A method for controlling output voltage of a four-quadrant rectifier of a motor train unit

Abstract

The application provides a motor train unit four-quadrant rectifier output voltage control method, comprising: obtaining transformer secondary voltage, four-quadrant input current and four-quadrant output voltage; sending the transformer secondary voltage, four-quadrant input current and four-quadrant output voltage into a DSP chip, which is used for calculating and generating a PWM pulse signal based on the transformer secondary voltage, four-quadrant input current and four-quadrant output voltage; inputting the PWM pulse signal into a driving circuit to generate a driving signal to drive the turn-on and turn-off of a power switching device, so as to maintain the stability of the four-quadrant output voltage. The application not only has the advantages of a direct current control method, but also accelerates the response speed of the intermediate voltage, thereby maintaining the stability of the intermediate voltage.

Description

Technical Field

[0001] This invention relates to the field of rail transit control technology, and more particularly to a method for controlling the output voltage of a four-quadrant rectifier in a high-speed train. Background Technology

[0002] In the 1960s, my country built its first electrified railway. This railway was initially powered by a DC 3000V power supply system. After continuous comparison and demonstration by domestic scholars and experts, and after studying the AC power supply of power frequency EMUs used in Europe, Japan and other countries, it was finally decided to adopt the 25KV, 50Hz AC power supply system for EMUs, which laid the foundation for the development of railways in my country for decades to come.

[0003] The traction power of railway locomotives and EMUs comes from DC or AC motors, but the 25kV, 50Hz AC power of EMUs cannot be directly used as a power source for traction motors. As AC motors become increasingly widely used in rail transit, DC motors are gradually being phased out of railway traction applications. However, AC motors typically employ variable voltage variable frequency (VVVF) control, requiring a constant voltage source. Four-quadrant rectifiers were developed to meet this need.

[0004] Four-quadrant rectifiers have inherent advantages: low harmonics, resulting in less pollution to the power grid; high power factor, leading to efficient energy utilization; constant output voltage, providing a constant voltage source for the load; and input voltage and current operating in all four quadrants, ensuring no energy waste during traction and braking. These advantages make them an indispensable part of the railway traction field.

[0005] Four-quadrant rectifier control can be divided into two categories: one is the indirect current control strategy, and the other is the direct current control strategy.

[0006] like Figure 1 As shown, indirect current control achieves the goal of controlling the input current iN by controlling the rectifier input voltage uS to maintain a certain amplitude and phase with the grid-side voltage uN. Its specific principle is as follows: Figure 2 The four-quadrant rectifier vector diagram is shown. uN is known. Adjusting the rectifier input voltage uS controls uLN, where uLN and iN are in a 90° relationship, thereby controlling the input current iN.

[0007] Indirect current control methods offer good static characteristics, a simple control structure, and eliminate the need for current sensors, resulting in lower costs. However, they suffer from slow dynamic response, severe current overshoot, intense oscillations, and poor overall system stability. Considering railway applications, where four-quadrant rectifiers experience large load variations and wide grid-side voltage ranges, indirect current control methods are currently less commonly used.

[0008] Direct current control (DCC) directly controls the four-quadrant input current to track the current command signal. DCC includes hysteresis current control, predictive current control, and transient current control. DCC controls the input current according to the given four-quadrant input current. Hysteresis current control compares the actual value of the four-quadrant input current with the command value, outputting the deviation to a hysteresis comparator. The hysteresis comparator generates a pulse width modulation (PWM) signal, which controls the on / off state of each bridge arm switch, thereby controlling the four-quadrant input current. Predictive current control uses the given system state as the future output state to determine the switching action, aiming to reach the given state in the next cycle. Transient current control is similar to predictive current control, but the difference is that transient current control uses the current command value calculated by the control algorithm as the current value for the current cycle.

