents of each pulse rectifier + compensation current) / n

[0145] Where n is the primary-to-secondary transformation ratio of the traction transformer;

[0146] When the current actual current of the primary winding is less than the target current of the primary winding, the compensation current is increased; when the current actual current of the primary winding is greater than the target current of the primary winding, the compensation current is reduced.

[0147] When in regenerative braking mode, the current compensation controller adjusts the compensation current generated by the current compensation unit according to a preset second current compensation formula; the second current compensation formula is:

[0148] The actual current of the primary winding = (the sum of the actual currents of each pulse rectifier - compensation current) / n

[0149] Where n is the primary-to-secondary transformation ratio of the traction transformer;

[0150] When the current actual current of the primary winding is less than the target current of the primary winding, the compensation current is reduced; when the current actual current of the primary winding is greater than the target current of the primary winding, the compensation current is increased.

[0151] For example, see also Figure 2 、 Figure 4 、 Figure 6 、 Figure 7 、 Figure 8 and Figure 9The feedback value of the current sensor CS (hereinafter uniformly represented by ipf) is the actual current of the primary winding P of the traction transformer TR. The current compensation controller CTR controls the current compensation unit CP to generate a compensation current icpr (not shown in the figure). The compensation current icpr of the current compensation unit CP corresponds to the current on the primary winding ipcpr (see Figure 8 and Figure 9 ), after compensation, the feedback value ipf of the current sensor CS is equal to or closest to the target current ipe of the primary winding P. The control basis is:

[0152] In traction operation, ipf = (isr1 + isr2 + icpr) / n. When the actual current ipf of the primary winding P fed back by the current sensor CS (not shown in the figure) is less than the target current ipe of the primary winding P, the compensation current icpr of the current compensation unit CP (not shown in the figure) is increased, thereby increasing the actual current ipf of the primary winding P fed back by the current sensor CS, until the actual current ipf of the primary winding P fed back by the current sensor CS is equal to the target current ipe of the primary winding P or the compensation current icpr of the current compensation unit CP cannot be increased any further (here, it is equivalent to the actual current ipf of the primary winding P having reached the level closest to its target current ipe); when the actual current ipf of the primary winding P fed back by the current sensor CS is less than the target current ipe, the compensation current icpr of the current compensation unit CP can be increased any further. When the actual current ipf of the primary winding P is greater than the target current ipe of the primary winding P, the compensation current icpr of the current compensation unit CP is reduced, so that the actual current ipf of the primary winding P fed back by the current sensor CS is reduced, until the actual current ipf of the primary winding P fed back by the current sensor CS is equal to the target current ipe of the primary winding or the compensation current icpr of the current compensation unit CP can no longer be reduced (here it is equivalent to the actual current ipf of the primary winding P having reached the level closest to its target current ipe); when the actual current ipf of the primary winding P fed back by the current sensor CS is equal to the target current ipe of the primary winding P, the compensation current icpr of the current compensation unit CP is kept unchanged.

[0153] During regenerative braking, ipf = (isr1 + isr2 - icpr) / n. When the actual current ipf of the primary winding P group fed back by the current sensor CS (not shown in the figure) is less than the target current ipe of the primary winding P, the compensation current icpr of the current compensation unit CP is reduced (not shown in the figure), thereby increasing the actual current ipf of the primary winding P fed back by the current sensor CS, until the actual current ipf of the primary winding P fed back by the current sensor CS is equal to the target current ipe of the primary winding P or the compensation current icpr of the current compensation unit CP can no longer be reduced (here it is equivalent to the actual current ipf of the primary winding P reaching the level closest to its target current ipe); when the actual current ipf of the primary winding P fed back by the current sensor CS is equal to the target current ipe of the primary winding P, the compensation current icpr of the current compensation unit CP can no longer be reduced. When the actual current ipf of the primary winding P is greater than the target current ipe of the primary winding P, the compensation current icpr of the current compensation unit CP is increased, so that the actual current ipf of the primary winding P fed back by the current sensor CS is reduced, until the actual current ipf of the primary winding P fed back by the current sensor CS is equal to the target current ipe of the primary winding or the compensation current icpr of the current compensation unit CP can no longer be increased (here it is equivalent to the actual current ipf of the primary winding P having reached the level closest to its target current ipe); when the actual current ipf of the primary winding P fed back by the current sensor CS is equal to the target current ipe of the primary winding P, the compensation current icpr of the current compensation unit CP is kept unchanged.

