Method, apparatus, and system for power-on startup of voltage compensation converter of HDT without bypass

Abstract

The present invention relates to the technical field of transformer control. Disclosed are a method, apparatus, and system for power-on startup of a voltage compensation converter of a HDT without a bypass. In the method, an HDT startup process is divided into an uncontrollable rectification stage and a controllable rectification stage by means of a grid-side current control unit, a direct-current bus voltage control unit, a split capacitor voltage balance control unit, and a load voltage control unit. During the power-on process in the present invention, there is no need to close bypass anti-parallel thyristors of a voltage compensation converter, and two transformers of the HDT are used to simultaneously charge direct-current buses capacitor by means of respective converters, making the power-on process simpler. In addition, by improving existing steady-state control strategies, the inrush current at the initial phase of the controllable rectification stage can be effectively eliminated.

Description

A bypass-free power-on starting method, device and system for a voltage compensation converter of an HDT TECHNICAL FIELD

[0001] The present application belongs to the field of transformers, and particularly relates to a bypass-free power-on starting method, device and system for a voltage compensation converter of an HDT. BACKGROUND

[0002] A hybrid distribution transformer (HDT) is a new type of controllable distribution transformer, which is characterized in that a voltage compensation converter and a current compensation converter are connected in a traditional distribution transformer, and the two converters share a DC bus capacitor. Compared with the traditional distribution transformer, the HDT can eliminate the harmful effects of harmonics, reactive power and asymmetric current in the load current on the distribution network with the help of the current compensation converter; and the HDT can eliminate the adverse effects of voltage fluctuation and asymmetry on load power supply with the help of the voltage compensation converter.

[0003] In engineering practice, power-on starting is an inevitable process for the HDT to run on the network. In the traditional power-on starting strategy of the HDT, the voltage compensation converter needs to be closed through its anti-parallel thyristor in advance, and the DC bus capacitor is naturally charged by the current compensation converter of the voltage compensation converter through uncontrolled rectification. After the bus voltage rises to the rated value, the anti-parallel thyristor is opened, and then the closed-loop control of the voltage compensation converter of the HDT is started at the current zero-crossing moment of the thyristor.

[0004] However, in actual distribution network applications, the above starting strategy has a significant defect. Specifically, before the HDT is connected to the network, the system as a whole has no power, the control circuit cannot send control signals, and the anti-parallel thyristor cannot be closed. In order to control the closing of the anti-parallel thyristor, an additional auxiliary power supply needs to be added. This not only increases the overall investment of the system, but also increases the complexity of the starting strategy.

[0005] SUMMARY

[0006] The present application aims to overcome the above-mentioned shortcomings of the prior art, and provides a bypass-free power-on starting method, device and system for a voltage compensation converter of an HDT, to solve the problem that in the prior art, in order to control the closing of the anti-parallel thyristor, an additional auxiliary power supply needs to be added, increasing the complexity of the starting strategy.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] A bypass-free power-on starting method for a voltage compensation converter of an HDT, comprising an uncontrolled rectification stage and a controllable rectification stage.

[0009] The uncontrolled rectification stage comprises the following steps:

[0010] S101, disconnecting the anti-parallel thyristor on the voltage compensation converter bypass and the contactor on the DC bus damping resistor bypass, and closing the circuit breaker of the HDT;

[0011] S102, when the DC bus voltage exceeds the threshold value, the power module of the control circuit and the detection circuit of the HDT is powered on;

[0012] S103, after the control circuit of the HDT is stabilized, the contactor on the DC bus damping resistor bypass is closed after a set delay time;

[0013] The controllable rectification stage comprises the following steps:

[0014] S201, starting the current compensator for closed-loop control;

[0015] S202, after the current compensator is started, the voltage compensation converter is started when the DC bus voltage rises and exceeds the uncontrolled rectification end value.

[0016] Further improvements of the application are as follows:

[0017] Preferably, in S101, the isolation transformer maintains a fixed voltage ratio with the main transformer, and the voltage compensation converter and the current compensation converter simultaneously charge the DC bus capacitor.

[0018] Preferably, in S103, the detection circuit sends a contactor closing signal after a set delay time, and the contactor on the DC bus damping resistor bypass is closed.