[0009] Direct current control allows the four-quadrant input current to quickly track the reference current, but it relies on the magnitude of the output intermediate voltage deviation to determine the speed of current tracking. Therefore, the overall system response will be linear with the intermediate voltage deviation after the intermediate voltage deviates. Thus, when there are fluctuations in the load or input power of the four-quadrant rectifier, it may cause relatively large fluctuations in the intermediate voltage. Summary of the Invention

[0010] The purpose of this invention is to address the shortcomings of existing four-quadrant rectifier control methods, which cause large intermediate voltage fluctuations when the input power supply voltage or output load fluctuates. This invention proposes a method that can quickly adjust the intermediate voltage. This method not only has the advantages of direct current control methods, but also accelerates the response speed of the intermediate voltage, thereby maintaining the stability of the intermediate voltage.

[0011] The technical means employed in this invention are as follows:

[0012] A method for controlling the output voltage of a four-quadrant rectifier in a high-speed train includes:

[0013] Obtain the transformer secondary voltage, four-quadrant input current, and four-quadrant output voltage;

[0014] The transformer secondary voltage, four-quadrant input current and four-quadrant output voltage are sent to the DSP chip, which is used to calculate and generate PWM pulse signals based on the transformer secondary voltage, four-quadrant input current and four-quadrant output voltage.

[0015] The PWM pulse signal is input to the driving circuit to generate a driving signal to drive the power switching device to turn on and off, thereby maintaining the stability of the four-quadrant output voltage.

[0016] Furthermore, the transformer secondary voltage, four-quadrant input current, and four-quadrant output voltage are obtained, including: the transformer secondary voltage is obtained through a voltage transformer, the four-quadrant input current is obtained through a current sensor, and the four-quadrant output voltage is obtained through a voltage sensor.

[0017] Furthermore, the DSP chip calculates and generates switching signals based on the transformer secondary voltage, four-quadrant input current, and four-quadrant output voltage, including:

[0018] The voltage deviation is obtained by comparing the four-quadrant output voltage with the preset output voltage target value.

[0019] The voltage deviation is fed into a fast-adjustment voltage loop for calculation and processing to generate a four-quadrant input current setpoint.

[0020] The given value of the four-quadrant input current is input into the no-delay current loop for calculation and processing, thereby generating the input current at the four-quadrant pulse output time.

[0021] The difference between the given value of the four-quadrant input current and the input current at the time of the four-quadrant pulse output is then input into the proportional resonant current adjustment circuit.

[0022] The difference between the detected value of the transformer secondary voltage and the output value of the PR circuit is used as the modulation signal to generate a PWM pulse signal.

[0023] Furthermore, the voltage deviation is fed into a fast-adjustment voltage loop for calculation and processing to generate a four-quadrant input current setpoint, including:

[0024] The voltage deviation is calculated as the input data for the proportional-integral circuit using the following formula:

[0025] (︱(u * d -u d )︱ / K d +1)×(u * d -u d )

[0026] Among them, u d The output voltage value in four quadrants, u * d K is the preset target value for output voltage. d For fast voltage loop speed adjustment parameters;

[0027] The output of the proportional-integral circuit is multiplied by the sine value of the secondary voltage phase to obtain the four-quadrant input current setpoint. The secondary voltage phase of the transformer is calculated and obtained.

[0028] Furthermore, the given four-quadrant input current value is input into a no-delay current loop for processing, thereby generating the input current at the four-quadrant pulse output moment, including:

[0029] The no-delay current loop calculates the input current i2 at the four-quadrant pulse output moment using the following formula:

[0030]

[0031] Where i1 is the four-quadrant input current at the sampling time, θ is the secondary voltage angle at the sampling time, L is the filter inductance, R is the filter resistance, t0 is the sampling time, t1 and t2 are the pulse switching times calculated in the previous control cycle of the DSP chip, and U N For the power grid amplitude, u N This is the actual sampled value of the secondary voltage.

[0032] The technical solution of this invention can quickly adjust the output voltage of a four-quadrant rectifier when it deviates from a predetermined value. The greater the deviation, the greater the adjustment capability, effectively suppressing four-quadrant output voltage fluctuations. The beneficial effects of this invention are as follows:

[0033] 1. In the four-quadrant rectifier control method of the present invention, the larger the output voltage deviation, the stronger the regulation capability, effectively suppressing the four-quadrant output voltage deviation and accelerating the response capability.