[0154] The target current ipe of the primary winding P of the traction transformer TR is a sinusoidal wave. Therefore, when the actual current ipf of the primary winding fed back by the current sensor CS equals the target current ipe, the actual current waveform of the traction transformer primary winding is a sinusoidal wave. Compared to the current waveform of a pulse rectifier, which consists of multiple straight lines, the application of this device and method improves the sinusoidality of the primary winding current. When the current waveforms of the primary windings of all traction transformers in the traction power supply network are sinusoidal and all pulse rectifiers operate at unity power factor, the current waveform of the traction power supply network is a sinusoidal wave.

[0155] Compared with the existing technology, the device and method for improving the sinusoidality of the current in the traction power supply network provided in this application effectively improve the sinusoidality of the current in the traction power supply network, reduce the current distortion rate, and improve the current performance and stability of the traction power supply network; at the same time, it is beneficial to improve the economy of electricity billing in the traction power supply network.

[0156] In another specific embodiment, the present invention also provides a second device for improving the sinusoidality of the current in the traction power supply network. Figure 10As shown, this second device for improving the sinusoidality of the traction power supply network current includes a traction transformer TR and at least one current compensating device; each current compensating device is connected to a secondary winding of the traction transformer TR. Typically, the number of current compensating devices is equal to the number of secondary windings included in the traction transformer TR. This application uses the example of a system including one secondary winding and one current compensating device. In practical applications, more than one secondary winding and current compensating device may be included.

[0157] One end of the primary winding P of the traction transformer TR is connected to the traction power supply network L through the pantograph PT, and the other end of the primary winding P is connected to the grounding device G, which is connected to the track Z.

[0158] For each pair of secondary windings and current compensation devices, each current compensation device includes: a current sensor CS1, an inductor I1, a pulse rectifier 4QC1, a pulse rectifier controller QT1, a current compensation unit CP1, and a current compensation controller CTR1. The inductor I1 is connected in series with the pulse rectifier 4QC1 and then in parallel with the current compensation unit CP1 to form a parallel circuit. One end of the parallel circuit is connected to one end of the secondary winding S1 of the traction transformer TR through the current sensor CS1, and the other end of the parallel circuit is connected to the other end of the secondary winding S1.

[0159] A first terminal of the current compensation controller CTR1 is connected to the current compensation unit CP1 , a second terminal of the current compensation controller CTR1 is connected to the current sensor CS1 , and a third terminal of the current compensation controller CTR1 is connected to the pulse rectifier controller QT1 .

[0160] The structure and current compensation principle of the current compensation unit CP1 included in the second device for improving the sinusoidality of the traction power supply network current are consistent with the current compensation unit CP included in the first device for improving the sinusoidality of the traction power supply network current. Therefore, the current compensation unit CP1 can refer to Figure 3 The only difference is that the connection relationship between the current compensation unit CP1 and other components is as follows (see Figure 3 and Figure 10 ): The anode of the first diode D1 and the cathode of the second diode D2 are connected to one end of the secondary winding S1 of the traction transformer TR through the first terminal T1; the anode of the third diode D3 and the cathode of the fourth diode D4 are connected between the current sensor CS1 and the parallel circuit through the second terminal T2.

[0161] Based on the second device for improving the sinusoidality of traction power supply network current, the present invention also provides a corresponding method for improving the sinusoidality of traction power supply network current using the second device. Using this method, the current waveform of each secondary winding connected to the pulse rectifier is a sinusoidal wave, and the current of the primary winding of the traction transformer is also a sinusoidal wave.

[0162] like Figure 11 As shown, the method includes steps S110 to S113:

[0163] In step S110 , the current compensation controller obtains the expected current and the actual current of the corresponding pulse rectifier from the pulse rectifier controller.