[0019] A voltage compensation converter non-bypass power-on starting device of an HDT for implementing the above-mentioned non-bypass power-on starting method, comprising:

[0020] a grid-side current control unit for controlling the current compensation converter; before closed-loop control of the current compensation converter, each IGBT in the current compensation converter is in a blocked state; after the current compensation converter is enabled, a driving pulse signal of each IGBT is obtained;

[0021] a DC bus voltage control unit for obtaining a deviation by comparing a real-time value of the DC bus voltage with a reference value, and obtaining a reference instruction of the grid-side current inner loop after the deviation is operated by a PI controller, a low-pass filter and a notch filter;

[0022] a split capacitor voltage balance control unit for obtaining a difference value by comparing the voltages of the two DC bus capacitors; when the current compensation converter is not enabled, the difference value is a 0-axis reference signal of the load; when the current compensation converter is enabled, the difference value is separated by integration and used as the 0-axis reference signal of the load;

[0023] A load voltage control unit is configured to control the voltage compensation converter; before closed-loop control, each IGBT in the voltage compensation converter is in a blocking state; after the voltage compensation converter is enabled, the drive pulse signals of each IGBT are obtained.

[0024] Preferably, when the DC bus voltage is not higher than the rated value, the DC bus voltage control unit applies a small limiting threshold; when the DC bus voltage is higher than the rated value, the DC bus voltage control unit applies a normal limiting threshold corresponding to the rated grid-side current.

[0025] The small limiting threshold is 20% to 30% of the rated grid-side current.

[0026] Preferably, the PI parameters in the grid-side current control unit, the DC bus voltage control unit, the split capacitor voltage balance control unit and the load voltage control unit are adjusted by corresponding dynamic adjustment factors.

[0027] Preferably, when the current compensation converter is enabled, the DC bus voltage control unit, the split capacitor voltage balance control unit and the grid-side current closed-loop control unit are simultaneously enabled; the PI controller of the DC bus voltage control unit is provided with a variable parameter and an integral separation link.

[0028] Preferably, in the grid-side current control unit, when the current compensation converter is enabled, the real-time i Psk is obtained, and then i Psd , i Psq and i Ps0 are obtained, and then the modulation signals m Psk , m pd and m pq are generated by the i p0 variable PI controller, and then the drive pulse signals are obtained by SPWM.

[0029] Preferably, in the load voltage control unit, when the voltage compensation converter is enabled, the real-time u 2k is obtained, and then u 2d , u 2q and u 20 are obtained, and then the modulation signals m 2k , m td and m tq are generated by the u t0 variable PI controller, and then the drive pulse signals are obtained by SPWM.

[0030] Preferably, the i Psk variable PI controller of the grid-side current control unit and the u 2k variable PI controller of the load voltage control unit are provided with a variable parameter and an integral separation link.

[0031] A voltage compensation converter no-bypass power-on starting system for implementing the above no-bypass power-on starting method, characterized in that it comprises a main transformer, an isolation transformer, a current compensation converter and a voltage compensation converter; the main transformer and the isolation transformer are connected in series;

[0032] The primary side of the main transformer is connected to the power grid in a delta mode through a circuit breaker, and the secondary side is connected to the load in a star connection mode through a circuit breaker;

[0033] The current compensation converter is connected in parallel with an auxiliary winding in the main transformer, and the voltage compensation converter is connected in series with the primary winding through the isolation transformer;

[0034] The current compensation converter and the voltage compensation converter share a DC bus capacitor, the DC bus capacitor comprises two capacitors connected in series, each capacitor is connected with a damping resistor, and each damping resistor is provided with a bypass, and each bypass is provided with a bypass contactor.

[0035] Compared with the prior art, the present application has the following beneficial effects:

[0036] The application discloses a voltage compensation converter no-bypass power-on starting method, device and system of an HDT, which is a short-time delay input voltage compensation converter and variable parameter control HDT voltage compensation converter no-bypass power-on starting technology, so as to ensure that the HDT can be safely and stably started and operated on the grid. In the power-on process, the anti-parallel thyristor of the voltage compensation converter does not need to be bypassed and closed, and the two transformers of the HDT can be used to charge the DC bus capacitor at the same time by means of the respective transformers, so that the power-on process is simpler. In addition, by improving the existing steady-state control strategy, the impact current in the initial stage of the controllable rectification stage can be effectively eliminated. The starting method does not need to bypass and close the voltage compensation converter anti-parallel thyristor. The method has the following advantages:

[0037] 1) Simple process: compared with the traditional starting strategy, the starting strategy does not need to close the bypass anti-parallel thyristor throughout the process, does not need to disconnect the bypass contactor after the power-on starting is completed, and does not need to control the voltage compensation converter to start at the zero-crossing point, so that the process is simpler and more reliable.

