CN103532163A

CN103532163A - Topological structure of hybrid direct-current power transmission system based on polarity switching and starting method

Info

Publication number: CN103532163A
Application number: CN201310434656.XA
Authority: CN
Inventors: 刘开培; 秦亮; 陈灏泽; 杨洁
Original assignee: Wuhan University WHU
Current assignee: Wuhan University WHU
Priority date: 2013-09-23
Filing date: 2013-09-23
Publication date: 2014-01-22
Anticipated expiration: 2033-09-23
Also published as: CN103532163B

Abstract

The invention relates to a topological structure of a hybrid direct-current power transmission system starting way and a staring method, in particular to a topological structure of a hybrid direct-current power transmission system based on polarity switching and a starting method. The topological structure is specific to a dual-end large power grid hybrid direct-current transmission system; a VSC (Voltage Source Converter) is adopted on a rectifying side; an LCC converter is adopted on an inversion side; the two poles of a direct-current circuit are connected to opposite poles via circuit breakers respectively. The aim of starting the system is fulfilled by matching control of the LCC converter with polarity switching of the direct-current circuit. The topological structure has the advantages that 1, the problem of the lack of starting direct-current voltage can be solved effectively when the topological structure is applied to the starting process of a practical dual-end large power grid hybrid direct-current transmission system; 2, due to the adoption of the starting method, impacts of system voltage and current can be reduced effectively in a starting process, and the safety of power equipment is protected.

Description

The Hybrid HVDC system topology and the starting method that based on polarity, switch

Technical field

The present invention relates to a kind of topological structure and starting method of Hybrid HVDC system Starting mode, especially relate to a kind of Hybrid HVDC system topology and starting method switching based on polarity.

Background technology

In recent years, along with the development of high voltage dc transmission technology, the consideration based on technology and economic factor, the Hybrid HVDC system that LCC converter and VSC converter form has good application prospect.At present, Hybrid HVDC system is in wind-electricity integration, light current net and passive network power supply, the fields such as load center transmission of electricity have outstanding superiority of effectiveness to big city etc., believe that Hybrid HVDC system will have very wide application prospect along with the development of national wind-powered electricity generation and the continuous increase of urban power consumption.Due to the particularity of Hybrid HVDC system-comprise one-way flow and the inconsistent problem of two ends current conversion station entry condition of trend, when connecting AC system, it is constant DC voltage control that most mixed DC system is all preferentially selected VSC side, like this Hybrid HVDC entire system control strategy and application have all been formed to great restriction, and when LCC realizes DC voltage control (or determining gamma kick) as Inverter Station, its difficulty is that the entry condition of VSC and LCC is conflicting, in order to solve this bottleneck, must solve the starting problem of Hybrid HVDC system under this application scenarios, and the research of this respect, in open source literature and report, be not reported at home.

Summary of the invention

Above-mentioned technical problem of the present invention is mainly solved by following technical proposals:

A kind of Hybrid HVDC system topology switching based on polarity, it is characterized in that, rectification side is that electric network source connects VSC converter by first converter transformer, the first converter transformer primary side arranges first AC circuit breaker, the AC of VSC converter in parallel one group corresponding to the characteristic harmonics filter under VSC converter switching frequency, the converter reactor of connecting on alternating current circuit simultaneously;

Inversion side is through the second converter transformer and the 3rd converter transformer, to be linked into electrical network respectively after six pulsation LCC converters and intermediate point ground connection of two parallel connections, and the second converter transformer secondary side is connected with the second AC circuit breaker with the 3rd converter transformer primary side simultaneously;

Described VSC converter is connected with LCC converter through DC line.Between the flat ripple reactance of DC line the two poles of the earth LCC side and DC filter, DC circuit breaker SA, a SD are set respectively, at DC line the two poles of the earth same position, by a DC circuit breaker SB, SC parallel connection, are wired in another utmost point DC line respectively more simultaneously.

At the above-mentioned Hybrid HVDC system topology switching based on polarity, described DC line comprises two electric capacity of voltage regulation that are connected in parallel on the outlet of rectification side VSC converter; Two LCC Converter DC-side ports of export are connected respectively after a flat ripple reactance and are connected with the rectification side at VSC converter, and a stack features subharmonic filter in parallel is also distinguished at DC line the two poles of the earth.

A starting method for the Hybrid HVDC system that polarity is switched, is characterized in that, comprises the following steps:

Step 1, first closed DC line is switched circuit breaker SB, SC and LCC side AC circuit breaker, start LCC converter with and controlling unit, by logic control, make LCC converter now make rectification pattern and determine direct voltage and operate to DC capacitor and charge.

Step 2, when direct voltage reaches 0.95pu, cut-off breaker SB, SC and locking LCC converter and controlling unit thereof, now close immediately circuit breaker SA, SD and VSC AC circuit breaker start VSC converter and do determine active power control, meritorious command value is 0.2pu.

Step 3, when direct voltage continuation rising reaches 1.05pu, again start LCC converter and controlling unit thereof, guarantee that its control loop is switched to inverter mode operation simultaneously, now power starts to be transferred to inversion top-cross streaming system by rectification top-cross streaming system gradually, increase gradually VSC converter active power command value to 1.0pu, through-put power also will raise gradually and reach rated power, and whole start-up course completes substantially.