[0164] Specifically, see Figure 6 The pulse rectifier controller QT1 controls the pulse rectifier 4QC1 so that the expected current ist1 of the pulse rectifier 4QC1 is a sine wave, while the actual current isr1 of the pulse rectifier 4QC1 is composed of multiple straight lines. The pulse rectifier 4QC1 operates at a unity power factor.

[0165] In step S111 , a current compensation controller obtains a target current of the secondary winding according to an expected current of the pulse rectifier.

[0166] Specifically, the current compensation controller CTR1 substitutes the expected current of the pulse rectifier into the preset secondary current calculation formula

[0167] Target current of secondary winding = k × expected current of pulse rectifier

[0168] Among them, when in traction mode, k is a constant that makes the target current of the secondary winding not less than the actual current of the pulse rectifier; when in regenerative braking mode, k is a constant that makes the target current of the secondary winding not greater than the actual current of the pulse rectifier.

[0169] For example, see also Figure 6 、 Figure 10 、 Figure 12 and Figure 13 The expected current ist1 of the pulse rectifier 4QC1 is calculated by the coefficient k to obtain the target current ise1 of the secondary winding S1. The target current ise1 is a sine wave:

[0170] ise1=k×ist1

[0171] In traction mode, the coefficient k makes the target current ise1 of the secondary winding S1 not less than the actual current isr1 of the pulse rectifier 4QC1, that is: ise1 ≥ isr1, such as Figure 12 As shown;

[0172] During regenerative braking, the coefficient k makes the target current ise1 of the secondary winding S1 no greater than the actual current isr1 of the pulse rectifier 4QC1, that is, ise1≤isr1. Figure 13 shown.

[0173] In step S112 , the current compensation controller obtains the actual current of the secondary winding from the current sensor.

[0174] See also Figure 10 The two terminals of current sensor CS1 are connected to the secondary winding S1 of the traction transformer TR and one terminal of the parallel circuit, respectively. The current passing through current sensor CS1 is the current passing through the secondary winding S1. Therefore, current sensor CS1 can provide real-time feedback of the actual current in the secondary winding S1 to the current compensation controller CTR1.

[0175] In step S113 , when the actual current of the secondary winding is not equal to the target current of the secondary winding, the current compensation controller adjusts the compensation current generated by the current compensation unit until the actual current of the secondary winding is equal to or closest to the target current of the secondary winding.

[0176] Specifically, when in the traction working state, the current compensation controller adjusts the compensation current generated by the current compensation unit according to a preset third current compensation formula; the third current compensation formula is:

[0177] Actual current of secondary winding = (actual current of pulse rectifier + compensation current)

[0178] When the actual current of the secondary winding is less than the target current of the secondary winding, the compensation current is increased;

[0179] When the actual current of the secondary winding is greater than the target current of the secondary winding, the compensation current is reduced.

[0180] When in the regenerative braking state, the current compensation controller adjusts the compensation current generated by the current compensation unit according to a preset fourth current compensation formula; the fourth current compensation formula is:

[0181] Actual current of secondary winding = (actual current of pulse rectifier - compensation current)

[0182] When the actual current of the secondary winding is less than the target current of the secondary winding, the compensation current is reduced;

[0183] When the actual current of the secondary winding is greater than the target current of the secondary winding, the compensation current is increased.

[0184] For example, see also Figure 6 、 Figure 10 、 Figure 12 and Figure 13The feedback value of the current sensor CS1 (hereinafter uniformly represented by isf1) is the actual current of the secondary winding S1 of the traction transformer. The current compensation controller CTR1 controls the current compensation unit CP1 to generate the compensation current icpr1 (see Figure 12 and Figure 13 ), after compensation, the feedback value isf1 of the current sensor CS1 is equal to or closest to the target current ise1 of the secondary winding S1. The control basis is:

[0185] In traction mode, isf1=isr1+icpr1. When the actual current isf1 (not shown in the figure) of the secondary winding S1 fed back by the current sensor CS1 is less than the target current ise1 of the secondary winding S1, the compensation current icpr1 of the current compensation unit CP1 is increased (see Figure 12 ), thereby increasing the actual current isf1 of the secondary winding S1 fed back by the current sensor CS1 until the actual current isf1 of the secondary winding S1 fed back by the current sensor CS is equal to the target current ise1 of the secondary winding S1 or the compensation current icpr1 of the current compensation unit CP1 can no longer increase; when the actual current isf1 of the secondary winding S1 fed back by the current sensor CS1 is greater than the target current ise1 of the secondary winding S1, reducing the compensation current icpr1 of the current compensation unit CP1, thereby reducing the feedback amount isf1 of the current sensor CS1 until the actual current isf1 of the secondary winding S1 fed back by the current sensor CS is equal to the target current ise1 of the secondary winding S1 or the compensation current icpr1 of the current compensation unit CP1 can no longer decrease; when the actual current isf1 of the secondary winding S1 fed back by the current sensor CS1 is equal to the target current ise1 of the secondary winding S1, keeping the compensation current icpr1 of the current compensation unit CP1 unchanged.

[0186] In regenerative braking mode, isf1 = isr1 - icpr1. When the actual current isf1 (not shown in the figure) of the secondary winding S1 fed back by the current sensor CS1 is less than the target current ise1 of the secondary winding S1, the compensation current icpr1 of the current compensation unit CP1 is reduced (see Figure 13), thereby increasing the actual current isf1 of the secondary winding S1 fed back by the current sensor CS1 until the actual current isf1 of the secondary winding S1 fed back by the current sensor CS is equal to the target current ise1 of the secondary winding S1 or the compensation current icpr1 of the current compensation unit CP1 can no longer be reduced; when the actual current isf1 of the secondary winding S1 fed back by the current sensor CS1 is greater than the target current ise1 of the secondary winding S1, increasing the compensation current icpr1 of the current compensation unit CP1, thereby decreasing the actual current isf1 of the secondary winding S1 fed back by the current sensor CS1 until the actual current isf1 of the secondary winding S1 fed back by the current sensor CS is equal to the target current ise1 of the secondary winding S1 or the compensation current icpr1 of the current compensation unit CP1 can no longer be increased; when the actual current isf1 of the secondary winding S1 fed back by the current sensor CS1 is equal to the target current ise1 of the secondary winding S1, keeping the compensation current icpr1 of the current compensation unit CP1 unchanged.

[0187] The target current ise1 of the secondary winding S1 of the traction transformer TR is a sinusoidal wave. Therefore, when the actual current isf1 of the secondary winding S1 fed back by the current sensor CS is equal to the target current ise1, the actual current waveform of the secondary winding S1 of the traction transformer is a sinusoidal wave. Compared to the current waveform of a pulse rectifier composed of multiple straight lines, the application of this device and method improves the sinusoidality. When the currents of all the secondary windings of the traction transformer are sinusoidal, the current of the primary winding of the traction transformer is also a sinusoidal wave. When the currents of all the primary windings of the traction transformers in the traction power supply network are sinusoidal and all the pulse rectifiers are operating at unity power factor, the current waveform of the traction power supply network is also a sinusoidal wave.

[0188] Compared with the existing technology, the second device for improving the sinusoidality of the current in the traction power supply network and the corresponding method of use provided in this application also effectively improve the sinusoidality of the current in the traction power supply network, reduce the current distortion rate, and improve the current performance and stability of the traction power supply network; at the same time, it is beneficial to improve the economy of electricity billing in the traction power supply network.

[0189] The various embodiments in this specification are described in a progressive manner. Similar parts between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from other embodiments. In the description of this specification, the reference terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiments of this specification.

[0190] In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples, unless they contradict each other. The above is only an embodiment of the embodiment of this specification and is not intended to limit the embodiment of this specification. For those skilled in the art, the embodiment of this specification may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiment of this specification shall be included within the scope of the claims of the embodiment of this specification.