[0038] 2) Good economy: compared with the traditional starting strategy, an additional auxiliary power supply is not needed to specially control the bypass closing of the anti-parallel thyristor.

[0039] 3) Safety and reliability: the improved measures of short-time delay starting of the voltage compensation converter, variable parameter control and condition limiting can effectively avoid the impact current caused by various factors, so as to ensure the safety and reliability of the power-on process. BRIEF DESCRIPTION OF DRAWINGS

[0040] Fig. 1 is a HDT main circuit topology related to the present application;

[0041] Fig. 2 is a detailed process of the power-on starting strategy related to the present application;

[0042] Fig. 3 is an improved DC bus voltage control block diagram;

[0043] Fig. 4 is a split capacitor voltage balance control block diagram;

[0044] Fig. 5 is an improved grid-side current control block diagram;

[0045] Fig. 6 is an improved load voltage control block diagram. DETAILED DESCRIPTION

[0046] The present application will be further described below in conjunction with the accompanying drawings:

[0047] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application; the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance; in addition, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixed connection, or detachable connection; it can be directly connected, or indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0048] The first aspect of the present application discloses a voltage compensation converter without bypass power-on starting system of hybrid distribution transformer, the main circuit of the voltage compensation converter without bypass power-on starting method of hybrid distribution transformer is three-phase HDT, including main transformer (including primary winding, secondary winding and auxiliary winding), isolation transformer (including grid-side winding and valve-side winding), voltage compensation converter and current compensation converter.

[0049] The current compensation converter is connected in parallel with the auxiliary winding to realize network-side current regulation; and the voltage compensation converter is connected in series with the primary winding through an isolation transformer to the 10kV medium voltage side to realize load voltage stability control. The two converters share a DC bus capacitor, the bus capacitor is connected in series with a damping resistor, the damping resistor is equipped with a bypass contactor, and a circuit breaker is arranged at the 10kV side. The control system hardware includes a control circuit, an IGBT drive circuit and a detection circuit; wherein the control circuit mainly receives the collected signals of the detection circuit and sends level signals to control the on-off of switches according to the power-on starting strategy.

[0050] The second aspect of the present application discloses an HDT non-bypass power-on starting device for implementing a voltage compensation converter non-bypass power-on starting method of the HDT, which further comprises an improved network-side current control unit, an improved DC bus voltage control unit, an improved split capacitor voltage balance control unit and an improved load voltage control unit. The output of the DC bus voltage control unit is the d-axis reference signal of the network-side current PI control system, and the output of the split capacitor voltage balance control unit is the 0-axis reference signal of the network-side current PI control system. The reference signal of the DC bus voltage control unit is its rated voltage, and the d-axis reference signal of the load voltage control unit is the rated peak load voltage.

[0051] Based on the above device, the present application discloses a voltage compensation converter non-bypass power-on starting method of an HDT, which includes two stages, an uncontrolled rectification stage and a controllable rectification stage.

[0052] In the uncontrolled rectification stage, the following steps are included:

[0053] S101, the HDT keeps idle, the bypass anti-parallel thyristor of the voltage compensation converter is in an open state, and the bypass contactor of the DC side damping resistor keeps an open state. Under this premise, the network-side circuit breaker of the HDT is closed. Then the isolation transformer and the main transformer keep a fixed voltage ratio, and the DC bus capacitor is charged through the voltage compensation converter and the current compensation converter at the same time. Due to the effect of the damping resistor, the starting impact current in the initial stage of the uncontrolled rectification stage is limited.

[0054] S102, when the DC bus voltage exceeds the threshold value, the power supply module of the HDT control system enters a normal working state; then, the control circuit and the detection circuit can work normally, and the IGBT drive circuit and the contactor can be turned on or turned off through the level signal generated by the control circuit.

[0055] S103, the control chip in the control circuit of the HDT enters an interrupt waiting state, the control chip of the detection circuit enters an interrupt waiting state, after a set delay time, a contactor closing signal is sent, so as to bypass the DC bus damping resistor, and enter the end of the uncontrolled rectification stage.