[0034] 2. In the four-quadrant rectifier control method of the present invention, the current loop is calculated based on the current at the predicted pulse output time, without the delay link in the traditional control method, and the current regulation capability is faster.

[0035] 3. The method of the present invention does not require additional hardware circuitry in most applications, thus avoiding additional costs and making it easy to promote. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a circuit diagram for the indirect control of the input current of a conventional four-quadrant rectifier.

[0038] Figure 2 This is a schematic diagram of the indirect control principle of the input current of a four-quadrant rectifier in the existing technology.

[0039] Figure 3 This is a flowchart of a method for controlling the output voltage of a four-quadrant rectifier in a high-speed train according to the present invention.

[0040] Figure 4 This is a schematic diagram of the DSP chip processing flow of the present invention.

[0041] Figure 5 This is a schematic diagram illustrating the control effect in an embodiment of the present invention. Detailed Implementation

[0042] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0043] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0044] This invention provides a method for controlling the output voltage of a four-quadrant rectifier in a high-speed train, including a signal acquisition circuit detecting the secondary voltage u of the transformer. N Four-quadrant input current i N Four-quadrant output voltage u d The data is sent to the DSP chip circuit, and the DSP circuit follows the instructions. Figure 4 The principle flow shown is used to calculate the PWM drive signal sent to the drive circuit, which drives the power switching device to turn on and off according to a certain rule to ensure the stability of the intermediate voltage in the four quadrants.

[0045] Specifically, such as Figure 3 As shown, the secondary voltage u of the transformer N The four-quadrant input current i is obtained through a voltage transformer. N With output voltage u dThe signal acquisition circuit obtains the secondary voltage signal, four-quadrant input current signal, and four-quadrant output voltage signal from the voltage transformer, current sensor, and voltage sensor respectively, and sends them to the DSP chip circuit. The DSP chip then processes the signals according to its operating principle. Figure 4 The calculation generates a switching signal, which is then sent to the drive circuit to generate a drive signal that drives the power switching device to turn on and off according to a certain pattern. The power switching device can be a semiconductor power device such as an IGBT or GTO, and its specific configuration is set in the auxiliary circuit. Figure 1 Positions T1-T4 and D1-D4 in the circuit control the four-quadrant input current through power device switches to stabilize the intermediate voltage. The signal acquisition circuit and DSP chip circuit are on a PCB board, while the drive circuit is a dedicated drive circuit for semiconductor power devices such as IGBTs and GTOs.

[0046] The control method for the output voltage of the four-quadrant rectifier of the EMU provided by the present invention processes the voltage deviation signal through a fast voltage loop: as the voltage deviation signal increases, the adjustment speed also increases rapidly, thereby accelerating the response of the output voltage fluctuation of the four-quadrant rectifier of the EMU; the output current adjustment signal of the fast voltage loop is then output through a non-delayed current loop to output an adjustment signal, and after calculation with the grid voltage signal, a pulse switch adjustment signal is output, eliminating the delay link from calculation to output in the control.

[0047] The following specific application examples will further illustrate the solution and effects of the present invention.

[0048] like Figure 3-4 As shown in the figure, the four-quadrant rectifier control method for high-speed trains provided in this embodiment specifically includes the following steps:

[0049] a. Signal acquisition circuit detects mains voltage u N Four-quadrant output voltage value u d Four-quadrant input current value i N The acquired signal is then sent to the DSP chip circuit.

[0050] b. The DSP chip circuit's voltage loop fast adjustment stage calculates the deviation between the four-quadrant output voltage setpoint and the detected value, using the formula (︱(u*)). d -u d )︱ / K d +1)×(u* d -u d The calculated value is fed into the proportional-integral (PI) stage, K d To accelerate voltage loop adjustment, the smaller the set value, the faster the adjustment speed.