Claims

1. A device for improving the sinusoidality of current in a traction power supply network, characterized in that: include: a traction transformer, a current sensor, at least one pulse rectifier, at least one pulse rectifier controller, a current compensation unit, and a current compensation controller; The traction transformer comprises: a primary winding, one end of which is connected to the traction power supply network, and the other end of which is connected to the grounding device via the current sensor; at least one first secondary winding; and a second secondary winding; Both ends of each first secondary winding are connected to one of the pulse rectifiers; Each of the pulse rectifiers is connected to a pulse rectifier controller; The current compensation unit is connected to both ends of the second secondary winding; The current compensation controller is respectively connected to the current compensation unit, the current sensor and each of the pulse rectifier controllers; The current compensation unit includes: a first diode, a second diode, a third diode, a fourth diode, a fixed resistor, and an impedance adjustable component; Wherein, the first diode, the fixed resistor, the impedance adjustable component and the second diode are connected in sequence; the third diode, the fixed resistor, the impedance adjustable component and the fourth diode are connected in sequence; The anode of the first diode and the cathode of the second diode are connected to one end of the second secondary winding through a first terminal; the anode of the third diode and the cathode of the fourth diode are connected to the other end of the second secondary winding through a second terminal; The impedance adjustable component is used to adjust the impedance value of the current compensation unit to adjust the current of the second secondary winding; The number of the first secondary winding, the pulse rectifier and the pulse rectifier controller are all the same.

2. The device for improving the sinusoidality of current in a traction power supply network according to claim 1, characterized in that: One end of at least one of the first secondary windings is connected to the corresponding pulse rectifier via an inductor.

3. The device for improving the sinusoidality of current in a traction power supply network according to claim 1, characterized in that: The impedance adjustable component is connected to the current compensation controller and is used to adjust the impedance value of the current compensation unit according to the control of the current compensation controller.

4. The device for improving the sinusoidality of current in a traction power supply network according to claim 3, characterized in that: The impedance adjustable component is a semiconductor device.

5. A device for improving the sinusoidality of current in a traction power supply network, characterized in that: include: a traction transformer and at least one current compensating device; One end of the primary winding of the traction transformer is connected to the traction power supply network, and the other end of the primary winding is connected to the grounding device; The current compensation device includes: a current sensor, an inductor, a pulse rectifier, a pulse rectifier controller, a current compensation unit, and a current compensation controller; the inductor and the pulse rectifier are connected in series to form a parallel circuit with the current compensation unit, one end of the parallel circuit is connected to one end of the secondary winding of the traction transformer through the current sensor, and the other end of the parallel circuit is connected to the other end of the secondary winding; The first end of the current compensation controller is connected to the current compensation unit, the second end is connected to the current sensor, and the third end is connected to the pulse rectifier controller; the current compensation controller is used to obtain the expected current and actual current of the pulse rectifier corresponding to the pulse rectifier controller; The current compensation unit includes: a first diode, a second diode, a third diode, a fourth diode, a fixed resistor, and an impedance adjustable component; Wherein, the first diode, the fixed resistor, the impedance adjustable component and the second diode are connected in sequence; the third diode, the fixed resistor, the impedance adjustable component and the fourth diode are connected in sequence; The anode of the first diode and the cathode of the second diode are connected to one end of the secondary winding of the traction transformer through a first terminal; the anode of the third diode and the cathode of the fourth diode are connected between the current sensor and the parallel circuit through a second terminal; The impedance adjustable component is used to adjust the impedance value of the current compensation unit to adjust the current of the secondary winding; The number of the first secondary winding, the pulse rectifier and the pulse rectifier controller are all the same.

6. The device for improving the sinusoidality of current in a traction power supply network according to claim 5, characterized in that: The impedance adjustable component is connected to the current compensation controller and is used to adjust the impedance value of the current compensation unit according to the control of the current compensation controller.

7. The device for improving the sinusoidality of current in a traction power supply network according to claim 6, characterized in that: The impedance of the adjustable impedance component is continuously adjustable.

8. The device for improving the sinusoidality of current in a traction power supply network according to claim 7, characterized in that: The impedance adjustable component is a semiconductor device.