[0056] In the controllable rectification stage, the following steps are included:

[0057] S201, start the closed-loop control of the current compensation converter. Specifically, the DC bus voltage control unit, the split capacitor voltage balance control unit, and the grid-side current closed-loop control unit are started simultaneously; wherein the DC bus voltage control unit adopts an integral separation strategy, that is, the initial value of the integral coefficient is kept as zero until the DC bus voltage rises to the rated value, and then the integral coefficient returns to the normal value, thereby preventing the overshoot caused by the large difference between the DC bus voltage reference value and the actual value at the initial stage of power-on, and the load voltage control system has not started to operate.

[0058] S202, after the current compensation converter is started, the voltage compensation converter is not started immediately, but is started after the DC bus voltage rises appropriately and exceeds the uncontrolled rectification end value by a certain degree. The role of this is that at the moment of switching from uncontrolled rectification to controllable rectification, the winding voltage will change abruptly. At the initial stage of controllable rectification, the DC bus voltage is very low, and the control capability of the current compensation converter is very weak, which cannot suppress the current impact caused by the abrupt change of the winding voltage. After setting a short time delay and then putting the voltage compensation converter into operation, the DC bus voltage becomes high, and the anti-winding capability increases, thereby effectively suppressing the impact current.

[0059] In the controllable rectification stage, the existing closed-loop control system of the HDT also needs to be improved, otherwise the impact current will still be caused at the initial stage of controllable rectification. Improvement 1, limit the output condition of the DC bus voltage control unit; specifically, before the DC bus voltage exceeds the rated value, a smaller limit threshold is applied to the control unit, which is 20% to 30% of the rated grid-side current; when the DC bus voltage exceeds the rated value for the first time and enters the stable state, after the power-on start is completed, the normal limit threshold corresponding to the rated grid-side current is applied; the role of this is to directly reduce the reference value of the grid-side current at the power-on start, thereby reducing the charging current. Improvement 2, multiply the PI parameters of all four control units except the deviation suppression system by the corresponding dynamic adjustment factor, and the dynamic factor of each controller can change in real time based on the DC bus voltage as required, overcoming the influence of the change of the DC bus voltage. The most critical is that when the bus voltage is very low at the initial stage of controllable rectification, the dynamic factor of the grid-side current controller can provide a large open-loop gain for the current compensation converter, so that it can quickly track the reference instruction, thereby greatly reducing the impact current.

[0060] It should be noted that there is a short invalid waiting time between the uncontrolled rectification stage and the controllable rectification stage, which is the time gap between the two stages.

[0061] The following will be further described in conjunction with specific embodiments.

[0062] Embodiment

[0063] The embodiment discloses a voltage compensation converter no-bypass power-on starting system for HDT, as shown in FIG. 1, the HDT main circuit topology involved is composed of four parts: T m (main transformer), T se (isolation transformer), CV p (current compensation converter) and CV t (voltage compensation converter).

[0064] The main transformer T m includes a primary winding W 1k , a secondary winding W 2k and an auxiliary winding W 3k , wherein k represents phase sequence, a, b or c in the application; the isolation transformer T se includes a valve side winding W 4k and a network side winding W 5k , the main transformer T m and the isolation transformer T se are arranged in series.

[0065] The medium voltage (MV) side of the HDT is connected to the power grid in a delta mode through a circuit breaker S sk , and the low voltage (LV) side supplies power to the load in a star connection mode through a circuit breaker S Lk .

[0066] The current compensation converter CV p and the auxiliary winding W 3k are connected in parallel to realize network side current regulation; and the voltage compensation converter CV t is connected in series with the primary winding through the isolation transformer T se to realize load voltage stability control. The current compensation converter CV p and the voltage compensation converter CV t share a DC bus capacitor C D , the bus capacitor is connected in series with a damping resistor R D , the damping resistor is equipped with a bypass contactor, and a circuit breaker is arranged on the 10kV side. Among them, S Ds and S Dx are bypass contactors for supporting HDT soft start, S tk is an anti-parallel thyristor for bypassing the voltage compensation converter CV t .