Therefore; tool of the present invention has the following advantages: 1. while being applied in the large electrical network Hybrid HVDC system starting process of actual two ends; for VSC converter, start and need direct voltage, LCC converter to start required power feed-in; but before starting, the two all can not give required separately condition this contradiction mutually; the impact that can provide a good solution 2. this kind of starting method can effectively reduce system voltage electric current in start-up course, thus protection power equipment, extend its useful life.

Accompanying drawing explanation

Fig. 1 is overall topological schematic diagram of the present invention.

Fig. 2 is the control block diagram of the rectifier that relates in the present invention.

Fig. 3 is the control block diagram of the inverter that relates in the present invention.

Fig. 4 is the start-up course flow chart relating in the present invention.

Embodiment

Below by embodiment, and by reference to the accompanying drawings, technical scheme of the present invention is described in further detail.

Embodiment:

If Fig. 1 is that whole Hybrid HVDC starts system topological figure, wherein 1 is two ends AC system, and 2.1 is the first AC circuit breaker, 2.2 is the second AC circuit breaker, and 3.1 is the first converter transformer, and 3.2 is the second converter transformer, 3.3 is the 3rd converter transformer, and 4 is alternating current filter, and 4.5 is converter reactor, 5 is VSC converter, 6 is LCC converter, and 7 is electric capacity of voltage regulation, and 8 is polarity switching DC circuit breaker, 9 is DC filter, and 10 is flat ripple reactance.

Fig. 2,3 is respectively the basic controlling block diagram of rectification side VSC converter and inversion side LCC converter.Wherein VSC converter adopts the Direct Current Control mode of d-q decoupling zero, meritorious amount is controlled as determining active power and is controlled, idle amount is controlled as determining Reactive Power Control, LCC converter adopts the control of two groups of changeable PI rings to determine direct voltage, wherein do the control of rectification pattern for one group, another group is made inverter mode and is controlled.

Fig. 4 has provided the basic procedure of two ends large electrical network Hybrid HVDC system starting process, its embodiment is first closed DC line switching circuit breaker SB, SC and LCC side AC circuit breaker, start LCC converter with and controlling unit, by logic control, be that LCC converter is now made rectification pattern and determined direct voltage and operate to DC capacitor and charge.When direct voltage reaches 0.95pu, cut-off breaker SB, SC and locking LCC converter and controlling unit thereof, circuit breaker SA immediately now closes, SD and VSC AC circuit breaker also start VSC converter and do determine active power control, meritorious command value is 0.2pu, when direct voltage continuation rising reaches 1.05pu, again start LCC converter and controlling unit thereof, guarantee that its control loop is switched to inverter mode operation simultaneously, now power starts to be transferred to inversion top-cross streaming system by rectification top-cross streaming system gradually, increase gradually VSC converter active power command value to 1.0pu, through-put power also will raise gradually and reach rated power, whole start-up course completes substantially.

Specific embodiment described herein is only to the explanation for example of the present invention's spirit.Those skilled in the art can make various modifications or supplement or adopt similar mode to substitute described specific embodiment, but can't depart from spirit of the present invention or surmount the defined scope of appended claims.

Claims

1. the Hybrid HVDC system topology switching based on polarity, it is characterized in that, rectification side is that electric network source connects VSC converter by first converter transformer, the first converter transformer primary side arranges first AC circuit breaker, the AC of VSC converter in parallel one group corresponding to the characteristic harmonics filter under VSC converter switching frequency, the converter reactor of connecting on alternating current circuit simultaneously;

Inversion side is through the second converter transformer and the 3rd converter transformer, to be linked into electrical network respectively after six pulsation LCC converters and intermediate point ground connection of two parallel connections, and the second converter transformer primary side is connected with the second AC circuit breaker with the 3rd converter transformer primary side simultaneously;

Described VSC converter is connected with LCC converter through DC line, between the flat ripple reactance of DC line the two poles of the earth LCC side and DC filter, DC circuit breaker SA, a SD are set respectively, at DC line the two poles of the earth same position, by a DC circuit breaker SB, SC parallel connection, are wired in another utmost point DC line respectively more simultaneously.

2. the Hybrid HVDC system topology switching based on polarity according to claim 1, is characterized in that, described DC line comprises two electric capacity of voltage regulation that are connected in parallel on the outlet of rectification side VSC converter; Two LCC Converter DC-side ports of export are connected respectively after a flat ripple reactance and are connected with the rectification side at VSC converter, and a stack features subharmonic filter in parallel is also distinguished at DC line the two poles of the earth.

3. a starting method for the Hybrid HVDC system of switching based on polarity, is characterized in that, comprises the following steps:

Step 1, first closed DC line is switched circuit breaker SB, SC and LCC side AC circuit breaker, start LCC converter with and controlling unit, by logic control, make LCC converter now make rectification pattern and determine direct voltage and operate to DC capacitor and charge;

Step 2, when direct voltage reaches 0.95pu, cut-off breaker SB, SC and locking LCC converter and controlling unit thereof, now close immediately circuit breaker SA, SD and VSC AC circuit breaker start VSC converter and do determine active power control, meritorious command value is 0.2pu;