[0051] c. The DSP chip circuit calculates the secondary voltage phase θ based on the obtained transformer secondary voltage, and multiplies its sine value by the PI loop output to obtain the four-quadrant input current setpoint.

[0052] The formula for calculating PI is as follows:

[0053]

[0054] d. No-delay current loop according to formula

[0055]

[0056] The current i2 at the pulse output moment is calculated, where i1 and θ are the sampling moment current and the grid angle, and L and R are the filter inductance and resistance in the secondary winding of the transformer. Filtering the four-quadrant input current can reduce the harmonic content in the current. t0 is the sampling moment, t1 and t2 are the pulse switching moments calculated in the previous control cycle of the DSP chip, and U... N u N The amplitude of the power grid is compared with the actual sampled value.

[0057] The difference between the input current calculated by the DSP chip's delay-free current loop at the four-quadrant pulse output moment and the current setpoint calculated by the fast voltage loop is sent to the proportional resonance (PR) current regulation circuit.

[0058] The formula for calculating PR is as follows:

[0059]

[0060] f. The DSP chip circuit calculates the difference between the detected value of the transformer secondary voltage and the output value of the PR stage, and uses it as a modulation signal to generate a PWM pulse signal.

[0061] g. The PWM pulse signal is amplified by the driver circuit and then sent to the power module circuit to drive the power switching device to turn on and off, thereby maintaining the stability of the four-quadrant output voltage.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling the output voltage of a four-quadrant rectifier in a high-speed train, characterized in that, include: Obtain the transformer secondary voltage, four-quadrant input current, and four-quadrant output voltage; The transformer secondary voltage, four-quadrant input current, and four-quadrant output voltage are fed into a DSP chip. The DSP chip is used to calculate and generate a PWM pulse signal based on the transformer secondary voltage, four-quadrant input current, and four-quadrant output voltage, including: The voltage deviation is obtained by comparing the four-quadrant output voltage with the preset output voltage target value. The voltage deviation is fed into a fast-adjustment voltage loop for calculation and processing to generate a four-quadrant input current setpoint, including: The voltage deviation is calculated as the input data for the proportional-integral circuit using the following formula: (︱（ u d -U d ）︱ / K d +1)×（ u d -U d ） in, U d The output voltage values ​​are in four quadrants. u d The preset output voltage target value, K d For fast voltage loop speed adjustment parameters; The four-quadrant input current setpoint is obtained by multiplying the output of the proportional-integral circuit with the sine value of the secondary voltage phase. The secondary voltage phase is obtained based on the zero-crossing time of the transformer secondary voltage. The given four-quadrant input current is input into a non-delayed current loop for processing, thereby generating the input current at the four-quadrant pulse output moment, including: The no-delay current loop calculates the input current at the four-quadrant pulse output moment using the following formula. i 2: in i 1 represents the four-quadrant input current at the sampling time. θ The angle of the secondary side voltage at the sampling time. L For filter inductance 、R For filter resistors, t 0 represents the sampling time. t 1. t 2 represents the pulse switching time calculated in the previous control cycle of the DSP chip. U N For the power grid amplitude, u N This is the actual sampled value of the secondary voltage; t 3 is t The time after one DSP control cycle from time 0, i.e. t 3 distance t 0 intervals represent one DSP control cycle; The difference between the detected value of the transformer secondary voltage and the output value of the PR circuit is used as the modulation signal to generate a PWM pulse signal. The PWM pulse signal is input to the driving circuit to generate a driving signal to drive the power switching device to turn on and off, thereby maintaining the stability of the four-quadrant output voltage.

2. The method for controlling the output voltage of a four-quadrant rectifier in a high-speed train according to claim 1, characterized in that, The transformer secondary voltage, four-quadrant input current, and four-quadrant output voltage are obtained, including: the transformer secondary voltage is obtained through a voltage transformer, the four-quadrant input current is obtained through a current sensor, and the four-quadrant output voltage is obtained through a voltage sensor.

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