[0067] Two DC bus capacitors C D are arranged in series on the public DC bus, and one damping resistor R D is arranged on the two sides of the two DC bus capacitors C D , respectively.D A bypass is provided, and bypass contactors S Ds and S Dx are provided on the two bypasses respectively.

[0068] The voltage compensation converter without bypass for HDT has two stages in the time process, i.e. an uncontrolled rectification stage and a controlled rectification stage, and the detailed process is shown in Fig. 2.

[0069] The uncontrolled rectification stage starts when S sk is closed (t=0s) and ends when S Ds and S Dx are closed (t=T SX ). In this stage, the HDT is charged for the DC bus capacitor through the isolation transformer and the anti-parallel diodes (D tsk , D txk , D psk and D pxk ) in the main transformer, which is a natural charging and cannot be actively controlled, so it is called the uncontrolled rectification stage. In order to limit the initial impact current during the power-on, the bypass contactors S D and S Ds of R Dx are initially in the open state, so that the DC bus capacitor is charged through R D . Assuming that u en reaches the minimum level of the required input voltage of the system switching power supply at t=T D , the hardware circuits of the control system can be stably operated; then, the control chip sends a closing instruction after a corresponding delay according to the set timer delay time, and S Ds and S Dx are closed at t=T sx after the mechanical delay of the contactor, R D is bypassed, the uncontrolled rectification stage ends, and the steady-state value of u D is recorded as U Dremax , which can be calculated as follows:

[0070] In the formula, U s is the effective value of the grid-side voltage, K 54 is the turns ratio of the grid-side winding to the valve-side winding of the isolation transformer, and K 13 is the turns ratio of the primary winding to the auxiliary winding of the main transformer.

[0071] The controlled rectification stage starts when the CV p closed-loop control is enabled (t=T CV ), and u D (u D =u Ds )+u Dx ) reaches its rated value U D End of time (t=T) UD Specifically, firstly at t=T CV When enabling CV p Closed-loop control, via CV p Tracking control of the active current command keeps the HDT DC bus capacitor continuously energized. After a certain delay (let's assume it's δ), t δ t Approximately several fundamental cycles of the power grid (usually related to the power-on speed), at t=T CV +δ t Enable CV t Closed-loop control, thereby avoiding enabling CV t A surge current occurs instantaneously during closed-loop control.

[0072] Referring to Figures 3, 4, 5, and 6, the corresponding control devices for this system include a grid-side current control unit, a DC bus voltage control unit, a split capacitor voltage balancing control unit, and a load voltage control unit. The output of the grid-side current control unit is the d-axis reference signal of the grid-side current PI control system; the output of the split capacitor voltage balancing control unit is the 0-axis reference signal of the grid-side current PI control system; the reference signal of the DC bus voltage control unit is its rated voltage; and the d-axis reference signal of the load voltage control unit is the rated peak load voltage.

[0073] The CV involved p With CV t The improved closed-loop control block diagram can be seen in Figures 3-6, where K PuD K PuDδ K Pp and K Pt These are the proportional gain ω of the PI controllers used in DC bus voltage control, split capacitor voltage balance control, grid-side current control, and load voltage control systems, respectively. PIuD ω PIuDδ ω PIp and ω PIt These are the cutoff frequencies of the respective PI controllers. Dref is u D The reference input, i Psdref i Psqref and i Ps0ref They are i Psd i Psq and i Ps0 The reference input, i Psd i Psq and i Ps0 These are the grid-side currents i Psa i Psb i PscMapping quantities corresponding to the d, q, 0 axes of the synchronous coordinate system after coordinate transformation; u 2dref 2qref 20ref are the reference inputs of u 2d , u 2q and u 20 respectively, and u 2d , u 2q and u 20 are the grid-side currents u 2a , u 2b and u 2c respectively.

[0074] In the controllable rectification phase, for the control block diagram of the improved DC bus voltage control unit shown in FIG. 3, u Dref = U D is first set, and then the real-time value of u D is fed back, the deviation between the two is calculated through a u D PI controller, a low-pass filter and a notch filter, and finally through a limiting link, the reference instruction i Psdref of the inner loop of the grid-side current is obtained. Considering that u D and u Dref have a large difference in the controllable rectification phase, in order to avoid overshoot, three improved links of variable parameter and integral separation are added in the u D PI controller. The integral separation link functions to keep the integral coefficient as 0 before u D exceeds U D , so that the integral output remains 0; and the integral coefficient is added when u D first exceeds U D . The variable parameter link is K PuD multiplied by (U D / u D ) λD , and λ D takes -1, so that the influence of the change of u D on the control performance can be offset. The limiting link keeps a small threshold before the controllable rectification phase ends, so that a small reference value can be output, thereby reducing the initial impact current.