9. A method for improving the sinusoidality of current in a traction power supply network using the device according to any one of claims 1 to 4, characterized in that: include: The current compensation controller obtains the expected current and actual current of the corresponding pulse rectifier from each pulse rectifier controller; The current compensation controller obtains the target current of the primary winding of the traction transformer according to the expected current of each pulse rectifier; The current compensation controller obtains the current actual current of the primary winding from the current sensor; When the current actual current of the primary winding is not equal to the target current of the primary winding, the current compensation controller adjusts the compensation current generated by the current compensation unit until the current actual current of the primary winding is equal to or closest to the target current of the primary winding.

10. The method according to claim 9, characterized in that Obtaining the target current of the primary winding of the traction transformer according to the expected current of each pulse rectifier includes: Substitute the expected current of each pulse rectifier into the preset primary current calculation formula Target current of the primary winding = k × the sum of the expected currents of each pulse rectifier / n Among them, n is the primary-to-secondary transformation ratio of the traction transformer; when in traction working condition, k is a constant that makes the target current of the primary winding not less than the current on the primary winding corresponding to the sum of the actual currents of each pulse rectifier; when in regenerative braking working condition, k is a constant that makes the target current of the primary winding not more than the current on the primary winding corresponding to the sum of the actual currents of each pulse rectifier.

11. The method according to claim 10, characterized in that When in traction mode, the compensation current generated by the regulating current compensation unit includes: adjusting the compensation current generated by the current compensation unit according to a preset first current compensation formula; The first current compensation formula is: The current actual current of the primary winding = (the sum of the actual currents of each pulse rectifier + the compensation current) / n, where n is the primary-to-secondary transformation ratio of the traction transformer; When the current actual current of the primary winding is less than the target current of the primary winding, increasing the compensation current; When the current actual current of the primary winding is greater than the target current of the primary winding, the compensation current is reduced.

12. The method according to claim 10, characterized in that When in the regenerative braking state, the compensation current generated by the regulating current compensation unit includes: adjusting the compensation current generated by the current compensation unit according to a preset second current compensation formula; The second current compensation formula is: The current actual current of the primary winding = (the sum of the actual currents of each pulse rectifier - the compensation current) / n, where n is the primary-to-secondary transformation ratio of the traction transformer; When the current actual current of the primary winding is less than the target current of the primary winding, reducing the compensation current; When the current actual current of the primary winding is greater than the target current of the primary winding, the compensation current is increased.

13. A method for improving the sinusoidality of current in a traction power supply network using the device according to any one of claims 5 to 8, characterized in that: include: The current compensation controller obtains the target current of the secondary winding according to the expected current of the pulse rectifier; The current compensation controller obtains the actual current of the secondary winding from the current sensor; When the actual current of the secondary winding is not equal to the target current of the secondary winding, the current compensation controller adjusts the compensation current generated by the current compensation unit until the actual current of the secondary winding is equal to or closest to the target current of the secondary winding.

14. The method according to claim 13, characterized in that Obtaining the target current of the secondary winding according to the expected current of the pulse rectifier includes: Substitute the expected current of the pulse rectifier into the preset secondary current calculation formula Target current of secondary winding = k × expected current of pulse rectifier Among them, when in traction working condition, k is a constant that makes the target current of the secondary winding not less than the actual current of the pulse rectifier; when in regenerative braking working condition, k is a constant that makes the target current of the secondary winding not greater than the actual current of the pulse rectifier.

15. The method according to claim 14, characterized in that When in traction mode, the compensation current generated by the regulating current compensation unit includes: adjusting the compensation current generated by the current compensation unit according to a preset third current compensation formula; The third current compensation formula is: Actual current of secondary winding = (actual current of pulse rectifier + compensation current) When the actual current of the secondary winding is less than the target current of the secondary winding, increasing the compensation current; When the actual current of the secondary winding is greater than the target current of the secondary winding, the compensation current is reduced.

16. The method according to claim 15, characterized in that When in the regenerative braking state, the compensation current generated by the regulating current compensation unit includes: adjusting the compensation current generated by the current compensation unit according to a preset fourth current compensation formula; The fourth current compensation formula is: Actual current of secondary winding = (actual current of pulse rectifier - compensation current) When the actual current of the secondary winding is less than the target current of the secondary winding, reducing the compensation current; When the actual current of the secondary winding is greater than the target current of the secondary winding, the compensation current is increased.

Images