[0075] For the split capacitor voltage balance control block diagram shown in FIG. 4, in the controllable rectification phase, the value of u Dx -u Ds is taken as the input of the PI controller thereof, and an integral separation link is added to avoid overshoot, which functions to keep the integral part from producing control action before CV p is enabled, until CV p ​​When enabled, the integral begins to produce an integral output from the current value.

[0076] For the control block diagram of the improved grid-side current control unit shown in Figure 5, during the controllable rectification stage, T abc / dq0 and T dq0 / abc These are matrices used for coordinate transformation and inverse coordinate transformation, respectively. When CV is enabled... p Before closed-loop control, maintain CV p The drive signals for each IGBT are in a blocked state. When CV p Once closed-loop control is enabled, real-time feedback i Psk i is obtained through coordinate transformation matrix operations. Psd i Psq i Ps0 Combined with reference input i Psdref i Psqref and i Ps0ref , through i Psk The variable PI controller generates the modulation signal m pd m pq m p0 After inverse coordinate transformation, the drive pulse signals for each IGBT are obtained via SPWM. To reduce the inrush current during initial power-on, i Psk The variable PI controller incorporates two improvements: variable parameter control and integral separation. The variable parameter control involves adjusting K... Pp Multiply by (U) D / u D ) λp , and λ p Choose 3 to 4; thus, in the initial stage of power-on, due to u D Less than U D This results in a larger open-loop gain, thereby improving the CV. p The tracking performance is improved to reduce the initial power-on inrush current during the initial stage of controlled rectification. The integral separation stage involved is in the CV... p Before being enabled, the integral part remains inactive and does not exert any control effect until the CV (Continuous Transmission) is activated. p When enabled, the integral begins to produce an integral output from the current value.

[0077] In the controlled rectification stage, for the control block diagram of the load voltage control unit shown in Figure 6, T abc / dq0 and T dq0 / abc These are the matrices used for coordinate transformation and inverse coordinate transformation, respectively. As shown in Figure 2, CV... t Closed-loop control is enabled when CV is activated. p Closed-loop control delay δ t Later enabled, with CV p Similar to the improved closed-loop control, in CV t Maintain CV until closed-loop control is enabled.t The drive signals for each IGBT are in a blocked state. When CV t Once closed-loop control is enabled, real-time feedback u is provided. 2k u is obtained through coordinate transformation matrix operations. 2d u 2q u 20 Combined with reference input u 2dref u 2qref and u 20ref Then through u 2k The variable PI controller generates the modulation signal m td m tq m t0 After performing an inverse coordinate transformation on the modulated signal, the drive pulse signals are obtained through SPWM. To improve control performance, u 2k The variable PI controller incorporates two improvements: variable parameter control and integral separation. The variable parameter control involves K... Pt Multiply by (U) D / u D ) λt , and λ t Take 1, so that u can be canceled out. D The impact of changes on load voltage control; the integral separation stage involved is in CV. t Before being enabled, the integral part remains inactive and does not exert any control effect until the CV (Continuous Transmission) is activated. t When enabled, the integral begins to produce an integral output from the current value.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A voltage-compensated converter start-up method without bypass for HDT, characterized in that, The rectification stage comprises an uncontrolled rectification stage and a controlled rectification stage. The uncontrolled rectification stage comprises the following steps: S101, disconnecting the anti-parallel thyristor on the voltage compensation converter bypass and the contactor on the DC bus damping resistor bypass, and closing the circuit breaker of the HDT; S102, when the DC bus voltage exceeds the threshold value, the power module of the control circuit and the detection circuit of the HDT is powered on; S103, after the control circuit of the HDT is stabilized, the contactor on the DC bus damping resistor bypass is closed after a set delay time; The controlled rectification stage comprises the following steps: S201, starting the current compensator for closed-loop control; S202, after the current compensator is started, the voltage compensation converter is started when the DC bus voltage rises and exceeds the uncontrolled rectification end value.

2. A method for starting up a voltage-compensated converter without bypass according to a HDT, characterized in that, In S101, the isolation transformer and the main transformer maintain a fixed voltage ratio, and the voltage compensation converter and the current compensation converter simultaneously charge the DC bus capacitor.

3. A method for starting up a voltage-compensated converter without bypass according to a HDT, characterized in that, In S103, after the detection circuit is set for a delay time, the contactor on the DC bus damping resistor bypass is closed.

4. A voltage-compensated converter no-bypass power-up start device of an HDT for implementing the no-bypass power-up start method of claim 1, characterized by, It comprises: a grid-side current control unit for controlling the current compensation converter; Before the closed-loop control of the current compensation converter, each IGBT in the current compensation converter is in a blocked state; After the current compensation converter is enabled, the driving pulse signals of each IGBT are obtained; a DC bus voltage control unit for obtaining a deviation by comparing the real-time value of the DC bus voltage with the reference value, and obtaining the grid-side current as the reference instruction of the inner loop after the deviation is operated by a PI controller, a low-pass filter and a notch filter; a split capacitor voltage balance control unit for obtaining a difference value by comparing the voltages of the two DC bus capacitors, and taking the difference value as the 0-axis reference signal of the load when the current compensation converter is not enabled, and taking the difference value as the 0-axis reference signal of the load after the difference value is integrated and separated when the current compensation converter is enabled; a load voltage control unit for controlling the voltage compensation converter; before the closed-loop control, each IGBT in the voltage compensation converter is in a blocked state; after the voltage compensation converter is enabled, the driving pulse signals of each IGBT are obtained. When the DC bus voltage does not exceed the rated value, the DC bus voltage control unit applies a small amplitude limiting threshold; when the DC bus voltage exceeds the rated value, the DC bus voltage control unit applies a normal amplitude limiting threshold corresponding to the rated grid-side current.

5. A voltage-compensated transformer no-bypass start-up device for HDT according to claim 4, characterized in that, The small amplitude limiting threshold is 20% to 30% of the rated grid-side current. The PI parameters in the grid-side current control unit, the DC bus voltage control unit, the split capacitor voltage balance control unit and the load voltage control unit are adjusted by corresponding dynamic adjustment factors.

6. A voltage-compensated transformer no-bypass start-up device for HDTs according to claim 4, wherein, When the current compensator is started for closed-loop control, the DC bus voltage control unit, the split capacitor voltage balance control unit and the grid-side current closed-loop control unit are simultaneously started; the PI controller of the DC bus voltage control unit is provided with a variable parameter and an integral separation link.

7. A voltage-compensated transformer no-bypass start-up device for HDTs according to claim 4, wherein, SPWM obtains each driving pulse signal.

8. The voltage-compensated transformer no-bypass start-up device of claim 4, wherein, The grid-side current control unit, when the current compensation converter is enabled, obtains i Psk , i Psd , i Psq , i Ps0 in real time through i Psk , and generates modulation signals m pd , m pq , m p0 through a PI controller, and further obtains each driving pulse signal through SPWM. The load voltage control unit, when the voltage compensation converter is enabled, obtains u 2k , u 2d , u 2q , u 20 in real time through u 2k , and generates modulation signals m td , m tq , m t0 through a PI controller, and further generates a PWM signal through a It comprises a main transformer, an isolation transformer, a current compensation converter and a voltage compensation converter; the main transformer and the isolation transformer are connected in series; 9. The voltage-compensated transformer no-bypass start-up device of claim 8, wherein, The i of the grid-side current control unit Psk The u in the variable PI controller and the load voltage control unit 2k In the variable PI controller, both variable parameters and integral separation are provided.

10. A voltage-compensated converter no-bypass power-on system for implementing the no-bypass power-on method of claim 1, wherein, ​ The primary side of the main transformer is connected to the power grid in a delta mode through breakers, and the secondary side is connected in a star mode and connected with loads through breakers; The current compensation transformer and the auxiliary winding in the main transformer are connected in parallel, and the voltage compensation transformer is connected in series with the isolation transformer and the primary winding; The current compensation transformer and the voltage compensation transformer share a DC bus capacitor, the DC bus capacitor comprises two capacitors connected in series, each capacitor is connected with a damping resistor, each damping resistor is provided with a bypass, and each bypass is provided with a bypass contactor.

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